The high-temperature work function of sintered dilute solution tungsten-iridium alloys

Journal Article · Mon Feb 01 00:00:00 EST 1993 · Journal of Materials Engineering and Performance; (United States)

DOI:https://doi.org/10.1007/BF02649678· OSTI ID:6395293

D'Cruz, L A; Bosch, D R; Jacobsen, D L ^[1]

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1. Arizona State Univ., Tempe (United States)

The effect of transition element additives molybdenum, rhenium, iridium, and osmium on the effective work function of tungsten has been the focus of thermionics research for several years. In this study, iridium-added tungsten powder mixtures were cold compacted and sintered to produce a range of tungsten-iridium electrodes. An electron emission study was subsequently carried out to evaluate the work function behavior of the consolidated alloys. The work function was obtained from measurements of the current emitted from the electrode surface under ultrahigh vacuum conditions in the temperature range of 1,800 to 2,500 K using a vacuum emission vehicle (VEV). The data show that the magnitude of the work function in these alloys varied with temperature. Microstructural evaluation of the alloys indicated that the tested surfaces displayed accentuated thermal etching of the grain boundaries together with the fact that the final grain sizes in the sintered alloys were three to five times smaller than those found in equivalent arc-melted alloys that were studied in earlier work. Scanning electron microscopy (SEM) micrographs of the tested surfaces of the sintered alloys containing the highest iridium levels ([approximately]2 wt%) show a high level of structural distortion, particularly in the vicinity of grain boundaries and corners. The extent of these distortions was found to vary with the iridium content, i.e., the W-IR3M and W-IR2M. The samples with compositions lower than 0.5 wt% Ir were virtually devoid of distortions.

• OSTI ID: 6395293
• Journal Information: Journal of Materials Engineering and Performance; (United States), Vol. 2:1; ISSN 1059-9495
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
30 DIRECT ENERGY CONVERSION
IRIDIUM ALLOYS
WORK FUNCTIONS
TUNGSTEN ALLOYS
COMPACTING
ELECTRODES
ELECTRON EMISSION
EXPERIMENTAL DATA
GRAIN BOUNDARIES
MICROSTRUCTURE
PRECIPITATION
SCANNING ELECTRON MICROSCOPY
SINTERING
TEMPERATURE RANGE 1000-4000 K
THERMIONIC CONVERTERS
ALLOYS
CRYSTAL STRUCTURE
DATA
DIRECT ENERGY CONVERTERS
ELECTRON MICROSCOPY
EMISSION
FABRICATION
FUNCTIONS
INFORMATION
MICROSCOPY
NUMERICAL DATA
PLATINUM METAL ALLOYS
SEPARATION PROCESSES
TEMPERATURE RANGE
360104* - Metals & Alloys- Physical Properties
300403 - Thermionic Converters- Materials
Components
& Auxiliaries