Microstructure refinement and physical properties of Ag-SnO2 based contact materials prepared by high-energy ball milling

Abstract

High energy ball milling was used in order to improve dispersion of metal oxide in Ag-SnO2 electrical contact materials. The processed Ag-SnO2 (92:8) and Ag-SnO2In2O3 (87.8:9.30:2.9) powder mixtures were subsequently consolidated to bulk solid pieces by conventional powder metallurgy method. The characterization of the prepared samples included microstructural analysis by XRD and SEM, as well as measurements of physical properties such as density, hardness and electrical conductivity. The results of X-Ray analysis point to reduction of crystallite size after milling of about ten times. Microstructures of sintered Ag-SnO2 and Ag-SnO2 In2O3 materials display very fine dispersion of the oxide components in silver matrix. Somewhat higher uniformity was obtained for Ag-SnO2 In2O3 material which was illustrated by results of SEM analysis and more consistent microhardness values. The obtained values of studied physical properties were found to be in accordance with observed higher dispersion of metal oxide particles and comparable to properties of commercial electrical contact materials of this type.

Metoda visokoenergetskog mehaničkog mlevenja je primenjena za pripremu elektrokontaktnih materijala na bazi Ag-SnO2 sa ciljem postizanja visokog stepena disperzije čestica metalnih oksida u srebrnoj matrici. Smeše prahova sastava Ag- SnO2 (92:8) i Ag-SnO2In2O3 (87.8:9.30:2.9) su posle mlevenja procesuirane konvencionalnim tehnikama metalurgije praha. Karakterizacija sinterovanih uzoraka obuhvatila je mikrostrukturnu analizu (XRD, SEM) kao i merenje važnijih fizičkih svojstava: gustina, tvrdoća i električna provodljivost. Rezultati XRD analize su pokazali značajno smanjenje veličine kristalita od oko deset puta. Mikrostrukturna analiza sinterovanih materijala ukazala je na veoma finu i uniformnu disperziju oksidnih komponenti u srebrnoj matrici. SEM mikrofotografije takođe pokazuju veću uniformnost mikrostrukture uzorka Ag-SnO2In2O3 što potvrđuju i ujednačenije vrednosti mikrotvrdoće dobijene za ovaj materijal. Izmerene vrednosti analiziranih fizičkih svojstava su u saglasnosti sa postignutim većim stepenom disperzije čestica metalnih oksida u srebrnoj matrici i uporedive su sa svojstvima komercijalnih elektrokontaktnih materijala ovog tipa.