Search results for "phase diagram"
showing 10 items of 346 documents
Switching direction of laterally ordered monolayers induced by transfer instability
2007
Langmuir-Blodgett monolayers may show nanoscopic periodic patterns parallel and/or perpendicular to the transfer direction. The experimental findings are interpreted by a nonequilibrium model based on the stability of surfactant concentration and film thickness coupled fluctuations near the meniscus of a surfactant-covered receding thin film. In the high and low transfer speed limits, periodic fluctuations of the fluid subphase thickness, respectively perpendicular and parallel to the transfer, are selected. A qualitative phase diagram shows how transfer speed and film density manage the pattern shape.
Phase behaviour and interfacial tension of polysiloxane blends
1998
Abstract The cloud point curve for blends of poly(dimethyisiloxane) (PDMS, M w = 2.5kg mol −1 ) and poly(hexylmethylsiloxane) (PHMS, M w = 113kg mol − ] was determined turbidimetrically. The system demixes upon cooling and the UCST amounts to 36°C. The interfacial tension γ was determined at the critical composition for three temperatures by means of a spinning drop tensiometer. The dependence of γ on the reduced critical temperature can be described within experimental error by both the mean field theory and the Ising-3D theory.
Rheology of a Lower Critical Solution Temperature Binary Polymer Blend in the Homogeneous, Phase-Separated, and Transitional Regimes
1996
Small amplitude oscillatory shear rheology is employed in order to investigate the linear viscoelastic behavior of the lower critical solution temperature blend polystyrene/poly(vinyl methyl ether), PS/PVME, as a function of temperature and composition. At low temperatures, where the mixture is homogeneous, the dependence of the zero shear viscosity (η0) on concentration is measured and is well-described by means of a new mixing rule, based on surface fractions instead of volume fractions. Shift factors from time-temperature superposition (TTS) exhibit a Williams−Landel−Ferry (WLF) behavior. As the macrophase separation temperature is approached (the phase diagram being established by turbi…
Ab initio thermodynamic study of (Ba,Sr)(Co,Fe)O3 perovskite solid solutions for fuel cell applications
2013
(Ba,Sr)(Co,Fe)O3 (BSCF) perovskite solid solutions are promising materials for solid oxide fuel cell cathodes and oxygen permeation membranes. Cathode performance strongly depends on the morphology of these materials remaining as a single phase or two-phase mixture. Combining ab initio calculations of the atomic and electronic structure of different supercells with thermodynamics of solid solutions, we have constructed and discussed phase diagrams of several important BSCF chemical compositions. It is demonstrated that in BSC cobaltite solid solution the spinodal decomposition may occur already at relatively low temperatures, while ferrite (BSF and SCF) solid solutions decompose at relative…
Equilibrium phase behavior of polyethylene oxide and of its mixtures with tetrahydronaphthalene or/and poly(ethylene oxide-block-dimethylsiloxane)
2002
Liquid/solid and liquid/liquid (LL) transition temperatures were measured by means of an automated device that monitors the light passing through the systems as a function of T at different constant cooling or heating rates q. For pure polyethylene oxide (PEO) crystallization and melting temperatures depend on |q|0.3 and become identical at the equilibrium transition temperature Tm=61.0 °C in the limit of infinitely slow cooling/heating. The reduction of Tm for PEO dissolved in tetrahydronaphthalene (THN) yields information on the Flory–Huggins interaction parameter ξ between these two compounds; ξ results negative and decreases markedly with rising polymer concentration. A tentative explan…
Dynamics of the incorporation of Co into the wurtzite ZnO matrix and its magnetic properties
2015
Made available in DSpace on 2022-04-29T07:25:55Z (GMT). No. of bitstreams: 0 Previous issue date: 2015-07-25 Financiadora de Estudos e Projetos Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) Abstract Bulk Co-doped ZnO (Zn1-xCoxO) samples were prepared and studied with particular emphasis on their compositions, structures, and magnetic properties. A detailed microstructural analysis was conducted to investigate the nature of Co incorporation into the wurtzite ZnO matrix. The Zn1-xCoxO ceramic samples were prepared using the standard solid-state reaction method with different Co molar concentrations of u…
On the Theory of Domain Structure of Disordered Ferroelectrics
2009
We present a comprehensive analysis of domain structure formation in ferroelectric phase of incipient ferroelectrics with off-center dipole impurities like KTaO 3 :Li, Nb,Na. Our analysis is carried out on the base of effective free energy of disordered ferroelectrics, derived by us earlier. This free energy permits to apply the standard approach to domain structure calculation. Using coupled system of Maxwell equations with those obtained by minimization of above free energy, we calculate the physical characteristics of domain structure as functions of impurity dipoles concentration n. Our theory can be easily generalized for arbitrary temperature and crystal shape including thin films.
Thermal Expansion, Burns Temperature and Electromechanical Properties in Na1/2Bi1/2TiO3-SrTiO3-PbTiO3Solid Solutions
2011
Thermal expansion and electromechanical properties are studied for compositions Na1/2Bi1/2TiO3-SrTiO3-PbTiO3, belonging to various locations in the phase diagram. The main purpose of the studies is to extend the range of physical properties, which characterise the relaxor state and could be used for comparison with other relaxors. Possibility to evaluate Burns temperature from thermal expansion is discussed. The obtained results are compared to the well-know relaxor ferroelectric PLZT.
Phase diagram ofN2:Ar:CO solid solutions
1991
Ces solutions sont etudiees par diffraction des rayons X. Le diagramme de phase ternaire presente trois regions monophases (hc, cfc et Pa3) et de larges regions a deux phases (Pa3 cfc et hc cfc). On demontre l'influence de la vitesse de refroidissement sur la structure a basse temperature
The phase diagram of Ti-6Al-4V at high-pressures and high-temperatures.
2020
Abstract We report results from a series of diamond-anvil-cell synchrotron x-ray diffraction and large-volume-press experiments, and calculations, to investigate the phase diagram of commercial polycrystalline high-strength Ti-6Al-4V alloy in pressure–temperature space. Up to ∼30 GPa and 886 K, Ti-6Al-4V is found to be stable in the hexagonal-close-packed, or α phase. The effect of temperature on the volume expansion and compressibility of α–Ti-6Al-4V is modest. The martensitic α → ω (hexagonal) transition occurs at ∼30 GPa, with both phases coexisting until at ∼38–40 GPa the transition to the ω phase is completed. Between 300 K and 844 K the α → ω transition appears to be independent of te…