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By Shuqiang Guo, Gonghui Yang, Xingxing Zhang, Yuyang Bian, Song Chen, Weizhong Ding, Yinhe Liu, Lan Jiang

One of the most promising refractory materials for application is zirconia in melting superalloy. In this work, the properties and phase composition of magnesia partially stabilized zirconia ceramics (MgO-PSZ) under different sintering temperatures were systematically investigated. Commercial magnesia partially stabilized zirconia (MgO-PSZ) powders were selected as the starting materials. The magnesia partially stabilized zirconia phase composition was measured by X-ray diffraction (XRD), the density of sintered samples was tested by vacuum density instrument, the thermal expansion were obtained by thermal dilatometer from ambient temperature up to 1450°C, and the microstructures of MgO-PSZ were characterised by scanning electron microscope (SEM). The results indicated that the properties of thermal expansion, densification, microstructures and phase composition were significantly affected by sintering temperature. Densification was consistent with SEM micrographs of MgO-PSZ at different sintering temperatures.

Jan 1, 2015

By Andrew L. Puwis

Methodologies were presented for computing the thermal gradient associated with single crystal solidification in macroscopic computer modeling. The. heat transfer, and solidification of a shaped investment casting model were simulated using properties from three different alloys. Following the simulation of solidification, the resultant thermal gradients (G) and rates of solidification (R) from representative points were extracted in various ways and compared: It was discovered that alloy properties have a strong influence on the computed thermal gradient and rate of solidification for the three methods investigated. Data also showed that the computed gradient for each model was very different depending on the temperature range used to compute these values.

Jan 1, 1994

By Roberto Parra

The selective reduction smelting of Cu2O in Cu2O-FeOx-SiO2 melts has been studied at laboratory level, using as a feed a dead roasted calcine from a copper concentrate. The purpose of the study was to evaluate the kinetic and mechanisms of the indirect reduction with CO and the direct reduction with graphite from 1260°C to 1350°C. The reduction rate by CO was found to be 10-2 to 10-1 mole Cu2O m-2s-1. The graphite reduction macrokinetics for FeO and. Fe2O3 containing melts, was found to be a first order reaction with respect to the Cu2O concentration, with a kinetic constant of 104 to 10-3 s-1. The reduction rate was not sensitive to temperature nor to stirring, in the range studied. The measured reduction rate is almost one order of magnitude larger than the observed rate for the direct reduction of FeO.

Jan 1, 1999

By Katsunori Yamaguchi

Secondary materials, that contain relatively high concentrations of platinum group metals, (PGMs) are treated in copper smelting process. The PGMs lost in the slag is increasing with increasing quantities of scrap treated amount. To determine the portion of the PGMs chemically dissolved and that associated with the mechanically trapped matte in the slag will be a key factor to improve the recovery of those metals. An experimental study was carried out to determine the distribution of palladium between the FeOx–SiO2 slag and the liquid Cu2S–FeS matte at 1573 K and a fixed partial pressure of SO2 of 0.1 atm. It was found that the distribution ratios are around 10−3 for platinum and palladium. The distribution ratios show a tendency to increase when the grade of matte is increased above 60 mass% Cu. In addition, the solubility of platinum in FeOx–SiO2 slag equilibrated with a pure palladium and the Pd-Cu alloy was determined at 1573 K and the range of oxygen partial pressure from 10−9 to 10−7 atm. The solubility of palladium in the slag tends to increase with increasing oxygen partial pressure and activity of CuO0.5 in the slag.

By Rui Mao, Ke-Xin Nao, Jian-Liang Zhang, Xiang-Nan Xu, Meng-Fang Wei

"In this research, fundamental characteristics of dust and sludge containing iron from the dusting system of sintering process, blast furnace, oxygen converter and rolling process in steel enterprise were studied by chemical analysis, X-ray diffraction analysis, optical microscope analysis, scanning electron microscopy analysis, particle size analysis and other analysis means. Development direction of resource utilization for dust and sludge containing iron from steel enterprise was put forward on the basis of above study.IntroductionDust and sludge containing iron for steel enterprise mainly come from the dusting system of sintering process, pelletizing process, blast furnace, oxygen converter, rolling process and other related process. Iron content of dust and sludge is between 30% and 70%, and they also contain certain content of carbon, calcium oxide, magnesium oxide and harmful elements [1-3]. Output of dust and sludge is determined by raw materials conditions, technological processes, equipment configuration and management level. Dust output in sintering process accounts for about 2% to 3% of the sinter production, while dust and sludge from iron making and steel making process respectively take up 3% to 4% of hot metal and crude steel production, and the solid waste from rolling process accounts for about 0.8% to 1.5% of the output of rolled products [4,5]. Dust and sludge contains Fe, CaO, MgO, C and other valuable resources, it will not only result in the waste of resources, but also cause serious pollution to environment ifthe dust and sludge are not recycled. China's crude steel production in 2012 is about 700 million tons and output of dust and sludge containing iron is nearly 60 million tons, so, it is of great significance to have a resource recycling for dust and sludge containing iron from steel enterprise."

Jan 1, 2014

By Zhihao Yue, Honglie Shen, Yahui Teng, Ye Jiang

"In this paper, manganous nitrate [Mn(NO3)z] was used to assist the etching of silicon wafer in hydrofluoric acid (HF) for the antireflective application, and alumina (Al2O3) layer was deposited on the surface of the etched sample by atomic layer deposition method for further antireflection. The surface morphological and compositional studies of these samples were performed by scanning electron microscopy attached with an energy-dispersive X-ray spectrometer. The surface reflectance measurements were carried out using UV-Vis-NIR spectrophotometer. Binary structures of pyramids and nanopores were obtained by etching the alkaline textured monocrystalline silicon wafer in HF and Mn(NO3)z mixed solution for not more than 15 min. But excessive increase of etching time of up to 30 min resulted in the whole destruction of pyramids. The average reflectances of the 5-min-etched sample before and after being coated with 75-nm-thick Al2O3 layer are 4.62% and 3.47% in the range of 200-1000 nm, respectively.1. IntroductionAs we know, the reflectance of silicon wafer after being sliced is so high that the maximal photoelectric conversion efficiency of silicon based solar cells is limited. Therefore, alkaline texturization process was used for silicon solar cell in industrial production. But the reflectance of this alkaline textured wafer is still greater than 10% and this process can only be used for monocrystalline silicon solar cell."

Jan 1, 2013

By Nexhmedin Lohja

The production of high-carbon ferrochromium in a submerged electric furnace based on double-level technology has some advantages compared to close-type furnaces with one tap hole. These advantages include the reduction of the specific energy consumption for the overall process, good separation of ferrochromium from slag, an effective treatment of raw materials including lean chrome ores (low percentage of Cr2O3) etc. An outline of the operation of this furnace along with the production line of briquettes from fines of chrome ore by using organic and inorganic binders, will be followed by a description of the recent work carried out to improve the energy consumption in this furnace through a pre reduction process of Cr2O3 ores by the off-gas energy recuperated from the furnace and the use of SiC in the feed. A short theoretical analysis of the new work will also be given.

Jan 1, 2006

By V. I. Lakshmanan

"Historically flowsheets are developed for efficient separation of metals for economic recovery. With increasing emphasis on reduction, reuse and recycle (3Rs) efficient methods are sought to recover values from a variety of feeds where cost of collection, transportation, local consumer behaviour and regulatory guidelines dictate the development of economically viable flowsheets. Innovative understanding of potential market applications can provide means to develop value added end products. The paper with examples will discuss the use of innovative-separation technologies to obtain value added end use materials from secondary sources.IntroductionFlowsheets are developed for the efficient separation of materials of value for economic recovery. However with increasing societal pressures and regulatory initiatives for stricter environmental guidelines, there is strong need to provide focus to recover materials efficiently and economically in an environmentally accepted manner. North American industries are increasingly caught between demands for high technology value added products and responsibility for environment. An aspect that is receiving increasing attention is Design for Environment'. This incorporates a system wide approach for product design and incorporates environmentally preferable features such as recyclability, disassembly, maintainability, reusability and use of safe materials as part of a product's design objectives.The present paper with case histories will address innovative flowsheet development to convert wastes into recyclables value added products or for minimising generation of waste materials. Case HistoriesProcess for Separating Fibres from Composite Materials 1In the automotive industry, sheet molded compound (SMC) is used to produce panels, bumpers and the like. During the manufacture and at the end of life, considerable waste materials are generated which are potentially recyclable. Fibre reinforced plastics where fibre substrate impregnated with thermosetting resin, find applications in several manufacturing processes and are potentially recyclable at the end of life."

Jan 1, 1996

By James W. Evans, Dong Xu, Jr. Jones

A physical (water) model based on particle image velocimetry (PIV) has been constructed at UC Berkeley. The PIV technique enables the use of water modeling to quantitatively characterize the fluid flow behavior in the mold during the continuous casting of steel, in a whole field sense, i.e., section by section. A method to obtain e\e time-averagevelocity (TA V) vector maps was developed by averaging 40 instant aneous vectc -r plots revealing the time average features of the flow. Another benefit of TAV vector maps is the ability to compare with present mathematical models, which are mostly based on the time-average technique. Bifurcated submerged entry nozzles (SEN) with ports inclined at various angles to the horizontal were used in the modeling to study their effects on the flow inside the caster. Argon was also introduced into the model to simulate the influence of argon injection on the metal delivery from the tundish into the caster. The bubble sizes and distribution (in specific sections) of argon were characterized, at the same time, by the imaging system of the PIV. This will allow for validation of current mathematical models that were developed to simulate argon injection in casters. Comparison with results calculated by the commercial finite element package FIDAP is also presented.

Jan 1, 1998

By Xirneng Zhu

The electrochemical behavior of Pittsburgh and Illinois coal pyrite in basic and neutral borate/sulfate solutions was investigated. In the transpassive region, aggressive oxidation of pyrite occurred. The reaction products in this region were Fe(III) oxide, sulfate ion and partially oxidized sulfur intermediates. The formation of sulfur and polysulfides was identified by in-situ Raman spectroscopy. The growth kinetics of the reaction product film, resulting from transpassive oxidation of coal pyrites, were studied using chronoamperometry measurement with both stationary and rotating disk electrodes. The reaction rate was well correlated by a paralinear rate equation. The effects of electrode rotation speed, solution pH and temperature were examined. The kinetics were compared to those for mineral pyrite.

Jan 1, 1994

By R. Hurman Eric

The electrode in a slag-resistance electric furnace is the central factor in the design and operation of the furnace by its role of conveying the smelting power, i.e. heat needed for the operation. The control parameters are the size and positioning in the slag bath which are defined by slag resistivity, furnace resistance, cell constant and power input sequence all of which are closely interrelated. The flow of heat generated by the electrode current determines the energy distributions and thus the furnace dimensions. Heat flow models concerning vertical, horizontal and combined two-dimensional flows are discussed. All these considerations are based on the experimentally determined slag properties such as its resistivity.

Jan 1, 1995

By Kazuyuki Kikuta

MMAJ, a govemmental organization in Japan, has carried out a 4 year project for the development of the decontamination and metals recovering technology for the fly ashes from municipal waste incineration. Heavy metals (zinc, lead and copper) are recovered as raw materials for the non-ferrous metals production, without formation of any waste materials to be disposed. More than 500 thousands tonnes a year of fly ashes generation from the municipal waste incineration has been one of the main social issues in Japan, because most of them need to be disposed to the registered areas after decontamination, and occupy 5% of the municipal wastes disposed. The segregation, flotation and chemical process are applied to the treatment of the primary fly ash from municipal waste incineration, and MF (Mitsui-type blast furnace) Process after the chlorine removal to the secondary fly ash. The main results of experiments are -About 90% of heavy metals, zinc, lead and copper, can be recovered from the primary and the secondary fly ashes to the products for the non-ferrous metals production. -Both of the leaching residue from the primary fly ash treatment and the slag from the secondary fly ash treatment can be used as a raw material for the cement production, meaning that the decontamination technology for the ashes without the landfill has been established. -Dioxins in the primary ash can be decomposed satisfactorily, and the dioxins content in the segregation furnace gas is less than O.lng-TEQ/Nm3 without any gas cleaning system

Jan 1, 2003

By David Dreisinger

The cyanidation of copper containing gold ores results in the co-dissolution of copper along with gold. Copper dissolution results in elevated cyanide consumption that may make the treatment of the gold ore uneconomic. Copper-cyanide species in gold mill effluents may increase the environmental toxicity of the gold mill solutions. The objective of this study was to examine the use of solvent extraction to recover the copper cyanide species from gold mill effluents. Solvent extraction with Cognis (formerly Henkel) reagents LIX 79 and LIX 7950 was studied. Excellent extraction of copper and cyanide was achieved using pH control in extraction. Copper and cyanide may be stripped from the reagents using basic eluants. Various routes for copper and cyanide recovery from the strip solution were studied. Excellent results were obtained using electrowinning in both divided (Nation membrane) and undivided cells. Cyanide recovery was obtained by AVR treatment of a bleed stream from electrowinning. Full results of solvent extraction, copper and cyanide recovery are reported.

Jan 1, 1998

By Gong-yi Guo, Yu-li Chen

"A partially-stabilized zirconia powder was prepared by metalorganic precipitation process from technical-grade zirconium oxychloride and the effluent of an acrylic acid plant. The effluent contained low molecular weight carboxylic acids, i. e., acrylic acid and acetic acid. The· developed process is based on the selective precipitation of acrylic acid at suitable pH values by the addition of zirconium oxychloride to the effluent. The resulting precipitate is a precursor that can yield a pure, ultrafine, and partially-stabilized zirconia powder. The evolution of formation of the partially-stabilized zirconia in the present process was investigated using thermal analysis, infrared spectroscopy, and X-ray diffraction technique. Environmental, technological and cost advantages will make the present process feasible for manufacturing advanced zirconia ceramics.IntroductionIn recent years the superior mechanical, thermal, electrical and chemical properties of stabilized zirconia have become the focus of growing scientific and technological interest, and hence resulted in various structural and functional applications. The great potential of the material has given rise to numerous preparation approaches to obtain the material with the excellent properties; nevertheless, an extensive number of programmes are underway worldwide aimed at understanding and improving both the preparation and behavior of stabilized zirconia ultrafine powders. (1 – 8)."

Jan 1, 2000

By R. G. Haire

Studies of the f-elements under pressure provide important insights into their solid state chemistry and physics. From such studies, of the elements and their alloys, it has been established that the normally localized f- electrons of several of these elements can become, involved in bonding under pressure. The electronic behavior of f-element compounds under pressure tend to be more difficult to interpret, due to the variety and the nature of electronic orbitals that are present. The 4f-elements and some 60% of the 5f-elements have been studied under The systematic comparisons that have been established for these materials are discussed.

Jan 1, 1992

By S. G. Galbraith

We have used the principles of supramolecular chemistry to develop reagents to transport metal salts. These reagents have separated charged "compartments" which recognize a metal cation and its attendant anion(s). They are easy to manufacture as they are structurally related to the commercial hydroxy-oxime extractants for copper. Efficient protocols for loading and stripping of these extractants depend on the novel feature that they bind the metal salt in a zwitterionic form of the ligand. Transfer of the phenolic protons to the pendant amines generates the charged "compartments" to accommodate the metal cation and its attendant anion(s). This paper focuses on how these types of reagent can be used to recover base metals from sulfate and chloride media in flowsheets in which solvent extraction effects separation and concentration operations, interfacing between conventional leach and electrowin/reduction processes. Work on the development of reagents that have high selectivity for metal chloride/sulfate transport, convenient stripping protocols and appropriate hydrolytic stability will be described.

Jan 1, 2003

By B. A. Paponetti

The following report discusses the bioleaching of chalcopyrite of italian origin catalyzed by Thiobacillus ferrooxidans. The developments vcr.ius time of the main .biochemical and chemical reactions involved in the production of soiuble and insoluble species were investigated focusing on the times at which they begin and bow long they last. The precipitates were characterized both in quantity and in quality relating the rate of the process to the precipitates fonnatiom. A material. balance has been made to verify the proposed mechanism.

Jan 1, 1991

By Kouji Mimura, Manabu Kishida, Minoru Isshiki

"Purification of metallurgical grade silicon (MG-Si) by the plasma-arc zone melting method (PZM) has been examined. The process consisted in the horizontal displacement of a molten zone heated by Ar- and 10%H2+Ar- plasma-arc under atmospheric pressure. This technique, especially using hydrogen plasma-arc, promoted the segregation of impurities from the head to the tail of the bar and the vaporization of impurities of higher vapor pressures. Metallic impurities such as Fe, Ti, Cr, Mn,. Cu, Al and Ca were reduced to less than 1 mass ppm at the head side of the Si bar. Non-metallic impurities such as boron, phosphorous, carbon and oxygen were also reduced by the zoning effect and, furthermore, by activated hydrogen atoms dissociated in the high temperature plasma-arc according to the following reaction: Q (in liq.Si) + 2H = H20. Plasma-arc zone melting with hydrogen plasma has been recognized to become an effective purification technique of MG-Si for the production of a low cost solar grade Si (SOG-Si).IntroductionDemand of high-purity Si for solar grade silicon (SOG-Si) is supposed to be further growing in the near future. The purity of SOG-Si required for the photovoltaic cell is more than six nines. An expensive semiconductor grade silicon (SEG-Si) with the purity of around eleven nines has been used to satisfy the demand. Development of techniques and processes for the production of a low cost SOG-Si is therefore necessary [l]. Although many purification techniques, such as directional solidification, plasmaarc melting and electron beam melting [1-6], and processes, such as carbothermic reduction of high purity silica [7], have been examined and proposed for this purpose, a more efficient and practical purification technique is still required.In the present work, the purification of MG-Si has been investigated using a plasma-arc zone melting (PZM) technique developed by the authors. Plasma-arc melting, which is well· known as a useful melting method for various metals and alloys, has been recognized to be efficient for refining and degassing several metals if hydrogen is added to the plasma generating gas, resulting in the so-called hydrogen plasma-arc. For example, deoxidation of Fe, Co and Ta [8,9], decarburization of Fe [9] and removal of metallic impurities from Zr, Ta and Fe [10-12] have been reported. This excellent refining effect is considered to be caused by dissociated and activated hydrogen atoms formed in the high temperature plasma-arc."

Jan 1, 2000

By Yanhui Sun, Yanan Zeng, Kaike Cai

"Hot ductility of Nb-V-containing steel has been studied by theoretical calculation and thermal simulation experiment. Meanwhile, microsegregation and precipitates were analyzed. The results showed that segregation degree of elements S, P, 0 is greater in mushy zone, while, the hot ductility was deteriorated by inclusions of Fe(S,O), (Fe,Mn,Si,Al)(S,O) in the interdendritic region. At the temperature 1100°C, a few NbN particles, 60-70nm, have little effect on mechanical property. In the temperature range 1000°C to 975°C, R.A declined rapidly from 82.36% to 69.61% with the diameters decreasing from 20 to 10nm and quantity of particles increased 23 to 45inds/µm2, respectively. In the temperature range from 900°C to 850°C, R.A reduced unobviously from 34.27 % to 30.01 % with ferric films thickening gradually. The critical stress, 52.38MPa, was equal to tensile strength at 975°C. Intergranular fracture was easy to occur with higher critical stress below 975° C.IntroductionProductivity and product quality of slab are seriously affected by cracks during continuous casting and the influencing factors of cracks are various[l]. From microcosmic angle, resisting deformation ability of initial solidification shell decreases obviously with solute elements segregation which can urge the low melting point ofliquid film to form at grain boundaries[2, 3]. Meanwhile, with temperature decreasing, particles would precipitate as the practical solubility product is greater than equilibrium solubility product. The carbonitrides would lead to stress concentration at austenite grain boundaries. Therefore, the transverse cracks of microalloyed steel would form during the straightening operation in the continuous casting process. The hot ductility of steels in the temperature of mushy zone was characterized by microalloy elements segregation, zero strength temperature (ZST) and zero ductility temperature (ZDT). The nature, shape, and size of precipitates have been investigated by TEM (JEM2100). Hot tensile test with low strain rate was simulated by Gleeble-1500. The objective of present study is to provide reference for zero defect of microalloyed steel during continuous casting process."

Jan 1, 2013

By E. A. van Dijk

Dusts from steel-making processes contain substantial amounts of zinc. Such dusts are also a hazardous waste and dumping them becomes unacceptable from environmental point of view. Therefore processes that can recover zinc and possibly other metals from steel-making dusts are being investigated. The aim of this paper is a contribution to the more fundamental kinetic aspects of zinc reduction from silica free calcium ferrite slags. The effects of alumina, lime and magnesium oxide contents of the slag, the COICO, ratio and the effect of initial Fe2O3/CaO ratio were studied experimentally at 1400°C The results indicated that the reduction of zinc from molten slag was possibly a first order reaction. As expected higher COICO, ratios increased both the extent and the rate of reduction. It was also observed that a higher iron content of slag improved the reduction of zinc from calcium ferrite slags. This fact seems to support the proposed mechanism that zinc is partly reduced by ferrous iron to zinc vapour and that ferric iron is reduced by carbon monoxide. The reduction rate of zinc in these slags was decreased by increasing alumina content of the slag. Alumina decreased the calculated optical basicity of the slag showing the fact that reduction of zinc oxide was more favorable in more basic slags. Probably the formation of complex ions by alumina and zinc oxide such as ZnAl2O32+ lowers the activity of Zn2+ ions in the slag and hence render them more difficult to reduce.

Jan 1, 1999