Patents Represented by Attorney D. R. Howard
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Patent number: 5417887Abstract: Aluminum nitride powder slurry viscosity reductions occur with addition of an amount of a process aid such as a C.sub.1 -C.sub.11 aliphatic carboxylic polyfunctional acid, an ammonium salt or alkali metal salt of such an acid, ethylenediaminetetraacetic acid, ammonium salts or alkali metal salts of ethylenediaminetetraacetic acid, and succinic anhydride.Type: GrantFiled: May 18, 1993Date of Patent: May 23, 1995Assignee: The Dow Chemical CompanyInventor: Frank P. Skeele
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Patent number: 5374392Abstract: Densify powdered materials, either ceramic or metal or both, at temperatures of 1400.degree. C. or higher using a fluid die fabricated from a mixture of alumina and a calcium aluminate cement. The fluid die may be separated from a fluid pressure-transmitting medium by a barrier material such as graphite foil.Type: GrantFiled: December 4, 1991Date of Patent: December 20, 1994Assignee: The Dow Chemical CompanyInventors: James S. Skelcey, Craig J. Bartkowiak
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Patent number: 5342811Abstract: 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.Type: GrantFiled: May 10, 1991Date of Patent: August 30, 1994Assignee: The Dow Chemical CompanyInventors: Bijan Khazai, William G. Moore
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Patent number: 5340417Abstract: A process for preparing silicon carbide by carbothermal reduction is disclosed. This process involves rapidly heating a particulate reactive mixture of a silica source and a carbon source to form a product which shows improved uniformity of crystal size. The product of this process can be used to form a densified part.Type: GrantFiled: June 28, 1991Date of Patent: August 23, 1994Assignee: The Dow Chemical CompanyInventors: Alan W. Weimer, William G. Moore, William Rafaniello, Raymond P. Roach
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Patent number: 5320990Abstract: Prepare sintered aluminum nitride bodies having a thermal conductivity of at least 200 W/m-K by sintering under non-reducing conditions and controlling interrelated parameters such as binder burnout atmosphere, heating rate, sintering temperature, time at sintering temperature, cooling rate and cooling temperature. Sintered bodies having thermal conductivities in excess of 200, especially in excess of 270, W/m-K result from this process.Type: GrantFiled: March 30, 1993Date of Patent: June 14, 1994Assignee: The Dow Chemical CompanyInventors: Theresa A. Guiton, Lynne K. Mills
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Patent number: 5269989Abstract: Infiltrate a porous, self-reinforced .beta.-Si.sub.3 N.sub.4 preform with a metal or a crystallizable glass to yield a composite material. The preform possesses a low glass phase and has a density of from about 50 to about 70 percent of theoretical density. Prepare the .beta.-Si.sub.3 N.sub.4 preform by subjecting a porous body formed from an .alpha.-Si.sub.3 N.sub.4 powder composition to two sequential heat treatments. The first heat treatment occurs below the .alpha.- to .beta.- conversion temperature and results in a strengthened body that can be machined. The second heat treatment occurs above that temperature and yields the self-reinforced .beta.-Si.sub.3 N.sub.4 preform. Conventional infiltration procedures with an infiltrant that is a metal or a glass results in a Si.sub.3 N.sub.4 /metal or Si.sub.3 N.sub.4 /glass composite material that has 50 to 70 percent of its volume occupied by .beta.-Si.sub.3 N.sub.4 whiskers.Type: GrantFiled: September 1, 1992Date of Patent: December 14, 1993Assignee: The Dow Chemical CompanyInventor: Aleksander J. Pyzik
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Patent number: 5256608Abstract: A powdered admixture of a boron, carbon, nitrogen or silicon derivative of a first metal is combined with a source of a second metal and, optionally, a source of a third metal or an iron-group metal, subjected to densification conditions (heat and pressure), partially reacted and converted to a hard, wear resistant material. The wear resistant material contains an amount of the first metal derivative as well as a material of varying stoichiometry which is the partial reaction product of components of the powdered admixture. The material may also contain residual, unreacted portions of components other than the first metal derivative. Articles formed from this material can be useful as, for example, nozzles in abrasive or nonabrasive waterjet cutting machines and various parts of wire drawing apparatus.Type: GrantFiled: December 13, 1991Date of Patent: October 26, 1993Assignee: The Dow Chemical CompanyInventors: Ellen M. Dubensky, Edward E. Timm, Ann M. McCombs, Julie L. Board
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Patent number: 5223460Abstract: A powdered admixture of a boron, carbon, nitrogen or silicon derivative of a first metal is combined with a source of a second metal and, optionally, a source of a third metal or an iron-group metal, subjected to densification conditions (heat and pressure), partially reacted and converted to a hard, wear resistant material. The wear resistant material contains an amount of the first metal derivative as well as a material of varying stoichiometry which is the partial reaction product of components of the powdered admixture. The material may also contain residual, unreacted portions of components other than the first metal derivative. Articles formed from this material can be useful as, for example, nozzles in abrasive or nonabrasive waterjet cutting machines and various parts of wire drawing apparatus.Type: GrantFiled: December 13, 1991Date of Patent: June 29, 1993Assignee: The Dow Chemical CompanyInventors: Ellen M. Dubensky, Edward E. Timm, Ann M. McCombs, Julie L. Board
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Patent number: 5219804Abstract: 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.Type: GrantFiled: January 10, 1992Date of Patent: June 15, 1993Assignee: The Dow Chemical CompanyInventors: Alan W. Weimer, Gene A. Cochran, John P. Henley, Glenn A. Eisman
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Patent number: 5194234Abstract: 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.Type: GrantFiled: September 12, 1991Date of Patent: March 16, 1993Assignee: The Dow Chemical CompanyInventors: Alan W. Weimer, William G. Moore, Raymond P. Roach
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Patent number: 5160508Abstract: A process for preparing a self-reinforced silicon nitride ceramic body of high fracture toughness comprising hot-pressing a powder mixture containing silicon nitride, a densification aid such as sodium oxide, a conversion aid such as lanthanum oxide and a compound, such as gallium oxide, which enhances growth of .beta.-silicon nitride whiskers-under conditions such that densification and the in situ formation of .beta.-silicon nitride whiskers having a high aspect ratio occur. A novel silicon nitride ceramic of high fracture toughness and high fracture strength is disclosed comprising a .beta.-silicon nitride crystalline phase wherein at least about 20 volume percent of the phase is in the form of whiskers having an average aspect ratio of at least about 2.5; a glassy second phase containing the densificaton aid, the conversion aid, the compound which enhances growth of .beta.-silicon nitride whiskers, and an amount of silica; and not greater than about 10 weight percent of the total weight as other phases.Type: GrantFiled: January 24, 1992Date of Patent: November 3, 1992Assignee: The Dow Chemical CompanyInventors: Aleksander J. Pyzik, Harold E. Rossow, Douglas B. Schwarz, Donald R. Beaman, Barbara M. Pyzik, William J. Dubensky
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Patent number: 5156725Abstract: A process is disclosed for forming a ceramic coating on a substrate. A metal layer is placed onto the substrate by means such as sputtering. After a carbon-containing foil is applied to the metal-coated substrate, it is subjected to rapid omnidirectional compaction. The resulting product is a densified coated ceramic composition which exhibits improved mechanical properties.Type: GrantFiled: October 17, 1991Date of Patent: October 20, 1992Assignee: The Dow Chemical CompanyInventors: Stephen J. Doktycz, Kevin E. Howard
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Patent number: 5145833Abstract: This invention provides a process for producing a ceramic body by heating a ceramic material, such as particulate zirconium oxide, to a temperature greater than about 30 percent of the material's melting temperature, but less than said melting temperature, and thereafter applying sufficient isostatic pressure to consolidate the ceramic material into a body having a density of at least 85 percent of the theoretical density of the material.This invention also provides a process for producing superconducting ceramic articles such as those represented by the general formula YBa.sub.2 Cu.sub.3 O.sub.7-x where 0<x<0.6. Starting materials for such articles include sources of yttria, cupric oxide and barium monoxide. The general process parameters for the ceramic body process are modified to accomodate the starting materials.Type: GrantFiled: March 14, 1990Date of Patent: September 8, 1992Assignee: The Dow Chemical CompanyInventors: Arthur R. Prunier, Jr., Stanley F. Spangenberg, Sunil Wijeyesekera
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Patent number: 5126121Abstract: 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.Type: GrantFiled: May 3, 1991Date of Patent: June 30, 1992Assignee: The Dow Chemical CompanyInventors: Alan W. Weimer, John P. Henley, Gene A. Cochran, Glenn A. Eisman, William G. Moore
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Patent number: 5118645Abstract: A process for preparing a self-reinforced silicon nitride ceramic body of high fracture toughness comprising hot-pressing a powdcer mixture containing silicon nitride, a densification aid such as sodium oxide, a conversion aid such as lanthanum oxide and a compound, such as gallium oxide, which enhances growth of .beta.-silicon nitride whiskers-under conditions such that densification and the in situ formation of .beta.-silicon nitride whiskers having a high aspect ratio occur. A novel silicon nitride ceramic of high fracture toughness and high fracture strength is disclosed comprising a .beta.-silicon nitride crystalline phase wherein at least about 20 volume percent of the phase is in the form of whiskers having an average aspect ratio of at least about 2.5; a glassy second phase containing the densification aid, the conversion aid, the compound which enhances growth of .beta.-silicon nitride whiskers, and an amount of silica; and not greater than about 10 weight percent of the total weight as other phases.Type: GrantFiled: August 24, 1990Date of Patent: June 2, 1992Assignee: The Dow Chemical CompanyInventors: Aleksander J. Pyzik, Harold E. Rossow, Douglas B. Schwarz, Donald R. Beaman, Barbara M. Pyzik, William J. Dubensky
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Patent number: 5112579Abstract: A reactor for carbothermal reduction is disclosed. By supplying gaseous nitrogen throughout a discrete aliquot of a preferably pelletized mixture of aluminum oxide, carbon and, optionally, calcium oxide during the carbothermal reduction thereof to aluminum nitride and continuously removing gaseous reaction products therefrom, a high quality aluminum nitride is produced. One means of supplying gaseous nitrogen to the mixture of solid reactants is a perforated tray having a hollowed-out bottom. Gaseous nitrogen supplied to the hollowed-out portion flows through the perforations and throughout solid reactants contained in the tray. The carbon may be alternatively supplied, in whole or in part, as a gaseous reactant.Type: GrantFiled: December 12, 1990Date of Patent: May 12, 1992Assignee: The Dow Chemical CompanyInventors: David A. Dunn, Michael S. Paquette, Henry Easter, Roger K. Pihlaja
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Patent number: 5110565Abstract: 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.Type: GrantFiled: February 5, 1988Date of Patent: May 5, 1992Assignee: The Dow Chemical CompanyInventors: Alan W. Weimer, William G. Moore, Raymond P. Roach
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Patent number: 5108962Abstract: 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.Type: GrantFiled: May 26, 1988Date of Patent: April 28, 1992Assignee: The Dow Chemical CompanyInventors: Bijan Khazai, William G. Moore
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Patent number: 5098631Abstract: Use a material which has a coefficient of thermal expansion greater than silicon nitride and does not react with silicon nitride under hot pressing conditions either to fabricate or to coat hot-pressing die plates suitable for densification of silicon nitride. The die plates separate cleanly from the silicon nitride thereby allowing preparation of near-net shapes having complex geometries, but without post densification grinding or machining.Type: GrantFiled: September 13, 1990Date of Patent: March 24, 1992Assignee: The Dow Chemical CompanyInventors: Aleksander J. Pyzik, Timothy L. Allen
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Patent number: 5091347Abstract: Prepare a self-reinforced silicon nitride ceramic body of high fracture toughness by hot-pressing a powder mixture containing silicon nitride and three other components under conditions such that densification and the in situ formation of .beta.-silicon nitride whiskers having a high aspect ratio occur. The other components are silicon dioxide as a densification aid, a conversion aid such as yttrium oxide and a compound, such as calcium oxide, which enhances growth of .beta.-silicon nitride whiskers. The resultant silicon nitride ceramic has a .beta.-silicon nitride cyrstalline phase, at least 20 volume percent of which is in the form of whiskers or elongated grains having an average aspect ratio of at least about 2.5, and a glassy second phase. The glassy phase contains the silicon dioxide, the conversion aid and the compound which enhances growth of .beta.-silicon nitride whiskers. The glassy phase may also include a minor amount of aluminum nitride or boron nitride.Type: GrantFiled: August 15, 1990Date of Patent: February 25, 1992Assignee: The Dow Chemical CompanyInventors: Aleksander J. Pyzik, Barbara M. Pyzik