Iron-graphite reduction

The successive step in sample preparation is graphitization. Several different reactions can be used. The most well known is probably the iron-catalysed reduction of the collected C02 by reaction with hydrogen [71]... 

Sodium dithionite in water or aqueous dimethylformamide is an economic, efficient system for the dehalogenation of a-halo-ketones. Other reagents that have been described recently for dehalogenation include iron-graphite (prepared by reduction of ferric chloride with potassium-graphite), sodium 0,0-diethyl phosphorotelluroate, and sodium borohydride in the presence of a catalytic amount of bis(2-thienyl) ditelluride. ... 

Barium- and calcium-bearing manganese siUcon is used as an inoculant in gray and ductile iron. The alloy contains 60—65% Si, 9—11% Mn, 4—6% Ba, 1—3% Ca, and 1—1.5% Al. The combination of barium, calcium, and manganese provides excellent chill reduction, improves the graphite stmcture, and minimizes section sensitivity in castings having thin and thick sections. 

Graphitic corrosion is a slow corrosion process, typically requiring many years to effect significant damage. Complete penetration of thick cross sections has, however, occurred in as little as 2 years in adverse environments. On the other hand, cast iron components can be found in use in Europe after 160 years of service. Although graphitic corrosion causes a substantial reduction in mechanical strength, it is well known that corroded cast iron, when sufficiently supported, may remain serviceable when internal pressure is low and shock loads are not applied. 

Of special Interest as O2 reduction electrocatalysts are the transition metal macrocycles In the form of layers adsorptlvely attached, chemically bonded or simply physically deposited on an electrode substrate Some of these complexes catalyze the 4-electron reduction of O2 to H2O or 0H while others catalyze principally the 2-electron reduction to the peroxide and/or the peroxide elimination reactions. Various situ spectroscopic techniques have been used to examine the state of these transition metal macrocycle layers on carbon, graphite and metal substrates under various electrochemical conditions. These techniques have Included (a) visible reflectance spectroscopy (b) laser Raman spectroscopy, utilizing surface enhanced Raman scattering and resonant Raman and (c) Mossbauer spectroscopy. This paper will focus on principally the cobalt and Iron phthalocyanlnes and porphyrins. 

Shigehara K, Anson EC. 1982. Electrocatal3dic activity of three iron porphyrins in the reduction of dioxygen and hydrogen peroxide at graphite cathodes. J Phys Chem 86 2776. 

Wan G-X, Shigehara K, Tsuchida E, Anson EC. 1984. Virtues of a copolymer containing pyr-rolidone and iron porphyrin groups in the catalysis of the reduction of dioxygen at graphite electrodes. J Electroanal Chem 179 239. 

Kozawa, Zilionis and Brodd 32> have recently reported a 4-electron mechanism in the reduction of oxygen at a graphite electrode coated with iron phthalocyanine... 

A large fraction of the iron and steel produced today is recycled scrap. Since scrap does not require reduction, it can be melted down directly in an electric arc furnace, in which the charge is heated through its own electrical resistance to arcs struck from graphite electrodes above it. The main problem with this process is the presence of tramps (i.e., copper from electrical wiring, chromium, nickel, and various other metals) that accompany scrap steel such as crushed automobile bodies and that lead to brittleness in the product. Tin in combination with sulfur is the most troublesome tramp. Only the highest quality recycled steel—specifically, steel with no more than 0.13% tramps—can be used for new automobile bodies, and usually reprocessed scrap has to be mixed with new steel to meet these requirements. 

However, it is recognized that slightly soluble intermediates such as CdO(OH) and Cd(OH)3 are involved. Cadmium does not corrode since its equilibrium potential is more positive than that of hydrogen in the same solution. The active material in pocket plate cells consists of metallic cadmium, with up to 25% of iron and small quantities of nickel and graphite to prevent agglomeration. Two methods of preparation are used. One involves the electrochemical co-reduction of a solution of cadmium and iron sulphate in the other, dry mixtures of cadmium oxide or hydroxide and Fe304 or iron powder are used. In some methods of pocket plate manufacture, the electrode material is pressed into pellets or briquettes before being inserted into the pockets, and various waxes or oils may be used to facilitate this process. 

In pocket plate cells, the active materials are a mixture of finely powdered metallic iron and Fe304. The preparation of this mixture varies from manufacturer to manufacturer, but generally involves a final process in which controlled air oxidation of iron powder or reduction of Fe304 with hydrogen is used to form the appropriate composition. Additives such as cadmium, cadmium oxide or graphite are commonly included to improve the capacity retention and electronic conductance. The performance of the electrode is improved by the addition of up to 0.5% of FeS the mechanism of the sulphide involvement is not well understood. If sulphide is lost by oxidation after prolonged use, small amounts of soluble sulphide may be added to the electrolyte,... 

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