Electrodeposition of Ag-W Alloy Films from Ionic Liquid for Electrical Contacts

Monday, 14 October 2019: 14:40
Room 310 (The Hilton Atlanta)
D. Höhlich, M. Müller, T. Mehner, I. Scharf, and T. Lampke (Technische Universität Chemnitz)
The global e-mobility market is experiencing strong growth. As a driving force, China increased its share of electric vehicles by nearly 400% from 0.3 million in 2015 to 1.25 million in 2018. The increase in registrations of electric vehicles in the US shows a similar percentage, from 0.14 to 0.36 million in the last five years. Within twenty years, electric vehicles may account for 45 percent of total car sales worldwide. In the automotive industry, the present motor performance along with its steady increase suggests using very powerful electric motors with, at least temporary, very high power consumption. For the required high currents, new coating concepts for build-in electric contacts are necessary. By far, silver-tungsten alloys are the most popular contact materials. Tungsten is the choice of material when currents are switched. Sintered or infiltrated tungsten-silver contacts can be used from the 1 to 800 kV range. At high voltages, arcing can briefly occur at the contacts during switching with currents up to 100 kA, which results in very high temperatures (> 10,000 K). In silver-tungsten alloys, the ability of tungsten to withstand thermal, mechanical, and electrical wear, combined with the high electrical conductivity of silver make them the appropriate materials. However, the electrodeposition of these alloys from aqueous solutions is not yet state of the art. This presentation shows a way to produce these contact materials by electrodeposition from non-aqueous ionic liquids. Silver-tungsten alloy films for application as electrical contacts were prepared using tungsten hexachloride, silver chloride and anhydrous 1-ethyl-3-methylimidazolium chloride (EMIMCl) ionic-liquid solution with aluminium chloride in different ratios. The deposition takes place outside the glove box. The crystalline structure of the alloys were investigated by X-ray diffraction (XRD). The chemical composition was characterized by scanning electron microscopy (SEM) and inductively-coupled plasma optical emission spectroscopy (ICP-OES). The shown electrodeposition of tungsten-base alloys with silver make the time-consuming and expensive sintering process redundant and lead to thin, lightweight, and low-cost contacts while saving resources.