Thermochemistry of Nanoceramics: Understanding and Controlling Densification and Grain Growth

非技术描述：当陶瓷材料的特征尺寸接近纳米尺寸时，它们可以显示出独特的物理和化学性能。这些特性激发了在多个领域的各种应用，并开启了解决方案的开发，以应对当前美国面临的挑战，如对能源和国家安全日益增长的需求。然而，在纳米尺度上设计和制造最佳和耐用的陶瓷仍然面临着巨大的困难，需要在这些工艺的基本水平上有更多的了解。在这个项目中，卡斯特罗教授专注于纳米陶瓷中存在的更大体积分数的界面，以通过对其固有热力学性质的修改来改善工艺控制。这种方法挑战了该领域中推断热力学与工艺优化无关的旧范式，并为前所未有的突破提供了机会。卡斯特罗教授致力于研究产品背后的科学，即粉末的固结。目标是实现更快、更便宜、更可控的加工和更耐用的材料。这项研究调查了一种具有重要技术意义的材料(铝酸镁)。该项目还包括重要的教育组成部分，重点是在初中和高中推广工程学；以及培训本科生和研究生进行研究和开发。K-12课程包括在学校活动中展示有趣的加工和特性，让学生接触到基本材料的概念。本科生课程包括当代技术方面的竞争和实践研究机会，而研究生则直接参与尖端研究。技术细节：该项目使用高灵敏度的量热技术来测量纳米级陶瓷的界面能量，目的是通过监测和操纵驱动力来改善对烧结和颗粒生长的控制。其目的是量化掺杂对界面能的影响，并将它们与工艺参数和动力学联系起来。通常在动力学的基础上考虑掺杂剂的影响，但随着加州大学戴维斯分校的高分辨率量热的出现，卡斯特罗？S教授的团队能够量化组成变化对体系能量学的影响，为基于热力学的过程控制开辟了一条新的途径。在本项目中，使用了差示扫描量热法、氧化物熔滴溶液量热法和水吸附微量热法对铝酸镁的性质进行了热力学表征。一种具有战略意义的材料，用于装甲、激光和耐火应用。然后将数据与烧结和晶粒生长行为相关联。更好地理解界面能量学和掺杂剂在加工中的作用有助于改进工业中的成分设计，从而实现更节能、更具成本效益的产品，以及更稳定的颗粒尺寸(陶瓷控制的关键因素？属性)。从教育的角度来看，参与该项目的学生正在接受指导，正在使用战略材料和流程，并正在接受作为材料的未来职业培训？专业人士。

NON-TECHNICAL DESCRIPTION: Ceramic materials can exhibit unique physical and chemical properties when their feature size approaches nanometer dimensions. These properties have inspired a variety of applications in several fields and opened the development of solutions in response to current U.S. challenges such as the increasing demand for energy and national security. However, design and fabrication of optimal and durable ceramics at the nanoscale still face significant difficulties, and more understanding at the fundamental level of these processes is required. Within this project, Prof. Castro focuses on the larger volume fraction of interfaces present in nanoscaled ceramics to improve processing control by targeting modifications on their intrinsic thermodynamic properties. This approach challenges old paradigms in the field that infer thermodynamics is irrelevant on processing optimization, and offers opportunities for unprecedented breakthroughs. Prof. Castro works on the science behind products, i.e. the consolidation of powders. The goals are to enable faster, less expensive, and more controlled processing, and more durable materials. This research investigates a technologically-important material (magnesium aluminate). The project also has important education components that focus on the promotion of engineering in middle and high-schools; and training of undergraduate and graduate students in research and development. The K-12 program involves demonstrations of interesting processing and properties at school events to expose students to basic materials' concepts. The undergraduate program involves competitions and hands-on research opportunities in contemporary technologies, while the graduate students are directly involved in cutting-edge research.TECHNICAL DETAILS: This project uses highly-sensitive calorimetric techniques to measure interface energies of nanoscaled ceramics with the goal of improving the control of sintering and grain growth by monitoring and manipulating driving forces. The aim is to quantify the effects of dopants on the interface energies and correlate them with processing parameters and kinetics. The effect of dopants in processing is typically considered exclusively on a kinetic basis, but with the advent of high-resolution calorimetry available at University of California-Davis, Prof. Castro?s group is capable of quantifying the effect of composition change on the energetics of the system, opening a new avenue for processing control on a thermodynamic basis. Within this project, differential scanning calorimetry, oxide melt drop-solution calorimetry and water adsorption microcalorimetry are used to thermodynamically characterize magnesium aluminate properties ? a material of strategic interest for armor, laser, and refractory applications. The data is then correlated with sintering and grain growth behavior. A better understanding of the role of interface energetics and dopants in processing fosters improvement of composition design in industries, enabling more energy and cost efficient products, with more stable grain sizes (a key element on the control of ceramics? properties). From an education perspective, students participating in the project are being mentored, are working with strategic materials and processes, and are receiving training for their future careers as materials? professionals.