Selenium-tellurium alloys

The experiments on sulfur, tellurium, and selenium-tellurium alloys reveal a systematic character to the optical properties of these fluids. With increasing temperature and pressure, sulfur becomes more like selenium near its melting point while with decreasing temperature, tellurium begins to resemble selenium at very high temperatures and pressures. Addition of tellurium to selenium simulates the effect on pure selenium of increasing the temperature and pressure. 

Betts Electrolytic Process. The Betts process starts with lead bullion, which may carry tin, silver, gold, bismuth, copper, antimony, arsenic, selenium, tellurium, and other impurities, but should contain at least 90% lead (6,7). If more than 0.01% tin is present, it is usually removed from the bullion first by means of a tin-drossing operation (see Tin AND TIN alloys, detinning). The lead bullion is cast as plates or anodes, and numerous anodes are set in parallel in each electrolytic cell. Between the anodes, thin sheets of pure lead are hung from conductor bars to form the cathodes. Several cells are connected in series. 

Welcher et al. [ 10] have described the direct determination of trace quantities of lead, bismuth, selenium, tellurium and thallium in high-temperature nickel alloys using electrothermal atomisation. 

Welz, B. Melcher, M. Determination of antimony, arsenic, bismuth, selenium, tellurium and tin in metallurgical samples using the hydride atomic absorption technique. 1. Analysis of low alloy steels. Spectrochim. Acta B 1981, 36, 439-462. 

For the homogeneous alloys, the solidus curves for systems 1 and 2 are situated higher than for system 3. This was also to be e ected for the solutions because the interatomic interaction forces between cadmium and the elements decrease in the series sulfur-selenium-tellurium. 

Lea.d nd Le d Alloys. Selenium is reported to lower the surface tension of lead. The addition of 0.1% selenium and tellurium to solder improves its fluidity. 

Nickel—Iron and Cobalt—Iron Alloys. Selenium improves the machinabifity of Ni—Ee and Co—Ee alloys which are used for electrical appfications. Neither sulfur nor tellurium are usefiil additives because these elements cause hot britdeness. The addition of 0.4—0.5% selenium promotes a columnar crystal stmcture on solidification, doubling the coercive force of cobalt—iron-titanium alloy permanent magnets produced with an equiaxial grain stmcture. 

Of the elements commonly found in lead alloys, zinc and bismuth aggravate corrosion in most circumstances, while additions of copper, tellurium, antimony, nickel, silver, tin, arsenic and calcium may reduce corrosion resistance only slightly, or even improve it depending on the service conditions. Alloying elements that are of increasing importance are calcium especially in maintenance-free battery alloys and selenium, or sulphur combined with copper as nucleants in low antimony battery alloys. Other elements of interest are indium in anodesaluminium in batteries and selenium in chemical lead as a grain refiner ". 

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