原位反应固相法合成低热膨胀ZrW2O8／ZrO2复合材料

Synthesis of ZrW_2O_8/ZrO_2 composites with low thermal expansion using in-situ solid state reaction method

以分析纯ZrO2、WO3为原料，采用分步焙烧-原位反应固相法成功合成了低热膨胀ZrW2O8/ZrO2复合材料，着重研究了不同烧结温度和烧结时间对产物的影响。通过X射线衍射仪（XRD）、扫描电镜（SEM）、能谱仪（EDS）和热膨胀仪对合成的ZrW2O8／ZrO2复合材料的晶体结构、断面形貌和热膨胀性能进行表征。研究结果表明，在1125、1150、1200℃烧结6h都可以合成高纯度的ZrW2O8／ZrO2复合材料，其组元为α-ZrW2O8和m-ZrO2相；随烧结时间的延长，衍射半峰宽逐渐减小，晶粒在不断长大，致密度相对提高；随着ZrW2O8质量分数增加，复合材料的热膨胀系数减小，其中25％（质量分数）ZrW2O8/ZrO2复合材料在30-600℃的平均热膨胀系数为0．2153×10^-6K^-1。

A low-thermal-expansion composite of ZrW2O8/ZrO2 was successfully synthesized by stepwise calcination and in-situ solide reaction route using analytically pure ZrO2 and WO3 as starting materials. The effects of sintering temperature and time on the products were investigated. The crystal structure, cross-section morphology and thermal expansion properties of the products were investigated by X-ray diffraction （XRD）, scanning electron microscopy （SEM）, energy dispersive spectrometer （EDS） and dilatometry. The results indicate that ZrW2O8/ZrO2 composites are synthesized after sintering at 1125, 1150 or 1200℃ for 6h. The obtained composites contain only a-ZrW2O8 phase and m-ZrO2 phase without other phases. With the increase of sintering time, the full width at half maximum （FWHM） of the ZrW2O8 and ZrO2 diffraction peaks decreases, the grains grow up gradually and the density increases to some extent. The average thermal expansion coefficient of ZrW2O8/ ZrO2 composites decreases with the increased mass content of ZrW2O8. In addition, 25wt%ZrW2O8/ZrO2 composites show nearly zero thermal expansion, and the average thermal expansion coefficient is 0. 2153×10^-6 K^-1 from 30-600℃.