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By Kazuaki Mita

There are various intermetallic compounds in the Zn-Fe system. We synthesized them at about 673K. A specimen was examined chemically and X-ray diffraction was applied to ensure the formation of intermetallic compounds. Material containing two phases was placed in a Knudsen type effusion cell and the mass spectrum studied to evaluate the vapor pressure of zinc. The thermodynamic properties of intermetallics was then evaluated through measured intensity.

Jan 1, 1999

By Sedef Pinar Basag, Onuralp Yucel, Ahmet Turan

Niederschlag process is commonly used to produce metallic antimony. The process is a metallothermic process which is conducted in one step for metallic antimony production. Using this method Sb2S3 is mixed with coal and metallic iron and subjected to reduction. During heating, antimony sulfide is decomposed and sulphur combines with iron to form the matte phase. Metallic antimony is collected at the bottom of the crucible. In this study, evaluation of Sb2S3 concentrate, extracted and obtained from West Anatolian Region of Turkey was investigated by using Niederschlag process. The reductant stoichiometry, reduction temperature and duration were carried out in the experiments. Chemical analysis methods by using atomic absorption spectrometry (AAS) and X-ray diffraction spectrometry (XRD) techniques were used for the characterization of the concentrate, metallic nuggets and matte phases.

Jan 1, 2016

By H. Y. Sohn

A novel solvent extraction process in which the emulsion is generated by bottom gas injection rather than mechanical stirring has been developed. This process has a number of advantages over the mixer-settler unit or the spray column in terms of simple equipment configuration and the ease of cleaning and process control while providing a large interfacial area for mass transfer. The equipment consists of a horizontal cylindrical vessel in which the two immiscible liquids flow countercurrently. High-strength gas jets are injected from the bottom at certain intervals along the length of the vessel. The gas jet creates a plume zone consisting of an emulsion of the two liquids which contains a large interfacial area for rapid mass transfer. The two liquids then disengage and flow in the opposite directions before entering another plume zone. Thus, the process combines the simplicity of a cylindrical vessel, having no moving parts, with the contacting efficiency of a mixer-settler. The gas can be recycled in a closed loop, thus eliminating mist and other emission problems. These advantages would be especially significant for treating large-volume/low-value liquid streams which contain hazardous substances and/or suspended solid particulates.

Jan 1, 1996

By Sung Jin Han

Magnesia-based refractory is generally used in an electric arc furnace (EAF) due to its relatively high corrosion resistance and strength at high temperatures. However, the magnesia refractory is attacked by EAF slag and thus the lining life continuously decreases. Thus, it is significant to identify the interfacial reaction between magnesia refractory and FeO-rich EAF slags. In the present study, the influence of FeO-rich slag on the corrosion behavior of MgO refractory was evaluated. The (Fe,Mg)Oss layer was observed at the slag-refractory interface and its thickness increased with increasing content of FeO in the slag. The specific reaction phenomena and formation behavior of (Fe,Mg)Oss layer were evaluated by thermochemical computing program, FactsageTM7.0.

By O. Chemezov, Yu Zaikov, A. Apisarov, A. Isakov

"Silicon deposits containing 99,9 wt.% of main component were obtained by SiO2 electrolysis from chloride-fluoride melts. The operating temperature was varied from 973 up to 1073 K. The conditions for obtaining crystalline fibrous micro- or nanodeposits were determined. The deposits were investigated by ESM methodIntroductionThere are large reserves of natural quartz of high purity in Russia. Processing of this raw material by electrolysis in molten salts produces silicon containing 99.9 weight percent of basic substance.[1]This method is less energy-consuming in comparison to existing methods for producing high purity silicon from gas phase.Another advantage of the electrolytic method for producing silicon from its oxide in molten salts is the possibility of production of high-purity silicon under air atmosphere. It dramatically reduces costs of the electrolytic cell construction, and the operating costs at electrolysis.On our opinion, the main advantage of the electrolytic production from SiO2 in molten salts is a unique opportunity to obtain micro-and nanostructures of silicon deposits. In particular, it is possible to obtain fibrous structures of silicon. The electrolytic method allows smoothly adjusting the thickness and length of silicon micro- and nano-wires by varying the cathode current density and temperature of the process."

Jan 1, 2012

By Li Yuhai

Kinetics of non-isothermal precipitate process and crystal growth of perovskite (CaO ? Ti02) phase in CaO-TiOz-Si02-AlP3-MgO system were studied. The experimental results show that the relative volume fraction can be described by the equation given by K. Matusita et at. and the experiential expression of average crystal radius was obtained. The particle coarsening in non-isothermal process has important effects on the crystal growth of perovskite phase.

Jan 1, 2000

By Larry B. Fiske

Elimination of dust and processing of fines for both thermal and metallurgical coals is addressed. The efficiency of treatment with lignosulfonates compares favorably to oil in thermal coal. Effect of treatment with various lignosulfonates upon cokability of metallurgical coal was determined by Free Swelling Index, Gieseler Plasticity and Arnu Dilatation.

Jan 1, 1992

By Ayşe Ece Yıldızçelik, Mehmet Buğdaycı, Onuralp Yücel

ZrB2 and TiB2 are significant metal borides. They are being used in various industrial areas from space technology to nuclear industry owing to their physical properties such as high melting point, high thermal/electrical conductivity and low density. Present study was conducted in two main stages: self-propagating high-temperature synthesis (SHS) reactions and leaching. ZrO2, TiO2, B2O3 were used as starting material and Mg was used as a reductant to produce ZrB2-TiB2 powders via SHS. Therefore, it was aimed to determine production parameters, leaching conditions and comprehensive examination of final product features. The samples were characterized by using chemical analysis (AAS), XRD, XRF and SEM/EDS techniques.

Jan 1, 2015

By M. H. Lin, S. Kou

"Czochralski pulling has been a very widely used process for growing single crystals for electronic and optical applications. Dopant segregation can significantly degrade the quality and yield of single crystals. We have used the floating-crucible technique for segregation control in Czochralski pulling, our floating crucibles being unique in that the melt passageway is very long. As such, dopant back diffusion is suppressed, even when the cross-section of the melt passageway has to be relatively large to help the melt go through or when the pulling rate is very low. Single crystals of model materials K-doped NaN03 and Pb-doped Sn have been grown with very uniform dopant concentrations. IntroductionSingle crystals of electronic and optical materials are often doped with a small amount of impurities to develop required physical properties, e.g., P and B in Si for n-type and p-type semiconductors, respectively, and Nd in YAG lasers. Dopant segregation can result in nonuniform physical properties, thus degrading the quality and yield of the resultant crystals.Figure 1 is an illustration of the conventional Czochralski process for crystal growth. Several techniques have been developed to control dopant segregation in Czochralski pulling, including the push-pull technique (1,2), the drop-pull technique (3-7) and the floating-crucible technique (8-13). The first two techniques require precise sensing devices and feedback control systems to keep the feeding rate equal to the pulling rate. The last technique is simple since the feeding rate is automatically equal to the pulling rate."

Jan 1, 1994

TiO2 and Ti/TiO2 thin films were deposited on a quartz substrate by laser ablation of Ti02 and Ti targets using Nd:YAG pulsed laser. After sulfurization of the Ti02 film in H2S or CS2 gas at 1273 K for 1 hour, the surface atomic structure was changed. Furthermore, the Ti/TiO2 film was successfully prepared by the subsequent ablation of Ti and TiO2 targets. The morphology and structure of the films were characterized by XRD, XPS and AFM analyses.

Jan 1, 2003

By Lennart Hedlund

There is today a long and well-documented experience of the use of Boliden "Kaldo' technology for treatment of various feed matedals. The process is In commercial' operation in the Boliden Mineral's Rönnskär plant In Sweden for treatment of copper scraps and lead concentrates (In campaigns). This plant was built In 1976 for treatment of lead dusts from the copper plant but later modified to take other raw materials. Boliden's Kaldo techr:lology Is also In operation since 1991 for treatment of low-grade copper scraps In Enlrlsorse's plant In Porto Marghera (Venice), Italy. The plant is producing 25 000 tons of blister copper ,per year. The Kaldo furnace Isa high :Intensity smelting unit, where several successive treatment steps can be done In the same vessel. The furnace can be totally enclosed to protect the working environment, and the small off-gas volume can easily be dedusted. Input materials can vary over a very wide range, the products will be a dump slag with low (0,5%) copper and lead contents and black copper or blister copper. The dust from the process can be used for zinc production. A new development is autogenous smelting of scrap in a Pierce-Smith converter, implemented at Compagnie Générale d' Èlectrolyse du Palais in France.

Jan 1, 1995

By D. J. Wang

Based on the thermodynamic arid kinectic aspects, the vaccum distillation processes for the separation and recovery of metals from wastes are analyzed. As to the separation criteria, The separation coefficient and equilibrium composition relation between vapor phase and liquid phase are the bases of recovery of metals by vacuum distillation, The vaporization rates and condensation mechanisms are also discussed. Some experimental results which deal with metals-containing wastes are described and the performances of a new kind of horizontal vacuum furnace are introduced, which demonstrate that , vacuum distillation may be a prospective technique for circulation and regeneration of some non-ferrous metals from industrial wastes.

Jan 1, 1996

By Chikabumi Yamauchi, Masami Tashiro, Toshiharu Fujisawa, Hiroyuki Snano

"Rare earth metals usually contain large amount of oxygen because of their reactiveness, and therefore oxygen removal is one of the major problems on the purification of rare earth metals. In the present research work, halide flux treatment at high temperature under inert gas atmosphere was applied to the oxygen removal from neodymium. NdF3 was used as a halide flux. Deoxidation reaction and its mechanism were discussed based on the experimental results. Halide flux treatment is very effective for oxygen removal from rare earth metals.IntroductionSolid Sate Electrotransport (SSE) process has been successfully applied for the elimination of interstitial gaseous impurities from chemically active metals[l]-[5]. However, to achieve a higher effectiveness of the SSE process, it is required a very low initial impurity content in the metal. In case of rare earth metals, it is known that they usually contain large amount of oxygen that should be lowered as much as possible before applying the SSE process. In addition, if effective oxygen removal is achieved by simple process, it is significant also from the industrial viewpoint. In the present work, the application of a halide flux treatment is investigated to remove oxygen from neodymium by using NdF3 as a flux. At first, deoxidation reaction and its mechanism were discussed based on the phase diagram of the Nd-NdF3-Ndp3 quasi-ternary system. Based on the results, oxygen content in deoxidized neodymium was calculated theoretically and it was verified by deoxidation experiments."

Jan 1, 1998

By Giulio R. Altoé, Sergio N. Monteiro, Ygor M. Moraes, Rômulo L. Loyola, Frederico M. Margem, Gabriel O. Glória

The tensile properties of DGEBA/TETA epoxy matrix composites reinforced with different amounts of PALF fibers were evaluated. Composites reinforced with up to 30% in volume of long, continuous and aligned PALF fibers were tested in an Instron machine at room temperature. The fracture was analyzed by SEM. This one revealed a weak fiber/matrix interface, which could be responsible for the performance of some properties. The results showed significant changes in the mechanical properties with the amount of PALF fibers.

Jan 1, 2015

By Wenjun Duan, Zongliang Zuo, Qingbo Yu, Qin Qin, Junxiang Liu

Moving bed has been widely used in the field of heat and mass transfer and reaction between solid particles and gas. In order to enhance the heat exchange coefficient, there will be tube banks inserted in the moving bed. In the process of drying ammoniates particles or heat recovery from high-temperature particles with moving bed, the particles flow behavior around the tube banks is significant. In this paper, the particles flow behavior around the tube banks is investigated, and all the results can provide guidance for the design and operation of a moving bed.

Jan 1, 2016

By Kenneth G. Thomas

This paper reviews the alkaline and acid gold autoclaving experiences gained at Barrick Gold Corporation. Alkaline autoclaving was operational at Barrick Mercur, Utah, U.S.A., on carbonaceous/sulphide refractory ore for eight years commencing in 1988. Acid autoclaves have been operational at Barrick Goldstrike, Nevada, U.S.A., on sulphide refractory ore since 1990 and now process 17,500 stpd of ore through six large autoclaves. Information is presented on operating costs, materials of construction, reagent requirements and flow sheet developments that reduced capital and operating costs.

Jan 1, 2000

By Seong-Jong Kim

The formation behavior and corrosion characteristics of anodic oxide films on pure Mg and Mg-AI alloys were investigated focusing on the effects of anodizing potential, Al content, temperature and NaOH concentration. Pure Mg and Mg-AI alloys were anodized for 10 min at 3, 10, 40, and 80 V in NaOH solutions. Mg(OH)2 was generated by an active dissolution reaction at the surface of the specimen and the product was affected by temperature while MgO generation increased with NaOH concentration. Moreover, the current density after anodizing for 10 min at a constant potential decreased with increasing AI content in Mg-AI alloys,

Jan 1, 2003

By J. D. Sloop

This paper discusses the current state of EAF dust recycling at AmeriSteel's Dust Processing Division in Jackson, Tennessee. Included are a brief history of the plant, a description of the facility, a description of the process, and operating data.

Jan 1, 2000

By William Petruk

The behaviour of sphalerite during mineral beneficiation of base metal ores has been studied at CANMET and other institutes for at least 15 years by determining the liberations of sphalerite in mill products and calculating the recoveries of liberated and unliberated sphalerite in zinc concentrates. Sphalerite in base metal ores commonly occurs as layers and as interstitial material between pyrite. Layered sphalerite is generally liberated during primary grinding, but interstitial sphalerite requires re-grinding to achieve liberation. Around 95% of liberated sphalerite is generally recovered in zinc concentrates frau zinc circuit feeds. A series of tests was conducted on sphalerite in the ore of Brunswick Mining and smelting during a continuous fine tuning operation of the concentrator. It was found that a grind of 80% minus 37 micrometres was required to liberate the interstitial sphalerite. The fine grind increased Zn recoveries from 75% to 78-80%, but produced liberated slimed sphalerite which was lost. Since regrinding to a fine grain size is needed to obtain the desired sphalerite liberation, a method of recovering the slimed sphalerite is required.

Jan 1, 1990

By Yuan Lu, Yiming Rong, Richard D. Sisson Jr

With the development of quench technology, there is a trend of using gas quench to replace liquid quench for less distortion and residual stress. The fundamental difference between the liquid and gas quench is the heat transfer coefficient, not only the values but also the shape of the curve as a function of temperature. The equivalent heat transfer coefficient for the liquid and gas quench is analyzed by simulations and experiments. Even it may result in the same hardness in the liquid and gas quench, the steel microstructure may be different because of the different cooling processes, and therefore other steel properties, such as toughness, may be different. The cooling process, microstructures and properties such as hardness and toughness should be examined when designing the liquid or gas quench processes.

Jan 1, 2015