Thermal shock resistance of nextel/silica—zirconia ceramic-matrix composites manufactured by freeze-gelation

• Published in: Journal of the European Ceramic Society Vol. 15; no. 5; pp. 455 - 461
• Main Authors: Twitty, A., Russell-Floyd, R.S., Cooke, R.G., Harris, B.
• Format: Journal Article
• Language: English
• Published: Oxford Elsevier Ltd 1995; Elsevier
• Subjects: Acoustic emission testing; Applied sciences; Bending strength; Building materials. Ceramics. Glasses; Ceramic industries; Chemical industry and chemicals; Elastic moduli; Exact sciences and technology; Freezing; Gelation; Heat resistance; Miscellaneous; Processing; Silica; Sol-gels; Technical ceramics; Temperature; Zirconia; Fiber reinforced material; Aluminosilicates; Thermomechanical properties; Experimental study; Silica; Freezing; Oxide ceramics; Composite material; Zirconia; Sol gel process; Thermal shock resistance; Silicon Oxides; Zirconium Oxides; Manufacturing; Ceramic fiber
• ISSN: 0955-2219; 1873-619X
• DOI: 10.1016/0955-2219(95)00003-D

Ceramic-matrix composites consisting of a silica—zirconia matrix reinforced by 25% by volume continuous Nextel alumino-silicate fibres have been manufactured by a sol-gel route incorporating freeze-gelation and subjected to thermal shock by water quenching from temperatures up to 800 °C. Although it was demonstrated that the Nextel fibres exhibited significant degradation of properties during composite processing, they still had a significant reinforcing effect. The material showed a critical temperature of approximately 550 °C, below which it was unaffected by water quenching. Above this level there was a 40 and 50% step reduction in modulus and strength respectively. Acoustic emission monitoring showed a significant difference in materials subject to quenching from beyond the critical temperature. There was a lower initial yet higher final AE event rate for a monotonically increasing flexural load, and a bimodal amplitude distribution. This indicated that the material responds in general terms in the manner corresponding to the well-known Hasselmann model of thermal shock of monolithic ceramics, but the presence of fibres appears to improve the thermal shock resistance by raising the predicted critical temperature somewhat.