Spark generation of monometallic and bimetallic aerosol nanoparticles

This paper reports the generation and characterization of monometallic (palladium (Pd), platinum (Pt), gold (Au), and silver (Ag) from electrodes of the same material) and bimetallic (Pd-Pt, Pd-Au, and Pd-Ag from electrodes of different materials) aerosol particles produced using a spark discharge. The Ag, Pd, Pt, and An monometallic particles were agglomerates with a mean diameter of 14.9, 26.7, 37.7, and 48.8 nm, respectively. The agglomerates consisted of primary particles ranging in size from 2 to 4 nm (Ag < Pd < Pt < Au). The corresponding rates of particle generation were 0. 12, 1.68, 16.00, and 40.30 mu g/min. A hypothesis was suggested that there is a correlation between the generation rate and the ionization potential of a metal (Ag < Pd < Pt < Au). The bimetallic particles were found to be binary mixtures (not alloys) of two individual monometallic particles. The compositions of the bimetallic particles were measured at different combinations of materials and polarity of the spark electrode. When the ionization potential of an anode material was higher than that of a cathode material, the hypothesis that there is a correlation between the ionization potential and the generation rate was valid. Even if the ionization potential of the anode material was lower than that of the cathode material, the generation rate of the anode metal particles was higher than that of the cathode metal particles. This might be caused by higher temperature channel formed near the anode and thus higher evaporation and subsequent nucleation/condensation near the anode. (c) 2008 Elsevier Ltd. All rights reserved.