The matrix of NITE-SiC/SiC comprises polycrys­talline SiC and a small amount of isolated oxides. The microstructure is highly crystalline and highly dense. Table 5 lists the typical available pro­perties of NITE-SiC/SiC.7 Thermal conductivity (~30Wm-1K-1) is quite high when compared to CVI SiC/SiC (below 15Wm-1K-1) reinforced with either Nicalon (Table 1) or Hi-Nicalon fibers.37 The high proportional stress limit is claimed to be an inter­esting feature.7 However, it is worth pointing out that it reflects a high load-carrying capacity. By contrast,

the low strain-to-failure indicates a limited damage tolerance. The strain-to-failure does not increase after aging at high temperatures up to 1500 °C. This trend is consistent with the strong fiber-matrix interactions induced by the surface roughness of Tyranno-SA3 fibers.38 A comprehensive database on properties of NITE-SiC/SiC is not available. NITE-SiC/SiC has been reported to retain ultimate strength and a propor­tional stress limit after exposure at temperatures up to 1300 °С6