Preparation of lithium aluminosilicate glass-ceramic monolith from metal alkoxide solution
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Glass-ceramic monoliths with a composition of Li2O·Al2O3·4SiO2 have been synthesized by the sol-gel technique using metal alkoxides as starting materials. Heating dried gel monoliths of about 36 mm diameter and height to appropriate temperatures gave glass-ceramic monoliths of about 20 mm diameter and height without the occurrence of cracks, while a melt-derived glass body of the same composition was cracked or softened on heating. The glass-ceramic monoliths obtained by heating gel monoliths at 1000 ‡C for 40 h were a porous body, whose bulk density and porosity were 1.62 g cm−3 and 34%, respectively. On heating gel monoliths, Β-eucryptite crystals were first precipitated around 750 ‡C, followed by precipitation of Β-spodumene crystals at 830 ‡C. At higher temperatures the latter grew at the expense of the former phase. The crystallized specimens exhibited very low thermal expansion coefficient ranging from −13-12×10−7 ‡C−1 at temperatures from room temperature to 700 ‡C depending on the heat-treatment temperature of gels, indicating that a porous glass-ceramic monolith with ultra-low thermal expansion can be prepared using the present sol-gel method.
KeywordsAl2O3 Thermal Expansion Aluminosilicate Thermal Expansion Coefficient Alkoxide
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