An equiatomic TiZrHfMoNb high-entropy alloy (HEA) was developed as a solar thermal energy storage material due to its outstanding performance of hydrogen absorption. The TiZrHfMoNb alloy transforms from a body-centered cubic (BCC) structure to a face-centered cubic (FCC) structure during hydrogen absorption and can reversibly transform back to the BCC structure after hydrogen desorption. The theoretical calculations demonstrated that before hydrogenation, the BCC structure for the alloy has more stable energy than the FCC structure while the FCC structure is preferred after hydrogenation. The outstanding hydrogen absorption of the reversible single-phase transformation during the hydrogen absorption–desorption cycle improves the hydrogen recycling rate and the energy efficiency, which indicates that the TiZrHfMoNb alloy could be an excellent candidate for solar thermal energy storage.

Due to the large thermal neutron absorption cross section of ¹⁰B, B₄C-Al composites have been used as neutron absorbing materials in nuclear industries, which can offer not only good neutron shielding performance but also excellent mechanical properties. The distribution of B₄C particles affects the mechanical performance and efficiency of the thermal neutron absorption of the composite materials. In this study, 15 wt % B₄C-Al and 20 wt % B₄C-Al composites were prepared using a powder metallurgy process, i.e., ball milling followed by pressing, sintering, hot-extrusion, and hot-rolling. The yield and tensile strengths of the composites were markedly increased with an increase in the milling energy and the percentages of B₄C particles. Microstructure analysis and neutron radiography revealed that the high-energy ball milling induced the homogeneous distribution of B₄C particles in the Al matrix and good bonding between the Al matrix and the B₄C particles. The load transfer ability and mechanical properties of the composites were consequently improved. The results showed the high-energy ball milling process is an appropriate fabrication procedure to prevent the agglomeration of the reinforcement particles even if the matrix to reinforcement particle size ratio was nearly 10.

High entropy alloys (HEAs) are composed of multiple main metal elements and have attracted wide attention in various fields. In this study, a novel Ti_0.20Zr_0.20Hf_0.20Nb_0.40 HEA was synthesized and its hydrogenation properties were studied, including sorption thermodynamics and hydrogen absorption/desorption kinetics. The maximum hydrogen absorption capacity was 1.5 H/atom at 573 K. X-ray diffraction (XRD) analysis indicated that the crystal structure of Ti_0.20Zr_0.20Hf_0.20Nb_0.40 HEA transformed from body-centered cubic (BCC) to body-centered tetragonal (BCT) with increasing hydrogen content, and to face-centered cubic (FCC) after hydrogen absorption to saturation. As a multi-principal element alloy, the Ti_0.20Zr_0.20Hf_0.20Nb_0.40 HEA possesses unique hydrogen absorption characteristics. The hydrogen absorption platform pressure rises gradually with the increase of the hydrogen absorption amount, which is caused by multiple kinds of BCT intermediate hydrides with consecutively increasing c/a. The full hydrogen absorption of the Ti_0.20Zr_0.20Hf_0.20Nb_0.40 HEA was completed in almost 50 s, which is faster than that of the reported hydrogen storage alloys in the literature. The experimental results demonstrate that the Ti_0.20Zr_0.20Hf_0.20Nb_0.40 HEA has excellent kinetic properties, unique thermodynamic hydrogen absorption performance, as well as a low plateau pressure at room temperature.