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By Masayuki Kudoh, Kiyotaka Matsuura

"Molten aluminum and nickel cast onto a steel block exothermically react and produce molten nickel monoaluminide, NiAI, which is simultaneously joined to the steel. The heat of the exothermic reaction is transferred to the steel block, and steel near the surface of the block is melted. The depth of the melted steel increases with both the initial temperature of the steel block and the thickness of the produced NiAI. Iron from the melted steel dissolves in the molten NiAI, and an intermetallic compound of NiAI-Fe pseudo-binary system is produced. During solidification of the intermetallic compound, it is strongly joined to the steel. The Ni.Al-Fe intermetallic compound has an excellent resistance to oxidation and corrosion.IntroductionAn intermetallic compound of nickel monoaluminide, NiAl, offers many advantages over conventional superalloys, such as higher melting temperature, lower density, greater specific modulus and higher thermal conductivity [1]. NiAl also exhibits excellent high-temperature oxidation resistance when doped with zirconium or hafnium, and excellent high-temperature corrosion resistance when doped with chromium or yttrium, that are superior to existing high temperature alloys or coating materials [1-4]. On the other hand, NiAI is significantly brittle at temperatures below 600 K [5-7], which is the most sigriificant disadvantage of NiAI. A possible way to overcome the disadvantage and to utilize NiAl as an environmental-resisting high-temperature structural material may be joining of NiAl to a ductile material."

Jan 1, 2000

By S. H. Castro

The El Teniente molybdenite plant (Chile), with a nominal capacity of 3,200 tpd of bulk Cu-Mo concentrate, produced approximately 3,385 metric tonnes of Mo during 1998 by using the phosphate Nokes process (LR-744 reagent). This is the only Chilean moly plant which traditionally has depressed copper and iron sulfides with LR 744 reagent, which is a hydrolysis product of P2S5 and NaOH. El Teniente's ore Mo grade is 0.02%Mo and is concentrated to 0.45%-0.50% Mo in bulk Cu-Mo flotation. Subsequently, molybdenite is floated by selective flotation to depress Cu and Fe sulfides, such as chalcopyrite, bornite, digenite and pyrite, to produce typically a 49%-50%Mo molybdenite concentrate. An optimisation program during the last two years was undertaken to improve molybdenite recoveries. Current molybdenite plant technology at El Teniente and use of phosphate Nokes in the process process is reported. Use of phosphate Nokes reagent has increased average Mo recovery from 70.5% in 1977 to a mean 74.7% for the first 4 months of 1999. The global Mo recovery, including bulk flotation, incresed from 42.3% in 1997 to 46.8% in 1998, with a projection of 55.5% for 1999. Mo production per year has increased from 3,181 tons in 1997 to 3,385 tons in 1998 and a projected 4,000 tons for 1999.

Jan 1, 1999

By Tiejun Chun, Marcus Emrich, Jian Pan, Deqing Zhu, Vinicius Mendes

"Joint projects of studies of hematite acid pellet have been implemented to develop technological solutions for using Vale hematite pellet feed in Chinese palletizing plant. Beneficial improvements on the pellets quality were achieved by adjusting the blends composition and using new technology of pre-treating the blended pellet feed with HPGR (High Pressure Grinding Roller) on rotary kiln pellet technology. The drop strength of green balls increased from 3.4 to 6.0 times from 0.5m height, at the same time, the bentonite dosage decreased from 1.5wt% to 0.7wt%. The compressive strength of roasted pellets reaches 2500 N/pellet. The reduction swelling index of roasted pellets is below 15%.IntroductionWith the fast development of steel industry in China, the production of pellets has been further expanded. Pellets are used as a high quality charge for blast furnace and the annual output is around 80Mt pellets [1]. According to the developmental trend, sinter will be replaced by pellets due to the larger environmental impact of sintering plants when compared to pelletizing plants. For example, the specific CO2 emission in sintering process is around 2.5 times higher than in pelletizing process. However, the steel industry of China has been confronted with a serious shortage of domestic pellet feed due to the low iron grade of Run-of-Mine ore despite of huge reserves of iron ores [2]. Therefore, more pellet feed, mainly hematite, has been imported to make pellets."

Jan 1, 2011

By Patrick R. Taylor

Iron phosphate glasses are promising host matrices for vitrifying actinide rich nuclear wastes materials because of their high solubility of actinide oxides, high chemical durability, and relatively low melting temperatures. An iron phosphate waste form was developed at the University of Missouri-Rolla. The structure and property of the waste form were well characterized by materials techniques. However, to scale the process and advance it to commercial viability, it is necessary to understand the processing parameters, such as the partitioning of waste elements and the viscosity as a function of temperature. Viscosity of 40 Fe203 - 60 P205 mole % iron phosphate melts (prepared with phosphorous pentoxide and ferric oxide) at 1000-1200 C was measured by the rotating-spindle method. It was discovered that this fluid has non-Newtonian behavior. Experiments were performed to study flow properties following the Standard Test methods for Rheological Properties of Non-Newtonian Materials by Rotational (Brookfield) Viscometer (ASTM D 2196-86). Samples prepared using ammonium phosphate and ferric oxide showed Newtonian behavior and the temperature dependence of the viscosity was studied over the range of 1000 to 1200 degrees C. The difference in flow behavior between the two fluids was analyzed in terms of preparation conditions and variation in the final composition and phases. The partitioning behavior of waste elements in the iron phosphate glass was studied by melting in a high temperature furnace and JCP analysis. The experimental results show that the solubility of Ce and Sr in phosphate glasses is significantly higher than the solubility associated with borosilicate glasses. This strengthens the conclusion that iron phosphate may be a viable alternative to borosilicate glass for immobilization of high heavy-metal-content wastes and actinide rich wastes.

Jan 1, 2002

By J. M. Tourre

1995 have seen a continuation of a positive trend in the Rare Earth industry The availability of a greater diversity of Raw Material has brought additional flexibility to the Producers permitting better economics China remains the major raw material source; Chinese concentrate producers have increased capacity in 1995 (Baotou, Sichuan, etc) China's role in the Rare Earth industry will continue to evolve; the acquisition of a majority equity position by San Huan/CNNC will have a significant impact on both the Rare Earth and Magnet markets Chinese producers are increasing the quality of their products and realize their true values Chinese market, itself, is also changing as the internal needs for separated rare earth's grow Already already producer of Lamps, Loudspeakers, Magnets, and TV tubes, China is in an unique position where the potential of its internal market might be more promising than the prospects outside China 1995 has also seen the application market become more diverse and complex. There are new applications growing at a very strong pace (such as battery alloy), applications that are now penetrating their target markets with significantly increased growth rates (such as bonded NdFeB), and some applications that became more complex requiring much more sophisticated products (such as catalysis). Rare Earth producers have to spend significant ressources in order to monitor the market trends in order to predict the demand and then adjust their raw material mix. Even though there is a greater diversity of raw material available, there is still some Rare Earth elements that are in excess, while other are just in balance. As a consequence rare earth producers invest heavily in R&D in order to develop new applications for these excess elements.

Jan 1, 1997

By Hiroshi Nakajima, Kotobu Nagai, Toshihiro Hanamura

"Low carbon ferritic steel bars with ultra-fine grain structure was developed through a warm rolling for the first time by the present authors. They show better low temperature toughness than conventionally hot-rolled plates. Hence, the brittle fracture surfaces in Charpy tests were examined in terms of the effective grain size of fracture, compared with those of conventional QT steels. The ductile-to-brittle transition temperatures were in good accordance with those for the QT steels if referred to the effective grain size of fracture: · However, the size was a few times that of the ferrite grain. This means the grain refining is not yet fully utilized from the viewpoint of low temperature toughness. The anisotropy of· the impact properties and the annealing effect of highly dislocated structure on the toughness are also discussed in the present paper.IntroductionFor structural materials, both high strength and good toughness are required. Well-known approaches for obtaining better toughness for steels are as follows:1) Grain refining2) Addition of Ni3) Thin plate effect by cracking parallel to the rolling direction prior to crack propagation4) Contribution of metastable austenite.Among them, only the grain refining can raise the strength and improve the toughness. And it is well known that the finer the ferrite grain size, the lower the ductile-to-brittle transition temperature. For example, in the case of 0.11 carbon steel, the transition temperature decreases linearly to in d 1/2 [1 ]. However, these have been told in the regime of coarse grain size that is larger than 10 µm in diameter. There ~as .been no study dealing with the low temperature toughness in the regime of ultra-fine grain size with a diameter in the order of 1 µm."

Jan 1, 2000

By A. P. Paiva

Studies focused on the recovery of precious metals by solvent extraction have recently increased. either to devise suitable solvents or to clarify the involved extraction mechanisms and kinetics. In this work, a comparison of the performance exhibited by triphenylphosphine (TPP), bis-(penty1thio)-ethane (BPTE) and triisobutylphosphine sulfide CI"I'BPS) in the extraction of silver from acidic chloride media is carried out. Extraction and stripping isotherms involving the three extractants are presented together with the results obtained on the selectivity of silver extraction against high contents of iron, copper and lead. Attempts to clarify the mechanism of silver extraction by TIBPS were performed by studying the distribution coefficient dependence on ligand and chloride concentrations. The effect of temperature on extraction and stripping is also considered. The interfacial tension for the system, measured with different concentrations of extractant in the organic phase, is analysed.

Jan 1, 1994

By Jefferson Caponero

The tire is an expressive component of Municipal Solid Waste, manly when its occupied volume is considered. Its treatment by pyrolysis stands for a list of advantages, such as: landfill releasing and a production of a high quality fuel. The exploitation of new natural resources is becoming more difficult each day, basically due to the environmental damages caused by this type of activity. This work presents a study on the thermal behaviour of Brazilian tires using thermogravimetric analysis and differential thermal analysis, in order to optimise the pyrolysis process of tires. Samples of I to 2 mm were investigated at atmospheres of nitrogen, argon, oxygen and mixtures of these gases at temperatures up to 1273K, under heating rates between 1 to 50 Klmin . The results showed that the behaviour of each sample is related to both the atmosphere composition and the heating rate.

Jan 1, 2001

By F. Patisson

One of the major issues with multiparticle reactors is to handle their multiscale aspect. For modeling, it usually comes to coupling a reactor model (describing the phenomena at the macroscopic scale) with a so-called grain model (simulating the behavior of a single grain or a particle). An interesting approach proposed by H.Y. Sohn (1978) is to use the law of additive reaction times in order to calculate, approximately but analytically, the reaction rate of a particle in the reactor model. Its great advantage, compared to a numerical grain model, is to drastically reduce the computation time, particularly in the case of complex reactor models. This is the approach we retained for modeling the moving bed furnace, a counter-current gas-solid reactor used in the nuclear fuel-making route for producing uranium tetrafluoride from uranium trioxide. The numerical model we developed is 2-dimensional, steady-state and based on the finite volume method. It describes solid and gas flow, convective, conductive and radiative heat transfers, and six chemical reactions involved in the process. The law of additive reaction times is used to calculate analytically the rate of the three principal gas-solid reactions at every discrete point in the reactor. We have demonstrated the validity of this approach by comparing its results with those calculated from a numerical grain model. Also detailed in the paper are the main results of the moving bed furnace model itself and the possibilities of optimizing the process revealed by the calculations.

Jan 1, 2006

By Takafumi Kondo, Satoshi Yamashita, Noboru Masuko

"Aqueous oxidation of phosphite ions to phosphate ions with dissolved oxygen was examined at 80° C and pH 4.5 mainly from the stichiometric point of view. Dissolved oxygen alone can not oxidize sodilim phosphite in aqueous solution, but when sulfur dioxide is coexistent, cooperative oxidation for both sulfite and phosphite can occur in aqueous solution. Sulfur dioxide itself is well known as a reducing agent, but it also reacts as an oxidation-promoting agent for other species under a certain condition. So sulfur dioxide is· a promising cheap reagent for waste phosphite processing.IntroductionIn a liquid-phase oxidation reaction using the dissolved oxygen gas, the eoexistence of a copper salt is required generally. Recently, it was reported that the oxidation reaction progressed by using mixed gas of sulfur dioxide and oxygen without the copper catalysis, and the attention has been collected1·3). The present authors also noticed the phenomenon since the early time and have been studying on the reaction mechanism of sulfur dioxide in liquid phase oxidation 4l. It was found that; by using the SO2-O2 mixed gas, the oxidation of phosphite ions to phosphate ions proceeded efficiently in sulfuric acid solutions. In the present report, the applicability of SO2-O2 mixed gas as a cheap oxidizing agent to the industrial processing of the waste solution of electroless nickel· plating is investigated. It is well known that the sulfur oxide dissolved in aqueous solution is oxidized ·by the oxygen in the air to sulfuric acid according to the following equation"

Jan 1, 2000

By Frustino L. Prado

For more than a century, the AAC (ammonia I ammonium carbonate) process has been applied to the recovery of various metals. A variation of it, the Caron Process was first used in the early 1940's in Cuba for the extraction and recovery of nickel from laterites. The original Nicaro plant has been in continuous operation since then. Years later the Caron process was used again in Australia at the Greenvale (Yabulu) NickelICobalt plant, commissioned in 1974. Other projects (Sered, Niquelandia, Nonoc, Punta Gorda, Albania) as well as several studies have been carried out. The Caron Process is alive and still promising. Members of our organization have been working with AAC and the Caron Process since 1952. This paper will review current approaches and potential improvements (enhancement of recoveries of Ni and Co, reduced energy consumption and maintenance simplification). Keywords: Caron Process, Ammonia, Ammonium Carbonate, Laterites, Nickel, Cobalt

Jan 1, 2004

By Baokuan Li, Fang Wang, Meilong Shan

"As the advantage of uniform bus loading, the electroslag remelting (ESR) furnaces with three - phase installation by delta or star connection are mainly used to produce the large or super large ingot. The electrical efficiency is significantly improved as the short circuiting through the molten slag. However, little is found about fiindamental research on the electromagnetic field of the ESR system with three -phase installation. A three-dimensional (3D) finite element model was developed to simulate the current density, magnetic field, electromagnetic force and Joule heating for a system of electrode, slag and ingot in the ESR system with three -phase installation.IntroductionThe metallurgical performance of the ingot is the fundament and precondition to obtain the large forging of high quality, which has a critical role in the producing of forging. The electroslag process (ESR) to product the metal materials of high homogenization and clarity become more and more popular[1].The electroslag process is a special smelting technology of producing small ingots, which originate in 1950[2].At present the three, four or six electrode is used in large scale electroslag furnace. It has been found that the deeper molten pool and the wider of the two-phase zone with only one large diameter of electrode to product large ingot effect the solidification microstructure of ingot[3]. However, the molten pool becomes shallow relatively with several electrodes producing the large ingot, which is benefit to the solidification microstructure of ingot. Three electrodes electroslag remelting furnace take the three phase equilibrium power supply to making the load and electric power network balance, avoiding the distortion phenomenon induced by single phase power supply and saving electric power. It also can uniformize the distribution of heat source."

Jan 1, 2012

By Kanchan Mondal

"Methanol, lower hydrocarbons, CO, and HCOOH formation have been by the reduction of CO2 with H2. Un-catalyzed electro-reduction requires a significant overvoltage. An alternate route has been conceptualized. Production of hydrogen from water can be achieved by chemical oxidation of a metal in water followed by oxidation of the hydronium ion by the released electrons to form hydrogen radical. It is hypothesized that circumventing the problem of the formation of hydrogen molecule is essential while having the hydrogen radical to react with CO2 forming methanol, etc. This may be possible by a bimetallic catalyst acting as a galvanic couple, wherein one metal acts as the electron donor for the production of hydrogen radical while the other acts as a catalyst for the reduction of CO2. This may enhance the reaction rates. The current concept circumvents the need for an external electric field unlike the electrochemical process.IntroductionUtilization of carbon dioxide as a raw material, not only as carbon sources but also as useful chemical feedstock is a more holistic approach to reduce air pollution by flue gases (1-3). Several methods have been proposed to maintain the concentration of atmospheric CO2 or to reduce and recycle it. One of these is the chemical fixations using catalysts. The conversion of CO2 to methanol by hydrogenation over copper containing catalysts is one of the most widely studied subjects in this area. The limitation in this reaction is the low conversion of CO2."

Jan 1, 2008

By J. Tang

The major problem with the Nd-Fe-B magnet is its low operating temperature, i.e., the coercivity decreases so rapidly with increasing temperature that the practical maximum operating temperature-is only 100 °C. Meanwhile, it has been reported that nitrogen addition can drastically increase the Curie temperature of both R2Fe17 and RTiFe11 (R = rare earths). A reasonable question is, then, can one see a similar effect in Nd-Fe-B system? Experiments have been conducted to examine how magnetic properties of Nd-Fe-B magnet are affected by the nitrogen addition. Our results show that part of Nd2Fe14B maintains its original crystal structure and no substantial change in To, due to such N2 treatment is found. However, part of the sample decomposes into a-Fe and, possibly, Nd nitride as a result of nitrogen treatment.

Jan 1, 1992

By Aly M. Abdel-Rehim

The present work deals with a study of the mechanical activation of processing of Egyptian monazite by its simultaneous ball-milling and pressure leaching in order to improve the recovery of thorium and lanthanides from monazite. Experiments of simultaneous ball-milling and alkaline leaching of monazite contrary to autoclave leaching were carried out in stainless steel ball-mills of cylindrical shape under different conditions of temperature, pressure, time and alkali amount and strength. The ball-mills were heated and mechanically rotated in an electric furnace by means of roll mechanism. The effective rotation speed was fixed at 130 rpm in all tests. The charge of steel balls of different diameters was equivalent to 45% of the total mill volume. Monazite was charged in ball-mill without preliminary grinding. It is found that high rate of monazite leaching by ball-milling leaching method is achieved at lower temperature, shorter time and lower expense of alkali than in autoclaves. The results obtained show that complete recovery of thorium and lanthanides from monazite (99.8%) by simultaneous ball milling and alkaline leaching is attained at 140°C within 2 h. It is concluded that processing of monazite by its simultaneous ball-milling and leaching is mechanically activated and accelerated as a result of grinding action of steel balls that caused the continuous removal of the hydroxide product from reacting particle surfaces. This leads to the exposing of fresh and activated monazite particles surfaces to alkali leach solution and consequently the acceleration of the reaction of monazite processing.

Jan 1, 2006

By R. Vasant Kumar

Measurement and control of trace elements in molten metal are often critical in order to achieve optimum production, refining, alloying or recycling. Solid electrolyte sensors for monitoring oxygen and very recently for hydrogen have made major impact in the metal industry. It has not proved straightforward to develop solid electrolyte sensors for many other elements that can be industrially applied in metal production. Novel self-tuning chemical sensors have been developed by the authors that may open up new technological opportunities. Three such examples will be presented in this paper: (i) a self-selecting oxygen-sulfur dual sensor using a composite beta-alumina/zirconia solid electrolyte; (ii) a copper sensor for liquid matte based upon cusicon solid electrolyte operating in a current reversal mode; and (iii) an aluminium sensor on solid NaCl containing channels of molten NaAlCl4 electrolyte formed by electrochemical charging in molten zinc.

Jan 1, 2006

By Raj Mutharasan

The phenomena of gas-molten metal reactions for the production of metal matrix composites consist typically of a combination of one or more gas transport steps and a liquid gas reaction step. Reaction products include such strength enhancers, grain refiners, or high thermal conductivity phases as TiC, AIN, SIC, Si3N4, TiN in aluminum alloys. Nitrides, carbides and oxides can be produced at various volume fractions and in fairly fine sizes (500 am to 5 um) in laboratory melts by Reactive Gas Injection method (RGI). Gas injection methodology to produce the reinforcements is attractive because it can potentially be scaled to production scales in excess of 10,000 kg/h. For continuous production, the reactant molten metal can be continuously fed into the .crucible where the reactive gas is injected. The molten metal phase reactant may also be involved in a controlling transport step, depending on its concentration and viscosity. It is well known that the reaction product reinforcement size and shape of these phases have significant impact on the physical, mechanical and thermal properties. The current state of knowledge is unable to predict the kinetics and growth of solid reaction products obtained. The primary goal is to develop a fundamental framework for the understanding and prediction of the particle size in such reaction systems. In addition, the role of gas transport, liquid hydrodynamics and decomposition are important issues. A reaction-transport model is being developed using a reaction, transport, and thermodynamic framework, both at macro and at atomistic level to assess gas - liquid interactions.

Jan 1, 1996

By Roger Wilmoth

Exposed, open pit mine highwalls contribute significantly to the production of acid mine drainage (AMD) thus causing environmental concerns upon closure of an operating mine. Four innovative technologies were evaluated under the U.S. Environmental Protection Agency?s, Mine Waste Technology (MWTP), Prevention of AMD Generation from Open-Pit Highwalls Demonstration Project. This project is funded by the U.S. Environmental Protection Agency (EPA) and jointly administered by the EPA and the U.S. Department of Energy (DOE) through an Interagency Agreement. The objective of the field demonstration was to evaluate the technologies ability to decrease or eliminate acid generation from treated areas of the highwall in comparison an untreated highwall area. The field demonstration was performed at the Golden Sunlight Mine (GSM) a subsidiary of Placer Dome U.S., located near Whitehall, Montana. GSM is an operating gold mine. The highwall at GSM was divided into five plots measuring 15.24 by 15.24 metres (m) and each technology was assigned a plot with the fifth plot being used for comparison as a background control plot. The four technologies were spray-applied. The applied insitu treatment technologies included: 1) A modified, furfuryl alcohol resin sealant, utilizing wood and agricultural by-products to coat the rock surface. 2) EcobondTMARD, a phosphate based process that forms a stable, insoluble compound, coating the rock surface. 3) Two ARD passivation technologies, magnesium oxide and the Dupont technology developed to create an inert layer/coating on the pyrite, preventing oxidation. The technologies were evaluated using the following methods: 1) ASTM D 5744-96, Accelerated Weathering of Solid Materials using a Modified Humidity Cells, 2) mine wall residual wall rinse sampling, 3) microscopy, and 4) core drilling followed by water injection testing.

Jan 1, 2003

By Vahid Rastegar

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

Jan 1, 2012

By M. H. Lin, S. Kou

"Czochralski pulling has been a very widely used process for growing single crystals for electronic and optical applications. Dopant segregation can significantly degrade the quality and yield of single crystals. We have used the floating-crucible technique for segregation control in Czochralski pulling, our floating crucibles being unique in that the melt passageway is very long. As such, dopant back diffusion is suppressed, even when the cross-section of the melt passageway has to be relatively large to help the melt go through or when the pulling rate is very low. Single crystals of model materials K-doped NaN03 and Pb-doped Sn have been grown with very uniform dopant concentrations. IntroductionSingle crystals of electronic and optical materials are often doped with a small amount of impurities to develop required physical properties, e.g., P and B in Si for n-type and p-type semiconductors, respectively, and Nd in YAG lasers. Dopant segregation can result in nonuniform physical properties, thus degrading the quality and yield of the resultant crystals.Figure 1 is an illustration of the conventional Czochralski process for crystal growth. Several techniques have been developed to control dopant segregation in Czochralski pulling, including the push-pull technique (1,2), the drop-pull technique (3-7) and the floating-crucible technique (8-13). The first two techniques require precise sensing devices and feedback control systems to keep the feeding rate equal to the pulling rate. The last technique is simple since the feeding rate is automatically equal to the pulling rate."

Jan 1, 1994