Our Mission
Grain boundaries and internal interfaces decide how materials fail, conduct,
and age. Our mission is to understand these interfaces at the atomic scale and to use that
understanding to design better structural and energy materials.
We combine aberration-corrected scanning transmission electron microscopy and spectroscopy
at the Ernst Ruska-Centre with in-situ experiments and small-scale mechanical testing,
linking the structure and chemistry of individual grain boundaries to the macroscopic
behavior of the material.
Highlights
Grain boundary structure and chemistry
We image individual grain boundaries atom by atom with aberration-corrected STEM and
resolve their local chemistry by STEM-EELS and STEM-EDX. Segregation, co-segregation,
and grain boundary complexions can switch a boundary between different structural
states - and with it the strength, transport, and stability of the material.
Model systems range from copper and tungsten bicrystals with well-defined boundaries
to nanocrystalline alloys, where we follow faceting transitions and
segregation-induced phase behavior of the boundaries themselves.
In-situ microscopy and small-scale mechanics
Using MEMS-based holders for heating, biasing, and deformation, we watch interfaces respond to load and temperature inside the microscope. Together with micro- and nanomechanical testing, this connects atomic-scale interface processes to plasticity, fracture, and fatigue - in nanometallic multilayers, thin films, and refractory alloys.
Interfaces in energy materials
Interfaces control performance in energy materials: twin and grain boundaries in the solid electrolyte LATP, interconnects and contacts in solar cells and fuel cells, and microstructures produced by advanced manufacturing routes such as projection micro-stereolithography and preceramic polymers.
Projects
SISTer - Segregation engineering of tungsten alloys
Mechanisms of segregation induced strengthening and toughening of ultrafine-grained tungsten alloys at elevated temperatures. A DFG-FWF Weave project with the group of Daniel Kiener at Montanuniversität Leoben: in-situ TEM deformation and atomic-resolution grain boundary characterization in Jülich, alloy synthesis and high-temperature micromechanics in Leoben.