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By R. Singh, C. Gong, J. Chaudhry

"Metalorganic chemical vapor deposition (MOCVD) is an ideal technique for the deposition of conducting and non-conducting oxide based thin film materials. In this paper we have presented a study of photo assisted MOCVD for the low temperature deposition of a number of oxide based advanced materials. We have used incoherent light sources as the source of optical and thermal energy in our MOCVD system. The vacuum ultraviolet (VUV) and ultraviolet (UV) photons can enhance the surface reaction of the absorbed molecules through the perturbation of the electronic state of binding between the absorbed molecules and the solid surface. Unlike plasma process, no surface damage is expected and high quality materials have been deposited. At a given substrate temperature, the performance of deposited film depends on the lamp configuration.INTRODUCTIONMetalorganic chemical vapor deposition (MOCVD) has become the standard manufacturing technique for the deposition of large area thin films of compound semiconductors. l.(.w-cost, high crystalline quality, atomically clean and sharp interfaces, atomic layer epitaxy, high throughput rates and potential for direct writing are some attractive features of MOCVD. Due to a number of potential advantages mentioned above, MOCVD is considered as an ideal technique for the deposition of various electronic and optical materials for a wide variety of applications. Rapid isothermal processing based on incoherent radiation as the source of optical and thermal energy is emerging as the key low thermal budget (integral of processing time and temperature) processing technique for the fabrication of current and next generation of microelectronic and optoelectronic devices and circuits [1]. In this paper we have demonstrated that the design of the lamp assembly plays an important role in determining the properties of the materials deposited by RIP assisted MOCVD. We have studied the growth rates, structural properties and electrical properties of Y2O3/Si structure. At a given substrate temperature, best results are obtained for the lamp assembly that provides maximum number of VUV and UV photons."

Jan 1, 1994

By Robert Mensah-Biney

The loading characteristics of gold-tetrabromide species onto a weak-base resin, PAZ-4, were evaluated using a completely mixed batch reaction system. The time. to attain equilibrium loading was substantial, on the order of several days. However, abnormally high loading capacity values of 15 to 20 meq Au/g dry resin (1000 to 1300 kgAu/tonne) were attainable in 24 hours. The loading of gold-bromo species by P AZ-4 was visualized as consisting of two processes: (i) the rapid adsorption of [AuBr4r species by simple ion exchange mechanisms and (ii) reduction of [AuBr4r to metallic gold by an electron exchange mechanism. Elution of gold from loaded resin was feasible provided the resin had not been loaded to high capacity values. If loading is carried to high levels, complete elution becomes impractical and the gold may be recovered by ashing the loaded resin. For the high loading capacities observed this option would appear to be cost effective.

Jan 1, 1991

By C. A. Morais

The present work describes the development of an efficient and relatively simple process to obtain high grade CeO2 from a mixed rare earth chloride solution. The process involves cerium oxidation and precipitation by addition of a KMnO4-NaCO3 solution. The experiments were carried out at room temperature (25 1° C). The results indicated that the major parameters affecting cerium recovery are the molar ratio of KMnO4/Ce, the initial acidity of the chloride feed solution and final pH of Ce(OH)4 precipitation. In strong acid solutions (pH < 1), the oxidation of Cl to Clo took place in addition to the oxidation of Ce(III) to Ce(IV), so increasing the permanganate consumption. Conversely, low acidity (pH >3) led to coprecipitation of the other rare earth elements. Under the selected conditions, cerium was selectively precipitated as ceric hydroxide, together with some manganese dioxide. Further purification was carried out by the dissolution of Ce(OH)4 in HCl, followed by precipitation as cerium carbonate. The filtrate was neutralised with a Na2CO3 solution in order to recover the associated rare earth elements for further separation. The final product, assaying 99.7 % CeO2, was obtained with a recovery of nearly 100%.

Jan 1, 2003

By S. V. Cherty

The utilization of natural gas in non-ferrous industries during smelting and refining stages of copper , aluminum, zinc and lead was studied. The total amount of nonelectrical energy consumed in the production of zinc, copper, lead and aluminium, are 96.5% ,93%,92%, and 6 % respectively. It is calculated that 9.45 wt %of air of stoichiometric amount can be substituted by natural gas to the total air input in the nonelectrical energy utilization processes. The results showed that the non electrical energy may be substituted to an amount of 71 % ,52 % ,35 % ,32 % ,and 26% ,in the production of lead, aluminium (plates, foils) copper, aluminium, zinc, respectivelly. Similar calculations are carried out in terms of energy in Btu for the total production of non-ferrous metals in the U.S. It shows that 51.866~106 millions of Btu of nonelectrical energy can be substituted by 54.58~106 cu. ft of natural gas. Finally, the substitution of non electrical energy in terms of equivalent coal energy is discussed. 1t is shown that total non electrical energy is equal to 1.852 million tones of coal .If this 1.852 million tones of coal is replaced by natural gas, a total savings of 22.14 million dollars are achieved. The total or partial substitution of coal by the natural gas in the existing industrial processes and modification of redesigning the processes is discussed.

Jan 1, 1993

By Ann M. Hagni

The mineralogical, chemical, microtextural, and particle size character of electric arc furnace (EAF) dusts are being studied by reflected light microscopy, scanning electron microscope-energy dispersive spectroscopic analysis (SEM-EDS) and electron probe microanalysis (EPMA). The dusts consist predominantly of metallic iron, iron oxide, and calcium-iron-manganese silicate phases, together with smaller amounts of iron-manganese-zinc-calcium, iron-calcium-zinc-manganese, and calcium-iron-manganese silicates. The samples vary in their zinc contents. Chlorine occurs in phases containing iron, lead, zinc, manganese, and calcium. The dust particles range greatly in size from 1 to more than 300 ~m, but most particles are about 1 to 6 ~m. Larger particles. about 20-50 um across. also are present. They are predominantly spherical in shape, but some are cenospheres, and others are more angular particles, some of which are broken spheres and cenospheres. Their internal microtextures exhibit evidence of liquid immiscibility, exsolution, skeletal crystal growth, and oxidation react i on rims. Because EAF dusts have been classified by EPA as hazardous wastes, there is heightened interest in the treatment of these dusts to render them non-hazardous. The mineralogy of products of pyrometallurgical treatment of EAF dusts by flash furnace and pyrohydrolysis are currently under study.

Jan 1, 1991

By Thomas P. Battle

Modern-day direct reduction of iron first developed as a small-scale, low capital and operating cost alternative to the blast furnace. Since commercialization of continuous DR technology in the late 1960s, the market for the products of direct reduction has grown to more than 74 million tonnes in 2012. The initial advantages of DR plants over BF facilities have grown over the years, for several reasons, including the increased size of DR modules, lower energy and emissions (particularly CO2), along with the flexibility to use a number of different reductants. The development of DR technology over the past forty years will be emphasized in this presentation, including recent developments that allow for even more direct sustainability comparisons with the iron blast furnace – and even combine the two technologies for improved synergies. Also briefly discussed will be the possibilities of using direct reduction for non-ferrous ores.

Jan 1, 2014

By D. E. Woolley

The rate of reduction of iron oxide from calcia-silica-alumina slag by carbon in liquid iron has been measured over the temperature range 1400-1600°C by monitoring the rate of carbon monoxide (CO) evolution. Slags containing ferric iron have been used in order to study the reduction of both ferric and ferrous cations. Results show that ferric iron is reduced before ferrous iron, so that the ferrous iron concentration increases initially. It is also shown that the rate constant, k, decreases at low reaction rates, or, equivalently, at low concentrations. The authors conclude that the reaction occurs in two periods. During the first period, ferric iron is reduced to ferrous iron. During the second period, ferrous iron is reduced to metallic iron, and the rate-limiting step during the second period is the mass transfer of ferrous cations in the slag phase to the slag-metal interface.

Jan 1, 1998

By Jay Black

In the thiosulfate gold leaching process gold is oxidized to Au+ by a copper(II) ammine catalyst and complexed by thiosulfate. Copper(I) complexes, formed during gold oxidation, are reoxidised to Cu(II) complexes by oxygen. In this study, we present the results of a spectrophotometric study of the Cu(I)-NH3-Cl system, which follows on from our recent investigations of speciation in the Cu(I)-Cl and Cu(I)-S2O3-Cl systems and is part of a detailed study of copper(I) speciation associated with the gold leaching process. Formation constants for Cu(I)-NH3-Cl complexes have been determined by modeling the systematic changes in the UV spectra that occur as the concentration of the components is varied. The analysis of the data indicates that three Cu(I)-ammonia complexes are present, i.e., [Cu(NH3)2]+, [Cu(NH3)Cl2]- and [Cu(NH3)2Cl] and their respective log Kf values are 11.13, 8.33 and 10.79 at 25°C. Investigations of the oxidation of Cu(I)-NH3-Cl solutions by oxygen in the atmosphere are also presented. These experiments indicate that the reaction of copper(I) complexes progresses through various intermediates. The presence of many copper(I) and copper(II) complexes in ammonia thiosulfate solutions complicates the task of determining optimal conditions for gold leaching. Further studies are needed to identify the complexes and chemical processes that are important in the Cu(I)-NH3-S2O3-Cl system.

Jan 1, 2003

By Muammer Kaya, Sait Kursunoglu

"The aim of this study was to investigate the effectiveness of ascorbic (C6H8O6) / oxalic (C2H2O4) acid as a reductant for the simultaneous recovery of zinc and manganese from a spent and mixed zinc-carbon and alkaline battery powder in sulphuric acid leaching. The effects of sulfuric acid concentration, ascorbic/oxalic acid dosages, reaction temperature and leaching time on the zinc and manganese dissolutions were investigated according to 2k full factorial experimental design; then, a simple optimization study was carried out for the best reductant. The optimum reductive acid leaching conditions were determined at 3 hours leaching time, 70°C leaching temperature, 0.5M sulfuric acid concentration, 13 g/L ascorbic acid dosage, 1/20 g/mL solid/liquid ratio and 200 rpm stirring speed. Under these conditions, the dissolution efficiencies were 99.9% for Zn and 99.3% for Mn. When our results were compared with the previous results, our findings were better than previous studies.In addition, the manganese dissolution kinetics was undertaken, and the activation energy was found to be 7.04 kJ/mol. Selective precipitations of Zn and Mn from acid solutions were carried out using NaOH and KOH. Using 3M NaOH as precipitating agent at room temperature and at pH 8; 95.4% of Zn and at pH 10; 93.7% of Mn were precipitated from the leaching solution. Under the same conditions, using 3 M KOH at pH 8; 91.6% of Zn and at pH 10, 96.4% of Mn were precipitated. Based on the experimental results obtained, an appropriate flow sheet was proposed to recover zinc and manganese."

Jan 1, 2012

By M. Hamamoto, S. Tanaka, K. Noda

"Tamano Smelter or Hibi Kyodo Smelting Co. Ltd. is operating with the Tamano Type Flash Smelting Furnace method which is a flash smelting furnace without slag cleaning furnace but which can discharge a slag equivalent to that from the slag cleaning furnace and with the development or coke combustion technology which is the basis of this world's only one type flash smelting furnace process, the smelter exhibits a low operation cost under high productivity operation. Utilizing this experience and improving it we have developed and put to practice an operation guide system using a general purpose computer in order to further establish s stable operation. In this paper these improvements are described. Background of System DevelopmentWith the recent rapid progress of general purpose computers and improvements in their performance an environment for the use or computer in process simulation at low cost and simple operation has been established. If an accurate operation simulation can be done with the Tamano Type Flash Smelting Furnace the merits would be very great and thus we started development of the system. The official name of this system is Computer guide system for Coke Combustion in the T-FSF and taking the initial letters we call it CCCT. We aim to achieve operation with stable mane grade, temperature and slag loss in the furnace by maintaining the most suitable combustion conditions of concentrate and coke in the flash furnace with the assistance of CCCT to the flash smelting furnace operators.Through several production expansion projects clone in the past by oxygen enrichment the copper concentrate treatment quantity and matte grade have increased step by step as shown in Figure I. Following this increase the difference between the operation calculation results al the initial stage of coke combustion and the actual behavior of furnace (matte grade. temperature in the furnace. etc.) gradually became bigger. Further operation procedures taken by different operators against the same phenomenon were sometimes different depending on each individual, which from time to time caused the operation to become unstable. Prior to the development of the system we checked out thoroughly the weak points of operation calculation procedures which were in practice until that time. The results were analyzed and study was carried out to establish a most suitahle operation calculation procedure and finally we reached this system"

Jan 1, 2000

By Yoshio Waseda, Tetsuya Uda, Tom H. Okabe

"Halide salt has been tested as a reductant for producing titanium powder directly from TiCl4. From the results of thermodynamic investigation for several rare earth chloride systems, DyCl2 was found to be used for the reduction of TiCl4 instead of the conventional metallic reductant. When TiCl4 was fed into molten salts containing DyCl2 at 1073K, titanium powder of several ten micron meters in diameter was obtained. In contrast to the sponge titanium produced by the conventional Kroll process, the present new process using a halidothermic reduction in a reactive molten salt appears to be suitable for producing metal powder. From the thermodynamic point of view, the resultant DyCl3 can be reduced to DyCl2 by magnesium. By utilizing the multivalent halide redox couple, some possible ways of titanium powder production directly from TiCl4 by magnesiothermic reduction are shown to be feasible. This can also be applied to the development of a new continuous titanium reduction process.1 IntroductionTitanium and its alloys show attractive mechanical properties such as strength-to-weight, rigidity-to-weight ratios and excellent corrosion resistance. Nevertheless, the application of titanium alloys is limited compared to other structural materials (e.g. steels, aluminum alloys) because of its high cost of production. Currently, almost all of titanium is produced by metallothermic reduction of TiCl4 by magnesium (Kroll process)[1] in an airtight metallic reactor. This process is batch type and labor intensive. Therefore, many attempts to develop new process for producing titanium are investigated so far."

Jan 1, 2000

By Katia Vutova, Vania Vassileva

Investigations and results on the refining of tungsten scrap applying electron beam melting (EBM) in vacuum are presented and discussed. In this work EB melting experiments were performed in single or double-melt operations with different power inputs and refining times for tungsten purification and recovery of multiple metals (including refractory and other metals such as Mo, Nb, Cu, Zn, etc.), which are alloyed elements or impurities with high concentrations in the initial materials. Evaluations for extraction of some valuable metals, generated in the condensate at their removal from the liquid metal during the refining process are provided. Efficient technological regimes for e-beam melting and refining that enable the simultaneous production of pure metal ingots and condensates that can be used directly or can be used for subsequent extraction of expensive and valuable metals are presented.

Jan 1, 2016

By Eric J. Grimsey

Nickel smelting and converting can be viewed as processes in which iron is either partitioned or transported between matte and slag. Metal recovery depends on the mass of iron transported to slag, the thermodynamic environment in which the transport is made, and the extent to which the slag, once formed, is left in contact with the matte. The importance of these effects is discussed with reference to a new equation which describes metal recovery in terms of a mass balance and a thermodynamically related parameter which is easily measured in practice.

Jan 1, 1993

By H. Ikeda

The new Onahama N0.3 tankhouse was put into operation early in 1973. This new tankhouse, which has a capacity of 90,000 metric ton cathode per year, is distinct in many important respects from conventional tankhouses. The major objectives in design were to simplify the construction and ope- ration for reduction of the costs for labor, interest and depreciation and also to reduce the copper inventory in the tankhouse by the use of conti- nuously-cast anodes. As a result, the investment cost was decreased by approximately 30% and the inventory cost by approximately 600, while the production per unit area of the tankhouse was increased by 80 - 100% as compared with the existing conventional-type tankhouses at Onahama. By abolition of cell inspection and maximum mechanization of materials handling the labor cost was decreased by as much as 80%. On the other hand, the new system has some disadvantages, such as increase in anode scrap ratio and increased cost of anode casting. The No.3 tankhouse system is, however, still at its starting point, while conventional methods have been continuously improved over the past years of operation. It is expected that the innovational ideas behind this system will serve as bases for a more efficient electrolytic refining system in future.

Jan 1, 1976

By Axel Hoppe

Although Tantalum is not usually regarded as a precious metal, its pricing structure is very similar to that of Silver. Different from precious metals, Tantalum has only industrial applications and its use is about 1000 metric tons per year. The intrinsic value of Tantalum already in .the past was a driving force for its recycling. Based on these facts the Tantalum industry world-wide is approaching the closed-loop concept of its recycling. A detailed material flow of Tantalum processing as well as recovery of residues and used products will be discussed.

Jan 1, 1995

By Alicia Esther Ares

This study was conducted to investigate the directional solidification of Zn-20%A1 and Zn20% A1-1O%Si-3o/oCu alloys under different conditions of heat transfer at the metal/mould interface. The type of structure obtained in both cases was analyzed and related to the solidification thermal parameters such as cooling rate, growth rate, thermal gradient and recalescence which were determined from the temperature versus time curves. These parameters were correlated with the structure-like length of columnar grains and size of equiaxed grains. The metallographic analyses were done performing quantitative metallography and composition analysis of the different alloying elements along the cast samples by SEM (Scanning Electron Microscopy) and EDXA (Energy Dispersive X-Ray Analysis). Correlations between properties, structures and thermal parameters were found.

Jan 1, 2008

By Zizheng Zhou

The separation of cobalt from other base metals can be achieved using diffusion dialysis in a two-compartment reactor separated by an anion exchange membrane. In this work, a Neosepta AFX membrane was used to study the separation of various metals in an acid-chloride solution. The separation of one metal from another was investigated on the basis of the various chloro-complex stabilities. The metals investigated included cobalt, nickel, copper(II), iron(III), aluminum, zinc and cadmium. The impact of several critical experimental conditions, including the initial metal and chloride concentration in the feed solution and their initial concentration in the receiving solution, on the separation factor and the metal transfer rate is reported in this work. Effective separation of different metal pairs was achieved under the experimental conditions.

By Takuya Shinagawa

After vitrification of the residues from a municipal solid waste incinerator, the vitrified products can be used as a construction material, and the dust can be used as raw materials for the non- ferrous industry. The NKK electric-resistance furnace is operated under a reducing atmosphere, and heavy metals such as zinc and lead in the ash vaporize to form dust. Also, dust from the NKK electric-resistance ash melting furnace is composed of water insoluble zinc and lead components and water soluble NaCl and KCI. This is why, The concentration of zinc and lead in the dust after washing is sufficiently high for the dust to be used as a raw material for the zinc and lead industry. NKK developed a heavy metal recovery process in which zinc and lead in the dust are reclaimed as a raw material for smelting by making the best use of the characteristics of the dust.

Jan 1, 2002

By Rodney J. Ishak

The reduction of Mn3O4 to MnO has been investigated in a thermobalance apparatus. The charge was composed of manganese ore (decomposed by heating/calcination or pre-reduction to mainly Mn304) and coke. The material was charged to a crucible, which was suspended in the balance. CO-gas was distributed through a grid in the bottom of the crucible. Two sizes of ores were used; 2.4-4.8 mm and 6.7-9.5 mm. Coke particles were in the size range 4.8-6.7 mm. Experiments were conducted in the 900-1100°C temperature range. The composition of the product gas was monitored continuously. External mass transport between bulk gas and particle surface does not seem to limit the rate of reduction. Assuming that both diffusion through product layer and chemical reaction at the interface between MnO and Mn304 are rate controlling, the data was tried both in a shrinking core model and in a grain model using regression. The grain model gives the best physical description of the process, because the reactant is in fact a porous medium. With this model the effective diffusivity was calculated to be in the 1.5-6.10-5 m2/s range. The pore size was mainly between 0.1 and 10 um.

Jan 1, 2003

By K. A. Brunk

Newmont&apos;s research, operations, history and experience with pre-treatment of preg-robbing carbonaceous ores are described, with emphasis on the chemistry, physics and kinetics of chlorine treatment. Present operations, control strategy and projected changes are also described, including a summary of the adsorption of chlorine into pulps and off-gas scrubbing. Conditions of chlorination have been optimized by the use of Eh-pH diagrams of the gold-chlorine-water system, and have resulted in significant increases in gold recoveries and decreases in chlorine consumptions.

Jan 1, 1987