The Dow Chemical Company

William G Moore

Alan W Weimer

Stephen D Dunmead

Bijan Khazai

Raymond P Roach

Kevin E Howard

Glenn A Eisman

John P Henley

William Rafaniello

Kevin C Morse

Gene A Cochran

Theresa A Guiton

Aluminum nitride powder, aluminum nitride platelets, powdered solid solutions of aluminum nitride and at least one other ceramic material such as silicon carbide, and composites of aluminum nitride and transition metal borides or carbides are prepared by combustion synthesis at low gaseous nitrogen pressures. Porous bodies of aluminum nitride or composites of aluminum nitride and transition metal borides or carbides are also prepared by combustion synthesis at these pressures. The porous bodies are suitable for infiltration, either as formed or after being coated with at least one layer of a silicate material, by polymers or metals. The powders are also suitable for preparing dense sintered bodies. The aluminum nitride powder is also used to prepare AlN sintered bodies.

Aluminum nitride, aluminum nitride containing solid solutions and

A method for making submicrometer metallic carbides and submicrometer solid solution metallic carbides from sources of at least one metallic oxide and carbon involves the rapid heating of a reactive particulate mixture of at least one metallic oxide and carbon in order to achieve a resulting particulate size of less than 1 micrometer. Submicrometer sized metallic carbides and solid solution metallic carbides have found great use in commercial ceramic applications. It has been found that the smaller sized particles produce a product having superior toughness and hardness. In addition, the submicrometer sized solid solution metallic carbide resulting from this method is also disclosed.

Method for making submicrometer carbides, submicrometer solid solution

A method for forming monotungsten carbide, comprising heating a solid, non-elemental tungsten-containing material in a flowing atmosphere containing molecular hydrogen and molecular methane for a time sufficient to convert substantially all of the tungsten-containing material to monotungsten carbide, The heating brings the temperature of the tungsten-containing material to a first elevated temperature of from about 520 to about 550.degree. C. and, subsequently, at a rate of from about 3 to about 10.degree. C. per minute, the heating brings the temperature from the first elevated temperature to a second elevated temperature of about 800 to about 900.degree. C. Thereafter the temperature is held at the second elevated temperature for at least about 15 minutes. At least about 50 weight percent of the monotungsten carbide formed is formed while holding the temperature at the second elevated temperature.

Low temperature method for synthesizing micrograin tungsten carbide

A composition and method for producing boron carbide/titanium diboride composite ceramic powders is disclosed. The process comprises the ordered steps of (a) intimately mixing as reactants boron carbide and a titanium source, such that the average reactant particle size is less than about 20 microns and substantially all discrete reactant areas are less than about 50 microns, and (b) reacting the product of step (a) under conditions sufficient to produce a boron carbide/titanium diboride composite ceramic powder wherein at least a portion of the boron carbide particles form substrates to which at least a portion of the titanium diboride particles are attached. The method can be used to produce a composite ceramic powder having boron carbide and titanium diboride particles less than about 20 microns in diameter. This powder can then be densified using known densification techniques to form a densified part wherein the titanium diboride grains have an average size of less than about 20 microns in diameter and the boron carbide grains having an average size of less than about 50 microns.

Composition and method for producing boron carbide/titanium diboride

Process for preparing silicon carbide by carbothermal reduction

Uniform, fine ceramic powder is prepared using an apparatus comprising (a) a cooled reactant transport member; (b) a reactor chamber; (c) a heating means; and (d) a cooling chamber. The reactant transport member comprises a wall defining a conduit that communicates with the reactor chamber, with a gas-flow space being defined along the perimeter of the transport member and in communication with the reactor chamber. The reactor chamber comprises a wall defining a reaction zone, and the heating means is associated with the reaction zone, and adapted for heating reactants in the reaction zone. The cooling chamber comprises a wall defining a cooling zone that communicates with the reactor chamber. In one embodiment the communication is by means of a cooling inlet, the diameter of the cooling zone being larger than the diameter of the cooling inlet. The temperatures of the reactant transport member, the reactor chamber, and the cooling chamber are independently controllable. Reactants can be fed through the reactant transport member into the reaction zone and reacted to form products, and the products then fed into the cooling zone to produce uniform, fine ceramic powders.

Method for producing uniform, fine boron-containing ceramic powders

Metal boride powders can be produced with a predetermined particle size by controlling reaction conditions. The metal boride powder is produced by reacting a solid boron source, a metal source and a reductant under conditions sufficient to produce a metal boride powder with a particle size correlating to that of the solid boron source. The reaction is preferably stopped after the formation of products but before any apprecible crystal growth occurs.

Synthesis of refractory metal boride powders of predetermined particle

A mixture of reactants having a particle size of about 200 microns is heated to convert said mixture comprising a metal compound, carbon, and a boron source to a metal boride having an average particle size of about 0.05 to about 0.5 micron. Said metal compound is one which can be converted to the corresponding metal boride by reaction with carbon and a boron source under controlled conditions of time and temperature.

Process for producing metal borides using finely comminuted mixture of

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.

Process for preparing aluminum nitride powder via controlled combustion

Uniform, fine ceramic powder is prepared using an apparatus comprising (a) a cooled reactant transport member; (b) a reactor chamber; (c) a heating element; and (d) a cooling chamber. The reactant transport member comprises a wall defining a conduit that communicates with the reactor chamber, with a gas-flow space being defined along the perimeter of the transport member and in communication with the reactor chamber. The reactor chamber comprises a wall defining a reaction zone, and the heating element is associated with the reaction zone, and adapted for heating reactants in the reaction zone. The cooling chamber has a wall defining a cooling zone that communicates with the reactor chamber. In one embodiment, the communication is through a cooling inlet, the diameter of the cooling zone being larger than the diameter of the cooling inlet. The temperatures of the reactant transport member, the reactor chamber, and the cooling chamber are independently controllable. Reactants can be fed through the reactant transport member into the reaction zone and reacted to form products, and the products then fed into the cooling zone to produce uniform, fine ceramic powders.

Apparatus for producing uniform, fine ceramic powder

A composition and method for producing boron carbide/titanium diboride composite ceramic powders is disclosed. The process comprises the ordered steps of (a) intimately mixing as reactants boron carbide and a titanium source, such that the average reactant particle size is less than about 20 microns and substantially all discrete reactant areas are less than about 50 microns, and (b) reacting the product of step (a) under conditions sufficient to produce a boron carbide/titanium diboride composite ceramic powder wherein at least a portion of the boron carbide particles form substrates to which at least a portion of the titanium diboride particles are attached. The method can be used to produce a composite ceramic powder having boron carbide and titanium diboride particles less than about 20 microns in diameter. This powder can then be densified using known densification techniques to form a densified part wherein the titanium diboride grains have an average size of less than about 20 microns in diameter and the boron carbide grains having an average size of less than about 50 microns. Because of the uniformity of dispersion that can result, the densified part shows a microstructure that is also very uniform in distribution of boron carbide and titanium diboride.

A method of producing submicron size boron carbide powder by heating a reactive mixture containing a boric oxide source and a carbon source at a high temperature for a sufficient length of time to form submicron particles of uniform size.

Producing boron carbide

An improved method to prill calcium chloride comprising feeding a molten, aqueous calcium chloride solution into a boiling refrigerant with a boiling temperature less than the freezing temperature of the solution. The solution is fed into the boiling refrigerant from an opening positioned upwardly from and spaced apart from the upper surface of the refrigerant.

Growing community of inventors

Midland, MI, United States of America

William G Moore