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Near‐zero thermal expansion transparent lithium aluminosilicate glass‐ceramic by microwave hybrid heat treatment
Author(s) -
Venkateswaran C.,
Sharma Sharad C.,
Chauhan Vishal S.,
Vaish Rahul
Publication year - 2018
Publication title -
journal of the american ceramic society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.9
H-Index - 196
eISSN - 1551-2916
pISSN - 0002-7820
DOI - 10.1111/jace.15178
Subject(s) - crystallization , materials science , aluminosilicate , thermal expansion , nanocrystalline material , nucleation , ceramic , microwave , lithium (medication) , mineralogy , thermal stability , chemical engineering , composite material , nanotechnology , thermodynamics , chemistry , medicine , biochemistry , physics , quantum mechanics , endocrinology , engineering , catalysis
The material of choice for space applications which demand very high dimensional stability is lithium aluminosilicate ( LAS ) based Ultra Low thermal Expansion Glass‐Ceramic ( ULEGC ). Generally, the controlled crystallization process recommended for the processing of transparent ULEGC involves a long soaking duration to achieve the required crystal number density. This paper brings out the process optimization procedure adopted for realizing transparent and nanocrystalline ULEGC from conventionally processed LAS glass using microwave‐assisted (hybrid) crystallization. The experimental strategy involves two stages (i) identification of the optimum crystallization temperature ( T c ) under a microwave field (ii) optimization of a microwave‐assisted crystallization process to achieve near zero Coefficient of Thermal Expansion (CTE).. Optimum heat‐treatment schedules for nucleation and crystallization under a microwave environment were found to be 720°C/24 hours and 775°C/0.3 hours, respectively. The optimized heat‐treatment condition revealed the efficacy of the microwave hybrid heating, by producing nanocrystalline (35‐50 nm) and transparent (>82%) ULEGC having a thermal expansion of −0.03 × 10 −6 K (0°C to 50°C).