Lead-tellurium copper

Copper-lead-tellurium alloys, 24 426 Copper metallization, electroless, 9 696-697... 

Extrinsic detectors, 22 180 Extrinsic fiber-optic sensors, 11 148 Extrinsic photoconductors, 19 138 Extrinsic semiconductors, 22 236-237 Extrinsic wastes, 10 68 Extruded food packaging, 18 45 Extruded lead-copper alloys, 14 776 Extruded lead-tellurium alloys, 14 778 Extruded rigid foam, 23 404-405 Extruders... 

Copper—lead—tellurium alloys have high wear resistance in sliding contacts. In copper—zinc alloys, the benefits of tellurium decrease with increasing zinc content and almost disappear when the zinc content exceeds 35%. 

Tellurium is also added to copper to improve machinability. Tellurium-copper alloys are also easier to work with than pure copper. And the essential ability of copper to conduct an electric current is not affected. Tellurium is also added to lead. Tellurium-lead alloys are more resistant to vibration and fatigue than pure lead. Metal fatigue is the tendency of a metal to wear out and eventually break down after long use. 

In certain systems ascorbic acid was so effective in lowering the valence state of metals that it was used in analytical chemistry (8). Ascorbic acid was used with gold, lead, bismuth, tellurium, copper, phosphorus, uranium, halogens, mercury, and cobalt. 

Showa Denko has developed such a direct oxidation process and commercialized the technology in 1997 (100000ta ). The catalyst consists of three components (i) palladium supported on a carrier (0.1-2 wt%) (ii) a heteropoly add (e.g., phos-photungstic acid or silicotungstic acid) or its related lithium, sodium and copper salts (iii) selenium, tellurium, copper, silver, tin, lead, antimony, or bismuth. The process is operated in a fixed bed reactor at 150-160 °C and up to 8 bar. The gas stream entering the reactor consists of the reactants ethylene and oxygen, steam, and nitrogen as diluent. Water/steam is needed because it enhances the activity and selectivity of the reaction. The selectivity to acetic acid is 86%. The main byproducts are carbon dioxide and not fully converted acetaldehyde. 

Copper 142 Tellurium Copper 1462 OFHC Sulfur Copper 147 Amzirc (Zirconium Copper) 150 Hitenso 162 Hitenso 1622 Hitenso 165 Chromium Copper 182 Leaded Copper 187 Deoxidized Leaded Copper 1870 Anaconda Copper 189 Gilding 210 Phosphor Bronze 605 Phosphor Bronze 507 Silicon Tin Bronze 5072 Calsun Bronze 607 Leaded Nickel Copper 7021... 

Lead consumption in the cable industry has declined because of the introduction of plastic sheathing and insulation (see Table 1). However, the total amount of lead used in the industry is significant. Cadmium, tellurium, copper, antimony, and arsenic are trace contaminants in alloys used for cable sheathing [77]. 

Tellurium improves the machinability of copper and stainless steel, and its addition to lead decreases the corrosive action of sulfuric acid on lead and improves its strength and hardness. Tellurium is used as a basic ingredient in blasting caps, and is added to cast iron for chill control. Tellurium is used in ceramics. Bismuth telluride has been used in thermoelectric devices. 

The pure acid does not react in the cold with sulfur, selenium, tellurium, carbon, silver, copper, zinc, iron, chromium, or manganese, but slowly dissolves mercury and tin (20). At higher temperatures, lead, mercury, tin, and sulfur react rapidly, eg ... 

The lead buUion, ready to be shipped to the refinery, contains in solution impurities such as silver, gold, copper, antimony, arsenic, bismuth, nickel, 2inc, cadmium, tin, tellurium, and platinum metals. 

Pemoval of Other Impurities. After softening, the impurities that may stiU remain in the lead are silver, gold, copper, tellurium, platinum metals, and bismuth. Whereas concentrations may be tolerable for some lead appHcations, the market values encourage separation and recovery. The Parkes process is used for removing noble metals and any residual copper, and the KroU-Betterton process for debismuthizing. 

Like selenium, tellurium minerals, although widely disseminated, do not form ore bodies. Hence, there are no deposits that can be mined for tellurium alone, and there are no formally stated reserves. Large resources however, are present in the base-metal sulfide deposits mined for copper, nickel, gold, silver, and lead, where the recovery of tellurium, like that of selenium, is incidental. 

Other Metals. Tellurium has been added to copper-base, lead-base, and tin-base bearing aUoys. In babbit-type aUoys, teUurium controls the stmcture and improves uniformity and fatigue resistance by restraining the tendency to segregation (see Bearing Materials). 

Production and Economic Aspects. Thallium is obtained commercially as a by-product in the roasting of zinc, copper, and lead ores. The thallium is collected in the flue dust in the form of oxide or sulfate with other by-product metals, eg, cadmium, indium, germanium, selenium, and tellurium. The thallium content of the flue dust is low and further enrichment steps are required. If the thallium compounds present are soluble, ie, as oxides or sulfates, direct leaching with water or dilute acid separates them from the other insoluble metals. Otherwise, the thallium compound is solubilized with oxidizing roasts, by sulfatization, or by treatment with alkaU. The thallium precipitates from these solutions as thaUium(I) chloride [7791 -12-0]. Electrolysis of the thaUium(I) sulfate [7446-18-6] solution affords thallium metal in high purity (5,6). The sulfate solution must be acidified with sulfuric acid to avoid cathodic separation of zinc and anodic deposition of thaUium(III) oxide [1314-32-5]. The metal deposited on the cathode is removed, kneaded into lumps, and dried. It is then compressed into blocks, melted under hydrogen, and cast into sticks. 

Specia.lty Coppers. Additions are made to copper to satisfy specific needs. Tellurium at a nominal 0.5 wt % addition, sulfur at 0.35 wt %, and lead at 1 wt % enhance machinabiHty. These alloys are identified as C145, C147, and C187, respectively. The solubiHty limit for each element is <0.001%, so that the excess is present as second-phase particles which assist in fracture of chips and lubrication during machining. 

Another important factor in the selection of a lead alloy is fatigue strength, which may arise from high-frequency vibration from pumps and stirrers or from differential expansion from heat and cooling cycles. The marked increase of fatigue strength obtained by alloying with copper, silver and tellurium can be seen from Table 3.25. 

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