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By K. Yamaguchi, Y. Takeda

"Partial pressure - temperature - composition correlation diagrams of the Ga-As, In-As, Ga-P and In-P systems were contracted based on the obtained experimental data of the phase diagram and thermodynamic properties for the III-V systems. The total vapor pressures of arsenic or phosphorus at melting point of GaAs, InAs, GaP and InP were determined as 101, 10.1, 1510 and 253 kPa, respectively, at the corresponding melting points of 1509, 1211, 1739 and. 1336K , These diagrams are applied to the analysis of the horizontal Bridgman method and the liquid phase epitaxial growth technique. On the other hand, the analysis of the equilibrium state of the. chloride-CVD process was carried out using the data of the Gibbs energy of the compounds obtained by· authors.IntroductionThe group III-V compound semiconductors ate important materials used in optoelectronic liquid high speed electronic device. The crystal growth of the III-V compounds can involve processes that require contact between the solid, liquid and vapour phases at near equilibrium condition. Examples of processes that involve contact between the solid, liquid and vapour phases include bulk crystal growth such as the horizontal Bridgman and the liquid encapsulated Czochralski method and liquid epitaxy, and between the solid and vapor include chemical vapour deposition and molecular beam epitaxy. Therefore, the knowledge of the phase diagram and thermodynamic properties for the III-V binary alloys is essential for the analyses of crystal growth techniques of III-V compounds.For these reasons, a series of different · types calorimetric measurements had been carried out: (1) The heat contents of alloys for the Ga-As, In-As, Ga-P and In-P systems by a drop calorimeter [1;2,3]; (2) the heats of formation of the GaAs, InAs, GaP and InP compounds by a twin solution calorimeter [4]; and (3) the standard entropy of these compounds by an adiabatic calorimeter [5]. Based on the third law method, the Gibbs energies of these compounds were derived from the heat capacity, standard heat of formation and standard entropy data obtained by authors. Integral molar thermodynamic quantities of the liquid III-V .alloys were also determined from combining the heat contents of alloys with standard heat of formation and standard entropy data of the compounds· by applying the thermodynamic analysis method developed by Oelsen [6]. In the present study, the thermodynamic calculations for the crystal growth processes of the III-V compound were carried out using newly experimental data of the phase diagram and thermodynamic .properties measured by authors"

Jan 1, 2000

By Ramiro Escudero G.

Since the introduction of column flotation almost forty years ago the column technology has grown into several non-mineral applications such as among others the effluent treatment, soils recovery and de-inking of recycled paper. Recent studies have demonstrated that particular characteristics of the dispersion (bubble size, gas holdup, bubble surface area flux) are needed for a given flotation column duty. In this work, two kind of spargers were tested (i.e., internal and external) using a 4 inch column lab in a two phase system. Results show that the external sparger provides a dispersion with characteristics that include those produced by the two internal spargers.

Jan 1, 2003

By J. Leon-Torres, D. M. Stefanescu, P. A. Curreri, S. Sen

"Experiments were performed under terrestrial gravity (lg) and during parabolic flights (10·2 g) to study the solidification and macrosegregation patterns of Al-Cu alloys. Alloys having 2% and 5% Cu were solidified against a chill at two different cooling rates. Microscopic and Electron Microprobe characterization was used to produce rnicrostructural and macrosegregation maps.In all cases positive segregation occurred next to the chill because of the shrinkage flow, as expected. This positive segregation was higher in the low-g samples, apparently because of the higher heat transfer coefficient.A 2-D computational model was used to explain the experimental results. The continuum formulation was employed to describe the macroscopic transports of mass, energy, and momentum, associated with the solidification phenomena, for a two-phase system. The model considers that liquid flow is driven by thermal and solutal buoyancy, and by solidification shrinkage. The solidification event was divided into two stages. In the first one, the liquid containing freely moving equiaxed grains was described through the relative viscosity concept. In the second stage, when a fixed dendritic network was formed after dendritic coherency, the mushy zone was treated as a porous medium.The macrosegregation maps and the cooling curves obtained during experiments were used for validation of the solidification and segregation model. The model can explain the solidification and macrosegregation patterns and the differences between low- and high-gravity results."

Jan 1, 1999

By Jesse White, Tyler Salisbury

Research projects contain many stages of development from the conception of an idea to a fullscale commercial operation. The transition from laboratory-scale research to bench-scale roasting can represent a significant increase in complexity and cost, depending on how many variables are being evaluated. Thermogravimetric analysis (TGA) can simulate roasting conditions and produce a small sample for chemical analysis or materials characterization. A simultaneous thermogravimetric and differential scanning calorimetry (TG–DSC) can identify endothermic and exothermic reaction temperatures. Using thermal analysis, some of the process variables can be tested and eliminated such as ore and reagent blends, retention times, operating temperatures, and some atmospheres.

Jan 1, 2015

By Gus Van Weert

Hydrometallurgical oxidation of sulphides is capital and energy intensive, with autoclave and bio-technology competing for lowest overall cost status. The use of surface aerators instead of stirred tank reactors could provide lower costs for bio-oxidation of concentrates. With this in mind, the Delft Inclined Plate reactor was designed with inclined plates above a settler shaped reactor to continuously return slurry from the lowest point in the settler to the surface of the liquid. The multiplate superstructure overcomes the scale-up restriction of the standard circular surface aeration patterns. DIP aerator energy and volume requirements for oxygen transfer from air will be presented in terms of kg O2/kWh and kg O2/m3/h transferred as a function of wt % sand in the slurry and compared to stirred tank performance. Scale up from the 4 m3 pilot unit will be discussed.

Jan 1, 1996

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 N. V. Gorelikova

A new type of zirconium mineralization has been recognized in the Devonian volcanic rocks from an orogenic depression in the Central Kazakhstan. The most characteristic features of this deposit are the fine-grained nature of the zirconium mineralization, an unusual texture of the zirconium ores, and a close association of zirconium with phosphorus in the ores. Zircon grains form fine globular aggregates with the features of hexagonal crystal habit. In addition to crystalline zircon, the ores contain metacolloidal zircon, similar to hydrozircon. The morphological and textural features of the zirconium ores suggest that the deposition of ore deposits took place at a low temperature from colloidal solutions. It is believed that this deposit should be considered to be a new type of zirconium mineralization that is related to low-temperature hydrothermal processes.

Jan 1, 1995

By Pinakin C. Chaubal

Today?s steel industry is in a vibrant and resurgent mode. This transformation has been in the making for some time now. Over the last few decades, the industry was steadily transforming itself into becoming a high tech industry. New technology was adopted, efficiencies were enhanced, lean manufacturing concepts were brought in and a strong customer focus was developed. Today?s mills employ sophisticated instrumentation, computerized monitoring, on-line smart systems etc. driving processes that are producing at rates of many tons/minute. All this is not possible without judiciously using the latest available technologies in various fields and developing a more sophisticated work force. Prof. Sohn has been a pioneer in driving the concept of process engineering in process metallurgy. In this paper the focus is on some aspects of process engineering ? primarily process modeling - as applied to iron and steelmaking processes. Examples are shown to demonstrate how problems have been addressed. Some thoughts on future directions are presented.

Jan 1, 2006

By Barry J. Welch

The production of primary aluminium can potentially lead to metal that, with minimum treatment, meets a high purity standard. Smelters that can achieve a significant proportion of their production in this manner have a competitive edge which is of growing importance as the use grows for such items as compact discs and the like. Superimposed on the desire to produce high quality metal are stringent environmental requirements that the industry must adhere to. The environmental 'legislation focuses on fluoride emissions and the approach adopted is towards a zero waste management philosophy. The fluoride recycling process does, however, result in volatile impurities being captured and recycled to the cell. Aluminium has an extremely high reduction potential and this results in a significant proportion of the recycled impurities being reduced at the electrolyte metal interface and thus contaminating the metal. This paper reviews sources of impurities and the impact of the operating procedures adopted on metal treatment.

Jan 1, 1996

By C. Damiani

The Chuquicamata smelter, operating since 1952, has gone through several developing stages which have been characterized by the addition of peak technology for copper concentrate smelting (Teniente converter and Outokumpu flash furnace) with an intensive use of technical oxygen, which has permit-ted to partially discontinue the reverberatory furnace utilization. This paper shows the main indicators and operational practices at present, as well as those concerning maintenance aspects. Finally, the most relevant topics related to the future development of the smelter are mentioned with special remarks on the Decontamination Plan, which allows US to keep the high level of production, reducing the emission of contaminants according to the legal requirements in force.

Jan 1, 1993

By V. Vergara

Four copper composites were obtained by mechanical alloying, using as dispersed phases of four carbide powders; they were: boron carbide, chromium carbide, silicon carbide and zirconium carbide. The purpose of this work was to study some characteristics of these compounds and their feasibility for use as materials for electrical equipment. Raw materials used were copper powder finer than 150 mesh, and 2-4 vol % of powder carbides finer than 325 mesh. The alloying process was carried out using both a Spex 800-D mill with tungsten jars and balls and a hardened stainless steel jar and balls, the purpose of which was to measure the degree of contamination induced by the milling media. The changes in particle size, morphology and microstructure of copper alloys were studied with SEM and TEM for each alloyed powder. The degree of saturation of copper by the carbides was measured by X-ray diffraction. Sound samples were obtained by hot isostatic pressing at 1073°K. The best characteristics were obtained for the compound copper-chromium carbide, based on their hardness, tensile strength and electrical conductivity values. The other alloys failed due to their excessive brittleness after hot pressing.

Jan 1, 1999

By L. Filip

The roast-leach-electrowinning (RLE) process for zinc was modified to treat two typical complex concentrates containing zinc, lead, copper, gold and silver. Laboratory testwork results indicated that the optimum roasting temperature ranged from 700 to 800°C, in order to produce acceptable residual sulfur levels. The calcined concentrate was subjected to a three-stage leach sequence. The resulting leach solution was purified by hematitic precipitation and directed to the recovery of copper and zinc by solvent extraction and electrolysis. Alkaline smelting and subsequent electrolytic purification recovered the lead and precious metals from the leach residue. A flowsheet was developed based on the laboratory testwork results, and demonstrated in a large-scale pilot plant. The recoveries produced during the pilot plant operation ranged from 90 to 92% for zinc and copper, 85% for lead and 90% for gold and silver, respectively.

Jan 1, 1999

By I. A. H. Schneiderl

Eichhornia crassipes approaches being a scourge in many parts of the world, .choking waterways and hindering transport upon them. At the same time it is known to readily abstract heavy metal ions from water and, thus, aids in the removal of heavy metals found in such waters. This paper considers the possibility of using specific parts of the plant as an inexpensive adsorbent for the removal of heavy metals from contaminated chemical and mining industry waste waters. In particular the root of the plant was found to be an excellent accumulator of 'heavy metal ions including uranium from solution. It is. also suggested that dried roots of the plant ?might be placed in simple bags and used in a very low cost metal ion removal system.

Jan 1, 1995

By A. René Silva

The separation of Fe(III) from simulated Ni(II) solutions using different ion exchange resins was studied. The resins tested included cation exchangers with sulfonic and carboxylic groups and chelating resins with iminodiacetic, aminophosphonic, and mixed sulfonic and phosphonic groups. The dosage of resins was varied from 0.1 to 0.5 g/mL to study the impact of resin type and dosage on iron separation from simulated nickel leach solution containing 25 g/L Ni(II) and 25 g/L Fe(III) at pH 1.5. Also, the effects of different metal ion concentrations, Fe (III):Ni(II) ratios in solution, pH, and adsorption times were investigated. Experimental results demonstrate that all the chelating resins selected favored the adsorption of Fe(III) over Ni(II) with high Fe(III) loading. Soft cation exchange resins also favored the adsorption of Fe(III) over Ni(II), but no significant Fe(III) loading was observed. In contrast, strong cation exchange resins did not show adsorption preferences. The most efficient separation was observed using resin with aminophosphonic groups at resin dosage of 0.2 g/mL, having a Fe(III) adsorption over 94% and Ni(II) adsorption below 5%.

By G. Gao

Flyash from municipal solid waste (MSW) incinerators is frequently classified as a characteristic hazardous waste due to its lead and cadmium content. Extensive investigation has therefore been carried out to detoxity the flyash by leaching and to recover lead, cadmium and zinc. Detoxification can be accomplished by leaching in HCI/NaCI solutions. Optimization of leaching conditions for effective detoxification and subsequent metal recovery can be achieved by controlling the acidity of the lixiviant and flyash to lixivaint ratio. Lead and cadmium In the leaching solution is recovered by cementation with zinc dust. Leaching and cementation experiments have shown that zinc concentrations suitable for electrowinning, > 15 g/liter, can be achieved. Experiments have also been performed to determine the effects of pH, particle size of the zinc dust used, quantity of zinc added and dissolved impurities on the cementation kinetics. After recovery of lead and cadmium, electrowinning or electrowinning coupled with solvent extraction can be used to recover zinc. A process flowsheet is presented.

Jan 1, 1991

By Peter V. Barr

Despite the advent of modem firing control systems reheating furnace operations frequently allow significant thermal excursions in the discharged slabs or billets after furnace delays. Although HSM furnaces are not immune to this and other related problems, mini-mill operations are most vulnerable due to their more frequent delays and (often) less sophisticated control systems. In order to reduce these problems control systems will commonly include a thermal model, operating either on-line (interacting directly with the controller logic) or in an advisory, off-line mode. Using a new 'fast' thermal model, the paper examines the thermal response of a typical mini-mill furnace during both delays and the subsequent recovery period. A variety of firing strategies are explored and compared on the basis of maintaining thermal excursions within allowable limits for rolling. Other factors, such as the potential for overheating of billets within the furnace during delays and the overall thermal state of the furnace, are also considered in some detail. Although common practice, the use of conventional thermocouple zone temperatures for furnace control during and after delays is shown to be a dubious proposition. Keywords: Reheat Furnace, Modeling, Process Control

Jan 1, 2003

A strategy is presented for a relatively. "low-tech" means for decontamination of streams . containing .low concentrations of toxic metals. Metal ion solutions were . circulate through fluidized beds of activated carbon which support bio-films ?of bacteria .that naturally excrete exopolysaccharides. The attached 'biomass is shown to significantly enhance nickel, cadmium and silver extraction from dilute solutions (5- l00mg/l). By heat treating (at 300º C) the metal/biomass/carbon particles, bio-sorbed silver was subsequently fixed to the carbon surface. This approach to metal decontamination may therefore also provide a route for dispersing and fixing catalytic metal particles over an activated carbon surface.

Jan 1, 1991

By Jian Li, P. Liu, R. Zhang and J. Lo

In the past decades, focused ion beam (FIB) has evolved into a powerful microscope that provides capabilities that no other microscopes can offer. The combination of high-resolution imaging and stress-free ion beam cross sectioning provides valuable microstructure information both at the specimen surface and beneath. FIB techniques are also the preferred method to prepare site-specific transmission electron microscope (TEM) specimens. CanmetMATERIALS owns a world-class microscopy facility, where advanced microscopy work provides strong supports to research programs that cover a wide range of subject areas. This paper is aimed to provide a few practical examples of FIB applications in microstructure characterizations that include cross-sectioning and imaging, serial sectioning, and advanced TEM specimen preparation in materials research at CanmetMATERIALS.

Jan 1, 2015

By P. R. Taylor

Titanium carbide and titanium diboride powders have been successfully synthesized by direct treatment of ilmenite concentrates in a non-transferred arc thermal plasma reactor. Methane gas was used as the reducing agent and boron oxide was used as the boron source in these processes. Free energy minimization plots were used to predict the behavior of each system under different molar ratios and operating conditions. Products were characterized by XRD, SEM and chemical analytical techniques. The average size of the ceramic product is in the submicron range. Metallic iron apparently is finely deposited on the surface of the titanium carbide or titanium diboride particles. Minor impurities such as silica, manganese and zircon were converted to the carbide form.

Jan 1, 1995

By Pinakin C. Chaubal

Today?s steel industry is in a vibrant and resurgent mode. This transformation has been in the making for some time now. Over the last few decades, the industry was steadily transforming itself into becoming a high tech industry. New technology was adopted, efficiencies were enhanced, lean manufacturing concepts were brought in and a strong customer focus was developed. Today?s mills employ sophisticated instrumentation, computerized monitoring, on-line smart systems etc. driving processes that are producing at rates of many tons/minute. All this is not possible without judiciously using the latest available technologies in various fields and developing a more sophisticated work force. Prof. Sohn has been a pioneer in driving the concept of process engineering in process metallurgy. In this paper the focus is on some aspects of process engineering ? primarily process modeling - as applied to iron and steelmaking processes. Examples are shown to demonstrate how problems have been addressed. Some thoughts on future directions are presented.

Jan 1, 2006