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By Chunyang Guan, Jilai Xue, Zengjie Wang, Qiaochu Liu

Molten salts electrolysis method to prepare Al-RE alloys has attracted increasing attention recently. CaCl2 and Na3AlF6 were the most often used melts for this purpose. In this work, Al-Sc alloys prepared by electrolytic deposition process in both CaCl2 and Na3AlF6 melts were investigated, respectively. It was found that Sc distributes almost uniformly and Sc contents increase with increasing current intensity in both melts. Current efficiency was measured for comparison among various current densities applied. The alloy products were analyzed using XRD and SEM, where the formation behaviors of Al-Sc intermetallics were investigated in details. The experimental and theoretical results demonstrate that Al3Sc and Al0.968Sc0.032 are the major precipitates in the Al-Sc alloys prepared by molten electrolysis. The results are useful for selection and optimization of the molten salts compositions and the parameters of electrolysis operation.

Jan 1, 2015

By Gordon Irons, Kevin Graham, Krishnakumar Krishnapisharody

Ladle or secondary metallurgy in steelmaking is an essential process step for the production of high-quality steel. Professor David Robertson was a pioneer in the modeling of these processes, in particular gas-metal fluid dynamic interactions and the rates of slag-metal reactions. This is now a highly active area of research, and some of the recent developments in this area will be reviewed.

Jan 1, 2014

By Chen Song

Cobalt basic carbonate particles were precipitated from 1.0mol cobalt nitrate or cobalt sulfate solution with ammonia carbonate. By controlling the zeta-potential of the particles and the ionic strength of the solution, the uniform particles with ellipsoid or rod shapes were obtained. During the precipitation process, the interface tension was diminished to the minimum and therefore the Ostwald ripening and secondary nucleation were both inhibited. The morphology and the size control by zeta-potential seem to be the result of thermodynamics rather than classical crystalline kinetics. The particle sizes were in the range of 0.4-0.6, 0.3-0.4 micrometer. After thermolysis, the spinel-type C0304 particles were produced. The morphologies of C0304 particles were similar to that of their precursors.

Jan 1, 2003

By Victoria Vaccarezza, Corby Anderson

Due to the demand for rare earth elements for everyday technology and applications, there has been much research initiation into the extraction and recovery of rare earth elements. An otherwise unknown mineral, eudialyte is a zircon silicate consisting of rare earth oxides, specifically the heavy REO yttrium (III), with only trace amounts of thorium and uranium. The first part of this project aimed at finding an efficient way to liberate and upgrade eudialyte to concentrate the REO content. A combination of gravity and magnetic separation techniques were employed, resulting in limited success. The second part looked at the hydrometallurgical processing of eudialyte through various leaching experiments with sulfuric acid. In all, this project will discuss why certain processes were utilized over others, as well as the difficulties that arose during processing.

Mar 1, 2018

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

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

Mar 1, 2017

By Jesus Gonzalez

Peirce-Smith converters (PSC) are long cylindrical chemical reactors where copper matte reacts with air. Traditionally, air is injected laterally through submerged tuyeres at different subsonic velocities. However, the accumulated experience in steelmaking, particularly in the basic oxygen furnace (BOF) process, shows that the gas bottom injection may improve the mixing efficiency of a liquid pool. The aim of bottom injection is to maximize the copper kinetic energy meanwhile avoiding excessive reactor splashing. When gas is injected from a single orifice at the bottom of a liquid pool, two main gas flow regimes can be identified, bubbling and jetting. In this work, a PSC with bottom air injection is studied by means of multiphase 3D CFD numerical simulations considering multiple air velocities. Special attention is paid to the bubbles and jet formation mechanism. The mixing efficiency is measured by calculating the turbulent kinetic energy of the copper matte.

Jan 1, 2008

By D. P. Cook, Jr. Jones, J. W. Evans

"It is well understood that the flow of liquid metal in the mold region of the caster can have a notable effect on the overall solidification behavior in aluminum casting. Previously our group has characterized the flow in this region in a water model, using particle imaging velocimetry. The flow is significantly effected by the specifics of the metal delivery system, i.e. size, geometry, used during the cast. Recently, a time-averaged 3D numerical model of the nozzle, combo bag and sump region has been developed and its validity has been tested against experimental data. Cases were run for different sized combo bags as well as bags that have been blocked. The results show satisfactory agreement between the physical and mathematical models.IntroductionFluid flow in the head of an electromagnetic (EM) and direct chill (DC) ingots has been shown to effect many important operational parameters in casting such as superheat removal, macrosegregation, and hot cracking. In most cases, the momentum from the nozzle is diverted through a delivery system, termed a bag, before entering the mold region. The specific geometries of the bags vary widely from operator to operator suggesting that there is still some question as to the optimum design. Several studies [1-4] have been carried out to understand the influence of the bag design on the solidification behavior in aluminum casters. However, few studies have included numerical prediction with experimental verification. Unfortunately, many simulations performed today still do not accurately account for flow in such devices.Recently, a significant amount of research into the flow resulting from the metal delivery systems has been performed [5-8]. The thrust of this research has been characterizing the flow patterns by a measurement technique called particle imaging velocimetry. The data suggest that the method of delivering the liquid metal into the mold region has a significant effect on the nature of the flow. With a detailed set of quantitative data from a water model, a numerical model can be built and tested to ensure a proper description of the flow field. The computational model used in these simulations is designed to represent a laboratory scale model of a caster in which ""combo"" bags were simulated. Such bags are mostly of a densely woven glass fiber material with low permeability to aluminum. ""Windows"", of a more open weave, permit aluminum to flow from the bag, see Fig. I. Two different sized combo bags were modeled, each subject to two different outflow window configurations. Furthermore, experimental measurements [9] were used to validate the model results."

Jan 1, 1999

By R. Padilla

A thermogravimetric study has been conducted to follow the decomposition and volatilization of arsenic from enargite concentrate in nitrogen and slightly oxidizing atmospheres. Temperature has a large effect on the rate of volatilization of arsenic. Fractional volatilization of arsenic as high as 98% were obtained in less than 60 min at 650°C in nitrogen atmosphere, while in slightly oxidizing atmosphere the same volatilization could be achieved in 30 min. It was found that arsenic volatilizes as sulfide in nitrogen atmosphere and as 4xture of sulfide and oxide in atmospheres containing 1% oxygen. By using the pore blocking and the first order kinetic models, apparent activation energies of 213 and 200 kJ/mol for the temperature range of 780 - 900 K and 205 and 184 kJ/mol for the temperature range of 900 - 985 K were determined for enargite and copper concentrate, respectively.

Jan 1, 1997

By Mick O'Meara

Metal Organic Chemical Vapour Deposition (MOCVD) is used in the production of computer circuit boards and metal shapes in nickel, gold, copper, cobalt, etc. All varieties of .MOCVD use the decomposition of a vapour of organometallic compounds to produce different forms of ultra-pure metals, or alloys. CVD Manufacturing's proprietary MOCVD process has been adapted and developed to produce commercially ultra-pure metal shapes, metal powders, and metal foams. Therefore, it is a purification process. The typical process has three steps. First, a volatile metal organic compound is produced from volumetrically contaminated metals, metal oxides, etc. Typical feed materials are metal powders, ores, concentrates, or a slurry of metals and contaminants. Secondly, the volatile. metal organic compound is purified by fractional distillation. Thirdly, the purified metal organic compound is decomposed into different forms of ultra-pure metals, such as net shapes, powders, or metal foams. A mixture of metals can be purified either by the selective production of volatile materials, or a separation can be achieved during the second step, in the fractional distillation stage. The purification and recycling of metals by the MOCVD process will be discussed, particularly with regard to nickel, aluminum, gold, the platinum group and other metals.

Jan 1, 2000

By Akira Kaneda, Nozomu Hasegawa

"In the Mitsubishi Continuous Copper Smelting and Converting Process, slag/matte mixture overflowed from the smelting furnace is separated continuously in an electric furnace (slag cleaning furnace, CL-furnace). In order to improve the separation efficiency of slag and matte and to minimize power consumption, the design and the operating conditions of the CL-fumace should be optimized. In the previous study, the authors developed a mathematical model for simulating phenomena in the CL-furnace. The model consisted of 3 modules, electric field analysis, heat and fluid flow analysis and the particle tracking method. In this study, the model was partially modified: k -E. model was adopted, and the effects of various conditions, such as furnace shape (including accretion) and scale, electrodes configuration, immersion depth of electrodes, and thickness of slag layer, were evaluated. And the optimum design and operating conditions were discussed.IntroductionUnder the recent environmental restriction, advantageous features of the Mitsubishi process have attracted much attention. The process uses 3 furnaces connected by launders. Mixture of matte and slag formed in a smelting furnace flows continuously to a slag cleaning furnace (CL-furnace), where the matte is separated from the slag. The matte is continuously siphoned out to a converting furnace and converted to blister copper. The slag overflowed from the CL-furnace is discarded. Because the slag contains about 0.6 % copper, improving slag/matte separation efficiency and decreasing copper loss make a great profit. Moreover the process requires a large amount of electric energy, so reduction of electric power consumption brings in enormous benefit.The objective of this study is to optimize the design and the operating conditions of the process, especially the CL-furnace. This will be achieved by developing the mathematical model and clarifying relations between the design or the operating conditions and various phenomena in the furnace. Fig. 1 shows an outline of the CL-furnace. The mixture entering through an inlet is separated to slag layer and matte layer . In order to maintain the temperature of the melt at a predetermined level, 6 electrodes are immersed into the lag and Joule's heat is generated by 3-phase alternating current flowing."

Jan 1, 2000

By Shigeru Ueda, Shin-ya Kitamura, Dong Jun Shin, Xu Gao

Steelmaking slag contains useful elements such as P and Mn. Generally, in the carbothermic reduction of slag, not only P but also Mn are reduced and a Fe–P–Mn alloy is formed. In this study, the possibility of the separation of Mn and P was investigated. A mixture of synthesized slag and graphite was heated at 1773 K, and the compositions of the separated slag and metal were analyzed. The results showed that with a decrease in basicity, the reduction of P was enhanced but that of Mn was suppressed. Thus, under an optimum condition, steelmaking slag was separated into a Fe–P alloy and a high MnO-containing slag. Although further investigation is necessary, the formed alloy and slag could be used as raw materials for fertilizers and Fe–Mn alloys, respectively. This paper elucidates the concept of this process and the results of the fundamental experiments.

Mar 1, 2018

By J. Pérez

A lead smelter slag with high copper, lead, arsenic and silver contents was treated at laboratory scale for arsenic removal. The slag was first leached at atmospberic pressure with sulfuric acid and oxygen. According to arsenic contents leaching of most of the arsenic was achieved in either one or two stages, producing a lead-silver rich residue and a solution high in copper and arsenic concentrations. Alternative routes were considered to treat the resulting solution. Firstly, solvent extraction of arsenic with a mixture of TBP and 2-etbyl-bexanol was tested and extractions of over 95 percent of arsenic were achieved. Secondly, a copper arsenate precipitation treatment was done to eliminate arsenic and copper from solution.

Jan 1, 1996

By G. Kugler, M. Tercelj

"The 1.2690 high alloyed tool steel is usually applied for cold working and is alloyed with carbide-forming elements Cr, V, W and Mo. It exhibits very poor hot deformability. Since there is no enough available data in literature for elucidation of this problem, hot workability and development of microstructure during hot deformation was studied. Hot compression tests were carried out in temperature range 850-1150 °C and strain rates range 0.001-6 s-1. SEM and OM were used for observation of microstructure. Results revealed very complex precipitation of carbides that depends on deformation temperature as well as on strain rate. It was found that especially at lower temperatures of hot working range the precipitation of carbides strongly depends on strain rate. Three different hot deformation behaviors’ were observed depending on temperature and strain rate range.IntroductionThe hot workability of highly alloyed high speed steels is usually described as relatively poor in comparison to other steels due to their tendency of cracking during hot working especially when inappropriate hot working conditions are applied. Alloying elements such as Cr, W, Mo and V in ledeburitic tool steels form carbides that improve hardenability, strength, hardness, wear resistance, etc., but they decrease hot workability and narrow hot working temperature range in comparison to conventional steels. The size, distribution, type and fraction of carbides, as well as the thermomechanical history of material and hot working parameters have major influence on the hot workability. The microstructure of ledeburitic tool steels during hot deformation can be characterized as a two-phase system consisting of an austenite matrix and a combination of ledeburitic carbides [1-4]. In the soft-annealed condition the total volume fraction of carbides is in the range 19-30% and in the quenched condition in the range 9-25%, depending on the chemical composition. During heating before deformation a large quantity of carbides dissolve, but non-dissolved carbides can have an extremely diverse influence on the hot workability due to variations in their composition, size, distribution, hardness and shape, and their different behavior during the deformation phase [5-7]."

Jan 1, 2011

By A. Navarra

Peirce-Smith converting (PSC) is applied for roughly 50% of primary nickel and 70% of primary copper production. PSC cycles produce batches of ironfree sulfide matte (or blister copper, in the case of copper smelters), that are subject to further processing. However, the number of cycles that can be performed simultaneously is limited by the offgas handling system. Moreover, PSC suffers from variation in the yield and duration of the cycles. This variation is managed by conventional smelter designs, in which the upstream smelting capacity exceeds the nominal converting capacity; PSC is thus a major bottleneck in conventional nickel and copper smelters. Stabilization and standardization of PSC operations can therefore increase smelter throughput. The current paper presents a discrete event simulation (DES) framework to assist in smelter debottlenecking. It features random number generation to represent cycle variability, and time-adaptive finite differences to represent thermochemical complexity. Preliminary computations are presented.

By W. S. Hui, M. G. Silva-Valenzuela, H. Wiebeck, F. R. Valenzuela-Diaz, B. B. Michel

Biodegradable polymer microcapsules have been used as a control sustained release system with many applications. Studies reveal that the incorporation of nanoparticles improves matrix properties, even more so if the clay is modified. The objective of this work was to compare microcapsules of poly (succinate-co-butylenelactate) (PBSL) reinforced with Brazilian clay, composed of smectites and kaolinite, in its natural (MMT/K) and modified (O-MMT/K) forms. Nanocomposites and microcapsules were synthesized by emulsification-diffusion of solvent and solvent diffusion methods. Its characterization was then performed by scanning electron microscopy (SEM), stereo microscopy and wide-angle X-ray diffraction (XRD). The results reported corroborate that PBSL/OMMT-K form an intercalated montmorillonite and kaolinite nanostructure, capable of generating uniform spherical microcapsules with diameter values smaller than that of PBSL/MMT-K, reaching 5–10 lm. DRX indicates that there was a real change in the clay structure. The incorporation of modified clay showed an improvement in surface quality and the strength of microcapsules, making it possible to produce smaller sizes.

Mar 1, 2018

By Petrus Christiaan Pistorius, Ming Tang

Magnetite concentrate is pelletized and then hardened by elevated-temperature oxidation to hematite, to produce pellets for ironmaking. Previous work showed that the rate of oxidation is under mixed control of gaseous mass transfer of molecular oxygen through the pellet pores, and solid-state diffusion into the oxidizing grains. Because of the partially limiting role of solid-state diffusion, concentrate size distribution strongly affects pellet oxidation. Previously, a simple mixed-control model was formulated to describe isothermal oxidation. In that model, the main effect of concentrate size distribution was on the plateau level of oxidation which is reached at a given temperature. However, the extent of plateau oxidation increases with increased temperature, requiring a more complex model for non-isothermal oxidation. In this paper, predictions of the non-isothermal model confirm the strong effects of concentrate size distribution and oxygen enrichment. In particular, a greater fraction of coarse magnetite particles would be beneficial, decreasing the size of the macroscopic unoxidized pellet core.

Jan 1, 2015

By Truan-Sheng Lui, Li-Hui Chen, Fei-Yi Hung, Cheng-Yi Chen

"This research used the austempering heat treatment on the SCM435 thin specimen with a type of double loop and obtained the Cr-Mo bainite structure, and then we could further investigate the mechanical properties of SCM435 bainite structure. Experimental data showed the stability of the mechanical properties of specimen with austempering temperature 830°C for 25 minutes was better than that of 15 minutes. The size of austenite grain affected the strength of thin specimen. After austempering at 830°C-25minutes and salt bath at 290°C, the stability of UTS was better than that of salt bath at 310°C and 330°C. The average hardness of all specimens was about more than HRA70. The specimen with austempering at 830°C-25minutes and salt bath at 290°C-30minutes had bigger grain size of austenite and retained y, it also had higher hardness and strength toughness. So, its stability was improved for tensile strength comparing with traditional tempered martensite process.IntroductionSCM435 is a Cr-Mo steel with high strength and high hardness properties, and it has been widely used in machine parts, shafts, gears and strength screw products [1-3]. However, this system often has lower reliability due to the brittleness of high-temperature tempering and quenching inequality. Considering the austempering heat treatment can obtain the uniform bainite structure to improve the temper brittleness, and the austempering heat treatment is a continuous process that it also has efficiency and uniformity. For the thin plate specimens, the mechanical properties of the bainite structure are better than traditional martempering structures."

Jan 1, 2013

By Dumitru Mitrica, Vasile Soare, Elvira Alexandrescu, Mihai Ghita, Marian Burada, Petru Moldovan, Raluca Maria Florea

"Aluminum metal matrix composite Al-Si /SiCp was prepared by reactive gas injection and subsequent remelting. The influence of the remelting process on the microstructure and physicalmechanical properties of the resulted material was investigated. Samples resulted from the synthesis process contained silicon carbide agglomerations in the vicinity of primary silicon and large pore concentrations. In-situ formed silicon carbide presented mostly a polymorphic structure with particle sizes varying from 1 to lOµm. Physical and mechanical properties were largely influenced by the porosity distribution. The remelting process provided a decrease in the composite material porosity and pore size, with significant improvements in the particle distribution and physical-mechanical properties of the composite material. Additions of up to lwt.%Mg in the starting alloy improved the in-situ carbide formation and particles distribution in the solidified material. However, stable and large particle agglomerations were detected in the material in absence of conventional stirring or controlled solidification techniques.IntroductionThe remarkable properties of composite materials (yield strength, stiffuess, hardness and resilience at a reduced specific weight) make them attractive for applications in automotive, aerospace and military industries. Particle reinforced aluminum metal matrix composites (PAMMC) are known for their high strength to weight ratio. The recent development of P AMMC created the possibility to obtain large particles concentrations, exceeding 10% by volume ofreinforcement (SiC, AIN, Al203, etc.). The improvement ofhigh temperature strength and wear resistance made them appropriate for the use in automotive applications, such as the pistons, rotors, disc brakes, and propeller shafts [ 1]. The present main disadvantage of the P AMMCs is their high costs for obtaining and processing related to the final product performance. In order to benefit from the advantages that offer composite materials properties a reasonable production cost - performance ratio must be obtained [2]. Recent innovations in the manufacturing of aluminum-based metal matrix composites provided notable performance improvements but no feasible solutions were found for lowering their present high prices."

Jan 1, 2014

By Ricardo Melamed

Metallic mercury has been extensively used for gold recovery. Although the solubility and mobility of metallic mercury is low, this metal can undergo many transformations, leading to mercury contamination in humans. The complexity of Hg chemistry in the environment reflects its different possible oxidation states and species, with different physical-chemical properties. The interaction of Hg in the terrestrial system, as well as in the aquatic environment, is important to understand the mercury cycle. This paper reports data on the adsorption of Hg onto an Oxisol soil. Results show that the interaction of Hg(II) at the soil-solution interface depends strongly on ligand concentration in solution, which can affect Hg mobility. The presence of the chloride anion in solution increases the mobility of Hg(II) through the soil, due to a relative lower affmity of mercury chloride at the oxide surface. In the absence of chloride, Hg(II) form strong complexes with the surface, and its adsorption behaviour is similar to the adsorption of other hydrolizable cations.

Jan 1, 1996

By R. M. Reynolds

Engitec Impianti, S?.p.A. of Milan, Italy has successfully designed, constructed and has in operation state-of-the-art battery breaker systems at two European locations. A third facility i:s partially completed in Toronto, Ontario, Canada. The CX system crushes whole batteries, separates the various components and desulfurizes the battery paste. The system also produces sodium sulfate from the sulfuric acid and lead sulfate contained in the batteries. Actual plant operating data indicates that the desulfurized paste contains less than 0. 6 percent sulfur and less than 0. 5 percent antimony. The CX system utilizes mechanical screening and an up-flow hydrodynamic separator to accomplish the component separation. Sodiwn hydroxide or sodium carbonate is used for desulfurization. The sodium sulfate brine is evaporated and crystallized to produce clean anhydrous sodium sulfate suitable for use by detergent or glass manufacturers. Plant data also indicates that an increase in furnace productivity of about 25 to 30 percent is achieved using feed from the CX system. The desulfurized paste is very suitable for electrolytic processing as an alternative to pyrometallurqical processing.

Jan 1, 1990