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Acicular Mullite–Cordierite Composites with Controllable CTE Values
Author(s) -
Grohol Daniel,
Han Chan,
Pyzik Aleksander J.,
Goss Janet M.,
Todd Clifford S.
Publication year - 2010
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/j.1551-2916.2010.04129.x
Subject(s) - mullite , cordierite , acicular , cristobalite , materials science , composite material , thermal expansion , composite number , porosity , microstructure , ceramic , quartz
A new, two‐step method for the synthesis of porous mullite–cordierite composites with controllable coefficients of thermal expansion (CTE) values is reported. In the first step, a porous structure of interconnected acicular mullite grains with high aspect ratios is formed by using SiF 4 gas at elevated temperatures. This intermediate contains particles of MgF 2 and cristobalite that are attached to the mullite grains. In the second step, MgF 2 and cristobalite react with parts of the acicular mullite structure, and they form cordierite, while maintaining the acicular nature of the resulting mullite–cordierite composite. CTE of mullite–cordierite composites synthesized using this method decrease about linearly with increasing cordierite content, and porosities range from 49% in cordierite‐rich composite to 54% in a mullite‐rich composite. The CTE value of a desired porous composite can be easily controlled by choosing the appropriate ratios of reactants Al 2 O 3 , SiO 2 , and MgO, which result in the desired mullite‐to‐cordierite ratio with its characteristic CTE value.