CATHODIC PROCESSES DURING BORON REDUCTION IN FLUORIDE MELTS

The electrochemical behavior of boron in eutectic melts of lithium, so dium, and potassium fluorides, which contain additives of potassium te trafluoroborate, is studied on a silver electrode using linear voltamm etry. At tetrafluoroborate concentrations below 5.7 x 10(-2) mol % the cathodic process B(III) + 3e --> B(0) is irreversible, and the diffus ion coefficient for the BF4- complexes is equal to 2.06 x 10(-5) cm(2) s(-1) at a temperature of 700 degrees C. At concentrations higher tha n that mentioned above, the cathodic process proceeds under the surfac e ohmic control. The ''apparent surface resistance'' of the cathodic f ilm of boron, which determines the mechanism of the electrode process, varies from 21.6 to 3.3 Ohm cm(2) in the temperature interval from 55 0 to 700 degrees C.