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By Bora Derin

The synthesis of titanium diboride (TiB2) by carbothermal reductions of TiO2 and B2O3 was investigated. For this aim, TiO2, B2O3 and carbon black powders were dried, weighed out and mixed in stoichiometric molar proportions (TiO2:B2O3:C = 1:1:5). The experiments were carried out in a graphite resistance furnace in argon media using different range of temperature (1400- 1700 °C) and time (0 and 15 min). The phase analyses observation of the products were examined by using XRD.

Jan 1, 2008

By N. V. Gorelikova

A new type of zirconium mineralization has been recognized in the Devonian volcanic rocks from an orogenic depression in the Central Kazakhstan. The most characteristic features of this deposit are the fine-grained nature of the zirconium mineralization, an unusual texture of the zirconium ores, and a close association of zirconium with phosphorus in the ores. Zircon grains form fine globular aggregates with the features of hexagonal crystal habit. In addition to crystalline zircon, the ores contain metacolloidal zircon, similar to hydrozircon. The morphological and textural features of the zirconium ores suggest that the deposition of ore deposits took place at a low temperature from colloidal solutions. It is believed that this deposit should be considered to be a new type of zirconium mineralization that is related to low-temperature hydrothermal processes.

Jan 1, 1995

By Guo Chang Jiang

In order to improve the IIAZ toughness of X-60 pipe steel, the intragranular ferrite plate (IFP) technology was used. The characteristics of IFP is claimed to be much fine ferrite plates appear inside the original austenite grains. By means of suitable Re, Zr, Ti additions in a bath with a higher initial oxygen potential, a good control of the peak temperature and the cooling rate during welding simulation, one can get a %IFP in volume over 50%, and the toughness gets up from 55 J to 160 J. It was found that the inclusions most effective in nucleating IFP are some deformable complex silicates which either entrap Re, Zr, Ti oxides or contain these elements. The greater the number of the evenly distributed and effectively nucleating inclusions, the more the %IFP in volume, and the finer the microstructure of the HAZ, so the better the relevant toughness. Generally, these silicates bahave as fine spheres along a line. The present authors revealed that these fine spheres result from the remelting of the shuttle- like silicates due to heating in the process of welding simulation. These silicates used to get a higher sulphur capacity, so MnS deposits might be observed on the periphery of the silicates. IFP was proved to be directly rooted in the [Mn] depleting zone which locates beside MnS deposits.

Jan 1, 1997

By V. I. Lakshmanan

"Historically flowsheets are developed for efficient separation of metals for economic recovery. With increasing emphasis on reduction, reuse and recycle (3Rs) efficient methods are sought to recover values from a variety of feeds where cost of collection, transportation, local consumer behaviour and regulatory guidelines dictate the development of economically viable flowsheets. Innovative understanding of potential market applications can provide means to develop value added end products. The paper with examples will discuss the use of innovative-separation technologies to obtain value added end use materials from secondary sources.IntroductionFlowsheets are developed for the efficient separation of materials of value for economic recovery. However with increasing societal pressures and regulatory initiatives for stricter environmental guidelines, there is strong need to provide focus to recover materials efficiently and economically in an environmentally accepted manner. North American industries are increasingly caught between demands for high technology value added products and responsibility for environment. An aspect that is receiving increasing attention is Design for Environment'. This incorporates a system wide approach for product design and incorporates environmentally preferable features such as recyclability, disassembly, maintainability, reusability and use of safe materials as part of a product's design objectives.The present paper with case histories will address innovative flowsheet development to convert wastes into recyclables value added products or for minimising generation of waste materials. Case HistoriesProcess for Separating Fibres from Composite Materials 1In the automotive industry, sheet molded compound (SMC) is used to produce panels, bumpers and the like. During the manufacture and at the end of life, considerable waste materials are generated which are potentially recyclable. Fibre reinforced plastics where fibre substrate impregnated with thermosetting resin, find applications in several manufacturing processes and are potentially recyclable at the end of life."

Jan 1, 1996

By Jan Yaozhong

The composition and the possible utilization of Ti bearing blast furnace from a titanomagnetite blast furnace smelter were studied. The slag contained about 20% Ti02 and trace Sc. The mineralogical analysis indicated that Ti in the slag is mainly as perovskite. By means of magnetite separation, the Ti containing phase could not be enriched. An effective hydrometallurgical approach was proposed with sulphuric acid leaching. The method proposed for processing the studied slag renders product Ti02 and SC203. Besides the recovery ofTiO2 and SC2O3' the leaching process yields fine grained residues which can used as additives for making cement.

Jan 1, 1996

By T. H. Courtney, B. R. Murphy

"Nominal room temperature mechanical alloying (MA) has been used to synthesize the high melting temperature NbC and Cu-NbC composites. Elemental powders of Cu and Nb were alloyed in the presence of either graphite or hexane to form nanocrystalline NbC or a Cu-NbC composite. Through control of hot-isostatic-pressing (H/Ping) parameters, we have been able to minimize microstructural coarsening during densijication, and have processed fully dense bulk compacts of both single phase NbC and two-phase Cu-NbC while maintaining a nanocrystalline or near-nanocrystalline structure. These materials generally exhibit high strength and low fracture toughness. However, mechanical properties vary significantly depending upon the Cu content and the method of NbC synthesis (graphite or hexane).INTRODUCTIONMechanical alloying (MA) has been recently used to synthesize a variety of inorganic solids; sulfides (1-2), nitrides (3), borides (4), and carbides (3, 5-8). One advantage of this processing route is that synthesis of fairly high melting temperature materials takes place at what is nominally room temperature. Another advantage is that the structures generated are often nanocrystalline in scale, with attendant interesting properties. The consolidation of these fine structures into near fully dense or fully dense materials while limiting microstructural coarsening is a challenge that has just recently seen limited success (5, 9). We report here on some recent studies of ours dealing with crystallite size and structural analysis of NbC and CuNbC composites consolidated to full density from mechanically alloyed powders. Bulk mechanical properties and their dependence on milling parameters are also presented."

Jan 1, 1994

By K. Nona C. Liddell

There is a significant amount of early work that has been largely forgotten that deals with the validity of the pseudo-steady approximation for liquid-solid reactions. Much of this was originally published in the chemical engineering literature but is highly relevant to hydrometallurgical processes. The purpose of this paper is to summarize some criteria that were been developed by various authors for determining the error associated with use of shrinking core models for liquid-solid systems.

Jan 1, 2002

By T. Ahokainen, J. Pitkälä, J. L. Xia, A. Jokilaakso, J. Vaamo

"The aim of the present paper is to use the two CFD codes to model the two phase flow in a water model ladle with central gas injection. The codes examined are CFX and Phoenics. An Eulerian two phase model is used and predictions are compared against the experimental data available. The results show that the codes can reasonably well predict the gas-liquid plume in the ladle, and predictions are generally in a good agreement with experimental data. However, differences do exist in predicting the gas volume fraction and velocity profiles. The results should be interpreted most carefully and cautiously, because they are very sensitive to the boundary conditions and dependent on the models for the physical phenomena involved. IntroductionSubmerged gas injection has widely been used in the metallurgical industry for more than a century. At the present, the use of gas is most effective in steelmaking industry where the advantages of the gas injection have already been long well understood. Effective mixing, large contact area between reactants, easy modifications and flexibility of the processes are the most important advantages. Disadvantages include refractory wear, blocking in the tuyeres, and splashing. These disadvantages can be reduced and advantages further improved by studying the flow phenomenon in process vessels. However, it is difficult to study flow in a real vessel because of the high temperatures and physical and mathematical modelling is therefore increasingly used in the process development work."

Jan 1, 1999

By Levente Becze

The zinc bottom dross is obtained as a by-product from hot dip galvanizing operations and contains at least 92 % zinc, which is recycled mainly by pyrometallurgical processes. The overall costs of such a treatment, however, are often relatively high, and the very strict environmental protection regulations might also cause additional difficulties for the high temperature procedures in the future. Therefore, a novel hydro-electrometallurgical process has been developed in our laboratory, by which one can reclaim zinc of high purity, while attempting to achieve low energy consumption and making allowances for all the environmental restrictions. This aqueous processing technique, based on electrolytic refining in a cell equipped with anion-exchange membrane to separate the anode and cathode compartments, allows the indirect purification of the anolyte. Zinc is dissolved from the anode along with some of the impurity elements, while the intermetallic compounds (Fe-Zn, Fe-AI- Zn) are accumulated in the anode slime.

Jan 1, 2003

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

By Mohamed Ahmed, A. Kawy

"Smelting of scrap copper and residual anodes and cathodes carried out in a reverberatory type furnace. In this, deoxidation process is carried out by wood, which acts as a resource of reduction gases such carbon monoxide, hydrogen and methane. Use of wood causes the formation of soot pollutants and efficiency of oxygen removal from copper is low leading to added costs in removing contaminants. This expensive problem was solved by using of reformed natural gas as a source of reduction gases (CO+ H2).IntroductionThree reverberatory furnaces were used for smelting of scrap copper and residual anodes and cathodes. Each furnace had a 7tpd capacity and was operated at 1183 °C.In this furnace, Step1-compressed air supplied by tubes from the side of the furnace to remove sulfur from copper matte by oxidation .The copper is also oxidized to copper oxide .[1]Step 2- copper from matte is deoxidized by a reductant. Typically deoxidation process is carried out using wood as a resource of carbon monoxide, hydrogen and methane which are the reduction gases. Use of wood causes the following:1- Forms soot pollutants2- Oxygen removal efficiency from copper is low; more contamination in copper matte increased energy in deoxidation3-the process is highly expensive.In the recent trends, this problem has been solved by using reformed natural gas as a source of reduction gases (CO+ H) .This results in 1-Reduced pollution during smelting.2- High efficiency in the removal of oxygen from copper to produce oxygen free copper. The surface of copper produced from this method is smooth which helps in forming and machining.3- Low cost and natural gas is more readily available in Egypt than wood."

Jan 1, 2010

By J. M. Khodadadi

"A computational study of the effect of thermocapillary convection on melting of a droplet under the influence of an incident uniform heat flux is presented. The computations are based on an iterative, finite-volume numerical procedure using primitive dependent variables, whereby the time-dependent continuity, momentum and energy equations in the spherical coordinate system are solved. During the early periods of the melting process, conduction mode of heat transfer is dominant. As the thermocapillary convection is strengthened due to the growth of the melt zone, melting on the side of the droplet is observed to be much faster in comparison to the conduction-only case. Due to the skewedness of the temperature field, a new recirculating vortex is created which promotes melting within the droplet. The effects of the change in the sign of the surface-tension temperature coefficient on the melting pattern are also investigated.1. IntroductionMelting and solidification of materials are important processes which are encountered in nature and numerous industrial applications. Due to the recent upsurge of interest in such processes as spray casting, space radiators, rapid solidification, purification of materials, containerless processing, etc., there is a need to analyze the transport phenomena of melting and solidification in spherical configurations. Specifically, the effect of thermocapillary convection on the melting of metallic droplets has not been addressed at all. Only a few authors have studied the transport phenomena without phase change in spherical droplets. Oliver and DeWitt [l] worked out a series solution for the thermal and surface-tension-driven flow fields for a droplet experiencing an irradiant energy flux in the microgravity environment. Kudo et al. [2] solved the coupled momentum and energy equations numerically for the same problem without dropping the convective terms. Due to the nonexistence of any previous work on transport phenomena during the thermocapillary-assisted melting of metal droplets, this study was initiated to elucidate the features of the phenomenon."

Jan 1, 1999

By Keith M. Axler

This report addresses issues specific to the generation of hydrogen fluoride via reaction of calcium fluoride with sulfuric acid. This process has been established on a commercial scale and is under consideration for treatment of calcium fluoride residues from uranium processing. Magnesium fluoride slags are also available as a product of uranium processing. The technique of using sulfuric acid for the production of hydrogen fluoride from magnesium fluoride is also under consideration as a residue processing scheme. In the current study, thermodynamic modeling was used to investigate these chemical processing systems. The results presented herein reveal information relevant to the selection of processing temperatures and conditions. Details include predicted effects in system composition based on operating temperatures for both the calcium fluoride and the magnesium fluoride systems.

Jan 1, 1996

By W. G. Davenport

A survey of world copper refining tankhouse .practices has been carried out. This paper compiles the results and examines changes in operating practices .since the similar 1987, 1991 and 1995 surveys. Continuing trends are the installation of ISA Process and Kidd Process stainless steel cathode technology, polymer concrete cells, anode preparation machines and automatic cranes. Instrumentation and automatic control are increasing, particularly for addition agent optimization; solvent extraction .and ion exchange techniques are being increasingly applied for electrolyte purification. The overall consequences of these changes have been 'improved cathode purities and enhanced tankhouse productivities.

Jan 1, 1999

By Shane Andrews, Gustavo Vasquez, S. K. Varma

"The effect of solutionizing time on the corrosive wear behavior of 2014 aluminum alloy has been studied using the impact and continuous mode of scratching techniques. The transient currents (TC) evolved during the scratching of the alloy shows a linear dependence between the TC and the solutionizing time. Higher TC values at longer solutionizing time may be associated with the changes in the concentration of quenched-in vacancies, grain sizes and dislocations generated during scratching. These factors can either create (a) anodic sites or (b) pitting corrosion resulting in the generation of transient currents. The results have been compared with the similar study carried out for 6061 aluminum alloys. This 6061 aluminum alloy shows similar behavior but the rate of TC generation per unit solutionizing time is much lower than 2014 aluminum alloy. The morphological changes in the impact scratches and the TEM investigation in the scratch have been presented in this paper.IntroductionThe technique of studying corrosive wear of composites of 6061 aluminum in the monolithic and reinforced forms has been reported in the literature [1]. Two modes of scratching, consisting of impact and continuous, in a corrosive environment indicate that the composites, containing 0.10 and 0.20 volume fractions of alumina particles (VFAP), have higher corrosive wear rates than the monolith. A graph between the transient current (TC) generated during the impact scratching as a function of solutionizing time at 540°C indicates linear relationship between them. A similar slopes for the composites were observed and the TC values were less for the composite containing lesser VFAP."

Jan 1, 1998

By T. Mason, R. Macko

Electroless nickel (EN) coatings are widely used in the manufacture of automotive parts, providing uniform coating, corrosion protection, wear resistance and lubrication. In contrast to EN plating benefits, the disposal and treatment of waste solutions can cause many difficulties. The use of electrochemical treatment technology greatly improves _the operation of the main wastewater treatment process and reduces operation costs. A new, state-of-the-art job shop in the Chicago area, which provides EN plating for the automotive industry, has installed a large separated electrolytic cell for the treatment of spent EN solution (from dumps and wastewater). The waste/wastewater is handled by the separated electrolytic cell, batch treatment system, filter press and neutralization station. The implementation of modem electrolytic technology and auxilliary equipment provides an effective waste treatment process that meets environmental compliance criteria.

Jan 1, 2000

By Lei Wang, Jianjun Wang, Lingen Luo, Zhengbang Li

Dearsenication in molten steel was studied by adding Ca-Fe Alloy-based arsenic removal agent. In order to improve the utilization rate of Calcium Iron Alloy and improve arsenic removal ratio, [O] is less than 0.0005% and [S] is less than 0.0035%, Al is added into the molten steel. In the processes of adding CaO-Al2O3 based alkalinity slag for arsenic removing in molten steel (initial arsenic content is 0.0080%), arsenic removal ratio reaches 50% when Ca-Fe Alloy addition amount is 18%. During the arsenic removal experiment, adding Rare Earth promotes the arsenic removal reaction and makes the arsenic removal more effectively.

Jan 1, 2015

By Alessandro Blasi, Massimo Morgana, Corradino Sposato, Pietro Garzone, Giuseppe Devincenzis

The rare earth elements are essential for a diverse and expanding array of high-technology applications, which constitute an important part of the industrial economy of the 21st century. As a matter of fact, rare earth has been listed in the category of strategic elements in many countries becoming a core business for international research. Experimental tests have been carried out on a bench scale battery of mixer settler composed of 24 stages, each one with a volume of 150 ml. These trials have been performed at room temperature checked by a micro-climatic control system. The battery was setted in two sections: extraction and scrubbing section. Rare earths concentrations were obtained by ICP-OES analysis made on aqueous phase and on the stripped from organic phase. We obtained a complete separation of light rare earth (La, Ce, Pr, Nd) in two sub-groups: La/Ce and Pr/Nd.

Jan 1, 2014

By Hüseyin Aydin

TWIP (Twinning-Induced Plasticity) steels have exceptionally good combinations of strength, ductility and damage tolerance which satisfy the recent requirements of automotive industries. Firstly, TWIP has the most beneficial effect on the work-hardening. It is believed that deformation twins increase the work-hardening rate by acting as obstacles against gliding dislocations. Moreover, TWIP steels have low to intermediate stacking fault energy and hence undergo extensive mechanical twinning during deformation, which in turn leads a good combination of both strength and ductility. To explain the mechanical characteristics and the mechanical behavior of the TWIP steels, we have been made some investigations and experiments that show the effects of microalloying elements and deformation mechanisms. In this study, three different compositions of TWIP steels have been produced. The microstructure and mechanical properties are characterized by using optical, electron microscopy and mechanical tests.

Jan 1, 2009

By Lianjun Liu, Ying Li, Qianyi Zhang

"Photocatalytic reduction of CO2 by H2O for production of Cl fuels (CO and CH4) was studied using copper and iodine co-modified TiO2 (Cu-IffiO2) nanocomposites, with copper deposited on the surface and iodine doped in the lattice. The nanocomposites were prepared via a combined hydrothermal and wet impregnation process. All I-doped samples demonstrated visible light activity. Under UV-vis irradiation, co-modification of Cu and I significantly increased TiO2 photoactivity compared with bare TiO2 or those modified with only one species.IntroductionThe photoreduction of CO2 into fuels on photocatalysts such as TiO2 has been regarded as an important approach to solve both energy shortage and globe warming problems [1]. However, the wide band gap and fast recombination ofphotoinduced hole (h+) and electrons (e"") limited the application of TiO2 in CO2 photoreduction reaction. Extensive research has been conducted to improve the photocatalytic ability ofTiO2 by depositing or doping foreign ions that can enhance charge transfer and/or creates intra-band-gap states to induce visible light absorption at the subband- gap energy. Compared with mono-doping, co-doping of metal/nonmetal species has been reported to have higher photocatalytic activity for TiO2 [1-3]. Our previous studies showed that Cu deposited on TiO2 [4] or iodine doped in TiO2 [5] significantly enhanced the catalytic efficiency for CO2 photoreduction and increased the response to visible light. We hypothesize that there could be a synergetic effect if TiO2 is co-modified by both Cu and I species resulting in further improvement in CO2 reduction efficiency. In this work, we synthesized and characterized Cu-IffiO2 samples and investigated their activity toward CO2 reduction under visible and UV-vis illumination, respectively.Experimental MethodsMaterialsTitanium tetra-isopropoxide (TTIP, 98%) and isopropanol (C3HsO, 99.8%) were purchased from Acros Organic. Iodic acid (HIO3,99.8%) and Copper Chloride (CuCh, 99.9%) were purchased from Alfa Aesar. All other chemicals were analytical grade and used without further treatment."

Jan 1, 2012