Volume 31, Issue 4-5 - In memory of Professor Dr. Masanori Iwase on “Thermodynamics and Kinetics of Materials Processing”

This paper is dedicated to the memory of the of Prof. Masanori Iwase and his life and work. The factors which affect the thermo-physical properties of silicate and aluminno-silicate slags are reviewed. These include (i) the polymerisation of the silicate network (ii) various cation effects and (iii) temperature. Of these, the degree of polymerisation of the silicate network (expressed here through the parameter Q (= 4-NBO/T)) is the most important and the viscosity (η), electrical resistivity and thermal conductivity all increase as Q increases. Various ways in which different cations affect the properties are considered for each individual property viz . the -M-O bond strength affects (i) liquidus temperature (ii) activity coefficient of SiO 2 and (iii) thermal expansion coefficient and whereas both the size and number of available cations affect the electrical conductivity and resistivity. The following observations were made: There is less scatter in property data for liquid slags at a specific temperature than that for the liquidus temperature. The relation between Arrhenius parameters, lnA and B for viscosity and electrical resistivity is non-linear. The magnitude of the thermal conductivity (k) in solid slags is related to the rigidity of silicate network and the rapid decrease in k with increasing temperature occurs at a temperature where the viscosity reaches η = 10 6 dPas. The introduction of Al 2 O 3 into the silicate chain results in significant changes to the properties The ways in which the various properties can be calculated from chemical composition are outlined.

The authors have investigated metastable phase separation in multi-component silicate glass for the fabrication of porous glass from multi-component slag. Spinodal decomposition forms an interconnected microstructure in glass spontaneously, and porous glass is obtained by leaching one of the decomposed phases with an acid solution. This porous glass can be used for a filter to remove impurities in polluted water or air. In this study, the metastable miscibility gap was predicted in multi-component silicate glass using thermodynamic analyses where glass was regarded as a super-cooled liquid phase. Occurrence of spinodal decomposition was observed in annealed glass, and it corresponded to the predicted miscibility gap. Then, we fabricated porous glass using spinodal decomposition in multi-component borosilicate glass and by removing one of the decomposed phases. Furthermore, for the creation of functional porous glass applicable for environmental purification, the spinodal decomposition was prepared in multi-component borosilicate glass containing titanium oxide based on the predicted metastable miscibility gap in multi-component silicate glass.

Most of the phosphorus in slag forms a solid solution of dicalcium silicate (C 2 S) and tricalcium phosphate (C 3 P), and the process used to separate this solid solution from the matrix phase is the same technology used to separate P from other valuable elements such as Mn and Cr containing in the matrix phase. Although it is known that the solubility of C 2 S in an aqueous solution is much greater than that of C 3 P, the solubility of the solid solution and that of the matrix phase have yet to be investigated. To clarify the possibility of selectively extracting P from slag through a leaching process, the dissolution behaviors of the solid solution at various compositions and that of the matrix phase were investigated. The following results were obtained: The dissolution ratio of Ca to the aqueous solution at pH = 7 was close to 1.0 in the case of pure C 2 S and decreased greatly with increasing C 3 P content. The dissolution ratio of P was about 0.1 and did not change relative to the C 3 P content. When the ratio of C 3 P in the solid solution was higher than 0.3, hydroxyapatite (HAP) formation was observed in the residue. The dissolution ratio of P increased for 30 min, and after reaching the maximum value, started to decrease owing to the precipitation of HAP. The dissolution ratio of each element from a glassy slag sample (matrix phase) was lower than that from the solid solution at every pH level. In this study, the possibility to extract a solid solution containing P without dissolving the matrix phase was found through the use of an aqueous solution at pH = 7, although the dissolution ratio of P was not sufficiently high.

Severe plastic deformation by the high pressure torsion (HPT) leads to the phase transitions and strong grain refinement. The starting α Zr-phase in Zr alloyed by 2.5 and 8 mass% Nb transforms into β  +  ω mixture. This β  +  ω phase mixture can be found in the equilibrium phase diagram at higher (effective) temperature ( T eff  = 620°C for Zr-2.5 mass% Nb and ( T eff  = 550°C for Zr-8 mass% Nb). The published papers on phase transitions during HPT are analysed and the values of effective temperature are estimated. Contrary to the increasing temperature, the increasing pressure slows down the diffusion and grain boundary migration. Therefore, the forced atomic movement during HPT produces the states equivalent to higher temperature, but not to the higher pressure.

The following paper revolves around the research work conducted in collaboration during Professor Iwase's brief visits to the Materials Process Science Division at Royal Institute of Technology, Stockholm. The paper focuses on the thermodynamic aspects of CaO–FeO–SiO 2 and CaO–FeO–SiO 2 –MnO slag oxidation in air and sulfur transport through CaO–Al 2 O 3 –SiO 2 slag. Thermodynamics of slag oxidation in air opens potential new areas in terms of focus on effective recovery of iron oxide from slag. The slag transport studies are of fundamental nature and focuses on a novel technique to calculate the diffusion of species through slag by analyzing its corresponding concentration in the metal phase.

A method of mechanical alloying process is described. Carbon transformation to Al 4 C 3 is characterized within the different heat treatment schedules and nine commercial carbon powders are tested. The micromechanism of carbon incorporation into the metallic powder, and its compacting are described. The influence of dispersed carbides on mechanical properties is evaluated together with the influence of deformation on microstructure and properties. It was proved that the transformation efficiency of carbon to Al 4 C 3 by heat treatment of aluminium with the porous furnace black and electrographite is higher than that of the hard cracked graphite. Microstructure changes consisted of the fracture processes and welding of the particles with incorporation of C phase and forming of final granules. The dispersed phase Al 4 C 3 particle size was measured on thin foil structures, and it was constant and as small as 30 nm. The particle size was influenced neither by the carbon type nor by the heat treatment technology applied. Subgrain size measured in the range of 100 grains in thin foils depended on the carbon type, as well. It ranged from 0.3 to 0.7 µm. Using a DSI (depth sensing indentation technique), the Martens hardness, indentation modulus E and deformation work W for Al matrix and Al 4 C 3 particles have been measured. The temperature dependence of ductility, and reduction of area in the temperature range of 623–723 K and strain rate of 10 −1 s −1 , indicated a considerable increase of these properties. In a case when the volume fraction of Al 4 C 3 changes from lower to higher, the grain rotation mechanism dominates instead of the grain boundary sliding. The comparison of the tensile test results and changes in fracture for the Al-Al 4 C 3 system at two temperatures and two strain rates is summarized. The dependence of the minimum deflection rate on the applied force as well as the dependence of the time to fracture on the applied force for two temperature levels (623 and 723 K) by small punch testing are depicted. The composite was tested in two different states: a) as received by mechanical alloying with hot extrusion (HE) as the final operation and b) ECAPed (mean grain size of 100–200 nm). The dependence of the minimum deflection rate on the applied force as well as the dependence of the time to fracture on the applied force for two temperature levels are evaluated. The anisotropy of the creep properties and fracture using small punch tests for the Al-Al 4 C 3 system produced by ECAP were analysed.

Defect structure and transport properties of Co 3 O 4 cobalt oxide have been studied as a function of temperature and oxygen pressure, using marker and thermogravimetric techniques. It has been found that the oxidation of CoO to form Co 3 O 4 follows parabolic kinetic, being thus diffusion controlled. Marker experiments have demonstrated that cation sublattice of Co 3 O 4 oxide is predominantly disordered, but the defect structure is rather complex. At very low oxygen pressures, close to the dissociation pressure of the oxide, interstitial cations are the predominant point defects, while at high pressures cation vacancies predominate. This behavior is reflected in complex dependence of the parabolic rate constant of CoO oxidation on oxygen pressure. At low pressures, namely, parabolic rate constant of the reaction increases with oxygen pressure, reaching then virtually constant value in intermediate pressure range and increases again in highest pressure range. Theoretical analysis of kinetic results in terms of point defect thermodynamics confirmed the above conclusion, concerning complex defect structure of Co 3±y O 4 oxide. Finally, self-diffusion coefficient of cations in the discussed oxide has been calculated as a function of temperature and oxygen pressure from kinetic rate measurements, using Wagner's theory of metals oxidation.

The phase development in the course of carbothermal reduction and nitridation of ilmentie concentrates and synthetic rutile was studied in temperature programmed reduction (623–1873 K) and isothermal reduction experiments. Ilmenites and synthetic rutile were reduced in a tube reactor with continuously flowing hydrogen-nitrogen mixture or pure nitrogen. The rate and extent of reduction were monitored by online off-gas analysis. Samples reduced to different extent were subjected to XRD and SEM/BSE analyses. Pseudorutile and ilmenite were the main phases in ilmenite concentrates; rutile was the main phase in synthetic rutile. Pseudorutile was first converted to ilmenite and titania which occurred at temperatures below 623 K; iron oxides in ilmenite were quickly reduced to metallic iron. Titania was reduced to titanium suboxides and further to titanium oxycarbonitride. Reduction of ilmenites and synthetic rutile in hydrogen-nitrogen mixture was much faster than in pure nitrogen. The rate of conversion of titanium oxides to oxycarbonitride was affected by iron content in the ilmenites. The rate of reduction increased with increasing iron content in ilmenite (decreasing grade) when ilmenites were reduced in the hydrogen-nitrogen gas mixture, but decreased with decreasing ilmenite grade in reduction experiments in nitrogen; reduction in nitrogen was the fastest for synthetic rutile. The difference in the reduction behaviour was attributed to different chemical compositions and morphologies of ilmenites of different grades.

The most common slag fluidiser in steelmaking is fluorspar, a mineral primarily composed of CaF 2 . Because of increasing consumption and decreasing availability of inexpensive fluorspar, steelmakers are seeking alternative means of achieving slag fluidity. One possible alternative to fluorspar is salt cake from secondary aluminium production. This salt is obtained from the used flux in remelting aluminium scrap and dross. This material is widely available and considered toxic (meaning that use in steelmaking helps to reduce environmental impacts from disposal). This project is an investigation of salt cake as a replacement for fluorspar in slag-fluidising applications by viscosity measurements and mass loss measurements at high temperatures (to evaluate the amounts of gases formed). In addition, characterisation of raw materials and melted slags by XRD, chemical analysis, and EPMA have been undertaken. The salt cake addition has a positive effect on slag fluidity, and shows promise for use in steelmaking slags.

Congruent oxidation occurs when an alloy oxidizes at constant oxygen chemical potential and temperature to an oxide in which the ratio of metallic components is the same as in the alloy. In alloys that undergo congruent oxidation concentration gradients near the surface are minimized. In this work thermodynamic conditions for congruent oxidation of binary and ternary alloys are formulated using the regular solution model to describe thermodynamic mixing properties. The conditions under which congruent oxidation can occur are identified. Congruent oxidation of a binary alloy X-Y will occur only if difference in oxygen potential for the oxidation of the two pure metals is less than twice the difference in regular solution parameters for the oxide and alloy phases (Ω 0  − Ω A ). In the case of ternary alloys, congruency requirements for both two-phase and three-phase equilibria are discussed. Since the conditions for congruent oxidation of ternary alloy X-Y-Z depends on many parameters, the effect of systematic variation of the binary sets of regular solution parameters on the congruent composition is explored by numerical solution of the governing equations.

This paper aims to computationally investigate flow patterns of gas-liquid two-phase with an abrupt expansion. To do so, the present computation is nicely verified against the previous experimental results for a good wettability surface. These rectangular channels have a thickness narrower than the Laplace constant of the present situation. Under a poor wettability condition, this narrow thickness affects the flow pattern; e.g., the air phase forms channeling behind the expansion in a low airflow rate whereas the air phase becomes fragments of bubbles due to the expansion under a good wettability condition.

This paper computationally visualizes two-phase flow patterns through a horizontally placed hydrophilic or hydrophobic rectangular channel with an abrupt contraction. The rectangular duct used in this study has a thickness narrower than the Laplace constant so that the surface tension governs the fluid system rather than the inertia force. In particular, the computed bubble behavior at the abrupt contraction seemed to be a similar nature against the preliminary experimental result.

Electrochemical measurements of the solid-oxide galvanic cell of the type Mo/Mo + MoO 2 /ZrO 2 (MgO)/Fe + {Na 2 O-Al 2 O 3 -SiO 2 -Fe x O} slag/Ag/Fe were conducted at 1673 K in order to obtain the activities of Fe x O in Na 2 O-Al 2 O 3 -SiO 2 -Fe x O system. The iso-activity curves for Fe x O at 1673 K were determined for Na 2 O-(Al 2 O 3  + SiO 2 )-Fe x O pseudo-ternary slags with an Al 2 O 3 /SiO 2 molar ratio of 33/67.

For a better understanding of phosphorus removal from hot metal, the Gibbs free energies of solid solutions between di-calcium silicate and tri-calcium phosphate were derived through applications of solutions models. The regular solution model with the parameters determined in this study gave the activities of the components thermodynamically consistent with the literature data and the phase diagrams.

In order to obtain a better understanding of the dissolution behavior of calcium into molten steel, laboratory-scale experiments and plant tests were performed. The dissolution ratio of calcium in the molten steel clearly depended on the nickel concentration in the steel. The experimental results were consistently explained using a model calculation that takes into consideration the interatomic forces between calcium, silicon, iron, and nickel inside the boundary layer around the calcium alloy during dissolution. The critical pressure of calcium required for vaporization in molten steel was also evaluated.

The compositional change of stabilized zirconia upon the change of oxygen chemical potential was studied by applying DC-polarization method to a galvanic cell using stabilized zirconia as the electrolyte. The flow of excess charge observed upon the change of the DC-polarization condition was found due to the oxygen liberation from the bulk of the electrolyte. The total amount of liberated oxygen determined by the excess charge was analyzed in terms of the compositional change of the electrolyte due to the change of oxygen chemical potential profile in the electrolyte. The calculated values based on the increase or decrease of the electronic defects could not account for the experimental values. However, the ones based on the reduction of impurity oxides were in good agreement with the experimental values. Considerable amount of oxygen can be released from or absorbed into the zirconia electrolyte by the redox reaction of impurity oxide. It is noteworthy that this phenomenon may cause serious errors to the transport properties of electronic defect determined with the use of the relaxation processes.

A novel process for preparing scorodite particles with a diameter of approximately 20 µm from Fe(II) and As(V) in aqueous solution has been developed by DOWA Metals and Mining. In the present study, the dissolution characteristics of iron and arsenic from the scorodite particles synthesized by this process have been investigated under different conditions. The results show that the concentration of arsenic dissolved from the particles in aqueous solution is very low, but it has a complicated dependence on the temperature and pH of the solution. Transmission electron microscopy (TEM) with an energy dispersive X-ray spectrometer (EDS) was used to analyze the morphology, structure, and composition of the scorodite particles. The results indicate that the scorodite particles exhibit a nearly octahedral shape with planes composed of almost (111) planes in the orthorhombic structure. The concentration of iron at the surface of the particles is higher than that of iron inside of the particles. This characteristic morphology, along with the minimal surface defects of the scorodite particles, is considered to be responsible for the low dissolution of arsenic from the particles in aqueous solution. Atmospheric temperature and solution conditions were also found to be important for the safe, long-term storage of arsenic using scorodite particles.

The effect of shear stress on the crystallization behavior of molten 50CaO-50SiO 2 (mol%) slag was investigated by in-situ measurements of its electrical capacitance in wide temperature range including supercooled region. It is well known that the electrical capacitance of liquids should be generally much higher than that of solids because of the differences in their respective polarization mechanisms. The difference was employed as a sensitive indicator of the crystallization of molten silicates in an experimental furnace equipped with an electrical-capacitance measurement system. The system comprised a Pt-based alloy crucible and a rotating rod that allow us to evaluate the effect of shear stress, both connected to a capacitance meter (LCR meter). As expected, at a particular temperature, the electrical capacitance of the molten calcium silicate abruptly decreased by roughly three orders of magnitude, which clearly indicated crystallization confirmed by corresponding microstructural analyses. It was also found that, for the rotating-rod measurements (with shear stress), the temperatures at which the capacitance abruptly dropped were higher than that without the shear stress. This suggests that the agitation effect by the rotating-rod accelerates the crystallization of molten calcium silicate.

After Kyoto protocol, many companies and institutions in the industrialized countries focused on the energy saving and the utilization of waste heat and materials widely for reducing the CO 2 emission. In such a circumstance, it is key technology for reducing CO 2 emission by using the waste materials efficiently such as a plastic and wood biomass. In this paper, a method for improving the reactivity of plastic char using wood biomass was investigated. The XRD analysis was performed for elucidating the carbon structure change by addition of wood to PE (polyethylene) and reactivity test with O 2 gas was carried out to clarify the reaction rates of the mixtures of PE and wood. It was found that the crystallization degree of char decreased continuously with the addition of wood to polyethylene, which meant that the reactivity of polyethylene char increased.

In order to optimize a boron removal process by slag refining to obtain solar grade silicon, the rate of boron removal from molten silicon using CaO-SiO 2 slag was investigated at 1823 K in an Ar atmosphere. The rate of boron removal was found to be controlled by mass transfer in molten slags, and the mass-transfer coefficient of boron in molten slag in the present experimental condition was evaluated. Some experiments on chlorination of boron in silicon and that of borate in slag using Cl 2 gas were also carried out. Experimental results showed that the slag refining process with chlorination was proposed as a promising method for the boron removal from molten silicon.

In order to obtain a physicochemical knowledge of complex industrial slags, the activities of FexO in the industrial slags used for external dephosphorization of hot metal performed at practical steelmaking plants in Japan were measured by means of a solid-oxide galvanic cell in a temperature range between 1523 K and 1673 K. XRD study showed the presence of solid phases in all the slags, showing the heterogeneous character of the slags employed. With respect to the effect of CaF 2 on FexO activity, the FexO activities of the heterogeneous slags were correlated with the ratio X(FeO)/X(CaF 2 ) . High X(FeO)/X(CaF 2 ) values corresponded to high FeO activity. This tendency is interpreted based on the phase relationship in a CaO-CaF 2 -FexO ternary system. A favorable condition for external dephosphorization with less addition of CaF 2 is discussed.

Accurate values of thermal conductivity of the silicate melts systematically measured as a function of chemical composition are necessary to understand a mechanism of heat transfer in the silicate melts. Hot wire method and laser flash methods have been used to measure thermal conductivity or thermal diffusivity of oxides melts at high temperatures. Laser flash method has been improved to measure thermal diffusivity of oxides melts with high accuracy. However the effects of radiative heat transfer and low electrical resistivity of samples have been made it difficult to derive precise values. To overcome these difficulties, a front-heating front-detection laser flash method with use of high time resolution detector has been proposed. The temperature response at the bottom surface of thin platinum cell containing sample irradiated by pulse laser is measured. The measurement techniques used for measurement oxide melts are compared. Then, thermal conductivity of Al 2 O 3 -Na 2 O-CaO-SiO 2 silicate melts was measured at temperature up to 1830 K. Thermal conductivity of the molten silicate shows insignificant temperature dependence for all investigated melts. A fairly good correlation has been found between the thermal conductivity and the value of NBO/T (Non-Bridging Oxygen ions/Tetrahedrally coordinated cation) calculated from the chemical composition. The thermal conductivity increases with decrease of NBO/T for small NBO/T value and becomes constant for larger NBO/T value.

Full exploitation of the many attractive engineering properties of ultra-high temperature ceramics (UHTCs) requires that they can be joined. This paper explores progress in identifying joining strategies based on the use of transient liquid phases (TLPs). Wetting studies are used to explore the suitability of specific liquids for joining, while bonding studies provide the ultimate test. Sintering aids in the UHTC provide a major potential obstacle to successful joining, and dissolved impurities in the TLP can also complicate the joining process. Nonetheless, we show that well-bonding interfaces can be achieved when ZrC ceramics are bonded at 1673 K using a Ni/Nb/Ni multilayer interlayer.

The La 1−x Sr x Mn y Fe 1−y O 3 samples of perovskite-type oxides were synthesized by Self-propagating High-temperature Synthesis (SHS) method. In this study, first, we synthesized B-site substituted perovskite-type oxides, LaMn x Fe 1−x O 3 . The SHS method successfully synthesized LaMn x Fe 1−x O 3 . The most active composition for soot combustion among synthesized samples of LaMn x Fe 1−x O 3 was x = 0.4, LaMn 0.4 Fe 0.6 O 3 , from model-soot combustion experiment with TG/DTA analysis. We then examined the effect of A-site substitution by Sr on LaMn 0.4 Fe 0.6 O 3 perovskite. The SHS of La 1−x Sr x Mn 0.4 Fe 0.6 O 3 was successfully ignited, propagated and completed. XRD peaks of perovskite-type oxide phase was detected in all the synthesized La 1−x Sr x Mn 0.4 Fe 0.6 O 3 but unreacted material, SrCO 3 , was also detected in the sample above x = 0.6 from XRD analysis. The soot combustion activity of Sr-doped LaMn 0.4 Fe 0.6 O 3 was not enhanced according to the impurity in the samples. The most active composition among synthesized samples of La 1−x Sr x Mn y Fe 1−y O 3 was LaMn 0.4 Fe 0.6 O 3 which exhibited lower activation energy than conventional Pt/Al 2 O 3 catalyst, that is, LaMn 0.4 Fe 0.6 O 3 synthesized by SHS method had superior soot combustion activity despite its relatively small specific area.

In this paper, the sources, properties and possible applications of waste residues from the aluminum industry as refining agents for the steel industry were investigated. Characterization of the potential fluxing agents was performed using a combination of XRD, XRF, DTA, and TGA. Experiments were carried out to examine the potential of hot metal desulphurization with fluxes made from these residue materials in comparison with those obtained from bauxite. To facilitate this comparative behavior of fluxes derived from different source materials, particular attention was given to the enhancing effects of controlled amounts of sodium oxide in contrast to the deleterious effects associated with the presence of silica and titanium dioxide on the desulphurization process. A major advantage of refining fluxes made from white mud waste products is that they contain significant amounts of sodium oxide and only very small concentrations of the oxides of silicon and titanium.

Fluorspar, a mineral primarily composed of CaF 2 is the most commonly used slag fluidizer in steelmaking. Due to increasing costs for fluorspar steelmakers are seeking alternative means of achieving slag fluidity. The research has concentrated on other minerals or the wastes of other high temperature operating industries. A promising alternative to fluorspar has been identified in a previous work from this laboratory which is the salt cake from secondary aluminum production such as the flux in remelting aluminum scrap and dross. This material is widely available and also considered toxic (meaning that use in steelmaking helps to reduce environmental impacts from disposal). The present work is an investigation of the viability of using mixtures of salt cake and KAlF 4 in slag-fluidizing applications by measurements of viscosity and weight loss at high temperatures (to evaluate whether large amounts of potentially harmful gases are formed). In addition, characterization of raw materials and melted slags has been performed. In terms of fluidity the mixtures of aluminum salt cake and KAlF 4 are qualified for use as fluidizers. The results of the present study will be used to design plant trials.

Basing on actual theoretical approach and experimental results, the mechanism of sulphide formation beneath the oxide scale grown on metals in SO 2 -O 2 atmospheres has been described. It has been shown that in spite of much lower sulphur partial pressure in the oxidizing atmosphere than the dissociation pressure of the sulphide to be formed, the sulphidation process takes place beneath the oxide scale. This, at the first sight, unexpected behavior results from the fact that sulphur is diffusing inwards through the primary oxide scale in the molecular form, i.e. SO 2 molecules. Reaching thus metal-scale interface, where the oxygen partial pressure is very low, virtually equal to the dissociation pressure of the oxide forming the scale, SO 2  ⇔ O 2  + ½S 2 equilibrium is shifted to the right, as a result of which the partial pressure of sulphur vapor dramatically increases, reaching the value several orders of magnitude higher than that needed for sulphide formation. Analogous situation is observed during oxidation of chromium steels in CO 2 -O 2 atmospheres. In this case, namely, carburisation process is observed beneath the oxide scale, in spite of the fact that carbon activity in this environment is several order of magnitude lower than that required for chromium carbide formation. This again unexpected situation becomes understandable if one assumes – like in the case of metal oxidation in SO 2 containing atmosphere – that carbon is transported through the oxide scale in the form of CO 2 molecules. The final conclusion is, that the explanation of the mechanism of sulphide formation beneath the oxide scale on metals and of carburization beneath the oxide scales on steels constitutes the important step forward, leading to the better understanding of high temperature corrosion mechanisms of metallic materials, observed in multicomponent agresive gases.

A new route to prepare polycrystalline CdTe films using electrodeposition of amorphous Cd-Te films and subsequent annealing was investigated. Amorphous Cd-Te films with Te-rich compositions could be electrodeposited from ammoniacal alkaline aqueous solutions. The deposition rate of the amorphous film was much higher than that of crystalline CdTe. Annealing of the Te-rich amorphous Cd-Te film at 400 °C in air yielded a crystallized CdTe film with a nearly stoichiometric composition. Thermodynamic calculations of the vapor pressures of Cd and Te species suggested that the decrease in the Te content of the annealed film was due to the vaporization of Te in the forms of oxides. Although an isothermal annealing generated a number of large holes in the film, an annealing with a slow temperature ramp resulted in a crystalline CdTe film without the large holes.

Woody materials treated by chromated copper arsenate (CCA) preservative containing copper, chromium and arsenic had been widely used, and thus it is anticipated that a lot of wood waste treated by CCA will be generated as the industrial waste in the future. The environmental pollution by the released heavy metals becomes a serious problem when the wood treated by CCA was incinerated inadequately. There needs the investigation for the behaviors of heavy metals during incineration of wood treated by CCA. The wood sample treated by CCA was incinerated at temperature range between 873 and 1673 K with the oxygen partial pressure between 0.21 and 0.40 atm completely. The proportion of evaporated arsenic increased with increasing temperature and most of arsenic evaporated at about 1600 K. It was suggested that arsenic evaporated as As 2 O 3 or As 4 O 6 during the incineration. On the other hand, most of copper and chromium remained in the bottom ash. The evaporation behaviors of arsenic largely depended on the incineration temperature, while the effects of the oxygen partial pressure of inlet gas and gas flow rate on those were small. Powder XRD analysis of bottom ash revealed that copper and chromium existed as CuCr 2 O 4 and CuCrO 2 . CuCr 2 O 4 was mainly contained in the bottom ash incinerated at temperature below 1273 K, whereas the ratio of CuCrO 2 increased with increasing incineration temperature above 1273 K. Therefore, most of copper and chromium were bivalent and trivalent, respectively, in the bottom ash, and some copper was converted to a monovalent over 1273 K. Almost all arsenic was contained as pentavalent Cu 3 (AsO 4 ) 2 , and arsenic was not identified in bottom ash incinerated at temperature above 1273 K.

In entrained slagging gasifiers, the fluidity of the molten ash is a critical factor for process control since it affects slag formation, the capture of inorganic constituents, refractory wear, and slag drainage along the gasification chamber walls. The use of western coal, or mixtures of eastern and western coals as gasifier feedstock, is likely to occur as western coals become available and technological issues that hinder their use are being resolved. In the present work, the viscosity of synthetic slags with ash chemistries simulating the western U.S. coals, was experimentally measured at a P o 2  = 10 −8 atm in the temperature range of 1773–1573 K (1500–1300 °C) using a rotating-bob viscometer. Alumina spindles and containment crucibles of both alumina and zirconia were used. Crystallization studies of this slag using a confocal scanning laser microscope found that a (Mg,Fe)Al 2 O 4 -based spinel precipitated at temperatures below 1723 K (1450 °C), and this agreed with FactSage equilibrium phase prediction. The same spinels were observed in the post-viscometry experiment slags when ZrO 2 crucibles were used and assumed to be in equilibrium with the slag at the higher temperatures. Zirconia dissolution resulted in a slight increase in the solid fraction present in slags at lower temperatures, compared to spinel fraction. Crystal precipitation changed the apparent activation energy and required a longer stabilization times for viscosity measurements. The viscosity results were used in predictive equations based on Veytsman and Einstein's models, with critical nucleation temperatures and the solid fraction calculated with FactSage. In the simulated eastern/western coal feedstock blends based on ash compositions, the fractions of the solid precipitates were also calculated using the thermodynamic program FactSage for each blend composition, and the plastic viscosity of each eastern/western coal slag blend was predicted using Veytsman's model and compared to available experimental data.

The effective thermal conductivities of various Mn-Al powder compact compositions were measured using an Inverse Heat Transfer Procedure, and extensive validation work was also carried out. Specially fabricated cylindrical compact specimens were used equipped with two thermocouples at strategic locations. The porosity of these specimens was also measured. The estimated effective thermal conductivities of various Mn-Al compacts were in the range of 5.5 to 10.5 W m −1 °C −1 , which are much lower than that of Al (237 W m −1 °C −1 ), and close to that of Mn (7.8 W m −1 °C −1 ). The effective thermal conductivities of Mn-Al powder compacts decreased with an increase in the compact's Mn composition and porosity. Within the examined temperature range of 250 to 600 °C, the effect of temperature on the effective thermal conductivity was minimal. A purely theoretically derived prediction of Mn-Al compact thermal conductivity is substantially higher than the estimates of using the IHTP.

Synopsis End of life tyres are discarded at an alarming rate reflecting the strength of developing countries economy and the intensity of trade and transportation. Conversely, environmental concerns are increasing the need for alternative materials in steelmaking industries. The solution to this problem involves the development of environmentally-friendly technologies that would utilize these waste products. The present study investigates carbon/slag reactions, including slag foaming and FeO reduction, for a range of coke/rubber blends. Off-gas emissions (CO and CO 2 ) were monitored and correlated with dynamic changes in volume as a result of iron oxide rich EAF slag and carbon. The gaseous emissions from metallurgical coke showed lower concentrations in comparison to the emissions from the coke-rubber blends. With an increase of rubber in the blend, gaseous emissions were enhanced. Significant carbon/slag interactions occurred when coke/rubber blends were used, with associated iron oxide reductions within the slag phase. The quantitative estimation of the slag droplet volume was performed by using the Vt/Vo ratio as a measure of slag foaming. These results indicate that partial replacement of coke with rubber is not only viable, but efficient leading to improved interactions with EAF slag.

The production of a nickel sulphide concentrate through selective sulphidation of a nickeliferous lateritic ore at temperatures lower than current smelting temperatures, is being studied as a potential production method for upgrading lateritic ores. The ability to produce such a nickel sulphide concentrate at economically attractive grades, while achieving reasonable nickel recoveries, relies on the conversion of the maximum amount of nickel oxide to sulphide, while minimizing the amount of iron sulphide. This paper examines the thermodynamic basis for this selective sulphidation. The analysis includes both pure component equilibrium as well as various solid and liquid solution phases, which are anticipated to set limits on the maximum achievable grade/recovery combinations. Thermodynamic calculations show that, for high iron limonitic ores, grades of up to 20 to 25 mass percent nickel should be possible, while maintaining recoveries of greater than 80 percent.

The mining industry is under increasing pressure to assess the extraction of value from complex copper ores, such as those containing enargite (Cu 3 AsS 4 ), due to the rising demand for copper and gold. A sulphation roast, weak acid leach, and electrowinning process flowsheet has been studied to address the treatment of copper concentrates containing significant amounts of enargite. Copper is recovered from the calcine by acid leaching, with most of the arsenic being fixed in the leach residue after gold extraction by cyanidation. The relative simplicity of roasting combined with proven hydrometallurgical technologies has the potential to be economically advantageous and readily scaled for commercial operation. Based on a proposed reaction mechanism, a thermodynamic analysis has been performed using HSC Chemistry® 6.1 in order to establish an operating window and assess the overall potential feasibility of the proposed flowsheet.

Refining of silicon for solar applications using metallurgical approaches has attracted a considerable attention in the recent years. The present study involves employing solvent refining as a purification technique in which silicon recrystallization takes place from an iron-silicon alloy melt. It is believed that iron will perform as the impurity “getter” and purified silicon crystals grow from the alloy melt, while the impurities are segregated to the liquid alloy. The focus of this article is on removal of phosphorus, as a critical impurity in solar silicon. In order to assess the feasibility and efficiency of phosphorus removal through solvent refining, the distribution of phosphorus between solid Si and Fe-Si melt at 1483–1583 K (1210–1310 °C) was measured. Interaction parameter between phosphorus and iron was calculated by varying the concentration of phosphorus at each temperature.

The development of effective methods for directly measuring liquid metal quality, prior to casting and final solidification, has long been a goal for Process Metallurgists. For aluminum, which is generally much cleaner than steel, it is first necessary to concentrate the inclusions by filtering the metal through a porous frit, before then freezing the remaining metal, and subjecting it to microscopic examination (e.g. PoDFA). An alternative method is to take a sample of metal, freeze it, and then dissolve the metal to release the particles (inclusions) through elutriation (the Slime Technique). The only true on-line, in-situ , methods are the Ultrasonic Liquid Metal Sensors (such as the Mansfield Molten Metal Sensor), and the Electric Sensing Zone Methods (such as LiMCA and ESZ-pas). Currently, perhaps the most reliable, but least satisfying, technique is to wait for customer complaints to identify problems. JFE has developed an ultrasonic, on-line, system that registers larger inclusion clusters in rolled steel sheets as they are produced. Alternatively, many steelmakers will use PDA (Pulse Discrimination Analysis) on a small surface of solid steel, to arrive at conclusions concerning inclusions less than 10 microns. Unfortunately, this ignores the much larger inclusions normally present within a steel melt that are responsible for compromising metal properties. The late Professor Iwase was a strong believer in the development of good techniques and methods to monitor and control metallurgical processes, including those related to metal quality. This review is dedicated to his memory, and to his strength of perseverance.

Titanium carbide is used as reinforcement component in composites due to its stability, hardness and wear resistance. A potential application is local reinforcement of stainless steel castings in which TiC is added only to the surfaces, which acquire wear resistance. This work is part of the study in which Ti and C are added in the mould during casting of stainless steel to form TiC at a specific surface. Wettability, stability and dissolution of the reinforcement particles are key phenomena in producing these composites in liquid state. Wetting experiments between TiC and Fe as well as FeNi and FeCr alloys were performed in order to get information about wettability, dissolution and formation of TiC and other phases related to the systems. Contact angles for the systems were attained without any reactions between the substrate and the alloy during heating. Wetting was not significantly improved by adding Ni or Cr. Dissolution of TiC was very strong into all the alloys. No new phases at the interface were formed in the experiments except for Cr-carbides in Cr-containing alloys. These results gave important information about the interfacial phenomena needed in developing the production methods.

It is widely recognized that alkali metals, such as, potassium and sodium can cause operational problems in the iron blast furnace. These elements can influence properties, such as, the softening and melting of ores, formation of scaffolds, coke properties, and refractory life. It has been established that recirculation of these elements occurs within the furnace. In the lower furnace vaporization occurs in the high temperature hearth and bosch regions, and condensation occurs in the upper furnace below or in the cohesive zone. For these reasons the input of alkalis into the furnace is strictly controlled. Optimized thermodynamic databases describing slags in the system Al 2 O 3 -CaO-FeO-Fe 2 O 3 -Na 2 O-K 2 O-MgO-SiO 2 have been developed and, combined with the computer software FactSage; these databases have been used to predict the possible behaviour of alkalis in the blast furnace and to examine the effects of changing process variables on reactor performance. To demonstrate this approach to process modeling the furnace is considered as a two-stage equilibrium reaction system and the results of initial analysis are reported.

Synopsis Oxidation behavior of CaS in oxidizing atmosphere has been investigated for the regeneration process of desulfurization slag by oxidation. The temperature range of oxidation of CaS reagent with Ar-21%O 2 gas was 973 to 1423 K. The weight gain was observed in the lower temperature range and reached at the maximum value at 1173 K while weight gain turned to decrease when the reaction temperature was higher than 1173 K. It was clarified that CaS was oxidized to CaSO 4 under 1173 K or to CaO over 1373 K by the measurement of oxidation rate, XRD and thermodynamic analysis. The results strongly suggested that sulfur removal from the sulfur containing slag may be possible at temperatures of 1223 K or higher by the oxidation of with air.