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By Bo Zhou

During secondary aluminum recovery, complex aluminum scraps are melted and refined often in a rotary melting furnace and the aluminum metal has to pass through a molten salt layer and melt down in a bottom aluminum bath. Previous experimental study and industrial observations have indicated that salt shell formation and re-melting on the metal solids in the early stage plays a critical role in the overall melting process of the scrap. In the present paper, mathematical models are developed to simulate the process of salt shell formation and its re melting, as well as aluminum melting in the molten melt. Influence of the salt layer properties, the residence time of the metal particles in the salt layer, the particle size, the temperature of bulk melt were investigated. Reasonable agreement with the measurement data was reached. The developed melting model will be used to construct a population balance model of the scrap melting behavior for a rotary melting furnace, taking into account the distributed characteristics of the scrap. Finally, an overall process model based on Computational Fluid Dynamics (CFD) for the rotary furnace will be constructed, coupling with the population balance model for the scrap melting.

Jan 1, 2003

By Erwin Flender, Preben N. Hansen, Peter R. Sahm

"Until now FDM-Techniques have been widely used for Modeling Solidification Processes in Castings. Often a rigid, regular type of enmeshment (cubes, , --) have been used. This has the advantage of low CPU-costs, but the disadvantage of a zig-zag presentation of the interface between the casting and the mold. The last point is the reason why FEM-Techniques, giving the possibility of a true presentation of the shape in the enmeshment, are increasingly used. The disadvantage is the high CPU-costs. In this paper, a technique is presented, which uses the FDM-Mesh with the zig-zag presentation of shape and ADI-Algorithms to calculate temperatures and gradients. The new idea is that the calculated parameters are not presented related to the mesh in which they are calculated, but displayed using the true shape of the casting. Such an advantage of both low CPU-costs and shape correct presentation of the calculated results are achieved. IntroductionThe main reason for using a regular type of enmeshment is that it gives the possibility, via ADI-Algorithms, of obtaining a very fast FDM-Technique. The technique presented by P.R. Sahm and P. N. Hansen (1984), and also used by E. Flender (1985), is numerically so stable that average time steps, at least 200 times larger than the limit given by the explicit FDM-Technique, can be applied. To obtain reasonably good results, average time steps in the range of 20 to 50 times the explicit limit seems to be applicable. It should be pointed out,however, that FDM-Techniques can be used on arbitrary nets, the disadvantages being the same as for the FEM-Techniques. This has, among others, been discussed by P.R. Sahm and P.N. Hansen (1984)."

Jan 1, 1986

By H. Kung, T. R. Jervis, M. Nastasi, T. E. Mitchell

"A systematic study of the structure-mechanical properties relationship is reported for nanolayered composites of MoSh-SiC, Mo-MoSh, Mo-MoShNx, MoSi2-MoSi2Nx, and Mo-MoShMoSi2Nx (x=3-4) synthesised by sputtering techniques. These composites have been studied by nano-indentation and cross-sectional TEM as a function of annealing temperature. As-deposited layers are amorphous except for Mo. With increasing annealing temperature, first MoSh and then SiC crystallize, while the hardness progressively increases until the layers start to spheroidize and grain growth sets in at 900ºC. For the case of Mo-MoSi2, the layers react and the composite deteriorates rapidly. However, MoSi2Nx remains amorphous up to 1000ºC, suggesting that it could act as a diffusion barrier between Mo and MoSi2. In fact the Mo. MoSi2Nx, MoSi2-MoSi2Nx and Mo-MoSi2-MoSi2Nx nanolayers are found to remain stable up to such temperatures. IntroductionMolybdenum dislicide, MoSh, is a potential matrix material for high temperature structural composites due to its high melting point and good oxidation resistance at elevated temperature [1]. The two major drawbacks for structural applications are inadequate high temperature strength and poor low temperature ductility. Silicon Carbide (SiC) being hard and thermally compatible with most ceramics and intermetallic compounds, has been found to be suitable for second phase reinforcement in various structural applications and, in particular, the addition of SiC whiskers improves the high temperature yield strength of MoSi2 [2]. While most of the research in MoSb-SiC composites has been on the particulate form of SiC, laminated composites may offer unique properties. It has been shown that synthetic multilayers with alternating layers of metal and/or compounds may exhibit interesting mechanical properties [3]. Enhancement in mechanical properties by decreasing the wavelength of multilayer spacing has been studied extensively. In general, two types of strengthening have been proposed: (1) Hall-Petch strengthening [4,5], where the strength increase is inversely proportional to the square root of the layer thickness; (2) Koehler modulus strengthening [6], which increases with modulus difference and decreasing layer thickness. In the present study, we have performed a systematic study of the relationship between strength and structure in a number of different nanolayered systems based on MoSh. Layer thicknesses have been varied and their nanostructures have been varied by heat treatment. Previous work on MoSi2-SiC is summarized [7]. In an attempt to improve fracture toughness, MoSh-Mo nanolayered materials have been prepared but are found to react and deteriorate. Previous work has shown that nitrided MoSi2 (MoSi2Nx with x=3-4) is highly stable [8] and so nanolayered composites of MoSi2-MoSi2Nx and Mo-MoSi2-MoSi2Nx have been prepared to assess the' stability and mechanical properties of these composites. Preliminary results are presented."

Jan 1, 1994

By Krzyszof Borowiec

With the aim of determining the thermodynamic conditions for sulfation of impurity elements, in particular magnesium, in titaniferous slags the equilibrium gas composition for the sulfation reaction: MO + so2 + 1/2 02 = MS04 has been studied by an EMF technique with a solid zro2 + Cao electrolyte. Here M denotes the impurity elements: Mg, Ca and Mn, and the following _oxide systems have been studied: Ti02-MgO-Fe2 o 3 , Ti02-MnO-Mn2 o 3 , and Ti02 -CaO-Si02 , all in the . temperature range 700-1000ºc. Reproducible EMF values were obtained by adding small amounts of -Na2so4 to the oxide-sulfate mixture. From the observed results the Gibbs energy of formation of the phases Mg 2Ti04 , MgTi03 , MgTi 2o 5 , MnTi03 , CaTi03 , and CaTiSio5 , as well as the activity of MgTi05 in the solid solution with Fe2Ti05 have been calculated. The results show that, from a thermodynamic viewpoint, sulfation of these impurities in titaniferous stags i:s favorable- at around and below 800ºC.

Jan 1, 1985

By Toru H. Okabe

As part of a systematic study on the thermodynamic properties of complex nitrides, phase equilibria of the system Li-M-N (M Mg, AI, Ga) at 900 K were investigated. An attempt to determine the thermodynamic properties of complex nitrides was made by using the galvanic cell method, which utilizes LiMgN as an electrolyte under nitrogen atmosphere. The electromotive force (Emf) of ilie cell at temperatures between 800 and 1100 K was measured. Whilc the Emf of the cell at 900 K was measured to be 0.137 V, data discrepancies of ±0.03V were found. It was difficult to determine temperature dependence of ilie Emf. The Gibbs energy change for the reaction, 113 LbN (s) + 1/3 Mg3N2 (s) = LiMgN (s), at 900 K was determined to be tJ.Gor (LiMgN) -13.2 (±2.9) kJ/mol. Using thermodynamic information on ilie binary nitride from literature, the standard Gibbs energy of LiMgN was derived to be AGO f (LiMgN)= - 121 kJ at 900 K. The thermodynamic stability range of nitride was discussed by constructing isothermal chemical potential diagrams that provide a better understanding of ilie stability region of the LiMgN phase. The diagram was found to be in good agreement with the isoiliermal phase diagram determined by ilie alloy equilibration meiliod. Although the obtained data includes large uncertainties, the results provide a better understanding of the iliermodynamic stability of nitrides. The potential application of this complex nitride to nitrogen chemical sensors or a medium for controlling nitrogen potential is also shown.

Jan 1, 2003

By Stuart D. Miller, Clayton L. Rumble

"A field net acid generation (NAG) test procedure has been utilized on-site to identify, classify and map potentially acid forming overburden at the PT Kaltim Prima Coal (K.PC) mining operation situated in the tropical equatorial region of East Kalimantan, Indonesia. The field procedure involves routine use of a calibrated, site specific NAG test (rapid oxidation test using hydrogen peroxide) which has a tum-around time of less than 24 hours and requires minimal sample preparation. It is used on geological drill-hole samples, for forward planning and overburden management; blast-hole samples, for day-to-day operational control and overburden scheduling; and final dump surface samples, for verification testing. This operational monitoring program has been in use at KPC for the past four years.Calibration and implementation of the field procedure has involved validating the NAG test using conventional acid-base accounting techniques, producing an overburden geochemical classification scheme, optimizing laboratory and sample preparation procedures, and ongoing quality management. This paper presents background theory and practical application in a case study format."

Jan 1, 1999

By In-Ho Chi

In copper metallization, resistivity of copper seed layer is very important since the thickness of seed layer is less than 200iun. Conventionally MOCVD has been used for this purpose however electroless copper plating is simple process and the resistivity of copper deposit is less than that of copper prepared by MOCVD. In this study eIectroless depositions of copper were conducted on different substrate to find optimum conditions of electroless copper plating for electronic applications. To find optimum conditions, the effects and selectivity of activation method on several substrates were investigated. The effects of copper bath composition on morphology were investigated. The effects of pH and stabilizer on deposition rate was investigated. The resistivity of copper with thickness was also measured.

Jan 1, 2001

By Byung-Su Kim

The reaction between calcium sulfate and hydrogen is of interest both as a means of regenerating calcium sulfide as a reductant of sulhr dioxide to elemental sulhr and for producing elemental sulhr from gypsum. This reaction was investigated using a thermogravimetric analysis technique in the absence and presence of nickel catalyst. The reaction temperature was varied between 973 and 1153 K, while the hydrogen partial pressures of 12.9 - 86.1 kPa were utilized. At 1073 K and a hydrogen partial pressure of 86.1 kPa, 60 % of the original calcium sulfate in the absence, and 95 % in the presence, of the nickel catalyst was converted to calcium sulfide in one hour.

Jan 1, 1999

By Ma Keyi, Yang Xianwan, Zhu Xiaoyun, Guo Zhongcheng, Zheng Yanping

"The oxidation of the Multifunctional Electrodeposited RE-Ni-WP- SiC Composites at high temperature is investigated. The results show that during high temperature oxidation the relationship between the mass change of pure Ni , Ni-W-P, Ni-W-P-SiC or RE-Ni-W-P-SiC coating and the oxidation time follows a mixed curve, i.e. it is approximately a linear relationship when the oxidation time is less than 60 mins while it is a power function relationship when the oxidation time is over 60 mins. The order for the oxidation rate of the four coatings is Ni> Ni-W-P> Ni-WP- SiC>RE-Ni-W-P-SiC. The mass change of Ni-W-P, Ni-W-PSiC or RE-Ni-W-P-SiC coating increases exponentially with a rise of oxidation temperature. The high temperature-oxidation resistance of RE-Ni-W-P-SiC composite coating is 3-4 times that ofNi-W-P alloy coating. The cross section morphologies and Xray diffraction patterns indicate that the high temperature oxidation resistance of RE-Ni-W-P-SiC composite coating is better than any other coatings.1. IntroductionWith the rapid development of modem industries the products in engineering industry are continually challenged by the requirements of long-term and stable working at higher temperature, pressure, speed and under adverse conditions. Consequently, the surface properties of the products, such as the resistance to oxidation at high temperature, the resistance to wear and the resistance to corrosion, should be improved continually."

Jan 1, 2000

By David G. C. Robertson

A new approach is described for the calculation of the kinetics of metal/slag, metal/slag/gas, and metal/matte/slag/gas reactions. The algorithm assumes that equilibrium is achieved at the interface between phases, and uses an equilibrium solver (such as SOLGASMIX) to compute the equilibrium state at the interface at each time step during the reaction. For multiple phase systems a number of unit operations, representing the different phases and interfaces, must be connected together in a reasonalbly complex manner, and the METSIM software package has been utilized for this purpose. The new approach is superior to the SMAK software developed by the author and his co-workers over the past decade, for the reasons discussed in this paper.

Jan 1, 1995

By M. del C. Ruiz

The extraction of Nb and Ta from a columbo-tantalite of San Luis, Argentina, is being studied by using a pressure reactor and HF as leaching agent. The reagents and products have been characterized by several techniques such as scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDXS), X-ray fluorescence (XRF), X-ray difracction (XRD), surface area (BET) and size particle analysis. Experimental results have shown that the extraction of niobium and tantalum increases with increasing temperature, reaction time and acid concentration. For particle size between +80 and -355 mesh no significant changes are detected. It is also slightly affected by the stimng speed. XRD analysis of the residues did not show formation of new crystalline structures.

Jan 1, 1999

By Wan Pu

Chrysotile asbestos samples from different mines have been studied by SEM and TEM, including high resolution electron microscopy, to find reasons for differences in physical properties of different types of asbestos fibres. The results show that the inner diameters of fibre tubes and the lattice images of fibres are different for soft and hard asbestos fibres. These differences are related to temperatures and geochemical conditions during the growth of chrysotile asbestos.

Jan 1, 1989

By Cheng Yan, Yugang Li, Qian Wang, Lizhi Zhang

In continuous casting process, mold powder has lots of metallurgical effects, such as covering the molten steel to prevent liquid steel from oxidation by air, preserving heat for top layer liquid steel, lubricating initial shell and so on. However, mold powder also can deteriorate the quality of final products obviously after the entrapment of mold powder in steel. In the present work, based on the similarity theory the effect of technological parameters on mold powder entrainment was investigated by water model. Experiment was carried out in the water mold using oil and water to simulate slag and steel, respectively. The results showed that increasing casting speed increased the water-oil interfacial fluctuation and entrainment frequency; viscosity of oil also had a great impact on the interface fluctuation and entrainment; water-oil interfacial tension effect the entrainment while not changing the interfacial fluctuation; submergence depth had little impact on entrainment and interfacial fluctuation.

Jan 1, 2015

By JiaPeng Xu, Brian Lo, Uday B. Pal, Yihong Jiang, Soumendra N. Basu

"The Solid-Oxide Oxygen-Ion-Conducting Membrane (SOM) electrolysis process has been successfully tested on a laboratory scale, producing silicon directly from silica in a cost-effective and environmentally friendly way. A yttria-stabilized zirconia (YSZ) tube, closed at one end was employed to separate the molten salt containing dissolved silica from a liquid metal anode placed inside the YSZ tube. When the applied electric potential between the liquid tin cathode in the molten salt and the anode exceeds the dissociation potential of silica, oxygen ions are pumped out of the molten salt through the YSZ membrane and oxidized at the anode while the silicon cations in the flux are reduced to silicon at the liquid tin cathode. The presence of high-purity silicon crystals on the surface of liquid tin cathode was confirmed by scanning electron microscopy (SEM) and energy dispersive x-ray spectroscopy (EDS). Silicon crystals were extracted from tin cathode by chemical etching.IntroductionPhotovoltaics (PV) generate electrical power by using solar cells, and dramatically reduce the emissions of greenhouse gases (GHG). Through 2006 to 2011, it grew the fastest of all renewable technologies with operating capacity increasing an average of 58% annually [l]. However, the cost of manufacturing solar-grade silicon (SoG-Si) for high-efficiency solar energy production represents a major barrier to achieving the industrial goal for solar power of $1/Wp (watt at peak exposure) which would enable widespread grid parity. The current contract price of silicon to PV manufacturers is $50-$60/kg, with the spot market in 2007-2008 showing prices as high as $300/kg [2]. This makes the development of low cost and environmentally friendly manufacturing of high purity silicon very important."

Jan 1, 2013

By Takayoshi Fujii, Mitsumasa Hoshi, Chikashi Suenaga, Yoshiaki Suzuki

"In a bid to renovate its Saganoseki Smelter & Refinery and to establish a leading production unit in terms of global competitiveness, Nippon Mining & Metals undertook major - restructuring efforts since 1993.One of its themes was the shift from a two-flash furnaces operation to a single-flash furnace operation. The shift was successfully completed in 1996 while maintaining the production at the same level (330,000 metric tons per year of copper) by adopting such measures as improvements in pneumatic concentrate dryers, the concentrate feeding system, concentrate burners, the furnace cooling system, and a new cryogenic oxygen plant was constructed.With a view to realizing high matte grade operation (at 65%Cu) and increasing the concentrate feeding rate, further steps were taken the capacity of waste heat boiler was expanded and technical improvements were added, including optimization of the smelting reaction in the furnace shaft. As a result, the smelting capacity, as of the year 2000, has increased to 450,000 metric tons per year of copper.IntroductionThe feed rate to the flash furnace was doubled to 140 t/h from 70 t/h in 1996. Teething problems, as a result of the renovation, were almost solved by the end of 1996, and the operation of the single furnace operation has become stable.The main theme was the shift from a two-flash furnaces operation to a single-furnace operation to maintain the production capacity at the same level, namely 330,000 metric tons of copper per year. Then, in a bid to further renovate the Saganoseki Smelter & Refinery and to establish a leading production unit in terms of global competitiveness, further enhancement of the flash furnace's productivity was planned.The purpose of this plan was to raise the copper production capacity to 450,000 mtpy building on the potentialities of existing plants and without installing new equipment."

Jan 1, 2000

By P. D. Navarro

The behavior and operability of LIX 1104SM extraction was studied at laboratory scale on the Solvent Extraction at Sb3+, from high concentration sulfuric acid. In order to evaluate the reactant batch tests were made at laboratory scale as well for extraction as for re-extraction of Sb3+. Experiences achieved were: extraction kinetics, temperature effects, selectivity tests and re-extraction selectivity. A extraction kinetics was found, reaching equilibrium in 2 min, high selectivity of Sb3+ extraction in front of Cue , existing As5+ co-extraction and Fe3+ At the re-extraction stage, equilibrium was reached in 3 min, getting high Sb3+ re-extraction efficiency with HCl concentrations within 6 and 8 M. A high selectivity was achieved on Sb3+ re-extraction in front of As+5, existing Fe+5 re-extraction.

Jan 1, 1999

By Aarne Kopanen

In recent years, various renovations have been carried out in the production chain of the Outokumpu copper refinirg process. The anode casting shop, which is the final integral production section at the Harjavalta copper smelter built in its original form in 1945, was fourxl unsuitable for technical and capacity demads during longer periods of operation, and a new casting shop was built in 1974. The electrolytic copper refinery of Outokumpu Oy at Pori was built in 1941, and subsequently expanded in two stages. Even with its present limited scale of production it has been fom important to mechanize the main operations. This work was started in 1967 with the design and construction of the starting sheet machine connected with the cathode washing and unloading machine as a combined unit. Mechanized treatment of anodes has gained advantage particularly from the new design of a highly automated anode casting shop. In the further development of the mechanization a stripping machine for, starting sheets was designed and installed, starting operation in 1974.

Jan 1, 1976

Silver has the highest electrical conductivity of all metals and consequently this property is an attractive feature which makes it a leading candidate for use in electronic devices. The research conducted was focused primarily on the development of a process for obtaining a deposited silver-coating onto alumina, for applications related to electrical-conducting devices and, ancillarily, catalysts. Alumina balls and plane substrates were utilized for the investigation. The coating process employed an aqueous arnmoniacal silver-nitrate electrolytes with a formaldehyde solution as the reductant. Modifying additives - an activator which would be expected to promote good deposition-characteristics onto the (dielectric) substrate and an inhibitor which would obviate homogeneous reduction (precipitation) of silver was observed when the activator-containing silver-electrolyte reductant constituents were combined. However, the silver-electrolyte/reductant system with inhibitor could be employed (at 80°C) to achieve a viable (subject to future research optimization) coating on alumina. The influence of the processing temperature on the deposition process was delineated during the course of the research. The morphology of the deposited-silver on the alumina balls was assessed by SEM imaging. A tape-peel test was employed, with the plane substrates, to semi-quantitatively characterize the adhesion to the alumina.

Jan 1, 1998

By J. N. Kondo, M. Hara, T. Smida, N. Ooto, K. Domen

"A porous material composed of two-dimensional anionic sheets of a layered perovskite, KSrNb30 10, was studied as photocatalyst for the production of Hz in the presence of alcohol sacrificial donors. Colloidal single and multi-layered HSr2Nb30 10 sheets were formed by intercalating ietra(n-buthylammonium) cations into the interlayeres of H+-exchanged KSr2Nb30 10 (HSr2Nb30 10), and addition of HN03 solution to the colloidal suspension precipitated the porous materials in which HSrNb30 10 sh~ets rand~mly stuck together. Original HSr2Nb30 10 before exfoliation had a BET surface area of 1 m2 g-1, whereas the surface area of a porous material prepared under optimal conditions exceeded 100 m2 g-1. The porous HSr2Nb30 10 had considerably higher photocatalytic'activitie8 for oxidation of 1-propanol and 1-buthanol than HSr2Nb39io, indicating that in the porous materials many niobate sheets are available for decomposition of these large alcohols.IntroductionQuite a research effort has gone into the design and study of porous materials. Such materials with large surface areas would have applications in highly efficient adsorbents or catalytic reactions.We have been studying photocatalytic reaction by cation-exchangeable layered metal oxides, where alkali metal cations are intercalated into the interlayers of inorganic sheets.[1,2] There are several advantages to using layered compounds rather than bulk powders for photocatalysis. Layered compound is rich in variety, in addition, modifications of them are easily performed by exchanging alkali metal cations in the inter layers for H + or other metal cations. The most important advantage is that some layered compounds have considerably high photocatalytic activities than bulk catalysts because the electrons and holes generated in each thin inorganic sheet readily reach interlayer spaces as reaction sites at the illterlayer spaces. It should be very important for further improvements· of layered photocatalysts to utilize two-dimensional inorganic sheets effectively."

Jan 1, 2000

By Dorothée Proffit

Characterization of solids containing cyanides is carried out according to recommendations and standard guidelines. Most of these procedures are based on the analysis of leachates collected either on site or after leaching in the laboratory of samples. Unfortunately, these sole results are often insufficient to identify the source of the pollution. To provide 'a more complete characterization of polluted solids, optical and electron microscopy, XRD, Mossbauer spectroscopy, and transmission infrared spectroscopy were combined to analyze leachates and raw or ground samples. This combination of techniques allows the determination of the kind of cyanoferrate complexes are present in the solid state, different from insoluble Prussian Blue, since they do not have the same extraction' behavior. The use of all these techniques to characterize solid samples combined ,to the usual analysis of solutions gives a better understanding of ' the cyanide behavior.

Jan 1, 1998