Patents Represented by Attorney D. R. Howard
  • Patent number: 5417887
    Abstract: 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: Grant
    Filed: May 18, 1993
    Date of Patent: May 23, 1995
    Assignee: The Dow Chemical Company
    Inventor: Frank P. Skeele
  • Patent number: 5374392
    Abstract: 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: Grant
    Filed: December 4, 1991
    Date of Patent: December 20, 1994
    Assignee: The Dow Chemical Company
    Inventors: James S. Skelcey, Craig J. Bartkowiak
  • Patent number: 5342811
    Abstract: 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: Grant
    Filed: May 10, 1991
    Date of Patent: August 30, 1994
    Assignee: The Dow Chemical Company
    Inventors: Bijan Khazai, William G. Moore
  • Patent number: 5340417
    Abstract: 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: Grant
    Filed: June 28, 1991
    Date of Patent: August 23, 1994
    Assignee: The Dow Chemical Company
    Inventors: Alan W. Weimer, William G. Moore, William Rafaniello, Raymond P. Roach
  • Patent number: 5320990
    Abstract: 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: Grant
    Filed: March 30, 1993
    Date of Patent: June 14, 1994
    Assignee: The Dow Chemical Company
    Inventors: Theresa A. Guiton, Lynne K. Mills
  • Patent number: 5269989
    Abstract: 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: Grant
    Filed: September 1, 1992
    Date of Patent: December 14, 1993
    Assignee: The Dow Chemical Company
    Inventor: Aleksander J. Pyzik
  • Patent number: 5256608
    Abstract: 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: Grant
    Filed: December 13, 1991
    Date of Patent: October 26, 1993
    Assignee: The Dow Chemical Company
    Inventors: Ellen M. Dubensky, Edward E. Timm, Ann M. McCombs, Julie L. Board
  • Patent number: 5223460
    Abstract: 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: Grant
    Filed: December 13, 1991
    Date of Patent: June 29, 1993
    Assignee: The Dow Chemical Company
    Inventors: Ellen M. Dubensky, Edward E. Timm, Ann M. McCombs, Julie L. Board
  • Patent number: 5219804
    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.
    Type: Grant
    Filed: January 10, 1992
    Date of Patent: June 15, 1993
    Assignee: The Dow Chemical Company
    Inventors: Alan W. Weimer, Gene A. Cochran, John P. Henley, Glenn A. Eisman
  • Patent number: 5194234
    Abstract: 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: Grant
    Filed: September 12, 1991
    Date of Patent: March 16, 1993
    Assignee: The Dow Chemical Company
    Inventors: Alan W. Weimer, William G. Moore, Raymond P. Roach
  • Patent number: 5160508
    Abstract: 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: Grant
    Filed: January 24, 1992
    Date of Patent: November 3, 1992
    Assignee: The Dow Chemical Company
    Inventors: Aleksander J. Pyzik, Harold E. Rossow, Douglas B. Schwarz, Donald R. Beaman, Barbara M. Pyzik, William J. Dubensky
  • Patent number: 5156725
    Abstract: 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: Grant
    Filed: October 17, 1991
    Date of Patent: October 20, 1992
    Assignee: The Dow Chemical Company
    Inventors: Stephen J. Doktycz, Kevin E. Howard
  • Patent number: 5145833
    Abstract: 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: Grant
    Filed: March 14, 1990
    Date of Patent: September 8, 1992
    Assignee: The Dow Chemical Company
    Inventors: Arthur R. Prunier, Jr., Stanley F. Spangenberg, Sunil Wijeyesekera
  • Patent number: 5126121
    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.
    Type: Grant
    Filed: May 3, 1991
    Date of Patent: June 30, 1992
    Assignee: The Dow Chemical Company
    Inventors: Alan W. Weimer, John P. Henley, Gene A. Cochran, Glenn A. Eisman, William G. Moore
  • Patent number: 5118645
    Abstract: 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: Grant
    Filed: August 24, 1990
    Date of Patent: June 2, 1992
    Assignee: The Dow Chemical Company
    Inventors: Aleksander J. Pyzik, Harold E. Rossow, Douglas B. Schwarz, Donald R. Beaman, Barbara M. Pyzik, William J. Dubensky
  • Patent number: 5112579
    Abstract: 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: Grant
    Filed: December 12, 1990
    Date of Patent: May 12, 1992
    Assignee: The Dow Chemical Company
    Inventors: David A. Dunn, Michael S. Paquette, Henry Easter, Roger K. Pihlaja
  • Patent number: 5110565
    Abstract: 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: Grant
    Filed: February 5, 1988
    Date of Patent: May 5, 1992
    Assignee: The Dow Chemical Company
    Inventors: Alan W. Weimer, William G. Moore, Raymond P. Roach
  • Patent number: 5108962
    Abstract: 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: Grant
    Filed: May 26, 1988
    Date of Patent: April 28, 1992
    Assignee: The Dow Chemical Company
    Inventors: Bijan Khazai, William G. Moore
  • Patent number: 5098631
    Abstract: 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: Grant
    Filed: September 13, 1990
    Date of Patent: March 24, 1992
    Assignee: The Dow Chemical Company
    Inventors: Aleksander J. Pyzik, Timothy L. Allen
  • Patent number: 5091347
    Abstract: 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: Grant
    Filed: August 15, 1990
    Date of Patent: February 25, 1992
    Assignee: The Dow Chemical Company
    Inventors: Aleksander J. Pyzik, Barbara M. Pyzik