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By Hongmin Zhu, Guihua Wang, Xiangsheng Wang

"The anode process of carbon electrode in fluoride melt was studied by voltammetry and chronoamperometry. Anode gases were analyzed by gas chromatography on-line during controlled-potential electrolysis. Two peaks were observed on the cyclic voltammograms. According to the results of gas chromatography, the first peak was corresponded to the discharge of residual oxide ions, with the formation of CO and CO2. Discharge of fluoride ions occurred at 4.1 V vs. Li+/Li, and leading to the anode effect. With the occurrence of anode effect, small amount of CF4 was detected. As the potential reached 4.5 V, CF4 and C2F6 gas evolution occurred, and the current increased to form the second peak.1.IntroductionIn the primary production of Aluminum and some rare earth metals like neodymium, a departure from normal cell operation known as anode effect results in the generation of perfluorocarbons (PFCs), which have high global warming potentials [1]. Owing to the pressure of environmental protection, considerable research has been carried out to clarify the mechanism of anode effect and PFC generation of industry and laboratory cells in the aluminum electrolysis system [2-9]. The common result on PFC generation is that the PFCs are emitted from Hall-Heroult cells only when they are on anode effect. In this article, we selected LiF, the main electrolyte for the neodymium electrolysis [10-11], to perform further investigation on the underlying kinetics of PFC generation and the nature of the reactions at the electrode.2. ExperimentalAll experiments were carried out in an alumina tube reactor, which was filled with high purity helium atmosphere. Spectrographic graphite crucibles were used, which played the dual role of molten fluoride container and the counter electrode. Lithium fluoride was analytical grade. The experiments were carried out at 900 °C."

Jan 1, 2011

By A. Rojo, N. J. Ramirez, J. E. Salgado

"This work aims to characterize the plastics used in a handgrip located in the car interior body in order to improve its design process and be able to predict its behavior when the part is subjected to impact test involving human casualties.Through stress analyses at high speeds and a video camera set up (front and side view), the reduction of area of specimen was obtained from image analysis, allowing to get the stress-strain real curve of the material.Continuing the characterization process a set of impact test was developed, where standard lzod configurations were used in unnotched specimens. From these tests were gotten displacement curves and absorption energy estimations.The proposed testing procedure allowed the acquisition of force and displacement data through time at various strain rates which are indispensable for the characterization of dynamic events. Using a specimen with a special configuration has shown a more detailed dynamic behavior resulting into more accurate numerical analyses within the design process.IntroductionIn the design process, one of the many analyses which take place is the impact test of the designed part. Nowadays there are many software capable to do these kind of analysis and each industry use the one they think it is convenient for them, but also the selected software has mathematic models that help to find the solution and the simulation of the case of analysis. These are not the only considerations that a company has to take into account, other one is the type of information and data necessary to feed the software. For this study we are going to focus on the acquisition of these data.The mail reason of this work is that generally the supplier gives the card of the material with all the characteristics and information requested by the buyer, but all of that information is acquired by standard methods, but it is inconvenient when the materials are polymers."

Jan 1, 2011

By Honorio Oliveros Gómez, Oscar Jaime B. Restrepo

"Colombia produces nine tons of electronic waste per year and there are approximately 60 tons accumulation generated in the last nine years. This work aims to establish a general methodology in the laboratory to recover gold, silver and platinum group present in electronic waste, also explore other forms of recovery of metals contained in electronic waste. We selected seven types of electronic cards present in the computers, which have their parent desoldering electronic components. Initially, we characterized the components of the cards through X-ray diffraction and SEM, to identify the metal species and composition. Tests were conducted laboratory hydrometallurgical recovery of metals. This paper proposes a methodology for laboratory-scale work.INTRODUCTIONColombia produces nine tonnes of electronic waste per year and build there in about 60 tons generated in the last 9 years [1], Computers, TVs, audio equipment, monitors, cell phones, remote controls, printers and operated toys battery, among others are part of this inventory, which mostly comes to landfills, because the lack of legislation to control the final destination of waste electrical and electronic equipment, and lack of efficient technologies to recover materials [2]. Under these circumstances which have environmental implications, technological and economic recovery is essential metals present in the electronic cards of computers, by hydrometallurgical with subsequent base metal electrodeposition [3]. Pyrometallurgical route is discarded by major implications for economic and environmental [4]. Recovery From this perspective, the determination of the metal fraction and the relationship between the different metals, using the SEM characterization techniques - BSE and XRD is indispensable [5] It follows with electrolytic dissociation processes in the leaching and electrodeposition [6], and unit operations in the laboratory to carry out successfully these processes on a larger scale. Were randomly selected computer twenty-four postcards for nine types of cards have different functions in the computer, which, through the absorption desoldering technique, they broke the resistance (thermal, surface, photoresist, power), capacitors (ceramic, electrolytic), diodes (silicon, germanium, high frequency), transistor (NPN, PNP), processors, integrated (high, medium and low frequency), the RAM card and pin parallel port serial"

Jan 1, 2011

By N. J. Rarmrez, C. Perez, J. D. Calderon, L. Lopez

"Among the thermal characterization of any material, one of the variables to know is the coefficient of thermal conductivity because this value can tell how much heat passes through the material and if the material could be used as an isolator. In order to determine this parameter is required some kind of special equipment and controlled conditions which implies high costs in the development of tests. The present paper proposes a design of a low cost measurement system in order to determine this coefficient with the lower possible error. This equipment was thought for companies or labs where they do not have the economic resources or the infrastructure (environmental controlled labs, heat flux transducers, human resources with specialized knowledge) to do this kind of tests.The system is based on ASTM C 518 - 04 [l] and integrated by two plates (one that contains a thermal resistance and which temperature is controlled by a closed loop controller and the other one with a route of water flow). The thermal resistance is actuated by a relay and a supervisor system checks the total time the relay is on in order to determine the effective power applied to the system. The contact faces of the plates contain a group of temperature sensors connected to a data acquisition system that process and record the temperature in each measurement point.With the power applied to the system, the measurement of temperatures and a process of calibration is possible to determine the coefficient of thermal conductivity. IntroductionWithin the thermal characterization of a material of known variables is the coefficient of heat transfer, since this value can know the amount of heat the material is capable of transferring or isolating. To determine this ratio requires specialized equipment and controlled conditions, which implies high costs in the development of a test. This article proposes a design of a low cost machine to allow closer this coefficient with the least possible error. This equipment was done thinking about companies that do not have the infrastructure (laboratories, controlled environment, heat flux sensors, human resources expertise) and financial resources to conduct these tests."

Jan 1, 2011

By Onder Guney, Erdem Demirkesenm

"In this study, the crystallization behavior and thermal expansion coefficient of a lithium disilicate (LS2) based glass-ceramic derived from SiO2-Li02-AhO3-K2O-ZrO2 system was investigated by using x-ray diffraction (XRD), high temperature x-ray diffraction (HTXRD), differential thermal analysis (DTA) and dilatometer techniques. Analytical reagent grade chemicals were chosen as raw materials for preparing glass batches. Nucleation and crystal growth heat treatments were planned according to DTA results. The amounts of the amorphous and crystalline phases developed during the heat treatments were determined by quantitative XRD. XRD results of crystallized samples showed simultaneous formation of lithium silicate (LS) and quartz in the early stage of the crystallization followed by formation of lithium disilicate (LS2) at higher temperatures. The thermal expansion coefficients of glassceramics were also measured depending on the applied heat treatments.IntroductionSignificant developments occurred in all ceramic materials provide the fabrication of high quality dental implants [1]. Glass ceramic based dental restorations like dental inlays, crowns, bridges and veneers are becoming increasingly popular with their reliable and durable performance [2,3]. In addition to their advanced functional properties, glass ceramic implants especially lithium disilicate glass ceramics also face the esthetics expectations of patients and dentists and in this way they are starting to take the place of metal based restorations today [1,3,4,5]. Lithium disilicate glass-ceramics derived from multicomponent glass systems have some superior mechanical and optical properties comparable to natural teeth [ 6]. In restorative dentistry, mechanical characteristics of biomaterials play very crucial role in order to resist the masticatory forces occurred during biting and chewing [7] According to three point bending test results of Roland, flexural strength of the lithium disilicate glass-ceramics were 400±40 MPa and their fracture toughness (K1c) are approximately 3,3 MPa m112 [2,6]. In addition to high mechanical strength, aesthetic appearance is another important prerequisite as material for dental restorative applications. Translucency and light transmission of the LS2 glass ceramics mimic enamel. Moreover, opacity of the material can also be adjusted depending on the restoration types [2,6, 7]. These superior properties of the LS2 glass ceramics are directly related with chemical composition of the base glasses and controlled crystallization heat treatments [ 4, 7]. The aim of the present work is to determine the effect of heat treatment schedules on the crystallization behavior and thermal expansion of the LS2 glass-ceramics."

Jan 1, 2011

By M. Wu, A. Kharicha, A. Ludwig

"The droplet formation during melting of a 400 mm diameter electrode is simulated with a multiphase-MHD approach. The computational model includes a layer of slag and a layer of liquid steel. A VOF approach is used for the interface tracking and a potential formulation is used for the electric and the magnetic field. The Lorentz force and the Joule heating are recalculated at each time step in function of the phase distribution. The first results provided by this model are presented.IntroductionThe Electro-Slag-Remelting (ESR) process is an advanced technology for the production of components of e.g. high quality steels [ 1-9]. An alternating current (Figure 1) is passed from a conventionally melted and cast solid electrode through a layer of molten slag to the baseplate. Because of the electrical resistivity of the slag, Joule heating is generated and the slag transfers this energy to ingot and mould surfaces and to the melting electrode tip. The molten metal produced in the form of droplets passes through the slag and feeds a liquid pool from where directional solidification takes place. The slag and the ingot are contained in a water cooled copper mould. As also the baseplate is water cooled, a heat flow regime is imposed that gives controlled solidification, and this results in improved structure characteristics of ESR ingots.This process involves two liquids, a liquid metal and a liquid slag. Each liquid is subject to a phase change due to melting and/or solidification. From a fluid dynamic point of view, the ESR process is clearly a multiphase process, with free interfaces (slag/pool, gas/slag), and with a mixed area (slag and falling steel droplets) [ 10-15].Physically, the development of the heat and mass transfer at the slag/droplet interface is important for the final ingot quality, composition and cleanliness. Visual observations of the droplet formation just under the electrode being melted is almost impossible. Due to the presence of high temperatures, opacity of the materials, and the presence of the mould it is not possible to directly observe the behaviour the slag/pool interface. Although usually assumed flat [1-9], a previous work [10] using a Volume of fluid (VOF) model has shown that the interface shape between a layer of slag and steel layer in a cylindrical cavity is highly coupled with the distribution of the electric current. A full scale simulation of the ESR process using a VOF model has shown that the shape of the pool interface is likely to be non flat."

Jan 1, 2011

By Mei Yang, Wei Gao, Jian Yang, Qingcai Liu, Wenchang Xi

"TiO2 has been loaded on cordierite porous ceramic to prepare the SCR catalyst carrier by using both APCVD and sol-gel technology. In APCVD method, TiC14 and O 2 were used as reaction precursor. TiC14 was gasified by using N2 as carrier gas which was controlled to 500sccm. Its reaction temperature and reaction time were limited to 773K and 30min respectively. The physical properties, SEM and SEM-EDX of the TiO2-cordierite carrier and the properties of SCR catalysts prepared by these carriers have been tested. The tests showed that TiO2 loaded by APCVD method were of graininess shape and even accumulation. The loading rate of TiO2 and the specific area of carrier sample were increased 114% and 21 % respectively comparing with sol-gel technology. In the result of sol-gel method, the maximal difference of Ti content was 66.92%, while the result of APCVD method was 18.89%. It demonstrated that TiO2 was uniformly attached with the cordierite ceramic by using APCVD method, which would ensure more active ingredients well loaded on the Ti02-cordierite carrier. This difference made the denitrification ratio of catalyst prepared by APCVD method was 8.1 % higher than that of catalyst prepared by sol-gel method.IntroductionIn recent years, the emission of NOx, which were caused by coal-fired power plants, has gotten more and more attention. SCR (selective catalytic reduction) is the most effective technology to DeNOx [ll. The core technology of it is the catalyst. The SCR catalyst usually uses Ti02 as the carrier, and V2O 5 as the active component [2, 3] . However, the thermal stability and mechanical properties of TiO2 carrier are unstable, which would influence the performances of the catalyst. The commercial catalyst generally uses WO3 or MoO3 to promote its heat stability at present [4-7] Besides, TiO2 is expensive. Compared with TiO2, the cordierite is of good thermal stability and lower price. So loading Ti02 on cordierite porous ceramic as carrier to produce SCR catalyst is of good prospects [S, 91 • Currently, TiO2 is usually loaded on cordierite by the sol-gel method. But some research has shown that the sol-gel method easily reduced the loading performances of TiO2, such as distribution, combination, etc. APCVD (atmospheric pressure chemical vapor deposition) has many advantages to preparing TiO2 films, such as high bonding strength, fast reaction rate and so on [l0-13l_ In this paper, TiO2 has been loaded on cordierite porous ceramic to prepare the SCR catalyst carrier by using both APCVD and sol-gel methods. The properties of the carriers prepared by the two processes have also been compared."

Jan 1, 2011

By Guangchun Yao, Chuan Li, Hongjie Luo, Zhuokun Cao

"The expansion rate and collapse time of liquid aluminum foams are essential for the determination of operating time and quality of the resulting foam. In the present paper, liquid aluminum foams was fabricated by adding in TiH2 as blowing agent, and the variation of expansion rate with foaming time was non-contact detected by a laser distance measurer. The influence of different stabilizing agent and alloying elements was studied. The results show the fact that the fraction of stabilizing agent only perform little effects on the maximum expansion rate of liquid aluminum foams, while the influence of alloy elements are remarkable. The maximum expansion rate would increase much when Mg is added, and the liquid foam also collapse at a shorter time. Comparison was made between experimental results and mathematic calculations, which reveal the fact that it is the change of TiH2 decomposition responsible for the change.IntroductionMetal foams, combining light weight with other unique mechanical and physical properties, have gained wide interest and been developing fast during past few decades. However, manufacture of this new material is quite challenging since it involves simultaneous occurrence of gas, liquid and solid phase at high temperature [1-2].Quite some manufacture routes have been developed for manufacturing metal foams, and the structure and quality of resulting foam are remarkably improved during the last decades. However, most of the past works seems to be experiential, and because the lack of basic knowledge of foaming process, the start material is limited and the production technologies are far from reliable and reproducible.[3-4]In direct foaming process, decomposition of blowing agents, TiH2 for example, is the main force for foam expansion. The density and foam structure changes with time during the foaming process, so it is expected that foams of certain structure can be obtained by solidification of the liquid foam at a certain time [5-6]. However, the foaming process is weak in reproducibility and the influence of stabilization additives and alloying elements is unclear."

Jan 1, 2011

By Yuanbo Zhang, Guihong Han, Guanghui Li, Tao Jiang, Zengqing Sun, Yanfang Huang

"Because of small specific surface area and poor ballability, vanadium/titanium-bearing magnetite is difficult for production of oxidized pellet. A novel organic copolymer binder, modified humic acid (MHA), has been authorized recently in China. Effects of the novel MHA binder on the quality of V/Ti-bearing magnetite pellets are studied in this paper. Experimental results show the MHA binder can obviously improve the strength of green pellet. Because of better heat endurance, the MHA binder pellet has a higher strength than Peridur pellet under the same preheating conditions. Moreover, TFe grade of pellet with the MHA binder is much higher than that of the bentonite pellet. The strength of preheated pellet containing MHA binder of 0.25%~1.0% meets the requirements of oxidized pellet production by grate-kiln process. Comparatively, MHA is a promising orgainc binder for iron ore pellets. Its price is only one tenth of Peridur price and about 3 times of bentonite price.IntroductionThe iron-making practices show that the use of pellet is beneficial to blast furnace life, productivity and fuel savings. Therefore, many iron-making plants have expanded the production of oxidized pellets in order to meet the needs of modern large-scale blast furnaces [1]. Presently, bentonite is widely used to improve the quality of iron ore pellets. The negative effects of using bentonite include decreasing total iron (TFe) grade and degrading the metallurgical properties of the final products [2, 3]. Many studies, therefore, have been conducted on the application of organic binders to overcome the weakness of the inorganic bentonite. In comparison with inorganic binders, one of the biggest strengths of organic binders is low residual silica content [4]. However, those studies showed that the economics of foreign organic binder addition into pellets was not attractive. For example, the compression strength of preheated pellets and roasted pellets are both too low, resulting in powder generation and ring formation in the industrial rotary kiln [3, 4]."

Jan 1, 2011

By Shufeng Yang, Anping Dong, Yongfeng Chen, Jingshe Li, Lifeng Zhang, Liyuan Sun

"Instead of nickel-based stainless steel, a nitrogen-bearing stainless steel was produced to reduce the production cost stemming from the shortage of nickel recourses. Thermodynamic model to calculate the saturation nitrogen content in the stainless steel were developed and the model was validated by experimental measurement. The experiments were performed with a high temperature induction furnace. Nitrogen gas under constant pressure was injected into the crucible with a top lance by which the nitrogen was transferred to the molten stainless steel. The effects of chemical composition, temperature, superficial active elements and nitrogen-flow rate on transferring nitrogen to the steel were investigated and discussed.IntroductionWith the rapid production growth of stainless steels, nitrogen-bearing stainless steel has recently attracted more and more attention for their high strength and excellent corrosion resistance imparted by interstitial nitrogen without decreasing its toughness and ductility. Moreover, the addition of nitrogen to the stainless steel as a substitute for nickel leads a lower consumption of nickel, so significantly lowers the high production cost stemming from the shortage of nickel recourses. However, production of the nitrogen-bearing steel is difficult since nitrogen is a gas element and has a low solubility in the steel. So efficiently increasing the amount of nitrogen in steel continues to be one of the main concerns for the production of nitrogen-bearing steels.Currently there are some special processes to produce austenitic stainless steels with a very high N content, including pressurized electroslag remelting, counter-pressure casting, special induction melting and powder metallurgy, etc [1]. Special expensive vacuum system was required for these processes. Alloying nitrogen at a normal pressure can be performed by alloy addition or gas injection. Blowing nitrogen gas is a more economic and advisable method since the nitrogen-bearing alloy is quite expensive and contains high content of impurities. A number of investigations have been reported on the solubility of nitrogen gas in pure iron [2] but few in iron-based multi-component alloys such as stainless steel.In the current study, the effects of steel chemical composition, temperature, superficial active elements and nitrogen-flow rate on transferring nitrogen to the steel were experimentally investigated with a high temperature induction furnace."

Jan 1, 2011

By Alice Barreto Bevitori, Felipe Perissé Duarte Lopes, Denise Cristina Oliveira Nascimento, Sergio Neves Monteiro, Isabela Leão Amaral da Silva

"The piassava fiber is one of the most rigid natural lignocellulosic fibers, which has since the last decade been investigated as possible reinforcement for polymeric composites. In the present work, the tensile properties of polyester composites reinforced with piassava fibers with thinner diameters were investigated. Composites with volume fractions up to 30% of continuous and aligned piassava fibers were tensile tested at room temperature to evaluate the ultimate strength, elastic modulus and total strain. For each volume fraction, individually separated fibers with the smaller diameters were tested. The results indicated that the tensile properties tend to improve with increasing volume fraction of the thinner piassava fibers. The role played by the fiber/matrix interaction was analyzed by scanning electron microscopy.IntroductionA significant change in the transportation sectors mainly the aerospace and automotive, occurred last century with the introduction of stronger and lighter materials. The most relevant example was the polymer composite reinforced with synthetic fiber. They are nowadays replacing conventional materials such as the aluminum alloys in airplane body owing to superior specific strength. in recent years, however, environmental problems in a global scale are imposing a reversion in the use of synthetic fiber specially the glass fiber. In spite of its higher specific strength, this fiber and its polymer composites can neither be recycled nor incinerated in a thermal plant to generate electricity [1]. Moreover, the fabrication, processing and transportation of a glass fiber composite are associated with C02emission, the major responsible for global warming [2].A possible substitute for glass fiber without the above-mentioned environmental problems, could be a natural fiber. In fact, natural fibers obtained from cellulose-rich plants, also called lignocellulosic fiber, are already being used in several engineering fields, particularly the automobile industry [3-6]. Figure 1 illustrates an automobile and its many components made of lignocellulosic fiber composite [7]."

Jan 1, 2011

By Muhlis Nezihi Saridede, Burak Birol

"The scraps of high quality steels generally contain expensive alloying elements such as chromium, vanadium, nickel, etc. These scraps are melted in an induction or an electric arc furnace and refined in ESR (Electroslag Remelting) purification process. A significant amount of alloying elements are lost during these processes. In order to avoid these losses, scraps can be utilized directly in ESR by skipping the melting step. In this study, 316L stainless steel scraps were refined in ESR with selected synthetic slags. The products were analyzed by optic emission spectrometry and the effects of slag compositions on the alloying element losses were examined. According to the analysis of the scrap and the products, generally chromium, nickel and manganese losses were encountered. It was determined that the alloying element losses has no connection with electrical conductivity. The slag containing CaF2, Al2O3, and FeO gives the optimum Cr and Ni losses.IntroductionElectroslag remelting (ESR), which is the consumable electrode refining process, finds a wide range of utilization for the production of high quality, low inclusion alloys. This process is based on melting a consumable electrode under a molten synthetic slag containing CaF2, Al2O3, CaO etc. The synthetic slag provides the chemical refining and insulation of molten metal from air which leads to a higher purity and an inclusion-free product. [ 1,2] A schematic diagram of ESR system is shown in Figure 1."

Jan 1, 2011

By Nils Eivind Kamfjord, Mari K. Næss, Gabriella M. Tranell

"In oxidative ladle refining (OLR) of silicon, the metal surface is oxidized resulting in the formation of a condensed silica fume (SiO2). In the current work, industrial measurement campaigns were performed aiming to measure the fume generation during OLR. A thorough discussion of the possible mechanisms has been included in order to improve our understanding of the Si(1)-O2(g) system.The measurement campaigns were performed at the Elkem Salten plant in Norway. In addition to fume generation from OLR, the metal temperatures and ladle purge gas amount were recorded. The results of this work suggest that fume generation during OLR results from splashing of the metal and/or oxidation of the metal surface, with oxygen transport to the metal surface being the limiting factor. Other mechanisms of SiO2 formation were investigated, however insignificant.IntroductionOne of the main environmental and economical challenges facing the metallurgical industry is fugitive emissions of both materials and energy. In the production of metallurgical grade silicon (MG-Si), refining of the silicon generally takes place through an oxidative ladle treatment (purging with an air-O2 mixture). In the refining process, exposure of silicon to air results in the formation of condensed silica fumes (SiO2) – one of the main sources of fugitive emissions in silicon production plants. The oxidation of liquid silicon, as opposed to solid silicon, has not been widely studied and described in the literature [1], thus a thorough investigation of the oxidation mechanisms, and factors affecting the oxidation reaction rate are essential in order to deal with the problem. In the current work, the rate of liquid silicon oxidation has been studied through industrial measurements of fume generation from refining adles, where the purge gas rate and composition have been varied. The results from these measurements were discussed in light of existing models describing the liquid silicon oxidation kinetics."

Jan 1, 2011

By K. Morsi, S. K. Kassegne, A. El-Desouky, K. S. Moon

"Current Activated Tip-based Sintering (CATS) is a new process for the powder-based fabrication of macro, micro and possibly nano-scale features and shapes. This new and unique process enables selective sintering of powders by localizing electrically activated sintering conditions through a stationary or moving electrically conducting tip. We present preliminary experimental results on the effect of tip size in the CA TS process as well as the effect of initial powder particle size on the sintering behavior of nickel powder.IntroductionSpark Plasma Sintering (SPS) has been the center of attention of numerous researchers due its noticeable advantages over conventional sintering techniques such as rapid heating rates, lower sintering temperature and shorter holding times. Research on SPS has been applied on a wide variety of materials such as pure metals [ 1], ceramics [2], composites [3], nano-materials [ 4], biomaterials [ 5], shape memory alloys [ 6] and many other material systems. However, it has been mostly limited to bulk materials with simple shapes with a few exceptions ofresearch efforts where the effect of electric current was combined with metal forming processes such as spark plasma extrusion [7,8] and electric rolling of powders[9]. In this paper a novel process (Current-Activated Tip-Based Sintering (CATS)) is discussed where electric current and pressure are applied simultaneously through a small conducting tip (stationary or moving) over a conducting powder compact. This process has the potential advantages of sintering complex geometries with minimum energy requirements as unconventionally high current densities can be achieved due to the small contact area between the tip and the powder compact. Furthermore, by controlling the tip size, it can be possible to sinter features on the macro-, micro- and even nanoscales."

Jan 1, 2011

By Yongzhong Xiao, Tiejun Chun, Jian Pan, Deqing Zhu

"An innovative process of reverse floatation-direct reduction-low intensity magnetic separation was developed to effectively beneficiate the superfine run-of-mine (ROM) ore mined from Hunan Province, China. Mineralogy was measured that the ROM ore is of superfine low grade hematite ore type, assaying 27.2wt%Fetotal and with main valuable minerals of hematite occurring at size between 3 to 5µm. The upgrading results show that the final iron concentrate, assaying 88.3wt%Fe total and 94.5% metallization degree was obtained at an overall iron recovery of 69.9% under the following conditions: rough concentration by grinding of ROM up to 88.7% passing 0.074 mm and reverse flotation at pH=9.4, 100 g/t starch and 200 g/t dodecylamine (DDA), and coal reducing the rough concentrate pellets containing 12% calcium containing complex additive at 1200 oC for 120 min, and finally magnetic separation of the reduced pellets by grinding up to 89.2% passing 0.043 mm at 0.08 T field intensity.IntroductionWith the rapid development of iron and steel industry in China, there has been a soaring demand for iron ores in the past decade. The imports of iron ores have increased from 148 million ton in 2003 to 628 million ton in 2009 [1]. Iron making industries increasingly demand for high grade raw materials to improve product quality and reduce operation cost. However, availability of high grade natural ores is limited and enrichment of lower grade ores is necessary to meet the demand. Therefore, large quantities of superfine low grade iron resources are necessary to utilize in China at the moment."

Jan 1, 2011

By Luben Xie, Lin Hu, Qiang Wang, Min Gan, Tao Jiang, Wenqi Li, Xiaohui Fan, Zhiyuan Yu

"Crystal precipitation behavior of calcium ferrite (CF) during iron ore sintering process along with the effect of cooling rate, SiO2 and Al2O3 on crystalline condensation were studied. The results show that CF, has strong ability of precipitation. The precipitation is barely affected by extenal factors. It begins to precipitate when the liquid phase cools down to about 1200oC. CF could crystallize rapidly at the cooling speed of 150 °C /min. Furthermore, decreasing of the cooling rate favors the development of crystal. Binder phase transformed from CF system to silicate system when SiO2 content was increased to 5~6%, with a constant basicity (R) 2.0. Increasing Al2O3 content could promote the precipitation of CF and the development of crystal.IntroductionCrystalline condensation is the last stage of sinter mineralization. It includes the processes that crystalline substance and amorphous substance precipitate from high temperature solution phase and the consolidation of material when melt cools down. During the crystallization process, minerals precipitate following the order from high to low melting point coupled with the decreases of free energy. Most of binder phase minerals and part of iron oxides crystallize in this process, which have an important influence on mineral composition and microstructure of sinter. They finally determine the sinter strength and metallurgical properties."

Jan 1, 2011

By Jozef Zmik, Sergey Dobatkin, Martin Fujda, George Raab, Libor Kraus

"The present work, likewise, deals with grain refinement of medium carbon steel AISI 1045 having different initial microstructure resulting from thermal and/or thermomechanical treatment (TM) applied prior severe plastic deformation. In case of TM treated steel, structure refinement was conducted in two steps. Preliminary structure refinement has been achieved due to multistep open die forging process which provided total strain Eef ~ 3. Uniform and fine recrystallized ferrite structure with grain size of the order of 2-5 µm and with nest-like pearlite colonies was obtained. The further grain refinement of steel samples having different initial structure was accomplished during warm Equal Channel Angular Pressing (ECAP) at 400°C. The microstructure development was analyzed in dependence of effective strain introduced ( Eef ~ 2.5 - 4). Employment of this processing route resulted in extensive deformation of ferrite grains where mixture of subgrains and ultrafine grain was found regardless the preliminary treatment of steel. As straining increases the dynamic polygonization and recrystallization became active to form mixture of polygonized subgrains and submicrocrystalline grains having high angle boundaries. The intensive straining and moderate ECAP temperature caused the partial cementite lamellae fragmentation and spheroidization as straining increased. The lamellae cementite spheroidization was more extensive in TM treated steel samples. The deformation behavior of for both steel structural state confirm the strength increase; however the work hardening behavior was modified with respect to initial structure of steel prior SPD processing.IntroductionIn the last years, ultrafine grained materials have attracted considerable research interest because they tend to possess high strength without sacrificing toughness and ductility. Microstructural refinement of steel is usually achieved by alloying and/or by thermomechanical treatment process, which modifies phase transformation. Recently, advancement of severe plastic deformation (SPD) techniques provides another efficient access for grain refinement of metals and alloys. The fabrication of bulk materials with ultrafine grain sizes has attracted a great deal of attention over the past two decades because of the materials' enhanced properties [ 1, 2]. In last decade a worldwide effort in manufacturing process to obtain ultrafine grain structures in steels is persisting."

Jan 1, 2011

By Jason H. Nadler, Jason A. Kulpe, Stephanie J. Lin

"A numerical method has been developed to predict the microstructural characteristics of reticulated metal foam. The porosity of this foam is derived from sacrificial template particles of known particle size distribution, which are incorporated with other precursor components. In this approach, a porous structure is numerically generated starting with Powell's sphere packing algorithm. The resulting stochastic structure has characteristics similar to those of corresponding metal foam. Deterministic inter-sphere connections are calculated to more accurately model the pore morphology that evolves during thermochemical synthesis. Estimations of pore morphology and specific surface area of the simulated material are compared to lab-synthesized materials composed of equivalent constituent compositions. In addition, the effect of template particle size, inter-sphere connections, and the geometric constraints on pore morphology and permeability are investigated to refine microstructural evolution and design.IntroductionReticulated foams, characterized by their interconnected pore network, can be obtained by incorporating spherical sacrificial template particles into precursor materials followed by template removal processes. The resulting structure is composed of contiguous spherical pores whose morphologies reflect those of the original templates. Based on some of the unique features of this synthesis approach, a methodology is introduced in this work whereby these foams are digitally constructed using experimental data from the template particle sizes and precursor formulation. Digitally constructed porous structures can then be compared to their laboratory synthesized counterparts through the quantification of structural features such as porosity and surface area per unit volume, which in tum are used to inform the foam's fluid transport propertiesThe spherical template particle packing algorithm developed here is adopted from Powell's work [1], which also includes approaches to obtain percolation and density in random packings [2]. Gervois gives a mathematical development for the stereological sectioning of packed hard spheres [3]. Stereological sectioning facilitates determination of relevant three dimensional morphological properties from two-dimensional data [4]. Studies on the sphere distribution size and the related particle packing density and coordination number results are studied in [5, 6]. Lastly, Kato describes a sintered neck structure, which is used with these packings [7]. This neck structure, as a model of the particle shape following heat treatment, is implemented here in a similar manner. A strong difference between the available literature and the methodology here is that spheres are packed to ultimately represent porous space, not rigid solid space."

Jan 1, 2011

By Hylton McWhinney, Doanh Tran, Jewel Andrew Gomes, George Irwin, Sameer Pallavkar, Md Islam, David Cocke, Mohammad Rafiqul Islam

"High-performance nickel-based nanocrystalline zinc oxide adsorbents have been prepared adjusting Ni/Zn mol ratio of 1 :5 by thermal decomposition, coprecipitation and sol-gel method for selective adsorption of thiophene in liquid hydrocarbon fuels at ambient temperature and pressure. To understand the nature of reactive adsorption of thiophene (C4H4S) on Ni/ZnO, the effect of preparation techniques, morphological and textural structure on the desulfurization activity was investigated. A model fuel (20 mL) consisting of pentane (C5H12) and thiophene was prepared and adsorption experiments were performed by a batch method under ambient conditions. The physicochemical behaviors of the fresh adsorbents were obtained using X-ray diffraction (XRD) with EDAX, scanning electron microscopy (SEM). The sulfur concentration in the mixture was monitored by UV-vis spectrophotometry. The adsorption reaction confirmed that ZnO played a crucial role in taking up S element to convert it into ZnS. The deposition of nickel on ZnO is an innovative approach which takes advantage of the selectivity of Ni towards S-species and the high adsorptive capacity of ZnO support.IntroductionLow temperature deep desulfurization of fuels via selective adsorption of sulfur compounds keeping coexisting aromatic hydrocarbons and olefins intact is receiving increasing attention in the research community worldwide in order to satisfy the upcoming environmental regulations and fuel specifications. The sulfur compounds in the transportation fuels is a matter of concern when global crude oil slate is becoming heavier and sourer and environmental restrictions on both the refining process and the refined products are becoming more stringent. According to the current refinery technologies, the sulfur content in refinery fuel is typically around 300-500 ppm by weight (ppmw) [1-3]. Starting in 2006, sulfur limits in highway diesel and gasoline were set to 15 ppm and 30 ppm, respectively. During combustion sulfur in the fuel are converted to toxic sulfur oxide (SOx) and contributes to air pollution and acid rains [ 4]."

Jan 1, 2011

By Edgar Peek

"The two dominant metallurgical problems in treating most base metal sulphide concentrates in both the chloride and sulphate system are iron removal and sulphur elimination, respectively [1-3]. In this paper the opportunities, limitations and fundamentals of the chloride metallurgy system are described against this background. Only the treatment of oxide and sulphide ores is considered. Both hydrometallurgical and pyrometallurgical unit process operations are highlighted, since most successful base metal processes are based on a combination of the two. Hence, an overview of the technical and also some economical aspects of chloride metallurgy are presented.This overview summarizes the successful applications of chloride metallurgy, but it will not give exhaustive process and plant descriptions. It predominantly focuses on the essential technical features of the metallurgical unit process operations, while providing numerous references separately."

Jan 1, 2011