US20110005564A1

US20110005564A1 - Method and Apparatus Pertaining to Nanoensembles Having Integral Variable Potential Junctions

Info

Publication number: US20110005564A1
Application number: US12/860,405
Authority: US
Inventors: Dieter M. Gruen
Original assignee: Dimerond Technologies LLC
Current assignee: Dimerond Technologies LLC
Priority date: 2005-10-11
Filing date: 2010-08-20
Publication date: 2011-01-13
Also published as: US20110147669A1; US8257494B2

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.

Description

RELATED APPLICATION(S)

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

This invention relates generally to nanocrystallite particles 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 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

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:

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;

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

FIG. 8 comprises a side-elevational schematic view as configured in accordance with various embodiments of the invention;

FIG. 9 comprises a side-elevational schematic view as configured in accordance with various embodiments of the invention;

FIG. 10 comprises a side-elevational schematic view as configured in accordance with various embodiments of the invention;

FIG. 11 comprises side-elevational schematic view as configured in accordance with various embodiments of the invention; and

FIG. 12 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 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.
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.
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 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.
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.
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.
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.
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 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
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 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.
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 times 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 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.
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 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.
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.
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.)
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/cm³.
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.
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.
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.
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).
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.)
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.
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.
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.

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.