Abstract: Sintered ceramic products comprised of from about 55 to about 99.5 percent by weight of silicon carbide co-sintered with from about 0.5 to about 45 percent by weight aluminum nitride containing a dispersion of free carbon in amounts between about 0.5 and about 4.0 percent by weight of the product are described. The sintered products have a bulk density of at least 75 percent of the theoretical density of silicon carbide. The products are produced by sintering, under substantially pressureless conditions, mixtures of silicon carbide, carbon, or a carbon source material, and aluminum nitride. The aluminum nitride component, in ranges of from about 3.0 to about 45 percent, may be initially mixed with the silicon carbide and carbon or carbon source material. In ranges of from about 0.5 to about 3.0 percent, the aluminum nitride component may be added to the mixture in vapor form during sintering.

Abstract: Sintered articles made from binary compositions of silicon carbide and titanium diboride are described. The articles may be prepared by initially mixing finely-divided silicon carbide, carbon or a carbon source material, a densification or sintering aid, and finely-divided titanium diboride, forming the mixture into a desired shape and subsequently heating at temperatures sufficiently high to form a sintered ceramic article of silicon carbide and titanium diboride. When the present sintered ceramic articles contain high amounts of titanium diboride, generally between about 65 and about 95 percent, and more preferably, between about 80 and about 95 percent, by weight, they are quite electrically conductive, generally having less than 0.2 ohm-cm electrical resistivity, and are useful as electrical ignitors. Such articles are also extremely resistant to corrosion by molten aluminum and aluminum alloys; thus, they are aptly suited to use as electrodes in aluminum refining processes.

Abstract: A method for making a dense thermal shock resistant silicon carbide ceramic body by hot pressing a blend of silicon carbide and from about 0.2 to about 2 weight percent of aluminum diboride and the resulting body.

Abstract: A dense thermal shock resistant silicon carbide ceramic body and its method of manufacture which comprises heat sintering a shaped body comprising particulate silicon carbide and an additive selected from boron nitride, boron phosphide, aluminum diboride and mixtures thereof.

Abstract: Cellular fused silica having a bimodal closed cell structure is produced by mixing finely divided silica with finely divided boron oxynitride as a cellulating agent and heating the mixture to a temperature of at least the melting point of the silica, whereby the silica melts and is cellulated by gas generated as a result of decomposition of the boron oxynitride. The cellular silica consists of a multiplicity of primary closed cells defined by a matrix consisting essentially of silica, the matrix also containing a multiplicity of secondary macroscopic closed cells which are at least an order of magnitude smaller than the primary cells. Cellular fused silica bodies according to the invention are characterized by superior mechanical strength in addition to extreme whiteness and high purity of color, as well as other desirable properties, and are particularly useful for high temperature thermal insulation. Carefully controlled and defined shapes having very smooth surfaces may be obtained.

Abstract: Cellular fused silica having a bimodal closed cell structure is produced by mixing finely divided silica with finely divided boron oxynitride as a cellulating agent, and heating the mixture to a temperature of at least the melting point of the silica, whereby the silica melts and is cellulated by gas generated as a result of decomposition of the boron oxynitride. The cellular silica consists of a multiplicity of primary closed cells defined by a matrix consisting essentially of silica, the matrix also containing a multiplicity of secondary macroscopic closed cells which are at least an order of magnitude smaller than the primary cells. Cellular fused silica bodies according to the method of the invention are characterized by superior mechanical strength in addition to extreme whiteness and high purity of color, as well as other desirable properties, and are particularly useful for high temperature thermal insulation. Carefully controlled and defined shapes having very smooth surfaces may be obtained.