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By V. Jiricny

The novel spouted-bed electrode (SBE) is a cathode system where copper is deposited at a high current density in a moving bed of copper particles. Preliminary results on the deposition of copper from acidic sulfate electrolytes using this novel cathode system were described during Copper '95 conference. Despite a high current density, the electrical energy consumption was equal to or lower than that in the conventional electrowinning. The present paper describes more investigations on SBE. The SBE consists of copper particles with approximately 1 mm diameter onto which copper is deposited from acidic sulfate electrolyte whose composition is similar to conventional electrowinning. Three types of anodes were used in conjunction with the spouted-bed cathode, namely, DSA anode for oxygen evolution, and two novel anodes. One anode is less expensive than DSA; however it showed much promise in energy consumption. At a superficial current density of 2200 A/m2, the energy consumption was around 1.0 kWh/kg copper. The research activities described in this paper were supported by BHP Copper.

Jan 1, 1999

By Patrick F. Mahoney

Each year in the United States over 10 million tons of metal are discarded with our municipal waste. This, includes, not only ferrous metals, aluminum and copper but gold, silver, platinum and every other precious metal. Resource recovery, as an approach to waste management, is replacing disposal and it presents great opportunities for those in the metal refining and recovery industry. Combustion of waste enriches the metal fraction left in the ash to the point where metals can be efficiently recovered. The recovery and quality of metals can be enhanced by good combustion control. Innovative technology is needed to efficiently tap this generous, and renewable mine.

Jan 1, 1995

Electrocrystallization studies were conducted in a concentrated acid-copper electrolyte to determine the influence of chloride ions and glue on copper nucleation and on the structure of thin copper layers. Electrochemical experiments allied to SEM and XRD examination were performed to characterize the mechanism of nucleation in the presence of additives at 65°C. Results indicated that most of the copper nucleation from a 83 g dm-3 Cu2+ solution, with 140 g dm-3 of H2SO4 is achieved in a matter of milliseconds, Although the presence of chloride and glue, at the concentration levels tested, does not seem to substantially modify the nucleation mechanism, the morphology, nuclei density and the copper film structure and orientation are changed by the presence of additives and by electrolyte stirring.

Jan 1, 1999

By Lijuan Li, Xin Xia, Junjun Huang, Qijie Zhai, Xiang Jiang

"Some experiments with different temperatures (1173, 1223, and l273K) and different annealing times (3, 4, 5, 6min) were carried out on cold-rolled plate of Fe-36Ni invar alloy. The microstructure and the mechanical properties were observed and tested respectively, and the fracture morphology was observed by SEM. The results show that with increasing of the temperature and the annealing time, the austenite grains gradually grow up accompanied by a small amount of annealing twin crystals, meanwhile, its plasticity and toughness are improved, and it is typical ductile fracture under the condition of tensile failure. After annealed at l223K, the invar alloy has better comprehensive properties than that at the other annealing temperatures, and the grains size is more uniform. Furthermore, when the annealing time is 4min, the invar alloy has the best comprehensive properties.IntroductionAs we known, most metals and alloys expand with increasing temperature. More than one hundred years ago (in 1897), Guillaume observed that Fe-Ni alloy with face-centered cubic (fcc) crystal structure, consisting of36%Ni, showing a very small thermal expansion coefficient below the ferro-to-paramagnetic transition, the thermal expansion coefficient around room temperature( <2 X 1O-6K-1 compared to most metallic materials which have a thermal expansion coefficient of 10-20 X 1O-6K-1) [1,2]. Since then, the subject has attracted many researchers, and various alloys with low thermal expansion coefficients have been developed. These alloys, generally known as ""invar alloys"", are in demand where dimensional changes due to variation in temperature must be minimized and where high stability is required [3, 4]."

Jan 1, 2012

By Fu-Shen Zhang, Mengjun Chen, Jianxin Zhu

"A novel approach for foam glass preparation, namely vacuum-aided powder sintering technique, was preliminarily investigated in the present communication. The key point of which was to prepare foam glass at a negative pressure. Compared to normal powder sintering process, the new approach could benefit the foaming process by shorting the holding time, reducing the amount of foaming agent and especially decreasing relative density of the product. Optimum conditions were 750 °C, 1000 Pa, 5 min and 1 wt.% foaming agent, respectively.IntroductionFoam glass represents a highly valuable solution for thermal and acoustic insulation, since it possesses a generally higher mechanical, chemical and thermal stability than other foams'1'. The first industrial processing for foam glass production, the direct introduction of gases (""blowing"") into the special molten glass, can be dated back to the end of 1930s'2'. At present, almost all foam glasses is prepared by powder sintering technique instead of blowing,3 since it reduces the temperature by several hundred degrees. Moreover, as fine glass powders or similar powders can be used to substitute corresponding glasses by this technique, considerable attention has been focused on the production of foam glass by considering fully recycled glasses, coal fly ash, or other solid wastes as raw materials,4 especially CRT glasses'3' 5', on the point of environmental protection.In a previous report'6', when discussing the lead removal and recovery from CRT funnel glass by a pyrovacuum process, we found that foam glass could be prepared at a negative pressure. Therefore, in this communication, the similarities and differences between the powder sintering process for foam glass at normal and negative pressure was preliminarily discussed."

Jan 1, 2011

By Toshitaka Ota, Hisao Suzuki, Minoru Takahashi

"Perovskite-type lead zinc niobate (PZN) exhibits excellent electrical properties such as high dielectric constant, high electrostrictive coefficient and superior piezoelectricity. Therefore, PZN ceramics are very promising for high performance electronic devices. However, perovskite phase PZN is not stable under the ambient atmosphere. Accordingly, it is very difficult to prepare single-phase perovskite PZN ceramics. In this study, A-site cation of lead was partially substituted for barium to stabilize the perovskite phase of the PZN (Ba-doped PZN) powder. In addition, molecular design of an alkoxide precursor was controlled for a low-temperature processing. As a result, molecular design to suppress the lead-volatilization during calcination was preferred for a low-temperature processing. Processing temperature for a single-phase perovskite was depended on the amount of barium dopant. Doping of20 mole% of barium resulted in the single phase perovskite at 900 °C. The temperature for the single phase perovskite of Ba-doped PZN powder, which depended upon the amount of Ba-doping, was lower than that of the powder prepared by the atmosphere controlled conventional powder processing at least by 150 °C.IntroductionFerroelectric thin films and powders with perovskite structure are of renewed interest for micro-electronic applications, including ferroelectric random access memory (FRAM), dynamic random access memory (DRAM), and thin-layer capacitors integrated onto a silicon wafer [1-3]. In addition, recent advancement in micro-machine requires a high performance micro-actuator [4]. A perovskite type relaxor of Pb(Zn113 Nb213)03 is one of the promising materials for a high performance capacitor and microactuator because of their high permittivity and electrostrictive coefficient [5]. Therefore, this paper focuses on the low temperature processing of Ba-doped PZN powders.Chemical solution deposition (CSD) from molecular-designed alkoxide precursor solution is one of the most promising techniques for processing high-performance powders and thin films because it offers precise control of compositions on a molecular scale as well as a low processing temperature [6]. However, chemical solution deposition of perovskite type PZN powders and ceramics are very difficult because of the formation of stable pyrochlore phases. Therefore in the past, PZN powders and single crystal have been prepared by the hydrothermal method or flux method as well as the partial substitution method of a A-site cation [7-10]. In this study, a suitable molecular design for a preparation of perovskite type Ba-doped PZN powders with a chemical solution deposition process is investigated as well as the effect of A-site cation substitution. Chemical solution deposition from molecular-designed alkoxide precursor solution is expected to decrease the amount of a A-site substitution and/or a crystallization temperature for a single phase perovskite. This paper describes ""the relation between molecular-design and processing temperatures for a single-phase perovskite of Ba-doped PZN powders in comparison with the conventional oxides mixing method."

Jan 1, 2000

Most of the world's zinc metal is produced via the roast- leach-electrowinning (RLE) process. The process is well established, but most of the sulphur in the sphalerite concentrates reports in the acid, which has to be stored and/or sold. There are significant incentives to develop a simpler process with much reduced acid generation. Ferric ion is a well known oxidant for most sulphides, in particular sphalerite, and it converts the sulphide to elemental sulphur. Based on stoichiometry, however, the amount of ferric ion needed to achieve acceptable zinc extractions is prohibitive for downstream zinc recovery from the leach solutions. The process suggested here makes use of less-than-stoichiometric ferric sulphate additions because the ferric ion is regenerated by sparging SO2/O2 mixtures. This regeneration can be effected in-situ in the leach vessel or outside the leach vessel. An example of the application of this new process is presented for a Canadian sphalerite concentrate assaying 60% Zn. The effects of temperature, ferric concentration and ferric ion regeneration are presented. Options to recover zinc from the leach solution are also briefly discussed.

Jan 1, 2000

By Jitka Jandová

A laboratory process based on simple and environmental friendly operation, aimed at recycling of spent Li/MnO2 batteries, is described in this study. This process involves roasting Li/MnO2 batteries in a vacuum furnace at 650°C, followed by selective leaching Li2CO3 from calcined electrode material in distilled water at ambient temperature and controlled crystallization of pure Li2CO3.

Jan 1, 2006

By Józef Czernecki

Chalcocite-bornite concentrates of KGHM contain, similarly to chalcopyrite concentrates, 20-30 wt.% Cu but several times less iron (2-7 wt.%) and sulphur (9-12 wt.%). Another useful characteristic of KGHM concentrates is the presence of organic carbon (5.5-8.5 wt.%) in them, which serves as fuel in the flash smelting process. The main contaminants of the concentrates are lead (1.3-2.5 wt.%) and arsenic (0.05-0.4 wt.%) which require appropriate technological treatment in order to remove them from the copper pro-duct. Chalcocite-bornite concentrates are processed in KGHM by two different processes: ? a flash smelting process (Glogow 2 Smelter) ? a shaft smelting process (Glogow 1 Smelter, Legnica Smelter) The shaft smelting process used in the Glogow 1 Smelter and in the Legnica Smelter has higher production costs than the flash smelting process of HM Glogow 2. Additionally, the shaft smelting process employs several concurrently running installations (six dryers, seven briquetting lines, six shaft furnaces, nine converters), the operation of which, including maintenance, requires significant financial expenditure. Therefore, the Company is currently considering the substitution of the shaft furnace process in the Glogow 1 Smelter and in the Legnica Smelter by the one stage flash smelting process located in the Glogow Smelter, with output equaling the copper production capacity of both smelters, i.e. 320 000 ? 350 000 t/a. There are two technological options being considered which differ from each other in their man-ner of flash slag cleaning. In the first, the slag cleaning would be the same as in the existing Glogow 2 Smelter, i.e. the slag would be cleaned by pyrometallurgical reduction of the oxide copper and other metal compounds in the electric furnace in order to produce waste slag containing below 0.6 wt.% Cu. However, the other option of the flash slag cleaning would be carried out in two stages. After preliminary slag reduction in the electric furnace to 3-5 wt.% Cu, there would be flotation of the partially reduced slag.

Jan 1, 2006

By Bora Derin, Adnan Aydin, Onuralp Yucel, Hakan Morcali

"The steelmaking industry which uses electric arc furnaces (EAF) generates approximately 250.000 tons of EAF flue dusts annually in Turkey. These flue dusts contain valuable metals such as zinc, iron and lead. For example, if these flue dusts can be treated efficiently, disposal problems certainly decreases and annually almost 40.000-75.000 tons of zinc can be recovered. In this study, powder and pellet forms of EAF flue dusts taken from a steel mill were carbothermally treated in a temperature controlled pilot scale rotary furnace via carbothermal reduction in order to investigate the reduction behavior of Zn and Pb. Temperature (900-1000 and 1100 °C) and time (0-90 minutes) were selected as reaction parameters. The chemical analysis was performed for the sample residues.IntroductionTurkey’s steel production reached to 23.3 million tons in 2006. There are three integrated steel plants of which capacities vary from 0.7 to 3 million tons per year and seventeen EAF steel plants of which capacities vary from 0.06 to 2 million tons per year [1]. When it is considered that more than 74 % of the Turkish steel production is produced by EAF method and approximately 10 - 15 kg of dust is formed per ton of steel during this process, the amount of annual generated EAF dust may be estimated at approximately 0.25 million tons. EAF dust which contains valuable metals such as zinc, lead, iron, cadmium, and chromium, is considered as hazardous waste product in steelmaking industry. If these flue dusts can be treated efficiently, not only the disposal problems certainly decrease, but also annually almost 40.000-75.000 tons of zinc can be recovered. Many studies which exist on recovering of the valuable metals from EAF dust, propose and practice many hydro-metallurgical and pyro-metallurgical treatments [2- 7]. In this study a laboratory scale work were performed to investigate reduction behavior of zinc and lead in EAF dust by carbothermal process in a rotary furnace."

Jan 1, 2008

By Wellington Pereira Inácio, Frederico Muylaert Margem, Artur Camposo Pereira, Sergio Neves

"Natural fibers are currently gaining attention as reinforcement of polymer composites for uses in engineering parts for automobile and building construction. In spite of environmental, economical and societal advantages, the natural lignocellulosic fibers are not as uniform in their dimension and properties as compared to synthetic. In recent works it was found that the variation in strength could be correlate to the equivalent diameters for several lignocellulosic fibers including the sisal fibers. In the present work an investigation on a possible correlation of the equivalent diameter with changes in density and elastic modulus was carried out. Precise measurements of the equivalent diameter, conducted in a profile projector, were correlated with the density and the elastic modulus by means of the Weibull statistic analysis. The results showed that an inverse correlation with the diameter also applies for both the density and the elastic modulus with a high degree of precision. SEM observation of the sisal fiber in structure and fracture aspects strongly indicate that defects and microfibril participation could be responsible for the inverse correlation.IntroductionAccording to Kalia [1], cellulose-based fibers are currently being pushed owing to their ""green"" image. Contrary to synthetic glass fiber, extensively used in our modem technology, these lignocellulosic fibers are renewable and can be incinerated at the end of the material's lifetime without adding pollution in the atmosphere moreover, the amount of CO2 released during incineration process is negligible as compared to the corresponding amount taken up by the plant throughout its lifetime. Even if an industrial processing equivalent of C02 release is added, the lignocellulosic fiber is considered neutral with respect to the emission of gases responsible for the global warming [2]."

Jan 1, 2012

By Peter G. Smith

Tri-calcium aluminate (TCA) is a dominant alkaline component of the red mud residue from the Bayer process. A method being considered for industrial implementation partially neutralizes the residue by contacting it with gaseous CO2. This paper outlines the chemistry of CO2neutralisation of TCA under conditions relevant to the treatment of Bayer residue. CO2 neutralisation of the liquor is fast. It results in the formation of amorphous aluminium hydroxide and dawsonite that agglomerate together. Neutralisation of solid TCA is slower and leads to the formation of calcite, dawsonite and amorphous aluminium hydroxide. The dissolution of TCA in partially neutralised slurries causes pH reversion. However the carbonated solutions contain a store of bicarbonate that can supply aqueous carbon dioxide to complete the transformation. The pH at which the carbonation is carried out will affect the degree of TCA transformation during the carbonation process. In particular, if the pH of the carbonation is too low (near 7.0), calcite precipitation is inhibited and the degree of transformation is low. Controlling the carbonation pH helps to optimise the neutralisation process.

Jan 1, 2003

By Marcos V. F. Fonseca, Gilson V. Fernandes, Caroline G. de Oliveira, Sergio N. Monteiro, Frederico M. Margem, Anna C. C. Neves

Natural fibers represent an economic and environmental motivation for replacing the synthetic fibers, mainly as composite reinforcement material, which is one of their major applications. Some advantages of the natural fibers are the biodegradability, low cost and renewability. Among the natural fibers, the lignocellulosic ones are highlighted for their high resistance. One of the most cultivated lignocellulosic fibers in Brazil is the Eucalyptus fiber, extracted from the bark of Eucalyptus citriodora plant. In this work, it was investigated the tensile behavior of the epoxy matrix composites reinforced with different volume fractions of Eucalyptus fibers. The specimens were made by pouring the still liquid resin into the mold and laying the fibers onto the resin. The results show a decrease in the tensile resistance with the increase of volume fraction. It is due to the low adhesion between the fibers and the matrix.

Mar 1, 2017

By Yuanbo Zhang, Mingjun Rao, Guanghui Li, Chongzhong Ouyang, Shuhui Zhang

Oolitic hematite ore with high-phosphorus content is currently recognized as one of the most refractory iron ore resources in the world. The high-phosphorus content and unique structure of the oolitic hematite ore make it difficult to be beneficiated. The process of direct reduction followed by magnetic separation has significance to the utilization of oolitic hematite ore, and sodium salts can improve the dephosphorization. However, the behavior of phosphorus during reduction roasting, and the intensified dephosphorization mechanism of sodium salts are not clear. In this study, by using chemical analysis, chemical phase analysis, XRD analysis, optical microscopy, and scanning electron microscopy analyses, the behavior of phosphorus during reduction roasting of high-phosphorus content oolitic hematite ore and the effect of sodium salts on behavior of phosphorus were studied.

Jan 1, 2015

By Jean Igor Margem., Lucas Barbosa de Souza Martins, Frederico Muylaert Margem, Sergio Neves Monteiro, Artur Camposo Pereira, Rômulo Leite Loiola

"The fibers extracted from the stem of the bamboo plant have been investigated as possible reinforcement composites due to their relatively high tensile strength. Although previous works have already been conducted about the mechanical properties, up to now a dimensional characterization of the distribution and the effect of diameter on the elastic modulus of bamboo fiber of the specimen dendrocalmus giganteus has not been performed. The aim of the present work was to statistically characterize the distribution of the diameter of a lot of bamboo fibers of that specimen. Based on this characterization, diameter intervals were set and the dependence of the Elastic Modulus (E) of theses fibers with a corresponding diameter was analyzed by the Weibull Method. The results indicated an inverse dependence, in which the highest Elastic Modulus were obtained for the thinnest fibers. Moreover, it was found that a mathematical hyperbolic relationship fit well this inverse correlation between the Elastic Modulus and the bamboo fibers diameters.IntroductionBamboo is a well known grass-type plant with a hard and stiff stem or culm that can reach, in some species, more than 10 cm in cross section diameter and stand several meters height. Owing to its low density, approximately 0.9 g/cm3, bamboo culms have been used in house construction from scaffoldings to panels. As an abundant natural resource in tropical and temperate regions, specially in Asia and South America, bamboo is also a substitute for wood and plastics in furniture and lightweight parts of automobile [1,2]. The cylindrical shape of the culm is, however, a limitation for its direct use in engineering systems. Consequently, research works have been conducted on bamboo fibers stripped off from the culm as reinforcement of polymer composites. [1-12]. According to Shin et al [3] bamboo fiber-epoxy laminates can be made into specific sizes and shapes, preserving the natural microstructural properties. These fiber composites overcome the limitation of the culm's cylindrical macrostructure. As a further advantage, Shin et al [3] indicated that cracking and bioerosion caused by insect pests is prevented."

Jan 1, 2013

By J. Tang

The major problem with the Nd-Fe-B magnet is its low operating temperature, i.e., the coercivity decreases so rapidly with increasing temperature that the practical maximum operating temperature-is only 100 °C. Meanwhile, it has been reported that nitrogen addition can drastically increase the Curie temperature of both R2Fe17 and RTiFe11 (R = rare earths). A reasonable question is, then, can one see a similar effect in Nd-Fe-B system? Experiments have been conducted to examine how magnetic properties of Nd-Fe-B magnet are affected by the nitrogen addition. Our results show that part of Nd2Fe14B maintains its original crystal structure and no substantial change in To, due to such N2 treatment is found. However, part of the sample decomposes into a-Fe and, possibly, Nd nitride as a result of nitrogen treatment.

Jan 1, 1992

By Irsan Chandra

It is generally recognized that the gold thiosulfate leaching system requires the presence of copper and ammonia in order for acceptable leaching kinetics to be observed. However, the presence of copper and ammonia complicate the chemistry of the system as thiosulfate is rapidly oxidized by oxygen under these conditions. In addition, the environmental impact of ammonia would need to be considered before the adoption of this system. This paper describes fundamental studies into the thiosulfate oxygen system. The two reagents for this system are thiosulfate and oxygen, and leaching is carried out at pH < 7. It will be shown using electrochemical techniques that both the reduction of oxygen and the oxidation of gold-to-gold thiosulfate are hindered. Thus, if leaching is to work under these conditions, then both half reactions need to be improved. The use of additives, such as thiourea and lead have been shown to dramatically improve the oxidation of gold and the reduction of oxygen respectively. The leaching of gold in the presence of such additives is discussed.

Jan 1, 2003

By Núbia Suely Silva Santos, Alexandre da Silva Crespo, Frederico Muylaert Margem, Sergio Neves Monteiro, Anderson de Paula Barbosa, Michel Picanço Oliveira

"Environmental considerations in addition to technical, economical and societal benefits are increasingly promoting the substitution of natural fibers for glass fiber in polymer matrix composites. However, natural fibers are heterogeneous in their dimensions, specially the cross section, which plays an important role in their mechanical strength. The fibers extracted from the petiole of the buriti palm tree is a relatively unknown but promising natural fiber for composite reinforcement. In this work, a statistical analysis of the density of buriti petiole fibers using the Weibull methodology was performed. An attempt to correlate the fiber density with the diameter, precisely measured by means of a profile projector, was carried out. The results revealed an inverse dependence between the buriti petiole fiber diameter and corresponding density. Fracture tip observation by SEM suggested a possible mechanism that could justify this inverse correlation.INTRODUTIONIn the past decade polymer composites reinforced with natural fibers obtained from cellulose-based plants, known as lignocellulosic fibers, have been applied in several engineering sectors, specially the automobile industry as both interior and outside component [1-4].Environmental benefits as well as economical, social, and technical advantages are actually promoting the substitution of these lignocellulosic for the traditional glass fiber in polymer matrix composites [5]. Today several lignocellulosic fiber are being extensively investigated [6-11] and considered for reinforcement of polymer composites. Some relatively unknown lignocellulosic fiber with reinforcement potential, however, still need to be characterized aiming at future application in composites. This is the case of the fibers stripped of from the petiole of the buriti palm tree, which is endemic in the central and northern regions of South America [12,13]. Preliminary works on the possibility of using the buriti petiole fibers as composite reinforcement, has shown favorable results [14,15]."

Jan 1, 2012

By William Petruk

The behaviour of sphalerite during mineral beneficiation of base metal ores has been studied at CANMET and other institutes for at least 15 years by determining the liberations of sphalerite in mill products and calculating the recoveries of liberated and unliberated sphalerite in zinc concentrates. Sphalerite in base metal ores commonly occurs as layers and as interstitial material between pyrite. Layered sphalerite is generally liberated during primary grinding, but interstitial sphalerite requires re-grinding to achieve liberation. Around 95% of liberated sphalerite is generally recovered in zinc concentrates frau zinc circuit feeds. A series of tests was conducted on sphalerite in the ore of Brunswick Mining and smelting during a continuous fine tuning operation of the concentrator. It was found that a grind of 80% minus 37 micrometres was required to liberate the interstitial sphalerite. The fine grind increased Zn recoveries from 75% to 78-80%, but produced liberated slimed sphalerite which was lost. Since regrinding to a fine grain size is needed to obtain the desired sphalerite liberation, a method of recovering the slimed sphalerite is required.

Jan 1, 1990

By Patrice Chartrand, Halvor Dalaker, Philippe Ouzilleau

A size-dependant thermodynamical model for the carbon-hydrogen previously developed by Ouzilleau et al. [1] has been expanded here to include chemisorption of methyl groups. Gibbsenergy minimalisation calculations using FACTSAGE software on this model indicates that hydrogen bonding through methyl groups is energetically favoured as an intermediate between bonding as monoatomic hydrogen to edge hexagons (which is more favourable) and as monoatomic hydrogen to corner hexagons (which is less favourable). The model has also been applied to methane decomposition and oxide reduction using natural gas. A C-H solid solution as a thermodynamic description of the solid carbon phase influences calculations of carbon activity in metastable methane, and gives different results than when using graphite.

Jan 1, 2015