WORK FUNCTION MEASUREMENTS IN EXPERIMENTAL TUBES CONTAINING CATHODES OF URANIUM AND ZIRCONIUM CARBIDES
Work function measurements are reported for carburized tantalum cathodes coated electrophoretically with uranium and zirconium carbides. Thermionic methods for the determination of work function were used together with the Zisman modification of the Keivin technique. The poor agreement found between the two sets of results is thought to indicate that thermionic emission takes place from only a fraction of the total cathode area. Work function measurements were also made on the thin films that evaporate from these cathodes during their operation at high temperatures on to fixed anodes. When the cathode is uranium carbide, our measurements can be interpreted in terms of an evaporated film of uranium metal and uranium monoxide on the anode surface. All of this work was performed under ultra-high vacuum conditions. The mean work function values for tubes containing uranium carbide cathodes are as follows: the work function from the Kelvin measurements at 300 deg K is 3.81 plus or minus 0.01 ev and that from the slope of a Richardson line plotted from retarding field data and applying to 0 deg K is 2.9 plus or minus 0.1 ev. The temperature coefficient of the work function of uranium carbide is 5 x 10/sup -4/ ev per deg. For zirconium carbide cathodes the mean values are: 3.62 plus or minus 0.01, 2.5 plus or minus 0.1 ev, and 7 x 10/sup -4/ ev per deg. The work function of the anode in a tube containing a uranium carbide cathode reaches a constant value in a few hours of 3.0 plus or minus 0.1 ev. This, like the Kelvin results quoted above, is an arithmetic average over the area of any high and low work function patches and in this case applied to the unmeasured temperature of the anode when the cathode was operating at 1300 deg K. (auth)
- Research Organization:
- Southampton Univ., Eng.
- NSA Number:
- NSA-17-027975
- OSTI ID:
- 4714030
- Journal Information:
- Advanced Energy Conversion, Journal Name: Advanced Energy Conversion Vol. Vol: 3
- Country of Publication:
- Country unknown/Code not available
- Language:
- English
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Related Subjects
CATHODES
DIAGRAMS
ELECTRON TUBES
ELECTRONICS
EMISSION
ENERGY
ENERGY RANGE
EQUATIONS
EV RANGE
EVAPORATION
FILMS
HIGH TEMPERATURE
LOW TEMPERATURE
MEASURED VALUES
METALS
OPERATION
PHYSICS
RICHARDSON EQUATION
SURFACES
TANTALUM
THERMIONICS
THERMODYNAMICS
URANIUM
URANIUM CARBIDES
URANIUM OXIDES
VACUUM
WORK FUNCTIONS
ZIRCONIUM CARBIDES