Search Documents

By Tseng. B. H.

Samples of unchlorinated and chlorinated carbonaceous concentrate from a carbonaceous gold ore were analyzed by transmission electron microscopy (TEM) for organically bonded sulfur and chlorine. The concentrate assayed 1.53 oz/t gold and 6.01% organic carbon. Much of the organic carbon occurred as sizable coarse particles up to several hundred microns in size, which showed no visible evidence of reaction with chlorine after chlorination treatment. Both the untreated and chlorinated fractions of the carbonaceous concentrate were analyzed by the TEM method, which detected organically bonded sulfur in all of the carbon particles examined in the untreated sample, ranging from about 1 to 5% organic sulfur, and averaging near 3.1%. TEM analysis of 40 carbon particles in the chlorinated sample indicated that organic sulfur was reduced significantly in the carbon and replaced in part by the chlorine, as the result of chlorination.

Jan 1, 1987

By Shadia J. Ikhmayies

Polycrystalline CdTe thin films were prepared by vacuum evaporation on glass substrates. The I-V plots which were linear were used to find the resistivity. A value of 2.10×106 .cm was obtained. The transmittance was measured in the wavelength range 400-1100 nm. The bandgap energy was found to be 1.48 eV. X-ray diffraction pattern shows that the material deposits in the zinc blend structure with one strong reflection from the C(111) plane. The scanning electron microscope image shows a uniform surface with a small density of large (mµ1£) grains scattered on the surface.

Jan 1, 2009

By B. R. Adams

This paper discusses the use of a reacting CFD model to determine chalcopyrite kinetics in a drop tube furnace and to predict the reaction of a chalcopyrite concentrate in the reaction shaft of an industrial smelter. Reacting CFD codes can be applied to determine the consequences of the interaction of gas with particles and therefore improve the ability to derive kinetic parameters that take into account the temperature and oxidation histories that different particles will see. This paper describes the application of such a model to derive improved kinetic parameters for the pyrolysis and oxidation of chalcopyrite. The reaction shaft model includes the effects of turbulent fluid mechanics, entrained flow mixing, turbulent particle dispersion, heterogeneous particle reactions, radiative and convective heat transfer, and' surface and bath deposition rates. Particle reaction and composition characteristics are predicted as a function of particle trajectory and deposition and are used to aid in evaluating shaft performance.

Jan 1, 1999

By Z. Smieszek, J. Botor, Z. Miczkowski, S. Sobierajski

"From 1978, the direct process for the smelting of chalcocite concentrates in a flash furnace by the Outokumpu method has been applied at the Glogów II copper smelter. The chemical composition of these concentrates make it necessary to control the process very strictly. In this paper, the method for controlling and measuring the main technological parameters of the copper production by flash smelting is being presented. It includes the determination of the chemical composition of the concentrate, its grain structure, the temperature of liquid products of the process, oxygen content in process gases, as well as lead concentration in copper and copper concentration in slag.The main process parameters are determined from the mass and energy balances. The relations between parameters, such as an effect of grain structure of a concentrate on oxygen and oil consumption, and dependence of chemical composition of a concentrate on capacity and products quality are discussed. 1. IntroductionThe Polish copper concentrates, as most concentrates occurring worldwide, contain from 18% to 30% Cu, and less sulphur (7-11%) and iron (2-5%). The main copper-bearing mineral contained in the concentrates is chalcocite, while bornite and chalcopyrite are present in smaller quantities. Moreover, the organic carbon (5-7.5%), arsenic (0.05-0.3%) and lead (1.2-3.0%) are also contained in the concentrates. The gangue consists mainly of silica, aluminosilicates, calcium carbonate and magnesium carbonate. Their proportions make the addition of slag-forming agents unnecessary.The composition of Polish concentrates, especially their low iron content, allows their application in the direct flash smelting process for blister copper production. Low sulphur content is the factor which determines the necessity of oxygen application in this process."

Jan 1, 1989

By Dajian Wang

To obtain the thermodynamic properties of a multicomponent liquid alloy system over the whole range of concentration at an arbitrary temperature, the free volume cell theory has been applied to derive the formula of activity coefficients of liquid solutions based on the infinitely dilute solutions at some temperature. The linear logarithmic relationship between activity coefficients of binary dilute solutions and reciprocal of absolute temperature have been verified, and are in good agreement with the experimental values from the literature. The Monte-Carlo algorithm was used to calculate the nonlinear end value equations of binary systems, then the free volume parameters obtained were correlated with the activity coefficients of liquid binary, ternary, and quaternary systems at an arbitrary temperature. Three dimensional a-X-T diagrams of some binary systems representing the temperature and concentration dependence of activities were plotted. The calculated results regarding non-ferrous alloy systems have been statistically examined with the experimental values from the literature. Hence, this simple approach could be useful for analyzing thermodynamic properties of liquid alloy systems.

Jan 1, 2000

By Takeshi Yoshikawa

For the sake of effective control of titanium-compound inclusions in the steel-making processes, especially for stainless steel production, the influences of alloying elements of chromium, nickel, manganese, molybdenum, copper and oxygen on the thermodynamic property of titanium in molten iron were investigated at 1873K. At a certain titanium potential controlled by the coexistence of Ti3O5 and Ti2O3 doubly saturation of steels, the interaction parameters between alloying elements and titanium in molten iron were determined as follows. [ ] From the investigations on the equilibrium of titanium deoxidation in molten iron, the activity coefficient of titanium and the first order interaction parameter between oxygen and titanium were determined as follows. [ ] Also, deoxidation equilibrium for titanium in molten 304 stainless steel was measured and compared with the calculated results using the determined interaction parameters.

Jan 1, 2006

By M. G. Silva-Valenzuela, H. Wiebeck, F. R. Valenzuela-Diaz, J. C. Arjona, S. H. Wang

Urea is the most used nitrogen fertilizer around the world being responsible for many environmental problems. Preparation of microcapsules from biodegradable polymer has been reported as a main system to sustain active substances, finding application in different areas. The objective of this work was to sustain urea in nanocomposite microcapsules of poly(3-hidroxybutyrate) (PHB) reinforced with a smectite Brazilian clay in its natural (MMT) and modified (OMMT) form. PHB/MMT and PHB/OMMT microcapsules were obtained by w/o/w emulsion. Characterization were performed by XRD and optical microscopy. Structural and morphological differences observed by XRD and optical microscopy shown that PHB/OMMT microcapsules are smaller than PHB/MMT microcapsules, with average size diameter ranging * 49 μm. Results indicate that PHB/OMMT microcapsules present more defects and fractures than PHB/MMT microcapsules.

Mar 1, 2018

By Susumu Okabe

Injection metallurgy is widely adopted in various fields of metallurgical operations to achieve high productivity. The Mitsubishi Continuous Copper Smelting and Converting Process employs the top blown lance technique for the continuous supply of solid charges and reaction gases into the molten bath, where the agitated bath contributes to enhance the heat and mass transfer and the increased gas/liquid interface area accelerates the reaction. However, excessive splashing of the molten materials accompanied by the injection may cause an unexpected wear of the furnace lining. In order to estimate the splashing rate quantitatively, and to optimize the furnace design and the blowing condition, a physical model study of the top blown gas injection onto the liquid bath was carried out. An equation of the splashing rate was obtained as the function of cavity size, gas velocity and bath properties.

Jan 1, 1995

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

The paper describes the propensity of tin to form intermetallic compounds with microalloying elements such as Nb, Ti and aluminium, which are commonly used as additions to achieve particular combination of strength and toughness. Two series of alloys were prepared by arc melting under an argon atmosphere. Each series was based on Fe, Sn and A1 with either Nb or Ti additions. The microstructures were studied using scanning electron microscopy, transmission electron microscopy, energy dispersive X-ray spectroscopy and microprobe analysis. It was found that the level of Nb addition has an effect on the formation of Sn-rich compounds. For small Nb additions, no Sn containing compounds were found, whereas in higher Nb alloy, a Laves phase (FezNb, hexagonal, a = 0.4830 nm and c = 0.7879 nm) containing about 1 at % Sn was found. A FezNb3 phase (cubic, a = 1.1261 nm) associated with the formation of alumina was also found but did not contain tin. No Sn containing compounds were found with Ti additions. The experimental observations have been compared with thermodynamic calculations performed using MTDATA.

Jan 1, 1999

By A. V. Tarasov

The proposed process is based on creating a controlled frothed layer of molten slag, in which fine particles of carbonaceous reductant and raw material to be processed are mixed with emulsified iron. Frothing of the slag layer without external blowing occurs as a result of intensive evolution of gaseous reduction products. The froth reaction process is maintained due to the heat of an electric arc in the slag layer. When the metal bath is heated by the arc to 1400- 1 500°C, the low temperature of the slag surface of about 1200-1 300°C is maintained due to low thermal conductivity of slag froth preventing heat loss. In order to maintain the required slag froth level and control the process temperature, air tuyeres are installed above the slag bath; blowing air serves also for oxidation of zinc in fumes and for its transportation. High adsorption and thermal insulating properties of slag froth ensure virtually complete elimination of dust and mist entrainment along with low heat losses. The main macrokinetic regularities of the carbon thermal reduction of zinc-containing slag melts have been studied under frothing conditions. The mechanism of formation of gas-slag emulsion has been identified under the conditions of reaction [C]+[O]=CO occurring locally at the slag-metal interface. It has been demonstrated that under the froth reduction conditions the zinc removal rate from the melt increases on the average by 3 to 5 times. Based on the physical and chemical data obtained, basic principles of the dezincing technology have been developed for different intermediate oxide iron-containing products produced in the process of ferrous and non-ferrous metals production.

Jan 1, 2002

By N. Kanari

The kinetics of oxychlorination of MgO by C12+02 was studied in the temperature range of 850 °C - 1025 °C, using thermogravimetric analysis. The effects of C12/02 ratio, gas velocity, temperature and partial pressure of reactive gases on the reaction rate were investigated. The oxychlorination process was characterized by an apparent activation energy of about 214 kJ/mol. The reaction orders with respect to C12+02, C12 and 02 at 950 °C were about 0.65, 0.98, and -0.37, respectively. Some data about oxychlorination kinetics of MgO, Cr2O3, and MgCr2O4 contained in chromite were compared. Efficiency of using oxychlorination for the removal of iron oxides contained in magnesia was demonstrated.

Jan 1, 1999

By Dian Adisty, Leiv Kolbeinsen, Eli Ringdalen

In Si and FeSi production, the main Si source is SiO2, in the form of quartz. Reactions with SiO2 generate SiO-gas that further reacts with SiC to Si. During heating, quartz will transform to other SiO2 modifications with cristobalite as the stable high temperature phase. Transformation to cristobalite has been investigated and shown to be a slow process where the rate varies between the investigated quartz types. The effect of quartz versus cristobalite as SiO2 source has been studied for reaction (1) 2SiO2 + SiC = 3SiO + CO, by heating of pellets with SiO2 + SiC in Ar-gas. The reaction was faster with cristobalite than with quartz. Initial experiments indicates that this is the case only in Ar and not in CO-atmosphere The higher specific surface area of cristobalite is believed to contribute to the higher rate. The industrial consequences of the observed difference between quartz types are discussed.

Jan 1, 2014

By Atsuhiro Nabei, Ken-ichi Yamaguchi

"Wet chlorination process of de-copperized anode slime is followed by de-chlorination stage in which lead-sulfate and metallic silver form silver residue. The silver residue is subsequently reduced to Ag2Se matte and PbO-SiO2 slag to remove lead to the slag in a short rotary furnace. Although this smelting process is proven well in actual operations, few papers have investigated its metallurgical aspects. This paper will describe the effectiveness of controlling parameters adopted at the Naoshima Smelter & Refinery and discuss the decisive factors influencing silver loss to PbO-SiO2 slag.IntroductionThe precious metals plant at Naoshima smelter & refinery was established in 1989, and has produced electrolytic silver, refined gold and platinum-group metals (PGM) from de-copperized anode slime as by-products of electrolytic copper. The process for gold production has been innovated from conventional smelting process to hydrometallurgical process since 2004 [1], while the process for silver production has still remained the same.The process for silver production at the Naoshima smelter & refinery is illustrated schematically in Figure 1. De-copperized anode slime is, at first, concentrated in the froth flotation process, then leached in the wet-chlorination process, and converted to silver residue in the de-chlorination process. The silver residue, which is a mixture of lead-sulfate and metallic silver, is charged to a short rotary furnace for the oxidation roasting to volatilize selenium dioxide and subsequent reduction smelting. In the smelting stage, silver residue and reverts containing selenium are smelted with flux and carbonaceous materials to form PbO-SiO2 slag and Ag2Se matte. Furthermore, Ag2Se matte is transferred to a rotary cupell and oxidized by air with the addition of sodium carbonate and sodium nitrate to produce silver anodes while removing impurities into litharge. Silver anodes are electrolytically refined by the Moebius process. Electrolytic silver is washed, dried and, finally, cast into 30kg-bars."

Jan 1, 2011

By F. Shahbazian

attempt to systematize the knowledge on slag viscosities, the present work was carried out. The Among the physical properties of slags, viscosity is very important in understanding the mass out in the temperature range 1438-1762 Q The rotating cylinder method was used in the viscosity measurements. Crucibles and spindles made out of pure iron were employed. The transfer phenomena in metallurgical processes. The viscosities of fayalitic slags are of great interest in the non-ferrous metal industry, with special reference to copper production. In an slags were prefused before the measurements. In order to take into account the vaporization reactions involving CaF2, pre- and post measurement samples of the slags were chemically analysed and the compositions were ascertained. The results show that in the case of the CaO-SiO2 system, CaF2 additions tend to decrease the viscosity, in accordance with the expectations. In the case of the "FeO"-SiO2 system, at higher "FeO" / SiO2 ratios in the slags, a reverse trend was observed. The results are discussed on the basis of a viscosity model for silicate melts developed in the present laboratory as well as the structural considerations of silicates.

Jan 1, 2000

By Yuanbo Zhang, Mingjun Rao, Weiguang Tian, Huimin Tang, Guanghui Li, Lei Ye, Guoshen Liang, Zhiwei Peng, Foquan Gu, Tao Jiang

The amount of slag produced from a typical ferronickel smelting pro- cess is 4 to 6 times that of the metal product, and handling this slag is a huge challenge to the ferronickel industry. The feasibility of a technological route for preparing refractory materials from a ferronickel slag was verified in this study. Based on the thermodynamics analysis, the effect of the sintering temperature on the properties of refractory material from the slag was studied in the presence of magnesia. The results of thermodynamics calculation showed that the reaction of MgO with SiO generated forsterite and enstatite, whereas the reaction between 2 MgO and Fe O /Al O produced corresponding magnesia spinels. The experi- 2 3 2 3 mental results showed that a refractory material with refractoriness of 1580 °C, bulk density of 2.88 g/cm3, compressive strength of 106.9 MPa, and apparent porosityof 5.8%was obtained under the conditions ofmagnesia addition of 15 wt %, sintering temperature of 1350 °C and sintering time of 3 h. With increasing sintering temperature, the bulk density and the compressive strength of refractory material increased but the apparent porosity decreased, mainly attributed to the formation of the liquid phase which promoted the densification of the refractory material. (cid:1) (cid:1) (cid:1)

Mar 1, 2018

By Scott Samson, Weidong Wang, Shekhar Bhansali, Vandana Upadhyay

"We present an improved design for the two-arm polysilicon thermal actuator. The classic thermal actuator design produces a localized hot spot at approximately the center of the thin actuator arm. This phenomenon limits the actuator efficiency, lifetime, and reliability. Since the actuator deflection is based on thermal expansion of the material, advantage may be gained by making the temperature profile more uniform along the hot-arm length. In our design, the geometry of the thin arm is modified by forming a nonlinear structure near the approximate location of the original hot spot. Electromechanical simulations of this design show an increase in deflection, due to a flattening of the temperature profile along the hot arm. The solid model generation, finite element analysis and simulations are carried out using PEA software. Experimental devices are in the process of being fabricated by using a polysilicon rnicromachining process.1. IntroductionMost active MEMS devices employ some kind of actuating mechanism to increase functionality. Various actuating mechanisms like magnetic, electrostatic, thermal, magnetostatic and piezoelectric have been investigated and incorporated for actuating microstructures. The primary features required from many on-chip actuating mechanisms are large deflection (>10 µm), low actuation voltage, low power.consumption, reliability, fast response, ease of design and fabrication, and small size. Thermal actuation is an attractive mechanism for rnicromechanical devices requiring high actuation forces, large deflections, good linearity and low actuation voltage. Thermal actuators, also known as ""electrothermal actuators"", ""heatuators"" or ""U-shaped thermal actuators"", have been largely used in MEMS based devices to provide both in-plane and out-of-plane actuation [l] .Thermal actuators are also easily compatible with standard CMOS circuitry due to their low driving voltage. However, high power consumption remains a major drawback of the thermal actuation mechanism."

Jan 1, 2004

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 Susanne Pignolet-Brandom

QEM*SEM is an automated scanning electron microscope/computer system that characterizes samples with regard to mineral modal abundances, mineral grain and particle sizes, mineral associations, and particle surface areas. Additional information, based on the classification of particles according to the area percentage of a mineral of interest, can be obtained for samples of particulates. QEM*SEM is capable of analyzing a wide variety of materials although it was originally developed for applications to the minerals industry.

Jan 1, 1988

By Staia. Mariana H.

Thermochemical equilibria of the heterogeneous system Ti-N-H-CI-Fe-Cr-Mo-Ni-Mn-C were calculated by using a commercial software based on the minimization of the free energy. Equilibrium calculations were done for temperatures varying between 800" and l 100°C and an initial molar relationship between reactants, a=NJTiCI,, of 0.1 to 2. The deposition process was considered to occur at atmospheric pressure. The activities of the alloying elements of the stainless steel were considered equal to their molar fractions. It was shown that for the conditions studied the substrate is no inert with respect to the gaseous phase. The existence of liquid chlorides was predicted for temperatures between 800" and 850°C and a ratio between 0.3 and 0.9. The most important metallic chlorides which appears to be present from the calculations in appreciable quantities in the gaseous phase are iron dichloride and manganese dichloride. In the low-temperatures zone and for low initial nitrogen contents, it result that the appearance of the liquid chlorides seems that partially inhibits the production of gaseous HCI. The highest deposition process efficiency calculated is obtained at a temperature 2 900°C and a N2/TiCI, ratios 2 0.7.

Jan 1, 1995