The Surface Migration of Carbon on Tungsten

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Abstract
The surface migration of carbon on tungsten was observed with the field‐emission microscope technique. The tungsten point was shadowed with carbon and heated to a given temperature; observations of the emission patterns were made at room temperature at various time intervals. The migration occurs at a measurable rate starting about 850°K. It is characterized by a sharp boundary of a form which clearly shows that the (011) and (121) planes are avoided. An activation energy of 55±7 kcal/mole was calculated for the process by application of the theory of diffusion with a sharp moving boundary.