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During electrowinning of nickel chloride, hydrochloric acid was regenerated instead of chlorine in a two membrane cell, by segregating the chloride catholyte with an anion exchange membrane, and the sulphate anolyte with a cation exchange membrane from the middle electrolyte (ampholyte) compartment. Successful operation of such a cell depends on controlling chloride leakage through the cation exchange membrane to the anolyte. Small amounts of chlorine gas could be detected in the oxygen evolved at the anode. In this paper, the chloride. leakage as a function of various types of cation exchange membrane and different composition of the anolyte is reported and discussed. Ag+ was added to the anolyte to eliminate chloride leakage to the anode. The cell voltage, electrode potential and voltage drop over the membrane as a function of current density has also been investigated.

Jan 1, 1996

By Hans Jürgen Maier, Gregory Gerstein, Florian Nürnberger

Microstructural analysis to support the development of material models provides valuable information to design complex forming operations. Damage models such as e.g. by Gurson consider spherical voids only. However, investigations of bcc steels by scanning electron microscopy reveal that voids exhibit an ellipsoidal shape with progressing deformation. The material’s weakening in the Gurson model is taken into account by the void volume fraction. Therefore, a three-dimensional characterization of the void shape offers important data for modelling. Thus, information on the anisotropy of the process of void evolution and accordingly, about the anisotropy of the deformation process is provided. Application of the information regarding the void shape anisotropy within the Gurson model is discussed.

Jan 1, 2016

By Zhao-cheng Liu

Iron oxide red pigment powders of high quality were synthesized from pyrite cinders. Iron ox-ide red pigment powders were synthesized by hydrothermal method from the precursor of Fe(OH)3 and Fe(OH)2 colloid, which were obtained after ammonia solution reacted with acidic leaching solution produced by the reaction of pyrite cinders with sulfuric acid. Effects of reaction concentration, reaction temperature, reaction time, pH value and n(Fe2+)/n(Fe3+) on main properties of oxide iron red were studied by experiments. The prepared particles were characterized by means of X-ray diffraction (XRD) and scanning electron microscope(SEM). The results revealed that the synthesized iron oxide red particles were _-Fe2O3 and pseudocubic with particle size of 0.50~0.75µm. Furthermore, the quality of iron oxide red pigment powders reached the first grade of national standard (GB1863-89 ).

Jan 1, 2009

By Donald J. Hallbom

Limonitic nickel laterites slurries exhibit complex rheological properties including time dependency that varies from thixotropy to rheopexy. Chronic problems may occur if plant designers and operators fail to take time dependency into account. Stress decay tests indicate that laterite slurry takes roughly two minutes to approach steady state after a step change in the shear rate. As a result, most rheometer measurements are taken at a non-equilibrium state, making evaluation difficult. Two minutes is also long relative to the time that a unit of slurry in a processing plant is at any given shear state, so the slurry may never reach equilibrium. This paper presents a method to describe the rheology of laterite slurry using a Flow Array, which describes the rheology using an array of instantaneous flow curves crossed by an equilibrium flow curve. A rate equation for structural change in non-equilibrium conditions allows time dependence to be efficiently modeled. This flow array allows the flow behavior of time- dependent slurry to be predicted in non-equilibrium conditions using a simple time-step methodology. Keywords: Rheology. nickel laterite, hydraulic transport, pressure acid leach, flow array

Jan 1, 2004

By N. Menad

The formation of the dioxins can be dependent on the quantities of carbon, hydrogen, chlorine and oxygen present in a given system, as well as on parameters such as temperature and pressure. Inadequate supply of combustion air ( incomplete oxidation ), low combustion temperatures ( incomplete combustion ), and insufficient turbulence in the combustion are factors which can favour their formation. Dioxins were produced also calatytically from chlorinated phenol precursors, non-chlorinated compounds that were chemically, and reaction of phenol with inorganic chloride. In this paper different precursors such as combination of C, H, 0, Cl, rapid formation/combustion intermediates and routes to PCDFs are reviewed, and the influence of PVC amount on the formation of these isomers is discussed.

Jan 1, 2000

By Atsuhiro Nabei, Ken-ichi Yamaguchi

"Wet chlorination process of de-copperized anode slime is followed by de-chlorination stage in which lead-sulfate and metallic silver form silver residue. The silver residue is subsequently reduced to Ag2Se matte and PbO-SiO2 slag to remove lead to the slag in a short rotary furnace. Although this smelting process is proven well in actual operations, few papers have investigated its metallurgical aspects. This paper will describe the effectiveness of controlling parameters adopted at the Naoshima Smelter & Refinery and discuss the decisive factors influencing silver loss to PbO-SiO2 slag.IntroductionThe precious metals plant at Naoshima smelter & refinery was established in 1989, and has produced electrolytic silver, refined gold and platinum-group metals (PGM) from de-copperized anode slime as by-products of electrolytic copper. The process for gold production has been innovated from conventional smelting process to hydrometallurgical process since 2004 [1], while the process for silver production has still remained the same.The process for silver production at the Naoshima smelter & refinery is illustrated schematically in Figure 1. De-copperized anode slime is, at first, concentrated in the froth flotation process, then leached in the wet-chlorination process, and converted to silver residue in the de-chlorination process. The silver residue, which is a mixture of lead-sulfate and metallic silver, is charged to a short rotary furnace for the oxidation roasting to volatilize selenium dioxide and subsequent reduction smelting. In the smelting stage, silver residue and reverts containing selenium are smelted with flux and carbonaceous materials to form PbO-SiO2 slag and Ag2Se matte. Furthermore, Ag2Se matte is transferred to a rotary cupell and oxidized by air with the addition of sodium carbonate and sodium nitrate to produce silver anodes while removing impurities into litharge. Silver anodes are electrolytically refined by the Moebius process. Electrolytic silver is washed, dried and, finally, cast into 30kg-bars."

Jan 1, 2011

By Emma Arakelova

An increase in concentration of a Zn-containing volatile complex for synthesis of ZnO films was investigated when processing their target by ultraviolet radiation emitted by mercury lamp. The experiments were carried out using a flow-type quartz reactor. ZnO tableted target was preliminarily irradiated during 2 to 7 hours. H2O2 (98%) vapor at 25Pa passed through the reactor with ZnO target at 373K. As substrate material, five subsequent quartz cylinders were used at 423K. The experiment lasts 4 hours. H2O2 decomposition on ZnO surface was accompanied by formation of a Zn-containing volatile complex which passed in gas phase and decomposed on the substrates with isolation of final ZnO. The concentration of the Zn-containing volatile complex (N) in gas phase increases with UV pre-irradiation time (t) (without irradiation N = 1.05 1011 particles/cm3; after t=2 hours, N = 5.19 1011 particles/cm3, after t=4 hours, N = 9.95 1011 particles/cm3; after t=7 hours, N = 1.86 1012 particles/cm3.

Jan 1, 2006

By Priscilla Aki Mori de Hanashiro, Viviane Tavares de Moraes, Denise Crocce Romano Espinosa, Hugo Hashimoto

"The LCDs are used in televisions, calculators, mobile phones, computers (laptops and tablets), video games and other electronic devices. The advancements in technology make obsolete these devices, causing excessive disposal of LCDs and therefore decreasing life span of landfills. In this context, the LCDs from LED LCD TVs arise as an additional source of waste electrical and electronic equipment (WEEE). Thus, it is essential to develop LCDs recycling methods, beginning with the LCD characterization followed by displays processing, aiming the materials separation and using some Ore Treatment Techniques, and finally, the recovery of indium using acid leaching. The analysis methods that will be used in this work are: Fourier Transform Infrared (FT-IR) and Inductively Coupled Plasma Optical Emission Spectrometry (ICP-OES).IntroductionLiquid Crystal Display (LCD) technology is applied in modem televisions, calculators, mobile phones, computers and a wide range of electronic devices. It has replaced Cathode Ray Tube (CRT) technology as the most advantageous display product, due to lower electrical power consumption, size and weight reduction, and no radiation emission [ 1]. The constant improving of LCD screen technology reflects on its growing contribution to the amount of waste electrical and electronic equipment (WEEE): an estimated 50 million tons of WEEE are produced every year [2]. Once the most common method of its disposal are landfills, the LCD technology therefore became an environment issue [3].LCD structure is composed by components made by different materials. In order to develop a LCD recycling methodology that gives the right destination to these materials, a previous characterization stage is required. This characterization includes a disassembly process and material identification analysis. One of the LCD components is the screen, which is composed by polymeric and glass layers. The liquid crystal glass was the starting material of this study. It contains indium in the form of indium tin oxide (ITO) film. This ITO film is deposited in the glass by a sputtering process and acts as the electrode material [4,5]. It has in its composition 90% ofln203 and 10% ofSn02 [6]."

Jan 1, 2014

By Beate Ina Jenssen

Ferric iron removal from the nickel electrolyte at Glencore Nikkelverk AS in Kristiansand, Norway, is achieved by precipitation of iron hydroxide followed by filtration, and it is desirable to improve filtration properties of the precipitated iron hydroxide in order to decrease the filtration time. The effect of increasing the residence time from the current 45 min to 75 min and temperature from 65 °C to 90 °C on the filtration properties of the precipitated iron hydroxide (akaganéite) was studied by simulating the industrial process conditions in a continuous reactor setup operating at steady state, using ferrous-containing process solution as feed material. It was possible to decrease the filter cake resistance by both increasing residence time and temperature, but temperature gave the most pronounced effect and reduced the filter cake resistance by one order of magnitude.

By Wayne Bell, Xiaodi Huang, Matthew Andriese, Jiann-Yang Hwang, Zhiwei Peng

"The equations for determining microwave field attenuation length and half-power depth in magnetic materials were derived from Maxwell’s equations. The microwave field attenuation length and the half-power depth for a magnetite concentrate were calculated and the temperature dependence of them was determined. It is demonstrated the microwave field attenuation length and the half-power depth highly depend on temperature and decrease with increasing temperature up to 900 °C. The variations of field attenuation length and the half-power depth with temperature indicate the microwave power attenuates much faster than the field strength in materials. The evaluations of field attenuation length and microwave half-power depth can be used to characterize the microwave dissipation behaviors in the sample and optimize the dimensions of the material in microwave heating.IntroductionMicrowave has been applied in materials processing for its distinguished advantages including rapid heat transfer, volumetric and selective heating [1,2]. However, most research work involving microwave heating are confined to non-magnetic materials (e.g. ceramics), with limited attention paid to the heating of mixed property materials (e.g. magnetite and other ferrites) under microwave irradiation [3-5]. Since many magnetic materials exhibit good and even better microwave absorption capability than non-magnetic counterparts, it is quite necessary and deserved to take advantage of this property and then improve the heating efficiency. To achieve this aim, further understanding on the microwave heating mechanism, especially the microwave propagation/dissipation behaviors in magnetic materials is required.The dissipation behavior of microwave in materials has been identified as one of the key factors that affect the efficiency of heating under microwave irradiation and this behavior can be characterized by several parameters. Apart from traditional penetration depth (TEM power penetration depth, Dp = 1/(2*a), where a is the TEM field attenuation factor), two other parameters, field attenuation length (Df) and half-power depth (Dh), are also applied to indicate the microwave dissipation in materials [6].The accurate determination of such parameters can help in optimizing the dimensions of the load in a microwave furnace, producing more uniform heating under microwave irradiation and avoiding thermal runaway."

Jan 1, 2011

By M. Tomita

One of the most essential factors for a custom smelter to strengthen its competitive power is to Improve its comparative standing in purchase of concentrates from the world market. It is especially critical for Japanese smelters who depend almost 90% of their raw materials on import. In order to accomplish this breakthrough, the development of the new technology which enables us to treat concentrates containing higher Impurities is inevitable. Nippon Mining Company Ltd. made an intensive research on processing complex ore for three years from 1979, and successfully developed an original hydrometallurgical process to treat converter dust for eliminating impurities from the copper smelting circuit. The commercial plant was constructed at the Saganoseki Smelter & Refinery in 1982, and its nine years operation has been satisfactorily proven the advantages of the technology. The concept of this process and its operational performance are discussed.

Jan 1, 1992

By Shunli Zhang

Metals recovery from electronic scrap by physical separation may provide an alternative to the current recycling approach, through which halogenated flame retardants can result in hazardous dibenzo-p-dioxins and dibenzo-furans. On the basis of a complete sink-float analysis of personal computer and printed circuit board scrap, and in view of the advantages of dry processes for electronic scrap recycling by mechanical separation, air table separation is prioritized in an attempt to separate metals from plastics and glass involved. In the present paper, theoretical and practical considerations of air table separation have been detailed. It has been shown that air table separation is effective for recovering copper and precious metals from this specific waste stream. With the feed rate of 60 kg per hour, the combined grade and recovery of copper, gold, and silver attainable for the two heavy products produced by the air table used in the present study was shown in the following table:

Jan 1, 1998

By Debbie Marshall

Nickel and cobalt in lateritic ores can be extracted by either a hydrometallurgical or a pyrometallurgical route. The high-iron limonitic fraction of a deposit is best processed' hydrometallurgically while the magnesium-rich transitional and saprolitic fractions are more suited for pyrometallurgical processing. During hydrometallurgical processing, it may be attractive, for economic reasons, to blend the limonitic component with transitional and saprolitic ores, which contain higher nickel levels. However, blending increases the concentration of magnesium in the feed, leading to increased acid demands. The decision on how much ore to process then becomes an economic one. Ore samples with different magnesium contents were prepared for the leach test program by blending limonitic and transitional ores. The ore samples were slurried in seawater and tested in the Falconbridge Hydrometallurgical Pilot Plant. As expected, acid consumption increased with increasing magnesium content of the ore. For target extractions of 95% nickel and 92% cobalt, the required residual free acid concentration increased from 30 g/L at 1.7% magnesium to 50 g/L at 2.7% magnesium. When the magnesium content was raised to 3.8% and 4.6% in subsequent pilot plant testing, the final free acid requirements did not increase beyond what was observed at 2.7% magnesium. Thus, the cut-off ore composition to maximize nickel units and minimize acid requirements is between 1.7- 2.7% magnesium. Keywords: high pressure acid leaching, laterites, magnesium

Jan 1, 2004

By Toru Taniguchi

In the Mitsubishi smelting furnace, copper concentrate, silica sand and water granulated slag from the converting furnace are injected through the process lances, together with oxygen enriched air, into the melt. Because bath smelting is used, the rates of particles/melt and gas/melt reactions are high enough and therefore tine grinding of the solid materials is' not necessary. Among these reactions, the dissolution rate of silica sand is the slowest and limits the overall reactions in the smelting furnace. Information on the dissolution rate of silica sand plays an important role for design of a new furnace. Theoretical calculations of the dissolution rate .of silica particles have been reported elsewhere. The authors conducted cold model experiments and could verify the calculation. In this paper, the dependence of dissolution rates of particles on the gas blowing rate, particle size and solid penetration depth in the bath is discussed.

Jan 1, 2002

By Anna Wasilkowska

The study concentrates on the effects exerted by microstructure, deformation history and uniaxial stress conditions (temperature, stress state, strain rate) on the mechanical properties offerritic TRIP-aided steels for automotive applications. In low-alloyed TRIP-steels it is quite difficult to separate the effect of the austenite to martensite phase transformation from the influence of the ferritic matrix contributing to the yield stress and uniform elongation. Investigation of transformation kinetics of retained austenite as a function of the deformation temperature show that using the parameter k to characterize the retained austenite stability allows to identify regious of different temperature sensitivity separated by a transition temperature of 10±5°C. The observed low strain-rate sensitivity of the flow stress is an intrinsic property of the ferritix matrix and points to defomtation governed by slip. The ultimate tensile strength is much stronger affected by temperature than the yield stress. The influence of the temperature on the elongation is complex, because of the heating of the specimens by 60-l20°C at moderate and high strain rates. The increase of the total strain can be understood in terms of thermal softening of the ferrite. On the other hand, the steep increase of the stress during dynamic testing is an effect of accommodated elastic and plastic strains in the matrix. The strain- hardening exponent is dependent on the conditions imposed during testing. The martensite transfomtation rate is lower and the critical stress for martensite nucleation is much higher under compression compared to tensile loading. In secondary tensile tests, the yield stress increases steeply, and the ultimate tensile strength and the total elongation depend linearly on the amount of pre-straining. The results confirm that in the range of 8=10-4 s-l the TRIP-effect governs room temperature plasticity. Keywords: TRIP-steels, mechanical properties, strain rate sensitivity, temperature sensitivity, austenite stability

Jan 1, 2003

By Chang Wei, Zhigan Deng, Jiqiang Liao, Minting Li, Hongsheng Xu, Yan Song, Cunxiong Li, Xingbin Li

"Abstract: Direct ?otation of oxidized zinc-lead ore is characterized by recovery of zinc and lead only around 55% and 50%, respectively. Mineralogical analysis shows that the sample used in the present study is a carbonate hosted zinc-lead ore, with a zinc and lead carbonate content that accounts for 80.14% and 75.63% of the total minerals, respectively. The carbonate hosted zinc-lead ore was hydrothermally sulfidized with elemental sufur and the experimental data indicated that under the conditions employed up to 75% zinc and 82% lead sulfidation extent were achieved. As a result of pre-sulfidation followed by flotation, the recoveries of zinc and lead into flotation concentrate were over 90%. A flotation concentrate was obtained with 52% Zn and 37% Pb from the materials which was treated by sulfidation.IntroductionSulfide ores are the primary source of zinc and lead, and they are becoming depleted; thus, metallurgical investigators are interested in using abundant oxidized zinc-lead ore reserves. The high-grade zinc-lead oxidized ore, which normally has a zinc content higher than 15%, can be disposed of by acid leaching and electrolysis. However, the low-grade ore, which has a zinc content lower than 10%, is difficult to smelt with pyrometallurgy and hydrometallurgy, and the processes are very complicated and expensive in terms of production flow and energy consumption. Therefore, making the low-grade oxidized zinc-lead ore more beneficial has become more important in recent years. Flotation is the most common process, and the primary method of recovering zinc and lead from sulfide or oxide minerals. It is well known that there is a difference between sulfurized and oxidized minerals regarding their separation by flotation. Flotation of zinc and lead oxidized minerals is extremely complex because of the similarities in the physicochemical and surface chemistry of the constituent minerals. There are no known direct-acting collectors capable of producing single metal concentrates [1-3]."

Jan 1, 2012

By Virgil Optasanu, Yvon Lacroute, Eric Lesniewska, Tony Montessin, Pauline Vitry, Eric Bourillot, Cédric Plassard

A general challenge in metallic components is the need for materials research to improve the service lifetime of the structural tanks or tubes subjected to harsh environments or the storage medium for the products. One major problem is the formation of lightest chemical elements bubbles or different chemical association, which can have a significant impact on the mechanical properties and structural stability of materials. The high migration mobility of these light chemical elements in solids presents a challenge for experimental characterization. Here, we present work relating to an original non-destructive, with high spatial resolution, tomographic technique based on Scanning Microwave Microscopy (SMM), which is used to visualize in-depth chemical composition of solid solution of a light chemical element in a metal. The experiments showed the capacity of SMM to detect volume. Measurements realized at different frequencies give access to a tomographic study of the sample.

Jan 1, 2015

By J. W. Bridge

Triaxial compression tests at various confining pressures and temperatures, as well as tangent modulus tests using ultrasonic waves, were conducted for wax-coated granular composite materials. The material used is a surface for Thoroughbred horse racing. The purpose of these tests is to examine how track shear strength and tangent modulus at a range of loads respond to changing temperatures. Previous work has shown that a wide range of operational temperatures are experienced which have been reproduced in the lab. Using differential scanning calorimetry, it is confirmed that these operational temperatures correspond to distinct thermal transition regions for the wax that is used to coat the sand in these surfaces. Preliminary results show that both shear strength and tangent modulus are sensitive to temperature changes with maximum strength and modulus correlating with major DSC wax transition regions.

Jan 1, 2010

By M. Tamura, K. Fujita, K Shinozuka, H. Daimon, H. Esaka

"In-situ observation of unidirectional solidification using transparent substance has been performed to investigate the growth direction of solid phase. Cell or dendrite of which preferred growth direction is not parallel to the heat flow direction was observed with various solidification conditions. Dimensionless growth direction (p) changes from 0 to 1 with increasing growth velocity at a constant temperature gradient. Introducing the dimensionless growth velocity, the relation between p and growth condition could be correlated.IntroductionTransition in macroscopic solidified structure from chill to columnar zone which is found in normal castings takes place via grain selection1). Cast products such as turbine blades are unidirectionally solidified, grain selection plays an important role to choose suitable crystals which have reasonable orientation in the region called ""starter"", which is a very initial part of casting2). Therefore, grain selection is a very important process in the formation of casting structure. The present authors have been studying on the process of grain selection using succinonitrile, which is a transparent organic substance and have found that the growth distance necessary for grain selection depends upon the solidification condition3-5). When the solid/liquid interface is dendritic, the grain selection occurs quickly. On the other hand, when the solid/liquid interface is cellular, it occurs slowly. We supposed that the growth direction of dendrite is different from that of cell when the substance is unidirectionally solidified. Indeed, Kurz and Fisher wrote in their text book that dendrite grows along its preferred growth direction, <100>, regardless of heat flow direction and that cell grows along heat flow direction regardless of its preferred growth direction1). However, there is no quantitative description about the growth direction when the solid/liquid interfacial morphology is cellular. Furthermore, there have been little works6) to study the growth direction of cell and dendrite."

Jan 1, 2000

By Jie Ma, Shun-Li Zhao, Jian Zhao, Jie-Yu Zhang

"Microstructural morphology evolution of Ni-45wt.%Mo droplets during rapid solidification process was investigated using an advanced modified 3D cellular automaton-finite element(CAFE) model by CALCOSOFT software. The model was modified by User-defined functions (UDFs) and validated with experimental solidification microstructural morphology of Ni-45wt.%Mo droplets available in the literature. Then, the influences of convection heat transfer coefficient, superheat of the alloy droplets and droplets size were investigated during the rapid solidification process. The predictions show that microstructural morphology is obviously sensitive to convection heat transfer coefficient and droplet size. With the decrease of convection heat transfer coefficient, the grain density decreases. In addition, the decrease of the droplet size could obtain refined microstructure. However, decrease the superheat ofNi-45wt.%Mo droplets has little effect on microstructural morphology.IntroductionFor several decades, much attention has been paid to undercooled alloy droplets of rapid solidification process for which can obtain refined microstructure, decreased microsegregation and extended solubility of alloying elements [1-3]. Extensive prior work shows that solidification of droplets plays an essential role in advanced material properties [ 4]. Consequently, it is very important to investigate the microstructural morphology evolution, especially for dendrite growth during non-equilibrium solidification process, for dendrite growth reflected the kinetics of the crystal growth process."

Jan 1, 2013