Evaluation of the activity and molecular form of bi in cu smelting slags: Part I. ternary silicate slags

The thermodynamic behavior of bismuth in the chemical systems associated with copper processing is not well understood. This study was designed to further the understanding of the physical chemistry of bismuth in slags that have similar compositions to those found in copper extractive metallurgical processing. The silicate system investigated was the FeO-Fe₂O₃-SiO₂ ternary system in which bismuth was dissolved using an isopiestic experimental technique. Bismuth vapor pressures of 1 • 10⁻⁵ atm and 7.5 • 10⁻⁴ atm were used, and the silicates were equilibrated with this vapor at temperatures of 1458 K and 1523 K. In these experiments, the slag composition was varied such thatP _{O 2} ranged from 10⁻¹² to 10⁻⁸ atm. Bismuth was found to enter the silicate slag in both neutral and oxidic molecular forms. The oxidic form identified was that of BiO. The data suggest that the activity coefficient of neutral bismuth, γ_Bi, is dependent on the solubility of that species in slag, even at the low concentrations observed in this study. It has been hypothesized, based on the large diameter of neutral Bi, that only a limited number of sites are available to accommodate neutral Bi, and that as the limit is approached γ_Bi increases significantly. That hypothesis is shown to be consistent with the experimental results obtained in the present work as well as the results obtained by other investigators.     

Evaluation of the activity and molecular form of bi in cu smelting slags: Part I. ternary silicate slags

The thermodynamic behavior of bismuth in the chemical systems associated with copper processing is not well understood. This study was designed to further the understanding of the physical chemistry of bismuth in slags that have similar compositions to those found in copper extractive metallurgical processing. The silicate system investigated was the FeO-Fe₂O₃-SiO₂ ternary system in which bismuth was dissolved using an isopiestic experimental technique. Bismuth vapor pressures of 1 ? 10^?5 atm and 7.5 ? 10^?4 atm were used, and the silicates were equilibrated with this vapor at temperatures of 1458 K and 1523 K. In these experiments, the slag composition was varied such thatP _{O 2} ranged from 10^?12 to 10^?8 atm. Bismuth was found to enter the silicate slag in both neutral and oxidic molecular forms. The oxidic form identified was that of BiO. The data suggest that the activity coefficient of neutral bismuth, γ_Bi, is dependent on the solubility of that species in slag, even at the low concentrations observed in this study. It has been hypothesized, based on the large diameter of neutral Bi, that only a limited number of sites are available to accommodate neutral Bi, and that as the limit is approached γ_Bi increases significantly. That hypothesis is shown to be consistent with the experimental results obtained in the present work as well as the results obtained by other investigators.     

Critical assessment of activity coefficients of oxides in molten binary and ternary silicates,aluminates and aluminosilicates

Critical assessment is made of the activity coefficients of CaO, MgO, MnO, FeO, Al₂O₃ and SiO₂ in molten silicates, aluminates and aluminosilicates. In this assessment due consideration is given to the consistency of the free energies of formation of the interoxide compounds derived from the oxide activity data, compared with those derived from the compiled thermochemical data. For most oxides, it is found that by using an empirical formulation of the melt composition in ternary systems, the composition dependence of the oxide activity coefficient, γOX, can be represented by a single curve. For example, over a wide composition range in the FeO‐CaO‐SiO₂ system, the log(γCaO) is a single function of the melt composition in mol fraction as (?SiO₂ + 0.3xFeO); this relation being similar to that in the binary CaO‐SiO₂ melts. Therefore, with respect to γCaO, this ternary system is reduced to a pseudo binary system as xCaO ‐ (?SiO₂ + 0.3xFeO). With respect to γCaO, the ternary system CaO‐Al₂O₃‐SiO₂ is reduced to a pseudo binary system as xCaO ‐ (?SiO₂ + 0.4 xAl₂O₃). With γSiO₂, this ternary system is reduced to a pseudo binary system as (?CaO + xAl₂O₃) ‐ xSiO₂.     

The acid decomposition of silicate minerals part I. Reactivities and modes of dissolution of silicates

Factors determining the modes of dissolution and reactivities of silicates in acids are discussed. Under the action of acids, ortho-, pyro- and cyclosilicates decompose with dissolution of metal cations and silica. In contrast, partial decomposition of the chain, sheet and framework silicates is the normal result of acid attack. This leads to dissolution of metal cations and leaves a siliceous residue. Silicate reactivity is determined by a combination of structural factors and the properties of the metal cation of the silicate. Complexing of the metal ion with anions is capable of enhancing the dissolution rate of metal silicates in acids. Cases where silicate reactivity is determined by diffusion processes or by properties of the ore containing the silicate are considered.     

Hydrodynamics of gas stirred melts: Part I. Gas/liquid coupling

A hydrodynamic model of submerged gas injection systems and their effects on liquid metal stirring is presented. It is argued that hydrodynamic conditions at the nozzle, tuyere, or plug are not critical to flow recirculation produced in large cylindrical vessels(i.e., furnaces or ladles). An analysis of a buoyancy driven plume generated through gas injection shows that gas voidages are usually quite low (less than 10 pct). By equating the energy supplied by rising bubbles to turbulent energy losses within the bath, it is shown that mean plume velocities can be predicted using the relationship,U _p α (Q ^1/3 L ^1/3)/R^1/3 whereU _p equals mean plume velocity,Q is gas flow rate (at mean height and temperature),L is depth of liquid, andR is radius of the vessel. Associated rates of liquid turnover as a function of vessel dimensions and gas flow rate can also be predicted and these are similarly presented.     

ICP-AES法测定铁矿石中SiO_2,CaO,MgO,Al_2O_3,MnO和TiO_2

采用电感耦合等离子体发射光谱法对铁矿石中SiO2 ,CaO ,MgO ,Al2 O3,MnO ,TiO2 的分析进行了试验研究。试液中10mg/mLFe存在时 ,基体效应明显 ,采用基体匹配办法消除铁的干扰。Ca ,Mg ,Al,Si,Ti,Mn ,Ni,Cr ,Cu ,Co ,Zn ,V ,Ba之间没有干扰 ;稀土元素对SiO2 的测定有干扰。Al,Ca ,Mg ,Mn ,Si,Ti的检出限分别为 0.5 ,0.12 5 ,0.0 5 ,0.0 5 ,0.2 5 ,0.0 0 2 5 μg/mL ,回收     

The thermodynamic activity of MnO in melts containing SiO2, B2O3, and TiO2

The activity of MnO in the systems MnO-Ti₂ and MnO-B₂O₃, and in pseudobinary sections in the systems MnO-TiO₂-SiO₂, MnO-TiO₂-B₂O₃ and MnO-SiO₂-B₂O₃ have been measured at temperatures in the range of 1400 to 1550 °C by means of the technique in which equilibrium is established between the melt, a gaseous atmosphere of fixed oxygen pressure and a Pt-Mn foil immersed in the melt. The excess free energies of melts in the system MnO-TiO₂ at 1500 and 1550 °C are closely represented by the regular solution formalism withG _xs = −55280N _MnO ·N _{TiO 2} J, and the form of the variation ofa _MnO, within the narrow composition range amenable to study at 1400 °C in the system MnO-B₂O₃, is characteristic of a system of polyanions. The negative deviations ofa _MnO from a proposed model behavior, observed in melts in the systems MnO-SiO₂-TiO₂ and MnO-B₂O₃-TiO₂, are explained in terms of the influence of preferred ionic interactions between Ti₄₊ and O₂ and between Mn₂₊ and the O₋ groups on the polysilicate or polyborate anions. The activity of MnO is independent of composition in the system 2MnO · SiO₂−3MnO · B₂O₃ and the thermodynamics of mixing are calculated from application of polymer theory. The influence of B₂O₃ and TiO₂ on the activity of MnO in manganese silicates is discussed with reference to the proposed use of B₂O₃ and/or TiO₂ as substitutes for CaF₂ as the flux for steelmaking slags.     

The sulfide capacities of CaO-SiO2 melts containing MgO,FeO, TiO2, and Al2O3

The sulfide capacities of CaO-SiO₂ melts containing MgO, FeO, TiO₂, and A1₂O₃ have been measured by simultaneous equilibration within quartz capsules at 1776 K (1503 °C). The compositions of the melt samples and static gas phase within each capsule adjusted to establish a mutual equilibrium. The sulfide capacities, C_s, of all equilibrated samples must satisfy the following equation: $$C_{{\text{S(}}j{\text{)}}} = \frac{{{\text{pctS}}_j }}{{pctS_i }} \bullet C_{S(i)} $$ The inclusion of several reference slags for which values of C_s are known from previous measurements enabled the calculation of the sulfide capacities of unknown samples. The influences of basic oxide substitutions (FeO and MgO) for CaO and acidic oxide substitutions (TiO₂ and A1₂O₃) for SiO₂ on the sulfide capacities of CaO-SiO₂ melts have been measured. When a basic oxide/acidic oxide ratio of 1.21 is maintained, MgO additions decrease sulfide capacity, while FeO, TiO₂ and A1₂O₃ additions increase sulfide capacity. The results are compared with earlier measurements on the influences of CaF₂ and B₂O₃, and the relative effects are discussed in terms of the activity of free oxide ions.     

Infiltration of fiber preforms by a binary alloy: Part I. Theory

During infiltration of a fiber preform by a binary hypoeutectic alloy, solid metal can form in the composite because of cooling at the fibers or at the mold wall. Contrary to the case of an unalloyed matrix, temperature, composition, and fraction solid may vary in the composite. This results in macrosegregation and microstructural heterogeneity within the composite casting. It is shown that solid metal that forms because of cooling at the fibers grows gradually behind the infiltration front, while the local temperature increases. Metal superheat, when present, serves to progressively remelt solid metal in the composite during infiltration and increases compositional and microstructural heterogeneity within the composite. General expressions are derived to describe heat, mass, and fluid flow during the infiltration process. In the case of unidirectional adiabatic infiltration driven by a constant applied pressure, a similarity method can be used to reduce the mathematical complexity of the problem. Numerical solution of the resulting equations then allows us to predict temperature, fraction solid, and composition profiles within the composite. With the further assumption of negligible thermal conduction, the problem lends itself to an analytical solution. The analysis is performed for the case of unidirectional adiabatic infiltration under constant applied pressure of 24 vol pct δ-alumina preforms by Al-4.5 wt pct Cu. Results indicate that there is significant latitude for control of macro-segregation and microstructure within cast fiber-reinforced alloys.     

Nucleation and phase selection in undercooled Fe-Cr-Ni melts: Part I. Theoretical analysis of nucleation behavior

The selection of the primary solidifying phase in undercooled stainless steel melts is theoretically analyzed in terms of nucleation theory. Nucleation phenomena are considered using different models for the solid-liquid interface energy. The classical nucleation theory for sharp interfaces and an improved modification, the diffuse interface theory, are applied. The influence of deviations of the nucleus composition from the overall alloy composition is also revealed. A preferred nucleation of the metastable bcc phase in fcc equilibrium solidification-type alloys is predicted. The critical undercooling of metastable crystallization as a function of alloy composition is calculated for an isoplethal section at 69 at. pct Fe of Fe₆₉Cr_31-x Ni _x alloys. The results are summarized in a phase selection diagram predicting the primary solidification mode as a function of undercooling and melt composition.     

Review of cerebral palsy, Part I: Description, incidence, and etiology

Cerebral palsy (CP) is a nonprogressive disorder of motor function. Although it has been recognized for more than a century, much remains unknown regarding its etiology. It has been estimated that 17 to 60 percent of the cases of CP have no known perinatal or neonatal complications. Undocumented antenatal events may cause brain damage or increase the infant's vulnerability to future events. The prevalence of CP has remained relatively constant; however, its incidence in the preterm population has increased with the improving survival of the very low birth weight infant.     

Interaction of oxyfluoride melts of Ca,Si, Mg,Al, and Na with steels: I. Chromium-carbon-containing melts

The interaction of a mixture of Ca, Si, Mg, Al, and Na oxides and fluorides with two chromium-carbon-containing iron-based melts are experimentally studied at 1600°C and p _Ar = 0.1 MPa. The equilibrium concentrations of the components in the slag at a holding time of 500 s are determined. The chromate capacities of the oxyfluoride melts are calculated and related to the composition of the melted slag using its optical basicity.     

Sulfide and sulfate solid solubility in lime,magnesia, and calcined dolomite: Part I. CaS and CaSO4 solubility in CaO

In the present work the solid solubilities of CaS and CaSQ, in burnt lime were investigated by equilibrating lime with CO-CO₂-SO₂ mixtures at temperatures from 950 to 1300°C. Also, the equilibrium constants for the formation of CaS and CaSO₄ were determined. At high oxy-gen activities, corresponding to a CO₂/CO ratio >100 in the gas, the sulfur dissolves in lime primarily as sulfate ions. At lower oxygen activities (CO₂/CO <30), the sulfur goes into so-lution in lime essentially as sulfide ions. Over the temperature range investigated the limit-ing sulfide solubility is within 0.01 to 0.03 pct S, whereas the sulfate solubility is within 0.03 to 0.1 pct S, increasing with increasing temperature. An erratum to this article is available at .     

Influence of the Al2O3-contents in the ternary-systems (FeO,MnO, CaO,MgO)- Al2O3-SiO2 on the course of the mixture gaps in the ternary space

In accordance with the previous phase equilibria in the ternary systems (FeO, MnO, CaO, MgO)- Al₂O₃-SiO₂ even small Al₂O₃-contents should be sufficient to close the wide mixture gaps in the binary edge systems of FeO-SiO₂, MnO-SiO₂, CaO-SiO₂ and MgO-SiO₂, which are stable in the temperature range from 1700 to 2100-2200°C. Thermodynamically this acceptance is not impossible but rather improb-able. Based on phase-theoretical considerations and the previous results of literature about the course of an unstable mixture gap in the system SiO₂-Al₂O₃ two thermodynamically founded versions were developed as possible, resulting phase equilibria in the SiO₂-rich, but experimentally not exactly examined part of the mentioned ternary-systems, and were added to the experimentally secured sections of these systems unproblematically.     

Rate of decarburization of iron-carbon melts: Part I. experimental determination of the effect of sulfur

The kinetics of decarburization of iron-carbon melts with CO-CO₂ gas mixtures were investigated at 1700 ° using the levitation technique. The influences of different experimental variables on the decarburization kinetics were determined. It was found that sulfur has a clear and reproducible retarding effect on the decarburization of iron-carbon melts; and this effect is most pronounced at sulfur concentrations in the range of 0 to 0.05 wt pct. The initial carbon concentration has no discernible effect on the decarburization kinetics. Melts containing 2.48 wt pct C and 0.92 wt pct C initially were found to decarburize at virtually identical rates until a substantial portion of the carbon was removed. The decarburization rate of a melt with a specified initial carbon content was found to remain essentially constant until the carbon content fell to a characteristic level below which the rate tended to level off. The partial pressure of CO₂ of the gas mixture has a marked effect on the decarburization kinetics. The flow-rate of the gas mixture has a small but finite effect on the rate of decarburization.     

Modeling of gas-liquid reactions in ladle metallurgy: Part I. Physical modeling

A physical model of a ladle degassing operation was developed to simulate the reactions at rising bubbles and at the free surface. Carbon dioxide desorption from a sodium hydroxide solution was used to simulate the liquid-phase diffusion-controlled decarburization of liquid steel. It was found that under reduced pressure, the reactions were faster than attributable to solely the increase in volumetric flow rate. It was possible to separate the reactions with the bubbles from the free surface reactions; 20 to 40 pct of the reactions occurred at the free surface, depending on injection conditions. The free surface desorption rate depended on the gas flow rate and the number of injectors. The mass transfer coefficients to the bubbles were in reasonable agreement with previous work. Plume bending was observed when small bubbles were influenced by the bulk liquid flow patterns.     

Macrotransport-solidification kinetics modeling of equiaxed dendritic growth: Part I. Model development and discussion

An analytical model that describes solidification of equiaxed dendrites has been developed for use in solidification kinetics-macrotransport modeling. It relaxes some of the assumptions made in previous models, such as the Dustin-Kurz, Rappaz-Thevoz, and Kanetkar-Stefanescu models. It is assumed that nuclei grow as unperturbed spheres until the radius of the sphere becomes larger than the minimum radius of instability. Then, growth of the dendrites is related to morphological instability and is calculated as a function of melt undercooling around the dendrite tips, which is controlled by the bulk temperature and the intrinsic volume average concentration of the liquid phase. When the general morphology of equiaxed dendrites is considered, the evolution of the fraction of solid is related to the interdendritic branching and dynamic coarsening (through the evolution of the specific interfacial areas) and to the topology and movement of the dendrite envelope (through the tip growth velocity and dendrite shape factor). The particular case of this model is the model for globulitic dendrite. The intrinsic volume average liquid concentration and bulk temperature are obtained from an overall solute and thermal balance around a growing equiaxed dendritic grain within a spherical closed system. Overall solute balance in the integral form is obtained by a complete analytical solution of the diffusion field in both liquid and solid phases. The bulk temperature is obtained from the solution of the macrotrasport-solidification kinetics problem.     

Oxidation Studies of SiAlON/MgAlON Ceramics with Fe2O3 and CaO Impurities, Part I: Kinetics

The oxidation behaviors of composites SiAlON/MgAlON phases (β-SiAlON, 15R-SiAlON and MgAlON) synthesized from the residue during the leaching treatment of salt cake and corresponding synthetic samples were investigated in air by thermogravimetric measurements. Combined kinetics, viz. linear law + arctan law + parabolic law, are used to describe the kinetics of oxidation in isothermal mode. The oxidation studies reveal the effects of impurities, namely, Fe₂O₃ and CaO, present in the salt cake residue. The addition of Fe₂O₃ results in a lower activation energy and more aggressive oxidation. The addition of CaO caused the shrinkage during the synthesis and liquid formation during the oxidation above 1673 K (1400 °C). The impurities of CaO and Fe₂O₃ in the leaching residue can result in an aggressive oxidation at low temperature and a protective oxidation at temperatures above the eutectic point.