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By E. Gutierrez-Miravete

Hot pressing processes are widely used to shape metallic, ceramic, and glass components. The process is an essential step in manufacturing ceramic fibre-glass matrix composites. The paper describes the use of computer simulation by the particle method, to the analysis of the deformation and flow of glass during hot pressing. The hot glass is represented by an assembly of interacting particles which deform in response to the applied pressure. The results, which should be regarded as complementary to continuum-based studies, provide useful insight about the hot pressing process.

Jan 1, 1990

By Tengfei Qi, Liqiang Fan, Huiqing Tang

A new method to process the oolitic high phosphorus iron ore for phosphorus removal has been proposed in this research. It is an integration of direct reduction and melting separation with carbon-containing pellets prepared using biomass char. Experiments of direct reduction were preceded using a tubular furnace and three parameters were investigated and they were reduction temperature, biomass char adding ratio(molar ratio of carbon to oxygen） and atmosphere. Results show that the optimum condition is of reduction temperature is 1373 K, biomass adding ratio 0.9, PCO2/PCO 1.0 and reduction time 15~25 min. Under this condition, the reduced briquettes with a metallization of 75.0~80.0 % and a residual carbon content of 0.69~0.11 wt% could be obtained. Subsequent melting separation experiments were conducted using a Si-Mo high temperature furnace. Results show metal with phosphorus content of about 0.4 mass% could be obtained from the reduced sample.

Jan 1, 2015

By Kurt A. M. Westerlund

The basic function of primary gas handling downstream non-ferrous pyro-metallurgical processes is cooling hot sticky gases to treatable temperature levels (e.g. entering ESP). That means managing efficient the critical gaseous components from a molten via a sticky to a solid phase. The article outlines the modem gas cooling methods combined with efficient heat recovery. Examples of the alternative use of recovered steam energy are outlined; as e.g. drying of concentrate and power generation. The heat transfer impact of the insulating dust is called fouling and circumstances causing fouling are described. Modem cooling surface design and cleaning techniques to keep fouling in reasonable limits are described. Leakage- and false air ingress into the gas handling lines often limits smelting capacity. The objective is generally to minimize the infiltration of air but it still takes place at open interfaces (e.g. at reactor hood, feed port). Leakage air at furnace roofs for example can be reduced to a minimum by adopting the pressure gas sealing used at present In-Bath-Lance furnaces. Modernization and optimization methods to de-bottleneck existing waste heat boiler gas cooling capacity by highly efficient surface cleaning systems and false air avoiding (e.g. bundle roof boxes, dust discharge) are detailed described.

Jan 1, 1999

By Robert E. Moore

Renewed interest in olivine refractories has led to efforts to characterize them employing modern techniques of experimentation and data analysis. Initial studies have focused on determination of physical and thermophysical properties. Special equipment for the determination of thermal shock resistance and creep behavior have been constructed. Optimal compositions for maximizing various properties are being identified using appropriate statistical techniques. The overall goal is to develop response surfaces for each of a selected group of engineering design and use properties. Development of ?olivine Refractories? in the United States The term "olivine refractories" is used here because it does appear that domestic deposits of this rock will be the focus of renewed interest and "olivinell is the preferred term in this country. There are extensive deposits of high quality olivines extending through parts of Georgia. North Carolina and in the state of Washington. The eastern olivines are much more localized and extensively altered compared to the western materials. The Washington olivines exist as massive rock deposits in the Twin Sisters mountain area northeast of Seattle and their inaccessi-bility has slowed efforts to develop them. The North Carolina olivines have been used in steel plant applications since the 1930's. Geologists use the term "olivine" to describe assemblages of ortho-silicates. 2RO.SiO2, wherein the RO may be MgO. FeO. MnO. etc. When the RO consists essentlally of MgO and FeO. the material is called dunite and. as such, is synonymous with "refractory olivine." Refractory olivines utilizing North Carolina materials were developed for brick products by Birch and Harvey in this country around the mid-1930's. (I) Their work was completely independent of that of V. M. Goldschmidt and co-workers who used massive dunites located in Denmark. (2) These deposits are currently being mined by A/S Olivine of Denmark for the manufacture of a rather complete line of brick shapes for use in steel-plant. glassplant. and cement kiln applications. Birch and Goldschmidt

Jan 1, 1982

By Evgueni Jak

Recent advances in analytical, experimental techniques, and computer-based theoretical modelling of fundamental properties and elemental processes, provide new opportunities to develop the next level of whole-of-reactor pyrometallurgical furnace models. These models have the potential to significantly improve the prediction of, and adding value to, industrial operations. In non-ferrous smelting, the starting point of these models is the development of multicomponent thermodynamic databases for gas-slag-matte-speiss-metal-solids phases supported by systematic experimental research. The whole-of-reactor-models additionally should take into account kinetic processes taking place at micro- and macro- scales, and other key factors. Examples of applications of the latest research tools and modelling approaches to analysis of industrial flash and top submerged lance (TSL) sulphide smelting processes are presented. Different levels of industrial modelling are discussed from elemental local reactions, through general and more detailed whole-of-reactor-models, to plant sections and further to whole plant operation models. Some principles for development of pyrometallurgical reactor models are discussed.

By John Wallace

"Monitoring compound semiconductor crystal growth using multifrequency eddy currents for sensing illustrates some of the extreme problems of measurement and interpretation that are not often seen in metallic systems. Using sensor arrays and scanning sensors have produced a qualitative and quantitative understanding of some of the high temperature electrical conductivity mechanisms in several compound systems. A detailed review of the CdTe/CdZnTe data is presented showing some of the complexity in the data as opposed to what is found in elemental semiconductors.HistoryThe most common goal in the use of eddy current measurement in crystal growth is to deter-mine the curvature of the liquid solid interface during growth to test if the heat transfer estimates of the thermal design were adequate for single crystal growth[l]. This aim could be met but represented only a small fraction of the data that was produced observing a growth cycle. A secondary consideration was what could be discovered in the recorded data about the growth and subsequent heat treatment as the boule cooled. This is usually a more difficult task because a crystal growth process is not a controlled experiment so much as a process that continually sees modification. Using a sensor arrays or a scanning loop has produced a qualitative and quantitative basis for understanding some of the high temperature electrical conductivity mechanisms. The implication of the these measurements of electrical conductivity variations are important in that they reflect the complex defect states that will occur on cooling and heat treatment following crystal growth. In contrast to the complex behavior of the conductivity of these compound semiconductors in the solid and liquid state we have the very well characterized system silicon to compare. Initially the interest on using eddy currents to monitor compound semiconductors came from G. Westphal at the Texas; Instruments Company in 1987 to monitor aspects of growth and compounding of GaAs. This was followed by work on solution growth of HgCdTe with D. Witter. The initial interest in the use of eddy cur-rents for monitoring CdTe crystal growth came from Prof. Wilcox at Clarkson University in the practical interest to determine and control the crystal interface curvature during vertical brigdeman growth. The first actual work was done by one of his former students. G. Neuge-bauer at the II-VI Corporation which was carried on by G. Rosen at Clarkson and R. Shetty at II-VI Corporation and with A. Socha at Johnson-Matthey Electronics. The work on CdTe extends over four years and yielded sufficient data to allow one to evaluate the utility of the information produced as compared to what could be obtained from monitoring an elemental semiconductor such as silicon."

Jan 1, 1997

By Akira Yazawa

In the field of pyrometallurgy, the equilibrium evaluation has recently become easy by use of thermodynamic software, but it is strongly desired to estimate the amounts of non-equilibrium minor components to simulate practical processes. However, simple physico-chemical technique can not be applied to evaluate practical non-equilibrium components for many reasons. As an engineering solution for postulated equilibrium system, the activity coefficient is modified and introduced as the simulation parameter referred to as the "adjustment coefficient." This modified thermodynamic calculations were adopted to various sulfide roasting processes where many solid phases are participating and the system is not necessarily in equilibrium. Successful simulation was realized by assigning suitable adjustment coefficients for minor components which form a pseudo solid solution in the calcine. Some examples from sulfation roasting and dearsenizing roasting were discussed. In the smelting system, the loss of copper in slag is caused by equilibrium and non- equilibrium reasons, that is, chemical dissolution and entrainment of copper in slag. The total copper content of slag was simulated by use of the adjustment coefficient for entrained copper.

Jan 1, 1998

Microstructural investigation has shown that grain splitting or deformation banding ( DB ) develops progressively with increasing strains during cold rolling. Of particular significance to simulating texture development in cold rolled BCC polycrystals is the operation of higher order slip systems other than 110 and, the occurrence of DB in the rolling plane since the latter allows a new relaxation of the shears. Deformation banding ( DB ) model includes grain subdivision in the rolling plane and applies the Relaxed Constraints ( RC ) mechanism for the other shears. An energy criterion for deciding whether deformation banding occurs or not has been postulated, referred to as Deformation Banding Criterion ( DBC ). This paper reports the results of the investigations into the effects of different slip systems, i.e., those based on 110, 112 and 123 slip planes and their combinations using RC, DB and DBC models, in developing simulated BCC rolling textures.

Jan 1, 1999

By Shivendra Sinha

Total pressure oxidation (TPOX) is widely outreached leaching practice for base metals from sulfide minerals, wherein high temperature (T ∼ 200 °C) and oxygen pressure (pO2 ∼ 25 bar) are required. These aggressive conditions intensify the oxygen mass transfer, and therefore facilitate metal dissolution. However, challenging-cum-negative aspects of such practice are energy and material intensive requirements and high oxygen demand. Thus, the present study explores the novel emulsified medium for enhancement of oxygen mass transfer, which assists faster metal dissolution at significantly lower temperature and pressure condition. It is possible to achieve quantitative dissolution (>95%) of Cu, Ni and Co from mixed sulfide minerals at T ∼ 95 °C and pO2 ∼ 2 bar using an emulsion of 2.5% (v/v) n-Hexadecane in dilute sulfuric acid. In addition, n-Hexadecane was found to be inert, stable and immiscible in a pressurized leaching system, thus can be easily separated and recycled in subsequent leaching stages. Thus, this study offers an energy efficient route for low temperature-pressure leaching of sulfides.

By Jie Li, Thomas A. Rawdanowicz, W. J. Collis, S. Venkatraman, S. Iyer

"InSb being the lowest band gap. material amongst the 111-V semiconductors with low effective mass has long attracted research interest, due to its potential application in far infrared devices and for high speed circuit elements. In this paper, we report, for the first time, Te-doping of InSb on GaAs substrate using SnTe doping source with molecular beam epitaxy (MBE) technique and its electrical characterization. The undoped epilayers are n-type in the temperature range of 10 K to 300 K investigated. The room temperature (RT) mobility as high as 64,810 cm2/V·s (1.9x1016 cm-3) have been measured on a 4.8 µm thick epilayer. Sn Te doping at different doping levels were investigated. 5. 7 µm thick doped layers with RT carrier concentrations ranging from 2x1016 cm-3 to 3.2x1018 cm-3 with corresponding full width at half maximum (FWHM) of x-ray (400) rocking curve varying from 170-200 arc-seconds have been achieved. The Hall mobility of 20,000 cm2/V·s at 1.3xl018 cm-3 carrier concentration was obtained indicating that SnTe is a good candidate as source material for n-type doping of InSb.IntroductionThe thin films of InSb and InSb-based alloys have found considerable interest because of potential applications in III-V semiconductor-based infrared optoelectronic devices1• In addition, the advantage of the small effective mass and the consequent high mobility can be utilized in high frequency and high-speed circuit devices2 InSb can also be used in magnetoresistive sensors for position sensing3. Epitaxial InSb films grown by MBE may be doped n-type with Si or Sn, or with the group VI elements, namely, S, Se, or Te. Of the group VI elements, Te may be advantageous because of its relatively low vapor pressure. However, the vapor pressure is high enough to have sufficient memory effect during MBE growth. Hence different telluride compounds such as GaTe45, PbTe6 and Sb2Te37 have been used as the dopant source for Sb-based compounds. SnTe has also been used as a successful n-type dopant in the MBE growth ofGaSb8 But, to our knowledge, there is no report on the investigation of SnTe doping of InSb. In this paper, we report the first doping characteristics of SnTe in InSb layers grown on GaAs substrate."

Jan 1, 1998

By Zhihong Liu

Monodisperse micron size nickel oxalate particles with rhombohedron morphology were prepared from condensed Ni(OH)2 suspension by a novel gel-sol process proposed by one of the authors. Firstly, condensed nickel hydroxide gel was formed by fast adding 1 mol dm-3 NaOH solution into 0.2 mol dm-3 nickel chloride solution, and then oxalic acid solution with a concentration of 0.25 mol dm-3 was dropped into the gel drop wise through a pump equiped with a pH controller under preset pH value, and in this process, Ni(OH)2 gel was converted gradually into monodisperse nickel oxalate sol. The formation of the nickel oxalate particles was found to proceed through a dissolution-recrystallization mechanism from the nickel hydroxide gel. The product particles exhibited rhombohedron like shape with micron size long axis and sub-micron size short axis. The effects of such factors, as temperature, surfactants, et al, were evaluated experimentally on the particles sizes and morphologies.

Jan 1, 2006

By Shizhe Liu, Bing Li, Heng Wang, Zuxin Zhao

In this paper, cyclic voltammetry and chronoamperometry have been applied to investigate the effects of Nd2O3 concentration on the anode effects, critical potential for the anode effects and Nd2O3 reduction in LiF-NdF3-Nd2O3 melts at 950℃. The results show that the oxidation peaks in the potential of about 2.7V are attributed to the oxygen ions oxidation and the peak current density increases with Nd2O3 concentration increase from 0 to 0.5wt%. The critical potential caused the anode effects shifts to 0.3V more positive value as Nd2O3 content in the melts decreases from 0.01wt% to 0.5wt%. The cyclic votammograms on W electrodes in the LiF-NdF3-Nd2O3 melts present two pairs of reduction and oxidation peaks, indicating that the reduction of Nd ions in the LiF-NdF3-Nd2O3 melts in two steps rather than one step.

Jan 1, 2014

By Manuel Pérez-Tello

An experimental study on the oxidation of chalcopyrite (CuFeS2), pyrite (FeS2), covellite (CuS) and chalcocite (Cu2S) particles was conducted by means of differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA) techniques. Oxygen concentration in the process gas was set to 40 and 70% by vol. and a heating rate of 40 °C/min was used. Response variables included: the temperature of incipient reaction, the total exothermic heat of reaction, particle mass, morphology, and mineralogy of the reacted particles. Based on the experimental data and phase stability calculations, reaction mechanisms were proposed to represent the behavior of the particles during oxidation. The reaction mechanisms were verified by X-ray diffraction (XRD) analyses of the oxidized particles, and by thermochemical and mass balance calculations to reproduce the DSC and TGA thermograms. Overall kinetic models were developed to represent the evolution of the exothermic heat of reaction for each mineral as a function of time. Experiments conducted with copper concentrate particles containing the minerals studied suggest that the reaction mechanisms for the individual minerals can be used to represent the oxidation behavior of the copper concentrate particles.

Jan 1, 2006

By Lucas Lopes da Costa

Bamboo fibers were characterized in terms of diameter distribution and tensile properties. Polyester matrix composites reinforced with these fibers were investigated for their flexural mechanical behavior. Specimens with up to 30% in volume of continuous and aligned bamboo fiber composites were bend-tested until fracture. The results showed an improvement in the composite strength and stiffness with the amount of bamboo fiber. A microstructure analysis by scanning electron microscopy revealed a reasonable adhesion between the fiber and the polyester matrix which justifies the improved mechanical properties of the composites.

Jan 1, 2010

By Walter Curlook

An atmospheric acid leaching process for leaching nickel and cobalt from highly-serpentinized saprolitic fractions of nickel laterite deposits has been developed and patented [I]. The process involves leaching the highly-serpentinized saprolitic portion of the nickel laterite ore profile in strong sulphuric acid solutions at atmospheric pressure and temperatures between 80°C and 100°C, essentially autogenously, to extract over 85% of its contained nickel content and a large proportion of its cobalt content after leaching times of about one hour. The amount of sulphuric acid used in the leaching process is between 80% and 100% by weight of the finely ground highly-serpentinized saprolite ore on a dry weight basis. The metal values are recovered as intermediate products. Key words: Atmospheric Leaching; Nickel Oxide Ores; Laterites

Jan 1, 2004

02, NaCI03, H202, Na0CI and Ce+4 have been examined as oxidants in an alkaline carbonate system for uranium in in situ leaching. The South Texas and New Mexico ores contained up to 2.6 meqJg of reducing compounds which consume oxidants in the leading operation. Leaching rates did not increase linearly with the oxidation potential of the oxidants. A mild oxidant can be used to maximize uranium oxidation selectively and oxidant efficiency. 02 can oxidize most of the uranium mineral with an adequate rate and high oxidant efficiency.

Jan 1, 1990

By Fernanda de Paula, Lázaro A. Rohen, Sérgio N. Monteiro, Rafael G. de Castro, Carlos Maurício. F. V, Maycon A. Gomes, Frederico M. Margem, Anna C. C. Neves

Synthetic fiber has been gradually replaced by natural fiber, such as lignocellulosic fiber. In comparison with synthetic fiber, natural fiber has shown economic and environmental advantages. The natural fiber presents interfacial characteristics with polymeric matrices that favor a high impact energy absorption by the composite structure. However, until now little has been evaluated about the hemp fiber incorporated in polymeric matrices. This study has the purpose of evaluate the impact resistance of this kind of epoxy matrix composite reinforced with different percentages of hemp fibers. The impact resistance has substantially increased the relative amount of hemp fiber incorporated as reinforcement in the composite. This performance was associated with the difficulty of rupture imposed by the fibers resulting from the interaction of hemp fiber / epoxy matrix that helps absorb the impact energy.

Jan 1, 2015

By S. R. Reddy

Thennodynamic properties of several quaternary systems are calculated using our recently modified Margules equations. The modified Margules equations are expressed up to infinite order in the vicinity of solvent. Quaternary system of one solvent and three,solute partials are derived. First order interaction coefficients of binary, ternary and cross -interaction parameters of quaternary system are used to'evaluate the partial functions. In the original fonn of Margules equations,derived partial functions are convergent and same 'as Unified ,Interaction Parameter Fonnalism. But considering up to infinite order of the Margules coefficients, the functions are divergent, in order to overcome this restriction, Margules equations are modified to get consistent equations. Derived partial functions are thennodynamica Hy consistent with Maxwell and Gibbs Duhem relations. The derived logarithmic activity coefficient of the solvent and solutes are consistent with the ternary systems. The calculated data, ie., activity coefficient values of nitrogen and interaction coefficients are in good agreement with the data of Fe-Cr-V -N. Fe-Ni-V -N, Fe-Cr-Ta-N and Fe-Ni-Ta-N systems.

Jan 1, 1999

By P. A. Botha

The coal seams in the Waterberg basin occur in correlates of the Vryheid and Volksrust Formations as developed in the main Karoo basin. In the Vryheid Formation, five thick seams of predominantly dull coal are present, whereas a multitude of thin, lenticular seams (a few millimetres to 2 metres}, predominantly of bright coal, are developed in the overlying Grootegeluk Formation. During exploration, the coal seams were divided into 11 zones. Analytical data on float and middlings fractions (RD less than 1.40 and between 140 and 1.80, respectively} were used mainly for stratigraphic correlation of the zones in the Grootegeluk Formation. The affinities of the major and trace elements for different mineral phases and/or organic material are discussed on the basis of correlation matrices and vertical variation diagrams. Titanium and vanadium clearly show some degree of organic affinity. P 205' AI203 and alkaline-earth elements are also positively correlated by the presence of goyazite in the coal. This type of investigation gives an indication of the degree to which undesirable elements like P and S can be removed during coal beneficiation, of which coal zones are unsuitable for the production of metallurgical coal on account of a high content of these elements, and to what extent the blending of different coal zones is required to keep the concentration of these elements within acceptable limits.

Jan 1, 1991

By Jozef Zmik, Sergey Dobatkin, Martin Fujda, George Raab, Libor Kraus

"The present work, likewise, deals with grain refinement of medium carbon steel AISI 1045 having different initial microstructure resulting from thermal and/or thermomechanical treatment (TM) applied prior severe plastic deformation. In case of TM treated steel, structure refinement was conducted in two steps. Preliminary structure refinement has been achieved due to multistep open die forging process which provided total strain Eef ~ 3. Uniform and fine recrystallized ferrite structure with grain size of the order of 2-5 µm and with nest-like pearlite colonies was obtained. The further grain refinement of steel samples having different initial structure was accomplished during warm Equal Channel Angular Pressing (ECAP) at 400°C. The microstructure development was analyzed in dependence of effective strain introduced ( Eef ~ 2.5 - 4). Employment of this processing route resulted in extensive deformation of ferrite grains where mixture of subgrains and ultrafine grain was found regardless the preliminary treatment of steel. As straining increases the dynamic polygonization and recrystallization became active to form mixture of polygonized subgrains and submicrocrystalline grains having high angle boundaries. The intensive straining and moderate ECAP temperature caused the partial cementite lamellae fragmentation and spheroidization as straining increased. The lamellae cementite spheroidization was more extensive in TM treated steel samples. The deformation behavior of for both steel structural state confirm the strength increase; however the work hardening behavior was modified with respect to initial structure of steel prior SPD processing.IntroductionIn the last years, ultrafine grained materials have attracted considerable research interest because they tend to possess high strength without sacrificing toughness and ductility. Microstructural refinement of steel is usually achieved by alloying and/or by thermomechanical treatment process, which modifies phase transformation. Recently, advancement of severe plastic deformation (SPD) techniques provides another efficient access for grain refinement of metals and alloys. The fabrication of bulk materials with ultrafine grain sizes has attracted a great deal of attention over the past two decades because of the materials' enhanced properties [ 1, 2]. In last decade a worldwide effort in manufacturing process to obtain ultrafine grain structures in steels is persisting."

Jan 1, 2011