Al₂O₃‐mullite composites were prepared under the synergy effect of AlF₃ and SiC aids by microwave heating. The phase composition, microstructure, porosity, flexural strength, thermal shock resistance, and thermal conductivity were investigated. The XRD results revealed that the content of mullite phase steadily increased with the increasing of AlF₃ content. The microstructure showed that the lower content (≤1 wt%) of AlF₃ led to the formation of granular mullite and the higher content (≥3 wt%) of AlF₃ led to the formation of mullite whiskers, which could form an interlocking structure. In addition, the SiC hot spots can also promote the generation of mullite whiskers by microwave sintering. The thermal shock resistance was significantly improved by the interlocking structure of mullite whiskers. The residual rate of flexural strength of the composite with 3 wt% AlF₃ was 86%. The composite with 3 wt% AlF₃ additives got its optimized thermal conductivity from 30°C to 950°C, the value was between 0.819 and 1.021 W/(mK), which possess excellent thermal insulation performance.

中文翻译：

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微波烧结以AlF3和SiC为辅助材料制备Al2O3莫来石保温材料

在AlF ₃和SiC助剂的协同作用下，通过微波加热制备了Al ₂ O ₃莫来石复合材料。研究了相组成，微观结构，孔隙率，抗弯强度，抗热震性和导热性。XRD结果表明，莫来石相的含量随着AlF ₃含量的增加而稳定增加。显微组织表明，较低含量（≤1wt％）的AlF ₃导致形成粒状莫来石，较高含量（≥3wt％）的AlF ₃导致莫来石晶须的形成，可能形成互锁结构。另外，SiC热点还可以通过微波烧结促进莫来石晶须的产生。莫来石晶须的互锁结构显着提高了耐热冲击性。具有3wt％的AlF ₃的复合材料的挠曲强度的残留率为86％。具有3 wt％AlF ₃添加剂的复合材料在30°C至950°C的温度下具有最佳的导热率，该值介于0.819至1.021 W /（mK）之间，具有出色的隔热性能。