Abstract: Shaped silicon carbide ceramic articles of high density, e.g., at least 90 percent of theoretical, are produced by cold pressing and sintering boron-containing high purity, submicron beta silicon carbide powder. The silicon carbide powder is produced preferably by gas phase reaction of silicon halide, e.g., silicon tetrachloride, carbon source reactant, e.g., halogenated hydrocarbon, and boron source reactant, e.g., boron trichloride, with a hydrogen plasma.

Abstract: Shaped silicon carbide ceramic articles of high density, e.g., at least 90 percent of theoretical, are produced by cold pressing and sintering boron-containing high purity, submicron beta silicon carbide powder. The silicon carbide powder is produced preferably by gas phase reaction of silicon halide, e.g., silicon tetrachloride, carbon source reactant, e.g., halogenated hydrocarbon, and boron source reactant, e.g., boron trichloride, with a hydrogen plasma.

Abstract: Refractory metal diboride articles having an overall density of 50-90 percent of theoretical and a matrix of near theoretical density, e.g., 95-99 percent are described. They may be made by cold pressing and sintering an intimate mixture of submicron Group IVb metal diboride powder and finely divided solid hydrocarbon, e.g., microcrystalline petroleum wax. The hydrocarbon remains particulate in the cold pressed piece but is driven out by heat at the beginning of the sintering operation, thereby leaving voids which remain as gross pores surrounded by a dense matrix in the sintered article. Submicron boride powders capable of forming the dense matrix contain a minor proportion of a sintering or densifying aid such as carbon or a metal carbide such as titanium carbide, tungsten carbide, or boron carbide. The articles so produced are lighter in weight than non-porous articles of the same size, have high electrical conductivity and, by virtue of the dense matrix, have excellent resistance to chemical attack.