Compression experiments on micron-scale specimens and acoustic emission (AE) measurements on bulk samples revealed that the dislocation motion resembles a stick-slip process – a series of unpredictable local strain bursts with a scale-free size distribution. Here we present a unique experimental set-up, which detects weak AE waves of dislocation slip during the compression of Zn micropillars. Profound correlation is observed between the energies of deformation events and the emitted AE signals that, as we conclude, are induced by the collective dissipative motion of dislocations. The AE data also reveal a two-level structure of plastic events, which otherwise appear as a single stress drop. Hence, our experiments and simulations unravel the missing relationship between the properties of acoustic signals and the corresponding local deformation events. We further show by statistical analyses that despite fundamental differences in deformation mechanism and involved length- and time-scales, dislocation avalanches and earthquakes are essentially alike.

In this work, a comprehensive investigation of amorphous and crystalline modification of identical electrode active material as a thin-film electrode for a future all-solid-state Li-ion battery application is presented and discussed. Using the proposed micro-battery system, we aim to unravel the effect of the crystallinity of the positive electrode material on the intrinsic durability of all-solid-state thin-film Li-ion batteries during prolonged electrochemical cycling. We demonstrate the preparation, structural-, nanomechanical and electrochemical characteristics of molybdenum (VI) oxide (MoO₃) thin-film cathodes based on their different crystallinity. The nanomechanical properties of the electrode layers were determined using nanoindentation along with acoustic emission studies. Based on the electrochemical test results, as-prepared thin films that did not go under any heat treatment showed the best performance and stability throughout cycling around 50 μAh initial capacity when cycled at C/2. This suits well their nanomechanical properties, which showed the highest hardness but also the highest flexibility in comparison with the heat-treated layers with lower hardness, high brittleness, and numerous cracks upon mechanical loads. According to our results, we state that amorphous-type electrode materials are more durable against electro-chemo-mechanical-aging related battery performance loss in all-solid-state Li-ion batteries compared to their crystalline counterparts.

Aluminum matrix (Al99.5) syntactic foam containing expanded perlite particles was produced using the pressure infiltration technique. The dominant deformation mechanisms during compression of this foam were determined by sequential k-means analysis of the acoustic emission data. Since the different deformation mechanisms were concurrently active even at small strains, successive unloading and reloading measurement was proposed for cluster identification. The repetitive unloading and reloading allowed us to identify two mechanical parameters, namely the unloading modulus and the loss for unloading-reloading cycles. Based on the correlations among the strain localization within the specimen, the acoustic emission results, the changes in these mechanical parameters, and the transition from quasi-elastic deformation to plasticity were revealed in this material.

The A356 aluminum alloy is a very commonly used alloy in the automotive industry, for parts such as pistons, cylinder heads, and connecting rods, for which the mechanical properties can be effectively increased by anodizing. In this work, oxide layers were formed in oxalic acid solution with defined parameters on A356 aluminum alloy and then studied by using a novel combination of the scanning electron microscope (SEM) and in-situ nanoindentation. The purpose of this research is to understand the relationship between the substrate and the oxide layer by examining its microstructure and nanohardness. Based on the experimental results showing special composite microstructure and corresponding high hardness, this alloy seems to be a good alternative for replacing steel brake disks in an environmentally conscious manner.