Abstract: A method for making aluminum nitride whiskers comprising reacting a reactant bed of aluminum, alumina, ammonium chloride, with a metal-containing carbon catalyst in the presence of a nitrogen gas flow, such that a direct nitridation reaction, a carbothermal reaction and a transport species reaction occur concurrently.

Abstract: The invention relates to a continuous process for the preparation of aluminum nitride by the carbonitriding of alumina. According to this process, a reaction that uses alumina, carbon, and a resin that generates carbon by pyrolysis is performed in a methodical reactor. The invention relates to a continuous process for the preparation of aluminum nitride by the carbonitriding of alumina.

Abstract: An aluminum nitride powder comprising polycrystalline particles which have clearly observed grain boundaries, an agglomerated particle size of 0.1 to 100 .mu.m when measured by a particle size distribution analyzer, a tapped bulk density of 0.55 to 2.0 g/cm.sup.3, and a ratio of a number average particle size calculated from a SEM photograph image to a particle size calculated from a BET specific surface area of 1.1 to 3.

Abstract: Disclosed are basic aluminum antiperspirant materials having univalent complex oxoanions (e.g., nitrate); methods of making such materials; antiperspirant compositions containing such basic aluminum materials, another antiperspirant active material (e.g., a basic zirconium halide salt), and optionally a neutral amino acid; and methods of making such compositions. Size exclusion high performance liquid chromatography chromatograms of the disclosed basic aluminum materials have a peak 4 relative area of at least 25%, a peak 3 relative area of less than 60%, the sum of the peaks 3 and 4 being at least 50%; and less than 10% of the chromatographic peaks eluting at peaks 1 and 2. The disclosed basic aluminum materials have less than 25% of the aluminum in the form of Al.sup.b polyhydroxyaquoaluminum, and have a .sup.27 Al NMR spectrum in which the area of the 71.5-73.5 ppm resonance line includes more than 50% of the combined areas of the 62.5-63.5 ppm and 71.5-73.

Abstract: A process and apparatus for making high purity aluminum nitride from organometallic aluminum, such as an alkylaluminum compound. A gaseous alkylaluminum compound and gaseous ammonia are introduced into a heated reaction zone where the gases are mixed and high purity aluminum nitride is produced. The high purity aluminum nitride is collected in the form of a powder or deposited as a thick, dense layer on an appropriate substrate mounted in the reaction chamber. A carrier gas such as hydrogen gas, may be used to conduct the alkylaluminum compound from a suitable reservoir containing liquid alkylaluminum compound to the reaction chamber. A preferred alkylaluminum compound is triethylaluminum.

Abstract: An aluminum-nitrogen polymer is prepared by reacting an organic nitrile with a dialkylaluminum hydride to form an organoaluminum imine, and heating the imine to a temperature of 50.degree. to 200.degree. C. for at least 2 hours. The polymeric product can be subjected to an additional heat treatment to form a more highly cross-linked polymer. After either heat treatment the polymeric product can be further reacted with a primary amine or ammonia. The organoaluminum imine as well as the aminated or non-aminated polymers can be pyrolyzed to form an aluminum nitride-containing ceramic.

Abstract: Aluminum nitride (AlN) is continuously produced by continuously carbonitriding a continuously replenished charge of alumina, for example successive charges of alumina/carbon extrudates, in a reaction zone comprising at least one conduit, the ratio of the exchange surface area/volume of which at least one conduit ranging from 5 to 50 m.sup.-1, preferably from 10 to 50 m.sup.-1, and continuously withdrawing product AlN therefrom.

Abstract: Processes for the direct manufacture of nitride powders suitable for low temperature sintering are provided. An elemental vapor is contacted with a nitriding gas at temperatures between 1400 and 1973 K and atmospheric pressure to produce nitride powder.

Abstract: The invention relates to a continuous process for the preparation of aluminium nitride by the carbonitriding of alumina.According to this process, the reaction, which employs alumina, carbon and nitrogen, is carried out in a moving-bed reactor characterized in that the reaction area has a plurality of conduits.

Abstract: Ultrafine particles of aluminum nitride having a morphologically anisotropic structure of columns, plates, or whiskers such that the ratio of thickness or width to length or the ratio of thickness to width or length of particle is not less than 1 are produced by thermally melting a binary alloy of metallic aluminum and a rare earth element in a nitriding atmosphere containing nitrogen. By this method are produced composite ultrafine particles which substantially comprise ultrafine particles of aluminum nitride having the morphologically anisotropic structure and ultrafine particles of the rare earth nitride which functions as a sintering auxiliary therefor. The composite ultrafine particles or an aggregate thereof are usable as a raw material for the production of a sintered article, a reinforcing material for various metal-based composite materials, a blast powder, and the like.

Abstract: A method of manufacturing a powdery AlN comprising steps of: a) providing an airtight vessel, b) preparing a powdery Al and a solid-state nitride, c) wrapping up the powdery Al and the solid-state nitride with an igniting agent, d) putting the wrapped Al and nitride into the vessel, e) evacuating the airtight vessel and filling therein with an N gas, and f) igniting the igniting agent. Since the powdery Al and solid-state nitride are completely wrapped up with an igniting agent, the reaction can be more rapidly and fully completed under a relatively low pressure. In addition, the present method can be used to obtain an AlN having a high purity.

Abstract: A sinterable aluminum nitride powder composition is prepared by adding about 0.05-10.0 parts by weight of at least one compound selected from the group consisting of calcium tungstate and calcium molybdate and optionally about 1.0-7.0 parts by weight of at least one compound selected from the group consisting of yttria, calcium oxide, and calcium carbonate to 100 parts by weight of an aluminum nitride powder prepared by the alumina reduction method without decarbonization and having a residual carbon content of about 2%-10% by weight. The resulting powdery composition is subjected to mixing and deagglomeration in a dry process so as to form a powder mixture having a bulk density of about 0.3-0.5 g/cm.sup.3, and then to decarbonization by heating in an oxidizing atmosphere. The aluminum nitride powder composition has a pressurized bulk density of about 1.50-1.75 g/cm.sup.3 as measured at a pressure of 500 kg/cm.sup.2 and an average particle diameter of about 1.0-3.0 .mu.

Abstract: This invention provides a process for manufacturing aluminum-nitrogen polymers (i.e., polymers having a backbone of alternating aluminum and nitrogen atoms) in which portions of the polymer have an organic substituent on each aluminum and nitrogen atom. The novel polymers so produced are useful for making green shapes pyrolyzable to AlN articles suitable for high performance applications. The process generally comprises reacting an organic nitrile having the formula R.sup.1 CN with a trialkylaluminum compound having the formula R.sup.2 R.sup.3 R.sup.4 Al, and optionally heating the reaction product, to form an organoaluminum imine, and heating the organoaluminum imine to a temperature of at least 300.degree. C. and less than 600.degree. C. for at least two hours to form an aluminum-nitrogen polymer. The polymer or the imine can be pyrolyzed to form an aluminum nitride ceramic article. In the foregoing formulae, R.sup.

Abstract: A method for producing nitride ceramic powders includes steps of a) providing a powder, b) providing a nitride, c) providing a salt of ammonium halide, d) mixing the powder, the nitride, and the salt to form a reactant, e) wrapping up the reactant with an igniting agent, f) placing the reactant wrapped up with the igniting agent in a vessel, g) evacuating the vessel, h) igniting the igniting agent for initiating a combustion reaction to form the nitride ceramic powders. Such method can permit excellent nitride ceramic powders to be effectively produced.

Abstract: A ceramic material based on Sialon, in particular on .beta.'-Sialon is obtained by reducing an aluminosilicate precursor by means of a gas phase comprising a mixture of hydrogen and nitrogen doped with a gaseous carbon compound. The gaseous carbon compound is a gas containing carbon in combined form, e.g. an alkane, and its concentration by volume in the gas is less than 3%. The method is particularly suitable for forming Sialon-based coatings on substrates that are solid or fibrous. For composite materials constituted by a fiber preform densified by means of a matrix, the method can be used to form an interphase coating on the fibers of the preform prior to densifying the preform, or the method can be used to form a matrix that is based on Sialon.

Abstract: A method of processing water-sensitive ceramic powders, particularly carbothermically produced aluminum nitride, whereby the ceramic powder is deagglomerated in a dry milling step with addition of an alkylamine which is liquid at room temperature is disclosed. The alkylamine is added in an amount sufficient to produce a monomolecular layer on the surface of the ceramic powder. The deagglomerated powder subsequently is vigorously stirred with a concentrated aqueous solution or dispersion of binder and rapidly and gently dried, preferably by freeze drying. Aluminum nitride powder prepared by this process can be further processed into shaped parts with a high thermal conductivity.

Abstract: A metal nitride powder can be made by heating a reactant powder that includes an oxide or hydroxide of Al, Ti, or Zr to a reaction temperature in a nonreactive atmosphere. The heated reactant powder is contacted with a gaseous reactant mixture comprising a nitrogen source and a carbon source. The molar ratio of nitrogen to carbon in the gaseous reactant mixture is at least about 15. The reactant powder is maintained at the reaction temperature for a sufficient time to convert a portion of it to metal nitride powder.

Abstract: Carbothermally reduce a metal oxide to its corresponding metal nitride or metal carbide powder in a vertical gravity flow reactor by adding precursor pellets containing the metal oxide, a thermally decomposed binder material and carbon or a source of carbon directly to a heated reaction zone within the reactor. The pellets form a pellet bed, the top of which must be maintained within the heated reaction zone. The binder material is a blend of wheat and corn starches, optionally in conjunction with another binder such as melamine. The binder material thermally decomposes to a carbonaceous residue which functions both as an additional source of carbon and as a binder for the precursor pellets. The reactor may be modified by adding an internal vent line to remove volatile materials from the heated reaction zone before they have an opportunity to condense on internal reactor surfaces.

Abstract: A process and apparatus for making high purity aluminum nitride from organometallic aluminum, such as an alkylaluminum compound. A gaseous alkylaluminum compound and gaseous ammonia are introduced into a heated reaction zone where the gases are mixed and high purity aluminum nitride is produced. The high purity aluminum nitride is collected in the form of a powder or deposited as a thick, dense layer on an appropriate substrate mounted in the reaction chamber. A carrier gas such as hydrogen gas, may be used to conduct the alkylaluminum compound from a suitable reservoir containing liquid alkylaluminum compound to the reaction chamber. A preferred alkylaluminum compound is triethylaluminum.

Abstract: An aluminum nitride powder that has substantially no ammonia odor after exposure to atmospheric moisture is obtained by admixing the powder with a gettering compound that sublimes or decomposes at a temperature below 500.degree. C. The gettering compound is a C.sub.1 -C.sub.11 aliphatic carboxylic mono- or polyfunctional acid, an anhydride or an ester of such an acid or an anhydride of an aromatic carboxylic acid.

Abstract: Disclosed is a basic aluminum material having enhanced antiperspirant activity, the material having the empirical formula Al.sub.2 (OH).sub.6-a X.sub.a, where 0.5.ltoreq.a.ltoreq.5.0, and X is a univalent complex oxoanion of nitrogen, chlorine and other halogens, which forms salts with Al.sup.3+ in aqueous solution so that these salts are essentially completely dissociated, which is readily soluble in water with metallic ions in the solution, and which forms conjugate acids that are strong acids; and wherein the material is characterized by:(a) size exclusion high performance liquid chromatography peaks corresponding to peak 3 and peak 4 of size exclusion chromatograms formed by HPLC technique;(b) a peak 4 relative area of at least 25%, a peak 3 relative area of less than 60%, the sum of the relative peak 3 and peak 4 areas being at least 50%; and(c) less than 10% chromatographic peaks eluting at shorter retention times than peak 3, corresponding to peaks 1 and 2.

Abstract: A powder mixture of aluminium nitride in the form of sintered agglomerates with fractions of different particle size, which mixture comprises (1) 80 to 50% by weight of aluminium nitride in the form of sintered agglomerates having a mean particle diameter of 30 to 50 .mu.m, and (2) 20 to 50% by weight of aluminium nitride in the form of unsintered particles and having a mean particle diameter of 0.1 to 5 .mu.m. The mixture is suitable for use as filler for polymer materials, especially for casting resins, from which moulded parts of high thermal conductivity can be fabricated, for example potted electronic components.

Abstract: Aluminum-nitrogen polymers comprising a backbone of alternating aluminum and nitrogen atoms both having pendant organic groups, wherein some of the pendant organic groups are unsaturated, are prepared by reacting an unsaturated organic nitrile with a dialkylaluminum hydride. The polymers are crosslinked by supplying energy to generate free radicals. The crosslinked polymers can be pyrolyzed to form an aluminum nitride ceramic.

Abstract: A metal nitride powder can be made by heating a reactant powder that includes an oxide or hydroxide of Al, Ti, or Zr to a reaction temperature in a nonreactive atmosphere. The heated reactant powder is contacted with a gaseous reactant mixture comprising a nitrogen source and a carbon source. The molar ratio of nitrogen to carbon in the gaseous reactant mixture is at least about 15. The reactant powder is maintained at the reaction temperature for a sufficient time to convert a portion of it to metal nitride powder.

Abstract: Aluminum-nitrogen polymers comprising a backbone of alternating aluminum and nitrogen atoms both having pendant organic groups, wherein some of the pendant organic groups are unsaturated, are prepared by reacting an unsaturated organic nitrile with a dialkylaluminum hydride. The polymers are crosslinked by supplying energy to generate free radicals. The crosslinked polymers can be pyrolyzed to form an aluminum nitride ceramic.

Abstract: A process for producing small particles of aluminum nitride suitable for sintering and the particles thus-produced. The process comprises reacting particles of gamma alumina, or a precursor thereof, of less than 1 micron in size with a stoichiometrical excess of finely divided carbon in the presence of nitrogen, or a precursor which provides nitrogen in the reaction conditions, first at a temperature in the range of 1550.degree. to 1700.degree. C. for a period of between 1 and 6 (preferably 1 to 4) hours and then at a temperature in the range of 1750.degree. to 1850.degree. C. for a period of 1 to 4 (preferably 1 to 2) hours, followed by cooling said reaction mixture and reheating to a temperature in the range of 500.degree. to 700.degree. C. in an oxygen-containing atmosphere, and maintaining the temperature until excess unreacted carbon is removed.

Abstract: An aqueous composition containing aluminum nitride powder which exhibits a reduced tendency for hydrolysis of the aluminum nitride contained therein. The aqueous composition comprises (a) a liquid medium containing water, (b) aluminum nitride powder, and (c) a combination of buffering agents which controls the pH of water from about 5.5 to about 7.5, wherein the combination of buffering agents is employed at a lower weight percent concentration than that of the aluminum nitride powder. In another embodiment of the invention, a method of processing aluminum nitride powder in water which exhibits a reduced tendency for hydrolysis of the aluminum nitride is disclosed, which method involves mixing the above-described aqueous composition.

Abstract: A block copolymer is prepared by reacting an aluminum-nitrogen polymer and a silazane polymer at a temperature not greater than 400.degree. C. Block copolymers containing alkenyl or alkynyl groups can be crosslinked by supplying energy to generate free radicals. An AlN/SiC containing ceramic is formed by pyrolyzing the crosslinked block copolymer in a nonoxidizing atmosphere.

Abstract: A process for refining calcium containing aluminum as an impurity in the form CaAl.sub.2. The calcium is nitrided to form Ca.sub.3 N.sub.2, and that Ca.sub.3 N.sub.2 is made to react with CaAl.sub.2 initially present and with the particulate aluminum in such a manner as to form calcium, which is isolatable in the form of high-purity calcium containing less than 0.1% by weight of aluminum, and aluminum nitride.

Abstract: For producing finely disperse aluminum nitride by reacting hydroxides of aluminum with carbon in a molar ratio of (1:1.5) to (1:2.5), the hydroxides of aluminum are intensively ground together with carbon, in particular carbon black, using a non-aqueous grinding fluid. After the non-aqueous grinding fluid has been separated off from the suspension, the ground material obtained is calcined at 400.degree. to 1000.degree. C., while passing nitrogen through. The material obtained is then treated under intensive contact with nitrogen for 1 to 100 hours at 1400.degree. to 1700.degree. C., before the excess carbon contained in the reaction product is removed by heating to 500.degree. to 900.degree. C. in contact with oxygen-containing gases.The hydroxides of aluminum and the carbon can also be intensively ground separately from one another, using a non-aqueous grinding fluid, and the suspensions obtained can be mixed.

Abstract: Rapidly heat powdered aluminum, an admixture of powdered aluminum and a compatible solid material, a powdered admixture of alumina and carbon, or aluminum nitride powder having a surface area lower than desired in the presence of a source of nitrogen at a temperature of 2473 to 3073K to produce aluminum nitride, then promptly quench the aluminum nitride product. The product has a surface area of greater than 10 m.sup.2 /g, preferably greater than 15 m.sup.2 /g.

Abstract: A process for preparing fine aluminium nitride (AlN) powder is described using an inorganic flocculant based on polyaluminium chloride (PAC) having the following structural formula:Al.sub.n (OH).sub.m Cl.sub.3n-mwhere n and m are positive whole numbers and n is greater than m/3.

Abstract: A process for producing a sintered AlN ceramic body by mixing an organic solution comprising a hydrocarbon solvent and an organometallic compound with AlN powder to produce a slurry, removing the solvent from the slurry to form a mixture of organometallic compound and AlN, forming the mixture into a shape, and heating the shape in a non-oxidizing atmosphere to sintering temperature to obtain densification.

Abstract: An aluminum nitride structure is prepared by placing an oxygen-trapping substance at at least one position on an aluminum nitride substrate having a first concentration of solution oxygen, and heating the resultant structure in a non-oxidizing atmosphere to locally reduce the first concentration of solution oxygen in said aluminum nitride substrate under said oxygen-trapping substance to a second concentration of solution oxygen by trapping the solution oxygen in the oxygen-trapping substance, thereby forming an aluminum nitride structure in which at least one region of the aluminum nitride structure corresponding to the position of said oxygen-trapping substance, which position has said second oxygen concentration, is integrally formed with aluminum nitride regions having said first concentration of solution oxygen. The aluminum nitride structure of the present invention exhibits anisotropic physical properties.

Abstract: A process for producing unagglomerated single crystals of aluminum nitride of low oxygen content having a size of at least 10 microns suitable for the reinforcement of metal, ceramic and polymeric matrix composite materials, and especially metal matrix materials. The process involves producing a reaction mixture of alumina (or a precursor), carbon (or a precursor), and an alkali metal oxide (or precursor such as a carbonate) as a crystal growth promoter or catalyst. The alkali metal oxide is present in an amount required for the formation of crystals of the required size, preferably in the range of 10-60 microns. The reaction mixture is subjected to a preheating step under nitrogen at a temperature in the range of 1600.degree.-1700.degree. and is then subjected to a heating step under nitrogen at a temperature in the range of 1800.degree.-1950.degree. C. This two-stage heating process ensures that the resulting crystals are of low oxygen content and thus good thermal conductivity.

Abstract: A method and apparatus are provided for producing a product comprising a nitride compound, such as for example silicon nitride. A reactor is provided which has a chamber defined therein which is divided into a combustion zone and a reaction zone. A combustible mixture is injected into the combustion zone in a direction generally toward the reaction zone, and is accordingly combusted in the combustion zone. At least one reactant is injected at the boundary between the zones into the reactor chamber in a direction generally parallel to the longitudinal axis of the chamber so as to react to from raw product comprising the nitride compound. According to another aspect, a raw product powder as produced by the reactor comprises silicon nitride as the nitride compound and further comprises elemental silicon.

Abstract: A process is provided for the preparation of metals, metal carbides, nitrides, borides, silicides, sulfides and phosphides by low temperature pyrolysis of a selected organometallic precursor. The precursor, in addition to containing organic ligands, contains the metal M, which is a transition metal or tin, and the element X (C, N, B, Si, S, or P), which may be bound directly to M, contained within the ligands, or both. The process enables one to provide surface coatings or shaped articles of metals, metal carbides, nitrides, and the like.

Abstract: An aluminum nitride-based sintered product can be produced at a relatively low heating temperature by mixing at least 20% by weight of ultrafine aluminum powder having an average size of not exceeding 0.5 .mu.m with other powdery raw material, compression molding the resultant powdery mixture, and heating the molded article under a nitrogen atmosphere at a heating temperature ranging from 600.degree. to 800.degree. C. to nitride the ultrafine aluminum powder, whereupon the heat of nitridation is utilized to sinter the molded article.

Abstract: Methods are described for preparing aluminum nitride of controllable morphology for ceramic and heat conduction applications. The methods comprise forming spherical particles or flakes of an intermediate, RAlNH, followed by heating the spheres or flakes of RAlNH at elevated temperatures to produce high purity aluminum nitride of corresponding morphology. Spheres of RAlNH are formed by (i) freezing a suspension of RAlNH in a liquid medium and thawing, by (ii) aging the suspension, or by (iii) dissolving RAlNH in a liquid medium and precipitating it. Flakes are formed by freezing a suspension of RAlNH in a liquid medium and removing frozen medium from the frozen suspension.

Abstract: A process for the manufacture of high purity, ultra-fine aluminum nitride powder by the carbo-nitridization of alumina. Agglomerates uniform in both size, chemical composition and porosity are formed containing a stoichiometric mixture of alumina and carbon with the addition of a small amount of catalyst. The agglomerates are furnaced in a controlled manner in a well-mixed reaction vessel to achieve a uniform and consistent level of conversion. Milling of the as-reacted agglomerates under a controlled atmosphere will produce high purity, micron sized aluminum nitride powder.

Abstract: Disclosed is a process for preparing fine powders of aluminum nitride, by starting from an aqueous solution of an inorganic aluminum salt, characterized in that said process comprises the following steps:(a) the anion of the inorganic salt of aluminum is at least partially removed by heating, with a colloidal solution of an aluminum compound being obtained;(b) carbon powder is dispersed in said colloidal solution, with a suspension of an aluminum compound and carbon being obtained;(c) said suspension is mixed with a carbohydrate, with a suspension being obtained of an aluminum compound and carbon in a solution which contains the carbohydrate;(d) the suspension obtained from the (c) step is sprayed onto, or dropwise added to, an alkaline solution, with spherical bodies being obtained, which contain aluminum hydroxide and carbon;(e) said spherical bodies are carbothermally reduced and nitrided at a temperature comprised within the range of from 1350.degree. to 1650.degree. C.

Abstract: A low temperature process is described for forming a coating or powder comprising one or more metals or metal compounds by first reacting one or more metal reactants with a halide-containing reactant to form one or more reactive intermediates capable of reacting, disproportionating, or decomposing to form a coating or powder comprising the one or more metal reactants. When one or more metal compounds are formed, either as powders or as coatings, a third reactant may be injected into a second reaction zone in the reactor to contact the one or more reactive intermediates formed in the first reaction zone to thereby form one or more metal compounds such as metal nitrides, carbides, oxides, borides, or mixtures of same.

Abstract: The present invention relates to a novel method of manufacturing a composite body, such as a ZrB.sub.2 -ZrC-Zr composite body, by utilizing a post-treatment technique which may improve the oxidation resistance of the composite body. Moreover, the invention relates to novel products made according to the process. The novel process modifies at least a portion of a composite body by exposing said body to a source of second metal.

Abstract: Production of composite ceramic articles by infiltration of a particulate, permeable bed or permeable preform with a polycrystalline matrix produced as a metal-oxidant reaction product, wherein the bed or preform is comprised of dross.

Abstract: Lewis base-borane complexes such as (CH.sub.3).sub.2 S.BHBr.sub.2 are utilized as molecular precursors for the formation of both bulk powders, films and coatings of boron nitride. The complexes are subjected to slow heating under an ammonia atmosphere to displace the base and pyrolyze the resulting complex to BN. Analogous processes may be used to prepare Group IIIA-VA compounds of the formula MM' where M is selected from the group consisting of B, Al, Ga, In, and Tl, and M' is selected from the group consisting of N, P, As, Sb and Bi.

Abstract: Rapidly heat powdered aluminum in the presence of a source of nitrogen at a temperature of 1873 to 2373 K. to produce aluminum nitride, then promptly quench the aluminum nitride product. The product has a surface area between 2 and 8 square meters per gram and an oxygen content of less than 1.2 weight percent.

Abstract: A process of producing nitrides of aluminum and titanium. The process involves producing a uniform dispersion of microfine particles of the corresponding metal oxide in an infusible polymer, carbonizing the resulting dispersion in a non-oxidizing atmosphere and heating the carbonized product in a nitrogen atmosphere at high temperature to cause the oxide to react with the carbon and nitrogen to form the nitride. Before carbonization, however, the dispersion is formed into shapes in which none of the oxide particles is more than about 2.5 mm (0.098 inch) from an external surface and the shapes are loosely packed in a reactor. The process can achieve a good conversion of the oxide to the nitride to yield a product of high purity and small particle size.

Abstract: Sinterable crystalline aluminum nitride powder is produced by reacting alkyl aluminum with ammonia in a gas phase to produce an amorphous aluminum nitride presursor powder, and subjecting the precursor powder to a primary calcination in a reducing gas containing at least 20% (vol.) ammonia at 600.degree. C. to 1300.degree. C., and then subjecting the calcined aluminum nitride to a secondary calination in an inert gas or a reducing gas at 1400.degree.-1750.degree. C.

Abstract: A method is disclosed for purifying aluminum nitride produced by carbothermal reaction of aluminum oxide, carbon and nitrogen. Precursor pellets including aluminum oxide and carbon are exposed to nitrogen under conditions sufficient to carbothermally produce aluminum oxide, thereby producing aluminum nitride pellets having surface portions relatively rich in thermal conductivity-lowering and color-causing impurities compared to core portions of the aluminum nitride pellets. Significant amounts of the surface portions are thereafter removed to thereby significantly increase the purity of the aluminum nitride pellets.

Abstract: This invention relates generally to a novel method of preparing self-supporting bodies and to the novel products made thereby. In its more specific aspects, this invention relates to a method of producing self-supporting bodies having controlled porosity and graded properties and comprising one or more boron-containing compounds, e.g., a boride or a boride and a carbide. The method comprises, in one embodiment, reacting a powdered parent metal, in molten form, with a bed or mass comprising a boron carbide material and, optionally, one or more inert fillers, to form the body. In another embodiment, both of a powdered parent metal and a body or pool of molten parent metal are induced to react with a bed or mass comprising a boron carbide material and, optionally, one or more inert fillers. in addition, combustible additives (e.g., gelatin, corn starch, wax, etc.) can be mixed with the bed or mass comprising a boron carbide material to aid in the porisity producing process.