U.S. patent application number 12/860405 was filed with the patent office on 2011-01-13 for method and apparatus pertaining to nanoensembles having integral variable potential junctions.
This patent application is currently assigned to DIMEROND TECHNOLOGIES, INC.. Invention is credited to Dieter M. Gruen.
Application Number | 20110005564 12/860405 |
Document ID | / |
Family ID | 43426523 |
Filed Date | 2011-01-13 |
United States Patent
Application |
20110005564 |
Kind Code |
A1 |
Gruen; Dieter M. |
January 13, 2011 |
Method and Apparatus Pertaining to Nanoensembles Having Integral
Variable Potential Junctions
Abstract
Carbon-containing sp3-bonded solid refractory nanocrystalline
particles that are each sized no larger than about 100 nanometers
have a metal of choice disposed thereabout. A variable potential
junction is formed between the metallic coatings and the particles
that enables carrier entropy to be efficiently transported from the
variable potential junction to the coating.
Inventors: |
Gruen; Dieter M.; (Downers
Grove, IL) |
Correspondence
Address: |
FITCH EVEN TABIN & FLANNERY
120 SOUTH LASALLE STREET, SUITE 1600
CHICAGO
IL
60603-3406
US
|
Assignee: |
DIMEROND TECHNOLOGIES, INC.
Downers Grove
IL
|
Family ID: |
43426523 |
Appl. No.: |
12/860405 |
Filed: |
August 20, 2010 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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12297979 |
Oct 21, 2008 |
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PCT/US07/67297 |
Apr 24, 2007 |
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12860405 |
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11674810 |
Feb 14, 2007 |
7718000 |
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12297979 |
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11380283 |
Apr 26, 2006 |
7572332 |
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11674810 |
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60725541 |
Oct 11, 2005 |
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Current U.S.
Class: |
136/239 ;
257/E21.101; 438/508; 438/54; 977/773 |
Current CPC
Class: |
H01L 35/22 20130101 |
Class at
Publication: |
136/239 ;
438/508; 438/54; 257/E21.101; 977/773 |
International
Class: |
H01L 35/22 20060101
H01L035/22; H01L 21/205 20060101 H01L021/205 |
Claims
1. An article of manufacture comprising: a carbon-containing
sp3-bonded solid refractory nanocrystallite particle sized no
larger than about 100 nanometers; and a metallic coating
conformally disposed about the particle; such that there is a
variable potential junction between the metallic coating and the
particle that enables carrier entropy to be efficiently transported
from the variable potential junction to the coating.
2. The article of manufacture of claim 1 wherein the
carbon-containing sp3-bonded solid refractory nanocrystallite
particle comprises silicon carbide.
3. The article of manufacture of claim 1 wherein the metallic
coating comprises a silicide.
4. The article of manufacture of claim 3 wherein the silicide
comprises a silicide from the group consisting of nickel silicide,
chromium silicide, iron silicide, and manganese silicide.
5. The article of manufacture of claim 1 wherein the metallic
coating exerts inwardly-directed pressure on the particle.
6. The article of manufacture of claim 5 wherein the
inwardly-directed pressure at least equals one giga-Pascal.
7. The article of manufacture of claim 1 wherein the metallic
coating has a thermal expansion coefficient that is at least twice
the thermal expansion coefficient of the carbon-containing
sp3-bonded solid refractory nanocrystallite particle.
8. The article of manufacture of claim 1 wherein the
carbon-containing sp3-bonded solid refractory nanocrystallite
particle comprises a mixture of a plurality of differing
polytypes.
9. The article of manufacture of claim 1 wherein the
carbon-containing sp3-bonded solid refractory nanocrystallite
particle is doped with a doping material.
10. The article of manufacture of claim 9 wherein the doping
material comprises at least one of aluminum, boron, and
nitrogen.
11. The article of manufacture of claim 1 comprising a plurality of
the carbon-containing sp3-bonded solid refractory nanocrystallite
particles, wherein each of the particles has one of the metallic
coatings formed there around.
12. The article of manufacture of claim 1 wherein the plurality of
particles and the metallic coating in combination are comprised of
X atoms, and wherein the variable potential junction comprises an
interfacial region made up of atoms that comprise at least about
ten percent of X.
13. A method comprising: providing a plurality of carbon-containing
sp3-bonded solid refractory nanocrystallite particles sized no
larger than about 100 nanometers; conformally forming a metallic
coating around each of the particles to thereby form a variable
potential junction between the metallic coating and the particle
that enables carrier entropy to be efficiently transported from the
variable potential junction to the coating.
14. The method of claim 13 wherein the carbon-containing sp3-bonded
solid refractory nanocrystallite particle comprise silicon
carbide.
15. The method of claim 13 wherein the metallic coating comprises a
silicide.
16. The article of manufacture of claim 15 wherein the silicide
comprises a silicide from the group consisting of nickel silicide,
chromium silicide, iron silicide, and manganese silicide.
17. The method of claim 13 wherein the metallic coating exerts
inwardly-directed pressure on the particle.
18. The method of claim 17 wherein the inwardly-directed pressure
at least equals one giga-Pascal.
19. The method of claim 13 wherein the metallic coating has a
thermal expansion coefficient that is at least twice the thermal
expansion coefficient of the carbon-containing sp3-bonded solid
refractory nanocrystallite particle.
20. The method of claim 19 wherein conformally forming a metallic
coating around each of the particles comprises using one of spark
plasma and chemical vapor deposition processing to form the
metallic coating around each of the particles to thereby form the
variable potential junction.
21. The method of claim 13 wherein conformally forming a metallic
coating around each of the particles comprises forming a mixture of
a plurality of differing polytypes of the carbon-containing
sp3-bonded solid refractory nanocrystallite particles.
22. The method of claim 13 further comprising: doping the
carbon-containing sp3-bonded solid refractory nanocrystallite
particles with a doping material.
23. The method of claim 22 wherein the doping material comprises at
least one of aluminum, boron, and nitrogen.
24. The method of claim 13 wherein the plurality of particles and
the metallic coating in combination are comprised of X atoms, and
wherein forming the variable potential junction comprises forming
an interfacial region made up of atoms that comprise at least about
ten percent of X.
Description
RELATED APPLICATION(S)
[0001] This application is a continuation-in-part of and claims
benefit of U.S. patent application Ser. No. 12/297,979 filed on
Oct. 21, 2008, which is the U.S. national phase of International
Application No. PCT/U.S.07/67297 filed Apr. 24, 2007, which is a
continuation of U.S. patent application Ser. No. 11/674,810 filed
on Feb. 14, 2007 that issued as U.S. Pat. No. 7,718,000 on May 18,
2010, which is a continuation-in-part of U.S. patent application
Ser. No. 11/380,283 filed on Apr. 26, 2006 that issued as U.S. Pat.
No. 7,572,332 on Aug. 11, 2009, which claims the benefit of U.S.
Provisional Patent Application No. 60/725,541 filed Oct. 11, 2005,
all of which are hereby incorporated herein by reference in their
entirety.
TECHNICAL FIELD
[0002] This invention relates generally to nanocrystallite
particles as well as to thermoelectric, nuclear, medical, and other
materials and practices.
BACKGROUND
[0003] The direct conversion of thermo energy into electrical
energy (without the use of rotating machinery) is known in the art.
This technology typically finds little practical application,
however, as presently achievable conversion efficiencies are quite
poor. For example, while such mechanisms as steam turbines are
capable of conversion efficiencies in excess of about 50%, typical
prior art direct conversion thermoelectric energy (TE) techniques
offer only about 5 to 10% conversion efficiencies with even the
best of techniques yielding no more than about 14% in this
regard.
[0004] TE technologies generally seek to exploit the thermo energy
of electrons and holes in a given TE material to facilitate the
conversion of energy from heat to electricity. An expression to
characterize the maximum efficiency for a TE power generator
involves several terms including the important dimensionless figure
of merit ZT. ZT is equal to the square of the Seebeck coefficient
as multiplied by the electrical conductivity of the TE material and
the absolute temperature, as then divided by the thermo
conductivity of the TE material. With a ZT value of about 4, a
corresponding TE device might be expected to exhibit a conversion
efficiency approaching that of an ideal heat-based engine. Typical
excellent state of the art TE materials (such as Bi2Te3--Bi2Se3 or
Si--Ge alloys), however, have ZT values only near unity, thereby
accounting at least in part for the relatively poor performance of
such materials.
[0005] To reach a value such as 4 or higher, it appears to be
useful to maximize the power factor while simultaneously minimizing
the thermo conductivity of the TE material (where the power factor
can be represented as the product of the square of the Seebeck
coefficient and the electrical conductivity). This has proven,
however, a seemingly intractable challenge. This power factor and
thermo conductivity are transport quantities that are determined,
along with other factors, by the crystal and electronic structure
of the TE material at issue. These properties are also impacted by
the scattering and coupling of charge carriers with phonons. To
maximize TE performance, these quantities seemingly need to be
controlled separately from one another and this, unfortunately, has
proven an extremely difficult challenge when working with
conventional bulk materials.
BRIEF DESCRIPTION OF THE DRAWINGS
[0006] The above needs are at least partially met through provision
of the method and apparatus pertaining to nanoensembles having
integral variable potential junctions described in the following
detailed description, particularly when studied in conjunction with
the drawings, wherein:
[0007] FIG. 1 comprises a flow diagram as configured in accordance
with various embodiments of the invention;
[0008] FIG. 2 comprises a schematic perspective view as configured
in accordance with various embodiments of the invention;
[0009] FIG. 3 comprises a schematic perspective view as configured
in accordance with various embodiments of the invention;
[0010] FIG. 4 comprises a flow diagram as configured in accordance
with various embodiments of the invention;
[0011] FIG. 5 comprises a flow diagram as configured in accordance
with various embodiments of the invention;
[0012] FIG. 6 comprises a flow diagram as configured in accordance
with various embodiments of the invention;
[0013] FIG. 7 comprises a flow diagram as configured in accordance
with various embodiments of the invention;
[0014] FIG. 8 comprises a side-elevational schematic view as
configured in accordance with various embodiments of the
invention;
[0015] FIG. 9 comprises a side-elevational schematic view as
configured in accordance with various embodiments of the
invention;
[0016] FIG. 10 comprises a side-elevational schematic view as
configured in accordance with various embodiments of the
invention;
[0017] FIG. 11 comprises side-elevational schematic view as
configured in accordance with various embodiments of the invention;
and
[0018] FIG. 12 comprises a block diagram as configured in
accordance with various embodiments of the invention.
[0019] Skilled artisans will appreciate that elements in the
figures are illustrated for simplicity and clarity and have not
necessarily been drawn to scale. For example, the dimensions and/or
relative positioning of some of the elements in the figures may be
exaggerated relative to other elements to help to improve
understanding of various embodiments of the present invention.
Also, common but well-understood elements that are useful or
necessary in a commercially feasible embodiment are often not
depicted in order to facilitate a less obstructed view of these
various embodiments of the present invention. It will further be
appreciated that certain actions and/or steps may be described or
depicted in a particular order of occurrence while those skilled in
the art will understand that such specificity with respect to
sequence is not actually required. It will also be understood that
the terms and expressions used herein have the ordinary meaning as
is accorded to such terms and expressions with respect to their
corresponding respective areas of inquiry and study except where
specific meanings have otherwise been set forth herein.
DETAILED DESCRIPTION
[0020] Generally speaking, pursuant to certain of these various
embodiments, one provides carbon-containing sp3-bonded solid
refractory nanocrystalline particles that are each sized no larger
than about 100 nanometers. By one approach this can comprise
providing nanocrystalline diamond material that comprises a
plurality of substantially ordered diamond crystallites that are
each sized no larger than about 100 nanometers. One then disposes a
non-diamond component within the nanocrystalline diamond material.
By one approach this non-diamond component comprises an electrical
conductor that is formed at the grain boundaries that separate the
diamond crystallites from one another. The resultant nanowire is
then able to exhibit a desired increase with respect to its ability
to conduct electricity while also preserving the thermo
conductivity behavior of the nanocrystalline diamond material.
[0021] The nanocrystalline diamond material may comprise, for
example, nanocrystalline diamond film, bulk nanocrystalline diamond
material, and so forth. The non-diamond component can comprise, for
example, one or more of disordered and defected carbon, defected
graphite crystallites that are sized no larger than about 100
nanometers, and pristine or defected carbon nanotubes.
[0022] By one approach the nanocrystalline diamond material can be
doped to achieve n or p-type deposits that further enhance a
desired level of electrical conductivity. This doping can be
inhomogeneously achieved if desired. It is also possible, if
desired, to achieve inhomogeneous sp2/sp3 distributions as pertains
to the nanocrystalline diamond and the non-diamond component.
[0023] Also pursuant to various of these embodiments, one provides
disperse ultrananocrystalline powder material that comprises a
plurality of substantially ordered crystallites that are each sized
no larger than about 100 nanometers. One then reacts these
crystallites with a metallic component. The resultant nanocarbon
encapsulated nanowires or quantum dots are then able to exhibit a
desired increase both with respect to an ability to conduct
electricity and in the density of states leading to an increase in
thermo power while also preserving close to the thermo conductivity
behavior of the disperse ultra-nanocrystalline diamond material
itself.
[0024] The disperse ultra-nanocrystalline diamond powder material
may comprise, for example, bulk disperse diamond powder having a
very low density as compared to diamond's density. The reaction
process is preceded, for example, by combining the crystallites
with one or more metal salts in an aqueous solution and then
heating that aqueous solution to remove the water. This heating can
occur in a reducing atmosphere (comprising, for example, hydrogen
and/or methane) to reduce the metal ions in the solution to the
metallic state. The reaction process carried out at a higher
temperature involves the conversion of part of the diamond to form
fullerenic, graphitic, or carbon nanotube encapsulates of
nanoparticles of metal. In this way a nanoporous nanocomposite is
formed that is stable to temperatures at least up to 1000 degrees
C.
[0025] By one approach this reaction of the crystallites with a
metallic component can comprise inhomogeneously combining the
crystallites with the metal salt(s) in the aqueous solution. This,
in turn, can yield a resultant thermoelectric component having an
inhomogeneous concentration of metal between a so-called hot and
cold terminus of the thermoelectric component. Combining different
metal salts in the same solution results in alloy formation during
the reduction step.
[0026] Also pursuant to these teachings a plurality of
carbon-containing sp3-bonded solid refractory nanocrystalline
particles (such as silicon carbide particles), each sized no larger
than about 100 nanometers, can have a metallic coating conformally
formed thereabout to thereby form a corresponding variable
potential junction between the metallic coating and the particle.
So configured, this variable potential junction enables carrier
entropy to be efficiently transported to the metallic coating.
[0027] By one approach this metallic coating has a thermal
expansion coefficient that is at least twice the thermal expansion
coefficient of the carbon-containing sp3-bonded solid refractory
nanocrystalline particles. By employing a spark-plasma process to
form the described metallic coating, both the particles and the
coating experience very high temperatures. Accordingly, as the
coated particles cool, the differing thermal expansion coefficients
cause the metallic coating to exert inwardly-directed pressure on
the particle of considerable magnitude. This pressure can equal or
exceed, for example, one giga-Pascal. This pressure aids, in turn,
in causing each particle to comprise a mixture of a plurality of
differing polytypes of the carbon-containing sp3-bonded solid
refractory nanocrystalline material that contributes to the
suitability of this material as a TE material.
[0028] So configured, these teachings appear able to yield
appreciable quantities of a material having properties well suited
to TE power generation. It appears reasonable, for example, to
expect such materials to exhibit a level of conversion efficiency
that compares well against existing non-TE approaches. This, in
turn, presents the possibility and hope of providing improved TE
power generators not only in situations where TE generation is
already used but as a substitute for existing
rotating-machinery-based power generation. Those skilled in the art
will also appreciate that these teachings can be readily applied to
obtain a resultant product having essentially any shape or form
factor as desired.
[0029] At least some of these teachings also appear able to yield
appreciable quantities of a material well suited as a fuel and
cladding in a "pebble bed" type gas cooled nuclear reactor. Those
skilled in the art will also recognize and understand that these
teachings similarly appear well suited for medical applications and
in particular for radiation-based cancer treatments
[0030] These and other benefits may become clearer upon making a
thorough review and study of the following detailed description.
Referring now to the drawings, and in particular to FIG. 1, an
illustrative corresponding process 100 begins with provision 101 of
nanocrystalline diamond material comprising a plurality of
substantially ordered (and preferably self-assembled) diamond
crystallite particles each sized no larger than about 100
nanometers. This material might also comprise occasional
larger-sized particles, of course, but should nevertheless be
substantially if not exclusively comprised of particles of about 1
to 100 nanometers in size
[0031] By one approach this nanocrystalline diamond material can
comprise nanocrystalline diamond film. By another approach this
nanocrystalline diamond material can comprise bulk nanocrystalline
diamond material. Further description regarding both of these
approaches will be provided further below
[0032] This process 100 then provides for disposing 102 a
non-diamond component within the nanocrystalline diamond material.
By one approach this non-diamond component comprises at least one
of disordered and defected carbon, defected graphite crystallites
each sized no larger than about 100 nanometers, and/or at least
singly-walled (or multi-walled) pristine or defected carbon
nanotubes. There are various ways by which this step can be carried
out as well and further details in this regard are also set forth
further below.
[0033] By one approach these teachings can be employed to yield
superlattice nanowires (having a width, for example, of no greater
than about 40 nanometers and an aspect ration exceeding ten to one
or even 100 to one) comprised of such materials. As will be
illustrated below, each such nanowire can itself be comprised of
nanocrystalline diamond that presents itself as helically arranged
diamond nanocubes with the aforementioned non-diamond component
being disposed between the grain boundaries of such diamond
nanocubes
[0034] As mentioned above, the nanocrystalline diamond can comprise
a nanocrystalline diamond film. By one approach, the
above-mentioned non-diamond component in the form of single-wall
and/or multi-wall carbon nanotubes are conformally coated with n or
p-type nanocrystalline diamond. As noted above, the formation of n
or p-type nanocrystalline diamond is known in the art. By one
approach, an Astex PDS 17 vapor deposition machine serves to
generate a microwave plasma in a gas that comprises about 1% C60 or
other hydrocarbon of interest (such as CH4) and 99% argon to which
either nitrogen (for n-type doping) or trimethylboron (for p-type
doping) has been added. A small amount of oxygen containing species
can also be introduced, if desired, to aid with reducing soot
formation.
[0035] To illustrate further, nanocrystalline diamond having n-type
deposits can be prepared using a mixture of argon, nitrogen (about
20% by volume), and CH4. The nitrogen content in the synthesis gas
produces highly aligned, oriented, and textured nanocrystalline
diamond formations on the carbon nanotubes. Resultant electrical
conductivity can be increased by using and controlling high
temperature annealing in a vacuum furnace where the latter serves
to graphitize the disordered carbon at the grain boundaries of the
nanocrystalline diamond grains and to induce transformation of
three layers of (111) nanocrystalline diamond into two (002)
graphitic layers. Both graphitic layers result in the introduction
of narrow electronic peaks near or at the Fermi level into the
density of states. If desired, by establishing a temperature
gradient in the vacuum furnace, inhomogeneous graphitization can be
induced.
[0036] The useful orientation imposed on the nanocrystalline
diamond by the nitrogen is due, it is believed, to changes in the
alpha parameter (i.e., the ratio of growth velocities of different
diamond crystal directions). Relatively high growth temperatures as
employed pursuant to these teachings strongly enhance texture that
results in a profound conformational transformation that may be
characterized as a helix comprised of nanocrystalline diamond
crystallites possessing a cubic habit. By increasing the growth
temperature by about 300 degrees centigrade (as compared to a prior
art value of about 800 degrees centigrade) the alpha parameter is
decreased from a more typical value that is larger than unity to a
value that is essentially equal to unity. This, in turn, tends to
lead to a crystal habit that is a perfect cube which in turn
facilitates the self-assembling self-ordering creation of the
previously mentioned helix configuration
[0037] Referring to FIG. 2, an exemplary illustrative nanowire 201
may comprise a single helix of diamond nanocubes 201 having the
aforementioned non-diamond components at the grain boundaries 203
between such diamond nanocubes. Those skilled in the art will
appreciate that the nanowire 201 depicted has a length that is
shown arbitrarily short for the sake of illustrative clarity. In an
actual embodiment this nanowire 201, though perhaps only 10 to 20
nanometers in width, can be hundreds (or even thousands) of
nanometers in length.
[0038] Those skilled in the art will further recognize and
appreciate that such ordering is quite the opposite of the random
orientation that one typically associates with prior art
nanocrystalline diamond procedures and materials. It is believed
that, at least in theory, this ordered construction should account
for a 10 times or better improvement with respect to electrical
conductivity as compared to a non-ordered construction.
[0039] Those skilled in the art will further understand and
appreciate that each diamond nanocube 202 comprises a lattice
structure. Accordingly, when these nanocubes 202 self-order
themselves in the ordered helical structure shown, the resultant
ordered and arranged structure can properly be viewed as a
superlattice nanowire.
[0040] With reference now to FIG. 3, it is also possible for these
teachings to result in the self-assembly and self-ordering of
diamond nanocubes as a double helix nanowire 301 where, again,
non-diamond components such as disordered and defected carbon,
defected graphite crystallites, and/or carbon nanotubes are
disposed at the grain boundaries of these diamond nanocubes.
[0041] It is believed that post-growth relatively high temperature
annealing further aids to bring about the above-described carbon
structures and in particular a second helix of graphitic or
otherwise conductive nanowires that are covalently bonded to the
helix of nanocrystalline diamond material. Those skilled in the art
will appreciate that a relatively wide range exists for the
manipulation of electronic structures such as p-n junctions as both
the nanocrystalline diamond and the non-diamond component helices
can be separately and independently formed with n or p-type
deposits. As both the helices and the nanotubes are covalently
bonded to each other, efficient electron transport between these
helices and nanotubes is easily facilitated.
[0042] A transition metal catalyst such as ferrocene or iron
trichloride can be continuously added throughout the synthesis
process. This so-called floating catalyst methodology aids with
ensuring that simultaneous growth of the nanocrystalline diamond
and of the carbon nanotubes occurs throughout the resultant thick
film(s). The ratio of nanocrystalline diamond to carbon nanotubes
can be at least partially controlled by adjusting the
catalyst-to-carbon ratio. The latter may be accomplished, for
example, by controlling the rate and/or quantity of catalyst
introduced into the process.
[0043] By one approach, the Astex PDS 17 machine is modified to
include a ferrocene transpiration apparatus comprising a tube
having segmented, differentially heated zones that allow the
establishment of a temperature gradient between the catalyst bed
and the Astex PDS 17 reaction chamber. Adjustment of the
temperature in this way produces locally useful ferrocene vapor
pressures.
[0044] A small positive bias of a few volts can be applied to the
substrate during growth to facilitate the extraction of negatively
charged C2 species from the aforementioned plasma. Such components
will react with the carbon nanotubes to effect alteration of the
electronic structure of the latter. The magnitude of the bias can
be controlled to thereby select for specific structural carbon
nanotube alterations via this reaction.
[0045] By one approach n-type nanocrystalline diamond can be formed
using N2/Ar/PH3/CH4 mixtures. This approach will place phosphorous
in the nanocubes and also in the grain boundaries themselves with a
given corresponding distribution ratio between these two points of
reference. Phosphorus in the grain boundaries will tend to enhance
the formation of pi-bonded carbon (much like nitrogen) and will
also promote (111) texturing. In addition, p doping of the diamond
nanocubes will occur primarily due to boron substitution for carbon
in the diamond material.
[0046] The presence of phosphorous in the diamond nanocubes and in
the grain boundaries will simultaneously provide two different
mechanisms for enhancing the density of states at the Fermi level,
thus increasing the Seebeck coefficient for this material. In
particular, in the grain boundaries, pi-bonded disordered carbon
due to the presence of the phosphorous gives rise to a new
electronic state. In addition, substitutional phosphorous in the
diamond nanocubes themselves introduces a doping level situated
about 0.6 ev below the diamond conduction bands. This level
introduces new electronic states and contributes to conductivity
particularly at the higher temperatures envisioned for
thermoelectric application of these materials.
[0047] By one approach p-type nanocrystalline diamond can be formed
using AR/B2H6/CH4 or Ar/B2H6/CH4/N2 mixtures using plasma enhanced
chemical vapor deposition techniques as are known in the art. Using
this approach boron will be situated in both the diamond nanocubes
and in the grain boundaries themselves. Concentrations between
these two locations will again be determined by a corresponding
distribution coefficient. When both N2 and B are present,
compensation between n and p-type behavior in the grain boundaries
will tend to occur. The behavior of B doped nanocrystalline diamond
will be largely equivalent to that of p doped nanocrystalline
diamond in that both will behave as semiconductors or semimetals
depending on the concentration of the dopant.
[0048] Boron doping of nanocrystalline diamond introduces states
near the Fermi level. As a result, the simultaneous presence of
states near the Fermi level as introduced by defects in the carbon
grain boundaries (or, for example, in graphitic nanowires when
present) provides a powerful methodology for manipulating the
states that control the magnitude of the Seebeck coefficient in
ways not available by any other known materials system. Much the
same occurs when considering the aforementioned n doped
nanocrystalline diamond.
[0049] So configured, the electrically conducting but thermally
insulating conformal coating of nanocrystalline diamond on the
non-diamond component also presents high carrier concentrations of
10+19 to 10+20 per cubic centimeter. Being covalently bonded to,
for example, a carbon nanotube-underpinning, the nanocrystalline
diamond injects carriers into the carbon nanotubes which, upon
reaching the end of a particular carbon nanotube, returns to the
nanocrystalline diamond which then transports those carriers to the
next carbon nanotube in the thick film deposit. An apt analogy
might be a relay race being run by alternatively fast and slow
runners with the baton comprising an electron that is moving
through a thermal gradient as is imposed on this material.
[0050] As mentioned above, the carbon-containing sp3-bonded solid
refractory nanocrystalline material can also comprise bulk
nanocrystalline material if desired. For example, ultradispersed
diamond crystallites (as may be formed, for example, using
detonation techniques) are commercially available in bulk form
having particles sized from about 2 to 100 nanometers. More
particularly, coupons are available that are comprised of
ultradispersed diamond crystallites and single-wall or multi-wall
carbon nanotubes.
[0051] With this in mind, and referring now to FIG. 4, a
corresponding process 400 begins with providing 401 such a
composite material and then exposing the carbon nanotubes to a mass
and energy selected beam of negatively charged C2 molecules. This
may comprise use, for example, of either photofragmentation or
electron bombardment of C60 in order to produce the desired states
at the Fermi level that are responsible for the desired high
resultant Seebeck coefficients.
[0052] As a next step, this process 400 reacts 403 both the
nanocrystalline diamond material and the carbon nanotubes in
appropriate amounts with one or more monomers. Depending upon the
monomer employed, the monomer will react with the composite
material to produce n or p-type deposits. For example, when the
monomer comprises an organic azide that attaches covalently at a
nitrogen site n-type deposits will result. As another example, when
the monomer comprises an organoboron monomer (in particular, an
organoboron monomer that is capable of forming conducting
functionalized polyacetylenes such as, but not limited to,
mesitylborane, 9-borabicyclo[3.3.1]noane, and the like) that
attaches at a boron site p-type deposits will result. By one
approach, ultrasonic techniques are employed to facilitate coating
substantially each nanocrystalline diamond and carbon nanotube with
the monomer of choice.
[0053] This process 400 then provides for converting 404 the
monomer(s) to an electrically conductive polymer such that the
composite material is now substantially coated with the resultant
polymer. Such polymerization can be achieved, for example, via
pulsed plasma chemical methods or by use of other traditional
catalyzed chemical reactions. By one approach, the resultant
polymer comprises a functionalized polyacetylene.
[0054] As a next step one processes 405 the composite material and
polymer coating to form the aforementioned non-diamond component.
By one approach this comprises heating the composite/polymer
material at high pressures to decompose the organic constituents
and to induce incipient sintering. This procedure will lead to the
formation of the previously described electrically conducting grain
boundaries between the diamond crystallites that conformally coat
the carbon nanotubes.
[0055] It would also be possible to initially provide a
nanocrystalline diamond material that already includes n or p-type
deposits. For example, boron or phosphorous can be added when
forming such material using detonation techniques. A conducting
compact is made by reacting the doped nanocrystalline diamond power
with a C2 containing microwave plasma. The electrical conductivity
can be further enhanced by partial graphitization of the compact at
high temperatures.
[0056] As another approach, n or p-type nanocrystalline diamond can
be prepared by mixing nanocrystalline diamond powder with nitrogen,
boron, or phosphorous containing monomer molecules that are
subsequently polymerized (with 5 to 10% of the total volume of the
composite result being the resultant polymer). This polymer will
act as a matrix to provide mechanical rigidity to a sheet that is
then heated about 800 degrees centigrade while being exposed to a
C2 containing microwave plasma. The C2 will react with the
pyrolyzed polymer which in turn becomes a grain boundary bonding
the nanocrystalline diamond particles into an n or p-type compact.
Electrical conductivity can then be further enhanced by use of post
plasma high temperature processing.
[0057] In some cases these teachings may further accommodate
post-synthesis processing that serves to establish inhomogeneous
sp2/sp3 distributions of segmented nanocrystalline
diamond/nanographitic nanowires. Such structures have been shown
theoretically likely to provide conditions under which these
nanomaterials can function as reversible thermoelectric materials
and reach considerably improved figures of merit and conversion
efficiency. This inhomogeneous sp2/sp3 distribution can be caused,
for example, by imposing a temperature gradient as described above
in the vacuum furnace.
[0058] Those skilled in the art will recognize that a wide variety
of modifications, alterations, and combinations can be made with
respect to the above described embodiments without departing from
the spirit and scope of the invention, and that such modifications,
alterations, and combinations are to be viewed as being within the
ambit of the inventive concept. To illustrate, n and p-type
nanocrystalline diamond can also be prepared by adding elements
such as sulfur, lithium, aluminum, and so forth. Such dopants can
substitute for carbon in volumetrically expanded grain boundaries
(with those skilled in the art recognizing that such dopants will
likely not be suitable substitutes in the diamond lattice itself).
These possibilities exist in large part owing to the opportunity
presented by the volumetrically expanded ubiquitous grain
boundaries that tend to characterize at least certain of these
teachings.
[0059] As another illustrative example in this regard, the
above-described superlattice nanowires can be obtained separate
from the substrate on which they are formed by dissolution of the
substrate. These nanowires can be separated from the supernatant by
filtration or centrifugation. The separated diamond nanowires can
then be reacted with nanotubes to produce TE materials. Those
skilled in the art will appreciate, however, that many other uses
are also possible such as electron emitters for flat panel displays
or for thermionics. In biological applications, after surface
derivatization, biological molecules (such as, but not limited to,
DNA, enzymes, and so forth) can be attached to the nano-diamond
rods. These biologically active nano-diamond rods can then be
injected, for example, into biological tissue for purposes of drug
delivery, biological sensing, and so forth.
[0060] As yet one more illustrative example in this regard,
nanocrystalline diamonds and carbon nanotube composites can be
formed by thermal processing of appropriately functionalized
dispersed nanocrystalline diamonds and carbon nanotubes such as
(but not limited to) a mixture of hydrogen terminated dispersed
nanocrystalline diamond and hydroxylated carbon nanotubes.
[0061] Referring now to FIG. 5, another illustrative process 500 as
corresponds with these teachings begins with provision 501 of
refractory nanocrystalline powder material comprising a plurality
of substantially ordered crystallites each sized no larger than
about 100 nanometers. This material might also comprise occasional
larger-sized particles, of course, but should nevertheless be
substantially if not exclusively comprised of particles of about 1
to 100 nanometers in size.
[0062] By one approach this refractory nanocrystalline powder
material can comprise bulk disperse ultra-nanocrystalline diamond
material as referred to above. Again, such powder will typically
comprise a disperse diamond powder having a very low density as
compared to diamond's density. This very low density might
comprise, for example, only about one fourth or even only about one
tenth of diamond's density.
[0063] This process 500 then provides for reacting 502 these
crystallites with a metallic component. Various metals will serve
in this regard, though cobalt may be particularly useful for TE
application settings (where those skilled in the art will
appreciate that other metals, including 3D, 4D, 5D, 4F, and/or 5F
series of elements could be similarly employed if desired). These
teachings will also accommodate, if desired, reacting 502 these
crystallites with a plurality of different metallic components
comprising a metallic alloy component. By one approach, this step
can comprise reacting the crystallites with a metallic component to
thereby form nanocarbon encapsulated electrically conductive
nanowires (and/or quantum dots) that are comprised of that metal or
a corresponding metal carbide (for the sake of simplicity, many
further references to the metal or metal carbide portion of such
nanowires/quantum dots will refer only to "metal," with those
skilled in the art understanding that both metal and metal carbide
are necessarily included in such references). This step can also
comprise, if desired, forming nanotubes, at least in part, of these
crystallites.
[0064] Those skilled in the art will recognize and appreciate that
such an approach can serve to form a material having high
electrical conductivity, high thermo power, and low thermal
conductivity while being protected from agglomeration and other
reactions. Such properties, of course, are of great interest
particularly in thermoelectric settings. It will also be seen that
these teachings are readily usable to form such material in any of
a wide variety of particular predetermined shapes (including simple
geometric shapes as well as more complicated and/or convoluted
shapes of choice).
[0065] These teachings will accommodate reacting these crystallites
with a metallic component using any of a variety of approaches as
desired. For the purposes of illustration and example, and not by
way of limitation, some particular approaches in this regard will
now be presented. Such approaches could involve among others using
an aqueous solution of the metallic salt, ultrasonication of
disperse ultrananocrystalline diamond with a metal oxide powder, or
thermal decomposition of an organometallic compound on a bed of
disperse ultrananocrystalline diamond.
[0066] Referring to FIG. 6, this can comprise, for example,
combining 601 these crystallites with at least one metal salt in an
aqueous solution. Generally speaking it may be useful for most
application settings to use a salt that exhibits a relatively high
solubility in water (or alcohol, if desired) to thereby achieve a
relatively highly concentrated solution (of, say, between five and
ten moles per liter of the salt). As one example in this regard,
the metal salt might comprise cobalt nitrate (taken twice
bivalent).
[0067] Exact proportions of these materials can vary with the
application setting and the specific intended result. By one
approach, however, this can comprise making a five molar solution
of this cobalt nitrate in water and then combining this solution
with a sufficient amount of the disperse ultra-nanocrystalline
diamond material to permit, generally speaking, one cobalt atom to
be absorbed on essentially every exposed carbon atom on the exposed
surface of the diamond material. Generally speaking, the size of
the metallic nanowires/quantum dots as are formed by these
processes can be effectively controlled, at least in part, by
controlling the concentration of this salt in the aqueous
solution.
[0068] Those skilled in the art will recognize and understand that
the disperse ultrananocrystalline diamond material offers,
relatively speaking, a relatively high quantity of such exposed
surface opportunities. Material such as that suggested above, for
example, can offer between 500 and 1,000 square meters of such
surface area for each gram of this powder. This, in turn, permits a
relatively large quantity of metal salt to be absorbed as
essentially each exposed carbon atom absorbs a corresponding cobalt
atom. At this point in the process, the resultant combination will
comprise a paste-like material having a density that has increased
to about unity.
[0069] As noted earlier, this step can comprise combining the
crystallites with a plurality of different metal salts in the
aqueous solution. Examples might include, but are not limited to,
boron, aluminum, magnesium, iron, nickel, copper, manganese,
uranium, plutonium, europium, gadolinium, and so forth. As will
become clearer below, combinations of such metals will form a
corresponding alloy, thereby rendering these teachings a simple and
elegant technique for making alloys of virtually any desired
composition.
[0070] Optionally, if desired, these teachings will also
accommodate further adding 602 a water based adhesive to the
aqueous solution. As will be understood by those skilled in the
art, such a component will serve to enhance the mechanical
integrity of the aforementioned coating. The particular adhesive
employed in a given setting can of course vary, but
polymethacrylate and polyvinylpyrrolidone (in combination with one
another) will serve well in a variety of application settings.
[0071] In any event, these teachings then provide for heating 603
the aqueous solution to thereby remove at least some of the water.
This can comprise, by one approach, heating the aqueous solution to
at least 600 degrees Centigrade (or even 700 or 800 degrees
Centigrade) until a sufficient quantity of water has been so
removed. By one approach this can comprise removing essentially all
of the water and carrying out the reaction described below.
[0072] This step can also comprise heating the solution in a
reducing atmosphere to thereby also reduce the metal ions to metal.
This can comprise, but is not limited to, use of a reducing
atmosphere comprised substantially (or exclusively) of hydrogen and
methane. By this approach, the nitrate is at least substantially
decomposed, and the oxide reduced to cobalt metal. Those skilled in
the art might recognize such a process as resembling, at a
nano-scale, a kind of smelting process.
[0073] Those skilled in the art will also recognize and understand
that such a process will cause the metal component to become
encapsulated with layers of nanocarbons composed of fullerenes,
graphite, or multi-walled carbon nanotubes. More particularly, the
cobalt in this example will form carbon encapsulated nanowires
and/or quantum dots of cobalt, thereby yielding a highly conducting
nanomaterial composed of disperse ultra-nanocrystalline diamond,
cobalt, and nanocarbons
[0074] This cobalt can also serve as a catalyst for growing
nanotubes during this process. Furthermore, excess methane and
hydrogen in the reducing atmosphere are also conducive to the
growth of nanotubes. Consequently, nanotubes are growing as the
cobalt nanowires are forming to thereby yield a resultant material
comprising diamond, cobalt, and nanotubes tightly intergrown with
one another. The resultant material therefore exhibits high
mechanical rigidity, is relatively highly densified (though still
likely less than half the density of diamond itself, and perhaps as
low as one third diamond's density), is electrically conducting,
and is also thermally insulating.
[0075] Because the diamond component begins as a powder, it is
possible to essentially form and shape these materials as desired
to yield a resultant rigid material having essentially any desired
form factor.
[0076] These teachings will also accommodate inhomogeneously
combining the crystallites with one or more metal salts in the
aqueous solution to thereby yield a resultant material having an
inhomogeneous metal concentration. This, in turn, can serve to
yield a material having an inhomogeneous metal concentration
between a hot and cold terminus of a corresponding thermoelectric
component.
[0077] Referring now to FIG. 7, yet another illustrative process
700 that accords with these teachings will be described. At step
701 of this process 700 one provides a plurality of
carbon-containing sp3-bonded solid refractory nanocrystalline
particles that are each sized no larger than about 100 nanometers.
By one approach, these particles can comprise silicon carbide.
Referring momentarily to FIG. 8, these particles 800 can be
essentially and substantially uniformly sized as practical or
desired or can include a variety of differently-sized particles.
(Although represented here as spheres, it will be also be
understood that these particles 800 can have any of a wide variety
of form factors. It will also be understood that this plurality of
particles 800 can include a variety of differing form factors and
that it is not necessary that the particles 800 all share a common
form factor.)
[0078] By one approach these particles can be relatively pure. By
another approach, and referring now to both FIGS. 7 and 9, at
optional step 702 these carbon-containing sp3-bonded solid
refractory nanocrystalline particles 800 (some or all) can be doped
with a doping material 900. This doping material 900 can vary with
the needs or opportunities that tend to characterize a given
application setting. By one approach, this doping material 900 can
comprise at least one of aluminum, boron, phosphorus or nitrogen. A
useful dopant range, by way of illustration, comprises
10+18-10+21/cm.sup.3.
[0079] In any event, and referring now to FIGS. 7 and 10, at step
703 this process 700 provides for conformally forming a metallic
coating 1000 around each of these particles 800 to thereby form a
variable potential junction between the metallic coating 1000 and
the particle 800 that will enable carrier entropy to be efficiently
transported from the variable potential junction to the coating
1000. As one non-limiting example in these regards, this variable
potential junction can comprise an ohmic junction. Generally
speaking, for many application settings this variable potential
junction can comprise a junction range of from about 0 volts to 1
volt. By one approach this metallic coating 1000 can comprise a
silicide of choice. Useful examples include, but are not
necessarily limited to, nickel silicide, chromium silicide, iron
silicide, and manganese silicide.
[0080] Generally speaking, by one approach, this step 703 comprises
disposing the metal of choice around the particle and then causing
a chemical reaction between these materials to achieve the desired
result. This can comprise, by way of illustration, disposing nickel
around a particle comprising silicon carbide and causing a chemical
reaction to form a resultant coating comprised of nickel silicide
as suggested above. One can vary the ratio of resultant nickel
silicide to silicon carbide to achieve a particular desired
result.
[0081] By one approach the metallic coating 1000 has a thermal
expansion coefficient that is at least twice the thermal expansion
coefficient of the carbon-containing sp3-bonded solid refractory
nanocrystalline particle 800. (By way of illustration, the
above-mentioned nickel silicide has a thermal expansion coefficient
that is thrice the thermal expansion coefficient of silicon
carbide.) By using a spark plasma or chemical vapor deposition
process (both of which are well-understood prior art processes that
require no further elaboration here) to carry out step 703, these
various materials are greatly heated to temperatures ranging from
about 500 degrees Celsius to about 1,500 degrees Celsius depending
upon the process employed. In turn, then, as these materials cool,
they will cool at different rates in accord with their different
thermal expansion coefficients. As a result, and as symbolized in
FIG. 10 by the inwardly-directed arrows denoted by reference
numeral 1001, the metallic coating 1000 exerts tremendous
inwardly-directed pressure on the particle 800. By one approach
this pressure equals or exceeds at least one giga-Pascal.
[0082] This pressure, in turn, aids in causing the
carbon-containing sp3-bonded solid refractory nanocrystalline
particle material to form a mixture of a plurality of differing
polytypes of the carbon-containing sp3-bonded solid refractory
nanocrystalline particle material. By one approach, for example,
there may be upwards of nearly two hundred such differing
polytypes. (The "differences" referred to in these regards will be
understood to refer to geometrically different structural forms and
not differs with respect to stoichiometry.) An increased number of
polytypes, in turn, will contribute to stacking differences that
will contribute to an increased entropy as pertains to the mixing
of electronic and quantum states that arise out of the different
resultant structural sequences (as well as any related
contributions from dopants, if any).
[0083] Depending upon the application setting, the relative size of
these components can be important with respect to assuring that the
desired macroscopic influence on the properties of the resultant
material are achieved. In particular, it can be important that the
particles 800 be no larger than about 100 nanometers in order to
assure that the desired results occur. Generally speaking, for many
application settings and materials and presuming that a given
particle 800 and its corresponding metallic coating 1000 are
comprised, in the aggregate, of X atoms, the aforementioned
variable potential junction as formed during step 703 should be
made up of atoms that comprise at least about ten percent of X.
(For example, in some application settings nine percent may suffice
while in other application settings at least eleven percent may be
more appropriate.)
[0084] In any event, and now referring to FIG. 11, such a process
700 will yield a plurality of encapsulated particles 1100 each
comprising a carbon-containing sp3-bonded solid refractory
nanocrystalline particle 800 having a metallic coating 1000
conformally formed thereabout. For many purposes the material
comprising the metallic coating 1000 will comprise only about five
percent of the material comprising the encapsulated particles
1100.
[0085] So configured, and referring now to FIG. 12, the various
materials described above can be readily applied as a key TE
component. To illustrate, a temperature gradient 1203 based in part
upon a heat source will drive electrons in an n-type block 1201
toward a cooler region, thus creating a current through the
circuit. Holes in a p-type block 1202 flow in the direction of the
current. The resultant current can then be used to power a load
1204, thus providing a TE power generator 1200 that effectively and
efficiently converts thermal energy into electrical energy.
[0086] Other applications for these teachings exist as well. As one
example, these teachings can be employed to produce a material that
can materially facilitate a controlled nuclear reaction. Gas cooled
nuclear reactor designs are ordinarily based primarily on fissile
fuel pellets coated with pyrolitic graphite. One of the factors
limiting the performance of such reactors is heat transfer from the
fissile uranium (plutonium) core to the helium gas coolant. This
limitation can be overcome by applying these teachings to yield
nanometer sized pellets that are clad in a nanocarbon material (or
materials) (simply using nanosized materials, alone, will not
adequately address this problem as the temperatures are so high
that nanosized materials would ordinarily not be expected to remain
nanosized). The elimination of heat transfer limitations in this
application setting would reduce helium pumping requirements
substantially and improve the energy efficiency of "pebble bed"
reactors.
[0087] As another example, these teachings can be employed to yield
a composite that can be used as a delivery mechanism for a medical
procedure. To illustrate, the efficacy of cancer treatment strongly
depends on the degree to which the curative agent reaches cancerous
and only cancerous cells. Ultrananocrystalline
diamond/metal/nanocarbon composites formed via these teachings are
small enough to diffuse through cell membranes. Such composites can
include and be coated with a substance that seeks out cancer cells.
Using a radioactive metal component, requisite radiation doses can
be delivered directly to the interior of the cancer cell to destroy
it in a highly targeted fashion.
[0088] As yet another example in this regard, such composites also
have clear application as a battery energy storage medium or as a
hydrogen storage mechanism for use in a fuel cell. As to the
latter, the metal content can include, for example, one or more of
titanium, magnesium, lanthanum, or the like which will absorb
hydrogen. To illustrate, such a composite can be formed using an
alloy of lanthanum and nickel 5 to yield a resultant material that
will readily serve as a hydrogen sponge as heat is withdrawn. Such
hydrogen can later be recovered by heating this material
[0089] To provide yet another illustrative example in this regard,
such materials and processes can be leveraged with respect to
providing a high density magnetic data storage platform. By using
one or more ferro magnetic particles (i.e., single domain particles
such as iron, cobalt, chromium, nickel, or the like) when forming
such composites, extremely high storage densities can be
anticipated. As one illustrative example in this regard, a ferro
magnetic particle so formed could be magnetized to reflect a
particular data value with that information being recoverable
through laser heating sufficient to release that preferential
magnetization.
[0090] As yet a still further example in this regard, such
materials as are described herein can serve as a Peltier-based
refrigeration source by properly applying and exploiting the colder
side of the temperature gradient that forms upon placing an
electrical potential across such material.
[0091] Other applications of the unique nanocarbon encapsulated
metal or metal carbide nanowires or quantum data are too numerous
to be separately mentioned here but will be readily apparent to
those skilled in the relevant arts.
[0092] Those skilled in the art will recognize that a wide variety
of modifications, alterations, and combinations can be made with
respect to the above described embodiments without departing from
the spirit and scope of the invention, and that such modifications,
alterations, and combinations are to be viewed as being within the
ambit of the inventive concept.
* * * * *