CAREER: Thermochemistry of Nanoceramics: Understanding and Controlling Phase Transformation and Sintering via Interface Energetics

非技术描述：陶瓷材料通常表现出新的物理和化学性能，因为它们的尺寸接近纳米尺寸。这些新特性激发了多个领域的各种新应用，从纳米传感器到燃料电池和锂电池的阴极材料。此外，为应对当前的能源问题，如美国对能源的需求增加，对外国石油的依赖和气候变化，开发新材料提供了可能性。然而，纳米陶瓷加工的优化仍然是一个挑战，理解基本概念需要进一步的研究。在这个项目中，Castro教授专注于纳米陶瓷中存在的较大体积分数的界面，以改善加工控制。他假设，界面组成的操纵可以用来改变热力学基础上的加工和产品性能。特别是，卡斯特罗教授致力于改善致密化和相变，这是加工的两个基本部分，通过调整成分可控地改变界面能，实现更快，更便宜，更可控的加工和产品。这种独特的热力学方法是通过提供前所未有的关于技术重要材料的界面能量学（文献中很少发现）的数据来进行的，使这些重大进展更接近工业制造。该项目还有一个重要的教育部分，重点是在初中和高中推广工程学。该计划，材料你，涉及有趣的处理和性质在学校活动的示范，让学生接触到基本的材料的概念。选择了两所拥有大量拉丁美洲学生的高中，其基本目标是让所有学生毕业。技术优势：该项目使用独特的量热技术测量纳米铈的界面能，并通过监测和操纵驱动力来改善对烧结和相变的控制。目的是量化掺杂剂对界面能的影响，并将其与工艺参数和动力学相关联。掺杂剂在加工过程中的影响通常仅在动力学基础上考虑，但随着加州大学戴维斯分校实验室提供的高分辨率量热法的出现（最近由Castro教授及其合作者开发），Castro教授的小组能够量化组成变化对系统能量学的影响，为加工控制开辟了新的途径。在该项目中，高温滴液量热法用于测量三种技术相关氧化物的界面能（表面和晶界）：二氧化锡，氧化锌和氧化锆，以及与烧结和多晶型稳定性相关的数据。更好地理解界面能量和掺杂剂在纳米陶瓷加工中的作用，能够改进工业中的组合物设计，从而实现具有可预测的相/尺寸/密度的更具能量和成本效益的产品。从教育的角度来看，参与该项目的学生得到指导，并与战略材料和流程合作，为他们未来的材料专业人员职业生涯提供培训。

NON-TECHNICAL DESCRIPTION: Ceramic materials often exhibit novel physical and chemical properties as their sizes approach nanometer dimensions. These new properties have inspired a variety of new applications in several fields, ranging from nanosensors to cathode materials for fuel cells and lithium batteries. As well, the possibility is opened for the development of new materials in response to the current energy problems such as the U.S. increasing demand for energy, dependence on foreign oils, and climate change. However, the optimization of nanoceramic processing is still a challenge, and understanding the fundamental concepts requires further research. Within this project, Prof. Castro focuses on the larger volume fraction of interfaces present in nanoceramics to improve processing control. He hypothesizes that manipulation of the interface composition can be used to change processing and product properties on a thermodynamic basis. In particular, Prof. Castro works on improving densification and phase transformation, two fundamental parts of processing, by controllably changing interface energies by tuning composition, enabling faster, less expensive, and more controlled processing and products. This unique thermodynamic approach is carried out by providing unprecedented data on interface energetics (rarely found in the literature) on technologically important materials, bringing those significant advances closer to industrial manufacturing. The project also has an important educational component that focuses on the promotion of engineering in middle and high-schools. The program, Materials&You, involves demonstrations of interesting processing and properties at school events to expose students to basic materials' concepts. Two high-schools with significant Latin American students and the underlying goal of getting all students to graduate have been selected.TECHNICAL DETAILS: This project uses unique calorimetric techniques to measure interface energies of nanoceramics and use them to improve the control of sintering and phase transformation 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 the University of California at Davis laboratories (recently developed by the Prof. Castro and collaborators), 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. Within this project, high-temperature drop solution calorimetry is used to measure the interface energies (both surface and grain boundary) of three technologically relevant oxides: tin dioxide, zinc oxide, and zirconia, and those data correlated with sintering and polymorphic stability. The better understanding of the role of interface energetics and dopants in nanoceramic processing enables improvement of composition design in industries, enabling more energy and cost efficient products, with predictable phases/sizes/densities. From the educational perspective, students participating in the project are mentored and work with strategic materials and processes, providing training for their future careers as materials' professionals.