PRE-STABILIZATION AND CRYSTALLIZATION OF AMORPHOUS SiCN MATRIX OF C/SiCN COMPOSITE UNDER VACUUM AND TENSILE CREEP STRESS

Abstract

Crystallization of amorphous SiCN matrix of carbon fiber reinforced SiCN matrix composite ( C / SiCN ) under vacuum and tensile creep stress was investigated. The phase and microstructure evolution of amorphous SiCN matrix were examined by X-ray diffraction and transmission electron microscopy, respectively. The crystallization behavior of the as-received and 1900°C-annealed C / SiCN during tensile creep test conducted at 1500°C was analyzed. The results indicate that crystallization takes place after annealing at 1900°C for 0.5 h, and the phases formed are β- SiC and α- SiC . Decomposition of amorphous SiCN produces gaseous species such as SiO and CO , and vapor reaction between them and carbon induces SiC nucleation. Local atomic ( Si -, C -, N -) rearrangement due to SiCN degradation also yields a large number of Si - C -enriched regions which gradually induces SiC nucleation. The annealing treatment of C / SiCN shows stabilization effect to some extent on the SiCN matrix, but is not sufficient to get a thorough stable phase.