Abstract: A carbon/carbon (C/C) composite comprising crystalline silicon carbide which is essentially uniformly distributed on both internal and external surfaces of the composite in a low concentration, as well as a process for producing the composite and the use of the composite in brake materials for industrial roll goods, automotives, trucks, trains and aircrafts. It has been discovered that small amounts of crystalline silicon carbide uniformly distributed throughout the carbon/carbon composite results in reduced wear with either no change or a slight increase in the friction coefficient.

Abstract: A sintered, Si.sub.3 N.sub.4 -containing ceramic article is prepared by a reaction injection molding process comprising (1) injecting into a heated mold a fluid, nondilatant mixture of (a) at least 40% by volume of a powder mixture of (i) Si.sub.3 N.sub.4, (ii) a silicate glass-forming sintering aid and (iii) a high metal content silicide, and (b) a curable Si.sub.3 N.sub.4 precursor binder, to cure the binder and produce a hardened molded article, and (2) heating the molded article under a suitable atmosphere to convert the cured binder to a Si.sub.3 N.sub.4 -containing ceramic. The molded article is then sintered under a vacuum to crystallize the silicate glass phase by deoxygenation.

Abstract: A sintered, Si.sub.3 N.sub.4 -containing ceramic article is prepared by a reaction injection molding process comprising (1) injecting into a heated mold a fluid, nondilatant mixture of (a) at least 40% by volume of a powder mixture of (i) Si.sub.3 N.sub.4, (ii) a silicate glass-forming sintering aid and (iii) a high metal content silicide, and (b) a curable Si.sub.3 N.sub.4 precursor binder, to cure the binder and produce a hardened molded article, and (2) heating the molded article under a suitable atmosphere to convert the cured binder to a Si.sub.3 N.sub.4 -containing ceramic. The molded article is then sintered under a vacuum to crystallize the silicate glass phase by deoxygenation.

Abstract: The present invention relates to preceramic polymers incorporating boron and their application in the sintering of SiC ceramics. The present invention is also directed to a process for preparing a boron-substituted polysilazane which involves preparing a silazane ammonolysis product by reacting ammonia with a halogenated silicon compound selected from the group consisting of RSiX.sub.3, RR'SiX.sub.2, RR'R"SiX, SiX.sub.

Abstract: A silicon nitride ceramic having crystalline grain boundary phases is prepared by heating a composition comprising silicon nitride, a silicate glass-forming sintering aid and a high metal content transition metal silicide, to a temperature of 1300.degree. to 1800.degree. C. under vacuum until a glass forms, oxygen is removed from the glass, and the glass crystallizes. Alternatively, the grain boundaries of a sintered composition comprising silicon nitride, a silicate glass and a high metal content transition metal silicide can be crystallized by heating to at least 1300.degree. C. under a vacuum.

Abstract: A silicon carbide ceramic having crystalline grain boundary phases is prepared by heating a composition comprising silicon carbide, a silicate glass and a high metal content transition metal silicide, to a temperature of 1300.degree. to 2100.degree. C. under vacuum until oxygen is removed from the glass as SiO gas, and the glass that remains within the silicon carbide ceramic crystallizes.

Abstract: A sintered, Si.sub.3 N.sub.4 -containing ceramic article is prepared by a reaction injection molding process comprising (1) injecting into a heated mold a fluid, nondilatant mixture of (a) at least 40% by volume of a powder mixture of (i) Si.sub.3 N.sub.4, (ii) a silicate glass-forming sintering aid and (iii) a high metal content silicide, and (b) a curable Si.sub.3 N.sub.4 precursor binder, to cure the binder and produce a hardened molded article, and (2) heating the molded article under a suitable atmosphere to convert the cured binder to a Si.sub.3 N.sub.4 -containing ceramic. The molded article is then sintered under a vacuum to crystallize the silicate glass phase by deoxygenation.

Abstract: A silicon nitride ceramic having crystalline grain boundary phases is prepared by heating a composition comprising silicon nitride, a silicate glass-forming sintering aid and a high metal content transition metal silicide, to a temperature of 1300.degree. to 1800.degree. C. under vacuum until a glass forms, oxygen is removed from the glass, and the glass crystallizes. Alternatively, the grain boundaries of a sintered composition comprising silicon nitride, a silicate glass and a high metal content transition metal silicide can be crystallized by heating to at least 1300.degree. C. under a vacuum.

Abstract: The present invention relates to preceramic polymers incorporating boron and their application in the sintering of SiC ceramics. The present invention is also directed to a process for preparing a boron-substituted polysilazane which involves preparing a silazane ammonolysis product by reacting ammonia with a halogenated silicon compound selected from the group consisting of RSiX.sub.3, RR'SiX.sub.2, RR'R"SiX, SiX.sub.

Abstract: A sintered silicon carbide product having improved fracture toughness contains from 1% to 80% by weight of (a) a uniformly dispersed, nonagglomerated, high metal content silicide of iron, nickel, cobalt or molybdenum in which the metal/silicon ratio is equal to or greater than 1. The silicon carbide starting material can be alpha-phase, beta-phase or a mixture of the two.

Abstract: Disclosed is a wear resistant sintered ceramic product comprising (a) 40-98 weight percent silicon nitride having a high alpha-phase content, (b) 2-60 weight percent of a silicide of iron, cobalt or nickel and (c) up to 20 weight percent of at least one oxide, nitride, or silicate of an element of IUPAC groups 2, 3, 4, 13 or the lanthanide series. A method for making such a product is also disclosed.

Abstract: Disclosed is a sintered ceramic product comprising (a) 20-98 percent by weight silicon nitride, (b) 1-80 percent by weight of a silicide of iron, cobalt or nickel and (c) 0.02-20 parts by weight of at least one oxide, nitride, or silicate of an element of IUPAC groups 2, 3, 4, 13 or the lanthanide series. A method for making such a product is also disclosed.

Abstract: A ceramic comprising a matrix of Al.sub.2 O.sub.3, ZrO.sub.2 (partially or fully stabilized) or mixtures of Al.sub.2 O.sub.3 and ZrO.sub.2 with strontium aluminate plate-shaped grains distributed throughout the matrix results in a ceramic with high toughness, high strength and good hardness. SrO/Al.sub.2 O.sub.3 molar ratios between 0.02 and 0.20 result in in-situ formation of plate-shaped grains approximately 0.5 .mu.m in thickness and 5.0 .mu.m in breadth in tetragonal zirconia polycrystalline ceramic matrices. The in-situ formation of strontium aluminates allows high volume loading of platelets to occur and high toughness is achieved without the loss of strength. High alumina compositions have the added benefit of higher strength, lower thermal expansion, higher modulus and higher thermal conductivity than zirconia ceramics with comparable toughness.