Study On Production Of Zr-Ni Alloy By Electro-deoxidization In Molten Salt

ZrNi alloy is widely used in the areas of nuclear industry, astronautics, seabed detector, et al. It is also used to decompose vapour or methane for hydrogen preparation, and it plays an important role in the application popularization of hydrogen and the promotion of fuel cells. ZrNi alloy is an excellent hydrogen storage material, and it is one of the most important hydrogen storage materials. The method of molten salt electro-deoxidization is a new metallurgic technology developed in recent years, it can lower production costs, simplify process flow and reduce pollution.In the paper, the novel method of electro-deoxidization, namely, FFC Cambridge Process method was used to reduce solid ZrO2-NiO directly to ZrNi alloy in a eutectic melt of CaCl2-NaCl. A graphite rod was employed as the anode and the sintered ZrO2-NiO pellet served as cathode.The relation of time-current in the process of electrolysis was recorded. X-ray diffraction (XRD) was used to analysis the phase composition of the cathode film, scanning electron microscopy (SEM) was used to analysis the microstructure of the cathode film in different process conditions, energy disperse spectrum (EDS) was used to measure the content of elements in the cathode film before and after electrolytic, and the Archimedes drainage was used to measure the porosity of cathode film. The influence of some factors on the electro-deoxidation was investigated.The results showed that the intensity of the cathode pellet increased and the secondary crystallization of the inner oxide particles occurred with the increasing of sintering temperature and extending of sintering time. The inner particles of cathode pellet sintering at 1100℃for 12h had moderate size, higher porosity, and better deoxidization effects. When the molding pressure was lower, the particles could not combine closed, the electrical conductivity was poor, was not in favor of electro-deoxidation, and the cathode was easily pulverized. When the molding pressure was too higher, the inner pellet was highly compact, its porosity was very low, it was difficult for molten permeating into the cathode, and it was also not in favor of electro-deoxidation. The oxide deoxidation became completer with the extending of sintering time, and the oxgen content of product was lower. With the increasing of electrolyzing temperature, the diffusion of oxygen ion was promoted, the electro-deoxidation reaction was accelerated, however, when the temperature of deoxidation was too high, the reaction was unstable, and it caused current volatile that was not conducive to the control of reaction. It was found that the addition of NiO promoted the electrical effective deoxidation of ZrO2, it could be improved more than 80%.The best process conditions were as follows:molding pressure was lOMPa, sintering temperature was 1100℃, sintering time was 12h, electrolyzing under 3.1V for 8 hours. The ZrNi alloy pellets formed under these conditions had higher level, the residual oxygen content was lower than 0.9%.