U.S. patent application number 12/968224 was filed with the patent office on 2011-05-19 for method and apparatus for growing fullerene nanotube forests, and forming nanotube films, threads and composite structures therefrom.
Invention is credited to Charles A. Lemaire.
Application Number | 20110117316 12/968224 |
Document ID | / |
Family ID | 38575665 |
Filed Date | 2011-05-19 |
United States Patent
Application |
20110117316 |
Kind Code |
A1 |
Lemaire; Charles A. |
May 19, 2011 |
METHOD AND APPARATUS FOR GROWING FULLERENE NANOTUBE FORESTS, AND
FORMING NANOTUBE FILMS, THREADS AND COMPOSITE STRUCTURES
THEREFROM
Abstract
The present invention provides apparatus and methods for growing
fullerene nanotube forests, and forming nanotube films, threads and
composite structures therefrom. In some embodiments, an
interior-flow substrate includes a porous surface and one or more
interior passages that provide reactant gas to an interior portion
of a densely packed nanotube forest as it is growing. In some
embodiments, a continuous-growth furnace is provided that includes
an access port for removing nanotube forests without cooling the
furnace substantially. In other embodiments, a nanotube film can be
pulled from the nanotube forest without removing the forest from
the furnace. A nanotube film loom is described. An apparatus for
building layers of nanotube films on a continuous web is
described.
Inventors: |
Lemaire; Charles A.; (Apple
Valley, MN) |
Family ID: |
38575665 |
Appl. No.: |
12/968224 |
Filed: |
December 14, 2010 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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11220454 |
Sep 6, 2005 |
7850778 |
|
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12968224 |
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Current U.S.
Class: |
428/113 ;
156/494; 156/542; 422/129; 423/447.1; 977/742; 977/752;
977/843 |
Current CPC
Class: |
C01B 32/162 20170801;
B82Y 30/00 20130101; Y10T 156/171 20150115; B82Y 40/00 20130101;
C01B 2202/06 20130101; Y10T 428/24124 20150115; Y10T 428/30
20150115; C01B 32/154 20170801 |
Class at
Publication: |
428/113 ;
156/494; 156/542; 423/447.1; 422/129; 977/742; 977/843;
977/752 |
International
Class: |
B32B 5/12 20060101
B32B005/12; B29C 65/00 20060101 B29C065/00; D01F 9/12 20060101
D01F009/12; B01J 19/00 20060101 B01J019/00 |
Claims
1. A nanotube article comprising: a plurality of nanotube films
stacked in a continuous web, the plurality of nanotube films
including: a first nanotube film having nanotubes substantially
aligned in a first direction, the first direction being at a first
angle relative to a length-wise edge of the web; and a second
nanotube film having nanotubes substantially aligned in a second
direction, the second direction being at a second angle relative to
the length-wise edge of the web, wherein the second angle is
different than the first angle.
2. The article of claim 1, wherein the web is densified and wound
on a take-up roll.
3. The article of claim 1, wherein each of the plurality of
nanotube films includes carbon fullerene nanotubes.
4. The article of claim 1, wherein the web includes a first set of
parallel nanotube films that is woven into a second set of parallel
nanotube films.
5. The article of claim 1, wherein the web includes a first set of
films having a plurality of nanotube warp films oriented at the
first angle to the length-wise edge of the web woven with a second
set of films having a plurality of nanotube weft films oriented at
the second angle to the length-wise edge of the web.
6. The article of claim 1, wherein the web includes a first set
having a plurality of nanotube films parallel to one another and
crossed-but-not-woven with a second set having a plurality of
nanotube films parallel to one another.
7. An apparatus for continuous fabrication of a carbon nanotube
film comprising: a first film-transport mechanism having one or
more nanotube-film-holding surfaces, and movable along a first
fabrication path; and a layer-build-up mechanism operable to place
carbon nanotube film across the nanotube-film-holding surfaces
while the one or more nanotube-film-holding surfaces are moving
along the fabrication path.
8. The apparatus of claim 7, wherein the nanotube-film-holding
surfaces include one or more adhesive surfaces along a surface of a
flexible sheet belt, wherein the layer-build-up mechanism lays each
film at a non-parallel non-perpendicular angle to a lengthwise edge
of the sheet belt, and wherein the nanotube film is placed across
the belt and held by the one or more adhesive surfaces, the
apparatus further comprising a second film transport mechanism
having a plurality of spaced-apart adhesive surfaces on a sheet
belt, and movable along a second fabrication path that connects to
the first fabrication path in a manner to allow transfer of the
nanotube film from the first film transport mechanism to the second
film transport mechanism.
9. The apparatus of claim 7, wherein the layer-build-up mechanism
includes a first set of one or more warp-film holders operable to
hold a first set of warp films stretched to a first adhesive strip
along a distal first edge of the first film-transport mechanism
from the first set warp-film holders, and a second set of warp film
holders operable to hold a second set of warp films stretched to
the first adhesive strip, wherein the first film-transport
mechanism includes a second adhesive strip along a second edge
opposite the first edge, and a weft-film placement mechanism
operable to place a weft film in a shed between the first set of
warp films and the second set of warp films and attach opposite
ends of the weft to the first and second adhesive strips
respectively and then separate from the attached weft.
10. The apparatus of claim 9, wherein the first set warp-film
holders moves in a direction opposite relative to the second set
warp-film holders after deposition of a weft film placed from the
first adhesive strip to the second adhesive strip, and wherein the
warp-film holders successively attach a near end of each warp film
to the second adhesive strip as it completes its weave and then
separate from the attached warp.
11. The apparatus of claim 7, wherein the first film-transport
mechanism includes a vacuum table, wherein the
nanotube-film-holding surfaces are operable to hold and release
nanotube film using a gas-pressure difference, the vacuum surface
movable relative to layer-build-up mechanism to position itself for
a predetermined film deposition layout.
12. The apparatus of claim 7, wherein the first film-transport
mechanism includes a vacuum table, wherein the
nanotube-film-holding surfaces are operable to hold and release
nanotube film using a gas-pressure difference, the vacuum surface
movable relative to layer-build-up mechanism to position itself for
a predetermined film deposition layout.
13. The apparatus of claim 7, wherein the layer-build-up mechanism
includes a first set of one or more warp-film holders operable to
hold a first set of warp films stretched to a first adhesive strip
along a distal first edge of the first film-transport mechanism
from the first set warp-film holders, and a second set of warp film
holders operable to hold a second set of warp films stretched to
the first adhesive strip, wherein the first film-transport
mechanism includes a second adhesive strip along a second edge
opposite the first edge, and a weft-film placement mechanism
operable to place a weft film in a shed between the first set of
warp films and the second set of warp films and attach opposite
ends of the weft to the first and second adhesive strips
respectively and then separate from the attached weft.
14. The apparatus of claim 7, wherein the first film-transport
mechanism includes a vacuum table, wherein the
nanotube-film-holding surfaces are operable to hold and release
nanotube film using a gas-pressure difference, the vacuum surface
movable relative to layer-build-up mechanism to position itself for
a predetermined film deposition layout.
15. A method comprising: providing an interior-flow substrate
having a first major face, a first nanoporous surface layer in
fluid communication with the first major face, an interior flow
system operable to deliver gasses to the nanoporous layer from a
side or face of the substrate other than the first major face, and
a nanotube-synthesis catalyst on the first nanoporous layer; and
delivering one or more nanotube-precursor gasses into the interior
flow system and through the nanoporous layer to the first major
face.
16. The method of claim 15, further comprising: placing the
interior-flow substrate in a reaction chamber of a furnace; heating
the reaction chamber to a temperature effective for forming carbon
nanotubes, wherein the delivering of the gasses includes delivering
carbon-bearing precursor gas into the interior flow system and
through the nanoporous layer to the first major face to form carbon
nanotubes thereon; and removing the formed carbon nanotubes from
the interior-flow substrate without removing the substrate from the
reaction chamber.
17. The method of claim 15, wherein the providing of the
interior-flow substrate includes forming, in the first major face
of the substrate, a first plurality of interior gas passages having
a longest dimension that is parallel to the first major face and
having a depth measured in a direction perpendicular to the first
major face that is greater than a width measured in a direction
parallel to the first major face.
18. The method of claim 15, wherein the forming of the first
plurality of interior gas passages includes forming the first
plurality of interior gas passages having a length along a
Y-direction, the method further comprising: forming a second
plurality of gas passages that extend to a depth more distal from
the first major face than the depth of the first plurality of gas
passages, and wherein each of the second gas passages is configured
to be in fluid communication with a plurality of the first
plurality of gas passages, in order to form a flow-through
substrate.
19. The method of claim 15, wherein the delivering of gasses
includes delivering one or more reactant gasses to a side or face
of the substrate other than the first major face, the method
further comprising: controlling a temperature of the reaction
chamber to maintain an effective temperature for nanotube
synthesis; a substrate-holding mechanism; exhausting spent gasses
from a vicinity of the first major face; and removing nanotube
product without interrupting a substantially continuous operation
of the furnace at substantially its effective temperature for
nanotube synthesis.
20. The method of claim 15, wherein the substrate is a side-flow
substrate, wherein the delivering of the carbon-bearing precursor
gas is done from one or more sides of the substrate adjacent the
first major face, and wherein the forming of the first plurality of
interior gas passages includes forming the first plurality of
interior gas passages having a length along a Y-direction, the
method further comprising: holding the interior-flow substrate in a
reaction chamber of a furnace; heating the reaction chamber to a
temperature effective for forming carbon nanotubes, wherein the
delivering of the gasses includes delivering carbon-bearing
precursor gas into the interior flow system from a side or face of
the substrate other than the first major face and through the
nanoporous layer to the first major face to form carbon nanotubes
thereon; controlling a temperature of the reaction chamber to
maintain an effective temperature for nanotube synthesis; a
substrate-holding mechanism; exhausting spent gasses from a
vicinity of the first major face; and removing nanotube product
without interrupting a substantially continuous operation of the
furnace growing nanotubes at substantially its effective
temperature for nanotube synthesis.
Description
RELATED APPLICATIONS
[0001] This is a divisional of U.S. patent application Ser. No.
11/220,454, filed Sep. 6, 2005 and titled "APPARATUS AND METHOD FOR
GROWING FULLERENE NANOTUBE FORESTS, AND FORMING NANOTUBE FILMS,
THREADS AND COMPOSITE STRUCTURES THEREFROM" (to issue as U.S. Pat.
No. 7,850,778 on Dec. 14, 2010), which is incorporated herein by
reference in its entirety. This application is related to U.S. Pat.
No. 7,744,793 titled "APPARATUS AND METHOD FOR GROWING FULLERENE
NANOTUBE FORESTS, AND FORMING NANOTUBE FILMS, THREADS AND COMPOSITE
STRUCTURES THEREFROM" which issued Jun. 29, 2010, which is
incorporated in its entirety herein by reference.
FIELD OF THE INVENTIONS
[0002] This invention relates to the field of nanotechnology and
specifically to an apparatus and method for generating multi-wall
carbon fullerene nanotube "forests," and drawing therefrom sheets,
threads, yarns, and/or films using, e.g., various types of
adhesion, vacuum holding, surface tension, transport, transfer,
weaving, bending, densifying and related techniques.
BACKGROUND OF THE INVENTION
[0003] Carbon-based materials, in general, enjoy wide utility due
to their unique physical and chemical properties. Recent attention
has turned to the use of elongated carbon-based structures, such as
carbon fullerene filaments, carbon tubes, and in particular
nanosized carbon structures. It has been shown that these new
structures impart high strength, low weight, stability,
flexibility, good heat and electrical conductance, and a large
surface area relative to volume for a variety of applications, such
as high-strength fibers, threads, yarns, fabrics, and reinforcement
for composites, e.g., nanotube-reinforced epoxy structures.
[0004] Of growing commercial interest is the use of single-wall
carbon nanotubes to store hydrogen gas, especially for
hydrogen-powered fuel cells. Other applications for carbon fibers
and/or nanotube materials include catalyst supports, materials for
manufacturing devices, such as a tip for scanning electron
microscopes, electron field emitters, capacitors, membranes for
filtration devices as well as materials for batteries. In short,
interest in nanotube technology arises from the very high strength,
and electrical and thermo-conductive properties of individual
nanotubes.
[0005] Finer than carbon fibers, the material with one micron or
smaller of diameter is generally called carbon nanotubes and
distinguished from the carbon fibers, although no clear line can be
run between the both types of carbon fibers. By a narrow
definition, the material, of which carbon faces with hexagon meshes
are almost parallel to the axis of the tube, is called a carbon
nanotube and even a variant of the carbon nanotube, around which
amorphous carbon and metal or its catalyst surrounds, is included
in the carbon nanotube. (Note that with respect to the present
invention, this narrow definition is applied to the carbon
nanotube.)
[0006] Usually, the narrowly-defined carbon nanotubes are further
classified into two types: carbon nanotubes having a structure with
a single hexagon-connected carbon-mesh in a tube form are called
single-wall nanotubes (hereafter, simply referred to as "SWNT");
the carbon nanotubes made of multi-layer hexagon-connected carbon
tubes are called multi-wall nanotubes (hereafter, simply referred
to as "MWNT"). When grown from a substantially flat substantially
planar surface (e.g., a nanoporous surface coated with an
iron-oxide catalyst), the typical result is MWNTs. When grown in a
dense aligned structure, the parallel nanotubes somewhat resemble a
forest, and are referred to generally as a nanotube forest or more
specifically as an MWNT forest. The type of carbon nanotubes may be
determined by how they are synthesized and the parameters used to
some degree, but production of purely one type of the carbon
nanotubes has not yet been achieved.
[0007] U.S. Pat. No. 6,232,706 entitled "Self-oriented bundles of
carbon nanotubes and method of making same" issued May 15, 2001 to
Hongjai Dai et al. is incorporated herein by reference. Dai et al.
describe a method of making bundles of aligned carbon nanotubes
(e.g., for a field-emission device, such as a plasma TV screen) on
a porous surface of a substrate, the method comprising the steps
of: a) depositing a catalyst material on the porous surface of the
substrate and patterning the catalyst material such that one or
more patterned regions are produced; and b) exposing the catalyst
material to a carbon-containing gas at an elevated temperature such
that one or more bundles of parallel carbon nanotubes grow from the
one or more patterned regions in a direction substantially
perpendicular to the substrate.
[0008] Nanotube forests can be combined together to form structures
possessing extreme strength characteristics. These strength
characteristics, however, are limited by impurities in the
structures themselves arising during the manufacturing process,
and/or from the design of the structures such that the maximum
possible surface-to-volume ratio is not used by the structure. The
present invention addresses these and related issues.
SUMMARY OF THE INVENTION
[0009] In some embodiments, the present invention provides improved
apparatus and methods for growing nanotube forests (such as carbon
fullerene nanotubes arranged in a densely packed aligned
configuration synthesized from a catalyst-covered substrate). Some
embodiments provide apparatus and methods for making and using
improved nanotube-growth substrates. Some embodiments provide
apparatus and methods for making and using reaction chambers having
access ports for removing nanotubes during the growth cycle on a
continuous or repeated basis. Some embodiments provide apparatus
and methods for making and using composite structures from the
nanotube films.
BRIEF DESCRIPTION OF THE DRAWINGS
[0010] FIG. 1A is a perspective schematic diagram of a
film-holding-sheet pull initiation using an adhesive sheet to pull
a film starting from the top of a carbon-nanotube forest grown on a
substrate.
[0011] FIG. 1B is a perspective schematic diagram of a
film-holding-sheet pull initiation using an adhesive sheet to pull
a film starting from the front face of a carbon-nanotube
forest.
[0012] FIG. 1C is a perspective schematic diagram of a
film-holding-bar pull initiation using a cylindrical
adhesive-coated bar to initiate a pull at the top and/or front face
of a nanotube forest.
[0013] FIG. 1D is a perspective schematic diagram of a
film-holding-bar pull initiation using an adhesive bar to pull a
film starting from the front face of a carbon-nanotube forest.
[0014] FIG. 1E is a perspective schematic diagram of a
film-holding-sheet pull from the face of a carbon-nanotube forest
using an adhesive sheet.
[0015] FIG. 1F is a perspective schematic diagram of a
film-holding-bar pull from the face of a carbon-nanotube forest
using an adhesive bar.
[0016] FIG. 1G is a perspective schematic diagram of a
film-holding-bar pull from the face of a carbon-nanotube forest
using a rounded-front adhesive bar.
[0017] FIG. 1H is a perspective schematic diagram of a second
adhesive-sheet attachment to the second end of a film already
pulled from a face of a carbon-nanotube forest using an adhesive
sheet in order to remove the film from the carbon-nanotube
forest.
[0018] FIG. 1I is a perspective schematic diagram of a carbon
nanotube film held at its ends by a first and second adhesive sheet
after the film has been removed from the nanotube forest.
[0019] FIG. 1J is a perspective schematic diagram of a first,
second and third adhesive bar being attached to a film pulled from
face of a carbon-nanotube forest using an adhesive bar.
[0020] FIG. 1K is a perspective schematic diagram of a carbon
nanotube film held at its ends by the first and second adhesive bar
after removing the film from the carbon-nanotube forest, while the
third adhesive bar is used to pull an additional length of film
from a face of the carbon-nanotube forest.
[0021] FIG. 1L is a perspective schematic diagram of a stack of
carbon nanotube films, each film in the stack being held at its
ends by a first and second adhesive sheet, the films stacked one
upon another, in order to obtain a plurality of carbon-nanotube
films stacked to form a single thicker film structure.
[0022] FIG. 1M is a perspective schematic diagram of a flattened or
densified stack of carbon nanotube films, the stack held at its
ends by the respective stacks of adhesive sheets.
[0023] FIG. 1N is a perspective schematic diagram of a flattened or
densified stack of carbon nanotube films being removed from the
respective stacks of adhesive sheets by other adhesive-sheet
members.
[0024] FIG. 1-O is a perspective schematic diagram of a flattened
or densified stack of carbon nanotube films being held only by the
other adhesive-sheet members.
[0025] FIG. 1P is a perspective schematic diagram of a flattened or
densified stack of carbon nanotube films being removed from the
respective stacks of adhesive sheets by other adhesive-bar
members.
[0026] FIG. 1Q is a perspective schematic diagram of a flattened or
densified stack of carbon nanotube films being held only by the
other adhesive-bar members.
[0027] FIG. 1R is a perspective schematic diagram of a first carbon
nanotube film being pulled from a first carbon nanotube forest
about to be spliced to a second carbon nanotube forest.
[0028] FIG. 1S is a perspective schematic diagram of a first carbon
nanotube film being pulled from a first carbon nanotube forest
being spliced to a second carbon nanotube forest.
[0029] FIG. 1T is a perspective schematic diagram of a first carbon
nanotube film being pulled from the second carbon nanotube forest
after being spliced and removed from the first carbon nanotube
forest.
[0030] FIG. 1U is a perspective schematic diagram of a first carbon
nanotube film being pulled from a first carbon nanotube forest on
the top of a first double-sided substrate about to be spliced to a
second carbon nanotube forest on the top of a second double-sided
substrate.
[0031] FIG. 1V is a perspective view of a film-holder opener for a
clamping holder.
[0032] FIG. 1W is a top view of the film-holder opener.
[0033] FIG. 1X is an end view of the film-holder opener.
[0034] FIG. 1Y is a side view of the film-holder opener.
[0035] FIG. 1Z is a perspective schematic diagram of a carbon
nanotube film being inserted into a clamping film-holding-bar such
as a split rubber tube.
[0036] FIG. 2A is a perspective schematic diagram of an assembly of
carbon nanotube films, each film in the assembly being held at its
ends by a first and second adhesive rod, band or other or member,
the films placed one next to another and each transferred from its
respective transportation holder, in order to obtain a plurality of
carbon-nanotube films placed to form a single wider and/or woven
film structure.
[0037] FIG. 2B is a perspective schematic diagram of an assembly of
carbon nanotube films, each film in a first direction being held at
its ends by a first and second adhesive member, the films placed
one next to another and each transferred from its respective
transportation holder, each film in a second direction being held
at its ends by a third and fourth adhesive member, the films placed
one next to another and each transferred from its respective
transportation holder, in order to obtain a crossed-film structure
of a plurality of carbon-nanotube films.
[0038] FIG. 2C is a perspective schematic diagram of a loom that
provides a woven assembly of carbon nanotube films, each film in
the assembly being held at its ends by a first and second adhesive
rod, band or other or member.
[0039] FIG. 2D is a perspective schematic diagram of an assembly of
carbon nanotube films, each film in a first direction being held at
its ends by a first and second adhesive member, each film in a
second direction being held at its ends by the first and second
member, the films placed one next to another and each transferred
from its respective transportation holder, in order to obtain a
crossed-film structure of a plurality of carbon-nanotube films in a
continuous web.
[0040] FIG. 2E is a perspective schematic diagram of loom that
provides a woven assembly of carbon nanotube films, each film in
the assembly being held at its ends by a first and second adhesive
member, in order to obtain a crossed-film structure of a plurality
of carbon-nanotube films in a continuous web.
[0041] FIG. 2F is an end-view schematic diagram of the
continuous-loop loom.
[0042] FIG. 3A is a perspective schematic diagram of a carbon
nanotube film being pulled from a carbon nanotube forest having a
gap in the nanotube forest.
[0043] FIG. 3B is a perspective schematic diagram of a carbon
nanotube film being pulled from a carbon nanotube forest having a
gap in the nanotube forest in a manner that suppresses any gap in
the film.
[0044] FIG. 4A is a perspective cross-section schematic diagram of
an apparatus for the continuous synthesis and collection of carbon
nanotubes.
[0045] FIG. 4B is a cross-section side view of an apparatus for the
continuous synthesis and collection of carbon nanotubes.
[0046] FIG. 4C is a top-view of an apparatus for the continuous
synthesis and collection of carbon nanotubes.
[0047] FIG. 5A is a perspective schematic diagram of an apparatus
for the continuous synthesis and collection of carbon nanotubes
during an intermediate collection stage of one round of
synthesis.
[0048] FIG. 5B is a cross-section side view of an apparatus for the
continuous synthesis and collection of carbon nanotubes during an
intermediate collection stage of one round of synthesis.
[0049] FIG. 5C is a cross-section side view of an apparatus for the
continuous synthesis and collection of carbon nanotubes at a later
collection stage of one round of synthesis.
[0050] FIG. 5D is a cross-section side view of an apparatus for the
continuous synthesis and collection of carbon nanotubes at a
cutting and reattachment collection stage of one round of
synthesis.
[0051] FIG. 5E is a cross-section side view of an apparatus for the
continuous synthesis and collection of carbon nanotubes following
reattachment to initiate a fresh collection stage.
[0052] FIG. 5F is a cross-section side view of an apparatus for the
synthesis of carbon nanotubes using a double-sided flow-through
substrate.
[0053] FIG. 5G is a cross-section side view of a system for growing
densely packed carbon nanotube forests continuously to very long
lengths.
[0054] FIG. 5H is a cross-section side view schematic of a
carbon-nanotube-synthesis apparatus having a heat trap.
[0055] FIG. 6A is a cross-section side view of an apparatus that
includes flow-through linked substrates for the continuous
synthesis of carbon nanotubes.
[0056] FIG. 6B is a close-up side view of flow-through linked
substrates used for the continuous synthesis of carbon nanotubes
that illustrates the continuous collection of carbon nanotubes from
the flow-through linked substrates.
[0057] FIG. 6C is a cross-section side view of an apparatus for the
continuous synthesis of carbon nanotubes in which the nanotubes are
continuously collected in a downward manner.
[0058] FIG. 6D is a cross-section side view of an over/under
furnace and cool-box apparatus.
[0059] FIG. 7A is a cross-section side view of an apparatus for the
continuous synthesis of carbon nanotubes in which the nanotubes are
continuously collected from a substantially cylindrical
flow-through substrate.
[0060] FIG. 7B is a side-view of an apparatus for the continuous
synthesis of carbon nanotubes in which the nanotubes are
continuously collected from a substantially cylindrical
flow-through substrate.
[0061] FIGS. 8A-8K are perspective schematic diagrams of steps in
making a flow-through substrate for growing carbon nanotube
forests.
[0062] FIG. 8L is a bottom-view schematic diagram of a flow-through
substrate for growing a carbon nanotube forest.
[0063] FIG. 8L1 is a close-up bottom-view schematic diagram of a
flow-through substrate for growing a carbon nanotube forest.
[0064] FIGS. 8M-8P are perspective schematic diagrams of
alternative steps in making a flow-through substrate for growing
carbon nanotube forests.
[0065] FIGS. 9A, 9B, 9C, 9D, 9E, 9F, and 9G are perspective
schematic diagrams of steps in making a substrate 977 into a
flow-through substrate 905 for growing carbon nanotube forests.
[0066] FIG. 9H is a perspective schematic diagram showing the step
that substrate 977 (e.g., made of a silicon wafer having a
100-crystal orientation at its top surface) is deep etched to
create grooves or channels 919 by deep reactive ion etching (DRIE),
as described for FIG. 9A.
[0067] FIG. 9I is a perspective schematic diagram showing the step
that substrate 977 is processed to fill channels 919 and channels
920 with SiO2, to form silicon dioxide strips 918, which support
the epitaxial lateral overgrowth (ELOG) of silicon top layer 930,
but will then later be etched away to leave lateral gas passages
having at least one gas inlet port through a side wall 960 of
substrate 978.
[0068] FIG. 9J is a perspective schematic diagram showing the step
that substrate 977 has been processed with a nanoporous etch as
described above for FIG. 8G.
[0069] FIGS. 9K and 9L are perspective schematic diagrams of steps
in making a substrate 977 into a side-flow or through-flow dugout
substrate 982 for growing carbon nanotube forests.
[0070] FIGS. 9M, 9N, and 9O are perspective schematic diagrams of
steps in making a substrate 977 into a side-flow or through-flow
substrate 985 for growing carbon nanotube forests.
[0071] FIGS. 10A, 10B, 10C, and 10D are schematic perspective-view,
cross-section view, close-up perspective view and top view
diagrams, respectively, of making a continuous-web carbon nanotube
film structure.
[0072] FIG. 10E is a perspective schematic diagram of densification
steps in making a densified continuous-web carbon nanotube film
structure.
[0073] FIGS. 11A, 11B, 11C, 11D, 11E, and 11F are perspective-view
schematic diagrams of system 1100 making a continuous web of
crossed films, where each film in the assembly is being held at its
ends by a first and second adhesive member of a conveying
mechanism, in order to obtain a crossed-film structure of a
plurality of carbon-nanotube films in a continuous web.
[0074] FIGS. 11A1, 11B1, 11C1, 11D1, 11E1, and 11F1 are side-view
diagrams of system 1100 as shown in FIGS. 11A-11F.
[0075] FIGS. 12A and 12B are perspective-view schematic diagrams of
making a continuous web of crossed films, where each film in the
assembly is being held at its ends by a first and second adhesive
member of a conveying mechanism, in order to obtain a crossed-film
structure of a plurality of carbon-nanotube films in a continuous
web.
[0076] FIGS. 13A and 13B are perspective schematic diagrams of
making a plurality of continuous yarns from a plurality of
carbon-nanotube films pulled from carbon-nanotube forests.
[0077] FIGS. 13C and 13D are perspective-view schematic diagrams of
splicing films and/or yarns while making a plurality of continuous
yarns from a plurality of carbon-nanotube forests on different
substrates.
[0078] FIGS. 14A and 14B are perspective-view schematic diagrams of
initiating and pulling a continuous film from a carbon-nanotube
forest using vacuum film-holding bars.
[0079] FIGS. 14C and 14D are perspective schematic diagrams of
transferring films pulling a continuous film from a carbon-nanotube
forest using vacuum film-holding bars.
[0080] FIG. 14E is a perspective schematic diagram of splicing
films while pulling a continuous film from carbon-nanotube forests
on different substrates using vacuum film-holding bars.
[0081] FIGS. 15A, 15B, 15C, 15D, 15E, and 15F are top-view
schematic diagrams of system 1500 building a cross-woven nanotube
cloth on a vacuum table.
[0082] FIGS. 16A and 16B are perspective schematic diagrams of
system 1600 building a cross-woven nanotube airfoil using a
continuous web of crossed films, where each film in the assembly is
being held across its entire length and width by a curved vacuum
table.
DESCRIPTION OF EMBODIMENTS
[0083] In the following detailed description of the preferred
embodiments, reference is made to the accompanying drawings that
form a part hereof, and in which are shown by way of illustration
specific embodiments in which the invention may be practiced. It is
understood that other embodiments may be utilized and structural
changes may be made without departing from the scope of the present
invention.
[0084] The leading digit(s) of reference numbers appearing in the
Figures generally corresponds to the Figure number in which that
component is first introduced, such that the same reference number
is used throughout to refer to an identical component which appears
in multiple Figures. Signals and connections may be referred to by
the same reference number or label, and the actual meaning will be
clear from its use in the context of the description.
The Formation of Nanotube Fibers
[0085] The generation of carbon nanotube fibers is an aspect of
some embodiments of the present invention and can be achieved using
known techniques, such as those described in U.S. Pat. No.
6,232,706 (the Dai et al. patent), incorporated by reference herein
in its entirety. The Dai et al. U.S. Pat. No. 6,232,706 patent
discloses a method of making carbon nanotube bundles attached to
substrates.
[0086] Some embodiments apply a modification of a method disclosed
in U.S. Pat. No. 6,232,706 in order to make large areas of aligned
and closely packed carbon nanotubes across substantially the entire
top surface of a solid silicon substrate: in a first step A, in
some embodiments, a highly P-doped n.sup.+ type silicon substrate
(100-oriented-crystal top surface, resistivity 0.008-0.018 Ohm-cm)
is electrochemically etched in 1:1 HF (49% in water) ethanol with
an anodization current density of 10 mA/cm.sup.2 (typical etching
time is 5 minutes). This forms a thin nanoporous layer (pore size
about 3 nanometers) on top of a microporous layer (pore size about
100 nanometers). Next, in a step B, in some embodiments, the top of
the porous layer is covered substantially in its entirety (unlike
Dai et al.) with a five-nanometer thick iron (Fe) film by e-beam
evaporation. In some embodiments, after deposition of iron, the
substrate is annealed in air at 300 degrees C. overnight. This
annealing step oxidizes the surface of the silicon as well as the
iron, converting the iron patterns into catalytically active
iron-oxide. The resulting silicon dioxide layer formed on the
underlying porous silicon prevents the porous structure of layers
from collapsing during the following high-temperature chemical
vapor deposition (CVD) step.
[0087] Next, in a step C, in some embodiments, the substrate is
placed in a tube reactor housed in a tube furnace. The furnace is
preheated to 700 degrees C. (or 680 degrees C.) in a flowing inert
gas such as argon (or helium). Then, at 700 degrees C. (or 680
degrees C.), the argon (or helium) supply is turned off, and
ethylene is flown through the tube reactor at a rate of 1000
sccm/min for 15-60 minutes, (or a mixture of 5 mol % acetylene in a
Helium carrier is flown through the tube reactor at a rate of 850
sccm/min for about 10 minutes). The boat for the substrate(s) is
sealed at one end, and the sealed end is placed downstream in the
furnace. While ethylene is flowing, the iron-oxide surface
catalyzes the growth of carbon nanotubes, which grow perpendicular
to the substrate. In some embodiments, the iron film is patterned
(e.g., by deposition through a shadow mask). If the iron is
patterned (e.g., into islands or strips), the width of the bundles
is the same as the width of the iron-oxide patterns. Accordingly,
the width of the bundles can be tailored to a specific width
depending upon the iron oxide patterns used in forming the
bundles.
[0088] Other embodiments use methods to generate carbon nanotube
fibers such as those described in an article by Zhang, Atkinson
& Baughman titled "Multifunctional Carbon Nanotube Yarns by
Downsizing an Ancient Technology," Science; Vol. 306 Nov. 19, 2004
at 1358-1361 (the Zhang et al. 2004 article, which is incorporated
herein by reference). Zhang et al. 2004 give credit to, and build
on, important advances of the Dai group (S. Fan et al.,
"Self-Oriented Regular Arrays of Carbon Nanotubes and Their Field
Emission Properties," Science 283, 512 (1999)) and the Ren group
(Z. F. Ren et al., Synthesis of Large Arrays of Well-Aligned Carbon
Nanotubes on Glass, Science 282, 1105 (1998)). Zhang et al. 2004
disclose a method of manufacturing an aligned nanotube forest,
whereby MWNTs (for example) are synthesized in a quartz tube 45 mm
in diameter by atmospheric-pressure CVD of 5 mol % C.sub.2H.sub.2
in He at 680 degrees C., at a flow rate of 580 sccm for 10 minutes.
In some embodiments, the nanotube forest is grown on an iron (Fe)
film, 5 nm thick, which, in turn, is deposited on a silicon (Si)
wafer substrate by electron beam evaporator. Using this method,
various yarns composed of carbon nanotube fibers were generated by
Zhang et al. 2004, with a purity of between 96 to 98% and 2 to 4%
Fe and amorphous carbon.
[0089] Additionally discussed in Zhang et al. 2004 is a method by
which various yarns are generated using the fibers created from a
MWNT forest, wherein these fibers are twisted together to
approximately 80,000 turns/meter such that once the ends of the
twisted fibers are released the twisted structure is retained.
According to Zhang et al. 2004, this twisted structure is retained,
in part, because of the very high surface-to-volume ratio between
the MWNTs.
[0090] The generation of carbon nanotube forests is a component of
some embodiments of the present invention and can be achieved
either using the new techniques described herein, or by known
techniques, such as those described in an article titled "Strong,
Transparent, Multifunctional, Carbon Nanotube Sheet," Science, Vol.
309 Aug. 19, 2005 at 1215-1219 (the Zhang et al. 2005 article,
which is incorporated herein by reference).
[0091] Zhang et al. 2005 mention a method of manufacturing a MWNT
forest based upon the techniques as described above by Zhang et al.
2004 and apply these techniques to the manufacture of MWNT sheets.
In manufacturing such sheets, a MWNT forest is generated applying
the techniques of Zhang et al. 2004. The techniques of Dai et al.
could also be applied to generate such forests. Zhang et al. 2005
draw MWNT sheets from the MWNT forest using an adhesive strip
(e.g., a 3M Post-It Note.TM.) to contact the MWNTs and draw a sheet
therefrom. In some embodiments, a 1-cm length of 245-micron-high
(i.e., about 0.25 mm) forest converts to about a 3-m long (a 300:1
ratio) strip of freestanding MWNT sheet. Once drawn, these sheets
can be stacked one on top of another for increased strength, set in
an overlay or crossed-film pattern.
[0092] Moreover, Zhang et al. 2005 describe a process of densifying
these MWNT sheets whereby the sheets are placed/attached onto a
planar substrate composed of glass, gold, silicon, aluminum, steel,
plastic or some other substrate known in the art. The process
includes immersing the substrate and attached MWNT sheet vertically
into a bath of a liquid, such as ethanol, and then retracting the
substrate vertically from the liquid and drying. The thinning and
surface tension of the liquid evaporating shrinks the thickness of
the MWNT sheet, thus making the carbon nanotube sheets themselves
denser. Some embodiments of the invention use improved methods for
applying and evaporating a densifying liquid on a continuous basis
to a web moving in a continuous or roll-to-roll manner.
[0093] Some embodiments of the present invention use improved
MWNT-forest-growing techniques to make carbon nanotubes, the
methods modified from those described in the above-mentioned
published articles and U.S. Pat. No. 6,232,706. Other embodiments
of the present invention use improvements of methods such as
described in U.S. Patent Application US 2004/0062708A1 published
Apr. 1, 2004 by Remskar et al., in order to make nanotubes from
materials other than carbon, for example synthesis and
self-assembly of single-wall subnanometer-diameter molybdenum
disulfide tubes. In some embodiments, the nanotubes contain
interstitial iodine, which is removed as the
molybdenum-disulfide-nanotube forest is pulled into
molybdenum-disulphide nanotube films. In some embodiments,
synthesis is performed using a catalyzed transport reaction similar
to that described by Remskar including C60 as a growth promoter. In
contrast to Remskar et al., the present invention, in some
embodiments, uses modifications and new techniques similar to those
described below, but using a quartz substrate for the
molybdenum-disulfide-nanotube growth surface.
[0094] FIG. 1A is a perspective schematic diagram of system 100 in
which a film-holding-sheet pull initiation uses an adhesive sheet
110 (such as a Post-It.RTM.-brand sticky note, Scotch.RTM.-brand
transparent sticky tape or other suitable substrate having an
adhesive area 112) from the top 87 of a carbon-nanotube forest 89
grown on a substrate 77. In some embodiments, substrate 77 has a
nanoporous top surface 79 having a catalyst (such as iron oxide,
for example--in some embodiments, a 5-nm iron film is oxidized to
form the catalyst; in other embodiments, one or more other
transition metals are substituted for, or added to, the iron, such
as nickel, cobalt, or other suitable composition) suitable for
growing tubular fullerene structures (e.g., multi-walled carbon
nanotubes, or MWNTs). In some embodiments, nanotube forest 89
includes a large plurality of substantially aligned, densely packed
MWNTs. In other embodiments, forest 89 includes a large plurality
of substantially aligned, densely packed single-walled nanotubes,
or SWNTs. In other embodiments, nanotubes made of other materials
such as Forest 89 includes a nanotube forest front wall 86 that
exposes the left-hand sides (relative to the drawing) of an outer
row of nanotubes and from which a film will be drawn, nanotube
forest base 85 where the nanotubes are connected to the catalyst
surface of substrate 77 (where it is believed that growth takes
place), nanotube forest top 87, nanotube forest back wall 88, and
nanotube forest side walls 84. In some embodiments, a nanotube film
99 is started by pressing adhesive sheet 110 onto forest top 87
where it meets forest front 86, and then pulling adhesive sheet 110
towards the right. Other embodiments substitute a film-holding
sheet 110 having a liquid such as alcohol, water, and/or oil to
hold nanotube film 99 in place, rather than (or in addition to)
adhesive 112 (this optionally applies to all embodiments described
herein).
[0095] FIG. 1B is a perspective schematic diagram of system 100 in
which a film-holding-sheet pull initiation uses an adhesive sheet
110 where adhesive area 112 is initially pressed against front face
86 of carbon-nanotube forest 89, and then adhesive sheet 110 is
withdrawn towards the right.
[0096] FIG. 1C is a perspective schematic diagram of system 100 in
which a film-holding-bar pull initiation uses an adhesive bar 114
having an adhesive surface 116 from the top 87 and/or front face 86
of carbon-nanotube forest 89. In some embodiments, adhesive surface
116 (and/or the other adhesive surfaces described herein) includes
an adhesive such as found on a Post-It.RTM.-brand sticky note,
Scotch.RTM.-brand transparent sticky tape, such as described in
U.S. Pat. No. 6,479,073 entitled "Pressure sensitive adhesive
articles and methods for preparing same" or U.S. Pat. No. RE 24,906
entitled "Pressure-sensitive adhesive sheet material" by inventor
Erwin W. Ulrich (both of which patents are incorporated herein by
reference) or other suitable adhesive.
[0097] Other embodiments substitute a film-holding bar 114 (and/or
similar structures for the other adhesive surfaces described
herein) having a liquid such as ethanol or other alcohol (such as
poly(vinyl alcohol)), water, and/or oil selected for its ability to
hold nanotube film 99 in place, rather than (or in addition to)
adhesive 116 (this optionally applies to all embodiments described
herein). Still other embodiments substitute a vacuum film-holding
bar 1410, as described below in FIG. 14E, to hold nanotube film 99
in place, rather than (or in addition to) adhesive 116 (this
optionally applies to all embodiments described herein).
[0098] FIG. 1D is a perspective schematic diagram of system 100 in
which a film-holding-bar pull initiation uses an adhesive bar 118
having an adhesive surface 119 from front face 86 of
carbon-nanotube forest 89. In some embodiments, bar 118 has a
bottom surface 116 that rests on substrate surface 79 as the
adhesive-coated rounded front nose 117 of bar 118 is moved into
engagement with forest front face 86, wherein the spacing between
bottom 116 and nose 117 is selected such that nose 117 first
contacts approximately the midpoints of nanotubes 80. In other
embodiments, the spacing between bottom 116 and nose 117 is
selected such that nose 117 first contacts below the midpoints of
nanotubes 80, and bar 118 is first moved upward slightly while
adhesive 119 is in contact with the front face 86 and then bar 118
is pulled to the right or in a general direction to the right
relative to the orientation in FIG. 1D.
[0099] FIG. 1E is a perspective schematic diagram of a
film-holding-sheet pull or draw from the face 86 of a
carbon-nanotube forest 89 using an adhesive sheet 110.
[0100] FIG. 1F is a perspective schematic diagram of a
film-holding-bar pull from the face 86 of a carbon-nanotube forest
89 using an adhesive bar 113 having an adhesive face 112.
[0101] FIG. 1G is a perspective schematic diagram of a
film-holding-bar pull from the face 86 of a carbon-nanotube forest
89 using a rounded-front adhesive bar 118. Generically, all of the
film-holding bars (including the vacuum bars of FIG. 14) herein can
be used for pulling or holding film 99, and are referred to simply
as film-holding puller bar 199 when being used to pull a carbon
nanotube film 99 from a forest 89.
[0102] FIG. 1H is a perspective schematic diagram showing
attachment of a second adhesive sheet 111 to the second end of a
film 99 pulled to a desired length from a face of a carbon-nanotube
forest 89 using an adhesive sheet 110. In some embodiments, a third
adhesive sheet is simultaneously attached to the bottom of film 99
at a location closer to forest 89, and the film 99 is cut, torn, or
otherwise separated between the second adhesive sheet 111 and the
third adhesive sheet, which then becomes adhesive sheet 110 for the
continued pulling of additional film 99 from forest 89, while the
removed film 98 is held by first and second adhesive sheets 110 and
111.
[0103] FIG. 1I is a perspective schematic diagram of a carbon
nanotube film 98 held at its ends by first adhesive sheet 110 and
second adhesive sheet 111, after the film 98 has been pulled and
then removed from the carbon-nanotube forest 89. In some
embodiments, a spacer bar 121 is used to hold one or more first
adhesive sheets 110 and second adhesive sheets 111 at a fixed
distance apart to prevent sagging or overstretching of film 99. In
some embodiments, a handle 122 and/or feet 123 are provided so a
person can manually handle the fragile film 98 more easily. (While
film 98 is very strong compared to other materials of similar
weight and length, multiple layers must be aggregated and/or
embedded in a polymer to achieve noticeable strength on a macro
scale.)
[0104] FIG. 1J is a perspective schematic diagram of a first
adhesive bar 131, second adhesive bar 132 and third adhesive bar
133 being attached to a film 99 pulled from face 86 of a
carbon-nanotube forest 89 using adhesive puller bar 199.
[0105] FIG. 1K is a perspective schematic diagram of a carbon
nanotube film 98 held at its ends by first adhesive bar 131 and
second adhesive bar 132 after removing the film 98 from the
carbon-nanotube forest 89, while the third adhesive bar 133 is used
as adhesive puller bar 199 to pull an additional length of film 99
from a face of the carbon-nanotube forest 89. In some embodiments,
first adhesive bar 131 and second adhesive bar 132 are held at a
fixed distance apart by a spacer bar similar to spacer bar 121 of
FIG. 1I. In some embodiments, a strong magnet 144 is positioned
adjacent the face of substrate opposite where the nanotube forest
89 is being harvested. The nanotube formation process as described
by Zhang et al. 2004 yields nanotube fibers with a purity of
between 96 to 98% and 2 to 4% Fe and amorphous carbon. In some
embodiments, an adhesion layer of nickel (Ni), titanium (Ti),
vanadium (V), or some other suitable metal or composition is placed
onto the nanoporous substrate (such as that disclosed in Zhang et
al. 2004) and the iron (Fe) catalyst deposited thereon. The Fe
layer is oxidized in order to form the catalyst. One purpose of
this adhesion layer is to suppress separation of iron (Fe) or iron
oxide from the catalyst layer and thereby placing impurities in the
nanotube fiber. Keeping the iron oxide on the substrate also allows
the substrate to be reused to grow more carbon nanotubes. In some
embodiments, the strong north-south magnet 144 is placed, or a
similar magnetic field is generated, under the substrate at or near
the area of release (i.e., where the bases of the nanotubes are
separating from the substrate) during the pulling of the nanotube
film from the nanotube forest to attract the iron or iron compounds
so as to prevent iron (Fe) from contaminating the nanotube fibers,
by keeping iron on the surface of the nanoporous layer. In some
embodiments, both the adhesion layer and the magnetic field are
used to retain the catalyst material.
[0106] FIG. 1L is a perspective schematic diagram of a stack 105 of
carbon nanotube films 98, each film in the stack 105 being held at
its ends by a first adhesive sheet 110 and second adhesive sheet
111, the films 98 stacked one upon another, in order to obtain a
plurality of carbon-nanotube films 98 stacked to form a single
thicker film structure. In some embodiments, one or more stacks of
adhesive strips are used to generate a layered, thinned, and
flattened nanotube structure. In these embodiments, a first
adhesive strip is placed at each end of a nanotube film 98 drawn to
a suitable length (e.g., 3 meters or other suitable length). A
second nanotube film 98 is placed on top of the first single
nanotube film 98, and the adhesive strips holding its ends are
placed on top of the adhesive strip holding the first film. This
process is continued until a nanotube structure of a suitable
number of layers is obtained. The suitability of a particular
number of layers can be determined by empirical testing and/or
modeling. As this nanotube structure 97 is completed, the stacks of
adhesive strips 110 are built up at the ends of the structure 97,
layered one on top of another.
[0107] Once a nanotube structure of a suitable thickness is
created, each stack of adhesive strips 134 and 135 is turned or
bent to an angle of ninety (90)-degrees to the nanotube structure
such that it is perpendicular to the length of the nanotube
structure 97 in a direction opposite that of the other end. In some
embodiments, the angle to which both the stack of adhesive strips
and substrate are bent is greater than ninety (90) degrees. The
optimum angles can be determined through empirical testing or
modeling. Thus, in some embodiments, the stacks of adhesive strips
134 and 135 are bent to ninety-degree angles to the film stack 97
in directions opposite from one another (and perpendicular to the
nanotube structure 97).
[0108] FIG. 1M is a perspective schematic diagram of method 106 to
form a flattened or densified stack 97 of carbon nanotube films 98,
the stack 97 held at its ends by the respective first stack 135 of
first adhesive sheets 110 and second stack 134 of second adhesive
sheets 111, which, in some embodiments, are each folded at a right
angle to film stack 97 (in some embodiments, one stack (e.g., stack
135) is folded up and the other (e.g., stack 134) folded down, in
order to keep all films 98 at the same length and tautness).
[0109] In some embodiments, as a result of bending the first and
second stacks of adhesive strips such that their ends are coplanar,
the layered nanotube structure will be condensed, thinned and
flattened, and the strength of the nanotube structure will be
increased due, in part, to very high surface-to-volume ratio
between the various layers of single nanotubes (i.e., by the
nanotubes of the parallel layers sticking to one another across
greater surface areas). Specifically, a greater portion of the
surface area of a single nanotube will come into contact with the a
greater portion of the surface area of a second single nanotube,
and the second nanotube sheet will come into contact with a third,
and so on and so on, resulting in a very strong layered and
flattened nanotube structure.
[0110] FIG. 1N is a perspective schematic diagram of a flattened or
densified stack 97 of carbon nanotube films 98 being removed from
the respective stacks 134 and 135 of adhesive sheets 111 and 110 by
other adhesive-sheet members 136 and 137. In some embodiments, the
adhesive 112 on adhesive-sheet members 136 and 137 will stick to
all layers of film stack 97, and the film ends attached to stacks
134 and 135 can be cut or torn off.
[0111] FIG. 1-O is a perspective schematic diagram of a flattened
or densified stack 97 of carbon nanotube films being held at their
ends only by adhesive-sheet members 136 and 137. In some
embodiments, the resulting stack is densified by placing film stack
97 on a surface, applying a liquid, and having the liquid evaporate
to draw the fibers together by surface tension. In some
embodiments, the densification is performed with the stack of films
97 held on a sheet or backing, and in some embodiments, is
performed on an endless belt such as shown in FIG. 10E.
[0112] In at least one embodiment, a series of layered and
flattened nanotube structures 97, e.g., created using the method
described above, is used to form a further nanotube structure in a
cross-hatch pattern as described in FIGS. 2A-2E below. In some
embodiments, the above described layered and flattened nanotube
structures 97 are used to form a nanotube structure in a
cross-layer pattern. In some embodiments, a parallel-oriented
layered nanotube structure is created. A plurality of these layered
nanotube structures is then placed into a cross-hatch, cross-layer,
woven or some other pattern. Once placed into one of these
patterns, the adhesive-strip stack and substrates are folded to
densify the nanotube structure in the above described manner. The
result of this bending is that these nanotube structures that make
up the above described patterns are flattened and densified, and
hence stronger than they would otherwise be.
[0113] FIG. 1P is a perspective schematic diagram of a flattened or
densified stack 97 of carbon nanotube films 98 being removed from
the respective stacks 134 and 135 of adhesive sheets by
adhesive-bar members 138 and 139 having adhesive coatings 115.
[0114] FIG. 1Q is a perspective schematic diagram of a flattened or
densified stack 97 of carbon nanotube films 98 being held only by
adhesive-bar members 138 and 139.
[0115] FIG. 1R is a perspective schematic diagram of a splice
process 107 in which a first carbon nanotube film 99 being pulled
from a first carbon nanotube forest 89 about to be spliced to a
second carbon nanotube forest 89' using splicer bar 130. In some
embodiments, splicer bar 130 includes a non-adhesive front nose 141
configured to press film 99 into approximately the center of front
face 86' of forest 89'. In some embodiments, front nose 141
includes a porous front surface (see FIG. 14A) through which a
vacuum is selectively applied in order to hold and later release
film 99 during the splice process 107. Some embodiments of splice
bar 130 also include a cutting edge 142 for severing the initial
film 99 once the splice has been made.
[0116] FIG. 1S is a perspective schematic diagram of a first carbon
nanotube film 99 from a first carbon nanotube forest 89 being
spliced to a second carbon nanotube forest 89'.
[0117] FIG. 1T is a perspective schematic diagram of carbon
nanotube film 99' being pulled from the second carbon nanotube
forest 89' after being spliced and removed from the first carbon
nanotube forest 89. Splicer bar 130 is being withdrawn.
[0118] In some embodiments, a small amount of forest 89 and a small
film tail 92 may remain unused, and may be removed and recycled as
ordinary carbon nanotube material. Once the remaining forest 89 is
removed from substrate 77, additional carbon nanotube forest can be
re-grown from catalyst surface 79, which, in some embodiments, may
or may not be porous. It is believed that when a nanotube is grown
from a catalyst-covered porous surface such as described herein,
each MWNT grows from its base at or near the iron-oxide catalyst.
It is believed that when a nanotube film is pulled from a nanotube
forest, the MWNTs break at or near the iron-oxide catalyst (where
the molecular bonds are perhaps not as strong and/or not aligned as
they are elsewhere in each MWNT). This would typically leave most
or all of the catalyst attached to the growth surface, available to
catalyze further growth if the substrate is again placed in a
growth furnace and supplied with carbon-bearing source gas.
[0119] FIG. 1U is a perspective schematic diagram of a system 108
wherein a first carbon nanotube film 99 being pulled from a first
carbon nanotube forest on the top of a first double-sided substrate
76 is about to be spliced to a second carbon nanotube forest 89' on
the top of a second double-sided substrate. In the embodiment
shown, a bottom-side nanotube forest 81 is grown on the
opposite-face growing surface 78, at the same time as top-side
forest 89 is grown on top-side growing surface 79 of double-sided
substrate 76. At a later time, substrate 77 may be flipped and a
film 99 may be spliced to its nanotube forest 81. At a still later
time, substrate 77' may be flipped and a film 99 may be spliced to
its nanotube forest 81'. In this manner, a much longer film can be
pulled than if the film 99 is pulled from only a single substrate
77.
[0120] FIG. 1V is a perspective view of a film-holder opener 185
for a clamping holder such as a split rubber tube. In some
embodiments, film-holder opener 185 includes a bulb nose 186 to
insert into the hollow core 183 of a clamping holder 181 (see FIG.
1Z), opposing separating surfaces 189 for holding the slit 182 of
clamping holder 181 open as it is slid past film-holder opener 185.
Opening 187 provides a space in which to insert film 98, for
example by air flow (either pressure from outside or vacuum from
inside). In some embodiments, pressurized air is directed through
nozzle 188 (see FIG. 1Z), in order to push a film 98 through
opening 187 and thus into film-holder 181. In some embodiments, a
vacuum is applied to the conduit extending from the top of
film-holder opener 185 in order to suck a film 98 through opening
187 and thus into film-holder 181. In some embodiments, the bottom
of film-holder opener 185 is open from the film-depositing area and
downstream in order that more of the film 98 comes in contact with
the walls of hollow core 183, so that the film 98 moves with and is
gripped by film-holder 181 rather than sticking to film-holder
opener 185. In some embodiments, a flat surface 179 is provided
next to film-holder opener 185 and supports film 98 as it is
inserted into opening 187, wherein surface 179, film 98, and
film-holder 181 do not move laterally relative to one another
during the insertion process. Film-holder opener 185 is then moved
towards the right (in the orientation shown the drawing), and slot
182 closes, thus gripping film 98. FIG. 1W is a top view of the
film-holder opener 185. FIG. 1X is an end view of the film-holder
opener 185. FIG. 1Y is a side view of the film-holder opener
185.
[0121] FIG. 1Z is a perspective schematic diagram of a carbon
nanotube film 99 being inserted into a clamping film-holding-bar
181, such as a split rubber tube, for example. In some embodiments,
a clamping film-holding-bar 181 includes a tube made of synthetic
rubber or other elastomeric material having a hollow core 183
(which helps keep film-holding-bar 181 on film-holder opener 185 as
it is slid right-to-left (in the orientation shown the drawing))
and a slit 182. In some embodiments, film-holder opener 185 (the
embodiment shown in FIG. 1Z is slightly different than that of
FIGS. 1V-1Y) has a bulb nose 186 and a top slot 187, which holds
the slit 182 open as the film 98 is inserted. In some embodiments,
pressurized air is directed through nozzle 188 to push a film 98
through opening 187 and thus into film-holder 181. In some
embodiments, a vacuum is applied to the conduit extending from the
top of film-holder opener 185 in order to suck a film 98 through
opening 187 and thus into a film-holder 181.
[0122] FIG. 2A is a perspective schematic diagram of a system 200
and a method for assembling a plurality of carbon nanotube films 98
into a wider structure 95, each film 98 in the assembled structure
95 being held at its ends by a first adhesive rod, band or other or
member 231 and second adhesive rod, band or other or member 232,
the films 98 placed one next to another and each transferred from
its respective transportation holder 230, in order to obtain a
plurality of carbon-nanotube films placed to form a single wider
and/or woven film structure 95. In some embodiments, each
transportation holder 230 includes a first adhesive member 131 at
one end and a second adhesive member 132 at the other end, each
attached to a rod or other structure to keep them at a constant
distance to prevent sagging or stretching of film 98. In some
embodiments, as transportation holder 230 is pressed downward,
adhesive member 131 drops below adhesive member 231 on its outside
(right) edge, and adhesive member 132 drops below adhesive member
232 on its outside (left) edge, such that film 98 sticks to the
adhesive surfaces of adhesive member 231 and adhesive member 232,
whereupon further pressing down pulls or tears film 98 from
adhesive member 131 and adhesive member 132. In other embodiments,
a cutter is provided to cut the film 98 from adhesive member 131
and adhesive member 132. In some embodiments, a plurality of layers
of films 98 are stacked one upon another. In some embodiments, an
overlap is provided between adjacent films 98.
[0123] In some embodiments, members 131, 132, 231, and/or 232 use a
liquid coating (such as ethanol or water or oil or other suitable
chemical or mixture) rather than an adhesive coating to hold carbon
nanotube film 98 (e.g., by surface tension).
[0124] FIG. 2B is a perspective schematic diagram of a system 202
and a method for criss-cross assembly of carbon nanotube films 98.
In some embodiments, each film 98'' in a first direction 215 (e.g.,
the X direction) being held at its ends by a first adhesive member
231 and second adhesive member 232, the films 98'' placed one next
to another and each transferred from its respective transportation
holder 230 as described for FIG. 2A (although small gaps between
films 98 are shown in some of the figures throughout this
application for clarity, in some embodiments, the films are tightly
spaced and/or overlapped such that no such gaps are in the
completed product). In some embodiments, each film 98' in a second
direction 216 (e.g., the Y direction) is being held at its ends by
a third adhesive member 233 and fourth adhesive member 234, the
films 98' placed one next to another and each transferred from its
respective transportation holder 235 in a manner such as described
for FIG. 2A, in order to obtain a criss-crossed-film structure 94
made of a plurality of carbon-nanotube films. In some embodiments,
the films are deposited in an order A, A, B, B, C, C, D, D, and so
on. In some embodiments, after one complete layer 94 is deposited,
one or more additional layers are stacked on the earlier
layer(s).
[0125] FIG. 2C is a perspective schematic diagram of a loom system
204 that provides a woven assembly 93 of carbon nanotube films 98,
each weft film 98' in the woven assembly 93 being held at its ends
by a first and adhesive member 233 second adhesive member 234. Each
warp film 98'' is held at the right-hand end by adhesive member 239
(also called the cloth beam), and at its opposite (left-hand) end
by one loom rod of the moving sets of loom rods 236 and 246. The
warp films 98'' marked A (e.g., every other warp film) are each
connected to an adhesive-covered portion of a respective one of
loom rods 246, and the warp films 98'' marked B (e.g., the other
set of every other warp film) are each connected to an
adhesive-covered portion of a respective one of loom rods 236. Loom
rods 236 and 246 alternately move up and down, as in a cloth loom,
and between each movement, a weft film 98' is inserted sideways
(lower left to upper right, then rightward in the figure), but then
adhesively attached to adhesive member 234 and adhesive member
235.
[0126] For the various embodiments described herein, any of the
described film-holding members (including those that operate by
vacuum (see FIG. 14A) or surface tension of a liquid to hold the
carbon nanotube film to a surface, those that clamp the film
between two surfaces (see FIG. 1Z), as well as those members having
an adhesive surface) can be substituted for one or more of the film
holders called adhesive members.
[0127] FIG. 2D is a perspective schematic diagram of a system 205
and a method of assembly of carbon nanotube films 98, each film
98'' in a first direction being held at its ends by a first
adhesive member 237 and second adhesive member 238 (in some
embodiments, each having an adhesive coating 115), each film 98' in
a second direction also being held at its ends by the first
adhesive member 237 and second adhesive member 238, the films
placed one next to another and each transferred from its respective
transportation holder 235 as described above, in order to obtain a
crossed-film structure 93 of a plurality of carbon-nanotube films
98 in a continuous web. In some embodiments, the first adhesive
member 237 and second adhesive member 238 are closed loops that are
driven parallel to one another (e.g., on pulleys--see, for example,
FIG. 10A, FIG. 11A, and FIG. 12A) to move in a conveyor-belt
fashion so the continuous web 93 of criss-crossed films is
obtained.
[0128] FIG. 2E is a perspective schematic diagram of
continuous-loop loom 206 that provides a continuous web of woven
carbon nanotube films, each film in the assembly being held at its
ends by a first adhesive member 239 and a second adhesive member
238, in order to obtain a woven-film structure 92 of a plurality of
carbon-nanotube films in a continuous web. In the embodiment shown,
the left adhesive conveyor-loop band 239 is designated the cloth
beam 239 and the B warp films are attached from this cloth beam to
the loom rods 236 alternating with the A warp films that are
attached from this cloth beam 239 to the loom rods 246. In some
embodiments, since the free movable portions of the warp films 98''
get shorter as the conveyor moves to the left, the loom rods 236
and 246 towards the left (downstream) do not move up and down as
much as those to the right (upstream). Once a downstream warp film
98'' has completed its weaving, it is attached to adhesive member
238 and its loom rod (236 or 246) is moved to the upstream end and
a new film 98 is attached as warp film 98'' to it and to cloth beam
239 from transportation holder 235. Between each loom rod movement,
a weft film 98' is inserted to the shed between the A films and the
B films (shown by solid-line arrows), and attached to the
conveyor-belt cloth beam 239 at one end and to the conveyor belt
238 at the other end. Its transportation rod 235' is then
withdrawn, new warp film 98'' is attached to the upstream loom rod
236 that is now empty and to the cloth beam 239 (shown by
solid-line arrows) and detached from its transportation rod 235
(which is then removed), and the loom rods 246 that were down move
up, and the loom rods 236 that were up move down. The next weft
film 98' is then inserted. This process is unique in that, in some
embodiments, the cloth beam adhesive member 239 is used to attach
and convey the first end of every warp film 98'' and the first end
of every weft film 98', while adhesive member 238 is used to attach
and convey the second end of every warp film 98'' and the second
end of every weft film 98', and adhesive member 239 and adhesive
member 238 can be moved in parallel as a conveyor belt to generate
a continuous web 90 of woven carbon nanotube films 98. In other
embodiments, carbon nanotube threads or yarns (e.g., see FIG. 13B)
are substituted for carbon nanotube films 98, and in some
embodiments, are dispensed continuously from spools to the
respective conveying adhesive members 238 and 239, as can be
understood by a person skilled in the art.
[0129] In other embodiments, threads such as nanotube threads 1398
(such as described in FIG. 13B), or previously woven nanotube
structures (such as web 1193 of FIG. 11F, or a densified stack of
parallel films 97 such as in FIG. 1-O) are substituted for the
nanotube films 98 of FIG. 2C, 2D or 2E. That is, in some
embodiments, nanotube threads are woven by attaching (in some
embodiments, adhesively, or in other embodiments, with a vacuum)
warp threads to a cloth bar (such as conveyor belt 239) at one end
(the far end) and to a loom rod at the other end (the near end),
the loom rod being a member of one of a plurality of loom-rod sets.
Wefts are inserted between the alternate up-and-down movements of
the warps, and attached at their ends to holders 237 and 238 (see
FIG. 2D), or holders to holders 239 and 238 (see FIG. 2E) to
achieve the desired weave. When, in an embodiment such as FIG. 2E,
a warp thread or film is finished (all the wefts to be woven with
that warp have been woven), the near end of that warp is attached
to belt 238, and a new warp thread or film is attached from belt
239 to a warp loom rod (e.g., the rightmost rod 246 in FIG. 2E) at
the other side of the warps. In this way, the wefts are
sequentially placed parallel to one another and attached at a first
diagonal angle between adhesive belt 238 at their near end and
adhesive belt 239 at their far end and woven with the warps, which
are sequentially placed parallel to one another and attached at a
second diagonal angle between adhesive belt 239 at their far end at
the start of their weaving and adhesive belt 238 at their near end
at the finish of their weaving.
[0130] FIG. 2F is an end view schematic diagram of continuous-loop
loom 206, showing the shed between the warp films 98'' connected to
loom rods 236 and the warp films 98'' connected to loom rods 246
into which the weft film 98' is inserted.
[0131] FIG. 3A is a perspective schematic diagram 300 of a carbon
nanotube film 99 being pulled from a carbon nanotube forest 89
having a gap 389 in the nanotube forest 89. Such a gap 389 will
cause a lengthwise gap in the midst of film 99, and when the side
films have been pulled even with the back of the gap, there may be
an island of nanotube forest behind the gap to which the films are
unable to pull nanotubes, further lengthening the lengthwise gap in
the midst of film 99.
[0132] FIG. 3B is a perspective schematic diagram of a repair
method for a possible gap in a carbon nanotube film 99 being pulled
from a carbon nanotube forest 89 having a gap 389 in the nanotube
forest 89 in a manner that suppresses any gap in the film. In some
embodiments, both the puller member 199 and the substrate 77 are
rotated nearly 90 degrees or more in the same rotational direction
(e.g., clockwise), and the pull then continues at that acute angle
until the pull reaches the end of gap 389, whereupon the puller
member 199 and the substrate 77 are rotated back the nearly 90
degrees or more in the same rotational direction (e.g.,
counterclockwise) to the orientation shown in FIG. 3A. When the
substrate 77 and puller member 199 are in the rotated position of
FIG. 3B, so that the film from the far edge of the gap contacts or
nearly contacts the forest 89 at the near end of the gap, the film
can be gap-free or nearly so. Further, the rotated orientation
prevents the formation of a forest island (as described above)
behind the gap.
[0133] In some embodiments, a forest-merging press arm 665 (such as
described below for FIG. 6C) is selectively moved when needed to
press together the forest portions across a gap 389. This can be
used to press across small gaps within a nanotube forest 89, such
as can occur due to defects in the catalyst surface or other
reasons. This pressure or contact between forest portions allows
for the continuous or gap-free collection of the nanotube film 99
even if there is a slight gap due catalyst defects, flow-through
defects or growing conditions in the nanotube forests 89.
[0134] In some embodiments, the present invention provides
substantially continuous growth and harvesting of carbon-nanotube
forests on one or more synthesis substrates within a
carbon-nanotube forest "farm" chamber. In some embodiments, each
synthesis substrate is reused for a plurality of growth cycles,
wherein the substrate, having one or more catalyst-covered faces,
is placed in a reaction chamber in a furnace (e.g., in some
embodiments, operating at about 680 degrees C.) and a
carbon-bearing precursor or reactant gas (e.g., in some
embodiments, 5 mol % acetylene in a Helium carrier) is provided to
the vicinity of the catalyst-covered face(s). In some embodiments,
an interior-flow synthesis substrate is used, wherein the reactant
gas is supplied through a face opposite the growth surface (called
a flow-through substrate--see, e.g., FIG. 9F, 5B or 8K) or through
a side face (called a side-flow substrate--see, e.g., FIG. 9J or
5F). In some embodiments, a nanotube film 99 is pulled directly
from the nanotube forest 89 through an access port (e.g., 414) into
the reaction chamber (e.g., 412) while the substrate 77 remains in
the furnace (e.g., 410). In some embodiments, the forest 89 and
substrate 77 remain at about the growth temperature (e.g., 680
degrees C.) while nanotube film 99 is pulled, while in other
embodiments, the forest 89 and substrate 77 are cooled at least
somewhat before nanotube film 99 is pulled (e.g., in various of the
embodiments, to about 650.degree. C. or higher, to about
625.degree. C. or higher, to about 600.degree. C. or higher, to
about 575.degree. C. or higher, to about 550.degree. C. or higher,
to about 525.degree. C. or higher, to about 500.degree. C. or
higher, to about 475.degree. C. or higher, to about 450.degree. C.
or higher, to about 425.degree. C. or higher, to about 400.degree.
C. or higher, to about 375.degree. C. or higher, to about
350.degree. C. or higher, to about 325.degree. C. or higher, to
about 300.degree. C. or higher, to about 275.degree. C. or higher,
to about 250.degree. C. or higher, to about 225.degree. C. or
higher, to about 200.degree. C. or higher, to about 175.degree. C.
or higher, to about 150.degree. C. or higher, to about 125.degree.
C. or higher, to about 100.degree. C. or higher, to about
75.degree. C. or higher, or to about 50.degree. C. or higher),
while in yet other embodiments, the forest 89 and substrate 77 are
cooled to about room temperature before nanotube film 99 is pulled.
In other embodiments, a substrate 77 and its nanotube forest are
withdrawn through access port (e.g., 414) from reaction chamber
(e.g., 412) while one or more other substrates remain in the
reaction chamber at about the growth temperature (e.g., 680 degrees
C.). The methods of the present invention thus allow continuous or
substantially continuous growth and harvesting of nanotube forests
89.
[0135] FIG. 4A is a perspective block diagram of a system 400 that
illustrates the continuous synthesis and collection of nanotube
films. Here, an input reactant gas 61 is shown flowing through an
input gas inlet 408 into the interior of a furnace 410. Within the
furnace 410 is situated a reaction chamber 412. Input reactant gas
61 is shown flowing into the interior of the reaction chamber 412.
Within the reaction chamber, the input reactant gas 61 comes into
contact with a substrate 77 that is located within the reaction
chamber 412. The substrate has a growth surface 79. Contact of the
input reactant gas 61 with the growth surface 79 of the substrate
77 provides for the synthesis of a nanotube forest 89. The nanotube
forest 89 is shown as having a leading edge 86, a trailing edge 88,
a top 87 and a bottom 85. Also shown is a new growth nanotube
forest 81. The leading edge 86 of the nanotube forest is
illustrated as being pulled into a nanotube film 99 by a pulling
bar 199. The nanotube film 99 passes through an access port 414
that is positioned in a side of the furnace 410. The nanotube film
99 then passes through the passage of the access port 414 through a
cooling jacket 416.
[0136] In some embodiments, it is undesirable to have a direct
sideways flow of gasses across the growing nanotube forest 89. The
reaction chamber 412, with its closed upwind end and its open
downwind end allows reaction gasses to readily diffuse into the
growth zone while preventing a direct breeze. In some embodiments,
a gas pressure is maintained at access port 414 to also suppress
any flow of gas through the access port. In some embodiments, an
inverted-U-shaped heat trap is placed in the path of the access
port 414.
[0137] FIG. 4B is a side view of system 400. Input reactant gas 61
is shown flowing through an input gas inlet 408 into the interior
of a furnace 410 in which a reaction chamber 412 is positioned.
Within the reaction chamber 412 is shown a substrate having a
growth surface 79 on which a nanotube forest 89 has been grown.
Output exhaust gas 62 is shown flowing out of the furnace 410
through an exhaust outlet 409.
[0138] FIG. 4C is a top view of system 400 of the invention. Input
reactant gas 61 is shown flowing through an input gas inlet 408
into the interior of a furnace 410 in which a reaction chamber 412
is positioned. Within the reaction chamber 412 is shown a substrate
having a growth surface 79 on which a nanotube forest 89 has been
grown. The nanotube forest 89 is illustrated as being pulled into a
nanotube film 99 by a pulling bar 199. The nanotube film 99 passes
through an access port 414 that is positioned in a side of the
furnace 410. The nanotube film 99 then passes through a cooling
jacket 416. Output exhaust gas 62 is shown flowing out of the
furnace 410 through an exhaust outlet 409.
[0139] FIG. 5A is a perspective block diagram of a system 500 that
illustrates the continuous synthesis and collection of nanotube
films using a method of the invention. Here an input reactant gas
61 is shown flowing through an input gas inlet 508 into the
interior of a furnace 510. The input reactant gas 61 passes through
a flow-through substrate 75 that is located within the furnace 510
and contacts a growth surface 79 positioned on the flow-through
substrate 75. Contact of the input reactant gas 61 with the growth
surface 79 of the flow-through substrate 75 provides for the
synthesis of a nanotube forest 89 within a reaction chamber 512
positioned within the furnace 510. The output exhaust gas 62 then
exits the furnace through an exhaust outlet 509. The nanotube
forest 89 is shown as having a leading edge 86, a trailing edge 88,
a top 87 and a bottom 85. Also shown is a new growth nanotube
forest 81. The leading edge 86 of the nanotube forest is
illustrated as being pulled into a nanotube film 99 by a pulling
bar 199. The nanotube film 99 passes through an access port 414
that is positioned in a side of the furnace 510. The nanotube film
99 then passes through a cooling jacket 416. Positioned within the
furnace are baffles 520 that direct the flow of outlet exhaust gas
62 from the reaction chamber 512 to an exhaust outlet 509. Also
positioned within the furnace is a splicer-cutter 530 that is
positioned above the leading edge of the new growth forest 81 that
acts to cut the nanotube film from the old growth nanotube forest
82 and attach the nanotube film to the leading edge of the new
81.
[0140] FIG. 5B is a side view diagram of a system 501 that
illustrates the continuous synthesis and collection of nanotube
films using a method of the invention. Here an input reactant gas
61 is shown flowing through an input gas inlet 508 into the
interior of a furnace 515. The input reactant gas 61 passes through
a flow-through substrate 75 that is located within the furnace 510
and contacts a growth surface 79 positioned on the flow-through
substrate 75. Contact of the input reactant gas 61 with the growth
surface 79 of the flow-through substrate 75 provides for the
synthesis of a nanotube forest 89 within a reaction chamber 512
positioned within the furnace 510. The output exhaust gas 62 then
exits the furnace through an exhaust outlet 509. The nanotube
forest 89 is shown as having a leading edge 86, a trailing edge 88,
a top 87 and a bottom 85. Also shown is a new growth nanotube
forest 81. The leading edge 86 of the nanotube forest 89 is
illustrated as being pulled into a nanotube film 99 by a take-up
reel 550. The nanotube film 99 passes through an access port 514
that is positioned in a side of the furnace 510. The nanotube film
99 then passes through a cooling jacket 416. Positioned within the
furnace are baffles 520 that direct the flow of outlet exhaust gas
62 from the reaction chamber 512 to an exhaust outlet 509. Also
positioned within the furnace is a splicer-cutter 530 that is
positioned above the leading edge of the new growth forest 81 that
acts to attach the nanotube film to the leading edge of the new
growth nanotube forest 81 and cut the nanotube film from the old
growth nanotube forest. The take-up reel 550 is positioned within a
cooling box 511 that is continuously connected to the access port
514. A pulling bar 199 is also positioned within the cooling box
511 that can be contacted with the leading edge 86 of a nanotube
forest 89 to initiate formation of nanotube film 99. The cooling
box 511 is illustrated as having a gas inlet 552 to provide input
of gas (e.g., inert gas) to provide backpressure in the cooling box
511 relative to the furnace 510 (to prevent passage of reactant
gasses and heat) and relative to the outside environment (to keep
out oxygen and other contaminants). Also illustrated is movement
564 of the take-up reel 550 to change the angle of the nanotube
film 99 as the leading edge 86 of the old growth nanotube forest 82
recedes toward the trailing edge 88 of the old growth nanotube
forest 82 as the old growth nanotube forest 82 is collected.
[0141] FIG. 5C shows a later stage of nanotube film 99 collection
relative to FIG. 5B. As illustrated, the leading edge 86 of the old
growth nanotube forest 82 has receded toward the trailing edge 88
of the old growth nanotube forest 82 as the old growth nanotube
forest 82 is collected. In addition, movement 564 of the take-up
reel 550 is shown to illustrate movement of the take-up reel 550 so
that the nanotube film 99 does not come into contact with the new
growth nanotube forest 81.
[0142] FIG. 5D shows a later stage of nanotube film 99 collection
relative to FIG. 5C. As illustrated, the leading edge 86 of the old
growth nanotube forest 82 has receded toward the trailing edge 88
of the old growth nanotube forest 82 as the old growth nanotube
forest 82 is collected. The splicer-cutter 530 is positioned to
attach the nanotube film 99 to the leading edge of the new growth
nanotube forest 81, and, in some embodiments, slice the nanotube
film 99 from the old growth to provide for continuous collection of
the nanotube film 99. Slicing the nanotube film 99 produces a film
tail 92 that represents the remainder of the old growth nanotube
forest 82. In addition, movement 564 of the take-up reel 550 is
shown to illustrate movement of the take-up reel 550 so that the
nanotube film 99 comes into contact with the new growth forest
81.
[0143] FIG. 5E shows a later stage of nanotube film 99 collection
relative to FIG. 5D. As illustrated, the nanotube film 99 has been
attached to the leading edge of the new growth nanotube forest 81
to facilitate continuous collection of the nanotube film 99. In
addition, movement 564 of the take-up reel 550 is shown to
illustrate movement of the take-up reel 550 so that the nanotube
film 99 comes into contact with the new growth forest 81. This
action transforms the formerly new growth nanotube forest 81 into
the old growth nanotube forest 82 to continue the synthesis and
collection cycle.
[0144] FIG. 5F is a side view diagram of a system 505 that
implements a method of some embodiments of the invention, which
provides for nanotube synthesis on multiple double-sided
flow-through substrates 74. Input reactant gas 61 is shown flowing
through a side-inlet 508 into the interior of a furnace 515. The
input reactant gas 61 passes through a double-sided flow-through
substrate 74 that is located within the furnace 515 and contacts a
growth surface 79 positioned on the double-sided flow-through
substrate 74. Contact of the input reactant gas 61 with the growth
surface 79 of the double-sided flow-through substrate 74 provides
for the synthesis of a nanotube forest 89 within a reaction chamber
512 positioned within the furnace 515. The outlet exhaust gas 62
then flows through a side-outlet 509.
[0145] In some embodiments, the source reactant gas 61 includes
acetylene in a helium carrier, and the exhaust or output gas 62
includes some of the acetylene, the helium carrier, and waste
byproducts of the nanotube synthesis reaction such as hydrogen gas
and/or other hydrocarbons. In some embodiments, the exhaust gasses
are recycled, e.g., by compressing and separating the gasses, then
remixing the recovered acetylene and helium carrier, adding
supplemental new gasses as needed, and using the result as input
reactant gas 61.
[0146] FIG. 5G is a side view diagram of a system 506 that
implements a method of some embodiments of the invention, which
provides for nanotube synthesis on an extended basis from
flow-through substrates 594. Input reactant gas 61 is shown flowing
through a side-inlet 508 into the interior of a furnace 515. In
some embodiments, the input reactant gas 61 passes through a
flow-through substrate 594 that is located within the furnace 515
and contacts a growth surface 79 positioned on the flow-through
substrate 594. Contact of the input reactant gas 61 with the growth
surface 79 of the flow-through substrate 594 provides for the
synthesis of a nanotube forest 89 within a reaction chamber 512
positioned within the furnace 515. The outlet exhaust gas 62 then
flows through a side-outlet 509. In some embodiments, a puller bar
590 is attached (e.g., using a suitable pressure-sensitive
adhesive), and operated by weight and/or servo control to gently
pull on the tops (i.e., the end distal to the growing surface 79 of
substrate 594) in a direction 591. In some embodiments, direction
591 is substantially vertical and downward. In other embodiments,
direction 591 is upward. In some embodiments, substrate 594 is
porous to allow reactant gasses 61 access to growing surface 79. In
some embodiments, exhaust ports 509 are provided through puller bar
590.
[0147] FIG. 5H is a cross-section side view schematic of a
carbon-nanotube synthesis apparatus 507 having a heat trap 576. In
some embodiments, nanotube film 99 is passed across one or more
rollers 577 in a raised portion (heat trap 576) of access port 514.
In some embodiments, hot gasses and/or helium (in embodiments that
use helium in the process) and/or less dense gasses, from furnace
590 (which can be any of the furnaces described herein such as 510
described above or 610 described below) will tend to rise to the
top of heat trap 576, while the cooler and/or more dense gasses
(e.g., argon) remain in the cool box 518. In some embodiments, the
vertical rise used by heat trap 576 is up to a meter or more,
(e.g., in some embodiments, about 0.5 meters or more, about 1 meter
or more, about 2 meters or more, about 3 meters or more, about 4
meters or more, about 5 meters or more, about 6 meters or more, or
about 7 meters or more) in order to suppress gas diffusion effects
that might otherwise cause undesired gas to flow through port 514.
Thus, in some embodiments, such a heat trap is used in a passageway
through which nanotube film 99 is passing, while in other
embodiments, such a heat trap is used for a passageway through
which nanotube forests 89 on substrates 77 are passing.
[0148] FIG. 6A is a side view block diagram of a system 600 that
illustrates the continuous synthesis and collection of nanotube
films using a method of the invention. Here, an input reactant gas
61 is shown flowing through an input gas inlet 608 into the
interior of a reaction chamber 612 that is positioned within a
furnace 610.
[0149] In some embodiments, at least one substrate 74 of the
plurality of substrates 74 in linked-substrate loop 674 is a
flow-through nanoporous substrate such as described in FIG. 8J,
FIG. 8P, FIG. 9F, or FIG. 9J. In other embodiments, a conventional
non-flow-through substrate is used such as described in U.S. Pat.
No. 6,232,706 or the articles listed above as Zhang et al. 2004 or
Zhang et al. 2005. In yet other embodiments, non-porous substrates,
such as rough- or smooth-textured silicon wafers are used.
[0150] In some embodiments, the input reactant gas 61 passes
through distribution baffles 621 and then through one or more
side-by-side flow-through linked substrates 74 that are located
within the reaction chamber 612 of the furnace 610. In some
embodiments, reaction chamber 612 forms, or is moveable to form, a
fairly tight seal around the bottom of the substrates in the
reaction chamber 612 (e.g., 6747, 6746, and 6745 in the embodiment
shown) in order to force the gas through the flow-through
substrate(s) (or into the sides of a side-flow substrate, in other
embodiments). By providing a flow-through substrate, reactant gas
reaches all parts of the growing forest, such that nanotubes near
the edges grow at about the same rate as nanotubes on the center of
the forest, thus avoiding forests with concave tops that grow that
way because they do not have sufficient gas reaching the center of
the forest due to blockage from the nanotubes around the edge. The
input reactant gas 61, upon reaching the top of substrate 74,
contacts a catalyst-covered growth surface 79 on the flow-through
linked substrate 74. Contact of the input reactant gas 61 with the
catalyst on growth surface 79 of a substrate 74 in the
linked-substrate loop 674 provides for the synthesis of nanotube
forests 89 within a reaction chamber 612 that is positioned within
the furnace 610. It is believed that growth occurs at the bottom of
each nanotube (i.e., next to the catalyst). The exhaust or output
gas 62 then exits the furnace through an exhaust outlet 609.
[0151] The nanotube forests 89 are shown as having a leading edge
86, a trailing edge 88, a top 87 and a bottom 85. The
linked-substrate loop 674 includes individual substrates 74 that
are linked by substrate connectors 662. The linked-substrate loop
674 forms a continuous loop that can be intermittently or
continuously advanced. As the loop is advanced, the individual
linked flow-through substrates 74 pass through a preheat furnace
618 that is included within the furnace 610, enter into a reaction
chamber 612 where synthesis of nanotube forest 89 occurs, exit the
reaction chamber 612 through an access port 614 in the side of the
furnace 612, pass through a cooling jacket 616, have their nanotube
forests 89 harvested, and then reenter the furnace through another
access port 615 after their forests 89 have been harvested.
[0152] In some embodiments, linked-substrate loop 674 forms a
continuous loop that can be continuously advanced, or in other
embodiments, the loop is advanced (for example, by the length of
the center-to-center distance between substrates 74) and then
substantially stopped for a period of time. For example, in the
embodiment shown, three substrates are in growth chamber 612 at any
one time, and each substrate 74, after entering reaction chamber
612 spends one-third of its growth time in the position of
substrate 6747, the next one-third of its growth time in the
position of substrate 6746, and the last one-third of its growth
time in the position of substrate 6747 (e.g., in some embodiments,
about 200 seconds in each station for a total of ten minutes). In
some embodiments, the substrates 74 are cooled at least somewhat by
resting in cooling jacket 616 while subsequent substrates 74 grow
their nanotube forests 89 in reaction chamber 612.
[0153] In some embodiments, after an individual substrate 74 passes
through the cooling jacket 616, the leading edge 86 of the nanotube
forest 89 grown on a leading (i.e., an initial) individual
substrate 74 is contacted with a pulling bar 630. The pulling bar
630 (which, in some embodiments, has an adhesive front surface such
as shown in FIG. 1D, a vacuum front surface as shown in FIG. 14B,
or other suitable film-pull-starting mechanism) pulls the leading
edge of nanotube forest 89 from substrate 6741 to form a nanotube
film 99. In some embodiments, the nanotube film 99 is attached to
be wound around rotating take up reel 650. The pulling bar 630 is
then retracted and the take up reel 650 turns in direction 651 to
continuously pull and take up the nanotube film 99 from the
individual linked substrate 74 and form nanotube-film spool
652.
[0154] In some embodiments, when the continuous closed loop of
linked-substrate loop 674 is advanced (or advanced and then
stopped), the portion of continuous loop 674 immediately next to
the film pull (i.e., substrate 6741, which has the nanotube forest
89 that is currently being harvested into film 99, and substrate
6742 that has the nanotube forest 89 that will next be harvested)
is bent inward to form a folded junction 660 where the trailing
edge 88 (see FIG. 1A) of the preceding nanotube forest 89 on
substrate 6741 is placed into contact with the leading edge 86 of
the following nanotube forest 89 on substrate 6741.
[0155] FIG. 6B is a close-up side view of the folded junction 660
of FIG. 6A. It illustrates the nanotube film 99 being pulled and
collected from the leading edge 86 of a nanotube forest 89 on
linked substrate 6741 as the trailing edge 88 of that nanotube
forest 89 is being placed into contact with the leading edge 86 of
another nanotube forest 89 grown on the next following linked
substrate 6742 at a folded junction 660. This intimate contact
allows the film harvest to jump from the depleted nanotube forest
on linked substrate 6741 to the unharvested forest on linked
substrate 6742, for the continuous collection of the nanotube film
99 from the individual linked substrates 74 of the advancing
linked-substrate loop 674.
[0156] FIG. 6C is a side-view diagram of a system 602 that provides
the continuous synthesis and collection of nanotube films used by a
method of the invention. In some embodiments as shown, an input
reactant gas 61 is flowing through an input gas inlet 608 into the
interior of a reaction chamber 612 that is positioned within a
furnace 610. The input reactant gas 61 passes through distribution
baffles 62 and then through linked substrates 74 that are located
within the reaction chamber 612 of the furnace 610. The input
reactant gas 61 contacts a growth surface 79 positioned on the
linked substrates 74. Contact of the input reactant gas 61 with the
growth surface 79 of the linked substrates 74 provides for the
synthesis of nanotube forests 89 within the reaction chamber 612
that is positioned within the furnace 610. The nanotube forests 89
are shown as having a leading edge 86, a trailing edge 88, a top 87
and a bottom 85. The linked-substrate loop 674 includes individual
substrates 74 that are linked by substrate connectors 662.
[0157] In some embodiments, at least one linked substrate 74 in
linked-substrate loop 674 is a flow-through nanoporous substrate
such as described in FIG. 8J, FIG. 8P, FIG. 9F, or FIG. 9J. In
other embodiments, a conventional non-flow-through substrate is
used such as described in U.S. Pat. No. 6,232,706 or the articles
listed above as Zhang et al. 2004 or Zhang et al. 2005. In yet
other embodiments, non-porous substrates, such as rough- or
smooth-textured silicon wafers are used.
[0158] In some embodiments, linked-substrate loop 674 forms a
continuous loop that can be continuously advanced, or in other
embodiments, the loop is advanced (for example, by the length of
one linked substrate 74) and then substantially stopped for a
period of time. For example, in the embodiment shown, three
substrates are in growth chamber 612 at any one time, and the
substrates stop for a period of time (e.g., one-third of the
nanotube growth time) in each position around the loop, then move
one substrate length (i.e., by the center-to-center distance
between linked substrates 74) to the next position and again stop.
In other embodiments, a slow continuous movement is used that moves
the loop at a rate approximately equal to the rate of harvest at
the front nanotube forest 89.
[0159] In some embodiments, the already-harvested linked substrates
re-enter furnace 610 and pass through an optional heat trap 649,
which suppresses convective heat flow. As the linked-substrate loop
674 is advanced, the individual linked flow-through substrates 74
pass through a preheat furnace 617 that is included within the
furnace 610, enter into reaction chamber 612 where synthesis
(lengthwise growth) of nanotube forest 89 occurs, exit the reaction
chamber 612 through a first access port 614 in the side of furnace
610, pass through a cooling jacket 616, pass through a second
cooling jacket 618, and then reenter the furnace through another
access port 619. After an individual substrate 74 passes through
the cooling jacket 616, the leading edge 86 of the nanotube forest
grown on the individual substrate 74 is contacted with a pulling
bar 630. The pulling bar 630 pulls the nanotube forest 89 to form a
nanotube film 99. The nanotube film 99 is attached to and wound by
a take up reel 650. The pulling bar 630 is then retracted and the
take up reel 650 turns 651 to continuously take up the nanotube
film 99 from the individual substrate 74. As the continuous loop
674 of linked substrates is advanced, the continuous loop 674 forms
a folded junction 660 where the trailing edge 88 of the preceding
nanotube forest 89 (on substrate 6741) is placed into contact with
the leading edge 86 of the following nanotube forest 89 (on
substrate 6741). In addition, in some embodiments, the nanotube
forest 89 grown on preceding linked substrate 6741 is pressed into
the leading edge of a nanotube forest 89 growing on the following
linked substrate 6742 by a forest-merging press arm 665 which is
selectively moved when needed to press the two forests together.
This can be at the junction between different nanotube forests 89
on separate substrates 6741 and 6742 as shown, but, in some
embodiments, can also be used to press across small gaps within a
nanotube forest 89, such as can occur due to defects in the
catalyst surface or other reasons. This pressure or contact between
forests allows for the continuous collection of the nanotube film
99 from the separate substrates 74 of the advancing continuous loop
674 even if there is a slight gap due to spacing between substrates
and/or growing conditions at the edges of the substrates.
[0160] Also illustrated is an input gas inlet 607 positioned next
to the take up reel 650 in some embodiments, and through which gas
(e.g., an inert gas such as helium or argon, or other gas that does
not detrimentally react with the warm or hot nanotube forests 89)
can flow to maintain a slight positive gas pressure that acts to
exclude oxygen from the cool chamber 618 of the invention during
collection of nanotube-film 99.
[0161] FIG. 6D is a side cross-section view diagram of a system 604
that provides continuous nanotube synthesis, wherein the chamber of
furnace 610 is located generally above cool chamber 618, in order
to suppress convection between the chambers. The features are the
same as, or similar to, like-numbered features described in FIGS.
6A and 6C.
[0162] FIG. 7A is a side cross-section view diagram of a continuous
nanotube synthesis device or system 700 of some embodiments of the
invention. Here, an input reactant gas 61 is shown flowing into the
interior of a closed-ended substantially cylindrical substrate 71
that is positioned within a furnace 710. In some embodiments,
cylinder substrate 71 has an outer layer formed of microporous
ceramic of the type used to cold filter beer, for example having an
inner structure and composition similar to the ceramic filters
described in U.S. Pat. No. 6,394,281 by Ritland et al., which is
incorporated herein by reference.
[0163] In some embodiments, the outer surface of the starting
material is formed or machined to a substantially smooth outer
surface in the shape of a cylinder. In other embodiments, the shape
of a truncated cone or other solid prism shape is used. In some
embodiments, this outer layer's surface is covered with a
CVD-deposited layer of polysilicon, which is then treated with an
anodic etch in ethanol and hydrofluoric acid to create a nanoporous
surface as described above for silicon wafers, and then covered
with a 5-nanometer (for example) layer of iron that is then
oxidized to form the nanotube catalyst. This forms a flow-through
substrate cylinder 71. Other embodiments use other materials to
create cylinders (that may be, but need not be, flow-through) that
will operate at the high temperatures (e.g., 680 to 700 degrees
centigrade, in some embodiments). In some embodiments that use a
porous material for cylinder substrate 71, the slightly pressurized
input reactant gas 61 passes or permeates through the substantially
cylindrical porous substrate 71 and contacts a catalyst-covered
growth surface 79 located on the outside of substantially
cylindrical substrate 71. Interaction of the input reactant gas 61
with the catalyst-covered growth surface 79 of cylindrical
substrate 71 provides for the synthesis of a radially-aligned,
densely packed continuous nanotube forest 89 on the
catalyst-covered growth surface 79. This synthesis occurs within a
reaction region 712 that is located within furnace 710. In some
embodiments, no reaction chamber enclosure is used since the
nanotube forest is continuously grown in a radial direction as
cylinder 71 rotates, and the nanotube film 99 is harvested
continuously from front face 86 of forest 89 while still at the
reaction temperature (e.g., 680 to 700 degrees centigrade, in some
embodiments).
[0164] The nanotube forest 89 is shown as having a leading edge 86,
new growth nanotube forest 81, a top 87 distal from growth surface
79 of cylinder 71, and a bottom 85 adjacent to growth surface 79 of
cylinder 71. The exhaust or output gas 62 then exits the furnace
710 through an exhaust outlet 709. In some embodiments, a leading
edge 86 of the nanotube forest 89 is initially contacted with a
pulling bar 630 that then withdraws from nanotube forest 89 to form
and pull nanotube film 99. In some embodiments, nanotube film 99 is
attached to a take up reel 750. The pulling bar 630 is then
retracted and the take up reel 750 turns in direction 751 to
continuously collect the nanotube film 99 from cylindrical
substrate 71. In some embodiments, cylindrical substrate 71 is very
slowly turned as the nanotube film 99 is collected from the
substrate to provide for continuous collection of the nanotube film
99. In some embodiments, an optical sensor is connected to a servo
motor used to rotate cylindrical substrate 71 in order to keep
front edge 86 of nanotube forest 89 at an optimal position or angle
for pulling the nanotube forest 89. In some embodiments, nanotube
film 99 passes through a side access port 714 in furnace 710 and
through cooling jacket 716 into cool chamber 718 before it is
collected on the take up reel 750 positioned within cooling box
711. In some embodiments, cooling box 711 includes a
positive-pressure gas inlet 752 that provides for entry of gas to
maintain a positive pressure within the cooling box 711 that acts
to exclude oxygen or other potential contaminants from the cooling
box 711. Also illustrated are insulation walls 713.
[0165] FIG. 7B is side cross-section view of system 701, a
variation where the take up reel 750 is positioned within the
cooling box 711 such that the nanotube film 99 forms a forest-merge
pull angle 731 from the normal vector to forest front face 86 (or
the tangent vector to cylinder substrate 71). In some embodiments,
forest-merge pull angle 731 forces nanotubes on the leading edge 86
of the nanotube forest 89 into better contact with nanotubes that
are slightly behind the leading edge 86, in order to increase
collection efficiency from the leading edge 86 of the nanotube
forest 89. In some embodiments, system 700 or system 701 also
includes a press bar.
[0166] Some embodiments of the below methods use techniques as
described in U.S. Pat. No. 6,428,713 to Christenson et al.,
entitled "MEMS sensor structure and microfabrication process
therefor" which is incorporated herein by reference.
[0167] FIGS. 8A-8K are perspective schematic diagrams of a
substrate 877 going through steps in making a flow-through
substrate for growing carbon nanotube forests 89, this method used
in some embodiments of the present invention. In FIG. 8A, a
substrate 877 (e.g., made of a silicon wafer having a 100-crystal
orientation at its top surface) is overlaid by SiO.sub.2 strips or
islands 801 by well-known semiconductor-processing techniques.
(E.g., in some embodiments, the top layer is thermally oxidized;
the pattern is photo-lithographically defined, and etched to leave
strips 811. In some embodiments, one approach is to heat substrate
877 to a high temperature, for example, 850 to 1200 degrees C., in
a controlled atmosphere containing either pure oxygen or water
vapor. At such high temperatures, the oxygen and/or water vapor
diffuse into and react with the silicon of substrate 877, thereby
forming a silicon dioxide layer on the exposed top surface of
substrate 877. This silicon dioxide is patterned into strips 811
that serve as a bonding oxide for epitaxial growth, as an
etch-termination layer, and are later removed to leave lateral gas
passages and an inner surface for the porous-etch process.) This
results in partially processed substrate 800. In some embodiments,
strips 811 are periodically connected to one another with narrow
bridges along their lengths or near their ends, in order that the
gas passages that result from later processing are all connected to
one another. Other materials can be substituted in other
embodiments.
[0168] In FIG. 8B, substrate 877 is processed to grow epitaxial
single-crystal silicon 820 to the tops of SiO.sub.2 strips 811 by
well-known semiconductor-processing techniques. This results in
partially processed substrate 801.
[0169] In FIG. 8C, substrate 877 has experienced further epitaxial
single-crystal silicon growth laterally 822 over the edges
SiO.sub.2 strips 811 by well-known semiconductor-processing
techniques (lateral epitaxial growth). This results in partially
processed substrate 802.
[0170] In FIG. 8D substrate 877 has experienced further epitaxial
single-crystal silicon growth laterally, completely covering
SiO.sub.2 strips 811. This results in partially processed substrate
803 having an outer silicon surface 821 that is substantially
covering at least one face of substrate 877, wherein underlying at
least a portion of the outer silicon surface 821 are silicon
dioxide strips 811.
[0171] In FIG. 8E, substrate 877 has been covered with silicon
dioxide, wherein the top surface is left completely covered with
SiO.sub.2 and the bottom has been patterned into SiO.sub.2 strips
831. This results in partially processed substrate 804.
[0172] In FIG. 8F, substrate 877 has been etched from the bottom.
For example, in some embodiments, using deep reactive ion etching
(DRIE), e.g., as described in U.S. Pat. No. 6,685,844 to Rich et
al. and/or as described in U.S. Pat. No. 6,127,273 to Laermer et
al., which are incorporated herein by reference. In some
embodiments, an Alcatel 601 DRIE machine and a pulsed-gas process,
as described in the just-mentioned patents, is used to form back
channels 834 and leaving silicon beams 830. In some embodiments,
silicon cross beams 832 are also left. This results in partially
processed substrate 805. FIG. 8G shows this result along section
line 8G.
[0173] FIG. 8G shows a cross-section view of processed substrate
805 showing silicon cross beam 832 that was left. The bottom etch
was stopped before penetrating top layer 821.
[0174] In FIG. 8H substrate 877 has been etched to remove
substantially all the silicon dioxide. This results in partially
processed substrate 806, having upper channels 841 and bottom
channels 834. FIG. 8I shows this result along section line 8I.
[0175] FIG. 8I shows a cross-section view of processed substrate
806 showing silicon cross beam 832 that was left.
[0176] In FIG. 8J, substrate 877 has been processed with a
nanoporous etch as described above. E.g., in some embodiments, at
least top layer 821 is a highly P-doped n.sup.+ type silicon
substrate (100-oriented-crystal top surface, resistivity
0.008-0.018 Ohm-cm), and is electrochemically etched in 1:1 HF (49%
in water) ethanol with an anodization current density of 10
mA/cm.sup.2 (in some embodiments, typical etching time is five
minutes). This forms a thin nanoporous layer (pore size about 3
nanometers) on top of a microporous layer (pore size about 100
nanometers). In some embodiments, the other exposed surfaces of the
channels are also affected similarly, and have a nanoporous
surface. Next, in a step B, in some embodiments, the top of the
porous layer is covered substantially in its entirety (unlike Dai
et al. describe in U.S. Pat. No. 6,232,706) with a five-nanometer
thick iron (Fe) film by e-beam evaporation. The inner and bottom
surfaces are not iron coated, in order to prevent nanotube growth
inside substrate 877. In some embodiments, after deposition of
iron, the substrate is annealed in air at 300 degree C. overnight.
This annealing step oxidizes the surface of the silicon as well as
the iron, converting the iron patterns into catalytically active
iron-oxide. The resulting silicon dioxide layer formed on the
underlying porous silicon prevents the porous structure of layers
from collapsing during any following high-temperature chemical
vapor deposition (CVD) step. This results in partially processed
substrate 807, having upper channels 841 and bottom channels 834.
The top growing surface 79 has an iron-oxide catalyst layer and a
large plurality of nanopores that conduct reactant gasses from the
bottom of substrate 807 through to the top layer 79.
[0177] FIG. 8K shows a cross-section view of processed substrate
807 showing silicon cross beam 832 that was left. The
two-dimensional X-Y grid of beams 830 and 832 provide structural
integrity to substrate 807. In some embodiments, the cross beams
832 are at a slant angle to direction Y, in order that all passages
841 connect to at least one gas passage 834 through the back of
substrate 807. Region 871 represents where the bottom etch was
stopped before eating through top layer 821.
[0178] FIG. 8L is a bottom-view schematic diagram of a flow-through
substrate 807 for growing a carbon nanotube forest 89.
[0179] FIG. 8L1 is a close-up bottom-view schematic diagram of a
flow-through substrate for growing a carbon nanotube forest. In
some embodiments, the cross beams 832 are at a slant angle to
direction Y, in order that all passages 841 connect to at least one
gas passage 834 through the back of substrate 807.
[0180] FIGS. 8M-8P are perspective schematic diagrams of
alternative steps in making a flow-through substrate for growing
carbon nanotube forests. In some embodiments, these steps represent
processing done after that of FIG. 8G.
[0181] FIG. 8M is a perspective schematic view of a substrate 808,
wherein the nanopore etching described for FIG. 8J above is
performed before etching to remove silicon dioxide strips 811, in
order that the etching operation occurs only from the top surface
of top layer 821 to form porous top layer 861. FIG. 8N shows this
result along section line 8N.
[0182] FIG. 8N shows a cross-section view of processed substrate
808 showing silicon cross beam 832.
[0183] In FIG. 8O substrate 877 has been etched to remove
substantially all the silicon dioxide of strips 811. This results
in completed substrate 809, having upper channels 841 and bottom
channels 834. FIG. 8I shows this result along section line 8I.
[0184] FIG. 8I shows a cross-section view of completed substrate
809 showing silicon cross beam 832.
[0185] FIGS. 9A-9G are perspective schematic diagrams of steps in
making a flow-through substrate for growing carbon nanotube
forests. The processing here is similar in some respects to that
described in FIGS. 8A to 8K, except that narrow, deep channels 919
are used rather than the less-deep channels 811 used in FIGS. 8A to
8K.
[0186] In FIG. 9A, a substrate 977 (e.g., made of a silicon wafer
having a 100-crystal orientation at its top surface) deep etched to
create grooves or channels 919 by deep reactive ion etching (DRIE),
e.g., as described in U.S. Pat. No. 6,685,844 to Rich et al. and/or
as described in U.S. Pat. Mo. 6,127,273 to Laermer et al., which
are incorporated herein by reference. In some embodiments, an
Alcatel 601 DRIE machine and a pulsed-gas process, as described in
the just-mentioned patents, is used. Channels 919 will delineate
lateral gas passages that extend in the Y direction in the final
processed substrate, while reducing the lateral extent (the size of
the top porous membrane between support pillars in the Z direction)
of the nanoporous top surface in order to increase the strength of
the top surface.
[0187] In some embodiments, as described below for FIG. 9H,
additional occasional cross channels 920 (e.g., along the X
direction, left-to-right in the diagram and each connecting to a
plurality of the channels shown (those extending in the Y
direction, from lower left in the diagram to upper right)). In some
embodiments, these cross channels 920 are wider than channels 919,
and thus etch deeper than channels 919. In some embodiments, the
cross channels 920 are positioned in a staggered manner along the Y
direction, in order to prevent any straight channel completely
crossing the substrate in the X direction, which could weaken the
substrate along that line. In some embodiments, cross channels 920
are etched completely through substrate 977, eliminating the need
for, and the steps used to separately create, the back channels
915, since the wider cross channels serve a similar purpose.
[0188] In FIG. 9B, substrate 977 is processed to fill channels 919
and channels 920 with SiO.sub.2. to form silicon dioxide strips
918, which support the epitaxial lateral overgrowth (ELOG) of
silicon top layer 930, but will then later be etched away to leave
lateral gas passages.
[0189] In FIG. 9C substrate 977 has experienced epitaxial
single-crystal-silicon growth laterally, completely covering
SiO.sub.2 strips 911. This results in partially processed substrate
902 having an outer silicon surface 921 that is substantially
covering at least one face of substrate 977, wherein underlying at
least a portion of the outer (e.g., top) silicon surface 921 are
silicon dioxide strips 918 having a greater vertical extent than
width, and extending lengthwise in the Y direction.
[0190] In FIG. 9D, substrate 977 has been covered with silicon
dioxide, wherein the top surface is left completely covered with
SiO.sub.2 and the bottom has been patterned into SiO.sub.2 strips
931. This results in partially processed substrate 804. Further,
substrate 977 has been etched from the bottom (for example, in some
embodiments, using DRIE) to form back channels 915 and leaving
silicon beams 939. In some embodiments, silicon cross-beams
extending in the Y direction or at an angle to the Y direction are
also left, as described in FIG. 8G. This results in partially
processed substrate 903. The bottom etch was stopped after the
bottom channels 915 reach the silicon dioxide strips 918, but well
before penetrating top layer 921. This provides greater strength
than in FIG. 8G, and is also easier to accomplish because the
silicon dioxide strips 918 are so much deeper than silicon dioxide
strips 811 of FIG. 8G.
[0191] In FIG. 9E substrate 977 has been etched to remove
substantially all the silicon dioxide. This results in partially
processed substrate 904, having upper channels 918 extending in the
Y direction and bottom channels 915 extending in the X
direction.
[0192] In FIG. 9F, substrate 977 has been processed with a
nanoporous etch as described above for FIG. 8G. The top growing
surface 79 has an iron-oxide catalyst layer and a large plurality
of nanopores that conduct reactant gasses from the bottom of
substrate 977 through porous layer 951 to the catalyst-covered
growth surface 79. In some embodiments, the initial channels 919
are spaced far enough apart that the vertical walls are initially
thick enough such that after nanopore etching creates porous layer
952, there is still a wall of substantially solid silicon 953 to
help support and strengthen top layer 951. FIG. 9G shows the
resulting completed substrate along section line 9G.
[0193] FIG. 9G shows a cross-section view of processed substrate
905 showing silicon bottom cross beam 932 that was left after the
bottom etch earlier. The two-dimensional X-Y grid of beams 915 and
932 provide structural integrity to substrate 905. In some
embodiments, the cross beams 932 are at a slant angle to direction
Y, in order that all passages 917 connect to at least one gas
passage 934 through the back of substrate 905.
[0194] In FIG. 9H, a substrate 977 (e.g., made of a silicon wafer
having a 100-crystal orientation at its top surface) is deep etched
to create grooves or channels 919 by deep reactive ion etching
(DRIE), as described for FIG. 9A. In some embodiments, additional
occasional cross channels 920 (e.g., along the X direction in the
diagram and each connecting to a plurality of the channels 919 that
extend in the Y direction). In some embodiments, these cross
channels 920 are wider, and thus etch deeper than channels 919. In
some embodiments, the cross channels 920 are moved back and forth
along the Y direction, in order to prevent any straight channel
completely crossing the substrate in the X direction, which could
weaken the substrate along that line. In some embodiments, at least
some of either channels 919 or channels 920 are etched out to a
point that will be outside side wall 960 in the completed
substrate, in order to provide a gas inlet port through a side wall
of substrate 978.
[0195] In FIG. 9I, substrate 977 is processed to fill channels 919
and channels 920 with SiO.sub.2, to form silicon dioxide strips
918, which support the epitaxial lateral overgrowth (ELOG) of
silicon top layer 930, but will then later be etched away to leave
lateral gas passages having at least one gas inlet port through a
side wall 960 of substrate 978. Further, substrate 977 has now
experienced epitaxial single-crystal-silicon growth laterally,
completely covering SiO.sub.2 strips 919 and 920. This results in
partially processed substrate 906 having an outer silicon surface
921 that is substantially covering at least one major face of
substrate 978, wherein underlying at least a portion of the outer
(e.g., top) silicon surface 921 are silicon dioxide strips 919
having a greater vertical extent than width, and extending
lengthwise in the Y direction, and silicon dioxide strips 920
having a greater vertical extent than width, and extending
lengthwise in the X direction to contact a plurality of strips 919.
Processing continues as described for FIGS. 9A-9G,
[0196] In FIG. 9J, substrate 977 has been processed with a
nanoporous etch as described above for FIG. 8G. The top growing
surface 79 has an iron-oxide catalyst layer and a large plurality
of nanopores that conduct reactant gasses from the bottom of
substrate 978 through porous layer 951 to the catalyst-covered
growth surface 79. In some embodiments, the initial channels 919
are spaced far enough apart that the vertical walls are initially
thick enough such that after nanopore etching creates porous layer
952, there are still walls 953 of substantially solid silicon to
help support and strengthen top porous layer 951.
[0197] FIG. 9K is a perspective-view schematic diagram of a
substrate 977 made into a side-flow or through-flow dugout
substrate 981 for growing carbon nanotube forests. In the
embodiment shown, dugout substrate 981 includes a plurality of
long, deep, narrow slots 971, over which roofs 972 have been grown
(for example, by epitaxial lateral overgrowth over silicon dioxide
that was later removed), such that the leading edge of each roof
972 extends to or slightly over the opposite sidewall 973 (thus
giving the appearance of the structure an impression of a baseball
stadium dugout).
[0198] FIG. 9L is a perspective-view schematic diagram of a
side-flow dugout substrate 982 on which has been grown a nanotube
forest 89. The roofs 973 and the remaining top surface 974 together
form a growing surface that allows growth of nanotube forest 89 on
a substantially continuous basis in the X and Y directions, wherein
the reactant gas flows through channels 971, then permeates up and
out of the dugout to feed the growth of nanotube forest 89 at its
base. This allows even the interior of forest 89 to be fed with a
sufficient supply of reactant so all the nanotubes grow at the same
rate.
[0199] FIGS. 9M, 9N, and 9O are perspective-view schematic diagrams
of making a substrate 977 into a side-flow or through-flow
substrate 985 for growing carbon nanotube forests 89, according to
some embodiments.
[0200] FIG. 9M shows a substrate 977 after having channels 975 that
have been etched using DRIE in order to form wide-bottomed channels
976, in some embodiments, for example, as described in U.S. Pat.
No. 6,127,273 mentioned above.
[0201] FIG. 9N shows substrate 977 after having added epitaxial
growth 987 that substantially closes the tops of channels, while
leaving the wide channel bottoms substantially open.
[0202] FIG. 9O shows substrate 977 after having anodic nanoporous
etching, as described above. In some embodiments, the anodic
nanoporous etching forms micropores and nanopores 988 into the top
layer 987, such that reactant gas can flow through channels 976 and
the micropores and nanopores in order to supply nanotube growth in
the interior portion of growing nanotube forest 89.
[0203] FIG. 10A is a perspective schematic diagram of apparatus
1000 and method for making a continuous-web carbon nanotube film
structure 1093. In a manner similar to that shown in FIG. 2D,
criss-crossed lengths of carbon nanotube film 1098 are laid across
film-holding belts 1037 and 1038, which, in some embodiments, are
at least partially coated with pressure-sensitive adhesive. In some
embodiments, one or more spools 652 (e.g., from an apparatus such
as shown in FIG. 6A) dispenses nanotube film 1098, which is laid
across the span between holding belts 1037 and 1038, pulled
sufficiently tight for the desired resulting structure 1093, and
then attached to holding belt 1037 and holding belt 1038. E.g., in
some embodiments, a non-stick bar 1011 is used to press film 1098
into the adhesive on belt 1037 when it reaches that side, and
non-stick bar 1012 is used to press film 1098 into the adhesive on
belt 1038 when it reaches the opposite side. Illustrated
schematically in FIG. 10A, the films 1098 are dispensed at an angle
to the direction of movement of structure 1093 (e.g., at 10 to 80
degrees to the direction of movement 1030. In some embodiments,
belts 1038 and 1039 are continuous-loop belts that run as a
conveyor around pulleys 1039. In some embodiments, the completed
structure 1093 is a continuous web that is transferred to sheet
holder belt 1050 for further processing downstream (to the right).
In some embodiments, sheet holder belt 1050 includes a flexible
sheet 1055 having adhesive strips 1057 and 1058 along opposite
edges.
[0204] In other embodiments, as described below for FIG. 10E, sheet
holder belt 1050 instead includes a microporous surface through
which air is pulled (e.g., from a vacuum applied through a smooth
perforated support surface 1061 underneath sheet holder belt 1050)
in order to hold structure 1093 sheet holder belt 1050 without
adhesive strips 1037 and 1038. This has the advantage of being able
to reverse the air flow to provide a pressure (rather than vacuum)
in order to easily release the assembled criss-cross film structure
1093 from sheet holder belt 1050 as desired.
[0205] In some embodiments, a plurality of films 1098 (e.g., A, B,
and C shown here) are laid side-by-side, back and forth,
edge-to-edge, across the build area as the conveyor mechanism moves
in direction 1030.
[0206] In some embodiments, belts 1037 and 1038 are omitted, and
the films 1098 are assembled in a like manner directly onto sheet
holder belt 1050 (e.g., using non-stick bars 1011 and 1012 being
used to press the taut film into adhesive strips 1057 and 1058.) In
other embodiments, sheet holder belt 1050 instead includes the
microporous surface through which a vacuum is pulled as described
above. This has the advantage of directly laying and holding the
films 1098 with vacuum to hold the films, and then being able to
reverse the air flow to provide a pressure (rather than vacuum) in
order to easily release the assembled criss-cross film structure
1093.
[0207] FIG. 10B is a cross-section view schematic diagram of a
transfer step in making a continuous-web carbon nanotube film
structure 1093. In this view, holder belts 1038 and 1037 are moving
towards the viewer outside the edges of sheet 1055 on which
adhesive strips 1058 and 1057 are affixed. Other embodiments use
vacuum attachment to a microporous sheet member 1050 as just
described.
[0208] FIG. 10C is an enlarged perspective schematic diagram of a
transfer step in making a continuous-web carbon nanotube film
structure 1093. In the embodiment shown, non-stick presser rollers
1013 and 1014 press crossed-film structure 1093 onto conveyor 1050,
thus removing crossed-film structure 1093 from belts 1038 and 1037.
In some embodiments, presser rollers 1013 and 1014 also include a
cutting edge 1015 to help cut crossed-film structure 1093 from
belts 1038 and 1037.
[0209] FIG. 10D is a top-view schematic diagram of the transfer
step described in FIG. 10C.
[0210] FIG. 10E is a perspective schematic diagram of system 1005
showing assembly and densification steps in making a densified
continuous-web carbon nanotube film structure 1094. In some
embodiments, a continuous-loop microporous plastic sheet 1056 is
passed across perforated vacuum table 1061, and air 1062 is pulled
through microporous plastic sheet 1056 to hold a cross-cross
pattern of nanotube films 1098 as it is formed into crossed-film
structure 1093 as described above. (In other embodiments,
continuous adhesive strips 1058 along the edges of sheet 1055 such
as shown in FIG. 10B are used.) In some embodiments, belt 1056 and
the as-laid (undensified) continuous-web nanotube film structure
1094 on its surface are then dipped into a liquid bath 1066, such
as ethanol, for example, and then withdrawn vertically and dried
using air 1065 to densify the carbon-film that is drawn thinner
with the shrinking and thinning liquid film on the surface of sheet
holder belt 1050. In some embodiments, once the densified film is
dry (e.g., at the top of FIG. 10E), air pressure is applied through
the microporous plastic sheet 1056, in order to separate the
densified film 1094 from microporous plastic sheet 1056 in a
continuous web for later processing or spooling onto a take-up
reel.
[0211] FIGS. 11A-11F are perspective schematic diagrams of steps in
making a continuous web of crossed films, where each film in the
assembly is being held at its ends by a first and second adhesive
member of a conveying mechanism that is moved in a rotary rocking
motion, in order to obtain a crossed-film structure of a plurality
of carbon-nanotube films in a continuous web.
[0212] FIG. 11A is a perspective-view schematic diagram of system
1100 that includes endless-belt adhesive holder 1137 and
endless-belt adhesive holder 1138 each moving diagonally downward
at an angle ALPHA such that film 1198, which is being dispensed
from spool 652, travels substantially straight down in direction
1190. This forms a crossed-film structure 1193 having crossed films
at angle two times alpha. In some embodiments, a non-stick bar 1111
is used to press film 1198 into the adhesive on belt 1038 from the
left when it reaches that side, and non-stick bar 1112 is used to
press film 1198 into the adhesive on belt 1037 from the left. Once
film 1198 is attached to belts 1137 and 1138, the conveying
mechanism 1139 is swung (e.g., in the embodiment shown, clockwise)
in direction 1151.
[0213] FIG. 11A1 is a side-view of system 1100 as shown in FIG.
11A.
[0214] FIG. 11B is a perspective-view of system 1100 while the
conveying mechanism 1139 is in the midst of swinging in direction
1151. In some embodiments, conveying mechanism 1139 continues to
maintain angle ALPHA.
[0215] FIG. 11B1 is a side-view of system 1100 as shown in FIG.
11B.
[0216] FIG. 11C is a perspective-view of system 1100 after the
conveying mechanism 1139 has completed swinging in direction 1151.
In some embodiments, a non-stick bar 1113 is used to press film
1198 into the adhesive on belt 1037 from the right when it reaches
that side. In some embodiments, conveying mechanism 1139 continues
to maintain angle ALPHA, and is swung in direction 1152 once the
film has attached to adhesive member 1137.
[0217] FIG. 11C1 is a side-view of system 1100 as shown in FIG.
11C.
[0218] FIG. 11D is a perspective-view of system 1100 while the
conveying mechanism 1139 is in the midst of swinging back
(counterclockwise) in direction 1152. In some embodiments,
conveying mechanism 1139 continues to maintain angle ALPHA.
[0219] FIG. 11D1 is a side-view of system 1100 as shown in FIG.
11D.
[0220] FIG. 11E is a perspective-view of system 1100 after the
conveying mechanism 1139 has completed swinging in direction 1151.
In some embodiments, a non-stick bar 1113 is used to press film
1198 into the adhesive on belt 1037 from the right when it reaches
that side. In some embodiments, conveying mechanism 1139 continues
to maintain angle ALPHA, and is swung in direction 1152 once the
film has attached to adhesive member 1137.
[0221] FIG. 11E1 is a side-view of system 1100 as shown in FIG.
11E.
[0222] FIG. 11F is a perspective-view of system 1100 while the
conveying mechanism 1139 is in the midst of swinging in direction
1151. In some embodiments, conveying mechanism 1139 continues to
maintain angle ALPHA. Film structure 1193 now has three layers of
film strips, and can continue indefinitely to form a continuous
web. In some embodiments, once the end of film 1198 on a first
spool is reached, it is spliced (in some embodiments, for example,
using the technique described below for FIG. 14E) to the beginning
of a film 1198 on a second spool.
[0223] FIG. 11F1 is a side-view of system 1100 as shown in FIG.
11F.
[0224] FIG. 12A is a perspective schematic diagram of system 1200
showing steps in making a continuous web of crossed films, where
each film in the assembly is being held at its ends by a first and
second adhesive member of a conveying mechanism, in order to obtain
a crossed-film structure of a plurality of carbon-nanotube films in
a continuous web. In some embodiments, system 1200 that includes
endless-belt adhesive holder 1237 and endless-belt adhesive holder
1238 (in some embodiments, each having an adhesive coating 115)
moving downward at an angle ALPHA such that film 1198, which is
being dispensed from spool 652, travels substantially straight down
in direction 1190. The film 1198 here is dispensed to stick to
moving conveyor 1239, which, in some embodiments, includes flexible
adhesive belts 1237 and 1238. In some embodiments, the lower ends
of belts 1237 and 1238 are positioned as defined by fixed
horizontal axle 1217, while the upper ends of belts 1237 and 1238
are twisted to follow axle 1216, which is swung back and forth as
in FIGS. 11A-11F above. This allows the final end of conveying
mechanism 1239 to remain fixed relative to machinery further
downstream.
[0225] FIG. 13A is a perspective schematic diagram of a system 1300
that shows a method for making a plurality of continuous yarns from
a plurality of carbon-nanotube films pulled from carbon-nanotube
forests. In some embodiments, system 1300 includes a plurality of
film-holding bars 1399 pulling a film 99 from the face 86 of a
carbon-nanotube forest 89, each using a rounded-front adhesive bar
1318. In other embodiments, other non-adhesive methods, such as
described elsewhere herein are used to affix the leading ends of
the films to film-holding bars 1399. In some embodiments, every
other one of the film-holding bar 1399 (e.g., the even-numbered
second and fourth film-holding bars 1399 in the diagram) are
initially extended further (to the left, in the negative X
direction in the diagram) in order to start their pull first, and
in order to move further right with their film pull than the
odd-numbered film-holding bars 1399, in order that they can spin
without interfering with one another. Once sufficient film 99 has
been initially pulled, rods 1319 will start to spin, to create a
plurality of nanotube yarns similar to the single yarn described in
the Zhang et al. 2004 article referred to above. In some
embodiments, each film-holding bar 1399 includes a reference
surface 1316 that is configured to rest on surface 79 of substrate
77, in order that the rounded front adhesive surface 1318 engages
face 86 of nanotube forest 89 at a height (e.g., the middle)
suitable to start a film pull. In some embodiments, the height is
empirically determined. In some embodiments, a slight vertical
motion is imparted as adhesive surface 1318 engages face 86 of
nanotube forest 89 to get better contact for starting the film
pull.
[0226] FIG. 13B is a perspective schematic diagram of system 1300
after spinning 1351 of each rod 1319 has started, making the
plurality of continuous yarns 1398 from the plurality of
carbon-nanotube films 1311 pulled from carbon-nanotube forest 89.
In some embodiments, once the initial nanotube forest 89 has been
harvested and spun into yarns 1398, carbon nanotubes from another
forest 89' (or from a film 98 formed as described above) are
spliced to the tail end(s) of the films 1311 pulled from the
initial nanotube forest 89. In some embodiments, the spinning 1351
of each rod 1319 is stopped first, in order to pull more film 99
for the splicing process 1303.
[0227] FIG. 13C is a perspective schematic diagram of a splice
process 1303 in which a first carbon nanotube film 99 (or the
individual portions 1311 of that film) being pulled from a first
carbon nanotube forest 89 is about to be spliced to a second carbon
nanotube forest 89' using splicer bar 130, in a manner similar to
that described above for FIGS. 1R-1T. In some embodiments, splicer
bar 130 includes a non-adhesive front nose 141 configured to press
film 99 into approximately the center of front face 86' of forest
89'. In some embodiments, front nose 141 includes a porous front
surface (see FIG. 14A) through which a vacuum is selectively
applied in order to hold and later release film 99 during the
splice process 1303. Some embodiments of splice bar 130 also
include a cutting edge 142 for severing the initial film 99 once
the splice has been made.
[0228] FIG. 13D is a perspective schematic diagram of carbon
nanotube yarns 1398 being pulled from nanotube films 1311 the
second carbon nanotube forest 89' after being spliced and removed
from the first carbon nanotube forest 89. Splicer bar 130 is being
withdrawn. In some embodiments, substrate 77' is swung in direction
1351 back to a normal pulling position. In this manner a plurality
of continuous yarns 1398 are continuously pulled from a
successively presented plurality of carbon-nanotube forests 89 from
different substrates 77.
[0229] FIG. 14A is a perspective schematic diagram of a system 1400
for in initiating and pulling a continuous nanotube film 99 from a
carbon-nanotube forest 89 using a vacuum film-holding bar 1499. In
some embodiments, vacuum film-holding bar 1499 includes one or more
internal channels 1417 leading to a microporous front interface,
e.g., made of porous ceramic having a composition similar to the
ceramic filters described in U.S. Pat. No. 6,394,281 by Ritland et
al., which is incorporated herein by reference.
[0230] FIG. 14B is a perspective schematic diagram of system 1400
with a vacuum film-holding bar 1499 pulling nanotube film 99 from
carbon-nanotube forest 89.
[0231] FIG. 14C is a perspective schematic diagram of system 1402
useful for transferring films 98 obtained by pulling a continuous
film 99 from a carbon-nanotube forest 89 using vacuum film-holding
bar 1499, in a manner similar to that shown in FIGS. 1J and 1K. In
some embodiments, each of vacuum film-holding bars 1431, 1432, and
1433 are of a construction substantially similar to vacuum
film-holding bar 1499. The use of vacuum film-holding bars allows a
vacuum/air suction to be applied at a time when adhesion or holding
of the film is desired, and then for air pressure to be applied at
a later time when release of the film is desired. In some
embodiments, vacuum film-holding bar 1431 is omitted, and vacuum
film-holding bar 1499 serves that purpose.
[0232] FIG. 14D is a perspective schematic diagram of system 1402
after transferring film 98 to vacuum film-holding bars 1431 and
1432 and separating it from continuous film 99 that continues to be
pulled from carbon-nanotube forest 89 using vacuum film-holding bar
1433.
[0233] FIG. 14E is a perspective schematic diagram of splicing
films 99 and 99' while pulling a continuous film 99 from
carbon-nanotube forests 89 and 89' from different substrates 77 and
77' using vacuum film-holding bars 1499 and 1499'. In some
embodiments, film 99 is being pulled from front face 86 of forest
89 using vacuum film-holding bar 1499. The harvest of nanotube
forest 89 is nearly complete. New film 99' is pulled from front
face 86' of forest 89' using vacuum film-holding bar 1499'. Film 99
is moved into contact with new film 99' using vacuum film-holding
bar 1499, which, after sufficient contact has spliced film 99 to
film 99', then applies air pressure to release the films from
vacuum film-holding bar 1499. In some embodiments, a cutting or
tearing operation severs the remaining tail of film 99 from the
sliced film.
[0234] FIGS. 15A, 15B, 15C, 15D, and 15E are top-view schematic
diagrams of system 1500 building a cross-woven nanotube cloth 1593
on a vacuum table 1561. FIG. 15A shows system 1500 after laying
nanotube film strip 1511 and holding it by vacuum to table 1561. In
some embodiments, nanotube film 99 is directly pulled from nanotube
forest 89 that was grown on substrate 77, and is laid on vacuum
table 1561 to form strip 1511. Upon reaching an edge (the bottom
edge in the diagram) of the vacuum surface 1562, substrate 77 is
raised and inverted at an angle of reflection equal to the angle of
incidence. FIG. 15B shows system 1500 in state 1502 after laying
second nanotube film strip 1512 and holding it by vacuum to table
1561. Upon reaching the next edge (the left edge in the diagram) of
the vacuum surface 1562, substrate 77 is again raised and
un-inverted at an angle of reflection equal to the angle of
incidence. FIG. 15C shows system 1500 in state 1503 after laying
third nanotube film strip 1513 and holding it by vacuum to table
1561. Upon reaching the next edge (the top edge in the diagram) of
the vacuum surface 1562, substrate 77 is raised and again inverted
at an angle of reflection equal to the angle of incidence. FIG. 15D
shows system 1500 in state 1504 after laying fourth nanotube film
strip 1514 and holding it by vacuum to table 1564. FIG. 15E shows
system 1500 in state 1505 after laying fifth nanotube film strip
1515 and many more and holding them by vacuum to table 1564.
[0235] FIG. 15F is a side view partially in cross section of system
1500 in state 1505, showing an air-flow connection 1564 for
selectively applying either vacuum (to attach and hold nanotube
film 99 to surface 1562 of substrate 1561 for formation of film
structure 1593 and/or for further processing such as coating film
structure 1593 with a liquid such as ethanol which is then
evaporated to thin and densify film structure 1593, or for
impregnating film structure 1593 with a binder such as PVA, epoxy,
and/or the like) or air pressure (to release the completed film
structure 1593 from its surface). In some embodiments, substrate
1561 includes a plurality of interior passages 1563 coupled between
air-flow connection 1564 and a microporous surface layer 1562
(e.g., in some embodiments, for example, having an inner structure
and composition similar to the ceramic filters described in U.S.
Pat. No. 6,394,281 mentioned above, or in other embodiments,
substrate 1561 is a flow-through (e.g., silicon) wafer such as
described in FIG. 8K, FIG. 9J or FIG. 9N) through which the vacuum
or air pressure are applied. In some embodiments, film 99 is
applied directly as it is pulled from nanotube forest 89 on
substrate 77, while in other embodiments, a preformed film 98 (as
described in any of the embodiments above) is applied to surface
1562. In some embodiments, the vacuum holds a plurality of stacked
film layers because each film is essentially an aerogel-type
material through which air can readily pass. In some embodiments,
the microporous top layer has through openings small enough that
the sideways-oriented nanotubes are not sucked into its surface,
but rather lie across it until released by a reverse of the air
flow or pressure. In some embodiments, top surface 1562 is an
essentially flat plane; while in other embodiments, the top surface
has a three-dimensional shape in the form of the desired end
product, used as a mold.
[0236] FIGS. 16A and 16B are perspective schematic diagrams of
system 1600 building a cross-woven nanotube airfoil 1693 using a
continuous web of crossed films 98, where each film 98 in the
assembly is being held across its entire length and width by a
curved vacuum table 1677. In some embodiments, film 99 is applied
directly as it is pulled from nanotube forest 89 on substrate 77,
while in other embodiments, a preformed film 98 (as described in
any of the embodiments above) is applied to surface 1562. In some
embodiments, film structure 1593 is coated with a liquid such as
ethanol (e.g., by spraying a mist or dipping into the liquid),
which is then evaporated to thin and densify film structure 1593.
In some embodiments, once the film structure 1693 is completed, a
binder of, e.g., PVA, epoxy, or the like is applied.
[0237] Various embodiments of the invention include combinations of
subsets of features from a plurality of embodiments described
herein, and are specifically contemplated by the inventor.
The Use of Adhesive-Coated Rods to Create Layered and Flattened
Nanotube Structures
[0238] In some embodiments, adhesive strips and/or adhesive-coated
rods are used in conjunction to create a layered and flattened
nanotube structure. In such an embodiment, an adhesive strip of an
appropriate width is used to draw a nanotube sheet. Once drawn with
the adhesive strip, the end of the nanotube sheet to which the
adhesive strip is attached is, in turn, attached to a second
adhesive-coated rod, and the adhesive strip is removed. This
nanotube sheet is attached by folding the end of the nanotube sheet
over the second rod, such that the rod is connected to the nanotube
sheet. In some embodiments, these adhesive-coated rods are 1 to 2
mm in diameter and of some suitable length corresponding to the
width of the nanotube-forest-bearing substrate. In some of the
various embodiments, these "rods" are made from steel, iron,
aluminum, plastic, rubber, rubber-coated steel cable, or some other
suitable material.
[0239] In some embodiments, once the second adhesive-coated rod is
employed, a first adhesive-coated rod is placed at the first end of
the nanotube sheet. The first and second adhesive-coated rods are
used in combination to manipulate an individual nanotube sheet. In
some embodiments, the first and second adhesive-coated rods are
used to manipulate and/or transfer a nanotube sheet to a second set
of rods comprising a third and fourth adhesive-coated rods. Using
the adhesive strips and the first and second adhesive-coated rods
to transfer a nanotube sheet, a layered nanotube structure can be
built up, whereby the process of generating nanotube sheets is
repeated, as is the transfer of these sheets from the
adhesive-strip holder to the first and second rods, and finally to
the third and fourth rods. Specifically, several nanotube sheets
are layered one on top of another, with the ends of the nanotube
sheets attached to the adhesive-coated third and fourth rods.
[0240] In at least one embodiment, once a nanotube structure of a
suitable thickness is created through the layering of the nanotube
sheets, the third and fourth adhesive-coated rods are rotated in
opposite directions (i.e., one in a clockwise and another in a
counter-clockwise direction) to flatten the layers that comprise
the nanotube structure.
The Use of Adhesive-Coated Rods to Create a Cross-Hatch Structure
Composed of Layered and Flattened Nanotube Structures
[0241] In some embodiments, once a series of nanotube structures
are created, they are combined to generate a cross-hatch or
cross-layer pattern. These cross-hatch or cross-layer patterns and
the size of the nanotube structures generated in a cross-match or
cross-layer pattern are only limited by the number of the nanotube
structures used. Once the requisite cross-hatch or cross-layer
patterns is formed, the third and fourth adhesive rods used to
manipulate each individual nanotube structure are removed, leaving
a complete nanotube structure formed in a cross-layer or
cross-hatch pattern.
The Use of Adhesive-Coated Rods to Create a Woven Structure
Composed of Layered and Flattened Nanotube Structures
[0242] The process of generating a structure or fabric using a loom
is well known. U.S. Pat. No. 169 (by Erastus B. Bigelow, issued
Apr. 20, 1837), which is incorporated herein in its entirety,
describes a power-loom for weaving coach lace and other similar
fabrics. Common to most looms is the use of warp threads, weft
threads, and a space between the warp threads called a shed.
Typically, the process of weaving fabrics using a loom includes
alternately raising and lowering a series of warp threads oriented
to each other in a generally parallel manner, such that one set of
parallel warp threads would be raised, and an adjacent set of
parallel warp threads would be lowered. In some embodiments, each
thread of the second set is located between two threads of the
first set. Between each alternate raising and lowering of these
sets of warp threads, a weft thread is passed through the space (or
"shed") between the sets of warp threads. Looms automate this
process of raising, lowering and the passing through of weft
threads to create fabrics.
[0243] In at least one embodiment, modifications of traditional
weaving techniques utilizing a loom, such as disclosed in U.S. Pat.
No. 169, are used to form a single nanotube structure consisting of
multiple smaller structures of nanotubes. In such an embodiment, a
set "A" of layered, condensed nanotube structures are attached to a
loom. A second set "B" of layered, condensed nanotube structures is
also attached to a loom. Collectively, set A and set B are referred
to as warp films and individually as a warp film. In some
embodiments, set A and set B are spread out in a horizontal array
(i.e., a horizontal loom) while in other embodiments, a vertical
array (i.e., a vertical loom) is used. In some embodiments, the
distance or "shed" between the outer-most A and B warp films is
greater than the distance between other warp films in the set A or
B as attached to a loom, such as described in FIGS. 2E and 2F. In
some embodiments, the shed is the same between all warp-film sets
as described in FIG. 2C. In some embodiments, when a loom
containing sets A and B is operated, the nanotube structures of set
B are placed in an up position, while the nanotube structures of
set A are placed in a down position. Once the loom is operated to
place a weft structure, the positions of sets A and B alternate.
While sets A and B alternate, a series of additional nanotube
structures serve as wefts and are passed into the shed existing
between the members of set A and set B. These wefts are thus, in
effect, woven into the warps forming set A and B. In some
embodiments, the wefts are shifted toward the point at which the
warp sets are attached so as to strengthen the woven nanotube
structure. Once this process is competed, a woven nanotube
structure is created.
An Automated Process for Generating a Nanotube Layer of Sheets
[0244] In some embodiments, a combination of adhesive-coated rods
and rollers are utilized to draw nanotube sheets from one or more
nanotube forests attached to one or more substrates. In some
embodiments, the substrate is formed from a glass, silicon (Si) or
sapphire, and, in some embodiments, is between 1 and 50 cm wide or
wider. In some embodiments, the substrate has a porous surface,
wherein in some embodiments, the surface pores are about 10
nanometers or smaller across. In some embodiments, the height of
the forest of nanotubes is grown to approximately 0.25 mm. This
height can be varied based upon the process used to form the
nanotube fibers as is described above. In one embodiment, one or
more nanotube sheets are drawn, pulled together to form multiple
layers, and flattened using a series of rollers. Once flattened, in
some embodiments, a PVA (poly(vinyl alcohol)) solution or some
other suitable solution is sprayed onto the newly formed nanotube
structure in order to densify the structure. Specifically, the
effect of the liquid evaporating is to shrink the nanotube sheet,
thus making the sheets themselves denser. In some embodiments, a
PVA (poly(vinyl alcohol)), ethanol or some other suitable liquid
bath is used whereby the nanotube structure is passed through the
bath to allow for the nanotube structure to densify. After being
passed through the bath, the nanotube structure is passed around a
rotating drum, allowed to dry, and accumulated in a roll. In some
embodiments, strips of the nanotube structure are cut at a
predetermined length, and spliced together to form a long
continuous piece of layered, flattened nanotube film.
[0245] Some embodiments of the invention provide a nanotube article
that includes a plurality of nanotube films stacked on a continuous
web in each of one or more directions relative to a length-wise
edge having the longest dimension of the web. In some embodiments,
the web is densified and wound on a take-up roll. In some
embodiments, the web and each of the plurality of nanotube films
includes carbon fullerene nanotubes. In some embodiments, the web
includes woven nanotube films. In some embodiments, the web
includes a first set having a plurality of nanotube warp films
positioned at a first angle to a length-wise edge of the web woven
with a second set having a plurality of nanotube weft films
positioned at a second angle, different than the first angle, to a
length-wise edge of the web. In some embodiments, the web includes
crossed-but-not-woven nanotube films. In some embodiments, the web
includes a first set having a plurality of nanotube films parallel
to one another crossed-but-not-woven with a second set having a
plurality of nanotube films parallel to one another.
[0246] Another aspect of the invention, in some embodiments,
includes an apparatus for continuous fabrication of a carbon
nanotube film, wherein the apparatus includes a first
film-transport mechanism having one or more nanotube-film-holding
surfaces, and movable along a first fabrication path; and a
layer-build-up mechanism operable to place carbon nanotube film
across the nanotube-film-holding surfaces while the holding
surfaces are moving along the fabrication path. In some
embodiments, the nanotube-film-holding surfaces include one or more
adhesive surfaces along a surface of a flexible sheet belt, wherein
the layer-build-up mechanism lays each film at a non-parallel
non-perpendicular angle to a lengthwise edge of the sheet belt. In
some embodiments, the belt is a continuous-loop made of a polymer
material having the adhesive surfaces along its two opposite outer
edges, and wherein the nanotube film is placed across the belt and
held by the one or more adhesive surfaces. In some embodiments, the
nanotube-film-holding surfaces include one or more adhesive
surfaces along a surface of each of a plurality of separate
spaced-apart endless-loop belts moved substantially piecewise
parallel to one another. Some embodiments further include a second
film transport mechanism having a plurality of spaced-apart
adhesive surfaces on a sheet belt, and movable along a second
fabrication path that connects to the first fabrication path in a
manner to allow transfer of the nanotube film from the first film
transport mechanism to the second film transport mechanism. In some
such embodiments, the layer-build-up mechanism includes a first set
of one or more warp-film holders operable to hold a first set of
warp films stretched to a first adhesive strip along a distal first
edge of the first film-transport mechanism from the first set
warp-film holders, and a second set of warp film holders operable
to hold a second set of warp films stretched to the first adhesive
strip, wherein the first film-transport mechanism includes a second
adhesive strip along a second edge opposite the first edge, and a
weft-film placement mechanism operable to place a weft film in a
shed between the first set of warp films and the second set of warp
films and attach opposite ends of the weft to the first and second
adhesive strips respectively and then separate from the attached
weft. In some such embodiments, the first set warp-film holders
moves in a direction opposite relative to the second set warp-film
holders after deposition of a weft film placed from the first
adhesive strip to the second adhesive strip, and wherein the
warp-film holders successively attach a near end of each warp film
to the second adhesive strip as it completes its weave and then
separate from the attached warp. In other embodiments, the first
film-transport mechanism includes a vacuum table, wherein the
nanotube-film-holding surfaces are operable to hold and release
nanotube film using a gas-pressure difference, the vacuum surface
movable relative to layer-build-up mechanism to position itself for
a predetermined film deposition layout.
[0247] Another aspect of the invention, in some embodiments,
includes an apparatus on which to synthesize a carbon nanotube
forest, wherein the apparatus includes an interior-flow substrate
having a first major face, a first nanoporous surface layer in
fluid communication with the first major face, an interior flow
system operable to deliver gasses to the nanoporous layer from a
side or face of the substrate other than the first major face, and
a nanotube-synthesis catalyst on the first nanoporous layer. In
some embodiments, the interior flow system includes a first
plurality of gas passages having a depth greater than their width.
In some embodiments, the substrate is a side-flow substrate wherein
each one the first plurality of gas passages provide fluid
communication to the porous layer from one or more sides adjacent
the first major face. In some embodiments, the interior flow system
includes a first plurality of gas passages having a depth greater
than their width and having a length along a Y-direction, and a
second plurality of gas passages that extend to a depth more distal
from the first major face than the depth of the first plurality of
gas passages, and wherein each of the second gas passages is in
fluid communication with a plurality of the first plurality of gas
passages, in order to form a flow-through substrate. Some
embodiments further include a furnace having a temperature control
and heating unit operable to maintain an effective temperature for
nanotube synthesis; a substrate-holding mechanism; a gas-flow
system operable to deliver one or more reactant gasses to a side or
face of the substrate other than the first major face and to
exhaust spent gasses from a vicinity of the first major face; and
an access port through which nanotube product can be removed
without interrupting a substantially continuous operation of the
furnace at substantially its effective temperature for nanotube
synthesis. In some such embodiments, the substrate is configured to
have plurality of successive nanotube forests grown and
harvested.
[0248] Some embodiments of the invention provide a method that
includes stacking a plurality of nanotube films on a continuous web
in each of one or more directions relative to a length-wise edge
having the longest dimension of the web. In some embodiments, the
method further includes densifying the web and winding it on a
take-up roll. In some embodiments, the web and each of the
plurality of nanotube films includes carbon fullerene nanotubes. In
some embodiments, the method further includes weaving nanotube
films to form the web. In some embodiments, the method further
includes positioning and holding a first set having a plurality of
nanotube warp films at a first angle to a length-wise edge of the
web, and weaving the first set with a second set having a plurality
of nanotube weft films positioned at a second angle, different than
the first angle, to a length-wise edge of the web. In some
embodiments, the method includes crossing-but-not-weaving the
nanotube films. In some such embodiments, the web includes a first
set having a plurality of nanotube films parallel to one another
crossed-but-not-woven with a second set having a plurality of
nanotube films parallel to one another.
[0249] Another aspect of the invention, in some embodiments,
includes method for continuous fabrication of a carbon nanotube
film, wherein the method includes moving a first film-transport
mechanism, having one or more nanotube-film-holding surfaces, along
a first fabrication path; and placing carbon nanotube film across
the nanotube-film-holding surfaces while the holding surfaces are
moving along the fabrication path. In some embodiments, the
nanotube-film-holding surfaces include one or more adhesive
surfaces along a surface of a flexible sheet belt, wherein the
layer-build-up mechanism lays each film at a non-parallel
non-perpendicular angle to a lengthwise edge of the sheet belt. In
some embodiments, the belt is a continuous-loop made of a polymer
material having the adhesive surfaces along its two opposite outer
edges, and wherein the method includes placing the nanotube film
across the belt and holding it by the one or more adhesive
surfaces. In some embodiments, the method performs one or more
processes associated with the individual features of the above
described apparatus.
[0250] Another aspect of the invention, in some embodiments,
includes a method for synthesizing a carbon nanotube forest,
wherein the method includes flowing reactant gasses to an interior
of a nanotube-growth substrate having a first major face, a first
nanoporous surface layer in fluid communication with the first
major face, an interior flow system operable to deliver gasses to
the nanoporous layer from a side or face of the substrate other
than the first major face, and a nanotube-synthesis catalyst on the
first nanoporous layer. In some embodiments, the interior flow
system includes a first plurality of gas passages having a depth
greater than their width. In some embodiments, the substrate is a
side-flow substrate wherein each one the first plurality of gas
passages provide fluid communication to the porous layer from one
or more sides adjacent the first major face. In some embodiments,
the interior flow system includes a first plurality of gas passages
having a depth greater than their width and having a length along a
Y-direction, and a second plurality of gas passages that extend to
a depth more distal from the first major face than the depth of the
first plurality of gas passages, and wherein each of the second gas
passages is in fluid communication with a plurality of the first
plurality of gas passages, in order to form a flow-through
substrate. Some embodiments further include a furnace having a
temperature control and heating unit operable to maintain an
effective temperature for nanotube synthesis; a substrate-holding
mechanism; a gas-flow system operable to deliver one or more
reactant gasses to a side or face of the substrate other than the
first major face and to exhaust spent gasses from a vicinity of the
first major face; and an access port through which nanotube product
can be removed without interrupting a substantially continuous
operation of the furnace at substantially its effective temperature
for nanotube synthesis. In some such embodiments, the substrate is
configured to have plurality of successive nanotube forests grown
and harvested.
[0251] Some embodiments provide a method that includes holding a
first end of a nanotube film, pulling a length of nanotube film
attached to the first end from a nanotube forest, holding a second
end of the nanotube film, and separating the second end of the film
from the nanotube forest. In some embodiments, the holding includes
adhesively holding. In some embodiments, the holding includes
vacuum holding. In some embodiments, holding includes clamping the
film between two surfaces. Some embodiments further include holding
the film between the second end and the nanotube forest before
separating.
[0252] Some embodiments of the invention include splicing a
nanotube film to a nanotube forest and pulling additional length of
nanotube film from the nanotube forest. In some embodiments, the
splicing includes pressing a nanotube film against the nanotube
forest. In other embodiments, the splicing includes pressing a
portion of one nanotube film against a portion of another nanotube
film. In some embodiments, splicing includes wetting overlapped
portions of two or more nanotube films and then drying the wetted
films to draw the fibers closer to one another.
[0253] Another aspect of the invention, in some embodiments,
includes a splicing bar having a rounded nose configured to press a
nanotube film onto another nanotube film and/or to a nanotube
forest. In some embodiments, the slicing bar further includes a
cutting edge configured to cut a film end off the spliced
joint.
[0254] Another aspect of the invention, in some embodiments,
includes a film-holder opener 185 configured to open a split
resilient nanotube-film holder, to insert the nanotube film therein
and then to release the nanotube-film holder with the nanotube film
held therein. In some embodiments, the nanotube-film holder is made
of split rubber tubing.
[0255] Another aspect of the invention, in some embodiments,
includes a method for preventing or repairing gaps in a nanotube
film being pulled from a nanotube forest. In some embodiments, the
method includes rotating a distal nanotube film holder and a
substrate holding the nanotube forest both in the same angular
direction as shown in FIG. 3B. In other embodiments, the method
includes pressing a face of the nanotube forest with an implement
that reduces a gap in the forest as shown in FIG. 6C.
[0256] It is to be understood that the above description is
intended to be illustrative, and not restrictive. Although numerous
characteristics and advantages of various embodiments as described
herein have been set forth in the foregoing description, together
with details of the structure and function of various embodiments,
many other embodiments and changes to details will be apparent to
those of skill in the art upon reviewing the above description. The
scope of the invention should, therefore, be determined with
reference to the appended claims, along with the full scope of
equivalents to which such claims are entitled. In the appended
claims, the terms "including" and "in which" are used as the
plain-English equivalents of the respective terms "comprising" and
"wherein," respectively. Moreover, the terms "first," "second," and
"third," etc., are used merely as labels, and are not intended to
impose numerical requirements on their objects.
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