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PREPARATION OF STOICHIOMETRIC URANIUM MONOCARBIDE CYLINDERS
Employing a modified arc-melting technique, homogeneous cylinders of stoichiometric UC were consistently produced. The cylinders ranged in size from 0.25-in. dia. by 1 in. long to 0.375-in. dia. by 3 in. long. The top 10% of nearly all cylinders did, however, contain shrinkage voids that could not be eliminated. UC buttons previously prepared by arc melting the elements were placed over a graphite-mold cavity, but in contact with Cu in an Aratmosphere arc furnace. When the UC charge became fully molten, it dropped into the cavity and solidified instantaneously. The measured densities of the arc-cast cylinders were 99.8% of theoretical with compositional limits of plus or minus 30 ppm C. The study was initiated because of a need for pure stoichiometric UC radiation specimens and a need for nonstoichiometric specimens containing controlled C concentrations. Therefore, emphasis was placed on purity control of the starting material and furnace atmosphere, rate of power consumption, accuracy of weighing procedures, and arc-melting procedures. Variations in either of these preparational steps would result in an undesirable pr oduct. (auth