High-temperature heat transfer and thermionic properties of tungsten alloys
Influences of temperature, environment, and composition on the heat transfer and thermionic properties of tungsten alloys were determined experimentally using two hard-vacuum systems. Rhenium, tantalum, osmium, iridium and thorium dioxide constituted the minor alloying elements used to fabricate by sintering or casting the thirteen samples tested. Temperature was measured using either a photon-counting or a micro optical pyrometer focused on circular cylindrical cavities, with a length-to-diameter ratio equal to 10, built into the disk-shaped specimens. Results indicate that a linear function is appropriate to describe the effect of temperature on the heat-transfer properties of the refractory alloys studied. Normal spectral emissivity, at 0.535 {mu}m, was found to decrease linearly as temperature increased. On the contrary, thermal conductivity and total hemispherical emissivity were found to increase with temperature. The process of fabrication resulted in variations on the heat-transfer properties. Sintered alloys were found to have 50% higher thermal conductivity than those obtained by casting and marginally higher normal spectral and total hemispherical emissivity. Environment (pressure and gaseous composition) caused changes on the electron emission even at pressures lower than 1.3 {times} 10{sup {minus}5} Pa.
- Research Organization:
- Arizona State Univ., Tempe, AZ (USA)
- OSTI ID:
- 5658967
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
360104* -- Metals & Alloys-- Physical Properties
ACTINIDE COMPOUNDS
ALLOYS
CHALCOGENIDES
CHEMICAL COMPOSITION
ENERGY TRANSFER
FABRICATION
HEAT TRANSFER
IRIDIUM ALLOYS
METALLURGICAL EFFECTS
OSMIUM ALLOYS
OXIDES
OXYGEN COMPOUNDS
PLATINUM METAL ALLOYS
PRESSURE EFFECTS
RHENIUM ALLOYS
TANTALUM ALLOYS
TEMPERATURE EFFECTS
THERMIONICS
THORIUM COMPOUNDS
THORIUM OXIDES
TUNGSTEN ALLOYS
TUNGSTEN BASE ALLOYS