Tso-Fu Mark Chang
Tokyo Institute of Technology, Yokohama, Japan
Title: Effect of pressure on crystal structure of metal oxides formed in supercritical CO 2 emulsified solution
Biography
Biography: Tso-Fu Mark Chang
Abstract
Metal oxides such as TiO2 and ZnO are widely applied as biosensors, biomaterials and as the support in a drug delivery system because of the high biocompatibility. The synthetic approaches include hydrothermal methods, cathodic deposition, anodic oxidation and sol-gel method. Among them, cathodic deposition offers a low-cost yet effective process for production of metal oxides with controllable morphology. However, the as-deposited TiO2 and SnO2 are usually amorphous. An additional heat treatment process, for example, annealing at 400°C for 1 hr, is needed to obtain crystalline TiO2. The need of the post-heat hinders the applicability of the products. Therefore, it is practically significant if crystalline metal oxides can be obtained directly from the cathodic deposition without the additional heat treatment, or lower the temperature needed in the heat treatment. On the other hand, the effect of pressure on the crystallinity of metal oxides deposited from the solution phase is rarely investigated. In a previous study, grain size of the TiO2 cathodically deposited with a supercritical CO2 (sc-CO2) emulsified electrolyte (SCEM) was found to be increased with an increase in the pressure. In this later study, crystal structure of the TiO2, ZnO, and SnO2 were found to be affected by the applied pressure used during the deposition. The as-deposit TiO2 and SnO2 were found to be composed of nano-crystallines when the SCEM was applied. In this presentation, the effect of pressure on crystal structure of metal oxides deposited using the SCEM will be reported.