Processing and Testing of RE ₂ Si ₂ O ₇ Fiber–Matrix Interphases for SiC–SiC Composites

Abstract

Rare‐earth disilicates ( RE 2 Si 2 O 7 ) are investigated for use as oxidation‐resistant alternatives to carbon or BN fiber–matrix interphases in ceramic matrix composites ( CMC ). Dense α, β, γ‐Y 2 Si 2 O 7 , and γ‐Ho 2 Si 2 O 7 pellets were formed at 64 MPa and 1050°C–1200°C for 1 h using the field‐assisted sintering technique ( FAST ). Pellet modulus was measured using nanoindentation, and Vickers hardness was measured at loads of 100, 500, and 1000 g. The sliding stress of SCS ‐0 SiC fibers incorporated in α‐, β‐, and γ‐ RE 2 Si 2 O 7 matrices were measured by fiber push‐out. Deformation of RE 2 Si 2 O 7 after indentation and after fiber push‐out was characterized by TEM . Implications of the results for use of RE 2 Si 2 O 7 as a fiber–matrix interphase in CMC s are discussed.