Search Documents

By B. Zeytuncu, O. Yucel, O. H. Celik, M. H. Morcali

"The Taguchi method was used as the experimental design to determine the optimum conditions of cementation behavior of the ruthenium chloride solution. Cementation was carried out using metallic zinc powder. The experimental conditions were studied in the range of 25-45°C for reaction temperature (A), 30--60 min for reaction time (B), 0.5-1.5 for pH of solution (C), and 30--50 mg for zinc powder (D). Experimental parameters and their levels were determined in the light of preliminary tests. Orthogonal array (OA) L9(34) consisting of four parameters each with three levels, was chosen. The optimal conditions found for ruthenium, such as a reaction temperature, reaction time, pH of the solution and mass of zinc, are respectively: 45°C, 45 min, 1.5 and 50 mg. Under these conditions, the ruthenium cementation efficiency obtained by theoretically and experimentally was in good agreement, which were 99.8% and 99.7% respectively."

Jan 1, 2013

By Jiang Feng, Zhang Libo, Peng Jinhui, Guo Zhanyong, Ju Shaohua, Lei Ting

The basics of microwave drying process of CuCl residue were studied by comparing the dielectric property of the residue with different moisture contents. The dielectric properties were measured by microwave cavity perturbation method. The dielectric constant and dielectric loss factor of the CuCl residue have a linear correlation with the moisture content. With this relationship, we can realize on-line measurement of moisture content of the CuCl residue by dielectric properties. The microwave drying experiments with different thicknesses (1-5cm) of CuCl residue were carried out, and the heating curve of the materials under different microwave powers (250-450W) was made. From these parameters, an optimized operation parameter of microwave roasting technology, the thickness of CuCl residue filter cake to be microwave roasted should be 2cm , was deduced.

Jan 1, 2015

By K. Prashant Sarswat

Isotopes are critical to a variety of applications including physical science analyses, biology, medicine, pharmaceuticals, and national security. In most cases isotopes must be relatively pure or highly enriched before they become useful. Current isotope separation technologies are relatively inefficient, capital and labor intensive, and often produced by a limited number of suppliers. In the category of isotopes, lithium is among other important candidates. Lithium is found naturally in two isotopes, 6Li which accounts for 7.5% of all lithium, and 7Li which makes up the balance of 92.5%. Each of these isotopes is important to the nuclear industry. 7Li is often used in the form of lithium hydroxide which is used to control pH in pressurized water reactors. The current supply of 7Li is based mostly outside of the United States, and its long-term supply is uncertain. Apart from supply issues, the use of mercury for 7Li separation is also a concern in commercial processing using the most common and efficient approach [1–3]. Hence, a reliable, environmentally friendly, and efficient technique is needed to produce 7Li. In this line of investigations, the authors used a two-compartment system and significant separation was achieved. In this piece of research, some preliminary results are presented including cell design and actual isotope ratio after enrichment. Applying an electro-potential across two electrodes can be used to drive electromigration of Li isotopes. The electromigration is in addition to normal diffusion. Note that 6Li diffuses faster and hence there will be a lowering of the 6Li concentration near the positively charged electrode and an enhancement in 6Li near the negative electrode during the separation process. Similarly, 7Li will be more prevalent near the positive electrode and less prevalent near the negative electrode during the initial separation stage [1].

By M. R. Jolly, J. -C. Gebelin

"A number of different types of so-called ""filters"" are used in the metal casting industries to impart some cleaning effect and flow control on the liquid metal as it passes through them. The filters range from simple planar meshes through extruded channels to reticulated foam structures and they are manufactured from a range of material going from metals to glass or ceramics. It is most common that software packages used in the industry model the filters by a simple pressure drop associated with some area fraction and permeability parameters.Recent experimental work at the IRC in Birmingham [1] has shown that filters of the same type can behave very differently depending upon the casting process in which they are employed. Modelling filter geometries for a range of different casting processes has indicated that the flow of metal and heat losses through the filters are rather complex and should be considered when using filters in the casting processes. This paper will present a number of cases of different types of filters modelled and different processes and indicate some of the sensitivities of the processes to boundary conditions imposed by the process.IntroductionFilters are commonly used in the foundry industry. The real action of the filters on the liquid metal is not really understood. Some filters are claimed to have a chemical action on the liquid metal or to be able to clean the metal by stopping the impurities or oxides that will result in inclusions in the cast part. However, some recent experiment carried out at the University of Birmingham in investment casting and results available on sand casting [2] have shown that the action of filters may be different in these two processes. As the main difference between these two processes is the mould temperature, the hypothesis of a partial solidification of the metal in the filter occurring in the sand casting process during the primary stage of the filling has been advanced, whereas there is little or no solidification in investment casting. In order to verify this hypothesis, and to reach a better understanding of how filters work, a numerical investigation of the flow and heat transfer in filters in both sand and investment casting has started at the University of Birmingham, in the framework of the FOCAST project. The FOCAST project is an EPSRC project aimed to increase the understanding of the investment casting process. Another issue is the way the simulation packages predict the influence of the filters on the metal flow. The filters are most of the time modelled as porous obstacles characterised by a pressure drop calculated from porosity and some surface ratios or proprietary coefficients. This paper will present the preliminary results of this numerical investigation. First, the different models that have been used are presented, followed by the obtained results. A discussion of these results and their perspectives conclude the paper."

Jan 1, 2001

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 A. Erçin Ersundu

In the present work, three different domestic iron ores; Sivas Divrigi B Head high grade hematite lump ore, Malatya-Hekimhan-Hasançelebi medium and low grade magnetite lump ores reduced with Soma-Kisrakdere lignite coal to investigate their suitability for sponge iron production. A laboratory scale box furnace was used to carry out the reduction experiments. In the experimental studies different operation parameters were selected being Cfix/Fetot. ratio, temperature in the range of 1100 - 1250 oC and time, to determine their effects on metallization. Metallization degree up to 90 % was found in the reduction experiments realized by using Sivas Divrigi B Head high grade hematite lump ore, whereas for Malatya-Hekimhan-Hasançelebi medium and low grade magnetite lump ores 60 - 65 % metallization degrees were obtained.

Jan 1, 2008

Testing is in progress to address compatibility issues with regard to long term storage of plutonium in contact with two different intermetallic systems. The two intermetallic systems are: 1. dental amalgam, i.e., mercury plus silver alloy powder, and 2. liquid gallium alloy plus copper powder. Both of these are plasto-metallic materials that undergo a solidification reaction at room temperature. Each system is allowed to react in contact with both high-purity alpha plutonium and a delta stabilized plutonium alloy at varying temperatures in an argon atmosphere. Wetting characteristics and possible interaction will be studied metallographically in the post-mortem condition. Complete results including metallographic examinations will be presented.

Jan 1, 1995

By Sergio N. Monteiro

Lignocellulosic fibers obtained from plants like cotton, flax, hemp, sisal, jute and many others are natural materials used, since long time, in basic items such as textile, baskets, roofing and carpets. These traditional natural fibers as well as some new ones are nowadays replacing synthetic fibers as composite reinforcement owing to environmental advantages. The heterogeneous characteristic of lignocellulosic fibers is, however, a limitation for application in composites. The buriti fiber, extracted from a tropical plant tree, is recently being investigated as a possible reinforcement for polymeric matrix composites but no complete information exists regarding its mechanical behavior. The objective of this work was then to carry out a statistical analysis on the mechanical properties? uniformity of buriti fibers. By precise dimensional measurements in association with tensile tests, it was found that the mechanical properties depend on the range of the fibers? dimension.

Jan 1, 2009

By Suzzann Nordwick

The metallurgical treatment of mercury-containing materials for precious or base metals recovery imposes many processing and environmental challenges. Mercury is usually present as elemental or cinnabar. Historically, mercury has been removed from mined ores pyrometallurgically by roasting, but hydrometallurgical methods have also been employed. For example, alkaline sodium sulfide solution acts as an universal solvent for most mercury compounds. While, most other metals are highly insoluble in this solution. This allows for a high degree of selective separation of mercury from other metals with the exception of tin, antimony and arsenic. Mercury leached with a solution of sodium hydroxide and sodium sulfide or sulfur can be re-covered by cementation or stabilized through sulfide precipitation. Hydrometallurgical technology for the pretreatment of mercury removal from gold, silver, and base metal ores using alkaline sulfide leaching will be discussed with a focus on alkaline sulfide leaching of mercury sulfide-containing materials.

Jan 1, 2003

By Sayan Sarkar

HAMR (Hydrogen Assisted Magnesiothermic Reduction) process is a promising alternative route of titanium production, which is convenient due to reduction at relatively lower temperatures below 750 °C and usage of cost-efficient TiO2 as the starting material. A crucial step involved in this process requires the Mg reduction of TiO2 subjected to H2 atmosphere which produces porous TiH2 along with residual magnesium impurities. Before the final heat treatment and deoxygenation steps for consolidation of the Ti powder, leaching plays a significant role in the removal of Mg impurities. In this report, we present a systematic study on the role of acid concentration (HCl), temperature and the kinetics of MgO dissolution. In addition, we also report the controlling mechanism during kinetics of MgO dissolution in acid. This parametric study will provide a platform to ensure very low Mg content that meets with ASTM standards during production of Ti in the HAMR process.

By Xinli Wang, Matthew Andriese, Jiann-Yang Hwang, Zhiwei Peng, Byoung-Gon Kim

"The microwave dielectric properties of silicon dioxide at frequencies of 915 and 2450 MHz were characterized in the temperature range of 24 to approximately 1000 °C using the cavity perturbation technique. It is shown that the relative dielectric constant of silicon dioxide at both frequencies remains almost unchanged below 500 °C, above which there is a slight increase of 2%. The relative dielectric loss factor of silicon dioxide exhibits a strong temperature dependence above 500 °C and increases by approximately 7 and 5 times at 915 and 2450 MHz, respectively. The substantial increase in the relative dielectric loss factor is mainly attributed to the enhanced dielectric polarization and accelerated electrical transport in silicon dioxide at elevated temperatures.IntroductionSilicon dioxide (Si02) is usually considered a microwave transparent material due to its poor absorption capability at room temperature [1]. This characteristic has led to various applications of silicon dioxide in microwave processing of materials and communication. For instance, Si02 has been used to produce sample holders for microwave heating and substrates for electronic devices [2,3]. These applications generally require the material to withstand high temperatures under microwave irradiation. This indicates that microwave absorption capabilities of silicon dioxide at elevated temperatures are also important for its utilization.The microwave absorption capability of Si02 can be determined based on dielectric characterization (permittivity measurement) of the material at commonly used microwave frequencies, 915 and 2450 MHz, in a broad temperature range. To date, however, no detailed work on the dielectric properties (permittivity) of silicon dioxide at high temperatures has been reported. The present work is aimed to study the dielectric properties of silicon dioxide from room temperature to approximately 1000 °C at 915 and 2450 MHz. The results show that the permittivity of silicon dioxide has a strong temperature dependence above 500 °C, suggesting a substantial increase in its microwave absorption capability."

Jan 1, 2013

By Kenneth N. Han

Ammonia has been found to be an effective leaching reagent for gold, silver and platinum group metals in the presence of appropriate oxidants. Electrochemical and kinetic aspects of the dissolution of elemental gold in ammoniacal solutions have been investigated. The cathodic reaction of aurous di-ammine on the gold cathode has been investigated first. From this investigation, the standard electro-potential of the cathodic reaction .and hence. the Gibbs free energy of formation of the aurous di-ammine were established. The solubility of gold in ammoniacal solutions was also examined in relation to ammonia concentration, temperature and concentration of various oxidants. The anodic reaction of the gold disk in ammonia? in the presence? of various oxidants including oxygen, ozon, hypochlorite, hydrogen peroxide, cupric and cobaltic ammine, and iodine was also examined and the results have been discussed. Excellent dissolution yielding of gold and many other metals, typically better than 95% recovery in 1'-2 'hours of leaching at a temperature ranging 80°C to 190°C has been observed. Test results of the dissolution of gold from elemental state as well as other sources including sulfidic ores and scrap are presented.

Jan 1, 1998

By Jerome Feinman, Sven O. Santen

"The principles involved in the generation and application of plasma energy are reviewed briefly and the major developments in commercial and semi-commercial primary metal and alloy production are described and discussed in broad outline, with emphasis on present performance and future potential. New concepts in the application of plasma energy in primary operations are described with emphasis on the expected advantages over conventional technology and the problems that have to be solved to enable effective implementation.IntroductionThe use of plasma energy in industrial processes is generally considered to have started in 1905 with the operation of the Birkeland process for nitrogen fixation for fertilizer production. Although it seems logical to apply plasma energy to metallurgical processes, which also usually require considerable energy at high temperature levels, serious development work along these lines did not begin until the early 1970's. The reasons for this hiatus are associated in part with recognized difficulties in applying plasma energy in processes involving tonnage quantities of solids in severe industrial environments and the delicate nature of the earlier plasma generators. Another, and perhaps overriding factor, is the fairly steady improvement in efficiency and economy of most primary metal producing processes by conventional developments and modifications through the 1950's and 60's. Examples of these evolutionary changes include burden preparation and fuel injection in blast furnace applications and prereduction treatments in ferroalloy operations. By the end of the 1970's most primary metal producing processes had been optimized close to the limit, at least in terms of those operations that were able and willing to implement the developed improvements. In this context, plasma energy offered the possibility to achieve further significant improvements in primary operations where conventional means were exhausted."

Jan 1, 1988

By Jilai Xue, Jun Zhu, Germain Kouma Ndong, Qiaochu Liu, Luxing Feng

"High-temperature oxidation and corrosion behaviors of Ni-Fe-Cr alloy as inert anodes for aluminum electrolysis have been studied in oxygen and molten electrolyte. The oxidation and corrosion scales on the anodes tested were analyzed using XRD and SEM-EDS. The oxidation rate is found to increase with increasing temperature from 700 °C to 950 °C, which can be approximately described by an inverse power rate function. The oxidation scales at 750 °C, 920 °C and 950 °C contain Cr-rich phase along with FeCr204 and (Feo.6Cro4)203. The corrosion extent of Ni-Fe-Cr anodes in electrolyte is dominated by temperature, which can make the scales thickness double from 700 °C to 750 °C or from 920 °C to 950 °C. Cr and Fe in the scales on the anode in electrolysis corrode preferentially into the molten electrolyte, while the nickel oxides could better sustain the corrosive environment in electrolysis. The results can be useful for developing inert anode material for potential application in aluminum electrolysis.IntroductionThe development of an inert anode for aluminum electrolysis has been a long term goal for aluminum industry. The present process for primary aluminum production involves the reduction of alumina with carbon anodes, forming carbon dioxide:"

Jan 1, 2013

By Mitchell L. Spencer, Viswanathan Panchanathan

"Bonded magnets are important category in permanent magnets. They are made by one of the following processes: compression bonding, injection molding, extrusion, calendering. An overview of the various bonded magnet processes and properties of products made with different magnet materials along with their applications are discussed. The main emphasis will be on the use of bonded NdFeB and ferrite magnets.IntroductionBonded magnets are a major growth area in permanent magnets. Bonded magnets are made by any one of the following processes: Compression bonding; Injection Molding; Extrusion and Calendering [1,2]. Compression and injection molded magnets are rigid magnets. Materials used in calendering process produce flexible magnets. Only the extrusion process makes both rigid and flexible magnets. The binders used for the bonded magnets vary depending on the processes. Thermoset, thermo-plastic and elastomeric binders are respectively used in compression, injection and the calendering process. Extrusion molding uses elastomers or thermo-plastic materials. The most co=on magnetic materials, Ferrite, SmCo, Alnico and NdFeB can be used in any of the above processes either alone or in combination as hybrid magnets. Another material that has been developed for co=ercial application is SmFeN. Making the material has been challenging and it is being used in niche market applications in limited quantitiesIn the extrusion process, a highly loaded compound is used to produce strip or sheet and is continuously extruded through a die. In calendering the granulated compound is rolled to produce a continuous wide sheet. In the compression bonding process a uniaxial pressing force is used. These magnets have higher loading compared to injection molded magnets. In injection molding the material is forced into a mold cavity and has lower loading compared to compression molded magnets [2,3]. Most of the flexible magnets are made using extrusion and calendering processes and the most co=on magnet material is inexpensive ferrite. Flexible magnets have been made using rare earth materials, but on a very limited basis.The major advantages of magnets processed by extrusion and calendering are as follows: inexpensive tooling, automation; practically any 2D geometry; fast production rates; no chipping or breaking; a wide range of properties; on-line magnetization; easy to convert (e.g. cut, punch or shape).Compression bonded magnets are inexpensive to manufacture. They have higher magnetic properties compared to injection molded magnets; however lower than their sintered counterparts. The magnet shape is restricted to simple geometries and they require careful handling. Their isotropic nature allows complex magnetizing patterns."

Jan 1, 2013

By Edward Peters

Scandium (Sc) has unique properties and is one of the more valuable elements in the periodic table. Scandium can be used in solid oxide fuel cells and to produce high strength aluminium alloys of value, for example, in the aerospace industry. Scandium is often grouped together with the rare earth elements (REE). Amongst others, scandium can be found in bauxite residues, so called red mud. It is possible to extract and enrich scandium from red mud by leaching and solvent extraction. Scandium can then be recovered from the pregnant strip liquor by crystallization. The strip liquor will however still contain certain impurity elements. In the present work, a method for obtaining a pure scandium solid phase by direct crystallization from the strip liquor is evaluated. It was found that Fe and Ti co-precipitate with Sc under the conditions employed.

By Laurentiu Nastac, Ruslan Mudryy

"This paper investigates the solidification of cast energetic materials. An active cooling and heating (ACH) technology and a mechanical vibration (MV) technology were applied to achieve unidirectional solidification during casting and to reduce cracks, gas pores, and shrinkage defects. The design parameters of these technologies were developed via Computational Fluid Dynamics (CFD) modeling and thermal stress analysis. Concerning the ACH technology, the number of cooling/heating sections and their temperature profiles and time sequences were optimized based on the thermo-physical properties of the energetic material as well as the riser and mold diameter, thickness and type. The ACH technology will also decrease the thermal stresses during casting of energetic materials and therefore minimize the formation of potential cracks that may form during the casting process. The MV technology will help to remove air entrapped during pouring process and decrease the detrimental gap size between the projectile and the solidified energetic material.IntroductionCasting processes are widely employed in the manufacture of products with intricate shapes and, in particular, in applications where the material of the final product is sensitive to machining. It is especially useful in processing of energetic materials. The cooling conditions applied in the casting process can affect the quality of the final cast in terms of void formation, residual stress distributions, and mold separation. Substantial shrinkage is also observed due to the density change upon solidification [1-3]. Residual stresses are known to be closely related to the formation of cold cracks and hot tears during casting. The formation of a gap between the mold and the cast material is of critical importance due to its deleterious effect on heat removal and on crack formation. In the casting of energetic materials all these defects can significantly impair the detonation velocity, Gurney energy, and insensitive munitions characteristics of the formulation, and lead to catastrophic accidents in explosives handling [ 4-5]. Imposition of carefully controlled cooling condition is thus critical in optimizing the cast quality that could help avoid such destructive effects."

Jan 1, 2013

By Florian Kongoli

The production of a homogeneous self-fluxing sinter is an important step in iron making processes. A good sinler should have good permeability and reducibility and has to keep those characteristics for a certain time. An early melt down of the sinter in the blast furnace, where its solid state reduction is essential, would cause many problems such as low permeability and reductibility. Nevertheless, the important factors that influence these characteristics, such as the chemistry of the sinter and the fluxing effect during sintering and sinter reduction conditions have not yet been clarified, In today's new reality where many new minor components such as Al2O3 and MgO enter to the sinter through raw materials, the quantification of the fluxing effects during sintering becomes even more important. In this work, the liquidus surface and phase relations of the sinter primary melts in the CaO-FeO-Fe203-Si02 system at sintering conditions have been quantified. The fluxing effect of oxygen potential, Al2O3 and MgO has also been quantified by the means of some practical diagrams that can directly help the optimization of the sintering processes.

Jan 1, 2003

By Wenbin Liu

A novel route for rapid synthesis of ultrafine WC-Co cemented carbides with homogeneous binder phase distribution is reported. The composite powder is produced by in situ reduction-carbonization reactions by using WO2.9, Co3O4 and carbon black as raw powders. The reaction equilibrium and phase stability are studied by thermodynamic calculations. The WC-Co composite powder is condensed by spark plasma sintering (SPS) to obtain the cemented carbides bulk. The sintering temperature is lower than that in the conventional sintering methods by 1500C, while the sintering time is remarkably reduced by 3-5 times. The high performances of the hardness and the fracture toughness are obtained. The experimental results confirm that the present processing scheme of in situ reduction-carbonization reactions and subsequent SPS sintering is an efficient way to prepare WC-Co cemented carbides, and is apparently superior to the conventional long-period techniques of preparing composite powder and cemented carbides bulk.

Jan 1, 2008

By Jian-hua Ren, Guang-liang Wu

A lot of dust is produced in iron and steel enterprises, giving rise to serious environment pollution, with which all countries are trying to find methods to deal. The influence of relevant technological factors on dephosphorization was investigated in laboratory, and the effect laws of that were analyzed. The results demonstrate that, in the given conditions of the best slag-metal proportion for hot metal dephosphorization is 1:10, and the optimum temperature is 1350 , The phosphorus distribution ratio of dephosphorization agent containing converter dust of 30% has the maximal value, with dephosphorization rate reaching 85%. Under the optimal conditions, premelting dephosphorization agent can significantly improve the ability of dephosphorization, dephosphorization efficiency increasing to 92%. Therefore, the dust can substitute the oxidant and fixative of dephosphorization agent, be used in hot metal dephosphorization, to enhance the efficiency of utilization.

Jan 1, 2016