ABSTRACT
Fumes are aerosols of ultrafi ne solid particles produced by evaporation of metals or salts and subsequent condensation of their vapors, usually in high-temperature systems. Electrical resistance heaters, high-frequency induction furnaces, and infrared ovens are used to heat materials to the temperature at
TABLE 1.2 Organic Liquids Used in the Laboratory Generation of Mists
TABLE 1.1 Aerosol Generation Methods
which they will evaporate. Thermal plasmas and pulsed laser ablation are also used, particularly for compound materials for which composition control becomes a problem when less vigorously heated sources are employed. Homogeneous nucleation and condensation of the vapors occur when the hot, vapor-laden gases are cooled. Particle sizes are generally below 1 µm. Rapid cooling, often by dilution with a cold gas, favors the formation of ultrafi ne particles ( D
p < 0.1 µm). A major mechanism of particle growth is Brownian coagulation. In addition to promoting condensation, dilution serves to slow particle coagulation. Nonetheless, agglomerate particles are commonly produced by this method.
