Narrow Results

Metal-hydride solid state hydrogen storage (H-storage) has the advantages of high bulk density, good safety, easy operation and low operating cost, and is considered to be the most ideal H-storage method. High entropy alloys (HEAs), which contain at least five principal elements and each with an atomic percentage in the range of 5–35%, have gained continuous increasing attention in the material science community. Since large entropy encourages the generation of single-phase solid solutions with severe lattice distortions and more suitable reaction sites, HEAs have become a research hotspot for better performance in hydrogen storage. Body-centered cubic (BCC) alloy systems can theoretically store double amounts of hydrogen compared with commercial metal hydrides at room temperature, and BCC structural HEAs have shown the potential to reach this theoretic limit. The thermal conductivity of HEAs seriously affects its hydrogen storage performance, but little research has been conducted on the thermal conductivity of HEAs. In this study, as-cast ${\mathrm{\text{V}}}_{35}$Ti${}_{35}$Cr${}_{10}$Fe${}_{10}$M${}_{10}$ (M $=$ Mn, Co, Sc and Ni) HEAs were fabricated by arc-melting. The microstructure and thermal conductivity behavior of the HEAs were systematically investigated. It is found that the main phase of the HEAs is a BCC-structured solid solution. The alloys also have high thermal diffusivity, specific heat capacity and thermal conductivity. The ${\mathrm{\text{V}}}_{35}$Ti${}_{35}$Cr${}_{10}$Fe${}_{10}$Sc${}_{10}$ sample exhibit the highest thermal conductivity of $2.865\mathrm{\text{W}}/(\mathrm{\text{m}}\cdot \mathrm{\text{K}})$ at $100^{\circ }$C. The factors affecting the thermal conductivity of HEAs were systematically analyzed. This study provides a new perspective on alloys applied to solid-state hydrogen storage.

Electrolytic Plasma nitrocarburizing was carried out on the hard chromium coating deposited in SM45C mild carbon steel substrate by electroplating in two different times and voltages. The electroplated samples were connected cathodically to a high-current pulsed power supply and biased with a negative voltage of 400 V. The treatment times were 5 and 60 minutes. A 5-μm thick layer was formed on the surface of Cr coating with microhardness of about 950- 1200 HV0.1. The microstructure of the treated layers depends strongly on the treatment time length. The corrosion properties of the treated layers depend on microstructure and can be improved, especially if a thin and dense complex layer is produced at the surface.

Nanocrystalline FeNi and Ni₃Fe alloys were prepared by mechanical alloying of Fe and Ni elemental powders using a planetary ball mill under protection atmosphere. X-ray diffraction measurements were performed to follow alloy formation process in these alloys. A heat treatment of 1 h at 800°C was carried out to relax the internal stresses of the milled samples. Morphological evolution of powder particles was revealed by scanning electron microscopy. The value of lattice parameter was reached to 0.35762 nm and the hardness was found to be 686 HV at 30 h milled FeNi powder. In the case of Ni₃Fe the values of 0.3554 nm and 720 HV were obtained for lattice parameter and hardness, respectively.