Process for producing shaped articles of reaction bonded silicon nitride by nitriding under high nitrogen gas pressure

摘要

the subject of the invention is a method for the production of formku00f6rpern from reaktionsgebundenem siliciumnitrid in which the preformed body siliciumpulver using a stickstoffgasdruckes of at least 6 mpa in a first stage at a rate of not me hr than use per hour at a temperature below the melting point of silicon heatat this temperature for at least 0.5 hours and then kept in a second stage at a rate of at least) per hour at a temperature above the melting point of silicon heating at this temperature 1 to 7 hours are kept.;this procedure can be pre formed body, the siliciumpulver and fire up to 15 wt.% si3n4 powder are such that up to 10 wt.% sinterhilfsmittel from the group of oxides, such as y203 included nitridiert.in the former case, porous formku00f6rper with a density of 87 to 91% td and in the latter case, formku00f6rper density with a density of more than 98% td.in all cases, in a gesamtnitridierzeit of less than 15 hours a conversion of at least 95% of the initially present in siliciumnitrid silicon reached the final formku00f6rper essentially in the beta - modification is presented.