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By Sergey Komarov, Manuela Diaz, Sano. Masamichi

"Mixing time, bubble behavior and absorption rate of gas injected into a liquid bath through rotary L-shaped lances have been studied by cold models with an effort to improve refining characteristics of metallurgical processes. Two kinds of the rotary lances were tested, namely the single-hole lance and the multi-hole lance. The effects of gas flow rate, bath depth and rotation speed were examined.It is found that when gas is injected through the rotary lances, the mixing intensity and the gas absorption rate are larger than that for the gas injection through stationary lances. The effect of rotation speed decreases as the bath depth and the gas flow rate increase.The multi-hole lance produces much smaller bubbles, which lead to an increase in the volumetric mass transfer coefficient by 3-4 times as compared with the single-hole lance. However, the effect of rotation speed is smaller for the multi-hole lance. The obtained results are explained in terms of the bubble coalescence and fragmentation, the rate of which depends on the departure bubble size and the power supplied to the liquid bath.IntroductionIn recent years, there has been a growing interest in the development of gas injector for metallurgical processes. The majority of the previous work was focused on modification to the injector design to improve mixing and to increase the of chemical reaction rate. These two goals can not be necessarily achieved by the same way. Bottom nozzles and stationary immersed top lances, which have been widely applied to steelmaking processes, are effective for the bath mixing, but have a limit to decrease in the bubble size. This results from a vigorous coalescence occurring between the bubbles when they rise in the molten bath as a bubble swarm.One of the ways to ensure the small bubble size and the effective bath stirring is the gas purging through rotary injectors. A number of studies have been undertaken to improve the refining characteristics by using rotary injectors. All of them are related to aluminum refining. The SNIF equipment (The Spinning Nozzle Inert Flotation) has significantly improved the quality of aluminum products at National Luxemburg Aluminum [1]. Rotary injectors made in the form of a disc have been applied to the Alcoa 622 [2] and the GBF processes [3]. A study of the gas injection by a rotary impeller has been carried out by C. Leroy and G. Pignacelt [4]. All researchers note the significant improvement in removal of sodium, calcium, hydrogen and non-metallic inclusion."

Jan 1, 1996

By C. D. Adams, R. T. Tuenge, C. N. King, J. A. Samuels, B. F. Espinoza, R. C. Dye, C. F. Schaus, D. C. Smith, N. M. Peachey

"Recently, doped calcium thiogallate (CaGa2S4) phosphors have been investigated for use in electroluminescent flat panel displays. The current technique used for the deposition of thin film calcium thiogallate is sputtering. Unfortunately, this requires a high temperature annealing process to provide the desired crystallinity of the phosphor. Recent efforts have focused on the possible use of metal-organic chemical vapor deposition (MOCVD) to produce the CaGa2S4 layer. The use of MOCVD provides an attractive alternative to sputtering since it does not require heating above the strain point temperatures of the glass substrates used for the display panels. To accomplish this, the deposition of both Ga2S3 and CaS is investigated as these compounds are intermediate steps in the development of the phosphor deposition. Uniform, crystalline films of both Ga2S3 and CaS were deposited and the process shows promise for successful deposition of the CaGa2S4 phosphor.IntroductionThe lack of a satisfactory blue phosphor having sufficiently high luminances at low power has hampered the development of high resolution flat panel displays. Recently, a new series of blue emitting materials have been investigated for use in thin film electroluminescent (TFEL) devices. l ,2,3 These phosphors are based on a series of alkaline earth thiogallate host materials of the form MGa2S4:RE where M can be either calcium, strontium, zinc, or barium and RE is a rare earth ion. A full-color VGA TFEL panel using CaGa2S4:Ce as the blue phosphor has recently been fabricated and tested. l This FPD provided a luminance of 10 cdlm2 at 60 Hz. The enhanced blue in this display allowed its color capabilities to approach those of the conventional CRT.The method of depositing the phosphor onto the display panels in these test devices has been sputtering. Unfortunately the phosphor as deposited does not possess the crystalline properties required for optimum luminance. The crystalline structure is achieved by subsequent annealing of the deposited material. Although this post deposition anneal provides the desired crystal structure, it occurs above the strain point temperature of ordinary glass. Consequently, the implementation of these phosphors requires the use of glasses capable of withstanding high temperatures, adding to the cost of the final display unit."

Jan 1, 1994

By N. Ono, H. Fujiwara, S. Otsuka-Yao-Matsuo, T. Omata

"The electrical conductivity and the oxygen release and uptake of sintered indium tin oxide (ITO) upon heating and cooling under the condition that P(O2)/P*=4.9X10-4 (P* = atmospheric pressure), :when P(O2) was approximately 50Pa, were simultaneously measured by using a closed-system oxygen-gas analyzer. A large increasing in -the electrical conductivity - upon the· oxygen release detected in 1130<T<1273K was observed. Quantitative relationship between the number of oxygen atom released from ITO and the conduction electron density in ITO was studied. The release of one oxygen atom agreed with the generation of two conduction electrons, i.e., the efficiency-carrier-generation for the oxygen release from the ITO was almost one. The oxygen atom released must be originally at the quasi-anion site in the C-type rare-earth lattice, i.e., the 16c site in the space group of Ia3, as an interstitial excess oxygen, Oi"". It was concluded that the mechanism of conduction carrier generation and compensation upon SnO2 doping into In2O3 can be expressed by the defect equation, 2SnO2-2Sn1n +2(1-z)e'+zOi""+3O0 x+(l-z)/2O2, and that the oxygen release bringing the increase in the electrical · conductivity can be expressed by the equation, Oi""-1/2O2+2e'.IntroductionThin films of SnO2-doped In2O 3 (generally designated as ITO, for indium tin oxide), which have high optical transparency for visible light and high electrical conductivity, have been used as transparent electrodes for liquid crystal and electrochromic displays. It is well known that the electrical conductivity of ITO depends on the content of SnOi-dopant and oxygen. However, a reliable relationship between electrical conductivity and the absolute oxygen content in ITO has yet to be reported. The elucidation of such a relationship is one of the important clues for realizing extremely highly conductive ITO electrodes."

Jan 1, 2000

This report presents overview of the authors&apos; results of thermodynamical investigation of some important metallurgical processes and phenomena. Among them: carbo thermal reduction of silica, and boron oxide, silicon carbide obtaining from different precursors, investigations on copper and manganese ores processing, investigations on pollution from different sources. Special attention is paid-to thermodynamical approach to investigation and estimation of multi component multi element compositions stability, developed by the authors. Also are discussed some auxiliary but&apos; important for the thermodynamical investigations issues.

Jan 1, 1997

By Yong Kuk Park

The horizontal cold chamber die casting process can produce a wide range of near-net shape, non-ferrous castings with small dimensional variation, excellent surface finish and very complex geometries. However, top quality die castings can be achieved only when optimal performance of the cold chamber and plunger is maintained during the molten metal injection phase of the process. Cold chambers (shot sleeves) are known to deteriorate fast and sometimes fail catastrophically because of poor design. Catastrophic fracture and wear due to deformation are leading causes to degrade quality, increase downtime and thereby decrease productivity and profitability. Therefore, a systematic approach to minimize irregular and adverse conditions which prevent an intended injection profile, is highly desirable. To eliminate them, design criteria for shot sleeves were developed using analytical tools and available experimental data. The correlation between design and mechanical failures of shot sleeves was shown by the data obtained from the die casting industry. Also, the relationship between die casting process parameters and deterioration/ failure mechanisms were carefully evaluated.

Jan 1, 1996

By L. Petitnicolas

The experimental study of nitrogen absorption and its removal from a liquid Ni-20%Cr alloy at 1873 K has been undertaken, using an experimental, apparatus based on the Sieverts technique in order to determine the solubility of nitrogen in the alloy. as well as the kinetics of nitrogen transfer across the gas/melt interface. Experiments show that nitrogen solute equilibrium content can be calculated using the Sievens law. Measurements point out the nitrogen absorption reaction rate to be well described by first order kinetics, whereas experiments on nitrogen removal reveal that the rate is better expressed using a second order equation.

Jan 1, 1996

By M. Patel, A. W. Piper, R. A. Forsdick

"Lead bullion is refined in kettles to remove the contained impurities such as copper, antimony, silver and bismuth. These impurities are removed sequentially by the addition of one, or more, reagents to the bath. Impurity elements react selectively with the reagents to form a dross layer on the surface that is subsequently removed for further processing. Mixing the lead bath using specific impeller designs, which form a vortex to ensure that good contact takes place, carries out the reactions. It is important that the mixing is controlled to achieve the optimum bath conditions and hence good dross grades.This paper presents initial modelling work on the kettle refining process using both physical modelling (Water Models) and mathematical modelling (Computational Fluid Dynamics - CFD). Comparisons between measured plant data and simulation results are given.IntroductionThe refining of lead bullion takes place in hemispherical kettles of varying sizes. It is normal practice to remove the impurity elements sequentially, by the addition of reagents, which selectively react with the impurity element. The impurity element forms a dross layer on the surface, which can be removed for subsequent processing at the end of the reaction period.All the refining stages in the production of lead and lead alloys involve mixing the lead bath, although different conditions are required for each stage. At Britannia Refined Metals mixing is achieved using either 3 or 4 angled or flat blade impellers, which generate a vortex in the central region of the kettle. However, throughout the industry a wide range of mixer types are used which are all trying to achieve the same result."

Jan 1, 1999

By Dorothée Proffit

Characterization of solids containing cyanides is carried out according to recommendations and standard guidelines. Most of these procedures are based on the analysis of leachates collected either on site or after leaching in the laboratory of samples. Unfortunately, these sole results are often insufficient to identify the source of the pollution. To provide &apos;a more complete characterization of polluted solids, optical and electron microscopy, XRD, Mossbauer spectroscopy, and transmission infrared spectroscopy were combined to analyze leachates and raw or ground samples. This combination of techniques allows the determination of the kind of cyanoferrate complexes are present in the solid state, different from insoluble Prussian Blue, since they do not have the same extraction&apos; behavior. The use of all these techniques to characterize solid samples combined ,to the usual analysis of solutions gives a better understanding of &apos; the cyanide behavior.

Jan 1, 1998

By B. Zeytuncu, O. Yucel, O. H. Celik, M. H. Morcali

"The Taguchi method was used as the experimental design to determine the optimum conditions of cementation behavior of the ruthenium chloride solution. Cementation was carried out using metallic zinc powder. The experimental conditions were studied in the range of 25-45°C for reaction temperature (A), 30--60 min for reaction time (B), 0.5-1.5 for pH of solution (C), and 30--50 mg for zinc powder (D). Experimental parameters and their levels were determined in the light of preliminary tests. Orthogonal array (OA) L9(34) consisting of four parameters each with three levels, was chosen. The optimal conditions found for ruthenium, such as a reaction temperature, reaction time, pH of the solution and mass of zinc, are respectively: 45°C, 45 min, 1.5 and 50 mg. Under these conditions, the ruthenium cementation efficiency obtained by theoretically and experimentally was in good agreement, which were 99.8% and 99.7% respectively."

Jan 1, 2013

By He Jing, Wang Changhong, Chen Yongming, Wu Yanzeng, Yang Xiyun, Tang Chaobo, Yang Shenghai

Pitting of Hf in Et4NBr t-butanol and acetonitrile (ACN) solutions was studied by means of cyclic voltammetry, potentiodynamic anodic polarization,galvanostatic, potentiostatic and impedance techniques. The potentiodynamic anodic polarization curves did not exhibit an active dissolution region near corrosion potential due to the presence of an oxide film on the electrode surface, which was followed by pitting corrosion resulting from the passivity breakdown by the aggressive attack of bromide (Br−) ion. The pitting potential (Epit) increased with increasing potential scanning rate but decreased with increasing temperature and Br− concentration. Cyclic voltammetry and galvanostatic measurements allowed the pitting potential (Epit) and the repassivation potential (Ep) to be determined. Analysis of the potential/time transients revealed that the applied anodic current density had a significant influence on the values of Epit. On the other hand, the Ep values were independent on the applied current density. The current/time transients indicated that the incubation time (ti) for passivity breakdown decreased slightly with increasing potential and solution temperature. The impedance spectra showed that the resistance of passive layer decreased with increasing potential.

Mar 1, 2017

By Laurentiu Nastac, Ruslan Mudryy

"This paper investigates the solidification of cast energetic materials. An active cooling and heating (ACH) technology and a mechanical vibration (MV) technology were applied to achieve unidirectional solidification during casting and to reduce cracks, gas pores, and shrinkage defects. The design parameters of these technologies were developed via Computational Fluid Dynamics (CFD) modeling and thermal stress analysis. Concerning the ACH technology, the number of cooling/heating sections and their temperature profiles and time sequences were optimized based on the thermo-physical properties of the energetic material as well as the riser and mold diameter, thickness and type. The ACH technology will also decrease the thermal stresses during casting of energetic materials and therefore minimize the formation of potential cracks that may form during the casting process. The MV technology will help to remove air entrapped during pouring process and decrease the detrimental gap size between the projectile and the solidified energetic material.IntroductionCasting processes are widely employed in the manufacture of products with intricate shapes and, in particular, in applications where the material of the final product is sensitive to machining. It is especially useful in processing of energetic materials. The cooling conditions applied in the casting process can affect the quality of the final cast in terms of void formation, residual stress distributions, and mold separation. Substantial shrinkage is also observed due to the density change upon solidification [1-3]. Residual stresses are known to be closely related to the formation of cold cracks and hot tears during casting. The formation of a gap between the mold and the cast material is of critical importance due to its deleterious effect on heat removal and on crack formation. In the casting of energetic materials all these defects can significantly impair the detonation velocity, Gurney energy, and insensitive munitions characteristics of the formulation, and lead to catastrophic accidents in explosives handling [ 4-5]. Imposition of carefully controlled cooling condition is thus critical in optimizing the cast quality that could help avoid such destructive effects."

Jan 1, 2013

By M. Kawakami

In relation to the designing of a new-type blast furnace, the reaction of carbonaceous materials with CO2 is expected to occur at as low temperature as possible. In order to get a highly reaetive carbonaceous material at low temperature, the reaction kinetics was investigated by measuring such quantities as the reaction rate from weight loss, the amount of CO adsorption and specific surface area by BET method. The reaction rates were large in the order of the Bintyo char, metallurgical coke, graphite and glassy carbon. If the rate was converted to the rate per unit area, however, those of the Bintyo char was smaller than that of graphite. Thus, it is suggested that the rate of the Bintyo char is influenced by the pore diffusion of CO2. The rate had a positive relation with the amount of CO adsorption, showing that the rate determining step would be the desorption of CO from the active side on the surface. The rate independent of surface area was derived, combining all the obtained data.

Jan 1, 2003

By G. Djambazov, D. Shevchenko, D. Burnard, V. Bojarevics, K. A. Pericleous, W. Griffiths

Contactless ultrasound treatment can be useful for high-temperature or reactive alloys in the liquid state, where contact with an immersed vibrating probe is undesirable. The alternating component of the Lorentz force can generate sound pressure levels leading to cavitation of gas bubbles in the melt, through acoustic resonance. Resonance is a function of the speed of sound in the liquid, the shape of the volume containing it and surrounding boundary conditions. Induction forces applied to a crucible lead to bulk stirring and in general deform the free surface, whose precise shape may influence the resonance conditions. This effect is investigated here b ymulti-physics computer modelling. Calculated results for aluminium melts are compared with experimental data and conclusions are drawn as to the sensitivity to process parameters and the reliability of this type of ultrasound metal processing.

Mar 1, 2017

By Carl C. Nesbitt

A study was conducted to investigate the claims of early observers who noted an increase in the rate of gold dissolution when chlorine was chemically produced in the leach vessel compared to sparging with chlorine gas. This "nascent" chlorine was presumed to be an active intermediate in the production of chlorine (C1,l from chloride ions. The study used UV light to produce an activated chlorine atom intended to recreate the observed increase in the gold dissolution rate. Although no change in the kinetic rate was observed, the reaction mechanism by which chlorine reacts with particulate gold was instead determined. Various concentrations of multivalent cationic chloride salts were added to the leach solution to demonstrate that the increased dissolution rate was due to the increased concentration of the chloride ion and ionic strength of the solution.

Jan 1, 1992

By K. Itagaki, H. Henao

"The experimental study on the phase equilibrium and distribution of minor elements such as chromium and copper between magnesia saturated FeOx-MgO-SiO2 slag and Fe-Ni alloy were carried out under controlled oxygen partial pressure between 10-6-5 and 10-10 using CO and CO2 mixed gas at 1773 and 1873 K.The effect of slag additives such as lime (CaO/SiO2 molar ratio: 1) and alumina (AlO1.5/SiO2 molar ratio: 0.1) on the distribution behavior of the minor elements was also investigated.The value of distribution ratio for chromium, defined by (%Cr in slag)/[%Cr in alloy], is larger than 70 at the pO2 region conducted in the present study for the MgO saturated FeOx-MgO-SiO2 slag at 1773K. These value are almost 4-order higher then that of nickel though the distribution ratio of copper shows similar values with nickel. Analysis of the data indicates that addition of lime in the slag and the increase of temperature reduce the dissolution of chromium into the slag and the addition of aluminum increases the dissolution of chromium into the slag while reduces the dissolution of copper and nickel.IntroductionChromium. is a minor element in a nickel oxide ore but a Japan major component in the secondary material of stainless steel and is also introduced in the Fe-Ni production process due to dissolving bricks of a furnace. Chromium is a concerned matter for the beneficial utilization and disposition of ·slag because Cr6+ is a harmful element. Considering Fe-Ni as an alloy component in steel making, and the demand of high purity nickel, chromium is an -undesirable element that has to be eliminated into slag prior to the steel making, or the production of high temperature refractory alloys. On · the other ·hand chromium is an element of steel alloy for many applications, thus Fe-Ni containing chromium in minor element is desirable in some stainless steel making."

Jan 1, 2000

By Stein Tore Johansen

Some ferro-silicon furnaces have heat-recovery equipment. Here, the recovery of electric energy from the off-gases can be increased by increasing the off-gas temperature. This is easily done by reducing the amount of air which usually is mixed into the?off?gas to cool the gas mixture. If the off-gas becomes too hot problems with severe fouling or clogging of the gas channels close to the furnace is observed. The result is irregular stops to clean the off-gas channels. The paper focuses on the nature of the clogging phenomena and some of the ways to avoid clogging. A detailed experimental study was carried out at the Elkem Thamshavn Plant. Theoretical studies were performed to understand the particle deposition, turbulent multiphase fluid flow and off gas combustion in the off-gas channels. The study has resulted in reduced clogging.

Jan 1, 1992

By Glenio F. Daniel, Vinícius O. Barbosa, André R. Gomes, Sergio N. Monteiro, Victor B. de Souza, Frederico M. Margem

Nowadays notorious technological growth is encouraging research natural materials in substitution to more usual synthetic ones. One of those initiatives is the vegetable fibers that have been studied for the replacement of glass and carbon fibers. This research addresses broadly the study of the natural fibers mechanics properties, but none study have been made with natural fabrics, such as the pure jute fabric used in Brazil to make ropes and carpets. This work aim to evaluate the mechanical behavior of jute fabric strips with different dimensions to be used as reinforcement into polymeric composites Lots of those fabric strips were subjected to tensile tests in order to obtain the tensile resistance for each strip size. The results obtained during the tests were satisfactory and indicated that 160 × 160 × 1 mm correspond to the best result and the perfect fabric strip for the composite reinforcement.

Mar 1, 2017

By B. C. F1intoff, R. G. Bradburn, E. Groiss

"The concentrator at Brenda Mines Ltd. treats a copper - molybdenum porphyry ore with current head grades of 0.185% Cu and 0.036% Mo. The consistently low head grades provided the driving force to explore methods of improving plant productivity. Computer based process control was recognized as one means of addressing this objective. Over the period from 1974 to 1982 a control system evolved which now extends to every area of the mill. Control strategies are built on elements of classical, modern and rudimentary expert control. In addition, the control system has often served as a catalyst for other technological developments. The economic returns associated with the system are very significant and it has played an important role in the mine's survival in times of poor metal markets. This paper presents an overview of the computer control system at Brenda.PreambleOne can scarcely avoid picking up a trade magazine or newspaper today without seeing some reference to technology and its potential impact on North American business. _A recurring theme is the need to apply technology to raise our standard of plant automation in the manufacturing and process industries. The general thesis of these articles has been concisely captured in the mutually exclusive set:AUTOMATE or EMIGRATE or EVAPORATEProcess control is one form of automation that has been successfully exploited by various sectors of these industries. In minerals and metal processing the wide scale adoption of process control technology has, until recently, been largely limited to a few companies - most of whom have a history in the area dating back to the early 1970’s. However, there is definitely an increased and much broader interest in process control as a technology which can improve performance, productivity and profit.The economic hardships that were visited on the mining industry in the early 1980's are not easily forgotten. It is the authors' conviction that the mining industry must move to implement proven technology, in particular process control, in order to be well postured for the next (inevitable) down cycle.In pursuing the technical and trade literature, one can discover a number of example of the successful utilization of process control systems in mining and related applications. In the text which follows, the authors describe the process control efforts undertaken in the Brenda Mines Ltd. concentrator."

Jan 1, 1989

By J. Huot

It has been shown that magnesium-based metal hydrides such as Mg2Ni could be synthesized by high energy mechanical alloying. This process creates a nanocrystalline alloy that has enhanced hydrogen sorption properties due to the high density of defects and grain boundaries. Unfortunately, this process also requires a long synthesis time (up to 100 hours in some cases). In order lo reduce processing time and cost of synthesis, we have investigated the effect of milling at elevated temperature under an inert atmosphere. Milling at high temperature improves interdiffusion of the elements and reduces the number of structural defects such as vacancies, dislocations and internal strain. It was found that by milling elemental powders at 200°C. a complete synthesis of Mg2Ni could be achieved in 8 hours. This synthesis time is roughly an order of magnitude lower than that of the process conducted at room temperature. The hydrogen sorption kinetics and capacity of this material are comparable to Mg2Ni synthesized at room temperature.

Jan 1, 2002

By Kerri-Ann Hue, Kerry Hasapidis, Ken Babcock, Patrick O'Hagan

"Metallic nanoparticles exhibit properties that are significantly different from individual atoms or bulk materials. Their applications are diverse and have varying uses in areas such as cancer treatment, biochemical sensors, nanoelectronics, and drug delivery. For each application extensive characterization must be performed in order to probe the unique properties of these nanoparticles. In this study, ultra-high resolution mass sensors consisting of MEMs-fabricated, suspended microchannel resonators (SMRs) were used to determine the size and concentration of metallic nanoparticles. With femtogram (10- 15 g) mass resolution, ultra-high resolution mass sensors can weigh individual particles suspended in fluid, and so measure their mass, density, and size. Particle size analysis with these sensors provides excellent accuracy and resolution compared to mature technologies such as light scattering. This technique also provides quantitative information via the ability count particles.IntroductionThe unique electronic, chemical, and optical properties associated with nanoparticles vary with their size, shape, and composition[ 1-4]. These properties are attributed to increased surface area and nanosized mean free path of electrons to the particle surface. Nanoparticle colloidal solutions have been prepared and are commercially available. In recent years, noble metals such as gold, copper, and silver have been extensively researched[5-7]. In order to tailor the optical, electronic, and electrical properties of nanoparticles, size and shape must be controlled. For many applications a monodisperse colloidal solution is ideal. Methods of size characterization include Transmission Electron Microscopy (TEM), Dynamic Light Scattering (DLS), and Electrophoretic Mobility Measurements to name a few[6, 8]. Although TEM can provide shape and size distributions, sample preparation requires that samples be dried on a metal grid and cannot be analyzed in solution. DLS uses curve fitting algorithms that while useful for determining mean particle diameters are not ideal for polydisperse colloidal solutions. New technologies are therefore needed to accurately determine the particle size distributions of metallic nanoparticles."

Jan 1, 2011