C - Chemistry – Metallurgy – 04 – B
Patent
C - Chemistry, Metallurgy
04
B
25/128
C04B 35/58 (2006.01) C04B 35/584 (2006.01) C04B 35/591 (2006.01) C04B 35/593 (2006.01)
Patent
CA 1272581
ABSTRACT The invention is a process for the manufacture of shaped articles of reaction-bonded silicon nitride in which pre-shaped articles of silicon powder are heated in a first stage under a nitrogen gas pressure of at least 6 MPa at a heating rate of not more than 50°C per hour to a reaction temperature below the melting point of silicon, the article is maintained at the reaction temperature for at least 0.5 hours and subsequently, in a second stage, heating the article at a heating rate of at least 500°C per hour to a temperature above the melting point of silicon and maintaining the article at that temperature for from 1 to 7 hours. The process can nitridate both pre-shaped articles consisting of silicon powder and, optionally, up to 15% by weight Si3N4 powder and those containing up to 10% by weight of a sintering aid such as Y2O3. In the former case, porous shaped articles having a density of from 87 to 91% TD and, in the latter case, dense shaped articles having a density of more than 98% TD, are obtained. In all cases, in a total nitridation time of less than 15 hours, a conversion of at least 95% of the silicon originally present into silicon nitride is achieved, which, in the finished shaped article, is substantially in the .beta.-modification.
506606
Arnold Peter
Hunold Klaus
Lipp Alfred
Napholcz Johannes
Reinmuth Klaus
Arnold Peter
Elektroschmelzwerk Kempten G.m.b.h.
Gowling Lafleur Henderson Llp
Hunold Klaus
Lipp Alfred
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