(550c) Gas Phase Production of Metal Oxide Nanowires and Nanoparticles Using a Microwave Plasma Reactor

Nanowires have attracted great interest because of their promise in a variety of applications such as electronics, optoelectronics, nano electro-mechanical devices, catalysis and several other fields. Hence, the synthesis of bulk quantities of nanowires with controlled composition, and high crystallinity is important. However, bulk production of nanowires has been challenging using the techniques known so far.

A novel reactor and method for bulk production of high purity metal oxide nanowires using a high throughput micro wave plasma reactor has been developed. The metal oxide nanowires are produced directly in the gas phase without the need of any catalyst, substrate or template. Each run for processing metal powders into metal oxide nanowires took less than a second. So, this process is capable of making a kilogram per day. We have produced nanowires of tin oxide, zinc oxide, titanium oxide, alumina and copper-zinc alloy so far. Nanoparticles of Alumina and Titania were also produced at the temperatures above the melting points of their corresponding metals. Pure nanowires are purified by a dispersion in 1-methoxy 2-proponal followed by horn sonication and gravity sedimentation.A simplified analysis followed by experiments suggest that the metal powders melt in the plasma primarily with the heat generated from chemical reactions, i.e., radical recombination and oxidation reactions on particle surface.