CAREER: Controlling Pressure-Induced Transformation in Rare Earth Orthophosphates

非技术描述：在飞机发动机、涡轮机和火箭的燃烧室、喷嘴和隔热层等高温陶瓷部件中，突然通过到缓慢增长的裂缝可能导致灾难性的故障。一些独特的陶瓷在变形时，其形状和体积会发生变化，形成一种新的晶体结构，这可以通过吸收撞击或裂纹传播产生的能量来增强材料的韧性。该项目正在确定如何利用化学来控制新晶体结构发生变化的点及其转变速度。在这项研究中发现的信息和新材料可以用于设计陶瓷基复合材料的纤维涂层，具有更好的性能（优越的机械性能），用于高温航空航天应用。材料科学与工程专业的本科生和研究生都在接受培训和指导。该项目正在开发科学学习模块，供来自少数民族学生比例较高的学区的当地小学教师和落基山诵读障碍营地的教师使用。这些互补性的教育和推广组成部分扩大了未被充分代表的群体在科学和工程领域的参与，以满足美国扩大高素质人才的科学和技术劳动力的需求。这个项目将有助于加强美国在涡轮发动机领域和教育方面的创新和经济竞争力。技术细节：本项目是建立化学、晶粒尺寸、温度和应力状态对稀土（RE）正磷酸盐陶瓷（REPO4晶体结构）压力诱导相变动力学的影响。这些材料的相变正在使用一系列技术进行检测，包括高温纳米压痕、透射电子显微镜和金刚石砧细胞（结合拉曼光谱）。一个目标是能够精确控制改进陶瓷基复合材料涂层中塑性转变的触发器。确定了动力学效应对转化起始压力和可逆性程度的影响。通过这项研究获得的见解有助于基于科学的陶瓷复合材料、组件和器件的设计，在这些设计中，压力诱导的转换必须在精确的时间内触发，以达到最大的效果。这项工作解决了该领域的一个重大挑战，即了解控制相变动力学的因素，这些因素可以直接导致新的方法来处理具有增强功能的亚稳材料。

NON-TECHNICAL DESCRIPTION: Sudden through to slowly growing cracks in high temperature ceramic components such as combustors, nozzles, and thermal insulation in aircraft engines, turbines, and rockets can lead to catastrophic failure. Some unique ceramics undergo a change in their shape and volume to a new crystal structure when they are deformed, which can be harnessed to impart increased toughness in a material by absorbing energy caused by an impact or propagating crack. This project is determining how to use chemistry to control the point at which the change to a new crystal structure occurs and its speed of transformation. The information and new materials discovered in this research can be useful in designing fiber coatings for ceramic matrix composites with better performance (superior mechanical properties) for high temperature aerospace applications. Both undergraduate and graduate students in Materials Science and Engineering are being trained and mentored. This project is developing science learning modules for use by local elementary school teachers from school districts with a high percentage of minority students and the Rocky Mountain Camp for the Dyslexic. These complementary education and outreach components broaden the participation of underrepresented groups in science and engineering in an effort to meet the U.S. need for expanding the science and technology workforce with more highly qualified people. This project will help strengthen U.S. innovation and economic competitiveness in the area of turbine engines and in terms of education.TECHNICAL DETAILS: This project is establishing the influence of chemistry, grain size, temperature, and stress state on pressure-induced phase transformation kinetics in rare earth (RE) orthophosphate ceramics (REPO4 crystal structure). Phase transformations in these materials are being examined using a range of techniques that include high-temperature nanoindentation, transmission electron microscopy, and diamond anvil cell (combined with Raman spectroscopy). One goal is to enable precise control over the trigger for the plasticity transformation in coatings for improved ceramic matrix composites. The influence of kinetic effects on the transformation onset pressure and degree of reversibility are being identified. Insights gained through this research are aiding in the science-based design of ceramic composites, components, and devices in which pressure-induced transformation must be triggered with precise timing for maximal effect. This work addresses a grand challenge of the field to understand the factors controlling phase transformation kinetics that can lead directly to new ways to process metastable materials with enhanced functionality.