Effect of Cristobalite on the Strength of Sintered Fused Silica Above and Below the Cristobalite Transformation
Porous fused silica ceramics which had been partially devitrified to cristobalite were stronger at 350°C in the beta‐cristobalite stability range, but weaker at 25°C after the transformation to alpha‐cristobalite. The tensile strength distribution for different cristobalite fractions are compared for three types of specimens. These were beta‐cristobalite samples which had never been transformed to alpha‐cristobalite; room‐temperature samples with alpha‐cristobalite; and samples at 350°C which had retransformed to beta‐cristobalite after prior transformation to alpha‐cristobalite. The alpha‐cristobalite samples displayed 50%–75% the strength of samples tested on beta and the difference in strength was dependent on cristobalite content. Specimens retransformed to beta‐cristobalite had strength similar to virgin specimens. Microcracking associated with the transformation to alpha‐cristobalite contributes to the strength changes but cannot fully explain the impact of the beta–alpha transformation on strength.
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Document Type: Research Article
Publication date: May 1, 2015