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By A. Elizabet Serna

The weak acid is a by product obtained in a pre-treatment of gases from a copper smelter prior to sulfuric acid manufacture and the main components of this weak acid are: sulfuric acid. copper, arsenic. antimony, bismuth and iron. Usually, this effluent is neutralized with lime and the solid residues are stored in a landfill as a hazardous waste. This work was directed at determining the optimal conditions to recover copper from weak acid using a cementation process before the neutralization of the effluent. The variables investigated are: Effluent temperature, iron scrap amount and acid concentration versus reaction time. The results of these experiments show that the cementation process of copper and the co-cementation of impurities such as arsenic, antimony and bismuth were in accord with the theory of the electrode potentials.

Jan 1, 1996

By J. D. Ecuyer, L&apos

he microstructure of galvanneal coatings formed on extra low carbon and interstitial free steel substrates has been characterized using electron microscopy (TEM and SEM) and x-ray diffraction. The coatings are found to consist of a mixture of gamma, delta and zeta phases, of which delta is the main constituent. The amounts of each phase influences the powdering resistance of the coating which was evaluated using reverse Olsen testing and 60" bending. For the three heat input conditions considered, IF coatings were always found to contain a significant amount of gamma and only those which retained zeta phase on the surface exhibited a satisfactory powdering resistance. In much the same way, ELC coatings with relatively thick gamma layers performed satisfactorily only when some zeta was retained. It was also found, however, that coatings with minimal zeta and gamma had an excellent powdering resistance. The latter coatings were produced under galvannealing conditions of lower relative heat input. These results indicate that in addition to the zinc bath composition, coating weight and galvanneal thermal cycle, the base steel chemistry also has an effect on the coating microstructure. Knowledge and control of all aspects of galvannealing is therefore essential to consistently produce acceptable coatings.

Jan 1, 1992

By David G. C. Robertson

A new approach is described for the calculation of the kinetics of metal/slag, metal/slag/gas, and metal/matte/slag/gas reactions. The algorithm assumes that equilibrium is achieved at the interface between phases, and uses an equilibrium solver (such as SOLGASMIX) to compute the equilibrium state at the interface at each time step during the reaction. For multiple phase systems a number of unit operations, representing the different phases and interfaces, must be connected together in a reasonalbly complex manner, and the METSIM software package has been utilized for this purpose. The new approach is superior to the SMAK software developed by the author and his co-workers over the past decade, for the reasons discussed in this paper.

Jan 1, 1995

By R. W. McCallum, B. Jensen, K. W. Dennis

"There are substantial challenges in the exploration of magnetic materials in the R-TM-X system (R =rare earth, TM= transition metal, X =stabilizing element) where Xis an element which has high vapor pressure, high reactivity, toxicity, or a refractory nature. This research focuses on discovering new phases with high anisotropy and high magnetization through closed diffusion couples inside high purity Fe crucibles. Either vapor-solid reactions or powder metallurgy techniques are then employed to isolate a stoichiometric sample based on a potentially magnetic phase found in the diffusion couple. For this research, X = F, Ca, Sr, Se, Zn, Bi or Cd, TM= Fe, and R = Nd. New ternary phases have been discovered with WDS and EDS, and magnetic transition temperatures have been measured with a SQUID magnetometer and VSM.IntroductionSince the discovery of the RCo5 compounds in the 1960s, rare earth- transition metal (R-TM) magnets have been the main focus of permanent magnetic research over the last five decades. Iron-based magnetic materials were studied next in attempts to avoid the unstable price of cobalt as well as the high price of Sm, the top performer in the RCos and RzC011 series. This hunt eventually led to the discovery of Nd2Fe14B with a theoretical BHmax of 64 MGOe, nearly double that of the previous samarium based magnets. The next few decades were devoted to enhancing the magnetic properties ofNd2Fe14B by the improvement of processing techniques and the additions of alloying elements. The only complete elemental substitution discovered in this system was R1Fe14C, which did not improve magnetic properties. It is probably safe to say that most ternary R-TM-X systems, where Xis any element that may stabilize a ternary phase, have been investigated if they may be prepared by conventional processes such as arc or induction melting. The present study offers a systematic approach to developing a novel diffusion couple technique in which the volatile, reactive or toxic alloying elements are laser welded inside a high purity Fe crucible. This experimental setup will prevent the oxidation of the rare earth element, as well as contain the volatile X element. As the goal of the research was to find new rare earth permanent magnets, only phases which contained greater than 60 wt% Fe were investigated. 247"

Jan 1, 2012

By J. Huot

It has been shown that magnesium-based metal hydrides such as Mg2Ni could be synthesized by high energy mechanical alloying. This process creates a nanocrystalline alloy that has enhanced hydrogen sorption properties due to the high density of defects and grain boundaries. Unfortunately, this process also requires a long synthesis time (up to 100 hours in some cases). In order lo reduce processing time and cost of synthesis, we have investigated the effect of milling at elevated temperature under an inert atmosphere. Milling at high temperature improves interdiffusion of the elements and reduces the number of structural defects such as vacancies, dislocations and internal strain. It was found that by milling elemental powders at 200°C. a complete synthesis of Mg2Ni could be achieved in 8 hours. This synthesis time is roughly an order of magnitude lower than that of the process conducted at room temperature. The hydrogen sorption kinetics and capacity of this material are comparable to Mg2Ni synthesized at room temperature.

Jan 1, 2002

By Dale Zacherl, Andreas Buhr, Rainer Kockegey-Lorenz

"The microporous calcium hexaluminate insulating material SLA-92 has been introduced as an alternative to refractory ceramic fiber and other insulating refractory materials. Key properties associated with this product include: high chemical purity, long term high temperature stability up to 1500 °C, low thermal conductivity up to 1500 °C, and high thermal shock resistance. The properties of the new material and various applications in the steel and ceramic industries have been reported in previous papers. The current paper summarizes the industrial application experiences with innovative refractories based on SLA- 92 and discusses potential new applications in various manufacturing as well as energyrelated industries.IntroductionSLA-92 was introduced to the refractories industry in 1998 by van Garsel, et al. [1] as a new insulating raw material for high temperature applications, followed by investigations [2] of long term temperature stability for this new lightweight aggregate up to 1500°C.SLA-92 was developed as an innovative alternative to commonly used refractory ceramic fibers. It has unique properties regarding chemical purity and mineral composition and is a microporous, silica-free calcium hexaluminate (CA6 – mineral name: hibonite)."

Jan 1, 2010

By M. I. Novgorodova

Most of the gold in the earth's crust occurs as finely-dispersed gold and accounts for much of the gold lost in extraction processes and during exploration for gold. The Compositions, sizes, and morphology of fine gold particles (0.01 to 10 ~m in diameter) were studied with high resolution electron microscopy coupled with electron microprobe and microdiffraction devices, using colloidal carbon replicas. Correlations were made between fine gold, mineral associations and ore genesis. The results provide qualitative information on the proportions of finely dispersed, invisible and visible gold distribution in ores. Such knowledge is fundamental when planning an optimum technological recovery process.

Jan 1, 1991

By A. McLean, S. Dawson, N. D. G. Mountford

"IntroductionIn order to predict the accepted industrial practice for the year 2000, it may be helpful to first consider the rate of development of scientific knowledge. If the speed with which man can travel on commercial vehicles is taken as a criterion for determining the rate of progression, then it can be seen from Figure 1 that advancement in our present century is very rapid. Likewise, if computer technology is used as a criterion for the measurement of scientific advancement, it becomes evident that technological evolution can be highly exponential. These two examples are sufficient to demonstrate that engineers and managers cannot afford to regard scientific development as being linear with respect to time if they are to avoid underestimating the needs of society.Within this framework of overall development, the time required for individual ideas to progress from inception to regular application has decreased considerably. For example, X-rays first discovered by Roentgen in the 1890's and now used widely in medicine and engineering, required a developmental period of some eighty years. The motorcar evolved from early beginnings at the turn of the century to a position of great social impact in sixty years. Rectifier materials used in high frequency radar to the present explosion in communications, required forty years. As illustrated in Figure 2, the period is shortening rapidly.The use of sound waves appears to be following a similar path. There is now a considerable body of knowledge concerning their behaviour and exceptional advances have been made. In medicine and engineering the sonic approach to examination is well established, and acoustic testing forms the basis of several diagnostic and quality control applications. With respect to metals engineering, ultrasonic testing has contributed to the understanding of the relationship between the size and number of internal defects and the probability of premature failure. This has allowed the designer to incorporate appropriate safety factors in his designs; but more importantly, the realization of the deleterious effect of inclusions on the performance of the final product has resulted in a continuous pressure on the material suppliers to reduce the number of defects in their products.It is not only the designer who is demanding defect free material but also the fabricator, as material breakdown during manufacture can be prohibitively expensive. Examples of this can be found in both the aluminum and steel industries where ultra clean sheet is required to ensure that rejections are minimized during beverage can manufacture and other deep drawing operations."

Jan 1, 1988

By Kerri-Ann Hue, Kerry Hasapidis, Ken Babcock, Patrick O'Hagan

"Metallic nanoparticles exhibit properties that are significantly different from individual atoms or bulk materials. Their applications are diverse and have varying uses in areas such as cancer treatment, biochemical sensors, nanoelectronics, and drug delivery. For each application extensive characterization must be performed in order to probe the unique properties of these nanoparticles. In this study, ultra-high resolution mass sensors consisting of MEMs-fabricated, suspended microchannel resonators (SMRs) were used to determine the size and concentration of metallic nanoparticles. With femtogram (10- 15 g) mass resolution, ultra-high resolution mass sensors can weigh individual particles suspended in fluid, and so measure their mass, density, and size. Particle size analysis with these sensors provides excellent accuracy and resolution compared to mature technologies such as light scattering. This technique also provides quantitative information via the ability count particles.IntroductionThe unique electronic, chemical, and optical properties associated with nanoparticles vary with their size, shape, and composition[ 1-4]. These properties are attributed to increased surface area and nanosized mean free path of electrons to the particle surface. Nanoparticle colloidal solutions have been prepared and are commercially available. In recent years, noble metals such as gold, copper, and silver have been extensively researched[5-7]. In order to tailor the optical, electronic, and electrical properties of nanoparticles, size and shape must be controlled. For many applications a monodisperse colloidal solution is ideal. Methods of size characterization include Transmission Electron Microscopy (TEM), Dynamic Light Scattering (DLS), and Electrophoretic Mobility Measurements to name a few[6, 8]. Although TEM can provide shape and size distributions, sample preparation requires that samples be dried on a metal grid and cannot be analyzed in solution. DLS uses curve fitting algorithms that while useful for determining mean particle diameters are not ideal for polydisperse colloidal solutions. New technologies are therefore needed to accurately determine the particle size distributions of metallic nanoparticles."

Jan 1, 2011

By R. Mehta, M. Misra, X. Su

"The conventional methods to assess Acid Mine Drainage (AMD) potential of the waste rocks and tailings are based on wet chemistry and leachability tests. These methods are time consuming and expensive. There is a growing interest to develop alternate techniques to establish the reactivity of acid mine tailings and stability of treated waste forms. The Electrochemical Impedance Spectroscopy (EIS) is a reliable non-invasive technique which can be used for quick estimation of reactivity of the potential acid generating tailings. In this paper the utilization of the EIS technique for the estimation of reactivity of tailings is discussed. EIS can also be used to predict the long term stability of different stabilized waste forms.IntroductionMetal contaminated mine drainage is one of the most persistent environmental problems facing the mining and mineral processing industries today. Of all the mine drainage pollutants, acid mine drainage has become a substantial concern because of the potential long-term environmental implications and the accompanying liabilities. The main source of acid mine drainage is the tailings containing sulfide-ores which are generated during the ore processing. When these sulfide minerals, particularly pyrite and pyrrhotite, are exposed to oxygen and water they begin to oxidize. The initial chemical reactions produce acid and the acid dissolves heavy metals present in the tailings. Rainfall and snow-melt flush the toxic solutions from the waste sites into the downstream environment [1-2]. In addition to mining tailings, several Department of Energy (DOE) sites contain wastes which are contaminated with radionuclides and heavy metals."

Jan 1, 1999

By Run-bo Wang, Zhe Wang, Fan-yi Meng, Jian-Liang Zhang

The influence of semicharcoal substitution for coke breeze on sintering performance was investigated by pot-grate sintering test. At a fixed fuel ratio, sinter productivity and strength decreased with the substitution increasing from 0 to 100% due to better combustibility. To enhance the utilization efficiency of 100% semicharcoal, sintering parameters (moisture and suction pressure) was adjusted. With the moisture increasing, sinter performance of 100% semicharcoal increased because of the suppression of semicharcoal incomplete combustion. As the moisture further increasing to 9.0%, sinter quality gave rise to a decrease trend. The results also showed that the increase of suction pressure was benefit for the increase of heat transfer rate, leading to the improvement of heat utilization energy. Measures to enhance magnetite oxidation during sintering are discussed based on current understanding of the fundamentals that control the sintering process.

Jan 1, 2015

By S. N. Lekakh

Experimental work and thermodynamic simulations of cast iron refining were carried out using various additions of alkali and rare earth metals. The refining reactions for sulfur and oxygen removal were studied for melts treated with Mg, Ca, and Ce. The measured data and the results of the computer simulations were in agreement. Experimental kinetic data, together with the thermodynamic calculations, were used for optimization of the amount and sequence of the addition of nodulizers for ductile iron production.

Jan 1, 2009

By Thomas F. Hagelien, Stein Tore Johansen, Svend Graadahl

"The dross appearing at the surface of an aluminium melt consists, in addition to aluminium, of mainly oxide films but also other non metallic inclusions. The inclusion particles are often poorly wetted by the metal and accumulate at the metal surface. However, in impeller stirred reactors for melt refining stirring may be exceedingly strong and inclusions accumulated at the metal surface may be entrained into the bulk metal. Concerning inclusion removal, such effects may deteriorate the effectiveness of melt refining.In this paper we investigate the surface entrainment of buoyant particles in a water model of an impeller stirred refining reactor. Under varying operating conditions the particle concentration in the bulk liquid is measured by laser light attenuation. The observed entrainment of particles is explained theoretically and metallurgical consequences of the findings are discussed.IntroductionIn the modern cast house continuos metal refining and casting is well established. One of the most distinct advances in metal refining has been the introduction of degassers which introduce bubbles into the metal. The bubbles act to remove dissolved elements together with nonmetallic inclusions. In the most efficient degassers stirring by different kind of rotors is applied to increase mass transfer and inclusion removal. However, it has been known from experience in the cast house that for violent stirring the concentration of some types of inclusions may increase from inlet to outlet of the reactor. This phenomenon has so far been attributed to production of dross in the reactor due to oxidation of metal. Due to removal of inclusions by bubbles the dross layer inside the reactor must be expected to increase in thickness by time. The removed inclusions and produced oxides due to strong stirring is removed at regular interval by the operators of the degasser. However, a fundamental understanding of the phenomena which take place in and below the dross layer is lacking. In the present work we add buoyant particles to the surface of a refining reactor and investigate how these particles may be entrained and dispersed into the liquid depending on the flow conditions. Similar investigations for gas stirred ladles have been performed by Taniguchi et al [1] who found that below a critical gas flow rate all particles are trapped at the surface. Above the critical gas flowrate the surface velocity are sufficiently high to entrain the particles. In this situation it looks like all particles are ready for the melt and a balance between terminal velocity and turbulent dispersion determine the concentration in the liquid."

Jan 1, 1999

By M. del C. Ruiz

The extraction of Nb and Ta from a columbo-tantalite of San Luis, Argentina, is being studied by using a pressure reactor and HF as leaching agent. The reagents and products have been characterized by several techniques such as scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDXS), X-ray fluorescence (XRF), X-ray difracction (XRD), surface area (BET) and size particle analysis. Experimental results have shown that the extraction of niobium and tantalum increases with increasing temperature, reaction time and acid concentration. For particle size between +80 and -355 mesh no significant changes are detected. It is also slightly affected by the stimng speed. XRD analysis of the residues did not show formation of new crystalline structures.

Jan 1, 1999

By T. Ikeda, M. Maeda, K. Mita

Galvanized steel sheet is the major product for the automobile industry. Therefore, automotive recycling results in zinc-containing scrap that should be remelted in EAFs. Naturally, the EAF dust is a very important source of zinc for zinc recycling processes. The thermodynamic properties of the Fe-Zn intermetallic compounds formed on the surface of galvanized steel sheet should be clarified to make clear the evaporation mechanism of zinc; however, there are few reports on these compounds because of difficulties in their synthesis. There are various intermetallic compounds in the Fe-Zn system. We synthesized them at about 673K. A specimen was examined chemically and X-ray diffraction was applied to ensure the formation of intermetallic compounds. Material containing two phases was placed in a Knudsen type effusion cell and the mass spectrum studied to evaluate the vapor pressure of zinc. The thermodynamic property of intermetallics was then evaluated through measured intensity.

Jan 1, 2000

By Chen Zhang

Polycrystalline Ti-rich NiTi thin films have been deposited from a single NiTi target using a DC magnetron sputtering system. Free standing film was obtained by using a single crystal silicon substrate. Thickness ofthe thin films is controlled at around 12 pm. In this investigation, the effect of deposition temperature on the microstructure and transformation temperatures of the thin films is studied. Influence of post heat treatment temperatures on the properties of the thin films is also investigated. Transformation temperatures of the thin films are determined by differential scanning calorimetry (DSC). The surface microstructure of the thin films is studied using a scanning electron microscope (SEM), and the crystallinity is determined using x-ray diffractometry. It is found that the thin film deposited on a hot substrate is crystalline even when the substrate temperature is as low as 300°C, while the normal crystallization temperature for an amorphous thin film is around 500°C. The microstructure of the film deposited on a hot substrate shows a very fine grain size. The grain size increases with increasing substrate temperature during deposition. The effect of post deposition heat treatment on grain size is minimal.

Jan 1, 1999

By Niloy K. Nath

Two layer sintering by charging green sinter mix with normal coke rate in the upper layer and reduced coke rate in the lower layer, can substantially reduce the coke rate and also improve the sinter quality by producing more uniform thermal profile through out the bed height. The two-layer sintering process have been analyzed by numerical simulation of the process by a detailed CFD based model, considering all the important phenomena like gas-solid reaction, melting and solidification, flow through porous bed, heat and mass transfer etc. Optimization techniques like genetic algorithm, differential evolution is then applied to evaluate the optimum coke rate in the two layers of the bed to produce the ideal thermal profile and melting fraction in the sinter bed for optimum sinter quality. Through this optimization method both high quality sinter with minimum return fines can be achieved along with reduced coke rate. Application of a genetic algorithm for this type of process optimization has several advantages over the traditional optimization techniques since it can identify global optimum condition and perform multi-objective optimization much easily for complex industrial process like iron ore sintering. Keywords: Two-layer Sintering, Iron Ore Sinter Quality, Ergun's Equation, Gas-solid reaction, Melting Fraction, Multi Objective Optimization, Pareto Set, Genetic Algorithm

Jan 1, 2003

By F. J. J. van Loo, J. K. Kivilahti, M. Paulasto

"Activation mechanism and interfacial reactions in brazing of ShN4 with different AgCuTi filler alloys has been investigated thermodynamically and experimentally. During brazing the AgCuTi filler alloy is divided into two liquids Ll and L2, where the (Cu,Ti)-rich liquid L2 gathers at the ShN4 interface and reacts with it. The concentration of Ti in L2 is high, but due to the strong attractive interaction between Cu and Ti, the activity of Ti in L2 is considerably low. In reaction between ShN4 and Cu-containing brazes a Ti-Cu-Si-N compound is typically formed at the interface. In absence of Cu, in joints brazed with AgTi based filler alloys, extremely Ti-rich solution reacts with ShN4 and as reaction products TiN and TisSh[N] are formed. IntroductionAdvanced ceramics like silicon nitride are increasingly used as structural components in demanding applications as well as in electronics industry. Complex, multicomponent structures for engineering applications generally require interconnections and therefore joinability of ceramics largely determines the possibilities of metal-ceramic structures to enable demanding functions. Brazing with active filler metals, most of which are based on the Ag-Cu-Ti system, has been commonly employed for joining of ShN4 to other ceramics and metals. The interfacial microstructures formed when ShN4 is brazed with Ag-Cu-Ti braze alloys have been discussed in several recent studies [1-7]. However, some inconsistencies exist in the reported results. The formation of layers of TiN and titanium silicides, possibly TisSh, next to the ShN4 has been reported in several studies [1-5], while in another investigation, a layer of an orthorhombic TiSi- Cu-N phase was found beyond the TiN layer [6]. In few investigations the thermodynamics of the ShN4-Ti system has been considered, but no detailed thermodynamic analysis of the chemical interactions between the braze and ShN4 has been provided. In order to resolve which chemical reactions are possible under various joining conditions and thereby to be able to control the brazing of ShN4 the reactions in brazing has to be studied using both microstructural and thermodynamic analysis."

Jan 1, 1996

By Qingwei Qin, Ping Xue, Guangqiang Li

Ausmelt furnace slag contains about 0.9% Cu (mass %). With increasing the amount of Ausmelt furnace slag, the recovery of copper from it will produce an enormous economic yield. The recovery of copper by floatation from slow cooled Ausmelt furnace slag was studied in this paper. The phases and composition of the slow cooled slag were analyzed. The factors which affected the copper recovery efficiency such as grinding fineness, pH value of flotation medium, different collectors and floating process were investigated. It was shown that the size distribution of the primary grinding and secondary grinding of middling were 75% for particles less than 0.074mm and 82% for particles less than 0.043mm respectively. The closedcircuit experimental results with butyl xanthate as collector in laboratory showed that the copper grade reached 16.11% and the recovery rate of copper reached 69.90% and the copper grade of tailings was only 0.2%.

Jan 1, 2015

By Jafar Safarian, Merete Tangstad, Leiv Kolbeinsen

"Silicon and its binary alloys have several applications in metallurgical, chemical, photovoltaic and semiconductor industries. Silicon goes to its liquid state within its production, refining and when it is alloyed with other elements. Therefore, the characterization of silicon melts thermodynamics is important and useful. The liquidus and activities in several silicon binary systems have been recently calculated by the application of two liquidus constants, which were established using the experimentally determined liquidus data. In the present study, the thermodynamic properties of six silicon binary melts, which are simple eutectics, are calculated by analytical approaches. In this case, the changes in the partial and integral Gibbs free energies and enthalpies of mixing are calculated and compared with the experimental data in literature. The enthalpies are calculated by two methods and the calculation results are compared to the data from the literature. It is shown that thermodynamic properties of silicon binary melts can be accurately predicted without the use of complicated thermodynamic software.IntroductionSilicon and its alloys have several industrial applications. Silicon is used for making aluminium-silicon alloys to produce cast parts, mainly for automotive industry. Silicon in the form of ferro-silicon is used to deoxidize and alloy steel and cast iron. The photovoltaic (PV) industry has had a rapid growth in the recent years and silicon is the dominant material used for the fabrication of solar cells. Silicon is primarily produced through carbothermic reduction of quartz in electric arc furnaces and the produced metallurgical grade silicon (MG-Si) contains around 1 wt% impurities. It is further refined to produce solar grade silicon (SoG-Si) with above 99.9999 wt% Si to fulfil the chemical requirement for PV application. Since molten silicon is processed all along the metallurgical route, obtaining fundamental thermodynamics knowledge about silicon melts is valuable for the related industries."

Jan 1, 2012