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By Maria Salazar-Villalpando, Todd H. Gardner

"Efficient utilization of CO2 can help to decrease global warming. Methane reforming using carbon dioxide has been of interest for many years, but recently that interest has experienced a rapid increase for both environmental and commercial reasons. The use of CO2 provides a source of clean oxygen, which eliminates the need for costly oxygen separation plants. The product of dry reforming is useful syn-gas, which can be used to generate electrical power in a SOFC or in the production of synthetic fuels (hydrocarbons and alcohols). Hexaaluminate catalysts prepared at NETL may represent a product that can be utilized for the conversion of CO2 to syn-gas. In this work, transition metals dispersed in barium hexaaluminate have shown to be promising new catalysts for dry methane reforming. In this investigation, a series of BaNixAl12-yO19-d catalysts with varying Ni content were prepared by co-precipitation followed by calcination at 1400°C. CO2 reduction by dry methane reforming was carried out to determine catalyst performance as a function of temperature and carbon formation was also quantified after the reforming tests. Results of catalysts characterization, dispersion and surface area, were correlated to catalytic performance.IntroductionEfficient utilization of CO2 can help to decrease global warming. Methane reforming using carbon dioxide has been of interest for many years, but recently that interest has experienced a rapid increase for both environmental and commercial reasons. The use of CO2 provides a source of clean oxygen, which eliminates the need for costly oxygen separation plants. The product of dry reforming is useful syn-gas, which can be used to generate electrical power in a SOFC or in the production of synthetic fuels (hydrocarbons and alcohols). The dry reforming reaction has been known for a long time. Recent publications have reported studies over several catalysts. For example, the CO2 reforming of CH4 over mesoporous nanocrystalline zirconium powders (ZrO2–3%M2Ox; M: Ce, La and K) at 700ºC have shown methane conversion up to 60% (1). Similarly, the effect of Ni content (1–12 wt%) on the surface and catalytic behavior of bimetallic PtNi catalysts supported on ZSM-5 for reforming of methane with CO2 has been studied and report shows a maximum conversion of 16% and catalyst deactivation was observed during the first hour of time on stream (2). In another report, (3) Ni/a-Al2O3 catalyst was tested for syn-gas generation at 750ºC. The maximum methane conversion was 25%."

Jan 1, 2008

By Lztok Peruš, Goran Kugler, Matevz Fazarinc, Milan Tercel

"Hot deformability of M42 tool steel additionally alloyed with cobalt and molybdenum was investigated. Hot-compression tests were carried out in the temperature range 850 °C -1200 °C, at strain rates range 0.001--6s-l up to strain of0.9. Field-emission scanning electron microscope and optical microscopy were used for characterization of microstructure of deformed samples, which revealed a very complex precipitation of carbides that strongly depends on the soaking temperature, the soaking time, the stress state, the deformation temperature as well as on the strain rate. Gathered data was used to calculate the processing parameters such as process maps, apparent activation energies and strain hardening exponents. For better understanding of thermodynamical properties of the studied steel a simultaneous thermal analysis was conducted. Furthermore the analysis of phase equilibrium was calculated using Thermo-Cale software. On the basis of these studies the optimal soaking temperature and process windows were determined.IntroductionHot workability ofledeburitic tool steels is important economic factor. This means that for each tool steel individuallysafe range of hot working parameters should be revealed. Publications in the literature with regard to the hot workability of tool steels are rare and therefore more information from this research area is desired.The relatively low hot workability of ledeburitic tool steels, i.e. steels in which the solidification is completed by a eutectic transformation of the residual interdendritic liquid to austenite and various alloy carbides (ledeburitic carbides), is usually characterized by the production of surface and internal cracks during the hot deformation."

Jan 1, 2013

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 Qin Hua, Xiangru Chen, Qijie Zhai, Yongsheng Yan, Liang Chang

"In this paper, pure bainite ductile iron and their alloying form of 0.2wt% niobium were prepared by a controlled cooling heat-treatment. The effect of niobium alloying on the microstructure, hardness and impact toughness of bainite ductile iron was studied. The results show that adding niobium effectively improves the hardness and toughness of bainite ductile iron. The hardness and the impact toughness of niobium-alloyed bainite ductile iron were investigated by varying the temperature at which samples were fed to the incubator.IntroductionThere are two essential methods to prepare the bainite ductile iron: isothermal quenching [I-31, and alloying [4• 51• Isothermal quenching process is very time and energy consumable, concerned as a high cost technique for mass production. Besides, there are certain limitations on the size and shape of castings in this process. In addition, it potentially harms the environment. As for the alloying, Ni, Mo, and Cu have to be utilized to obtain bainite. However, the large demand and high cost of Ni makes it not feasible in practice.It is well known that niobium can promote the formation of carbon compound, and improves the stability ofundercooled austenite, which is preferred to the increase of the hardenability. Previous studies showed that niobium could refine the grain and improve the mechanical properties of gray cast iron [6-81 • Therefore, in the present work, the effects of niobium and the temperature at which samples were fed to the incubator on the microstructures and properties of niobium alloyed bainite ductile iron were investigated."

Jan 1, 2014

By George Grandy

Kvaerner experience is being used to develop software to design or simulate crushing and screening plants. The model techniques discussed are presently being used for open-circuit plants and are being extended to closed circuit plants. The program contains a library of routines, each representing a piece of equipment or unit operation, which are assembled into one of several open-circuit plant configurations. Routines include gyratory primary crushers; standard secondary and shorthead tertiary cone crushers; single, double or triple deck screens; and stockpiles, feed bins and belt conveyors. The program uses steady-state models to simulate the performance of crushers and screens that have small residence times and quickly reach equilibrium when operating conditions and/or parameters are changed. The dynamic aspect of the total circuit model concerns the storage units within the circuit, i.e. stockpiles and bins, and, in the closed circuit configuration, circulating loads and size distributions. In many cases, just vendor's catalog data are necessary for a pre-feasibility simulation; in other cases, actual plant test data are required to obtain more accurate simulations. The entire plant is shown in a single graphic screen so the user can see all the relevant information he might want, and soft-keys are provided for the user to make on- line parameter changes and observe the effects on storage elements, equipment feed rates and the final product size distributions. The model also reports equipment utilization in percentage, power consumption, and other related operating information, and soon, will be able to report estimated capital and operating costs.

Jan 1, 1999

By S. S. Babu, T. Hong, T. DebRoy, S. A. David

"Oxide inclusions form in welds because of deoxidation reactions in the weld pool. These inclusions control the weld microstructure development. Thermodynamic and kinetic calculation of oxidation reaction can describe inclusion characteristics such as number density, size, and composition. Experimental work has shown that fluid-flow velocity gradients in the weld pool can accelerate inclusion growth by collision and coalescence. Moreover, fluid flow in welds can transport inclusions to different temperature regions that may lead to repeated dissolution and growth of inclusions. These phenomena are being studied with the help of computational coupled heat transfer, fluid-flow, thermodynamic, and kinetic models. The results show that the inclusion formation in steel welds can be described as a function of the welding processes, process parameters, and steel composition.IntroductionThe relationship between inclusions and formation of a high-toughness phase, namely acicular ferrite in low-alloy steel welds, is well known (1-4). Past research has focused on maximizing acicular ferrite amount in welds by controlling welding processes, process variables, and welding consumable parameters. Research has shown that there is a complex interaction between inclusion characteristics, prior austenite grain size, and weld metal hardenability. In a low-alloy steel weld, the small addition of titanium lead to a change in the inclusion composition and resulted in a transition in the microstructure from bainitic to acicular ferrite [see Fig. I]. This in turn lead to the best combination of strength and toughness. This paper describes the inclusion formation in low-alloy steel welds."

Jan 1, 1999

By Yoshisada Michiura, Junko Umeda, Katsuyoshi Kondoh

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

Jan 1, 2008

By Maribel L- Saucedo-Muñoz, Toshiyuki Hashida, Victor M. Lopez-Hirata, Shin-Ichi Komazaki

"Small-punch tests were conducted at 4, 77 and 293 K on three types of austenitic stainless steels JNl, JJl and JK2, which were solution treated, water-quenched and then aged at 923, 973, 1023 and 1073 K for 5 h. Small-punch test energy was employed for the evaluation of the aginginduced embrittlement behavior in these materials. Fracture surface of small punch test specimen for the solution treated steels exhibited a ductile fracture, showing the highest SP test energy values. The presence of intergranular brittle fracture was observed in aged specimens. Smallpunch test energy decreased significantly as the aging process progressed. The highest and lowest decrease in small-punch test energy with aging temperature occurred in JNl and JK2 steels, respectively. The decrease in small-punch test energy showed to examine appropriately the aging-induced embrittlement in these materials. The difference in aging-induced embrittlement behavior for these steels was explained based on the volume fraction of intergranular precipitates in aged samples.IntroductionA high level combination of strength and toughness is required for cryogenic structural materials used in the superconducting magnets of fusion nuclear reactor. This requirement is beyond the capability of conventional austenitic stainless steels [1]. The Japan Atomic Energy Research Institute (JAERI) developed new cryogenic JNl, JJl and JK2 austenitic stainless steels. The structure of superconducting magnets is supposed to be constructed by welding thick plates of this kind of steels. Thus, most of the components are exposed to thermal cycles. The slow cooling may cause microstructure changes in both the base material and weld zone. These changes may also decrease the fracture toughness of these materials at cryogenic temperatures. Therefore, it is important to study the effect of thermal aging on fracture toughness behavior for these steels. Konosu et al. [2] carried out a study of the effect of thermal aging on the mechanical properties for JNl steel using tension and fatigue tests. Kwon et al. [3] evaluated the deterioration in fracture toughness at cryogenic temperatures for the isothermally aged JNl steel by means of the Small-Punch (SP) test. No other reports were found about the cryogenic fracture toughness behavior for this kind of steels. To evaluate the cryogenic fracture behavior, the elastic-plastic Jrc value is a good alternative [4,5]; nevertheless, the standard required specimen size makes it difficult to be used for the fracture toughness evaluation in small zones."

Jan 1, 2011

By Mahmoud A. Rabah

"In this work, metal values were prepared from used beverage cans. The cans are made of aluminum and minor alloying metals and printed with a multi-color printing ink. A method has been investigated to remove the printed coating using organic solvents or by sand blasting technique in a rotating drum. Metal values of the cleaned cans are prepared applying combined hydro and pyrometallurgical treatments. Factors affecting the efficiency of the suggested method have been studied.The results show that the extent of removal of the printing coating is successfully performed with recyclable methyl ethyl ketone I dimethyl formarnide mixture. With sand blasting, it proceeds regularly with the inner diameter, the rotation speed of the drum, the size of the sand grains and temperature. The removed coating is stripped with the same solvent. Metal alloy(s) are prepared in two ways. In the first way, the cans are pressed into solid blocks using hydraulic press before melting at temperatures up to 1000°C using borax-sodium chloride salt mixture as a flux. The quality of the metal obtained is a function of the salt and temperature. The slag so formed was leached with mineral acid solutions. In the second way, the used beverage cans are directly dissolved in mineral acids whereby different metal values are selectively precipitated. The undissolved part is fused with sodium carbonate at 800°C and processed in the same manner. Results were explained in the light of the thermodynamic properties of the species involved."

Jan 1, 2000

By A. V. Tarasov

The high efficiency of autoclave processes is attributed to the fact that they are suitable for processing of refractory raw materials, have low capital costs and high productivity, ensure integrated utilization of the feed materials, produce innovative saleable products, completely eliminate any air emissions, provide low-waste or waste-less technology, as well as mechanization and automation of production processes. In the immediate future, it might be expected that autoclave processes will find use on commercial scale for production of heavy non-ferrous metals in combination with other processes (hydrometallurgical, upgrading, sorption and solvent extraction, electrolytic, etc.) to ensure: -Integrated processing of refractory ores and concentrates (pyrrhotite, zinc, copper-zinc, lead-zinc, nickel-cobalt, copper, pyrite); -Production of metallic powders of base metals as commercial products (copper, cobalt, nickel, etc.), composites on their bases, final products and saleable salts. Processing technologies incorporating autoclave processes, especially, at the stage of liberation (chemical upgrading) of minerals, are characterized generally by high overall recoveries of valuable constituents significantly exceeding recoveries common for conventional pyrometallurgical processes (for some elements by several tens of percent). An example is processing of low-grade refractory pyrrhotite concentrates using autoclave liberation of feed material under pressure of a new reagent, i.e., sulfur dioxide. The use of sulfur dioxide ensures a significant improvement in the recoveries of non-ferrous metals and platinoids to sulfide concentrate and smelting of the latter increases the capacity of the smelting units employed and minimizes the yield of discard slag and loss of metals in slag; in addition, it resolves the problem of sulfur dioxide utilization.

Jan 1, 2003

By A. V. Tarasov

In order to improve technical, economic and environmental performance of hydrometallurgical processing of intermediate products containing copper and nickel, the Gintsvetmet Institute and the IMET Institute of the Russian Academy of Sciences have conducted studies into the efficiency of the use of alternating current of industrial frequency on processes applied for hydrochemical leaching of various copper- and nickel-containing materials. It has been found that: 1.Imposition of alternating current over the process of leaching of softly reduced nickel oxide with recycled copper sulfate solutions resulted in an increase by 20 to 30% of the rate of the copper cementation process and reduced by 20% its activation energy. At the same time, the recoveries of nickel, cobalt and iron to the leach solution increased up to 82.2%, 78.5% and 57.1%, respectively, and that of copper to the cement precipitate up to 74%. Optimal process conditions have been identified with respect to the current density, electrode material, copper concentration in solutions and the process temperature. 2.In the process of hydroelectrochemical sulfuric acid leaching of nickel and copper sulfides, the grain size, the phase form of sulfides, the solution composition (H2SO4, Cl?, Cu2+, Fe3+)and the current amperage had an effect on the nickel recovery to the solution, which reached 90%, while the degree of copper transfer to solution did not exceed 20%. The process of hydroelectrochemical sulfuric acid leaching of nickel and copper sulfides with an addition of Cl? made it possible to selectively recover nickel into the leach solution along with concentrating copper in the leach residue. 3.When subjecting samples of commercial-grade magnetic fractions of converter matte to sulfuric acid leaching, the imposition of electric current, the concentrations of sulfuric acid and chloride ion in the solution and the duration of the reaction process had an effect on the process. The nickel recovery was 85% and that of cobalt and iron was 95% and the recoveries reached 97.5%, 98.3% and 99.8% as a result of repeated treatment of the primary residue under similar process conditions. Up to 75% of copper, 75% of sulfur and 99.0-99.5% of palladium was concentrated in the solid reach residues. The experimental data obtained indicates that the use of AC for hydroelectrochemical sulfuric acid leaching for separation of copper- and nickel-containing intermediate products has favorable prospects.

Jan 1, 2003

By Rumen Markov, Lubomir Kuzev

"The treatment technologies for municipal solid waste (MSW) are effective mainly for components sized over 40 – 50 mm. This fraction is separated by screening in the beginning of the process. Usually the undersized product is deposited without additional treatment. Its quantity is variable from several up to 30 – 40 % of the total MSW. Both oversized and undersized fractions are formed by all types of primary matter. Adapted technologies from mineral processing will provide a suitable technology for treatment of MSW under 40 – 50 mm. The MSW content depends on the geographical location, the degree of urbanization and other factors. The methods can be applied for separations of different components suitable for recycling or other utilization are: • Separation by density; • Separation in thin liquid layer; • Selective grinding and screening; • Flotation, etc. Introduction Municipal solid waste (MSW) represents an integral part of public urbanization. However, there are some drawbacks stemming from MSW, in regard to its collection, transport and elimination. Different approaches exits worldwide for tackling the problems arising from MSW. For a short period of time, the attitude towards MSW has evolved in several levels, each further level being characterized by higher percentage of utilization of MSW components. Thus, the bottom line has been shifted from safety storage towards processing that includes recycling and maximal utilization of MSW components. Technologic processes applied for treatment of MSW have a common feature – that the fine components, having sizes under 20 mm, 30 mm, 40 mm, or 50 mm are excluded from treatment process trough screening, and in most cases diverted without any additional treatment to preliminary prepared storage sites. MSW in Sofia – current situation The amount of MSW collected daily in Sofia as around 1000 t/24 h. It is stored or baled. Baling is a spare alternative of storage, since baling insures only temporal keeping of MSW, till the building of suitable storage site where the bales will be transported and buried. The morphologic composition of MSW in Sofia has been determined several times at different time intervals, from some Bulgarian organizations as well as from the Japanese organization JICA. So far, however, there is still a lack of enough systematical and comprehensive study. Generalized results from the studies on the MSW components, as well as some important parameters are given in Table 1."

Jan 1, 2008

By Cheng Gong-jin, Chu Man-sheng, Liu Zheng-gen, Zhang Yong, Liu Jian-xing, Xue Xiang-xin

"High chromium vanadium-titanium magnetite is one kind of Fe-V-Ti-Cr composite ore resources, which owes high utilization value. Owing to lacking systematic study on the sintering of this ore home and abroad, effects of carbon addition and basicity on sintering process and sinter metallurgical properties, such as sinter yield, vertical sintering speed, tumbler strength, sinter machine utilization coefficient, and low temperature reduction degradation were investigated systematically under laboratory conditions in the paper. The results shows that, when high chromium vanadium-titanium magnetite proportion is kept unchanged as 13% in sintering feeds, sintering process index and metallurgical properties are the optimum under carbon addition 5.0% and basicity 2.70, which meets the requirements of blast furnace burdens. This research provides technical parameters for practical sintering production of high chromium vanadium-titanium magnetite.IntroductionHigh chromium vanadium-titanium magnetite (hereinafter abbreviated as hi§h-Cr V-Ti magnetite), in which Fe is closely symbiotic with Ti and isomorphous with V and Cr1'- l, is one kind of typical vanadium-titanium magnetite resources with high comprehensive utilization value but the difficulties are extremely high due to complex chemical composition and mineral structure. At present, the feasible and mainstream utilization process of high-Cr V-Ti magnetite should be the route of agglomeration-blast furnace smelting. Thus, sintering production is the foundation for high-Cr V-Ti magnetite utilization. However, till now there are few research documentations on high-Cr V-Ti magnetite sintering home and abroad. Under the above background, this study focused on detailed researches of high-Cr V-Ti magnetite sintering. Sintering process uses the powders or fine iron ores to produce artificial rich ore with good metallurgical properties 4l Solid fuel provides 90% heat requirement during sintering15J. The appropriate amount of fuel and flux should be added during sintering in order to provide necessary heat and maintain the desired basicity16l. That is to say, carbon addition and basicity are two key factors affecting metallurgical properties of sintering products17J. Therefore, the effects of carbon addition and basicity on sintering process and metallurgical properties, including sinter yield, vertical sintering speed, tumbler strength, sinter machine utilization coefficient, and low temperature reduction degradation, are systemically investigated under laboratory conditions in the study, on purpose to achieve the optimization of sintering process for high-Cr V-Ti magnetite."

Jan 1, 2013

By Riyad N. Ahmad-Bitar, Shadia J. Lkhmayies

"CdSi-xTex thin films were prepared by first producing CdS:In thin films by the spray pyrolysis (SP) technique and then annealing the films in the presence of Te vapor in nitrogen atmosphere. X-Ray diffraction (XRD) measurements showed that the films are polycrystalline with the wurtzite structure. Transmittance measurements were recorded at room temperature in the wavelength range 400-900 nm and used to deduce the absorbance. The first derivative of the absorbance was calculated and used to find the values of the bandgap energy, where more than one bandgap was obtained for each film. These results show that the films are inhomogeneous or the composition differs with location. The photoluminescence (PL) was recorded at T = 60 K and a deconvolution peak fit was performed for each spectrum. The results of the PL spectra are consistent with those obtained from the first derivative and confirm the inhomogeneity of the films.IntroductionPolycrystalline thin film CdS/CdTe solar cells are promising candidates for low cost and high efficiency photovoltaic applications. The CdS/CdTe interface plays an active role and a detailed knowledge of its properties is crucial for thorough understanding of the device. High efficiency devices have been obtained in spite of the large lattice mismatch (9. 7%) between hexagonal CdS and cubic CdTe. Interdiffusion at the CdS/CdTe interface is considered to affect the performance of the devices [1]. The formation of a mixed crystal or a graded layer at the interface causes a reduction in the lattice mismatch at the CdS/CdTe junction [2] and then a reduction in the number of interfacial states and recombination centers, thus enhancing the solar cell performance [3, 4].The objective of this work is to investigate the transmittance, photoluminescence (PL) and structure of CdSi-xTex thin films prepared by annealing the spray-deposited CdS:In thin films in the presence of tellurium vapor. X-ray diffraction (XRD) was used for exploring the structure. Transmittance is used to deduce the absorbance where its first derivative was used to find the bandgap energy which varies with composition. The evolution of the PL spectra as functions of tellurium concentration was evident and it confirmed the inhomogeneities of the films."

Jan 1, 2011

By Zhongliang Tian, Yun Cheng, Yexiang Liu, Ming Jia, Yanqing Lai

"A fundamental electrochemical study of Si ions in Na3AlF6-LiF melts and electrolysis using liquid cathodes was conducted. Cyclic voltammograms (CVs) clearly showed the depolarization of silicon deposition on liquid cathode by forming chemical complexes with the liquid solvent metals. Besides, co-deposition of Al and Si is possible when Si ions are insufficient in the molten salt. Based on the electrochemical results, silicon diffusion into liquid cathode is modelled and evolution of Si activity with concentration is deduced by a mathematic approach. Electrochemical study using liquid metals as working electrodes, can be used as an alternative approach for the acquisition of basic data on alloy behavior. Galvanostatic electrolysis showed that liquid cathodes are appropriate to collect the deposited solid silicon and the highest collection efficiency is almost 85%.IntroductionRecent years have witnessed an increasing demand for solar-grade silicon (Si) by the photovoltaic industry [1-4]. The preparation of high-purity metals through electrolysis and electrorefining offer many advantages such as low cost, low-energy consumption, and environment-friendly process, and thus has been widely used worldwide. From the perspective of electrochemistry [5-7], by utilizing the electronegativity difference between the impurities and Si and controlling the relevant process parameters, it is possible in principle to electrodeposit monatomic Si from a Si4+-containing compound melt. Moreover, because the carbon content of the high-purity Si obtained through electrolysis can be effectively controlled and used as a very ideal raw material in the preparation of electronic-grade and solar-grade Si, the preparation of high-purity Si through electrolysis has received widespread attention [8,9]. Monnier et al. [9] used a graphite electrode to obtain high-purity Si (99.9 %-99.99 %) from Si02/Na3AlF6 system through electrolysis; however, because the Si was precipitated in a solid form and showed poor conductivity, the deposition rate was too slow. Olsen et al. [10] obtained high-purity Si films via electrodeposition in K2SiF6/KF-LiF system by selecting electrode materials with high surface quality (such as Ag and graphite). However, in order to ensure the film quality, the deposition current density must be relatively low (10-50 mA/cm2), resulting in a low current efficiency and low deposition rate, which are not conducive to reducing energy consumption and applying to practical use"

Jan 1, 2014

By T. Watanabe, T. Fujiwara, S-Wan Song, Y. Nakagawa, R. Teranishi, M. Yoshimura

"We have tried a new method to fabricate cobalt oxide films onto porous films directly by an electrodeposition method at low temperature. The porous substrate films (membrane-filters and paper) were placed between a LiOH solution and a CoSO4 solution and treated under electricalcurrents of ~1 mA/cm2 using carbon cathode and anode. Effects of temperatures, flow rates and electrical currents have been investigated. As a result, we found that the LiCoO2 films and Co3O4 films were successfully fabricated on paper and/or porous PTFE filters at 120 °C, while CoOOH films were deposited at 80 °C. Furthermore, LiCoO2 films did not cover whole the substrates, but was fabricated just over the anode. The chemical reactions of electrodeposition were also considered from these results.IntroductionRecent agreements on global environment require rapid progress of low energy and low waste processings for the fabrication of thin films that succeed to the mass production with the high consumption of the fossil fuels (such as physical vapor deposition°, chemical vapor deposition2), dip coating with firing3) etc.). The total energy consumption in aqueous systems should be the lowest among all these processing routes, because a much lager excess of energy is necessary to create melts, vapor, gas, or plasma than to form an aqueous solution at the same temperature4)The ""Soft Solution-Process"" (SSP) was one of the best concepts to realize the low energy and low waste fabrication of inorganic materials. 5) Generally speaking, SSP gives similar results to any other processing using fluids (such as vapor, gas plasma) and/or beam/vacuum processing. However, the total energy consumption of all these possessing routes should be the lowest in aqueous systems, because a much larger excess of energy is necessary to create melts, vapor, gas or plasma than to form an aqueous solution at the same temperature (Fig. 1). This idea can be easily demonstrated, using the simple example of BaTiO3. The energy diagram for the formation of BaTiO3 from various precursors is shown in reference 4. The driving forces (AG) for representative synthesis reaction of (1), (2), (3), (4) and(5) are 38, 727, 3685, 17 and —14kcal/mol, respectively at room temperature. 6' 7"

Jan 1, 2000

By Metehan Erdogan, Ishak Karakaya, Fuat Erden, Emre Ergül

"The FFC Cambridge process was suggested as a promising Si production technique for the expanding solar energy industry. Direct electrochemical reduction of bulk SiO2 plates and porous SiO2 pellets in molten CaCl2-NaCl salt mixture were investigated at 750°C by applying 2.8 V potential difference. The produced Si powder was brown and found to be contaminated by the Ni and stainless steel plates used as the cathode contacting materials. The reduction rates of the bulk SiO2 plates and porous SiO2 pellets were compared from variations of current and accumulative electrical charge that passed through the cell during the electrochemical reduction. The amorphous bulk SiO2 plates were reduced slightly faster than porous pellets of crystalline SiO2. The overall reduction potential of SiO2 pellets against the graphite anode at 750°C in molten CaCl2-NaCl salt mixture was determined as 2.3 V by cyclic voltammetry. This potential was supported by calculations.IntroductionMetallurgical grade Si cannot be directly used in electronic industry and some intermediate steps are required to produce industrial solar grade silicon (SOG-Si). A promising alternative solar grade silicon production technique is the FFC Cambridge Process [1]. Production of Si by electrochemical reduction of SiO2 at 850oC in molten CaCl2 electrolyte was first studied by Nohira et.al. [2]. In their study; Si formation was observed on bulk SiO2 cathodes after 1 hour of electrolysis. Complete electrochemical reduction of porous SiO2 pellets was first reported by Jin and his coworkers [3]. The mechanism of electrochemical reduction of SiO2 to Si in molten CaCl2 was explained in another study [4]. Reduction rates of bulk SiO2 and porous SiO2 pellets were also compared previously and it was found that reduction rates for bulk plates were higher [5]. Furthermore, it was reported that mixing Si into porous SiO2 pellet increased the reduction rate [5]. Mo [2, 4-7], Ni [3, 8, 9] or Si [6] were used as cathode contacting materials in various studies. Yasuda et. al. [6] produced Si with 99.80 % purity using Si plates as cathode contacting material to reduce metal contamination."

Jan 1, 2012

By C. B. Solnordal, R. N. Taylor

"The heat transfer conditions on the outer side of a Sirosmelt lance have been determined using experimental measurements in combination with a mathematical model. By measuring the temperature distribution along the wall of an operating Sirosmelt lance, as well as the thickness of the slag layer on it, it was possible to use the model to determine both the heat transfer coefficient between the vessel contents and the lance, as well as the effective thermal conductivity of the slag layer. The effective thermal conductivity of the slag layer was found to be within the range 0.7-1.3 W.m-1. ºCl, which was in good agreement with measured values for magnetite. The outside heat transfer coefficient varied from 80 to ISO W.m-2. ºC1, which was smaller than quoted in the literature for metal/slag systems. The discrepancy was attributed to the high thermal resistance experienced between the lance wall and the slag layer, as well as the large quantities of combustion gases that envelop the lance tip and reduce convection and conduction from the melt to the lance. INTRODUCTIONThe Sirosmelt submerged combustion smelting process [1] utilizes top injection lances to deliver fuel and air into a metallurgical melt. To help prevent lance failure from attack by liquid slag, helical vane swirlers are used within the annular lance to impart swirl to the flowing air and enhance the heat transfer from the lance wall to the air. The swirlers thus cool the wall, and enable a frozen layer of slag to form on its outer surface. This solid layer ensures liquid slag cannot reach the lance surface, and the lance is protected.A mathematical model of the heat transfer processes associated with the lance has been developed, which combines heat balance equations with engineering correlations to predict the wall and cooling air temperature of the lance, as well as the air pressure distribution. An account of the model was given by Rankin et al. [2]. To further enhance the model and enable it to predict the thickness of slag accumulating on the lance, a detailed analysis of the heat flow through the slag layer commenced in 1992. By far the most complex aspect of the model, the flow of heat from the vessel contents to the outside of the lance was dependent on many factors, including:-"

Jan 1, 1996

By Vladyslav P. Yakubovsky, Boris I. Bondarenko, Valentin A. Noskov, Vladyslav M. Sokolov

"Each of Ukrainian producers of ferronickel, stainless steel and synthetic diamonds has the same basic problem with recycling their fine Ni-containing secondary materials. The conditions for generation of them along with the correspondent properties were investigated in details. The new approaches for their recycling have been proposed. They are based on application of some pyrometallurgical processes that are used in Ukraine. The proper equipment is also available. It has been shown that the dust from laterite calcining process of ferronickel production should be efficiently recycled by sintering. The stainless steel dust should be smelted after briquetting as a charge addition to the Ni-containing discarded batteries in the elaborated furnace. The sludge after synthetic diamonds production should be pelletized and processed by liquid cast iron with application of induction magnetodynamic forces in the specific furnace.IntroductionThe object of the investigation is recycling the Ni-containing secondary fines in a form of dust and sludge. There are several generators of the fines in Ukraine. Namely they are Pobuzhye Integrated Ferronickel Mill; Electrometallurgical Works “Dneprospetsstal” with stainless steel plant as well as Poltava Diamond Plant that produces synthetic hard materials. Their businesses are the largest in the Commonwealth of Independent States (CIS). However the status of handling with the fines is not perfect since the applied recycling technologies are low efficient. The landfilling option is often adopted for them. At the same in Ukraine there are some nontraditional pyrometallurgical recycling technologies and equipment that should be tried for application in smelting these secondary materials.Recycling the sludge of synthetic diamonds productionThe sludge of “Poltava diamond plant” from production of synthetic hard materials has a following chemical composition, %: iron oxide – 29.7; chromium oxide – 18.97; nickel – 4.27; manganese oxide – 15.2; sulphate – 3.85; natrium – 14.9. The content of moisture is 70-80%. The moisture quite quickly evaporates while keeping sludge out of doors. Sludge returns into the weak agglomerates. The sizing of the dried sludge particles presents the figures from 400 to 1000 µm. The moisture was extracted by sludge pressing. The content of the basic compounds of the moisture is, g/dm3: chromium oxide – 1.6; nickel – 0.001; manganese oxide – 0.002; lead – 0.005; sulphate – 13.6; natrium – 17.0."

Jan 1, 2008

By Ana P. Paiva, Marc F. Comella, Sandra S. Reis, Joao N. Reis, M. Soledade Santos

"In this work, the influence of the malonamide structure, acidity of the aqueous phase and diluent on the equilibrium interfacial tension (IT) of N,N'-dimethyl-N,N'-diphenylmalonamide (DMDPHMA) and N,N'-dimethyl-N,N'-dicyclohexylmalonamide (DMDCHMA) in 1,2- dichloroethane (1,2-DCE), and DMDCHMA in toluene, with aqueous HCl, were investigated. IT isotherms were determined using the Du N ouy ring method. Densities of the organic phases were determined, and used to screen solute-diluent interactions. Formation of third phases was never observed; furthermore, ITs increase with the phase separation period, constant values being obtained for separation periods larger than 1000 seconds. Each malonamide interfacial efficiency at the oil/water interface is interpreted in terms of malonamide basicity, diluent polarity and malonamide - hydrochloric acid- diluent interfacial interactions.IntroductionFor several years now, N,N'-tetrasubstituted malonamide derivatives have been extensively investigated as liquid-liquid extraction agents since they were first proposed as the organic components of the DIAMEX process, with the aim of advantageously replacing tributylphosphate in PUREX [1]. Therefore, a significant part of research studies with malonamides appearing in the literature deal with the extraction of major and minor actinides in real or simulated spent nuclear fuels in nitric acid solutions [2]. Under typical experimental process conditions, the tendency shown by some N,N'-tetrasubstituted malonamide derivatives to aggregate in the organic phase, leading in a few cases to the formation of undesirable third phases, has been remarked and consequently thoroughly investigated [3, 4]. The increasing use of chloride streams as hydrometallurgical aqueous feeds is becoming a reality, and this fact is obviously deeply founded on an extensive research carried out to recover value-adding metals from these media. Following this trend, a number of N,N'-tetrasubstituted malonamides have already been screened for the recovery of iron(III) [5, 6] and platinum-group metals [7] from hydrochloric acid solutions. The results obtained are quite promising either in terms of total metal ion recoveries or selectivity patterns achieved. The formation of a third phase when iron(III) was extracted by the tested N,N'-tetrasubstituted malonamide derivatives has never been observed under the adopted experimental conditions, and the extraction data collected would need to be reinterpreted accordingly if any aggregation phenomena involving the considered extraction systems were to take place."

Jan 1, 2011