Ion Exchange at Metal/Ceramic Interfaces

研究的目的是了解金属和陶瓷之间可能的键合机制的基本方面。由于离子交换反应可以极大地改变材料的几种基本性质，因此在定量水平上理解这种反应是很重要的。目标是研究具有特别简单的界面几何形状的模型系统，这将更适合于微分析，并将允许区分各种参数的影响。这项工作包括用薄膜技术制造理想的铝尖晶石界面。所得界面的原子结构以及铝、镁和氧在其直接环境中的空间分布将通过截面高分辨率分析TEM进行分析。对反应不同阶段的元素分布进行定量分析，将对这一技术上重要过程的动力学提供基本的见解。采用周期性开裂方法的力学测试将用于评估不同退火处理后的界面强度，并将其与观察到的三种元素在铝-尖晶石界面上的浓度分布相关联。实验得到的浓度曲线将用于离子交换反应动力学的建模，作为几个关键参数（如温度、扩散和活度系数）的函数。力学测试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-陶瓷粘附的影响，并研究离子交换反应导致实验观察到的铝和尖晶石之间强机械结合的假设。在离子交换反应过程中，通过施加外电场来实现操纵界面键合的可能性。本研究通过薄膜技术对铝尖晶石界面进行了基础研究。除了界面微观结构表征和定量分析元素分布以研究动力学外，还采用力学测试来评估界面强度。合成和HRTEM工作将在CWRU进行，而力学测试和离子交换与强度的建模/相关性将在UCB进行。该项目采用以团队为导向的方法，让本科生和少数民族参与研究。金属-陶瓷界面上的机械强度与离子交换之间的联系涉及到材料科学的基础，同时也将对金属-陶瓷键合技术在许多行业中产生重大影响。

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.