Showing papers on "Spinodal decomposition published in 1984"
TL;DR: Since then gradient theories have been used to analyze phase transitions, spinodal decomposition, and other physical phenomena and obtained several important results concerning the interfacial energy between phases.
Abstract: : VAN DER WAALS, in his classic paper, gave arguments in support of a compressible fluid whose free energy at constant temperature depends not only on the density, but also on the density gradient. CAHN & HILLIARD, apparently unaware of VAN DER WAALS' paper, rederived VAN DER WAALS' theory and, using this theory, obtained several important results concerning the interfacial energy between phases. Since then gradient theories have been used to analyze phase transitions, spinodal decomposition, and other physical phenomena.
286 citations
TL;DR: In this paper, the stable and metastable equilibria of the Fe-Cu system were derived using the thermodynamic equations derived from equilibrium data, and the calculated metastable miscibility gap of the liquid phase also agrees with the experimental data.
Abstract: Thermodynamic and phase diagram data in the Fe-Cu system are evaluated. For the liquid and fcc phases, the Margules-type of equations is used. For the bcc phase, the same type of equation is used to describe the non-magnetic contribution to the Gibbs energy. In addition, a magnetic term is included. Using the thermodynamic equations derived from equilibrium data, the stable and metastable equilibria of this system are calculated. Agreement between the calculated and experimental phase diagram is good except for temperatures higher than 1720 K. For these temperatures, the calculated liquidus tends to be higher. The possibility of supercooling which may account for some of the lower temperatures measured should not be excluded. The calculated metastable miscibility gap of the liquid phase also agrees with the experimental data.
129 citations
TL;DR: The phase diagram for nonstoichiometric ceria was determined from specific heat measurements in the temperature range 320-1200 K and composition range CeO2CeO1.72 as mentioned in this paper.
120 citations
TL;DR: In this paper, the phase diagrams of the binary and ternary limits, InP and In0.53Ga0.47As, respectively, were measured in the temperature range between 500 and 680 °C.
112 citations
TL;DR: In this article, the phase equilibria in Fe-Ni-Al and Fe-Al-Co systems have been investigated by diffusion couple technique, and the miscibility gap that separates α1 (Fe-rich disordered bcc phase) from α2 (NiAl-rich ordered bccphase) has been determined, and it has been ascertained that the three-dimensional shape of the MCG is not simple helmetlike, but has a peculiar ridge at the order-disorder transition temperature.
Abstract: The phase equilibria in Fe-Ni-Al and Fe-Ni-Al-Co systems have been investigated by the diffusion couple technique, and the miscibility gap that separates α1 (Fe-rich disordered bcc phase) from α2 (NiAl-rich ordered bcc phase) has been determined. It has been ascertained that the three-dimensional shape of the miscibility gap is not simple helmetlike, but has a peculiar ridge at the order-disorder transition temperature. The miscibility gap is narrowed and shifted to the Fe-rich corner by the addition of Co, and Co atoms are distributed to the α2 rather than the α1 Furthermore, by alloying Co, the fcc γ phase is stabilized and the miscibility gap between α1 and α2 is hidden to some extent by the phase regions concerned with the γ phase.
80 citations
TL;DR: In this article, the metastable alloys covering this entire composition range have been grown by organometallic vapor phase epitaxy (OMVPE) using trimethyl gallium, antimony and -arsenic as the source materials.
Abstract: The system GaAs1−xSbx has a solid phase miscibility gap ranging from x = 0.2 to x = 0.8 at the typical growth temperature of 600 C; however, metastable alloys covering this entire composition range have been grown by organometallic vapor phase epitaxy (OMVPE) using trimethylgallium, antimony and -arsenic as the source materials. The solid composition is studied for various values of growth temperature, the ratio of Sb to total group V elements in the vapor phase and the ratio of group III to group V elements in the vapor phase. The fraction of trimethylarsenic (TMAs) pyrolyzed in the vapor phase is found to be < 1 and to vary with temperature. Taking into account the incomplete pyrolysis of TMAs, solid composition is found to be controlled by thermodynamics. The effects of temperature and vapor composition are all accurately predicted using a simple thermodynamic model assuming equilibrium to be established at the solid-vapor interface. The properties of these metastable GaAs1−x Sbx alloys were explored using interference contrast microscopy, room temperature and 4 K photoluminescence, Hall effect and conductivity measurements. The alloy GaAs0.5Sb0.5 grown lattice matched to the InP substrate has excellent surface morphology, is p-type, and the photoluminescence spectrum consists of a single, intense, fairly broad (23.5 meV half width) peak at a wavelength of 1.54 Μm.
79 citations
TL;DR: In this paper, transmission electron microscopy, X-ray diffraction and photoluminescence were evaluated using GaAsP epitaxial layers emitting in the 1.25−1.37 μm wavelength region.
72 citations
01 Jan 1984
TL;DR: Theoretical Approaches to understand the properties of modulated structures are described in this article.However, the authors focus on the physics of the modulated structure materials and do not consider the physical properties of these materials.
Abstract: Modulated Structure Materials: A Selected Review.- 1: Theoretical Aspects of Modulated Structures.- Modulated Structures in a Simple Ising Model.- Composition Modulations in Solid Solutions.- Metal Insulator Transition in Modulated Crystals.- A New Theory of Polytypism.- Densities of States of Compositionally Modulated Alloys.- Time Evolution of Phase Separation in Binary Mixtures.- 2: Crystallography of Modulated Structures.- The Incommensurate Crystalline Phase and its Symmetry.- Superspace Transformation Properties of Incommensurate Irreducible Distortions.- Crystal Structures of Complex Sulfides: From Modulated to Modular Structures.- 3: Diffraction Methods.- High Resolution Electron Microscopy Study of Manganese Silicides.- The Use of High Resolution Electron Microscopy in the Study of Modulated Structures in Alloy Systems.- Electron Microscopic Study of Modulated Structures in (Au,Ag)Te2.- Incommensurate Structures in the Long-Period Ordered Alloys Studied by High-Resolution Electron Microscopy.- Analysis of Diffuse Scattering from Composition Modulations in Concentrated Alloys.- Neutron Investigation of Modulated Structure.- Atom Probe Field-Ion Microscopy Studies of Modulated Structures.- 4: Mechanics of Modulated Structures.- The Elastic Theory of the Defect Solid Solution.- On the Mechanics of Modulated Structure.- The Effect of Strain on the Elastic Constants of Copper.- 5: Spinodal Structures.- Mechanical Behavior of Spinodal Alloys.- A Numerical Study of Kinetics in Spinodal Decomposition.- 6: Composition Modulated Films.- Manufacture of Ternary Thin Film Layered Foils by Controlled Evaporation.- Theoretical Approaches to Understanding the Properties of Modulated Structures - A Review.- Mechanical and Thermoelectric Behavior of Composition Modulated Foils.- Effects of Short Wavelength Composition Modulations on Interdiffusion in Silver-Palladium Thin Foil.- Compositionally Modulated Metallic Glasses.- Electrical Properties of Multilayered Cr/Si02 Thin Films.- 7: Semiconductor Superlattices.- Tailored Semiconductors: Compositional and Doping Superlattices.- 8: Modulations in Solids.- Premartensitic Behavior and Charge Density Waves in TiNi Alloys.- Electronic Contributions to Mixing- and Gradient- Energy of Composition-Modulated Alloy System.- Mechanical Behavior of Solid Film Adhesives with Scrim Carrier Cloths.- Orientational Phase Transitions in a Quasi-One-Dimensional Conductor.- Electron-Libron Pairing in Quasi-One-Dimensional Conductors.
70 citations
TL;DR: In this paper, the pseudobinary III/V system GaAs1−ySby is well known to have a solid phase miscibility gap with a critical temperature of 751°C.
Abstract: The pseudobinary III/V system GaAs1−ySby is well known to have a solid phase miscibility gap with a critical temperature of 751 °C. We have succeeded in growing epitaxial layers of GaAs0.5Sb0.5 lattice matched to InP at temperatures of 600 and 630 °C using the organometallic vapor phase epitaxy technique. The key requirement is a III/V ratio of greater than unity. This leads to the incorporation of all As and Sb reaching the interface and the ability to grow metastable alloys. The epitaxial GaAs0.5Sb0.5 layers have excellent surface morphology and efficient photoluminescence at a wavelength of 1.6 μm.
62 citations
TL;DR: In this paper, a phenomenological theory for chemically quenched binary interpenetrating polymer networks (IPNs), considering both simultaneously crosslinked and sequentially crosslinked networks, is formulated.
Abstract: A phenomenological theory is formulated for chemically quenched binary interpenetrating polymer networks (IPNs), considering both simultaneously crosslinked networks and sequentially crosslinked networks, as well as pseudointerpenetrating networks (where only one component is crosslinked and the other is a linear polymer). The construction of free energy functionals for homogeneous weakly crosslinked IPNs and pseudo-IPNs and their spinodal curves and critical points of unmixing is described. These free energy functionals are augmented with gradient energy terms in order to consider effects due to spatially varying small inhomogeneities in the network chain concentration. The dynamic response and the initial spinodal decomposition of IPNs are discussed.
60 citations
TL;DR: In this article, InGaAsP and InGaP epitaxial layers lattice-matched to (001)-oriented GaAs substrates successfully grown by liquid phase epitaxy have been investigated by transmission electron microscopy, scanning transmission electron microscope and energy dispersive X-ray spectroscopy.
Abstract: InGaAsP and InGaP epitaxial layers lattice-matched to (001)-oriented GaAs substrates successfully grown by liquid phase epitaxy have been investigated by transmission electron microscopy, scanning transmission electron microscopy and energy dispersive X-ray spectroscopy. In both layers, periodic diffraction contrasts (modulated structures), are observed in two equivalent directions of the and the . Compositional variation has also been observed along these structures. These are associated with spinodal decomposition of the crystal during growth.
TL;DR: In this article, age hardening in Cu-9Ni-2Sn and 9Ni-5Sn alloys at 573 and 673 K was studied by means of TEM and ED: spinodal decomposition takes place (during quenching) followed by nucleation of the coherent (CUxNi1−x)3Sn particles.
TL;DR: In this paper, a partial plot of the miscibility gap in the Mg-Si-O-N system is established from analysis of the phases formed during phase separation of the glasses.
Abstract: Bulk oxynitride glasses in the Mg-Si-O–N system were prepared by melting mixtures of SiO2, MgO, and Si3N4 powders and the microstructures and compositions of the glasses were analyzed by electron microscopy, energy and wavelength dispersive X-ray analysis, and energy loss spectrometry. The melting experiments indicate the presence of a limited glass-forming region in the system. For the melting conditions used, nitrogen was found to be a necessary constituent of the melts to prevent crystallization on cooling. Extension of the miscibility gap in the binary MgO-SiO2 system into the Mg-Si-O–N system results in phase separation in most of the glasses. A partial plot of the miscibility gap in the Mg–Si-O–N system is established from analysis of the composition of the phases formed during phase separation of the glasses.
TL;DR: Fluorescence emission of labels appears to be a new technique for the investigation of the LCST behaviour of polystyrene-poly(vinylmethylether) (PS-PVME) blends as discussed by the authors.
TL;DR: In this paper, a linear stability analysis in the viscous-convective range of concentration fluctuations is presented, showing that spinodal decomposition can be suppressed entirely by sufficiently strong stirring.
Abstract: When a turbulent binary fluid mixture is quenched below its consolute point, turbulent mixing competes with an instability toward phase separation. A linear stability analysis in the viscous-convective range of concentration fluctuations shows that spinodal decomposition can be suppressed entirely by sufficiently strong stirring. An instability reappears, however, for deep quenches, when the injection rate of concentration fluctuations exceeds the rate of turbulent mixing. The growing concentration fluctuations which result appear to be confined to the viscous-convective range.
TL;DR: In this article, the kinetics of phase separation and coarsening occurring within the miscibility gap in the iron-chromium-cobalt system have been characterized using atom probe field-ion microscopy.
TL;DR: In this paper, a minimal parameter kinetic model which describes the corrosion and passivation of metal surfaces is presented, where two elementary steps are included, namely, the oxidation of surface metal atoms to produce adsorbed cations, and the subsequent dissolution of these cations into the electrolyte.
Abstract: We present a minimal parameter kinetic model which describes the corrosion and passivation of metal surfaces. Two elementary steps are included, namely, the oxidation of surface metal atoms to produce adsorbed cations, and the subsequent dissolution of these cations into the electrolyte. Oxide layer formation is represented by two‐dimensional condensation of adsorbed cations to produce a continuous phase; statistics of the condensation process are treated at the mean field level. The structure and magnitude of the i‐V curve in the active‐passive transition region is calculated for two cases: the limit of maximum passivation hysteresis (spinodal decomposition of the oxide phase), and the limit of zero hysteresis (equilibrated phase transition). Methods for analyzing experimental i‐V curves to yield the rate constants associated with the model are presented.
TL;DR: In this article, the coherent unmixing kinetics of various Al-Zn and Al-Ag Zn alloys were analysed in terms of nucleation and spinodal models.
Abstract: The coherent unmixing kinetics of various Al-Zn and Al-Ag-Zn alloys are analysed in terms of nucleation and spinodal models. For large solid-solution supersaturations, as obtained for deep quenches below the miscibility gap, the main feature is a scaling of the structure function of the alloys in the asymptotic or coarsening stage. The scaling function appears to be only slightly dependent on the supersaturation, in agreement with the kinetic Ising model and the two-phase model of Rikvold and Gunton. The scale length is the second-phase particle size, which generally varies with time as t 1/3. However, the kinetics appear to be more rapid than would occur in a simple Lifshitz-Slyozov process, and the possible reasons for this discrepancy are discussed in detail. For small supersaturations or shallow quenches the time variations of the particle size and number density, plotted in reduced units, compare favourably with the Langer-Schwartz theory for nucleation in off-critical fluid mixtures. The va...
TL;DR: In this paper, the scaling form of the scattering function is obtained with particular attention to the fluctuating thermal noises, and the sealing function is calculated explicitly in the region where the Brownian coagulation is most dominant for the phase separation.
TL;DR: In this paper, the state theory of Prigogine, Flory, and Patterson with suitable values for the contact energy and contact entropy parameters X12 and Q12 was used to predict the temperature of separation.
Abstract: Provided a polymer is soluble, i. e., molecularly dispersed in another polymer irrespective of the molecular weight of the components, the solution is exothermic. By increasing the temperature two effects, both unfavourable to mixing become larger: (i) the excess entropy of mixing caused by contact interaction and (ii) the total effect from the difference of the free volumes of the pure components. So, an upper miscibility gap occurs. The thermodynamic properties of the mixture cannot be derived from the properties of the pure components. They can be described by the corresponding states theory of Prigogine, Flory, and Patterson with suitable values for the contact energy and contact entropy parameters X12 and Q12. The temperature of separation can be predicted from measurements on the mixture at low temperatures.
TL;DR: Etude de la decomposition spinodale pour un systeme binaire avec des interactions a moyenne portee is described in this article, where Cahn et Hilliard show that spinodal decomposition can be used to solve problems.
Abstract: Etude de la decomposition spinodale pour un systeme binaire avec des interactions a moyenne portee. Theorie classique de Cahn et Hilliard
TL;DR: In this article, the authors extended the theory of spinodal decomposition in amorphous systems to include the effect of internal stress due to coherency strain and developed a quantitative treatment for the kinetics of stress relaxation via plastic deformation, which can become the rate-limiting step in the evolution of Fourier components having large wavenumbers.
Abstract: The theory of spinodal decomposition in amorphous systems is extended to include the effect of internal stress due to coherency strain. A quantitative treatment is developed for the kinetics of internal stress relaxation via plastic deformation. The general solution for the evolution of the composition and internal stress distributions during the early stage of spinodal decomposition is derived for a system obeying the visco-elastic constitutive relations of a Maxwell solid. A kinetic equation for the structure factor is obtained for the limiting case in which coherency strain is relatively large. In this case, it is found that plastic deformation to relieve internal stress can become the rate-limiting step in the evolution of Fourier components having large wavenumbers. The predicted shape of the structure factor as a function of wavenumber, time, and temperature can be very different from that obtained when the kinetics of internal stress relaxation are neglected. The theory is expected to be particularly applicable to amorphous systems in which the species of interest have very different mobilities, and can explain the discrepancies found in previous analyses of scattering data for the lead-aluminum-borate system and alkali-silicate systems.
01 Jan 1984
TL;DR: In this article, the authors used experimental coarsening rates to interpret the thermal histories of rapidly cooled cryptoperthites which are characterized by a coherent, lamellar microstructure.
Abstract: The coherent solvus and coherent spinodal for sanidine-high albite are reasonably well known from experimental studies. These relations together with experimental coarsening rates can be used to interpret the thermal histories of rapidly cooled cryptoperthites which are characterized by a coherent, lamellar microstructure. The lamellar spacing (λ) is largely dependent on the rate of cooling during the first 70°C after the sample has crossed the coherent spinodal; the compositional difference of the lamellae (∆C) is more dependent on the lower temperature history of these cryptoperthites.
TL;DR: In this paper, the Cook-de-Fontaine theory for the free energy of solid solutions has been evaluated for Au-40 at 1023 K above the miscibility gap, by combining results from neutron inelastic and X-ray diffuse scattering from the same single crystal.
TL;DR: The spinodal and the miscibility gap of relatively short chain polystyrene/polybutadiene (PS/PB) mixtures is shifted by 14°C towards higher temperatures, if the hydrogen in PB is replaced by deuterium.
Abstract: The spinodal and, hence, the miscibility gap of relatively short chain polystyrene/polybutadiene (PS/PB) mixtures is shifted by 14°C towards higher temperatures, if the hydrogen in PB is replaced by deuterium. The shift corresponds to a difference in the heat of mixing of about 0,2 kJ per mole of styrene units for a 1:1 PS/PB mixture. The effect has been observed by means of Gordon's Pulse Induced Critical Scattering method and the resulting spinodals are found to differ also with respect to the location of their maximum which indicates disparity in the entropy of mixing. For the prediction of the spinodal in a polystyrene/polybutadiene/perdeutereous polybutadiene (PS/PBH/PBD6) system the assumption of non-athermal mixing in PBH/PBD6 is needed. The value estimated for the PBH/PBD6 interaction parameter involves the second viral coefficient for solutions of PBD6 in PBH to be very close to zero. Expressions are presented for the second virial coefficient in quasiternary systems by scattering methods.
TL;DR: The phase diagram and the heat of transition of AgI-AgBr system have been determined by using the differential scanning calorimetry (DSC) with the help of X-ray diffraction patterns as discussed by the authors.
TL;DR: In this article, light scattering techniques have been used to study the phase separation of a sheared binary fluid of nitrobenzene and n-hexane at critical composition, and permanent anisotropic ring pattern was formed.
Abstract: Light scattering techniques have been used to study the phase separation of a sheared binary fluid of nitrobenzene and n-hexane at critical composition. Shear was seen to prevent the development of decomposition. The system is quenched when the shear is removed, allowing anisotropic spinodal decomposition rings to appear. When a periodic (frequency Ω) shear was applied, a permanent anisotropic ring pattern was formed. The radius of the ring, in units of the correlation length, exhibits a scaled behaviour versus Ω-1 or the time t after the quench, if Ω-1 or t are expressed in units of the fluctuation lifetime. Mean-field theory seems to be relevant.
TL;DR: In this paper, the possibilities of spinodal decomposition or homogeneous nucleation and growth were examined for two alloy systems, Al Ag and Al Cu, representing two extreme cases, a narrow and a (potentially) very wide miscibility gap, respectively, resulting in low and high interphase boundary energies.
TL;DR: In this article, a solidification model for the appearance of a supersaturated β-NiAl phase near the eutectic composition was presented based on the T 0 curves for this alloy system.