镁基复相陶瓷抗热震性与烧结行为的关联性及调控机制研究

Thermal shock resistance and sintering of MgO-based ceramic have been a major bottleneck in their high-temperature applications. relevance and regulation between sintering behavior and thermal shock resistance of ceramic materials, especially magnesia-based ceramic is not understood, although the thermal shock resistance and the sintering of MgO-based ceramic materials can be improved by using complex toughening technology and by introducing the sintering additives. On the basis of our previous work, MgO-based composite ceramics are prepared by solid reaction sintering using Al2O3, SiO2 additives in this project. The sintering behavior and the mechanism of thermal stability of MgO-based composite ceramics are systematically studied by establishing the composite model of magnesia as main crystalline and thermal shock resistance. The fracture mechanism and crack propagation kinetics of MgO-based composite ceramics under strong thermal shock are studied with self-made experimental equipment for thermal shock resistance and sintering. The effects of temperature on the microstructure and the crack, especially the mechanism of crack fracture and the healing mechanism are systematically studied. The relationship between the process parameters and the microstructure of the MgO-based ceramics is established. The method of solid reaction sintering to prepare MgO-based composite ceramics is dicussed. The regulation between sintering and thermal stability of high-density MgO-based ceramics is understood.

提高镁基陶瓷的抗热震性和烧结性是促进其在高温领域实际应用的关键，采用复相增韧技术在本质上是协同提升镁基陶瓷抗热震性及烧结性的有效手段，但目前对于该体系陶瓷抗热震性与烧结性的关联性及调控机制尚不明晰。基于前期研究工作，本项目提出以Al2O3、SiO2为添加剂，采用固相反应烧结工艺制备镁基复相陶瓷，构建以方镁石为主晶相的复相结构及热稳定机制模型，着重对镁基复相陶瓷的烧结行为及热稳定机理进行系统研究。利用自制的陶瓷抗热震稳定性/烧结性实验台架，研究镁基复相陶瓷在受到强烈热冲击时的断裂机理和裂纹拓展动力学，明晰热震过程中材料微观结构和裂纹对温度变化的响应机制，系统研究在温度急剧变化过程中裂纹形成机制及愈合机制。建立工艺参数与镁基复相陶瓷组成和微观形貌的关联性，探究固相反应烧结工艺制备高致密镁基复相陶瓷材料的方法，明晰材料热稳定性与烧结行为的调控机制。

项目重点围绕镁基复相陶瓷抗热震性与烧结行为的关联性及调控机制研究，以MgO为主要原料，Al2O3、SiO2为添加剂，采用固相反应烧结工艺制备镁基复相陶瓷，构建以方镁石为主晶相的复相结构及热稳定机制模型。通过向MgO中添加不同比例的Al2O3-SiO2复合添加剂，分析复合添加剂对MgO陶瓷烧结行为影响。随着Al2O3-SiO2复合添加剂比例的增加，烧结行为可分为三个阶段，促烧结阶段、原位反应阶段和堇青石形成及消失阶段。Al2O3-SiO2复合添加剂的促烧作用显著，大幅度提高了基体的致密化程度。通过向MgO中加入Al2O3-SiO2添加剂，由于体系存在热膨胀失配效应，导致在相界面处产生残余应力区，促使材料微裂纹的出现，缓和由于温度变化而产生的热冲击，从而提高镁基陶瓷的热震稳定性。研究了不同Al2O3-SiO2配比、不同添加量对镁基复相陶瓷材料的抗热震性与烧结行为的影响，确定最优Al2O3-SiO2的加入量，烧后试样的最大体积密度可以达到3.45 g/cm3，接近30次的热循环次数才使得试样发生断裂。深入研究镁基复相陶瓷抗热震性和烧结性的关联性及调控机制，探索固相反应烧结机理和热稳定机理，为研究具有良好热稳定的高致密镁基复相陶瓷制备技术以及镁基复相陶瓷在高温领域应用技术提供一定理论借鉴。