PREPARATION OF ULTRAFINE HIGH PURITY REFRACTORY METAL POWDERS
NATIONAL RESEARCH CORP CAMBRIDGE MASS
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Results are reported of an effort to establish procedures for producing ultrafine high purity powders of the refractory metals. The powders are to have smaller particle size and higher purity than those currently available. The power source was an electron beam originally it was recommended that the beam be bent 45 degrees to prevent cathode contamination. However, at a pressure of 20 microns, Mo metal vapor was condensed in a relatively short space the conclusion was made that the beam need not be bent to that great a degree, but could be nearly straight. The basic principles of the method proved sound a small quantity of submicron Mo metal powder was produced. Work reported on an aluminum-alumina alloy established that the strength of the alloy can be raised as the particle size is decreased. Specimens heated to 70 and 160 degrees above the melting point of Al were stiff and no melting was obtained.