Ion Exchange at Metal/Ceramic Interfaces

Case Western Reserve University, Cleveland OH

Investigators

Abstract

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.