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By Sheng-hai Yang

The ultrafine, monodispersed, spherical cobalt powder has been fabricated by reducing cobalt hydroxide with glycol. It were investigated that the effect of NaOH concentration on the reaction rate and the effects of the concentration of cobalt hydroxide and surfactant on the morphology and particle size. The particles were characterized by the X-ray diffraction(XRD), scanning electron microscope(SEM), laser diffraction particle size analyzer and BET specific surface analyzer respectively. The XRD shows that the cobalt powders exist mostly in face centered cubic (fcc) structure, a little in simple hexagonal. The cobalt powders prepared at Co(OH)2150g/L, NaOH 40 g/L and surfactant 30g/L, its average particle size, specific surface area and cobalt content, were 0.88µm, 2.705m2/g. and more than 99.5% respectively.

Jan 1, 2006

By Go-Gi Lee, Jae-Young Jung, Myung-Duk Seo, Hyun-Na Bae, Seon-Hyo Kim

"Bubbles form at the anode during the electrowinning of magnesium and cause hydrodynamic acceleration and electrical field disturbance. A three-dimensional computational model was developed to investigate the effects of the geometry of the electrochemical chamber and the size distribution of bubbles on the fluid flow in the pilot plant. The results are validated by measurements of the surface characteristics of molten salt and the bubbles formed. Fluid flow at the surface was recorded with a high speed camera, and the distribution of bubble size is determined by inspecting the video images frame by frame. The measured size distribution of the bubbles is entered into the computer simulation of a multi-phase flow. A sloped roof is installed above the electrodes, to enhance the flow of the molten salt, thus resulting in higher current efficiency, lower energy consumption, and higher quality of magnesium metal.IntroductionTitanium's excellent properties of low density, high specific strength, high temperature strength, and exceptional resistance to corrosion are highly beneficial to diverse applications including aerospace, automotive, construction, and medical implants. Although the Kroll process[l] and Hunter process have been used for the extraction of titanium in the 20th century, their complicated engineering stages and high production cost, have led to further research into new processes such as FCC Cambridge, Armstrong and TiRO. Despite these intense research efforts, no process has yet been developed that is more economical than the Kroll process, by which most of the global commercial titanium is still being produced."

Jan 1, 2011

By Steve Johnston, Mowafak Al-Jassim, Fei Yan, Omar Sidelkheir, Alain Blosse, Katherine Zaunbrecher

"Imaging techniques are applied to multi-crystalline silicon wafers and solar cells throughout the production process. Photoluminescence imaging, both band-to-band and defect-band, is used to characterize defects and wafer quality at all process steps. These steps include bricks sawn from ingots, wafer sawing, cleaning and texturing, emitter diffusion, edge isolation and glass removal, anti-reflective coating/passivation, and metallization of finished cells. Bricks, wafers, and cells can be imaged at a rate commensurate with in-line measurement, giving spatial information to characterize quality and defect content. Photoluminescence images on silicon bricks can be correlated to lifetime measured by photoconductive decay and could be used for high-resolution characterization of material before wafers are cut. The defect areas in as-cut wafers are compared to imaging results from electroluminescence and lock-in thermography, and cell parameters of near-neighbor finished cells, showing correlations to efficiency, open-circuit voltage, and short-circuit current.IntroductionImaging techniques can rapidly characterize material quality and defect density. Photoluminescence (PL) imaging can be applied to silicon from the brick level to all wafer process steps [1-8]. At the brick level, material thickness allows for measurement and correlation to lifetime where surface recombination effects are minimized [6, 7]. At the as-cut wafer level where thin unpassivated wafers prevent accurate lifetime assessment due to surfaces, defects can still be categorized and quantified to predict finished cell performance [3-5]. Defect regions can be identified by recombination-limited band-to-band PL or by defect-band emission [9-12]."

Jan 1, 2012

By M. J. Adam

The U.S. Bureau of Mines is investigating the partitioning of selected complex minerals into simple phases using sulfidation reactions. Successful partitioning of complex mineralogy to simple phases may afford an opportunity to improve selective extraction of mineral constituents of economic value. The research has shown that complex minerals, such as chalcopyrite (CuFeS2) and pentlandite [(Fe,Ni)9Se]' may be partitioned to the simpler phases covellite (CuS) plus pyrite (FeS2) and vaesite (NiS2) plus pyrite (FeS2), respectively. Demonstrations of these reactions were verified through long-react ion-time (24 h or more) experiments, but basic rate investigations and modeling were not included in the previous research. This report describes research aimed at determining the rate at which the complex mineral CuFeS2 converts to the simple sulfides CuS plus FeS2. Small samples of CuFeS2 were blended with elemental S prior to thermal treating under an He atmosphere for time periods up to 4 h. Products from each treatment period were characterized using metallography, chemical analysis, X-ray diffraction (XRD), and scanning electron microscopy (SEM). Results of the investigation revealed a rapid conversion of CuFeS2 to CuS plus FeS2 early in thermal treatment periods. As the reaction occurred, a CuS rimming of particles was observed which separated the reacting species (CuFeS2 and S) and caused a considerable decrease in transformation rate.

Jan 1, 1991

By K. Potluri, S. Akella, S. Bhansali

"This paper presents the design and angular strength analysis of microneedles for use as a transdermal interface for drug delivery, fluid analysis and sampling etc. Microneedles of different dimensions were designed and fabricated using various materials viz. Si02, OxideNitride- Oxide (O-N-0). The design, modeling and analysis was done using the Finite Element Analysis (FEA) software ANSYS™ 6.1. Angular strength analysis of the microneedles was done using angular loading in ANSYS™, with the corresponding inaterial property settings. Using the force-displacement settings, forces of magnitudes in the range of 10 mN - 25 mN were applied on the microneedles at loading angles ranging from 30° to 90° was applied on needles. Square and circular shaped microneedles were modeled and the displacements and stresses generated were studied to characterize the angular strength of the microneedles. The buckling and force-displacement analyses show that O-N-O microneedles are more strong and robust as compared to needles of other materials. The analysis shows that while circular microneedles have uniform stress distribution, square microneedles have low stresses concentrated along the edges.INTRODUCTIONIn modem clinical and biomedical applications, drug delivery is done either by oral administration or by hypodermic injection. Hypodermic injection of drugs using needles is often painful. Hence, transdermal drug delivery techniques are increasingly being sought out as an alternative. In transdermal drug delivery the needles puncture the Stratum comeurn - the outermost layer of the human skin. The advantage of transdermal drug delivery (or transdermal measurement) technique, is that it reduces pain and tissue trauma."

Jan 1, 2004

By T. V. Jayaraman, Kranti Kumar, Paul Praveen J., Dibakar Das, A. R. James

"Lead free piezoelectric ceramics with high piezoelectric coefficients are in great demand for sensor and actuator applications. Synthesis and characterization study of one such lead free system, barium zirconate titanate - barium calcium titanate [xBZT-(1-x)BCT] (x = 0.5), via solgel method have been carried out. X-ray diffraction (XRD) and transmission electron microscopy (TEM) confirmed the formation of single phase BZT-BCT nanoparticles (<50 nm). The as-synthesized powders were calcined at 1000°C and the powders were pressed into cylindrical pellets. Solid-state sintering of the green pellets at 1550°C for 2 hrs resulted in single phase perovskite structure. Hysteresis loops were obtained which indicates the ferroelectric nature ofBZT-BCT. The bulk ceramic samples with the highest sintered density (~93%) were subjected to electrical poling and the piezoelectric properties ( d33, kp, & i:,) were measured. The structure and piezoelectric properties were investigated and correlated for the given composition of the BZT-BCT system.IntroductionPiezoelectric ceramics are widely used in various sensors and actuators and most of the piezoelectric ceramics, which are presently used, are lead based, which contains at least 60% lead (Pb) by weight. The critical disadvantage of these lead based piezoelectric ceramics is their hazardous effect related to the toxicity of lead, which poses a serious environmental concern starting from their processing to the disposal stage[l]. It is well known that a material to be a good piezoelectric it requires a morphotropic phase boundary (MPB) i.e. the composition induced phase transition between any two ferroelectric phases."

Jan 1, 2013

By M. Radwan

This research reports on the synthesis of advanced silicon-based structural ceramics from mixtures composed of natural sand (Sinai white sand), reclaimed silicon and graphite by the nitriding combustion synthesis method. With pulverized sand (? 40 m), we found that the nitriding combustion can be realized at self-sustaining mode in the SiO2?Si?C system under 3 MPa nitrogen pressure. Depending on the composition of the starting mixtures, single-phase silicon oxynitride (Si2N2O) powder as well as new Si3N4?Si2N2O and Si2N2O?SiC composite powders with controllable chemical compositions were successfully developed. The measured thermograms of various combusted mixtures and the thermodynamic characteristics of possible exothermic reactions in this system were discussed to explain the nitriding combustion behaviour and mechanism. Near-full dense Si2N2O were fabricated from synthesized Si2N2O powder with 5 wt % oxide additive by the spark plasma sintering (SPS) method at 1600 °C. The dense Si2N2O samples had good mechanical properties (18.7 GPa Vickers hardness, 3.3 MPa m1/2 fracture toughness and 363 MPa strength) and excellent chemical and oxidation resistance. The synthesized composite powders were also densified to high densities (> 90 % of theoretical values) by SPS technique. The results obtained in this study can be seen as a new route to prepare important silicon-based structural ceramic powders with various compositions/properties from cheap starting materials which makes them potential for wide range of applications.

Jan 1, 2006

By P. K. Jha, M. M. Mahapatra, H. K. Mohanty, Pradeep Kumar

"During friction stir welding, the tool geometries affect the weld together with the process parameters like welding speed, vertical pressure and tool rotational speed. The present investigation deals with the three dimensional computational fluid dynamics modeling of friction stir welding process considering material flow around the tool, welding speed with respect to tool geometries. Friction stir welding tools with different tool geometries were used for the experiments to achieve acceptable aluminum welds. The temperatures near the welds for each tool were experimentally observed. A 3-D computational fluid dynamics (CFD) model was developed. Temperature-dependent material properties of the aluminum alloy were used in the CFD model. Thermal analysis was carried out considering rotational speed, vertical pressure and traverse speed for the tool geometries. The numerically predicted stirring patterns and temperature profiles closely matched with the experimental ones. IntroductionThe friction stir welding (FSW) is a solid state welding process where generally the metallic materials are joined by the combined action of frictional heating and weld zone stirring by a rotating tool [1]. The heat generated in the process is much below the requirement of melting the plates; hence the FSW process is devoid of harmful effects those are observed during arc welding. The FSW process utilizes a tool which has a shoulder and a protruding pin known as the probe. The shoulder is responsible for frictional heating while the pin probe facilitates stirring of the joint material. A schematic of FSW process is shown in Fig. 1."

Jan 1, 2012

By D. Valic

In 1997, 9.2 million tonnes of mined, recoverable copper was produced, of which, 1.8 million tonnes or 19.4% was produced by leaching, solvent extraction and electrowinning. The amount of copper produced by this method grew faster than those attained from concentrate smelting, signifying the growing importance of this low-cost production method. Statistical experimental design, unlike traditional approaches, allows for proper distribution of experiments within the boundaries of factors being studied such that the number of experiments required to develop a sound relationship between the factors and a response is minimized. In the past, very little use has been made of statistical experimental design in copper electrowinning studies. Traditional one- variable-at-a-time approaches are widely employed for this purpose. The present study employs a factorial experimental design to relate current efficiency with current density (180 and 300 A/m2), copper concentration (25 and 65 gL), and temperature (40 and 60 °C). Pure synthetic electrolyte with a constant acid concentration of 180 g/L was used throughout the study. The designed study produced a linear relationship where the independent variables of current density, copper concentration, and temperature, and their interactions, were found statistically significant. It was shown that current efficiency could not solely be used as a predictor of copper cathode quality. The quality of the deposit is difficult to be incorporated into a model or relation. It was determined that other measures, such as cathode morphology and crystal structure should be considered. This was done through XRD and SEM analysis.

Jan 1, 1999

By Ryszard Prajsnar

During copper production in shaft and flash smelting processes at KGHM Polska Miedz S.A., lead bearing material of sulfide, sulfate, and oxide character is generated in forms such as slime from shaft furnace gas handling systems, converter dusts, and dusts from an electric furnace for copper removal from flash smelting slag. These materials are polymetallic concentrates of Pb, Zn, and Cu, with As, Cl, and Cd as impurities. Shaft furnace slime, containing. about 50% PbS and 15% bituminous substances, is the main lead-bearing material. At the Glogów copper mill, a new plant was commissioned in June 2001 to process 80,000 tonnes per year of lead bearing materials to produce 26,000 tonnes per year of crude lead. The plant consists of a feed conditioning system, three (3) rotary rocking furnaces with a capacity of sixteen (16) tonnes of lead feed fired with natural gas and oxygen-enriched air containing up to 45 vol% O2, and a gas handling system. The gas handling system includes a post-combustion chamber, a gas cooling chamber with Cl neutralization, gas mixing chamber, bag filter, and dry limestone scrubbing system for SO2 removal. The lead-bearing feed is smelted with five (5) wt% Na2CO3 and thirteen (13) wt% iron scrap at a temperature of 950 to 1050°C for three (3) hours. The smelting process consists of four (4) stages; feed drying, firing of gaseous hydrocarbons and solid coal from the feed, lead reduction from slag, and separation of molten products. The flow rates of natural gas and oxygen to the burners are controlled to ensure combustion of the bituminous material in the furnace. The process produces crude lead bullion containing (wt%) 0.1 to 0.5% Cu, 0.02 to 0.5% As, 0.05 to 0.07% Bi, 0.1 to 0.5% Sb, and 0.1 to 0.6%Sn. The process also produces a mixture of sodium silicate slag, Fe-Zn-Pb-Cu-S matte, and Fe-As speiss containing (wt%) 5 to 10% Pb, 2 to 6% Cu, 10 to 15% Zn, 1 to 3% As, 10 to 15% S, 0.5 to 3.0% Cl, 2 to 4% K, 4 to 7% Na, 20 to 30% Fe, and 5 to 10% SiO2. The dust is made up of PbO, ZnO, PbSO4, and PbCI2, KCI, and NaCI with a chemical composition (wt%) of 35 to 50% Pb, 5 to 15% Zn, 3 to 6% As, 4 to 8% Cl, 2 to 5% K, and 2 to 5% Na. The construction of the new lead production plant at the Glogów copper mill will process both current lead-bearing materials as well as lead-bearing material that have been stockpiled over the last fifteen (15) years to give a significant improvement in protection of the natural environment.

Jan 1, 2002

By Tianming Sun, Gabriella Tranell, Ragnhild E. Aune, Mark William Kennedy

Rare Earth Elements (REEs) are critical for the production of many advanced materials and products. Mining and primary production of REEs are generally associated with significant environmental impacts. By recovery of REEs from secondary sources, through recycling or as a byproduct, the adverse environmental impacts may be partly avoided. In the present study apatite concentrate originating from iron ore beneficiation done by LKAB in Kiruna, Sweden, is explored as a possible source for REEs. The composition and distribution of the REEs within the concentrates are studied using ICP-MS, XRD and SEM-EDS/EPMA, as well as the melting point and heat of fusion using DTA-TGA-MS. The behavior of the material during melting has also been studied through wetting and slag saturation experiments. The overall aim of the study is to evaluate the implications for future smelting experiments aimed at concentration and recovery of the REEs.

Jan 1, 2015

By K. H. Bech, S. T. Johansen

"The mass transfer at fluid-fluid interfaces due to turbulent agitation is investigated theoretically. In particular a theory is derived for interface stresses due to interface energy and surface renewal. This theory indicates that surface renewal may take place if the geometry is sufficiently large and if surface tension is sufficiently low.By using a model for a typical turbulent structure we compute the interface mass transfer for a stressless interface and a fully interface. Results for the general situation is not presently available. The computed results are used to derive analytical expressions for the mass transfer based on turbulent kinetic energy and free stream turbulent length scales.One important application of the theory is the mass transfer at the electrolyte side of the bath-metal interface in the Hall-Heroult process. For this process we show that mass transfer should be expected to be of the rigid surface type."

Jan 1, 1999

By Carlos Maurício F. Vieira, Lázaro A. Pizatto, Marcus Paulo Cardoso, Sergio Neves Monteiro, Joao Victor C. Nunes, Gustavo S. R. Matheus, Frederico M. Margem

The interest in composites with natural fibers is due, among other factors, to the growing worldwide concern with the preservation of environment and renewable raw materials. The natural fibers have many particular properties that make them an attractive alternative to traditional synthetic fibers. The advantages of using these fibers are: low cost, renewability, biodegradability, low toxicity, abundance and specific strength. The searching for new suitable, economically viable and technologically advanced materials justifies the accomplishment of this work that aims at comparing the mechanical behavior of polyester matrix composites with epoxy matrix composites reinforced with hemp fibers Izod impact tested. The specimens with dimensions: 10 63 12.7 mm, made in different volume fractions of fiber: 0–30 vol%. The samples were tested at PANTEC pendulum model XC-50 located at LAMAV/UENF. With this research was possible to analyse the mechanical properties of these two new materials.

Mar 1, 2018

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 Sheng-li Wu, Guo-liang Zhang, Bo Su

The mineralogical characteristics of iron ores can influence their high temperature sintering performance. In this study, eight iron ore samples from Brazil, Australia, and South Africa were characterized by their chemical composition, mineral types, particle morphology, and gangue dispersity. Meanwhile the influence rules between the mineralogical characteristics and the high temperature characteristics were evaluated and analyzed. The results showed that the effect of SiO2 on assimilation characteristic of iron ores was relatively complex, Al2O3 and LOI of iron ores had negative correlation with assimilation temperature of iron ores, the dense slab-flaky mineral granule restrained to the assimilation characteristics of iron ores; liquid phase of iron ores with high SiO2 content and low Al2O3 content had high fluidity, and the higher dispersity of gangue minerals in iron ores was good to the fluidity of liquid phase.

Jan 1, 2015

By Dachun Liu, Xutao Guo, Wenlong Jiang, Baoqiang Xu, Bin Yang, Yong Deng, Heng Xiong

Typical copper dross, the byproduct of lead bullion pyrometallurgical refining for copper removal, mainly contains Pb, Cu, S, As, Sb and Sn etc. In traditional treatment process, copper dross is transformed to be copper matte by smelting with iron scarp and iron pyrite. Here, a new treatment process of converting-vacuum distillation (CVD) was proposed and investigated. Based on this concept, the converting process was tentatively investigated in this paper. The results of element distribution of converting samples showed the sample has three layers. The upper layer is mainly sulfides of lead and copper, the middle layer is mainly copper arsenide, and the lower layer is lead arsenide and crude lead. On the condition of oxygen flow rate 400 ml/min, the converting temperature 1000 °C, the holding time 1 h, the converting time 10 min, the lead copper alloy containing 0.17% S was obtained.

Mar 1, 2018

By Carlos Maurício. F. Vieira, Lázaro A. Rohen, Sérgio N. Monteiro, Rafael G. de Castro, Gustavo X. Borges, Maycon A. Gomes, Frederico M. Margem, Anna C. C. Neves

Economic and environmental benefits are motivating studies on natural fibers, especially lignocellulosic extracted from plants, have been studied to substitute synthetic fibers, such as glass fiber as reinforcement in polymer matrices. By contrast to synthetic fibers, natural fibers have the disadvantage of being heterogeneous in their dimensions specially the diameter. About the hemp fiber, little is known of their dimensional characteristics. The aim of the present work was to statistically characterize the distribution of the diameter of hemp fibers. Based on this characterization, diameter intervals were set and the dependence of the tensile strength of theses fibers with a corresponding diameter was analyzed by the Weibull method. The diameter was measured with precision using a profile projector. Tensile tests were conducted on each fiber obtain mechanical strength. The results interpreted by Weibull statistical showed a correlation between the resistances of the fiber to its diameter.

Jan 1, 2015

By Zongshu Zou, Qiang Li, Mingming Li, Mingxia Feng

The impingement onto the surface of bath by top-blown jets is a significant process characteristic in BOF and EAF steelmaking process. The cavity is one of the most important outcomes of the interaction and plays an important role on reaction kinetics and reactors performance. But to date, the understanding to cavity is still so limited. In present study, a water model for a BOF converter is established and the dimension of cavity profile is investigated. The effects of lance height, gas flow rate, nozzle inclination angle and the amounts of slag are discussed. The results show that penetration depth increases with the increase of gas flow rate and the amount of slag, and the decrease of lance height and nozzle inclination angle. Furthermore, a theoretical model of cavity dimension is proposed for multiply jets impinging liquid bath on the basis of energy balance at the stagnation point of cavity.

Jan 1, 2015

By Kun Wang, Weipeng Luan, Qingbo Yu, Qin Qin

The oxygen uncoupling property of the oxygen carrier is essential for the chemical looping gasification process. In this paper,the combined Cu-based oxygen carrier were prepared by mechanical mixing method. XRD and SEM were used to characterize the oxygen carrier prepared. TG experiments were performed in a thermal analyzer to investigate the oxygen uncoupling property. The XRD pattern of the fresh oxygen carriers showed that the phases of the oxygen carriers were stable.The active phase of oxygen carrier was CuMnO. With the increasing of x 3-x 4 heating rate, the starting and ending temperatures of the reduction reaction increased. However, the reaction time decreased and the reduction rate increased. With the increasing of oxygen concentration, the starting temperatures of the reduction reaction shifted to high level. Temperature had great effect on the reduction rate and the reduction rate increased with increasing of the reduction temperatures.

Mar 1, 2018

By Feng Liu, Bingji Yan, Zhiwen Shi, Hongwei Guo, Jianliang Zhang

During production of a large quantity of steel, slag is produced at the same time. This paper chooses blast furnace slag (BFS) as the main material for the research. The purpose of the research is to explore its optimal physicochemical properties and the use of BFS in building stone field. The paper elaborates the experimentation process of producing glass-ceramics and presents the results. The results show that SiO2 content in BFS and amount of Cr2O3 and Fe2O3 added as nucleating agents have certain effect on the properties of glass-ceramics. The results also show that the exothermic peak temperature of base glass is the lowest when adding 20% SiO2 to the BFS, and 2% Cr2O3 and 3% Fe2O3 as nucleating agents, which makes easy crystallization and optimal properties of the glass-ceramics.

Jan 1, 2015