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By Weng Fu

In this study, Resin-in-Pulp (RIP) technology is used to separate Pb from a chalcopyrite slurry. Solvent-impregnated resin, Lewatit® VP OC 1026, which contains di(2-ethylhexyl) phosphoric acid (D2EHPA) in a macroporous polystyrene matrix was used, as the functional group exhibits selectivity for Pb over Cu. Adsorption pH, kinetics, as well as resin and CuSO4 concentrations were investigated. The results show that the kinetics of Pb and Cu loading are fast, reaching the adsorption equilibrium within 30 min. The equilibrium pH of 2 was chosen as optimum for operation in order to achieve a high Pb extraction rate and extent as well as selectivity for Pb over Cu. High Cu(II) concentration in solution results in Pb(II) requiring a larger amount of resin for the same degree of extraction. Regeneration and reuse tests show that the loss of adsorption capacity happens in the 1st and 2nd cycles and then the adsorption capacity stabilises for the 3rd cycle.

By C. Flores

The direct cementation of copper from a loaded D2EHPA 20 % vol. in kerosene using zinc, zinc-lead alloy and iron metallic powders was studied. Copper was loaded into the organic solvent from an aqueous copper sulfate solution. Results indicated that copper is reduced spontaneously with relatively fast reaction rates. The effects of several operating parameters such as water content in the organic system, initial copper concentration, reductant surface area, oxygen and nitrogen atmosphere, intensity of the agitation and temperature on the galvanic stripping of copper were studied. For a better understanding of the electrochemical reactions involved in the galvanic stripping, the dissolution of metallic copper in the organic solvent was also studied. Copper did not dissolve unless a small amount of water was present in the organic system. The results and possible reaction mechanisms are discussed.

Jan 1, 1999

By P. G. McCormick

The refining of rare earth metals by the direct solid state reduction of their respective chlorides during mechanical alloying has been studied. Erbium and gadolinium were synthesised by milling their respective chlorides with calcium. The mechanical alloying of SmC13 with calcium resulted in partial reduction of SmC12. Examination of the milled powders using X- ray diffraction and analytical electron microscopy has enabled characterisation of product structure and morphology. The synthesis of Fe17Nd2 by the mechanical alloying of NdC13 and Fe with calcium has also been studied. The Fe17Nd2 phase forms during heat treatment of the mechanically alloyed powder.

Jan 1, 1992

By Wenxuan Xu, Shusen Cheng, Tian Chen

Pulverized coal injection (PCI) can generate heat and reducing gas in the raceway and replace some expensive metallurgical coke in the blast furnace ironmaking process. In this paper, a three dimensional mathematical model of the raceway including the coke bed has been developed to simulate the complicated phenomena of pulverized coal injection. The effects of oxygen enrichment, particle diameter in the raceway are investigated in this study. The establishment of the 3D model is expected to analyze the raceway working state accurately and optimising the PCI operation of blast furnaces.

Mar 1, 2017

By Jari Aromaa, Antti Kekki, Olof Forsén

"The deposition of copper on inert substrate depends on the number of active sites that will react at certain overpotential. The critical overpotential depends on surface morphology, surface film resistance and additives on cathode surface. The effects of surface properties on copper nucleation and growth rates were studied for used stainless steel blanks from several tankhouses. The surfaces of the blanks were characterized with electrochemical and mechanical methods. Electrochemical deposition tests were done at current density of 300 A/m2 for 10, 30 and 60 seconds. The nucleation density and copper coverage were estimated using image analysis. The surface film resistance did not correlate with copper growth. Increasing surface roughness correlated with lower copper growth.IntroductionStainless steel cathode blanks in copper electrorefming are usually made of AISI 3 I6L type steel. They have a typical lifetime over 10 years. During use the surface will collect deposits and become rough due to wear and corrosion. These factors can affect the nucleation and growth of copper. The nucleation and deposition of copper on inert substrate depends on the number of active sites that will react at certain overpotential. The critical overpotential can depend on surface film resistance, surface morphology, and additives adsorbed on cathode surface.The deposition potential of metallic ions on a foreign substrate is usually higher than the deposition potential on the electrode made of the same metal due to crystallographic substrate/metal misfit [I]. If the substrate has traces of the depositing metal they will be preferential growth sites. For a smooth deposit a large number of simultaneous nuclei is necessary. However, excessive nucleation density can lead to porous deposits [2]. Surface films of good conductivity are needed for dense nucleation and small nuclei. On cathode blanks the number of active sites increases with increasing surface film conductivity [3-5] and/or surface film porosity [6]. On AISI 3 I6 L stainless steel a more resistive oxide has been found to limit favourable sites for copper nucleation and more conductive film promoted high-density copper nucleation [7]. Also Urda-Kiel et al. have concluded that thicker oxide layers on AISI 304 stainless steel resulted in lower nucleation [8]. Increase in overpotential or current density activates more and more of the potential nucleation sites and this can be seen as higher number of nuclei [9] or smaller average distance between nuclei [10]."

Jan 1, 2012

By Hidekazu Nakagawa

We investigated the anodic dissolution behavior of titanium in TMHA-Tf2N molten salt, which has a wide electrochemical window of about 5 V, in order to develop an electrodeposition method for titanium. By etching a titanium electrode in HF?HNO3?H3PO4 solution, the titanium electrode became electrochemically active, and a redox reaction was observed at around -0.15 V vs. I-/I3- in (TMHA-Tf2N)?HTf2N solution. We identified the redox reaction consists of the reduction of the proton and the oxidation of hydrogen. The diffusion coefficient of the proton in TMHA-Tf2N was calculated to be 6.9 10-8 cm2 s-1 at 50 °C from the cathodic peak current in the cyclic voltammogram. Anodic decomposition of the molten salt was not observed up to 6.0 V vs. I-/I3- on titanium electrode, while it was observed at around 2.0 V vs. I-/I3- on platinum and glassy carbon electrodes. Cathodic decomposition of the molten salt was observed at around -3.0 V on the titanium electrode, as well as on the platinum and glassy carbon electrode.

Jan 1, 2006

By Teruo Bitoh, Shogo Izumi

"The effect of B203 flux melting on the structure and the soft magnetic properties of the (Feo.1sBo.20Sio.os)96Nb4 bulk metallic glasses prepared by casting has been investigated. The ringshaped bulk specimens were prepared by the B203 flux melting and copper mold casting. It was confirmed that the flux melting promotes the precipitation of the a-Fe(-Si) and Fe2B phases in the central region of the specimens. The ring-shaped bulk specimens show a flat hysteresis curve, indicating a good linear relationship between the magnetic induction and the applied magnetic field. These results show that it is possible to develop a new soft magnetic material that exhibits constant permeability, which is necessary for producing inductors and choke coils.IntroductionSince the success of forming Fe-based bulk metallic glasses (BMGs) with good soft magnetic properties, great attention has been developed to synthesis and properties of the BMGs [l, 2]. The BMGs have high glass-forming ability (GFA) and, therefore, they can be used to prepare bulk amorphous alloys with a thickness of the order of a few millimeters by casting. The soft magnetic properties of Fe-based BMGs are better than those of ordinary amorphous alloys; therefore, these BMGs have wider applications as soft magnetic materials [3-5]. It is often required for soft magnetic materials that the shape of the hysteresis curve is changed according to the demands of applications. For example, materials with ""flat hysteresis curves,"" which means the magnetic flux density (B) and the applied magnetic field (H) show a linear relationship up to rather high magnetic field, are necessary for producing inductors and choke coils. Flat hysteresis curves can be easily achieved by creating an air gap in the magnetic path. However, magnetic flux leakage generated in the air gap inhibits high-density packing of the electronic components. In order to achieve flat hysteresis curves without creating an air gap, Fe-based ordinary amorphous alloys are subjected to crystallization by annealing and transformed into thin surface layers of a-Fe; the crystallization results in the compression of the remained amorphous phase [6]. Another way to achieve flat hysteresis curves is the formation of secondary phase (such as Fe2B) that act as pinning site of magnetic domain wall displacements [7]."

Jan 1, 2013

By Renxing Li, Yongyong Gong, Yufeng Cheng, Zhenxing Yin, Xin Cao, Qijie Zhai

"This paper investigated the refinement effect of pulse magneto-oscillation (PMO) on the solidification structures of medium carbon steel S45C in metal mould. The induction coil was positioned at the middle of ingot. The results showed that solidification structure of the treated ingots was remarkably modified with a transformation from well-developed dendritic structures to small dendritic structures or globular structures compared to the untreated ingot. The area fraction of modified microstructure regions reached more than 80 percent. A further experimental investigation had been done to understand the influence of refinement effect on the solidification structure under different mould size. Theoretical analysis demonstrated that the mechanism for the refinement of solidification structure was that PMO promoted nucleation near the mould walls and changed the interface temperature gradient and concentration gradient in liquid, eventually leading to a transition from the columnar crystals to the equiaxed crystals.IntroductionIn recent two decades, the electromagnetic processing of materials (EPM) has been widely used in many fields such as ironmaking, steelmaking, and solidification processing [1-6], where EPM can control melt flow, modify melt shape, reduce macro-segregation and refine microstructure. Pulse magneto-oscillation [7-9] (PMO), as a novel technique of EPM, has a remarkable effect on grain refinement and high potentiality to be used in industrial production. Compared with ultrasound refinement technique, PMO can be easily employed to metal solidification processing for long time in no contact with hot metal liquid by using a water-cooled coil. Another important advantage is that PMO needs smaller energy compared to pulsed magnetic field which needs a very high current to obtain a strong magnetic field to get a satisfactory effect. These advantages mentioned above are beneficial for industrial application, which make it potential to be widely used in future. Gong et al. [7] have studied the refinement effect of PMO on pure aluminum and find that PMO can significantly modify the solidification structure of pure aluminum. Li et al. [9] have reported the effect of temperature field on solidification structure under the influence of PMO. On the basis of these works, this paper has studied the effect of PMO on solidification process of medium carbon steel S45C in a metal mould, which can also provide some information for industrial application of this new technique."

Jan 1, 2012

By Timothy W. Skszek, Adrian S. Sabau, Hebi Yin, Gerard M. Ludtka, Xiaoping Niu

"A constitutive model has been developed to predict the yield strength aging curves for aluminum casting alloys during non-isothermal age-hardening processes. The model provides the specific relationship between the process variables and yield strength. Several aging heat treatment scenarios have been investigated using the proposed model, including two-step aging recipes. Two-step aging heat treatments involve a low temperature regime to promote nucleation of secondary phases and a second step at higher temperature for the growth of the secondary phases. The predicted results show that a yield strength of approximately 300MPa might be obtained in a shorter aging time, of approximately 30 minutes. As a result, better mechanical properties can be obtained by optimizing the time-temperature schedules for the precipitation hardening process of heat treatable aluminum alloys.IntroductionA356 is one of the commercially heat treatable aluminum casting alloys, and T6 is one of the heat-treated conditions to improve mechanical properties. The first stage of a T6 temper is solution treatment at an elevated temperature, generally in the range of 480 - 540°C. After solution treatment, the cast part is typically quenched in water/air to retain the solute-rich homogeneous matrix chemistry at room temperature. Subsequent ageing treatment stages capitalize on this super-saturated solid solution to generate controlled dispersions of very small strengthening precipitates within the matrix of Al grains [l]."

Jan 1, 2013

By R. Upadhyaya

Aluminium alloy matrix cast composites have been synthesised by incorporating fine graphite powders (0.5 - 20 µm size) and chopped carbon fibres (6.5 pm P). 3-6 mm length) by liquid metallurgy technique. Incorporation of these second phase materials exceeding 6-8 wt% invariably resulted in agglomeration of the dispersoids and sometimes leading to even total rejection. It was found that small additions of mischmetal (1-3 wt%) during dispersion resulted in better incorporation without much agglomeration of the dispersoid as evident from the macro and micro structures of the composites. Further, the additions of mischmetal increased the volume of the effective incorporation of the dispersoid even to the extent 50- 60%. The mischmetal addition results in a significant increase in the power factor of the stirrer motor indicating an apparent increase in the viscosity of the system. The higher viscosity of the melt increase the shear transmission conditions within the melt during stirring thereby breaking the agglomerates of the dispersoids. The increased viscosity of the melt seems to be due to the formation rare earth - aluminium inter metallics precipitation, as observed in the metallographic studies, thereby making the process a "pseudorheocasting? technique. A provisional patent has been filed based on this work.

Jan 1, 1989

By Eustathios S. Kikkinides

This work presents an integrated approach for the optimal design and control of hydrogen storage beds. A detailed 2-D mathematical model is developed for metal hydride beds and validated against experimental and theoretical literature results. Based on recent advances in dynamic optimization, the model is used to find the optimal process design and operating strategy in order to minimize the storing time, while satisfying, a number of operating constraints (such as pressure drop limitations, cooling fluid availability and maximum tank temperature). Trade-offs between various objectives, alternative design options and optimal cooling control policies are revealed illustrating the potential of the approach. In a further step the model is used to exploit the benefits between material and process design. Systematic simulation and optimization studies are performed at two different length scales (tank and adsorbent pore level) for carbon based materials. The macroscopic approach determines the optimal values of the sorption parameters while, based on these results molecular simulation techniques are employed to determine the pore size distribution of the adsorbents.

Jan 1, 2006

By Matthew Jeffrey

Leaching, cementation, electroplating and flotation are all electrochemical phenomenon. They are also key processes in the hydrometallurgical treatment of metals. Unfortunately electrochemical methods tend to be under-utilized when studying these processes and one possible reason for this is the confusion surrounding the large number of electrochemical techniques available. In this paper four former PhD students of Professor Ian Ritchie present an insight into how one electrochemical technique can be used to compliment rate/kinetic studies. The paper details how to perform the experiments, interpret data, and recognize complications with the results. Examples where this approach has been highly successful are presented, and include: cementation of zinc by aluminium, cementation of copper by nickel, cyanide leaching of gold and the cementation of gold thiourea by mild steel. The examples illustrate that this universal approach adopted by Ian Ritchie provides the key to understanding the mechanism of many hydrometallurgical reactions.

Jan 1, 2003

By Laurentiu Nastac

"Two advanced control solidification technologies were studied in this article to improve the quality of the cast ingots as well as to control the solidification structure evolution during the plasma arc melting (PAM) processing of Ti-6-4 ingots: (i) electromagnetic stirring (EMS), and (ii) ultrasonic treatment (UST). The developed EMS modeling approach is based on the numerical solution of Maxwell's equations, fluid flow, and heat transfer equations, and mesoscopic modeling of the grain structure. The UST analysis tool is capable to model acoustic streaming and cavitation. It is used in this work to study ingot solidification under the presence of ultrasound. Predictions of the macrostructure, GET formation and primary dendrite arm spacing for PAM Ti-6-4 ingots processed with and without EMS or UST were discussed.1. IntroductionTitanium (Ti) alloys are melted, refined and cast into ingots through plasma arc cold hearth melting (PAM), electron beam cold hearth melting (EBM) and vacuum arc remelting (VAR) for jet engine applications. Process modeling has become a viable tool to optimize the PAM, EBM, and VAR processes. A comprehensive modeling approach to simulate ingot solidification phenomena in primary melting and secondary remelting processes of Ti alloys would include models for macroscopic mass transfer, heat transfer, fluid flow, acoustic, electromagnetic and species transport. The approach should also include microscopic models to predict the evolution of grain structure in solidifying ingots in conjunction with electromagnetic stirring (EMS) and ultrasonic stirring (UST)."

Jan 1, 2012

By Guy Deschênes

In spite of the wide use of lead compounds to enhance cyanidation of free milling sulphide-bearing gold ores, an industrial control method was only implemented four years ago. This study presents the results of the investigation that led to the development of the on-line control technology. Two free milling sulphide-bearing gold ores and high purity minerals were used to develop and test the concept. The first ore contains 2.8 g/t Au, 6.2% pyrrhotite, 2.1% pyrite 0.6 % arsenopyrite, 0.1% chalcopyrite and 0.1% organic carbon. The second ore contains 10.4 g/t Au, 3.2% pyrite, 0.8% pyrrhotite and 0.38% chalcopyrite. The first ore showed a much higher oxidation rate in the pre-leach than the second one and consumed seven times more cyanide. A relation between the formation of thiosulphate and thiocyanate and the additions of lead nitrate were quantified. The ?reducing power?, a titration with permanganate, predominantly determines the concentration of thiosulphate and thiocyanate in cyanide solution. The relation between the reducing power and the addition of lead nitrate at various concentrations of pyrrhotite and chalcopyrite in the ores was established, providing a monitor/control strategy for lead nitrate addition.

Jan 1, 2006

By Shaohua Ju, Feng Jiang, Jian Jian, Hongying Xia, Jinhui Peng, Libo Zhang

Microfluidic solvent extraction of zinc from sulfate solution was studied using di-2-ethyl hexyl phosphoric acid, D2EHPA, in sulfonated kerosene as diluent. The influence of different parameters on the extraction of zinc, such as flow rate, temperature, flow rate ratio, extraction concentration, and saponification ratio of extractant were investigated and the conventional and micro fluidic extraction were compared. Under the optimized conditions, micro fluidic extraction efficiency of zinc is up to 97.1%. It is better than that conventional extraction. Therefore, microfluidic solvent extraction can achieve high efficiency and low consumption of extraction process.

Mar 1, 2018

By Elsa Olivetti, Randolph Kirchain, Gabrielle Gaustad

"As scrap usage increases, it is often necessary to “dilute” the melt with primary aluminum to ensure the finished product meets compositional specifications. Secondary raw materials, particularly postconsumer scraps, often include high levels of unwanted or “tramp” elements, such as iron and silicon in the case of aluminum. Recent literature on this issue cites several causes including inherent contamination during processing as well as ineffective segmentation at end-of-life. To address this accumulation problem, “upgrading” solutions have been developed including: dismantling of end-of-life products, spectrographic or magnetic sorting of shredded scrap, and “filtration” technologies that remove tramp elements in the melt. Although it is clear that upgrading strategies enable increased usage of scrap, it is not clear that they would be economic or efficient. This work presents a set of analytical methods, based on chance constrained optimization, to quantify the potential environmental and economic value of several scrap upgrading technologies.IntroductionAluminum recycling has a number of key environmental and economic benefits. Compared to other materials, aluminum production has one of the largest energy differences between primary and secondary production: 175 MJ/kg for primary compared to 10-20 MJ/kg for secondary[1]. With energy and cost savings in mind, many producers now have targets of increasing their usage of secondary materials[2, 3]. However, the accumulation of impurities in these recycled material streams provides a significant compositional barrier to these goals[4].A growing number of studies and literature would suggest that accumulation of unwanted elements is a growing problem, in all recycled material streams. In the case of aluminum, the list of problematic impurities is quite large, including but not limited to: Si[5, 6], Mg, Ni, Zn, Pb, Cr[7], Fe[5-7], Cu[6, 7], V, and Mn[6]. Metals recycling is a metallurgical process and is therefore governed by the laws of thermodynamics. The removal of unwanted elements in the scrap stream is dictated by the energy considerations of the melt process. Compared to many metals, aluminum has a high degree of difficulty in the removal of tramp elements, due to thermodynamic barriers. Therefore, with no simple thermodynamic solution, producers must identify strategies through-out the production process to mitigate this elemental accumulation."

Jan 1, 2008

By T. Watanabe, T. Fujiwara, S-Wan Song, Y. Nakagawa, R. Teranishi, M. Yoshimura

"We have tried a new method to fabricate cobalt oxide films onto porous films directly by an electrodeposition method at low temperature. The porous substrate films (membrane-filters and paper) were placed between a LiOH solution and a CoSO4 solution and treated under electricalcurrents of ~1 mA/cm2 using carbon cathode and anode. Effects of temperatures, flow rates and electrical currents have been investigated. As a result, we found that the LiCoO2 films and Co3O4 films were successfully fabricated on paper and/or porous PTFE filters at 120 °C, while CoOOH films were deposited at 80 °C. Furthermore, LiCoO2 films did not cover whole the substrates, but was fabricated just over the anode. The chemical reactions of electrodeposition were also considered from these results.IntroductionRecent agreements on global environment require rapid progress of low energy and low waste processings for the fabrication of thin films that succeed to the mass production with the high consumption of the fossil fuels (such as physical vapor deposition°, chemical vapor deposition2), dip coating with firing3) etc.). The total energy consumption in aqueous systems should be the lowest among all these processing routes, because a much lager excess of energy is necessary to create melts, vapor, gas, or plasma than to form an aqueous solution at the same temperature4)The ""Soft Solution-Process"" (SSP) was one of the best concepts to realize the low energy and low waste fabrication of inorganic materials. 5) Generally speaking, SSP gives similar results to any other processing using fluids (such as vapor, gas plasma) and/or beam/vacuum processing. However, the total energy consumption of all these possessing routes should be the lowest in aqueous systems, because a much larger excess of energy is necessary to create melts, vapor, gas or plasma than to form an aqueous solution at the same temperature (Fig. 1). This idea can be easily demonstrated, using the simple example of BaTiO3. The energy diagram for the formation of BaTiO3 from various precursors is shown in reference 4. The driving forces (AG) for representative synthesis reaction of (1), (2), (3), (4) and(5) are 38, 727, 3685, 17 and —14kcal/mol, respectively at room temperature. 6' 7"

Jan 1, 2000

By T. T. Chen, J. E. Dutrizac

Noranda Inc., CEZinc presently employs a cement-stabilization (jarofix) process to stabilize its jarosite residues for direct disposal. In this process, Portland cement partly decomposes Na-jarosite to form Ca6Fe2(SC>4)3(OH)i2.nH20, ferric hydroxide and sodium sulphate which further reacts to form gypsum; approximately one-third of the Na-jarosite reacts in the current commercial product. The cured jarofix products also contain minor amounts of various Ca-Al-Fe silicate-sulphate-hydrate phases and traces of calcite. Together with gypsum and a Ca-Fe sulphate phase, these species bond the various particles together, imparting mechanical strength and reducing the permeability. Water-soluble Zn and Mg are stabilized in the Ca-Al-Fe silicate-sulphate-hydrate phases. The freshly cured products usually contain small amounts of moisture and traces of residual Portland cement, which provides additional alkalinity for the neutralization of any residual acid species. Jarofix products stored for more than six years in the laboratory, after curing, are usually dry and exhibit the same micro-textures as those of the freshly cured products. However, the stored products are depleted in the Ca6Fe2(S04)3(OH)i2.nH20 and Portland cement phases, and are enriched in gypsum and calcite which reflects the highly alkaline environment of the jarofix products. The aged products also have increased amounts of the Ca-Al-Fe silicate-sulphate-hydrate phases which have elevated Zn and Mg contents. This implies a further immobilization of residual water-soluble Zn and Mg during stora

Jan 1, 2000

By M. Sahoo

The development of new alloys containing bismuth and selenium for potable water supplies are reviewed. The new alloys are replacements for the leaded red- and semi-red brasses by the low-lead alloys, SeBiLOYS I and II, for sand casting, and SeBiLOY III replaces the lead containing yellow brass, C85800, for permanent mold casting. As the new alloys use bismuth and selenium, the supply and demand of these elements are discussed. The key casting characteristics discussed are: tendency to dross formation, freezing range (liquidus and solidus temperatures), fluidity, resistance to hot tearing, microstructures, mechanical properties, machinability, grain refinement and corrosion behaviour.

Jan 1, 1999

By Jin-Chun Kim

Nanosized W based powders (W, WC, WC-Co) were produced by chemical vapor condensation (CVC) process. Two different solid W(CO)6 and Co2(CO)8 metal-organic materials were used as precursors. CVC experiment was conducted in the temperature range of 400-1100. As-CVC WC1-x powder which had non-stoichiometric composition was carburized by using of the CH4-H2 mixed gas in temperature range of 750-850. The CVC W and WC1-x powders showed loosely agglomeration structure, and the Co powder had intricate long stand structure because of intrinsic magnetic properties of Co phase. Carbon content of the CVC powders controlled by gas-phase carburization was well matched with theoretical WC stoichiometry (6.13wt%).

Jan 1, 2006