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By Ramana. G. Reddy, Haoxing Yang

The electrodeposition of zinc from zinc oxide using urea and choline chloride mixture in a molar ratio 2:1 is investigated in different experimental variables, namely, the concentration of added [BMIM]HSO4, temperature, and applied cell voltage. The additive, [BMIM]HSO4, was determined to have beneficial effect on the current efficiency, energy consumed in the process and surface morphology of the deposits. The highest current efficiency (92.6%) and lowest energy consumption (2.92kWh/kg) was obtained for solution with 20mg/mL [BMIM]HSO4. The morphology showed the formation of absorbed additive layer on the cathode at higher concentration of additives. Experiments were conducted at different temperatures between 343K and 388K and at various applied cell voltages between 2.7V to 3.6V to determine the best experimental conditions. By varying temperature, highest current efficiency (91.3%) and lowest energy consumption (2.69 kWh/kg) was obtained at 373K. The electrodeposition process is enhanced between the applied voltage 3.0-3.3V by achieving lower energy consumption (2.75~3.06kWh/kg) and higher current efficiency (88.4~89.7%). SEM images showed grain size is significantly increased in higher applied voltages. While at higher temperatures, it seemed to generate particle growth as clusters at the outer deposit layer.

Jan 1, 2014

By Dong Joon Min, Joo Hyun Park, Mi Sun Choi, Jae Hong Shin

Sublimation of ZrCl4 is important for the production of nuclear grade metallic Zr in Kroll’s process. The sublimation kinetics of ZrCl4 was investigated by TGA under both isothermal and non-isothermal conditions. The sublimation rate of ZrCl4 increased with increasing temperature under isothermal conditions. ZrCl4 sublimation was confirmed to be a zero-order process under isothermal conditions, whereas it was first-order kinetics under non-isothermal conditions. The activation energy of ZrCl4 sublimation under isothermal conditions was 21.7 kJ/mol. The activation energy for non-isothermal sublimation was 101.4 kJ/mol and 108.1 kJ/mol with the Kissinger method and Flynn- Wall-Ozawa method, respectively. These non-isothermal activation energies were very close to the heat of sublimation (103.3 kJ/mol). Sublimation occurs by two elementary steps: surface reaction and desorption. Therefore, the overall activation energy of ZrCl4 sublimation is 104.8(±3.4) kJ/mol. The activation energy of the surface reaction and desorption steps are proposed to be 83.1 kJ/mol and 21.7 kJ/mol, respectively.

Jan 1, 2014

By Fumito Tanaka

The Mitsubishi process is the sole pyrometallurgical process for the continuous production of blister copper from Copper concentrates and has been successfully operated around the world. The development of calcium ferrite slag (CaO-FeOx-Cu10), the so-called "C-slag", has enabled continuous converting from matte to blister copper in the commercial scale operations. Commercial interests in the slag led to many papers over the CaO-FeOx slag. However, Cu2O bearing slag has not been studied well due to experimental difficulties. The authors have quantified the thermodynamic properties of the CaO-FeOX-Cu2O system. The results have been utilized to analyze various issues related to the converting furnace, such as the magnetite precipitation from the slag or from blister copper and to develop better controlling criteria for the continuous converting operation. -

Jan 1, 2003

By Frame Ritzert, Dennis Keller, Vijay Vasudevan, David Arenas

"An investigation was conducted to describe topologically close packed (TCP) phase instability as' a function of composition in the advanced ·Ni-base superalloy Rene N6. TCP phases are detrimental to overfill high-temperature performance of Ni-base superalloys because of their brittle nature and because they deplete the Ni-rich matrix of potent solid solution strengthening elements. Thirty-four variations of polycrystalline .Rene N6 determined from a design-of-experiments approach were cast and homogenized at 13 l5°C for 80 hours followed by exposure at 1093°C for 400 hours to promote TCP formation. The alloys had the following composition ranges in atomic percent: cobalt 10.61 to 16.73, Mo 0.32 to 1.34%, W 1.85 to 2.52%, Re 1.80 to 2.11%, Ta 2.36 to 3.02%, Al 11.90 to 14.75%, and Cr 3.57 to 6.23%. Physical and chemical characteristics of all microstructures obtained were described using various analytical techniques. From these observations, a mathematical description of TCP occurrence (s and P phase) was generated for polycrystalline Rene N6.IntroductionNi-base superalloy single crystals represent the state-of-the-art for turbine engine airfoil application as they offer the best balance of properties to allow for the high operating temperatures required: for efficient engine operation.1 Current trends in alloy design take advantage of improved creep rupture strength with the addition .of higher levels of refractory elements. 2 In .particular, the addition of significantly higher levels of Re in third generation superalloys is key for both microstructural stability and creep rupture strength. 3 While the presence of the refractories is thought to provide strength benefits from solid solution hardening, a tendency for alloy instability in the form of topologically-close-packed (TCP) phases or secondary reaction· zone (SRZ) ·phenomena accompanies the high refractory content. 3 The formation of these phases in sufficient amount is detrimental to the overall high temperature performance of Ni-base superalloys because of their brittle nature and because they deplete the Ni-rich matrix of potent solid solution strengthening elements.4 The tendency for a particular composition to form TCP may not be immediately known since the precipitation of TCP phases in Ni-base superalloys is nucleation controlled, thereby requiring long times at elevated temperatures to precipitate. 5 They preferentially nucleate along the octahedral planes of the Ni-base superalloys, usually in areas of refractory metal enrichment at grain boundaries or inside dendrites.5-6 In Rene N6, two closely related TCP phases, a and P, have been observed.2"

Jan 1, 1998

By J. S. Pitsillos

A new furnace tapping technique involving the simulation of a control valve at the exit to a furnace is being investigated. The purpose of this new tapping technique is to regulate the flowrate of liquid furnace products( slags, metals and mattes). Numerical modelling and experimental work has been carried out on tapping of slags leaving a SIROSMELT reactor and the results found to be in good agreement. Numerical modelling has also enabled prediction of the important industrial conditions for the onset of blockage from the shape of the pressure versus flowrate curves. Slag launder experiments have been carried out and a one-dimensional heat transfer model was used to evaluate the effectiveness of launder covers and different coolants. From the experimental results and mathematical model some launder design guidelines such as inclination angle, covers and coolants have been developed.

Jan 1, 1991

By Duclerc Fernandes Parra, Luis Filipe Carvalho Pedroso de Lima, Washington Luiz Oliani, Danilo Marin Fermino, Ademar Benevolo Lugao

The modified polypropylene was obtained from isotactic polypropylene (iPP) in spheres by irradiation with gamma rays in the presence of acetylene. A new morphology with distinct rheology is obtained by this process in which occurs: degradation, branching and/or crosslinking. The objective of this study was to investigate the effects of thermal aging on the crystallinity and morphology of the modified polypropylene, High Melt Strength Polypropylene (HMS-PP). The thermal stability was evaluated after aging of samples using a stove at temperature of 90 °C, in presence of air at different periods of time. Aging effects were characterized by: Thermogravimetry analysis (TG), Differential scanning calorimetry (DSC), Infrared spectroscopy (FTIR) and Scanning electron microscopy (SEM). In thermooxidative conditions, the formation of oxidation products essentially involves a hydrogen abstraction by the peroxyl radical, leading to hydroperoxides as primary products and chemical degradation in the immediate crack tips. The effect of thermal degradation (chain scission and oxygen diffusion) on iPP was a more intense crack formation. Surface cracks increased with the aging time. In comparison of iPP, the modified PP samples had a morphological barrier inhibiting the penetration of oxygen into the sample and in consequence limit the propagation of degradation

Jan 1, 2015

By Jayagopal Ucbil, M. Krishna, V. T. Vijayalakshmi

"The pitting susceptibility of aluminium metal matrix composites reinforced with garnet particles has been examined using static weight loss method by exposing the metal matrix composites (MMC) specimens to the action of IN HCI acid at laboratory temperature for different time intervals. It was found that the corrosion rate decreased with increase in weight percentage of reinforcement while the corrosion rate was a function of the matrix alloy but not of the reinforcement material. Further, it was found that the rate of corrosion was dependent on the interface region formed between the reinforcement and the matrix. A comparison of the base matrix with the corresponding composite when subjected to heat treatment for varying periods of 4, 8, and 12 hours respectively was made. The comparison revealed that corrosion resistance of the composite increased with the duration of heat treatment and this has established a considerable improvement in corrosion resistance of the composite when compared with the base matrix.IntroductionMetal matrix composites (MMCs) offer designers many added benefits, as they are particularly suited for applications requiring good strength at high temperature, good structural rigidity, dimensional stability, and light weight [1-5]. The trend is towards safe usage of the MMC parts in the automobile engine, which work particularly at high temperature and pressure environments [6-7]. Particles reinforced MMCs have been most popular over the last two decades. Among the MMCs, the most popular families are represented by aluminium reinforced with ceramic particles. Although the incorporation of the second phase into a matrix material can enhance the physical and mechanical properties of the base metal, it could also significantly change the corrosion behavior."

Jan 1, 2000

By R. A. Roberti

Most copper refineries use conventional wheel systems to cast anodes. over a period of time the copper moulds that are used become warped and cracks develop. To control mould warpage, the mould's are either rejected after a certain warpage is reached, or the shape is restored by mechanical means. The cracks, unless they are very severe, are repaired by a peening process. Even with regular maintenance to control warpage and cracks, the moulds have a limited useful life. If warpage and cracks are not controlled, anode quality deteriorates and tankhouse operations are seriously affected. -An intensive study was initiated to develop means of controlling mould warpage which culminated in the d?evelopment of technology to control mould warpage to within ±1. 5 mm, and at the same time effectively contr0l: cracking and significantly increase the mould life-. The warpage control has been achieved by using a unique mould design. Mould cavities are present on both sides of the mould and periodic inverting controls the wa-rpage in the cavities. The mould casting procedure has been developed and all production wheels have been converted to the new mould design. The performance characteristics of these moulds will be detailed. 21

Jan 1, 1987

By K. Narayana Swamy

Experimental results of 3-phase mixing in a physical model of a CCRL for metals refining, at high levels of bottom gas injection (up to a superfIcial gas velocity (Us) of 12.5 cm/min), are presented. A thermal tracer technique was used to elucidate both longitudinal mixing and interphase heat transfer. The results indicate that even under conditions of significant bottom gas injection, it should be possible to maintain acceptably low longitudinal mixing (D. < 20 cm2/s and D/uL < 0.1) in the CCRL. Interphase mass-transfer coefficients of the order of 0.02 cm/s and higher, are predicted from the measured interphase heat transfer coefficients using the mass and heat transfer analogy. Adequate performance is likely to be possible for an industrial CCRL, based on extrapolation of these results to full-scale conditions.

Jan 1, 1996

By Richard A. Leiby

The recycling of lead-acid batteries in the United States has become a challenge as to how to balance ever increasing environmental regulation and cost with efficient operations. East Penn&apos;s captive secondary lead smelter has developed into a recycling facility producing lead, polypropylene, sulfuric acid, ammonium bisulfite, and non-hazardous discard slag. The emphasis has been to design a facility to comply with environmental regulations, to eliminate wastes, and to produce products, while at the same time, continuing to supply the company&apos;s battery manufacturing raw material needs.

Jan 1, 1993

By Xin Li, Hai-Xing Fang, Bing Xie, Hong-Yi Li

Chromium-containing vanadium slag (V-Cr slag) was obtained by an industrial smelting process of Hongge Ore, which is valuable vanadium-titanium magnetite to extract V and Cr in China. Sodium roasting thermodynamics of V-Cr slag in presence of oxygen were calculated to evaluate the reactivity of chemical compounds. Results showed that the oxidation of FeV2O4 was intensified in presence of Na2CO3 while the oxidation tendency of FeCr2O4 was far lower than that of FeV2O4. It was probably that reactions of impurities including Al2O3, SiO2 and Fe2O3 with Na2CO3 happened and the products can promote the oxidation of vanadium or chromium compounds in lower valence. Based on thermodynamic analysis, a two-step selective extraction process of vanadium and chromium was proposed. Extraction rate of vanadium was 88.6% while 7.0% for chromium in the first extraction step; extraction rate of 90.7% and 95.4% for vanadium and chromium, respectively, were obtained in the second step.

Jan 1, 2014

By K. Yamada, T. Takaoka, A. Ozeki, M. Yamaga, Y. Kawai, S. Nishioka, Y. Kikuchi

"Recently, smelting reduction of chromium ore in BOF has been actively investigated as a key unit process for an innovative future stainless steelmaking. The prominent feature of this new process route is energy and process saving, and production cost saving. The development is already in the midst of application to the commercial production, however there still remain the following key technologies to be established for the full use of the process. One is a speed up of the reduction of chromium ore to match with sequential continuous casting, and the other is efficient combustion of carbonaceous materials in BOF to reduce their consumption, and hence to assure the steel quality. High degree of post combustion technology and new charging technology, i.e., ore-coal-flux-oxygen mixed injection, could be effective for those two subjects. In 2000 or beyond, the new process would have become quite popular owing to the establishment of those key technologies.Introduction Since stainless steel was invented, its production has continued to expand because of its attractive combinations of functions of excellent corrosion resistance, good formability, a pleasing appearance, and a wide range of strength levels. New types of stainless steels as well as new applications are continually being developed.Compared to the production of ordinary steels (1), stainless steel production (2,3) shows steady growth worldwide, while the former production remains on the same level, as Figure 1 shows. It can be estimated that future production would show further growth since materials consumer demands are more fashionable, or more functional, which could be satisfied by stainless steels.Thus market needs would be met, if it could be produced with reasonable production cost. The emergence of an innovative production technology is then potentially requested as VOD and AOD processes have emerged, which has saved substantial production cost. This paper describes a possibility of a future stainless steelmaking process, which uses the in-bath smelting reduction of chromium ore in BOF, and which would save production as well as energy cost."

Jan 1, 1988

By Merete Tangstad, Fei Li

This paper studies the quartz and carbon black pellets at elevated temperature with varying temperature and gas atmosphere. High-purity quartz and commercial ultra-pure carbon black was mixed (carbon content wt.15%), and then pelletized into particles of 1-3mm in diameter. The stoichiometric analysis of the pellet during heating is studied in thermogravimetric analysis (TGA) furnace at different temperature in CO and Ar atmosphere. The microstructure, phase changes and element content of sample before/after heating is characterized by X-ray diffraction, scanning electron microscope, X-ray fluorescence and LECO analyzer. The reaction process can be divided into two stages. Higher temperature and argon atmosphere are the positive parameters for SiC formation.

Jan 1, 2016

By S. Ozbilen

"Al-Li binary alloys with nominal Li contents of0.15, 1.1and2.8 (in wt%) were aged naturally at room temperature for two months, aged at low temperatures ( 65 and 1 OOEC) for up to 2 months and aged artificially at 190EC for 4 days after water quenching to 25EC following solutionizing at 530EC for 20 minutes. Ageing behavior of these binary alloys were studied by Vicker's Hardness measurements and DSC thermal analysis. Thermal analysis results indicate the formation of GP zones of Al-Li system in Al-2.8wt%Li binary alloy. In the same alloy, rapid quenching from one phase region (a) gives rise to precipitation of small o' particles in a matrix (a) with still high supersaturation. During ageing of this alloy below lOOEC an additional transformation, i.e., GP zone formation occurs proceeding at a very high rate which is described on the basis of the theoretical analysis for the quenched Al-Li system proposed by Khachaturyan et al [6]. Ageing at temperatures below 11 OEC takes place slowly by the formation of small d' particles of lower thermal stability than the quenched-in d precipitates in addition to GP zones resulting in an increase in hardness compared to water quenched samples. During artificial ageing, GP zones transform by dissolution to d' precipitates while d' particles already in the microstructure coarsen during under aged condition at which hardness increases with time till peak aged condition.IntroductionIn binary Al-Li alloys the d' (Al3Li) fully coherent internally ordered inetastable phase of Li2 structure with a=0.4038d [1-5] forms homogeneously between 120 and 190EC before the formation of stable d' (A!Li) phase and cause the superior mechanical properties. This is due to an appreciable age hardening effect resulting because of the d' precipitation during ageing [1]. The response of d' to decomposition and its formation kinetics have been studied previously and it is believed that the decomposition of the a-supersaturated solid solution occurs in a two stage process; i.e., a 6 d' (Al3Li) 6 d(A!Li). Khachturyan et al [6] theoretically investigated precipitation of the d' phase and gave an interpretation of the transformation paths of the quenched Al-Li alloys. They predict that the disordered supersaturated solid solution congruently orders, and then the uniformly ordered solution decomposes into ordered regions that differ in Li-content. Finally, ordered d' phase forms in the disordered matrix."

Jan 1, 1998

By J. L. Johnson

Remediation of small-arms firing ranges is being investigated by the Naval Civil Engineering Laboratory and the U.S. Bureau of Mines. Scheduled closures of military installations, as well as the management of active ranges, require the development of methodologies for heavy metals removal to prevent their entering the surrounding environment. The impact berms contain high concentrations of metals, and the soil and vegetation surrounding the berms were found to have slightly elevated levels. The heavy metals characterized are in the form of whole bullets, a wide size distribution of free fragments, smeared lead on the surface of the soil grains, and very finely attached particles. Gravity beneficiation can remove liberated metal contamination effectively. Weak acetic acid leaching shows promise in lowering the final metal contamination to allow the soil to pass the Environmental Protection Agency&apos;s (EPA) Toxicity Characteristic Leaching Procedure (TCLP) criteria.

Jan 1, 1991

By Kenshi Kawabata, Mitsuji Ueda, Junko Umeda, Katsuyoshi Kondoh, Kantarou Kaneko

Solid-state recycling process of in-house scraps of machined magnesium (Mg) alloy wastes has been established to directly produce wrought materials via the repetitively plastic deformation by Roll-compaction (RCP) and the conventional hot extrusion. The coarse chips, wasted in machining AMX602 (Mg-6Al-0.2Mn-2Ca) cast billets used for the gate bar used in Electronic Toll Collection (ETC) of the high-way system, were employed as the input materials in this study. RCP process enabled to serve coarse Mg alloy powder consisting of refined grains and intermetallics with no re-melting. They were easily consolidated by hot extrusion, and their wrought alloys showed both homogeneously refined grains less than 1~2 µm by dynamic recrystallization and randomized texture by repetitive plastic deformation on the input wastes. These materials revealed extremely advanced mechanical properties of high tensile strength of 356MPa and high ductility of 14.8%, compared to the originally virgin materials with 270MPa TS and 5% elongation. When applying the same Mg alloy wastes via RCP process to the mass production in the company, the large-scale extruded materials also indicated the superior tensile properties. It means that this direct solid-state process is held as “Up-grade recycle of metal wastes”.

Jan 1, 2008

By John J. Moore

This paper discusses the application of a video technique to construct stability diagrams for the combustion synthesis of ceramic-metal composites. Several model exothermic combustion synthesis reactions have been used to investigate the effect of the reaction parameters, eg. stoichiometry, green density, etc, on the stability of the propagating combustion reaction front and subsequent product morphology. The effect of varying the reactants and their stoichiometry to provide a range of reactant and product species ie. solids, liquids and gases, in the synthesis of both dense and expanded (foamed) ceramic and ceramic-metal composites was also investigated with respect to their corresponding combustion front stabilities.

Jan 1, 1993

By Bora Derin

This work deals with the recovery of valuable metals from the ancient copper smelting slags located in Küre-Turkey. In this process, copper and cobalt were recovered in metallic form and/or as their compounds, whereas iron was recovered as magnetic oxide or pigment. Abrasive grit material was produced using reduced final slag. The process stages involved carbothermal reduction in a DC arc furnace, granulation, leaching, chemical precipitation, selective sulfidizing roasting and product preparations. In this paper, the process stages were described as theoretically and experimentally whereas slag and products were characterized in detail.

Jan 1, 2003

By Bryce Clark

Cobalts history from the 14th Century is outlined, with a look at its various sources over that period. The present sources and quantities are given, when in 1994 it is an equal co-product of copper in Africa and nickel elsewhere (Canada, Australia, Russia). Future trends in this scene are also examined. The final section deals with cobalts uses in superalloys, magnets, colours, electronics, chemicals, and examines trends in its markets. Supply and demand in co-product cobalt are shown, based on the latest production figures.

Jan 1, 1995

By I. M. Ritchie

Cyanide owes its great success as a lixivant for gold to the great strength of the Au-CN bond. A replacement for cyanide must similarly be a strong complexant for gold (I) or gold (III). The various alternatives are briefly considered and it is concluded that only thiosulfate has a reasonable chance of replacing cyanide as a relatively non-toxic lixivant at the present time. However, there are considerable technical problems to be overcome before thiosulfate can be considered to be a realistic alternative to cyanide. Firstly, the leaching of gold using aerated ammoniacal thiosulfate with copper as a catalyst is a complex process which needs to be understood and controlled carefully in order to achieve maximum recoveries with minimum reagent losses. Secondly, there needs to be an option similar to the CIP process for recovering and concentrating the dissolved gold thiosulfate complex from pulps produced in the processing of low grade gold ores. The prospects for overcoming these technical&apos; challenges are evaluated and discussed.

Jan 1, 1998