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By Ramiro Escudero

Michoacan?s beach sands with interesting concentrations of ilmenite were studied to produce titanium by hydrometallurgical techniques. Nevertheless, among titanium species, there are different additional components of Michoacan?s beach sands which could be of interesting applications. Some of them are likely to be applied for the manufacture of nanocrystalline ceramics. Although, the most applied mineral dressing to treat these kind of sands, that contain magnetic species (i.e., ilmenite, magnetite), is a combination of gravity separation and magnetic separation, it could be of a great deal of benefit to apply the information regarding the surface characteristics of the sands? components, in order to study the application of flotation technologies to separate selectively those species with commercial value.

Jan 1, 2006

By Peter Forschner

Classical Mixing Theory is based on applying many fundamental correlations to standard baffled dished bottomed vertical cylindrical vessels with high degrees of symmetry. Horizontal autoclaves operating at elevated temperatures and pressures have been used for more than two decades. All compartments and especially the first and last compartments are asymmetrical. To date no comparison of the effects of the asymmetric geometry on mixing system design and scale-up has been published. The results of investigating solids suspension, mixing time, momentum transfer from the impeller to feed slurry and feed inlet location in the first autoclave compartment are presented as influences on residence time distribution. CFD modeling was developed and verified with the test apparatus.

Jan 1, 2003

By Jenq-Gong Duh, Jyh-Wei Lee

"Hard chromizing process is a method for developing a surface modified coating providing wear, corrosion resistance and high temperature surface protection. Two carbon steels with 0.45 wt% and 0.95 wt% carbon contents, respectively, were chromized with pack cementation process at 950'C for 4 and 9 hours, respectively. The phase transformation and microstructure phenomena of chromized coating layer and matrix of two steels were studied with X-ray diffractometer and electron probe microanalyzer. (Cr,Fe)23C6 and (Cr,Fe)7C3 carbides and (Cr,Fe)2N1-x nitride phases were observed on the chromized surfaces. The thickness of chromized layers obeyed the parabolic rate law. The mechanism and diffusional kinetics of the chromizing process were proposed. The diffusivity of chromium in the (Cr,Fe)7C3 carbide phase was calculated using the moving boundary method.IntroductionChromizing process is one of the surface treatment technologies that can produce a chromium contained surface layer with sufficient corrosion and wear resistance on the steel matrix [1-7]. The relatively low cost and no ""line-of-sight"" restrictions are main advantages of chromizing. Adequate bonding strength of these coatings to the substrate was reported [7]. Chromizing process can be classified into soft chromizing and hard chromizing [2]. Soft chromizing is applied to steels containing less than 0.1wt% carbon through which chromium will be diffused. High temperature oxidation resistance improvement is the main purpose of soft chromizing process. On the contrary, the hard chromizing can be applied to steel containing more than 0.3wt% carbon, and very hard chromium nitride and carbide layers will be formed on the surface, which are very resistant to wear, corrosion and temperature [5-7]. In the previous studies on the Fe-Mn-Al-Cr alloy [5,7] and carbon steels [6], the thickness (X) of chromizing layers was analyzed and found the parabolic rate Jaw prevailed:"

Jan 1, 2004

By Soumendra Basu, Uday Pal, Yang Yu, Srikanth Gopalan, Karl Ludwig, Deniz Cetin, Jacob Davis

"A limiting factor for Solid Oxide Fuel Cell (SOFC) performance is the oxygen reduction reaction (ORR) at the cathode surface. Changes in the surface composition and structure on annealing at 800°C has been studied, since these can influence the ORR. Idealized single crystals of cathode materials La0.8Sr0.2MnO3 (LSM) and La1-xSrxCoyFe1-yO3 (LSCF) were grown as heteroepitaxial thin films on lattice matched single crystal substrates. Changes upon heating the films to operating temperature and pressures were characterized using various synchrotron x-ray techniques. Total Reflection X-ray Fluorescence (TXRF) measurements, which probe compositional changes, were made at high temperature in real time. The LSM surfaces were found to develop manganese enrichment when heated. Highly strontium doped LSCF were found to develop strontium-rich surfaces. HArd X-ray PhotoElectron Spectroscopy (HAXPES) was used to investigate the electronic structure of the materials. Highly strontium doped LSCF precipitates a surface strontium phase that contains both oxide and carbonate contributions.IntroductionSolid oxide fuel cells (SOFCs) are chemical to electrical energy conversion devices that could potentially reshape how energy demands are fulfilled. SOFCs have a potential efficiency over 70%, fuel flexibility, low emissions, and low degradation over long time scales. Commonly, SOFCs are operated at high temperatures (above 800°C). At these temperatures expensive housing is needed to contain an operating stack as well as coatings to contain the oxidation of the metallic interconnects. Lowering the temperature of an operating device would allow for more conventional materials to be used, thus lowering overall cost. Understanding the reaction kinetics of the oxygen reduction reaction at the surface of the cathode is vital to designing a system that will perform well at lower temperatures. A commercialization goal is to reduce operating temperatures without sacrificing performance.In order to exploit the advantages of SOFCs, an understanding is needed of the surface chemical states of cations on the surface of the cathode and how this relates to the oxygen reduction reaction (ORR):"

Jan 1, 2014

By Yan Fu, Chuanlin Fan, Xiujing Zhai, Yongfeng Chang, Binchuan Li

"The mechanism of the selective chlorination of nickel and cobalt in reduced limonitic laterite was investigated. Reduced ores were obtained from the reduction roasting of a limonitic nickel laterite. The thermal decomposition of related chlorides and the selective chlorination of the reduced ore were carefully studied using Differential Thermal analysis - Thermogravimetry (DTA-TG), X-Ray Diffraction and chemical leaching methods. In the temperature range of 300 - 500 °C, aluminum chloride hexahydrate was chosen as chloride agent. During the selective chlorination, reduced ore was partly chlorinated by hydrogen chloride generated from the thermal decomposition of chloride agent. Then the oxydrolysis of ferrous chloride re-generated hydrogen chloride was used to further the chlorination. Finally, iron was mostly rejected as hematite, while nickel and cobalt were selectively chlorinated. More than 91 %Ni , 90%Co and about 4%Fe in the chlorinated ore was extracted using a water leaching method.IntroductionLimonitic nickel laterite is an important nickel reserve, which is rich in iron in the form of goethite and has low contents of magnesium, aluminum, silicon, and other elements. Goethite is the main nickel-bearing mineral in the laterite [1]. Nickel is generally present in goethite in three modes: (a) associated with amorphous or poorly crystalline goethite, (b) weakly adsorbed to the crystalline goethite surface, and ( c) as lattice substituents [2]. In addition, cobalt in limonite was found to be associated with a manganese phase rich also in nickel [3]. These results indicate that the extractions of nickel and cobalt are highly dependent upon the degree of the decomposition of the nickel, cobalt-bearing minerals.For the selective extraction of nickel and cobalt from limonitic laterite, the ore is usually processed by hydrometallurgical methods, including high pressure acid leaching (HPAL) [4] or reductive roasting - ammonia leaching (Caron process). However, there are still some disadvantages in these processes, such as the expense of autoclaves and scaling problems in HP AL [ 4, 5], and relatively low overall metal recovery, large energy and reagent requirements for the Caron process."

Jan 1, 2011

By Wilky Desrosin, Alicia E. Ares, Carlos E. Schvezov

"In the present research the horizontal directional solidification Zn-Sn alloys (Zn-4wt. %Sn, Zn- 6wt. %Sn, Zn-10wt.%Sn and Zn-30wt.%Sn) was carried out by extracting heat in two opposite directions. For this purpose, ceramic molds, a muffie, a horizontal furnace with two heat extraction systems at the ends, a measurement, acquisition and recording temperature system, eight K-type thermocouples and an electronic recorder were used. The main parameters involved in the columnar-to-equiaxed transition, CET, were: the moment of start and end of solidification at each position under consideration, cooling rates, the average temperature gradients and critical temperature gradients at the CET, the average speed of liquid and solid interphases left and right, advancing in opposite directions. Also, solidification kinetics was found to be different between horizontal solidification two-way heat extractions, with preliminary results of the vertical unidirectional solidification. In the solidification experiments, the velocity and accelerations of the liquidus and solidus interphases usually occurs at the end solidification zone of the samples.IntroductionSolidification of metal alloys, which starts in the external equiaxed region (chill), results in two basic types of structures in a single solidified alloy sample: columnar and equiaxed. The presence of both structures indicates the occurrence of the colunmar-to-equiaxed transition phenomenon[!].Studying the colunmar-to-equiaxed transition, CET, is of great technological interest for the evaluation and design of the mechanical properties of the solidification products. To this end it is necessary to understand the mechanisms by which it occurs. As found in previous studies [2-5], the CET occurs by competition between columnar and equiaxed growth. Mainly is controlled by the parameters of casting, such as the alloy composition, the density of the present nuclei in the liquid, the cooling capacity of the metal I mold, and the degree of convection in the liquid [7-10]."

Jan 1, 2014

By Tatiana Pereira Moreno, Priscilla Aki Mori de Hanashiro, Viviane Tavares de Moraes, Denise Crocce Romano Espinosa, Hugo Hashimoto

"Nowadays, End-of-Life (EoL) Liquid Crystal Displays (LCDs) are traditionally disposed in landfills. The increasing access to LCD technology over the last years by Brazilian consumers has intensified LCD' s disposal as an environmental and economic issue. This study aims to characterize used LCDs to identify the main components for recycling. Characterization was performed through scrap disassembly and its components were identified, separated, and weighted. LCDs were disassembled and the following divisions were applied: screen, metal frame, polymeric frame, polymeric sheets and electronic part. Some techniques were used to determine the concentration of Indium in the LCD, the glass/plastic ratio and the different kinds of polymers that compose the screen. The techniques used for characterization included inductively coupled plasma optical emission spectrometry (ICP-OES), Fourier transform infrared spectroscopy (FTIR) and thermogravimetric analysis (TGA). This method, when applied to a wide range of LCDs, can allow the development or improvement of an EoL management of LCD.IntroductionWaste Electrical Electronic Equipments (WEEEs) are waste from discarded equipment, such as computers, monitors and cellphones [1]. Over the past years, treatment of WEEE has been emphasized. It occurs due to the technology's advancement that leads to an even larger increase of WEEES [2].Among WEEEs, there are the liquid crystal displays (LCD). LCD technology is applied in cell phones, tablets, computers and monitors. Nowadays, it's the most well known technology when it refers to monitors, due to its advantages over the Cathode Ray Tube (CRT) technology. Some of them are energy saving, smaller size and no radiation emission [3].This feature in the LCD's global market along with the speed at which electronic equipment becomes obsolete affects society economically and ambiently.This issue becomes even more serious when considering the final destination of the liquid crystal displays. LCDs are lead to landfills as other WEEEs. Besides the different materials long degradation time, the environment is damaged by the disposal of the potentially reusable and hazardous materials [ 4]."

Jan 1, 2014

By Na Wang, Chao Du, Hongmin Zhu, Kai Huang, Shuqiang Jiao

"Niobium aluminides were directly synthesized by a sodiothermic reduction process of NbC15 - AlCb which was dispersed into LiCl - KCl - NaCl - CaCb melts. The melt supplied a homogenous reaction medium which was substantially beneficial to the co-reduction of Nb and Al to form niobium aluminides in situ. The reduction was performed at 500°C for 4 hours. The products were analyzed by X-ray diffraction (XRD) and scanning electron microscope (SEM). The corresponding results indicated that niobium aluminides powders were successfully synthesized.1. IntroductionNiobium aluminides have received considerable attention as high-temperature structural materials, due to their high melting points, relatively low density, high strength, excellent oxidation and creep resistance [1-4]. Figure 1 shows that there are three intermetallic compounds in the Nb - Al binary [5], which includes Nb3Al (A15 structure, Cr3Si type), Nb2Al (D8b structure, cr-CrFe type) and NbAb (D022 structure, TiAb type). These niobium aluminides have been used in turbine blades or in stationary gas turbines [6-8]. However, despite their attractive features, the ir applications are still limited by the long and costly fabrication process [9, 10].Niobium aluminides were industrially fabricated by the mechanically alloyed process [11-13]. Traditionally, niobium is extracted from Nb2O 5 or K2NbF7 by a metallothermic reduction process while aluminum is produced by the Hall-Heroult process of Ah03 electrolysis. Based on the extraction of Nb and Al, respectively, niobium aluminides is synthesized by a mechanical powder alloying process. The present process for making niobium aluminides requires a set of complicated equipment, has high production cost and time consuming [14, 15].The purpose of this work is to present the simple, economic and direct synthesis of niobium aluminides powders utilizing a sodiothermic reduction from NbC15 - Al Cb dispersed into molten salts."

Jan 1, 2011

By Somayeh Dashti, Ehsan Vahidi, Fereshteh Rashchi

"The main goals in zinc electrowinning process are decreasing of power consumption and increasing of current efficiency. In this study, the electrowinning of zinc in the presence of different additives in electrolyte were established and Arabic Gum, Gelatine, sodium lauryl sulphate and l-hexyl-3-methylimidazolium hydrogen sulfate in the five levels using Taguchi method was examined. In our previous researches, using orthogonal array, effect of zinc electrowinning parameters such as anode type, current density, sulphuric acid concentration, temperature and zinc ion concentration was studied and the optimized conditions for zinc electrowinning was obtained. Anode composition: Pb-Ag 0.5%-Sn2%-Sb1%, current density (A/m2):500, acid concentration (g/1):165, temperature: 60°C, zinc ion concentration (g/1):70. The main goals in zinc electrowinning process are decreasing of power consumption and increasing of current efficiency. ln this research, the effect of four additives: Gum Arabic, Gelatine, sodium lauryl sulphate and an organic material in the four levels with Taguchi method was examined. ln fact the effect of electrolyte environment and determining the best electrolyte under the optimized conditions is the main aim of this study.IntroductionDue to its low cost and abundance, zinc is widely used in the production of brass, galvanized steel, sacrificed anodes and primary and secondary batteries [I]. Some 80% of world primary zinc production is derived via roast-leach-electrowinning processes [2-4]. In the electrowinning process to both improve final product quality and current efficiency the leachate should be purified [5].To produce zinc a current method is to extractit from acidic zinc sulphate solutions by electrolysis with aluminum cathodes and insoluble lead-based anodes [6]. Though the electrolytic processing of zinc has been performed for many years, there are still current efficiency problems in the cathodic process. These low efficiencies (88- 93%) have a serious impact on the costs associated with the energy consumption. On the other hand, these low efficiencies increase energy consumption and decrease the quality of the surface morphology [7- 8]."

Jan 1, 2012

By Asok Kumar Das

"In steel making ferroalloys occupies a commanding role for production of varied quality of steel. Ferroalloys enable alloying elements such as chromium, silicon, manganese, vanadium etc to be safely and economically introduced into metallurgical processes thus giving certain desirable properties of the alloyed metal. Their importance grew with the progress of the steel metallurgy which implied more diversified alloying elements, in better controlled quantities, in purer steel. The ferroalloy industry became a key supplier to the steel industry. Production of ferroalloys generally involves the use of Electric Arc furnace(EAF) into which raw materials(e.g. various metal ores, quartz, coke, lime etc ) with relatively fluctuating physical compositions are loaded. Due to this, one of the major environmental impacts of producing ferroalloys is the emission of dust and fume from the smelting process. INTRODUCTIONFerro Alloys are essential ingredients used for refining, de-oxidation, desulphurization and alloying addition in the production of different types of steel and hence Ferro Alloy industry forms a back bone of iron and steel in the world. Indian ferro alloy industry is more than 45 years old. It produces most of the bulk ferro alloys and a large number of special ferro alloys. The present installed capacity of the Indian ferro alloy industry is sufficient to meet the requirement of existing level of indigenous steel production of about 46 million tonnes. Revised National Steel Policy – 2008 envisages production of more than 100 million tonnes of steel by the year 2011-12, at proportionate annual growth rate per annum. The focus of the policy is to achieve global competitiveness not only in terms of cost, quality and product-mix but also in terms of global benchmarks of efficiency and productivity. In order to achieve the objectives of National Steel Policy and also to meet the requirement of ferro alloys, the Indian Ferro Alloy Industry has to gear up in terms of enhancement in production capacity, sourcing of raw materials, up gradation of technology, improvement in productivity, automation / mechanization, customer satisfaction etc."

Jan 1, 2008

By Chu Yong Cheng

Synergists can be used in solvent extraction to improve the selectivity of extractants for metals. Research work carried out by the SX group at the AJ Parker Cooperative Research Centre for Hydrometallurgy / CSIRO Minerals has shown that the pH isotherm of nickel with Versatic 10 was significantly lowered by the addition of the synergist Acorga CLX50. The paper discusses how this synergistic shift can be used to alleviate a gypsum formation problem at Bulong nickel laterite operation in Western Australia. Metal pH isotherms were obtained with Versatic 10 and synergist CLX50 using synthetic leach solutions. In terms of pH50, the extraction order of the metals with 0.5 M Versatic 10 alone was Cu > Zn > Ni > Co > Mn > Ca > Mg, whilst the extraction order with Versatic 10 and 20% by volume CLX50 was Cu > Ni Zn > Co > Mn > Ca > Mg with the pH50 (Mn-Co) significantlyincreased. This is significant because the isotherms of valuable metals Ni, Cu, Co and Zn shift more towards low pH than those of the waste metals Mn, Mg and Ca, resulting in a possible good separation of Ni, Cu, Co and Zn from Mn, Mg and Ca. The use of intermediate precipitation, solids/liquid separation and re-leach in the three Western Australian nickel plants make these processes complicated and costly in capital and operation. The research work carried by the SX groupat the AJ Parker Centre has led to the development of direct SX (DSX) processes to recover nickel and cobalt from leach solutions using synergistic organic systems. Semi-continuous tests with a BHP Billiton pilot plant leach solution showed that Ni and Co together with Zn and Cu were separated from the major impurities, Mn, Mg, Ca, and Cl, in the first SX circuit. The co-extracted impurities were easily scrubbed. After stripping, Ni and Co together with Zn and Cu were concentrated, resulting in a much smaller second SX circuit in the down stream processes.

Jan 1, 2003

By Bora Derin, Adnan Aydin, Onuralp Yucel, Hakan Morcali

"The steelmaking industry which uses electric arc furnaces (EAF) generates approximately 250.000 tons of EAF flue dusts annually in Turkey. These flue dusts contain valuable metals such as zinc, iron and lead. For example, if these flue dusts can be treated efficiently, disposal problems certainly decreases and annually almost 40.000-75.000 tons of zinc can be recovered. In this study, powder and pellet forms of EAF flue dusts taken from a steel mill were carbothermally treated in a temperature controlled pilot scale rotary furnace via carbothermal reduction in order to investigate the reduction behavior of Zn and Pb. Temperature (900-1000 and 1100 °C) and time (0-90 minutes) were selected as reaction parameters. The chemical analysis was performed for the sample residues.IntroductionTurkey’s steel production reached to 23.3 million tons in 2006. There are three integrated steel plants of which capacities vary from 0.7 to 3 million tons per year and seventeen EAF steel plants of which capacities vary from 0.06 to 2 million tons per year [1]. When it is considered that more than 74 % of the Turkish steel production is produced by EAF method and approximately 10 - 15 kg of dust is formed per ton of steel during this process, the amount of annual generated EAF dust may be estimated at approximately 0.25 million tons. EAF dust which contains valuable metals such as zinc, lead, iron, cadmium, and chromium, is considered as hazardous waste product in steelmaking industry. If these flue dusts can be treated efficiently, not only the disposal problems certainly decrease, but also annually almost 40.000-75.000 tons of zinc can be recovered. Many studies which exist on recovering of the valuable metals from EAF dust, propose and practice many hydro-metallurgical and pyro-metallurgical treatments [2- 7]. In this study a laboratory scale work were performed to investigate reduction behavior of zinc and lead in EAF dust by carbothermal process in a rotary furnace."

Jan 1, 2008

By Wen-Ming Chien, Vamsi Krishna Kamisetty, Amrita Mishra, Ivan Gantan, Prathyusha Mekala, Dhanesh Chandra

"The phase equilibrium and characterization studies by using high temperature X-ray diffraction (XRD) and differential scanning calorimetric (DSC) methods have been performed for binary organic thermal energy storage materials. The organic thermal energy storage materials undergo a solid-solid state phase transition before melting which stores large amounts of thermal energy. Two materials [tris(hydroxymethyl)aminomethane(TRIS) and 2-Amino-2-methyl-l, 3- propanediol(AMPL)] were used for this study. Binary samples of AMPL-TRIS were prepared to perform high temperature XRD characterization and DSC studies and the binary AMPL-TRIS phase diagram was developed. The high temperature solid-state phases of AMPL and TRIS were characterized as a disordered BCC structure. It was found there is virtually no solubility of TRIS in AMPL or vice versa below -75 °C. The maximum solubility of TRIS in AMPL is 11% TRIS at 75 °C. The eutectoid transformation was shown at 19%TRIS-81%AMPL composition and at a temperature of 75°C. Lattice expansion calculations on single phase of TRIS and AMPL have been performed.IntroductionThermal energy storage materials can store a large amount of heat due to the presence of thermal transitions from the orientationally ordered to disordered phases occurring before melting. These molecules (such as amine and alcohol derivatives of neopentane) can reorient as a whole about the central carbon atom to form orientationally disordered crystals (ODIC) and their spherical shape makes them reorient relatively easier. Thermal energy storage materials are becoming increasingly important as a renewable energy resource. These molecules undergo large changes in enthalpies at solid-solid transitions. The presence of these compounds with large enthalpy changes are identified as potential thermal energy materials and some of die applications are solar cell systems [1-3]. Binary mixtures have been found as a way to adjust the transition properties in addition to pure compounds [4]. Tris(hydroxyrnethyl)aminomethane (TRIS, C(CH2OH)3NH2) and AMPL, CH3C(CH2OH)2NH2) are two important thermal energy storage materials."

Jan 1, 2012

By Per Anders Eidem, Merete Tangstad, Jens Davidsen

"During excavations of submerged arc furnaces producing silicomanganese, silicon carbide (SiC) has been found. Contributing to the size of the inactive area of the furnace, the active area of the furnace where reactions occur will decrease, thus reducing the potential for pre-reduction in the furnace.This work studied the formation of SiC from the liquid-solid reaction between slag, metal, and metallurgical coke. Slags and metals with different levels of silica (S1O2) and silicon (Si) have been studied. The slag and metal has been heated together with coke, and the samples investigated by microprobe. The results show that SiC was formed on the coke particle through reactions with both slag and metal. For the metal, the carbon most likely diffused through the SiC to react with Si in the alloy. SiC formation with slag is likely to go through the reduction of Si02 to Si.IntroductionToday, Silicomanganese (SiMn) is produced in submerged arc furnaces (SAF) by reduction of S1O2 and manganese oxides, mainly with metallurgical cokes. Typically, the tapped metal has a silicon content of 17 - 20 wt.%. To achieve higher levels of Si, the metal can be refined by adding off-grade silicon metal, yielding low carbon SiMn. [1]. What is believed to be SiC that has been found during dig-outs of SiMn furnaces producing high silicon alloy. It is possible that excess amounts of SiC in the furnace cause operational problems, since SiC will occupy furnace volume. As SiC accumulates, the active volume of the furnace will decrease, increasing the flow of material and gas in the active areas of the furnace. Formation of SiC is inevitable, so it is desired to keep the formation as low as possible. To be able to control the formation of SiC, one has to understand the basic mechanisms."

Jan 1, 2012

By John Snowberger III, J. Brent Hiskey

The electrochemical dissolution of super alloys containing different amounts of rhenium was investigated. The initial part of the investigation focused on the anodic dissolution of rhenium from second-generation (3% Re) and third-generation (6% Re) nickel based alloys. Exploratory electrochemical tests were conducted to evaluate solution chemistries and to establish fundamental dissolution behavior of the alloys. These included rotating disc electrode (RDE) cyclic voltammetry, linear sweep voltammetry, and chronoamperometry tests. Electrolytes comprising sulfuric acid, hydrochloric acid, and ammonium sulfate were examined. Of these, a 0.1 M HCl solution proved to be extremely effective for electrochemical dissolution of samples of CMSX-4, CMSX-10, and SC-180 alloys. This paper discusses in detail the electrochemical behavior of these alloys.

Jan 1, 2014

By Bingyi Bai, Wangjun Peng, Yanling Guo, Jieyu Zhang, Guoding Gao

The phase transformation of bayan obo ore with high concentration of iron and calcium was reduced at temperatures no more than 1000℃ were investigated in this study. The samples with insufficient carbon were treated at the temperature using a vertical furnace with a thermogravimetry (TG). The mineral phases and content were examined using Xray diffraction (XRD) and X-ray fluorescence spectroscopy (XRF) respectively. The complex phases of bayan obo ore transformed to some simple phases after treated with different content of carbon at the same temperature for 10 hours. The result of XRD、 XRF and TG showed that the reduction degree of Fe3O4 phase formation varied with the temperature and the carbon content of bayan obo ore.

Jan 1, 2015

By James A. Sommers

Hydrolysis of NbC15 is used to recover oxide values for ceramic and metals production. Reaction of NbC15 with water is rapid, exothermic and vigorous, yielding a gelatinous slurry. In contrast, dissolution of NbC15 in 12 N HCl is endothermic, resulting in a clear yellow solution. Such solutions can be de-hydrochlorinated by controlled contact with air, to precipitate a tantalum¬rich solids, depleting the liquid of its tantalum content. In this way, cheap, useful Nb-Ta partial separation is achieved. The separation is based upon differential oxide-chloride stability. Nb2O5 with <200 ppm Ta/Nb has obtained from starting levels of 2000 ppm. Observations are made on the different types of hydrolysis.

Jan 1, 1992

By Tarasankar DebRoy

Professor Robertson’s recognized research on metallurgical thermodynamics and kinetics for over 40 years facilitated the emergence of rigorous quantitative understanding of many complex metallurgical processes. The author had the opportunity to work with Professor Robertson on liquid metals in the 1970s. This paper is intended to review the advances in the quantitative understanding of welding processes and weld metal attributes in recent decades. Over this period, phenomenological models have been developed to better understand and control various welding processes and the structure and properties of welded materials. Numerical models and animations of melting, solidification and the evolution of micro and macro-structural features will be presented to critically examine their impact on the practice of welding and the underlying science.

Jan 1, 2014

By J. W. Perez

In the treatment of process effluents containing metal ions, it is sometimes desired to remove all of the heave metal ions while at other time it is, desired to remove one heavy metal ion from another, selectively. Ion and precipitate flotation processes were evaluated to perform these functions using the copper-iron aqueous system as a model. Because preliminary foam fractionation experiments proved to be relatively inefficient, most of this work has focused on precipitate flotation using both hydroxide and sulfide precipitation. Test results indicate that by proper control of reagents and operating conditions, it is possible to substantially reduce the froth volume over that achieved with foam fractionation and to separate copper from iron selectively. Mechanisms for collector attachment to precipitates were studied.

Jan 1, 1992

By W. Petruk

The silver-rich cobalt-nickel arsenides ores of the Cobalt area in Ontario, Canada were mined for silver from about 1904 to 1985. The ores contained about 8 oz to 100 oz Aglt and about 1 wt% Ni and 2 wt% Co. They were processed by gravitational techniques, screening and flotation to produce separate silver and Fe-Co-Ni arsenide concentrates. The silver concentrate was smelted, and in some cases the arsenide concentrate was sold to custom smelters which recovered silver and other metals. The ores display a wide variety of textures and contain many minor and trace elements. This paper presents an evaluation of mineral characteristics that have a bearing on extractive metallurgy and smelting of this type of ore.

Jan 1, 1993