RESUMEN
The WMoTaNbV alloy has shown promise for applications as a solid state hydrogen storage material. It absorbs significant quantities of H directly from the atmosphere, trapping it with high energy. In this work, the dynamics of the absorption of hydrogen isotopes are studied by determining the activation energy for the solubility and the solution enthalpy of H in the WMoTaNbV alloy. The activation energy was studied by heating samples in a H atmosphere at temperatures ranging from 20 °C to 400 °C and comparing the amounts of absorbed H. The solution activation energy EA of H was determined to be EA=0.22±0.02 eV (21.2 ± 1.9 kJ/mol). The performed density functional theory calculations revealed that the neighbouring host atoms strongly influenced the solution enthalpy, leading to a range of theoretical values from -0.40 eV to 0.29 eV (-38.6 kJ/mol to 28.0 kJ/mol).
RESUMEN
High-entropy materials emerged as a field of research in 2004, when the first research on high-entropy alloys was published. The scope was soon expanded from high-entropy alloys to medium-entropy alloys, as well as to ceramics, polymers and composite materials. A fundamental understanding on high-entropy materials was proposed in 2006 by the 'four core effects' - high-entropy, severe-lattice-distortion, sluggish-diffusion and cocktail effects - which are often used to describe and explain the mechanisms of various peculiar phenomena associated with high-entropy materials. Throughout the years, the effects have been examined rigorously, and their validity has been affirmed. This Perspective discusses the fundamental understanding of the four core effects in high-entropy materials and gives further insights to strengthen the understanding for these effects. All these clarifications are believed to be helpful in understanding low-to-high-entropy materials as well as to aid the design of materials when studying new compositions or pursuing their use in applications.