Abstract: The present invention relates to a novel process for coarse decarburization of a silicon melt, and to the use thereof for production of silicon, preferably solar silicon or semiconductor silicon.

Abstract: The present invention relates to a novel process for decarburizing a silicon melt, and to the use thereof for production of silicon, preferably solar silicon or semiconductor silicon.

Abstract: By providing a new method of producing sintered silicon nitride, this invention takes into account the fact that parts made of Si.sub.3 N.sub.4 are often used in temperature ranges below 1200.degree. C. and sometimes even below 500.degree. C. and therefore needn't be designed to withstand temperatures above 1200.degree. C. The sintered silicon nitride for these low-temperature applications is obtained by sintering silicon nitride powder of <2 .mu.m with 5 to 20 wt. % of one or more glass components of the same particle size at temperatures below 1400.degree. C. It is a prerequisite that the glass components used, preferably alkali metal borate glasses with a coefficient of thermal expansion .alpha. which matches that of Si.sub.3 N.sub.4, have a transformation point T.sub.g which is below 750.degree. C., and that the individual glass components have a free enthalpy .DELTA.G which is at least 60% of the free enthalpy of SiO.sub.2. For low-temperature applications, Si.sub.3 N.sub.

Abstract: The present invention provides a process for the production of silicon nitride by the reaction of silicon and nitrogen, wherein, in one reaction step, silicon powder is reacted with nitrogen which continuously rotates at a temperature of from 1000.degree. to 1800.degree. C. and at a pressure of from 1.01 to 1.8 bar up to a nitrogen content of 1 to 39.5% by weight.The present invention also provides a silicon nitride produced by this process wherein it is obtained in porous form and has the following properties.a) grain size of 0.1 to 20 mm.b) nitrogen content of 1 to 39.5% by weight,c) oxygen content of 1%,d) ratio of .alpha.:.beta.-phase of 1:9 to 9:1.