Abstract: High purity silicon nitride particles are disclosed which are essentially alpha crystalline and which have a surface area of greater than about 25 m.sup.2 /g.

Abstract: A method of forming preceramic polymers using a polysiloxane having repeat units of the formula [RSi(H)O].sub.n (where R is a lower alkyl group having from 1 to about 6 carbon atoms, a cycloalkyl group having from 3 to about 6 carbon atoms, a substituted or unsubstituted lower aryl group having from 6 to about 10 carbon atoms, n is an integer 1 or greater), by reacting it with a (poly)silylamide is disclosed. Preferably, the poly(silylamide) is a polymeric alkali metal silylamide of the formula [(R.sup.1 SiHNH).sub.a (R.sup.1 SiN).sub.b (R.sup.1 SiHNM).sub.c ].sub.m where a+b+c=1; R.sup.

Abstract: A polyhydridosilane has a catenated silicon backbone of 9 to 4000 silicon atoms with an average number of hydrogen atoms per silicon atom in the range of 0.3 to 2.2, at least 0.1 gram of the polyhydridosilane being soluble at 20.degree. C. in 100 grams of tetrahydrofuran, toluene, or methylene chloride. The polyhydridosilane can be derivatized or it can be converted to a pyropolymer or a nitrogen-containing pyropolymer which is useful as an abrasive, ceramic, electrical, or electro-optical material.

Abstract: A process for producing silane, which comprises forming a powdery mixture by mixing silica powder recovered from geothermal hot water with metallic magnesium powder, heating and reducing said powdery mixture to convert it to magnesium silicide and then reacting an organic acid with said magnesium silicide to produce silane and recovering said silane.

Abstract: Silicon nitride powder may be prepared by subjecting a composite comprising at least a monolayer of a carbonaceous pyropolymer possessing recurring units containing at least carbon and hydrogen atoms on the surface of a silica support to the action of nitrogen-containing atmospheres at nitriding conditions to form silicon nitride.

Abstract: A crosslinkable composition comprising at least one polysilazane containing at least 2, preferably at least 3, .tbd.SiH groups per molecule and at least 2 SiR.sub.2 groups per molecule, R.sub.2 being an unsaturated hydrocarbon radical and a catalytically effective quantity of a metal element or of a metal compound to catalyze the hydrosilylation reaction SiH/SiR.sub.2.The compositions according to the invention can crosslink under the effect of heat and can be used for coating or impregnating substrates with ceramic material after pyrolysis. The mechanical properties of the crosslinked compositions are assessed by evaluating the relative rigidity RR measured by the fiber torsion pendulum method (FIG. 1).

Abstract: The invention is a process for the manufacture of shaped articles of reaction-bonded silicon nitride in which pre-shaped articles of silicon powder are heated in a first stage under a nitrogen gas pressure of at least 6 MPa at a heating rate of not more than 50.degree. C. per hour to a reaction temperature below the melting point of silicon, the article is maintained at the reaction temperature for at least 0.5 hours and subsequently, in a second stage, heating the article at a heating rate of at least 500.degree. C. per hour to a temperature above the melting point of silicon and maintaining the article at that temperature for from 1 to 7 hours. The process can nitridate both pre-shaped articles consisting of silicon powder and, optionally, up to 15% by weight Si.sub.3 N.sub.4 powder and those containing up to 10% by weight of a sintering aid such as Y.sub.2 O.sub.3.

Abstract: Ultrapure silicon nitride precursor is made by: (a) continuously reacting liquid silicon halide (SiCl.sub.4) with an excess of liquid ammonia (NH.sub.3) (i) in the effective absence of contaminants, (ii) at a reaction situs in an inert atmosphere to form the silicon nitride precursor as a precipitate, and (iii) with a ratio of liquid ammonia to silicon halide (equal to or greater than 21 molar) effective to solubilize any gas reaction products; (b) providing a pressure differential to simultaneously and continuously withdraw a filtered portion of the excess liquid ammonia to leave the silicon nitride precursor precipitate in the reaction situs; and (c) adding ammonia to the excess of ammonia in said reaction situs to replace the withdrawn filtered portion of the liquid ammonia.The reaction is carried out with vigorous stirring of the liquid mixture and the atmosphere over the entire mixture is regulated to contain only ammonia vapor and nitrogen.

Abstract: A process is disclosed for producing high purity silicon nitride. The process involves contacting an organic compound which can be decomposed into silicon dioxide with essentially anhydrous ammonia at ambient temperature to form a two phase system consisting essentially of ammonia gas and the vapor of the organic compound and heating the two phase system at a sufficient temperature for a sufficient time to form the high purity silicon nitride.

Abstract: A method of preparing silazane polymers, with 3 or more repeating units, of the general formula--((CH.sub.3).sub.2 N).sub.e Si(R).sub.a (R'HN).sub.f H.sub.c (NR').sub.g --and a (CH.sub.3).sub.2 NH byproduct group where R is hydrogen, an alkyl group having 1-6 carbon atoms or an aryl group having 6-12 carbon atoms, a=0, or 1, b=2-4, C=0-2, d=0 or 1, e=0-2, f=0-2, g=1-3 and a+c+e+f+g=4 for the polymer units; and R' is hydrogen or methyl, whereby the silazane polymer is substantially free of halide impurities, and wherein this method comprises:transaminating an aminosilane of the general formula (R).sub.a ((CH.sub.3).sub.2 N).sub.b H.sub.c S; where R is defined as above and a+b+c=4 with an amine of the general formula (CH.sub.3).sub.d NH.sub.3-d whereby d is defined as above and the amine has a molecular weight lower than 45 all in the presence of an acid catalyst or the ammonium salt of the acid and thereafter condensing to form the polymer.

Abstract: Disilane Si.sub.2 H.sub.6 is obtained with good yield by reduction reaction of Si.sub.2 Cl.sub.6 with a mixture of LiH and LiAlH.sub.4 in an organic liquid medium such as n-butyl ether. Usually the reaction temperature is -25.degree. C. to 50.degree. C. A suitable range of the mole ratio of LiH to LiAlH.sub.4 is from 0.8 to 40. It is impracticable to reduce Si.sub.2 Cl.sub.6 to Si.sub.2 H.sub.6 by using LiH alone as the reducing agent, but the reaction proceeds smoothly when a LiH/LiAlH.sub.4 mixture is used. The use of the mixture is economically advantageous over the use of expensive LiAlH.sub.4 alone.

Abstract: A process is disclosed for producing high purity high surface area silicon nitride. The process involves contacting silicon tetrachloride with water to form a two phase system consisting essentially of a solid phase which is essentially silica gel and a liquid phase, heating the two phase system at a sufficient temperature for a sufficient time to partially dehydrate the silica gel followed by removing the solid phase from the liquid phase. A slurry is then formed of the solid phase in an aqueous solution of a water soluble organic carbon source. A dispersing agent is added to the slurry to disperse the silica gel, and the pH of the slurry is adjusted to greater than about 7, followed by heating the slurry at a sufficient temperature for a sufficient time to remove essentially all of the water and to decompose the carbon source.

Abstract: A method of improving the quality of hot pressed Si.sub.3 N.sub.4 bodies is disclosed. Unpurified silicon powder and admixed oxygen carrying agents are compacted to form a preform. The preform is nitrided, facilitated by the presence of certain impurities, to agglomerate the mixture to an increased density no greater than 2.7 gm/cm.sup.3. The nitrided preform is immersed in one or more stages in one or more leaching solutions of effective concentration to remove the selected impurities. The treated preform is then hot pressed to full density accompanied by a substantial reduction or absence of undesirable impurities such as iron silicide, which can conventionally form during hot pressing.

Abstract: A process for the preparation of silicon nitride powders, which are suitable for the manufacture of high quality structural ceramics is described. The synthesis process is based on the reduction of silicon dioxide by carbon in a nitrogen stream at elevated temperatures to form alpha silicon nitride. Silicon nitride powders of various morphologies are obtained by this technique by varying either the type of reactants used or the process conditions. Structural ceramics with densities exceeding 99% of theoretical and having satisfactory mechanical strength and oxidation resistance were sintered from powders synthesized by the method of this invention.

Abstract: Fine silicon nitride powders, fine silicon carbide powders, or fine powdery mixture of silicon nitride and silicon carbide are prepared by vapor phase reaction of an aminosilane compound, a cyanosilane compound, a silazane compound, an alkoxysilane compound or a siloxane compound and heat treatment of the resulting fine powders in a non-oxidizing gas atmosphere.

Abstract: A silicon nitride powder having an enhanced sintering activity is prepared by heating a mixture of a nitrogen-containing silane compound and a sintering aid in a non-oxidizing atmosphere.

Abstract: To efficiently produce a fine powder of silicon carbide or silicon nitride useful as engineering ceramics material, a granulated or pelleted mixture of silica powder and carbon powder is put into a plurality of containers each of which has ventilating means such as vent holes, and the containers are introduced into an upper section of a vertically extending heating zone in turn. In the heating zone a nonoxidizing gas atmosphere, which is a nitriding gas atmosphere when producing silicon nitride, is maintained at a temperature of 1400.degree.-2100.degree. C. The granulated or pelleted mixture in the containers undergoes reaction while each container is downwardly moved in the heating zone, either continuously or stepwise, so as to stay in the heating zone for a predetermined length of time.

Abstract: Disclosed is a process for producing silicon carbide whisker by mixing a silicon source with carbon black and subjecting the resultant mixture to heating treatment in an inert atmosphere, which comprises using a silica recovered from geothermal hot water as said silicon source.The process of the present invention has the advantages of (1) being capable of producing SiC whiskers with slender diameters and small variance of lengths, and (2) contributing to effective utilization of resources by utilizing the silica recovered from geothermal hot water as the silicon source, etc. and its industrial value is great as the method for providing SiC whisker reinforcing material for various kinds of composite materials.

Abstract: A process for the growth of silicon nitride whiskers consists of reacting a mixture of carbon and silicon dioxide powders at elevated temperature in a stream of nitrogen, said reaction mixture containing small amounts of metals such as chromium, magnesium, and nickel which promote the growth of silicon nitride whiskers by vapor phase transport. The whiskers obtained as a result of this invention are of much higher purity than those obtained by prior art.

Abstract: Fine spherical amorphous powder represented by the general formula:SiCxNyHzwherein 0.1<x<2.0, 0.1<y<1.5 and 0<z<4, is prepared by vapor phase oxidation of organosilicon compound substantially free from halogen atoms and oxygen atoms. An ultimately crystalline, uniform and fine powder of silicon nitride and silicon carbide is prepared by heat treatment of the fine spherical amorphous powder. The powder and the crystalline uniform, and fine powder are used as raw materials for composite ceramics and as functional materials for solar cell.

Abstract: A method for producing a high-grade fine powder of .alpha.-form silicon nitride (.alpha.-Si.sub.3 N.sub.4) for use as sintered bodies excellent in heat-stability and mechanical strength which comprises heat-treating, in an atmosphere containing nitrogen, a mixture prepared by adding additive:a mixture of at least one of Mg, Ca, and compounds thereof with 0.01-1 part by weight of silicon nitride powder,in a total amount of 0.001-0.1 part by weight calculated in terms of elemental weight(s) of Mg or/and Ca, and 1 part or less by weight of silicon nitride powder, to 1 part by weight of silicon oxide powder and 0.4-4 parts by weight of carbon powder.

Abstract: This specification teaches a method of making a special purity alpha silicon nitride powder which is free from halogen-containing and metal-containing compounds as trace constituents. The method has the following steps. Tetraethyl orthosilicate (TEOS) is prepared of requisite purity. A fine mist of the TEOS solution is delivered to a heated reaction zone. Ammonia is contacted with the fine mist of TEOS in the reaction zone. A reaction product of this reaction is collected, the reaction product being amorphous silica and carbon black. The reaction product is heated to a temperature in a range of 1300.degree.-1500.degree. C. The heated reaction product is subjected to a nitrogen gas treatment to convert the silica of the reaction product into a special purity alpha silicon nitride powder because of the chemical reactions occurring between the silica, carbon black, and nitrogen. The prepared alpha silicon nitride powder is then recovered.

Abstract: In a method of manufacturing parts or powders made of a compound of silicon or of a metal by exothermally reacting parts or powders of silicon or a metal in the solid state with a gas, wherein the differential flow rate or the pressure variation of the reactive gas in contact with the part or the powder is sensed, and the reaction is performed at increasing temperatures as a function of the said differential flow rate or pressure of the reactive gas:the improvement wherein a maximum differential flow rate or a maximum speed of pressure drop of the reactive gas is predetermined as a function of the chemical nature of the parts or powders, and optionally as a function of the density and the size of the parts, and the rise in temperature is suspended when the differential flow rate or the speed of pressure drop of the reactive gas reaches the predetermined maximum value, beyond which the reaction would run away and prevent complete transformation of the parts or the powders being obtained.

Abstract: After sintering, ceramic body of Si.sub.3 N.sub.4 -SiC is heat-treated at 500.degree.-1500.degree. C. in atmosphere of gas mixture of chlorine and nitrogen whereby SiC is converted into silicon chloride which in turn is nitrided to form Si.sub.3 N.sub.4 in the pores of the ceramic body to provide closed pore structure. Gas mixture may contain oxygen. Heat treatment may be conducted in pressurized atmosphere of gas mixture.

Abstract: Method produces reaction sintered silicon nitride complex shapes. Parent material (moldings of silicon powder-cured resin) and bonding or joint material (silicon powder-uncured resin) are integrally connected by steps of heat-curing the resin in the joint, heating the body thus bonded together to pyrolyze the cured resin and sinter the silicon powder, the pyrolysis gas reducing oxide film on silicon, and sintered parent material and joint material are simultaneously nitrided and integrally connected by continuous silicon nitride.

Abstract: A process for sintering or reaction sintering ceramic or refractory materials with hot plasma gases. The hot plasma gases are produced by injecting a combined primary plasma arc with a secondary gas stream directly into a reaction furnace. The secondary gas stream is tangentially injected into the primary plasma arc gas stream to mix the gases for the required sintering temperature at the highest energy efficiency. The plasma torches are positioned in the furnace ports so that the plasma gas flow is perpendicular to the furnace process gas flow. This process is inexpensive and efficient and results in a superior quality sintered product. It may be adapted to continuous or periodic kilns to achieve a high furnace productivity.

Abstract: In order to obtain substances that are optically transparent in the infrared range, usable in the manufacture of optical fibers or radiation emitters, a metal or metalloid chalcogenide other than an oxide is produced by a double-substitution reaction between a starting chalcogen compound--particularly a hydride such as H.sub.2 S, H.sub.2 Se or H.sub.2 Te--and a salt of the desired metal or metalloid, e.g. a chloride. The starting compound and the reactant salt preferably are vaporized at a temperature below the melting point of the resulting metal chalcogenide which thereupon precipitates in the reaction chamber.

Abstract: A method of producing ultrafine powders comprising metal silicide powder and the products produced by the method are disclosed. The ultrafine powders comprising metal silicide powders are ideally suited to form stable colloidal suspensions which are used in the production of conductive metal silicide containing films. The process employs gaseous reactants comprising a metal halide and a silicon-containing compound. The reactants are exposed to high intensity light to produce ultrafine powders. In addition to the production of metal silicide powders, the ultrafine powders may also include silicon powder and metal subhalide powder. The ultrafine powders are particularly suited for use in VLSI and VVLSI production.

Abstract: A process for producing amorphous or crystalline silicon nitride is disclosed which comprises reacting silicon disulfide ammonia gas at elevated temperature. In a preferred embodiment silicon disulfide in the form of "whiskers" or needles is heated at temperature ranging from about 900.degree. C. to about 1200.degree. C. to produce silicon nitride which retains the whisker or needle morphological characteristics of the silicon disulfide. Silicon carbide, e.g. in the form of whiskers, also can be prepared by reacting substituted ammonia, e.g. methylamine, or a hydrocarbon containing active hydrogen-containing groups, such as ethylene, with silicon disulfide, at elevated temperature, e.g. 900.degree. C.

Abstract: A process is disclosed for preparing R.sub.3 SiNH-containing hydrosilazane polymer by contacting and reacting trichlorosilane with a disilazane (R.sub.3 Si).sub.2 NH where R is vinyl, hydrogen, phenyl, or alkyl radicals containing 1 to 3 carbon atoms. These hydrosilazane polymers are useful, when fired at high temperatures, in the formation of silicon nitride and silicon nitride-containing ceramic materials.

Abstract: A process for the production of silicon nitride by reaction of silicon dioxide, carbon and nitrogen at temperatures above about 1300.degree. C. whereby a partial pressure of nitrogen above 1 bar is maintained during the reaction.

Abstract: Precursors, particularly of non-oxide ceramics, are prepared by special seeding, under carefully controlled conditions. Such procedures can lead to the preparation of unique powders, which may be useful, for example as abrasives, or further processed in special manner to prepare a variety of metal substances. Such procedures can permit final firing to sintered product.

Abstract: A method of manufacturing silicon nitride whiskers in which a carbon and silicon containing material having a thin configuration and sufficient porosity to permit both the passage of a gas therethrough and to provide spaces for growing whiskers therein is charged on a gas-permeable tray, and heated in a furnace of non-oxidizing atmosphere. The tray is moved intermittently through a series of temperature zones, increasing stage-by-stage from about 400.degree. C. to 1,300.degree. C., while a non-oxidizing gas is circulated through the porous material to remove any impurities. Thereafter, the heated tray is intermittently moved through a series of increasing temperature stages from about 1,350.degree. C. to 1,450.degree. C. in the presence of a flow of nitrogen gas to effect whisker growth. The heat-treated silicon nitride-containing material is dispersed in a two-phase mixture of a hydrophobic organic liquid and water. The desired silicon nitride whiskers can be isolated from the aqueous phase.

Abstract: Silicon nitride whiskers having a long fiber length in which .beta. type silicon nitride is well developed are produced by reacting a mixture of silica, carbon and cryolite in the specific molar ratio in a mixed gas atmosphere of N.sub.2 and NH.sub.3 by heating the mixture at a temperature of 1,250.degree.-1,450.degree. C. Kira of a ceramic industry waste may be used in place of silica and in this case N.sub.2 alone is used as a nitriding atmosphere.

Abstract: Crystalline silicon nitride powder in the form of granular particles having a large tap density and having good filling characteristics is produced by heating amorphous silicon nitride powder under an inert or reducing gas atmosphere. The amorphous silicon nitride powder is ground prior to the heating and the powder to be heated is maintained at a temperature of 1250.degree. C. to 1430.degree. C. for at least one hour in the course of temperature rise.

Abstract: Disclosed is a process for preparing silicon nitride powder, which comprises baking a powdery mixture comprising (i) 1 part by weight of silica powder, or a silica-containing substance in terms of silica, (ii) 0.4 to 4 parts by weight of carbon powder, or a substance generating carbon by baking, in terms of carbon and (iii) 0.005 to 1 part by weight of silicon nitride powder synthesized by a silica reduction method, at a temperature of from 1350.degree. to 1550.degree. C. in a non-oxidative atmosphere containing nitrogen.

Abstract: A method and device for conducting gettering. The gettering is conducted with one of an LiB, LiSi or LiAl system. Preferably the LiB system is of the formula Li.sub.x B.sub.1-x wherein 0<x<1 with gettering conducted at room or slightly elevated temperature of about 100.degree.-200.degree. C.

Abstract: A silicon aluminium oxynitride product having the crystal lattice structure of silicon oxynitride but of expanded cell dimensions is produced by sintering a powder mixture of 50 to 60 wt % of Si.sub.3 N.sub.4, 22 to 35 wt % SiO.sub.2, 1 to 20 wt % Al.sub.2 O.sub.3 and 1 to 15 wt % of at least one oxide of Y, Li, Mg, Ca, Sc, Ce or another rare earth element, the molar ratio of SiO.sub.2 to Si.sub.3 N.sub.4 being greater than 1:1 and the percentages being based on the total weight of the ingredients. Sintering is effected at 1600.degree. to 1900.degree. C. in a non-oxidizing atmosphere so that the Al.sub.2 O.sub.3, said at least one oxide and part of the SiO.sub.2 in the mixture react to form a liquid phase from which silicon aluminium oxynitride having an expanded silicon oxynitride crystal lattice is crystallized. The sintered material is cooled to form a product containing said silicon aluminium oxynitride and at least one grain boundary phase containing silicon and the metal(s) of said at least one oxide.

Abstract: Monolithic Si.sub.3 N.sub.4 ceramic bodies having a lower density outer layer are produced by a one-step sintering in an ambient atmosphere of water vapor and a nonreactive diluent gas, and are useful, for example, as abradable seal and impact resistant structural elements.

Abstract: Semiconductor doping compositions comprising a suspension of (a) a dopant material, in the form of finely divided spherical particles of narrow size distribution from about 0.1 D to D, where D is the diameter of the largest particle and is no more than about (1.mu.) comprising a member selected from the group consisting of B.sub.x Si.sub.y, B.sub.x N.sub.y, P.sub.x Si.sub.y, P.sub.x N.sub.y, As.sub.x Si.sub.y and Sb.sub.x Si.sub.y wherein x and y vary from about 0.001 to about 99.999 mole percent, (b) an effective amount of a thermally degradable polymeric organic binder such as polymethyl methacrylate; and (c) an amount of an organic solvent, such a cyclohexanone, sufficient to dissolve said polymeric organic binder, such as polymethylmethacrylate, and to disperse said dopant material are disclosed.

Abstract: Impurities are removed from chaff by acid treatment, and the chaff is heated for carbonization. Silicon is reduced from the carbonized chaff, and nitrided to form silicon nitride.

Abstract: What is disclosed is a process for preparing R.sub.3 'SiNH-containing metallosilazane polymer containing boron, titanium, or phosphorous by contacting and reacting chlorine-containing disilanes and certain reactive metal halides with [R.sub.3 'Si].sub.2 NH where R' is vinyl, hydrogen, or alkyl radical of 1-3 carbon atoms, or phenyl. Preferred reactive metal halides include BBr.sub.3, TiCl.sub.4, and PCl.sub.3. The metallosilazane polymers are useful as chemical intermediates to provide silicon-containing chemical compounds. The metallosilazane polymers are also useful in the formation of ceramic material. The ceramic materials may be formed by heating the metallosilazane polymer at elevated temperatures in an inert atmosphere or in a vacuum.

Abstract: A process for producing a silicon nitride sintered product having high toughness is described, comprising blending from 97 to 57% by weight of metallic silicon powder having a maximum particle size of 25 .mu.m or less with from 1 to 15% by weight, calculated as TiN, of a TiN powder having a maximum particle size of 20 .mu.m or less or a powder of titanium component capable of changing into TiN during reaction sintering, and from 2 to 28% by weight of one or more components selected from the group consisting of AlN, Al.sub.2 O.sub.3, SiO.sub.2 and oxides of rare earth elements, molding the resulting mixture, carrying out reaction sintering in a nonoxidizing atmosphere of a nitrogen gas or a nitrogen-containing mixed gas, and thereafter resintering in the same atmosphere at a temperature of from 1,600.degree. C. to 2,200.degree. C.

Abstract: .alpha.-Silicon nitride powder which is used as a raw material for the preparation of high strength silicon nitride with additives such as magnesia and yttrium oxide, and other sintered materials suitable for high temperatures gas turbine engine components and the like, is prepared by heating a powdered mixture of silica, carbon and at least one component selected from the group consisting of silicon nitride, silicon carbide and silicon oxynitride in a nitrogen containing atmosphere and then optionally subjecting the material to a heat treatment in an oxidizing atmosphere for decarbonization of said material as required.

Abstract: A printing member for electrostatic photocopying, comprises a substrate having a conductive surface and a photoelectric-sensitive, electrically chargeable layer deposited on the conductive surface of the substrate. The electrically chargeable layer has a non-single crystal semiconductor layer having a built-in-potential, or the non-single crystal semiconductor layer and an insulating or semi-insulating layer.

Abstract: A method for synthesizing amorphous silicon nitride, wherein silicon halide and ammonia are reacted in a reaction vessel at a high temperature in the absence of oxygen to thereby synthesize powder of amorphous silicon nitride, then the powder is separated from a gas containing therein gaseous ammonia halide which has been produced simultaneously with said amorphous silicon nitride by use of a collecting means, comprises directly mixing, in advance of the separation, cool gas containing therein neither oxygen nor moisture into said gas to cool down said powder and gas so that both substances may be put in said collecting means without deposition of ammonium halide to the inner wall of the reaction vessel, and other component parts.

Abstract: A method of producing silicon nitride which comprises heating wet process white carbon in the presence of a carbon source and a source of nitrogen.

Abstract: Silicon nitride powder having a uniform particle size of regular crystals is produced by a process comprising the steps of:(1) reacting (i) at least one compound having the general formula [I]R.sub.m SiCl.sub.4-m [I]wherein R is an aliphatic residual group having 1 to 4 carbon atoms or an aromatic residual group having 6 to 8 carbon atoms and m is 1, 2, or 3 and (ii) a compound having the general formula [II]H.sub.n SiCl.sub.4-n [II]wherein n is 0, 1, 2, or 3, the ratio of silicon atoms to carbon atoms (Si/C) in both compounds [I] and [II] being 0.5 to 50 with ammonia and, then,(2) calcining the resultant reaction product in the first step at a temperature of 1200.degree. C. to 1700.degree. C. under an inert or reducing gas atmosphere.

Abstract: Pre-polymers which are alkoxylated or phenoxylated methylpolysilanes are useful for the preparation of fine grained silicon carbide ceramic materials and silicon carbide-containing ceramics. The pre-polymers exhibit ease of handling and their use to obtain silicon carbide ceramic materials results in high yields.

Abstract: Fine metallic nitride powders having a high purity are prepared, without causing any plugging or other problems in the reaction apparatus and with easy heat control of the reaction, by reacting a metallic halide with liquid ammonia in the presence of an organic solvent which has a specific gravity higher than that of liquid ammonia, and also is not miscible or is only slightly miscible with liquid ammonia at a reaction temperature. The process according to the present invention is effected by introducing the metallic halide into the lower organic solvent layer of the reaction system.