| The interaction of mercury vapeur with tungsten has been studied by field-emission microscopy. Adserption of mercury at 295 K occurred on (111) planes and on regions surrounding (001), (112) and (011) planes. The adserption at a pressure of 10-6 N m-2 was complete within 2 minutes. An increase in the average work function of 0.182 volt has been estimated for the process. On heating a surface saturated with mercury at 295 K, surface migration began at temperatures > 750 K to and over the central (011) planes along the zones linking it with the other (011) planes ; the activation energy (E) of the process was 45-50 k J mol-1. Desorption of the absorbed mercury started above 1200 K and the values of E for surface migration and desorption increased with temperature attaining a constant value of 120 k J mol-1 at temperatures > 1700 K. The surface potential changes throughout adsorption, surface migration and desorption have been determined. |
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