【作者】 李中秋；

【导师】 刘家臣；

【作者基本信息】 天津大学 ， 材料学， 2009， 博士

【摘要】 针对氧化锆陶瓷的耐侵蚀性能与抗热震性能在拓展其应用方面的矛盾,以及传统抗热震理论的不足,以三种具有不同相组成的氧化锆（3Y-TZP、4Y-TZP和Mg-PSZ）为基体材料,加入LaPO₄组分,探索利用片晶LaPO₄的解理以及LaPO₄与ZrO2之间的弱界面对裂纹扩展能量的耗散,在不明显降低氧化锆陶瓷优良力学性能、致密度（以保证其抗侵蚀性能）的条件下,改善其抗热震性能的可能性。在力学性能、热学性能、显微结构及裂纹扩展状态研究的基础上,分别用淬冷-强度法和压痕-淬冷法,较系统地研究了ZrO2/LaPO₄复合陶瓷的抗热震性能及相关机理,主要得出如下结论:4Y-TZP陶瓷的抗热震性能随LaPO₄加入量的增加而升高。4Y-TZP/30vol% LaPO₄复合陶瓷的临界抗热震温差比单一4Y-TZP陶瓷提高了400 oC。氧化锆粒度为0.5μm和1.5μm时,对于单一4Y-TZP,粒度小的抗热震性较好;LaPO₄加入量小于15vol%时,两种粒度氧化锆陶瓷的抗热震性能相近;LaPO₄加入量为20vol%时,氧化锆粒度大的材料抗热震性较好。LaPO₄加入量保持15vol%不变, 1470 oC保温2h烧结时,加入粒度为13μm或35μm LaPO₄的3Y-TZP/LaPO₄复相陶瓷的抗热震性能较高;1470 oC保温3h烧结时,加入2.5μm的LaPO₄,3Y-TZP/LaPO₄复相陶瓷的抗热震性能最好,其空气淬冷下的临界抗热震温差为1300 oC。LaPO₄的添加促进了Mg-PSZ材料的致密化,并改善了其抗热震性能。Mg-PSZ/10 vol%LaPO₄复相材料的水淬临界抗热震温差比单一Mg-PSZ材料提高了100oC。Mg-PSZ/15 vol%LaPO₄复相材料的强度随热震温差的提高没有明显下降,表现了很好的抗热震损伤能力。相同热震条件下,加入15vol%、40μm LaPO₄的3Y-TZP/LaPO₄复相陶瓷,其裂纹扩展数量百分比和裂纹扩展长度百分比都最小。而加入30 vol%、13μm LaPO₄的3Y-TZP/LaPO₄复相陶瓷的相应值都最大。ZrO2/LaPO₄复相陶瓷的抗热震性能不能由传统抗热震参数的大小来准确预测。弱界面开裂、裂纹在弱界面处的偏转、分叉以及LaPO₄的解理等分散了热应力、耗散了热震作用积聚在陶瓷体内的弹性应变能,这是ZrO2/LaPO₄复相陶瓷具有较高抗热震性能的主要原因。更多还原

【Abstract】 Considering the contradiction between corrosion resistance and thermal shock resistance of Zirconia ceramics in expanding their application, and the insurfficiency of traditonal theory on evaluating the thermal shock resistance of ceramics, three different Zirconia ceramics--3Y-TZP, 4Y-TZP and Mg-PSZ were used to be the matrix to prepare ZrO2/LaPO₄ composites, the possibility of improving the thermal shock resistance of Zirconia ceramics by the elastic energy dissipation resulted from the LaPO₄ debonding and crack branching or bridging at the weak interface was investigated. Based on the study on the mechanical properties, microstructures and the growth behavior of microcracks, the thermal shock resistance of ZrO2/LaPO₄ composites was investigated systematically. The main conclusions are as follows:The thermal shock resistance of 4Y-TZP was improved with increasing the content of LaPO₄. Under the condition of air quenching,ΔTc of 4Y-TZP/LaPO₄ was 400oC higher than that of pure 4Y-TZP.In the particle size range from 0.5μm to 1.5μm, the monolithic 4Y-TZP ceramics with fine particle size had a higher thermal shock resistance. But for 4Y-TZP/LaPO₄ composites, when the content of LaPO₄ was up to 20 vol%, the thermal shcok resistance of the composites with coarser particle size was better.When LaPO₄ content was kept 15vol%, the composites containing 13μm or 35μm LaPO₄ and sintered at 1470 oC /2h has better thermal shock resistace; Under condition of 1470 oC /3h, LaPO₄ particle size was 2.5μm, theΔTc of the composites was 1300 oC under condition of air quenching,.The density and thermal shock resistance of Mg-PSZ/LaPO₄ ceramics increased with increasing the LaPO₄ content. Under water quench condition, the thermal shock resistance of Mg-PSZ/10wt% LaPO₄ composites was 100 oC higher than pure Mg-PSZ. The composites containing 15 wt % LaPO₄ behaves as a low strength refractory ceramic and has a good thermal shock damage resistance.Under the same thermal shock condition, the fraction of crack propagation and crack extension was the lowest for 3Y-TZP/LaPO₄ containing 15vol%、40μm LaPO₄, and the highest for that containing 30vol%、13μm LaPO₄.The thermal shock resistance of ZrO2/LaPO₄ composites can not be predicted accurately by the value of traditional thermal shock parameters. The partial relief of the elastic strain energy resulted from crack initiation, crack branching at weak interfaces and cleavage fracture of LaPO₄ grains was the main reason for the improvement of their thermal shock resistance.更多还原