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SYNTHESIS AND PROCESSING: MORPHOLOGICALLY SPECIFIC METHODS. 49 Figure 13 Computer-generated image of triply periodic surface of constant mean curvature; see also Figure 14c (Thomas et al., 1988). Figure 14 The four types of ordered microdomain morphology of diblock copolymers: (a) bcc spheres of A in B matrix, (b) hexagonally packed cylinders of A in B matrix, (c) bicontinuous double-diamond network, and (d) lamellae of A and B phases (Thomas et al., 1988). HETEROGENEOUS NANOCOMPOSITES The sol-gel route can be used to make heterogeneous materials with a high degree of interpenetration (Roy, 1985, 1987). A wide range of high
SYNTHESIS AND PROCESSING: MORPHOLOGICALLY SPECIFIC METHODS. 50 temperature ceramic examples of the sol-gel route has been demonstrated using two or more phases lying in the range of 1 to 10 nm derived from multiphasic xerogels. The multiphases may differ in either composition or structure or both. There are several varieties of reliable and unique high-temperature structural and electromagnetic ceramics made from this low-temperature process. Figure 15 shows the design of high-temperature calcium strontium zirconium phosphates with zero thermal expansion. This nanocomposite has zero thermal expansion from 0°C to at least 500°C. These materials can be designed to have electrically conducting or insulating properties, ferromagnetic properties, or low-frequency damping properties concurrently with ultralow thermal expansion. One series based on sodium zirconium silicate and yttrium iron garnet provides a high-temperature, low-thermal-expansion magnetically absorbing nanocomposite. Figure 15 Sol-gel design of zero-expansion nanocomposites.
