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By Elliot Schwartz, Julian Szekely

"In this paper we describe an experiment that was recently performed on the IML-2 Space Shuttle mission in which the thermophysical properties of molten metals were measured using electromagnetic levitation. In the planning of these experiments calculations had to be performed to predict the levitation and stirring forces, heating rates, sample deformation, and internal flows within the sample. These predictive calculations were essential for both the planning of the experiments and for the re-planning of experimental runs during the actual Space Shuttle mission.Introduction""Materials Processing in the Computer Age"" involves the use of mathematical modeling to obtain a quantitative understanding of the phenomena that govern materials processing operations. Microgravity, or space shuttle experimentation represents a specific case in point here; the very high cost of the space shuttle flights, the very limited flight opportunities that are available, and the tight resources aboard a shuttle clearly mandate that these experiments be very precisely planned and that all possible opportunities for mathematical modeling be fully exploited.The purpose of this paper is to present the results of calculations performed for the planning of a space shuttle experiment involving electromagnetic levitation and wherever possible present a comparison of the computational predictions with both experimental measurements and asymptotic analyses. Finally we shall seek to discuss the practical implications of both the computational methodologies and the potential experimental findings."

Jan 1, 1994

By N. Gopalakrishnana, R. Beccard, S. Lourdudoss, R. Holz, M. Deschler

"Rapid growth of conducting and/or insulating InP, GaAs, Gao.47In0.53As, and GaAs0.6Po.4 on one or more of (001), (110), (111)A, (3ll)A and (3ll)B surfaces by Hydride Vapour Phase Epitaxy (HYPE) is demonstrated. The maximum growth rate of the binaries lies between 12 and 300 µm/hr and of the ternaries between 7 and 170 µm/hr. A simple model is developed to describe the influence of crystallographic orientation on temperature dependent growth rates. The growth rates predicted by the model is compared with the experimental values. Room temperature resistivity of insulating InP:Fe can be as high as 5xl09 ohm cm. Temperature dependent differential resistivity is also analysed. This feasibility of growing conducting and insulating layers rapidly on different orientations is very useful for electronic and optoelectronic devices.IntroductionRecently there is a renewed demand for very thick layers of III-V compound semiconductors for high performance electronic and optoelectronic devices [1]-[2]. Long wavelength high speed lasers that can be modulated up to 30 GHz necessitate epitaxial growth of semi-insulating (SI) layers [3]. There is also an increased interest on the growth of epitaxial layers on surfaces other than (001) surface. Epitaxial growth of these materials on such surfaces is of theoretical importance besides being technologically relevant. These demands led us to focus on the growth of conducting and insulating III-V compounds by Hydride Vapour Phase Epitaxy (HYPE). lnP, GaAs, Gao.471no.s3As on lnP and GaAso.6Po.4 on GaAs were grown as conducting materials using Low Pressure HYPE (LP-HYPE) on (001) 2° off substrates. Gao511no.49P on (001) GaAs substrate and lnP on lnP substrates of (001), (110), (l 11)A, (31l)A and (3 ll)B orientations were grown as semi-insulating materials using Atmospheric Pressure HYPE (AP-HYPE). In this report we present the growth aspects of these materials. We also present a simple model on the growth of InP on substrates of various orientations. The theoretically obtained temperature dependent growth rates are compared with the experimental values. Differential resistivities of semi-insulating lnP grown on substrates of various orientations as a function of temperature are also summarised."

Jan 1, 1998

By S. Yuan

Oxygen ion conducting yttria-stabilized zirconia (YSZ) tube was used to remove oxygen from molten Cu at 1373K. Outer surface of the tube was in contact with the melt and the inner surface containing a thin layer of porous Ni-ZrO2 cermet electrode was in contact with a reducing gas. The migration of oxygen species (O2-) from the Cu melt through the YSZ tube is accompanied by an equal and opposite flux of electrons maintaining electroneutrality. Without applying an external EMF, the fluxes are maximized by short circuiting the melt with the cermet electrode. For efficient oxygen removal, the YSZ tube must be thin, contact resistances should be negligible, and the electrodes must be porous and cover the entire electrolyte surface for charge transfer. This refining process is environmentally sound, can use reducing gases such as H2, CH4 and CO without running the risk of increasing H or C content of the melt.

Jan 1, 1993

By Cesimiro Fabian

The crystallite size of copper electrodeposits was determined by X-Ray powder diffraction analysis using a General Area Detector Diffraction Solution (GADDS) diffractometer. Crystallite size was calculated for copper thin films which were deposited on a 316 stainless steel rotating cylinder electrode (RCE) in the presence and absence of additive ?A?. The crystallite size was calculated from a corrected full width at half maximum (FWHM) of the [110] peak profile using the Scherrer equation. The test of significant difference on crystallite size was derived using Kruskal-Wallis method. It was found that in the absence of the additive the median crystallite size was 426, which decreased to 364 in the presence of the additive. As the additive degraded, the crystallite size increased to a size similar to that observed in the absence of additive.

Jan 1, 2003

By H. Senoh

For the purpose of clarifying the reason caused a drastic decrease of discharge capacity for MmNi3.6Mn0.4Al0.3Co0.7 electrode at relatively low temperatures, various factors influencing the charge-discharge processes were investigated in the temperature range of 25°C to -40°C. The charge efficiency obviously decreased at low temperatures less than 0°C due to a decrease in the rate of the charge-transfer reaction on the electrode surface. Moreover, both the rate of the hydrogen diffusion from the alloy bulk to surface and the rate of the charge-transfer reaction significantly influenced the high-rate dischargeability. The addition of Mo to MmNi3.6Mn0.4Al0.3Co0.7 alloy was found to be effective for improving the electrocatalytic activity, leading to the improvements of the charge efficiency and the high-rate dischargeability at relatively low temperatures.

Jan 1, 2002

By H. V. R. von Rhaden

Systematic quantitative X-ray diffraction analyses performed on diamond-drill cores originating from the Aandenk formation at the Loraine Gold Mine, located in the Welkom goldfield, Orange Free State, South Africa, have revealed the presence of a number of phyllosilicate mineral assemblages which have not hitherto been reported from this region. Rectorite, a regularly interstratified 1:1 mica-montmorillonite "swelling clay", is found to occur together with paragonite, muscovite, pyrophyllite, kaolinite, and chlorite in highly-altered friable rocks. The presence of rectorite in mill feeds may have potentially serious implications with respect to gold recovery. Quantitative X-ray diffraction analysis for phyllosilicates can be used as an aid to correlation, and also to guide the widths of stopes in underground mining. Rectorite has a unique mode of origin, which is discussed.

Jan 1, 1991

By SenYang Qian, ShuangYu Du, Bo Wang, Jieyu Zhang, Jian Zhao

During the solidification process, the flow pattern of the molten steel has significant influence on the formation of solidification microstructure. In present study, the solidification microstructure of 30Cr2Ni4MoV steel ingot under different intensities of mechanical oscillation(forced convection) was simulated by using ProCAST®software. The results showed that the increase of the intensity of oscillation could restrain the development of the columnar grains and refine the grains. As the intensity of oscillation increased, the proportion of columnar grains decreased and the proportion of equiaxed grains increased. When the intensity of oscillation was at a low level, the effect of refining grains could be improved obviously by increasing the intensity. However, as the intensity increased to over 0.833, the effect of refining grains would not be improved.

Jan 1, 2016

By C. Pichler, A. Ressler, D. Gregurek, A. Spanring

In order to improve the refractory lining life at one of the RHI key customer test procedures were developed within a two years collaboration project. In the first year of cooperation detailed refractory corrosion work in the rotary kiln with Ca-ferritic slag was performed. The main results of the second year of cooperation, reported in this article, involve a detailed testing work with nickel matte and pre-selected refractory brands which was performed in TBRC. A first part of this work was a complete chemical and mineralogical characterization as well as FactSage calculations carried out on provided matte samples. According to these results testing in the TBRC was realized at different process temperatures with several magnesia-chromite bricks. Based on the mineralogical investigation a high chemothermal load caused by sulfidic matte resulted in a deep reaching infiltration of the brick microstructure and partly corrosion of main brick components.

Jan 1, 2015

By J. E. Dutrizac

Fracture-exposed surfaces of sphalerite samples having five different solid solution iron contents ranging from 0.0 wt% to 14.8 wt% Fe were leached for 15 to 120 s at 100°C in 0.3 M Fe(S04)1.5 -0.3 M H2S04 media. The reacted samples were examined using X-ray photoelectron spectroscopy (XPS) which provides chemical state information on the first few nanometers of the solid surface. Surface compositions show that the leaching rate increases with increasing solid solution iron content of the sphalerite. Detailed evaluation of high resolution S2p spectra show that the leaching progresses via the formation of polysulphide species. Disulphide species were not detected in any of the experiments. Examination of the Zn2p and Fe2p spectra indicate little change in the chemical states of these elements over the duration of the experiments. Longer leaching times resulted in the generation of elemental sulphur. The ratios of elemental sulphur to dissolved ferrous ions and zinc suggest that less than 5% of the sulphide is oxidized to sulphate. Morphological studies showed that the elemental sulphur commonly formed at a few isolated sites, such as the grain boundaries. Furthermore, euhedral sulphur crystals were often identified. These observations suggest that at least part of the elemental sulphur forms via dissolved sulphide species which are oxidized in solution by ferric sulphate.

Jan 1, 2003

By Z. Smieszek, W. D?browicz, J. Pawlowski, G. Krawiec, J. Czernecki, J. Por?mbski, S. Gizicki

Rapid development of the automotive industry and motorization has been observed in Poland over the last decade. This phenomenon has increased the amount of used car batteries requiring recycling and has thus posed new challenges for their processing. Orzel Bialy" S.A, is the major secondary lead smelter in Poland. Ibis paper describes the program for smelting technology modernisation and productivity increase through the application of oxy-fuel burners, which has been implemented at "Orzel Bialy'' S.A. The main objective of smelter modernisation, which was to increase the furnace productivity by 20%, has been achieved. This paper outlines the previous and present state of the lead acid battery scrap smelting technology at the "Orzel Bialy" S.A. Specifications of the burners and of oxygen installation are given. Industrial tests with the modernised smelting technology and optimisation of the process parameters are described, and the results obtained are discussed.

Jan 1, 2000

By J. R. Bhamidipati, Nagy EI-Kaddah

"Over the years, mathematical modeling has been established as a viable tool for design and analysis of melting and solidification processes. Modeling of electromagnetic casting and melting systems involves three coupled problems -- determination of the containment field, the shape of the meniscus, and the temperature field -- which have to be solved simultaneously. One of the difficulties in numerical simulation of these systems is in defining and gridding the solution domain as the meniscus shape of the liquid region is not known a priori. This paper describes a methodology for solving these coupled problems in a two-dimensional electromagnetic containment field. This method is based on the solution of the electromagnetic, free surface dynamic, and heat transfer equations in a fixed domain in computational space by mapping the physical space into an invariant computational space during the search for the equilibrium shape using a variable non-orthogonal coordinate transformation. This approach, also, eliminates the need for regridding the liquid and solid regions during phase change. This methodology is demonstrated for two electromagnetic confinement systems -- the Magnetic Suspension Melting process and the electromagnetic casting of aluminum. The model predictions are in good agreement with available data for these systems. It is suggested that the methodology presented here is likely to provide a useful tool in the design, analysis, and optimization of electromagnetic confinement systems. IntroductionDuring the past decade, mathematical modeling has emerged as a viable tool for the design, analysis, and optimization of casting and melting processes /1-2/. It is generally recognized that the usefulness of modeling to study the interplay between the various process parameters without resorting to extensive experimentation relies heavily on accurate representation of the physical phenomena in these systems. In modeling electromagnetic confinement casting and melting systems, it is important that the model address all aspects of electromagnetic field interaction with the metal, if accurate predictions are to be obtained /3/. The electromagnetic field affects the heat transfer phenomena primarily through joule heating. In addition, the electromagnetic forces play a key role in heat redistribution in the molten pool via melt stirring, and, in confinement systems, support the molten metal pool."

Jan 1, 1994

By Jose F. Hevia

This study is part of a broader project on the hydrothermal conversion of copper concentrates to metallic copper by solid state reactions in which the copper remains localized in the solid phases. The kinetics of the solid/solid hydrothermal hydrogen reduction of tenorite (CuO) and cuprite (Cu,O) to metallic copper are presented. After an induction period, the process is governed initially by a nucleation step followed by rapid solid state reduction. Nucleation promoter agents decrease the induction period and control the particle morphology. Separate nucleation and reduction rate processes have been identified. Following nucleation, reduction follows a shrinking core process.

Jan 1, 1994

By Peter K. Everett

One of the major driving forces behind the development of the Intec Copper Process has been the increasingly stringent regulations governing SO2 emissions and, in some parts of the world, a declining H2SO4 market. Other incentives include operating cost (9.2 US c/lb Cu), capital cost (US $1400/annual tonne Cu compared with smelter cost of US$3-4000/annual tonne Cu) and the ability to treat low grade and contaminated concentrates. With such advantageous features, widespread use of the process is expected over time, leading to the production of large amounts of residues containing around 25% elemental sulfur, together with approximately 50-60 % akaganeite (FeOOH) and the ganggue minerals originally present in the concentrate feed. This paper briefly describes the Intec process chemistry involved in the formation of elemental sulfur, thereby avoiding atmospheric sulfur dioxide pollution, and the investigations to be carried out either to extract it or to turn the residue into a valuable by-product while minimising any adverse environmental effects, The process is being developed jointly by a group of fifteen major international mining companies.

Jan 1, 1996

By Emil B. Milosavljevic

The photochemical reactions of cyanide ion induced by light were investigated in the presence or absence of a titanium(IV) oxide semiconductor photocatalyst. The light sources employed were the sun and arrays of either mercury or fluorescent (cool white) lamps. The results obtained verify that cyanide decomposes much faster when TiO2 is present in the solution and that it is first oxidized to cyanate. However, contrary to the previous studies, it is established that cyanide is subsequently further oxidized via nitrite all the way to nitrate irrespective of the light source. As expected, the rates of the oxidation processes decrease with the illumination source utilized in the following order: Hg-lamps > sunlight > fluorescent lamps. As nitrate is a significantly less hazardous contaminant than cyanide, complete photocatalytic oxidation of cyanide to nitrate may be a viable method for decontamination of cyanide wastes. Contrary to previous claims, we find that cyanide is slowly photochemically decomposed even in the absence of TiO2. For example, with the mercury lamps as the light source, in two hours, cyanide concentration decreases to essentially zero; up to 7% was converted to cyanate and the remainder to unidentified products.

Jan 1, 1992

By V. D. Tathavadkar

Natural chromite mineral is a solid solution of spinet end members namely: chromite (FeCr2O4), hercynite (FeA1204), magnetite (Fe3O4), magnesio-chromite (MgCr2O4), (MgA12O4), and magnesio-ferrite (MgFe2O4). A phase transformation in chromite minerals occurs in oxidising conditions during the soda-ash roasting reaction. This phase transformation plays an important role in improving the extraction efficiency of Cr3+ from mineral phase. The extraction efficiency of chromium (Cr3+) from chromite to a water¬soluble sodium chromate (Cr6+) salt depends upon the decomposition kinetics of the spinet phase. An investigation of the phase changes in chromite ores in the absence of sodium carbonate was carried out in air, argon, and in argon +5 % hydrogen gas mixture. The thermodynamics of phase transformation reaction in chromite solid solution phase is discussed using the solution model proposed by Sack and Ghiorso [1]. The microstructural changes and the changes in elemental compositions of different phases were examined by SEM and electron probe microanalysis (EPMA) respectively. The experimental results indicate that the solid solution spinet phase in chromite mineral undergoes spinodal decomposition under the influence of oxygen partial pressure and temperatures. The structure of phases formed and their morphologies suggest that the phase decomposition may be similar to those observed by Burkert et. a]. 121, although the scale of phase separation in chromite appears to be strongly dependent on oxygen partial pressure.

Jan 1, 2001

By Ann M. Hagni

Microscopic and sub-microscopic gold commonly occurs in the sulfides pyrite (FeS2) and arsenopyrite (FeAsS). To recover refractory gold from pyrite and arsenopyrite, these sulfides are roasted to create porosity and permeability prior to cyanide leaching. A new technique of adding Ca(OH)2 and roasting. lime roasting. is being tested for retention of contaminant sulfur and arsenic and effectiveness of gold extraction. The lime roasting of pyrite at 500°C contains anhydrite (CaS04). oldhamite (CaS). calcium sulfite (CaS03). hematite (Fe2O:J), magnetite (Fe304). and minor amounts of pyrrhotite (Fe1.xS) and pyrite. At 600°C. 650°C and 700°C. the main constituents are anhydrite. oldhamite. and hematite. At 750°C. 800°C. and 850°C. anhydrite and hematite are the predominant phases with minor oldhamite. The roasted arsenopyrite at 450°C contains arsenic sulfides. calcium sulfite. hematite. and minor oldhamite. magnetite. and pyrrhotite. At 650°C. 700°C, 750°C. and 800°C, anhydrite, oldhamite. arsenic sulfides, and hematite are present. At 850°C. the same minerals are present with only minor oldhamite. The textures indicate excellent porosity and permeability at high temperatures. At lower temperatures, rims of low porosity and permeability surround many of the pyrite and arsenopyrite particles, and the complete oxidation process from pyrite to pyrrhotite to magnetite to hematite can be observed in individual particles. Additional process mineralogy techniques employed in this study are electron spectroscopy for chemical analysis (ESCA) and cathodoluminescence microscopy (CIM) in the determination of the calcium-sulfur-oxygen phases. Automated scanning electron microscopy-energy dispersive spectroscopy was utilized to analyze particles for gold content. Reflected light microscopy (RIM) revealed arsenopyrite and pyrite encapsulated in quartz particles of the gold-bearing concentrate, gold roast calcine, and cyanide leach residue.

Jan 1, 1991

By Fatma Arslan

Alada (Kayseri-Turkey) lead-zinc sulfide-oxide ores contain 10.17% Pb, 10.98 %Zn, 164 g/t Cd and 57 g/t Ag. During the laboratory scale flotation tests of these ores, it was found that almost all zinc was remained in the tailings that contain 12.31% Zn, 1.35%Pb, 198.3 g/t Cd, and 22.3%Fe. Three different methods were studied such as basic (NaOH) leaching, roasting+acidic (H2SO4) leaching and direct acidic (H2SO4) leaching for recovering metals that these tailings contain. In the direct acidic leaching, which gave the best results, dissolution efficiencies of 91.5% zinc, 78.2% cadmium, and 14.3% iron were reached at the optimum leaching conditions while Pb remained in the leach residues and the acid consumption was 422.3 kg/ton of tailings.

Jan 1, 2006

By Jasper Kwong

The recycling of MgO-C refractories as a slag conditioner in EAF (electrical arc furnace) foaming slags have been evaluated by the Albany Research Center. The amount of MgO in the slags is critical for the foaming quality. Good foaming slags provide the benefits of high energy efficiency and low refractory consumption and require saturation with MgO. A computer model predicting the chemistry of MgO saturated foaming slags was designed to predict suitable amounts of MgO additives from MgO-C spent refractories. This model can also help to reduce the amount of slags and to improve the economics of producing steel. The implementation of this recycling program is underway at steel plants and the experience of recycling spent refractories will be discussed.

Jan 1, 2002

By Merete Tangstad, Gabriella Tranell, Jeff Kline

"Raman spectroscopy as an instrumental technique for the determination of silicate structure is widely accepted. This method was utilized for analysis of structural modifications associated with the addition of network modifying species. Silicate melts are described by the extent of oxygen bridging. Therefore, understanding the effect different oxides have on modifying the silicate structure will provide valuable information regarding the removal of boron from silicon in slag refining processes. Samples ranging from CaO/SiO2 = 0.56-1.2 were evaluated with and without varying concentrations of B2O3. The addition of CaO to SiO2 revealed Q2 species constitute 45% of the Qn species and addition of B2O3 to the high concentration CaO system results in an increase in Q2 and a decrease in Q0 . The disappearance of the Raman band associated to the three-member ring in the low concentrated CaO system indicates boron addition and destruction of the ring.IntroductionExtensive studies on the structure of silicate systems have been performed using Raman spectroscopy with consensus on the Raman shift associated with different bridging oxygen units [1]. Most of these studies are motivated by the lack of a fundamental understanding of the processes involved in petrology. Due to this, an opportunity exists to build on the knowledge obtained from these studies and conduct more research on slag structures relevant to industrial applications, as these systems are often compositionally similar to magmatic melts. Raman spectroscopic studies of industrial slags will provide insight into the possible structural modifications necessary to enhance removal of impurity species from the metal phase to the slag phase."

Jan 1, 2012

By J. Kevin Cotchen

The results of "submerged arc" electric furnace processing of a variety of materials is discussed with respect to the process and products, including the characteristics of the products (e.g. TCLP or Toxicity Characteristics Leaching Procedure). The materials melted include slags and wastes containing various metal oxides including copper, tin, lead, zinc, chrome, nickel and other associated elements. The findings of these tests are compared to those reported in the literature for other operations treating similar "wastes".

Jan 1, 1992