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By Guangliang Wu, Dong-chang Huang, Xin-bin Liu

High temperature mechanical properties of 50Cr5MoV roll steel was investigated by Gleeble 1500 thermal simulator testing machine The morphology, composition and microstructure of fracture surface were observed and analyzed by OM, SEM and EDS The results are indicative of that, there are two brittle temperature zones of 50Cr5MoV roll steel at the temperature of 600°C~950°C and 1300°C~1450°C, respectively. The section shrinkage rate is less than 60% The fracture mode changes from mixed ones dominated by intergranular to toughness transgranular one with the increase of temperature at the range of 650°C~1300°C. The fracture is along the solid--liquid phase at the range of 1300°C~ melting point It is crucial to formulate the 50Cr5MoV casting technology, to prevent the cracks and improve the quality of 50Cr5MoV roll steel.

Jan 1, 2016

By Rajashekhar Marthi

Lithium is a key component for future electric vehicle batteries and energy storage. The future availability of lithium to meet the growing demands remains in question. Around 60% of lithium resources exist in the form of continental brines. Traditional methods to recover lithium from brines use solar concentration with precipitation and have found limitations in lithium extraction due to interference of Mg in high Mg/Li brines. Thus, there is a need for highly selective adsorbents. Recently, spinel structured delithiated lithium manganese oxides have demonstrated promising results. However, due to the small particle sizes, it is economically difficult to recover the adsorbents and thereby limits industrial applications. In our work, LiMn2O4 ion sieve was synthesized and immobilized on diatomaceous earth. Fundamental adsorption studies were carried out in lithium buffer solutions to understand the nature of adsorption and kinetics. The adsorbents were also tested for recycle stability, as well as recovery of lithium from Great Salt Lake water samples.

By Jing Lin, Yuan Xu, Qingcai Liu, Dengfu Cheng

"Smelting reduction technology has been developed greatly in recent years. But one of the key problems for this technology is about the refractory that used as lining material in the molten bath. Investigation and test shown that corrosion rate of refractory was much higher and the corrosion mechanism was much more complexity in the molten bath of smelting reduction with iron bath than that of the blast furnace and rotary furnace technology [l-5]. The corrosion behavior and corrosion rate of Al2OrC-ZrO2 series refractory in the melt of smelting reduction with iron bath have been studied by rotary immersion and quasi-static immersion test in this paper. The major factors that affect the interaction between the melt and refractory were investigated. The test results shown that the corrosion rate of AI2O 3-C-ZrO2 series refractory decreased with the ZrO2 increasing when ZrO2 content was from 3% to 10%. Ferrous oxides content, relative moving speed between the melt and refractory and temperature of the molten bath were the important factors that affect the corrosion rate. But the ferrous oxides concentration was the most important one. The corrosion rate was increased as a linear relation with the rising of ferrous oxides content of the melt. The corrosion rate in the quasi-static immersion was much less than that of the dynamic immersion (rotary immersion) for the Al2O 3-CZrO2 series refractory in the same testing condition. The corrosion mechanism of Al2OrC-ZrO2 series refractory is: graphite oxidized in advance, then interaction between the constituents of refractory and melt taken place and deteriorate layer of refractory and new compounds were formed, the properties of refractory was changed.IntroductionSmelting reduction with iron bath is a typical technology [3, 4, 6]. The obvious features of the melt for smelting reduction technology with iron bath are much higher ferrous oxides and much more complexity melt composition and structure than that of the blast furnace technology [2, 5-8]. The properties of the melt were changed dynamicilly and constantly in reduction process. On the other hand, the behavior of the melt depends on the activity and the reduction rate of ferrous oxides in the molten bath[9]. Because of the high concentration of ferrous oxides in slag and high reduction rate in the molten bath, the corrosion behavior and corrosion mechanism of the refractory lining by melt are an important factor in development of the technology of smelting reduction with iron bath. Up to now, improving refractory quality to anti-corrosion of melt and developing high quality and long term refractory used as the lining refractory materials in the molten bath of the final reduction furnace are also the most important questions for developing smelting reduction technology."

Jan 1, 2000

By Mohamed Y. Bakr, Aly M. Abdel-Rehim

The present work is related with mechanical activation of processing of Egyptian wolframite by simultaneous ball-milling and pressure alkaline leaching, to improve the recovery of tungsten from wolframite. The results show a total recovery of tungsten from wolframite (97.8- 98.7%) by simultaneous ball–milling and alkaline leaching at temperature 175-200oC. It is concluded that processing of wolframite by simultaneous ball- milling and leaching is mechanically activated and accelerated as a result of the grinding action of steel balls that caused the immediate rupture by continuous removing the product layer of the reaction ( sodium tungstate and iron and manganese hydroxides ) from reacting particle surfaces. This leads to the exposing of fresh and activated wolframite particle surfaces to alkaline leach solution and consequently the acceleration of the reaction of wolframite leaching .The results of the kinetic study 0f alkaline processing of wolframite and its mechanical activation show that the system is under kinetic control.

Jan 1, 2015

By N. Bazzanella

The hydrogen desorption kinetics of pure and Nb-doped magnesium hydride film samples was investigated by using a Sievert-type apparatus. The overall activation energy and the reaction order controlling desorption are (141±5) kJ mol-1H and n 4 for Mg hydride and (51±5) kJ mol-1H and n 1 for Nb-doped (5% at) Mg hydride indicating that, in the doped sample, hydrogen desorption is controlled by the H migration in transformed h-Mg layers. Structural analysis performed by X-Ray Diffraction (XRD) and Extended X-Ray Absorption Fine Structure spectroscopy (EXAFS) show that the catalytic effect of the Nb dopant is connected with the formation of NbH0.89 nanoclusters dispersed in the Mg hydride matrix. It is suggested that the catalysis process is also connected to the presence of Mg-Nb hydride interfaces where the transfer of H atoms preferentially occurs by connecting h-Mg grains and by the role of the MgH2-NbH0.89 interface as preferential site for the dissociation of the hydride phase.

Jan 1, 2006

By Reza Kamali, Mohsen Bashiri, Hadi Fanisalek

"Half of the input energy to aluminum reduction cell will be lost as waste heat which could be studied for possible recovery. Since price of energy is increasing and the main production cost in primary aluminum industry is energy, so waste heat recovery consideration will be interesting. One of the possible choices for recovering is from aluminum exhaust gases that needs minimum modifications for reduction cell and has no influence on cell heat balance which is vital for the operation. By using heat exchangers with in-line and staggered tube arrangements which placed before fume treatment plant (FTP) we will be able to recover enough amount of heat. The main challenging problem which is necessary to overcome will be the heat exchanger material and its design because of corrosive and dusty exhaust gases from potroom. In this paper, a desalination system with six effects of evaporator is proposed for producing distilled water by using recovered heat from hot exhaust gases. The calculated amount of produced distilled water is around 27,000 / in this specific suggested desalination plant. The suggested desalination plant is based on Hormozgan Aluminum Company data (Hormozal) in Bandar Abbas, Iran which is constructed by the Persian Gulf.IntroductionWaste heat losses arise both from equipment inefficiencies and from thermodynamic limitations on processes. The exact quantity of industrial waste heat is poorly quantified, but various studies have estimated that as much as 20 to 50% of industrial energy consumption is ultimately discharged as waste heat [1]. In order to achieve a final decision for establishing the waste heat recovery plant in any type of industry, a strong feasibility study is mandatory. Also, we need to remember that the possible amounts of energy and suggested process plant for recovery have to be investigated before starting any feasibility study. This kind of study which is important to be finished before moving to feasibility step is mainly a theoretical study, and was done for the Hormozgan Aluminum Company (Hormozal). In addition to the exhaust gases from the potroom, the exhaust gases from anode baking plant appear to have a better potential for waste heat recovery compared to potroom exhaust gases. The average temperature of exhaust gases from anode baking kiln is 120°C higher than the exhaust gases temperature in the potroom. This needs further investigation in a different study, because this study is just focusing on potroom exhaust gases."

Jan 1, 2011

By Mim Li, Huimin Lu, Lisha Yang

"CuInS2 thin films solar cells have drawn much attention for their low-cost, stability and high conversion efficiency. The electrodeposition of Cu-In precursor films, as the first step in making CuinS2 solar cells electrochemically in the air-and water-stable ionic liquid based on choline chloride/urea eutectic mixture has been investigated at constant potential. Compared with aqueous electrolytes, the large electrochemical window as well as the high thermal stability of this ionic liquid allow the direct electrodeposition of Cu-In precursor films. Then the precursor films were sulfuretted in a tube furnace at different sulfurization temperatures to optimize the films properties. The films obtained were characterized by X-ray diffraction (XRD), scanning electron microscope (SEM), energy dispersive spectroscopy (EDS).IntroductionCuInS2 is one of the most prospective absorber materials for low cost thin film solar cells, with a high conversion efficiency that exceeds 32% in terms of theory and nearly 13% in laboratory level [1-2]. In addition to its long-term stability, CuinS2 has a band gap energy Eg ranging from 1.3 to 1.55 eV and an optimal optical absorption coefficient reaching 105cm-1 [3-4]. CuinS2 thin films have been prepared by several methods such as spray pyrolysis [5-6], r.f.sputtering [7], vacuum evaporation [8-9] and electrodeposition. Comparing with vacuum methods, electrodeposition has lots of advantages such as less energy consumption, preparation big area thin film, stable system and enabling cheaper films.The electrodeposition of most technologically important metals has been shown to be possible from a wide range of ionic liquids. These ionic liquids are currently applied in a wide variety area. It is reported that the cell efficiency of chalcopyrite absorber layer (CIS, CISeS, and CIGS) via an electrodeposition route in laboratory condition has reached 11.3% [10]. Copper and indium alloy film is regarded as important precursor for the production of compound semiconductors with sulfur. The electrodeposition of the alloy film from room temperature ionic liquid (RTIL) has not been widely investigated. Only few alloy films, such as ZnTe, CdTe, GaAs and AlSb have been electrodeposited."

Jan 1, 2011

By A. A. el-Geassy

High-grade iron ore fines rejected from the DRl plants (>96%Fe20) were isothermally reduced in 30-60%COIH2 gas mixtures at 973-1273K. The freshly reduced reaction products were then subsequently carburised in either H2/CO or H2/CO/S mixtures at 823-1073K for 30-120 min. The thermogarvimetric technique was used to follow up both of reduction and carburisation reactions as a function of time. The carburised samples were characterized by X-ray and Mossbauer techniques. Chemical and carbon analyses were also applied. The influence of temperature and gas composition on the reduction behavior was investigated. The calculated values of apparent activation energy, application of gas-solid mathematical formulations were correlated with the microstructures to predict the reduction mechanism, The influence of carburization time, temperature, CO contents in H2/CO or H2/CO/S were investigated. A conversion extent of Fe to Fe3C was taken as a measurable index for the efficiency of carburization reaction under the different experimental conditions.

Jan 1, 2003

By Lloyd R. Nelson

Experimental results of three-phase mixing in a physical model of a CCRL for metals refining are presented. The system was operated above a critical lower liquid height-to- width ratio (H,/W) of unity, with adequate bottom gas injection through a line of central, single tuyeres (Q,/A = 7.5 cm/min, or c = 17 W/m3) to sustain levels of interphase transport considered appropriate to an industrial pyrometallurgical refining operation. The application of a thermal tracer technique to elucidate both longitudinal mixing and interphase heat transfer is discussed. The results indicate that even under conditions of significant bottom gas injection, it should be possible to maintain acceptably low longitudinal mixing 1 (D, < 20 cm /s and D,/uL < 0.1) in the CCRL. Interphase mass transfer coefficients of the order of 0.004 cm/s are predicted from the measured interphase heat transfer coefficients (h = 1.3 to 2.0 kW/m2K), using the heat and mass transfer analogy. Adequate rates of rehning are predicted for an industrial CCRL operated under such conditions.

Jan 1, 1995

By Denise Cristina de O. Nascimento

Natural lignocellulosic fibers are increasingly being used as polymeric matrix composite reinforcement owing to economical and environmental advantages as renewable and biodegradable materials. Among these, the piassava fiber extracted from a palm tree native of South America stands as one of the most rigid with a potential to be used as composite reinforcement. Therefore, the present work investigates the notch toughness behavior, by Izod impact tests, of epoxy composites reinforced with up to 40 % in volume of continuous and aligned piassava fibers. It was found that the incorporation of piassava fibers results in significant increase in the impact energy of the composite. Scanning electron microscopy analysis showed that the nature of the piassava fiber interface with the epoxy matrix is the major responsible for the superior toughness of the composite.

Jan 1, 2009

By Dimitrios Fillippou

Magnesium hydroxide is used in a number of industrial applications, from the neutralisation of acid effluents to the production of pharmaceuticals. High-quality magnesium hydroxide powders can be produced by hydrating slow-reacting magnesia in dilute magnesium acetate solutions. The process of magnesia hydration shows many similarities with a typical hydrometallurgical leaching operation; however, its kinetics are crucial not only for process design and control, but also for the production of powders with a desirable particle morphology. This article shows the results of an experimental work whereby industrial heavily-burned magnesia powders were hydrated in 0.01 to 0.1 mol/L magnesium acetate solutions at temperatures ranging between 333 and 363 K. Examination of the magnesium hydroxide produced and the analysis of the kinetic data suggest that the hydration of heavily-burned magnesia in magnesium acetate solutions is a dissolution-precipitation process controlled by the dissolution of magnesia particles. The activation energy was estimated to be 60 kJ/mol, while the reaction order with respect to magnesium acetate concentration was found to be about one.

Jan 1, 1999

By Guo Chen, Jin Chen, Jinhui Peng

"In this paper, the methods of life cycle assessment for microwave hot air systems, and the concept of green degree were proposed. Greenness evaluation index, evaluation system and evaluation model of microwave hot air systems were established. Also, life cycle assessment processing based on these ideas was introduced. Analytic hierarchy process and fuzzy decision- making method were utilized to establish and solve the greenness evaluation of assessment model, while the scores of green degree in microwave hot air systems were obtained. The results show that Life cycle assessment can be applied effectively and efficiently to the microwave hot air systems.IntroductionHot air systems are an important industrial operation condition, which is used to provide high temperature air for materials processing. Nowadays, high temperature airs are manufactured by the conventional heating processes, in which some ceramic materials are used as heating materials. However, these processes pollute the environment. Therefore, to explore new method to produce high temperature air with low energy consumption and less environment pollution are necessary.Microwaves are now being used in various technological and scientific fields in order to heat dielectric materials [1]. Microwaves irradiation has been explored in materials processing in recent years [2-3]. The main advantage of using microwave heating is that the treatment time can be considerably reduced, which in many cases represents a reduction in the energy consumption as well. Since there is energy absorption but no heat conduction, the heating is very rapid and highly efficient, resulting in energy savings and the shortened processing time [2, 4]. Compared with conventional heating techniques, the additional advantage of using microwave irradiation is that microwave irradiation achieves both internal and uniform heating [5-7]. In addition, it is more convenient to control the microwave irradiation processing, because of no direct contact between the heating source and heated materials with less equipment size and waste [2, 8-9]. Life cycle assessment is used and accepted methods for the evaluation of the environmental impacts of products or systems [10]. Recently, many appropriate evaluation methods have been developed for life cycle assessment [11-12]. These proposed methods usually are employed for the evaluating product and analyzing results [13]. Among them, the analytic hierarchy process and the fuzzy comprehensive evaluation stand out as a popular method utilized in many fields [14-16]. Analytic hierarchy process and fuzzy comprehensive evaluation are a combination of mathematical and statistical technique that is useful for analyzing the effects of several independent assessment aspects on the system goal without the need of the predetermined relationship between the objective function and the assessment aspects [17-19]."

Jan 1, 2013

By Ryokichi Shimpo

Much amount of sludge is produced from the wastewater treatments in surface finishing industry. There are many problems for the abandonment of the sludge because of the high water content and heavy metals included. It is often observed that hexavalent chromium, which is toxic, is generated in the course of heat treatments of the sludge for reducing its amount by dispersing water. In this study, conditions of the sludge calcinations for reducing water contents have been examined. Maximum hexavalent chromium generation was observed in the temperature range around 773 K, at which most of the crystallization water decomposed from the sludge. When the heating temperature became higher than 1173 K, the amount of the hexavalent chromium extracted from the calcined sludge became as low as 10 mg/kg sludge. When the sludge was heated with iron oxides, FeO or Fe203, iron ferrite has been synthesized which may be used as a magnetic material. The amounts of hexavalent chromium generated in the heat treatment with iron oxides were not much different from those without iron oxides.

Jan 1, 2003

By Tianzu Yang, Weifeng Liu, Lin Chen, Wei Chen, DUCHAO ZHANG

Ni-M (Metal=Cu, Fe, Co, Mn, Zn, Cr) aerogel catalysts were tested for CH4 oxy-CO2 reforming. It was found that the Ni-Co bimetallic aerogel catalyst had the highest activity and stability in methane oxy-CO2 reforming among all the Ni-M aerogel catalysts. It exhibited a steady activity of 79 % (in terms of CH4 conversion) at 750 oC, which is the highest activity under a similar reaction condition as compared with those published in literature. Characterizations for the reduced catalysts indicated the formation of Ni-Co alloy, while other transition metals separated from Ni during the reduction process. Therefore, the active species in the Ni-Co bimetallic catalyst showed a stronger interaction than those in other Ni-M catalysts, which might be one of the main reasons for the better catalytic performance of the catalyst.

Jan 1, 2016

By Michael S. Moats, Scott C. Campin, J. Brent Hiskey

"Electrochemical techniques are a valuable means of analyzing the passivation of commercial copper anodes. Electrochemical impedance spectroscopy (EIS) provides information concerning transport and reaction phenomena occurring at an electrode surface. Commercial. copper anodes of varying compositions have been examined using EIS. Experiments were conducted in a flat cell with an electrolyte of 40 gil Cu2 + and 160 gil H2S04 maintained at 65 DC. Impedance spectra were obtained at the potentials characteristic of the open circuit voltage and passive region for each anode. The spectra of the passivating films exhibited a flattened resistive/capacitive loop at middle to high frequencies and an inductive loop at low frequencies. An equivalent· circuit utilizing an inductor-resistor series in parallel with the double layer capacitance and charge transfer resistance was adequate in modeling the impedance data. The influence of anodes impurities on the components of the equivalent circuit is discussed and correlated with a hi-layer passivation model.IntroductionPassivation of copper anodes during industrial electrorefining has received considerable attention in the past few decades. Great strides have been made in understanding the roles of anode impurities [1-25], electrolysis parameters [20,26], and electrolyte chemistries [20,26]. Even so, passivation still occurs even in the most modem of refineries. The exact cause of passivation is not fully understood. It is known that the anode surface becomes covered by a passivating film. This film has been proposed to be CuS04'&5H20, Cu20, or mixed oxides. The localized concentrations of Ft, Cu+, and Cu2+ ions determines which phase is more favorable. The presence of these ions is controlled by the reaction kinetics and diffusion of species through the slimes layer.Reaction kinetics between Cu, Cu +, and Cu2+ are based on the dissolution mechanism of copper. There exists four different models to describe the dissolution of pure copper. The classical model of Mattsson and Bockris [27] involves two single electron transfers with the cuprous-cupric reaction being the rate detennining step. More recently, Wong, Collier, and MacFarlane [28] used ac impedance to elucidate a more complex mechanism involving the affect of pH and anions. Their findings indicate that the formation of cuprous ions in solution, Cu(I)so~ is favored over Cu(1I) ions adsorbed to the electrode surface in the presence of sulfate and as pH increases from pH 1 to pH 5."

Jan 1, 1997

By Pan Gu, Zhen Zhang, Jiang Diao, Bing Xie, Hongyi Li

Furnace refractories are in most cases chemically incompatible with smelter slag, which leads to a steady erosion in their thickness over time. Once too thin, refractory walls become mechanically unstable and catastrophic failure can result. Historically, external shell cooling was applied to generate a freeze lining of slag and thus prevent refractory erosion. Many modern high intensity smelting furnaces instead maintain their physical integrity by the use of internally cooled wall panels, plates or finger coolers. An initial refractory lining is often installed inside of the coolers, such that the furnace originally operates with a temperature (insulated) rather than a heat flux (freeze lined) boundary condition. This paper examines the change in slag-wall heat transfer coefficient and slag superheat as a function of process intensity. The implications of the changes in heat transfer on residual brick thickness are explored using analytical modelling.

Jan 1, 2016

By Sergio N. Monteiro

Polymer matrix composites have been applied in components such as helmets and shielding for which toughness is a major requirement. Natural fiber presents interfacial characteristics with polymeric matrices that favor a high impact energy absorption by the composite structure. The objective of this work was then to assess the Izod impact resistance of polymeric composites reinforced with different amounts, up to 30% in volume, of a promising high strength natural fiber from the Amazon region known as curaua. The results showed a remarkable increase in the notch toughness with the amount of incorporated curaua fibers. This can be attributed to a preferential debonding of the fiber/matrix interface, which contributes to an elevated absorbed energy.

Jan 1, 2009

By R. Hamar, G. Lamanthe

"To realize complex shaped pieces, like turbine blades, superalloys are cast with the lost-wax process. The end properties of these parts depend upon their microstructure as well as upon the occurence of casting defects such as micropores and hot tears. Such features are governed by the local solidification conditions which may be describe by the calculation of thermal transfers between alloy and mould. It needs the evaluation of numerous parameters which are fitted from experimental measurements in real castings. In further simulations, any parameter may be changed, in order to determine its influence. Such a single modification is quite impossible to realize in real castings, which shows that numerical modeling is a very good way to study casting processes.This modeling technique of casting is applied here to the real study of a typical low pressure turbine blade of a civil engine.IntroductionAircraft engine manufacturers use superalloys to produce turbine blades. They have to obtain a given microstructure and to avoid solidification defects to give good mechanical properties to theirs castings. For example, microporosity is induced by a large shrinkage that cannot be completely fed with the remaining liquid alloy .The optimization of casting processes needs a good Knowledge of the solidification process, that must be controlled at every place in the casting, and at every time of its freezing. Material and heat transfers that occur during the solidification, can be estimated from rather complex calculations. To model these physical phenomena, the evaluation of many parameters must be made. In this aim, some casting experiments are fitted with numerous thermal captors. The identification of experimental and computed thermograms let us estimate these parameters.A long-range scientific cooperation between SNECMA and INPG has enabled the realization of such studies on this topic. From all of them, this paper describes an experimental and computed investigation which has been led on a typical low pressure turbine blade of a civil engine."

Jan 1, 1986

By Z. W. Zhang, Songsong Xu, Jinhui Li, Yun Zou, Yu Zhao

High strength low alloy (HSLA) steels with high strength, high toughness, good corrosion resistance and weldability, can be widely used in shipbuilding, automobile, construction, bridging industry, etc. The microstructure evolution and mechanical properties can be influenced by thermomechanical processing. In this study, themomechanical processing is optimized to control the matrix microstructure and nano-scale precipitates in the matrix simultaneously. It is found that the low-temperature toughness and ductility of the steels are significantly the matrix microstructure during enhancing the strength by introducing the nano-scale precipitates. The effects of alloying elements on the microstructure evolution and nano-scale precipitation are also discussed.

Jan 1, 2016

By Saskia Duyvesteyn

For many applications in hydrometallurgy and water treatment it would be advantageous to use ion-exchange resins in stirred reactors. However, attrition of the resin may lead to significant losses of both resin and metal values and prevent water quality goals from being reached. We have studied the recovery of fine resin particles by froth flotation, using the model copper - Dow XFS4195 chelating resin system. As the functional group on the resin is a bis-picolylamine, the resin should be amenable to flotation by anionic collectors, such as sodium dodecylsulfate and sodium dodecylsulfonate. The kinetics of copper loading from dilute aqueous solutions in an agitated vessel were studied as a function of copper concentration, pH and resin bead size. The flotation of unloaded resin was investigated for different types of collector, collector concentration, conditioning time, and resin bead size. Potential applications are discussed.

Jan 1, 1995