Abstract
Lithium aluminosilicate glass-ceramics have found widespread commercial success in areas such as consumer products, telescope mirrors, fireplace windows, etc. However, there is still much to learn regarding the fundamental mechanisms of crystallization, especially related to the evolution of viscosity as a function of the crystallization (ceramming) process. In this study, the impact of phase assemblage and microstructure on the viscosity was investigated using high temperature X-ray diffraction (HTXRD), beam bending viscometry (BBV), and transmission electron microscopy (TEM). Results from this study provide a first direct observation of viscosity evolution as a function of ceramming time and temperature. Sharp viscosity increases due to phase separation, nucleation and phase transformation are noticed through BBV measurement. A near-net shape ceramming can be achieved in TiO2-containing compositions by keeping the glass at a high viscosity (> 109 Pa.s) throughout the whole thermal treatment.
Highlights
There have been increasing uses of glass-ceramics in areas such as consumer, biomedical, and construction markets since their discovery by Stookey in 1950s (Stookey, 1960a,b; Holand and Beall, 2002; Zanotto, 2010)
When TiO2 concentrations were below 7.0 wt%, no phase separation or devitrification was observed in glass
An investigation on the evolutions of crystallization, microstructure, and viscosity in lithium aluminosilicate glass was conducted in this work
Summary
There have been increasing uses of glass-ceramics in areas such as consumer, biomedical, and construction markets since their discovery by Stookey in 1950s (Stookey, 1960a,b; Holand and Beall, 2002; Zanotto, 2010). Lithium aluminosilicate glass-ceramics have gained considerable commercial success due to the combination of low thermal expansion [coefficient of thermal expansion (CTE), close to 0 × 10−7/°C] and high mechanical strength attributed to its two main crystalline phases, β-quartz and β-spodumene (keatite) solid solutions (ss) (Ostertag et al, 1968; Holand and Beall, 2002; Dressler et al, 2011a) Both ZrO2 and TiO2 are commonly used as nucleation agents to produce controlled bulk crystallization in the precursor glass (Henderson, 1979; Holand and Beall, 2002; Zanotto, 2010). It has been used to study the crystallization kinetics of various glass systems including the lithium aluminosilicate
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