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

非技术描述：陶瓷材料往往表现出新的物理和化学性质，因为它们的尺寸接近纳米尺寸。这些新特性在多个领域激发了各种新的应用，从纳米传感器到燃料电池和锂电池的阴极材料。同时，为应对美国能源需求的增加、对外国石油的依赖、气候变化等当前能源问题，开发新材料也有可能。然而，纳米陶瓷加工的优化仍然是一个挑战，对基本概念的理解需要进一步研究。在这个项目中，卡斯特罗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，在热力学的基础上，对界面组成的操纵可以用来改变加工和产品的性质。特别是，Castro教授致力于通过调整成分来可控地改变界面能量来改善致密化和相变，这是加工的两个基本部分，从而实现更快，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在技术上重要的材料上提供前所未有的界面能量学数据（在文献中很少发现）来实现的，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组成部分，重点是促进初中和高中的工程。这个名为Materials&amp；You的项目包括在学校活动中展示有趣的加工过程和特性，让学生了解基本的材料概念。两所拥有大量拉美学生的高中已被选中，其根本目标是让所有学生毕业。技术细节：本项目采用独特的量热技术来测量纳米陶瓷的界面能，并通过监测和操纵驱动力来改善烧结和相变的控制。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联系起来。在加工过程中，掺入剂的影响通常只在动力学基础上考虑，但随着加州大学戴维斯分校实验室（最近由卡斯特罗教授和合作者开发）的高分辨率量热仪的出现，卡斯特罗教授的团队能够量化组成变化对系统能量学的影响，为加工控制开辟了一条新的途径。在这个项目中，高温滴液量热法被用来测量三种技术上相关的氧化物：二氧化锡、氧化锌和氧化锆的界面能（表面和晶界），这些数据与烧结和多晶稳定性相关。更好地理解界面能量学和掺杂剂在纳米陶瓷加工中的作用，可以改进工业中的成分设计，从而实现更具能源和成本效益的产品，具有可预测的相/尺寸/密度。从教育的角度来看，参与项目的学生受到指导，并与战略材料和流程一起工作，为他们未来的职业生涯提供材料专业人员的培训。

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.