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By Federica Paglietti

In this work is presented SEX (Structural & Elemental X-Ray Instrument), the first spectrometer completely portable which make non-destructive X-ray fluorescence and diffraction analysis, in contemporary and in real time. This instrument has been realized using miniaturized detectors, the same model installed on the mission Pathfinder NASA, and X-ray microtubes. SEX allows the chemical and mineplogical characterization of all kind of solid materials and allows to make chemical stratigraphy and liquids analysis.

Jan 1, 1998

By Satu Strömberg

Four different nickel concentrates were oxidized in a laboratory scale laminar flow furnace in simulated flash smelting conditions. The major nickel- and iron-bearing minerals in the con- centrates were pentlandite, violarite, gersdorffite, and pyrite and pyrrhotite, respectively. Thermal decomposition, ignition and oxidation behavior of nickel and iron sulfides were examined by using optical and scanning electron microscopy. General reactivity of the concentrates was monitored with sulfur removal which was most effective in violarite-based concentrate. Pentlandite-concentrates needed higher experimental temperatures for complete desulfurization and gersdorffite-based concentrate contained 5 - 10 % of the original sulfur even in the most oxidizing conditions studied (1 100°C, 50 vol-% 02). The reactivity of the iron minerals was found to depend on the other minerals present in the concentrate. In this paper, the observed re- action products and mineralogical changes are presented and preliminary conclusions of possible reaction mechanisms of nickel-bearing minerals are discussed.

Jan 1, 1997

By Marco A. S. Aguiar, Luis G. S. Sobral, Vânia Mori, Paulo A. Medeiros da Silva

"Copper occurs in the crust of the earth, predominantly, as sulphides. Among the copper sulphide minerals, the chalcopyrite is the most abundant and the most refractory to the conventional oxidative processes. This work aims at developing an electrolytic process for treating a copper sulphides flotation concentrate, more precisely chalcopyrite (CuFeS2) and bornite (Cu5FeS4) in the percentages of 70 and 30%, respectively.This paper presents a low-cost operational electroleaching process for treating copper sulphides flotation concentrates, with a high chalcopyrite content. This research practical work aims at improving the copper extraction from that sulphide mineral, in a relatively short time with low-operating cost taking into consideration the influence of a cationic surfactant. The electrolyte of the electrolytic reaction system was a 2,0 mol.L-1 NaCl solution containing CTAB, a cationic surfactant. The electroleaching system contains one DSATM (dimensionally stable anode) anode and two nickel or copper foams (threedimension electrodes. During the electroleaching process the chloride ions are oxidized to chlorine at the anode surface, which in contact with the aqueous phase generate enough hypochlorite ions to oxidize chalcopyrite.The copper ions released from the chemical oxidation process are reduced at the cathode surface as metallic copper."

Jan 1, 2008

By P. S. Dunn, A. D. Rollett, H. D. Lewis

"The results of preliminary work on the modeling and measurement of the heat transfer coefficients of metal/mold interfaces is reported. The system investigated is the casting of uranium in graphite molds. The motivation for the work is primarily to improve the accuracy of process modeling of prototype mold designs at the Los Alamos Foundry. The evolution in design of a suitable mold for unidirectional solidification is described, illustrating the value of simulating mold designs prior to use. Experiment indicated a heat transfer coefficient of 2 kW/m /K both with and without superheat. It was possible to distinguish between solidification due to the mold and that due to radiative heat loss. This permitted an experimental estimate of the emissivity, ~ = 0.2, of the solidified metal.IntroductionA feature that distinguishes casting processes from welding processes is the presence of an interface with a low heat transfer coefficient between the mold and the casting. Especially when chill casting, the interface delays the start of solidification and increases freezing times significantly. By comparison welds can be assumed to have a very high heat transfer coefficient. The heat transfer coefficient controls such phenomena as folds and laps on the surface of castings which can be crucial to the acceptability of a casting. The time delay for the start of solidification influences the occurrence of cold shut defects. The standard mold material for uranium casting is high quality graphite which is an excellent refractory when used in vacuum and coated with a refractory wash. Graphite is an effective chill material and has a thermal diffusivity approximately twice that of uranium. Experience has shown that practicable superheat without mold pre-heat is not sufficient for avoiding cold shut defects when casting in graphite molds.TheoryIt is possible to calculate the position of the freeze front s, as a function of time, t, the superheat and interface heat transfer coefficient, h, [1]. However, the value of h cannot be obtained explicitly. The Virtual Adjunct Method (VAM) [2] offers a method for extending the standard equation for an insulating mold where s is proportional to the square root of time. By considering the effect of the interface to be equivalent to finite thicknesses of mold and metal, the following quadratic equation is obtained,"

Jan 1, 1986

By Yoshisada Michiura, Junko Umeda, Katsuyoshi Kondoh

Rice husks or straws, one of the main agricultural wastes in South-east Asia, have a large possibility to be employed as usefully renewable resources to produce energy and high-purity silica (SiO2), because they consist of about 70% organics such as cellulose or hemi-cellulose, and 20% amorphous SiO2. The former is utilized as bio-mass energy; for example, thermal or electric energy, and bio-mass ethanol. High-purity silica can be used as raw materials in the industrial uses. It would be possible to extract silica elements from rice husks and straws by burning them in air because their main contents are organics. In the previous studies, a strong acid leaching treatment on rice husks before burning was carried out by using H2SO4, HCl and HNO3 to prepare high-purity silica materials. This was available to accelerate the hydrolysis of celluloses and hemicelluloses contained in rice husks, and remove the above metallic impurities. A strong acid leaching treatment, however, is significantly hazardous to environment and human life, and causes an increase of the process cost. In this study, the environmentally benign, harmless to human and economically effective process to produce high-purity amorphous SiO2 materials from rice husks has been established without using strong acids. From a viewpoint of the harmless influence on human body, the carboxylic acids were used in the leaching treatment on rice husks. TG-DTA measurement and GCMS analysis indicated that the leaching was effective for the hydrolysis of celluloses and hemicelluloses contained in rice husks at 473K~873K, which produced the same results in using the conventional sulfuric acid. The metallic impurities could be also removed from the husks via a chelate reaction between carboxyl groups (-COOH) and the metal elements. In particular, it was clarified that cadmium (Cd) were completely removed from rice straws by this reaction. Concerning the burning conditions of rice husks after the acid leaching, it was necessary to supply a suitable amount of air to completely combust organics; for example it required air supplement of 50 ml/min. or more. The burning temperature should be less than 1273K to obtain amorphous structured silica. High-purity amorphous silica materials with 99% or more were prepared from rich husks by applying the citric acid leaching treatment and burning process at 1073K in air.

Jan 1, 2008

By Baozhong Ma, Qian Li, Yonggang Wei, Shiwei Zhou, Bo Li, Chengyan Wang, Hua Wang

The magnesium-rich nickel oxide ore (w (Ni) =1.09 %, w (MgO)=29.08 %) mixed with 6 % and 8 % anthracite were roasted at different temperatures. XRD and SEM/EDS techniques were utilized to characterize the phase and microstructure transformation of the ores. The results show that lizardite and chrysotile of raw ore were converted into forsterite and enstatite during reduction roasting process. Simultaneously, iron and nickel oxide were reduced and migrated from the initial magnesium silicate. Fe3Si were formed when the roasting temperature went up to 1300 ℃ and 1350 ℃, and a small amount of Ni was observed in it. Temperatures got too high were not benefit to the polymerization of ferronickel.

Jan 1, 2015

By Honggang Zhong, Wei Du, Qijie Zhai, Junjie Sun, Jingzheng Ye

"Effects of pouring temperature and cooling water flux on solidification structure of ferritic stainless steel are investigated with a thermal simulation setup. The results show that with pouring temperatures 1518° C, 1528° C, 1538° C and 1548° C, both Lmean (the mean length between columnar to equiaxed transition(CET) position and chill surface of the samples) and the mean dimension of equiaxed grains increase. On the other hand, with cooling water flux 400, 800, 1200 and 1600mL/min, Lmean gradually increases, and the mean dimension of equiaxed grains decreases. In addition, low pouring temperature and cooling water flux enlarge the ratio of fine equiaxed grains.IntroductionFerritic stainless steel plays an important role in industry products nowadays. Compared with austenitic stainless steel which contains both chromium and nickel, ferritic stainless steel can obtain good corrosion resistance despite the absence of nickel [ 1]. F erritic stainless steel has been widely applied in automotive exhaust systems [2], electrical equipment, construction and chemical industries and also has broad development prospects. At present, continuous casting technique has developed into an important technology applied in iron and steel making. The solidification structure of continuous casting slab has significant influence on the final properties of stainless steel. The developed columnar grains of ferritic stainless steel would result in negative effects on mechanical property [3]. However, fine and homogeneou& equiaxed grains can improve the comprehensive properties of ferritic stainless steel [4] Therefore, it makes great sense to promote the columnar to equiaxed grain transition (CET). Recently Baosteel has developed a new type of Cr-saved ferritic stainless steel, but the effect of continuous casting conditions on its solidification structure is unknown. It is important to investigate the effects of solidification conditions on solidification structure of this new ferritic stainless steel, which can give guidance for optimizing the production process."

Jan 1, 2014

By Keiji Okumura, Jiayi Shan, Jian Yang, Masamichi Sano

"A new method of deoxidation and desulfurization of molten iron with magnesium vapor has been developed. An immersion tube, which was filled with pellets of the mixture of magnesia and carbon powders, was put into the molten iron. Magnesium vapor produced by carbothermic reduction of magnesia inside the tube was injected directly into the molten iron with argon carrier gas. The effects of temperature and carrier gas flow rate on deoxidation and desulfurization were investigated. A mathematical model of the reactions was developed. The rates of deoxidation and desulfurization were controlled by mass transfers of magnesium vapor in the gas-phase and oxygen and sulfur in the liquid-phase. This method may offer high efficiency for magnesium deoxidation and desulfurization of molten iron.IntroductionMagnesium is a strong refining agent in steel-making processes1 • At steelmaking temperatures, magnesium has a very low solubility in liquid iron, and a very high vapour pressure2 • Deoxidation and desulfurization with magnesium take place essentially through the interaction of magnesium vapor with oxygen and sulfur dissolved in molten iron, and magnesium can change chemical composition of nonmetallic inclusions3 • However, addition of magnesium to the steel bath is dangerous and does not give high efficiency in the refining process4 • Furthermore, as a refining agent, the price of magnesium is higher than aluminium and CaO fluxes. In the present study, a new method of the deoxidation and desulfurization of molten iron was developed using magnesium vapour in-situ produced by carbothermic reduction of magnesium oxide. Pellets made of mixture of magnesia and carbon powders were charged into an immersion tube, which was made of alumina or graphite. The magnesium vapor was injected directly into the melt. The effects of pellet mass, experimental temperature and carrier gas flow rate were studied on the refining rate. A mathematical model of the refining reaction was proposed on the basis of the experimental results."

Jan 1, 2000

By Zvi Rivlin

Classical nucleation theory states that in first order phase transformations, such as liquid to solid transition, nucleation of the product phase starts with the formation of small, unstable clusters (embryos). When the thermodynamic barrier to nucleation is overcome, the embryos grow and attain a critical size, beyond which they are stable, i.e. they become nuclei. If nucle- ation does not occur, the parent, liquid phase remains in metastable equilibrium. At temperature lowers, undercooling increase and atomic mobility decreases. The viscosity change in the undercooled liquid may result in the formation of glassy state. As demonstrated in previous papers [I-21, in solidification involving surface nucleation of the product phase, as the case is in rapid quenching by melt-spinning, both nucleation temperature and nucleation time depend upon the number of atoms available at the isothermal surface in contact with the substrate. As a result of the thinness of the melt-spun ribbons, the embryo clusters that form at the freezing temperature may not be supplied by the amount of atoms necessary for their growth to critical nuclei sizes. In such extreme conditions, the liquid does not crystallize, it forms a metallic glass. A numerical simulation method is proposed for the reactions involved in embryo cluster formation and growth, at the atomic level. The simulation enables the caIcuIation of either the nucleation or the glass transition temperatures. Calculations made for the well-known glass forming CuZr and FeB systems afford prediction of the geometrical and thermodynamically conditions necessary for the formation of either crystalline or amorphous ribbons in melt-spun ribbons.

Jan 1, 1994

By Ying-Chu Hoh

The extraction of cerium(IV) by valence change with two-phase electrolysis was studied experimentally. The results show that the electro-oxidation extraction depends mainly on the distribution of the solute between the two phases, the reaction on the electrode surface and the diffusion of the reactant and product between the electrode and aqueous interphases. The effects of various parameters on cerium extraction were also studied. The selected parameters were background current, catholyte acidity, agitation speed, operation current and voltage and surfactant addition. The electro-oxidation extraction mechanism can be divided into eight steps. In addition, Wee the rate of extraction is quite fast, the percentage extraction Ce+4 can be taken as an index to show the conversion rate of Ce+3 J to Ce+4.

Jan 1, 1989

By Pengfu Tan

A thermo-chemical model of the copper P-S converter and a viscosity model for the converter slag have been developed to predict the behavior of magnetite in the converter slag, amounts of slag and matte, compositions of slag and matte, volume of the bath, bath temperature, slag blow endpoint determination, SEMTECH OPC signals, and the viscosity of converter slags. The predictions of bath temperature, slag and matte compositions, and magnetite content in the slag have been validated by the industrial data. The effects of fluxing strategy, returns and skim charges, oxygen enrichment, and temperature on the magnetite formation in the slag have been predicted and discussed. The effect of oxygen potential, SiO2/Fe in slag, detection of slag blow endpoint, and temperature on Fe3O4 content in converter slag, slag viscosity, liquidus temperature of converter slag and skimming operation has been modeled and discussed as well. Some applications of the industrial operations have been presented.

Jan 1, 2009

By Selvin Yesilay, Munevver Caki, Canbora Bayraktar, Bekir Karasu, Rahmi Imrak

"In this study, the utilization capability of the solid wastes taken from a commercial roof tile and brick factory in Eskisehir of Turkiye has been investigated in the production of stoneware bodies which can be formed by slip casting. At the first stage, X-ray fluorescent (XRF) and X-ray difractometer (XRD) analyses of the wastes were performed. Depending upon the results, a body recipe with an optimum casting concentration was adjusted. The bodies obtained from prepared slips were fired at 1160 oC as glazed and unglazed forms. Then, they were undergone certain tests in order to determine their firing shrinkage values, water absorption levels and optical parameters. To establish what kind of phase formations occurred after firing as a result of waste incorporations into bodies XRD analysis was conducted. Additionally, effects of such a compositional modification on the microstructure of the bodies were examined by a scanning electron microscope (SEM). Consequently, it was concluded that fired roof tile and brick wastes could be evaluated in both glazed and unglazed stoneware bodies. Introduction Stoneware is the general name applied to many wares fired between 1150 and 1300 °C. It has a different and denser structure than those of ceramics produced at lower temperatures. Fired stoneware possesses a lower water absorption value. When matured at a high temperature, it gives a possibility for the use of feldspar as a main ingredient [1-2]. Colors of stoneware can be brown, red, white and most of the times beige. Firing usually takes place in oxidation atmosphere but also reduction can be rarely used. This naturally has an effect on the body colors [3]. Earth, which contains clay minerals, becomes plastic mud when mixed with water, has a capability to be easily shaped and can be hardened without cracking if fired at 900-1000 °C, is referred as one of the brick and tile raw materials [4]. Natural and aesthetic appearances of buildings obtained with brick and tile products, which make them preferable especially for construction sector, are of importance. Because clays being main raw material of that type of productions generally do not exist as pure materials in nature, their usability depends on their mineralogy and impurities they contain [5]."

Jan 1, 2008

By Yoji Imai, Akio Watanabe, Masakazu Mukaida

"To clarify the feasibility of alkoxides and acetylacetonates as precursors for laser CVD of metal oxides, vapors of tantalum or titanium alkoxides and zirconium acetylacetonate were irradiated by KrF excimer laser and deposits were characterized by XRD and XPS measurements. As for tantalum and titanium, non-stoichiometric crystalline oxides grew nearly phototropically, however, zirconium oxides deposited showed only halo-pattern by XRD measurements. Electric conductivity measurements of tantalum oxides implied the improvement of the insulating properties by the addition of activated oxygen to the ambient.IntroductionThere has been renewed increasing attention to the metallic oxide thin films because ofits promising usefulness in many applications, such as high-Tc superconductors and ferroelectric devices. A variety of thin film preparation techniques have been studied such as sputtering, chemical liquid deposition (sol-gel and metalorganic decomposition), pulsed laser deposition and chemical vapor deposition (CVD). Among them, we think CVD is the most promising method because it offers a high controllability of morphology and good step coverage at relatively high growth rate. Preparation of oxide films by CVD can be achieved using a precursor containing metallic element and oxygen containing gas such as N20 at the same time. However, metalorganic (MO) compounds which contain both metallic element and oxygen, directly bonded to metallic element, seems to be more favorable because some of MO has a good properties for CVD such as a rather high vapor pressure, stability in ambient and low toxicity."

Jan 1, 1998

By Arthur G. Hunt

Smelting using the direct-to-blister process commenced at Olympic Dam on 31 July 1988. The unique nature of the Olympic Dam ore body led to the selection of the direct to blister smelting process. Significant improvement in the design of the furnace and the understanding of the fundamentals of the process and its operation has occurred in the 10 years of operation. The paper will discuss the operation of the #1 Smelter and the design, preparation for start up and early operating experience of the #2 Smelter.

Jan 1, 1999

By Jason H. Nadler, Jason A. Kulpe, Stephanie J. Lin

"A numerical method has been developed to predict the microstructural characteristics of reticulated metal foam. The porosity of this foam is derived from sacrificial template particles of known particle size distribution, which are incorporated with other precursor components. In this approach, a porous structure is numerically generated starting with Powell's sphere packing algorithm. The resulting stochastic structure has characteristics similar to those of corresponding metal foam. Deterministic inter-sphere connections are calculated to more accurately model the pore morphology that evolves during thermochemical synthesis. Estimations of pore morphology and specific surface area of the simulated material are compared to lab-synthesized materials composed of equivalent constituent compositions. In addition, the effect of template particle size, inter-sphere connections, and the geometric constraints on pore morphology and permeability are investigated to refine microstructural evolution and design.IntroductionReticulated foams, characterized by their interconnected pore network, can be obtained by incorporating spherical sacrificial template particles into precursor materials followed by template removal processes. The resulting structure is composed of contiguous spherical pores whose morphologies reflect those of the original templates. Based on some of the unique features of this synthesis approach, a methodology is introduced in this work whereby these foams are digitally constructed using experimental data from the template particle sizes and precursor formulation. Digitally constructed porous structures can then be compared to their laboratory synthesized counterparts through the quantification of structural features such as porosity and surface area per unit volume, which in tum are used to inform the foam's fluid transport propertiesThe spherical template particle packing algorithm developed here is adopted from Powell's work [1], which also includes approaches to obtain percolation and density in random packings [2]. Gervois gives a mathematical development for the stereological sectioning of packed hard spheres [3]. Stereological sectioning facilitates determination of relevant three dimensional morphological properties from two-dimensional data [4]. Studies on the sphere distribution size and the related particle packing density and coordination number results are studied in [5, 6]. Lastly, Kato describes a sintered neck structure, which is used with these packings [7]. This neck structure, as a model of the particle shape following heat treatment, is implemented here in a similar manner. A strong difference between the available literature and the methodology here is that spheres are packed to ultimately represent porous space, not rigid solid space."

Jan 1, 2011

By Hiroshi Ono

"By newly developed ICP method, trace amounts of As(III), As(V) .,Sb(III) and Sb(V) were precisely determined within accuracy of sub ng/ml. As(III) and Sb(III) were separated from As(V) and Sb(V) by extracting into ·xylene as diethyldithiocarbamate complexes using diethylammonium diethyldithiocarbamate (DDDC), and then back-extracted into nitric acid for a quantitative determiruition by ICP-AES equipped with hydridegeneration system The recoveries of As(III) and Sb(III) were satisfactory throughout the extraction with 0.04mol/l DDDC in xylene from lmol/l hydrochloric acid solution and the back-extraction with 7 mol/l nitric acid. As(V) and Sb(V) were reduced to As(III) and Sb(III) by ascorbic acid and potassium iodide, and their quantities were determined as mentioned above. The detection limits were found to be 0.58ng/ml for As(III), 0.63ng/ml for Sb(III) using 50ml of a sample. The proposed method was applied to analysis of the real sample.Introduction In drain, arsenic(AS) concentration is prescribed below 0.lmg/l, so As must be removed. As is existed at .the form of As(III) or As(V) in solution. For t1Jeir difference of chemic;µ property, it is not easy to remove As in solution. So it is an urgent necessity to develop for determining concentration of As(III) and As(V). Antimony( Sb) has resemblance .chemical property to As. So Sb was experimented the same as As.The separation and determination of As(III) and As(V) have been carried out using several methods, such as ICP after copreclpitating separation, HPLC, direct hydride generation atomic absorption. However these methods have some problems. One of main problems is that HPLC and direct hydride generation atomic absorption methods are influenced by coexisting elements."

Jan 1, 2000

By Junji Shibata

Waste solution from the Ni non-electric plating process contains 4.0 kg/m3 Ni, 0.1 kglm3 Fe, 0.0 I kg/m3 Zn, 48 kg/m3 S042-, 98 kg/m3 HP032-and 31 kg/m3 laetic acid as a typical composition. Solvent extraction, cementation, ion exchange resin and precipitation methods are possible to use for the treatment of this kind of solution. In this study, solvent extraction of Ni was investigated using two kinds of extractants to clarify the relation between extraction percent and pH for various extractant mixtures. As Ni ion has an octahedral structure with ligands, the synergistic effect for Ni extraction is considered to take place in solvent extraction using two types of extractants. The investigation of the synergistic effect for Ni extraction was carried out in case of various extractant systems.

Jan 1, 2003

By Ann M. Hagni

Electric arc furnace (EAF) dust from the secondary steel industry contains lead, cadmium, and chromium that causes it to be classified as a hazardous waste. Pyrometallurgical treatment of EAF dust is directed at recovering zinc and simultaneously rendering the dust non-hazardous. The mineralogy of the EAF dust is important in determining the occurrence and phase relationships of the zinc, lead, cadmium, and chromium contents. The principle phases in EAF dust as determined by reflected light microscopy, SEM-EDS, and XRD are solid solutions of the iron spinels (franklinite, magnetite, and jacobsite), zincite, hematite, and Ca-Fe-Si glass. Chromium is present in small amounts in solid solution in the spinels. Cyclone sizing of the minus 53 pm particles shows that more than 50% of this size fraction are less than 10 pm in diameter. The <I0 pm particles contain zinc as both franklinite in solid solution with magnetite and jacobsite, and zincite as determined by transmission electron microscopy and XRD. Auger electron spectroscopy did not detect coatings of volatile phases on the surfaces of EAF dust particles.

Jan 1, 1994

By R. Dekkers

Non-metallic inclusions in liquid steel are mainly formed during killing. As far as these particles are not captured by the slag, they are found in the cast steel where they can deteriorate the mechanical properties. Inclusions may also disrupt the continuous casting process, affecting thus directly the quality of the steel and the production capacity. Steel pin samples from the Sidmar plant (Belgium) were taken in different steps of several ladle treatments and in the tundish. Also slab samples were studied. All samples concern the same type of low alloyed aluminium killed steel. The non-metallic inclusions were isolated from the steel matrix and investigated with scanning electron microscopy and energy dispersive spectrometry. The evolution of the non-metallic inclusions is described by their number, size, shape and elemental composition. The main non-metallic inclusions present are aluminium oxides and spinel type compounds.

Jan 1, 1999

By Finn Olesen, Melina Garcia, Mark William Kennedy

"Furnace resistance is a function of the complex interrelationship between many factors including: operating practice, slag conductivity, temperature, power intensity, and geometry (electrode shape, diameter, spacing, immersion, slag depth, etc.).Accurate prediction of resistance is critical for success of the overall furnace design. The sizing of electrodes, columns, bus-bars, and transformers are all impacted. Estimation of minimum and maximum resistance or maximum operational current, as well as the maximum operating voltage are of fundamental importance.Various mathematical tools have been developed to assist designers with the selection of furnace dimensions and the prediction of resistance. Elkem found the methods of Downing and Urban 1965 and Westly 1975, to be particularly useful.In the current paper, comparisons are drawn between data from spent aluminum pot lining (SPL) demonstration testing at Elkem Bjolvefossen and predictions based on these classical tools and 3D finite element modeling (FEM) with COMSOL.®"

Jan 1, 2012