Triple junction transport in nanocrystalline materials

Basic data for this project

Description

Nanocrystalline materials offer beneficial mechanical, magnetic or electronic properties for a variety of applications. However, because of their defect-rich structure, they are inherently metastable. Defects, such as grain boundaries (GB) or triple-junctions (TJ), the topological substructures where three GBs merge, appear in high density and thus may control atomic transport and in consequence thermal stability and degradation of devices. The main goal of our project is achieving a detailed knowledge on chemical transport and segregation in TJs by using local analysis by tomographic atom probe (TAP). As exemplified in the intermediate report, the TAP system at Münster University is well capable of resolving TJs in different metallic systems and determination of reliable quantitative diffusion and/or segregation parameters are close to be achieved. Thanks to the local character of the technique, the measurements involve concentrations in technically important range in contrast to the infinitesimal dissolution addressed by ideal tracer experiments. In the continuation stage of the project diffusion coefficient activation energies and segregation factors should be measured with statistical reliability. Since experiments are performed with thin film diffusion couples, also direct information on thermal stability and reaction in metallic multilayers should be obtained.