Polycrystalline and chemical‐vapor‐deposited (CVD) rhenium emitters were investigated in a demountable thermionic converter, against several collectors: polycrystalline Nb, polycrystalline W, polycrystalline Re and a single crystal Nb‐O alloy. For emitter performance comparison, the bare work function is the most important parameter: for polycrystalline Re the measured value was 5.20 eV, and for CVD Re it was 5.24 eV (fairly independent of the polycrystalline collector material). The bare work function of CVD Re increased to 5.50 eV, when tested opposite the oxygen‐dispensing Nb‐O alloy collector. However Re transport from the CVD Re to the oxygen‐dispensing collector occurred, which was unexpected. For the solar‐heated multi‐cell converter application, while CVD Re is the best emitter without oxygen, the difficulties involved in producing such surfaces inside a cylinder ruled against it in favor of polycrystalline Re. Similarly, consideration of ease of fabrication and of potential life‐limiting Re evaporation ruled out the use of Nb‐O collectors.


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    Title :

    Thermionic Performance of Rhenium Emitters


    Contributors:

    Conference:

    SPACE TECHNOLOGY AND APPLICATIONS INT.FORUM-STAIF 2005: Conf.Thermophys in Micrograv;Conf Comm/Civil Next Gen.Space Transp; 22nd Symp Space Nucl.Powr Propuls.;Conf.Human/Robotic Techn.Nat'l Vision Space Expl.; 3rd Symp Space Colon.; 2nd Symp.New Frontiers ; 2005 ; Albuquerque, New Mexico (USA)


    Published in:

    AIP Conference Proceedings ; 746 , 1 ; 910-917


    Publication date :

    2005-02-06


    Size :

    8 pages





    Type of media :

    Conference paper


    Type of material :

    Electronic Resource


    Language :

    English



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