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By N. Moelans

A method using an ex-situ electrochemical measurement device was developed to determine the oxygen potential of non-ferrous metallurgical slags. The electrochemical cell consists of the molten slag sample, an inert Ir electrode, a stabilized Zr02 solid electrolyte and a NiINiO reference electrode. Different slags from non-ferrous pyrometallurgical processes were analysed at 1100 and 1200°C and pO2 values between 10-3 and 10.12 bar were obtained. The measurements were evaluated with? thermodynamic calculations and using processing considerations. It was found that the reproducibility and stability of the measurement was significantly improved by shielding the molten slag from the atmosphere by a thin layer of carbon, especially for slags with a low oxygen potential.

Jan 1, 2003

By I. S. Escobar

Copper, particularly the oxygen-free grade Cu-OFP, is a candidate material for containers for the long-term isolation and disposal of high-level radioactive waste (HLW) in underground repositories. After having been buried for a few hundred years, all oxygen will have been consumed in the repository, and corrosion of the copper will be caused entirely by contact with dissolved sulfides. Chloride is another potential corrodant, but in deep repositories where groundwater is neutral or slightly alkaline, the effect of chlorides can be ignored on thermodynamic grounds. Thus, the corrosion of copper in the presence of sulfide ion and under reducing conditions has been studied using cyclic voltammetry and Tafel slope measurements. It is possible to determine the effect of sulphide ion on copper corrosion resistance which is minimized at low temperature and also at low sulphide concentration. The presence of anions such as HCO3 under environmental conditions produces a beneficial effect because these ions are inhibitors.

Jan 1, 1999

By Robert D. Boiler, Bill Wilkie

"There is a wide choice of different types of woven filter media for hundreds of different filtration applications. Factors such as type of fiber, synthetic polymers used, weave style, fabric finishes and fabrication techniques all play an important part in selecting the best choice for a specific type of filter and process application. The purpose of this paper is to offer some basic knowledge of these factors and how they can impact the performance of a filter, the life of the media and the overall cost of operation through case studies of actual plant filtration applications.IntroductionThe use of woven filter cloth in liquid/solid separation applications is generally well known. Woven filter cloth, by the nature of the weaving process, offers unique consistency and repeatability when compared to some other filter media such as needled felts, papers, sintered structures and knitted cloth. This unique consistency and repeatability is particularly applicable to woven filter cloth produced using monofilament fibers. These fibers are consistent in shape and form the basis for a woven cloth with predictable pore size and throughput characteristics. Woven filter cloth can be used in most wet filtration applications. Typical examples are the separation of chemical and pharmaceutical solids from process liquors, waste stream solids capture, liquid foods clarification, mining separations, and polymer filtration.EnvironmentOne of the first considerations is the environmental demand of the given process. Though it is tempting to look immediately at the particles in a filtration process, it is often better to consider some of the more basic needs of the system. There are numerous materials available, both synthetic and wire cloth. Each has its own unique set of properties."

Jan 1, 2012

By Kevin L. Purdy

The Process Technology Center of Phelps Dodge Mining Company (PDMC) .operates several test facilities in support of PDMC's hydrometallurgical operations. Installations for small leach columns, 15 cm. to 60 cm. (6 in. to 24 in.) in diameter, and large leach columns, 1.8 m. (6 ft.) in diameter, are complemented by a test facility for SX/EW operations. The history of and reasons for the development of these facilities: are described and original standard equipment is discussed. A primary goal in constructing these facilities was achieving a high degree of flexibility to allow for testing of new equipment and new leaching and SX/EW technologies as they are developed. Along with this challenge, construction of a filly integrated SX/EW test facility on a small scale brought its own set of challenges.

Jan 1, 1999

By Alireza Zakeri

To evaluate the behavior of minor elements in the copper smelting process, activities of silver, selenium and tellurium at minor concentration were determined at 1473 K within the miscibility gap of the Cu-S-Me (Me = Ag, Se, Te) and Cu-Fe-S-Me systems varied in Fe/Cu ratio. Phase relations between the immiscible metal and matte phases in the foregoing systems were first established by a quenching technique at 1473 K to supplement the activity measurement data. A Knudsen-effusion mass spectrometer, capable of handling complex gaseous systems and relatively small vapor pressures, was adopted for activity determination. Using a multiple Knudsen-cell, the ion intensity of minor element in the sample under study was measured simultaneously with that in a reference sample. Activity was obtained from the ratio between the measured ion intensities as well as the known activity value of the minor element in the reference sample. Limiting activity coefficients of the minor elements were correlated with composition of the matte. Based on the experimental results, the vaporization behavior of the minor elements has been discussed.

Jan 1, 1999

The reported values of the standard reduction potentials of the Au(NH3)2+/Au(0) and Au(S2O3)23-/Au(0) couples are reviewed to emphasise the experimental difficulties associated with the measurement of reliable values for these quantities. The standard reduction potential for Ag(I)/Ag(0) in ammonia and thiosulphate solutions measured at ionic strength 0.1 and 25oCis used to predict the following relevant stability constants () for gold complexes based on the linear free energy correlations: Au(NH3)2+2 = 1013, Au(S2O3)23-2 = 1024 and Au(NH3)43+4 = 1033. The equilibrium constant ( 10-11) for the reaction Au(S2O3)23- + 2NH3 = Au(NH3)2+ + 2S2O32- based on these stability constants is in reasonable agreement with the measured value (10-9) based on potentiometric and spectroscopic data when excess ammonia was added to a solution of Na3Au(S2O3)2. This also indicates that the stability constant of Au(NH3)2+ is 9 to11 orders of magnitude less than that of Au(S2O3)23-. Relevant species distribution and Eh-pH diagrams based on the revised data are presented.

Jan 1, 2003

By Michael G. King

The primary non-ferrous metals industry is the principal supplier of the minor metals selenium, tellurium and bismuth. It is also a major supplier of antimony. These minor elements are recovered from by-products of base metals production. To ensure that these elements remain available, the cost of production must be compatible with four other factors - method of production, available supply, technological niches, and product stewardship. This paper first describes the relationship between the copper industry and the production of tellurium and selenium. The more complex relationship between the lead industry and bismuth production is then discussed, followed by comments on antimony availability. Product stewardship programs are essential to the growth or certain specialized markets for these metals. Smelters and refineries of non- ferrous metals will play a major role in the recycling of scraps and wastes from these markets. Examples on how such materials can be recycled are given in the paper.

Jan 1, 1995

By Paul Dewison

For nine years, from mid-1987 to mid-1996, the copper market enjoyed what appeared to be an endless boom in which prices were much higher relative to production costs than for most other base metals. After the boom ended abruptly mid-1997 with the Sumitomo affair, copper was burdened by an overhang of new projects that promised to swamp demand in what, with the Asian financial and economic crisis of 1997, had become a considerably worse consumption environment. Now, demand prospects do not look so bad. If, as we suspect, we will be dealing with a more rational market in the future, it becomes all the more important to forecast accurately the prospects for consumption. In this paper, we present a new methodology for copper demand forecasting. The methodology forms the backbone of the demand-side analysis for the multi-client study entitled "Long Tenn Outlook for Copper", co-authored by Metalica Ltd. and Bloomsbury Minerals Economics (BME). Key components of the methodology are as follows. (1) Relate demand to economic structure. (2) Focus on products rather than refined consumption. (3) Apply a consistent products/applications analysis to all countries and time series. (4) Incorporate scrap market dynamics within the analytical framework.

Jan 1, 1999

By Chuan-fu Zhang

The fibrous precursor can be obtained by coordination precipitation process, using oxalate, cobalt chloride and ammonia. XRD pattern of precursor precipitated at pH=9.0 is different from that of ß-CoC2O4?2H2O precipitated at pH=1.0 which indicates that the precursor powders are one type of cobalt complex. According to the results of element analysis and IR spectra, it can be inferred that the composition of the precursor is [Co(NH3)x]C2O4?H2O(x=1.2?..6) formed by the coordination reaction at pH=9.00 in the Co(II)-C2O42--NH3-NH4+-H2O system. It?s found that the fibrous cobalt powders greatly inherited the morphologies of the precursors. Many factors could affect the formation of the fibrous cobalt precursor powders, such as the initial Co2+concentration, pH value and so on. The SEM images show how they influence the morphologies of the precursor powders. By adding proper surfactant, the dispersion of the precursor powders would be improved. At last, the final product-fibrous cobalt powders which are about 0.3~0.5min size and 40~60 in aspect ratio were produced by thermal decomposition of fibrous cobalt complex at 400~500°C in the weak reducing atmosphere.

Jan 1, 2006

By Michael Stelter

Lead alloys are a typical material for anodes in technical electrowinning processes. The life time of those anodes differs from 2 years to more than 5 years in tankhouse practice depending on the type of alloy, the mechanical damaging and last but not least the chemical corrosion in the electrolyte. Different types of alloys, such as PbSb, PbCa, PbAg, PbSnCa or PbAgCa have been developed and used in the past, their rate of corrosion being more or less a philosophic discussion. Comparable investigations on the corrosion behavior in dependence of the concentrations of alloying metals, the grain structure and the mechanical and thermal treatment during production have not been conducted before. In the last years the Institute for Nonferrous Metallurgy and Purest Materials of the TU Bergakademie Freiberg investigated the corrosion behavior of the typical lead alloys for metal electrowinning under comparable conditions. Correlations between different alloys, mechanical treatments like rolling or thermal treatment like annealing to the rate of corrosion were made, leading to the conclusion that grain structure and grain size are of eminent importance for the rate of corrosion in technical electrolytes. From these results new and optimized lead alloy anodes can be produced with an increase in life time of the factor 3 ? 5. The optimized lifetime in terms of corrosion stability can not protect from mechanical damaging in tankhouse practice, but with a careful practice the increase in lifetime can save a lot of money and problems.

Jan 1, 2006

By Shadia J. Ikhmayies

"Nanocrystalline fluorine-doped tin oxide, SnO2:F, thin films were prepared by the spray pyrolysis (SP) technique on glass substrates. The films were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), X-ray dispersive spectroscopy EDAX and transmittance measurements. X-ray diffraction patterns revealed the nanocrystalline nature of the films where the grain size was estimated based on the Sherrer formula. SEM micrographs showed that the films are uniform and totally covered with the material and they confirmed the nanocrystalline nature of the films. The absorbance was deduced from the transmittance measurements, and its first derivative was used to estimate the optical bandgap energy. Bandgaps larger than the bandgap of the bulk SnO2iF were obtained, indicating the presence of quantum dots. The hyperbolic band model was used to estimate the radii of the nanocrystallites. A comparison between the results of the different methods was performed.IntroductionTin oxide, SnO2, thin films are n-type semiconducting, transparent materials, which have numerous important applications in optical-electronic device technology. The optical transparency of SnO2, together with its chemical and mechanical stability, makes SnO2 films suitable for many other applications, such as transparent conductive coatings, gas sensors and heteroj unction solar cells [1]. In particular, SnO2 thin films have drawn much interest because of their potential application and integration with microsensor devices. Considerable attention has recently been focused on the development of solid state gas sensors based on thin films with a crystallite size smaller than the Debye length of the material, which show increased gas sensitivity and short response times [2]. In many of these applications, a doped SnO2 film is used as an active layer. Among the various dopants, fluorine is often preferred, because fluorine doping results in films with high transparency and good conductivity [1]."

Jan 1, 2012

By Kouji Mimura, Masahito Uchikoshi, Minoru Isshiki

"HfO2 is expected to be a gate dielectric used in ULSI alternatives to S1O2. Although the materials used in ULSI are required to be significantly pure, commercial Hf contains > 2 mass% Zr. It is important to establish a process for removing Zr from Hf. In the present study, anion-exchange separation using a multi-column method was employed. The separation tests were carried out at variety of temperatures and flow rates. The decrease in the flow rate of the mobile phase made the elution curves of both Hf(IV) and Zr(IV) broaden contrary to the case of Co(II), Cu(II), or Fe(III). This is caused by the difference in adsorption rate on the anion exchange resin. In addition, more than one column was connected in series in order to enhance the separation. As a result, the content of Zr(IV) was successfully reduced to 1/100 of that relative to the raw material.IntroductionHafnium is one of the most important materials in modem society. The main applications of Hf metal are as a control rod in a nuclear reactors because of its large neutron-capture cross-section and as an additive to various alloys because of its corrosion resistance [1]. In addition to those applications, attention has been recently paid to HfCh as a high-x"" dielectric used in ultra large scale integration, ULSI, as well as ZrCh, AI2O3 and La2C>3, which are expected to be alternatives to conventional S1O2 thin films [2].The materials used in ULSI are required to have a high purity in order to avoid unexpected errors due to impurities. Furthermore, high purity Hf is indispensable for investigating the intrinsic properties of Hf metal. Thus, it is significant to establish the purification process for Hf from both the industrial and academic perspectives."

Jan 1, 2012

By Mrutyunjay Panigrahi, Takashi Nakamura, Atsushi Iizuka, Etsuro Shibata

"The production of FeTi intermetallic alloys from mixed oxide precursors using direct electrolytic reduction was studied. Fe203 and Ti02 powders were mixed in appropriate molar ratios, pressed into small pellets, and then heat treated at temperatures in the range 1000-1300°C. The pellet heat treated at 1000°C was electrolyzed in molten CaCh at 950°C, using a graphite crucible as the anode and the oxide pellet as the cathode, at a potential of 3.0 V. The products of the electrolytic reduction of (Fe,Ti) oxide were examined by XRD, SEM and EPMA. It was found mat the (Fe,Ti) oxide was reduced progressively from the outside to the inside of the pellet until the metallic state was achieved.IntroductionFast and energy-efficient technologies for materials production are essential for the sustainable development of society, and such development is supported by advanced technologies. Since the introduction of titanium and titanium alloys in the early 1950s, these materials have, in a relatively short time, become major materials for the steel, aerospace, energy, and chemical industries. Its combination of a high strength-to-weight ratio and excellent mechanical properties and corrosion resistance make titanium the best material for many critical applications [1]. Titanium alloys are now used in demanding applications such as static and rotating gas-turbine engine components. Some of the most critical and highly stressed civilian and military airframe parts are made of titanium alloys. The use of titanium has expanded in recent years to include applications in nuclear power plants, oil-refinery heat-exchangers, marine components and medical prostheses.Ferrotitanium is one of the most widespread and effective ferroalloys. It is also a well-known hydrogen-storage material and will be extensively used in the future because hydrogen is emerging as an eco-friendly energy source [2], Ferrotitanium is an alloy consisting of iron and titanium, with a minimum titanium weight content of 20% and a maximum titanium weight content of 75%, and is manufactured by reduction or melting."

Jan 1, 2012

By P. M. Tait, N. A. Warner

"The refining of thermally produced zinc is currently performed using a highly energy intensive and arguably outmoded process, distilling zinc under atmospheric pressure at temperatures of 900°C to 1000°C. In order to produce refined zinc more profitably and with less environmental impact a new process has been proposed. This process is generic to all thermal zinc smelters and aims to match the purity of zinc from current technology (99.99%-99.999%). The objective is to perform all separation processes using only the heat contained in the smelter product stream. Vacuum conditions are extensively used lowering operating temperatures and enhancing separations. As part of this process zinc is distilled under vacuum from high concentration obtaining a refined product with respect to lead content. A mathematical model has been developed from fundamental principles to describe this stage, the distillation of zinc across a temperature difference between two circulating zinc streams in open channels under vacuum. Heat for the distillation is supplied by the liquid phase, necessitating a large recycle to maintain high operating temperatures, and keep zinc concentrations high. In determining this model and the operating conditions required, relationships between temperature, pressure and composition are considered.IntroductionCurrent technology (the Refluxer) used to refine thermally produced zinc is both expensive and highly inefficient. At present 80% of the worlds zinc is produced via the electrolytic process reflecting the poorer performance of the thermal route, the zinc-lead blast furnace and Refluxer. A new process is proposed to overcome the drawbacks of current processes. These drawbacks are both economic and environmental. The Refluxer requires 6.6 GJ of energy to refine one tonne of SHG zinc 1, other disadvantages of the Refluxer stem from high operating temperature, around 900°C, and liquid zinc being highly corrosive towards ferrous metals. The Refluxer is constructed from silicon carbide sections which join together by means of flat machined faces making liquid metal leaks inevitable. The Refluxer columns are very sensitive to thermal cycling, thermal shock and mechanical vibration, which easily lead to structural failure. To avoid thermal stress on the columns the feed rate and feed temperature need to be kept constant which means the feed baths to the columns must be able to accept solid and liquid feed as the Refluxer has to operate when the smelter is shut down."

Jan 1, 1998

By Richard Jack De Klerk

The standard industrial method of arsenic removal from acidic aqueous processing effluents involves coprecipitation of arsenic with ferric iron (Fe/As>3) by lime neutralization in continuous circuits. To better understand current industrial practice, continuous circuit coprecipitation experiments were performed to identify industrially relevant process parameters and co-ion solutes that contribute to improved arsenic removal and retention. The coprecipitated solids were subjected to accelerated ageing at 20°, 40° & 70°C and arsenic behavior was monitored and modeled. Staging and the presence of calcium ions were found to have the most significant impact on arsenic retention. In this paper the techniques used and major results obtained are discussed.

Jan 1, 2008

By Shunhong Huang

To improve understanding the effect of heavy metal chromium on soil biota, laboratory incubation experiment was carried out in the soils contaminated artificially with five concentrations of chromate (50, 250, 500, 1000 and 2000 mg kg_1 soil) over time (35 days). The population and diversity of bacteria, fungi and actinomycetes in soils were measured as indicators of soil microbial processes in the disturbances mentioned above. Incubation experiment results elucidated that the population and diversity of microorganisms decreased with increasing Cr (VI) concentration. Furthermore, various microorganisms showed different sensitivity to total Cr contamination. The sensitivity of microbial population to chromium contamination was in the order: actinomycetes >bacteria>fungi. The resulted implied that the microorganism can be used as an indicator of chromium contamination.

Jan 1, 2008

By Shanlu Yang

In this study, laser-GTAW hybrid welding was used to the lap joint of galvanized dual-phase (DP) 980 steel in a gap-free configuration. The effects of welding parameters such as the laser power, the distance between the laser beam and the electrode torch, the arc current on the quality of hybrid welds were fully studied. The reason for the formation of different weld defects arises from the development of the highly-pressurized zinc vapor at the interface of two metal sheets. Experimental results demonstrated that the elongated molten pool introduced by the GTAW can suppress the formation of spatters to some extent. However, the hybrid laser-arc welding process still suffers from a large amount of spatters that degrade the weld quality. Furthermore, it was found that the weld quality was enhanced with the increase in the laser beam-arc distance and welding current.

Jan 1, 2009

By O. G. Rivera, R. D. Moser, P. G. Allison, W. R. Whittington, P. Rivera-Soto, Z. McClelland, D. Francis

This research examined the evolving microstructure of quasi-static and dynamically loaded fully annealed metastable 301 austenitic stainless steel (SS). Experiments were performed to an interrupted strain value of 20% and to failure using a tension Kolsky bar (1000/s) and an electromechanical load frame (0.001/s). Electron Backscatter Diffraction (EBSD) identified the microstructural evolution from the as-received condition to the 20% strain level for the high and low rate interrupted samples. This material achieved over 60% elongation to failure with increasing strength as strain rate increased, as expected. Fractography analysis using SEM showed particles in the microstructure and a ductile failure mode. The 301 SS exhibited a greater amount of phase transformation from parent austenite to -martensite at the dynamic strain rate when compared to the quasi-static strain rate during the interrupted experiments. This result is indicative of the increased propensity for austenite to -martensite phase transformations at the high strain rate.

Jan 1, 2016

By Xingming Zhang, Huawei Zhang, Yanxiang Li

"A hybrid porous metal with nano-micro double scale pore size and regular-random bimodal porous structure has been fabricated by unidirectional solidification of a lotus-type alloy followed by dealloying treatment to the base alloy. The base alloy selected is a Cu-Mn binary alloy. The lotus-type porous Cu-Mn alloy with straight pores of several hundred micrometers in diameter was manufactured by unidirectional solidification with a mould casting process. Dealloying treatment was then done to the lotus-type porous structure of Cu-Mn alloy. The solid Cu-Mn alloy wall of the lotus-type porous structure was transformed to random porous structure of dozens to hundreds nanometers. The influence of corrosion parameters, such as the current and time in electrochemical corrosion, temperature and corrosion agent in chemical corrosion, on the nano-porous structure formed has been studied systematically.1. IntroductionA hybrid porous metal is a kind of cellular structure with different porous or cellular forms inside, which possesses special properties and can be applied in many fields as fuel cells, catalysis, sensors, etc. Several means have been developed to fabricate this kind of porous material [1-2]. In this paper, a novel process of Gasar plus dealloying is introduced to fabricate a new form of hybrid porous metal with nano-micro double size and regular-random bimodal structure.The Gasar process, also called the metal-gas eutectic directional solidification, that invented by Shapovalov [3] in Ukraine and now in USA some twenty years ago, is used to fabricate porous metals with regularly aligned pores basing on the solubility difference of a gaseous element in solid and liquid metal. Nakajima and his colleagues [4] in Japan studied this process further and called this kind of structure a lotus-type porous metal. They put more attention to various fabrication techniques and properties of lotus-type porous metals. Li heading a group [5-6] in P.R. China studied the mechanism of Gasar process and process controlling techniques. The Gasar pore structure and porosity can be controlled by processing parameters, and a regular Gasar structure with oriented pores distributing uniformly in the solid matrix can be obtained under optimized processing parameters."

Jan 1, 2014

By Dengfu Chen, Yi Yang, Chunmei Chen, Mujun Long, Shikai Gong, Junhao Sheng, Tao Liu

The relationship between thermo-physical properties of petroleum coke and temperature is of importance for determining of the operating parameters during the calcining graphitization process. In this paper, the variations of thermo-physical properties of petroleum coke versus temperature were investigated, such as the DSC-Tg curve, the specific heat capacity, the thermal diffusion coefficient, the thermal conductivity, and so on. The thermal analysis curve of petroleum coke showed synchronous thermal hysteresis at higher heating rates, indicating that a larger heating rate will cause delay of thermal effects. The thermal diffusivity of petroleum coke decreased during the calcining process. With increasing temperature, coefficient of heat conductivity and specific volume heat of the petroleum coke increased with a decreasing variation rate. The research provides a database for the calcining graphitization process of petroleum coke.

Jan 1, 2015