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Boron Nitride Interphase in Ceramic‐Matrix Composites
Author(s) -
Naslain Roger,
Dugne Olivier,
Guette Alain,
Sevely Jean,
Brosse Christian Robin,
Rocher JeanPhilippe,
Cotteret Jacques
Publication year - 1991
Publication title -
journal of the american ceramic society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.9
H-Index - 196
eISSN - 1551-2916
pISSN - 0002-7820
DOI - 10.1111/j.1151-2916.1991.tb06789.x
Subject(s) - interphase , chemical vapor infiltration , materials science , composite material , ceramic matrix composite , boron nitride , isothermal process , ceramic , annealing (glass) , graphite , stoichiometry , boron , chemical vapor deposition , exothermic reaction , chemistry , nanotechnology , genetics , physics , organic chemistry , biology , thermodynamics
A BN interphase has been deposited, by isothermal/isobaric chemical vapor infiltration (ICVI) from BF 3 ─NH 3 , within a preform made from ex‐polycarbosilane (ex‐PCS) fibers, at about 1000°C. In a second step, the BN‐treated preform was densified with SiC deposited from CH 3 SiCl 3 ─H 2 at about the same temperature. From a thermodynamic standpoint, ex‐PCS fibers could be regarded as unreactive vs the BF 3 ─NH 3 gas phase assuming they are coated with a thin layer of carbon or/and silica. The as‐deposited interphase consists of turbostratic BN (N/B < 1) containing oxygen. The SiC infiltration acts as an annealing treatment: (i) the BN interphase becomes almost stoichiometric and free of oxygen; (ii) the fibers undergo a decomposition process yielding a SiO 2 /C layer at the BN/fiber interface. The weaker link in the interfacial sequence seems to be the BN/SiO 2 interface. Deflection of microcracks arising from the failure of the matrix takes place at (or nearby) that particular interface.