Studies on multi-metal ion tolerance of Thiobacillus ferrooxidans

The influence of different concentrations of base metal ions, such as CU2+, Zn2+ and Fe3+, when present either alone or in different possible binary and ternary combinations in a 9K medium, on the fel rous ion oxidation ability of Thiobacillus ferrooxidans was studied. Levels and degree of toxicity of these ions have been quantified in terms of toxicity index (TI). Copper and zinc tolerant strains of the bacteria were developed through serial subculturing and their activity tested in the presence of the above metal ions in comparison with the behavior of wild unadapted cells under similar conditions. Copper tolerant strains (25 g/L Cu2+) were found to be more efficient in the bioleaching of both copper and zinc concentrates than wild unadapted strains, while zinc tolerant strains (40 g/L Zn2+) exhibited better leaching efficiency only in the bioleaching of sphalerite concentrates. The significance and relevance of multi-metal ion tolerance in Thiobacillus ferrooxidans has been highlighted with respect to bioleaching of sulphide mineral concentrates. (C) 1997 Published by Elsevier Science Ltd.

Lithium ion transport in Li2SO4-Li2O-B2O3 glasses

Electrical conductivity and dielectric relaxation studies with a wide range of compositions of lithium ion conducting glasses belonging to the ternary glass system Li2SO4-Li2O-B2-O3- have been carried out over the temperature range 150-450 K and between 10 - 10(7) Hz. DC conductivities exhibit two different activation regions. This seems to suggest the presence of a cluster tissue texture in these glasses with weakly ordered clusters of Li2SO4 and lithium berates being held together by a truly amorphous tissue of the same average composition as clusters. AC conductivity behaviour of these glasses has been analysed using both power law and stretched exponential relaxation functions. The variation of the power law exponent s and the stretched exponent beta with temperature seems to be consistent with the presence of a cluster tissue texture in these glasses.

Role of corundum-adapted strains of Bacillus polymyxa in the separation of hematite and alumina

Strains of Bacillus polymyxa, preadapted and grown in the presence of corundum, were found to be capable of the efficient separation of hematite from alumina. Results of rests peformed using binary hematite-corundum and ternary hematite-quartz-corundum mixtures in the presence of cells and metabolic products separated from the adapted bacterial culture indicated that more than 99% of the hematite could he efficiently separated through selective flocculation after desliming. It was found that alumina-specific bioproteins and other nonproteinaceous compounds were secreted by bacterial cells after adaptation to the mineral. The utility of this bioprocessing is demonstrated in the removal of iron from bauxite ores through selective flocculation in the presence of the adapted bacteria.

Role of PbO in lithium ion transport in Li2O-PbO-B2O3 glasses

Abstract: A wide range of compositions of grasses in the ternary Li2O-PbO-B2O3 glass system was prepared, and de and ac conductivity measurements were carried out on these glasses. The presence of lead leads to a decrease in de conductivities and an increase in the activation energies. This is likely to be due to the increase of the partial charges on the oxygen atoms and to the presence of the lone pair on the Pb atom; both of these factors impede lithium ion motion. The ac conductivity and dielectric behavior of these glasses support such a conjecture. (C) 2000 Elsevier Science Ltd.

Thermodynamic modeling of quaternary Al-Ga-In-As system

The present research describes the modeling of the thermodynamic properties of the liquid Al-Ga-In-As alloys at 1073 and 1173 K, and investigates the solid-liquid equilibria in the systems. The isothermal molar excess free energy function for the liquid alloys is represented in terms of 37 parameters pertaining to six of the constituent binaries, four ternaries and the quaternary interactions in the system. The corresponding solid alloys which consist of AlAs, GaAs and InAs are assumed to be quasi-regular ternary solutions. The solidus and liquidus compositions are calculated at 1073 and 1173 K using the derived values of the partial components for the solid and liquid alloys at equilibrium. They are in good agreement with those of the experimentally determined values available in the literature. (C) 1999 Elsevier Science S.A. All rights reserved.

The studies on micro-structural defects in deformed composite matrix of Al-Si-Mg and SiC

Detailed Fourier line shape analysis has been performed on three different compositions of the composite matrix of Al-Si-Mg and SiC. The alloy composition in wt% is Al-7%Si, 0.35%Mg, 0.14%Fe and traces of copper and titanium (similar to 0.01%) with SiC varying from 0 to 30wt% in three steps i.e., 0, 10 and 30wt%. The line shift analysis has been performed by considering 111, 200, 220, 311 and 222 reflections after estimating their relative shift. Peak asymmetry analysis has been performed considering neighbouring 111 and 200 reflections and Fourier line shape analysis has been performed after considering the multiple orders 111 and 222, 200 and 400 reflections. Combining all these three analyses it has been found that the deformation stacking faults both intrinsic alpha' and extrinsic alpha " are absent in this alloy system whereas the deformation twin beta has been found to be positive and increases with the increase of SiC concentration. So, like other Al-base alloys this ternary alloy also shows high stacking fault energy, and the addition of SiC introduces deformation twin which increases with its concentration in the deformed lattices.

High temperature phase chemistry of system Eu-Pd-O

An isothermal section of the phase diagram for the system Eu - Pd - O at 1223 K has been established by equilibration of samples representing 20 different compositions, and phase identification after quenching by optical and scanning electron microscopy, X-ray powder diffraction, and energy dispersive spectroscopy. Three ternary oxides, Eu4PdO7, Eu2PdO4, and Eu2Pd2O5, were identified. Liquid alloys and the intermetallic compounds EuPd2 and EuPd3 were found to be in equilibrium with EuO. The compound EuPd3 was also found to coexist separately with Eu3O4 and Eu2O3. The oxide phase in equilibrium with EuPd5 and Pd rich solid solution was Eu2O3. Based on the phase relations, four solid state cells were designed to measure the Gibbs energies of formation of the three ternary oxides in the temperature range from 925 to 1350 K. Although three cells are sufficient to obtain the properties of the three compounds, the fourth cell was deployed to crosscheck the data. An advanced version of the solid state cell incorporating a buffer electrode with yttria stabilised zirconia solid electrolyte and pure oxygen gas at a pressure of 0.1 MPa as the reference electrode was used for high temperature thermodynamic measurements. Equations for the standard Gibbs energy of formation of the interoxide compounds from their component binary oxides Eu2O3 with C type structure and PdO have been established. Based on the thermodynamic information, isothermal chemical potential diagrams and isobaric phase diagrams for the system Eu - Pd - O have been developed.

In situ synthesis of Al2O3-ZrO2-SiCW ceramic matrix composites by carbothermal reduction of natural silicates

In situ formations of Al2O3 + ZrO2 + SiCW ternary composite powders have been obtained by carbothermal reduction of a mixture of Sillimanite. Kaolin and Zircon using two different carbon sources. Products formed were mixtures of alumina and zirconia along with silicon carbide in the form of whiskers. The effects of composition of the reactants, the role of fineness of the starting precursors and the nature of the carbon Source on the final product powder obtained are presented. XRD and SEM analyses indicate complete reaction of the precursors to yield Al2O3 + ZrO2 + SiCW as product powders, with the SiC having whisker morphology. It is also seen that zirconia could be stabilised to some extent in the tetragonal form without any stabilising agent by tailoring the starting materials and their composition. (C) 2002 Published by Elsevier Science B.V.

Mechanical properties of Nylon-6/LDPE blends containing an epoxy resin compatibilizer

Binary and ternary blends of nylon-6/low density polyethylene (nylon-6/LDPE) and Nylon-6/LDPE/poly(ethylene-co-glycidyl methacrylate) were prepared by melt mixing. The blends exhibit two phase morphology with LDPE dispersed in the form of spherical domains in the nylon-6 matrix. The mechanical properties of the blends were measured by standard methods. It is shown that the use of the epoxy copolymer as a compatibilizer improves the impact strength of the blend as compared to nylon-6, which is attributed to better stress transfer across the interface due to the compatibilizer. The data for each mechanical property were also fitted into a best fit model equation and the method of steepest ascent was applied to arrive at the optimum composition of the blend for that property.

Phase diagram for the system Nd-Mn-O and thermodynamic properties of NdMnO3 and NdMn2O5

Studies on the phase relations in the system Nd-Mn-O at 1223 K showed two stable ternary compounds, NdMnO3 and NdMn2O5. An isothermal section of the ternary phase diagram for the system Nd-Mn-O was constructed based on phase analysis of samples quenched after equilibration using XRPD and EDS. An advanced version of the solid-state cell incorporating a buffer electrode was used to determine the Gibbs energies of decomposition of NdMnO3 and NdMn2O5 in the temperature range from 925 to 1400 K. Pure oxygen gas at 0.1 MPa was used as the reference electrode, and yttria-stabilized zirconia as the solid electrolyte. The buffer electrode was designed to prevent polarization of the three-phase electrode and ensure accurate data. The measured oxygen potential corresponding to the reaction,2 Nd2O3 + 4 MnO + O-2 --> 4 NdMnO3 can be represented by the equation,Amu(o2) / J.mol(-1) (+/-580) = -523 960 + 170.96 (T/K)Similarly, for the formation of NdMn2O5 according to the reaction,3 NdMnO3 + Mn3O4 + O-2 --> 3 NdMn2O5 Amu(o2) / J.mol(-1) (+/-660) = - 269 390 + 181.74 (T/K) (C) 2002 Elsevier Science Ltd. All rights reserved.

The thermodynamics and phase behaviour of Tb2Pd2O5 and Er2Pd2O5

Isothermal sections of the phase diagrams for the systems Ln-Pd-O (with Ln = Tb or Er) have been established by equilibration of samples at T = 1223 K, and phase identification after quenching by optical and scanning electron microscopy (OM, SEM), energy dispersive spectroscopy (EDS), and X-ray powder diffraction (XRPD). Two oxide phases were stable along the binary Tb-O: Tb2O3+x, a phase of variable composition, and Tb7O12 at T = 1223K. The oxide PdO was not stable at this temperature. Only one ternary oxide Tb2Pd2O5 was identified in the Tb-Pd-O system. No ternary compound was found in the system Er-Pd-O at T = 1223K. However, the compound Er2Pd2O5 could be synthesized at T = 1075 K by the hydrothermal route. In both systems, the alloys and inter-metallic compounds were all found to be in equilibrium with the lanthanide sesquioxide Ln(2)O(3) (where Ln is either Tb or Er). Two solid-state cells, each incorporating a buffer electrode, were designed to measure the Gibbs energy of formation of the ternary oxides, using yttria-stabilized zirconia as the solid electrolyte and pure oxygen gas as the reference electrode. Electromotive force measurements were conducted in the temperature range (900-1275) K for Th-Pd-O system, and at temperatures from (900-1075) K for the system Er-Pd-O. The standard Gibbs energy of formation Delta(f)G(m)degrees,, of the inter-oxide compounds from their component binary oxides Ln(2)O(3) and PdO are represented by equations linear in temperature. Isothermal chemical potential diagrams for the systems Ln-Pd-O (with Ln = Tb or Er) are developed based on the thermodynamic information. (C) 2002 Elsevier Science Ltd. All rights reserved.

Influence of synthesis route on structural phase transition in YBa2−xLaxCu3Oy (0

The compounds YBa2−xLaxCu3Oy, with compositions (0ternary phase formation temperature is influenced by the starting materials used and ionic size considerations. These factors are shown to determine the composition at which the changeover from orthorhombic (superconducting) to tetragonal (non-superconducting) phase transition (O–T transition) occurs.

Solubilities of resorcinol and pyrocatechol and their mixture in supercritical carbon dioxide

The equilibrium solubilities of dihydroxy benzene isomers (resorcinol and pyrocatechol) and its mixture were experimentally determined at different temperatures (308, 318, 328, and 338 K) in the pressure range of 9.8-16.2 MPa. In the ternary system, the solubilities of pyrocatechol increased while the solubilities of resorcinol decreased relative to their binary solubilities. A new association model was developed based on the concept of formation of solvate complex molecules to correlate the solubility of the solid for mixed solids in supercritical carbon dioxide (SCCO(2)). The model equation relates the solubility of solute in terms of the cosolute composition, temperature, pressure and density of SCCO(2). The proposed model correlated the solubilities of sixteen solid systems taken from the literature and current experimental data with an average absolute relative deviation (AARD) of around 4%. (C) 2011 Elsevier B.V. All rights reserved.

Calcium ruthenates: Determination of Gibbs energies of formation using electrochemical cells

Metallic Ru has been found to coexist separately with CaO, RuO2, and the interoxide phases, Ca2RuO4, Ca3Ru2O7, and CaRuO3, present along the pseudobinary system CaO-RuO2. The standard Gibbs energies of formation (Df((ox))G(o)) of the three calcium ruthenates from their component oxides have been measured in the temperature range 925-1350 K using solid-state cells with yttria-stabilized zirconia as the electrolyte and Ru+RuO2 as the reference electrode. The standard Gibbs energies of formation (Deltaf((ox))G(o)) of the compounds can be represented by Ca2RuO4:Deltaf((ox))G(o)/J mol(-1)=-38,340-6.611 T (+/-120), Ca3Ru2O7 : Df((ox))G(o)/J mol(-1)=-75,910-11.26 T (+/-180), and CaRuO3 : Deltaf((ox))G(o)/J mol(-1)=-35,480-3.844 T(+/-70). The data for Ca2RuO4 corresponds to the stoichiometric composition, which has an orthorhombic structure, space group Pbca, with short c axis ("S'' form). The structural features of the ternary oxides responsible for their mild entropy stabilization are discussed. A three-dimensional oxygen potential diagram for the system Ca-Ru-O is developed as a function of composition and temperature from the results obtained. Using the Neumann-Kopp rule to estimate the heat capacity of the ternary oxides relative to their constituent binary oxides, the standard enthalpies of formation of the three calcium ruthenates from the elements and their standard entropies at 298.15 K are evaluated. (C) 2003 The Electrochemical Society.

Standard Gibbs energy of formation of Pb2Ru2O6.5

Lead ruthenate is used as a bifunctional electrocatalyst for both oxygen evolution and reduction and as a conducting component in thick-film resistors. It also has potential applications in supercapacitors and solid oxide fuel cells. However, thermodynamic properties of the compound have not been reported in the literature. The standard Gibbs energy of formation has now been determined in the temperature range from 873 to 1123 K using a solid-state cell incorporating yttria-stabilized zirconia (YSZ) as the electrolyte, a mixture of PbO + Pb2Ru2O6.5 + Ru as the measuring electrode, and Ru + RuO2 as the reference. The design of the measuring electrode is based on a study of phase relations in the ternary system Pb–Ru–O at 1123 K. For the reaction,S0884291400095625_eqnU1 the standard enthalpy of formation and standard entropy at 298.15 K are estimated from the high-temperature measurements. An oxygen potential diagram for the system Pb–Ru–O is composed based on data obtained in this study and auxiliary information from the literature