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By R. Upadhyaya

Aluminium alloy matrix cast composites have been synthesised by incorporating fine graphite powders (0.5 - 20 µm size) and chopped carbon fibres (6.5 pm P). 3-6 mm length) by liquid metallurgy technique. Incorporation of these second phase materials exceeding 6-8 wt% invariably resulted in agglomeration of the dispersoids and sometimes leading to even total rejection. It was found that small additions of mischmetal (1-3 wt%) during dispersion resulted in better incorporation without much agglomeration of the dispersoid as evident from the macro and micro structures of the composites. Further, the additions of mischmetal increased the volume of the effective incorporation of the dispersoid even to the extent 50- 60%. The mischmetal addition results in a significant increase in the power factor of the stirrer motor indicating an apparent increase in the viscosity of the system. The higher viscosity of the melt increase the shear transmission conditions within the melt during stirring thereby breaking the agglomerates of the dispersoids. The increased viscosity of the melt seems to be due to the formation rare earth - aluminium inter metallics precipitation, as observed in the metallographic studies, thereby making the process a "pseudorheocasting? technique. A provisional patent has been filed based on this work.

Jan 1, 1989

By Duck Jae Lee, Kwan Ho Kim, Ji Whan Ahn

"In Korea, reutilization of constructions waste is gaining an increasing attention as generation of construction waste is projected to increase continuously. In current practices, the concrete waste is simply crushed and used as a low application such as paving, back filling, etc. In this study, a new process was developed comprising of heat pretreatment, autogenous milling, and density separation for complete reutilization of concrete waste. Firstly, the concrete waste was crushed using autogenous milling. The coarse size fractions from autogenous milling have a density of 2.5g/cm3 and a water absorption ration 3.0%, which meet the specification of the first class of KS F 2573. The fine size fractions were further separated using a hindered-settling column into two products 1) underflow, 2) overflow. The underflow sample was a high quality fine recycled aggregate which can be used for concrete making, and the overflow sample was an enriched cement material can be also used for CO2 sequestration by mineral carbonation. Introduction Kwan Ho Kim1, Ji Whan Ahn2, Duck Jae Lee1, Hee Chan Cho1 Recently, the importance of resource recycling is gaining a greater attention due to the increasing price of natural resource. Recycling is beneficial for not only the management of waste, but also the reducing of consumption of natural resources and huge energy consumption to treat of natural resource. The construction and demolition waste comprises the major industrial waste generated in Korea. It increased to 54 million tons in 2004, and is projected to increase to over 300 million tons in 2020, as many buildings reach the end of their 30 years life. Among total waste, the proportion of concrete waste was about 30% in Korea. Due to its large volume, recycling of concrete waste is the most important aspect of the waste management. In the current practices, the concrete waste is simply crushed and used as a recycled aggregate. The recycled aggregate has a low quality and most of them are down cycled for usage as paving material, back-filling material, concrete bricks, etc. It cannot be reused for replacement of natural aggregates because cement mortar is not separated perfectly from aggregates. These kinds of recycled aggregates tent to be weaker, more porous and have a higher value of water absorption. When these aggregates are used in concrete making, there are problems of higher total water demand, low compressive strength and durability [1-5]. And recycled fine aggregate is not almost recycled due to its low quality. In this study, a new processing circuit is developed to produce not only highquality recycled coarse aggregates but also fine aggregates and cement material from concrete waste."

Jan 1, 2008

By James R. Myers

A source of clean gas containing sulfur dioxide and sufficient oxygen for convers.ion to sulfur trioxide ?is essential to the production of sulfuric acid. S02 containing gases obtained from roasting sulfide ores are heavily contaminated with inorganic dust and volatile impurities. If not removed, these contaminants will reduce product acid quality, foul the catalyst beds and mist eliminators, and accelerate equipment corrosion. This paper reviews conventional gas cleaning systems for metallurgical acid plants, followed by a discussion of modern systems utilizing DynaWave Scrubber technology. This technology is based on a unique approach to? gas scrubbing that can concurrently accomplish several gas cleaning/processing tasks scrubbing liquid is injected into the gas stream to create. a "Froth Zone". This is a region of extreme turbulence, with a very high rate of liquid .surface renewal. It efficiently removes both particulate matter and gas contaminants, and is also a cost effective quenching device for gases as hot as 1250º C. Smelter

Jan 1, 1992

By Laurentiu Nastac

"An advanced casting simulation-based optimization approach was applied in this study to assist in the improvement of the mold design of aerospace components made of A3 56 alloy. By using this approach, mold filling and solidification related defects (including macro-shrinkage and shrinkage porosity) were significantly minimized and hence it helped in cost reduction, performance enhancement and quality assurance of complex A3 56 cast parts.An experimental validation and detailed calibration procedures of the models for prediction of macro-shrinkage and shrinkage porosities were performed using A3 5 6 plates cast in fiiran-silica sand molds using the Prometal's Rapid Casting Technology (RCT) - mold printing technology. Correlations between Niyama values and the pore percentage were also developed. Thus, the severity level of shrinkage porosity can be determined via the Niyama criterion. Predictions were then compared with the macro-shrinkage and porosity measurements in plates of various plate thicknesses and in other commercial A3 56 casting components.IntroductionThis paper describes the process modeling approach used in the development of the mold design technology used to produce assist in the improvement of the mold design of aerospace components made of A356 alloy. Nova Flow&Solid™ software [3] was applied in this study. This casting simulation software was previously validated for several alloys including Ti, steel and superalloys [1-4]. The objective of this paper is to calibrate and validate the simulation software for A356 alloy sand mold castings. For this purpose, an experimental validation and detailed calibration procedures of the models for prediction of macro-shrinkage and microshrinkage (e.g., shrinkage porosities) were performed using A356 plates cast in fiiran-silica sand molds using the Prometal Rapid Casting Technology (RCT) mold printing technology. The details of the RCT technology are shown in Fig. 1 [5]. Prometal's RCT technology is used for rapid production of sand molds and cores directly from CAD files. The RCT technology relies upon ink jet printer technology to selectively bind the grains of sand to create three-dimensional sand molds and cores. Mold filling and solidification modeling as well as stress analysis are typically performed to properly design the casting and the rig system of each prototype component."

Jan 1, 2012

By Shinya Otsuka

Activity coefficient of oxygen in sulfide-rich and metal-rich melts in copper-sulfur binary were determined at 1423 and 1523 K by means of a modified coulometric titration technique using the following cell: 0 ( is Cu-S melts) I Zr02 (+Ca0) I air, Pt The activity coefficient values obtained in the present study increase rapidly with sulfur composition in the vicinity of xs = 0.3333. The data obtained for the matte saturated with the metal-rich melts are in good agreement with those obtained by Kuxmann and Benecke, Schmied 1, and Eguchi and Yazawa. Those obtained for the metal-rich melts are in good agreement with the results of Sano and Sakao.

Jan 1, 1983

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

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

Jan 1, 2011

By Zhigang Zak Fang, Michael L. Free, Jaehun Cho, Syamantak Roy, Amarchand Sathyapalan

Leaching characteristics of impurity removal from the Upgraded Titania Slag (UGS) using hydrochloric and boric acids has been investigated. Specifically, this study has focused on removal of iron oxides from the UGS that has been reduced by hydrogen gas and magnesium at 750oC for 5 hours. Reduced UGS is mainly composed of titanium hydride and impurities like iron oxides, silicon oxide, aluminum oxide, and magnesium oxide. The concentration of hydrochloric and boric acids and the leaching temperature have been chosen as the prime variables to identify the optimum conditions and leaching characteristics for removal of iron oxides. It was observed that under the constraint that 1 wt % of titanium hydride loss is the maximum amount tolerable, 0.1M HCl with 1M boric acid and 90oC are the most effective parameters for iron removal from the reduced UGS. Also, the overall rate of reaction seems to follow interfacial reaction controlled kinetics. The calculated activation energy of the reaction is 73.90kJ/mol.

Jan 1, 2016

By Weyman Dunaway

This paper will present a description of the development and commissioning of the world?s most efficient process for manufacturing high purity aqueous zinc bromide. The method for making aqueous zinc bromide from metallic zinc and bromine comprises contacting zinc with bromine dissolved in a reaction solvent containing a metal halide salt. The reaction temperature is maintained at less than 60°C. The reaction solvent preferably comprises an alkali, alkaline earth, or transition metal halide; the halide salt preferably comprises a chloride or a bromide. One preferred method includes the step of recirculating the zinc bromide product stream back to the reaction vessel. The reaction vessel can be either a one stage or a multiple stage reactor. The resulting product stream is a high density aqueous zinc bromide solution. The process is so novel that Tetra Technologies, Inc. was awarded US Patent Number 6,036,937.

Jan 1, 2006

By Mao Chen, Baojun Zhao, Zhixiang Cui, Leonel Contreras

Viscosity is one of the important physiochemical properties of metallurgical slags which is important for slag tapping, metal loss in slag, freeze lining and fluid dynamics. High temperature viscosity measurements are time- and cost-consuming and the number of experiments is limited. Viscosity model is an effective way to predict the viscosities of the complex slags at high temperature. However, a reliable viscosity model can only be developed on the base of accurate experimental data. A unique high-temperature viscosity measurement apparatus developed at The University of Queensland enabled accurate viscosity data to be measured for the “FeO”-SiO2-CaO-MgO-Al2O3 system in equilibrium with Fe. An accurate viscosity model has been developed based on Eyring’s theory and extensive viscosity measurements. The viscosities of copper smelting, converting and cleaning slags over a wide range of compositions and temperatures can be predicted and applied in the process control.

Jan 1, 2016

By Sh. Najisi, O. Lashkari, M. R. Ghomashchi, A. Charette

"One of-the important parameters in casting and foundry technology is the fluidity of molten metal. This parameter becomes particularly important when casting thin wall parts. Therefore, understanding and controlling fluidity plays a major role in fabricating sound and defect-free cast components.Semi-Solid Metai SSM, slurry is a mixture of solid and liquid, mushy zone, with solid volume fractions of 0.1-0.5 and apparent viscosity close to oil viscosity at room temperature. It flows easily under pressure and capable of making complicated shapes with high degree of die filling and integrity.In this study, the ability of the semi-solid slurry to continue to flow is investigated through the effect of different fraction solids and holding temperatures. The results show that in mechanically stirred, MS, semi-solid 356 Al-Si alloy, increasing fraction solid reduces fluidity. Furthermore, the results of MS-alloy are compared with a newly patented Rheocasting route, i.e. SEED, Swirl Enthalpy Equilibrium Device to highlight the differences of the two processes. In addition, the interrelationships between microstructural evolution and fluidity are discussed."

Jan 1, 2004

By T. Watanabe, T. Fujiwara, S-Wan Song, Y. Nakagawa, R. Teranishi, M. Yoshimura

"We have tried a new method to fabricate cobalt oxide films onto porous films directly by an electrodeposition method at low temperature. The porous substrate films (membrane-filters and paper) were placed between a LiOH solution and a CoSO4 solution and treated under electricalcurrents of ~1 mA/cm2 using carbon cathode and anode. Effects of temperatures, flow rates and electrical currents have been investigated. As a result, we found that the LiCoO2 films and Co3O4 films were successfully fabricated on paper and/or porous PTFE filters at 120 °C, while CoOOH films were deposited at 80 °C. Furthermore, LiCoO2 films did not cover whole the substrates, but was fabricated just over the anode. The chemical reactions of electrodeposition were also considered from these results.IntroductionRecent agreements on global environment require rapid progress of low energy and low waste processings for the fabrication of thin films that succeed to the mass production with the high consumption of the fossil fuels (such as physical vapor deposition°, chemical vapor deposition2), dip coating with firing3) etc.). The total energy consumption in aqueous systems should be the lowest among all these processing routes, because a much lager excess of energy is necessary to create melts, vapor, gas, or plasma than to form an aqueous solution at the same temperature4)The ""Soft Solution-Process"" (SSP) was one of the best concepts to realize the low energy and low waste fabrication of inorganic materials. 5) Generally speaking, SSP gives similar results to any other processing using fluids (such as vapor, gas plasma) and/or beam/vacuum processing. However, the total energy consumption of all these possessing routes should be the lowest in aqueous systems, because a much larger excess of energy is necessary to create melts, vapor, gas or plasma than to form an aqueous solution at the same temperature (Fig. 1). This idea can be easily demonstrated, using the simple example of BaTiO3. The energy diagram for the formation of BaTiO3 from various precursors is shown in reference 4. The driving forces (AG) for representative synthesis reaction of (1), (2), (3), (4) and(5) are 38, 727, 3685, 17 and —14kcal/mol, respectively at room temperature. 6' 7"

Jan 1, 2000

By Bruno Augusto Batista Ribeiro, Felipe Terra Elias, Wagner Moulin Silva

In the pyrometallurgical production of copper from its sulfides, converting in the Peirce Smith (P-S) Converter is still the most widespread method to obtain white metal and blister copper from the matte. Despite the fact of being a century-old process, it is still possible to achieve improvements in the process, by the use of modern tools, one of the most valuable being numerical calculation and computer-aided simulation. The present study presents three cases in which the angle for the gas injection and the number of working tuyeres are changed during the slag blow phase of the converting process. It was noticed that a decrease of the number of tuyeres, followed by an increase in the injection gas velocity, results in improved reaction volume and less stress to the refractory lining. However, an increase in the amount of copper lost to the slag as oxide is likely to occur.

Jan 1, 2014

By Kenneth L. Reid

The Mineral Resources Research Center at the University of Minnesota has recently installed a QEM*SEM system (Quantitative E.valuation of Materials using Scanning Electron Microscopy) to aid in detailed mineralogical evaluation of potential mineral resource developments in Minnesota and to provide services to the North American mineral industry. A primary application for the unit is to serve the Minnesota taconite industry by providing mineralogical analysis of ores and concentrator products. Minnesota taconite ores contain fine-grained magnetite in a quartz matrix. The ores undergo several size-reduction/magnetic-separation steps to produce a final concentrate with approximately 75% passing 325 mesh and containing about 5% gangue. The paper describes a typical taconite concentrator flowsheet and reports some preliminary results of the applications of QEM*SEM particle image maps and cumulative yield liberation data to samples from selected points in the concentrator circuit.

Jan 1, 1988

By A. Navarra

Within conventional copper and nickel-copper sulfide smelters, ladles of molten matte are fed into converters. These converters blast oxygen-enriched air into the matte, thereby eliminating iron and sulfur. The converting reactions are exothermic and, indeed, the converter heat balance is often a limiting consideration on the smelter throughput. If a portion of the matte were fed in solidified (granulated) form, this would support higher oxygen enrichment, and lower volumes of converter offgas, allowing higher throughput. This approach is not applied in conventional smelters, partly because of the copious amounts of water that must be evaporated in typical granulators, as in the Kennecott-Outotec process. The current paper recalls a waterless matte granulator that had been pioneered in the 1990’s, and is applicable to conventional smelters. A mathematical formulation is presented that can be used in the context of simulation-based optimization, to estimate the size and impact of waterless matte granulation.

By Ken Baxter

The Sepon Copper Project is located in Laos and has a mineable reserve of approximately 16Mt of ore grading 5% copper with minor gold and silver values. The deposit is a clay-hosted secondary copper mineral suite, predominantly chalcocitic in nature with associated pyrite. The current project design is based on the production of 60,000t/a of LME Grade A cathode by an acid leaching process followed by solvent extraction and electrowinning. Significant metallurgical testwork was conducted as part of the Definitive Feasibility Study (DFS) with process challenges identified and overcome at each phase of testing. Flowsheet configuration is geared to autogenously generating sufficient acid and ferric iron to meet gangue acid consumption and to leach the copper. The ability to maintain acid and ferric levels in the process liquors is strongly influenced by the proportion of pyrite in the ore presented to the autoclave. This paper will outline flowsheet development from preliminary variability testing to pilot plant and DFS design. The Sepon process solution seeks a balance between operability and capital/operating costs, and provides insights into the basic mechanisms influencing flowsheet selection for these ore types.

Jan 1, 2003

By Mituo Tougo, Mitsuo Tokunoh, Takayasu Kisaragi, Fuminori Chiba

We have about 200,000 tons/year of dross residue produced after the collection of aluminum from the dross generated during the aluminum remelting process. 130,000 tons of the dross residue is used as a steel deoxidant or a cement material, and the remaining 70,000 tons is abolished and buried in the ground at authorized places. The dross residue is increasing along with the increase in the aluminum production. This situation will grow more serious with a large amount of aluminum window sashes which have been mass-produced since 60's and will return before long as scraps. Our effort is being directed to the development of technologies which enable the dross residue to be recycled and reused for some purposes such as road aggregates, refractories and others, in such a way as to comply with the social requirement which gives prfority to the recycling industry, as well as to the environmental preservation.

Jan 1, 2000

By Akram Salah Eddine Belaidi, Lakhdar Azzouz, Benchaa Benabed

"The dunes sand is a material of a large availability in Algeria. This material is practically unexploited. The introduction of this material as a new element in the construction can be more relieve the domain of building, and contribute to the development of the southern regions of Algeria, which are very rich in this material. The main objective of our work is to exploit a largely available material in the Algerian south which is the dunes sand, as a material of construction in the region of Laghouat.In this study, first we investigated the effect of the curing environment and the nature of the sand on the mechanical properties of the mortar, such as; flexural and compressive strengths. Then after, we studied the durability of the mortar under cycles of wettingdrying and the chemical attack of sodium sulfate (Na2SO4 5%).According to the results, we note that the mortar of the sand mixes (river sand plus dunes sand) present the best mechanical performances under different environment of curing. In addition result of durability studies put forward that the mortar of the sand mixes is more resistant to the sulfates attack."

Jan 1, 2008

By R. N. Reddy

The Pseudo capacitance of layered type Mn02 electrode material for electrochemical capacitors (EC's) was investigated. MnO2 was synthesized in our laboratory. Mn02 was prepared from heating of KMn04 at 300°C in air. Cyclic Voltammetry (CV) experiments were carried out using three electrode system, Saturated calomel electrode as reference electrode, platinum mesh as a counter electrode, and MnOz composite material mounted in a platinum mesh used as a working electrode. Two kinds of composite working electrode materials were used, one was mixture of MnOz and 25 wt% acetylene black, while the other was MnOz, 25 wt% acetylene black and 25 wt% carbon. All the experiments were carried out at 25OC. A maximum specific capacitance of 130 Fig and 118 Fig were observed at the scan rate of 2 mV/s and 20 mV/s respectively in 1M KC1 for composite electrode made with carbon. Results obtained in this study are compared with that of other electrode materials.

Jan 1, 2002

By Olga K. Karakasi, Angeliki Moutsatsou, Ioanna Kavallari

"The present study focuses on the amelioration of the behaviour of high calcium fly ash (HCFA), investigating its application in a new environmental field: oil spill clean up. High calcium fly ash is a by-product of electric power plants, produced annually in large quantities, whose greater amount is landfilled. Some of its properties, such as its chemical and mineralogical composition, its fine particle size, its porosity, floating ability and hydrophobic character make it an attractive material for this purpose. Researches showed that when added to an oil spill, it forms a semi-solid phase, which allows the quite total removal of the oil, but it is not stably retained on the surface. In order to ameliorate its floating ability, the decrease in its specific gravity by mixing with a lighter material is investigated. In the present study the mixing with two materials, already used in oil spill clean up, sawdust and a polymer, has been examined. Addition of 15-25% w/w sawdust to HCFA results in a material with better performance than HCFA or sawdust alone: it has a satisfactory floating ability and allows total removal of oil. Addition of the polymer, however, has resulted in no significant amelioration of the oil sorption behaviour of HCFA, probably because no affinity between HCFA and polymer has been achieved.IntroductionCoal fly ash is a by-product of coal combustion in electric power plants, produced worldwide in huge quantities, approximately 500 million tones annually. High calcium fly ash (HCFA) is classified to class C presenting a (Al2O3 + SiO2 + Fe2O3) > 50%. The production of lignite fly ash in Greece comes up to 13 million tones annually, of which only 12% is used in construction applications, the other being landfilled [5, 6].Besides its limited application worldwide as a construction material, research is focusing on the development of new environmental applications, such as waste stabilisation and solidification, soil and water environmental improvement [9, 12]. For the application of fly ash in further environmental fields several chemical modifications have been applied, in order to improve its properties. Extensive research has been focused on the conversion of both coal and lignite fly ash to zeolite and its further application in environmental field, such as the uptake of inorganic (heavy metals and ammonium [8, 11]) or even organic compounds (methylene blue [15]) from waste water streams, or the use as molecular sieves, to adsorb water molecules, SO2 and NH3 from gas streams, due to the high cation exchange capacity and porosity of the produced zeolithic material. Furthermore, lignite fly ash has been combined with sodium silicate solution, prepared by treatment of rice husk ash, and tetrapropylammonium bromide, to synthesise hydrophobic zeolite ZSM-5 [4]."

Jan 1, 2008

By S. Ikenobu

This paper describes a method for processing high-silicate zinc concentrates by hydrometallurgical zinc refining. Silica in concentrates reacts to form zinc silicate during roasting. The zinc silicate readily dissolves and slowly precipitates in sulfuric acid solutions during leaching. However, if proper operating parameters are not maintained, the colloidal silica may form an unfilterable gel. That is, according to the investigation results obtained, the silica concentration in the reactor has to be maintained at 5 g/1 or less (preferably 2 g/1 or less) by promoting the precipitation reaction. The proposed method has made it possible to precipitate silica in a form having excellent solid-liquid separation characteristics, without the need for facilities having a high filtration capacity, and to maintain a low silica concentration in the reactor by feeding a composition containing pre-adjusted silica contents.

Jan 1, 2000