Tailoring Parameters to Produce Nanowires on Metal Surface via Surface Oxidation Process

摘要

Thermal oxidation of iron, tungsten, titanium and copper was done in dry air to produce Fe_2O_3, WO_3, TiO_2 and CuO nanowires, respectively, at 500 - 600 °C. Whilst nanowires were observed on iron and copper, no nanowires were seen on titanium and tungsten. Keeping the temperature constant, oxidation of titanium and tungsten was continued but in the presence of water vapour. Through this method nanowires were successfully formed on titanium but not on tungsten. Potassium halide vapour was then introduced to the oxidation furnace for tungsten and after an hour of oxidation, nanowires were produced on the tungsten surface. Nevertheless, the growth mechanism of the nanowires on tungsten is thought to be very much different than iron, copper and titanium whereby on tungsten catalytic induced reaction is likely. Oxide nanowires on iron and titanium were further studied as oxide films on copper and tungsten were not well adhered to the substrate. Under sunlight radiation, ～90% of Cr(VI) was successfully removed on Fe_2O_3 nanowires compared to on TiO_2 nanowires (～ 40 % removal) after an hour process. This is due to the smaller energy band gap of Fe_2O_3 compares to TiO_2.