Speaker
Description
High entropy alloys (HEA) represent a relatively new class of materials with promising properties for various applications. In recent years, these alloys have received considerable attention as potential heterogeneous catalysts in chemical and electrochemical reactions. Their enhanced catalytic activity is controlled by chemical composition, surface atomic coordination, electronic configuration, and degree of microstructural metastability. Single–phase HEA are of particular importance because they possess a uniform microstructure that is useful for designing and prediction of mechanical and potential functional properties. The cooling rate has a significant impact on the formation of microstructure, affecting the size of grains, as well as distribution and composition of precipitates and phases that are being formed during solidification. In the frame of our research work, the influence of different cooling rates on the microstructure of Ag20Pd20Pt20Cu20Ni20 HEA were studied. The microstructure and phase constituents were characterized by scanning electron microscopy (SEM), X-ray Diffraction (XRD) and transmission electron microscopy (TEM). Liquid phase separation with consequential monotectic reaction resulted in an anomalous multiphase casted microstructure. With an increase in the cooling rate using melt spinning technique, the number of formed phases and the size of the grains decreased, and the high entropy supersaturated solid solution was attained as the atoms in the alloy did not have enough time to diffuse and to rearrange themselves into a stable, ordered structure. It was also confirmed that higher cooling rates cause severe lattice distortion and create at the surface coordinatively unsaturated sites which are essential for the bonding and activation of the reactants and therefore significantly improve the potential catalytic properties of the Ag20Pd20Pt20Cu20Ni20 alloy.