The crystallization of glass ceramics provides processing advantages for difficult shapes. Machining and sintering are limited to produce complex parts; similarly (superplastic) forming is limited to special ceramics. In theory, however, a liquid (or glass) may be simply poured into any shape, and then crystallized (or partially crystallized) to provide a strong, tough ceramic. In this work, a thin layer of glass ceramic, cordierite (2MgO.2Al2O3.5SiO2), joins SiC [1]. Tailoring secondary phases and percent crystallization provide flexible control of the coefficient of thermal expansion to minimize strain mismatches between the joint components.Three processing steps are involved in crystallization of glass ceramics: first a fast quench produces the initial glass; the second step is a lower temperature “nucleation” anneal, where phase separation and/or precursors and/or the final structure is nucleated and ideally as a fine dispersion; the third step is the higher temperature “crystallization” anneal, where renucleation and/or growth develops a homogeneous (ideally fine grained) final crystalline product [2, 3].
Nanocrystal Growth in Cordierite Glass Ceramics Studied with X-ray Scattering
