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Lookup NU author(s): Emeritus Professor Derek Thompson
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Nicalon SiC fibre tows have excellent properties for ceramic matrix reinforcement but residual oxygen within the fibres degrades fibre properties when these are incorporated into ceramic matrices at elevated temperatures. p-SiAlON ceramics also have excellent mechanical and physical properties, especially fracture toughness. However, sintering of β-SiAlON is generally carried out at 1650-1750°C, considerably higher than the temperatures above which fibre degradation occurs (> 1200°C). In the present study, the refractoriness and strength of Nicalon fibres were improved by high pressure CO heat treatment, and densification temperatures of β-SiAlON were lowered by using different kinds of sintering additives. Heat-treatment of the fibres under 45 bar CO pressure at 1500-1650°C led to an increase in fibre strength and to the formation of a thin carbon layer on the surface of the fibres. These improvements in the Nicalon SiC fibres allowed them to be incorporated successfully into β-SiAlON matrices. The as-received and heat-treated fibres were infiltrated with -SiAlON starting powder mixes and hot-pressed with low temperature sintering additives at 1600-1700°C for 30 min. Bending strength and fracture toughness measurements showed that samples containing heat-treated fibres provided a significant strength and fracture toughness increase compared with similar samples prepared using as-received fibres, and massive pull-out was observed because of the weak interface resulting from the surface carbon coating on the fibres.
Author(s): Demir A, Thompson DP
Publication type: Conference Proceedings (inc. Abstract)
Publication status: Published
Conference Name: 5th International Symposium on Nitrides
Year of Conference: 2007
Pages: 141-146
ISSN: 0255-5476
Publisher: Materials Science Forum, Trans Tech Publications Ltd.
Library holdings: Search Newcastle University Library for this item
ISBN: 0878494391
