Fracture-resistant ultralloys for space-power applications: Normal-spectral-emissivity and electron-emission studies of tungsten, rhenium, hafnium-carbide alloys at elevated temperatures
✍ Scribed by B.H. Tsao; D. Tang; D.L. Jacobson; J.F. Morris
- Publisher
- Elsevier Science
- Year
- 1990
- Tongue
- English
- Weight
- 870 KB
- Volume
- 35
- Category
- Article
- ISSN
- 0013-7944
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✦ Synopsis
A series in this journal on high-temperature properties of "fracture-resistant ultralloys for space-power systems" preceded the present paper: the antecedent publications covered tungsten(W), rhenium(Re) alloys with and without thoria(Th0,) (W, 23Re; W, 27Re; W, 30Re and W, 30Re, lTh0,). This paper reports radiative and thermionic effects of hafnium carbide(HfC) and Re variation in W alloys: normal spectral emissivity(6,) is used m pyrometry to determine the true temperature of a surface. Effective work function (4,) is an important consideration in the selection of the electrode materials for high-temperature thermionic energy converters in space-power applications. The e053Sp, L065p and 4, trends of W, Re, 0.35HfC with 5-20% Re were measured in the range of 170&2500 K. The results indicate that ti decreases with increasing temperatures and Re contents. The presence of HfC produced higher ci values than those of sintered materials with comparable W,Re alloy contents. The results also indicate that 4, increases with rhenium contents. This can be explained as growth of the potential barrier at the metal, vacuum boundary associated with a volume effect-the decrease in the lattice constant of W.