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Title
Kompositkeramik mit einer Gradientenstruktur und Verfahren zu deren Herstellung
Date Issued
1998
Author(s)
Schober, R.
Patent No
1997-19708509
Abstract
Production of a graded structure composite ceramic involves (a) pressing a powder mixture of at least 15 wt.% TiB2, at least 20 wt.% AlN and 0-50 wt.% Al, containing 2-10 wt.% added sintering aid; (b) nitriding at up to 1400 deg. C in a nitrogen atmosphere, if Al is present; and (c) heat treating by heating at at least 20 K/min to at least 1800 deg. C in an atmosphere having a nitrogen partial pressure of at most 0.2 MPa, holding for at least 2 h at a nitrogen partial pressure of at least 2 MPa and then cooling at at least 20 K/min to 1000 deg. C or below. Also claimed is a sintered graded structure composite ceramic which has a columnar AlN case region, incorporating finely dispersed TiN and BN, and has an equiaxial grain content increasing towards a core of equiaxial grains. USE - E.g. for evaporation boats used in high rate coating. ADVANTAGE - The composite ceramic consists of an AlN matrix incorporating TiN and BN formed in-situ during densification, the ceramic being densified by pressure-less reaction sintering to low porosity and having a graded structure providing improved corrosion and thermal shock resistance.
Language
de
Patenprio
DE 1997-19708509 A: 19970303