Classified
abstracts
460-463
Hall coefficient, and thermoelectromotive force of the samples are measured at temperatures up to 1OOO’C. G V Samsonov and G Sh Uoadkhava. Neora Muter. 7 (81. 1971. 13511354(inRussiun).
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tion of WxNb,.,Se, was investigated in a vacuum furnace with a background pressure of 5 x IO-“torr. It is found that the alloys W,Nb,_,Se, begin to dissociate at higher temperatures than WSe,. V L Kalikhman et al, Neorg Mater, 7 (7), 1971, 1165-l 168 (in Russian).
37 460. Effusion evaporation
of I&b.
(USSR) The evaporation rate of InSb as a function of temperature is investigated using an integral variant of the Knudsen effusion method. Effusion evaporation was performed in vacuum at lO-6 to 5 x lo-’ torr. Radioactive isotope lP5Sb was introduced in the investigated InSb Samples. The evaporated material was condensed on a copper filament. The evaporation rate was measured directly in the working chamber by means of a scintillation detector. V K Ilin and S I Aksenov, Neorg Muter, 7 (7), 1971, 1255-1256 (in Russian). 461. Synthesis and thermal dissociation NbSe,. (USSR)
of quasi-binary
37 alloys WSe,-
WSe, is a prospective material for application in arrangements with dry friction and thermoelectric elements. In many cases its poor electrical properties prevent its utilization. Substitution of a part of tungsten atoms in WSe, with niobium or tantalum atoms enables control of the electric properties over a broad range. Quasi-binary alloys W,Nb,,Se, with uniform concentration are synthesized using the method of ampoule synthesis from W-Nb alloys and high-purity selenium. W-Nb alloys were prepared by mixing, pressing and sintering of fine powders of W and Nb. Purities of the basic metal powders were not lower than 99.96 and 99.6 per cent respectively. Sintering was performed in vacuum at 3 to 5 x 10m5torr at 2200 to 2500°C. Uniformity of alloys was checked by x-ray diffraction. Powder of the prepared alloy was mixed with selenium and placed in quartz ampoules degassed and evacuated to 10e5 torr. Synthesis was performed at temperature of 700 to 800°C. It is found that the structure of W,Nb,_,Se, is analogous to the structure of WSe,. Thermal dissocia-
IV. Materials and techniques vacuum technology 47. OUTGASSING
DATA, VAPOUR
TERING DATA, RESIDUAL RESIDUAL GAS ANALYSIS.
GASES
used in
PRESSURE IN VACUUM
DATA, GETSYSTEMS,
47 462, Influence of pressure and residual gas composition in the working chamber on vapour pressure of metals and alloys. (USSR)
The data on investigation of the evaporation rates of metals and alloys are reported in dependence on pressure and composition of residual gas. Using an effusion Knudsen method, the vapour pressure of silver is measured in the temperature range 840 to 96O”C, using radioactive isotope I’OAg, and the vapour pressure p-zirconium is determined in the temperature range 1000 to 165O”C, using radioactive isotope 05Zr. The measurements were performed in an oil-free high-vacuum apparatus evacuated by electrical-discharge pumps to pressure of 10d8 torr. G B Fedorov et al, Zh Fir Khem, 45 (5), 1971, 1218-1219 (in Russian). 47 463. Dissociation pressure of lead selenite. (USSR) Lead selenide forms a component of materials for thermoelectric generators working at temperatures up to 1000°K. Lead selenide readily oxidized above 130°C and lead selenite is formed. At 650 to 700°C lead selenite begins to decompose. The dissociation pressure of lead selenite is measured. The pressure of SeO, above PbSeO, is determined as a function of temperature. S S Bakeeva et al, Neorg Muter, 7 (7), 1971, 1261-1262 (in Russian).
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