Electrochemical Synthesis of Titanium Oxide Nanopowders in a Molten Mixture of Alkali Chlorides and Nitrates

Abstract

Titanium oxide nanoparticles are synthesized in a molten mixture of alkali chlorides and nitrates. X-ray diffraction analysis, Raman spectroscopy, and scanning electron microscopy are used to identify the oxide powders. Titanium oxides of various modifications and compositions are synthesized by anodic polarization of high-purity titanium in a molten eutectic mixture of cesium and sodium chlorides containing 5 wt % sodium nitrate. Polarization is carried out under galvanostatic conditions at a current density of 3.5 mA/cm2 and a temperature of 540–700°C in an argon atmosphere. The phase composition of the oxidation products depends on the synthesis temperature. The particle size is controlled by varying the density and temperature. X-ray diffraction analysis and Raman spectroscopy show that the sample synthesized at a temperature of 540°C is single-phase and consists of Cs1.36Ti6.64O16. The samples synthesized at temperatures of 600 and 650°C form the TiO2 phase in mixed anatase and rutile modifications. The sample synthesized at a temperature of 700°C consists of TiO2 titanium dioxide (rutile and brookite modification) and NaTi8O13. According to scanning electron microscopy, the particle size decreases when the synthesis temperature increases. The sample synthesized at a temperature of 540°C and annealed at a temperature of 200°C contains a mixture of the nano- and microparticles of cesium trititanate (over 50 nm). The titanium dioxide particle size is 20 nm in the sample synthesized at a temperature of 600°C and is 10–20 nm in the samples synthesized at temperatures of 650 and 700°C.