Preparation of Al-Ni Alloys of Different Phases Through Direct Electro-Deoxidation of Al2O3-NiO in CaCl2-NaCl Molten Salt

Abstract

Al-Ni alloys have several common thermodynamically stable alloy phases. These alloys showed distinct physical properties and were applied in different fields, including aerospace and electrochemical catalysis. However, it is difficult to prepare Al-Ni alloys with the certain phase composition through traditional preparation methods, such as casting and mechanical alloying. Herein, Al-Ni alloys were prepared through electro-deoxidation in CaCl2-NaCl molten salt. Pure Al-Ni alloys phases (AlNi3, AlNi and Al3Ni2) were obtained after optimizing the electro-deoxidation conditions, such as the molar ratio of Al and Ni in the original tablet, the sintering temperature of the precursor, electro-deoxidation time and the molten salt temperature. The deoxidation processes of the Al2O3-NiO composite were investigated through various electrochemical methods, such as cyclic voltammetry, chronoamperometric curve and constant potential electro-deoxidation experiment. The loss of Al2O3 in the molten salt was confirmed to be responsible for the loss of Al in the electro-deoxidation processes. Meanwhile, it was proposed that the loss of Al could be efficiently delayed by increasing the precursor’s sintering temperature and the molten salt temperature. The obtained Al-Ni alloys (AlNi3, AlNi and Al3Ni2) could be used as efficient additives in the cathode of lithium–sulfur batteries to improve the charging/discharging capacity.