Field-Emission Observations of Carbon on Tantalum

Abstract

The carbon—tantalum system, observed with field emission, shows the temperature effects on the solubility and precipitation of the carbide phase. Carbon, once deposited on tantalum, cannot be removed by high‐temperature treatment, as in the case of tungsten. With low‐carbon contamination the 334 planes appear as dark areas, just as for carbon on tungsten. At temperatures in the region of 950°K, platelets, presumably Ta2C, form and migrate to the [111] zones of the emitter single‐crystal tip. The energy of activation of this surface migration process is 54 kcal.