4.1 - Introduction

Abstract

This chapter focuses on the use of ultrafine particles (UFPs) produced by the gas evaporation method. The use of evaporated UFPs has advanced to the industrial scale and the emphasis is on their development. Different electronic properties are expected for metallic UFPs and that such small bodies should possess unique properties. The principal application of UFPs as magnetic materials is as a recording medium. This technology has been extended to video recording and computer data storage using the same basic concept. The biggest advantage associated with the use of magnetic UFPs is the conservation of the alloy composition when an alloy of iron, nickel, and cobalt is evaporated because of the similarity of these three metals. For this material, however, the rare earth element evaporated first because its properties are vastly different from the iron group metals. This prevents effective use of the evaporation method for this system. In the laboratory, suitable UFPs with desired characteristics have been obtained. The application of UFPs has another important aspect that takes advantage of the nature of UFPs to sinter at very low temperatures and has wide possibilities. Magnetism was used as a way to probe sintering and the results from this study are presented. Sintering of UFPs has a wide range of applications, but UFPs are not suitable for general sintering because they are too small. The best uses of UFPs may lie in improving the sinterability of other materials by judicious mixing.