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By Robert E. Brown

Magnesium recycling has been used to recover both new scrap and old scrap. It was used extensively in Germany during WWII to expand the magnesium supply. There were a large number of magnesium recyclers in the US who got their start smelting old scrap, old airplanes and old waste dumps from the WWII build up. As the world magnesium industry dwindled, only a few companies were left that did magnesium recycling as a primary business. The sand foundries tended to recycle of their production scrap in their melting furnaces. Even the original die casters tended to put scrap directly back into melting furnaces at the die casting machines. As high purity alloys were developed and the use of die castings in automotive work increased, the tendency was to let the magnesium recyclers convert the scrap back to high quality ingot. Automotive use has grown because of the low density of magnesium. This property is the one of the biggest problems to overcome in shipping scrap. Gates and runners from die casting are very irregular shapes and it is very hard to load a truck with enough material to get a low shipping cost per pound. Recent new equipment companies have developed magnesium equipment that is specifically designed to recycle, refine and cast secondary magnesium metal. These melt cells are supplied as integrated units to magnesium casting sites. The cost and effectiveness of this approach will be discussed.

Jan 1, 2000

By Orion Ciftja, Arjan Ciftja

"The directional solidification method is routinely used to produce polycrystalline silicon, an important material for the photovoltaic (PV) industry. The form of the solid-liquid interface during solidification has considerable influence on the material quality. The dissolved impurities and the solid inclusions above the solidification front affect the interface and may cause interface breakdown. We investigate the effects of pushing and engulfment of silicon carbide (SiC) particles by the solidification front during directional solidification of silicon. We employ a 12kg directional-crystallization furnace to cast the molten silicon. We use upgraded metallurgical grade silicon with low concentrations of metallic impurities (< 5ppm) and a high content of carbon (700 ppm) present as SiC particles. Samples from the cast polycrystalline silicon ingots are investigated by light microscope. The expected interaction of impurities with the solidification front is investigated theoretically using empirical models. The data obtained from the models are in good agreement with the experimental results.IntroductionDirectional solidification is a well-known method for producing multi-crystalline silicon for the PV industry. In this method a planar front, achieved during solidification, results in a clearly defined interface between the solid and the liquid phase. The solubility of major impurities is higher in the liquid than in the solid phase. Therefore, directional solidification will work as a purification process where the impurities are retained in the liquid phase [1]. Apart from the process of removing the dissolved elements in molten silicon, the directional solidification plays also another role. It will interact with the solid particles that may be present in the melt. When a liquid containing an insoluble particle is solidified, three distinct interaction phenomena are observed: engulfment of particles, continuous pushing, and entrapment [2]. The term “engulfment” is used to describe incorporation of a particle by a planar interface, and the term “entrapment” is used for particle incorporation by a cellular or dendritic interface (see Figure 1) [3]."

Jan 1, 2014

By Viviane Tavares de Moraes, Denise Crocce Romano Espinosa, Jorge Alberto Soares Tenorio, Adriana Johanny Murcia Santanilla

"Increasing volumes of solid waste are generated worldwide, due to the continuous technological advances, the electronic scrap is part of these waste, requiring the study of recycling processes to stimulate this activity or the reuse of its components. The separation of nickel from sulphate leach solution, which also containing iron, zinc and aluminium was carried out using bis-(2,4,4-trimethylpentyl) phosphinic acid (Cyanex 272) as extractant, in order to determinate the effects of pH and temperature. The number of stages required for extraction was also assessed. The results showed that the metal extraction increased with increasing pH. On the other hand, increasing temperature was not favorable for all metals. However, under conditions used in this paper the purification of solution containing nickel was possible.IntroductionIncrease in the demand of metals in the world for use in industry causes a great exploration of natural resources. One outcome of this is increased investigations for the recovery of metals from industrial wastes. Nickel is found in wastes, such as batteries and electric and electronic devices, this kind of waste becomes a significant source for metals recovery. Since nickel is also present in printed circuit boards, which are associated with electric and electronic equipment, it can be recovered from this kind of waste through different techniques. It is important to highlight that iron is generally associated with this scrap [1] and for its removal chemical precipitation is often used. On the other hand, the solvent extraction process is widely used for treatment of leach liquors, because it can be produce high purity solutions [2, 3]. This technique is based on the purification of solution using contact between a liquor leaching and the immiscible organic solution, which contains an extractant that promotes the desired metal transfer [4]."

Jan 1, 2012

By Jie E. Zhou, Yu U. Wang

"Development of crystallographic texture in polycrystals during templated grain growth process is studied by phase field modeling and computer simulation. To characterize the grain texture development, X-ray diffraction peak intensities are computed for the evolving grain structures as simulated by the phase field model, based on which Lotgering factor is further calculated as a quantitative measurement of uniaxial texturing. While the phase field modeling allows direct comparison between simulated grain structures and experimental microscopy observations, the computational diffraction allows convenient correlation between computer simulation and experimental X-ray diffraction characterization. The latter feature is especially desirable, since microscopy experiments normally require more efforts than X-ray diffraction, and diffraction is usually the preferred choice for material characterization.IntroductionThe properties of individual grains in polycrystals are generally anisotropic, while untextured polycrystalline materials with random grain orientations exhibit isotropic macroscopic properties that are independent of directions. In order to achieve anisotropic response in polycrystals, crystallographic texturing of grains is required [1]. Texture refers to the collective distribution of grain orientations towards preferred orientation in a polycrystal. To develop texture, special processing routes are needed, such as templated grain growth (TGG) for uniaxial texture [2]. TGG has been shown to provide uniaxial texture in wide variety of materials. For example, [001]-textured ferroelectric polycrystalline ceramics have been fabricated by TGG process, which exhibit enhanced piezoelectric properties [3]. Such highly textured polycrystalline materials offer better cost-performance ratio than single crystals. Thus, texture development in polycrystals is of technological importance for material applications.In this computational work, grain texture development in polycrystals during TGG process is studied. Grain structure evolution is simulated by phase field model, X-ray diffraction peak intensities for the evolving grain structures are computed, and Lotgering factor is calculated to quantitatively measure the development of uniaxial texturing. The phase field modeling allows direct comparison between simulated grain structures and experimental microscopy observations using imaging techniques such as scanning electron microscopy or optical microscopy. The computational diffraction allows convenient correlation between computer simulation and experimental X-ray diffraction characterization. The latter feature is especially desirable, because microscopy experiments normally require more efforts than X-ray diffraction, thus diffraction is usually the preferred choice for material characterization."

Jan 1, 2014

By M. F. El-Demerdash

The activity distribution diagrams for different species in aqueous systems are developed. Computational method may be considered as an extension of the Activity-Term method introduced by the authors to construct EH-pH diagrams. In the Activity-Term method, all activities of different species are evaluated before deciding the most stable one. In the present study, a factor is assumed to allow for the conservation of the element. At any point, the total concentration of all species should contain only the input m moles of the element (elements) considered. This approach is applied to Zn-, 5-, and Zn-S-H2O and activity distribution diagrams are plotted as a function of pH, at different potential levels and at different temperatures.

Jan 1, 1990

By Jiang Fan, Wang Haigang

"The three-dimensional complex multiphase turbulent flow in U-beam separators was simulated using the Reynolds stress equation models (RSM). To account for the effect of the stochastic characteristic of the instantaneous gas velocity on the particles, the improved Lagrangian stochastic model based on the Reynolds stress model for gas phase was adopted, which attributed to the successful prediction of the turbulence anisotropy and particle crossing trajectories effects. The interaction between the particles was also considered using the HardSphere model. To treat the particle-wall collision, the influence of the roughness of the wall on the motion of the solid particles was taken into consideration by imposing random collision angles. The result from this study not only shows the dynamic characteristics of the multiphase flow- in the separators, but also gives the relationship among the efficiency, structure and pressure losses of the separator.IntroductionCirculating fluidized bed (CFB) combustion is one of the most promising clean coal techniques. A main feature of CFB boilers is the un-delayed recycle of solid, coal and sorbant particulate, in an external loop. Separator, which is required to separate the solid particle from the flue-gas leaving the reactor of CFB, plays an importance role in the external solids recycle loop. It affects the combustion of CFB system greatly. Presently cyclone is the most commonly used as separators for CFB system and other chemical industrial processes. It provides high level of separation for CFB system for fine particles. However it suffers from some inherent disadvantages. It's volume and size is huge. Moreover, it is difficult to design and install when the CFB workload rises. The application of U-beam separators instead of hot cyclone separators in CFB boilers has many advantages. Publications indicate proposals or successful use of Ubeam separators in Swedenr11, USA 21, Russia r3land China [4]• But it is not possible to find results in the literature of detailed investigations of this new. type of separators or recommendations on the choice and calculation of an optimal design. For this reason, numerical simulation for the three-dimensional gas-particle two-phase flows with several rows of vertical U-beam elements, local in the chess order and blocking a way of outgoing from a CFB boilers dusted gases was carried out in this study."

Jan 1, 2004

By Kai Kang, Jun Bao, Shouping Liu, Xiao Sun

Powder characteristics have a significant influence on selective laser melting (SLM) process. In this research, particle size, surface contour and the microstructure of IN718 powder used in SLM were tested, and the physical and chemical changes during heating process of the powder were investigated as well. The shape characteristic and fluid properties of IN718 powder were defined and measured. It is shows that most particles of IN718 powder exhibited nearly spherical shapes, and the particle size is about 22.95μm. On this basis, IN718 sample was fabricated by SLM process using the powder and the microstructure of the fabricated sample was investigated. The results indicated that the sample has a dense microstructure, no macro-defects but a few micropores and porosity. Compared with the powder, there was no new phase formed in the sample and melting point of the sample was little less than that of the powder.

Jan 1, 2015

By Serdar Aksu, Fiona M. Doyle

"CMP will be an essential process in the production of integrated circuits containing copper interconnects. This study aims to improve our mechanistic understanding of the role that organic chelating agents might play in the reactive slurries used in copper CMP. Copper dissolution behavior in EDTA arid glycine was first examined by producing potential-pH diagrams for the copper-water-EDTA and copper-water-glycine 'systems. The results of potentiodynamic polarization experiments were then considered in light of these diagrams. . In-situ polarization experiments were conducted to gain insight into the electrochemistry of copper during dynamic polishing in slurries prepared from EDT A and glycine.IntroductionCopper has recently started to replace aluminum as the interconnect metal in integrated circuits. Copper interconnection offers faster and more reliable integrated circuits due to its higher electrical conductivity and superior electromigration resistance (1). The damascene method is used to form multilevel interconnects in the manufacture of integrated circuit devices with copper metallization (2, 3). Copper is deposited by CVD or electroplating into vias and trenches etched in the interlayer dielectric (IDL), over a diffusion barrier usually made from titanium, tantalum or their nitrides. Chemical mechanical planarization (CMP) then prepares the wafer for the next deposition step, by removing excess copper and planarizing the surface. During CMP, the wafer is rotated and pressed against a rotating platen covered with a polishing pad. Chemically active slurries containing submicron size abrasive particles (Si02, Al20 3, ceria, diamond, etc.) are applied. Both the mechanical action of the abrasive particles and the chemical action of slurry constituents remove material from the wafer surface. Planarization results because material is removed faster from protruding regions on the surface than from recessed regions. Since CMP can globally planarize .the entire wafer, it has become one of the key technologies for producing integrated circuits with copper metallization."

Jan 1, 2000

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

By Ann M. Hagni

Flash reduction of zinc oxides is an alternative, environmentally safe method to leaching and electrowinning for zinc recovery. Zinc and lead are volatilized in a flash reactor, a non-hazardous residue is generated, and the fuel source is inexpensive coal in the flash reduction process. Results from experimental laboratory tests yielded low zinc recovery for this process. Mineralogical and textural characterization of the residues from the flash reduction tests for different feed materials and temperatures were conducted to determine the cause for the low zinc recovery. Reflected light microscopy, cathodoluminescence microscopy, scanning electron microscopy-energy dispersive spectroscopy, and X-ray diffraction were utilized in this applied mineralogical research. The original zinc calcine is composed primarily of fine-grained, iron-bearing zincite particles, 25-40 um in diameter, in a porous texture. Pellets processed at 1150°C were found to produce reaction rims of franklinite-magnetite-jacobsite solid solution that are 125-200 um thick and surround cores of unreacted iron-bearing zincite in a Zn-Fe-Si-Ca glass matrix. The reaction rims have subsequently oxidized to form an outer 10 ~m thick rim of hematite. Slags from calcines processed at 1275°C are primarily triangular particles with porous centers, cenospheres, and spheres of iron-bearing zincite, in addition to rectangular particles composed of non-porous franklinite-magnetite solid solution cores with iron-bearing zincite rims. Slag particles from calcine processed at 1200°C are predominantly 100-250 ~m triangular-shaped, spheres, and cenospheres containing fine-grained franklinite and franklinite-magnetite solid solution in an iron-bearing zincite matrix. Slag from calcine processed at 1300°C are also predominantly 1 00-250 um triangular-shaped, spheres, and cenospheres but contain coarser-grained iron-bearing zincite. The zincite in the penets and the slags typically contain 10-20% iron. Based upon these mineralogical observations, it is concluded that the significant amounts of iron in the zincite prevent volatilization of the zinc in the flash reduction process.

Jan 1, 1995

By Hiroshi Nakajima, Kotobu Nagai, Toshihiro Hanamura

"Low carbon ferritic steel bars with ultra-fine grain structure was developed through a warm rolling for the first time by the present authors. They show better low temperature toughness than conventionally hot-rolled plates. Hence, the brittle fracture surfaces in Charpy tests were examined in terms of the effective grain size of fracture, compared with those of conventional QT steels. The ductile-to-brittle transition temperatures were in good accordance with those for the QT steels if referred to the effective grain size of fracture: · However, the size was a few times that of the ferrite grain. This means the grain refining is not yet fully utilized from the viewpoint of low temperature toughness. The anisotropy of· the impact properties and the annealing effect of highly dislocated structure on the toughness are also discussed in the present paper.IntroductionFor structural materials, both high strength and good toughness are required. Well-known approaches for obtaining better toughness for steels are as follows:1) Grain refining2) Addition of Ni3) Thin plate effect by cracking parallel to the rolling direction prior to crack propagation4) Contribution of metastable austenite.Among them, only the grain refining can raise the strength and improve the toughness. And it is well known that the finer the ferrite grain size, the lower the ductile-to-brittle transition temperature. For example, in the case of 0.11 carbon steel, the transition temperature decreases linearly to in d 1/2 [1 ]. However, these have been told in the regime of coarse grain size that is larger than 10 µm in diameter. There ~as .been no study dealing with the low temperature toughness in the regime of ultra-fine grain size with a diameter in the order of 1 µm."

Jan 1, 2000

By Huaming Yang

The vanadium-doped SnO2 nanoparticle was synthesized by the co-precipitation reaction and subsequent calcination from the vanadium(III) chloride and tin(IV) chloride. The crystal size, pore size distribution, micrograph and properties of the nanocrystalline powders were examined by differential thermal analysis (DTA), thermogravimetric analysis (TGA), X-ray diffraction (XRD), desorption isotherm (Barrett-Joyner-Halenda method) and transmission electron microscopy(TEM). Thermal treatment of the precipitate powder at 600°C led to the formation of V -SnO2 nanoparticle of -10mm in crystal size. Most of the pores in the nanoparticle are about 5~15nm in diameter. Effect of doped vanadium on the crystal size of the nanopartic1e was discussed.

Jan 1, 2003

By Ronald H. Church

Dewatering of mine waste slurries has been successfully accomplished by the proper use of polymers in flocculating the fine particulate matter suspended in the slurry streams. Conventional treatment of fine waste slurries usually involves some form of impoundment treatment or storage. These impoundments present unique environmental problems. When filled to capacity, the impoundments are usually unloaded with a dragline and transported to a separate disposal area. The U.S. Bureau of Mines has conducted dewatering studies utilizing polymer technology in combination with a mobile field test unit designed by the Bureau. The purpose of these studies was to determine if the fine waste slurry from the mining operation could be successfully dewatered. Results of the investigation have shown that the slurry can be dewatered successfully. The dewatered products obtained from the tests ranged from 45 to 50pct solids. This material continued to dewater, approaching 70 pct solids within 24 h, and could be easily handled using conventional transportation equipment including conveyor belts.

Jan 1, 1994

By L. Katgerman, E. N. Straatsma, Suyitno

"Single-roll strip casting process is studied using computational fluid dynamics which takes into account fluid flow, heat transfer and solidification. The computational model is based on the conservation Jaws of momentum, energy and continuity. Correlation of strip thickness, solidification zone length, and puddle shape on single-roll strip casting of Al-1 %Mn is explored. Feeding pressure and roll speed are investigated. The results show that the··strip thickness slightly increases with pressure, similarly the length of solidification zone. The variations of strip thickness and solidification zone length with roll speed show a sharp decline for strip thickness and slight decline for the length of solidification zone with increasing roll speed. The constraint and free-jet flow have different feature in term of flow field. Severe turbulence is observed on the free-jet flow.IntroductionThe near-net shape casting of strip metals is a demand nowadays. The demand is particularly stimulated by the challenge to become more competitive through enhanced performance. The improvement in the existing processes and new innovative technologies are introduced by the metal industry to gain better product quality, more efficiency in energy consumption, low throughput, yield and operating costs [1-3].There are many advantages that can be obtained by the direct casting of strip. The most prominence is the elimination of hot rolling. Beside that the high rate of heat extraction associated with strip casting offers the possibility of a finer, Jess segregated cast structure. The microstructure will result in the improvement of mechanical properties compared to conventional material, or alternatively the opportunity of using grades of metal outside the normal range for continuous casting.The concept of single-roll strip casting has been difficult to commercialize, because of the complex interactions between fluid flow, solidification, shrinkage, and stress, which lead to serious quality problems. Besides that, the quality and the thickness of the strip are affected by the thermal properties of the strip, roll cooling conditions, roll geometry, and other process parameters. To understand how these parameters affect the strip formation, some researchers have modeled the process [4]."

Jan 1, 2004

By Claude Lorenson

"The Spyrometer™ imaging pyrometer brings new dimension of imaging capabilities to temperature measurement technology by combining a high temperature video camera with scanning optical pyrometry. This gives the operators the ability to observe process conditions while measuring the temperature of virtually any object or region in the field of view. Since the lens tube of the camera can be air or water cooled, it is possible to see inside furnaces giving a very good view of many different types of metallurgical processes. Specific benefits in process knowledge and maintenance tasks for furnaces in different types of metal industries are discussed.1-Principles of Imaging PyrometryLens tube, camera and processorImaging pyrometry is the combination of video imaging and computer-driven pyrometry that measures the temperature of certain zones (selected by the operator) within the image viewed on the monitor screen. To obtain a detailed image of the metallurgical process under observance, it is necessary to place the optical objective of the camera close to the process. The Spyrometer™ (which is Quadtek's tradename for its imaging pyrometer) objective is housed in a lens tube that is cooled and permits insertion inside the vessel of interest. The length of the lens tube is chosen on the basis of making sure that the tip of the tube is just beyond the refractories lining the inside of the furnace. In most pyrometallurgical processes, we have found that the most reliable system set-up uses a water cooled shroud to cool the lens tube optics. A sapphire window provides maximum protection from the environment. Even in the case of the water cooled version, there is an air purge for the lens that keeps the objective clean and protects against hot metal splashes."

Jan 1, 1997

By Moelans. N.

A method using an ex-situ electrochemical measurement device was developed to determine the oxygen potential of non-ferrous metallurgical slags. The electrochemical cell consists of the molten slag sample, an inert Ir electrode, a stabilized Zr02 solid electrolyte and a NilNiO reference electrode. Different slags from non-ferrous pyrometallurgical processes were analysed at I 100 and 1200 °C and pO2values between 10-3 and 10-12 bar were obtained. The measurements were evaluated with thermodynamic calculations and using processing considerations. It was found that the reproducibility and stability of the measurement was significantly improved by shielding the molten slag from the atmosphere by a thin layer of carbon, especially for slags with a low oxygen potential.

Jan 1, 2003

By Debbie Marshall

Process water is an important consideration in the development of a nickel laterite project. Depending on the location of the ore body, sufficient fresh water may not be available and it may be necessary to use seawater (or saline groundwater) for ore preparation. This introduces various species, which have major effects on materials of construction and leaching chemistry. This paper summarizes batch testwork completed at the Falconbridge Technology Center. The leaching behaviour of eleven different laterite ore samples were compared using seawater and fresh water. For brevity, six of the eleven samples are reported here-the other five samples showed similar results. Each ore type was leached under identical conditions in both freshwater and seawater and the leaching chemistry compared. The batch test results were confirmed in a continuous pilot plant, and leach kinetics for the two systems were compared. Keywords: high pressure acid leaching, laterites

Jan 1, 2004

By D. T. Smith, L. M. Hsiung, J. J. Schmitt, J. W. Golz, R. L. Lankey, H. N. G. Wadley, J. Z. Zhang, B. L. Halpern

"The microstructure and mechanical properties of Al/AI2O 3 metal-oxide nanolaminates fabricated by' a novel Jet Vapor Deposition (JVD) process at substrate temperatures of ~25° and -250°C have been investigated using transmission electron microscopy (TEM) and nanoindentation methods. The thickness of the oxide layer was held constant between 2 and 5 nm, whilst the Al layer thickness was systematically varied from -3 to -50 nm. Continuity of the Al layers was significantly improved when the nanolaminates were deposited at an elevated substrate temperature (-250°C). The yield strength of the nanolamintes with Al layers greater than -25 nm follows a Hall-Petch type relationship, whereas that of the nanolaminates with Al layers less than -25 nm is better predicted by a Koehler-Lehoczky strengthening model. IntroductionAluminum-aluminum oxide (presumably A12O3) nanolaminates have been recently fabricated using a novel Jet Vapor Deposition (ND) process developed and patented by Jet Process Corporation [1-4]. ND uses sonic, high purity helium (He) gas jets to entrain atomically dispersed vapor and deposit films. It is of interest here because it can deposit multilayered structures (laminates) inexpensively at high rates. Materials with a thin, multilayer structure are of interest because they potentially offer novel mechanical and physical properties [5]. Koehler in 1970 used an image force model to investigate the strength of laminated materials and proposed the use of alternating layers of high and low shear modulus metals to produce high strength composite materials [6]. He predicted that dislocations would have to overcome a large repulsive image force in order to move from metal layer B of lower shear modulus (uB) into metal layer A of higher shear modulus (uA)' The image force (F) is given by the relation:"

Jan 1, 1994

By Gabriel Plascencia

Copper was oxidized in the temperature range from 300 to 1000 °C under different pressures of oxygen, In the range from 300 to 500 °C, copper oxidizes following the logarithmic rate law; while in the range from 600 to 1000°C oxidation follows the parabolic rate law. Transition from logarithmic to parabolic growth occurs at about 525°C. X-ray diffraction was performed on oxide scales to account for the CuO/Cu2O ratio at different temperatures. Activation energies found in this work are in good agreement with reported values.

Jan 1, 2003

By A. Valenzuela

During the last years, Chile has been the largest copper producer, either as concentrates or cathodes. Copper obtained via pyrometallurgy is produced by seven smelters, which have carried out modernization plans to increase smelting capacity or to achieve environmental regulations established in the Chilean legislation. Thus, the present work updates technological innovations in smelters, environmental regulations and presents solutions for SO2 handling, particulate matter and arsenic. Also, the authors emphasize the important role of CODELCO Chile, the most important state-owned copper company, in developing technologies such as EI Teniente Converter and EI Teniente Slag Cleaning Furnace,

Jan 1, 2003