An Experimental Study of the Photoelectron Work Function Change of Silver-Based Contacts Induced by Arcing in Air
Keywords:electron work function, photoemission, Fowler’s method, contact materials, electrical arcs, cathode phenomena
The influence of industrial conditioning (polishing, mechanical shocks and electrical arcs in air) on the electron emission and morphology of contact pastilles made of pure silver [Ag (99.999%)], silver–nickel alloy [Ag–Ni (60/40)], silver–tungsten alloy [Ag–W (50/50)], and silver–tungsten carbide [Ag–WC (50/50)] was investigated. The electronic emission behavior of pure silver Ag and silver-metal alloys (Ag-Me), for both virgin and arced electrical contacts, were studied.
Contacts were mounted in a contactor working repeatedly on air (laboratory atmosphere). When submitted to 500 opening electric arcs, the electron work function of an electromechanically conditioned contact Ag-Ni (60/40), measured photoelectrically by using Fowler’s method of isothermal curves, is = (4.50 003) eV at room temperature, while for virgin Ag contacts, it was (4.30 003) eV. The in-crease in the electron work function (EWF) is due to the progressive inclusion of silver oxide in the Ag contact surface during arcing in air.
The conditioned (500 arcs) silver-metal alloys studied in this work exhibit the same electronic emission behavior, namely arcing in air increases their EWF. We demonstrated that the electromechanical conditioning by successive electrical arcs affects the surface characteristics such as microstructure, roughness and photoelectron work function.
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