Dual effect temperature-induced changes

Fig. 8.15 Changes in interface microstructure in SiC fiber-reinforced BMAS glass-ceramic composites induced by exposure to high temperature oxidizing environments, (a) After tensile stress-rupture experiment at 1100°C, the 90° fibers show a distinct dual layer at the BN coating-fiber interface, (b) After thermal aging for 500 h at 1200°C, a subtle double layer appears at the same site, (c) Near the composite surface, the effects of thermal aging (and oxidation) are more pronounced.24...

The formation of a dual-phase morphology in PEI-epoxy IPNs is explained in the following way [90,171]. Two cases were discussed. First, when phase separation is induced by the curing reaction, PEI-modified epoxy shows bimodal UCST behavior (Fig. 30). At composition (p (volume fraction of component 1) phase separation starts at conversion x when the curing temperature is Ti. Because of the spinodal mechanism of decomposition and due to the lower viscosity of the medium, the system will have macroscale phase separation and domains with volume fraction cp[ and. As the reaction proceeds and the conversion X2 is reached, an abrupt change in the equilibrium composition of the PEI-rich phase occurs from cp l to (p " in a very short time. This abrupt change is similar to the effect of the two-... 

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