Ion Exchange at Metal/Ceramic Interfaces

调查的目的是了解金属和陶瓷之间可能的结合机制的基本方面。由于离子交换反应可以实质上改变几种基本材料的性质，因此在定量水平上理解这一反应是很重要的。目标是研究具有特别简单的界面几何结构的模型系统，这种界面几何结构将更适合于微观分析，并将允许区分各种参数的影响。这项工作包括通过薄膜技术制造理想的铝-尖晶石界面。用横截面高分辨率分析电子显微镜分析了界面的原子结构和铝、镁、氧在其邻近环境中的空间分布。对反应不同阶段元素分布的定量分析将使我们对这一具有重要技术意义的过程的动力学有基本的了解。采用周期性裂纹方法进行力学测试，以评估不同热处理后的界面强度，并将其与铝-尖晶石界面上观察到的三种元素的浓度分布相关联。实验获得的浓度分布将用于模拟离子交换反应的动力学，作为几个关键参数的函数，如温度、扩散和活度系数。力学测试的结果及其与浓度分布的相关性将有助于模拟空间电荷层对金属-陶瓷结合的影响，并探讨离子交换反应导致实验观察到的铝与尖晶石之间的强烈机械结合的假设。在离子交换反应过程中，可以通过施加外加电场来控制界面结合的可能性。这项研究涉及通过薄膜技术对铝-尖晶石界面的基础研究。结合界面的微观结构表征和用于动力学研究的元素分布的定量分析，使用力学测试来评估界面强度。合成和HRTEM工作将在CWRU进行，而离子交换与强度的力学测试和建模/关联将在UCB进行。该项目以团队为导向，让本科生和少数族裔参与研究。金属-陶瓷界面的机械强度与离子交换之间的关系涉及到基础材料科学，这将对许多行业的金属-陶瓷连接技术产生重大影响。

The objective of the investigation is to understand the fundamental aspects on the possible bonding mechanism between metals and ceramics. Since the ion-exchange reaction can substantially change several fundamental materials properties, it is important to understand this reaction at a quantitative level. The goal is to study model systems with a particularly simple interface geometry that will be more suitable for microanalysis and will allow to distinguish the influence of various parameters. The work involves fabrication of ideal aluminum-spinel interfaces by thin-film techniques. The atomistic structure of the resulting interfaces and the spatial distribution of aluminum, magnesium, and oxygen in their immediate environment will be analyzed by cross-sectional high-resolution analytical TEM. Quantitative analysis of the elemental distribution at different stages of the reaction will give fundamental insight in the kinetics of this technologically important process. Mechanical testing, employing the method of periodic cracking, will be used to assess the interface strength after different annealing treatments and to correlate it with the observed concentration profiles of the three elements across the aluminum-spinel interface. The experimentally obtained concentration profiles will be used for modeling the kinetics of the ion-exchange reaction as a function of a few key parameters such as temperature, diffusion and activity coefficients. The results of mechanical testing and their correlation with the concentration profiles will serve for modeling the influence of a space-charge layer on metal-ceramic adhesion and to investigate the hypothesis that the ion-exchange reaction causes the experimentally observed strong mechanical bonding between aluminum and spinel. The possibility of manipulating the interfacial bonding will be pursued by applying an external electric field during the ion-exchange reaction. The study involves fundamental research on aluminum-spinel interfaces via thin-film techniques. Along with microstructural characterization at the interface and quantitative analysis of elemental distribution for studying kinetics, mechanical testing is used to assess the interface strength. Synthesis and HRTEM work will be carried out at CWRU while the mechanical testing and modeling/correlation of ion-exchange with strength will be performed at UCB. The project has a team-oriented approach to the involvement of undergraduates and minorities in research. The link between the mechanical strength and ion-exchange at the metal-ceramic interface involves fundamental materials science while will have major impact in the metal-ceramic bonding technology in many industries.