US20090092824A1

US20090092824A1 - Apparatus, methods, and articles of manufacture corresponding to a self-composite comprised of nanocrystalline diamond and a non-diamond component and corresponding to a composite comprised of nanocrystalline diamond, metal, and other nanocarbons that is useful for thermoelectric and other applications

Info

Publication number: US20090092824A1
Application number: US12/297,979
Authority: US
Inventors: Dieter M. Gruen
Original assignee: Dimerond Technologies LLC
Current assignee: Dimerond Technologies LLC
Priority date: 2006-04-26
Filing date: 2007-04-24
Publication date: 2009-04-09
Also published as: EP2015931A2; WO2007127727A2; WO2007127727A3; US20070137684A1; US7718000B2

Abstract

One provides nanocrystalline diamond material that comprises a plurality of substantially ordered diamond crystallites that are sized no larger than about 10 nanometers. One then disposes a non-diamond component within the nanocrystalline diamond material which may comprise an electrical conductor that is formed at the grain boundaries that separate the diamond crystallites from one another. One may also instead react the aforementioned crystallites with a metallic component. The reaction process can comprise 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 also reduce the salt to metal. Metal or metal carbide nanowires and/or quantum dots are produced as a result of the reaction with the ultrananocrystalline diamond. Such material exhibits thermoelectric and other useful properties.

Description

RELATED APPLICATIONS

This application claims benefit from and is a continuation of U.S. Patent application No. 11/674,810 filed on Feb. 14, 2007, which is a continuation-in-part of U.S. patent application Ser. No. 11/380,283, filed on Apr. 26, 2006, both of which are hereby incorporated herein by reference in their entirety.

GOVERNMENT RIGHTS

This invention was made with Government support under Contract No. W-31-109-ENG-38 awarded by the United States Department of Energy. The Government has certain rights in this invention.

TECHNICAL FIELD

This invention relates generally to ultrananocrystalline diamond, metal, and other nanocarbon nanocomposite materials as well as to thermoelectric, nuclear, medical, and other materials and practices

BACKGROUND

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.
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.
To reach a value such as 4 or higher, it appears to be necessary 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.
Bulk diamond materials are also known in the art. As bulk diamond comprises both an outstanding thermo conductor and a superb electrical insulator, bulk diamond is quite unsuited for use as a TE material for at least the reasons set forth above. In more recent times, however, nanocrystalline diamond material (having crystallite sizes of about 2 to 5 nanometers) has been successfully doped to achieve n or p-type electrically conducting material at ambient temperatures of interest while also exhibiting very low thermo conductivity. These characteristics of nanocrystalline diamond material suggest its possible employment as a useful TE material. To date, however, no one has suggested a way to make good upon this possibility and hopes for a useful TE material continue to remain mere unmet aspirations.

BRIEF DESCRIPTION OF THE DRAWINGS

The above needs are at least partially met through provision of the an apparatus, methods, and articles of manufacture corresponding to a self-composite comprised of nanocrystalline diamond and a non-diamond component and corresponding to a composite comprised of nanocrystalline diamond, metal, and other nanocarbons that is useful for thermoelectric and other applications described in the following detailed description, particularly when studied in conjunction with the drawings, wherein:

FIG. 1 comprises a flow diagram as configured in accordance with various embodiments of the invention;

FIG. 2 comprises a schematic perspective view as configured in accordance with various embodiments of the invention;

FIG. 3 comprises a schematic perspective view as configured in accordance with various embodiments of the invention;

FIG. 4 comprises a flow diagram as configured in accordance with various embodiments of the invention;

FIG. 5 comprises a flow diagram as configured in accordance with various embodiments of the invention;

FIG. 6 comprises a flow diagram as configured in accordance with various embodiments of the invention; and

FIG. 7 comprises a block diagram as configured in accordance with various embodiments of the invention.

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

Generally speaking, pursuant to certain of these various embodiments, one provides nanocrystalline diamond material that comprises a plurality of substantially ordered diamond crystallites that are each sized no larger than about 10 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.
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 10 nanometers, and pristine or defected carbon nanotubes.
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.
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 10 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.
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.
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.
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.
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.
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 10 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 10 nanometers in size.
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.
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 10 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.
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.
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.
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.
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.
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. 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× or better improvement with respect to electrical conductivity as compared to a non-ordered construction.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
As mentioned above, the nanocrystalline diamond 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 10 nanometers. More particularly, coupons are available that are comprised of ultradispersed diamond crystallites and single-wall or multi-wall carbon nanotubes.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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 10 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 10 nanometers in size.
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.
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.
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).
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.
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).
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
So configured, and referring now to FIG. 7, the various materials described above can be readily applied as a key TE component. To illustrate, an n-type block 701 of material and a p-type block 702 of material as described above, when subjected to a temperature gradient 703, will provide a voltage potential 704 (as electrons will seek to flow from the warmer area to the cooler area) at corresponding electrodes as shown to thereby provide an effective and efficient TE power generator 700.
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.
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.
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.
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.
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.
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.
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. As but one example in this regard, various other metals other than cobalt (such as, for example, other transition metals such as metals in the iron group, the rare earth group, gadolinium, and europium) are suitable candidates and particularly when considering TE applications.

Claims

1-92. (canceled)

93. An article of manufacture comprising:

diamond nanocrystallites comprising a plurality of substantially ordered diamond crystallites each sized no larger than about 10 nanometers; and

at least one of metal or metal carbide nanowires and quantum dots that are a product formed by reaction with the diamond crystallites.

94. The article of manufacture of claim 93 wherein the metal comprises cobalt.

95. An article of manufacture comprising:

a nanoporous nanocomposite stable to 1000 degrees C. composed of disperse ultrananocrystalline diamond and at least one metal notwithstanding a possible integral presence of at least one of:

nanotubes;

fullerenes; and

graphite.

96. The article of manufacture of claim 95 wherein the at least one metal comprises a metal alloy or metal carbide.

97. The article of manufacture of claim 95 wherein the metal comprises at least one of boron, aluminum, magnesium or a 3D, 4D, 5D, 4F, and 5F series of elements.

98. The article of manufacture of claim 95 wherein the nanotubes are formed in the presence of methane gas with a metal or metal carbide acting as a catalyst for nanotube growth.

99. An article of manufacture comprising:

substantially-pure carbon material nanocrystallites comprising a plurality of substantially-pure carbon material crystallites each sized no larger than about 10 nanometers; and

at least one of metal or metal carbide nanowires and quantum dots that are a product formed by reaction with the substantially-pure carbon material crystallites.

100. The article of manufacture of claim 99 wherein the metal comprises cobalt.