CAREER: Controlling Pressure-Induced Transformation in Rare Earth Orthophosphates

非技术描述：高温陶瓷部件(如燃烧室、喷嘴以及飞机发动机、涡轮机和火箭中的隔热材料)突然出现裂纹会导致灾难性故障。一些独特的陶瓷在变形时会在形状和体积上发生变化，形成一种新的晶体结构，这种晶体结构可以通过吸收冲击或扩展裂纹产生的能量来增加材料的韧性。这个项目正在确定如何使用化学来控制向新晶体结构发生变化的点及其转变的速度。本研究中发现的信息和新材料可用于为高温航空航天应用设计具有更好性能(优异机械性能)的陶瓷基复合材料的纤维涂层。材料科学和工程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和落基山读写困难者夏令营的当地小学教师使用。这些互补的教育和外展部分扩大了科学和工程领域代表性不足的群体的参与，以努力满足美国扩大科学和技术劳动力的需求，使其拥有更多高素质的人员。该项目将有助于加强美国在涡轮发动机和教育领域的创新和经济竞争力。技术细节：该项目正在建立化学、晶粒度、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。正在使用一系列技术来研究这些材料中的相变，这些技术包括高温纳米压痕、透射电子显微镜和金刚石砧座(结合拉曼光谱)。一个目标是实现对改进陶瓷基复合材料涂层中塑性转变触发因素的精确控制。确定了动力学效应对相变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、部件和设备的设计，在这些设备中，压力诱导的转变必须以精确的时间触发才能达到最大效果。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处理具有增强功能的亚稳材料的新方法。

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.