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By Michael D. Odekirk

The U.S. Bureau of Mines investigated solvent extraction methods for recovering scandium from water leach filtrates of sulfated tantalum tailings. These complex solutions typically contained 20 or more metals in significant quantities. Two commercially available organics, DEHPA and PC-88A, were identified as effective scandium extractants. The two organics were tested in continuous solvent extraction circuits to compare loading and stripping kinetics, recyclability, and general processibility. Results showed that 95 pct of the scandium, greater than 80 pct of the zirconium, and only small amounts of other solubilized metals were extracted. Scandium was stripped directly as a 3.6 pct Sc precipitate when a 3n NaOH liquor was used as the stripping agent. This precipitate was subsequently upgraded to 94 pct ScE3 via a selective HE leach.

Jan 1, 1993

By T. J. A. Smith

This paper provides an overview of some of the key issues in design of smelter gas handling systems, with particular reference to sulphide smelting plants. In both primary smelting and converting. gas handling and treatment systems often represent the major capital cost component. There is also ample evidence that poor system design can be a major cause of smelter down time, lost production and unforeseen high maintenance costs. The paper discusses these issues and offers guidance for improved design.

Jan 1, 1992

By A. De, J. S. Zuback, T. Mukherjee, T. DebRoy

For successful commercial applications of additive manufacturing, metallic parts need to be defect free, structurally sound and reliable. However, additively manufactured metallic parts are susceptible to distortion, lack of fusion defects and compositional changes. Methods to measure susceptibilities of various alloys to these defects are needed but not currently available. Here we show that the necessary theories can be developed based on a well-tested numerical heat transfer and fluid flow model and decades of research in the field of welding. The proposed theories are validated with experimental results reported in the literature.

Jan 1, 2016

By Phillip B. Messersmith, Emmanuel P. Giannelis

"A versatile in-situ polymerization approach is described for the synthesis of polymerceramic nanocomposites consisting of two-dimensional layers of mica-type silicate (MTS) within polymer matrices. Functionalized, organically modified mica-type silicates (OMTS) were used to promote delamination/dispersion of the host layers and initiate polymerization of organic rrionomer. Epoxy nanocomposites prepared in this manner exhibit substantial modulus reinforcement at low silicate loadings. The water vapor permeability of the poly(?-caprolactone) nanocomposite containing 4.8% silicate by volume was reduced by nearly an order of magnitude compared to pure poly (?-caprolactone).IntroductionPolymer matrix nanocomposites are a relatively new class of materials with dimensions typically in the range of 1-100 nm.1 In general, because of the ultrafine phase dimensions involved, nanocomposites exhibit new and improved properties when compared to their micro- or macrocomposite counterparts. We as well as others are currently investigating the design, synthesis and characterization of polymer-ceramic nanocomposites. Our effort, in particular, has focused on the use of mica-type silicates (MTS) with various thermoplastic and thermosetting matrices.2-5MTS's belong to the general family of 2: 1 layered silicates. Their crystal structure consists of layers of two silica tetrahedral sheets fused to an edge-shared octahedral sheet of either aluminum or magnesium hydroxide. Stacking of the layers leads to a regular van der Waals gap or interlayer.6 Isomorphic substitution within the layers generates negative charges that are counterbalanced by cations residing in the interlayers. Although the natural forms of MTS's usually contain hydrated Na+ or K+ ions, ion exchange reactions with organic cations (e.g. alkylammonium ions) can render the normally hydrophilic MTS's organophilic."

Jan 1, 1994

By K. Pagalthivarthi, P. V. Desai

"During solidification of alloys, many inter-related physical processes, such as melt convection, mass diffusion, heat transport, macrosegregation and melt-undercooling occur. Several research workers have studied one or more of these effects separately. To answer important questions on solidification behavior, an overall approach interrelating the processes is necessaryAs a first step toward accomplishing the overall modeling, the freezing of a binary liquid metal is examined. The various stages during freezing of the alloy are critically described to build a continuum model for the entire process. Diffusive mixture theory is used to write the conservation equations for the liquid and the mushy zones. The concept of local thermodynamic equilibrium in the presence of curvature effects is used to restrict the number of degrees of freedom within the mushy zone. Constitutive equations relating flux quantities and affinities, the governing differential equations and boundary conditions are discussed briefly for the freezing process.IntroductionA solidification study encompasses such facets as solifidication time, microstructure, macrosegregation of the solute, shrinkage effects and soundness of the casting. Influence of one or more of the coupled heat and mass transfer phenomena such as local solute redistribution, thermosolutal convection, melt undercooling at dendrite tips and heat dissipation to the ambient have all been previously examined [1-3J. Several studies have examined the individual facets of alloy solidification as isolated processses. In fact, the transport processes occur simultaneously and a comprehensive model should include their inter-relationships. In particular, some of the existing studies of the mushy zone [4-6J do not emphasize thermodynamic completeness. This work represents an attempt to develop a thermodynamically consistent model of the entire solidification process on physical grounds."

Jan 1, 1986

By William A. Apel

Several different strains of bacteria have been shown capable of reducing hexavalent chromium, Cr(VI), to Cr(III), a less toxic, .. more readily recoverable form of Cr. This paper examined the Cr(VI) reduction efficacies of 3 different Cr(VI) reducing bacteria: Pseudomonas f1uorescens LB300., Pseudomonas aeruginosa PAOI, and Pseudomonas aeruginosa PAOI (pCROI) It was demonstrated that all three bacterial stratns reduced Cr(VI) primarily during their exponential growth phases while using glucose as their carbon and energy source. Significant differences in the three organisms' Cr(Vl) reduction capabilities depending on initial Cr(VI) concentrations were also demonstrated. P. aeruginosa PAOI showed superior Cr(VI) reducing capabilities over the. entire range of Cr(VI) concentrations tested while the Cr(VI) reduction capabilities of the other two strains were increasingly inhibited as Cr(VI) concentrations increased.

Jan 1, 1991

By Jiann-Yang Hwang, Ying Qin, Shu-Jing Zhu

Metallurgical Oil Sludge (MOS) is a byproduct created in the process of steelmaking. More than a million tons of MOS are generated each year throughout the world. The material contains hazardous components such as heavy metals and pathogenic organics, which can cause serious environmental problems and health issues. Landfill, combustion, and pyrolysis have been investigated for the disposal of MOS. However, these methods are unsatisfactory since they are unable to reach the clean environment goal. In this study, we investigate the possibility of using MOS as a reductant in a high temperature metallurgical process. The results are reported and discussed.

Jan 1, 2015

By Patrick R. Taylor

A novel method for Chemical Vapor Infiltration (CVI) using plasma technology is proposed, Plasma Enhanced CVI (PE-CVI). Due to the low rates at which CVI is currently performed, the use of plasma as a source of heat may be considered to be a faster and less expensive production method. Precursors fed in the hot region of the plasma gas are completely vaporized and forced by the same flow through a porous preform where it condenses as a new material. In this research, silica and methane where used as precursors to form SiC/on a / graphite felt (preform). To enhance the infiltration process, vacuum was used to increase the flow through the preform. Characterization of infiltrated graphite was perfontied using Scanning Electron Microscopy (SEM) and X-Ray Diffraction (XRD). A uniform distribution of Sic was observed along the felt with only twenty minutes of infiltration process, yielding a 178% increment in weight.

Jan 1, 1997

By Ephraim Jeya Kumari

The demand for the titanium dioxide pigments and the shortage of higher-grade titaniferous ores with low radioactivity and zircon sands worldwide has encouraged the development of new techniques for the beneficiation of lesser grade titaniferous ores. The inferior quality ores are invariably richer in radio-active and lanthanide oxides, which severely interfere with the fluidized bed chlorination reaction (FBCR), in which ultra-high purity titanium tetrachloride is distilled off for pigment manufacture. However the present beneficiation techniques require high quality ilmenite ores and are not suitable for upgrading lower grade ilmenite ores which do posses trace metals in the form of lanthanides and actinides as Al-phosphates and zirconium silicates, respectively. The presence of mineral hosts, zircon sand and monazite in ilmenite and anatase also increase in chlorine gas consumption in the FBCR and contribute to a larger volume of hazardous waste production, which must be neutralised at a significant cost before being disposed off safely. In view of the problems described for lanthanide (Ce, Nd etc) and actinide (Th, U) trace impurities in titaniferous ores, an alternative route, which is flexible and more accommodating for processing difficult ores, is discussed. In the new process, which may be used for richer grades of ores too, the ore is roasted in air with sodium carbonate below 950°C to promote the formation of water-soluble sodium ferrite and insoluble sodium titanate phases. In this investigation, the high-temperature roasting process and the ensuing hydrometallurgical leaching steps have been analysed in the context of selective separation of lanthanide and actinide minerals from the main titaniferous mineral structures. Evidences for the selective separation are presented based on the chemical (XRD, XRF, AA) and microstructural analysis (SEM, EDX, EPMA) of roasted mass and the leached product. The efficiency of selective separation is also reported based on the chemicals analysis and the particle size of the materials derived after leaching. The paper highlights the various thermodynamic aspects of reaction equilibrium in the Fe-Ti-O-Na system, and the effect of Eh-pH diagram in the determination of pH required for the better control of the removal of iron and sodium. Two different types of Ti ores, namely ilmenite and anatase, their crystal structure and the phase transformation will also be explained on the basis of wet chemical analysis, XRF, XRD, EPMA and SEM-EDX studies. The method developed examines the technological feasibility of the selective separation process.

Jan 1, 2006

By R. Nilsson

In the present work the sulphide capacities of Ca0-Mn0-Si0, ternary slags have been measured in the temperature range 1798 - 1873 K by equilibrating the slag with a gas-mixture containing CO, CO,, SO, and Ar. The results are compared with the data reported in literature. A theoretical model has been developed in the present work where the sulphide capacity is expressed as a function of the slag composition and temperature. The model enables the estimation of sulphide capacities of complex slags with a knowledge of the capacities of simpler systems.

Jan 1, 1994

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 Balasivanadha Prabhu, Prasad P. Shanmugasundaram, Narayani Narasimhan

"The grain refinement and mechanical properties of 6061 aluminium alloy produced by equal channel angular pressing (ECAP) have been analyzed in this present study. A innovative triple shear ECAP die was developed for the processing.It was observed that the grain refinement takes place for greater number of passes. It was also found that reducing the process temperature gives fine grain and high microhardness and hence improved propertiesIntroductionTechnological changes in manufacturing industries have depended heavily on development in materials processing and process technologies. Modem industries need high performance materials for severe service conditions. Hence, it is necessary to improve required material properties to achieve better performance and greater service life. As mechanical properties of the materials strong! y depend on grain size ( d) - Hall-Petch relationship [ 1-4], the ultrafine grained (UFG) materials offer superior mechanical properties based on the above relation.Synthesising massive nanocrystalline materials presents a challenge to basic research as well as to application-related processing efforts. Production of ultrafine gram microstructures in metals and alloys having different crystal structures but always an initially coarse microstructure using severe plastic deformation can significantly enhance the physical and mechanical properties of materials. Severe Plastic Deformation (SPD) is an efficient method to induce ultra fine grained structure in materials by deforming it to large strains. Traditional techniques for introducing deformation of higher strains, such as forging, extrusion, drawing or rolling do have the inevitable limitation on required equipments of exerting enough load or pressure to cause uniform nanometer level grain refinement."

Jan 1, 2011

By S. Abe

Various copper anodes to be electrorefined were subjected to a heat treatment comprising annealing at a temperature in the range of 700 °c to 1,000 °c followed by a slow cooling preferably on the order of about 150 °c, and using these heat treated anodes , a series of dissolution experiments were conducted under conventional electrorefining conditions. The results obtained have indicated that the above annealing/slow cooling process dramatically improves the dissolution activity regardless of the type of anodes. As an example, passivation times of l to 3 minutes in a standard test have been increased to more than 80 minutes by this innovated heat treatment. Other advantages sterning from the improved anodic activity include reduced electrical short circuiting which results in substantial labor effort in the tankhouse, reduced energy requirement, and reduced cost of processing anode slimes because the amount of anode slimes is reduced. In addition, this process gives rise to a dramatic change in the nature of anode slime layer formed in such a way that a comparable final cathode copper product can be achieved even from high-impurity copper starting material.

Jan 1, 1987

By F. Mucciardi

With the increasing trend to continuous smelting and converting, granulation of copper matte is gaining prominence as a means of decoupling the smelting and converting operations. Moreover, granulation is also being seen as a possible avenue to using higher grade oxygen in converters. By feeding cold solid matte, the oxygen concentration can be increased to compensate for the lower enthalpy feed. This leads to a higher grade of SO2 in the off gas and a lower total flow rate. Current granulation technology relies on the cooling of a falling matte film by water jets. This technology while effective has several drawbacks including those related to safety. Noranda and McGill University have developed a new process (patent pending) for solidifying copper matte (or slag). It overcomes many of the negatives of current technology. The system is based on an air cooled twin roll caster. This: new system uses no water and instead incorporates heat pipe technology to transfer the heat from the solidifying matte to the cooling air to produce a thin strip of 1 to 2 mm in thickness. Testing of a prototype unit demonstrated its viability. This paper describes this newly developed, twin roll casting system that is completely waterless. The advantages of this process as well as the findings from several tests are also detailed.

Jan 1, 1999

By Gabriel Riveros, Ariel Balocchi, Andrzej Warczok, Daniel Smith

Blister copper from converting of copper matte is processed by fire refining prior to electrorefining. The fire refining consists of two steps: copper oxidation with impurities slagging and copper reduction. The classical batch process is carried out in vascular or reverberatory furnaces called anode furnaces. A new process for continuous copper fire refining has been proposed. The copper flows through two reactors in cascade, where is oxidized and reduced. The flow of a liquid copper through a ceramic packed bed increases the surface area and the rate of oxidation as well as the rate of reduction in the packed bed of charcoal. Mathematical modelling allowed for the design of a laboratory scale demonstration installation and industrial-pilot installation in Hernan Videla Lira Smelter (Paipote). The results have demonstrated the process feasibility and flexibility in operation.

Jan 1, 2009

By Robert S. Gärtner

The selective aluminum extraction by 3 different calixarenes (p-tert-butyl-calix[4]arene-tetra¬2-acetic-acid-ethyl-ester, p-tert-butyl-calix[4]arene-tetra-2-acetic-acid and p-tert-butyl-calix-[4]arene-di-2-acetic-acid-ethyl-ester) from an industrial pickling bath solution was studied. The pickling bath solution contained hydrofluoric and phosphoric acid as its main components. The aluminum removal was not successful and also no significant extraction of trace metals present was observed.

Jan 1, 1999

By H. H. Law

Large amounts of waste material in the form of flue dust are generated in the operation of copper smelter furnaces. As a result of increasingly stringent disposal, it has become important to develop methods for treating such metallurgical wastes to extract metals and convert them into salable products. A two-step closed-loop hydrometallurgical process, has been developed: (1) extraction with sulfuric acid removes about 90% of zinc and decreases the dust volume by 50%; (2) extraction with hydrochloric acid dissolves the lead and further decrease the dust volume by 75%. A process scheme for generating salable products is proposed.

Jan 1, 1992

New method for processing of copper and nickel production feed has been developed and tested at pilot unit having 10 t/hr capacity. The process allows single-stage treatment of ore feed including that with high magnesium oxide content and resulting in the production of rich matte, high-grade matte, or moralised alloy for further leaching, as well as dump slag and off-gasses suitable for production of elemental sulphur, liquid sulphur dioxide, or sulphuric acid. Tests results and principal technical and economical parameters are presented.

Jan 1, 2006

By Lars O. Werme

Already the KBS Project proposed copper as a suitable material for encapsulation of spent nuclear fuel. The basis for this choice was the thermodynamic stability of copper in water and the fact that deep granitic groundwaters in Sweden are oxygen free. With a limited supply of oxidants, a copper canister would have the potential for a very long service life. The research and development work aiming at encapsulating nuclear fuel entered a new phase in 1993, when SKB launched its Encapsulation Plant Project. Within this project, SKB has: ? designed a facility for encapsulation of nuclear fuel, ? laid down the design premises for a canister for disposal of nuclear fuel, ? tested and developed fabrication methods for copper canisters, ? evaluated the long term chemical and mechanical behavior of the canister, ? made preliminary plans for a factory for the production of copper canister, ? constructed a canister laboratory for full scale testing of the key operations in an encapsulation plant. The conclusions of this project were that a canister consisting of an outer layer (50 mm) of copper over an insert of cast nodular iron would provide sufficient corrosion protection and would have sufficient mechanical strength. This canister can be produced by several methods of which forming from rolled plates, hot extrusion, and "pierce and draw" have been tested at full scale. The canister will be sealed by electron beam welding in the encapsulation plant, and the integrity of the weld will be verified by ultrasonic testing and' high-energy radiography. The final development work in this area will be performed in the canister laboratory.

Jan 1, 1999

By Carole Read

Hydrogen is under consideration by several countries for its potential as an energy carrier for transportation applications. In order to compete with vehicles in use today, hydrogen-powered vehicles will require a driving range of greater than 300-miles in order to meet customer needs and expectations. For the overall vehicular light-duty fleet, this dictates that a range of 5 to 13 kg of hydrogen be stored on-board (assuming a fuel cell power plant) within stringent system weight, volume, and cost constraints. Vehicular hydrogen storage thus constitutes a major scientific and technological challenge. To meet this challenge, the U.S. Department of Energy (DOE) initiated a ?National Hydrogen Storage Project? with roughly 40 universities, 15 companies and 10 federal laboratories, actively engaged in hydrogen storage research. Centers of Excellence in metal hydrides, chemical hydrides, and carbon-based materials have been established, as well as independent university and industry projects in the areas of new concepts/materials, hydrogen storage testing, and storage system analysis. Recent technical progress in each of these areas is discussed, as well as collaborative hydrogen storage activities under the recently established International Partnership for the Hydrogen Economy (IPHE).

Jan 1, 2006