Michiko Ito

Preparation of Aqueous Dispersion of Titanium Dioxide Nanoparticles using Plasma on Liquid Surface

A method for preparing an aqueous dispersion of titanium dioxide (TiO2) nanoparticles by generating plasma on the liquid surface was developed. The plasma was generated between the tip of a needle electrode in the gas phase and the liquid surface. A 0.01 wt % aqueous dispersion of TiO2 was prepared by plasma treatment with ultrasonication. Dynamic light scattering measurements indicated that the average TiO2 nanoparticle sizes in the dispersions with plasma treatment in air and Ar atmosphere were approximately 150 and 180 nm, respectively. Although the pH of the dispersion prepared by Ar plasma treatment was fairly close to the isoelectric point of TiO2, the dispersion maintained a finely dispersed state. The surface potentials of TiO2 nanoparticles in the dispersions treated with plasma were confirmed to be positively charged. This suggests that the dispersions formed by plasma treatment were stabilized by electrostatic repulsion between the particles.

Effects of shot-peening and atmospheric-pressure plasma on aesthetic improvement of Ti–Nb–Ta–Zr alloy for dental applications

Ti and Ti alloys are widely used for biomedical applications such as artificial joints and dental devices because of their good mechanical properties and biochemical compatibility. However, dental devices made of Ti and Ti alloys do not have the same color as teeth, so they are inferior to ceramics and polymers in terms of aesthetic properties. In a previous study, Ti?29Nb?13Ta?4.6Zr was coated with a white Ti oxide layer by heat treatment to improve its aesthetic properties. Shot-peening is a severe plastic deformation process and can introduce a large shear strain on the peened surface. In this study, the effects of shot-peening and atmospheric-pressure plasma on Ti?29Nb?13Ta?4.6Zr were investigated to form a white layer on the surface for dental applications.

Enhancement of liquid treatment efficiency by microwave plasma under flow-induced reduced pressure

A new microwave plasma device system for in-line solution treatment is developed. In this system, the Venturi effect for pressure reduction is utilized for stable and effective plasma production. The decomposition of phenol solution is tested to verify the efficiency of an in-line plasma treatment system, and such a treatment system is confirmed to have a higher decomposition efficiency than our previously developed batch-type treatment system. Increases in phenol decomposition speed and decomposition energy efficiency with increasing solution flow rate are observed, which suggests the suppression of OH radical recombination and the utilization of OH radicals under flowing solution conditions.