Nanoparticles and Nanostructures: Aerosol Synthesis and Characterization

Abstract

The remarkable properties of materials synthesized from nanometer-sized particles were discovered using particles that were formed as aerosols. Although other routes for nanoparticle synthesis have evolved, aerosol routes remain a major method. The original processes employed by Gleiter and coworkers entailed evaporation of a metal into a low density gas where the vapors formed nanoparticles by homogeneous nucleation. Those nanoparticles were then collected by thermophoresis for subsequent consolidation. In a study that predated the use of vapor condensation as a step in the production of consolidated nanostructures, Granqvist and Buhrman provided empirical observations of the role of major control variables. A number of points of confusion remain in this method of nanoparticle synthesis, notably the distinctions between particle size, and the sizes of the microstructures that attract the attention of materials scientists.

This paper will examine the aerosol physics of nanoparticle synthesis with emphasis on unraveling this distinction. The physical processes that govern particle formation growth, structure, and deposition will be examined. The on-line characterization of aerosol nanoparticles will also be probed, with a view toward monitoring of the synthesis process.