OElectrochemical Conversions of Soluble Borates to CaB6 with Superior Optical Property in NaCl-CaCl2 Melt

A novel method for the direct conversion from soluble NaBO2 or Na2B4O7 to CaB6 by molten salt electrolysis was provided for the high-value utilization of boron slag. The deposited CaB6 was characterized by XRD, SEM, EDS and TEM. The light absorption and magnetic properties were analyzed by an ultraviolet-visible-near infrared spectrometer and a SQUID magnetometer, respectively. The reduction behavior of NaBO2 was also investigated by cyclic voltammograms, square wave voltammograms and open circuit potential technique. The results indicated that nano cubic CaB6 crystals can be obtained by molten salt electrolysis. The BO2- ion was first electro-reduced to element B by a three-electron transfer process and then combined with the deposited Ca to form CaB6. The diffusion coefficient of BO2- was 1.1 x 10(-6) cm(2) s(-1) at 1073 K. The prepared CaB6 showed a saturation magnetization value of similar to 8 x 10(-8) A m(-2) and a high absorbance value of 0.5 for ultraviolent spectrum. (C) 2018 The Electrochemical Society.