Abstract: By using a halogen-free siloxane and an organometallic compound containing at least one metal other than silicon as feed stocks, and simultaneously atomizing and burning them in a flame, spherical particles of silica-containing compound oxide are prepared which are substantially halogen-free, consist of 0.5-99% by weight of metal oxides and the balance of silica, and have a particle size of 10 nm to 3 ?m. The particles are useful as a filler in epoxy resin base semiconductor sealants, a refractive index modifier or the like.

Abstract: A hydrophobic silica fine powder is prepared by premixing a hydrophilic silica fine powder with a dimer diol siloxane or cyclic siloxane as a hydrophobizing agent, mixing them in a ball mill for achieving dispersion and for achieving cleavage or disintegration and consolidation, and thereafter heating at 100-300° C. in an ammonia or amine-containing atmosphere. The powder has an aerated bulk density of 100-300 g/l, a specific surface area of 40-300 m2/g, a primary particle diameter of 10-120 nm, and a degree of hydrophobization of 40-80 as measured by methanol titration and is less bulky, easy to handle and disperse and stable in a kneaded mixture.

Abstract: A hydrophobic silica fine powder is prepared by premixing a hydrophilic silica fine powder with a dimer diol siloxane or cyclic siloxane as a hydrophobizing agent, mixing them in a ball mill for achieving dispersion and for achieving cleavage or disintegration and consolidation, and thereafter heating at 100-300° C. in an ammonia or amine-containing atmosphere. The powder has an aerated bulk density of 100-300 g/l, a specific surface area of 40-300 m2/g, a primary particle diameter of 10-120 nm, and a degree of hydrophobization of 40-80 as measured by methanol titration and is less bulky, easy to handle and disperse and stable in a kneaded mixture.

Abstract: By simultaneously atomizing a siloxane and two organometallic compounds of different metals M1 and M2 exclusive of silicon in a flame for combustion, spherical amorphous ternary complex oxide fine particles are obtained which are substantially free of chlorine, have a particle size of 10-500 nm, and have a silica content A of 1-99 wt %, a M1 oxide content B of 1-90 wt % and a M2 oxide content C of 1-90 wt %, all based on the weight of oxides excluding carbon, provided that A+B+C≈100. An electrostatic image developer comprising the fine particles is improved in fluidity and cleanability and bears a uniform and stable quantity of electric charge.

Abstract: By atomizing a siloxane and an organic titanium compound for flame combustion, spherical complex oxide fine particles of amorphous silica-titania are obtained having a particle size of 10-300 nm, a specific surface area of 10-100 m2/g, and a titania content of 1-99% by weight. By hydrophobizing the fine particles and adding them to a toner, a developer is obtained which is improved in fluidity, cleanability and uniform and stable charging.

Abstract: By simultaneously atomizing a siloxane and two organometallic compounds of different metals M1 and M2 exclusive of silicon in a flame for combustion, spherical amorphous ternary complex oxide fine particles are obtained which are substantially free of chlorine, have a particle size of 10-500 nm, and have a silica content A of 1-99 wt %, a M1 oxide content B of 1-90 wt % and a M2 oxide content C of 1-90 wt %, all based on the weight of oxides excluding carbon, provided that A+B+C≈100. An electrostatic image developer comprising the fine particles is improved in fluidity and cleanability and bears a uniform and stable quantity of electric charge.

Abstract: A hydrophobic silica fine powder is prepared by premixing a hydrophilic silica fine powder with a dimer diol siloxane or cyclic siloxane as a hydrophobizing agent, mixing them in a ball mill for achieving dispersion and for achieving cleavage or disintegration and consolidation, and thereafter heating at 100-300° C. in an ammonia or amine-containing atmosphere. The powder has an aerated bulk density of 100-300 g/l, a specific surface area of 40-300 m2/g, a primary particle diameter of 10-120 nm, and a degree of hydrophobization of 40-80 as measured by methanol titration and is less bulky, easy to handle and disperse and stable in a kneaded mixture.

Abstract: By using a halogen-free siloxane and an organometallic compound containing at least one metal other than silicon as feed stocks, and simultaneously atomizing and burning them in a flame, spherical particles of silica-containing compound oxide are prepared which are substantially halogen-free, consist of 0.5-99% by weight of metal oxides and the balance of silica, and have a particle size of 10 nm to 3 &mgr;m. The particles are useful as a filler in epoxy resin base semiconductor sealants, a refractive index modifier or the like.

Abstract: Spherical, non-crystalline silica particles made by burning a non-halogenated siloxane starting material are substantially halogen-free, and have a content of metallic impurities other than silicon of not more than 1 ppm, a particle size of 10 nm to 10 &mgr;m and a specific surface area of 3-300 m2/g. Production of the particles is carried out by oxidative combustion of the non-halogenated siloxane in a flame at a high adiabatic flame temperature to effect the formation of a large number of core particles and promote their coalescence and growth.

Abstract: By atomizing a siloxane and an organic titanium compound for flame combustion, spherical complex oxide fine particles of amorphous silica-titania are obtained having a particle size of 10-300 nm, a specific surface area of 10-100 m2/g, and a titania content of 1-99% by weight. By hydrophobizing the fine particles and adding them to a toner, a developer is obtained which is improved in fluidity, cleanability and uniform and stable charging.

Abstract: By atomizing a siloxane and an organic titanium compound for flame combustion, spherical complex oxide fine particles of amorphous silica-titania are obtained having a particle size of 10-300 nm, a specific surface area of 20-100 m2/g, and a titania content of 1-99% by weight. By hydrophobizing the fine particles and adding them to a toner, a developer is obtained which is improved in fluidity, cleanability and uniform and stable charging.

Abstract: Spherical silica powder is produced by feeding silica powder having an average particle size of 0.3-40 &mgr;m to a burner flame formed with a flammable gas so as to continuously melt and spheroidize the particles within the flame. The use of a non-halogenated siloxane and/or alkoxysilane as an auxiliary flame-generating source raises the flame temperature and increases the length of the composite flame formed by combustion of the fuel gas with the siloxane or alkoxysilane. Moreover, the fine particles of silica that form as a result of siloxane or alkoxysilane combustion unite and coalesce with the particles of starting silica. These effects accelerate melting and spheroidization of the starting silica powder, resulting in thermally efficient and cost-effective spherical silica powder production.

Abstract: Spherical, non-crystalline silica particles made by burning a non-halogenated siloxane starting material are substantially halogen-free, and have a content of metallic impurities other than silicon of not more than 1 ppm, a particle size of 10 nm to 10 &mgr;m and a specific surface area of 3-300 m2/g. Production of the particles is carried out by oxidative combustion of the non-halogenated siloxane in a flame at a high adiabatic flame temperature to effect the formation of a large number of core particles and promote their coalescence and growth.

Abstract: Spherical silica powder is produced by feeding silica powder having an average particle size of 0.3-40 &mgr;m to a burner flame formed with a flammable gas so as to continuously melt and spheroidize the particles within the flame. The use of a non-halogenated siloxane and/or alkoxysilane as an auxiliary flame-generating source raises the flame temperature and increases the length of the composite flame formed by combustion of the fuel gas with the siloxane or alkoxysilane. Moreover, the fine particles of silica that form as a result of siloxane or alkoxysilane combustion unite and coalesce with the particles of starting silica. These effects accelerate melting and spheroidization of the starting silica powder, resulting in thermally efficient and cost-effective spherical silica powder production.

Abstract: In a first step, a crosslinkable organopolysiloxane oil (2) is mixed with an inorganic filler (3) in a flow jet mixer (1) to form a flowing silicone rubber compound. In a second step, the silicone rubber compound is fed into a tank (6) equipped at the bottom with a vacuum discharge pump (8) and maintained in vacuum where the compound is continuously deaerated, and a thixotropy controlling agent (10) is then added and mixed with the compound in a mixer (9). In a third step, a crosslinking agent (12) is added and mixed with the silicone rubber compound in a KRC kneader (11), and the compound is degassed in a mixer (13). The process continuously produces an RTV silicone rubber composition which is anti-sagging and improved in applicability on use.

Abstract: Silicon nitride powder is continuously prepared by feeding metallic silicon powder into a fluidized bed comprising silicon nitride powder and nitrogen or ammonia gas and discharging a nitrided product from the fluidized bed. The metallic silicon powder is pretreated at a temperature of 1,000.degree.-1,400.degree. C. under a vacuum of 0.001-100 Torr before it is subject to nitriding reaction.

Abstract: In a fluidized bed reactor for preparing a metal nitride by feeding metal powder and a non-oxidizing gas containing N.sub.2 or NH.sub.3 into a reaction tube (1) to form a fluidized bed (2) therein and heating the fluidized bed for nitriding the metal powder, an envelope (11) encloses the reaction tube (1) for preventing the surrounding air from entering the reaction tube. A heater (9) is disposed outside the envelope (11) for heating the fluidized bed (2) to 1,200.degree. C. or higher. The envelope prevents penetration of the surrounding air into the reaction tube and also prevents deterioration of the heater and surrounding components by scattering of metal fines. The reactor ensures safe operation to prepare metal nitride powder of high purity on an industrial scale.

Abstract: Silicon nitride powder is prepared by nitriding metallic silicon powder in a nitriding gas atmosphere at a temperature of 1,000.degree. C.-1,500.degree. C. Midway the nitriding step, the nitrided product is heat treated in an inert non-oxidizing gas atmosphere or vacuum at a temperature higher than the nitriding temperature, but lower than 1,600.degree. C. The product is nitrided again, obtaining high .alpha.-content silicon nitride powder.

Abstract: In a method for preparing a high .alpha.-type silicon nitride powder by adding to and mixing with metallic silicon powder a copper catalyst and nitriding the mixture in a non-oxidizing gas atmosphere containing nitrogen or ammonia at 1,000.degree. to 1,500.degree. C., the amount of copper catalyst is limited to from 0.05 % to less than 0.5 % by weight of copper based on the weight of the metallic silicon. There is obtained silicon nitride powder of high purity at low cost and high efficiency since the copper catalyst can be efficiently removed from the silicon nitride powder through conventional acid treatment.

Abstract: The invention provides an efficient method for the dehydration, i.e. removal of silicon-bonded hydroxy groups, of a porous silica body before vitrification as a precursor of quartz glass-made optical fibers obtained by the flame hydrolysis of a silicon compound and deposition of fine silica particles formed therefrom. The problems and disadvantages accompanying the use of conventional dehydrating agents can be solved in the invention by heating the hydroxy-containing porous silica body at 1000.degree. to 1300.degree. C. in an atmosphere containing thionyl fluoride or sulfuryl fluoride as the dehydrating agent which is also effective as a dechlorinating agent so that the optical fibers prepared from the quartz glass material of the invention are highly transparent and resistant against hydrogen-containing atmosphere at elevated temperatures.