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Equilibrium Phase Diagrams (equilibrium + phase_diagram)
Selected AbstractsEquilibrium Phase Diagram of the Ag,Au,Pb Ternary System.CHEMINFORM, Issue 25 2005S. Hassam No abstract is available for this article. [source] Isograds and P,T evolution in the eastern Lepontine Alps (Graubünden, Switzerland)JOURNAL OF METAMORPHIC GEOLOGY, Issue 3 2002T. Nagel Abstract Reactions producing Al-rich index minerals in the south-eastern part of the Lepontine Dome (Central Alps, Switzerland) are investigated using mineral distribution maps, microstructural observations and equilibrium phase diagrams. The apparent staurolite mineral zone boundary corresponds to the paragonite breakdown reaction Pg + Grt + Qtz = Pl + Al2O3 + W. Equilibrium phase diagrams show that most natural metapelites do not contain staurolite or alumosilicates as long as univalent cations are predominantly accommodated in white mica. For a wide range of metapelitic compositions the paragonite breakdown releases sufficient Al for the formation of these minerals. Rare occurrences of staurolite and kyanite, north of the formerly mapped mineral zone boundaries, coexist with paragonite and are restricted to extremely Al-rich bulk compositions. The stable branch of the kyanite-forming paragonite breakdown reaction above 660 °C yields an additional mapable isograd. The second set of Al-releasing reactions is biotite-producing phengite breakdown. However, these reactions are less suitable to produce well defined reaction isograds in the field as they are more continuous and their progress is strongly dependent on bulk composition. Well developed fibrolite in metapelites does not appear until staurolite starts to breakdown. We conclude that amphibolite facies conditions in the study area were attained by decompression, without substantial heating at low pressures. [source] Effect of Oxygen Partial Pressure on the Formation of Metastable Phases from an Undercooled YbFeO3 Melt Using an Aerodynamic LevitatorJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 4 2009Malahalli S. Vijaya Kumar The Yb2O3,Fe2O3 system was studied to investigate the effect of oxygen partial pressure on the formation of metastable phases over a wide range of oxygen partial pressures from 105 to 10,1 Pa. Two kinds of metastable phases, with space groups of P63cm and P63/mmc, were found through rapid solidification of an undercooled YbFeO3 melt in an atmosphere with reduced Po2. The crystal structure of the as-solidified samples changed from orthorhombic Pbnm to hexagonal P63cm and P63/mmc with decreasing Po2. X-ray diffractometric and scanning electron microscopic results confirmed the existence of various phases in the as-solidified samples. The stabilities of each phase were studied by annealing the bulk sample in the thermogravimetric,differential thermal analysis (TG-DTA) furnace up to 1673 K, and the equilibrium phase diagram was constructed for the Yb,Fe,O system at 1473 K. TG analysis showed an increase of the sample mass during annealing and revealed that the existence of Fe2+, which has an ionic radius larger than that of Fe3+, decreases the tolerance factor and therefore destabilizes the perovskite structure. [source] Electronic Structure and Bonding of All Crystalline Phases in the Silica,Yttria,Silicon Nitride Phase Equilibrium DiagramJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 11 2004Wai-Yim Ching This paper reviews the structures and properties of 10 binary, ternary, and quaternary crystals within the equilibrium phase diagram of the SiO2,Y2O3,Si3N4 system. They are binary compounds SiO2, Y2O3, Si3N4; ternary compounds Si2N2O, Y2Si2O7, and YSi2O5; and quaternary crystals Y2Si3N4O3 (M-melilite), Y4Si2O7N2, (N-YAM), YSiO2N (wallastonite), and Y10(SiO4)6N2 (N-apatite, N-APT). Although the binary compounds are well-known and extensively studied, the ternary and the quaternary crystals are not. Most of the ternary and the quaternary crystals simply have been referenced as secondary phases in the processing of nitrogen ceramics. Their crystal structures are complex and not precisely determined. In the quaternary crystals, there exists O/N disorder in that the exact atomic positions of the anions cannot be uniquely determined. It is envisioned that a variety of cation,anion bonding configurations exist in these complex crystals. The electronic structure and bonding in these crystals are, therefore, of great interest and are indispensable for a fundamental understanding of structural ceramics. We have used ab initio methods to study the structure and bonding properties of these 10 crystals. For crystals with unknown or incomplete structural information, we use an accurate total energy relaxation scheme to obtain the most likely atomic positions. Based on the theoretically modeled structures, the electronic structure and bonding in these crystals are investigated and related to various local cation,anion bonding configurations. These results are presented in the form of atom-resolved partial density of states, Mulliken effective charges, and bond order values. It is shown that Y,O and Y,N bonding are not negligible and should be a part of the discussion of the overall bonding schemes in these crystals. Spectroscopic properties in the form of complex, frequency-dependent dielectric functions, X-ray absorption near-edge structure (XANES), and the electron energy-loss near-edge structure (ELNES) spectra in these crystals also are calculated and compared. These results are discussed in the context of specific bonding configurations between cations (silicon and yttrium) and anions (oxygen and nitrogen) and their implications on intergranular thin films in polycrystalline Si3N4 containing rare-earth elements. [source] Separation of fullerenes C60 and C70 using a crystallization-based processAICHE JOURNAL, Issue 7 2010Kui S. Kwok Abstract A crystallization-based process that separates pure fullerenes C60 and C70 from their mixture using o-xylene as the solvent has been developed. Isothermal solid,liquid equilibrium phase diagrams of the C60 -C70 -o-xylene ternary system for a number of temperatures were first determined at 1 atm. Taking advantage of the shift in solvent-free composition of the C60 -C70 double saturation point with temperature and based on the solid solution-forming phase behavior between C60 and C70, the flowsheet of a general crystallization process was then synthesized. It involved the fractionation of a C60 -C70 fullerene mixture into C60 -rich and C70 -rich solid solutions using temperature-swing crystallization, followed by purification of the solid solutions with multistage crystallization into pure C60 and C70 solids. To demonstrate process feasibility, bench-scale batch experiments were performed using a commercially available fullerene mixture that was pretreated by adsorption to remove higher fullerenes. C60 and C70 solids of purity higher than 99 wt % were obtained. © 2009 American Institute of Chemical Engineers AIChE J, 2010 [source] Isograds and P,T evolution in the eastern Lepontine Alps (Graubünden, Switzerland)JOURNAL OF METAMORPHIC GEOLOGY, Issue 3 2002T. Nagel Abstract Reactions producing Al-rich index minerals in the south-eastern part of the Lepontine Dome (Central Alps, Switzerland) are investigated using mineral distribution maps, microstructural observations and equilibrium phase diagrams. The apparent staurolite mineral zone boundary corresponds to the paragonite breakdown reaction Pg + Grt + Qtz = Pl + Al2O3 + W. Equilibrium phase diagrams show that most natural metapelites do not contain staurolite or alumosilicates as long as univalent cations are predominantly accommodated in white mica. For a wide range of metapelitic compositions the paragonite breakdown releases sufficient Al for the formation of these minerals. Rare occurrences of staurolite and kyanite, north of the formerly mapped mineral zone boundaries, coexist with paragonite and are restricted to extremely Al-rich bulk compositions. The stable branch of the kyanite-forming paragonite breakdown reaction above 660 °C yields an additional mapable isograd. The second set of Al-releasing reactions is biotite-producing phengite breakdown. However, these reactions are less suitable to produce well defined reaction isograds in the field as they are more continuous and their progress is strongly dependent on bulk composition. Well developed fibrolite in metapelites does not appear until staurolite starts to breakdown. We conclude that amphibolite facies conditions in the study area were attained by decompression, without substantial heating at low pressures. [source] Experimental determination of solid-liquid-liquid equilibrium phase diagramsAICHE JOURNAL, Issue 6 2007Sau M. Lai Abstract Liquid,liquid phase separation is undesirable in crystallization as it leads to slow crystal growth and uncontrollable crystal morphology. Therefore, it is necessary to identify the conditions under which liquid,liquid phase split occurs, so as to avoid crystallization process taking place at such conditions. In this study, an experimental approach is developed to systematically construct the solid-liquid-liquid equilibrium (SLLE) phase diagram. A four-component system is used to demonstrate the experimental technique and the overall workflow in developing an SLLE phase diagram. © 2007 American Institute of Chemical Engineers AIChE J, 2007 [source] | ||||||||||