Formation and structure of reaction layers in SiC/glass and SiC/SiC composites

Abstract

The structure and composition of interlayers between the fibre and matrix in Nicalon/borosilicate glass and Nicalon/SiC composites depend strongly on their formation mechanism. The applicability of existing models for interface reaction is limited, if the results of electron microscopic characterization are taken into account. The thermodynamic fundamentals illustrated by a volatility diagram of the ES-C-0 system reveal that variations in the pressures of 02, SiO and CO, respectively, are responsible for the occurrence of various phases (carbon, carbon and silica, silica) between the fibre and matrix. The thermodynamic approach yields a four-stage model of layer formation including the active oxidation of Sic.(Keywords: Nicalon/borosilicate glass; Nicalon/SiC; interlayer formation; volatility diagram; Si-C-O system; transmission electron microscopy)

Platinum-enhanced graphitisation in sandwich structures of silicon carbide and borosilicate glass

“…Thus, even at the high reaction temperature of 1164 • C, the formation of texturised turbostratic carbon is shown to be limited to the region between carbon and silica, whereas the most part of the layer occurs amorphous. This indicates a mechanism of formation of turbostratic carbon via an intermediate step of CO generation as we have shown in [15,27]. Firstly, Fig.…”

“…Based on the observed interlayer phenomena, we could explain the layer forming processes by use of volatility diagrams of the system Si-C-O revealing that variations in the pressures of O 2 , SiO and CO are responsible for the occurrence of various phases (carbon, carbon/silica mixtures, silica) between fibre and matrix [14][15][16]. Thus, we could develop a four-step model of the layer formation [15].…”

Selection criteria for sealing glasses for SiC packaging

“…The reactivity of the SiC fibers is then controlled by the presence of the oxycarbide phase. A carbon interphase interface can be created between the glass and SiC [27,28]. The layer not only allows accommodation of the interfacial stresses, acting as a compliant layer but also minimizes reaction between fiber and matrix.…”

Electronic structure analyses of the interface between a high refractive index optical glass and carbides

“…As oxidized carbon is gaseous such as carbon monoxide CO, which cannot remain in the structure but departs from the interface between the SiO 2 and C layers [8]. Therefore this result suggested the possibility that oxidation and reduction processes took place on the glass and the GC, respectively.…”