共沉淀法合成近零膨胀ZrW2O8/ZrO2复合陶瓷的致密化

采用化学共沉淀法合成前驱体,经1150℃ 烧结3.5 h得到近零膨胀26 wt% ZrW₂O₈/ZrO₂复合陶瓷，并利用X射线衍射仪、扫描电镜和热膨胀仪研究了原料中加入Al(NO₃)₃·9H₂O对26 wt% ZrW₂O₈/ZrO₂复合陶瓷的相组成、致密度和热膨胀性能的影响。研究结果表明，少量添加Al(NO₃)₃·9H₂O可有效提高复合材料致密度，所得复合陶瓷的组分仍为立方结构的α-ZrW₂O₈和单斜的m-ZrO₂，其中添加2.21 wt% Al(NO₃)₃·9H₂O的复合材料的致密度达到理论密度的98.67%，且对复合陶瓷的热膨胀性能影响不大。其促进致密化机制为晶界处低熔点液相物质Al₂(WO₄)₃提高了复合材料的烧结性能，消除气孔促进致密化。

Densification of nearly-zero-thermal-expansion ZrW_2O_8/ZrO_2 ceramics synthesized by chemical co-precipitation method

A kind of nearly-zero-thermal-expansion 26 wt% ZrW2O8/ZrO2 ceramics was prepared by calcining the precursors synthesized by the chemical co-precipitation method at 1150℃ for 3.5 h. The effects of Al(NO3)3·9H2O addition on the phase composition，density and thermal expansion properties of the 26 wt% ZrW2O8/ZrO2 composites were investigated by X-ray diffraction，scanning electron microscopy and dilatometry. The results indicate that the composites with Al(NO3)3·9H2O added in the precursor contain only α-ZrW2O8 and m-ZrO2 phases，and a small amount of Al(NO3)3·9H2O additive can increase the density of the 26 wt% ZrW2O8/ZrO2 composites with slight effects on the thermal expansion properties. The relative density of the 26 wt% ZrW2O8/ZrO2 composites doped 2.21 wt% Al(NO3)3·9H2O can reach 98.67% of the theoretical density. The densification mechanism can be at tributed to the formation of the Al2(WO4)3 liquid phase，which accelerates the diffusion and promotes the sintering process and leads to the increasing of the density of the composites to some extent.