Preparation Of Mg-based Alloy By Electrodeposition In Low-temperature Molten Salts

The Mg-based hydrogen storage alloys are considered as one of the most promising hydrogen storage alloys, offering the combination of great hydrogen storage capacity, low density, abundant resource and Alrge electrochemical capacity. Mg-based alloys were electrodeposited in urea-acetamide-NaBr low temperature molten salts, and the electrochemical performance of the alloys was studied. The details of the study and its results are introduced as follows:(1) The electrochemical behaviors of Ni(Ⅱ)-Mg(Ⅱ) on Cu electrode was investigated in urea-acetamide-NaBr low temperature molten salts, respectively. The reduction processes of Ni(Ⅱ)-Mg(Ⅱ) were proved as irreversibility by cyclic voltammetry experients. The reduction of Mg is controlled by the diffusion of Mg2+and the reduction of Ni is controlled by the diffusion of Ni2+. The nucleation processes were only one nucleus-grow up, which was studied by transient potentiostatic polarization methods, and transient galvanostatic polarization methods. At the same time, the influences of deposition parameter on the Ni-Mg alloy’s composition were studied. The results showed that the atomic percentage of magnesium alloys, decreased with the increasing of deposition temperature. The best temperature is 383 K. The best doposition potential is-0.5 V or-0.6 V. With the increase of the deposition time, the atomic percentage of magnesium alloys increased first and then decreased. The best deposition time is 40 min. The atomic percentage of magnesium is best at CR=1:2 of NiCl2 and MgCl2.(2) The electrochemical behaviors of Ni(Ⅱ)-Mg(Ⅱ)-Al(Ⅲ) on Cu electrode was investigated in urea-acetamide-NaBr low temperature molten salts, respectively. The reduction of Mg. Al is controlled by the diffusion of Mg2+, Al3+ and the reduction of Ni is controlled by the diffusion of Ni2+. The nucleation processes were only one nucleus-grow up, which was studied by transient potentiostatic polarization methods, and transient galvanostatic polarization methods. At the same time, the influences of deposition temperature and time on the Ni-Mg-Al alloy’s composition were studied. The results showed that the atomic percentage of magnesium alloys decreased with the increasing of deposition temperature and increased first and then decreased of deposition time. The best temperature is 383K and the best doposition time is 40 min.(3) Ni-Mg and Ni-Mg-Al alloy films were prepared by using potentiostat methods at best conditions. Scanning electron microscopy (SEM), spectroscopy (EDS), X-ray diffraction (XRD) and X-ray Photoelectron Spectroscopy (XPS) analysis were used to characterize the coating surface morphology, phase composition and structure elements. The results showed that alloy thin film is uniform and compact. The alloys were observed in a different intermetallic compounds.