U.S. patent application number 09/967674 was filed with the patent office on 2002-02-14 for net shape manufacturing using carbon nanotubes.
Invention is credited to Herman, Frederick James.
Application Number | 20020018745 09/967674 |
Document ID | / |
Family ID | 24178780 |
Filed Date | 2002-02-14 |
United States Patent
Application |
20020018745 |
Kind Code |
A1 |
Herman, Frederick James |
February 14, 2002 |
Net shape manufacturing using carbon nanotubes
Abstract
The present invention provides methods and systems for net
shaped manufacturing using carbon nanotubes. Generally, an
automatic control unit is used to place reaction units in the
proper location to produce a component part of carbon nanotubes in
a predetermined configuration. The reaction units include a carbon
vaporization unit, a carbon feed/injection unit and a gas
pressure/temperature control isolation unit. The carbon
feed/injection unit advantageously operates to inject carbon based
materials (e.g., graphite powder, solid graphite or carbon based
gas) into an reaction area at a predetermined rate in which the
carbon vaporization unit provides energy capable of dissociating
carbon atoms from the injected carbon based material to produce a
predetermined concentration of carbon vapor within the reaction
area. The gas pressure/temperature control isolation unit operates
to control the pressure and temperature of the reaction area to
promote the growth of carbon nanotubes.
Inventors: |
Herman, Frederick James;
(Fort Worth, TX) |
Correspondence
Address: |
JACKSON WALKER LLP
2435 NORTH CENTRAL EXPRESSWAY
SUITE 6000
RICHARDSON
TX
75080
US
|
Family ID: |
24178780 |
Appl. No.: |
09/967674 |
Filed: |
September 27, 2001 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
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09967674 |
Sep 27, 2001 |
|
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|
09546081 |
Apr 10, 2000 |
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Current U.S.
Class: |
423/447.1 |
Current CPC
Class: |
Y10S 977/833 20130101;
Y10S 977/743 20130101; B82Y 30/00 20130101; Y10S 977/888 20130101;
B82Y 40/00 20130101; C01B 32/162 20170801; Y10S 977/843 20130101;
Y10S 977/742 20130101 |
Class at
Publication: |
423/447.1 |
International
Class: |
D01F 009/12 |
Claims
What is claimed is:
1. A method of manufacturing a component part having a
predetermined configuration using carbon nanotubes, comprising the
steps of: injecting carbon based material into a reaction area at a
predetermined rate; dissociating carbon atoms from said carbon
based material at a predetermined rate; isolating the reaction area
at a predetermined temperature and a predetermined pressure,
wherein said carbon nanotubes nucleate in said reaction area; and
dynamically locating said injecting, dissociating and isolating
steps to nucleate said carbon nanotubes in said predetermined
configuration.
2. The method of claim 1 further comprising the steps of:
decomposing said predetermined configuration into multiple
cross-sectional layers; and repeating said step of dynamically
locating said injecting, dissociating and isolating steps for each
said multiple cross-sectional layer, wherein each successive
cross-sectional layer is stacked on a previous cross-sectional
layer.
3. The method of claim 1 further comprising the step of dynamically
varying a rate of injection of said carbon based material.
4. The method of claim 1 further comprising the step of dynamically
varying a rate of dissociation from said carbon based material.
5. The method of claim 1 further comprising the step dynamically
varying said predetermined pressure and predetermined
temperature.
6. The method of claim 1, wherein the step of dissociating is
effectuated by a laser, an electron beam, or an electrical arc
discharge unit.
7. The method of claim 1, wherein said carbon based material
further comprises a metal based material.
8. The method of claim 7, further comprising the step of
dynamically varying a concentration of said metal based
material.
9. The method of claim I further comprising the steps of: injecting
a carbon based material having a first metal based material; and
injecting a second carbon based material having a second metal
based material.
10. The method of claim 1, further comprising the step of adjusting
a growth direction of said carbon nanotube during a growth
period.
11. A system of manufacturing a component part having a
predetermined configuration using carbon nanotubes, comprising:
carbon injection unit, said carbon injection unit injecting a
carbon based material into a reaction area; carbon dissociation
unit, said carbon dissociation unit dissociating carbon from said
carbon based material; isolation unit, said isolation unit
controlling the pressure and temperature of said reaction area,
wherein said carbon nanotubes nucleate within said reaction area;
and control unit in communication with and capable of dynamically
locating said carbon injection unit, carbon dissociation unit and
isolation unit in a predetermined pattern to nucleate said carbon
nanotubes in said predetermined configuration.
12. The system of claim 11, wherein said control unit further
decomposing said predetermined configuration into multiple
cross-sectional layers, wherein nucleation of said carbon nanotubes
is repeated for each said multiple cross-sectional layer, and
wherein each successive layer of carbon nanotubes is stacked on a
previous layer.
13. The system of claim 11, wherein said control unit further
dynamically varies carbon based material injection rate.
14. The system of claim 13, wherein said control unit further
dynamically varies dissociation rate.
15. The system of claim 11, wherein said control unit further
dynamically varies said pressure and temperature of said reaction
area.
16. The system of claim 11, wherein said carbon dissociation unit
comprises a laser, an electron beam and an electrical arc discharge
unit.
17. The system of claim 11, wherein said carbon based material
further includes at least one type of metal based material.
18. The system of claim 17, wherein said control unit further
dynamically varies an amount and type of metal based material
within said carbon based material.
19. The system of claim 12 further including a substrate capable of
providing an initial nucleation surface for said carbon
nanotubes.
20. The system of claim 19, wherein said substrate includes seed
material arranged in a predetermined pattern consistent with a
first cross-sectional layer of said multiple cross-sectional
layers.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Technical Field of the Invention
[0002] This invention relates to manufacturing carbon based
materials and, more particularly, to a method and system for net
shape manufacturing using carbon nanotubes.
[0003] 2. Background of the Invention
[0004] In addition to the more common allotropes of carbon, namely
diamond and graphite, there exist a third form which forms a
network of structures called fallerenes. The best known, discovered
in 1985, is called the Buckyball or to give its technical name Buck
minster fullerene. ABuckyball structure is a pure carbon molecule
comprising exactly sixty carbon atoms. Generally, each carbon atom
is bonded to three other carbon atoms in the form of a spherical
structure. Recent research has identified another type of fallerene
which appears as a hollow tubular structure known as the nanotube.
The carbon nanotube appears as an elongated fiber and yet it is
hollow and inherits the perfection of atomic arrangements made
famous by its predecessor the Buckyball. Carbon nanotubes consist
of two dimensional hexagonal sheets folded together and capped at
both ends by a fullerene cap. There length can be millions of times
greater than their small diameter. Thus, carbon nanotubes are
effectively Buckyball structures extended out as long strands
rather than spheres.
[0005] Development of carbon molecular growth began with the
manufacture of carbon fibers and, while these conventional carbon
fibers are readily made very long, the graphite sheets within the
carbon fibers are either not closed tubes or do not extend
continuously along the length of the fiber. The result is sharply
decreased tensile strength, electrical conductivity and chemical
resistance compared to a carbon nanotube. Thus, development of
fullerenes, such as carbon nanotubes, has continued in an effort to
develop materials with improved physical properties.
[0006] Carbon nanotubes exhibit mechanical, electronic and magnetic
properties which are in tuneable by varying the diameter, number of
concentric shelves and orientation of the fibers. Practical carbon
nanotube based materials require eliminating defects and other
reaction products, maximizing the nanotube yield, and synthetically
controlling the tube length and orientation. Currently there exist
three primary methods for producing carbon nanotubes. These methods
include, for example, Electric Arc Discharge, Resistive Heating and
Laser Ablation.
[0007] The Electric Arc Discharge process works by utilizing two
carbon (graphite) electrodes in an arc welding type process. The
welder is turned on and the rod ends are held against each other in
an argon atmosphere to produce or grow carbon nanotubes. The yield
rate of carbon nanotubes of this process is extremely low and the
growth of the carbon nanotube orientation are random in nature
delivering only undefined configurations of growth material.
[0008] In Resistive Heating type processes, the flllerenes are
formed when a carbon rod or carbon containing gas is dissociated by
resistive heating under a controlled atmosphere. A resisted heating
of the rod causes the rod to emit a faint gray white plum soot like
material comprising fullerenes. The fallerenes collect on glass
shields that surround the carbon rod and must be separated from
non-desirable components in a subsequent process. Again, the yield
rate ofthe carbon nanotubes is extremely low and orientation is
random delivering only undefined configurations of growth
material.
[0009] The Laser Ablation batch type process works by ablating a
graphite target containing a small metal particle concentration
with a pulsed laser while providing a temperature controlled space
for the carbon atoms and carbon vapor to combine to grow a
fullerene structure such as a nanotube. The fallerene structure
falls out in a type of carbon soot. The desired fullerene structure
is subsequently extracted from the soot by an acid reflux cleaning
system. Although the Laser Ablation process has experienced an
improved yield rate, relative to the above-mentioned processes,
this batch type process approach is uneconomical for use in
industrial application because there currently exist no method for
controlling the orientation and shaping of the carbon nanotubes.
None of the above-mentioned batch methods are used to delivered
large-scale production of carbon nanotubes or crystalline type
carbon nanotubes with a defined orientation in a net shape type
manufacturing arrangement.
[0010] The above-mnentioned and other disadvantages of the prior
art are overcome by the present invention, for example, by
providing a method and system for net shape manufacturing using
carbon nanotubes.
SUMMARY OF THE INVENTION
[0011] The present invention achieves technical advantages as a
method and system for net shaped manufacturing using carbon
nanotubes. An automatic control unit is used to place reaction
units in the proper location to produce a component part of carbon
nanotubes in a predetermined shape. The reaction units include a
carbon vaporization unit, a carbon and catalyst feed/injection unit
and a gas pressure/temperature control isolation unit. The
carbon/catalyst feed/injection unit advantageously operates to
inject carbon based materials (e.g., graphite powder, solid
graphite or carbon based gas) into an reaction area at a
predetermined rate in which the carbon vaporization unit provides
energy capable of dissociating carbon atoms from the injected
carbon based material to produce a predetermined concentration of
carbon vapor within the reaction area. The gas pressure/temperature
control isolation unit operates to control the pressure and
temperature of the reaction area to promote the growth of carbon
nanotubes.
[0012] Among the new advantages of the present invention are:
First, preferentially oriented carbon nanotubes can more
economically be fabricated into component parts; And, since
preferentially oriented carbon nanotubes exhibit both superior
strength and electrical conductivity, stronger structural materials
can be fabricated into a component which utilizes both structural
advantages and electronic applications.
BRIEF DESCRIPTION OF THE DRAWINGS
[0013] For a more complete understanding of the present invention,
reference is made to the following detailed description taken in
conjunction with the accompanying drawings wherein:
[0014] FIG. 1 illustrates a flowchart of a method for net shape
manufacturing using carbon nanotubes in accordance with the present
invention;
[0015] FIG. 2 illustrates one embodiment of a system architecture
embodying the present invention; and
[0016] FIG. 3. is an exemplary illustration of a synthesis head
which can be used to implement the present invention.
DETAILED DESCRIPTION OF THE INVENTION
[0017] The numerous innovative teachings of the present application
will be described with particular reference to the presently
preferred exemplary embodiments. However, it should be understood
that this class of embodiments provides only a few examples of the
many advantageous uses of innovative teachings herein. In general,
statements made in the specification of the present application do
not necessarily delimit any of the various claimed inventions.
Moreover, some statements may apply to some inventive features but
not to others.
[0018] Referring now to the Drawings, and more particularly, to
FIG. 1, there is illustrated a method of manufacturing using carbon
nanotubes in accordance with the present invention, The process
begins with an injection step 122. In the injection step 122,
carbon based material is injected into a reaction area for further
operations to be performed. The reaction area is the area in which
carbon nanotubes nucleate or grow. The carbon based material is the
feed stock for carbon atoms necessary for the nucleation of carbon
nanotubes. In a preferred embodiment, the carbon based material is
a pure carbon molecule. However, the feed stock can be a
combination of carbon and other types of material. The carbon based
material can be, for example, apowder, solid or gaseous form (such
as graphite powder, solid carbon rod or carbon gas).
[0019] Next, in a dissociation step 124, carbon atoms are
dissociated or vaporized from the carbon based feed stock which is
injected into the reaction area. Dissociation is attained by
heating the carbon based feed stock to a temperature sufficient to
form a carbon vapor. The temperature will depend on the type of
carbon based feed stock used, however, temperatures can range from
800.degree. C. to 3000.degree. C. These temperatures can be
attained through the use of, for example, electric arc discharge
electrodes, resistive heating elements, laser, electron beam or
other heating type processes.
[0020] In an isolating step 126, the reaction area is maintained
under a controlled pressure and temperature profile. The controlled
pressure is used to control the location of the dissociated carbon
atoms at an optimum distance from the nucleating carbon nanotubes.
The absolute pressure of the atmosphere selected to form carbon
nanotubes can be a minimum of 0.001 Torr and can range up to a
maximum of 20,000 Torr. Lower pressures produce carbon vapors
having a lower carbon concentration, which allows production of
carbon nanotubes with predetermined orientations. Smaller diameter
carbon nanotubes can be attained at higher pressures. Also,
although the dissociated carbon vapor will initially reside at very
high temperatures, the carbon vapor needs to be cooled at a
controlled rate to reach an energy state to allow the vapor to form
into a predetermined solid nanotube structure. In the isolating
step 126, the pressure controlled area can be temperature
controlled to allow a gradual cooling from the initial temperature
needed to dissociated the carbon atoms.
[0021] Finally, in a controlling step 128, the above-mentioned
reaction components (i.e., injection step 122, dissociation step
124 and isolating step 126) are precisely and accurately placed in
a location predetermined by the configuration of a component part
to be fabricated. A component part is fabricated by stacking
multiple cross-sectional layers of carbon nanotubes until the
component part is completed in a predetermined physical shape.
Thus, this control type system is based upon material additive
layer manufacturing. The process can be computer aided by first
decomposing the predetermined shape into very thin cross-sectional
layers and subsequently placing the reaction components in the
proper locations to fabricate each cross-sectional layer from
carbon nanotubes. Subsequent cross-sectional layers are stacked on
the previous cross-sectional layer. The growth of previously
deposited carbon nanotubes can be continued with each subsequent
cross-sectional layer.
[0022] In another embodiment, to control nucleation of carbon
nanotubes with a predetermined physical properties, a catalyst or
metal compound or material can be combined with the carbon based
feed stock. The carbon based feed stock and the metal material,
when used, is combined prior to dissociation step 124. The
combination can be made, for example, by mixing graphite with the
metal material and then processing the relatively homogenous
mixture into a rod in accordance with methods known in the art. The
rod containing the combination carbon and metal material is then
utilized in the dissociation step 124 described herein. However, a
carbon based feed stock and a metal based feed stock can be
dissociated in separate steps and subsequently placed in the
reaction area. Additionally, the type and concentration of metal
material can be varied during the fabrication process of the
component part to allow further variance of the physical properties
of the carbon nanotubes.
[0023] For example, the process works by injecting methane gas into
the reaction area and dissociating the methane gas into ionized
hydrogen and carbon atoms. When this is done in the presence of a
metallic particle the ionized carbon atoms cover the surface area
of the metallic particle. When the carbon atoms on the metallic
particle come in contact with each other, they form covalent bonds
in the most energetically stable formation. By choosing a metallic
particle of the predetermined shape and size, carbon nanotubes form
with defined diameters and physical properties. As a carbon
nanotube is formed and it separates from the metallic particle, the
carbon on the surface area of the metallic particle is replaced
with more ionized carbon. Thus, the reaction can continue
indefinitely until one of the following occurs: 1) the carbon feed
stock is withheld from the reaction area; 2) the reaction isolation
conditions are changed so that the formation of carbon nanotubes is
no longer favorable; or 3) the concentration ofmetallic particles
are increased to allow the metallic particles to come in contact
with each other and grow to a size or shape that does not allow
further growth of the carbon nanotubes. Also, In situ diagnostics
can be used to evaluate the carbon nanotube growth process. Thus,
the nucleation of the carbon nanotubes can be varied to allow
custom tailoring of the physical properties in real time. In situ
diagnostics is the process of evaluating chemical reactions as they
occur to determine their exact conditions in terms of their energy,
chemical reactants, growth orientation, etc.
[0024] Now referring to FIG. 2, there is illustrated a system 200
for net shape manufacturing using carbon nanotubes in accordance
with the present invention. The system 200 comprises an automatic
control unit 210 and reaction units which includes a carbon
feed/injection unit 230, a carbon dissociation unit 220 and a gas
pressure/temperature control isolation unit 240.
[0025] The carbon feed/injection unit 230 is used to inject a
carbon based material into a predetermined area for further
operations to be performed. The arbon based material is the feed
stock for carbon atoms necessary for the nucleation ofcarbon
nanotubes. The injection rate is controlled by and through
communication with the automatic control unit 210. In a preferred
embodiment, the carbon based material is a pure carbon molecule.
However, the feed stock can be a combination of carbon and other
types of material. The carbon based material can be, for example, a
powder, solid or gaseous form (e.g., graphite powder, solid carbon
rod or carbon gas). The carbon feed/injection unit 230 can be
equipped with a type of hopper which allows the continuous
injection of feed stock without requiring the manufacturing system
to slow or pause for the reloading of feed stock.
[0026] The carbon dissociation unit 220 dissociates carbon atoms
from the feed stock which is injected into the predetermined area.
Dissociation is attained by heating the carbon based feed stock to
a temperature sufficient to form a carbon vapor. The carbon
dissociation unit 220 is capable of providing enough energy to
vaporizing the feed stock into carbon molecules. The carbon
dissociation unit 220 can comprise, for example, electric arc
discharge electrodes, resistive heating elements, laser, electron
beam or other heating type process. Energy level output, of the
carbon dissociation unit 220, is controlled and varied by and
through communication with the automatic control unit 210.
[0027] The gas pressure/temperature control isolation unit 240 is
capable of varying the pressure and temperature of an predetermined
area. Varying the pressure is effectuated by evacuating or pumping
a gas, preferably an inert gas, into the predetermined area. Inert
gases include, for example, helium, argon and xenon. Other gases,
which are not reactive with the vaporized carbon can be used. The
pressure can be varied from about 0.001 Torr to 20,000 Torr.
Pressure and temperature, of the gas pressure/temperature control
unit 240, is controlled and varied through communication with the
automatic control unit 210.
[0028] Although the dissociated carbon vapor will initially reside
at very high temperatures, the carbon vapor needs to be cooled at a
controlled rate to reach an energy state to allow the vapor to form
into a predetermined solid nanotube structure. The gas
pressure/temperature control unit 240 comprises a heating device
(not shown) to heat the pressure controlled area at temperatures
which allow a gradual cooling from the initial temperature needed
to dissociated the carbon atoms.
[0029] Finally, the automatic control unit 210 precisely and
accurately places the above-mentioned reaction units 220, 230, 240
in a predetermined area to nucleate carbon nanotubes into the
configuration of a component part. The component part is fabricated
by stacking multiple cross-sectional layers of carbon nanotubes
until the component part is completed in apredetermined physical
shape. The automatic control unit 210 can be computer aided to
allow the configuration of the component part to be decomposed into
very thin cross-sectional layers. Subsequently, the automatic
control unit 210 places the reaction units 220, 230, 240 in
apattern of reaction areas determined by the decomposed
cross-sectional layers. Carbon nanotubes are nucleated in the
multiple reaction areas to form the shape of each cross-sectional
layer pattern. Each subsequent cross-section is stacked upon the
previous cross-sectional layer. Thus, the component part is
fabricated by multiple stacked cross-sectional layers of nucleated
carbon nanotubes. Growth of previously deposited carbon nanotubes
can be continued with the stacking of each subsequent cross
sectional layer and additional layers of newly nucleated carbon
nanotubes can also be added.
[0030] In another embodiment, the net shape manufacturing system
200 can include a substrate (not shown) to support the nucleating
carbon nanotubes. Layers of sacrificial substrates can also be
simultaneously built up to support more complex comiponent part
configurations. The substrate can be embedded with seed particles
to assist the growth of the nanotubes. The seed particles, such as
carbon nanotubes or selected metal particles, are arranged in a
pattern consistent with the predetermined configuration of the
component part to be fabricated.
[0031] The strength of the component part can be improved by
defining the orientation of the nucleating nanotubes. When large
bundles of carbon nanotubes grow together, they eventually form
amacroscopic crystal. However, this type of crystal is not expected
to have good bulk mechanical strength when compared to single
carbon nanotubes. The bonds that hold the individual carbon
nanotubes together in the bundles are week Van der Waals bonds.
Essentially, these lateral bonds form slip planes in which bulk
material failure could occur. The automatic control unit 210 is
capable of placing and controlling the reaction units 220, 230, 240
to nucleated helical growth of short length carbon nanotubes such
that each successive layer of the helix blocks the slip plane of
the previous layer. In addition to the helical growth technique,
the growth direction vector of the crystal can be changed (either
allowed to happen randomly or in a controlled manner) such that
dislocation between individual carbon nanotubes are not allowed to
propagate through out the crystal. In either the random or
controlled manner, the growth properties are maintained to ensure
uniform mechanical and electrical properties. Thus, the problems
encountered with slip planes can be reduced or eliminated by using
the above-described net shape manufacturing system to control the
carbon nanotube growth in a component part. Additionally, the
automatic control unit 210 can use in situ diagnostics to evaluate
the carbon nanotube growth in real time and adjust during
processing to control and vary the physical properties of the
carbon nanotubes.
[0032] Now referring to FIG. 3, there is illustrated a synthesis
head 300 which can be used in net shape manufacture using carbon
nanotubes in accordance with the present inventor A control arm 310
is coupled to the reaction units 220, 230, 240. The control aim 310
can be, for example, a 5 or 6 axis rotating type arm. The movement
of the control arm 310 is controlled by the automatic control unit
210 (FIG. 2) through a wireline or wireless type connection. The
automatic control unit 210 instructs the control arm to place the
reaction units 220, 230, 240 such that carbon nanotube nucleation
is effectuated in the reaction area 320. Thus, the reaction area
320 can be continuously maneuvered in the pattern determined by the
decomposed cross-sectional layers.
[0033] Preferentially grown carbon nanotubes add tremendous
capability and functionality to materials and systems. For example,
carbon nanotubes for use as structural materials show strength to
weight ratios of up to 126 to 1 over titanium and 142 to 1 over
aluminum. Economic analysis indicates that this weight savings
translates into large production cost reductions depending on the
production rate. Along with use as a structural material, carbon
nanotubes have many other attributes that increase the capabilities
ofmaterials and systems.
[0034] Additionally, the carbon atomic bonds of carbon nanotubes
can be arranged in a multitude of ways giving the nucleated carbon
nanotubes conductivities ranging from an insulator to a
semiconductor to a metallic conductor. This range of conductivity
is due to the helical symmetry or chirality of the nanotubes. Thus,
the present invention can be used to integrate both structural and
electronic advantageous characteristics at the same time or within
the same component part. As the cross-sectional layers are added,
physical properties can be varied by individual control of the
reaction units 220, 230, 240. By custom tailoring physical
properties of individual or groups of carbon nanotubes,
multi-functionality can be achieved for applications such as
electronics, electrical routing, piezoelectric and power storage
systems. Thus, physical structures, such as aerospace wing
structures, can be produced with embedded electronics type
circuits. Assuming conventional manufacturing methods could be used
to fabricate these type products, such methods would in all
probability require additional time consuming operations, including
the need for custom fixturing and tooling, high strength material
joining processes, and complex assembly operations.
[0035] Although a preferred embodiment of the method and system of
the present invention has been illustrated in the accompanied
drawings and described in the foregoing detailed description, it is
understood that the invention is not limited to the embodiment
disclosed, but is capable of numerous rearrangements,
modifications, and substitutions without departing from the spirit
of the invention as set forth and defined by the following
claims.
* * * * *