Jing Ma

Mg₂Ni hydrogen storage alloy has the advantages of large hydrogen storage per unit mass, low price, and abundant resources, but there are shortcomings such as activation difficulties and poor kinetic performance. This paper improves the performance of Mg₂Ni hydrogen storage alloy by adding Ti and Mn alloying elements. Mg_1.6Ni_1-xTi_0.4Mn_x (x = 0~0.3) hydrogen storage alloys with different Mn contents were prepared by the solid phase diffusion method. The physical structure and microscopic morphology of the prepared alloys were characterized using XRD and SEM techniques, and their charge/discharge and electrochemical properties were tested using a battery tester and an electrochemical workstation. The results show that the solid phase diffusion reaction of the prepared alloys resulted in the formation of the Mg phase with a layered structure, a Mg₂Ni hydrogen storage phase, and intermetallic compounds Ni₃Ti and Mg₃MnNi₂ phases. The presence of Ni₃Ti and Mg₃MnNi₂ phases improved the activation properties and discharge capacity of the alloys. The alloys with Mn addition all reached the maximum discharge capacity at the first cycle. The maximum discharge capacity increased from 50.45 mAh/g without Mn addition to 96.67 mAh/g at x = 0.3. The maximum discharge capacity of the alloy increased to 165.52 mAh/g at 323 K. The maximum discharge capacity of the alloy increased from 50.45 mAh/g without Mn addition to 96.67 mAh/g. And its corrosion current density was reduced from 0.96 mA/g without Mn addition to 0.3 mA/g.

Protective coating is an effective way to extend materials’ high-temperature service life. In order to improve the high-temperature oxidation resistance of AISI 304 stainless steel, mullite films with different layers were successfully prepared by the sol-gel method and the sintering process on the surface of stainless steel. The effect of the film layers on the high-temperature oxidation resistance of stainless steel at 900 °C for 100 h was studied. The analysis results of oxidation kinetics, X-rays diffraction (XRD), scanning electron microscopy (SEM) and energy dispersive analysis (EDS) show that Al_1.4Si_0.3O_2.7 mullite film effectively improved the high-temperature oxidation resistance of stainless steel. The sample with three-layer mullite film has the best high-temperature oxidation resistance. The mass gain and oxidation spalling mass are only 4.6% and 34.5% of those of the uncoated sample after 100 h cyclic oxidation at 900 °C. A chromium oxide layer was formed at the interface of mullite film and the substrate during the sintering process. The generation of selective Cr₂O₃ scale was promoted at the cyclic oxidation stage so that the sample with three-layers has excellent high-temperature oxidation resistance.