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Due to problems with old technologies more and more product designers have turned to liquid crystal (LC) displays, which have consequently experienced phenomenal growth. The success of liquid crystal displays has fostered continued development, to the point where full-color video displays have been realized which can rival. The details of the lens structure and of the devices fabrication and performance are described using the Jones matrix method. Director n can change from point to point and is, in general, a function of space.. The transition can be approached by changing the impurity concentration or, indirectly, by tuning the temperature since the pinning strengths of the random and crystal potential have in general a different temperature dependence. Light from the conventional light source or laser is passed through a polarizer and then incident on the specimen. The resist profile simulation is carried out using the combined data thus obtained. The nematic liquid crystal is clear only when a long range order exists, in the whole medium. At the nematic-isotropic, transition temperature, the medium becomes isotropic and looks clear and transparent.

Jan 1, 2006

By V. A. Bryukvin

It has been found that by superimposing symmetric alternating current over the process, the rate of nickel and cobalt leaching from metallized products with copper sulfate solutions increases by a factor of 1.5 to 2.0 and the apparent activation energy of the process investigated is reduced from 12 down to 6.6 kcal/mole. It appears especially attractive to use alternating current for anodic dissolution (oxidation) of metallic scrap of refractory metals and their alloys in ammonia electrolytes permits production of high-grade commercial products in the form of respective ammonium salts using a short and virtually reagent-free process flowsheet. Similar approaches can be applied also for electrochemical processing of nickel and copper scrap in sulfuric acid media with subsequent recovery of pure sulfate salts or electrolytic processing. Electrochemical technology for recycling of tungsten-cobalt (WC 15) and tungsten-rhenium (WR 20) alloys has been also investigated. In the former case, anodic oxidation of carbide alloy was carried out in nitric acid electrolyte with production of pure tungstic acid. The research conducted has indicated that the physicochemical effect of alternating current results in a lower activation energy of electrode reactions due to changes in the mechanisms of the electrode reactions themselves.

Jan 1, 2006

By Xiaorong Liu

Interfacial emulsion generated in copper solvent extraction is an inhomogeneous O/W emulsion that consists of organic phase, aqueous phase and solid particles. In order to determine what kind of components in organic phase promotes the emulsion, the organic phase separated from the interfacial crud provided by Dexing Copper Mine in Jiangxi, China was analyzed for its components by combined gas chromatography-mass spectroscopy. It was found that many kinds of emphiphiles containing such hydrophilic groups as carbonyl, carboxyl, or acylamine existed in organic phase, most of which were originated from the reagent degradation. Conclusively, Lix984N would degrade gradually during a long-term contact with the acidic aqueous feed and strip reagents. Lix84 and nonylphenol, as effective components of Lix984N, degraded almost completely after long-term recycling. As a result, the effective components of Lix984N were far lower in concentration than the dense-aromatic impurities derived from the diluent and the degradation products in total. The degradation of Lix984N would deteriorate solvent extraction, disengagement performance and result in more serious interfacial emulsion.

Jan 1, 2006

By Xueming Lv

The rotary kiln-electric furnace (RKEF) process is the main method for producing ferronickel from nickel laterite ore. However, this process is energy intensive as it involves several high temperature steps. Therefore, a novel process is proposed to directly produce ferronickel from nickel laterite ore by semi-molten reduction, which is expected to be realized in a rotary hearth furnace (RHF). The RHF process is able to shorten the flow sheet, decrease the reaction temperature as well as reduce energy consumption. In this study, the influence of basicity on reduction of nickel laterite ore was investigated. The results showed that it is possible to produce the ferronickel nugget directly at 1400 °C when the quaternary basicity [(mCaO + mMgO)/(mSiO2 + mAl2O3)] was fixed at 0.60. Under this experimental condition, the grade and the recovery ratio of nickel reached 11.53% and 98.59%, and the grade and recovery ratio of Fe were 84.16% and 68.72%, respectively.

By John R. Howell

"SUMMARYThe process of producing a new cast component requires significant design and development by both the design engineer and the foundry engineer. This effort strives to produce a high quality component at minimum cost. To assist in this development, an analysis system, consisting of several computer programs, has been developed to simulate the metal casting process. This system incorporates analytical geometric solid modeling, finite element analysis, results display, and an innovative technique to model the casting mold with surface boundary conditions.The simulation has produced excellent thermal results and work is in progress to develop techniques to enable use of this data in additional analyses to predict porosity and residual stress. Research is required to produce working parametric formulations of material properties. Software development is required to develop good fluid flow analyses for large. 3D models to simulate filling of and convection in molds.Integrating this system of programs is difficult due to proprietary database structures used by software developers. However, an acceptable means has been accomplished' to move data from one program to another. Further software development is required to facilitate this task. INTRODUCTIONThe process of producing a new cast component requires significant design and development by both the design and foundry engineer. This effort strives to produce a high quality, reliable component at minimum cost in a timely manner. The design engineer needs to know the physical and mechanical properites which can be expected in the actual part at critical areas. This will enable him to design a part with minimum material while fulfilling the performance required. The foundry engineer needs to produce a sound, quality casting with a minimal amount of material In risers, the feeding system and machining stock. This must be done with a minimum· investment in tooling and development time and maximum productivity of labor and capital employed. This task Is continually being made more difficult because of increased competition in the marketplace and the use of castings in more severe service. This has strongly influenced the need for high quality castings.The task of developing a new casting is difficult for both the design and foundry engineer. To assist in this development, Deere & Company has been engaged in the development of an analysis system to simulate material processes. A major portion of this program involves simulation of the metal casting process. This analysis system has evolved into a package of computer programs which simulates casting solidification and subsequent cooling through the finite element method"

Jan 1, 1986

By Jürgen Antrekowitsch

Typical zinc oxides recovered from wastes like steel mill dusts and neutral leaching residues are of a low quality because of impurities like fluorine, chlorine, lead and others. Therefore, they are not comparable to technical grade zinc oxides produced in “French” or “American Process”. Some new developments, most of them still in pilot scale, try to establish processes where higher qualities of the product should be achieved. Zinc oxides are not only supposed to be an input material for electrolytic zinc production. Far more, they should find their way into the zinc oxide market as a substitute for technical grade zinc oxides. Furthermore, a new field of application for these oxides has been investigated at the department of Nonferrous Metallurgy, University of Leoben. Because of a higher acceptance concerning different impurities in relation to zinc winning electrolyses, a use in electrolytic galvanizing shows an interesting option. Therefore, synthetic zinc oxides with different impurities were generated to study the effect of these impurities especially on the quality of the zinc layer. Typical steel sheets, as used for car bodies, were electrolytically galvanized and the resulting layer was analysed, as main impurities compounds of fluorine, chlorine, iron, lead and calcium were used for the investigations. Beside the layer quality, the current efficiency and the possible galvanizing speed were examined. The results give an indication, weather such an alternative application can be feasible from a technical and economical point of view or not. 597

Jan 1, 2008

By C. M. Iheagwara

This paper has addressed the issues that constitute major obstacles to the cost- effective and efficient operation of metallurgical vessels from the refractory standpoint. Refractories generally withstand severe conditions of high temperature reactions as well as physical loading/impingement and hence degenerate and need replacement. Scarcity of some refractory materials especially high alumina and magnesite ores in some places, the prohibitive cost and the frequency of replacement of damaged refractories threaten the continued support for metallurgical operations. Some of the causes, prevention and cure for refractory wear have been discussed and rational strategies (short and long term) have been recommended which if implemented should go a long way towards arresting the perennial problems they portend.

Jan 1, 1991

By O. G. Yeremin

The Joint Venture "Inter-S" jointly with the Gintsvetmet Institute have developed a technology for manufacturing of sulphoconcrete and sulphoasphalt. The sulphoconcrete manufacturing technology comprises preliminary production of modified sulphur, which is blended in liquid form at a temperature of 120°C with an inert material preheated to the same temperature. The second promising area for the use of sulphur is partial substitution of modified sulphur for more expensive bitumen. The sulphoasphalt manufacturing process comprises preliminary production of a sulphur and bitumen mixture with a sulphur content of 30% to 40%, which is then blended with inert materials using conventional techniques. Sulphoasphalt manufactured at a full-scale plant meets all requirements set to its strength properties for road paving. Technology has been developed for production of high-purity sulphur based on rectification of liquid sulphur in a packed column. A commercial-scale plant with a capacity of up to 15 tonnes per year for production of sulphur with an impurities level of about 110-6 % by mass has been put into operation.

Jan 1, 2006

By Marcela C. Santini, Luiz A. Teixeira

"Surface conditioning (also referred as etching) of plastics prior to metallization is generally conducted with sulfuric I chromic acid solutions. Although these baths perform well technically, the presence of Cr (VI) imposes serious operating problems of an environmental nature. The present work reports ·the results of a study of surface conditioning o(ABS using solutions based. on sulfuric acid, with hydrogen peroxide and/or nitric acid, replacing chromic acid, as oxidants. Process performance was evaluated by SEM and by the uniformity and adherence of electroless nickel coatings applied on selected conditioned samples. The results showed that the evaluated types of solutions could be optimized to perform as well as the chromic-based baths, with a much superior environmental quality.IntroductionMetallization of plastics is normally undertaken for either decorative or functional purposes. Through metallization, the specific properties of plastics such as light weight, design flexibility, and low-cost of manufacturing are enhanced by the addition of properties usually associated with metals. These include reflectiveness, abrasion resistance, electrical conductivity, and a variety of decorative effects (1).The available processes that can be used for metallization of plastics are vacuum metallization or vapoµr deposition; indirect metallization and plating (1). Plating can be sub-divided into electroless plating and electroplating. In electroless plating, metal ions in aqueous solution are deposited on the .activated plastic surface by oxi-reduction reactions without the aid of an external electric potential, forming a thin metallic layer. This electroless deposited film has two functions: (a) it provides an electrically conductive substrate that allows further coating by electroplating; and (b) provides a secure bond between the plastic substrate and the electroplated layer (1,2). In case the electroless metallic part requires an additional layer for finishing purposes, or just an increase in thickness, the part can be additionally electroplated with a· variety of metals - in most cases those are copper, nickel or chromium (3)."

Jan 1, 2000

By He De-wen

The increasing population and living standard in urban areas, have been accompanied with the growing quantity and composition complexity of rubbish, which are causing well-known social effects of pollution, while rubbish (solid waste) is a recyclable resource. To convert rubbish into useful materials, the essential measure is to carry out sorted collection of rubbish. The preconditions of implementing sorted collection are presented in the paper. 1 Characteristics of rubbish composition and amounts of recyclable contents are basic condition to implement sorted collection. 2 The existing available technologies of recycling, economic benefit from recycling, and disposal scheme of residual rubbish are restrained condition for sorted collection. 3 Public understanding and support to sorted collection are the key to success. 4 The government policies to be favorable for sorted collection is the pledge of success. 5 The establishment of a steady solid waste recycling market is also a guarantee to implement sorted collection continuously. 6 To establish management system of rubbish recycling as soon as possible. Further, the methods and procedure of sorted collection are discussed in detail and beneficial comments and theoretical basis to promote sorted collection of rubbish in urban area are presented; it will contribute reference value to municipal solid waste management.

Jan 1, 2006

By Nagy El-Kaddah, Thinium T. Natarajan

A modeling strategy is presented for computing the electromagnetic field and the shape of the molten metal in electromagnetic confinement systems. This strategy involves the use of a hybrid finite element/integral technique to calculate the electromagnetic field and force distribution in the melt. The free surface shape is determined from minimization of electromagnetic, gravitational and surface tension energies using the Lagrange method of multipliers. This approach was applied to model the electromagnetic levitation melting process. The model was found to accurately predict the measured shape of levitated droplets.

Jan 1, 2014

By G. K. Ruhlandt, C. W. Kim

"A 3-D Finite Element Method program called ""SOLCAST"" has been developed to simulate the casting solidification process. Using the temperature recovery method to evaluate the latent heat of fusion and applying a new combination of the time integration scheme, SOLCAST reduces the computational time significantly compared to an existing commercial FEM program, and produces accurate results comparable to experimental casting results. Prediction of casting shrinkage porosity for A390 aluminum alloy will also be discussed. To make this FEM program useful for foundry engineers, this program was connected to a commercial pre- and post-processor.IntroductionBecause of recently increased competition, foundrymen must produce high quality castings more economically. Therefore, casting solidification analysis prior to casting production is an attractive way to reduce costs and development time.Although the actual casting solidification process is a very complicated phenomena, foundrymen could predict where shrinkage defects would occur based on a transient conduction heat transfer analysis that includes the liberation of latent heat. A numerical analysis is generally required to solve the heat diffusion equation with the latent heat diffusion term, because casting shapes are very complicated and pure materials are rarely used.Different numerical methods have been applied to the casting solidification analysis 1. Among them, a finite difference method 2 and a finite element method (FEM)3 are most commonly used.Each simulation method has one or more basic difficulties which are different for each method. These difficulties are:(1) Modeling casting shapes on a computer.(2) Time consuming computation.(3) Uncertain material properties."

Jan 1, 1986

By Noriaki Kurita, Norihiko Fulcatsu, Teruo Ohashi

"An electrochemical sensing device for hydrogen in molten metal has now been available owing to the development of the proton conducting solid electrolyte made of ceramics of metal oxide. The structure of the sensor and the theoretical limitations of its applications are discussed based on the electrochemical properties of the electrolyte used. The practical performance of the sensor is reviewed from the results of test measurements at the plants of aluminum and copper melting industries. The effectiveness of the sensor to the process control of continuous casting of copper is also discussed.IntroductionSince the in-line monitoring of the amount of oxygen dissolved in molten metal was realized by using the oxygen concentration cell based on zirconia solid electrolyte a similar method has been expected to be developed for sensing of hydrogen, which is a very important element of gas species in liquid metals, especially, in aluminum and copper. In 1981; Iwahara and coworkers found the dominant proton conduction at a high temperature in some perovskite-type oxide (1). Since then, the effort has been made to apply this proton conducting material as the electrolyte of the hydrogen concentration cell for high temperature use. The hydrogen sensor for liquid aluminum of this kind was first produced in 1991 (2) and released commercially from TYK Co., Ltd. Recently, we have developed the mother one usable at higher temperature such as copper and silver melting processes (3). In this note we discuss their structure, design and applicable limitations based on the electrochemical properties of this new type electrolyte. The performance of the sensor and benefit to use it to control the melting process is also discussed"

Jan 1, 2000

By Klaus-Markus Peters, Robert M. Cravens, James G. Hemrick

"Degradation of refractories in molten aluminum applications leads to energy inefficiencies, both in terms of increased energy consumption during use as well as due to frequent and premature production shutdowns. Therefore, the ability to enhance and extend the performance of refractory systems will improve the energy efficiency through out the service life. TCON_ ceramic composite materials are being produced via a collaboration between Fireline TCON, Inc. and Rex Materials Group. These materials were found to be extremely resistant to erosion and corrosion by molten aluminum alloys during an evaluation funded by the U.S. Department of Energy and it was concluded that they positively impact the performance of refractory systems. These findings were subsequently verified by field tests. Data will be presented on how TCON shapes are used to significantly improve the thermal management of molten aluminum contact applications and extend the performance of such refractory systems.IntroductionThe production of molten aluminum creates aggressive environments for processing equipment, thereby requiring refractory materials to contain the aluminum during melting, transfer, treatment, and casting operations. Degradation of these refractories not only causes issues with reduced product quality and production yields, but also increases heat losses as the insulative properties of the refractories are compromised. Furthermore, in addition to disrupting production output, refractory failures lead to further impacts upon energy efficiency as large amounts of energy are lost during the cooling and subsequent reheating of the equipment as the refractory linings are repaired or replaced.The need for improved refractory materials is recognized throughout the industry. A joint U.S. Department of Energy and industrial workshop held in 2000 on applications for advanced ceramics in aluminum production [1] noted that refractory materials used in melt processing equipment have many limitations. The workshop report noted that these issues may be addressed by using advanced ceramics, but new materials must be cost effective when compared to current refractory materials. Also, in 2005 the Canadian aluminum industry produced a technology roadmap [2] having the goal of identifying and bridging gaps between current technological resources in the industry and future requirements. One of the areas identified as being crucial to the future of the industry was the need for improved molten aluminum-resistant materials."

Jan 1, 2009

By Olga K. Karakasi, Angeliki Moutsatsou, Ioanna Kavallari

"The present study focuses on the amelioration of the behaviour of high calcium fly ash (HCFA), investigating its application in a new environmental field: oil spill clean up. High calcium fly ash is a by-product of electric power plants, produced annually in large quantities, whose greater amount is landfilled. Some of its properties, such as its chemical and mineralogical composition, its fine particle size, its porosity, floating ability and hydrophobic character make it an attractive material for this purpose. Researches showed that when added to an oil spill, it forms a semi-solid phase, which allows the quite total removal of the oil, but it is not stably retained on the surface. In order to ameliorate its floating ability, the decrease in its specific gravity by mixing with a lighter material is investigated. In the present study the mixing with two materials, already used in oil spill clean up, sawdust and a polymer, has been examined. Addition of 15-25% w/w sawdust to HCFA results in a material with better performance than HCFA or sawdust alone: it has a satisfactory floating ability and allows total removal of oil. Addition of the polymer, however, has resulted in no significant amelioration of the oil sorption behaviour of HCFA, probably because no affinity between HCFA and polymer has been achieved.IntroductionCoal fly ash is a by-product of coal combustion in electric power plants, produced worldwide in huge quantities, approximately 500 million tones annually. High calcium fly ash (HCFA) is classified to class C presenting a (Al2O3 + SiO2 + Fe2O3) > 50%. The production of lignite fly ash in Greece comes up to 13 million tones annually, of which only 12% is used in construction applications, the other being landfilled [5, 6].Besides its limited application worldwide as a construction material, research is focusing on the development of new environmental applications, such as waste stabilisation and solidification, soil and water environmental improvement [9, 12]. For the application of fly ash in further environmental fields several chemical modifications have been applied, in order to improve its properties. Extensive research has been focused on the conversion of both coal and lignite fly ash to zeolite and its further application in environmental field, such as the uptake of inorganic (heavy metals and ammonium [8, 11]) or even organic compounds (methylene blue [15]) from waste water streams, or the use as molecular sieves, to adsorb water molecules, SO2 and NH3 from gas streams, due to the high cation exchange capacity and porosity of the produced zeolithic material. Furthermore, lignite fly ash has been combined with sodium silicate solution, prepared by treatment of rice husk ash, and tetrapropylammonium bromide, to synthesise hydrophobic zeolite ZSM-5 [4]."

Jan 1, 2008

By Alan James Parker

Chalcopyrite can be converted to pure copper by the following five steps. An exothermic sulfation roast of chalcopyrite; leaching of cupric sulfate from the calcine with dilute acid; precipitation of Chevreul's salt and or other copper sulfites with ammonium sulfite or precipitation of crude copper by autoclaving ammonium sulfite and cupric sulfate at 150°C; dissolution of Chevreul's salt, or the crude copper, as cuprous sulfate, using acidic cupric sulfate in an acetonitrile-water solution as oxidant; precipitation of pure copper by thermal disproportionation of the cuprous sulfate solution. Acetonitrile and acidic cupric sulfate solution recycle. Advantages over conventional processes include lower cost, lower energy consumption as waste heat, sulfur removal as ammonium sulfate or gypsum, rather than as sulfur dioxide and rapid throughput. The net reaction is: 2 CuFeS2 + 4H20 + 15/2 02 + 8 NH3?2Cu + 4 (NR4)2 SO4 + Fe2O3

Jan 1, 1976

By Fernando Castro

Electric furnace steelmaking dust is a polluting residue that needs to be treated in order to recover metals contained and to produce an environmentally acceptable residue. Some hydrometallurgical approaches for its treatment have been evaluated, namely: caustic soda leaching followed by electrolytic recovery of zinc, ammonia leaching followed by zinc compounds precipitation and acetic acid leaching followed by lead, zinc hydroxide and gypsum precipitation.

Jan 1, 1992

By Kang Wan, Lei Tang, Jianchao Li, Jieyu Zhang, Minqi Sheng, Jifang Xu

"The viscous flow phenomenon in slag close to the liquidus temperature was considered. A simple approach that liquidus temperatures of melt could be derived from viscosity data was employed. The potential of this method for estimating the liquidus temperatures of pure water and binary alloy was demonstrated. The liquidus temperatures of the CaO-Alz03 based slags obtained from the second derivative method depends upon the number of viscosity values available at different temperature intervals. The results indicated that plots start deviating from the straight-line behavior at temperature as expect, and the second derivatives show the break points at a certain temperature, which is the liquidus temperature. Comparisons among the present observations as well as the characteristic temperature of the selected slags, which measured by the hemisphere method and DSC, indicated that it is possible to get a reasonable idea of estimate the liquidus temperatures from activation energies for viscous flow.IntroductionThe liquidus temperature of slag, which has a significant effect on the kinetics of chemical reactions and the slag-metal separation, is extremely important for metallurgical operations. Experimental measurements of the liquidus temperatures of slags are difficult, since slags invariable supercool. In addition, behavior of a single constituent in a multi-component slag is different in different circumstances due to its interaction with other constituents. Hence, it is essential to study the liquidus temperature of each particular slag resulting from a special process. Usually, the compositions of the slags aimed to the single liquid region of the phase diagram. However, the phase diagram of many slag systems, which back often to the 1950's, involves considerable uncertainties. Many liquidus temperatures are given as dotted lines in Slag Atlas [1]. Disagreements between the phase diagram and the reality have been found [2]."

Jan 1, 2013

By T. Langthaler, H. W. Engl, H. Holl, K. L. Schwaha

"The trend towards near net shape casting requires the development of more complex design and control algorithms for continuous casting ""machines in particular with respect to the solidification process.Compared to conventional continuous casting the reduction in casting thickness allows to influence more directly the solidification rate by control variables like surface cooling and/or casting speed.In order to enable the determination of these control variables for a given solidification profile, an algorithm (inverse solidification analysis) has been developed based on nonlinear constrained optimization. The application of the model is illustrated by practical examples ranging from conventional continuous casting to advanced thin slab casting.IntroductionProcess development in the Iron and Steel Industry is directed towards the realization of continuous process sequences. Since the direct linkage of processes imposes some restrictions onto the individual process steps, more complex algorithms are needed for design of equipment and control of operation. In particular the recent trend to reduce casting thickness, i.e. to cast thin slabs, has made the direct coupling of continuous casting and rolling absolutely necessary. The prospective development in strip production is schematically shown in fig. 1."

Jan 1, 1988

By C. Beckermann

"A diffuse interface model is derived for the direct simulation of two-phase flows with surface tension, density differences between the phases, and phase change. The derivation starts from the balance equations for a sharp interface and uses a formal averaging procedure on an atomic scale to obtain diffuse interface versions of the equations. Two approaches are considered: (i) the two phases have different velocities inside the interface and separate conservation equations are solved for each phase, and (ii) the two phases have the same velocity inside the diffuse interfuce and mixture conservation equations are solved. Based on a superposition of microscopic (atomic-scale) and macroscopic interface morphologies, an expression for the interfacial momentum source term is introduced that models surface tension effects and accounts for immiscibility between the phases.IntroductionDiffuse interface methods have been a popular tool in the direct simulation of two-phase flows [I]. In diffuse interface approaches, the interface between the two phases is characterized by a rapid but smooth transition in the properties, such as density and viscosity. Usually, a phase function ? is introduced to represent this transition, and the evolution of ? in the domain is computed from a separate equation or recipe. A unique set of conservation equations (e.g., mass and momentum) is solved on the entire domain, irrespective of the phase present, by accounting for the transition in the properties and introducing terms that account for interfacial sources. The continuum surface force (CSF) model of Brackbill et al. [2], which accounts for surface tension, is an example of the latter. The volume-of-fluid (VOF), level set, and phase-field methods are all examples of diffuse interface approaches. The major advantage of diffuse interface methods is that explicit tracking of the interface and the application of traditional sharp interface conditions are avoided. A disadvantage can arise from the artificial smearing of what is in reality an interface of atomic-scale width; however, techniques have been developed to overcome this problem."

Jan 1, 2004