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By William Petruk

The primary requisite for a successful extractive metallurgy operation is to grind an ore fine enough to liberate the minerals so that they can be concentrated, or to expose mineral surfaces so that the minerals can be leached. The ease or difficulty of liberating or exposing the mineral grains is dependent upon the mineral textures such as grain size, crystallinity and bonding between mineral grains. In particular, mineral grains with straight grain boundaries and a weak bonding to other minerals are easily liberated and readily concentrated into high grade concentrates. In contrast mineral grains that have re-entrant boundaries and are strongly bonded to their neighbours are not easily liberated and will not produce high grade concentrates, even with regrinding. Similarly, inclusions that occur along fractures and grain boundaries can be readily exposed and leached. Whereas minute random inclusions in large grains will not be liberated or exposed unless they occur along planes of weakness.

Jan 1, 1995

By Klaus Bauckhage

Phase-Doppler-anemometry (PDA)-measurements have to be taken from representative measuring positions from inside the spray cone, helping - with the support of simulated data of improved process models - to describe the multiphase flow situations within the spray cone - and accordingly to that - the heat transfer conditions for the rapid cooling and (partly) solidifying melt droplets before their impact onto the substratddeposit. Simulations and PDA-measurements thus give the base to confirm the hypothesis of the existence of a semisolid mixed-layer and it's influence on the resulting material structure during compaction. The dispersed particles in the spray cone exhibit a cooling and solidification process within a split of a second, which leads - as far as the particles solidify - to a dendritic structure with very short dendritic arm spacings. This causes within the particles extremely short distances for the following equalizing diffision processes taking place on a high temperature level (between liquidus and solidus) in the semisolid mixed-layer of the deposit and explaining the short residence times within this zone of only seconds up to a few minutes. This and the fact that the globular structure of the mushy zone (in the semisolid mixed-layer) leads to an unidirectional crystallization process over very short distances also explains the chemical and morphological ,homogeneity of the sprayed material. The dynamics of these process steps, the very special buffer function of the mixing layer during parameter variations as well as the controlled cooling process of the preform in order to avoid hot cracks influence the quality of the material. Due to the necessity of measuring and controlling the particle bound mass-, momentum- and enthalpy- fluxes to the deposit the PDA-technique has been adapted and modified in order to receive in-line and (in the future) also on-line data from the dynamics of the multiphase flow conditions within the spray chamber.

Jan 1, 1999

By Yasuhiko Ito

"This talk is concentrated on the topics of compound film formation on the substrate electrode by interdiffusion of substrate element and electrochemically deposited species and/or by direct electrochemical implantation of the component element of the film into the substrate. As a typical example, electrochemical implantation of nitrogen atom into Ti metal to form TiN surface film is described. Another example is the formation of various kinds of intermetallic compound films including Ni2Y, Ni2Dy and Pd3 Y by the electrochemical implantation of lanthanoid elements into transition metal electrodes. By combining these two methods, Sm-Fe-N ternary material film also could be formed. The principle and application of the ""electrochemical implantation"" are discussed in detail.IntroductionGenerally speaking, surface film formation by molten salt electrochemical process can be divided into the following three categories:(i) single element film formation on the electrode by electrodeposition,(ii) compound film formation on the electrode by electrocodepostion of more than two elements, and(iii) compound film formation on the substrate electrode by interdiffusion of substrate element and electrochemically deposited species and/or by direct electrochemical implantation of the component element of the film into the substrate.This talk is .concentrated on the topics of category (iii), especially on the electrochemical implantation. Typical example can be seen in the electrochemical implantation of nitrogen atom into Ti metal to form TiN surface film. Another example is the formation of various kinds of intermetallic compound films including Ni2 Y, Ni2Dy and Pd3 Y by the electrochemical implantation of lanthanoid elements into transition metal electrodes. By combining these two methods, Sm-Fe-N ternary material film also could be formed. The principle and application of the ""electrochemical implantation"" are discussed in detail with examples above as well as other experimental results also obtained very recently in the author's laboratory."

Jan 1, 2000

This report presents overview of the authors' results of thermodynamical investigation of some important metallurgical processes and phenomena. Among them: carbo thermal reduction of silica, and boron oxide, silicon carbide obtaining from different precursors, investigations on copper and manganese ores processing, investigations on pollution from different sources. Special attention is paid-to thermodynamical approach to investigation and estimation of multi component multi element compositions stability, developed by the authors. Also are discussed some auxiliary but' important for the thermodynamical investigations issues.

Jan 1, 1997

By Alexander I. Raitchenko

"Although one takes into account only thermal expansion usually at analysis of convection onset, the essential factors include magnetic and electric fields. If Lorentz-force originating from intercrossed electric and magnetic fields' action is directed downwards its effect strengthens gravitational action, and value of critical Rayleigh number (limit value for convection onset) must decrease; increasing of critical Rayleigh number should be observed in case of Lorentz-force directed upwards. Extent of such an influence is determined by relation of Lorentz-force to hydrostatic head in gravitational field. Competition between electromagnetic force due to nonuniformity of electroconductivity (on account of its temperature dependence) and electromagnetic buoyancy force may have ambiguous effect: both increase or decrease of critical Rayleigh numbers. Proposed conception is applicable to analysis of situations in liquid conductors and conductive gases.IntroductionStatic or dynamic situations in fluid media are determined besides properties of these media by a variety of external influences. However one correlate~ the onset of the convection and its development with influences of the minimum quantity of external causes frequently. Most known and usual factors are the gravitational and temperature fields. The number of processes includes heat generation in media volume, and theoretical analysis in these cases takes into account this interior heating together with boundary temperature conditions. But explanation of many natural and technical events is not complete and cogent within limits of thermo-gravitational terms. The whole complex of acting factors which influence convective processes in techniques and nature is greater in many cases. In particular the action of · electromagnetic nature often has not less importance than gravitation one. Stability or instability of a current layer in the plasma must be determined by non-uniformity of electroconductivity owing to non-uniformity of temperature [1]. The presence of Joule dissipation in the plasma through which the electric current flows stipulates initiation of origin of overheated instability [2]. It is known that electroconductivity of arc in the boundary zone changes sharply with radial distance [3], and this must influence its stability essentially. If the intercrossed electric current and magnetic field begin to act on an electroconductive fluid besides the non-uniform temperature field and the gravity, the conditions for the onset of the convection change radi- . cally: both the temperature field and their solutions have to be changed also. The analysis of equilibrium single-time correlation functions of fluctuations must be employed for situations with enlarged number of factors as this was in case for the Rayleigh-Benard problem where the object is a horizontal layer of liquid. This can be carried out by taking into account the detached forces' correlations [ 4, 5]"

Jan 1, 1999

By Georgios N. Anastassakis, Nickolaos Georgiou

"Soil contamination by oil as well as by other organic pollutants poses a major problem to the environment. Various methods have been used to remove organic contaminants from soil, such as: biological, thermal, chemical and physical. Methods based on Mineral Processing principles have also been used (cyclone separation, gravimetric separation, attritioning and washing). This paper studies the possibility to remove a rich-in-contaminant soil fraction by applying flotation. The contaminated soil was artificially prepared by mixing soil with diesel fuel. Sodium dodecylsulfate (SDS) and a tertiary amine (TA) were used as collectors. The effect of collector quantity added and conditioning time was studied. The results showed that the removal of a rich-in-contaminant soil is feasible while a clean fraction is also obtained. In several cases, the removal of oil-contaminated soil approaches or reaches 100%. Introduction Human activities are intimately associated with environmental pollution to the air, water and soil, as well. Soil pollution from inorganic and organic compounds is of equal importance with that of air and water, as it results in soil degradation and its concomitant problems with respect to meeting the human needs (house building, agriculture etc). Heavy metals along with their compounds are encountered among the most usual soil inorganic pollutants. The corresponding organic soil-pollutants are oil, oil-derivatives, pesticides, various aromatic (benzene, phenols, cresols, toluene etc) and poly-aromatic (naphthalene, anthracene etc) hydrocarbons, as well as various other organic compounds (pyridine, cyclo-hexane etc). Oil remains the basic energy source sharing 38% of the global needs, being followed by coal and gas with a share of 26 and 21% correspondingly [1]. The entire activities related with oil production, transport and consumption promote pollution in the air, water and soil. Consequently, soil pollution from oil is favoured at refineries, storage sites (due to possible pipe and tank leakage, tank cleaning works, loading and transportation) and, finally, at the oil-selling sites. Oil (or diesel-oil) fuel is a mixture of hydrocarbons, with 10-20 carbon atoms in the chain of each. It is mainly composed of paraffins, naphthenes and various aromatic compounds. In general, oil is composed of 20-30% in aromatic compounds, 5-6% in naphthenes and the rest is paraffins [1]."

Jan 1, 2008

By J. L. Jambor

Sulfide-rich tailings accumulated in a 4l-hectare impoundment at the Waite Amulet minesite near Noranda, Quebec, have undergone partial oxidation and destruction of the principal sulfides (pyrite and pyrrhotite) in the vadose zone. Mineralogical studies and whole-rock chemical analyses of 18 samples from 3 boreholes along a cross-section of the tailings pile indicate that the principal chemical manifestations of the alteration are a pronounced depletion in sulfide-sulfur, and an enrichment in total Fe as Fe203' Other elements such as Al, Mn, Mg, Ca, Na, and K in the solids show erratic or inconsistent variations, but a trend to Si enrichment in the oxidation zone is clear. The trend is interpreted to be a relative enrichment whereby the proportion of the stable silicate minerals has increased as a consequence of the consumption of pyrite and pyrrhotite in the oxide zone.

Jan 1, 1989

By Bowen Li

Copper vermiculite is a special nanomaterial with excellent antibacterial and antifungal performance. By means of ion exchange, copper vermiculite containing up to 5.8wt% copper was prepared. The chemical and mineralogical characterization of the material was investigated in this study based on the XRD, AAS, TEM and EDS analysis, as well as the calculation of crystalline parameters and crystal chemical formula. Cu2+ and Mg2+ have similar atom radius and same electrovalence. Correspondingly, the structure character of copper vermiculite is very close to that of standard Mg-vermiculite. Most of the CU21 may have occupied the interlayer cationic positions in the form of hydrate in vermiculite. However, some may have entered into octahedral coordinate positions. The values of au and bo of the copper vermiculite crystal cell have no obvious change compared to that of original vermiculite micropowder, but the Co value decreased slightly, which is desirable for the stabilization of the Cu2+ in copper vermiculite.

Jan 1, 2003

By M. Bhattacharya, A. Dutta, P. Barat

"Pinning of dislocations at nanosized obstacles like precipitates, voids and bubbles, is a crucial mechanism in the context of phenomena like hardening and creep. The interaction between such an obstacle and a dislocation is often explored at fundamental level by means of analytical tools, atomistic simulations and finite element methods. Nevertheless, such studies fail to predict the effect on the overall plasticity on account of insufficient information about the underlying statistics of this process comprising a large number of dislocations and obstacles in a system. Here we propose a new statistical approach, where the statistics of pinning at idealized spherical obstacles is explored by taking into account the generalized size distribution of the obstacle along with the dislocation density within a three-dimensional framework. The application of this approach has been demonstrated for dislocation pinning at nanovoids in neutron irradiated type 316-stainless steel.IntroductionPresence of nanoscale obstacles like precipitates, voids and bubbles play a crucial role in determining the deformation behavior of a crystalline solid on account of the interactions between the line defects and such localized obstacles. In the context of the glide motion of dislocations, the obstacles can offer resistance to a moving dislocation, thereby causing a hardening effect [l-3]. In some other cases, inclusions like voids and bubbles can affect the rate of dislocation climb through diffusive [4] and non-diffusive [5] mechanisms. Over the last few decades, numerous studies have been performed to gain an insight of the dislocation-obstacle interactions at a fundamental level. These include the interactions responsible for the hardening effect, in addition to those pertaining to the non-conservative motion of dislocations.Although the elementary mechanisms of the various dislocation-obstacle interactions have been vastly explored and understood by means of analytical theory and numerical simulations, it remains difficult to quantitatively understand their effects on the macroscopic deformation behavior. This is due to the fact that their influence on the gross plastic deformation of a bulk sample would be the collective outcome of a large ensemble of such interactions. As a result, it becomes infeasible to predict the bulk deformation behavior of a material until the statistics of pinning of the dislocations at the localized obstacles is available. In the context of precipitate hardening, some well known attempts to extract the pinning-statistics were made by Friedel-Fleischer [6] and Mott [7] by analytical means, which were later tested through simplified 2-dimensional in-silica modeling [8]."

Jan 1, 2014

By Yuya Nakai, Kuniaki Murase, Kazuhiro Fukami, Atsushi Kitada, Ken Adachi

Concerning nodulation in copper electrore fining, it has been reported that short circuits caused by nodulation have the largest impact on the current efficiency. Therefore, to improve the current efficiency, it is important to prevent nodulation. In this research, the nodulation growth was investigated by replicating nodulation in the laboratory. The experiments were conducted by cathodic electrodeposition on copper plates attached to copper sticks of various heights. The nodulation was analyzed in terms of growth rates versus the initial heights.

Mar 1, 2018

By T. T. Chen

Canadian Electrolytic Zinc has developed the "cement-stabilization of jarosite residue" Garofix) process to stabilize zinc plant jarosite residues for disposal. The cement-jarosite mixtures cure quickly, have good mechanical strength and low hydraulic permeability; they possess good neutralizing capability and chemical stability. In the jarofix process, Portland cement partly decomposes jarosite to form (SO4MOH)12.nH2O, ferric hydroxide and an alkali sulphate. Approximately 40% of the jarosite reacts in mixtures containing 30% cement. The jarofix product also contains various Ca-Al-Fesilicate-sulphate-hydrate phases and gypsum, which bond the individual particles together imparting mechanical strength and reducing the permeability. Most of the reactions take place in the first few hours of curing. Ammonium jarosite is slightly more reactive than sodium jarosite but releases NH3 gas; water-soluble Zn in the jarosite residue is stabilized in the cement reaction products.

Jan 1, 1996

By Dong Hoon Han

The simultaneous sulfation by sulhr dioxide and oxygen of CaO and MgO in calcined CMA (calcium magnesium acetate) were investigated. he experiments were carried out in the temperature range from 700 to 830 "C and at the SO2 concentrations of 0.3 to 1 mol %. The oxygen concentration was kept at 5 %. Each sample was calcined completely before the temperature was lowered to the sulfation temperature. According to the ranges of partial pressure of sulhr dioxide and temperature, there exist three regions for the sulfation reaction: region I in which neither oxide is sulfated, region I1 in which only CaO is sulfated, and region 111 in which both oxides are sulfated. It was shown that the MgO in calcined CMA is sulfated at a rate comparable to that of CaO by forming a mixed sulfate phase. Thus, unlike MgO contained in other desulhrization materials, the MgO content in calcined CMA can be fully utilized for flue gas desulhrization.

Jan 1, 1999

By T. K. Bundtzen

Placer gold in the Iditarod and Innoko mining camps of western Alaska is derived from a suite of comagmatic, Late Cretaceous to Early Tertiary, alkali-calcic, meta-aluminous. volcanic-plutonic complexes and peralumi-nous rhyolite sills that intrude Mesozoic flysch. Heavy-mineral concentrates from 42 mining operations and streams draining known mineralized areas in the igneous complexes contain placer gold and a variety of ore minerals derived from epithermal to hypothermal conditions of formation. The minerals include cassiterite, ilmenorutile, samarskite, cinnabar, scheelite, chromite, stibnite, silver sulfosalts, monazite, and zircon. Results of the study show that 1) cinnabar. stibnite, and quartz formed with the bulk of the placer gold in an epithermal lode environment, 2) chromite appears to have originated in mafic phases of monzonite plutons and alkalic basalts, and 3) niobium-tin-tungsten-uranium-silver values may have been derived from stockwork accumulations in cupolas of monzonite plutons.

Jan 1, 1987

By Lennart Hedlund

There is today a long and well-documented experience of the use of Boliden "Kaldo' technology for treatment of various feed matedals. The process is In commercial' operation in the Boliden Mineral's Rönnskär plant In Sweden for treatment of copper scraps and lead concentrates (In campaigns). This plant was built In 1976 for treatment of lead dusts from the copper plant but later modified to take other raw materials. Boliden's Kaldo techr:lology Is also In operation since 1991 for treatment of low-grade copper scraps In Enlrlsorse's plant In Porto Marghera (Venice), Italy. The plant is producing 25 000 tons of blister copper ,per year. The Kaldo furnace Isa high :Intensity smelting unit, where several successive treatment steps can be done In the same vessel. The furnace can be totally enclosed to protect the working environment, and the small off-gas volume can easily be dedusted. Input materials can vary over a very wide range, the products will be a dump slag with low (0,5%) copper and lead contents and black copper or blister copper. The dust from the process can be used for zinc production. A new development is autogenous smelting of scrap in a Pierce-Smith converter, implemented at Compagnie Générale d' Èlectrolyse du Palais in France.

Jan 1, 1995

By Hua-qing Li

Electromagnetic stirring process effectively improves the casting quality of metals. In this paper, the physical simulation experiment, in which the molten copper is displaced by mercury, was designed. The factory test parameters were determined according the simulated data. The flow behavior of the mercury to be stirred as well as the relations between the microstructure of plate blanks and the current parameters were analyzed. With an appropriate electromagnetic stirring, the inverse segregation of tin for C51900 alloy plant blank reduces from 15 % ~ 30 % to about 5 %, and the proportion of equiaxed grain rises to larger than 30%.

Jan 1, 2009

By Shizhe Liu, Bing Li, Heng Wang, Zuxin Zhao

In this paper, cyclic voltammetry and chronoamperometry have been applied to investigate the effects of Nd2O3 concentration on the anode effects, critical potential for the anode effects and Nd2O3 reduction in LiF-NdF3-Nd2O3 melts at 950℃. The results show that the oxidation peaks in the potential of about 2.7V are attributed to the oxygen ions oxidation and the peak current density increases with Nd2O3 concentration increase from 0 to 0.5wt%. The critical potential caused the anode effects shifts to 0.3V more positive value as Nd2O3 content in the melts decreases from 0.01wt% to 0.5wt%. The cyclic votammograms on W electrodes in the LiF-NdF3-Nd2O3 melts present two pairs of reduction and oxidation peaks, indicating that the reduction of Nd ions in the LiF-NdF3-Nd2O3 melts in two steps rather than one step.

Jan 1, 2014

By J. M. Khodadadi

"A computational study of the effect of thermocapillary convection on melting of a droplet under the influence of an incident uniform heat flux is presented. The computations are based on an iterative, finite-volume numerical procedure using primitive dependent variables, whereby the time-dependent continuity, momentum and energy equations in the spherical coordinate system are solved. During the early periods of the melting process, conduction mode of heat transfer is dominant. As the thermocapillary convection is strengthened due to the growth of the melt zone, melting on the side of the droplet is observed to be much faster in comparison to the conduction-only case. Due to the skewedness of the temperature field, a new recirculating vortex is created which promotes melting within the droplet. The effects of the change in the sign of the surface-tension temperature coefficient on the melting pattern are also investigated.1. IntroductionMelting and solidification of materials are important processes which are encountered in nature and numerous industrial applications. Due to the recent upsurge of interest in such processes as spray casting, space radiators, rapid solidification, purification of materials, containerless processing, etc., there is a need to analyze the transport phenomena of melting and solidification in spherical configurations. Specifically, the effect of thermocapillary convection on the melting of metallic droplets has not been addressed at all. Only a few authors have studied the transport phenomena without phase change in spherical droplets. Oliver and DeWitt [l] worked out a series solution for the thermal and surface-tension-driven flow fields for a droplet experiencing an irradiant energy flux in the microgravity environment. Kudo et al. [2] solved the coupled momentum and energy equations numerically for the same problem without dropping the convective terms. Due to the nonexistence of any previous work on transport phenomena during the thermocapillary-assisted melting of metal droplets, this study was initiated to elucidate the features of the phenomenon."

Jan 1, 1999

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

By Alicia Esther Ares, Carlos Enrique Schvezov, Alejandra Silvina Roman, Claudia Marcela Méndez

In this paper the structure of aluminum based alloys and their corrosion behavior by using different electrochemical techniques as characterization methods are considered. Currently, it becomes imperative to know the role of the Al2Cu against the susceptibility to corrosion of these alloys. The present work aims to studying the electrochemical behavior of aluminum base alloys with the following compositions: Al-1wt.%Cu, Al-4.5wt.%Cu and Al-15wt.%Cu (with different grain structures), in 1M NaCl solutions, at room temperature. Cyclic potentiodynamic polarization tests were performed and were found that the alloys with more than 1wt.%Cu in the matrix have an unstable behavior and without tendency to reach passivity. The equivalent circuits derived from electrochemical impedance spectroscopy technique (EIS) generally showed two capacitive contributions. The susceptibility to corrosion becomes a complex function, not only of copper concentration and structure, but also with interdendritic spacings and distribution of phases in the alloys.

Jan 1, 2015

By Matsufumi Takaya, Yukihiro Sakamoto

"Electric field emission properties from CVD diamond fabricated using pulse-modulated microwave plasma CVD were studied. Diamond was synthesized by microwave plasma CVD apparatus equipped with a pulse-modulated microwave power supply. Pulse conditions were varied from 1 to 10 seconds for pulse periods and from 0.1 to lHz for pulse frequency either. Surface morphologies of the deposits were differed by pulse frequency and duty cycle. As a result, FE properties prepared by different pulse duty cycle were different from continuous film which synthesized using continuous microwave significantly. Highest current density was obtained from the uneven morphology diamond film prepared at 17.5% pulse duty cycle.FE properties of the CVD diamond were depended on surface morphologies that related to the pulse conditions.1. IntroductionDiamond has excellent physical and chemical properties as an industrial material. Especially, hydrogen terminated diamond had the negative electron affinity (NEA) 1) and CVD diamond has this NEA property either as deposited 2). So the electron emission source to the FED is expected as one of this application of CVD diamond as cold cathode of electric devices. We studied on FE properties of various CVD diamond, pulse microwave plasma CVD diamond showed better property than those of other CVD diamond 3).This report studied on· the effect of the duty-cycle of pulse modulate microwave condition on FE properties of the diamond fabricated by pulse modulated microwave plasma CVD."

Jan 1, 2000