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By G. G. Richards

"The slag fuming process has operated for close to 70 years to recover zinc from lead blast furnace slag. The process is normally carried out through the batch treatment of slag by submerged injection of coal and air. Within the bath the coal acts as both a reductant, to reduce Zno to zinc vapour, and a fuel, to maintain bath temperature during the endothermic reduction process. The partition of coal between the slag, combustion and bypass is dependent on factors such as bath depth and injection pressure. The option of continuous fuming has been pursued at the D. Blagoev smelter in Bulgaria using heavy fuel oil as reductant/fuel. There has, however, been little attempt at commercial continuous fuming with coal. This paper presents an analysis of a coal-based continuous slag fuming furnace. The data on the Plovdiv fumer is used as a reference point. Critical design criteria for continuous fuming include the slag feed rate, degree of coal combustion and furnace size. Mathematical modelling analysis suggests that continuous fuming with coal can achieve respectable zinc/coal ratios.IntroductionThe slag fuming process was developed in the early part of this century to recover zinc from non-ferrous smelting slags [1-3]. The majority of installed furnaces were put in place to fume zinc from lead blast furnace slag on a batch basis. In most cases coal is used to effect reduction of zinc oxide, but one furnace uses natural gas [4] and, in a curious twist, a continuous fumer was developed based on fuel oil [5].Given the general nature of blast furnace lead smelting, it is not surprising that slag fuming has remained a batch process, in spite of the advantages that could be gained by moving to continuous fuming. Blast furnaces are usually operated as relatively independent units, and tapping has traditionally been done into ladles. The presence of a crane aisle makes direct coupling of the blast furnace to a slag fumer difficult, especially in a retrofit situation. Furthermore, steady-state blast furnace operation is not easy to achieve. The size of these furnaces and the nature of their feed make it difficult to guarantee constant operation."

Jan 1, 1996

By T. -M. Guo, M. J. Braun

"This paper presents an experimental and numerical study of melt flow near the solid-liquid interface and its effect on the interface curvature in a horizontal unidirectional solidification system with succinonitrile. Melt flow is introduced by increasing the ampoule channel thickness. Visualization techniques are employed to observe the flow field and the solid-liquid interface curvature. A numerical model is also developed to simulate the heat transfer, melt flow and phase change in the system. Quantitative information on the flow and temperature fields is generated. A good agreement is achieved between the experimental observations and model predictions. The results could be used for the study of the effect of the melt flow on interface morphology during solidification.IntroductionClassic unidirectional solidification experiments of transparent alloys are conducted with thin film samples sandwiched between two glass slides to investigate the development of interface morphology during solidification [1]. Samples with small channel thickness are usually used to suppress any melt flow due to natural convection and solidification in the channel would then be in the diffusive regime so that the solidification theory can be significantly simplified [2, 3]. Effects of melt flow, in particular due to natural convection, on solidification have also been studied extensively in those systems with large geometrical dimensions [4-6]. These studies indicate a strong effect of the melt flow on interface curvature during solidification [5, 6]. Only limited efforts were made to address the effect of the melt flow on interface morphology in horizontal unidirectional solidification, in particular for the cases when the channel thickness is not thin enough to suppress completely the natural convection [7]."

Jan 1, 2004

By Wiraseranee. Chompunoot, Kazuki Morita, Toru H. Okabe

"Aiming at the development of more effective recycling processes, dissolution behavior of rhodium into molten slag was investigated. Using a pure rhodium crucible and Na2O-SiO2 slag system, equilibration experiments were carried out for 18 h at 1423-1623 K under various oxygen partial pressures of 0.005-1 atm with varied slag basicity. Rhodium solubility increased with increasing oxygen potential, slag basicity, and temperature. Rhodium dissolved into slag as rhodate ion ([RhO2]-) by the endothermic reaction: Rh(s) + 3/4O2(g) + 1/2O2-(in slag) = [RhO2]-(in slag). In the dissolution reaction, the “rhodate capacity” of slag is newly-defined. The correlation between rhodate capacity and optical basicity is reported.IntroductionDue to its high chemical resistance and outstanding catalytic properties, rhodium (Rh), one of the platinum group metals (PGMs), is utilized in various applications such as catalysts, molten glass vessels and containers, and electronic devices. Owing to the rarity of Rh resources in nature, recycled Rh from scraps such as spent automobile catalytic converters is currently considered as an important source of Rh supply [1]. According to the recycling practices, Rh is currently mainly recovered from scraps along with other PGMs such as platinum (Pt) and palladium (Pd) by a dry process (e.g., smelting), a wet process (e.g., leaching and subsequent separation of PGMs from aqueous solution), or a combination of both processes [2]-[4]. Among these processes, smelting is commonly applied because PGMs can be effectively separated from a relatively large amount of various impurities coexisting in scraps. In the smelting process, Rh and other PGMs are collected in the collector metal (e.g., iron and copper), and impurities in scraps are removed into slag [4]-[6]. The process may be carried out at a temperature range of 1573-1973 K, in either an oxidizing or reducing atmosphere. Due to the high oxidation resistance at high temperatures, Rh is expected to be collected efficiently in the metal collector rather than being oxidized and forming RhOx in a molten slag. However, Rh loss into slag does occur in this process [7]."

Jan 1, 2011

By R. Stefaniuk, T. Le, J-Y Huôt, H. Henein

"One of the most important process variables in gas atomization is the gas to metal (G/M) mass ratio as it has a direct effect on the mean particle size of the atomized powder. If this ratio can be controlled during the atomization process, the powder produced would be more uniform and the d50 more predictable. Thus, atomization using a tundish or gravity feed from a crucible would be more stable. In gas atomization, the gas flow rate can be easily monitored; while it is very difficult to determine the molten metal flow rate. This research paper presents a new method of recording the molten metal height with time using a conducting metal height detector. The metal height recorded in real time during atomization was used to characterize using a model the friction losses in the metal delivery system. It is found that the integrity of the metal delivery tube and the cleanliness of the melt play a key role in the maintaining a stable metal feed.IntroductionIn the gas atomization process, molten metal is normally fed to the system either continuously using a tundish or in most cases a certain amount of metal is melted in a crucible and flows into the atomizing chamber under gravity. In the first case, the metal flow rate is believed to be constant during the atomization process despite the presence of slag or dross on the molten metal surface. In the second case, the amount of molten metal is depleted with time and the rate at which the metal flow decreases with time varies from test to test in a seemingly unpredictable fashion.' Furthermore, most atomization systems are confined units and the metal level in the crucible cannot be detected by a visualization method. In industry as well as in laboratories, the metal flow rate is normally calculated on either the mass of input material or the mass of total production divided by the duration of the test. This figure is not accurate enough and obviously cannot be used as a control parameter for the gas to metal ratio as it is only determined after the completion of an atomization run. The need exists for a metal flow rate measurement and control methodology; thereby the d50 of the powder produced may be estimated and controlled in real time. Clearly, the smaller the variation of the G/M ratio during the atomization process the more uniform the powder produced and hence the size of the particles can be predicted."

Jan 1, 1994

By Shekhar Bhansali, Shyam Aravamudhan

"This paper reports on the design and simulation results of a silicon bulk-micromachined diaphragm-type piezoresistive pressure sensor capable of operating linearly over a wide dynamic range (0-1000 meters of water). The piezoresistor elements of the sensor are arranged in a wheat stone bridge configuration to achieve a higher output response. Simulation results (output voltage and sensitivity analysis) obtained using coupled MemPZR-MemMech module of the CoventorWare2003 Finite Element tool are presented. The effect of diaphragm size, diaphragm thickness and thickness of the piezos on output sensitivity were analyzed and optimized to get a linear response over the wide dynamic range.IntroductionThe physical and biological processes in the ocean are critically influenced by ocean parameters (pressure, salinity and temperature). Thus there is a need to develop inexpensive and reliable sensors to continuously measure large volumes of sea-space over long time spans. A key component in any such system will be a pressure/depth sensor. This sensor is routinely employed in marine applications such as wave and tide gauges, tsunami detection, platform leveling etc. More significantly, pressure measurement is needed for depth determination. Depth sensors are vital for remote operated vehicles (ROVs), profiling instruments and towed arrays.Several techniques have been routinely used in the past to measure pressure in the marine environment [1-3]. In general, the pressure sensor design is based on a flexible membrane as the spring element for the sensing pressure [4]. The deflection of the membrane, induced by the applied pressure, is converted into an electrical output through a component that is sensitive to diaphragm deflection (capacitive coupling) or associated stresses (piezoresistors, strain gauges). The temperature compensated pressure measurement can be readily converted to depth using"

Jan 1, 2004

By Robert G. Telewiak

During the past few years, the international nickel industry has taken some important steps to respond to conditions of global production overcapacity, relatively flat demand and low prices. These include the implementation of major cost reduction programs by most producers, closure of some high cost operations and the establishment of the Nickel Development Institute. Consumption in the western world increased by about 7 per cent in 1987 compared to 1986, supplies were less than demand, inventories were low, and late in the year prices increased dramatically. By year-end 1987, most producers were operating at, or close to, their effective capacities. Nickel demand is expected to increase to the year 2000 at an annual rate of about 1.7 per cent, led by increasing usage in the stainless steel sector. If this rate of growth is realized, then there will be need for the effective capacity of the nickel industry to be increased. Producers in Canada have put considerable effort in the past few years into reducing costs - with impressive results. Mining costs, in particular, have been reduced dramatically. While production is still less than the peak years of the yearly 1970's, it has increased substantially from levels of the early 1980's. Over the next few years, production is expected to increase slowly. A key determinant of the level of production in the 1990's could be the effect that regulations on sulphur dioxide emissions have on limiting production.

Jan 1, 1988

By Olexandr Gydin

The evolution of grain and dislocation structures during cold deformation of the new steel LH800 of Salzgitter AG is investigated in the frame of this work. The main feature of this material is its ability to air-harden by carbon content of about 0.1%. The initial ferrite structure of the metal provides high plasticity at cold deformation and subsequent heat treatment increases tensile strength approximately two times. Described are results of in-situ tensile tests in the SEM. SEM and TEM analysis of grain and dislocation structures evolution in samples, which have been uniaxially deformed to certain strains, are carried out. After statistical evaluation of results the grain elongation against strain is determined. A microstructure of a deep drawn cup is analyzed by means of SEM. A quantitative evaluation of grain elongation on the different cup zones and comparison of these data with prediction results based on tensile tests are carried out.

Jan 1, 2009

By Francois Barthelat, Sam Goroshin, David Frost, Alexander Cappozi, Atefeh Nabavi

"In this study, a novel chromium–chromium sulfide cermet was produced by self-propagating high-temperature synthesis (SHS). Conventional techniques for manufacturing metal sulfides are complex, environmentally harmful, and not suitable for producing complex-shape articles. To overcome these disadvantages, a new method for the preparation of the metal-sulfur precursor charge is proposed, which can be described as reactive casting. The first cermet samples produced with the SHS process were found to be very porous, brittle, and have low mechanical strength. The possible sources for the generation of porosity were identified and analyzed and the process for manufacturing the cermet was modified. By improving the manufacturing process, the porosity inside the produced cermets was reduced from 70% to 12%.IntroductionMetal sulfide composites are in high demand in the chemical, metallurgical, and electrical industries because of their valuable characteristics such as hardness, semi-conductivity, electroluminescence, infrared transparency and catalytic properties. Current manufacturing methods for metal sulfides usually involve one of two different principal methods, including a complex multistage wet chemical process involving the precipitation of the corresponding salts from an aqueous solution with hydrogen sulfide, or hot sintering of the respective elemental reactant powders in a resistive furnace in a high-pressure inert or hydrogen-sulfide atmosphere [1, 2]. These conventional methods for synthesizing ceramic metal composites are complex, extremely time and energy consuming, environmentally harmful, and rarely able to manufacture articles with complex shapes. Therefore, in order to overcome these disadvantages, self-propagating high-temperature synthesis (SHS) was considered as an alternative method that offers significant improvements over the traditional cermet manufacturing methods [3]. SHS, which is a relatively new and attractive method for producing a wide range of advanced materials, is based on the self-sustaining feature of the highly exothermic reactions of the reactants. The SHS process results in high product purity, since the high temperatures generatedin the reaction cause any impurities to volatilize [4, 5]. SHS has low energy consumption and doesn’t require an external energy source and complex equipment, and it is self-contained [1, 5]. Since combustion synthesis has low power requirements, it is one of the few methods of materials synthesis that is feasible in outer space. Also, the process has a low cost and is capable of directly synthesizing articles with the desired shape, size and structure [5, 6]. The chemical reactions associated with SHS are typically completed in a few seconds leading to the formation of the condensed product. The high reaction rates and relatively rapid cooling in SHS reactions can avoid undesirable grain growth in products which often occurs with the conventional sintering method [3, 5, 7]. The traditional method for sample preparation in the SHS technique is to compact the reactant mixture powders in a steel die by a press to a typical density of about 80% of the theoretical maximum value, before igniting the mixture [8]. This method requires a large compression force to increase the green density and to minimize any pores in the green compact. To overcome these disadvantages, a new method for the preparation of the precursor charge in metal-sulfur by SHS is proposed which can be described as melt casting of a reactive mixture, or reactive casting in short."

Jan 1, 2012

By Akira Kaneda, Nozomu Hasegawa

"In the Mitsubishi Continuous Copper Smelting and Converting Process, slag/matte mixture overflowed from the smelting furnace is separated continuously in an electric furnace (slag cleaning furnace, CL-furnace). In order to improve the separation efficiency of slag and matte and to minimize power consumption, the design and the operating conditions of the CL-fumace should be optimized. In the previous study, the authors developed a mathematical model for simulating phenomena in the CL-furnace. The model consisted of 3 modules, electric field analysis, heat and fluid flow analysis and the particle tracking method. In this study, the model was partially modified: k -E. model was adopted, and the effects of various conditions, such as furnace shape (including accretion) and scale, electrodes configuration, immersion depth of electrodes, and thickness of slag layer, were evaluated. And the optimum design and operating conditions were discussed.IntroductionUnder the recent environmental restriction, advantageous features of the Mitsubishi process have attracted much attention. The process uses 3 furnaces connected by launders. Mixture of matte and slag formed in a smelting furnace flows continuously to a slag cleaning furnace (CL-furnace), where the matte is separated from the slag. The matte is continuously siphoned out to a converting furnace and converted to blister copper. The slag overflowed from the CL-furnace is discarded. Because the slag contains about 0.6 % copper, improving slag/matte separation efficiency and decreasing copper loss make a great profit. Moreover the process requires a large amount of electric energy, so reduction of electric power consumption brings in enormous benefit.The objective of this study is to optimize the design and the operating conditions of the process, especially the CL-furnace. This will be achieved by developing the mathematical model and clarifying relations between the design or the operating conditions and various phenomena in the furnace. Fig. 1 shows an outline of the CL-furnace. The mixture entering through an inlet is separated to slag layer and matte layer . In order to maintain the temperature of the melt at a predetermined level, 6 electrodes are immersed into the lag and Joule's heat is generated by 3-phase alternating current flowing."

Jan 1, 2000

By Yuanbo Zhang, Huanpeng Mi, Guanghui Li, Binjun Liang, Zhiwei Peng, Tao Jiang

Ludwigite ore has not yet been utilized on an industrial scale due to its complex mineralogy and fine mineral dissemination. In this study, sodium salts were employed to enhance the separation of iron and boron by reductive roasting-magnetic separation. It was found that the separation of iron and boron as well as the iron grade and recovery were significantly improved b y the addition of Na2SO4 or Na2CO3. Under the reduction temperature of 1050 °C, reduction time of 60 min and magnetic intensity of 0.1T. Compared with the inexistence of sodium salts, the iron grade and recovery of the magnetic concentrate increased from 83.3% and 88.6% to 93.2% and 95.1%, respectively, by adding 6% Na2CO3. The XRD and microstructure analyses indicated that the iron oxides were transformed into metallic iron and the average metallic iron grains were grown to over 40μm which was beneficial for separation of metallic iron from gangue.

Jan 1, 2016

By Sung Wng Kim

The binary antimonide compounds with the skutterudite structure have a potential for thermoelectric applications because of the high carrier mobility, high thermoelectric power, and relatively low thermal conductivity due to the complex crystal structure. However, the room temperature thermal conductivity of these skutterudite materials is as high as about IOW/mK with an estimated 80-90% contribution from the lattice thermal conductivity. Because the lattice thermal conductivity of related ternary skutterudite compounds can be substantially reduced due to the additional phonon scattering, a study of thermoelectric properties of these compounds is of interest. The binary IrSb3, ternary Ir1.xRuxSb3 and Ir(MxSb1.x)3(M=Ge, Sn) compounds were prepared by hot pressing of pre-reacted powders. We have measured the electrical resistivity, thermoelectric power, and thermal conductivity, in a temperature range from room temperature to 973K. The binary IrSb3 compound is found to have P-type electrical properties exhibiting a good Seebeck coefficient (up to 225µV/K around 773K), electrical resistivity(5x10-5Ohm M around 933K), and relatively low thermal conductivity(6W/mK around 950K). The lattice thermal conductivity, K[2] was calculated from the Wiedemann-Franz relationship.

Jan 1, 2002

By François Tremblay

It is well known that removal of organic material such ,as Jacquer, paint, plastic prior to melting improves aluminum recovery. In addition to being an important economically, decoating of aluminum scrap has a positive impact on the environment, through better control of gaseous emissions. Most of the existing thermal decoaters for aluminum have been designed to operate with scrap containing a level of organic material lower than 10%. The main field of their present application is for recycling of used aluminum can, where levels of organic material are lower than 4%. Alcan has recently developed a new thermal decoating system in order to extend applications of this process to a much wider variety of aluminum scrap. The new decoater efficiently processes aluminum scrap with a level of organic material up to 50%. This new technology features the use of fluidized bed technology to thermally control the process. This innovative feature improves both performance and control over conventional delacquering systems based on hot air convection. This paper describes the basic principles of the technology and the design of the? first industrial unit commissioned by the Alcan Recycling plant in Shelbyville (TN) at the beginning of 1994. Typical applications and operating advantages are discussed.

Jan 1, 1995

By H. Kohno

The Onahama No.3 tankhouse started commercial operation in early 1973, with the capacity of 8,500 metric tons per month. When the No.3 tankhouse was constructed, the starter sheet stripping section was rebuilt at the No.2 tankhouse and electrolyte purification section was expanded. The previous AIME paper in 1976 described the design principles of the No.3 tankhouse and its layout, This paper describes the starter sheet stripping machine in the No.2 tankhouse and the electrodes handling system in the No.3 tankhouse and all these equipments were developed for the operation of the No.3 tankhouse. A Hazelette continuous casting machine was also introduced in order to cast thin anodes with accurate shape. Owing to the adoption of thin anodes, gold, silver and copper inventory is reduced by 40%. Jumbo tanks and newly developed mechanical equipments were adopted and no work on cells during pulling up operation was achieved. Using thin anodes with accurate shape, inspection work was completely abolished while maintaining high current efficiency and high cathode quality. Labor cost was reduced by 70% and only six operaters can produce? 8,500 metric tons of cathodes per month. The same new electrolysis process is appreciated and has been used as a newly built independent tankhouse by Kidd Creek Mines Ltd., in Canada in 1981 with excellent results

Jan 1, 1987

By Takeshi Yoshikawa, Kazuki Morita, Kunitoshi Matsunaga

"In metallurgical grade silicon (MG-Si), most impurities mainly exist at the grain boundaries and distribute in silicon grains at extremely small contents. Grain boundary phases in MG-Si transform into liquid above the eutectic temperature, and migrate towards high temperature regions when heated under a temperature gradient. With the migration of all liquid phases in MG-Si to the surface, the impurity contents will be decreased less than their solubilities in principle.In the present work, the fundamental research was conducted to discuss the possibility for purification using the liquid phase migration technique. The purification limit was estimated by thermodynamic calculations, and metallic impurities were estimated to be effectively removed except for Fe and Al. The migration behavior of the liquid phase in the synthesized silicon substrate was investigated by unidirectional heating under infrared radiation at 1523-1548 K, and the proceeding of migration was confirmed. The migration velocity was 1.4--2.0xl0-7 mis, and found to be controlled by the liquid phase diffusion.IntroductionPhotovoltaic energy is one of promising energy resources in a sustainable society because of its inexhaustibility and cleanliness. Although the production and installation of solar cells have increased significantly during the last decade, the cost of solar cell installation is still high. To enable the widespread use of photovoltaics and for the photovoltaic electricity price to reach grid parity, a low-cost and abundant feedstock of solar grade silicon (SOG-Si) is essential. Recently, a modified Siemens process and a fluidized bed reactor process were developed to address the cost and energy issues associated with the conventional Siemens process. However, their cost reduction potential is limited because of the large energy consumption needed to convert silicon into gaseous compounds. Purification of silicon through metallurgical routes offers a promising way for producing SOG-Si from metallurgical grade silicon (MG-Si), because it enhances productivity and can also lower the process costs. Although several metallurgical processes such as directional solidification [l ], vacuum refining [2-4] and plasma oxidation [5-7], have been developed, processing times and refining efficiencies still have to be optimized."

Jan 1, 2013

By Andriy Burbelko, Daniel Gurgul, Wojciech Kapturkiewicz, Marcin Gómy

"The mathematical model of the globular eutectic solidification in 2D was designed. The proposed model is based on the Cellular Automaton Finite Differences (CA-FD) calculation method. The model has been used for studies of the primary austenite and of globular eutectic grains growth during the ductile iron solidification in the thin wall casting. The model mentioned above takes into account, among other things, non-uniform temperature distribution in the casting wall cross-section, kinetics of the austenite and graphite grains nucleation, solute diffusion and non-equilibrium nature of the interphase boundary migration.Some aspects of stochastic nature of the solidification processes are taken into account. The results of the CA solidification modeling have been shown, that differences between cooling curves obtained in the same conditions of the casting solidification may be a result of the stochastic nature of the grain nucleation.The results of modeling were compared with the experimental microstructure. The model is well worked for thin walled ductile iron casting, for fast solidification process.IntroductionNodular graphite cast iron, also known as ductile iron (DI), has major applications in critical engineering parts due to its mechanical properties and castability. The mechanical and physical properties of this material depend on the shape and number of the graphite grains andmicrostructure of the metallic matrix.Solidification of DI was a subject of many computer modeling programs described in literature [ 1-5], in which the stationary conditions of carbon diffusion in austenite is pre-assumed. Recently, a tendency for production of thin-walled castings has been observed [ 6-8]. In this technology, the process of the fast solidification may be very far from equilibrium and steadystate conditions [9].The purpose of the present work is a two-dimension model development for simulation of the DI structure formation during the solidification in the condition of non steady-state temperature and diffusion fields in the thin-wall casting.Model of process The CA-FD is one of the known methods of the simulation ofmicrostructure formation during the solidification [ 10, 11]. In the CA microstructure modeling the outer grain shape is the result of the simulation and does not superimposed beforehand. The model development for a onephase microstructure evolution is a subject of the numerous researches [12 -23]. Model of the eutectic solidification of DI in the uniform temperature field and superimposed cooling rate is known [24]."

Jan 1, 2013

By Ian F. Hughes

"Concepts of an integrated steel plant for sheet products to be built and operating in the year 2000 will be described. The design and operating methodology of this market driven facility will integrate process uniqueness, standardization, manufacturing automation, artificial intelligence and information flow.An integrated steel plant for the year 2000 is defined for this article as one that will be built on a greenfield site and ""started up"" in the year 2000 with a capacity of three million tons per year of flat rolled products ranging from cold rolled and electrical steels to high strength formable steels and a full range of coated products.It may seem that the 21st century and the steel plant we're discussing are far into the future. The startling truth, however, is quite the opposite. As shown in Figure 1, even with accelerated development, a new process on which laboratory development work is begun today might just barely pass through the laboratory phase, pilot plant, and commercial feasibility stages such that it can be considered viable for construction and start up in the year 2000.On that basis, it is very unlikely that this 21st century steel plant will utilize any technology that isn't at least under investigation in the laboratory in 1988. As a result, we recognize that planning and selecting the facilities for this plant is, in fact, a pragmatic rather than futuristic process, and that its main value is in providing a bridge to longer-term predictions."

Jan 1, 1988

By Hsing Kuang Lin

Extraction of zinc from chloride solution with dibutyl butylphosphonate (DBBP) in Escaid 110 has been investigated. The distribution coefficient of zinc was found to be independent of equilibrium pH. This independence indicates that the mechanism of the extraction may be solvation. Slope analysis for the system of dilute zinc chloride solution reveals that two moles of DBBP react with one mole of zinc. A series of tests were conducted to bring DBBP to its full loading capacity and the analysis of the results confirms this stoichiometric factor of 2. Extraction isotherms were established by varying either the AIO ratio or the concentration of zinc in the aqueous feed. Both curves were found to be identical.

Jan 1, 1990

By Vincent Canaguier

Methane is increasingly considered as a promising reductant for metal oxides, including chromite. To assess the possibilities of such reduction route, the gas-solid reactions between Ar–CH4–H2 gas mixtures and synthetic chromites are studied between 950 and 1050 °C. The influence of Mg and Al additions on the reduction-caburization of (Fe,Mg)(Cr,Al)2O4 solid solution is investigated thermodynamically, structurally and kinetically. The product phases are examined by x-ray diffraction (XRD), scanning electron microscopy (SEM), and electron probe microanalysis (EPMA). The reaction rate is derived from real-time exhaust gas measurements and post-reaction product analyses such as oxygen analysis. Kinetic models are proposed based on the product phase morphologies and confronted with the empirical data.

By Dianyuan Dang, Guihong Han, Wenjuan Wang, Tao Jiang, Yanfang Huang

In this study reduction kinetics and swelling behaviors in "two-step process” were investigated by weight-loss technique and visualizing physical changes of pellet. Results showed that reduction degree (r) increased with increasing temperature and time. According to the dynamic calculation, when reduction temperature was lower than 1000°C the reduction process was controlled by chemical reaction with apparent activation energy of 72.27 kJ/mol. When reduction temperature was higher than 1000 , the equation of t/[1-(1-r)1/3] against [1+2(1-r)-3(1-r)2/3]/[1-(1-r)1/3] followed straight lines, demonstrating that reduction was mixed-controlled. Swelling experiments indicated that the maximum swelling index increased with the increase of reduction temperature and CO content.

Jan 1, 2016

By Dumitru Mitrica, Vasile Soare, Elvira Alexandrescu, Mihai Ghita, Marian Burada, Petru Moldovan, Raluca Maria Florea

"Aluminum metal matrix composite Al-Si /SiCp was prepared by reactive gas injection and subsequent remelting. The influence of the remelting process on the microstructure and physicalmechanical properties of the resulted material was investigated. Samples resulted from the synthesis process contained silicon carbide agglomerations in the vicinity of primary silicon and large pore concentrations. In-situ formed silicon carbide presented mostly a polymorphic structure with particle sizes varying from 1 to lOµm. Physical and mechanical properties were largely influenced by the porosity distribution. The remelting process provided a decrease in the composite material porosity and pore size, with significant improvements in the particle distribution and physical-mechanical properties of the composite material. Additions of up to lwt.%Mg in the starting alloy improved the in-situ carbide formation and particles distribution in the solidified material. However, stable and large particle agglomerations were detected in the material in absence of conventional stirring or controlled solidification techniques.IntroductionThe remarkable properties of composite materials (yield strength, stiffuess, hardness and resilience at a reduced specific weight) make them attractive for applications in automotive, aerospace and military industries. Particle reinforced aluminum metal matrix composites (PAMMC) are known for their high strength to weight ratio. The recent development of P AMMC created the possibility to obtain large particles concentrations, exceeding 10% by volume ofreinforcement (SiC, AIN, Al203, etc.). The improvement ofhigh temperature strength and wear resistance made them appropriate for the use in automotive applications, such as the pistons, rotors, disc brakes, and propeller shafts [ 1]. The present main disadvantage of the P AMMCs is their high costs for obtaining and processing related to the final product performance. In order to benefit from the advantages that offer composite materials properties a reasonable production cost - performance ratio must be obtained [2]. Recent innovations in the manufacturing of aluminum-based metal matrix composites provided notable performance improvements but no feasible solutions were found for lowering their present high prices."

Jan 1, 2014