Abstract: The process of preparing silicon nitride is improved by reacting silicon-oxygen compounds and a carbon-containing material in an ammonia or ammonia/nitrogen atmosphere at 1300.degree. to 1600.degree. C.

Abstract: A method and composition for reducing ammonia emissions from non-acidic residue from the combustion of a carbonaceous fuel, such residue containing ammonium salts or absorbed ammonia, is presented, the method comprising applying to the residue either a physical barrier composition, a chemical barrier composition, or both, under conditions effective to reduce the emission of ammonia from the residue.

Abstract: A method for increasing the trichlorosilane yield in the hydrochlorination of silicon in a fluidized bed involves chilling the gas mixture issuing from the fluidized bed in the shortest possible time immediately after leaving the fluidized bed to temperatures below 550.degree. C. When the temperature of the fluidized bed is below 550.degree. C., the gas mixture is chilled to temperature 100.degree. C. lower than the reaction temperature in the fluidized bed. The method makes it possible, at a reaction temperature of, for example, 800.degree. C. to increase the 16 to 20% trichlorosilane yields obtained formerly at this temperature to 55%, especially when gaseous silicon tetrachloride is also added to the fluidized bed.

Abstract: A monocrystal growing apparatus having a separator provided in a chamber-defining housing for separating the part of a polycrystal rod supported by a vertical shaft, to produce a melt between the polycrystal rod and a seed crystal, from the doping gas atmosphere used during the melting operation. The separator is open to the chamber near the melt and a device passed an inert gas into the separator to prevent the doping gas from invading the chamber. The apparatus produces a monocrystal rod of a constant resistivity along its rod.

Abstract: An improved SOI structure 40 is provided. SOI structure 40 includes a semiconductor mesa 42 formed over a buried insulating layer 46 which overlies a substrate 48. Sidewall insulator regions 50 and 52 are formed along sidewalls 54 and 56, respectively, of semiconductor mesa 42. Sidewall spacers 62 and 64 are formed along sidewall insulator regions 50 and 52, respectively. Sidewall spacers 62 and 64 each include respective foot regions 66 and 68. Foot regions 66 and 68 effectively shift undercut areas 74 and 76 laterally away from semiconductor mesa 42.

Abstract: Quartz is purified by removing mineral impurities, particularly alkali metal impurities, from within the quartz crystal lattice structure. According to the disclosed process, quartz crystals are subjected to a pretreatment that removes surface bound impurities and then contacted with gaseous HCl at a temperature of from 800.degree. C. to 1600.degree. C. for a period of time of from a few minutes to several hours, thereby diffusing the mineral impurities to the quartz crystal surface where they form salts with chloride ion, removing the salts, and recovering the purified quartz crystals.

Abstract: A processing for producing silicon carbide whiskers in which a source of silica is mixed with a residual oil or crude petroleum and the resultant mixture is heated in a substantially nonoxidizing atmosphere at temperature sufficiently high to carbonize the residual oil or crude petroleum, thereby forming an intimate mixture of carbon and silica. The intimate mixture is then heated in a nonoxidizing atmosphere in the presence of a seeding component comprising an element selected from the group consisting of boron, the rare earths, Group IA, Group IB, Group VB, Group VIB, Group VIIB and Group VIII of the Periodic Table of Elements at temperatures sufficiently high to induce the reaction between carbon and silica to form silicon carbide. The resultant silicon carbide product will contain a relatively high concentration of silicon carbide whiskers.

Abstract: A process including bonding a first device wafer to a handle wafer by an intermediate bonding oxide layer and thinning the device wafer to not greater than 7 mils. An epitaxial device layer of under 1 mil may be added. Device formation steps are performed on a first surface of the first device wafer. This is followed by removing the handle wafer to produce a resulting wafer having substantially the thickness of the first device layer. To produce a silicon on insulator (SOI), a third device wafer is bonded to the first surface of the first device wafer by the intermediate oxide layer and the third wafer is thinned to not greater than 40 microns. The first and third device wafers form the resulting SOI wafer.

Abstract: A process for producing an SOI-structured semiconductor device substrate has the steps of: reducing the diameter of the one Si-monocrystal wafer of two bonded polished Si-monocrystal wafers to be slightly smaller than that of the other Si-monocrystal wafer so that the width of the annular margin defined between the bonded surfaces of the Si-monocrystal wafers is uniform; then forming an annular polishing guard on the cylindrical surface of the one wafer and the margin of the other wafer, the polishing guard having a predetermined thickness and being made of a material providing a polishing speed lower under the same condition than the one wafer; and then polishing the one wafer so as to make it in thin film. The polishing guard provides an accurate thickness control of the resulting Si-monocrystal thin film, in particular, even at a few micrometers level.

Abstract: A method of removing silicon from a waste hydrochloric acid pickling solution is disclosed which comprises stirring the waste solution long enough to form a sludge having a particle size such that the sludge can be separated by a conventional means such as filtration through a filter of at least 0.1 .mu.m in pore diameter, centrifugation or sedimentation. The stirring period can be greatly reduced by adding to the waste pickling solution sludge recovered from an aged waste hydrochloric acid pickling solution or a carbonaceous material such as carbon black having hydrophilic groups on the surface. The sludge is also useful as a filter medium in filtration of the waste pickling solution to remove silicon. The present method can decrease the silicon content to 0.01% or less in terms of converted SiO.sub.2 /Fe.sub.2 O.sub.3 weight ratio.

Abstract: Si.sub.3 N.sub.4 powders having a total oxygen content of less than 1.8% by weight with the proportion of surface oxygen content of more than 65% of the total oxygen content, and having a fluorine content of less than 35 ppm are prepared by annealing Si.sub.3 N.sub.4 powders having a total oxygen content of less than or equal to 0.4% by weight in an oxygen-containing atmosphere at temperatures of 700.degree. C. to 1200.degree. C. for 15 to 90 minutes or by grinding Si.sub.3 N.sub.4 powders having a total oxygen content of less than or equal to 0.4% by weight in water, alcohol or aqueous alcohol 15 to 120 minutes.

Abstract: Hydrophobic, essentially spheroidal precipitated silica particulates, well adapted as a reinforcing filler material for silicone elastomers, have a density of at least 0.15, a water wettability of at least 20% and a maximum water uptake of 5%.