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

0906874，0906931狄龙和卡特该奖项是根据2009年美国复苏和再投资法案（公法111-5）资助的。非技术说明：大多数陶瓷材料的生产方法取决于少量的化学添加剂，这些化学添加剂在材料中分布不均匀;这些少量可以支配陶瓷？的效用。 这些化学物质通常会产生额外的结晶或玻璃状特征。 通过选择正确的化学添加剂，通常可以促进特定功能;这种方法通常可以降低生产成本或显着改善材料的性能。 不幸的是，预测哪种化学品应该被选择用于任何特定系统仍然是一个持续的挑战，因此进展依赖于试验和错误。一种新的方法来预测潜在的化学添加剂将开发通过了解不同的结晶和玻璃的功能如何在其形成过程中的能量和动力学竞争。 将采用各种实验和理论技术相结合的方法来实现这一目标，其结果将为陶瓷工程化学提供一种重要的新的预测方法，可能会导致各种产品的成本降低和性能提高。 该项目将在整个项目期间资助和培训两名材料科学，工程和团队合作的博士生。 作为科学外展计划的一部分，将制作令人兴奋的科学现象的简短媒体剪辑，以供列入流行的病毒式网络媒体，如www.YOUTube.com。技术问题：晶界络合物（如晶间膜）类似于晶界？阶段？其稳定性取决于温度、化学和晶界晶体学;其厚度和结构是热力学平衡性质。 最近的研究表明，配合物取决于加工和确定一些技术上重要的陶瓷系统的性能。 现有的方法来预测易感系统是不够的，我们在这一领域的知识是经验。最近的初步结果表明，平衡与肤色往往没有达到，重要的是要考虑竞争过程，如沉淀。此外，络合物在使用中会改变其组成和结构，并可作为晶界沉淀物的成核位点。 像其他人？阶段？材料的选择问题，这一问题需要综合理解激活势垒、平衡热力学和动力学。据推测，竞争过程的活化能有一个占主导地位的影响？阶段？选择，极大地影响最终的微观结构演变和性能。 这种新颖的方法有可能从根本上重塑科学家和工程师解决这个问题的方式。 拟议的工作将量化的相关参数，确定活化能和自由能的变化与两个过程中，在一个模型陶瓷系统，使用实验和理论技术相结合。 研究生将开展这项工作，并将在诸如扫描探针显微镜，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进行培训。 结果将形成新的添加剂选择标准的基础上操纵晶界的陶瓷。

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.