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End date: 1999Subject: search.filters.subject.Work function

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    Work function measurements of contact materials for industrial use
    (IOP, 1998) Akbi, Mohamed; Lefort, André
    The nature of the contact material is important for the characteristics of electric arcs and particularly for the electronic emission. Work functions of new industrial materials made with silver alloys and silver oxide alloys are not known at present. An experimental set-up is described which allows work function measurements from room temperature up to 700 K. The Fowler method was used for the measurement of the work function by the photoelectric effect. As a first application of the experimental device, work functions of metals (Ag, Cu, Ni, Sn and Zn) were determined. Furthermore, the influence of industrial surface treatment such as the application of electric arcs and repeated mechanical shocks on the Ag contact work surface was studied by SEM to observe their effect on electron work function. Breaking arcs in air cause a remarkable increase in the work function of the silver contact material by progressive formation of silver oxides
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    Experimental determination of work function of silver alloys
    (1994) Lefort, Andre; Akbi, Mohamed; Parizet, Marie-Jose
    Models about arc roots need a good knowledge of physical constants characterizing contact material. With pure metal, all the constants are well known; but for alloys some are not known. In this paper we relate how we have measured work function of silver alloys. Measuring method used is the Fowler one where photoelectronic current produced by different ultraviolet radiations is measured in high vacuum. Experimental set-up have been tested for pure materials and then, have been applied to some silver alloys. Results about pure metals show an evolution of the work function with temperature; it decreases when temperature increases. Results about silver-nickel alloys show a large dependence of obtained results with the preparation of contact surface. For example, polishing and cleaning induce, because of atom migration, a large modification of the ratio of the two components on surface; this phenomenon induces a variation of work function comparatively with obtained values with prLtary product. By heating alloy contact in high vacuum we have observed large variations of work function, which result from material component vaporisation by sheets. Surface analyses by electron microscope produce proves of the phenomenon. An empirical relation is given to calculate work function of binary alloy when this constant is known for each alloy component