The mechanisms of the electrochemical reduction and nucleation process of B(Ⅲ) on the platinum electrode in the LiF-NaF-KF-KBF4 molten salt at 700°C were first investigated using cyclic voltammetry and chronoamperometry tech-niques. It was found that the electrochemical reduction of B(Ⅲ) occurs in single-step charge transfer: B(Ⅲ) + 3e → B, and the cathode process is reversible. The electrocrystallization process of B(Ⅲ) is instantaneous.
This paper focuses on the preparation of titanium diboride (TiB2) coatings on the graphite substrate by continuous current plating (CCP) and pulse current plating (PIC) electrochemical techniques in fluoride electrolytes (LiF-NaF-KF) containing K2TiF6 and KBF4 as the electrochemically-active components at 700°C. Thick leveled and uniform coatings were obtained and were composed of relatively pure TiB2. The effect of the experimental parameters on the microstructure of the coatings was studied. The results showed the electrodeposition with PIC produced coatings with better quality, when compared with those obtained by CCP, under the conditions of the current density i = 0.6 A/cm2, frequency = 100 Hz, and ton/toff = 4/1. XRD analysis indicated that the preferred orientation of coatings is (110) plane, which is in accordance with the prediction of the two-dimensional crystal nuclei theory. The effect of a ratio of ton/toff and frequency on the crystal size, tex- ture coefficient and microstress was also investigated.
