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By Tianyou Huang, Yuan Lu, Haimin Long, Jinwu Kang, Gang Nie

"The distortion of metal parts during heat treatment process is one of the main obstacles in industry to ensure high-quality work and less or no machining allowance, especially for large but thin steel castings such as heavy turbine blades. In the paper, a method is proposed to control the distortion by adjusting heat transfer coefficient of metal parts during heat treatment process. Required heat transfer coefficients can be realized by getting the metal parts into contact with various media such as water spray, insulation felt or materials with different heat conductivity. The control method based on this idea is set up and achieved. By using insulation felt and water spray to change the heat transfer coefficient during the stages of heat treatment process, the results indicate that the proper control time and vary with materials.IntroductionThe distortion of metal parts during heat treatment process is one of the main obstacles in industry to ensure high-quality work and to realize less or no machining allowance [1]. For example, the Three Gorges turbine blade’s distortion is as large as 50mm during heat treatment process. The uneven heating and cooling during heat treatment process is the main reason for distortion [2]. By adjusting heat transfer coefficient of different areas of metal parts, the heat treatment process could be controlled. The temperature variation, direct cause for distortion, could be under control. Loeser Klaus used high pressure gas to achieve uniform heat transfer during gas quenching and proposed the possibility to use ""Dynamic Quenching"" processes where the quenching severity is varied during quenching by stepwise control of either gas velocity or gas pressure [3]. Li Zhichao also suggested minimizing distortion by marking a component into several areas and imposing different heat transfer coefficients on each area [4]. Heat transfer coefficient can be controlled by getting the metal parts into contact with different media such as water spray, insulation felt, air or different heat conduction materials. In addition, the exact time to adjust the heat transfer coefficient is another factor for distortion. A method is presented in this paper by actively adjusting heat transfer coefficient for different areas of metal parts and different stages of heat treatment process to control their distortion. The corresponding experiments have been made by using different metal materials."

Jan 1, 2012

By K. Morsi, P. Mehra

"Spark plasma sintering has gained a considerable amount of attention over the past decade, due to its rapid sintering rates, and low temperature requirements, but has so far been usually limited to the production of simple geometries. The present paper examines the current-activated production of extended geometries through the process of spark plasma ""extrusion"". Of interest in the present study is exploratory research into the effect of electrical current activation on the reactive consolidation of powder systems to form intermetallic materials.IntroductionSpark Plasma Sintering (SPS) has been the subject of intense research over the past decade [ 1,2, 3,4,5,6]. The process boasts unique advantages which include ultra fast heating rates, shorter sintering times and lower sintering temperatures than needed in conventional sintering. The process is however limited to the generation of predominantly simple geometries. Recently one of the authors investigated the spark plasma extrusion of aluminum, where an aluminum powder compact is directly (Joule) heated through an applied DC electric current. Here extended geometries can be generated under the influence of electric current. A number of heating sources were identified including the heat source from current, i.e. Joule heating, frictional heating and heat from the deformation energy. However in the case of reactive powder systems, an extra ""one-time"" transient heating source can be supplied. By considering combustion synthesis of powders, this heating source is derived from the reaction between elemental powders to exothermically form a product at some ignition temperature [7]. This exothermic energy heats the compact to the maximum ""combustion temperature'', which could be hundreds of degrees higher than the ignition temperature. Hence a high temperature processing window (of short duration due to heat losses to the surroundings) becomes available in which the material is most suitable for stress-induced deformation and consolidation. For reactive spark plasma extrusion, two scenarios can be envisioned. The first is where the reactive powder compact is ignited through the application of current, and extruded within the high temperature processing window (also under the influence of current). The second scenario is to allow the heat of deformation/friction to heat the material during extrusion, to simultaneously force a reaction and consolidation. Here it is expected that the processing window will be very small if feasible."

Jan 1, 2011

By N. Can

Kinetics and mechanism of the chemical interactions between Si3N4 and TiC were investigated by isothermally reacting samples under nitrogen and argon atmospheres at temperatures between 1600°C and 1700°C? The initial composition of the powder compact contained 20, 30 and 40 volume per cent TiC? Kinetic analysis were performed by measuring mass losses and composition of the titanium carbonitride (TiC1-xNx) at predetermined time intervals? It was found that in the Si3N4-TiC system the degree and rate of the reactions increased with increasing temperature and content of TiC in both nitrogen and argon atmospheres? Si3N4 in the presence of TiC was stable in nitrogen atmosphere and the reactions were confined to Si3N4/TiC and TiC/N2 interfaces? At both interfaces interchange reaction occurs by simultaneous diffusion of nitrogen towards the centre of the particle and desoprtion of carbon in the opposite direction resulting in formation of titanium carbonitrides with various compositions? Reaction products under nitrogen atmosphere were B-SiC, TiCl1-xNx and N2? The maximum "x" value in TiC1-xNx was found to be 0?67 under nitrogen atmosphere? Si3N4 was found to be unstable in argon atmosphere in the presence of TiC and dissociated into liquid silicon and nitrogen gas within approximately four hours of reaction time, depending on temperature? The reaction mechanism in the initial stages of the interaction between Si3N4 and TiC under argon atmosphere proceeds similar to reactions under nitrogen atmosphere? However, considerable amount of Si3N4 dissociates within the first half hour? Liquid silicon aggressively attack both TiC1-xNx and unreacted or partially reacted TiC particles through cracks and pores and diffuses into interier part of the particle forming liquid solutions? After this stage, reactions under argon atmosphere proceeded according to Si-Ti-C ternary system?

Jan 1, 1999

By Matsufumi Takaya, Yukihiro Sakamoto

"Electric field emission properties from CVD diamond fabricated using pulse-modulated microwave plasma CVD were studied. Diamond was synthesized by microwave plasma CVD apparatus equipped with a pulse-modulated microwave power supply. Pulse conditions were varied from 1 to 10 seconds for pulse periods and from 0.1 to lHz for pulse frequency either. Surface morphologies of the deposits were differed by pulse frequency and duty cycle. As a result, FE properties prepared by different pulse duty cycle were different from continuous film which synthesized using continuous microwave significantly. Highest current density was obtained from the uneven morphology diamond film prepared at 17.5% pulse duty cycle.FE properties of the CVD diamond were depended on surface morphologies that related to the pulse conditions.1. IntroductionDiamond has excellent physical and chemical properties as an industrial material. Especially, hydrogen terminated diamond had the negative electron affinity (NEA) 1) and CVD diamond has this NEA property either as deposited 2). So the electron emission source to the FED is expected as one of this application of CVD diamond as cold cathode of electric devices. We studied on FE properties of various CVD diamond, pulse microwave plasma CVD diamond showed better property than those of other CVD diamond 3).This report studied on· the effect of the duty-cycle of pulse modulate microwave condition on FE properties of the diamond fabricated by pulse modulated microwave plasma CVD."

Jan 1, 2000

By Yuhua Pan

Generic mathematical models have been developed for simulating heat transfer in two types of slag resistance heating electric furnaces for sulphide smelting: i) six-electrode-in-line rectangular furnaces and ii) three-electrode circular furnaces. The models are based on three-dimensional steady-state heat transfer of conduction, convection and radiation. Solidification of liquid slag into solid slag by water-cooling units, for use as freeze lining of furnace walls, is also considered in the models. The developed models are capable of providing predictions with reasonable accuracy for electric furnaces on 1) temperatures in slag, matte, cooling water, freeze lining and other solid regions as well as temperatures at various fluid/solid interfaces, 2) freeze lining thickness, 3) furnace smelting rate and 4) furnace heat loss rate. These computer models are built into executable application programs that are very efficient, with execution time less than one second, and can be easily portable to most computing platforms. This paper describes, as an example, the modelling results on heat transfer in six-electrode furnaces. The major modelling results show that in six-electrode furnaces uniform electric power inputs to the electrodes likely lead to low temperature regions close to slag and matte tapping ends of the furnaces, and the power input and the formation of air gaps between freeze lining and cooling units have significant influences on the thickness of freeze lining maintained by the cooling units.

Jan 1, 2006

By Tian Tang, Sergio D. Felicelli

"The laser cladding is an important surface treatment for enhancing resistance against corrosion, abrasion, and wear. The focus of the present study is to develop a three dimensional finite element model to analyze the temperature history and thermal stress evolution during multi-pass laser cladding process on H13-H13 tool steel sample. A sequentially coupled thermal-stress analysis methodology was adopted in this study. The thermal model was firstly established to investigate the temperature history of the laser cladding process. Then the temperature history was used as input to mechanical model to calculate the thermal stress evolution during the process and the residual stress after the sample completely cooled down to room temperature. The influences of process parameters including the scanning speed and scanning strategies on temperature history, thermal stress evolution, and residual stress were investigated in details.IntroductionLaser cladding is an advanced material process technique, which is often used to improve mechanical properties or increase corrosion resistance, repair worn out parts, and fabricate metal matrix composites. In this process, the injected powder or wire feedstock material and a thin layer of substrate are melted and consolidated by use of a laser in order to coat part of a substrate or fabricate a near-net shape part.Numerous mathematical models have been established for analyzing the effects of process parameters, microstructure evolution, and thermo-mechanical behavior of laser cladding. Zhou et al. [1] established an analytical model to investigate the laser induction hybrid rapid cladding for Ni-based WC composite coatings. Huang et al. [2] also developed an analytical model to theoretically investigate the interaction between the laser beam and the powder stream of laser cladding process. A simple and realistic model of laser cladding was proposed by Picasso et al. [3]. The cladding layer is very sensitive to cracks due to the accumulation of residual stress, caused by non-uniform temperature changes, which have limited the wide application of laser cladding technique in industry. Recently, fmite element method has been increasingly used to simulate the laser cladding process [ 4-6]."

Jan 1, 2014

By Miaoyong Zhu, Sen Luo

"A two-dimensional CAFD model was developed for simulating the solute diffusion-controlled dentritic growth in the low Peclet number regime. Mass conservation and local equilibrium at the solid/liquid interface were solved to determine the growth velocity of interface with consideration of constitutional and curvature undercooling. The modified decentered square growth proposed by Wang et al was adopted to capture the first eight neighboring cells. The comparison between the classic Lipton-Glicksman-Kurz (LGK) analytical model for steady state tip variables and the simulated values showed that the present model was capable of quantitatively determining the dendritic growth, and the simulation tests demonstrated that the effects of the mesh anisotropy in growth kinetics and crystallographic orientation were eliminated. The numerical simulations were performed to the dendritic growth ofFe-0.6%C binary alloy in undercooled melt, and the results showed that the present model could predict the dendrite morphology with artificial growth orientation in acceptable level.IntroductionDuring the solidification of metals and alloys, the dendrite grows from the substance or the undercooling melt and solute redistributes between the dendrite and the interdendritic liquid. The solidification microstructure is close related to the phase and solute evenness and has a close linkage with the properties of final production.In the past few decades, various kinds of deterministic and stochastic models have been developed to predict the evolution of microstructures in solidification, with the fast development of computer power. Among these methods, Phase Field (PF) model [1, 2] has been known as one of the most adequate deterministic models for directly simulating the dendritic growth. However, there is a vital drawback that the PF method requires considerable computation time and is limited to simulate very small domains with a few dendrites [3]. On the other hand, stochastic models, such as Monte Carlo (MC) method [4, 5] and Cellular Automaton (CA) method [6-8], have been usually applied to predict the solidification microstructure evolution. Comparing with the MC method, the dendritic growth kinetics is explicitly integrated in the CA model, while the MC model doesn't. Therefore, the CA method is more reasonable to predict the dendritic growth during the solidification of melt."

Jan 1, 2013

By Anurag Tripathi, J. K. Saha, S. K. Ajmani, J. B. Singh

"The quality of steel is a major concern in the metallurgical industry. The control of liquid steel temperature can enhance the level of cleanliness in steel. Ladle is one of the major vessels used to transfer liquid steel between different stations. The heat transfer phenomenon taking place in this vessel needs to be monitored for controlling the liquid steel temperature. A CFD model was developed for prediction of liquid steel temperature during complete process cycle of ladles in direct heats. The model was validated with liquid steel temperature measured at on-line purging station and tundish during teeming from one of the actual steel plant. The accuracy of model was 96 %. The results obtained show insignificant effect of slag thickness, tapping temperature and ladle life on liquid steel temperature in the ladle. However, the importance of initial refractory temperature was noticed. The CFD model developed in present work can generate the thermal history of liquid steel and refractory walls of any ladle at any stage.1. IntroductionThe control of liquid steel temperature is desired to achieve required steel quality. The low casting temperature is detrimental and may result in nozzle blockages due to premature solidification in the tundish. The phenomenon of heat losses taking place in ladles needs to be understood for prediction of liquid steel temperature. The assessment of thermal profile of liquid steel from BOF converter to caster can be done through consideration of heat losses at all points. Hlinka and Miller [1] showed that the ladle pouring temperature varies due to heat losses from molten steel into surrounding refractory layers. The phenomenon of thermal stratification was numerically simulated by Ilegbusi and Szekeley [2]. The effects of slag cover on heat loss and liquid steel flow in ladle before and during teeming to a continuous casting tundish was numerically simulated by Chakraborty and Sahai [3]. Investigators also developed some simple models to predict the steel temperature for some of the processes taking place in ladles [4-9].The present work is an effort to generate the full information about the temperature drop taking place in any ladle throughout its process cycle. This information can be used to predict liquid steel temperature and to take decisions to minimize heat losses."

Jan 1, 2012

By A. A. Hejja

"Liquidus temperature and electrical conductivity data measured on synthetic slags were modelled by the use of neural nets (NN). In this work the applied multilayer feedforward NNs were trained by a conjugate-gradient optimisation for which a three layer formulation was used. Very good fits were obtained for both the liquidus temperature and the conductivity data. The synthetic slags were prepared from pure oxides to represent a wide range of compositions likely to be encountered in ferromanganese and silicomanganese smelting. The slag constituents were in the following range: Mn0;5-30%, Ca0;20-35%, Mg0;5-15%, Si02;27-58%, Al20 3;5%. Liquidus temperatures varied from 1300° to 1380° and increased with increasing basicity ratio. The electrical resistivity of slags decreased with the increase of basicity ratio from 0.55 to 1.1 but above 1.1 basicity ratio the resistivity tended to increase depending upon the MnO content.Neural NetsVarious neural net (NN) topologies such as Hopfied nets, Hamming nets, Carpenter/Grossberg classifiers have been discussed in some detail by Lipmann (1). In this work, the applied multilayer feedforward NNs are not trained by backpropagation (BP) using the generalized delta rule (2) (GDR), but by a conjugate-gradient optimisation [3,4] - a procedure similar to that proposed by Barnard and Cole [5]. A neural net is capable ·of learning the non-linear functional relationship existing between a set of inputs and outputs [ 6]. In this capacity a neural net is used to determine the functional relationship that exists . between N dependent and independent variables, which characterize the system under consideration For a three layer neural net [1] the following function may be formulated, which relates X; inputs to the output Y 0 from node o:"

Jan 1, 1997

By V. Montenegro

Smelting of copper concentrates in Teniente Converter produces highly oxidized slag, containing from 4 to 10 % Cu and from 15 to 25 % of Fe304. Copper recovery requires magnetite reduction at a level of 5%, determining the degree of cuprous oxide co-reduction and the liberation of copper matte inclusions. The rate of slag reduction is controlled by the mass transfer to the reaction interface. Slag stirring affects the rate of reduction and enhances coalescence of mechanically entrained copper matte inclusions. Slag reduction and sedimentation in the AC electric furnace is a commonly used method of slag cleaning. Utilization of DC electric furnace creates beneficial conditions introducing slag electrolysis additionally to chemical reductions with carbon of coke and electrodes. Application of external magnetic field, interacting with a direct current in an electric furnace, induces magnetohydrodynamic phenomena, such as intensive stirring and electromagnetic buoyancy force acting on inclusions. Laboratory scale research in simulated DC electric furnace with a superimposed magnetic field showed a significant acceleration of the rate of slag reduction and copper removal. Continuous measurement of gas flow and composition allowed for determination of the reduction rate along the time. Application of external magnetic field in the reduction of the industrial slag in a crucible simulated DC electric furnace results such as the increase of the reduction rate from 2 to 3 times, compared with the identical conditions in the AC electric furnace. Interaction of non-homogeneous electric field with crossed permanent magnetic field induces vigorous slag stirring, enhance mass transfer and accelerate the rate of the slag reduction. Additional participations of the slag electrolysis in the magnetite and cuprous oxide reduction as well as the acceleration of the settling of the inclusions by the electromagnetic buoyancy force affect the slag cleaning intensification.

Jan 1, 2003

By V. Montenegro

Smelting of copper concentrates in Teniente Converter produces highly oxidized slag, containing from 4 to 10 % Cu and from 15 to 25 % of Fe304. Copper recovery requires magnetite reduction at a level of 5%, determining the degree of cuprous oxide co-reduction and the liberation of copper matte inclusions. The rate of slag reduction is controlled by the mass transfer to the reaction interface. Slag stirring affects the rate of reduction and enhances coalescence of mechanically entrained copper matte inclusions. Slag reduction and sedimentation in the AC electric furnace is a commonly used method of slag cleaning. Utilization of DC electric furnace creates beneficial conditions introducing slag electrolysis additionally to chemical reductions with carbon of coke and electrodes. Application of external magnetic field, interacting with a direct current in an electric furnace, induces magnetohydrodynamic phenomena, such as intensive stirring and electromagnetic buoyancy force acting on inclusions. Laboratory scale research in simulated DC electric furnace with a superimposed magnetic field showed a significant acceleration of the rate of slag reduction and copper removal. Continuous measurement of gas flow and composition allowed for determination of the reduction rate along the time. Application of external magnetic field in the reduction of the industrial slag in a crucible simulated DC electric furnace results such as the increase of the reduction rate from 2 to 3 times, compared with the identical conditions in the AC electric furnace. Interaction of non- homogeneous electric field with crossed permanent magnetic field induces vigorous slag stirring, enhance mass transfer and accelerate the rate of the slag reduction. Additional participations of the slag electrolysis in the magnetite and cuprous oxide reduction as well as the acceleration of the settling of the inclusions by the electromagnetic buoyancy force affect the slag cleaning intensification.

Jan 1, 2003

By Y. H. Wang, S. Kou

"Three-dimensional weld pool convection was computer simulated using dimensionless variables. The electromagnetic force, the buoyancy force and the surface tension gradient on the pool surface were treated through the use of the dimensionless electromagnetic force, the Grashof number and the Marangoni number. Other typical dimensionless numbers such as the Prandtl number and the Peclet number were also used. The calculated and experimentally observed fusion boundaries were compared. The convection patterns were shown and the effect of the Marangoni number was demonstrated. IntroductionSeveral weld pool convection models have been developed by Oreper et al. (1,2), Chan et al. (3) and Kou et al. (4). These models describe two dimensional convection in stationary weld pools in a semi-infinite workpiece. Since the vast majority of arc welding practices involve a moving heat source and weld pool, and the workpieces are finite in thickness rather than semi -infinite, a 3-D convection model for a moving heat source and a workpiece of finite thickness is expected to be much more useful.Weld pool convection can strongly affect the structure and properties of the resultant welds. Variations in weld characteristics which are likely to occur from changes in weld pool convection are: weld penetration, macrosegregation, gas porosity, solidification structure, undercutting and surface smoothness. Apparently, the quantitative understanding of convection and heat flow in weld pools is of considerable practical interest. Mathematical models describing convection and heat flow in weld pools are essential, not only because of the quantitative understanding they provide, but also because of the difficulties associated with the experimental measurements of weld pool convection. These difficulties are mainly due to the fact that only surface flow, rather than the overall convection pattern in the weld pool, can be observed. In fact, due to arc glow even the observation of surface flow can be rather inconvenient."

Jan 1, 1986

By K. Morsi, S. K. Kassegne, A. El-Desouky, K. S. Moon

"Current Activated Tip-based Sintering (CATS) is a new process for the powder-based fabrication of macro, micro and possibly nano-scale features and shapes. This new and unique process enables selective sintering of powders by localizing electrically activated sintering conditions through a stationary or moving electrically conducting tip. We present preliminary experimental results on the effect of tip size in the CA TS process as well as the effect of initial powder particle size on the sintering behavior of nickel powder.IntroductionSpark Plasma Sintering (SPS) has been the center of attention of numerous researchers due its noticeable advantages over conventional sintering techniques such as rapid heating rates, lower sintering temperature and shorter holding times. Research on SPS has been applied on a wide variety of materials such as pure metals [ 1], ceramics [2], composites [3], nano-materials [ 4], biomaterials [ 5], shape memory alloys [ 6] and many other material systems. However, it has been mostly limited to bulk materials with simple shapes with a few exceptions ofresearch efforts where the effect of electric current was combined with metal forming processes such as spark plasma extrusion [7,8] and electric rolling of powders[9]. In this paper a novel process (Current-Activated Tip-Based Sintering (CATS)) is discussed where electric current and pressure are applied simultaneously through a small conducting tip (stationary or moving) over a conducting powder compact. This process has the potential advantages of sintering complex geometries with minimum energy requirements as unconventionally high current densities can be achieved due to the small contact area between the tip and the powder compact. Furthermore, by controlling the tip size, it can be possible to sinter features on the macro-, micro- and even nanoscales."

Jan 1, 2011

By Ying Li, Xuling Chen, Xiaohui Fan

"In the sintering process, the behavior and performance of iron ores is extremely complex. Different minerals have different sintering properties. In order to use iron ores rationally and effectively, multilevel fuzzy evaluation method is used to establish the comprehensive evaluation model of iron ores. Because of the relative independent characters of iron ores in sintering process, the characters can be divided into physical and chemical properties, granulation performance, and sintering properties, are divided, and together with iron ores prices as the first level index for judging, which are used as the second level index for judging. Using the analytic hierarchy process (AHP) to determine the weight of each index, which is used as the second level index. The relative membership matrix is determined by triangular membership function, the comprehensive evaluation model is established.IntroductionIn China, sintering is the main method for iron ores agglomeration. Sinter accounts for more than 80% of the blast furnace. Sinter production in the iron and steel enterprises in China plays an important role[l-2]. As the main raw material of iron ores sintering, the objectivity and integration of iron ores evaluation is essential. The iron ores evaluation methods include of metric ton price evaluation method, iron grade of a single iron ores sintering, acid-base balance method, composition assessment method and other methods which are based on the chemical composition and physical properties of iron ores to measure the quality of iron ores[3]. The high-temperature mineralization is an important process in sintering process, which affects the structure and mineral composition of the sinter, and has a close relationship with the quality of the sinter[ 4]. Therefore, in consideration of the physical and chemical properties, granulation properties, mineralization performance and sintering properties, the iron ores are evaluated by multi-level fuzzy comprehensive evaluation. The multi-level fuzzy comprehensive evaluation method makes a comprehensive evaluation, applying fuzzy transform principle and maximum membership degree principle, considering a number of factors related to the things which are evaluated. The method has lower requirements for the amount of data, and which integrates qualitative with quantitative judgment. It has a unique advantage to make up for the deficiencies of traditional evaluation methods. It also can comprehensively evaluate the iron ores in a relatively short period, reduce a lot of experiments, improve efficiency and guide the sinter production[5-6]."

Jan 1, 2013

By Paul Pajunen, Michael Sheedy

"Acid separation using short bed ion exchange is a now well established technology in copper refinery tankhouses. Refinery bleed streams from liberator cells are treated by short bed systems to produce an acid-free byproduct stream that contains the bleed metals and valuable nickel salts. Removing the acid eliminates the need for a black acid evaporator and reduces the amount of sodium carbonate required in nickel selective precipitation processes. The recovered sulfuric acid can be recycled to the tankhouse. This same technology is routinely used to treat other acids such as hydrochloric, nitric, and hydrofluoric. In the case of hydrochloric acid, the process can selectively separate chloro-anionic complexes such as Zn, Pb, and Cu, which are then eluted with water. The acid recovery technology can also be closely coupled with ion exchange processes in order to minimize regenerant acid consumption. In many hydrometallurgical applications resin regeneration often requires an acid dosage multiple times the stoichiometric minimum. Coupling an acid recovery bed with the IX column allows recovery and recycle of the free acid in the spent regenerant, thus reducing the overall acid consumption to just slightly more than stoichiometric.Short Bed Ion ExchangeThe short bed ion exchange process has been extensively used in the metal finishing industries since the early 1970s [1,2]. Short bed systems have also been sold to primary metals producers for the separation of sulfuric acid from copper refinery bleed streams [3] and for the recovery of nickel and cobalt from plant effluent streams. This unique technology optimizes the ion exchange process and offers a number of significant advantages over conventional ion exchange. The principal features and benefits of this technology are presented below."

Jan 1, 2012

By Frank Field, Randolph Kirchain, Elisa Alonso, Richard Roth, Nathan Fleming

"High material prices and price uncertainty can be harmful to manufacturing firms. Increased use of recycled materials, industry-wide, can lower both material prices and price variability; moreover, increased recycling decreases the use of primary material, which mitigates price increases due to scarcity effects. These stabilizing and price lowering effects are explored using an Aluminum industry model. We show that (a) increased recycling leads to smaller price fluctuations in the presence of a primary metal supply perturbation, and (b) that the more substitutable the secondary metal is for the primary metal, the lower the overall material price is.IntroductionThe price of an industrial metal is expected to be a function of both the marginal cost of extraction and its scarcity[l-2]: where scarcity can be defined as the degree to which anticipated demand exceeds the known supply. Recycling end-of-life metal increases the apparent supply of the metal, or-in a functionally equivalent, but alternative conception-lowers the demand for primary metal; this lowers primary metal scarcity and should, theoretically, reduce its price. To the extent that this theoretical prediction holds true, recycling can provide benefits to consumers of industrial metals in the form of lower prices.Using a platinum industry model, prior work by Alonso[3] has shown that increased industrywide recycling can reduce metal price volatility because the secondary metal production (a) offsets virgin metal depletion, and (b) responds to supply-demand balance fluctuations more rapidly than the primary market. However, Platinum is not a typical industrial metal in the sense that secondary metal is perfectly substitutable for primary metal: Both primary and secondary platinum metal are functionally equivalent and have a common price. Other metals, such as secondary aluminum which is used as an example case in this study, contain varying degrees of other elements that were either intentionally added, or were inadvertently mixed in with the metal during the scrap recovery process. Consequently, different grades of scrap exist that have different profiles of elements in their composition. Depending on their particular profile of elements, more or less of a given grade can be used as a mass fraction of the final alloy-the secondary metal is not perfectly substitutable for the primary metal. For the purposes of this paper, the aluminum mass fraction of the final alloy that can be made up of secondary aluminum is termed the secondary substitutability of that grade in that alloy."

Jan 1, 2011

By Ting Luo, Hongmin Zhu, Kai Huang, Shuanglong Du, Tao Gui, Yifan Xiu

"Poplar cotton, a cellulosic material, was found to adsorb metals ions effectively. In the present study, the biosorption characteristics of Pb(II) onto poplar cotton, were evaluated as a function of pH, contact time, biomass dosage, initial concentration and temperature. Within the pH range investigated (1.0-6.0), the optimal pH value suitable for the uptake of Pb(II) was determined. The maximum adsorption capacity obtained from the Langmuir model is around 0.52mol kg for the poplar cotton sorbent. Equilibration is achieved in 60min for the studied concentrations. Results suggest that the poplar cotton can be directly used as an effective and low-cost biosorbent for removal of Pb(II) from aqueous solution.IntroductionHigh value utilization of various biowastes produced in agricultural, forestry, fishing industries, etc. have attracted great interest from many researchers [1], Biomass, due to its easy availability, great abundance, low cost, easy processing, eco-friendliness and biodegradability, has exhibited exciting potential for being used as raw materials for the preparation of many new hi-tech functional products [2]. For example, using biowastes to synthesize sorbents for application in the removal of toxic substances such as dyes [3], heavy metals from the waste water [4] or in the recovery of valuable metals [5] from the ore tailings and secondary metals resources has made great progress in last decade. In present study, poplar cotton, a kind of white light fluff of poplar trees, like that of dandelion, usually flying in the air each spring was tested as a biosorbent for the remove lead ions from the water. It may also provide some good ideas for new sorbent design. Lead, as one of the typical poisonous heavy metals, for its typical toxicity and extensive pollution, was chosen to test the adsorption behavior of poplar cotton in aqueous solutions."

Jan 1, 2012

By Vahid Rastegar

"Characterization of the microstructure and revealing dendrites in the microstructure and also measuring the dendrites arm spacing and the distribution of silicon were studied in various pieces of compacted graphite cast irons with 0.17, 0.185, 0.2, 0.22 and 0.24 percent of mischmetal. Black-white and color metallography (quantitative and qualitative) were carried out on the various steps of the cast samples. Distribution of silicon was studied quantitatively using spot analysis with scanning electron microscopy. Furthermore, effects of two variables (cooling rate and mischmetal percentage) on dendrites arm spacing were investigated.In order to color metallography, the samples were plunged into a boiling solution of 18% KOH, 9% NaOH and 9% picric acid in distilled water. It was inferred that the microstructure coloration varies according to the sequence: green-->red-->yellow-->blue-->dark brown->light brown as the silicon content decreases. After observing dendrites, dendrites arm spacing was measured. In this method, it seems to be possible to predict the mechanical properties of compacted graphite cast irons by knowing dendrites arm spacing and without any destructive testing. After studying the two variables, it was concluded that dendrites arm spacing decreases as the amount of mischmetal increases and it increases as the cooling rate increases.IntroductionIn general, detecting of primary austenite dendrites is not possible in cast irons due to their solidification system. Observing the dendrites in the room temperature is possible only in those gray cast irons that contain type D graphite. With collecting data of dendrites arm spacing (DAS) measurements, it could be possible to achieve the mechanical properties of cast irons without any destructive testing. In this research by applying a particular method, primary austenite dendrites and also distribution of silicon in the microstructure has been observed."

Jan 1, 2012

By Alice Barreto Bevitori, Frederico Muylaert Margem, Noan Tonini SImonassi, Caroline Oliveyra, Sergio Neves Monteiro, Isabela Leão Amaral da Silva

"The mechanical behavior and the fracture characteristics of composites with DGEB/TETA epoxy matrix reinforced with up to 30% in volume of continuous and aligned ramie fibers were evaluated by tensile tests. Specimens with selected thin fibers aligned along the tensile axis were room temperature tested to rupture. The fracture surface was analyzed by scanning electron microscopy. The results showed significant increase in both the ultimate tensile strength and the elastic modulus. The fracture analysis indicated the possible mechanism for the fiber/matrix interaction, which could be responsible for the composite performance.IntroductionSince the middle of last century, polymer composites have substitute many conventional monolithic materials in applications ranging from aerospace to sport [l]. The main advantages of these composites are the low density and flexible properties specially using fiber as reinforcement to suit the mechanical performance requirements [2]. These are usually high strength and stiffuess requirements that could be reached with synthetic fibers such as gloss, carbon and aramid fibers. Its most commonly used example is ""fiberglass"", i.e., a thermoset polymer matrix composite reinforced with glass fiber. Indeed, ""fiberglass"" has a specific strength of the order of 500 MPa.cm3/g, which is the double of the strongest steels like the maraging. This motivated, at earlier times, ""fiberglass"" to replace many conventional materials including wood and natural fiber composites. Today, ""fiberglass"" has a wide range of uses from aerospace systems and appliances to sport and leisure components. However, its fabrication as well as those of any synthetic fiber such as carbon and aramid composites, requires a relatively large amount of energy. Presently, a growing concern exists regarding the consequences to the environmental by gases like C02 associated with both the energy consumption and the processing of synthetic fibers and their composites. These gases are well known responsible for global warming [3]."

Jan 1, 2013

By N. Moelans

A method using an ex-situ electrochemical measurement device was developed to determine the oxygen potential of non-ferrous metallurgical slags. The electrochemical cell consists of the molten slag sample, an inert Ir electrode, a stabilized Zr02 solid electrolyte and a NiINiO reference electrode. Different slags from non-ferrous pyrometallurgical processes were analysed at 1100 and 1200°C and pO2 values between 10-3 and 10.12 bar were obtained. The measurements were evaluated with? thermodynamic calculations and using processing considerations. It was found that the reproducibility and stability of the measurement was significantly improved by shielding the molten slag from the atmosphere by a thin layer of carbon, especially for slags with a low oxygen potential.

Jan 1, 2003