Mechanical and Aerospace Engineering

MAE 297 Seminar

Imaging Nanofunctionality: Evolution of Defect Structures under Applied Stress Fields

Klaus van Benthem

Department of Materials Science & Engineering UC Davis

Abstract:

The functionality and performance of materials critically depends on their local atomic and electronic defect structures, and local chemistry. On the other hand, materials’ reliability as well as materials synthesis and processing routines are determined by defect structure evolution under applied thermal, electric, mechanical, and/or electro-magnetic stress. In this presentation, I will briefly introduce the shared characterization facilities within the Department of Materials Science and Engineering, and subsequently review the utilization of atomic resolution and in-situ electron microscopy techniques to systematically characterize defect structure evolution in both ceramic oxides and bilayer metal thin films.

The application of electric fields to ceramic powder compacts often enables accelerated densification during field assisted sintering. Although such techniques are readily employed for the synthesis of a variety of microstructures with unique properties, a fundamental understanding of the atomic-scale mechanisms for grain boundary formation and subsequent migration in the presence of electrostatic potentials is lacking. The presentation will specifically report our recent experiments focusing on the effects of applied electrostatic fields on consolidation and grain growth in MgAl2O4 and SrTiO3. The results are promising for the consideration to control evolving microstructures by externally applied electrostatic fields during ceramic manufacturing.

In a separate project we have investigated wetting-dewetting transitions for metal-bilayer thin films. Both plan-view and cross-sectional characterization ex-situ and in-situ has revealed partial alloying of Au and Ni thin films, while interfacial re-ordering of the bilayer films results from kinetic constraints as well as the minimization of interface energies.

Date/Time
Date(s) - 03/08/2018
4:00 pm - 5:00 pm

Location
1062 Bainer Classroom

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