Abstract: Inorganic fibers having a high strength and a high modulus of elasticity at a high temperature are provided. The inorganic fibers are amorphous inorganic silicon nitirde-based fibers composed of silicon and nitrogen, optionally with oxygen, carbon and hydrogen, and having atomic ratio between above respective elements of N/Si=0.3 to 3, O/Si=up to 15, C/Si=up to 7 and H/Si=up to 15, wherein ratios of X-ray scattering intensity thereof to that of air at 1.degree. and 0.5.degree. are from 1 to 20 respectively and the silicon nitride-based fiber is still amorphous after heating in an inactive atmosphere at 1200.degree. C. for 1 hour. Composites of a metal, a ceramics, and a high molecular weight organic compound reinforced with the above fibers are also provided.

Abstract: A molded body formed of a silicon nitride-based ceramic containing Si and N and optionally O, C and/or a metal. The ceramic is formed from a polysilazane. A molded body may be a composite body which is composed of a matrix of the ceramic and a reinforcing material such as powder or fiber embedded within the matrix or which is composed of ceramic powder bound with a binder formed of the silicon nitride-based ceramic.

Abstract: A shaped body is disclosed which comprises substantially amorphous, silicon nitride-based ceramic containing Si, N and B as essential components and O, C and H as optional components in amounts providing the following atomic ratios:N/Si: 0.05 to 2.5,B/Si: 0.01-3,O/Si: 2.0 or less,C/Si: 1.5 or less, andH/Si: 0.1 or less.

Abstract: Novel polysiloxazanes comprising --SiH.sub.2).sub.n NH] and --SiH.sub.2).sub.m O] as the main repeating units are provided. The polysiloxazanes are produced by reacting a dihalosilane or an adduct thereof with a Lewis base, with ammonia and water vapor or oxygen. From the polysiloxazane, novel silicon oxynitride shapes can be produced and the silicon oxynitride shapes are essentially composed of silicon, nitride (5 mol % or more) and oxygen (5 mol % or more).

Abstract: Silicon nitride based ceramic fibers containing Si, N, O and at least one metal M in amounts providing the atomic ratios N/Si of 0.3 to 3, O/Si of 0.0001 to 15 and M/Si of 0.001 to 5 and exhibiting an X-ray small angle scattering such that the ratio of the intensity of the small angle scattering of the fibers to that of air is 1 to 20. The ceramic fibers are produced by spinning of a polymetallosilazane into fibers and calcining the spun fibers and are useful as reinforcing fibers for composite artices having a metal or resin matrix.

Abstract: Disclosed is a polyborosilazane having a B/Si atomic ratio of 0.01 to 3 and a number-average molecular weight of about 200 to about 500,000 which can be pyrolyzed to give ceramics. The polyborosilazane is produced by reacting a polysilazane having a number-average molecular weight of about 100 to about 50,000 with a boron compound.

Abstract: A novel, reformed polysilazane obtained by reacting a polysilazane with a compound selected from ammonia, primary and secondary amines, hydrazine and mono-, di- and tri-substituted hydrazines to cross-link the polysilazane with the compound serving as a cross-linking agent or to link the compound to the polysilazane.

Abstract: Novel polysiloxazanes comprising --SiH.sub.2).sub.n NH-- and --SiH.sub.2).sub.m O-- as the main repeating units are provided. The polysiloxazanes are produced by reacting a dihalosilane or an adduct thereof with a Lewis base, with ammonia and water vapor or oxygen. From the polysiloxazane, novel silicon oxynitride shapes can be produced and the silicon oxynitride shapes are essentially composed of silicon, nitride (5 mols % or more) and oxygen (5 mol % or more).

Abstract: A novel, reformed, inorganic polysilazane which is liquid or solid at room temperature and soluble in o-xylene at room temperature and which has (a) a number-average molecular weight of 200-500,000, (b) contents of Si, N and H of 50-70% by weight, 20-34% by weight and 5-9% by weight, respectively; and (c) --SiH.sub.2 -- and --SiH.sub.3 groups, the molar ratio of the --SiH.sub.2 -- groups to the --SiH.sub.3 groups being 2.0:1 to 8.4:1. The reformed polysilazane is obtained by reaction of a solution of a polysilazane in an organic base-containing solvent to polycondense the polysilazane.

Abstract: A novel polymetalosilazane having a metal/silicon atomic ratio of from 0.001 to 3 and a number average molecular weight of about 200 to 500,000 is prepared by a process comprising: reacting a polysilazane having a number average molecular weight of about 100 to 500,000, which has a skelton consisting substantially of units ##STR1## at least one R being hydrogen, with a metal alkoxide in which the metal is selected from metals of the groups IIA and III to V of the Periodic Table.

Abstract: Novel polysiloxazanes comprising [(SiH.sub.2).sub.n NH] and [(SiH.sub.2).sub.m O] as the main repeating units are provided. The polysiloxazanes are produced by reacting a dihalosilane or an adduct thereof with a Lewis base, with ammonia and water vapor or oxygen. From the polysiloxazane, novel silicon oxynitride shapes can be produced and the silicon oxynitride shapes are essentially composed of silicon, nitride (5 mol % or more) and oxygen (5 mol % or more).

Abstract: A novel, reformed, inorganic polysilazane which is liquid or solid at room temperature and soluble in o-xylene at room temperature and which has (a) a number-average molecular weight of 200-500,000, (b) contents of Si, N and H of 50-70% by weight, 20-34% by weight and 5-9% by weight, respectively; and (c) --SiH.sub.2 -- and --SiH.sub.3 groups, the molar ratio of the --SiH.sub.2 -- groups to the --SiH.sub.3 groups being 2.0:1 to 8.4:1. The reformed polysilazane is obtained by reaction of a solution of a polysilazane in an organic base-containing solvent to polycondense the polysilazane.

Abstract: Novel primarily chain inorganic polysilazanes of average molecular weight of 690 to 2000 are prepared from novel adducts of a halosilane and a base by reacting the adducts with ammonia in unreactive solvents. Silicon nitride is prepared by heating the polysilazanes at 1000.degree. to 1600.degree. C., preferably below 1300.degree. C., most preferably 1000.degree. to 1100.degree. C.

Abstract: Fired nitride-base ceramics, i.e., silicon nitride or oxynitride, having a low carbon content and, therefore, low electrical and thermal conductivities, can be produced by heat treating a ceramic precursor comprising polysilazane, polysiloxazane or polycarbosilazane or a mixture thereof as the main ingredient in a reducing atmosphere such as hydrogen, ammonia or a gas containing these components, followed by firing.

Abstract: Silicon nitride fibers having a carbon content of 5 weight percent or less have high heat insulating properties and favorable mechanical properties and are useful as heat resistant, highly insulating materials or reinforcing agents for composite materials, particularly in the aerospace industry. Such high purity silicon nitride fibers are produced by spinning a solution of perhydropolysilazanes, an inert solvent and a spinning agent into fibers, preferably continuous fibers, and firing the spun fibers at 800.degree. to 1300.degree. C. in an inert atmosphere to form silicon nitride fibers of high purity.

Abstract: A silicon halide, preferably SiCl.sub.4, is reacted with an excess of a base, e.g. a Lewis base or Bronsted base with steric hindrance group to produce an adduct. The adduct, which need not be separated, is treated with ammonia gas to produce the imide of silicon. A light organic solvent is used. The temperature used is -78.degree. C. to 100.degree. C. and the reaction is rapid.Byproduct ammonium halide is removed, and the imide is heated at 1000.degree. C. to 1600.degree. C. in an oven in an atmosphere containing nitrogen, to produce silicon nitride of good sintering characteristics and more than 70 wt % of which is of the .alpha.-crystal form.

Abstract: A novel polyorgano(hydro)silazane having the compositional formula: (RSiHNH).sub.x [(RSiH).sub.1.5 N].sub.1-x, wherein R is an alkyl group, an alkenyl group, a cycloalkyl group, an aryl group, another group in which the atom directly bound to Si is carbon, an alkylsilyl group, an alkylamino group, or an alkoxy group, and 0.4<x<1. This polyorgano(hydro)silazane is produced by reacting a complex of organo(hydro)diholosilane and a base with dry ammonia. This novel silazane is useful as a ceramic starting material, a polymer hardening agent, a densifying agent, a surface coating material, etc., and can be produced safely and at a low cost.