HIGH-RATE SYNTHESIS OF NANOPHASE MATERIALS

In 1986, Gleiter and co-workers introduced the concept of synthesis of non-agglomerated nanoparticles by rapid condensation from the vapor p hase in a reduced pressure environment. The source of the material was an evaporative source, which is ideally suited for low vapor pressure and low melting point metals. In order to broaden the scope of the ma terials synthesis, we have developed a variation in this process in wh ich the source of the nanophase material is a metalorganic precursor. In this new Chemical Vapor Condensation (CVC) process, the key paramet ers are gas phase residence time, temperature of the hot-wall reactor, and precursor concentration in the carrier gas. The CVC processing un it is an effective nanoparticle generator which is suitable for many d ifferent types of materials. Examples are, SiC, Si3N4, Al2O3, TiO2, Zr O2 and other refractory compounds. More recently, we have extended our processing capabilities to include a flat flame combustor unit which is particularly suited to synthesis of oxide phases either as powders, films, coatings or free standing forms. We are laying the groundwork of computer-integrated manufacturing of nanophase oxides by combining a high rate nanopowder production technology with laser diagnostics an d computer modeling. (C) 1997 Acta Metallurgica Inc.