Bureau of Mines / Minerals yearbook: Metals and minerals 1978-79
Year 1978-79, Volume 1 (1978-1979)
Alverson, Larry J.
Rhenium, pp. 743-749 ff. PDF (941.1 KB)
MINERALS YEARBOOK, 1978-79748 are generally low in molybdenum content but have a comparatively high rhenium content.1° To date no molybdenum or rhenium is believed to have been recovered; however, plans are being made to recover molybdenum and several other minor metals in the next few years. TECHNOLOGY The Bureau of Mines published the final report in its series on recovery of molybdenum and rhenium from offgrade molybdenite concentrates. The Bureau determined that current leakage losses that occur in operation of bipolar flow-through electrooxidation cells can be minimized by incorporating cell design factors that increase the current leakage path. This could be accomplished by sealing the edges of the electrodes in the sides of the cell enclosure and adding nonconductive extensions on the top and bottom of each electrode. Overall molybdenum and rhenium recoveries of 97% were obtained from flotation concentrates containing 16% to 35% molybdenum. Molybdenum-rhenium extraction was unaffected by the presence of chalcopyrite in the molybdenite concentrate; however, molybdenum extraction declined if the copper content, as chalcocite, exceeded 7%. High-purity molybdenum and rhenium compounds can be recovered from the electrolyzed reaction mass by liquid-solid separation, solvent extraction, and crystallization steps.1' Research was conducted to find new methods of warm-rolling work-hardened thin wires of high-strength refractory alloys such as molybdenum-rhenium and tungsten-rhenium into metallic tapes. Different methods of heating were tried. One method involved heating the wire with argon preheated to the desired temperature. The heated gas stream was directed into the space between the rolls, heating both the wire and the rolls. Due to the large difference between the masses and the heatremoval capacities of the rolls and the wire, the wire attained the maximum temperature, not in the deformation zone (at the point of contact with the rolls) but some distance away from the entry point. This resulted in some improvement in the form coefficient (width-to-thickness ratio) of the molybdenum-rhenium alloy wire and in the quality of its surface and edges. Similar results were obtained when both the rolls and the wire were indirectly heated by an electrically heated tungsten spiral. It was possible to obtain a molybdenum-rhenium tape with form coefficients of 20 to 25 and higher, retaining all strength and elastic properties with good quality of surface and edges. Also, for the first time, it became possible to cold-roll a difficult material like the tungsten-rhenium alloy (VR27-VP) and obtain a tape with a form coefficient of 10 to 12 from highly cold-hardened wire of 0.08 millimeter diameter, while retaining strength and elasticity." The need to construct reliable specialpurpose electrovacuum devices created demand for new materials for cores of oxide cathodes and for other parts of the cathode unit. Alloys of nickel with magnesium, silicon, calcium, aluminum, tungsten, and other metals had certain deficiencies. All suffered from a high ratio of volatilization, inadequate stability of form, and low strength at elevated temperatures. To meet the complex property requirements, a series of nickel-rhenium alloys with various additions was developed. It was found that rhenium improved the strength properties and the stability of nickel. Also, activating additions of elements of the IV-A group and rare-earth elements improved the emission characteristics of the cathode. The stability of the new alloys increased the rigidity of the cathode and ensured the stability of the emission characteristics of valves with short interelectrode distances. In pulse devices, valve life more than doubled. At 1,000'C the strength of nickel-10% rhenium alloys containing activating additions exceeded the strength of a nickel-vanadium cathode alloy by about 90% and exceeded its rigidity by 1.5 to 2 times. It was shown that in nickelrhenium alloys an intermediate layer of rhenium compounds did not form, and the service life of the valve increased several times.13 The catalytic properties of rhenium catalysts were studied in the process of liquidphase reduction of nitrobenzenes (NB). It was found that the specific activity of rhenium depends little on the concentration of the active component in the catalyst and was close to that of palladium and much
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