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
The segregation of impurity elements to grain boundaries largely affects interfacial properties and is a key parameter in understanding grain boundary (GB) embrittlement. Furthermore, segregation mechanisms strongly depend on the underlying atomic structure of GBs and the type of alloying element. Here, we utilize aberration-corrected scanning…
This project studies the influence of grain boundary chemistry on mechanical behaviour using state-of-the-art micromechanical testing systems. For this purpose, we use Cu-Ag as a model system and compare the mechanical response/deformation behaviour of pure Cu bicrystals to that of Ag segregated Cu bicrystals.
Nickel-based alloys are a particularly interesting class of materials due to their specific properties such as high-temperature strength, low-temperature ductility and toughness, oxidation resistance, hot-corrosion resistance, and weldability, becoming potential candidates for high-performance components that require corrosion resistance and good…
In this project, we aim to enhance the mechanical properties of an equiatomic CoCrNi medium-entropy alloy (MEA) by interstitial alloying. Carbon and nitrogen with varying contents have been added into the face-centred cubic structured CoCrNi MEA.
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.
Grain boundaries are one of the most prominent defects in engineering materials separating different crystallites, which determine their strength, corrosion resistance and failure. Typically, these interfaces are regarded as quasi two-dimensional defects and controlling their properties remains one of the most challenging tasks in materials…