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By M. Okido, R. Ichino, K. Kuroda

"Compound semiconductor, ZnTe, was electrodeposited in an acidic solution with K2TeO3, ZnSO4 and Na2SO4 solution. Since the reduction potential Te(IV)/Te(O) is remarkably noble from the solution comparing to Zn(II)/Zn(O), code position of Te and Zn was thought to be difficult from this solution. Resulting from EQCM analysis, furthermore, Te(IV) reduced to Te(O) and Te(-II) in this order so that Te catholically dissolved from the electrode surface at more negative potential. But ZnTe alloy were formed by the UPD of Zn at -0.7V at 298K on Te surface in lmM K2TeO3, 100mM ZnSO4 and 100mM Na2SO4 solution adjusted at pH 4. Content of Te in the deposits is, however, more than 80%.Electrolytic temperature is well known to affect on the deposits characteristics. The higher bath temperature was, the better ZnTe crystal was detected in this study. Thermal electrode method is a. process of heating only substrate by flowing ac current in substrate. This process makes the surface temperature of substrate higher than boiling point of the solution, 373K. From EDX analysis, deposits without thermal current were Te-rich, Te content in the deposits with thermal current decreased with increasing of thermal current. Te content was 62% for 5A ac current, 51 % for I OA and 45% for 20A, respectively. The deposits that produced with ac current of IOA were closed to the stoichiometric ratio, i.e. ZnTe.Consequently, thermal electrode method is more effective to obtain a good crystallized ZnTe without heat treatment after deposition.IntroductionThe current subject of solar cell materials is silicon. Compound semiconductors including GaAs and II-VI group are generally used in the developing field of digital information such as the rapid cellular phone and car telephone. Compound semiconductors consist of more than 2 kinds of element. There are many materials for these compound semiconductors such a SiC, InSb, CdS for binary system and CuinSe2 for ternary system. It becomes generally difficult, to produce high quality crystal with increasing of kinds of element due to a complicated structure and a compound ratio of element. Semiconductor materials as a device are usually simple binary compounds and/or these mixed crystals. Properties of compound semiconductors have variety of the forbidden band and lattice constant and that can be change easily by addition of another element for the usage of the solar cell. Since most compound semiconductors are direct interband transition type, which has steep optics absorption edge and large light absorption coefficient."

Jan 1, 2000

By Junji Shibata

As one of the effective usages of various wastes discharged in non-ferrous metal industry, the synthesis of hydrotalcite was carried out using aluminum dross as a raw material. Hydrotalcite is one of the inorganic anion exchangers and has layered structure of complex hydroxide. The removal of toxic metal ions such as As(III), As(V), Cr(VI) and Se(IV) with the hydrotalcite was investigated, and the removal properties were compared from the viewpoint of the anion exchange amount and exchange rate. Hydrotalcite can be obtained by a co-precipitation method from the aluminum dross and the waste MgCl2 solution discharged in an aluminum regeneration process. Slight amounts of SiO2, Al2O3, Fe2O3 and so on remain in the reaction product as an impurity component. Interlayer distance of the obtained hydrotalcite is about 0.3nm. Hydrotalcite changes to Mg-Al oxide by the calcination at 773K for 3h, and then hydrotalcite is formed again by a rehydration operation after calcination. The toxic metal ions are removed from aqueous solution by the anion exchange reaction in the pH region where toxic metal ions exist as the anionic species like AsO2-, HAsO42-,CrO42-, and SeO32-. The exchange amount is considerably concerned with the valence of anionic species and the size of anionic species. The removal of toxic metal ions were investigated from the engineering aspects such as the low concentration limit to be removed, the amount of hydrotalcite to be used for the perfect removal of toxic metal ions and so on.

Jan 1, 2006

By Jing Zhan, Gui Li, Wei-feng Li, Li-Hua Jiang, Chuan-fu Zhang, Jian-yang Hwang

Thermodynamics analysis for processing the charge with lead concentrate and lead sulfate-containing materials in bottom blowing smelting furnace was conducted. The results show that the technology of large-scale processing PbSO4- containing materials with PbS concentrate in bottom blowing furnace under the condition of using high-iron slag type, batch heat supplement, high temperature and rich oxygen is thermodynamically feasible. The exploration test and industrial experiment confirm the results. When S content in mixed ore is 16~17% with coke foam content of about 5%, the lead paste amount can be increased up to 40%.

Jan 1, 2015

By F. J. Hogan

In early 1982 Atlantic Cement Company, a wholly-owned subsidiary of Newmont Mining Corp. will come on line with a new water granulating grinding facility at Sparrows Point, Maryland to produce 800, 000 tons a year of separately ground granulated blast-furnace slag. The process and product will be unique to the United States. This paper will review some initial investigations undertaken to evaluate the cementitious properties of granulated slag. The effect of slag fineness on strength development is discussed and data is presented showing a relationship between glass content and hydraulicity and grindability of slag.

Jan 1, 1982

By Lakshman D. Jayaweera

Today's rapidly developing and changing technologies and industrial products and practices frequently carry with them the increased generation of materials that, if improperly dealt with, can threaten both public health and the environment. Mercury is an element that poses great problems in the many forms in which it is to be found in the mineral processing industry. These forms are often contained in hazardous wastes and residues which may be unstable, and in which the contained mercury has value. This paper presents some of the stabilisation and recovery methods which are based on hydrometallurgical techniques and thermodynamic stability considerations.

Jan 1, 1994

By C. J. Lewis

This presentation concerns calcium oxide-better known as high calcium quick lime High calcium quicklime is produced by calcining high calcium limestone, mostly in the many rotary kilns located throughout the United States and Canada. This paper presents suggestions on the handling of lime based on field experience. The subjects covered are chemical analyses, transporta¬tion, lime storage, lime slaking to form a water slurry of calcium hydroxide solids, slurry transportation, slurry viscosity, and scaling of lime slurries. It is hoped that the comments on the foregoing areas will be of use to those designing or operating lime systems.

Jan 1, 1992

By P. D. Nolan

Smelters operating under pollution control orders have become increasingly dependent upon the reliable operation of sulphuric acid plants and no factor affects the long term reliability of those plants more than efficient gas cleaning. The sources and characteristics of contaminants in smelter of fgases and the conventional approaches to removing these contaminants to accepted levels are discussed. New technology is described which offers advantages of lower capital cost, lower operating cost and reduced space requirements over the conventional approaches. This new technology has been developed by LAB s.a. and is licensed for metallurgical gas applications by Chemetics International Company.

Jan 1, 1983

By Xingye Guo, Yeon-Gil Jung, James Knapp, Zhe Lu, Jing Zhang, Li Li

La2Zr2O7 is a promising thermal barrier coating material due to its low thermal conductivity and superior high temperature stability. In this work, Bilayer La2Zr2O7 and conventional 8 wt% yttria stabilized zirconia (8YSZ) coatings were deposited using plasma spray technique. Both singlelayer La2Zr2O7 and double-layer 8YSZ/La2Zr2O7 coating architectures were designed. Thermal cycling and thermal shock tests were used to evaluate coatings’ thermomechanical properties. All La2Zr2O7 coats were delaminated in the furnace cycle test in less than 20 cycles. This is because residual thermal stresses accumulated during thermal cycling. In the jet engine thermal shock (JETS) tests, the SCL La2Zr2O7 and DCL dense 8YSZ/La2Zr2O7 coatings were fully delaminated. In contrast, the DCL porous 8YSZ/La2Zr2O7 coating sample only partially delaminated on the edge. This is because of the porous 8YSZ layer provides strain compliance. The findings will help to propose efficient thermal barrier coating systems.

Jan 1, 2016

By A. V. Tarasov

The lack of technology for processing of sub-grade ore concentrates and intermediate products for extraction of Zn, Pb, Cu and precious metals at the metallurgical stage was a constraint for an increase in the production of these metals. The technology developed in the Gintsvetmet Institute is based on an improved electrothermal smelting process for treating calcined charge, ensuring thereby a reduction in power requirement and improving the environmental performance of the process. Electric smelting of sub-grade polymetallic concentrates produces lead bullion, to which the bulk of gold and silver reports, as well as well segregated matte and slag concentrating the bulk of zinc. Lead bullion and matte are commercial-grade products; zinc is recovered from high-grade (15% Zn) slag by slag fuming process. Reduced loss of precious metals in slag ensured by the given technology is attributed to the fact that the slag contacts with matte with low contents of gold, silver and lead, rather than with lead bullion. Limited amounts of off-gas typical of electrothermal processes ensure cost-effective operation of dust recovery devices and a reduction in emissions of harmful pollutants into the ambient air.

Jan 1, 2002

By Rodney T. Jones

Mintek has developed and piloted a novel process for the treatment of nickel-copper and PGM (platinum group metal) sulphide concentrates. The ConRoast process is based on the removal of sulphur by roasting, followed by smelting of the dead-roasted concentrate in a DC arc furnace using an iron-based alloy as a collector for nickel, copper, cobalt, and PGMs. The environmental benefits with respect to sulphur emissions are considerable, in that essentially all of the sulphur is removed from the enclosed roasting equipment in a continuous stream of SO2 of an appropriate strength for feeding to a sulphuric acid plant. This process allows great flexibility with respect to the selection of ore types, and does not impose limits on the minimum quantities of contained base metals or sulphur, and can tolerate very high contents of chromite in the concentrate. The furnace alloy is water-atomized prior to leaching. Iron may be rejected from the alloy hydrometallurgically, by precipitation as hematite for example. The ConRoast process achieves very high metal recoveries, and produces high-purity metals, and a clean high- grade PGM concentrate.

Jan 1, 2002

By Armando Valenzuela

Arsenic has been a common impurity in copper sulfide concentrates treated pyrometallurgically in Chile, which inevitably during the smelting-converting process reports in the final copper product affecting its properties, but also affecting environment as a very toxic occupational hazard. The enforcement of air quality standards, which regulate pollutants such as sulfur dioxide, particulate matter, and arsenic, has resulted in the implementation of pollution abatement plans and emission reduction schedules mainly by state-owned copper concentrate smelters. Investments associated with these plans incorporated gas-handling systems in order to capture polluting emissions. Electrostatic precipitators recover dusts containing mainly Cu and As which are leached to recover copper, while arsenic is disposed currently in the form of ferric arsenate. Gases containing high sulfur dioxide content are treated in plants to produce sulfuric acid, which is used in various classical and new hydrometallurgical processes. Additionally, smelters have effluents treatment plants for arsenic disposal either as ferric arsenate or calcium arsenate/arsenite. This paper reviews the environmental situation of the Chilean metallurgical industry, and the present trends for arsenic management are particularly emphasized since Chile is the world?s largest copper producer.

Jan 1, 2006

By Manolete Mena

WC-Co nanocomposite powder is among the first group of materials with a promising potential for nanocrystalline-materials application. A chemical vapor synthesis (CVS) process that has previously been used for preparing the aluminides of titanium and nickel, and other metallic and intermetallic powders has been applied to the preparation of WC-Co nanocomposite powder. This CVS system was designed so that a tungsten precursor (WCl6 powder) and a cobalt precursor (CoCl2 powder) were separately fed into each evaporator in a reactor by means of specially designed powder feeders. The reduction and carburization of the vaporized chlorides by methane-hydrogen mixtures produced nanosized WC and Co composite powder. The product is a very uniform mixture of the constituent powders, which is important to ensure a high quality of the bulk cemented tungsten carbide product after consolidation. In the present work, the effects of reaction temperature, CH4 to WCl6 ratio, CH4 to H2 ratio, residence time, and Co content on the powder composition and particle size were determined. The products were characterized using XRD, carbon analyzer, and TEM.

Jan 1, 2006

By Manolete Mena

WC-Co nanocomposite powder is among the first group of materials with a promising potential for nanocrystalline-materials application. A chemical vapor synthesis (CVS) process that has previously been used for preparing the aluminides of titanium and nickel, and other metallic and intermetallic powders has been applied to the preparation of WC-Co nanocomposite powder. This CVS system was designed so that a tungsten precursor (WCl6 powder) and a cobalt precursor (CoCl2 powder) were separately fed into each evaporator in a reactor by means of specially designed powder feeders. The reduction and carburization of the vaporized chlorides by methane-hydrogen mixtures produced nanosized WC and Co composite powder. The product is a very uniform mixture of the constituent powders, which is important to ensure a high quality of the bulk cemented tungsten carbide product after consolidation. In the present work, the effects of reaction temperature, CH4 to WCl6 ratio, CH4 to H2 ratio, residence time, and Co content on the powder composition and particle size were determined. The products were characterized using XRD, carbon analyzer, and TEM.

Jan 1, 2006

By V. Panchanathan

The rapidly solidified Nd-Fe-B powders form the entire basis of the bonded magnet industry At present the rapid solidification is carried out exclusively by melt spinning, producing flake like particles having highly stable and magnetically hard microstructure These particles are comminuted into powder before being processed into bonded magnets These powders are magnetically isotropic having coercivities from 4 to 16 kOe The other type of powder recently introduced for bonded magnets is the anisotropic powder made by the hydrogen decomposition desorption recombination (HDDR) process. The characteristics and application of these isotropic and anisotropic powders are discussed.

Jan 1, 1997

By A. V. Tarasov

The insufficient scientific and technical level of a number of operations in the nonferrous metals industry encourages development of new processes and equipment, including smelting in liquid bath, flame-type sparged smelting unit for combined processes, electrothermal process with the use of alternating current (PDF furnace), electrothermal processing of complex raw materials and intermediate products at nonferrous metallurgical plants, etc. One of the most important aspects for development of new processes and equipment in the Gintsvetmet Institute is their environmental safety. Special attention is paid to environmental protection measures, which is also of important economic and social significance. This refers also to a complete extent to processing of reserves of man-made raw materials and wastes available at the existing operations with the use of innovative techniques ensuring not only resource conservation and environmental protection, but also abatement of negative impact on the nature due to accumulated industrial and domestic waste, reclamation of the land used for waste disposal and recycling of nonferrous metals. Technologies and equipment developed in the Gintsvetmet Institute and based on electrothermal processes determine the prospects for ensuring more integrated usage of ores and man-made raw materials.

Jan 1, 2006

By A. I. Okunev

The investigation results are submitted on separation into layers in the systems Cu (Ni) - Fe - Ca - 0 - S - (Si), as well as on physico-chemical properties of oxide - ferrite, oxide-sulfide melts (density, surface tention, viscosity, electric conductivity), on kinetics and oxidation macromechanism of iron and sulfur in the oxide-silicate, oxide-ferrite and oxide-sulfide melts, kinetics of reduction of oxide-silicate and oxide-ferrite systems. Conditions are discussed for copper, nickel and zinc recovery from oxide-silicate and oxide-ferrite slag in liquid and solid states. Some promising technique is the technique of future, as is considered.

Jan 1, 1988

By Roberto Parra

The operational control in a Flash Smelting Furnace is based on the mass and energy balance of the chemical and mineralogical composition of the concentrates. It is well known that many troubles in the dust formation and slag quality occur without a clear correlation to a specific process parameter such as the matte grade or heat balance. This paper outlines two new considerations that could both help improve the entire quality of the process: blend characterization and versatile slag composition control. Related to the blend control, laboratory scale study has shown that the magnetite and dust formation don't have a linear behavior with the weight proportion of the blend and some optimal blends of2 or 3 types of concentrates can be identified. Related to the control of stag composition, the quantification of the slag liquidus temperatures and viscosity could be an effective operational tool for both for ferrite and fayalite slag that can also directly help deciding the blending parameters. From these viewpoints the benefits of the combination of these two approaches for high temperature operation is discussed. Keywords: Optimization, Copper concentrates, Flash combustion, Blends, Slag composition

Jan 1, 2003

By M. Hadj Meliani

This paper explores direct use of finite element analysis by CASTEM 2000 in order to determine the evolution of T-stress term for arc of pipe specimens with external surface crack. A simple method, called the stress difference method proposed by Yang (1999), is used to compute the elastic T-stress in mode I at a crack tip. The different crack geometries and length-to-thickness ratio on T-stress and stress-intensity factor (SIF) are examined. The revisited stress difference method is shown to be an accurate and robust scheme for evaluating T-stress in arc of pipe.

Jan 1, 2006

By D. J. Brennan

A techno-economic study is in progress, examining process and product options for treating smelter gases containing various concentrations of sulphur dioxide. Key contenders have been examined within an Australian context using the following criteria: * Markets for products * Capital Costs * Operating Costs * Waste streams generated Product options considered thus far are sulphuric acid, sulphur, calcium sulphite and gypsum. The development of an appropriate overall framework for evaluating process and product options is discussed and findings thus far presented. The emerging techno-economic study offers promise as a constructive guide to future policy decisions by industry and government.

Jan 1, 1994

By John W. Pickens

The recycling of industrial wastes and by-products is an important component of ecologically responsible industrial management. Converting waste streams into value-added products or material and energy resources with a profit margin assures the continued viability and practice of recycling. The recycling of aluminum stands out as one of the best examples with major economic and environmental benefit. However, the benefits are compromised by landfilling of black dross and salt cake, waste streams produced from within the recycling process itself. This paper reviews Alumitech's strategy and progress in establishing a tertiary aluminum industry based on closed-loop recycling of black dross/saltcake; one which does not compete with the primary and secondary aluminum industries, but rather serves their needs to ensure the continued economic benefits of aluminum recycling and elimination of environmental liablJity associated with landfilling of black dross/saltcake. Alumitech has made significant progress toward that goal in operation of its new recycling facilities in Cleveland where recovered aluminum and nonmetallic residue from salt based drosses is being converted into commercial products, eliminating the landfilling of the greatest portion of dross/saltcake. The economic strategy for recycling saltcake and its progressive achievement is reviewed.

Jan 1, 2000