Effect of matrix crystallinity on the characteristics of the interfacial layer in SiC fiber-reinforced Si-Al-O-N composites

Abstract

Glass or glass-ceramics have been used as matrix materials for fiber reinforcing by the slurry infiltration process, followed by hot pressing. These matrices have been used for two major reasons: (i) They oxidize the SiC fiber to form a C-rich interfacial layer between the fiber and matrix during hot pressing (2SiC(s) + O2(g) = 2C(s) + 2SiO(g)). Such carbon-rich layers cause low fiber-matrix interfacial shear strength resulting in high composite fracture toughness. (ii) A low viscosity matrix is required to minimize fiber damage during hot pressing. In the present study, the Si2N2O - AI2O3 system was used as a new host material for Nicalon SiC fiber: it has a more refractory nature and is able to provide a liquid phase (with the presence of a sintering agent, e.g., A12O3, CaO, etc.) to avoid fiber damage during densification. This matrix system can also provide oxygen to form a C-rich interphase. In this paper, the effect of matrix crystallinity on the interfacial characteristics is described.