Internal interfaces in nanostructured materials

Gerhard Wilde / University of Münster, Münster, Germany

November 9, 2023


The large fraction of atoms situated at internal interfaces modifies the properties and behavior of nanostructured or nanocrystalline materials with respect to their conventional, coarse-grained counterparts. Such modifications can extend materials properties to ranges otherwise inaccessible to materials with conventional microstructures. One very prominent example is given by the mechanical properties. The size of coherently scattering regions starts to affect the mechanical properties of a material even when the characteristic length scale is on the micron scale. The behavior of the materials, however, can change in a noncontinuous manner at very small sizes of the coherently scattering regions. Therefore, attention is devoted to address the underlying fundamental issues related to interface structure, interface properties, and defect interactions in nanostructured materials.

The thermodynamic properties of a given material address the impact of the length scale of the internal “microstructure” of this material and its internal interfaces. These properties are immediately related to the maps of materials science (i.e., the constitutional phase diagrams that govern stability, composition selection, processing conditions, and performance of the materials). It is well known that the characteristic temperatures for phase transformations - such as melting - change when the characteristic size of a system is reduced to the nanoscale. However, is it “just” the size that controls the shift of the transformation temperature? Is just the characteristic temperature that is affected, or also, more generally, the so-called “thermodynamic potentials”? Is the way thermodynamics is described for multi-component materials still valid for nanostructured materials?

In this talk, examples concerning selected properties highlighting the role and importance of internal interfaces and their atomic structure and related properties will be given.

Gerhard Wilde

is Director of and Professor at the Institute of Materials Physics at the University of Münster, Germany, with a group of about 40 students and research associates. His research areas include nanostructured and nanocrystalline materials, microstructure evolution and defects and diffusion in solids.

The Wilde group has contributed fundamental research work on the thermodynamics and kinetics of metallic glasses and nanocrystalline materials and the structure, kinetics and mechanical properties of interfaces. Their work also encompasses functional properties of nanostructured surfaces and the thermodynamics and kinetics of phase transformations. Funding for their research has mostly been secured through the German Research Foundation.

Gerhard Wilde is a member of the German Physical Society, the U.S. Minerals, Metals and Materials Society (TMS) and the Materials Research Society (MRS) of the USA and has been elected several times as “outstanding reviewer of the year” by Acta Materialia and Scripta Materialia. He also serves as editor-in-chief of the Beilstein Journal of Nanotechnology.