The effect of the CaO/SiO2 ratio on the phase equilibria in the ZnO-“Fe2O3”-(PbO + CaO + SiO2) system in air: CaO/SiO2 = 0.1, PbO/(CaO + SiO2) = 6.2, and CaO/SiO2 = 0.6, PbO/(CaO + SiO2) = 4.3

Experimental studies on phase equilibria in the multi-component system PbO-ZnO-CaO-SiO2-FeO-Fe2O3 in air have been conducted to characterize the phase relations of a complex slag system used in the oxidation smelting of lead and in typical lead blast furnace sinters. The liquidus in two pseudoternary sections ZnO-Fe2O3-(PbO + CaO + SiO2) with the CaO/SiO2 weight ratio of 0.1 and the PbO/(CaO + SiO2) weight ratio of 6.2, and with CaO/SiO2 weight ratio of 0.6 and the PbO/(CaO + SiO2) weight ratio of 4.3, have been constructed.

Experimental study of phase equilibria in the Al-Fe-Zn-O system in air

The phase equilibria in the Al-Fe-Zn-O system in the range 1250 °C to 1695 °C in air have been experimentally studied using equilibration and quenching techniques followed by electron probe X-ray microanalysis. The phase diagram of the binary Al2O3-ZnO system and isothermal sections of the Al2O3-“Fe2O3”-ZnO system at 1250 °C, 1400 °C, and 1550 °C have been constructed and reported for the first time. The extents of solid solutions in the corundum (Al,Fe)2O3, hematite (Fe,Al)2O3, Al2O3*Fe2O3 phase (Al,Fe)2O3, spinel (Al,Fe,Zn)O4, and zincite (Al,Zn,Fe)O primary phase fields have been measured. Corundum, hematite, and Al2O3*Fe2O3 phases dissolve less than 1 mol pct zinc oxide. The limiting compositions of Al2O3*Fe2O3 phase measured in this study at 1400 °C are slightly nonstoichiometric, containing more Al2O3 then previously reported. Spinel forms an extensive solid solution in the Al2O3-“Fe2O3”-ZnO system in air with increasing temperature. Zincite was found to dissolve up to 7 mole pct of aluminum in the presence of iron at 1550 °C in air. A meta-stable Al2O3-rich phase of the approximate composition Al8FeZnO14+x was observed at all of the conditions investigated. Aluminum dissolved in the zincite in the presence of iron appears to suppress the transformation from a round to platelike morphology.

Phase equilibria at sub-solidus conditions in the Fe-Mg-Zn-O system in air

The phase equilibria in the Fe-Mg-Zn-O system in the temperature range 1100-1550degreesC in air have been experimentally studied using equilibration and quenching followed by electron probe X-ray microanalysis. The compositions of condensed phases in equilibrium in the binary MgO-ZnO system and the ternary Fe-Mg-O system have been reported at sub-solidus in air. Pseudo-ternary sections of the quaternary Fe-Mg-Zn-O system at 1100, 1250 and 1400degreesC in air were constructed using the experimental data. The solid solution of iron oxide, MgO and ZnO in the periclase (Mg, Zn, Fe)O, spinel (Mg2+, Fe2+, Zn2+)(x)Fe(2+y)3+O4 and zincite (Zn, Mg, Fe)O phases were found to be extensive under the conditions investigated. A continuous spinel solid solution is formed between the magnesioferrite (Mg2+, Fe2+)(x)Fe(2+y)3+O4 and franklinite (Zn2+, Fe2+)(x)Fe(2+y)3+O4 end-members at 1100 and 1250degreesC, extending to magnetite (Fe2+)(x)Fe(2+y)3+O4 at 1400degreesC in air. The compositions along the spinel boundaries were found to be non-stoichiometric, the magnitude of the non-stoichiometry being a function of composition and temperature in air. It was found that hematite dissolves neither MgO nor ZnO in air.

Phase equilibria in the ZnO-rich area of the Fe-Zn-O system in air

The phase equilibria in the Fe-Zn-O system in the range 900-1580degreesC in air have been experimentally studied using equilibration and quenching techniques. The compositions of the phases at equilibrium were determined using electron probe X-ray microanalysis (EPMA). The ferrous and ferric bulk iron concentrations were measured with a wet chemical analysis using the ammonium metavanadate technique. X-ray powder diffraction analysis (XRD) was used to characterise the phases. Iron oxide dissolved in zincite was found to be present principally in the ferric form. The XRD analysis and the composition measurements both indicate that zincite is the only phase stable in the ZnO-rich area in the range of conditions investigated. The solubility of the iron oxide in zincite rapidly increases at temperatures above 1200degreesC; the morphology of the zincite crystals also sharply changes between 1200 and 1300degreesC from rounded to plate-like crystals. The plate-like zincite forms a refractory network-the type of microstructure beneficial to the Imperial Smelting Process (ISP) sinter performance. The software program FactSage with a thermodynamically optimised database was used to predict phase equilibria in the Fe-Zn-O system.

A reinvestigation of phase equilibria in the system Al2O3-SiO2-ZnO

The phase equilibria and liquidus temperatures in the binary SiO2-ZnO system and in the ternary Al2O3-SiO2-ZnO system at low Al2O3 concentrations have been experimentally determined using the equilibration and quenching technique followed by electron probe X-ray microanalysis. In the SiO2-ZnO system, two binary eutectics involving the congruently melting willemite (Zn2SiO4) were found at 1448 +/- 5 degrees C and 0.52 +/- 0.01 mole fraction ZnO and at 1502 +/- 5 degrees C and 0.71 +/- 0.01 mole fraction ZnO, respectively. The two ternary eutectics involving willemite previously reported in the Al2O3SiO2-ZnO system were found to be at 1315 +/- 5 degrees C and 1425 +/- 25 T, respectively. The compositions of the eutectics are 0.07, 0.52, and 0.41 and 0.05, 0.28, and 0.67 mole fraction Al2O3, SiO2, and ZnO, respectively. The results of the present investigation are significantly different from the results of previous studies.

Phase equilibria in the system Fe-Zn-O at intermediate conditions between metallic-iron saturation and air

The phase equilibria in the FeO-Fe2O3-ZnO system have been experimentally investigated at oxygen partial pressures between metallic iron saturation and air using a specially developed quenching technique, followed by electron probe X-ray microanalysis (EPMA) and then wet chemistry for determination of ferrous and ferric iron concentrations. Gas mixtures of H-2, N-2, and CO2 or CO and CO2 controlled the atmosphere in the furnace. The determined metal cation ratios in phases at equilibrium were used for the construction of the 1200 degrees C isothermal section of the Fe-Zn-O system. The univariant equilibria between the gas phase, spinel, wustite, and zincite was found to be close to pO(2) = 1 center dot 10(-8) atm at 1200 degrees C. The ferric and ferrous iron concentrations in zincite and spinel at equilibrium were also determined at temperatures from 1200 degrees C to 1400 degrees C at pO(2) = 1 center dot 10(-6) atm and at 1200 degrees C at pO(2) values ranging from 1 center dot 10(-4) to 1 center dot 10(-8) atm. Implications of the phase equilibria in the Fe-Zn-O system for the formation of the platelike zincite, especially important for the Imperial Smelting Process (ISP), are discussed.

Phase equilibria in the Fe-Zn-O system at conditions relevant to zinc sintering and smelting

Zincite and spinel phases are present in the complex slag systems encountered in zinc/lead sintering and zinc smelting processes. These phases form extensive solid solutions and are stable over a wide range of compositions, temperatures and oxygen partial pressures. Accurate information on the stability of these phases is required in order to develop thermodynamic models of these slag systems. Phase equilibria in the Fe–Zn–O system have been experimentally studied for a range of conditions, between 900°C and 1580°C and oxygen partial pressures (pO2) between air and metallic iron saturation, using equilibration and quenching techniques. The compositions of the phases were measured using Electron probe X-ray microanalysis (EPMA). The ferrous and ferric bulk iron concentrations were determined using a specially developed wet-chemical analysis procedure based on the use of ammonium metavanadate. XRD was used to confirm phase identification. A procedure was developed to overcome the problems associated with evaporation of zinc at low pO2 values and to ensure the achievement of equilibria. An isothermal section of the system FeO–Fe2O3–ZnO at high ZnO concentrations at 1200°C was constructed. The maximum solubilities of iron and zinc in zincite and spinel phases in equilibrium were determined at pO2 = 1 × 10-6 atm at 1200°C and 1300°C. The morphology of the zincite crystals sharply changes in air between 1200–1300°C from rounded to plate-like. This is shown to be associated with significant increase in total iron concentration, the additional iron being principally in the form of ferric iron. Calculations performed by FactSage with a thermodynamically optimised database have been compared with the experimental results.

Edge-to-edge matching and its applications - Part I. Application to the simple HCP/BCC system

The edge-to-edge matching crystallographic model has been used to predict all the orientation relationships (OR) between crystals that have simple hexagonal close packed (HCP) and body-centered cubic (BCC) structures. Using the critical values for the interatomic spacing misfit along the matching directions and the cl-value mismatch between matching planes, the model predicted all the four common ORs, namely the Burgers OR, the Potter OR, the Pitsch-Schrader OR and the Rong Dunlop OR, together with the corresponding habit planes. Taking the c(H)/a(H) and a(H)/a(B) ratios as variables, where H and B denote the HCP and BCC structures respectively, the model also predicted the relationship between these variables and the four ORs. These predictions are perfectly consistent with the published experimental results. As was the case in the FCC/BCC system, the edge-to-edge matching model has been shown to be a powerful tool for predicting the crystallographic features of diffusion-controlled phase transformations. (C) 2004 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

Effects of Al2O3 on phase equilibria in the olivine primary phase field of the MgO-"FeO"-SiO2-Al2O3 system in equilibrium with metallic iron

Liquidus temperatures and phase equilibria have been determined in the olivine primary phase field of the MgO-FeO-SiO2-Al2O3 system. Liquidus isotherms have been determined in the temperature range from 1748 to 1873K. The results are presented in the form of pseudo-ternary sections of the MgO-FeO-SiO2 with 2 and 3wt% Al2O3 in the liquid. The study enables the liquidus to be described for a range of SiO2/MgO ratios. It was found that liquidus temperatures in the olivine primary phase field decrease with the addition of Al2O3.

Phase behavior, crystallization, and nanostructures in thermoset blends of epoxy resin and amphiphilic star-shaped block copolymers

This article reports thermoset blends of bisphenol A-type epoxy resin (ER) and two amphiphilic four-arm star-shaped diblock copolymers based on hydrophilic poly(ethylene oxide) (PEO) and hydrophobic poly(propylene oxide) (PPO). 4,4'-Methylenedianiline (MDA) was used as a curing agent. The first star-shaped diblock copolymer with 70 wt% ethylene oxide (EO), denoted as (PPO-PEO)(4), consists of four PPO-PEO diblock arms with PPO blocks attached on an ethylenediamine core; the second one with 40 wt% EO, denoted as (PEO-PPO)(4), contains four PEO-PPO diblock arms with PEO blocks attached on an ethylenediamine core. The phase behavior, crystallization, and nanoscale structures were investigated by differential scanning calorimetry, transmission electron microscopy, and small-angle X-ray scattering. It was found that the MDA-cured ER/(PPO-PEO)(4) blends are not macroscopically phase-separated over the entire blend composition range. There exist, however, two microphases in the ER/(PPO-PEO)(4) blends. The PPO blocks form a separated microphase, whereas the ER and the PEO blocks, which are miscible, form another microphase. The ER/(PPO-PEO)(4) blends show composition-dependent nanostructures on the order of 10-30 nm. The 80/20 ER/(PPO-PEO)(4) blend displays spherical PPO micelles uniformly dispersed in a continuous ER-rich matrix. The 60/40 ER/(PPO-PEO)(4) blend displays a combined morphology of worm-like micelles and spherical micelles with characteristic of a bicontinuous microphase structure. Macroscopic phase separation took place in the MDA-cured ER/(PEO-PPO)(4) blends. The MDA-cured ER/(PEO-PPO)(4) blends with (PEO-PPO)(4) content up to 50 wt% exhibit phase-separated structures on the order of 0.5-1 mu m. This can be considered to be due to the different EO content and block sequence of the (PEO-PPO)(4) copolymer. (c) 2006 Wiley Periodicals, Inc.

Synthesis and immunological evaluation of M protein targeted tetra-valent and tri-valent group A streptococcal vaccine candidates based on the lipid-core peptide system

Group A streptococcus (GAS) is responsible for causing many clinical complications including the relatively benign streptococcal pharyngitis and impetigo. However. if left untreated. these conditions may lead to more severe diseases such as rheumatic fever (RF) and rheumatic heart disease (RHD). These diseases exhibit high morbidity and mortality, Particularly in developing countries and in indigenous populations of affluent countries. Only ever occur following GAS infection, a vaccine offers Promise for their Prevention. As stich, we have investigated the Use of the lipid-core peptide (LCP) system for the development of multi-valent Prophylactic GAS vaccines. The current study has investigated the capacity of this system to adjuvant LIP to four different GAS peptide epitopes. Presented are the synthesis and immunological assessment of tetra-valent and tri-valent GAS LCP systems. We demonstrated their capacity to elicit systemic IgG antibody responses in B10.BR mice to all GAS peptide epitopes. The data also showed that the LCP systems Were self-adjuvanting. These findings are particularly encouraging for the development of multi-valent LCP-based GAS vaccines.