Si3N4 ceramic, Si-base composition for production thereof and processes for producing these

Abstract

A slurry Si-base composition comprising an Si powder having a thickness of a surface oxide film ranging from 1.5 to 15 nm, 50 to 90% by weight of water, 0.2 to 7.5% by weight, in terms of oxide, of a sintering aid and 0.05 to 3% by weight of a dispersant, the Si-base composition having a pH value adjusted to 8-12. This slurry Si-base composition is produced by a process which comprises subjecting Si powder to oxidation treatment at 200 to 800° C. in air, adding 50 to 90% by weight of water, 0.2 to 7.5% by weight, in terms of oxide, of a sintering aid and 0.05 to 3% by weight of a dispersant to the oxidized Si powder and performing such a pH adjustment that the resultant mixture has a pH value of 8 to 12. The slurry Si-base composition not only enables producing a ceramic of Si3N4 at a lowered cost without the need to install explosionproof facilities but also allows the obtained Si3N4 ceramic having a relative density of at least 96% and a flexural strength of at least 800 MPa can be obtained.

Dependencies are inferred from the claim text.