Metal dusting pure metals

The metal dusting of pure metals, especially Fe, was studied extensively by Hochman2. The Hochman mechanism for the metal dusting of iron involves three steps. The first step is the formation of metastable iron carbide, FejC, on the surface of iron. This reaction requires carbon activities higher than unity. 

Beryllium Beryllium was first detected in 1798 in the gemstones beryl and emerald (BesA SigOis) and was subsequently prepared in pure form in 1828 by the reduction of BeCl2 with potassium. It is obtained today from large commercial deposits of beryl in Brazil and southern Africa. Though beryllium compounds are extremely toxic, particularly when inhaled as dust, the metal is nevertheless useful in forming alloys. Addition of a few percent beryllium to copper or nickel results in hard, corrosion-resistant alloys that are used in airplane engines and precision instruments. 

Titanium is neither mutagenic nor carcinogenic. Ti-tanocene (an organic compound), however, induced fibrosarcoma when injected intramuscularly in rats. This same compound was carcinogenic against the Ehrlich ascites tumor in mice. There have been reports of tumors induced with the pure metal. Titanium dioxide did not induce tumors when administered orally however, a few lung tumors were detected after titanium dioxide dust was inhaled by rats. 

Thallium is obtained from the dust deposited in the flues of the pyrites burners used in the manufacture of sulphuric acid. The separation of thallium from other metals depends on the fact that it is the only metal with a soluble carbonate and an insoluble chloride. It is a bluish-white metal, easily deformed and softer than lead, being present at concentrations of 0.6-0.7 ppm in the earth s crust, and although it can be found in pure metallic form it is more commonly associated in mineral combination. 

An example of the high-temperature thermite process that seems to be little known and hence had completely escaped the author s attention earlier is the production of tungsten (wolfram) metal from the trioxide (WOg) with a large excess of zinc dust. The powder mixture tamped in a crucible and covered with zinc dust will start to react at about 500°C (dark red heat) and the process will be com pleted in a few minutes. It yields a fairly pure metal after chemical removal of other matter. The process has been described by Brauer as a preparative method and is also mentioned by Mellor. ... 

In hydrometaUurgical zinc production, with electrolysis, the roasted ZnO concentrate is leached with sulfuric acid. Zinc dust is added to the impure leach solution, which precipitates cadmium and other metals nobler than zinc, in metallic form. From this metal mixture, pure cadmium is prepared by different chemical and physical methods. 

Attachment of conductive plastics (filler types silver flake, gold dust, pure carbon- or metal-plated types) for the purpose of establishing necessary electrical contact should be engineered to suit the form of the product. 

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