Acicular Mullite–Cordierite Composites with Controllable CTE Values

作者：Daniel Grohol, Chan Han, Aleksander J. Pyzik, Janet Goss, Clifford S. Todd · 发表于：Journal of the American Ceramic Society · 年份：2010 · DOI：10.1111/j.1551-2916.2010.04129.x · 被引用次数：15 · 研究领域：Advanced ceramic materials synthesis、MXene and MAX Phase Materials、Advanced materials and composites

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.