Search Documents

By Cheng Gong-jin, Chu Man-sheng, Liu Zheng-gen, Zhang Yong, Liu Jian-xing, Xue Xiang-xin

"High chromium vanadium-titanium magnetite is one kind of Fe-V-Ti-Cr composite ore resources, which owes high utilization value. Owing to lacking systematic study on the sintering of this ore home and abroad, effects of carbon addition and basicity on sintering process and sinter metallurgical properties, such as sinter yield, vertical sintering speed, tumbler strength, sinter machine utilization coefficient, and low temperature reduction degradation were investigated systematically under laboratory conditions in the paper. The results shows that, when high chromium vanadium-titanium magnetite proportion is kept unchanged as 13% in sintering feeds, sintering process index and metallurgical properties are the optimum under carbon addition 5.0% and basicity 2.70, which meets the requirements of blast furnace burdens. This research provides technical parameters for practical sintering production of high chromium vanadium-titanium magnetite.IntroductionHigh chromium vanadium-titanium magnetite (hereinafter abbreviated as hi§h-Cr V-Ti magnetite), in which Fe is closely symbiotic with Ti and isomorphous with V and Cr1'- l, is one kind of typical vanadium-titanium magnetite resources with high comprehensive utilization value but the difficulties are extremely high due to complex chemical composition and mineral structure. At present, the feasible and mainstream utilization process of high-Cr V-Ti magnetite should be the route of agglomeration-blast furnace smelting. Thus, sintering production is the foundation for high-Cr V-Ti magnetite utilization. However, till now there are few research documentations on high-Cr V-Ti magnetite sintering home and abroad. Under the above background, this study focused on detailed researches of high-Cr V-Ti magnetite sintering. Sintering process uses the powders or fine iron ores to produce artificial rich ore with good metallurgical properties 4l Solid fuel provides 90% heat requirement during sintering15J. The appropriate amount of fuel and flux should be added during sintering in order to provide necessary heat and maintain the desired basicity16l. That is to say, carbon addition and basicity are two key factors affecting metallurgical properties of sintering products17J. Therefore, the effects of carbon addition and basicity on sintering process and metallurgical properties, including sinter yield, vertical sintering speed, tumbler strength, sinter machine utilization coefficient, and low temperature reduction degradation, are systemically investigated under laboratory conditions in the study, on purpose to achieve the optimization of sintering process for high-Cr V-Ti magnetite."

Jan 1, 2013

By Linli Wu, Guangchun Yao

"The influence of deformation on the properties of short-carbon-fiber reinforced 2024 alloy matrix composites was investigated in this study. It was found that the distribution of carbon fibers changed from the random state before deformation to the ordered state that carbon fibers arranged along the direction of rolling and extruding after deformation. Under the temperature range in control, the increase of rolling and extruding temperature would benefit to improve strength and elongation of composites, but was not conductive to improve the hardness of composites. With the increment of total deformation, all the strength and the hardness of composites became greater, nevertheless the elongation decreased. After being rolled and extruded, the strength and the hardness of composites were all bigger than those of composites before being rolled and extruded; moreover, the strength of extruded 2024 alloy matrix composites was higher than that of rolled 2024 alloy matrix composites under the same heat treatment conditions.IntroductionCarbon fibers have been reckoned as very important reinforcements due to the high specific strength, specific modulus, high thermal and electric conductivity, low expansion coefficient and good self-lubricant properties [1-4]. Light metal composites reinforced with carbon fibers, such as carbon fibers in an aluminum matrix, are widely used and studied. Some studies have concentrated on the interfacial characteristic of CF/Al composites in order to search for the way of improving the bonding between carbon fibers and the matrix alloy [5-8], and on the influence of the carbon fiber percent composition in the composites [9-11]. Some researchers began to take interest in the deforming characteristic and failure behavior of carbon fiber reinforced metal matrix composites [12-16]. However, the same with other metal materials, most of CF/AI composites were prepared by some single processes, such as powder metallurgy, extrusion casting and vacuum press infiltration, which caused that the composites products could not be manufactured directly. In order to cover the shortage of the mentioned above processes and get composites products with perfect mechanical properties and dimensional accuracy, the composites should be reworked by rolling, extruding or forging process. Compared with research about manufacturing process, the correlative investigation on the reworking of CF/Al composites was much less evidently, which restricted the application and the further development of CF/Al composites."

Jan 1, 2012

By Michael S. Moats, Alexander Derrick

"The Winand Diagram was developed and has been used for decades to illustrate the interaction between polarization, mass transport and inhibition on the resulting structure of a metal electrodeposit. Recently, Adcock et al. criticized the Winand Diagram and developed their own structural diagram based on nucleation and plating overpotentials. Their work was based on zinc electrodeposition using a galvanostatic staircase method. This work explores the nucleation and plating overpotentials for copper electrodeposition using conditions typical for primary electrowinning and the galvanostatic staircase experimental technique. Additionally, the effects of organic additives and plating substrate on these overpotentials are reported.IntroductionThe control of electrodeposited structures is critically important to modem electrometallurgy operations to insure proper quality and efficient energy use. Electrodeposition of base metals for primary recovery (e.g. electrowinning or electrorefining), while similar to plating for decorative or device manufacturing, differs in the need to produce deposits that cover large areas and grow to significant thickness. Thus, controlling nucleation and particularly growth of electrodeposits is critically important for base metal electrometallurgical operations.The control of nucleation and growth on an industrial scale is most influenced by five parameters - current density, temperature, metal concentration, electrolyte agitation and additives. The effects of these parameters on electrodeposition are interrelated. To describe their effects on the type ofelectrodeposits generated and provide practitioners with a useful tool, Winand developed what is known as the Winand Diagram [1-2]. An adapted version of the Winand Diagram is shown in Figure 1.Winand characterized electrodeposits using Fischer's classification [3] and plotted the various deposit types versus inhibition on a vertical axis and the ratio of current density to bulk metal concentration on the horizontal axis. Inhibition intensity is a complex parameter and is still not well understood even though Fischer introduced the term in 1960 [4]. Often, inhibition intensity is simplified to equal the concentration of organic additive at the deposit surface and is related to the inverse of the exchange current density of the metal being deposited. The ratio of current density to bulk metal concentration is used to represent the ratio of crystallization overvoltage to mass transport of the depositing ion. As such i/iL could also be along the horizontal axis, where iL is the limiting current density of the electrodeposition reaction."

Jan 1, 2012

By D. F. Liub, Z. Y. Liu, W. Y. Xue, Y. F. Shenb, Y. D. Wang

"The microstructure characteristics and deformation behavior of ultrafme grained (UFO) 304SS fabricated by accumulative rolling and armealing have been investigated by means of tensile tests, electron-backscatter-diffraction (EBSD) and transmission electron microscopy (TEM) techniques. The volume fraction of martensite phase decreases with increasing armealing temperature. In the grain sizes ranging from 300 nm to 10 µm, the strength held Hall-Petch relationship. The sample with an average grain size of 300 nm exhibited extra high yield strength of 1700 MPa and a tensile strength of 1780 MPa, while the elongation retains 12%. The limited uniform elongation in the UFO materials could be explained in terms of plastic instability. Very interestingly, for the bulk material with an average grain size of 1.200 µm, the high yield strength and uniform elongation were simultaneously achieved to be as 1000 MPa and 18%, respectively.IntroductionUltra-high strengths have been achieved in elemental metals by employing heavy plastic deformation, or by creating ultra-fine-grained (UFO) structure. Here UFO materials are defined as polycrystalline solids with property-controlling microstructural features below the 1 µm level. Typical processing routes include severe plastic deformation (SPD) [1, 2], which decomposes the grains through dislocation accumulation and reorganization (polygonization). Several different kinds of SPD process for bulk materials are typically as equal-charmel angular pressing (ECAP) [3], high-pressure torsion (HPT) [4] and accumulative roll-bonding (ARB) [5]. One of the main motivations for such a push for the very small grain sizes stems from the expectation of unprecedented mechanical strength, as predicted by the well-known Hall-Petch relationship that projects a continuous rise of strength with decreasing grain size [6]. However, these ultra-high strength metals no longer have the high ductility typical of their conventional coarse-grained counterparts, because the undesirable inhomogeneous deformation on the microstructure level can lead to the early onset of failure, severely limiting the useful ductility [2]. Recently, the interesting strategies have been performed to increasing simultaneously the ductility and strength ofUFG pure copper and nanostructured alloys by Zhao et al [7, 8]. In a pure copper, a high ductility has been achieved without sacrificing strength by introducing a high density of pre-existing twins and a large fraction of high-angle grain boundaries. Their encouraging results trigger our motivation to obtain high strength and ductility from the commercially bulk material."

Jan 1, 2013

By Reuben John Mathew

"Oxygen evolution is the main anode reaction in industrial copper electrowinning. The oxygen bubbles do not conduct electricity, thus increasing the electrolyte resistance. The oxygen bubbles formed at the anode rise to the surface, occupying a larger volume of the electrolyte at the top of the cell than at the bottom. This oxygen bubble concentration gradient contributes to a gradient in electrolyte resistance and consequently a tendency toward uneven current distribution. This phenomenon increases the chance for uneven growth on the cathode and/or short-circuits, particularly on the lower portions of the cathode. This issue may be ameliorated by increasing the charge transfer resistance for oxygen evolution down the height of the anode. This concept was studied by solving the current distribution for a 2-D model of a copper electrowinning cell using COMSOL.IntroductionA copper electrowinning tankhouse aims to operate at the highest current density that will deposit on the cathode a layer of copper metal possessing the desired physical and chemical characteristics. The operating current density is directly related to the physical nature of the copper deposit on the cathode (Figure 1), limiting a copper electrowinning tankhouse to some operating current density that produces acceptable copper deposits.[!] The ratio of the operating current density to the limiting current density is typically around 0.3.[2] If the limiting current density for a cell could be raised, the operating current density could also be raised and thus result in savings in capital cost for a tankhouse. [3]The average operating current density in a copper electrowinning plant is 270A·m- 2 .[4] The value for average current density, however, obscures the fact that the face of a cathode does not experience this value equally. Indeed, the current density varies along the height of an electrode and is independent of the height of the electrode.[5] This phenomenon partly explains why the lower portions of a cathode tend to display a rougher copper deposit.In order to utilize a higher operating current density but still remain at 30% of the limiting current density, the limiting current density must be raised, but it is affected by the mass transfer regime at the electrodes. The mass transfer regime is currently poorest at the lower portions of the cathode and this is part of the reason for the tendency for poor cathode deposits to occur at the lower portion of the cathode.[6]"

Jan 1, 2012

By M. J. Soria-Aguilar, F. R. Carrillo-Pedroza, S. Preciado-Nuñez

"Dust originated from the Iron Blast Furnace (BF) and the Basic Oxygen Furnace (BOF) containing alkalis and zinc are not completely recycled because due affects the process efficiency. These types of dust represents an economical lost as a consequence of values contents of iron and carbon. Several processes in aqueous media have been developed to treat the steelmaking dust. This work presents a laboratory study for reduce zinc and alkali containing in BF and BOF dust, using different acid and alkaline solutions and oxidants as ozone. The results obtained show that the elimination of zinc and alkalis can vary from 5 % to 80 % depending on the treatment conditions (the solution, the oxidant and the temperature). The dust obtained from this treatment can to be recycling to the steelmaking processes to recovery iron and carbon values.IntroductionEach one of the steel making industry processes generate several sub-products and residues containing useful units of iron, carbon and other elements that are or could be recycled to the productive process. Some of those sub products are the dust from the gas cleaning system of the blast furnace and the dust from BOF reductive process; such dusts are sent to the sedimentary lagoons. The dust represent a lost of 2 % of the total iron and coal mineral’s content feed to the process.The typical iron, carbon and zinc content of the blast furnace dust is approximately 40, 24 and 0.3 % and the content of the BOF dust are 50, 15 and 0.9 % weight respectively, with physics - chemical characteristics that became them susceptible to be agglomerated and feed to the blast furnace. But the high content of zinc does not allow recycling it into the process. At the blast furnace the presence of zinc propitiate the formation of film in the furnace wall; these elements are vaporized in the low section of the cube of the furnace and they are dragged by the gases to the top and condensed again at the cube. Part of these condensed materials strongly adheres to the furnace cover harming it and reducing the empty space of that section, causing eventually a severe perturbation of the ascendant gas flux [1]."

Jan 1, 2008

By P. Hanniala

In the day-to-day life the copper business of today is influenced directly by the ever-increasing general concern about the environment. In addition to that the inherent shortcomings of the copper smelting business, have since many years been the falling real price level of the metals and the relatively high initial capital investments required for the production units. These shortcomings have been compensated for by high productivity, low specific operating costs, low metal inventory and unbeatable technological superiority. Thus today more than 50 % of the world primary copper is today produced by utilizing Outokumpu Flash Smelting Technology. This figure is expected to grow at an increasing speed in the near future. Characteristic for the Outokumpu Flash Smelting technology is high flexibility for a wide grade of concentrates and the highest sulfur capture owing to at the same time competitive investment and operational costs. The Flash Converting technology offers new options for copper production and optimization of the mine- concentrator-smelter production chain. In the following years it is expected that the trend in copper making is that higher grade concentrates are produced at the mines. Thus increasing amount of high grade concentrate will be available for direct-to- blister Flash Smelting causing an overall cost reduction in copper smelting i.e. both in capital and operational costs. In the '90s new technologies based on Outokumpu Flash Smelting technology have been taken into operation, thus eliminating the non-continuous Peirce-Smith converting process step. New innovative solutions have been used in the latest projects, as in Kennecott Utah Copper, where the new Kennecott-Outokumpu Flash Converting process was started up in 1995. Also, in 1995 the new DON process was started at Outokumpu Harjavalta nickel smelter followed by the Fortaleza nickel smelter in Brazil in 1997. The aim of the continuous development work at Outokumpu has been the expansion of the direct-to-blister process towards lower grade concentrates. The most recent example of this is the start-up at the Olympic Dam smelter in Australia, where the existing direct-to-blister Flash Smelting furnace was replaced with a new one having a capacity of 200 000 t blister copper per annum in just one smelting step.

Jan 1, 1999

By Petr Sulovsky, Pavel Leber, Jaroslava Ledererova, Miroslav Svoboda

"The properties of raw materials used for the production of building materials play an essential role in their choice. Industrial waste materials can in some cases improve the performance of new building materials, when compared with classical raw materials. The addition of waste can however negatively impact some of the building material´s characteristics, influencing its stability, service time, durability, and can introduce undesirable variation of certain characteristics over time. It is necessary that each secondary raw material intended for such use be thoroughly investigated in terms of its chemical, physical, and mechanical properties, with special attention paid to the risk components and risk parameters. It is necessary to make many- sided technological tests in relation to the required characteristics of the resulting materials for each chosen application. Moreover, the limit values for the critical (risk) parameters, which the given secondary raw material must satisfy to be used in a specific technology, need to be defined. Introduction The risk components in the industrial waste materials to be used in the production of building materials fall into two groups: - components that pose a risk of development (instant or delayed) of a process deleterious to the utility properties and durability of the resulting materials. Such processes include volume change (expansion as well as shrinkage), alkali-silica reaction, delayed ettringite formation, thaumassite attack, aggressive carbonation, etc. - elements or components that can, if released from the waste-containing building material, pollute the environment. They involve the so called potentially hazardous elements as well as compounds like fenols, PCB, PAHs etc. From the viewpoint of the presence of both groups of risk components, the wastes can be classified as: • environmentally inert waste materials. They are produced in the largest volumes and do not pose a threat to human health. Their physical and/or chemical characteristics fail to satisfy all requirements for utilization in ordinary production. The aim of technology design is to work them into the building products with suitable utility properties. • easier workable waste materials containing toxic components are produced in large volumes. In spite of the content of toxic components, their physical and chemical properties make them suitable for ordinary production, provided that the harmful substances are immobilized by the chosen technology."

Jan 1, 2008

By Junhong Noh, Kug Sun Hong, Jung-Kun Lee, Bo Ding

"The photocatalytic splitting of water into H2 and O2 by oxide nanoparticles has received much attention. However, the full potential of photo-catalysts for efficient hydrogen generation out of water has not been fully realized yet due to unresolved limitations including the low electrical conductivity and ineffective carrier extraction. Here, we report composite oxide materials consisting of 1-dimensional (1-D) transparent conducting oxide (TCO) core and TiO2 shell. Highly conductive ITO nanowires were grown on a flexible SUS mesh as a core component. The photoelectrodes consisting of these 1-D nanocomposites have increased carrier mobility due to the TCO core, while the TiO2 shell provides the photocatalytic functionalities. In addition, the built-in-potential at the interface between TCO core and the TiO2 shell improves the collection of charge carriers from TiO2 to TCO. These factors altogether contribute to increasing the photocurrent of the device under light.I. IntroductionPhotocatalytic behavior of semicondcutors has been extensively explored since it was discovered in TiO2 in 197Os. When TiO2 is exposed to UV light, the light is absorbed and electron/hole pairs are generated in the conduction and valeence bands. Holes in valence band will oxide/mineralize pollutant target directly or indirectly (via mediator hydroxyl radical). If the adsorbed A is O 2, O 2 will react with electron from conduction band to generate hydroxyl radical as described in the second set ofreactions. The photocatalytic reaction is schematically explained in Figure 1.Photoelectrochemical (PEC) cells using the photocatalytic reaction have attracted emerging interest as a potential route to convert solar radiation into useful forms of energy by reaction such as water splitting to generate hydrogen1 or the reduction of carbon dioxide.2 Another application ofphotocatalysis is water splitting and CO2 reduction, both of which utilize the electrons that are optically excited to the conduction band. 3•4 For this purpose, the conduction level of the semiconductor should be higher than hydrogen production level (EHZ1HZO) while the valence band should be lower than water oxidation level (Eo21112O). Electrons and holes will be generated on the semiconductor site, and holes generate O 2 at semiconductor site, while electrons will migrate to counter electrode to execute reduction forming H2. In addition to that, materials should be chemically stable to resist photocorrosion and have long lifetime of electron/hole pairs. TiO2 is a suitable material from the viewpoint of band arrangement and chemical stability requirement"

Jan 1, 2012

By Hongmin Zhu, Suning Liu, Kai Huang

"Recovery of silicon particles from the cutting slurry for the manufacturing of solar grade silicon is very important to recycle this kind of special resource. The challenge is to separate the silicon particles from the mixed abrasive particles which contain SiC. Various methods such as sedimentation, centrifugation, and flotation have been conducted, while in present work, a simple and effective novel method was proposed to study the separation of Si and coexisting SiC particles in the cutting slurry. The new process is based on the size difference between the two kinds of microparticles. And the membranes with the different pore sizes of 1µm, 2µm, 3µm and 5µm were used to test the pass ratio and separation efficiency of the suspension. Results shows that the effective separation of Si and SiC microparticles was obtained under the optimal conditions, and indicating great potential of practical enrichment of Si from the coexisting abrasive particles.IntroductionWith the development of the world economy, energy shortage and environment problem is becoming more and more seriously. Solar energy, which is regarded as one of the most important new energy in the word, has received much attention and interest from the scientists [1, 2]. More than 80% solar cells are manufactured by the high purity polysilicon as the raw material. The main process of producing silicon wafer is by multi-wire slicing. In this slice processing, large amount of slurry is produced. The slurry contains more than 30% wt silicon powder, silicon carbide powder as the abrasive, scraps of metal chips, as well as cutting abrasive suspension polyethylene glycol (PEG). The high-purified silicon powders are worth recycling and reusing as the materials for preparing solar-grade silicon though it is a big challenge [3].Most of the current studies were focusing on the recycling of the silicon carbide and PEG, while work on the recycling of the high-purified silicon is not so been focused since there is lacking of very effective separation and recovery technologies till up now. Nishijima utilized the method of superconducting magnetic to recycle the abrasive [4]. Wang applied a combinational process of chemical treatment, high-gravity centrifugation, high-temperature precipitation technique and directional solidification to enrich the silicon [5]. And other purification methods, such as centrifugation [6], froth flotation technologies [7], electrical filed separation [8] and phase-transfer process [9] have been employed. The disadvantages such as using poisonous media or complex equipments decrease the feasibility and efficiency of the above mentioned techniques."

Jan 1, 2014

By Erich Hovestädt, Hans-Jürgen Odenthal, Christian Wuppermann, Herbert Pfeifer, Antje Rückert

"During the argon oxygen decarburization (AOD) process high-chromium steel melts are decarburized by oxygen and inert gas injection through sidewall nozzles and a top-lance. Due to the large amount of the injected processing gas, low frequency oscillations of the vessel can be observed. It is suspected that these oscillations can influence the converter's structure. The exchange of forces between fluid and the surrounding vessel is the focus of this study. An oscillation model was developed and tested, one objective being to limit the computational effort which is necessary for fully coupled and time resolved CFD and FEM simulations. Experimental results obtained from water-model studies as well as from on-sight measurements are available and were used in order to validate the numerical results. The authors' intention is a contribution towards a more in depth understanding of the factors influencing vessel vibration during the AOD process.IntroductionDuring the last four decades the AOD process has been established as a reliable and efficient refining process in stainless steel making. The injection of process gases (O2, N2, Ar) through sidewall nozzles shows advantages in mixing effectiveness compared to other injection geometries e.g. bottom blowing [1]. Stainless steel grades contain usually more than 10% chromium. With decreasing carbon content during the decarburization periods the tendency of chromium oxidation increases according to the varying chemical equilibrium which depends on the partial pressure of carbon-monoxide (CO) in the gas phase. That's why oxygen is gradually replaced by inert gases, usually argon or nitrogen, in order to lower the CO partial pressure and thus to minimize chromium oxidation. Despite the high injection velocity of approximately Ma = 1, the kinetic energy of the gas jets is consumed within a short distance from the nozzle exits due to the large density ratio between gas and melt of approximately 1:8000. With increasing distance to the nozzle exit, the initial horizontal velocity of the gas jet decreases and due to buoyancy force motion of the detached bubbles turns into a vertical direction. Subsequently a gas plume develops with its typical conical shape described by various authors [1-4]. Due to the drag force between gas bubbles and melt also the liquid phase is forced into a vertical motion. Near the free surface and the wall regions the melt flow is deflected in different directions. Subsequently, the typical flow pattern in the AOD vessel arises, as sketched in Figure 1 and described in literature [5-9]."

Jan 1, 2012

By M. M. Sadawy

"The increased rate of exploitation of iron ores has resulted in a rapid depletion of high-grade iron ore deposits in Egypt. New iron reserves have to be discovered to secure the iron ore for steel production. This paper aims to study the characterization and magnetic separation of low grade Aswan iron ore. The results showed that Aswan iron ore is composed of oolitic hematite, goethite, quartz and kaolinite. The screen analysis indicated that Aswan iron ore had a uniform distribution of iron and silica in the different particle size fractions and there is no any particle size has high amount of iron or low content of silica. On the other hand the results of dry high intensity magnetic separation illustrated that this technique is not suitable for upgrading this ore.IntroductionIron is one of the common metals used in industry, as well as being the fundamental raw material used in iron-steel industry; products are wide spread even in daily uses. The total iron ore reserves of the world have been estimated as 3 70 billion tones; 160 billion tones is classified as economical, while 210 billion tones as potentially economical [1]. An estimated 98% of the iron ore exploited in the world is used in the manufacture of pig iron and steel, which are non-substitutable backbones of modem society. The rapid increase of world steel production over the last few years have required an equal increase in iron ore production, from 876.8 Mt in 2006 to 948.1 Mt in 2007 [2]. The increased rate of exploitation of iron ores has resulted in a rapid depletion of known high-grade iron ore deposits. This, in turn, has led to a dramatic increase of prices. In the absence of any major new discoveries of high-grade iron ore deposits, mining companies have turned to lower-grade materials to assess their beneficiation potential to expand their production base and beneficiation capacity, in order to satisfy future demand. Egypt is going to face shortage in iron production, consequently new iron reserves have to be discovered to secure the iron needed for the country [3]. Exploitation of low grade ores requires special equipments and techniques for recovery of minerals values. High gradient magnetic separators offer promise and great potential of application both technologically and economically in the processing of fine particles containing weakly or feebly paramagnetic components [4-6]. Within this existing framework, this research was initiated to assess the beneficiation potential of low-grade Aswan iron ore by high intensity magnetic separation."

Jan 1, 2013

By Jie Li, Liangxing Jiang, Yexiang Liu, Junfeng Gui, Bo Hong, Xiaocong Zhong, Yanqing Lai, Xiaoying Yu

"Pb-based alloys with Pr and Ag were prepared in vacuum electromagnetic induction furnace. The tensile strength, corrosion rate and anodic potential in sulfate solution were measured, and the experimental data were analyzed according to the metallographic phases of alloys, the micromorphology and composition of their oxide films. The results show that, with the addition of Pr, the ultimate tensile strength and corrosion rate of pure lead were increased, and the anodic potential decreased. The extra addition of Ag can improve the properties of alloy further. Comparing with Pb-Ag0.8 alloy which is widely used in zinc electrowinning industry, the ultimate tensile strength of Pb-Ag0.6-Pr2.0 alloy was increased by 31.75%, the anodic potential under 50mA/cm2 was decreased by 30m V.IntroductionIn zinc electrowinning industry, the Pb-Ag (0.5-1.0 wt.%, 0.8wt.% normally) anode is widely used as an insoluble anode['l. It can meet the basic requirements, but still has several problems such as high oxygen evolution over-potential (about 860mV), unsatisfactory corrosion resistance, lead contamination of the cathode product and high consumption of Ag etc.In order to reduce the energy consumption, enhance the corrosion resistance, improve the product quality and reduce the consumption of Ag (or even dispense with it), much research has been done, mainly focusing on Pb-based alloy anodes and Ti-based coated anodes. Detailed investigations have already been carried out on binary alloys (Pb-Ca and Pb-Co), ternary alloys (Pb-Ag-Ca, Pb-Ag-Ti, Pb-Ag-Sn, Pb-Sr-Sn, and Pb-Ca-Sn) and quaternary alloys (Pb-Ca-Sr-Ag, Pb-Ca-Ce-Ag, and Pb-Ag-Sn-Co)[Z-4l, Although these anodes can effectively reduce the consumption of Ag, only the Pb-Co and Pb-Ag-Sn-Co anodes perform well with regard to reducing the anodic potential. However, their complicated manufacturing conditions restrict further commercial use.Besides its application in nonferrous metal electro-winning industry, Pb-based alloy is also used as grid alloy for lead-acid battery, serving as active materials supporter and current collector. In order to enhance the corrosion resistance and deep-cycling performance, reduce the impedance of the corrosion film, the addition of appropriate rare earth elements into anodic grid alloys has become a research focus. Studies proved that RE can enhance the mechanical strength of grids, inhibit the formation of anodic Pb(II) film on the surface of grids and then reduce the impedance of the film[ 10-12l."

Jan 1, 2013

By E. A. Chavarriaga, L. J. Jaramillo, O. J. Restrepo

"This paper presents the results of the manufacturing ceramic pigments with spinel structure, using methods of synthesis of low temperature. In this work we obtained spinel structures type by the methods of Self-combustion, Coprecipitation, Microemulsion, Gel citrate and Pechini. These methods become an attractive alternative to traditional method (ceramic method), since we can work at a lower temperature, reducing manufacturing costs, lower fuel consumption, less wear on equipment and other environmental and economic implications. Also it is possible to have control over features such as stoichiometry, morphology of the products, reaction times and structures. The products obtained by these routes will be used in the manufacture of ceramic pigments and characterized using different techniques such as X-ray diffraction (XRD), scanning electron microscopy (SEM) and UV-VIS spectrophotometry.IntroductionSpinels are ternary oxides AB204, where A and B are cations occupying tetrahedral and octahedral positions respectively. These oxides exhibit interesting electrical, magnetic and catalytic properties [1-4], depending on its nature, charging and intrinsic distribution of ions [5].The most widely used method to prepare spinels has been through solid state reaction, which consists of mixed oxides at high temperatures [6, 7]. In the last years, there have been a strong tendency to use chemical routes for the synthesis of crystalline ceramic particles at low temperatures [8,9]. Unconventional methods currently employed for the synthesis of complex oxides are Gel citrate method, Pechini, Spontaneous combustion, Microemulsion and Coprecipitation. Pechini method [10, 11], based on polymeric precursors, does not require high temperatures and allows stoichiometric control for greater reproducibility. This method involves the formation of a polymeric resin between a metal quelate and polyhydroxy acid of alcohol by polyestirification.Coprecipitation is important for many environmental problems related to water resources, including acid mine drainage, migration of radionuclides in waste repositories dirty, transport of contaminant metals in the industry, metal concentrations in aqueous systems and the technology of wastewater treatment. The coprecipitation process can vary in each case; the partition in the solid phase can be carried out by surface adsorption, ion exchange, surface precipitation, occlusion and formation of solid solution. The formation of solid solution is the result of structural incorporation of the marker in structural support sites resulting in a minor component in the solid solution with the host phase that has a very low solubility of pure solid [12]. Synthesis by gel citrate method allows the use of a route to obtain ceramic pigments from a very simple experimental system in which the stoichiometric control, the size and shape of the particles and the purity of the phases obtained can be controlled more accurately [13]."

Jan 1, 2012

By Xuewei Lv, Maojun Zhou, Xiaobo Huang, Rende Zhang

"The characterization of the surface roughness of the mineral particles is of vital importance for the studies of the mineral processing. In this study, an evaluation of the roughness of the iron ore particles, with the measurements of size distribution and the measurements of specific surface area with the liquid nitrogen absorption, was developed. The main theory of this method is the fact that the roughness of the particle influences the specific surface area apparently. The specific surface area of the particles can be measured with the laser diffraction method and the liquid nitrogen absorption method. The influence of the surface roughness of the particle can be measured with the nitrogen absorption and cannot be measured with the laser diffraction. Therefore, the roughness can be got by comparing the specific surface area with two measurement methods.IntroductionThe characterization of the surface roughness of the mineral particles is of vital importance for the studies of the mineral processing. There are three main methods for measuring the size distribution of mineral particles: sieving, laser diffraction, and sedimentationl). Many techniques involve sedimentation such as the Horiba2, 3) and the Cyclo-sizer1). In the mineral industry, size distribution is usually determined by sieving because it can be carried out accurately for all particle sizes larger than 45 . The preferred method to obtain the size distribution of finer particles is laser diffractometry. The technique has several advantages: it produces measurements in a few minutes with considerably less labor compared with the cyclo-sizer and for a range of sizes considerably wider in comparison with the sedigraph4). The equivalent-sphere size distribution reported by laser diffractometry is valid for metallurgical calculations and can be routinely used in mineral processing plants. The surface area of the particles can be measured by the BET method of nitrogen adsorption, or it can be calculated from the size distribution. However, the latter calculation requires the size distribution to be accurately known across the whole size range, and assumptions have to be made about the shapes and surface roughness of the particles and presence or absence of pores (see below). The BET method is based on the physical adsorption of gas over the whole exposed surface area and measures the surface area stemming from the roughness and open pores on the surface of the particle5). The calculation of the surface area from the size distribution is usually based on the assumption that all the particles are smooth spheres, without considering the shape and/or roughness of the particles. Determining the surface roughness of the particle with these methods, is the objective of this study."

Jan 1, 2012

By Roberto Giovanardi, Isabella Lancellotti, Luisa Barbieri, Ercole Soragni, Fernanda Andreola

"Recovery of precious metals (PMs) is a present topic, as they are used almost in every electronicelectric device. Gold is the second PM in order of consumption (following silver) and it is almost ubiquitary in electronics where it mainly finds application to produce bonding wires in integrated circuits and as a coating for contacts and connectors. Given this, discontinued electronic and, with a minor role, electric devices may represent a primary source of PMs as gold mines or jewelery wastes.At present the recovery of gold from such waste is generally accomplished by two strategies: by oxidative thermal treatment followed by metallurgical or chemical processes or by cyanide chemical etching; both techniques do not represent the optimum as the first one deserves a great amount of energy and non-combustible pollutant slag and fumes are produced, while the second procedure comports the use of a highly pollutant agent as cyanide.The aim of this work is the characterization of different electronics scraps to evaluate the gold concentration, and the selective recovery of this metal using enviromentally-friendly techniques. In particular, a new process was developed in order to overcome such environmental and efficiency issues. The process reaches the goal of detach the gold film from the substrate by selective leaching of the supporting metal.IntroductionThe treatment of waste from electrical and electronic equipments is a current topic as their role in modern life is increasing. The disposal of such waste represents both an environmental and an economical concern due to the vast amount of both precious and non precious metals.The use of precious metals (PM) in this field is of primary importance given PM’s unique properties, which give to each of them a specific and irreplaceable role. Silver is the most used, with a demand of over 5000 tonnes per year, mainly for switches and contacts in electric appliances. Gold is the second PM in order of consumption (over 250 tonnes per year and 8% of the total demand) and it is almost ubiquitous in electronics where it finds application to produce bonding wires in integrated circuits and as a coating for contacts and connectors. It is also used as solder in integrated circuits (in alloy with tin) or for wide coatings where it ensures protection against corrosion. Palladium, platinum, rhodium and iridium follow in order of consumption [1- 3]."

Jan 1, 2008

By Bob Drew, Alfred Spanring, Kirschen. Marcus

"Increasing material conversion and energy efficiency, and decreasing carbon dioxide emission levels are crucial for sustainable production processes in the aluminum, cooper, and steel industries. RHI supports these targets by providing a diverse range of solutions including high quality refractory linings, optimum lining maintenance, and process improvements. In this paper examples are provided of process improvements and increased energy efficiency in copper refining, potential energy savings during electric arc furnace and ladle operations in the steel industry, and increased energy efficiency by improved heat transfer in anode baking furnaces in the aluminum industry. In all cases, RHI’s expertise in close collaboration with the customer resulted in an improved performance of the reactor lining and the actual high temperature process with a positive impact on the material conversion and energy efficiency and as a result a decrease in specific carbon dioxide emission levels.IntroductionRefractory linings play an important role in heat transfer during high temperature processes in for example the aluminum, copper, and steel production industries. Due to constantly increasing energy prices worldwide and the increasing demands for environmental and climate protection, improving the energy efficiency and decreasing emission levels of these energy intensive production processes is of significant importance. In this paper, the contribution of modern RHI lining technologies to energy saving measures and the corresponding reduction of specific carbon dioxide emission are described. The type of current refractory solutions for energy intense processes are illustrated with four examples: Optimization and increase of material conversion and energy efficiency in copper refining, energy saving potentials in both electric arc furnace and transport ladle operations in the steel industry, and heat transfer improvements during the carbon anode annealing process in the aluminum industry. These examples focus on particular production processes operating with a high proportion of recycled copper, steel, and carbon anodes. Increased energy efficiency directly decreases the specific energy related carbon emission levels whereas improvements to the metallurgical processes aim to increase material conversion efficiency and, therefore, decrease specific process related carbon emission levels. Significant energy savings can be achieved by maximizing the refractory campaign length through a combination of appropriate refractory material selection, grade zoning, correct installation, careful preheating, and effective maintenance strategies. Besides the efforts to improve the performance and energy efficiency of customer high temperature processes, RHI continuously promotes the development of new low emission carbon-containing refractory bricks and unshaped products."

Jan 1, 2008

By Maria Kuttig, Christian Ruback, Gerhard Tober, Petra Maier

"It has been demonstrated that there is a strong relationship between work hardening with various post heat treatment and cyclic deformation behavior of structural steel S275. This study contributes to a project developing a process for the complex forming of steel, which combines rolling and bending. Due to the complex geometry of the final work piece, the deformation degree varies greatly. The forming temperature, as well as post heat treatruent, influences recrystallization processes in dependence of the local deformation degree, resulting in inhomogeneous microstructure of the work piece, which affects the quasi-static and dynamic properties. Cyclic creep and hardening or softening has been monitored during constant amplitude loading at stresses near fatigue strength in normalized condition. Work hardening, stress relief or recrystallization influence the cyclic deformation behavior and produces cyclic creep effects. Cyclic softening or hardening and creep were observed to occur in parallel. To what extent these properties are noted depends on the deformation degree.IntroductionThis work is part of a research project developing a new process for the three dimensional forming of steel. For the final product the fatigue strength influenced by the forming parameters is very important. Due to its complex geometry, the formed final plate has different deformation degrees. This leads to different recrystallization behavior and heat treatruent will have different effects on the microstructure. The peak deformation degree cp of the plate will be around -0.5 what leads to the analysis using rolling from 22 mm to 13 mm of thickness. The quasi-static material properties are very important for calculating the preliminary design. However, work pieces which are cyclic loaded need fatigue tests to describe the in-service material behavior. [l] For the prediction and to guarantee the wanted life-time of the part cyclic deformation tests are important. [2, p.23-32] When it is assumed that the work piece will only loaded in cyclic tension, fatigue testing will be done from zero to a maximum force value. In preliminary tests this value is the tensile fatigue strength from a Smith diagram. During processing, here forming, work hardening takes place resulting in strengthening. Therefore, in further tests maximum load can be increased to monitor cyclic deformation mechanism in more detail. However, to study cyclic creep and hardening and softening data should be evaluate over sufficient life time and should not fracture too soon."

Jan 1, 2013

By Norihiko Fukatsu, Takashi Iwamoto, Noriaki Kurita, Koji Katahira, Kunihiro Koide, Teruo Ohashi

"The galvanic cell-type hydrogen sensor employing CaZro.9Ino.t03-a. as the solid electrolyte was designed for the measurement of hydrogen activities in molten copper under industrial .conditions. The sensor probe consists of the cap-shaped solid electrolyte with porous platinum electrode on the inside and alumina refractory tube. The gas mixture of the composition 4%H2-0.5%02-Ar was made to flow on the inside electrode. The hydrogen sensor probe was inserted directly into molten copper and the melt was used as the outer electrode. The effect of oxygen activity gradient to EMF was eliminated theoretically by measuring the oxygen activity in the melt simultaneously with an oxygen sensor. The high stability of output and excellent response to the change of hydrogen activity were obtained over the wide range of industrial copper melting conditions.IntroductionIn the metal casting process, hydrogen easily dissolves in molten metals from water vapor in the surrounding atmosphere. Owing to the large difference in hydrogen solubility between liquid and solid metal, dissolved hydrogen becomes a cause of the defects of blowholes in castings or ingots. It is necessary to control the hydrogen content in the molten metals [l]. Using proton-conducting ceramics as a solid electrolyte, high temperature-type hydrogen sensor can be constructed [2]. SrCe03- and BaCe03-based perovskite-type oxides exhibit appreciable proton conduction under hydrogen containing atmosphere at high temperature [3-5]. A hydrogen sensor for molten aluminum using CaZro.91no.103-a. has been developed and widely used in the ·process control in the aluminum melting industry [6,7]. The same type of hydrogen sensor has also been expected in the copper melting industry. .. However, CaZro.91no.103-a shows ·not only proton but also oxide ion conduction in the high temperature and at low oxygen activies like the copper melting· conditions. Then we studied the oxide ion conduction in CaZro.91no.103-a. iit · detail [8]. From the consideration on the EMF of the galvanic cell employing this material as electrolyte, it was shown that the unknown hydrogen activity may be precisely determined from cell potential which is corrected for the effect of oxygen potential gradient And the hydrogen sensor based in this principle was constructed and tested in laboratory-scale [9,10]. We repeated the similar tests in factory-scale and developed the sensor system for practical uses [11, 12]. In this report, the structure and system of the hydrogen sensor for molten copper will be introduced first. The reliability of the sensor will then be demonstrated from the results of experiments for sensor probes carried out in TYK's laboratory."

Jan 1, 2000

By Olga K. Karakasi, Angeliki Moutsatsou, Ioanna Kavallari

"The present study focuses on the amelioration of the behaviour of high calcium fly ash (HCFA), investigating its application in a new environmental field: oil spill clean up. High calcium fly ash is a by-product of electric power plants, produced annually in large quantities, whose greater amount is landfilled. Some of its properties, such as its chemical and mineralogical composition, its fine particle size, its porosity, floating ability and hydrophobic character make it an attractive material for this purpose. Researches showed that when added to an oil spill, it forms a semi-solid phase, which allows the quite total removal of the oil, but it is not stably retained on the surface. In order to ameliorate its floating ability, the decrease in its specific gravity by mixing with a lighter material is investigated. In the present study the mixing with two materials, already used in oil spill clean up, sawdust and a polymer, has been examined. Addition of 15-25% w/w sawdust to HCFA results in a material with better performance than HCFA or sawdust alone: it has a satisfactory floating ability and allows total removal of oil. Addition of the polymer, however, has resulted in no significant amelioration of the oil sorption behaviour of HCFA, probably because no affinity between HCFA and polymer has been achieved.IntroductionCoal fly ash is a by-product of coal combustion in electric power plants, produced worldwide in huge quantities, approximately 500 million tones annually. High calcium fly ash (HCFA) is classified to class C presenting a (Al2O3 + SiO2 + Fe2O3) > 50%. The production of lignite fly ash in Greece comes up to 13 million tones annually, of which only 12% is used in construction applications, the other being landfilled [5, 6].Besides its limited application worldwide as a construction material, research is focusing on the development of new environmental applications, such as waste stabilisation and solidification, soil and water environmental improvement [9, 12]. For the application of fly ash in further environmental fields several chemical modifications have been applied, in order to improve its properties. Extensive research has been focused on the conversion of both coal and lignite fly ash to zeolite and its further application in environmental field, such as the uptake of inorganic (heavy metals and ammonium [8, 11]) or even organic compounds (methylene blue [15]) from waste water streams, or the use as molecular sieves, to adsorb water molecules, SO2 and NH3 from gas streams, due to the high cation exchange capacity and porosity of the produced zeolithic material. Furthermore, lignite fly ash has been combined with sodium silicate solution, prepared by treatment of rice husk ash, and tetrapropylammonium bromide, to synthesise hydrophobic zeolite ZSM-5 [4]."

Jan 1, 2008