AlON透明陶瓷的阻抗匹配设计与冲击物性研究

During shock-induced phase transition measurement of iron at about 13 GPa, the impedance mismatching between iron and sapphire, which will disturb the wave system evolution, is the big challenge to conquer. Hence, aluminum oxynitride or magnesium aluminum oxynitride, is suggested to be a more preferable window material in this research. The material has several superiorities such as density/impedance decrease by introducing N and Mg, wide adjustable impedance range due to high solid solution range of N/Mg, and abundant micro-structures including grain, grain boundary and defaults, which is benefit for impedance adjustion. After carful identification of above factors affecting on shock impedance by composition design, transparent ceramics preparation, shock property measurements, the relationship between shock impedance and above factors will be cleared and its related mechanism will be proposed. Finally, the impedance optimal design including composition ratio and micro-structure requirement will be given. By employing transparent ceramic in phase transition for the first time, the research not only can provide the feasibility of impedance matching with other phase transition materials and other transparent ceramic systems, but also can provide more precise results of other materials with wide impedance range in shock wave area, and can give many advantages for accurate physical measurement and practical applications.

现有透明窗口材料与Fe的冲击阻抗失配，导致波系演化受到干扰，制约了Fe冲击相变-逆相变实验研究的精度与置信度。本项目提出采用尖晶石结构Al2O3中固溶N/Mg两种元素形成的AlON/MgAlON体系透明陶瓷，以开发适用于Fe冲击相变-逆相变精密实验研究的新型阻抗匹配透明窗口。研究基于AlON/MgAlON体系中N/Mg固溶量高（可实现材料宽范围密度和模量调控）和多晶陶瓷晶粒、晶界等微结构可调控等优势，通过对体系阻抗的理论设计、高透明陶瓷制备和窗口冲击物性测试等探索，获得体系冲击阻抗随固溶比和微结构演变的变化规律和内在机制，从而提出阻抗匹配AlON/MgAlON体系透明陶瓷的成分和微结构优化设计方案，为实现Fe的精密实验研究奠定良好基础。本项目发展的设计理论与制备技术，还有望推广应用于指导开发更多体系的阻抗匹配型透明陶瓷，为冲击波研究领域中其它各类重要材料的精密测量与研究应用提供支撑。

本项目以透明窗口材料与Fe的冲击阻抗匹配为研究目标，以AlON/MgAlON体系为主要对象，开展了窗口体系设计、制备和冲击物性等研究。首先从理论上模拟计算建立了冲击响应与AlON/MgAlON体系透明陶瓷的关系，发现体系冲击响应可以通过成分改变来调节，为冲击阻抗匹配提供了理论指导。陶瓷制备过程中，在粉体制备上基于超声辅加旋蒸干燥技术，采用碳热还原法制备了高活性AlON/MgAlON陶瓷粉体，深入分析了粉体成分匀化相关机理；进一步成型上发展了适宜于大尺寸异形陶瓷制备的凝胶注模和适宜于薄片的流延成型技术，均成功制备出了高透过率AlON体系陶瓷样品，达到了窗口应用需求，分析了成型和致密化相关物理机制；项目中为探究不同晶界AlON透明陶瓷的冲击特性，采用了新型SiO2烧结助剂成功制备接近理论透过率透明陶瓷；另通过γ-Al2O3固溶实现了无烧结助剂掺杂的高透明AlON陶瓷，为研究AlON陶瓷的本征力学性能提供保障。在冲击实验上，为探究晶界影响首先开展了微米和纳米MgAl2O4透明陶瓷冲击响应性实验研究，发现了纳米晶粒在冲击阻抗窗口上的优越性；随后开展了AlON冲击透明性及与Fe阻抗匹配研究。通过计算结果以及冲击实验表明，AlON冲击阻抗与铁相一致，实现了较好的阻抗匹配。考虑到多晶陶瓷具有的晶界、晶粒和缺陷等复杂微结构，开展了不同N含量配比的AlON陶瓷和AlON、LiAlON、MgAlON的单晶粒冲击物性。最后，采用DDA模拟分析了透明陶瓷的散射系数和透光率与气孔尺寸、气孔率和入射波长关系，验证了DDA模拟可靠性，在此基础上对蓝宝石典型窗口冲击下的消光特性研究，得出了冲击加载对透明陶瓷力学、光学特性的影响规律。项目为透明陶瓷测量窗口在Fe/Cu等冲击相变-逆相变精密实验研究提供了指导，为冲击波研究领域中其它各类重要材料的精密测量与研究应用提供了支撑。