La2Ce2O7@La2Zr2O7核壳结构纳米粉体的制备及其抗烧结性能

Preparation and Sintering Resistance of Core-shell La2Ce2O7@La2Zr2O7 Nano-powder

针对La2Ce2O7抗烧结性能较差,La2Zr2O7的热膨胀系数较低的性能特点,采用水热法合成了La2Ce2O7内核,然后通过共沉淀法成功制备La2Ce2O7@La2Zr2O7核壳结构纳米粉体.将粉体预压成块,分别在1 100℃、1 300℃和1 500℃下进行了不同时间的烧结测试及在1 100~1 500℃烧结6 h以考察温度对其抗烧结性能的影响.采用扫描电镜、透射电镜、能谱仪分析了材料的形貌和成分,并测试了试样的密度和显微硬度.结果表明,La2Ce2O7内核具有立方结构或八面体结构外形,粒径约200 nm. La2Zr2O7壳层为非晶体,形成了包覆效果良好的La2Ce2O7@La2Zr2O7核壳结构.等温烧结时,核壳结构的密度变化率保持在2.1%以内,远低于La2Ce2O7和La2Zr2O7,孔隙和晶粒尺寸分布均匀,无裂纹和烧结现象出现.当烧结温度在1 300℃以内时,核壳结构组织均匀,多孔,密度变化率稳定在10.6%以内,晶粒尺寸约维持在450nm,晶粒长大速率与La2Zr2O7接近,抗烧结性能良好;当烧结温度高于1 300℃时,核壳结构孔隙增大且晶粒迅速长大,致密化加快,晶粒长大速率也变快,与La2Ce2O7接近,出现明显烧结现象;其显微硬度稍高于La2Ce2O7,而远低于La2Zr2O7.

In view of the poor sintering resistance of La2Ce2O7 and the low thermal expansion coefficient of La2Zr2O7,the La2Ce2O7 core was first synthesized by hydrothermal method,and then the La2Ce2O7@La2Zr2O7 core-shell nano-powder was successfully synthesized by coprecipitation method.The powder was pre-pressed into pellets and then sintered at 1100℃、1300℃and 1500℃for different hours and sintered at 1100~1500℃for 6 hours,so as to investigate the effect of temperature on its sintering resistance.The morphology and composition of the materials were analyzed by scanning electron microscopy,transmission electron microscopy and energy dispersive spectrometer.The density and micro-hardness of the samples were also tested.Experimental results showed that the La2Ce2O7 core had a cubic or octahedral shape with the average size of about 200 nm.The La2Zr2O7 shell was amorphous structure,and exhibited good enveloping effect on forming a La2Ce2O7@La2Zr2O7 core-shell structure.Constant temperature sintering tests found that the density change rate of the core-shell structure was kept within 2.1%,which was much lower than that of La2Ce2O7 and La2Zr2O7.The distribution of pore and grain size was uniform without cracks and sintering.When sintering temperature was below 1300℃,the La2Ce2O7@La2Zr2O7 was uniformly porous,its density change rate was stable within 10.6%,the grain size was maintained at about 450 nm,and the grain growth rate was close to that of La2Zr2O7,proving its good sintering resistance.When the temperature was higher than 1300℃,however,obvious sintering phenomenon occurred.The densification of La2Ce2O7@La2Zr2O7 accelerated,and its pore size increased and grains grew rapidly,nearly reaching to that of La2Ce2O7.Moreover,the micro-hardness of La2Ce2O7@La2Zr2O7 was slightly higher than that of La2Ce2O7,but much lower than that of La2Zr2O7.