4.6 - Film Formation by the Gas Deposition Method

Abstract

The gas deposition method has been established as an effective method for handling ultrafine particles (UFPs). The premise was confirmed by experimentation using slowly oxidized and freshly produced UFPs. Nickel UFPs having a specific surface area of 37.8 m2/g and an average diameter of 20 nm were used. Nickel UFPs in the mixing chamber floated when a gas entered the chamber and were then carried out with the gas. The mixture was sprayed from a small nozzle onto a substrate kept at a small distance from the tip of the nozzle. When the substrate was moved, a film having a width the same as that of the nozzle diameter was formed. The films that were formed were relatively firm. The films were formed at room temperature and required no heating of the substrate. The gas deposition method was used for making a film from freshly formed UFPs without exposure to the atmosphere. UFP films formed without exposure to air can be expected to see wider applications in such areas as gas sensors and other devices. Gas deposition as well as other techniques will find use in the preparation of these films. This is a new handling method that allows for films to be formed in a simple way. Different handling techniques are being developed, but the gas deposition method takes good advantage of the characteristic features of UFPs.