Abstract: A method for increasing the porosity and crushability characteristics thereof embodies the firing of a ceramic compact comprising a reactant fugitive filler material and a ceramic material in a controlled atmosphere.

Abstract: A core for investment casting directionally solidified eutectic and superalloy material consists of alumina which has a porous microstructure in which the grain morphology is characteristic of grains which have undergone vapor phase transport action.

Abstract: A dense polycrystalline silicon nitride body is produced by hot-pressing a particulate mixture of silicon nitride and a beryllium additive.

Abstract: A gas mixture of silane and ammonia is heated at temperatures between about 600.degree. C and 1000.degree. C producing an amorphous powdery reaction product which, when heated at a calcination temperature of at least 1100.degree. C yields ultrafine Si.sub.3 N.sub.4 powder of high purity.

Abstract: A dense polycrystalline silicon nitride body is produced by hot-pressing a particulate mixture of silicon nitride and a beryllium additive.

Abstract: A particulate dispersion of silicon nitride, magnesium additive and beryllium additive is formed into a green body and sintered at a temperature ranging from about 1800.degree. C to about 2200.degree. C in a sintering atmosphere of nitrogen at superatmospheric pressure producing a sintered body with a density ranging from about 80 to about 100%.

Abstract: A particulate dispersion of silicon nitride and beryllium additive is formed into a green body and sintered at a temperature ranging from about 1900.degree. to about 2200.degree. C in a sintering atmosphere of nitrogen at superatmospheric pressure producing a sintered body with a density ranging from about 80 to about 100%.

Abstract: A particulate dispersion of silicon nitride, magnesium additive and beryllium additive is formed into a green body and sintered at a temperature ranging from about 1800.degree. C to about 2200.degree. C in a sintering atmosphere of nitrogen at superatmospheric pressure producing a sintered body with a density ranging from about 80% to about 100%.

Abstract: A dense silicon carbide having improved properties is disclosed which is prepared by the addition of a carbonaceous additive to a boron doped silicon carbide and hot pressing the mixture at a sufficient temperature and pressure whereby a dense substantially nonporous ceramic is formed.

Abstract: A particulate mixture of .beta.-silicon carbide, boron carbide and a carbonaceous additive is formed into a green body and sintered producing a sintered body with a density of at least about 85% containing boron carbide in an amount ranging from about 10% to about 30% by weight of the total amount of silicon carbide and boron carbide present.

Abstract: A silicon carbide sintered body characterized by its microstructural stability at high temperatures is produced by forming a mixture of .beta.-silicon carbide powder, .alpha.-silicon carbide seeding powder, boron additive and a carbonaceous additive into a green body and sintering it to produce a sintered body with a density of at least 80% wherein at least 70% by weight of the silicon carbide is .alpha.-silicon carbide.

Abstract: A silicon carbide body with a density of at least 85% is machined to required specification and then fired at a temperature ranging from 1400.degree. C to 2100.degree. C in a firing atmosphere ranging in pressure from 10.sup..sup.-3 torr to 25 torr to increase its fracture strength by at least 10%.

Abstract: A polycrystalline silicon nitride body is produced by shaping a particulate mixture of silicon powder and boron into a green body, sintering the body to a density ranging from 60% to 75% of the theoretical density of silicon, said sintered body having pores which are interconnecting and open to the surface of the body, and reacting said sintered body with gaseous nitrogen to convert it to silicon nitride.

Abstract: A polycrystalline boron carbide sintered body containing beryllium carbide with a density ranging from 85% to 96% of the theoretical density of boron carbide and having a uniform microstructure of equiaxed grains.

Abstract: A method of making a dense silicon carbide ceramic is disclosed involving the steps of homogeneously dispersing silicon carbide with a sufficient amount of a boron containing additive and a carbonaceous additive, forming the powder mixture into a shaped green body and then sintering the body in a controlled atmosphere and in the absence of external pressure at a temperature of about 1900.degree.-2100.degree. C. such that density of the body is at least 85% of the theoretical density of silicon carbide. The complex shaped silicon carbide product formed thereby is also disclosed.

Abstract: Polycrystalline silicon carbide with increased electrical conductivity at room temperature is produced by shaping a particulate mixture of .beta.-silicon carbide, boron additive, beryllium carbide and a carbonaceous additive into a green body and sintering the body producing a sintered body having a density of at least about 85% of the theoretical density of silicon carbide.

Abstract: A dense silicon carbide material having improved electrically conducting properties is disclosed which is prepared by forming a homogeneous dispersion of silicon carbide, a sufficient amount of a boron containing additive, and 3.5-10.0% by weight of silicon nitride and hot pressing the dispersion at a sufficient temperature and pressure whereby a dense substantially nonporous ceramic is formed. The silicon carbide material can be machined by electrical discharge machining or by electrochemical machining.

Abstract: A dense silicon carbide material having improved electrically conducting properties is disclosed which is prepared by forming a homogeneous dispersion of silicon carbide, a sufficient amount of a boron containing additive, and 3.5-10.0% by weight of silicon nitride and hot pressing the dispersion at a sufficient temperature and pressure whereby a dense substantially nonporous ceramic is formed. The silicon carbide material can be machined by electrical discharge machining or by electrochemical machining.

Abstract: A dense silicon carbide material having improved electrically conducting properties is disclosed which is prepared by forming a homogeneous dispersion of silicon carbide, a sufficient amount of boron nitride, and optionally a boron containing additive and hot pressing the dispersion at a sufficient temperature and pressure whereby a dense substantially nonporous ceramic is formed. The silicon carbide material can be machined by electrical discharge machining or by electrochemical machining.