The Effect of CaO on Gas/Slag/Matte/Tridymite Equilibria in Fayalite-Based Copper Smelting Slags at 1473 K (1200 °C) and <Emphasis Type="Italic">P</Emphasis>(SO<Subscript>2</Subscript>) = 0.25 Atm

Fundamental experimental studies have been undertaken to determine the effect of CaO on the equilibria between the gas phase (CO/CO₂/SO₂/Ar) and slag/matte/tridymite phases in the Cu-Fe-O-S-Si-Ca system at 1473 K (1200 °C) and P(SO₂) = 0.25 atm. The experimental methodology developed in the Pyrometallurgy Innovation Centre was used. New experimental data have been obtained for the four-phase equilibria system for fixed concentrations of CaO (up to 4 wt pct) in the slag phase as a function of copper concentration in matte, including the concentrations of dissolved sulfur and copper in slag, and Fe/SiO₂ ratios in slag at tridymite saturation. The new data provided in the present study are of direct relevance to the pyrometallurgical processing of copper and will be used as an input to optimize the thermodynamic database for the copper-containing multi-component multi-phase system.     

Experimental Investigation of Gas/Slag/Matte/Spinel Equilibria in the Cu-Fe-O-S-Si System at 1473 K (1200 °C) and P(SO2) = 0.25 atm

Metallurgical and Materials Transactions B - New experimental data were obtained on the gas/slag/matte/spinel equilibria in the Cu-Fe-O-S-Si system at 1473&nbsp;K (1200&nbsp;°C) and...     

Phase Equilibria of “Cu2O”-“FeO”-CaO-MgO-Al2O3 Slags at PO2 of 10-8.5 atm in Equilibrium with Metallic Copper for a Copper Slag Cleaning Production

Limited data are available on phase equilibria of the multicomponent slag system at the oxygen partial pressures used in the copper smelting, converting, and slag-cleaning processes. Recently, experimental procedures have been developed and have been applied successfully to characterize several complex industrial slags. The experimental procedures involve high-temperature equilibration on a substrate and quenching followed by electron probe X-ray microanalysis. This technique has been used to construct the liquidus for the “Cu₂O”-“FeO”-SiO₂-based slags with 2 wt pct of CaO, 0.5 wt pct of MgO, and 4.0 wt pct of Al₂O₃ at controlled oxygen partial pressures in equilibrium with metallic copper. The selected ranges of compositions and temperatures are directly relevant to the copper slag-cleaning processes. The new experimental equilibrium results are presented in the form of ternary sections and as a liquidus temperature vs Fe/SiO₂ weight ratio diagram. The experimental results are compared with the FactSage thermodynamic model calculations.     

Phase Equilibria Studies in the System ZnO-“FeO”-Al<Subscript>2</Subscript>O<Subscript>3</Subscript>-CaO-SiO<Subscript>2</Subscript> Relevant to Imperial Smelting Furnace Slags: Part II

The phase equilibria and the liquidus temperatures in the system ZnO-“FeO”-Al₂O₃-CaO-SiO₂ have been determined experimentally in equilibrium with metallic iron. Specifically, the effects of Al₂O₃ concentrations in Imperial Smelting Furnace slags are identified, and the results are presented in the form of pseudo-ternary sections ZnO-“FeO”-(Al₂O₃ + CaO + SiO₂) in which CaO/SiO₂ = 0.93 and (CaO + SiO₂)/Al₂O₃ = 5.0 and 3.5, respectively. It was found that, in the presence of Al₂O₃, the spinel phase is formed, the spinel primary phase field expands, and the wustite and melilite primary phase fields are reduced in size with an increasing Al₂O₃ concentration. The implications of the findings to industrial practice are discussed.     

Heat transfer of an evaporator–condensing system with electrohydrodynamic coolant circulation and different spatial orientation

The influence of the spatial orientation of an evaporator–condensing system (ECS) on the heat transfer coefficient is considered. As found, it varies according to the cosine law, which implies that it is at its minimum when the evaporator is in the top position, and it is at its maximum when the heater is in the bottom position. This is consistent with the physical considerations about the effect of buoyancy forces on heat transfer. The average velocity of coolant circulation through the ECS loop is found, and on this basis, the “electric” Reynolds number and heat transfer coefficient are estimated. The influence of pressure on heat transfer in the ECS has been analyzed. The considered phenomena have been physically interpreted; they agree well with the experimental data.     

Phase Equilibria Studies of the Cu-Fe-O-Si System in Equilibrium with Air and with Metallic Copper

Phase equilibria of the Cu-Fe-O-Si system have been investigated in equilibrium: (1) with air atmosphere at temperatures between 1373?K and 1673?K (1100?°C and 1400?°C) and (2) with metallic copper at temperatures between 1373?K and 1573?K (1100?°C and 1300?°C). High-temperature equilibration/quenching/electron-probe X-ray microanalysis (EPMA) techniques have been used to accurately determine the compositions of the phases in equilibrium in the system. The new experimental results are presented in the form of ??Cu₂O??-??Fe₂O₃??-SiO₂ ternary sections. The relationships between the activity of CuO_0.5(l) and the composition of slag in equilibrium with metallic copper are discussed. The phase equilibria information of the Cu-Fe-O-Si system is of practical importance for industrial copper production processes and for the improvement of the existing thermodynamic database of copper-containing slag systems.     

Quasi-Chemical Viscosity Model for Fully Liquid Slag in the Al2O3-CaO-MgO-SiO2 System—Part I: Revision of the Model

A model has been developed that enables the viscosities of the fully liquid slag in the multi-component Al₂O₃-CaO-FeO-Fe₂O₃-MgO-Na₂O-SiO₂ system to be predicted within experimental uncertainties over a wide range of compositions and temperatures. The Eyring equation is used to express viscosity as a function of temperature and composition. The model links the activation and pre-exponential energy terms in the viscosity expression to the slag internal structure through the concentrations of various Si_0.5O, $ {\text{Me}}^{n + }_{2/n} {\text{O}} $ , and $ {\text{Me}}^{n + }_{ 1/n} {\text{Si}}_{0. 2 5} {\text{O}} $ viscous flow structural units (SUs). The concentrations of these SUs are derived from a quasi-chemical thermodynamic model of the liquid slag using the thermodynamic computer package FactSage. The model describes a number of slag viscosity features including the charge compensation effect specific for the Al₂O₃-containing systems. The predictive capability of the model is enhanced by the physical aspects of the model parameters—the correlation with other physicochemical properties as well as experimental viscosity data is used to determine model parameters. The present series of two papers outlines (a) recent significant improvements introduced into the model formalism and (b) application of the model to the Al₂O₃-CaO-MgO-SiO₂ system, review of experimental viscosity data, and optimization of the corresponding model parameters for this system.     

Effects of Al<Subscript>2</Subscript>O<Subscript>3</Subscript> and CaO/SiO<Subscript>2</Subscript> Ratio on Phase Equilbria in the ZnO-“FeO”-Al<Subscript>2</Subscript>O<Subscript>3</Subscript>-CaO-SiO<Subscript>2</Subscript> System in Equilibrium with Metallic Iron

The phase equilibria and liquidus temperatures in the ZnO-“FeO”-Al₂O₃-CaO-SiO₂ system in equilibrium with metallic iron have been determined experimentally in the temperature range 1383 K to 1573 K (1150 °C to 1300 °C). The experimental conditions were selected to characterize lead blast furnace and imperial smelting furnace slags. The results are presented in a form of pseudoternary sections ZnO-“FeO”-(Al₂O₃ + CaO + SiO₂) with fixed CaO/SiO₂ and (CaO + SiO₂)/Al₂O₃ ratios. It was found that wustite and spinel are the major primary phases in the composition range investigated. Effects of Al₂O₃ concentration as well as the CaO/SiO₂ ratio on the primary phase field, the liquidus temperature, and the partitioning of ZnO between liquid and solid phases have been discussed for zinc-containing slags.     

Effect of thermal treatment on the growth,structure and luminescence of nitride-passivated silicon nanoclusters

Silicon nanoclusters (Si-ncs) embedded in silicon nitride films have been studied to determine the effects that deposition and processing parameters have on their growth, luminescent properties, and electronic structure. Luminescence was observed from Si-ncs formed in silicon-rich silicon nitride films with a broad range of compositions and grown using three different types of chemical vapour deposition systems. Photoluminescence (PL) experiments revealed broad, tunable emissions with peaks ranging from the near-infrared across the full visible spectrum. The emission energy was highly dependent on the film composition and changed only slightly with annealing temperature and time, which primarily affected the emission intensity. The PL spectra from films annealed for duration of times ranging from 2 s to 2 h at 600 and 800°C indicated a fast initial formation and growth of nanoclusters in the first few seconds of annealing followed by a slow, but steady growth as annealing time was further increased. X-ray absorption near edge structure at the Si K- and L_3,2-edges exhibited composition-dependent phase separation and structural re-ordering of the Si-ncs and silicon nitride host matrix under different post-deposition annealing conditions and generally supported the trends observed in the PL spectra.     

Experimental study of the effect of tool orientation in five-axis micro-milling of brass using ball-end mills

The effect of tool orientation on the final surface geometry and quality in five-axis micro-milling of brass using ball-end mills is investigated. Straight grooves with a semicircular cross section are cut with different tool inclination and tilt angles, and the resulting surfaces are characterized using an optical profilometer and microscope. Micro-milling cutting forces are recorded synchronously with spindle electric current and cutting motions in order to investigate the correlation between the tool orientation and the achieved surface quality. Results of various cutting experiments and analysis of the final surface geometry show that varying the tool orientation reduces rubbing of the material at the bottom of the grooves, which often occurs in ball-end milling of brass, and improves the final surface quality. The experimental analysis for surface roughness shows that applying a tool inclination angle of 15° can considerably improve the surface roughness at the bottom of the grooves. Analysis of static and averaged peak-to-valley (P-to-V) values of the cutting forces show that the static cutting force values are reduced by half when the tool inclination was increased from 0 to 15°. P-to-V cutting force values in along-the-feed direction were also decreased in the inclined machining.