Tailoring nanostructured powders for functional and structural applications

Nanostructured powders, i.e, powders with nanoscale primary feature size, o ffer a host of attractive properties. With the growing number of applicatio ns in new as well as existing markets for this new dass of powders, several techniques have evolved for the synthesis of metal, ceramic, and composite nanoparticles, At issue In each of these processes Is the extent of aggreg ation, which depends on the technique used to produce the nanopowders. A va pour phase synthesis process is described in which vapours of chemical prec ursors are pyrolysed in a low pressure flat flame. By controlling the time- temperature history of the particles in the hot zone of the flame, high sur face area nanopowders of oxide materials are produced with minimal aggregat ion. In addition, the structure of the individual nanoparticles is controll ed to optimise properties. The use of such powders in the area of energy st orage is outlined. On the other side of the spectrum, for some applications , nanoscale particles are deliberately aggregated into a specific morpholog y to obtain the required functionality, or to facilitate processing. Two ex amples are described: extrinsic conducting polymers produced by the incorpo ration of nanoscale silver particles; and sintering of nanocrystalline phas e pure tungsten.