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By E. Gutierrez-Miravete

A computational method for the simulation of mold filling processes is described. The method is based on the representation of the flowing or deforming medium as a collection of mutually interacting parcels of material. Instantaneous positions of individual material parcels are calculated by numerical integration of the dynamic equations, subject to appropriate initial and boundary conditions. So far, the method has been used to produce qualitative simulations of some flowing and deforming systems encountered in mold filling technology, and our findings are summarized herein. In all cases, individual material particle motions can be followed in detail, allowing critical examination of potentially problematic mold design features.

Jan 1, 1992

By Shadia J. Ikhmayies

In this work the equilibrium temperature-composition phase diagrams of the Si-O2 system were calculated using Thermo-Calc software in the temperature range 500–3000 K. Constituents of stable phases were obtained, and the amounts of certain phases where investigated with the variations in the composition of oxygen and temperature. It is found that quartz with silicon represent a stable phase in the temperature range 500–1150 K, while tridymite with silicon represent a stable phase in the temperature range 1150–1700 K. A liquid phase is found besides tridymite in the temperature range 1700–1750 K, and a stable phase of cristobalite with liquid appears in the temperature range 1750–2000. The maximum amounts of quartz, tridymite, and cristobalite are found at oxygen mole percent of 67.7%.

Mar 1, 2017

By Metehan Erdogan, Furkan Özdemir, Ishak Karakaya, Mustafa Elmadaglı

Tungsten is mainly produced by H2 reduction of WO3 which makes its production difficult and costly. A promising method was recently reported for direct electrochemical production of tungsten from CaWO4 (scheelite) which is estimated as the seventy percent of the all tungsten reserves of the world. This paper investigates the application of pulse current in the electrochemical reduction of CaWO4 pellets attached to a current collector. The electrolyte was composed of calcium chloride and sodium chloride salts at eutectic composition (48 pct mol NaCl at 873 K). The reduced samples were cleaned with dilute hydrochloric acid solutions and characterized by X-ray diffraction and scanning electron microscopy. Examination of the results revealed that metallic tungsten was obtained by pulse current reduction.

Jan 1, 2016

By Kenji Monden

A thermal solution composite is made by incorporating dense inorganic fillers with high thermal conductivity into a resin. Silica, alumina, aluminum nitride, silicon nitride, and boron nitride are used for fillers of thermal solution composite. The thermal conductivities of composites are measured and the effect of inorganic fillers’ volume fraction is analyzed. The influence of percolation on thermal conductivity is considered. When percolation by random filling is assumed, the thermal conductivity of composite materials is expressed by the predictive expression using the effective thermal conductivity of filler. The relationship between the effective thermalconductivity of filler and its mean diameter is estimated by the equation. In the case of irregular AlN filler with average particle size 45 lm, the effective thermal conductivity of filler becomes 20 Wm−1 K−1. When the volume fraction of the fillers is 0.75, the thermal conductivity of the composite has been reported to 8 Wm−1 K−1. If the thickness of the interfacial region can be lowered, an effective larger thermal conductivity of the filler appears to set in and the thermal conductivity of the composite can be largely improved. The thermal conductivity of BN can approach 600 Wm−1 K−1. The BN constitutes the matrix of composite by causing percolation without interfacial region; high thermal conductivity of 55–100 Wm−1 K−1 has been achieved.

Mar 1, 2017

By Norbert Hort, Karl Ulrich Kainer, Carsten Blawert, Daniel Fechner

"With the development of new heat resistant magnesium alloys, the automotive industry has introduced several parts to the drive train. The rising number of large magnesium components will result in a higher quantity of automotive post consumer scrap and the changing legislation will force car manufacturers to take magnesium recycling into consideration. So far post consumer scrap has not been used for magnesium alloy production. Quite a reasonable amount of automotive scrap is likely to end up in a mixed light metal shredder fraction. The separation of mixed magnesium scrap according to several alloys is complex. Therefore secondary magnesium alloys made from blended post consumer scrap would be useful. For this work a matrix of potential recycling alloys was prepared by chill casting and high pressure die casting. The materials were investigated for their microstructure, mechanical properties, heat resistance and corrosion properties. The results will be presented in this paper.IntroductionWithin the last ten to fifteen years several heavy magnesium parts have been assembled in passenger cars, such as gear box housings and crank cases [1, 2]. Reasons are the lately developed new heat resistant alloys and the increasing responsibility of automotive manufacturers to reduce the vehicles weight and thereby CO2 emissions. The latter is pushed by international legislation [3, 4]. The rising quantity of magnesium in automobiles will result in an increasing amount of so called post consumer scrap at the end of the vehicles life.So far magnesium recycling was done only for clean scrap that is free from impurities, contaminations and sorted according to a chemical composition or a single alloy respectively [5- 15]. The latter is also called class 1 scrap and mainly consists of sprues and runners from magnesium die casters [15, 16]. For the upcoming automotive post consumer scrap the materials quality strongly depends on the way end of life vehicles are treated. By proper dismantling of old cars, the bigger magnesium components could be collected and possibly treated similar to class 1 scrap [15]. Up to date automotive manufacturers have no uniform recycling system for end of live vehicles. Most probably a considerable quantity of old cars will be shredded. The resulting light metal shredder fraction will contain aluminium and magnesium scrap, both from several alloys. A separation of mixed magnesium and aluminium scrap is feasible according to [17]. Other authors claimed that the grade of separation of magnesium from aluminium is still not sufficient for a proper industrial recycling process of magnesium post consumer scrap [15, 16]. If an automatic sorting is possible it will probably be very expensive [18]. Therefore, so far the main use of post consumer scrap has been the steel desulphurisation and aluminium production [15]. The use of post consumer scrap for magnesium alloy production has been considered already by [15] and [16] but some problems have to be approached."

Jan 1, 2008

By P. G. McCormick

The refining of rare earth metals by the direct solid state reduction of their respective chlorides during mechanical alloying has been studied. Erbium and gadolinium were synthesised by milling their respective chlorides with calcium. The mechanical alloying of SmC13 with calcium resulted in partial reduction of SmC12. Examination of the milled powders using X- ray diffraction and analytical electron microscopy has enabled characterisation of product structure and morphology. The synthesis of Fe17Nd2 by the mechanical alloying of NdC13 and Fe with calcium has also been studied. The Fe17Nd2 phase forms during heat treatment of the mechanically alloyed powder.

Jan 1, 1992

By Karl A. Gschneidner

Magnetic refrigeration was first used in the mid-1920's and new developments seem to have taken place about every 20 years, and this is especially true for the mid-1990's. The active magnetic regenerator magnetic refrigerator has the promise to become the first practical machine utilizing the magnetocaloric effect for cooling (and also heating). The basic principles are briefly discussed. Since the temperature lift for the magnetocaloric effect spans about 50 K, one will need to utilize several ferromagnets with different magnetic ordering temperatures in order to reach temperatures below ~250 K. The basic properties, behaviors, limitations, and new phenomena and knowledge are discussed.

Jan 1, 1997

By F. J. Tavera

The colloid flotation of lead carbonate precipitates in aqueous media is studied at a pH of 7. The flotation system consisted of five spargered flotation cells in a serial array. The flotation system was operated under controlled conditions of superficial air velocity, superficial liquid velocity, frother concentration, and collector concentration. The measured variables were gas hold-up, bubble size, superficial bubble surface flux, and lead recovery (reported to the concentrate). The experimental data show that it is possible to separate as much as 97% (w/w) lead from the aqueous media when the superficial gas velocity is 1 cm/s and the superficial liquid velocity is 0.19 cm/s.

Jan 1, 2006

By Hee Dong Jang

Crystalline metal oxide nanoparticles such as lithium cobalt oxide (LiCoO2) and indium tin oxide (ITO) were synthesized from sprayed droplets of aqueous precursor solution by flame spray pyrolysis. Complete thermal decomposition of the aerosol precursors was obtained at high flame temperature. Molar concentrations of the precursor solution, and the flow rate of combustion gas such as hydrogen, oxygen and air were varied to control particle size, size distribution and crystal structure. The crystalline nanoparticles synthesized were nearly spherical, and their average primary particle diameters ranged from 11 to 35 nm for LiCoO2 and from 8 to 15 nm for ITO.

Jan 1, 2006

By Bowen Li, Jiann-Yang Hwang, Mingsheng He, Huaguang Wang

Kyanite is one of the major high-alumina minerals for producing refractory ceramics. At high temperature, kyanite can be decomposed into mullite and amorphous silica. This change is an irreversible decomposition and provides potentials for fiber reinforcement of ceramic matrix. In this study, kyanite powder was compressed into a cylinder green body of ceramic and heated at 1150–1450 °C.The phase transformation of kyanite and sinterability were investigated by X-ray diffraction and scanning electron microscopy. The results showed that the phase transformation of kyanite started at 1150 °C when rising the temperature. At 1350 °C, kyanite is completely converted into mullite and silica. The compressive strength of the ceramics reached 73.3–134.8 MPa, while the bulk density was 1.95–2.47 g/cm3. The microstructure indicated the correspondence of the compressive strength to mullitization degree of kyanite.

Mar 1, 2017

By Dong Liang, Qijie Zhai, Zhichen Zhang, Qixin Li, Zhishuai Xu

"The formation, distribution and survival of pure Al nuclei under surface pulsed magneto oscillation (SPMO) treatment were investigated with thecombination of experiments and numerical simulation. The results indicated that the nuclei originated from the whole top surface of melt owing to the oscillation of top surface induced by SPMO. The temperature field significantly affected the survival of the nuclei The electromagnetic force and flow field of the melt with SPMO treatment were simulated by finite element software ANSYS. The electromagnetic force mainly distributed below the top surface near the mould wall. The electromagnetic farce not only made the melt oscillate but also increased the convection of meh below the top surface vigorously. The oscillation near the top surface of the melt promoted the nucleation largely, and the convection increased the uniform of the temperature distribution in the whole meh which favored the survival of nucleiIntroductionAs we all know, fine equiaxed grains are beneficial fur the improvement of the mechanical property, process ability and the uniformity of metallic materials [1-2]. With the researches of recent decades, people discovered that the electromagnetic field is an efficient method to refine the solidified structure of metals [3-7]. Pulsed magnetic field technology obtains more and more attentions in recent years due to its smaller power consumption, bigger instantaneous magnetic field intensity, non-contacting with the meh and simple convenient equipment manufacturing [8-9]. However, the melts would splash fiercely when pulsed magnetic field is applied with a slightly higher power. Thus, based on the understanding of the solidification refinement mechanism of electric current pulse (ECP) [10], Gong et al [11] developed a novel technology called pulse magneto-oscillation (PMO) to refine the solidification structure. The technology can be easily applied in the solidification structure refinement of continuous casting slab. But fur aluminum continuous casting, the sump is very shallow, which greatly limits the application of pulse magneto-oscillation technology."

Jan 1, 2014

By T. A. Larssen

The efficiency in production of manganese ferroalloys is dependent on the gaseous reduction of the higher manganese oxides in the ores used as raw materials. The materials, descending in the furnace, will meet the furnace gas that contains significant amounts of CO(g) and reduce in subsequent steps, the last step being reduction of Mn3O4 to MnO. This step may to varying extent occur at temperatures exceeding 800 °C, i.e. in the active region of the Boudouard reaction. The gas reduction of Assmang and Comilog manganese ores were investigated in CO-CO2-atmosphere at temperatures up to 1000 °C. It was seen that decreasing ore size correlates to a lower reduction temperature and increasing reduction rate. Similar effect was observed with increasing CO-content in the gas atmosphere. Further, it was found that Comilog ore obtained a complete prereduction at 600 °C, whereas reduction of Assmang ore was not complete at 800 °C for the majority of the experiments.

By Zeyun Cai, Gaoyang Song, Bo Song, Yuhou Yang

In this research, super gravity field was introduced in the solidification process of high carbon steel. The experimental results show that the solidification structure of Fe–1 wt% C steel can be largely refined by applying super gravity at the cooling rate of 10 °C/min. Both the primary and secondary dendrite length was markedly reduced. In addition, the eutectic structure in the inter-dendrite was also refined with the obvious reduce of eutectic space. However, the macro-segregation of C along the direction of super gravity was caused with higher weight percent at the upper area than that at the bottom of the sample. The mechanism of solidification structure refinement and the C macro-segregation of Fe–1 wt% C steel in super gravity field were also discussed in this paper.

Mar 1, 2017

By C. Hecker, J. A. Garcia

To determine the kinetic reaction mechanism, electrochemical experimental techniques of stationary polarization, linear voltammetry and faradaic impedance were used. Gold electrodeposition experiments were realized using an electrolysis cell, provided· by a rotary disk of vitreous carbon and or' platinum counter electrode of platinum mesh and reference electrode. Using an automatic measurement system voltarnmograrns and Nyquist faradaic impedance spectra were obtained. In this paper, responses for different cases were analyzed through faradaic impedance criteria, considering several kinds of diagrams obtained. The importance diffusion influence of aurocyanide ions and adsorption as controlling steps previous charge transfer was verified. A model of proposed mechanism is discussed.

Jan 1, 1997

By Kiyoshi Takai

The Para-Eco Incinerator Ash Processing System for cleaning slag has been developed after a seven-year pilot plant study. The major part of the system is an electric furnace heated to 1773 K. The feed material consists of a municipal solid waste incinerator ash mixture containing a reducing agent of a coke and an inorganic flux of calcium and magnesium. With this furnace system, three kinds of products are produced. They are an inorganic molten salt that is slag, molten iron alloy absorbing non-ferrous metals, and fly ash. Due to the reducing atmosphere in the furnace, the slag does not contain any metal components as well as chlorine components just like natural rock and/or aggregate. A retreatment plant modifies this slag into a practically useful aggregate. The plant consists of a slow cooling step for crystallizing the slag as well as a water granulation step. The iron components in the ash are reduced to molten iron droplets, which concentrate at the furnace bottom. The non-ferrous metal components such as copper, chromium, and others are absorbed into the molten iron but not into the molten slag. Volatile metals such as lead, zinc, cadmium and others as well as sodium, potassium, and chlorine go back into the fly ash. A solvent extraction method and/or other appropriate procedures can be used to extract the metal components from this fly ash.

Jan 1, 2003

By L. Katgerman, H. J. Brinkman, J. Duszczyk

"The phase formation sequence in the in-situ synthesis ofTiB2 in A1 from elemental A1, Ti and B powders is identified with a combination of DSC and XRD. After the melting of A1, A1B2 and A13 Ti are formed at the contact areas between A1-B and A1-Ti. The influence of variations in starting composition on the reaction kinetics is explained in terms of there effect on the different processes in the formation sequence. Parameters in the starting composition that were investigated are; fraction ofTiB2 forming reactants, non stoichiometric Ti:2B ratio's, and addition of alloying element Cu.It was found that a liquid Al phase is necessary for the in-situ TiB2 forming reaction from the intermediate A1B2 and A13 Ti phases. If all Al is consumed by the formation of A1B2 and A13 Ti the TiB2 formation is halted until the decomposition of A1B2 and A13 Ti .Overstoichiometric amounts of B are needed for complete conversion of the Ti, present in A13Ti, into TiB2 This is explained by the fact that some of the stable A1B12 phase is formed after the decomposition of A1B2•The addition of Cu leads to an increasing reaction rate in the A1-Ti reaction. A possible explanation for this is that the A1-Cu liquid penetrates more easily between the Ti and its surface oxide than the unalloyed A1 liquid."

Jan 1, 1998

By D. Zhao

High temperature deformation characteristics of austenitic 304L, and martensitic 410 and 416 stainless steels were investigated by conducting compression tests over a wide range of temperatures and strain rates (950-1250 C and 0.001-20 s-1). Flow behaviors of the three alloys were characterized. Optical metallography was performed to determine the as-deformed microstructures. The flow behaviors were related to microstructural phenomena during high temperature deformation. Dynamic recrystallization was responsible for the flow softening. Both dynamic and static recrystallization were operating, and the recrystallized grain size increased with increasing temperature and decreasing strain rate. Strain rate sensitivity was found to increased with increasing temperature and decreasing strain rate. No defects such as cracking and shear bands were observed at those test conditions. Preferred processing conditions can be selected by considering as-deformed microstructure and strain rate sensitivity.

Jan 1, 1994

By Du Sichen, S. Seetharaman, J. A. Bustnes

"The present study deals with the kinetic studies of reduction of some selected transition metal tungstates with hydrogen. The measurements were carried out by the isothermal thermogravimetric method. Shallow powder beds were employed in order to avoid the effects due to transport phenomena affecting the reaction rate. In this way, the chemical reaction rates could be selectively studied. The experiments were carried out in the temperature range 873 - 1173 K. From the experimental data, the activation energies were evaluated and were found to be around 88 kJ / mol in the case of both iron as well as cobalt tungstates indicating the similarities in W-O bonds in both cases. The activation energies obtained are discussed in the light of the position of the transition metal in the periodic table as well as the thermodynamic stabilities of the various tungstates.IntroductionThe tungsten containing hard metals, characterized by high density, belong to a class of two-phase metal matrix composites. While these types of materials have traditionally found their applications within the defence industry as armour-piercing projectiles, counterbalance in helicopters and military aircrafts, outer casings of hand-grenades, etc., commercial applications for this class of alloys also exist, including radiation shields, penetrators for the oil industry, turbines for turbo-jet engines and a wide range of sports related parts. A possible route to the production of these alloys is to reduce the tungstates such as FeW04, Co W04 and NiW04 using a reductant like hydrogen or carbon monoxide. In order to have a better understanding of the processes involved in the production, it is important to have a knowledge of the reduction kinetics for these tungstates. According to the knowledge of the present authors, while the reduction ofNiW04 by hydrogen gas has been investigated earlier in the present laboratorypl no systematic reduction study has been carried out previously for the tungstates of iron, cobalt."

Jan 1, 1996

By Jesse White, Arlin Olson

"An Engineering Scale Technology Demonstration (ESTD) unit utilizing the THOR fluidized bed steam reforming technology was built and operated by Hazen Research, Inc. for the purpose of denitrating and solidifying various Department of Energy (DOE) radioactive tank waste surrogates into granular products. The ESTD offered the opportunity to investigate the operational characteristics of two fluidized beds in series to test process system designs such as those for fluidization, feeding, and product collection. Operational characteristics that were evaluated included bed attrition rate, particle growth, and elutriation; and the effects that variations in process parameters (e.g., fluidizing gas flow rate, feed composition, feed injection method, and gas distributor design) had upon these characteristics were observed. Testing of the process systems on this scale allowed for design changes to be made where the cost in time and money were significantly less by comparison to those same modifications being made on the commercial scale.IntroductionFluidized bed steam reforming (FBSR) offers a moderate temperature (620-750°C) continuous method by which various liquid wastes can be processed irrespective of whether they contain organics, nitrates, sulfates/sulfides, chlorides, fluorides, volatile radionuclides or other aqueous components. The FBSR technology has exhibited the potential to process these wastes into either a carbonate or crystalline ceramic (mineral) granular product.Pilot scale testing was performed using the THOR Treatment Technologies, LLC (ITT) FBSR process, as it offered the opportunity to evaluate multiple aspects in an environment more conducive to experimentation. Process changes and system modifications could be made faster and with less cost impact as compared with changes to an assembled commercial plant. These aspects include verification of process chemistry and kinetics, evaluation of materials of construction, equipment sizing and design, and the interactions of the systems. Evaluation of process chemistry allowed for the verification of thermodynamic and kinetic models, and was used in conjunction with these models to improve the database and modeling assumptions. It also allowed for the reevaluation of data from earlier bench scale testing with the opportunity for long-term operations. These long-term effects may include the buildup of one or more elements that results in the formation of eutectics leading to the destabilization of a fluidized bed, or the shift in particle size as a result of attrition or agglomeration. The pilot plant also provided an environment to evaluate materials of construction."

Jan 1, 2014

By Tatsuro Ariyama, Michitaka Sato, Atsushi Sakai, Sumiyuki Kishimoto, Ryota Murai

"In order to achieve high pulverized coal injection operation in a blast furnace, optimization of the injection lance arrangement was carried out using an experimental furnace and mathematical models. To increase the injection rate of pulverized coal, it is required to raise the combustion efficiency of pulverized coal. It became clear that multi-point injection and the lance arrangement to avoid interference among the coal streams injected were so effective in increasing combustion efficiency. With these findings, the eccentric double lance arrangement has been newly developed.At NKK, Fukuyama No.4 Blast Furnace, after the improvement of the lance arrangement, the maximum injection rate reached up to 230 kg/thm and an average monthly record of 218 kg/thm was successfully achieved.IntroductionFrom the viewpoints of reducing the production cost of pig iron and prolonging coke oven life, high pulverized coal injection over 200 kglthm is actively pursued by ironmaking industries[1-2].Coal particles injected into the blast furnace are consumed by combustion in the raceway and also in-furnace reaction like solution-loss reaction (C + CO2 = 2CO). The amount of coal consumed by the latter process is determined by the carbon balance in the blast furnace and there is a limit. Therefore, to increase the injection rate, it is desirable to improve the combustion efficiency in the raceway. For these purposes, the optimization of the lance arrangement was examined by a hot model and mathematical models."

Jan 1, 1996