Collaborative Research: Development of an Additive Selection Criteria based on Interface Complexions

[0906874, 0906931] dillon和carter该奖项是根据2009年美国复苏和再投资法案（公法111-5）资助的。非技术描述：大多数陶瓷材料的生产方法依赖于少量化学添加剂，这些添加剂在材料中分布不均匀；这些微量元素可以支配陶瓷？年代的效用。这些化学物质通常会产生额外的晶体或玻璃状特征。通过选择合适的化学添加剂，通常可以促进特定的特性；这种方法通常可以降低生产成本或显著改善材料的性能。不幸的是，预测应该为任何特定系统选择哪些化学物质仍然是一个持续的挑战，因此进展依赖于试验和错误。一种预测潜在化学添加剂的新方法将通过了解不同的晶体和玻璃特征在它们形成过程中的能量和动力学竞争而发展。将采用各种实验和理论技术的结合来实现这一目标。该结果将为陶瓷工程化学提供一种重要的新预测方法，可能导致各种产品的成本降低和性能提高。该项目将资助和培训两名材料科学、工程和团队合作方面的博士生。作为科学推广计划的一部分，令人兴奋的科学现象的短媒体剪辑将被制作成流行的病毒网络媒体，如www.YOUTube.com.TECHNICAL。详细信息：晶界的颜色（如晶间膜）类似于晶界相。其稳定性取决于温度、化学和晶界晶体学；它们的厚度和结构是热力学平衡性质。最近的研究表明，肤色取决于加工，并决定了一些技术上重要的陶瓷系统的性质。现有的预测易感系统的方法是不充分的，我们在这个领域的大部分知识都是经验的。最近的初步结果表明，与肤色的平衡往往不能实现，重要的是要考虑竞争过程，如降水。此外，络合物在使用过程中会改变其组成和结构，并可能作为晶界沉淀的成核点。像其他阶段一样？材料的选择问题，这需要对活化障碍，平衡热力学和动力学的综合理解。据推测，竞争过程的活化能对这一阶段起主导作用。这种选择极大地影响了最终的微观结构演变和性质。这种新颖的方法有可能从根本上重塑科学家和工程师处理这个问题的方式。所提出的工作将量化所需的相关参数，以确定与两个过程相关的活化能和自由能的变化，在一个模型陶瓷系统中，使用实验和理论技术的结合。研究生将进行这项工作，并将接受扫描探针显微镜，高分辨率透射电子显微镜，计算相图方法和扩散界面相场方法等技术的培训。研究结果将为基于晶界调控的陶瓷添加剂选择新标准奠定基础。

0906874, 0906931Dillon and CarterThis award is funded under the American Recovery and Reinvestment Act of 2009 (Public Law 111-5).NON-TECHNICAL DESCRIPTION: The methods for production of most ceramic materials depend on a small amount of chemical additions that distribute non-uniformly within the material; these small amounts can dominate a ceramic?s utility. These chemicals often produce additional crystalline or glassy features. By selecting the right chemicals additives it is often possible promote particular features; such approaches can often reduce the cost of production or significantly improve the properties of the material. Unfortunately, it remains an ongoing challenge to predict which chemicals should be selected for any particular system and thus progress relies on trial and error. A new approach to predicting potential chemical additives will be developed by understanding how the different crystalline and glassy features compete energetically and kinetically during their formation. A combination of various experimental and theoretical techniques will be employed to achieve this goal.The results will provide an important new predictive approach to engineering chemistry in ceramics that may lead to cost reduction and performance improvement for a variety of products. The project will fund and train two doctoral students in materials science, engineering, and teamwork throughout its duration. As part of a science outreach program, short media clips of exciting scientific phenomena will be produced for inclusion on popular viral web-media outlets such as www.YOUTube.com.TECHNICAL DETAILS: Grain boundary complexions (such as intergranular films) are analogous to grain boundary ?phases? whose stability is dependent on temperature, chemistry, and grain boundary crystallography; their thickness and structure are thermodynamic equilibrium properties. Recent studies show that complexions depend on processing and determine properties of a number of technologically important ceramic systems. Existing approaches to predicting susceptible systems are inadequate and much of our knowledge in this realm is empirical. Recent preliminary results indicate that equilibrium with relation to complexions is often not achieved and that it is important to consider competing processes such as precipitation. Furthermore, complexions will change their composition and structure in use and may serve as nucleation sites for grain boundary precipitates. Like other ?phase? selection problems in materials, this one requires a combined understanding of activation barriers, equilibrium thermodynamics, and kinetics. It is hypothesized that the activation energies of the competing processes have a dominant effect on this ?phase? selection that dramatically impacts the ultimate microstructural evolution and properties. This novel approach holds the possibility to fundamentally reshape how scientists and engineers approach this problem. The proposed work will quantify the relevant parameters necessary for determining the activation energies and change in free energy associated with the two processes, in a model ceramic system, using a combination of experimental and theoretical techniques. Graduate students will carry out this work and will be trained in such techniques as scanning probe microscopy, high-resolution transmission electron microscopy, calculated phase diagram methods, and diffuse-interface phase field approaches. The results will form the basis for new additive selection criteria for ceramics based on manipulating grain boundary complexions.