燃烧合成水雾法ZrO2/Al2O3固溶体粉末的烧结特性、纳米析出和强韧化机理

Micron-sized Al2O3/ZrO2 uniformity solid solution powders were obtained using the ultra-high temperature combustion synthesis method combined with water spray cooling method. During the sintering of these powders in high temperature, plenty of nano ZrO2 were precipitated from the Al2O3 matrix dispersively, which indicated the high strength and high toughness for the nano Al2O3/ZrO2 ceramics. This new method has many advantages such as a low cost, being environmentally friendly, the high efficiency and the widespread application. As the solid solution powders were in a high energy state containing a really high vacancy concentration, it has a high sintering activity during densification process. This project characterizes the micron defects of these powders and digs for their effects on the densification process. In addition, the mechanism of the solid solution precipitation is explored by analyzing the effects of time and temperature on the precipitation of the nano ZrO2. The influence of spark plasma sintering and flash sintering on the rapid densification of solid solution powder is studied. The nano Al2O3/ZrO2 ceramics obtained using this method, presented a new morphology of nanostructures with uniformly dispersed intragranular and intergranular ZrO2. This project systematically researches the micron structure characterization and the mechanical properties of the nano ceramics to find the effects of the phase type, the particle size and the distribution of the ZrO2 on the mechanical properties of the ceramics and build a strengthening and toughening mechanism of new nanostructures.

采用超高温燃烧合成结合水雾化方法，获得微米级ZrO2/Al2O3固溶体粉末，在烧结致密化过程中，纳米ZrO2在Al2O3基体中高密度、均匀弥散析出，获得新型高强、高韧的ZrO2/Al2O3纳米复合陶瓷，这是一种新的低成本、绿色环保、高效的合成技术。该固溶体粉末含有高浓度的空位，处于高能亚稳态，具有极佳的烧结活性，项目对其微观缺陷进行表征，研究其对烧结特性影响，并开展固溶体粉末放电等离子烧结和闪烧结等快速致密化工艺的研究。研究温度、时间对纳米ZrO2固溶析出的影响，给出其微观机理和模型。研制ZrO2/Al2O3纳米复合陶瓷，在晶界、晶内实现高密度、均匀弥散的纳米析出，获得新型的纳米复合结构。我们将对产物的微观结构和力学性能进行综合分析，研究纳米ZrO2析出的结构特征（如尺寸、位相、分布等）对力学性能的影响，建立新型纳米结构的强韧化机理。

ZrO2/Al2O3陶瓷具有高模量、耐磨损、耐腐蚀、耐高温、电绝缘等优良性能，是应用广泛的先进陶瓷。采用燃烧合成水雾化方法，获得高纯度、扩散均匀的微米级Al2O3/ZrO2固溶体粉末，在固溶体粉末的快速致密化过程中，Al2O3基体中弥散析出高密度、均匀的纳米ZrO2，获得高强、高韧的Al2O3/ZrO2纳米复合陶瓷，发展一种新型低成本、绿色环保的纳米陶瓷合成技术。.研制了耐高温高压反应器，经过试制及优化后，可耐受1600~4000 ℃的高温和5~100 MPa的高压。通过超高温燃烧合成反应，形成高温熔体后保温一定时间，经过介质水快速冷却，可实现高能亚稳态粉末的制备。采用热力学计算和实验测量分析了Al-Zr(NO3)4燃烧合成特性，实现了反应温度、压力和成分比例的调控。通过对燃烧合成水雾化技术合成了高质量的过饱和Al2O3/ZrO2固溶体粉末,该粉末具有规则球形和均匀粒度，其平均颗粒尺寸为2~5 μm。研究表明，Al2O3基本固溶到ZrO2晶格中，实现了Al2O3在ZrO2中的高固溶度。烧结行为研究表明，亚稳相发生固溶脱附，析出的ZrO2相均匀弥散地分布在Al2O3相中，形成特殊的晶间/晶内纳米结构。随ZrO2含量改变，ZrO2/Al2O3纳米复合陶瓷表现出不同的且有规律的微观组织形貌。相比于热压烧结制备的复合陶瓷，放电等离子烧结制备的复合陶瓷具有较为细密的纳米复合结构。通过相场模拟结合固溶体粉体烧结试验，明确了Al2O3相和ZrO2相纳米析出机制。对纳米复合陶瓷强韧化机制的研究揭示了其以ZrO2颗粒强韧化、t-m相变强韧化、残余应力强韧化为主的强韧化机制。在Al-Zr(NO3)4超高温燃烧合成体系研究基础上，探索了Al-O2体系的超高温燃烧合成方法，并制备了亚稳纳米晶固溶体，在烧结成陶瓷过程中，原位诱发等轴晶与柱状晶的生长，在柱状晶内析出高密度纳米ZrO2相，构成多级微纳米结构。力学性能测试表明，3YSZ/Al2O3柱状晶纳米复合陶瓷的弯曲强度和维氏硬度分别可高达1278 ± 121MPa（25vol%ZrO2）和20.26 ± 0.30 GPa （30vol%ZrO2），断裂韧性达到15.07~15.59 MPa·m1/2（SENB），高于大部分ZTA及其它体系的纳米粉体制备的结构陶瓷，为氧化物及非氧化物纳米陶瓷的发展提供了新的借鉴和参考。