Characterization of Silver Powder Produced through Water Atomization and RF Plasma Treatment

Abstract

Silver powder was produced through water atomization with a pressure of 80 MPa and a flow rate of 220 L/min. Scanning electron microscopy analysis showed that as-prepared silver particles were aggregated and had various types of morphologies such as spherical, spheroidal and irregular. The volume average particle size of as-prepared silver powder was 7.7 μm at the drain rate of 0.024 kg/s. The particle size decreased with decreasing the drain rate. Powder X-ray diffraction revealed that the silver powder with a single phase and high crystallinity was formed. Surface treatment of silver powders classified to 5 μm was performed at 10,000°C by radio-frequency (RF) plasma under argon atmosphere. RF plasma treatment led to the formation of spherical particles from irregular particles. The crystallinity and crystallite of silver powder were increased by RF plasma treatment. X-ray photoelectron spectroscopy showed that the oxygen content in silver particles decreased from 500 ppm to 45 ppm. Thermomechanical analysis revealed that the shrinkage of silver powder reduced by the RF plasma treatment. It was clear that the particle characterization of silver powder was significantly modified by RF plasma treatment. The specific resistivity of silver paste sintered at 900°C exhibited 1.89×10 -8 Ωm.

The particle size distribution (PSD) as criteria for comparison of silver powders obtained by different methods of synthesis and by conditions of electrolysis

“…Also, chemical reduction method is a time-consuming and a complex process, as there are a number of processes involved, such as chemical reaction, separation, collection, and drying. Also, chemical reduction method has a high environmental-load because a large amount of solvent is discharged [4].…”

“…They are widely used in silver paints, conductive pastes and resins, as solid lubricants, in electronics for printed circuit boards and contacts, as a component of batteries as well as being a catalyst for a number of homogeneous chemical reactions used on the industrial scale [1][2][3]. Also, Ag powders find application as electrode material in ceramic capacitor and silicon solar cells [4][5][6].…”

“…For example, Ag powders consisting of irregular particles in the range 2-30 m can be produced by the mechanical decomposing and mechanochemical reductions of silver oxide [14]. The Ag powders obtained through water atomization process represented the mixture of spherical, spheroidal and irregular particles [4]. A wet-chemical method is also used for synthesis of Ag powders, and the microsized, uniform spherical particles with rough surfaces [15], as well as Ag nanoparticles were obtained [16].…”