Kazutoshi Kiyokawa, Akihiko Itou, Hiroyuki Matsuoka and Kazuo Sugiyama

Department of Applied Chemistry, Faculty of Engineering
Saitama University, Shimo-Okubo 225, Urawa, 338, Japan
sugi@apc.saitama-u.ac.jp

In trying to prepare perovskite-type oxide catalyst powders by microwave heating, we found out that an atmospheric pressure non- equilibrium plasma was generated around the powders. This phenomenon was peculiar to several kinds of materials, such as La0.8Sr0.2CoO3, which have good properties with respect to heat-resistive and electron emission characteristics. As an example of applications, we tried to remove a surface oxide layer of steel which was one of the problems in a steel manufacturing process.

The apparatus, which was used to generate the plasma, consisted of a microwave generator, a waveguide unit, and a quartz tube reactor. In this experiment, to remove the surface oxide layer a steel substrate was treated by the plasma using a gas mixture of argon and hydrogen. The distance between the substrate and the plasma source could be varied. The plasma-treated sample was qualitatively observed with an EDX-SEM.

Before the treatment an oxygen peak was observed in an EDX profile. However, the oxygen peak was diminished after the treatment by an argon and hydrogen plasma. The steel substrate was also treated with a dilute hydrochloric acid solution in order to compare their treatment effects. The surface morphology was investigated with a SEM. As a result, there was little damage at a surface of the plasma-treated steel, although the treatment by a dilute hydrochloric acid solution severely damaged a surface of the steel substrate. The effect of the plasma surface treatment was progressed with increase in microwave output power and treatment time.