Generation of silver/palladium nanoparticles by liquid flame spray
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M. Vippola Institute of Material Science, Tampere University of Technology, P.O. Box 589, FIN-33101 Tampere, Finland
M. Nurminen and J. Liimatainen Aerosol Physics Laboratory, Institute of Physics, Tampere University of Technology, P.O. Box 692, FIN-33101 Tampere, Finland
T. Lepisto¨ Institute of Material Science, Tampere University of Technology, P.O. Box 589, FIN-33101 Tampere, Finland
J. Keskinen Aerosol Physics Laboratory, Institute of Physics, Tampere University of Technology, P.O. Box 692, FIN-33101 Tampere, Finland (Received 5 August 2003; accepted 23 February 2004)
Ag–Pd alloy nanoparticles have been generated from silver and palladium nitrate precursors using a high temperature aerosol method, the liquid flame spray (LFS) process. In the LFS process, a spray aerosol of precursor liquid is introduced into a high-temperature H2–O2 flame. The primary micron-sized spray droplets evaporate in the flame, and the final particulate product is a result of the nucleation of the pure metal vapors shortly after the flame. In the study, three Ag–Pd molar ratios—10:90, 50:50, and 90:10—were used in the precursor. As a result of the synthesis, metal alloy nanoparticles with practically the same concentration ratios, correspondingly, were produced with the method. In the experiments, metal mass flow rates of 0.01– 0.8 g/min were covered. The size of the particles was determined to be in the range of 10–50 nm by aerosol instrumentation. The particles were spherical and slightly agglomerated. It was concluded that the particle size can be controlled via the total precursor mass flow rate, and the composition can be controlled by the molar ratio of Ag and Pd compounds in the precursor liquid. I. INTRODUCTION
Metal powders are prepared using various techniques such as powder mixing/calcination and metalorganic decomposition of nonaqueous solutions.1 Metal and metal alloy powders have also been produced from aqueous solutions of inorganic metal salts.2 Silver–palladium alloy particles have been previously produced by both aqueous solution precipitation3 and spray pyrolysis.4–6 When using spray pyrolysis, the aqueous solution of silver and palladium nitrates is sprayed as micron-sized droplets and directed through a heat source, where the solvent evaporates. The size of silver–palladium alloy particles produced by spray pyrolysis is commonly in
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Address all correspondence to this author. e-mail: [email protected] DOI: 10.1557/JMR.2004.0207 1544
http://journals.cambridge.org
J. Mater. Res., Vol. 19, No. 5, May 2004 Downloaded: 13 Mar 2015
the submicron range.5 The most common application for silver–palladium particles is for electronic devices. Conductive films made from the particles produced by pyrolysis have been studied.4 Multilayer ceramic capacitors have been fabricated using fine Ag–Pd alloy particles.3,4 Metal alloy particles also have a high technological potential in making conductive plastics. The high-temperature processes have been used for nanoparticle production, and particle formation in these proce
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