High-temperature heat transfer and thermionic properties of tungsten alloys

Thesis/Dissertation · Fri Jan 01 00:00:00 EST 1988

OSTI ID:5658967

Moraga, N O

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
• Resource Relation: Other Information: Thesis (Ph. D.)
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
HEAT TRANSFER
TEMPERATURE EFFECTS
IRIDIUM ALLOYS
OSMIUM ALLOYS
RHENIUM ALLOYS
TANTALUM ALLOYS
THORIUM OXIDES
METALLURGICAL EFFECTS
TUNGSTEN BASE ALLOYS
CHEMICAL COMPOSITION
FABRICATION
PRESSURE EFFECTS
THERMIONICS
ACTINIDE COMPOUNDS
ALLOYS
CHALCOGENIDES
ENERGY TRANSFER
OXIDES
OXYGEN COMPOUNDS
PLATINUM METAL ALLOYS
THORIUM COMPOUNDS
TUNGSTEN ALLOYS
360104* - Metals & Alloys- Physical Properties