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Oxidation of BN/Nicalon Fiber Interfaces in Ceramic‐Matrix Composites and Its Effect on Fiber Strength
Author(s) -
PérezRigueiro José,
Celemín José Antonio,
LLorca Javier,
Herrero Pilar
Publication year - 1999
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.1151-2916.1999.tb02271.x
Subject(s) - materials science , composite material , fiber , ceramic , ceramic matrix composite , coating , composite number , argon , oxygen , layer (electronics) , chemistry , organic chemistry , physics , atomic physics
Microstructural changes at the interface were analyzed in two Nicalon‐fiber ceramic‐matrix composites with a dual BN/SiC coating on the fibers after thermal exposure at different temperatures (in the range 800°‐1400°C) and in different environments (air and argon). The outer SiC coating acted as a barrier to oxygen, which penetrated into the composite via pipeline diffusion along the BN/fiber interfaces. Oxygen penetration led to the formation of an SiO 2 layer by oxidation of the fiber surfaces. The in situ fiber strength at different temperatures, as determined from the radius of the mirror region on the fiber fracture surface, indicated that this SiO 2 layer severely degraded the fiber strength. Oxidation was highly dependent on the nature of the BN/fiber interface. The presence of a thin carbon‐rich interlayer, which burned out rapidly at high temperature, favored the entry of oxygen and accelerated oxidation of the fibers.