Volume 14, Issue 5, 2005

Embrittlement behaviour and mechanism of silica FIBRES with polymer-derived silicon nitride coatings

Gong-jin Qi, Chang-rui Zhang and Hai-feng Hu

State Key Laboratory of Advanced Ceramic Fibres & Composites, College of Aerospace & Materials Engineering, National University of Defense Technology, Changsha 410073, P.R.China
E-mail:qgjin@tom.com (Gong-jin Qi)

(Received 1/06; accepted 3/06)

Abstract
Silicon nitride coatings were prepared on silica fibres using two polysilazanes, respectively, by dip coating with subsequent pyrolysis at 873 K in ammonia atmosphere. The silica fibres with polyhydridomethylsilazane derived coatings exhibited a residual tensile breaking force about 3.87 % of the original fibres, while the fibres with perhydropolysilazane derived coatings showed a lower strength with the tensile breaking force approaching null. Besides the intrinsic degradation of silica fibres, the chemical reactions between the hydroxyl groups on silica fibres and the active radicals in polysilazanes probably played an important role in the embrittlement of silicon nitride-coated fibres.

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