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Abstract

A specific test procedure has been developed to compare the high temperature lifetimes in air and under load of SiC/SiC microcomposites with various interphases.The interphases, viz. pure pyrocarbon (PyC) or C(B) materials with different uniform or variable boron contents in the thickness, were prepared by CVD. Uniform addition of boron in PyC interphases improved their oxidation resistance and consequently the lifetimes of the microcomposites. However, room temperature tensile tests have shown that this improvement occurs to the detriment of the mechanical properties even when a non-brittle behaviour is maintained. In the case of variable boron contents, compositional gradient interphases (CGI) in which boron content increases from the fiber interface to the matrix interface allow to combine the mechanical fuse properties of PyC with the oxidation resistance of a C(B) material.

Effect of BN nanoparticle content in SiC matrix on microstructure and mechanical properties of SiC/SiC composites

“…[19][20][21][22][23] Although carbon also has lower reactivity with respect to that of SiC, BN exhibits superior oxidation resistance to that of carbon. 24 We investigated the densification of SiC matrix containing hexagonal BN nanoparticles without fibers prior to the fabrication of SiC/SiC composites to confirm the decrease in strength and elastic modulus while maintaining high density. Previously, the densification of SiC matrix incorporating hexagonal BN reported difficult owing to its poor sinterability and the flack-like structure of hexagonal BN.…”

Advances in Inorganic Fibers

“…The high-temperature stability of SiC-based ceramics is well-known, and therefore its composite materials have been investigated for application to high-temperature structural materials [19][20][21]. However, well-known SiC-based fibers and matrix-materials stained with alkali salt are easily oxidized at high temperatures in air [22].…”

Methylene-bridged carbosilanes and polycarbosilanes as precursors to silicon carbide—from ceramic composites to SiC nanomaterials

“…27 SiC is also an important high temperature structural material, which is used in igniters, heating elements, and in high temperature structural composites for both industrial and aerospace applications. 28 While SiC has been obtained by several groups in the form of nanorods, [29][30][31][32][33][34][35][36] relatively little attention has been devoted to the preparation of SiC nanotubes. 37 Single-crystal ␤-SiC nanorods with and without amorphous SiO 2 wrapping layers have been prepared by well established methods, including the reaction of SiO (g) with elemental carbon in various forms (including C nanotubes) or with CO, 29-33 the reduction of silica or silica gel with carbon, 34 the direct reaction of Si and C, usually facilitated by a liquid metal "catalyst", 35 and reaction between SiCl 4 and CCl 4 with Na metal as the reductant.…”