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By Daniel Hoffman, Katerina Aifantis, Ibrahim Miskioglu, Jaroslaw Drelich

"A new method to determine the elastic modulus of a material using the atomic force microscope (AFM) has been proposed by Tang et al. (Nanotechnology 2008, 19, 495713). This method models the cantilever and the sample as two springs in a series. The ratio of the cantilever spring constant (k) to diameter of the tip (2a) is treated in the model as one parameter (a=k/2a). The value of a, along with the cantilever sensitivity, are determined on two reference samples with known mechanical properties and then used to find the elastic modulus of an unknown sample. To determine the reliability and accuracy of this technique it was tested on several polymers. Traditional depth-sensing nanoindentation was preformed for comparison. Using both methods, the elastic modulus of the polymers tested was calculated. The elastic modulus values from the AFM were within ±(5-20)% of the nanoindenter results.IntroductionThe atomic force microscope (AFM) has proven to be a useful tool for characterizing materials on the micro- to nano-scale. The most common use of AFM is to image and measure the topography of the sample surface, but AFM has also been used to characterize the mechanical properties of materials [1-3]. With AFM's ability to scan the sample surface, features of interest can be found and indented. It provides an advantage over traditional nanoindenters that use optical microscopes and thus cannot resolve nano-scale features. This makes AFM a useful tool for characterizing materials on the nano-scale."

Jan 1, 2011

By T. C. -M. Cheng

Iron removal and disposal in zinc plants has imposed a major environmental challenge to the industry. Among the existing options of precipitating iron as jarosite, goethite, and hematite, the Hematite Process seems to be the best candidate for the future development of a waste-free technology, because of its potential of producing saleable iron oxide residues for feed in iron-steel making industry. Unfortunately, under the current practice of the Hematite Process, it is not possible to produce iron residues clean enough to meet the specifications of the said industry. In this paper, the practice of industrial hematite precipitation and the relevant technical literature are reviewed with the objective to identify the critical processing parameters which are responsible for the contamination of hematite, particularly with sulfur and zinc. The analysis is conducted from a crystallization theory standpoint with emphasis given to the role of supersaturation with respect to the cleanliness of hematite precipitates.

Jan 1, 1997

By Shufang Ding, Fukun Yan, Zhiqiang Shan, Wei Chen, Cuicui Ji

"To remove aluminum ion from chlorinated rare earth solution, this paper used hydrolysis method to explore the hydrolysis behavior of aluminum ion in aluminum chloride solution and confirm the optimum conditions of aluminum ion hydrolysis, which are pH value, temperature and initial concentration of Al203 and so on. The experimental results show that single treatment can make aluminum precipitation rates of chlorinated rare earth solution reach about 90% by hydrolysis precipitation; and then several recycle disposal can get precipitation rates of 89% for aluminum and 2.86% for rare earth.IntroductionIn China, rare earth resources are very rich and unique minerals, complete variety, and rare earth products are very large in the domestic reserves. Rare-earth and application products have been deep into all areas of our life, permanent magnet material of rare earth is one of the most popular application areas[11. Binary oxides such as praseodymium neodymium have been widely applied in the fields of glass, ceramics, magnetic materials, catalysts and so on. Especially, the advent of the Pr-Nd-Fe-B magnets which makes the world magnetic material into a new stage of development [2•3]With the development of science and technology, for industrial, physical and chemical indicators of raw materials Pr-Nd oxides (such as particle size, specific surface area and non rare earth impurities etc.) are also getting higher and higher. The oxide size has an important influence on sludge formation in the electrolytic process. If the size is too large, added oxides have settled on the bottom of slot before melting, and then generated sludge; if the particle is too small, it can cause dust dispersion, enlarge oxide unit consumption and increase the cost of production in the charging process. Some early processes use oxalic acid to make chloride neodymium praseodymium settle, and impurity can be removed cleanly, but the cost is high, it is not suitable for production. At present, most enterprises are using ammonium hydrogen carbonate to precipitate chlorinated neodymium praseodymium, but chlorinated neodymium praseodymium such as iron and aluminum and so on can easily form gel in the precipitation process, seriously affect the growth of neodymium praseodymium carbonate crystal and often leads to particle meticulous, even may also generate gel-like neodymium praseodymium sediments and cause centrifugal or suction filtration difficult. Now the actions and their removal of impurity such as iron and aluminum have done a lot of research in the production process of rare earth, removing aluminum craft with alkaline (sodium hydroxide) and acid (oxalic acid) has good effect, but the cost is higher[41; used adding complex agent to remove aluminum method which is simple and easy to operate, but aluminum removal rate is not high, and also changed the sediment of crystal type[51, and etc. This paper discusses the removal of chlorine from rare earth solution on the basis of the hydrolysis property differences betweenAJ3+ and rare earth ion."

Jan 1, 2013

By J. J. Talja

An investigation of oxidation of various nickel concentrates was carried out using differential scanning calorimetry (DSC). The aim of this study was to determine the ignition temperature and investigate other oxidation behavior of various sulfide-based nickel concentrates. Variables in the experiments were mineralogy, particle size and partial pressure of oxygen with temperature increasing linearly at 25 K/min from 323 to 1023 K (50-750 °C). The igni¬tion temperature was determined to represent the starting point of rapid oxidation. The reac¬tion enthalpies of the concentrates were determined and the amount of heat generated up to various time were used to calculate the extent of reaction. Mineralogical changes at various stages of oxidation were also investigated. For this purpose a second set of DSC-experiments were carried out in which each experiment was interrupted at a desired temperature between 673-873 K. From these tests the weight loss of samples were determined and changes in the individual constituent of sulfide minerals were analyzed. For pentlandite-based Ni-concentrates the ignition temperature was 705-710 K (approximately 435 °C). Pyrite was the first sulfide to oxidize. Reactivity of the violarite-based concentrate was greater than those of the pentlandite-based concentrates. The stoi-chiometry of pentlandite changed before ignition because of preferential oxidation of iron. Rapid oxidation of the pentlandite mineral occurred at about 823 K (550 °C). By 900 K about 90 % of the iron in pentlandite was converted to hematite, and NiS containing some iron was formed.

Jan 1, 1994

By J. Y. Hwang

Microwave heating is an attractive alternative to conventional heating methods because heat is generated directly within the microwave absorbing materials. It has potential to be utilized for selective heating and removal of specified components from a materials mixture. This investigation was undertaken to explore the potential of selective heating and burning of binders for foundry sand reclamation. Selected raw materials and binders used in foundry operations were tested to determine their receptivity to microwave heating. Time needed to reach 600°C and/or the maximum temperature achieved for samples irradiated by microwaves for twenty minutes under 800 W microwave power are reported. The microwave heating characteristics of the selected materials are summarized and discussed. The interactions between microwaves and the raw materials used in a foundry. such as silica sand. chromite sand and bentonite (clay) binder were studied. The results showed that chromite sand coupled well with microwave energy at ambient temperature while silica sand did not. This was expected because the major component of chromite sand. iron chromite (FeCr2O4). is a good microwave absorber. while quartz, which is the major component of silica sand, is a microwave transparent material at ambient temperature. Bentonite absorbs microwaves well because it contains a hydroxyl functional group and water molecules in its structure. It was found that the structure of bentonite was changed through microwave irradiation. Microwave heating characteristics of silica sand mixed with different amounts of bentonite binders were investigated. The presence of bentonite in the mixture improved the microwave heating of silica sand significantly. and bentonite was deactivated by the microwave processing.

Jan 1, 1995

By Basant L. Tiwari

An electrolytic process, based on a three-layer concentration cell, to extract magnesium from commercial aluminum alloy scrap has been examined. The process was repeatedly tested at 1025 K with two cells of d1fferent sizes, 0.6 kg and 5 kg feed aluminum, to have a better understanding of the opera ting parameters and evaluate the scale-up potential. In both cells, the magnesium content of the scrap was selectively reduced ?from 1. 1 to less than 0.1 wt.% at anodic current dens-Hy as high as 1. 1 A/cm2 with current efficiency exceeding 85%. Magnesium was recovered in the form of salt coated globules. Comparison of performances for the two cells suggests that the process can be scaled up. With further development, this process could become a viable alternative for demagging secondary aluminum.

Jan 1, 1985

By H. J. Roorda

With an increasing need to obtain metals by processing complex fine intergrown ores, the use of electron-optical techniques will become more important as a tool for mineralogical studies. Electron images enable a higher spacial resolution than can be obtained by optical microscopy and thus provide a powerful and necessary aid for the examination of small grains and finely locked particles. In this paper the mineralogy of Meggen ore was investigated. Both light-optical and electron-optical techniques were used to evaluate the mill feed and products of the concentrator. Detailed examination by reflected-light microscopy to assess the comportment of galena in the complex pyritic ore was inconclusive in establishing the cause for low lead recovery of only forty percent of the ore's lead content. Electron microprobe analyses indicated that the majority of the lead lost to the tailings was accounted for by extreme fine (often smaller than one micron) and complex intergrowths of galena in pyrite. The remainder was lost as fine free galena grains.

Jan 1, 1987

By M. Neises, M. Roeb, C. Sattler, S. Stenger

"A two-step thermo-chemical cycle process has been developed and investigated. It is based on metal oxide redox pair systems, which can split carbon dioxide as well as water molecules by extracting oxygen atoms and reversibly incorporating them into their lattice. If concentrated solar radiation is used as the heat source, a promising method exists to produce synthesis gas from water and CO2. An easy way of operation is gained by the combination of a ceramic substrate as the absorber structure, which can be heated to high temperatures with concentrated solar radiation, and of a metal oxide coating which is capable to carry out the redox reactions. The performance and kinetics of a ferrite based redox material coated on ceramic substrates were investigated in a laboratory set-up. CO2 could be reduced with significant conversions. In addition, several side reactions were observed like the formation of carbon and like the Boudouard reaction.IntroductionThe search for alternative energy carriers and for processes able to reuse carbon dioxide stimulates the research for sustainable routes of alternative fuel production. In the scope of this search thermo-chemical processes combined with sources of concentrated solar energy have become more and more attractive. Ideally, the only raw materials for such processes are water (H2O) and carbon dioxide (CO2) enabling not only a process free of emissions, but also allow to reduce emissions of other processes by reusing CO2 to provide synthesis gas, which itself can be applied to produce chemical commodities or even better synthetic fuels like methanol or petrol.In contrast to the direct splitting of those raw materials, thermochemical cycles split water and CO2 in several steps and enable hydrogen (H2) and carbon monoxide (CO) generation at temperatures controllable by today’s technical equipment. One of the most interesting thermochemical cycles is a two-step process using metal oxide based redox systems. During the first step of this cycle (the regeneration step) the metal oxide is reduced setting some of its lattice oxygen free according to reaction (1). In the next step (the splitting) the reduced and activated material is oxidised by withdrawing oxygen from water and CO2 and at the same time hydrogen and CO is set free according to reactions (2a) and (2b) respectively."

Jan 1, 2011

By H. L. Fraser

A review of the possibilities of performing microchemical analysis in thin sections using a combination of scanning transmission electron microscopy and energy dispersive spectroscopy of x-rays is given. Particular attention is paid to the factors that limit accurate analysis at the highest spatial resolution. As an example of the use of these techniques applied to a potential problem in minerals processing, the identification of iron pyrite and pyrrhotite particles in Illinois, Herrin #6 coal is presented.

Jan 1, 1981

By N. A. Barcza

DC plasma-arc technology using a hollow graphite electrode (cathode) has been successfully implemented in the primary metallurgical industry in South Africa up to the 30 MW scale. Mintek has applied its expertise base, established over the past fifteen years, to testing the treatment of metallurgical wastes such as carbon- and stainless-steel plant dusts, lead- and zinc-containing slags, and residues from the base-metal industry. Favourable results have been achieved, and disposable products were produced. The evaluation of numerous wastes indicates that recovery of zinc as metal gives the best economic return from these sources. Direct recovery via a splash condenser or electrolytic zinc extraction from fume are the two preferred alternatives under review. In both instances dehalogenation is an important issue, but can be achieved by suitable treatment processes. The Enviroplas technology provides a flexible, commercially viable approach to the treatment of a wide variety of wastes. Mintek, together with its associate Pyromet CC, are installing a plasma- arc pilot-plant facility with both an ISP lead-splash condenser of about 5 t/d condensed zinc capacity and a combustion chamber to burn zinc vapour to zinc oxide. This will demonstrate the suitability of the Enviroplas technology for treating specific metallurgical wastes, so that customized industrial plants can be engineered based on large-scale testwork.

Jan 1, 1994

By John Dasher

One of our War Plants processed Bolivian concentrates as low as 17% Sn by the Arnhem process (pressure leach with HCL) and sent the waste acid down a ditch to Galveston Bay where the chlorides, mostly iron, hydrolyzed. Oyster men, and Texas, demandedimpoundment until a disposal process could be developed. A recycle process found by lab work was recommended, piloted and a plant built. This involved cementation of As Sb, Cu, Bi and Ag on light moving scrap iron and of Sn & Pb on Al turnings (then not recyclable), evaporation and crystallization of hydrous FeCl2, roasting crystals in a muffle furnace and absorbing HCI for reuse. The residue from leaching the low grade concentrates was floated to remove undissolved sulfides, classified and passed over sand and slimes tables to get a smeltable concentrate, a discardable sand tail and a slimes tail worth treating After desliming at 2 micro meters cassiterite, oxide flotation gave good, lab results; but commercial equipment wasn't adequate then. Chloride volatilization, with or without smelting gave high recoveries of Sn as SnCl2, whose marketing was questionable. I have heard this was finally fluxed and smelted.

Jan 1, 1992

By Jacques Magnaudet, Julie Cranga, Didier Huin, Pascal Gardin

"With the aim of controlling steel grade in steelmaking reactors, IRSID and IMFT are developing a numerical description of the evolution of bubbles in the vicinity of a liquid steel/ slag interface. The objective is to identify the main parameters affecting the hydrodynamics of the various phases. The goals of the present paper are:• To describe the numerical technique developed to predict the multi phase flow including bubbles, liquid metal and slag layer.• To analyze the influence of the absolute pressure on the bursting of bubbles in a RH degasser. Validation is given by comparison with results available in the literature. The major point concerns the distinct behaviors observed whether the pressure is low or high.• To study the influence of the properties of the slag layer (thickness, viscosity and interfacial tension) on the entrainment of liquid metal in the wake of the bubble and on the nature of the projections from the bath surface.IntroductionMost of secondary steelmaking processes use gas stirring for homogenization, removal of nonmetallic inclusions or decarburization under reduced pressure. The bursting of gas bubbles at the metal or slag layer surface produces a beneficial ejection of metal droplets in the low pressure atmosphere, provided that there is no violent projection, which may have detrimental effects on the process.Our objective is to develop a numerical tool to study the phenomena occurring in the vicinity of the bath surface, in particular bubble bursting under reduced pressure and entrainment of metal in the slag layer. In this paper we report the first conclusions of our study. In the first section we describe the numerical model used to describe the three-phase flow and the expansion of the gas bubbles under the effect of the ferrostatic pressure. The second section is devoted to the study of pressure effects on bubble rise and bursting. The third section reports some computational results about the rise of a gas bubble through the interface between the two liquids."

Jan 1, 2001

By S. Neven

The smelting of copper anode slimes, a material which contains mostly lead, silver, copper and selenium, has been practiced for many years with a view to recovering the silver and associated small amounts of gold. However, a theoretical understanding of the process has been lacking and this handicaps efforts to improve and intensify smelting operations. In the past few years work has been done in this area and this work will be reviewed in the paper. The underlying thermodynamics of the oxidation of silver-copper selenide mattes has been developed and used as a basis for the construction of a computational thermodynamics model which attempts to predict the composition of all condensed phases during the course of smelting. The model will be outlined and its successes in matching experimental data, as well as its current deficiencies, will be considered. Supporting work on the thermodynamics of silver solubility in slags, on activity-composition relationships in the Ag-Se system and work in progress on the oxidation state of copper in the slags will be reviewed. These projects are designed to provide further detailed data which will improve the robustness of the thermodynamic model.

Jan 1, 1999

By William Petruk

Many gold operations lose gold during processing because some ore characteristics which affect recoveries have not been determined, and consequently the plant could not be designed to account for them. The ore characteristics can be determined with mineralogical techniques by analyzing the plant feed, final tailings and mill products. The plant feed and/or final tailings are commonly analyzed first as a separate project. Mill products are analyzed only if the process employs a minerals separation circuit to produce a concentrate (e.g. secondary flotation circuit to concentrate gold-bearing arsenopyrite), and if assays and materials balances indicate a recovery problem in the minerals separation circuit. Many ores have been evaluated at CANMET on a confidential cost-recovery basis by custom-designing a work plan which was dependent upon the problem and on the characteristics of the ore. The reasons for gold losses have been identified in most cases, and suggestions for modifying flowsheets have been proposed. The methods used in performing the analyses are described in this paper, and non-confidential results from in-house projects are provided as examples of the benefits of such analyses. The analytical methodology involves a combination of the following procedures: -producing heavy mineral concentrates and identifying the gold minerals in the concentrates; -determining quantities of invisible gold in gold-bearing sulphides, sulpharsenides, etc. by SIMS; -determining quantities and liberation characteristics of all gold minerals and gold-bearing minerals in the sample; -finding and identifying gold minerals in silicates; -extensive grinding and cyanidation to determine the ultimate amount of cyanidable gold; -determining impact of clay minerals and graphite; -performing a mineral balance for the gold in each sample; -performing a materials balance to determine the distribution of the gold minerals, gold-bearing minerals, and other minerals throughout the flowsheet, and; -interpreting the results.

Jan 1, 1995

By D. M. Hausen

Applications of process mineralogy to the exploitation of molybdenum ores begins with early exploration and continues through the evaluation of mineralized prospects, to amenability testwork and pilot plant studies, to the development of a mineable orebody and to the development of a viable process for recovery. After plant construction, a broad range of products from a wide selection of sampling locations, i.e. grinding circuit, flotation cells, smelters and roasting kilns. etc., are evaluated analytically and microscopically, followed by periodic troubleshooting of problem points. The various crystalline phases of molybdenum that occur naturally and throughout various hydrometallurgical and pyrometal1urgica1 processes are identified and characterized by a variety of instrumental methods, including XRD-XRF, optical and electron microscopy, infrared spectrographic and differential thermal analysis.

Jan 1, 1989

By A. D. Damodaran

Batch scale and continuous rotary kiln carbothermic metallisation of ilmenite followed by different down-stream treatments such as catalytic rusting, acidic chloride leaching, oxidation-leaching etc. has given rise to a high grade synthetic rutile (98% TiO2). Rotary reactor metallisation experiments had concurrently given important information with respect to mean residence time, dispersion number, hold-up and axial velocity profiles of the solids bed. A mathematical model based on law of additive reaction times has indicated that Boudouard reaction becomes faster than reduction reaction at higher conversions. A possible use of high grade synthetic rutile in paint industry and metallised ilmenite as welding electrode flux material are discussed.

Jan 1, 1992

By Ko-ichiro Ohno

It is recently recognized that the iron reduction and melting as well as the slag separation of a composite of granular iron ore and coal are completed in a very short period of about 10 minutes when the composite is rapidly heated up to approximately 1673K. These phenomena are expected to be applied to a new iron-making process. The mechanism of iron ore reduction and iron-slag separation during rapid heating has not yet been revealed and the fundamental research has just started. Carburization of the reduced iron is regarded as one of the most important steps in this process. In the present work, the composite was prepared from four kinds of coal or graphite as a carbon source and electrolytic iron powder as a completely reduced iron ore. The temperature at which the liquid formation and iron carburization occurred was monitored. Direct observation of smelting reduction behavior was made by a confocal laser-scanning microscope combined with the infrared image-heating furnace to clarify the effect of molten ash on iron carburization. It was found that the meltdown temperature of composite became lower as the melting temperature of coal ash decreased. From the observed result, it was presumed that the liquid slag would act as an important media for the carbon transfer from coal to iron. The carburization mechanism during the smelting reduction was estimated as follows. When slag containing iron oxide melted down and contacted carbon, iron oxide in the slag was reduced and the formation of the metallic iron particle as well as the its carburization occurred simultaneously at the slag-carbon interface. Carburized iron particle was carried from slag-carbon to slag-iron interfaces due to the slag convection flow caused by the difference of the interfacial tension between the carbon-slag and iron-slag interfaces. Carburization of reduced iron could proceed with a repeat of the above-mentioned process.

Jan 1, 2003

By D. Lambert

Process modeling for large deformation metal forming processes has been developed into a very successful tool in commercial applications during the last two decades. DEFOR.MTM is a well-known metal forming process simulation program used by many industrial and research institutions. Recent developments include the ability to model multiple deforming body behavior during multi-pass pack rolling and microstructure prediction during multi-pass shape rolling. This paper summarizes how DEFOR.MTM can be applied to a number of rolling processes and briefly describes preliminary work carried out using the ALE technique. Keywords: Simulation, Rolling, Pack, Shape, Microstructure, FEM, ALE, Tantalum

Jan 1, 2003

By R. Angulo

Carbon nanotubes (CNTs) have recently emerged as materials with outstanding properties. This has promoted their consideration as reinforcements for other material systems, such as ceramics. However, one of the fundamental problems with producing CNT-reinforced ceramics is the effective dispersion of CNTs during processing. This has been successfully carried out recently using organic solvents. This paper is a preliminery investigation into the rheological behavior of aqueous CNT-alumina slips, with the objective of moving towards a more environmentally friendly aqueous tape casting process for the production of CNT-ceramic composites.

Jan 1, 2008

By Jinrong Zhang

Major components of soil were tested for their ability to attenuate cyanide. Feldspar, kaolinite, plagioclase and bauxite are found to degrade cyanide at an appreciable amount mainly through adsorption. A soil near a mining site in northern Nevada was studied in detail using a tall column. Many species of cyanide were anlyzed to determine the mechanisms of the reactions of cyanide with soil. Volatilization, adsorption, oxidation, precipitation and complexing were quantitatively identified, being 5 to 10, 11.7, 4.2, 7.3 and 4 per cent of the total cyanide added, respectively. It is found that the oxidation of cyanide to cyanate is due to the catalytic effect of nickel and copper leached from the soil. Precipitation of metal-cyanide complexes occurred at low pH values.

Jan 1, 1991