Abstract: A novel ceramic composition having high strength at high temperatures and needing no degreasing step before its sintering step, and a process for producing the same are provided,which composition is obtained by calcining a molded body composed of alumina powder and a polysilazane in an inert gas such as nitrogen, argon, etc. and/or ammonia, or under pressure and at 800.degree.-1950.degree. C.

Abstract: A process for producing a rod-form silica from a silicic acid ester according to a sol-gel process, which silica has a rod-form having a high aspect ratio and is advantageously used as a filler for resin sealants for semiconductors, is provided, which process comprises adding 35 to 150 parts by weight of a sol of a silicic acid ester to 100 parts by weight of a hydrophobic medium to form an emulsion, subjecting the emulsion to a temperature rise at two stages, the first temperature rise being by 5.degree. to 30.degree. C. at a rate of 10.degree. to 200.degree. C./min. or less and the second temperature rise being by 3.degree. to 20.degree. C. at a rate of 0.5.degree. to 10.degree. C./min., to form a rod-form silica.

Abstract: There is provided a new polysilazane product from a specific precursor. Desired molecular weight of the polysilazane can be obtained by selecting the proper molar ratio of R.sub.1 SiHX.sub.2 and R.sub.2 R.sub.3 SiX.sub.2 as raw materials. The polysilazane is stable during storage without gelation. The polymerization of the precursor can be carried out without gelation even at a high temperature and hence can be completed in a short time. The polysilazane can be made into ceramic fibers by spinning from a solution and subsequent firing.

Abstract: There is provided a new polysilazane product from a specific precursor. Desired molecular weight of the polysilazane can be obtained by selecting proper amount of a silazane or silylamine compound ##STR1## as an additive. The polysilazane is stable during storage without gelation. The polymerization of the precursor can be carried out without gelation even at a high temperature and hence can be completed in a short time. The polysilazane can be made into ceramics fiber by spinning from a solution and subsequent firing.

Abstract: A process for producing silicon carbide in the form of uniform fine particles and having a high purity with a good efficiency is provided, which process comprises subjecting an organosilicon compound expressed by the formula;R.sup.1 SiR.sup.2.sub.3wherein R.sup.1 represents a radial selected from the group consisting of saturated aliphatic hydrocarbon radicals, unsaturated aliphatic hydrocarbon radicals and aromatic hydrocarbon radicals and R.sup.2 represents chlorine atom or OR.sup.3 group wherein R.sup.3 represents an alkyl group of 1 to 4 carbon atoms to hydrolysis to obtain a hydrolyzate of said organosilicon compound having fluidity at normal temperatures, followed by calcining the hydrolyzate in an inert gas atmosphere.