C - Chemistry – Metallurgy – 04 – B
Patent
C - Chemistry, Metallurgy
04
B
261/1, 25/132
C04B 35/58 (2006.01) C04B 35/583 (2006.01) C04B 35/645 (2006.01)
Patent
CA 1194041
ABSTRACT The invention is a shaped article of boron nitride having a density of at least 95% of the theoretical density which consists of polycrystalline hexagonal boron nitride in the form of a homo- geneous isotropic microstructure and which has been manufactured from pure boron nitride powder without the concomitant use of sintering aids by isostatic hot-pressing in a vacuum-tight casing at temperatures of from about 1200 to 1500°C under a pressure of from about 50 to 300 MPa. Boron nitride powders having a free boric oxide content of not more than 1.0% by weight and having a specific surface area of from 5 to 30 m2/g are used as starting material. The powders either are filled into prefabricated casings consisting of steel or glass and densified by vibration or are preshaped to forms green bodies having pores open to the surface and then placed in prefabricated casings or coated with a material which forms a vacuum-tight casing. The powders or the preshaped green bodies in the vacuum-tight casings are then subjected to an isostatic hot-pressing process in a high-pressure zone using an inert gas such as argon or nitrogen, as the pressure-transfer medium.
419327
Hunold Klaus
Lipp Alfred
Reinmuth Klaus
Elektroschmelzwerk Kempten G.m.b.h.
Gowling Lafleur Henderson Llp
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