Papers by Author: T. Minami

Abstract: Anatase nanocrystals were formed on sol-gel derived SiO2-TiO2 coatings with water vapor or hot water treatments. The anatase nanocrystals were precipitated through hydrolysis of Si-O-Ti bonds, dissolution of SiO2 component, migration of hydrolyzed titania species, and nucleation and growth. The process temperatures can be lowered below 60oC, which should open new applications. It was found that the crystal habit of titania was changes from roundish anatase to sheet-like titania by applying vibration during the hot water treatment. The nanosheets were identified as hydrated titania, TiO2 . mH2O, with layerd structure. The coatings of hydrated titania showed high photocatalytic activities and excellent antifogging properties due to their unique morphology.

Abstract: V2O5 microparticles of 0.3-0.6 μm in diameter were prepared from VO(O-C3H7 i)3 in an ethanol solution by the sol-gel method. The addition of poly(ethylene glycol) and acetyl acetone into the sols was effective to control the size and spherical shape of V2O5 particles. The particles thus obtained were amorphous having a layered structure with hydrated water, and transformed into an orthorhombic phase at 500°C through a glassy state. The microparticles were positively charged in I2-containing acetone, so that they were electrophoretically deposited on the cathode with applied DC voltage. The prepared particles were used as a cathode in an electrochemical cell with a lithium metal as an anode. Discharge capacity of a rechargeable cell of Li / LiPF6 (ethylene carbonate + diethylene carbonate) / V2O5 -based composite was 110-180 mAh g-1 when the potential range and current density were 2-4 V and 0.1 mAcm-2, respectively.