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By Johan Sundström

Anhydrous DyC13 was prepared by dehydration of DyCl3?6H20 in a fluidized bed using both batch- wise and continuous feeding. A gas mixture with varied composition of argon and HCl was used. The productivity was high, reaching values of 0.25 mol H20/m2-st during the reaction step 6- 1 and 0.062 mol H2O/m2.s during the reaction step 1-0. The product was free from hydrolytic compounds, such as DyOCI, if control of inlet gas composition versus temperature was achieved. From the results of various experiments, some relations between HCI-concentration and temperature in order to avoid hydrolysis have been deduced. The fluidization process efficiency decreases drastically after the dehydration has proceeded down to about 10 mol% of remaining water. Therefore, in a final treatment the last traces of water were removed by slowly purging gas through a packed bed. The water content could thereby be reduced to less than 1 mol%.

Jan 1, 1997

The concepts of capacity and basicity have proved extremely useful in dealing with a wide range of solute species in metallurgical slags, and as a result have been widely applied. These two concepts are reviewed, and it is suggested that the Lewis approach to basicity has much to commend it. In some cases, it appears that the term capacity has been used without due consideration being given to the nature of the solution being formed, or even to whether a true solution was being formed at all. This paper proposes a rigorous definition of capacity, based on the true nature of the solution process in slags and glasses, and briefly reviews the repercussions of this approach on data available in the literature and the limitations which it may impose on future investigations in this area.

Jan 1, 1994

By P. M. Pincheira Brown

The widely accepted inverse relationship between copper prices ail stocks, has been commonly used by analysts to explain the behavior of the copper market and to forecast film copper pries. However, empirical data have not shown such a clear relationship between copper prices and stacks. Existing evidence only indicates a weak tong-nut relationship that vanishes in some periods. In this paper a simple comprehensive model is provided which explains both parallel and opposite direction movements between prices and stocks. Former are explained mainly by stocks demand expansions-contractions while the latter are in essence due to increases in the supply curve. Furthermore, econometric estimations are provided, thus giving a powerful tool to forecast and explain price developments of the copper market.

Jan 1, 1999

By Esperidiana A. B. Moura, Mariana N. Sartori, Vijaya K. Rangari, Angel Visentim Ortiz, Francisco R. V. Diaz, Rene R. Oliveira

"This work presents the preparation and characterization of a nanocomposite based on Poly(butylene terephthalate) PBT and Brazilian smectitic clay (bentonite chocolate clay). Before being incorporated as clay nanoparticles in PBT resin, the clay was organically modified by the addition of a quaternary salt and sodium carbonate. PBT/Clay nanocomposite (96.3:3.70 wt %) was obtained by using a twin-screw extruder machine. After extrusion process, the nanocomposite was characterized by tensile, flexural and impact tests, SEM, Vicat, HDT, DSC, TGA and XRD tests. The results showed that the properties of the nanocomposite obtained were superior to those of neat PBT. Concerning the temperature of thermal distortion (HDT) an expressive gain of around 45 % was presented to PBT/Clay nanocomposite compared to PBT evidencing the interaction of nanofiller with the polymeric matrix.IntroductionPolymer-clay nanocomposites, also called as polymer layered silicates nanocomposites have attracted much attention from both industry and academia over the past decade because they frequently exhibit unexpected properties. In contrast to the traditional fillers, nanofillers, in particular, nanoclay, is found to be effective. The addition of a small amount (< 5 wt.%) can show significant improvement in mechanical, thermal and barrier properties, flammability resistance, and electrical/electronic properties of the final polymer nanocomposite without requiring special processing techniques. Also, as with other nano-size particles, the overall crystallization rate and the glass transition temperature are also affected. It is generally believed that the improvement of properties of nanoclay composites is directly related to the complete exfoliation of silicate layers in the polymer matrix. However, a processing technique that produces complete exfoliation is still a technical challenge [1,2]."

Jan 1, 2012

By P. K. Narasimhargahavan

This paper discusses briefly the major reasons associated with the growth and its impact on the energy requirement and Environmental imbalance. A projection based on the present global Alumina and Al requirement indicate a substantial further growth of at least 30% over the next 10 years. It is indicated that the main factors which are likely to influence investments are the environmental factors such as the Climate Change and global response to the growing energy prices and sustainable development. Each of the developed / developing nations must find response to the GHG emissions which will encourage the Al Industry to make an effective contribution to global warming while preserving the international competitiveness of the industry - a challenging task. The efforts shall concentrate on improving energy efficiency in the industry possibly of the order of 25% over the next 10 to 20 years. The developments in this line are discussed.

Jan 1, 2010

By Cevat Serdar Kucukkaragoz

The kinetics of prereduction of Chromite by carbon was studied under argon atmosphere at temperatures between 1000°C and 1300°C . The compacted and agglomerated specimens were reacted by using a TGA system. The mixing characteristics and the degree of compaction of the chromite and coke particles were the main parameters influencing the reduction kinetics. The reduction rate increased with temperature reaching to 81% reduction at 1300°C. The metallization started as the metallic nucleation around the particles which was first observed at 1100°C. The particles were surrounded by the metallic phase at approximately 40 % reduction obtained at 1200°C. At 1300°C, the reduction proceeded with a high rate during initial stages and with a low rate at final stages. The reduction was found to proceed in the sequence of Fe3+to Fe2+, Fe2+ to Fe(metal) and Cr3+to Cr(metal) with the formation of carbides.

Jan 1, 2006

By María Guadalupe Sánchez-Loredo

Silver from nitrate aqueous solutions was extracted by commercial organophosphorous extractants (tri-n-butylphosphate, Cyanex 471x, Cyanex 301 and Cyanex 302). Quantitative silver extraction was obtained using the Cyanex reagents. After loading, aqueous solutions of several reducing reagents were used to prepare fine silver powders by reductive stripping. Only both extractants Cyanex 471x and tri-n-butylphosphate (TBP) could be reductive stripped and regenerated by aqueous solutions of ascorbic acid, and Cyanex 471x was decomposed to the corresponding phosphine oxide by using sodium borohydride as reducing agent. Silver was recovered as fine particles, which were characterised by means of scanning electron microscopy (SEM). Micrographs showed that the powder size and morphology were directly affected by the composition of the applied organic phases and aqueous reducing media.

Jan 1, 2003

By Vladimir Lobanov, Vladimir Skorohodov, Andrew Evdokimov, Ural State Technical University 19, Boris Radionov

"The bulk of raw materials in metallurgy of secondary platinum metals are the wastes such as multilayered ceramic-metal systems, e.g. the spent catalysts of the chemical and petrochemical industry, automobile catalysts, etc. Due high chemical resistance of a ceramic basis the extraction of platinum metals by leaching even at very fine crushing is poor. The study of sorption leaching of platinum and a palladium from the spent automobile catalysts are carried out. The average content of PGM is 0.5%. A few methods of raw materials sampling were compared: 1) direct hydrometallurgical leaching of platinum metals from the fine-grained catalyst and atomic absorption analysis of the obtained solutions; 2) fusion to a metal or sulphidic collector of precious metals with the alloy analysis by direct spectrometry; 3) fusion with dissolution of a precious metals collector and atomic absorption analysis of PGM in solutions. Leaching allows detecting out no more than 90% of a palladium and 80% of platinum. Fusion to a collector gives the best results at the chemical ending. Researches on sorption leaching are executed. Under optimum conditions the extraction of platinum metals to concentrates is comparable with similar indicators of collector fusion.The large part of raw materials in metallurgy of secondary platinum metals are the multilayered or tridimensional ceramic-metal systems, in particular the spent catalysts of the chemical and petrochemical industry, automobile catalysts, ceramic-metal condensers, etc. The content of the sum of PGMs can be from hundreds grams per ton to several percent. For processing of such materials the hydrometallurgical methods of platinum metals leaching by various reagents are used commonly. High chemical resistance of the ceramic basis covering the metal particles causes low recovery even at very fine grinding. Other fundamentally different method of catalysts opening includes dissolution of the ceramic basis in the solutions of hydrofluoric acid and the subsequent recovery of platinum metals from insoluble residue. Application of this method is associated to use of corrosive medias and appropriate equipment. Fusion of the specified materials with collecting of PGM by copper, nickel or lead at the specialized enterprises provides higher extraction in semiproduct. At the same time, complexity and duration of the subsequent extraction of platinum metals concentrates causes high total cost per unit. Thereby this method is economically acceptable only for rather poor raw materials (no more than 0,1%). Undoubtedly, that the raw materials with the high content of PGM are reasonable to process by individual technology. In the present work the processing of some kinds of ceramic-metal raw materials, particularly automobile catalysts (neutralizers) with various collectors at the conditions of a target fusion are investigated."

Jan 1, 2008

By Shadia J. Ikhmayies

"Cadmium telluride (CdTe) is a very interesting material that has many applications. Thin films of p-type CdTe can be used as the absorber layer in the heterojunction CdS/CdTe thin film solar cells in which n-type cadmium sulfide (CdS) works as the window layer. A review of the photoluminescence (PL) spectra ofp-type CdTe thin films prepared by different techniques was performed. The presence of defects and impurities such as oxygen and chlorine influence the PL spectrum. Copper and other dopants change the PL spectra and enhance the defects band. Chemical-heat treatment especially with CdCh is known to improve the quality of CdTe thin films because it decreases the Cd vacancies and quenches deep traps, so it enhances the PL signal. A discussion of chemical-heat treatment especially with CdCh, the effect of the ambient atmosphere, and that of the measuring temperature is performed.IntroductionCadmium telluride (CdTe) is a II-VI compound semiconductor that has a cubic zincblende (sphalerite) structure with a lattice constant of 0 A4~11]. Other than all of II -VI semiconductors, CdTe can be made both n- and p-type. But due to self compensation it is not easy to get p-type CdTe films [2]. Polycrystalline CdTe thin films are interesting because they have a lot of applications. Most of the problems associated with the use of these films are attributed to inhomogeneity, self-compensation, and the difficulty of forming a stable and lowresistivity ohmic contact [3]. CdTe technology has been established for a large number of applications, including solar cells, optical and nuclear detectors, and thermal- and radiationimaging devices [3]. At present, the highest demonstrated conversion efficiency for a CdTe based heterojunction (ID), with CdS as a window layer, is 16.5% [4, 5]. CdTe thin films can be prepared by different experimental techniques, such as thermal evaporation [l], electrochemical deposition (ED) [3], close-spaced sublimation (CSS) [3, 4, 6], physical vapor deposition (PVD) [3], chemical molecular beam deposition (CMBD) [7], and close space vapor transport (CSVT) [8].The objective of this paper is to make a review of the photoluminescence (PL) spectra ofp-type CdTe thin films prepared by different techniques and discuss the factors that influence the PL spectra. The composition of the film is very interesting in determining its PL spectrum. Different kinds of defects, impurities and dopants have their finger prints in the PL spectrum. Deposition techniques and deposition parameters such as the deposition temperature and ambient atmosphere also have their influence. Heat and chemical treatments which are known to improve crystallization and reduce the defects change the PL spectrum."

Jan 1, 2013

By Chen Zhang

Polycrystalline Ti-rich NiTi thin films have been deposited from a single NiTi target using a DC magnetron sputtering system. Free standing film was obtained by using a single crystal silicon substrate. Thickness ofthe thin films is controlled at around 12 pm. In this investigation, the effect of deposition temperature on the microstructure and transformation temperatures of the thin films is studied. Influence of post heat treatment temperatures on the properties of the thin films is also investigated. Transformation temperatures of the thin films are determined by differential scanning calorimetry (DSC). The surface microstructure of the thin films is studied using a scanning electron microscope (SEM), and the crystallinity is determined using x-ray diffractometry. It is found that the thin film deposited on a hot substrate is crystalline even when the substrate temperature is as low as 300°C, while the normal crystallization temperature for an amorphous thin film is around 500°C. The microstructure of the film deposited on a hot substrate shows a very fine grain size. The grain size increases with increasing substrate temperature during deposition. The effect of post deposition heat treatment on grain size is minimal.

Jan 1, 1999

By Kyong-Hwan Lee

This paper is focused on describing the pilot and demonstration plants for pyrolysis process of mixed plastic wastes developed at Korea Institute of Energy Research (KIER). These plants were constructed at KIER (300 ton/yr) and also Korea R & D Company (3,000 ton/yr) in Kimjae city, in Korea. The raw material used was mixed plastic wastes that were generated from household and industry, etc. The liquid products obtained by pyrolysis at around 400°C were used as an alternative fuel oil. These processes were controlled by automatic control system with continuous operation in a control room. Main process units consist of automatic feeding, melting, thermal cracking systems and vacuum distillation. Their characteristics were automatic pyrolysis operation under vacuum atmospheric pressure, continuous control in feeding of raw material and discharging of solid residue, the recirculation of cracked reactant with a high temperature into the melting reactor and continuous pyrolysis of reactant in circulation thermal cracking system such as constant stirred tank reactor (CSTR), plug flow reactor and light/heavy oil separator, in order to maximize the efficiency of light oil products like kerosene and diesel. In addition, the process performance of pilot plant was described.

Jan 1, 2006

By Gustavo E. Lagos

Mining is one of the oldest and most important productive activities in Chile. In the latter half of the 80&apos;s &d during the 1990&apos;s Chilean mining has experienced explosive growth fundamentally due to legislative changes which have encouraged an influx of foreign capital. Fine copper production has grown from 1,4 million tons in 1987 to 3,4 million tons in 1997. Gold production has increased from 17.03 tons in 1987 to 49.46 tons in 1997. In both cases private investment has driven this growth. The direct impact of mining on the Chilean economy has been considered one of the fundamental pillars of the growth of the country in the last years. The indirect impact that has generated on the other sectors of the Chilean economy and in particular the regional economies, has not been analyzed. This paper outlines a methodology for estimating the impact of mining investment and mining operations in different sectors of the Chilean economy at both regional and national levels. It applies this methodology to the case of Minera Escondida, the largest copper mine in the world, analyzing its economic impacts on the regional and national levels.

Jan 1, 1999

By Magdalena Regel-Rosocka

Extraction of zinc(II) from hydrochloric acid solutions is discussed. The literature on the extraction of zinc(II) in the presence of iron(III) and iron(II) with various basic and solvating reagents has been reviewed. It was found that tributyl phosphate (TBP) is the best compromise, and permits both effective extraction of zinc(II) and its stripping with water. The process was confirmed in a continuous laboratory mixer-settler circuit.

Jan 1, 2003

By Li Rongxing

A general regular solution model put forward in this paper defines a general interaction parameter that includes both composition and temperature dependence. On the basis of this model, analytic express of solution excess properties was obtained by least square fit using the composition and temperature relations in binary alloy phase diagram. After some solution excess properties analytic expresses of correlated binary alloy system obtained, the analytic express of ternary alloy system could be obtained by superposition of general geometrical model. The ternary alloy system Pb-Sn-Zn has been predicted in terms of this method and the result was very in agreement with actual measured value.

Jan 1, 2006

By Henry Salomon-De-Friedberg

Quebrada Blanca has had to overcome numerous challenges in achieving design throughput. The paper reviews how actual practice has evolved from the original design. The major challenges that were encountered from heap leaching to solvent extraction, the tankfarm and through to electro winning are discussed. The eventual solutions to some of the key issues are presented.

Jan 1, 1999

By Song Ning

The main mineral constituents of phase-transformed chalcopyrite are CuS and FeS2. CuS is more soluble than FeS2 in an acidic CuCl2 solution with presence of excessive NaCl, so that FeS2 could be removed as solid residue from a leached solution. The experimental results showed that the efficiency of the copper leaching is heavily determined by the following two factors: a) The degree of the chalcopyrite phase transformation to CuS and FeS2 b)The concentration of Cl during the leaching, specifically whether there is enough excessive Cl existed. I t was found that when the Cl in the solution is not excessive, the slowest step of the leaching is the dissolution of Cu2Cl2.

Jan 1, 2006

By Chang-hong Peng

Solubility phase equilibrium in the ternary system of Me2+-NH4+-SO42--H2O (Me2+ represented Mn2+, Zn2+ and Fe2+) was studied by the isothermal method at 298K and physicochemical properties of the saturated solution such as density, refractive index and pH were also investigated. The experimental results show that the solubility isothermal phase diagrams of these systems consist of three invariant branches, two invariant points and three crystallization fields. Corresponding to the three crystallization fields, there have three phases of solid, that is MeSO4?nH2O, (NH4)2SO4 and (NH4)2Me(SO4)2?6H2O, respectively. At the eutectic point, the concentration and the refractive indexes of the saturated solution change evidently. Otherwise, the pH value change slowly in all the systems. The calculated results of the density and refractive index agree with the experimental results.

Jan 1, 2006

By Chunlin Chen

Published data on thermodynamics of a number of minor elements (As, Sb, Bi, Pb, Zn, Se, Te, Cr, Sn) in liquid copper, matte and slag have been reviewed, assessed and used in development of thermodynamic solution models of melts. The behavior of antimony in alloys, mattes and slags is used as an example to illustrate the approach taken in assessment of published data and validation of the developed models with respect to the activity of Sb in condensed phases as well as the effects of matte grade, slag chemistry, temperature etc on the equilibrium distribution of Sb between melts and the gas phase. Results obtained from a comparison of different smelting processes with the modeled multi-phase equilibrium are presented and discussed. The predicted effects of slag chemistry and matte grade on the deportment of other minor elements during smelting of copper mattes will be presented and discussed.

Jan 1, 2006

By Tang Chaobo

According to the principles of simultaneous chemical equilibrium and electronic charge neutrality, the system of Mg(II)-NH3-CO32--SO42--H2O at 25°C has been thermodynamically analyzed. And the rule of solubility of MgCO3(s) in the system is discovered, the high dissolution field of MgCO3(s) is discovered too. Furthermore, the solubility of MgCO3(s) is increased with the increase of the concentration of SO42-, but it is decreased first then increased with the increase of the concentration of all the CO32- and the total concentration of ammonia and ammonium, and decreased with the value of pH being higher. Those results will has important significance on prepare magnesium chemical products and other salts carbonate that are strict with the content of magnesium with carburization method.

Jan 1, 2006

By Brian Lightfoot

Ausmelt Technology uses a furnace/slag/lance system in a way analogous to the way a chemical engineer would use a mixed reactor. The technology is sufficiently versatile to treat materials under a very wide range of temperature and chemical conditions. At one extreme the system has been operated at temperatures high enough and oxygen potentials low enough to make iron. At the other extreme it has been operated of temperatures as low as 800°C and oxygen potentials high enough to cupel lead from silver. This versatility permits the treatment of a great variety of wastes including asbestos, mixed organic\heavy metal wastes, incinerator ash smelter residues, waste water treatment sludges, organochlorine compounds and many others.

Jan 1, 1994