Investigation on the Thermodynamic Stability of Nanocrystalline W-Based Alloys: A Combined Theoretical and Experimental Approach

The stability of nanostructured metal alloys is currently being extensively investigated, and several mathematical models have been developed to describe the thermodynamics of these systems. However, model capability in terms of thermal stability predictions strongly relies on grain boundary-related parameters that are difficult to measure or estimate accurately. To overcome this limitation, a novel theoretical approach is proposed and adopted in this work to identify W-based nanocrystalline alloys which are potentially able to show thermodynamic stability. A comparison between model outcomes and experimental findings is reported for two selected alloys, namely W-Ag and W-Al. Experimental results clearly highlight that W-Ag mixtures retain a segregated structure on relatively coarse length scales even after prolonged mechanical treatments. Moreover, annealing at moderate temperatures readily induces demixing of the constituent elements. In contrast, homogeneous nanostructured W-Al solid solutions are obtained by ball milling of elemental powders. These alloys show enhanced thermal stability with respect to pure W even at high homologous temperatures. Experimental evidences agree with model predictions for both the investigated systems.

Using plasmons to harness infrared solar light

Using plasmons to harness infrared solar light The PLASMIONICO project aims to advance the sustainable production of electricity by harnessing infrared (IR) solar light, which is typically wasted in conventional solar cells. The key concept is to allow IR light to be absorbed at nanostructured metal cathodes to launch surface plasmons (rapid oscillations of electronic charge analogous to sound waves in liquids) to generate a photocurrent. Our strategy uses inverted silicon pyramid arrays covered with thin gold films, manufactured employing low-cost and scalable methods. After optimising the infrared absorption performance, we are set to improve photocurrent delivery with promising results.

In Situ Atomic-Scale Observation of Dislocation Climb and Grain Boundary Transformation in Nanostructured Metal

We report atomic-scale observations of grain boundary (GB) dislocation climb in nanostructured Au during in situ straining at room temperature. Climb of a dislocation occurs by stress-induced reconstruction of two atomic columns at the edge of an extra half atomic plane in the dislocation core. Different from the conventional belief of dislocation climb by destruction or construction of a single atomic column at the dislocation core, the new atomic route is demonstrated to be energetically favorable by Monte Carlo simulations. Our in situ observations also reveal GB transformation through dislocation climb, which suggests a means of controlling microstructures and properties of nanostructured metals.