Abstract: A process for the preparation of copper oxide superconductors which comprises (1) mixing and grinding yttrium nitrate hydrate, copper nitride, and an oxidizing agent such as barium peroxide in a suitable solvent; (2) forming a paste thereof; (3) applying the paste to a substrate; (4) heating the substrate with the paste thereon; and (5) therafter cooling. The process yields copper oxide superconducting compounds in a purity of at least 80 percent.

Abstract: A process for the preparation of copper oxide superconductors which comprises (1) mixing copper nitride, an oxidizing agent such as barium peroxide, and yttrium oxide; (2) forming pellets of the aforementioned mixture; (3) heating the pellets; and (4) thereafter cooling the pellets. The process yields copper oxide superconducting compounds in a purity of from about 60 to over 95 percent.

Abstract: A method for low temperature chemical vapor deposition of an SiO.sub.2 based film on a semiconductor structure using selected alkoxysilanes, in particular tetramethoxysilane, trimethoxysilane and triethoxysilane which decompose pyrolytically at lower temperatures than TEOS (tetraethoxysilanes). Ozone is introduced into the reaction chamber to increase deposition rates, lower reaction temperatures and provide a better quality SiO.sub.2 film by generating a more complete oxidation. Ozone is also employed as a reactant for doping SiO.sub.2 based films with oxides of phosphorus and boron.

Abstract: The present invention relates to a process for treating combustible exhaust gases containing poisonous and combustible component gases such as silane and so on, and a combustion system therefor. In the combustion system, the combustible exhaust gases are burnt by downward flames generated from a coaxial, fourfold-pipe burner wherein the flow rates of primary and secondary air are regulated, thereby preventing fine particles of oxides such as silicon dioxide resulting from the combustion of silane, etc. from being deposited onto the nozzle of said burner and allowing deposites, if any, to peel off immediately. Thus, there is no fluctuation in the pressure of the a combustible exhaust gas path, so that constantly stable and continuous combustion is achieved with no difficulty. Removal of dust contained in the exhaust gases comprising fine particles of silicon dioxide, etc.

Abstract: A laser initiated process generates a shock wave of sufficient strength to produce a sintered product. The sintered product is prepared from at least a fuel and an oxidizer that will sustain an explosion in a reaction vessel. The explosion is initiated by introducing a laser beam into the reaction vessel and a shock wave begins to propagate at the point where the explosion is initiated. A sintered product is prepared when the shock wave is sufficiently strong to densify the product. Although the reaction will proceed using a two-component fuel-oxidizer mixture, the reaction is especially useful for producing sintered doped or undoped silicon dioxide (SiO.sub.2) from a reaction mixture containing at least silicon tetrachloride, hydrogen and oxygen. The sintered SiO.sub.2 can be deposited on a deposition surface situated in the reaction vessel to produce a preform that can be processed to produce an optical fiber.

Abstract: While high-performance semiconductor devices encapsulated with a resin composition are subject to the problem of wrong operation due to the alpha-particles emitted from the trace amounts of radioactive impurities, e.g. uranium and thorium, contained in the silica filler incorporated in the resin composition, a means for solving this problem is provided by use of a silicon dioxide powder obtained by the pyrolysis of a volatilizable silicon compound free from radioactive impurities in an oxidizing condition and having an average particle diameter in the range from 0.5 to 100 .mu.m in place of the conventional silica fillers.

Abstract: A process for formation of a silica filler product comprising the steps of subjecting fluidized silicon powder to combustion at a temperature of about 3000.degree. K. and quenching the combustion products to form a silica powder characterized by a large proportion of discrete, non-agglomerated primary particles.

Abstract: Process and apparatus are provided for preparing finely-divided silicon dioxide in good yield by reaction of silicon fluoride in the vapor phase with water vapor, combustible gas and free oxygen-containing gas in a flame reaction zone to form hydrogen fluoride and silicon dioxide entrained in a gaseous reaction mixture; withdrawing the gaseous reaction mixture from the flame reaction zone; and then immediately and rapidly cooling the gaseous reaction mixture and entrained silicon dioxide to a temperature below 700.degree. C. by passing the gaseous reaction mixture in a turbulent flow at a Reynolds number above 300 under constraint through a straight narrow passage in alignment with the gas flow, the passage having a diameter within the range from about 20 to about 150 mm and smooth walls constituting a cooling surface.

Abstract: A process for the production of pyrogenic silicic acid having an increased thickening effect which comprises subjecting silicon-containing materials to a pyrolysis flame while introducing additional energy into the flame. The invention also relates to the product so obtained, particularly useful for articles of dental care.

Abstract: Process and apparatus are provided for preparing finely-divided silicon dioxide having high thickening capacity and good thixotropic properties by reaction of silicon fluoride in the vapor phase with water vapor, combustible gas and free oxygen-containing gas in a flame reaction zone to form silicon dioxide and hydrogen fluoride while cooling the gaseous reaction mixture in that portion of the reaction zone adjacent the base of the flame by contact with a cooling surface maintained at a temperature below 500.degree. C. but above the dew point of the reaction waste gases generated in the flame reaction.

Abstract: A method of burning exhaust gases containing gaseous silane in which the exhaust gases containing gaseous silane to be introduced into a combustion chamber are diluted with an inert gas so that the concentration of silane gas is reduced to less than 30% by volume and the diluted exhaust gases are fed from a nozzle to the combustion chamber and burnt through reaction with air in the combustion chamber while the region between the head of the nozzle top end and the base portion of the burning flame is shielded with an inert gas atmosphere.An inert gas mixing pipe is connected for dilution to an exhaust gas feed section, an enclosure pipe is fitted to the outer circumference of an exhaust gas introduction pipe introduced into the combustion chamber to constitute a double pipe structure, and the enclosure pipe is connected at the rear end thereof to an inert gas feed pipe and slightly protuded at the top end thereof ahead of the top end for the exhaust gas introduction pipe.

Abstract: A method for treating fumed silica in a continuous manner is provided by effecting contact between the fumed silica, while in a fluidized state, with a methyl substituted chlorosilane, hydrochloric acid and a surfactant.

Abstract: A battery of special burners, each adapted for the treatment of a particular range of waste material formed during the conversion of metallurgical grade silicon to high purity silane and silicon, is accompanied by a series arrangement of filters to recover fumed silica by-product and a scrubber to recover muriatic acid as another by-product. All of the wastes are processed, during normal and plant upset waste load conditions, to produce useful by-products in an environmentally acceptable manner rather than waste materials having associated handling and disposal problems.

Abstract: Waste gases resulting from the production of silicon in connection with the ormation or decomposition of chlorosilanes, which gases always contain hydrogen chloride, can be worked up without removal of the hydrogen chloride. For this purpose, the waste gases which, after separation from the chlorosilanes, only contain hydrogen and hydrogen chloride, are subjected to combustion with addition of air and, after addition of silicon tetrachloride, the result being highly dispersed SiO.sub.2. The hydrogen chloride then remaining in the gaseous phase is returned to the process stream for production of trichlorosilane.

Abstract: A method of recovering fumed hydrophobic SiO.sub.2, produced by the flame hydrolysis of a ternary azeotrope of H.sub.2 SiF.sub.6, HF, and H.sub.2 O, is disclosed. The method involves passing the fumed hydrophobic silica, as it leaves the combustion chamber, through a nonclassifying agglomerator at a residence (travel) time of from about 0.5 to several seconds, preferably about 1.0 to about 5.0 seconds, then separating the fumed silica from the product stream in a cyclone separator or other means for collecting dispersoids.

Abstract: Pyrogenically produced silica after separation of the hydrogen halide is mixed with nitrogen and conveyed into a cyclone. After separation of the gases, which are returned into the cooling stretch of the production apparatus, the silica is first mixed with organohalosilane and nitrogen and subsequently with steam and nitrogen. Subsequently the hydrophobization reaction is carried out in known manner in a fluidized bed reactor. The reaction waste gases are returned into the cyclone.

Abstract: A method for reducing surface-area decay of fluoride-containing fumed silica which comprises the step of providing an atmosphere of inert gas in which the fumed silica is disposed. The method, which can be used at ambient temperature, is particularly effective for the storage of a fluoride-containing fumed silica product prepared by a fluoride process, which fumed silica contains between about 2 and about 4 percent fluoride by weight.

Abstract: The residual gas obtained in the pyrogenic production of metal oxides or metalloid oxides contain besides the desired product elemental chlorine if a chlorine containing starting material is employed. After cooling the residual gas the elemental chlorine is reacted to form hydrogen chloride by using an aqueous solution of a reducing agent and in this form the chlorine is subsequently washed out of the residual gas.

Abstract: There is provided a pyrogenic process for the production of finely divided oxide of a metal and/or a metalloid in which there is employed as the starting material a vaporizable halogen compound of a metal and/or metalloid. Because of the starting material there is formed elemental halogen which is an impurity in the oxide formed. To remove the halogen there is supplied to the cooling section of the production plant a mixture of hydrogen and inert gas.

Abstract: Silica fume, the by-product from the manufacture of silicon and ferrosilicon alloys, is dispersed in water and the aqueous dispersion is stabilized to retain its fluidity and redispersibility by treatment with an acid or with a chelating agent.

Abstract: There is prepared pyrogenically produced silicon dioxide-mixed oxide having a BET surface area of 50 to 400 m.sup.2 /g which contains as a constituent of the mixed oxide:0.01 to 10 weight % zirconium dioxide or0.01 to 10 weight % iron oxide (ferric oxide) or0.01 to 9.9 weight % titanium dioxide.Because of the doping with the foreign oxide the silicon dioxide-mixed oxide is more temperature stable than the undoped silicon dioxide. The product can be used as thermal insulation either as unpressed material in free bulk form or as a compacted mixture.

Abstract: A hydrolysis method of purifying silicon tetrachloride is shown that reduces losses in optical fibers made from silica produced therefrom. Water is added to impure liquid silicon tetrachloride, which forms a gel which is then separated from the remaining SiCl.sub.4. Metal impurities, OH-containing impurities, and SiHCl.sub.3 are removed by this process. In a preferred embodiment, the water is added by bubbling a wet gas through the SiCl.sub.4. A residual amount of OH containing impurities and HCl is left after the hydrolysis, which impurities may be further removed by a refluxing technique.

Abstract: In an improved process for the production of a finely divided oxide of a metal, silicon or mixtures thereof by the hydrolytic conversion of a corresponding volatile chloride of said metal, silicon or mixtures thereof in a flame; wherein said volatile chloride or said mixture of volatile chlorides in admixture with a combustible hydrogen-containing gas and air or oxygen are fed to a flame emitting from a burner into a reaction chamber to thereby form an oxide aerosol in waste gases from said burner; cooling said oxide and said waste gases; and separating said oxide from said waste gases; wherein the improvement comprises maintaining said waste gases substantially free of chlorine by reducing chlorine that forms during said conversion in said flame with hydrogen while cooling said waste gas below the temperature at which hydrogen and oxygen react in said waste gas.

Abstract: In case of the pyrogenous production of metal oxides or metalloid oxides, whenever a halogen compound is used as a starting material, an elementary halogen is formed as a byproduct. This may be converted in the cooling section of the reaction apparatus with hydrogen into hydrogen halide.For a better temperature control and prevention of uncontrolled deflagration of the hydrogen in case of the halogen detonating gas reaction, according to the invention the hydrogen is introduced into the cooling section by means of a double jacket pipe, whereby an inert gas is introduced additionally by way of the interstice between the inside wall and the outside jacket of the double jacket pipe into the cooling section.

Abstract: Process for the preparation of a porous, pure silica which is particularly suitable as a catalyst support for a chromium-oxide catalyst used in polymerizing of olefins. The process comprises the steps of converting a silicon-halogen compound to a silica and then admixing with water to form a silica gel. The gel is then spray-dried to achieve the required particle size and pore volume.The silica can then be made into a catalyst by placing on the support a chromium compound and then heating in a non-reducing atmosphere.

Abstract: Process for the preparation of a porous, pure silica which is particularly suitable as a catalyst support for a chromium-oxide catalyst used in polymerizing of olefins. The process comprises the steps of converting a silicon-halogen compound to a silica and then admixing with water to form a silica gel. The gel is then dried and ground to a predetermined particle size. The silica can then be made into a catalyst by placing on the support a chromium compound and then heating in a non-reducing atmosphere.

Abstract: The present invention relates to a process for the continuous manufacture of vitreous synthetic silica doped with fluorine. This process consists of decomposing a silicon compound free of hydrogen in the flame of an inductive plasma burner, thereby forming silica upon reacting with the oxygen contained in the burner feed gas. A gaseous inorganic fluorine compound free of hydrogen, is sent into the flame preferably from outside the burner. Said fluorine compound simultaneously with the silicon compound decomposes whereby fluorine is introduced into the silica, lowering its index of refraction. The doped silica is then deposited on a heat-stable support in the form of a vitreous mass. The doped synthetic silica is particularly useful for making preforms for optical transmission fibers.

Abstract: A method of densifying a fumed metal oxide is disclosed wherein the metal oxide is converted to a flowable sol and then dried to form a fragmented solid which is calcined. The calcined oxide may be wet milled to provide a slip for casting articles such as fused silica crucibles used in melting silicon. The method also permits the production of very refractory fused glass compositions from fumed metal oxides at temperatures substantially below those required where a melting step is employed.

Abstract: An arc heater method and system for producing a high energy source characterized by a housing forming a mixing compartment, a plurality of arc heaters radially mounted on the housing and communicating with the mixing compartment, a reactor communicating with the downstream end of the mixing compartment with a reduced opening therebetween, inlet means at the downstream end of the compartment for introducing an oxidizable metal compound into the reactor, and means within the mixing compartment for flowing superheated gases from the arc heaters at the upstream end of the compartment and into the reactor.

Abstract: An improved process is described for converting aqueous fluosilicic acid waste product into anhydrous hydrogen fluoride and finely divided silica in which aqueous fluosilicic acid is pyrolyzed to produce silica and a dilute aqueous solution of hydrogen fluoride and fluosilic acid. The resulting dilute solution is subjected to electrodialysis, thereby obtaining a hydrogen fluoride concentration greater than that which characterizes the boiling point ridge which divides the phase diagram of the system hydrogen fluoride/fluosilicic acid/water, i.e. HF/H.sub.2 SiF.sub.6 /H.sub.2 O, into two regions. Anhydrous hydrogen fluoride is recovered from the resulting composition by distillation.

Abstract: A method of producing high-purity transparent vitreous silica body through flame hydrolysis of high-purity silane type gas, comprising forming the width in the sectional direction of the reduction area of said flame so as to be about more than 1.5 times as against the diameter of the formed vitreous silica body, and the length of the reduction area of said flame so as to be about more than 2.5 times as against said diameter, while retaining the head portion of the formed vitreous silica body within the reduction area of said flame to synthesize the high-purity transparent vitreous silica body.

Abstract: A process and device for the manufacture of highly disperse silicon dioxide by reacting gaseous organosilanes and other gases that burn with formation of water with oxygen-containing gases in a flame which comprises evaporating the organosilane in an evaporator in such a manner that the level of liquid organosilane is held constant at an organosilane evaporatinng vapor pressure of 0.2 to 1.2 atmospheres gage and, at most, at a temperature of 45.degree. C, preferably 20.degree. to 35.degree. C, above the boiling point of the particular organosilane, maintaining the temperature of the vapor until mixing with the other gases occurs, metering the gas mixture resulting from the mixing through a cone-shaped inlet into a combustion chamber, flushing oxygen-containing gases through an annular nozzle surrounding the inlet into the combustion chamber, and indirectly but positively, cooling the latter.

Abstract: The present invention provides a process for the production of aluminum chloride and alumina of metallurgical grade purity, and valuable by-products from aluminous ores like clay, bauxites and laterites. The process comprises carbo-chlorination of the ore to produce aluminum chloride and other metal chlorides. The aluminum chloride is separated, purified and utilized as such or oxidized to make alumina while the other metal chlorides are processed to recover maximum values.

Abstract: Process for the production of finely divided silicon dioxide having a surface of more than about 380 m.sup.2 /g BET which comprises converting a volatile silicon halide in an inert gas vehicle with a gas forming water upon combustion and oxygen gas or air in a flame, the quantity of oxygen being sufficient for the practically complete combustion of the combustible gas, and the quantities of oxygen or air and combustible gas being sufficient to produce a quantity of water which will at least suffice for the hydrolysis of the volatile silicon halide, said volatile silicon halide consisting essentially of trichlorosilane and said inert gas vehicle consisting for instance of nitrogen, carbon dioxide, noble gases or others the amount of trichlorosilane vapor being about 410-565 g trichlorosilane vapor per Nm.sup.3 /h total gas, the molar ratio of trichlorosilane vapor to nitrogen being about 0.5:1 - 5:1, the molar ratio of hydrogen in the combustible gas to oxygen being about 0.5:1 - 1.

Abstract: Fluorosilicic acid solutions, which normally undergo decomposition when distilled, thereby creating unwanted forms of SiO.sub.2, are rendered stable during distillation by providing in the fluorosilicic acid solution an amount of HF which is at least about 10 parts of HF per 36 parts of H.sub.2 SiF.sub.6 and an amount of H.sub.2 O which is at least about 54 parts of H.sub.2 O per 36 parts of H.sub.2 SiF.sub.6. The mixture is distilled to remove any excess H.sub.2 O and excess HF that is present, without encountering formation of SiO.sub.2, until an azeotropic solution containing about 36% H.sub.2 SiF.sub.6, about 10% HF and about 54% H.sub.2 O is reached. The ternary azeotrope, being of constant quality and concentration, is more suitable for use in various processes, such as processes for making fumed SiO.sub.2, than H.sub.2 SiF.sub.6 solutions which are not of constant quality or concentration.

Abstract: Method and apparatus for making vitreous silica of high purity including producing a melt of liquid silicon in a first chamber, mixing the liquid silicon with carbon dioxide in an upper zone of a second chamber to produce silicon monoxide, mixing the silicon monoxide with oxygen in a lower zone of the second chamber producing silicon dioxide in gaseous form, condensing the silicon dioxide on the wall of the second chamber, and withdrawing the resultant tube of vitreous silica from the lower end of the second chamber. The apparatus is lined with silica to prevent introduction of impurities. The liquid silicon is produced by mixing hydrogen and trichlorosilane.

Abstract: Method and apparatus for the production of high purity hydrogen fluoride by the flame hydrolysis of silicon tetrafluoride and the deliberate cooling of the silicon dioxide and hydrogen fluoride reaction products without appreciable dilution to promote agglomeration of the silicon dioxide and permit separation of the hydrogen fluoride with substantially no contamination.

Abstract: A process is provided for converting silicon and fluorine-containing waste gases into silicon dioxide and hydrogen fluoride, absorbing the waste gases in water to form hydrofluosilicic acid, decomposing the hydrofluosilicic acid in the presence of concentrated sulfuric acid to form silicon tetrafluoride and hydrogen fluoride, converting the silicon tetrafluoride in the vapor phase to silica and hydrogen fluoride, and recovering the hydrogen fluoride.

Abstract: Process for the production of a finely divided oxide of a metal or silicon by the hydrolytic conversion of a volatile corresponding metal halide or silicon halide in a flame, said process comprising feeding the volatile halide in a mixture with a combustible hydrogen-containing gas and air or oxygen to a burner provided with a mouth emitting a flame, burning the mixture in a fire tube to form a first portion of water vapor, said burner surrounded by an annular chamber forming a nozzle through which hydrogen is passed to keep the mouth of the burner free of attachments of solid substances, the quantity of oxygen or air being sufficient for the practically complete combustion of the combustible gas, and the quantities of oxygen or air and combustible gas being sufficient to produce the first portion of water vapor which will at least suffice for the hydrolysis of the volatile halides, and further wherein said flame is allowed to burn in an atmosphere consisting of gases containing a second portion of water vapo