This project aims to correlate the localised electrical properties of ceramic materials and the defects present within their microstructure. A systematic approach has been developed to create crack-free deformation in oxides through nanoindentation, while the localised defects are probed in-situ SEM to study the electronic properties. A coupling of dielectric spectroscopy is made with in-situ micro/nano-mechanical testing. The correlation between defects and electrical properties provides information about the local deformation-conductivity phenomena, improving electrical properties of material, and may enable predicting failure of materials.
Despite the brittleness of oxides, we are able to deform the material without crack-formation. This is done through nanoindentation pop-in-stop experiments utilising small indenter tip dimensions [1]. Mechanical behaviour of materials in the plastic regime is studied with electron channelling contract imaging (ECCI) to identify the deformation mechanisms (Fig. 1). The novel approach of this project involves performing low-load mechanical deformation which does not lead to failure of the material (Fig. 2), as well as having the ability to locally approach the plastic zone for electrical characterisation.
Local electrical properties of deformed zones in the oxides are studied through impedance spectroscopy inside SEM. Microcontacts are deposited with GIS-FIB system, while nanometre-sharp needles are driven by the micromanipulator to probe the microcontacts. Such experiments aim to develop a correlation between the changes in the dielectric properties and the plastic deformations inside the ceramic materials. This technique represents a promising non-destructive method to improve reliability of ceramic materials at the micro- and nanoscale as well as to predict their mechanical behaviour, while they are exposed to mechanical load.
International researcher team presents a novel microstructure design strategy for lean medium-manganese steels with optimized properties in the journal Science
Because of their excellent corrosion resistance, high wear resistance and comparable low density, Fe–Al-based alloys are an interesting alternative for replacing stainless steels and possibly even Ni-base superalloys. Recent progress in increasing strength at high temperatures has evoked interest by industries to evaluate possibilities to employ…
The goal of this project is to optimize the orientation mapping technique using four-dimensional scanning transmission electron microscopy (4D STEM) in conjunction with precession electron diffraction (PED). The development of complementary metal oxide semiconductor (CMOS)-based cameras has revolutionized the capabilities in data acquisition due to…
Grain boundaries (GBs) affect many macroscopic properties of materials. In the case of metals grain growth, Hall–Petch hardening, diffusion, and electrical conductivity, for example, are influenced or caused by GBs. The goal of this project is to investigate the different GB phases (also called complexions) that can occur in tilt boundaries of fcc…
In order to develop more efficient catalysts for energy conversion, the relationship between the surface composition of MXene-based electrode materials and its behavior has to be understood in operando. Our group will demonstrate how APT combined with scanning photoemission electron microscopy can advance the understanding of complex relationships…
In this project, we aim at significantly enhancing the strength-ductility combination of quinary high-entropy alloys (HEAs) with five principal elements by simultaneously introducing interstitial C/N and the transformation induced plasticity (TRIP) effect. Thus, a new class of alloys, namely, interstitially alloyed TRIP-assisted quinary (five-component) HEAs is being developed.
Despite the immanent advantages of metals and alloys processed by additive manufacturing (e.g. design freedom for complex geometry) and unexpected merits (e.g. superior mechanical performance) of AM processes, there are several remaining issues that need to be addressed in order to practically apply AM alloys to various industries. One of the most important issues is the mechanical behavior of AM alloys under hydrogen environments, since it is easily encountered in the industrial fields and has generally detrimental effects on metals and alloys.