Juanjian Ru

Electrochemistry of Pb(II)/Pb during preparation of lead wires from PbO in choline chloride—urea deep eutectic solvent

The electrochemistry of Pb(II)/Pb on a stainless steel electrode during the preparation of lead wires from PbO in choline chloride (ChCl)-urea deep eutectic solvent (DES) was investigated by means of cyclic voltammetry, cathodic polarization and chronoamperometry. The experimental results indicated that the reduction of Pb(II) to Pb is a quasi—reversible process controlled by diffusion at temperature varying from 323 to 343 K, and the corresponding apparent activation energy Ea is 52.37 kJ mol-1. The analysis of chronoamperometry measurements suggested that the initial stage of nucleation of lead on stainless steel electrode is a three-dimensional instantaneous nucleation under diffusion control. The effects of reaction time and temperature on the morphology of lead deposits are also examined. The lead wires obtained at 343 K for 120 min have a mean particle size of 30 µ.m in length and 2.5 µ.m in diameter. Based on experimental evidence, the deposition mechanism of sub-micrometer lead wires on stainless steel substrate is proposed by diffusion controlled growth mechanism.

Preparation and characterisation of TiN by microwave-assisted carbothermic reduction–nitridation in air atmosphere

ABSTRACT Titanium nitride (TiN) is prepared from ilmenite (FeTiO3) powders by microwave-assisted carbothermic reduction–nitridation in air atmosphere followed by acid leaching treatment. The thermal analysis of the reduction–nitridation of FeTiO3 powders is conducted by thermogravimetry/differential scanning calorimeter. The phase transition sequence of microwave carbothermal synthesis of TiN–Fe composite is: FeTiO3 → Fe + TiO2 → Fe + TiN. There is no any other oxygen-deficient titanium oxides detected. Particularly, FeTiO3 can be transformed into TiN–Fe composite completely at 900°C for 60 min by microwave heating. The increase in both the reaction temperature and dwelling time is in favour of the transformation of FeTiO3. The product morphologies are spherical about 2–5 μm in size. Then TiN is obtained with the removal of Fe and their oxides from TiN–Fe composite by acid leaching treatment. This method not only reduces the reaction temperature significantly through microwave heating but also can simplify the operation process effectively.