Correlating Grain Boundary Character to Micro-Fracture in Transparent Ceramic Materials

透明尖晶石是一种先进的陶瓷材料，具有作为高度抗损伤的窗户材料的巨大潜力。它是通过将单独的陶瓷粉末颗粒在高温下压制在一起，直到它们熔化形成具有极好的光学透明度和极高硬度的固体而制成的。不幸的是，以负担得起的成本形成实际尺寸的窗户是一个巨大的挑战。该奖项支持专注于了解和控制陶瓷材料特性的新方法的基础研究。特别是，这项工作将探索原子在加工过程中和加工后在单个颗粒之间的边界上的排列方式，以及不同的排列如何影响材料的强度。尖晶石加工的改进将使航空航天和军事应用受益，因为当需要防损坏窗时，它提供了一种经济高效的解决方案。这样的窗户将为士兵、水手、飞行员和宇航员提供更好的保护。两名女研究生将接受使用尖端技术和工具的培训。本科生将通过学年和暑期研究项目参与进来。将通过针对K-8学生的外联活动使当地社区受益。像像差校正电子显微镜这样的技术现在揭示出，晶界和界面构成了物质的不同热力学状态，在原子水平上具有一致的三维结构。这些结构被称为络合物，由热力学变量定义，如化学势、温度、压力和相邻颗粒的结晶学。此外，有强烈的迹象表明，控制边界络合是一种可以控制块体性质的方法。为了加速将肤色工程作为一种改善材料性能的工具，本研究项目致力于界面肤色时间-温度-转变图的创建和验证。这些图表将用于将肤色类型与界面断裂行为联系起来。像差校正的电子显微镜和小规模的机械测试技术将被用来阐明单个纯和掺杂边界的特征和行为。建立和利用边界转变图是可行的，而且控制界面也可以控制边界断裂行为，这将为陶瓷界提供一种新的工程块体材料行为的手段。

Transparent spinel is an advanced ceramic material that has great potential for use as a highly damage-resistant window material. It is fabricated by pressing individual grains of ceramic powder together at elevated temperature until they fuse to form a solid with excellent optical transparency and extreme hardness. Unfortunately, forming windows of practical size at an affordable cost is a significant challenge. This award supports fundamental research focused on a new approach to understanding and controlling the characteristics of a ceramic material. In particular, the work will explore the way that atoms arrange themselves at the boundaries between the individual grains during and after processing, and how different arrangements affect the material's strength. Improvements in spinel processing will benefit aerospace and military applications by providing a cost-effective solution when damage-resistant windows are needed. Such windows will offer improved protection for soldiers, sailors, pilots, and astronauts. Two female graduate students will be trained to work with cutting-edge techniques and tools. Undergraduate students will be engaged through academic-year and summer research projects. Benefits to the local community will take place through outreach events aimed at K-8 students.Techniques such as aberration-corrected electron microscopy are now revealing that grain boundaries and interfaces constitute distinct thermodynamic states of matter that have consistent three-dimensional structures at the atomic level. These structures, termed complexions, are defined by thermodynamic variables such as chemical potential, temperature, pressure, and crystallography of the abutting grains. Furthermore, there are strong indications that control of boundary complexions is a method by which bulk properties may be controlled. In order to accelerate the use of complexion engineering as a tool for improving material properties, this research project is focused on the creation and validation of interface complexion time-temperature-transformation diagrams. These diagrams will be used to relate complexion types to interface fracture behavior. Aberration-corrected electron microscopy and small-scale mechanical test techniques will be used to shed light on the character and behavior of individual pure and doped boundaries. The demonstration that it is feasible to create and utilize boundary transformation diagrams, and that controlling complexions can also control boundary fracture behavior, will provide the ceramics community with a new means of engineering bulk material behavior.