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By Katsukiyo Marukawa, Manabu Iguchi, Sigeta Hara, Shinichiro Yokoya, Sigeo Takagi

"A numerical analysis and water model study of the mold region of a continuous casting apparatus was performed with a novel injection concept using swirling flow in the pouring tube, to control the heat and mass transfer in the continuous casting mold.As a result, the following results were found:1) By changing swirl strength, it is easy to control the flow pattern as well as the direction of the flow.2) Uniform velocity distribution can be obtained within a very short distance from the outlet of the nozzle.3) Heat and mass transfer near the meniscus can be remarkably activated compared with a conventional straight type immersion nozzle without swirl.4) Swirl helps the superheat in the melt dissipate.S) Penetration depth of nozzle outlet flow is decreased remarkably by the application of swirling.6) For the case without swirl, the peak of the flow moves near the mold-wall with flowing down from the outlet of the nozzle due to the Coanda-effect. On the other hand, peak of the flow moves near the mold axis with flowing down from the nozzle-outlet within considerable short distance, namely axi-symmetric velocity distribution can be obtained within very short distance from the nozzle-outlet.Those findings mentioned above are very useful to control the flow pattern in the billet and bloom continuous casters."

Jan 1, 2001

By Tracy Morris, Weldon Read, Luis Navarro

"During the leaching of anodic slimes, tellurium dissolves into the leach liquor together with copper and must be removed before the solution is sent to liberator cells for copper recovery. Prior to the installation of autoclaves, tellurium was precipitated using raw slimes that caused a recirculation of tellurium in the leaching circuit. After autoclaves were installed the old leach tanks were converted into tellurium reactors utilizing copper chips, steam and agitation to form a copper telluride precipitate. Tellurium levels of less than 10 rng/L are achieved in a timely manner.IntroductionThe electrolytic refining of copper consists of an electrolytic cell provided with an anode of impure copper, a cathode of substantially pure copper (starter sheet) and an electrolyte made of copper sulfate and sulfuric acid [1]. When a direct electrical current is passed between the anode and cathode inside the cell, the impure copper anode dissolves in the electrolyte and pure copper is plated onto the cathode. During this operation, many of the impurities are deposited on the bottom of the cell as an anodic slime residue composed of insoluble chemical compounds. Slimes are a major source of rare and precious metals in the copper industry [2-5],In the Amarillo Copper Refinery (ACR), the anodic copper slimes are sent to the Precious Metals department in order to extract and then refine the gold, silver, platinum and palladium from them. The remaining impurities, in the form of a soda slag or copper slag are sent to the Hayden smelter for further processing. Copper telluride is sent to the Selenium/Tellurium department inside the plant for selenium and tellurium recovery. During the leaching process of the anodic slimes, copper, tellurium, and other metal species in the slimes are dissolved into leach liquor that cannot be returned to the tankhouse unless the tellurium concentration is below 10 mg/L."

Jan 1, 2012

By F. Kongoli

A computerized thermophysicochemical database is being developed for various processes involved in nickel smelting and converting. This database includes optimized models for slag, matte, liquid and solid alloys in the multicomponent system(s) as applied to batch and continuous nickel smelting and converting processes. This database can be used to quantify the multicomponent and multiphase slag/matte/alloy/gas equilibria, liquidus and solidus surface, tie-lines, solubility and/or losses of nickel and other components in the slag, distribution coefficients, components activities, heat and mass balance, etc. The database also includes optimized models for the viscosity of the slags associated with any of the above processes. Both databases are coupled and this constitutes a very effective method to quantify the effect of each component on several parameters of the smelting and converting processes and to diffuse the confusion that exists in the literature. Several application examples have been given to demonstrate the usefulness of this database for quantitative prediction of the thermophysicochemical properties of the phases involved in actual or developing processes, even in the areas where experiments are difficult or impossible. The considerable cost reduction that results ftom the use of this database as compared to other methods in the improvement of existing technologies or in the development of new ones is discussed along with continuing new developments of this database.

Jan 1, 2002

By Yoshiaki Suzuki

Since 1973, Saganoseki Smelter & Refinery had operated two flash smelting furnaces together to produce 330,000 mtpy of copper. However, in 1990's, economical situation required the smelter more increased productivity to remain competitive. The program, to integrate two flash furnaces into one was carried out maintaining the same production. Modifications were done on the pneumatic concentrate drying system, concentrate feeding system, concentrate burner and furnace cooling system, etc. to double the, furnace throughput. A new large cryogenic oxygen plant was constructed replacing two old plants. Single flash smelting furnace operation has started in March 1996. This paper describes about details of modifications and operational results.

Jan 1, 1998

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 C. Carreno, A. D. Gonzalez Escarcega, M. A. Neri, A. Martinez –Villafane, O. Cobarrubias-Alvarado

"Waspaloy is a superalloy used to manufacture some aeronautical parts subjected to high temperatures and stresses. During thermo-mechanical processing cracks are generated, causing some parts to be rejected. In order to determine the causes of these cracks, this alloy was characterized using techniques such as chemical analysis, optical microscopy, scanning electron microscopy, and EDX analysis. Heterogeneous grain sizes in the microstructure cause a non-uniform strain distribution in these parts, creating cracks in zones with different grain sizes.IntroductionNickel-base superalloys are important materials for high-temperature service applications. The manufacture of components from these materials is typically based on solidification or powder-metallurgy processes [1]. Solidification techniques comprise either the direct casting of parts or the casting of ingots which subsequently undergo a series of thermo-mechanical-processing steps to refine the microstructure. During solidification, microsegregation is usually unavoidable. The primary solidification product is a disordered nickel solid solution with an fee crystal structure (?). In many alloys, the material which solidifies last is a mixture of ã and an ordered fee phase (? '). In prototypical nickel-base superalloys, the ?'-phase is Ni3(Al,Ti) [2-3].Waspaloy is a superalloy that is used in demanding high-temperature environments in which good creep and fatigue resistance are required. One of the most common applications of Waspaloy is for turbine engine rings. To ensure the required mechanical properties, the rings are usually forged and heat treated (Figure 1). Two distinct types of microstructures are usually found to be attractive for such applications: a) A microstructure with a grain size of ASTM 10 to 14 for tensile strength, ductility, and resistance to crack nucleation in low-cycle fatigue; or b) A microstructure with a grain size of ASTM 4 to 8 required for creep strength and resistance to crack propagation [4]. Because it is impossible to refine the grain size through heat treatment, a skillfully designed forging process is crucial for the control of the grain size and, hence the properties of the forged ring [5-6]."

Jan 1, 2012

By Baicheng Liu, Houfa Shen, Wensheng Li

"In order to understand the formation of macrosegregation in steel ingots, a mixture model has been developed which accounts for coupled mass, momentum, species, and energy transport to describe the sedimentation of free equiaxed grains during solidification. In this model, the mushy zone is divided into the slurry and porous regimes according to a solid packing fraction. Settling velocity of equiaxed grains in the slurry regime is given by an explicit expression. The solidification of a binary steel ingot (Fe-0.36wt.%C) with a two-dimensional geometry is numerically simulated. It is demonstrated that the predicted macrosegregation patterns agree to some extent with classical experimental results. Further refinement of this model is still necessary for realistically simulating steel ingot solidification.IntroductionModeling macrosegregation in steel ingots is still a challenging study, mainly due to the length scale of the products and the complexity of global multiphase transport phenomena coupled with microscopic solidification kinetics [l]. The thermal-solutal convection and the motion of equiaxed grains are the two main mechanisms responsible for macrosegregation. But there are few models that deal with the motion of equiaxed grains, which is confirmed as the main phenomenon that explains the negative macrosegregation along the centerline of large steel ingots [2]. A model which takes into account melt convection and grain sedimentation was first proposed by Beckermann and co-workers ([3], and references therein). More recently, similar multiphase solidification models with advanced nature have been presented by Wu and Ludwig [1,4] and Combeau and co-workers [5,6]. It is known that the application of these sophisticated models to steel ingot casting is at its beginning.In this paper, a solidification model based on continuum mixture approach, using much less sophisticated relations to obtain the settling velocity of free equiaxed grains, has been proposed in order to predict the macrosegregation in steel ingots. The model is applied to simulate the solidification of a binary steel ingot with a two-dimensional geometry, and preliminary modeling results are presented."

Jan 1, 2011

By Ulrich E. Klotz, Gemot Pottlacher, Shahid Mehmood

"Platinum alloys are frequently used in technical applications and in jewellery. Their thermophysical properties such as density, heat capacity, thermal conductivity and surface tension play an important role in casting processes and are required as input data for casting simulation. Scope of this work was to investigate these properties by different methods. Platinum and four alloys namely, Pt96Cu4, Pt68Cu32, Pt50Cu50 and Pt25Cu75 were investigated. Melting range and thermal expansion was measured at fem by DSC and dilatometry, respectively.At TU Graz wire shaped samples were investigated by an ohmic pulse heating technique. This technique allows the calculation of specific heat capacity and the temperature dependencies of electrical resistivity, enthalpy, and density of these alloys in the solid and liquid phase. Experimental results were compared with available literature and data from thermodynamic calculation using the SNOBl database and ThermoCalc.IntroductionPlatinum is a precious element and its alloys are commonly used in jewellery. But Platinum is much more difficult to cast then other jewellery elements like silver or gold, because of its high melting temperature, large shrinkage during freezing, low thermal conductivity, high surface tension, and high viscosity. As a result there arise problems during casting. Hence to resolve these difficulties a detailed study of thermophysical properties of solid and liquid platinum and its alloys is necessary for simulation and casting. The Platinum alloy samples were prepared by vacuum induction melting and casting into copper molds. Rods of 3 mm in diameter and a length of 80 mm were prepared and drawn to wires of 0.5 mm in diameter."

Jan 1, 2011

By Yanxia Lu

Porous silicon carbide (SiC) has been the top selection for diesel particular filters (DPFs) since 2000 because of its high thermal diffusivity and strong body, which help it to survive in the harsh environment of a diesel exhaust system. However, the process to produce SiC DPFs is a costly one. The work presented herein describes more cost effective composite materials for this application, namely Si-SiC and Si₃N₄-SiC. Both composites have shown excellent filtration efficiency, low back pressure and outstanding survivability of regeneration at high soot loadings. Since the composites are batched from silicon metal, they can be prepared by a low temperature process that is impossible in the production of pure SiC PDFs. In fact, fabrication of SiC composites simply involves reactions between nitrogen gas and silicon metal, or silicon metal bonded with SiC, and as such uses a much less costly process when compared to the one employed to make SiC. In addition, the pore structure of the composites can easily be tuned by selecting raw materials and changing the ratio of two components. A typical pore structure consists of well connected pores with a median pore size of 5-20 µm and a porosity of 40-55%. This talk will describe the exothermic behavior as well as the mechanical and thermal properties of SiC composites in comparison to those of SiC filters. It will also show the superior thermal shock resistance of Si₃N₄ bonded SiC which is due to the unique combination of these phases that lowers the thermal expansion and elastic modulus relative to pure SiC.

Jan 1, 2006

By Ragnhild Aune

In fire refining of copper, the affinities of various impurity elements on dissolved oxygen is of great significance. Further, in the design of oxygen probes in liquid copper, the influence of solute interactions on the activity of oxygen need to be considered in order to evaluate the oxygen concentration in molten copper. The present paper presents a series of measurements of the activities of oxygen in liquid Cu-M-o alloys (where M stands for Mn, Zn, As, Se or Te) carried out by the present group employing the solid electrolyte galvanic cell technique. Extreme care was taken to control the oxygen potentials in the inert gas atmosphere, and to keep the oxygen levels very low in the molten metal. The oxygen content was determined by analysis of the samples taken out from the melt. The results obtained showed that Mn has a strong negative influence on the activity coefficient of oxygen in liquid copper. A similar, but less prominent effect was observed in the case of Zn. Arsenic had no influence on the activity of oxygen in Cu (liq.). Se and Te had slight negative effect on oxygen activities in copper at XO > 10-5, while at lower oxygen levels the interaction coefficients were found to be positive. The results obtained were compared with empirical models for the calculation of interaction coefficients available in literature.

Jan 1, 2003

By Ragnhild Aune

In fire refining of copper, the affinities of various impurity elements on dissolved oxygen is of great significance. Further, in the design of oxygen probes in liquid copper, the influence of solute interactions on the activity of oxygen need to be considered in order to evaluate the oxygen concentration in molten copper. The present paper presents a series of measurements of the activities of oxygen in liquid Cu-M-o alloys (where M stands for Mn, Zn, As, Se or Te) carned out by the present group employing the solid electrolyte galvanic cell technique. Extreme care was taken to control the oxygen potentials in the inert gas atmosphere, and to keep the oxygen levels very low in the molten metal. The oxygen content was determined by analysis of the samples taken out from the melt. The results obtained showed that Mn has a strong negative influence on the activity coefficient of oxygen in liquid copper. A similar, but less prominent effect was observed in the case of Zn. Arsenic had no influence on the activity of oxygen in Cu (liq.). Se and Te had slight negative effect on oxygen activities in copper at XQ >10-5, while at lower oxygen levels the interaction coefficients were found to be positive. The results obtained were compared with empirical models for the calculation of interaction coefficients available in literature.

Jan 1, 2003

By Ivanildo Hespanhol

"DALYs are a measure of the health of a population or burden of disease due to a specific disease or risk factor. It evaluates the time lost because of disability or death from diseases compared with a long life free of disability in the absence of disease. DALYs are calculated as the sum of years of life lost by premature mortality (YLL) and years of healthy life lost in states of less than fully health, i.e., years lived with a disability (YDL), which are standardized by means of severity weights, thus: DALY=YLL+YLD.WHO has established for wastewater use in irrigation (1) the same reference level of health protection as established for drinking water quality (2), i.e., the additional burden of disease from consuming water irrigated food should not exceed 10-6 DALY(Disability-Adjusted Life Years) loss per person per year (pppy). This level of risk means that a single additional case of disease may occur in a population of 1 million, during a life time (70 years). In a individual basis is equivalent to the occurrence of a mild disease during about 31,5 seconds.Such a restrictive risk is almost impossible to be attained in most developing countries which may not be able to afford the cost of wastewater treatment and of other protective measures, even for restrict irrigation.This paper presents proposals to adapt the reference level of risk to local technical, cultural, economical and social conditions of developing countries on the basis of a risk benefit approach."

Jan 1, 2008

By K. C. Mills, P. N. Quested, A. P. Day, R. F. Brooks

"Methods have been developed to measure the physical properties of molten materials relevant to the fluid flow in high temperature processes. Data for the densities, viscosities and surface tensions of Al-, Ni- and Fe-based alloys are compared with (i) values for the pure metals and (ii) estimated values obtained from models making use of chemical composition of the alloy. Experimental values for metallurgical slags are also given and compared with estimated values.1 IntroductionPhysical property data has proved very useful in improving process control and product quality. For instance, in the continuous casting of steel the viscosity (TJ) of the mould flux is important since it determines (i) the optimum casting conditions, nVc = 2.5±1 dPas (m min-1) where V c is the casting speed and (ii) the level of slag entrapment (which leads to inclusions) in the metal. Thus data for properties like viscosity are exceedingly useful in understanding the process and the problems encountered and the causes of defects and problems.Another interesting development which has helped to increase our knowledge of processes and improve process control and product quality is the development of mathematical models of the fluid and heat flow in the process. These models have been developed to the stage where one of the prime requirements is for good physical property data for the industrial materials involved. Recently, Oxley [1] has shown that the use of reliable, experimental, property values for the commercial alloy in a commercial software package produced a significant improvement in the prediction of casting defects. Thus reliable property data are required for liquid metals but also for (i) liquid slags since many processes involve the use of a slag to refine and protect the metal or to lubricate the mould and (ii) refractories, sand and investment moulds."

Jan 1, 1999

By Jian Pan, Zhen He, Deqing Zhu, Shouyan Yue

"The differences of raw material characteristic among six kind of iron concentrates and the influences on ballability were studied from the aspect of the size distribution, specific surface area and particles morphology. The results show that the specific surface area of iron concentrates has crucial influence on ballability, and the effective method of improving ballability for weak ballability iron concentrate has been found. It is of important guidance for Chinese steel mills to import and use iron concentrate from the whole world.IntroductionChina's steel industry has developed rapidly in recent years, crude steel production in 2011 is an unprecedented 683 million tons, which is almost half of the world crude steel production, and it is equivalent to the total sum production of the nations which rank at 2,3,4,5 and 6 in the world [1]. In order to match the development of steel industry, the blast furnaces are becoming larger and more modernization, therefore charging burden of higher quality is requested, and the reasonable blast furnace burden structure is more and more important, at the same time, for iron ore powder sintering process's continuous improvement and development, another method providing ""concentrate"" for blast fumace-pelletizing is also taken seriously. The grate-kiln method of pelletizing has achieved great development for its unique advantage, and in just a few years, there are over 60 rotary kiln production lines have built or being built in China, the sum of pellets has reached to more than 140 million [2, 3]. The rapidly growth of pelletizing yield demands diverse source of pellet, which include not only domestic magnetite concentrate, but also imported hematite which is high in iron and low in silicon. Usually the ratio of imported hematite concentrate increased gradually. The imported hematite concentrate has high grade and fine particle size (the content of -0.074 mm mostly higher than 90%), but the ballability of part of the concentrates is poor."

Jan 1, 2013

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 K. C. Liddell, B. Dou

"In producing multilayer films for magnetic data storage applications, the interfacial roughness must be controlled in order to obtain high quality materials with reproducible properties. The present understanding of the effect of roughness on multilayer properties such as magnetoresistance is sketchy, particularly for electrodeposited films. In this study, quantitative atomic force microscopy was used to characterize surface morphology before and after Ni films of varying thickness were deposited on Cu cathodes. A multinuclear multilayer growth mechanism is supported by both the deposition conditions and the AFM images, and a multinuclear multilayer model gave a satisfactory fit to measurements of the density of peaks on ultrathin Ni films between 0 and 8 nm thick.Alloys consisting of alternating ferro-and paramagnetic layers have begun to replace Permalloy in the sensing elements of magnetic hard drives. The operating principle of the new read heads is giant magnetoresistance (GMR), and they are smaller and more sensitive than previous inductive heads (1). Experimental studies on sputtered multilayers have emphasized the role of layer thickness and interlayer roughness in determining the presence and size of the GMR effect (e.g., 2,3,4,5,6). However, roughness in electrodeposited multilayers has rarely been measured, even though read heads are likely to continue to be made by this process for some time to come. Cu/Ni can be considered a model system for understanding processing-microstructure-property relationships in electrodeposited multilayers and is the most widely investigated of all such systems (e.g., 7,8,9,10,11,12). Nevertheless, the roughness of the interfaces in Cu/Ni electrodeposits has not been systematically characterized by quantitative techniques, and in all studies reported so far, the total deposit thicknesses were considerably greater than the 10 nm needed for most sensor applications (1). The thinnest such films were about 50 nm (7)."

Jan 1, 1998

By Dan Wang, Qian Li, Yong-bin Yang, Tao Jiang

"Thiosulfate is one of the most promising non-cyanide lixiviants for gold leaching. However, the undesirable reaction between thiosulfate and copper (II) gives rise to increased reagent consumption, which results in high cost and huge limit to its development. This paper presents study on the effect of ammonia, copper (II) and Cu(NH3)l+ ions on the oxidative decomposition of thioulfate. It shows that the presence of copper (II) and Cu(NH3)l+ can significantly increase the thiosulfate oxidation, while ammonia is relatively unaffected. The oxidation of thiosulfate by copper(II) in the absence of ammonia is fast at first and then decreases as time increased within a certain time, which can postulate that an intermediate product is responsible for the decreased consumption. The effect of ammonia is depended on the interaction with copper (II), which was found to significantly affect the consumption of thiosulfate.IntroductionFor over one century cyanidation is widely used in industrial production of gold, due to its simplity of process and low cost of production. However, cyanide is a highly toxic chemical reagent used dangerously and brings serious environmental pollution. What's more, cyanidation has slow speed of leaching gold and poorly leaching effective for refractory ores. With the exhausting of free-milling gold ores and promoted environmental protection requests, the disadvantage of cyanidation becomes a growing problem. In recent years, more and more research activities have been focused on alternative processes using non-cyanide lixiviants. Among the non-cyanide lixiviants, thiosulfate is considered as the most promising one[l-5].Compared to cyanide, thiosulfate is an inexpensive, nontoxic and less-pollution reagent, which can form complexes with many metal ions. Thiosulfate leaching of gold has an acceptable leaching rate and is insensitivity to impurities. Moreover it presents advantage on the treatment of refractory gold ores such as carbonaceous gold ores, copper gold ores, complex arsenic and sulfur gold ores, and so on[6]."

Jan 1, 2013

By Shenghui Guo, Dongbo Li, Lijun Liu, Chengdong He, Jinhui Peng, Libo Zhang

In present study, partially stabilized zirconia (PSZ) was prepared by CaO doped fused zirconia heated by microwave furnace at the temperature of 1450 oC and holding time of 120 min. The XRD results showed that untreated fused zirconia mainly consists of crystalline compounds of cubic ZrO2 phase; while the roasted one mainly is composed of crystalline compounds of cubic ZrO2 phase and monoclinic ZrO2 phase. It is shown through the optimization of structures of two phases that structure of cubic ZrO2 and monoclinic ZrO2 reject each other, revealing its difficulty in forming coinciding interface and linkage of two phases being of Ca atom. Introduction Due to advantages of zirconia, such as high melting point, chemistry inertia, low heat transmission and so on. Zirconia is always taken as megathermal refractory material[1]. However, in the heating and cooling processes of pure zirconium oxide, martensitic transformation will take place associated with greater shear force and volume change, which severely limits the industrial application of pure zirconia in some areas. Such as: Refractory materials, grinding materials and high temperature insulation materials[2]. Through adding a certain amount of MgO, CaO, or Y2O3 stabilizer, etc.[3,4], the zirconia can change into fully stabilized zirconia, which exists in cubic phase. But this high purity fully stabilized zirconia cracks easily because of thermal stress. Therefore, the thermal shock resistance variation is one of the most important quality indicators of zirconia-based materials. According to the heat treatment, the fully stabilized zirconia can be changed into the partially stabilized zirconia (PSZ)[5], which exists in cubic phase and monoclinic phase and has superior mechanical properties, such as anti-heat, low thermal conductivity, large coefficient of thermal expansion and stability, as well as good wear resistance[6].

Jan 1, 2011

By Esperidiana A. B. Moura, Michelle Gomes, Cordelia M. F. Escanhoela, Francisco R. V. Diaz, Angel Ortiz, Rene R. Oliveira

"This work evaluates changes in morphological, mechanical and thermo-mechanical properties of electron-beam irradiated HDPE/nanoclay and HDPE/Piassava fiber/nanoclay. Material samples irradiated with 100 and 200 kGy using a 1.5 Me V electron beam accelerator (room temperature, presence of air) were submitted to tensile, flexural, and HDT tests. MFI, SEM and XRD analyses were carried out. Correlation between properties was discussed. Results showed that incorporation of piassava (Attalea funifera Mart) fiber and nanoclay, followed by irradiation represented significant gain in thermo-mechanical properties. Changes in surface morphology and reduction in MFI were observed. In conclusion, it may be claimed that the incorporation of piassava fiber in small size particles and nanoclay in the HDPE followed by electron-beam irradiation effectively improved the polymer properties and led to materials with superior properties suitable for several industrial applications.1. IntroductionIn recent years, the preference for using natural fibers instead of synthetic ones in polymer composites has been growing significantly. In Brazil, due to the great diversity of woody and fibrous plants of our forests, a vast potential of natural fibers is found, presenting good mechanical strength properties, chemical and biological stability, fire resistance, abrasion resistance, shear strength and lightness, among other which may contribute to the development of new materials for different applications such as automotive, aerospace, construction, food segment, cosmetics and others [ 1]."

Jan 1, 2013

By Donghai Li, Cheng Pan, Xuyang Liu, Xuewei Lv, Chenguang Bai

"Fine chromite ore is the common raw material to produce ferrochrome alloy through the submerged electric furnace process. The electric resistivity of fine chromite ore plays an important role in the operation efficiency because it determines the current distribution. The effect of particle size and the contact area of the particles on electric resistivity for several of chromite were investigated at room temperature, and the relationship between the electric resistivity of mixed particles and the volume fraction of lump ore to fine ore was also studied. The results shown that the electric resistivity increases with the increase of particle size, and the electric resistivity of mixture decreases with the increase of volume ratio of fine ore.IntroductionChromium is one of the most important alloying elements in manufacturing of stainless steel that used at high temperature and corrosive environment applications [I, 2]. As the raw materials to be charged into the steel, ferrochromium alloys and charge chromium are produced directly by smelting of chromite ore with the reducing agent in submerged electric arc furnace (SAF). During the process, the oxides of chromium and iron were reduced by carbon and meanwhile the electrical energy were consumed [3,4]. The ideal industrial process is to achieve high recovery level of Cr and Fe with minimal power consumption. In SAF process, the electric resistivity of charge stock has significant effect on the current distribution, which determines the heat distribution, molten bath structure and chemical reactions in the furnace. High resistance of the charge is desired to reduce the current distribution through the charge stock, thus the electrodes may insert into the charge stock with proper depth to form a high temperature arc heat source, and proper smelting can be realized[5]."

Jan 1, 2012