Shift Of Phase Boundary Research Articles

Reversible superconducting-normal phase transition in a magnetic field: The energy-momentum balance including the velocity field of the Berry connection from many-body wave functions

The velocity field composed of the Berry connection from many-body wave functions and electromagnetic vector potential explains the energy-momentum balance during the reversible superconducting-normal phase transition in the presence of an externally applied magnetic field. In this formalism, forces acting on electrons are the Lorentz force and force expressed as the gradient of the kinetic energy. In the stationary situation, they balance; however, an infinitesimal imbalance of them causes a phase boundary shift. In order to explain the energy balance during this phase boundary shift, the electromotive force of the Faraday’s magnetic induction type is considered for the Berry connection. This theory assumes that supercurrent exists as a collection of stable quantized loop currents, and the transition from the superconducting to normal phase is due to the loss of their stabilizations through the thermal fluctuation of the winding numbers of the loop currents. We argue that an abrupt change of loop current states with integral quantum numbers should be treated as a quantum transition; then, the direct conversion of the quantized loop currents to the magnetic field occurs; consequently, the Joule heat generation does not occur during the phase transition.

A generalized rule for phase transition generated by additives in piezoelectric ceramics

The phase transition generated by additives has not been defined systematically in (1-x)Pb(Zr,Ti)O3-xPb(BI2+1/3Nb2/3)O3 (PZT-PBN, BI2+: Mg2+, Zn2+, and Ni2+, in this study). In order to define the phase transition of PZT-PBN, we identify the various phase transitions depending on the ionic site which an additive enters. The ionic site can be determined by the ionic size of a metal in an additive, and in the ABO3 of a perovskite structure, the phase transition is more significant when an additive enters the B site, compared to the A site. Until now, the phase transitions have mostly been described as the vertical or horizontal transitions in phase diagrams. However, in this study, we show that phase transitions actually occur in the diagonal direction. In particular, it is reported that a unique shift of morphotropic phase boundary (MPB) occurs, when the additive enters the BI2+ site in (1-x)Pb(Zr,Ti)O3-xPb(BI2+1/3Nb2/3)O3. The MPB shift is different from the normal phase transitions which are generally observed in PZT-based materials.

Pressure-induced shift of effective Ce valence, Fermi energy and phase boundaries in CeOs4Sb12

CeOs4Sb12, a member of the skutterudite family, has an unusual semimetallic low-temperature -phase that inhabits a wedge-like area of the field H—temperature T phase diagram. We have conducted measurements of electrical transport and megahertz conductivity on CeOs4Sb12 single crystals under pressures of up to 3 GPa and in high magnetic fields of up to 41 T to investigate the influence of pressure on the different H–T phase boundaries. While the high-temperature valence transition between the metallic -phase and the -phase is shifted to higher T by pressures of the order of 1 GPa, we observed only a marginal suppression of the -phase that is found below 1 K for pressures of up to 1.91 GPa. High-field quantum oscillations have been observed for pressures up to 3.0 GPa and the Fermi surface of the high-field side of the -phase is found to show a surprising decrease in size with increasing pressure, implying a change in electronic structure rather than a mere contraction of lattice parameters. We evaluate the field-dependence of the effective masses for different pressures and also reflect on the sample dependence of some of the properties of CeOs4Sb12 which appears to be limited to the low-field region.

Effects of a Multicomponent Perfume Accord and Dilution on the Formation of ST2S/CAPB Mixed-Surfactant Microemulsions.

Perfume mixtures contain perfume raw materials (PRMs) with varying structures and hydrophobicities, which influence PRM localization within a surfactant-based formulation and thereby affect the phase behavior. In rinse-off products, the addition of water can further affect the phase behavior. In this study, a mixture of 12 PRMs was used as the oil phase in an aqueous system consisting of sodium trideceth-2 sulfate as a primary surfactant, cocamidopropyl betaine as a cosurfactant, and dipropylene glycol as a cosolvent. A series of phase diagrams were constructed with increasing water content, simulating the use conditions for rinse-off products, to determine how the phase boundaries shift with dilution. Using these phase diagrams, the compositions of interest in the micelle without perfume, micelle with perfume, microemulsion, and micelle-microemulsion transition regions were identified at each dilution level. The structural changes were probed through combined small-angle neutron scattering (SANS) and cryo-transmission electron microscopy analyses. The SANS results showed that ellipsoidal micelles were maintained as the perfume content and the dilution level increased. With ≥50 wt % water, increasing the perfume content increased the micelle volume. Interestingly, a higher rate of volume increase was observed at ≥70 wt % water. Notably, the volumes of the micelles with and without perfume increased steadily with dilution, whereas the volumes of the assemblies in the transition region and the microemulsion region increased more rapidly once diluted to 70 and 80 wt % water, respectively.

Shear-induced breakdown and agglomeration in nanoparticles filled polymer: The shift of phase boundary and kinetics

For the nanoparticle-filled polymers, weak attractive interactions between nanoparticles lead to agglomeration and even formation of a network of nanoparticles in the polymer matrix. Both the agglomeration and the deagglomeration (breakdown) of the particle network are affected by the shear flow, resulting in shear-induced liquid-solid (L-S) transition and shear-induced solid-liquid (S-L) transition, respectively. In this study, we quantify the percolation threshold of both transitions under shear-induced agglomeration and shear-induced breakdown processes. Both the present shear condition and the preshear condition affect the percolation threshold, which turns to only shear rate dependence under steady shear condition, indicating no shear hysteresis. A scaling relation is suggested to describe the percolation threshold at low shear rate. The critical strains at both S-L and L-S transitions are inversely proportional to the distance of the particle concentration to the percolation concentration under steady shear. The apparent phase boundary under shear, represented by the shear rate and shear history-dependent percolation threshold, is further conceptually converted to the space of structural parameter, from which the possible transitions pathway under steady shear are discussed.

Esterification of Oleic Acid with n-Octanol in Three-Phase Microemulsions

AbstractIn the presence of dodecylbenzene sulfonic acid (DBSA), a part of the phase diagram of water, oleic acid, and n-octanol was constructed as a function of the temperaure dependent from DBSA-concentration. The liquid three-phases microemulsion region in the phase diagram was efficient for the esterification of oleic acid and n-octanol. The results exhibit that the shift of phase boundary contributed to product separation and catalyst recycling.

Dynamic Phase Diagram of Catalytic Surface of Hexagonal Boron Nitride under Conditions of Oxidative Dehydrogenation of Propane.

Partially oxidized surfaces of hexagonal boron nitride (hBN) and several metal borides are unexpectedly excellent catalysts for oxidative dehydrogenation of alkanes to olefins, but the nature of the active site(s) on these B-containing interfaces remains elusive. We characterize the surface of the partially oxidized B-rich hBN surface under reaction conditions from first principles. The interface has thermal access to multiple different stoichiometries and multiple structures of each stoichiometry. The size of the thermal ensemble is composition-dependent. The phase diagram of the interface constructed on the basis of the statistical ensembles of many accessible states is very different from the one based on global minima. Phase boundaries shift and blur, and phases consist of several stoichiometries and structures. The BO layer transiently exposes the reactive -B═O motifs in the metastable states. The fluxionality and structural diversity emerging under reaction conditions must be taken into account in theoretically descriptions of the catalytic interface.

Effect of Pore Size Distribution on Dissociation Temperature Depression and Phase Boundary Shift of Gas Hydrate in Various Fine-Grained Sediments

Capillarity in small, confined pores has a pronounced effect on the depression of the dissociation temperature of gas hydrates, known as the Gibbs–Thomson effect. However, this effect remains poorly understood in natural fine-grained sediments with wide pore size distributions. This study investigated the effect of pore size distributions of fine-grained sediments on the dissociation temperature of a gas hydrate. A gas hydrate was synthesized under partially water-saturated conditions in nanosized silica gels and in various natural fine-grained sediment samples, including sand, silt, diatoms, a diatom–sand mixture, and clayey sediment. The synthesized hydrate samples were thermally dissociated under isochoric conditions, while the melting temperature depression and the shifted phase boundaries were monitored. We observed a dissociation temperature depression of approximately 0.1–0.3 °C in silt, 0.2–0.4 °C in the diatom sample, and 1.2–1.5 °C in clayey silt, while no temperature depression was observed in ...

Enhanced depressurisation for methane recovery from gas hydrate reservoirs by injection of compressed air and nitrogen

Abstract Enhanced depressurisation for methane recovery from gas hydrate-bearing sediments was experimentally studied by injection of compressed air and nitrogen. Experiments were conducted in simulated sediments (silica sand) from 273.4 K to 283.0 K and initial system pressures ranging from 3.8 MPa to 7.2 MPa before air or nitrogen injection. The results show that injection of air and nitrogen made it possible to implement conventional depressurisation in multiple stages. In each pressure stage, methane hydrate was quickly dissociated by the injected air or nitrogen due to direct shift of the methane hydrate equilibrium phase boundary. Methane hydrate dissociation at high pressures enables methane recovery inside the methane hydrate stability zone. Depressurisation well above the methane hydrate dissociation pressure generated a methane-rich gas phase of up to 90 mol% methane depending on the injected gas. Injection of compressed air or nitrogen provides a potential approach to improve the technical feasibility and economic viability of conventional depressurisation method for methane recovery from most gas hydrate reservoirs with severe conditions such as low permeability or dispersed hydrates.

Phase equilibria of ternary systems of carbon dioxide + ethanol, dimethyl sulfoxide, or N,N-dimethyl formamide + water at elevated pressures including near critical regions

A visual and volume-variable high-pressure phase equilibrium analyzer was used for measuring the isothermal vapor-liquid equilibrium (or vapor-liquid-liquid) phase boundaries of CO2 with the mixed solvents of ethanol/water = 9/1, dimethyl sulfoxide (DMSO)/water = 9/1, and N,N-dimethyl formamide (DMF)/water = 7.5/2.5 in molar ratio at temperatures from 298.2 K to 348.2 K over wide composition range, including near critical regions. The isothermal phase equilibrium data obtained from this work are compared with those of water-free binary systems to investigate the effect of phase boundary shifts caused by introducing the phase modifier, water, into the organic solvents. The comparison shows that the bubble, dew, and critical pressures substantially increase in the presence of water for each system, especially for DMSO-containing system. The Peng-Robinson equation of state with Mathias-Copemen alpha function and the Wong-Sandler mixing rule is employed to the phase equilibrium calculation. While the UNIFAC model estimates the excess Helmholtz free energy at infinite pressure, the binary interaction parameters for calculating the second virial coefficient are determined by the phase equilibrium data of constituent binaries. The obtained parameters are directly adopted to the phase boundary predictions for the investigated ternary systems.

Morphologies Observed in Ultraflexible Microemulsions with and without the Presence of a Strong Acid.

We show that three different morphologies exist near the two-phase boundary of ternary systems containing a hydrotropic cosolvent. Based on synchrotron small- and wide-angle X-ray scattering combined with molecular dynamics, we rationalize the specific scattering signature of direct, bicontinuous, and reverse mesoscale solubilization. Surprisingly, these mesostructures are resilient toward strong acids, which are required in industrial applications. However, on a macroscopic scale, the phase boundary shifts in salting-in and salting-out in the direct and respectively reverse regime, leading to a crossing of the binodals.

The Stillwater Complex, Montana – Overview and the significance of volatiles

AbstractThe geology of the 2.7 Ga Stillwater Complex in South-Central Montana is reviewed with a focus on the role of volatiles in locally modifying both the crystallization sequence of the evolving parent magma and the initially precipitated solid assemblages to favour olivine ± chromite. A secondary origin for these two minerals is particularly probable for the olivine-bearing rocks of the Banded series and, at a minimum, also increasing their modal abundance in the Peridotite zone of the Ultramafic series. Direct evidence for volatiles includes the presence of high-temperature fluid inclusions in pegmatoids and hydrous melt inclusions (now crystallized) in chromite and olivine from both the Ultramafic and the Banded series rocks. Indirect evidence includes the boninitic character of the parent magma, the presence of volatile-bearing minerals including high-temperature carbonates, rock textures, and Cl / F variations in apatite. Mechanisms which favour the formation of olivine (± chromite) over pyroxene include volatile phase boundary shifts induced by added H2O, incongruent melting of pyroxene by hydration of a partly-molten mush, and the near- to sub-solidus replacement of pyroxene by olivine and chromite by silica-undersaturated fluids. These mechanisms cast doubt that magmas with different liquid lines of descent were involved in the crystallization of the Stillwater Complex. A dry Stillwater magma would have been mineralogically and modally much less varied and lacking in high-grade platinum-group element and chromium deposits.

Metal Seed Loss Throughout the Nanowire Growth: Bulk Trapping and Surface Mass Transport

The physical and chemical properties of metal-catalyzed semiconductor nanowires are very sensitive to their composition and morphology, which are very sensitive to the behavior of the catalyst nanodroplet during growth. Herein, we identify and investigate the main atomic pathways and processes governing the metal mass transport and the associated variation in the nanodroplet size throughout the growth of metal-catalyzed silicon nanowires. This includes surface diffusion and catalyst trapping in addition to the shift in phase boundaries of the eutectic nanodroplet to count for surface effects, capillarity, and related nanoscale stresses. On the basis of thermodynamic and kinetic considerations, a theoretical framework is presented to elucidate these catalyst nanodroplet instabilities. Moreover, we also address the influence of these phenomena on the shape and impurity concentration in silicon nanowires. Modeling results along with experimental data demonstrate that the combined effects of the kinetically d...

Phase separation of comb polymer nanocomposite melts.

In this work, the spinodal phase demixing of branched comb polymer nanocomposite (PNC) melts is systematically investigated using the polymer reference interaction site model (PRISM) theory. To verify the reliability of the present method in characterizing the phase behavior of comb PNCs, the intermolecular correlation functions of the system for nonzero particle volume fractions are compared with our molecular dynamics simulation data. After verifying the model and discussing the structure of the comb PNCs in the dilute nanoparticle limit, the interference among the side chain number, side chain length, nanoparticle-monomer size ratio and attractive interactions between the comb polymer and nanoparticles in spinodal demixing curves is analyzed and discussed in detail. The results predict two kinds of distinct phase separation behaviors. One is called classic fluid phase boundary, which is mediated by the entropic depletion attraction and contact aggregation of nanoparticles at relatively low nanoparticle-monomer attraction strength. The second demixing transition occurs at relatively high attraction strength and involves the formation of an equilibrium physical network phase with local bridging of nanoparticles. The phase boundaries are found to be sensitive to the side chain number, side chain length, nanoparticle-monomer size ratio and attractive interactions. As the side chain length is fixed, the side chain number has a large effect on the phase behavior of comb PNCs; with increasing side chain number, the miscibility window first widens and then shrinks. When the side chain number is lower than a threshold value, the phase boundaries undergo a process from enlarging the miscibility window to narrowing as side chain length increases. Once the side chain number overtakes this threshold value, the phase boundary shifts towards less miscibility. With increasing nanoparticle-monomer size ratio, a crossover of particle size occurs, above which the phase separation is consistent with that of chain PNCs. The miscibility window for this condition gradually narrows while the other parameters of the PNCs system are held constant. These results indicate that the present PRISM theory can give molecular-level details of the underlying mechanisms of the comb PNCs. It is hoped that the results can be used to provide useful guidance for the future design control of novel, thermodynamically stable comb PNCs.

Perturbation of the Experimental Phase Diagram of a Diblock Copolymer by Blending with an Ionic Liquid

Understanding the phase behavior of block copolymer/ionic liquid mixtures is an important step toward their implementation in commercial devices. Here we report a high throughput and systematic small-angle X-ray scattering study of the lyotropic phase behavior of a series of polystyrene-b-poly(methyl methacrylate) (PS-b-PMMA) block copolymers in the ionic liquid, 1-ethyl-3-methylimidazolium bis(trifluoromethane sulfonyl)imide (EMIM Tf2N). The ionic liquid induces disorder–order transitions for a number of low molecular weight systems, and the onset points of these transitions are used to calculate the dependence of the effective Flory–Huggins interaction parameter (χeff) on the ionic liquid concentration. This enabled construction of an experimental phase diagram, which reveals that after taking volumetric swelling into account, at higher ionic liquid concentrations, the experimental phase boundaries shift significantly when compared to theoretical calculations for block copolymer melts. It is also demons...

Producing Small Domain Features Using Miktoarm Block Copolymers with Large Interaction Parameters.

We demonstrate that small domain features (∼13 nm) can be obtained in a series of polystyrene (PS) and poly(lactic acid) (PLA) block copolymers, PS-(PLA)2 and (PS)2-(PLA)2, that combine miktoarm molecular architectures with large interaction parameters. To supplement the experimental work, we used self-consistent field theory in tandem with the random phase approximation to explore and contrast the phase behavior of ABn and AnBn types of miktoarm block copolymers. Specifically, AB2 and A2B2 were found to be effective molecular architectures for inducing strong shifts in phase boundaries with copolymer composition and to simultaneously tune domain feature sizes. The performance of these systems is markedly different from the corresponding linear diblock copolymers and indicates the potential of macromolecular architecture control for future applications in lithography.

Phase diagram of the one-dimensional t-J model with long-range dipolar interactions

We study systematically the effect of long-range dipolar interactions on the ground-state phase diagram of the one-dimensional model by means of the density matrix renormalization group. While the basic phases described by the Luttinger parameter , namely, the repulsive Luttinger liquid (metallic phase, ), attractive Luttinger liquid (superconducting phase, ), and the phase separation , are similar to those of the conventional model, the presence of the long-range dipolar interactions leads to significant differences. i) At high-density regime, the phase boundaries of these three phases are even pushed to the large-J region; ii) at low-density regime, these phase boundaries shift toward the small-J region and, most importantly, iii) the spin-gap region spreads across the boundary of , suggesting an exotic metallic phase with spin-gap, which is absent in the conventional model. The result indicates that the long-range dipolar interactions have a significant influence on the ground-state properties of the one-dimensional model. Its implication on the pseudogap phenomenon of the hole-doped cuprates is briefly discussed.

Stress engineering for the design of morphotropic phase boundary in piezoelectric material

Alkoxide-derived lead zirconate titanate thin films having Zr/Ti=50/50 to 60/40 compositions with different residual stress conditions were deposited on a Si wafer to clarify the effects of the residual stress on the morphotropic phase boundary shift. The residual stress condition was controlled to −0.1 to −0.9GPa by the design of the buffer layer structure on the Si wafer. Results show that the maximum effective piezoelectric constant d33 was obtained at 58/42 composition under −0.9GPa compressive residual stress condition. Moreover, the MPB composition shifted linearly to Zr-rich phase with increasing compressive residual stress.

Shift of morphotropic phase boundary in high-performance fine-grained PZN–PZT ceramics

Abstract The fine-grained xPb(Zn1/3Nb2/3)O3–(1 − x)Pb(Zr0.47Ti0.53)O3 system has been prepared from submicron precursor powders obtained by high-energy ball milling method. The addition of PZN induces a decrease of grain size from an initial micron scale to a submicron scale, accompanying with the phase transition from tetragonal to morphotropic phase boundary (MPB), and then rhombohedral side. Interestingly, compared to the former published data for coarse-grained ceramic, the MPB has shifted from 50% to 30% PZN content side due to the enhancement of the internal stress for fine-grained ceramic. The enhanced electrical and mechanical performances are closely associated with the phase structure and grain size. A high piezoelectric property (d33 = 380 pC/N and kp = 0.49) as well as mechanical performance (Hv = 5.0 GPa and KIC = 1.33 MPa m1/2) were obtained simultaneously for the MPB 0.3PZN–0.7PZT ceramics with an average grain size of 0.65 μm.

Electric field induced cloudy–clear transitions in micellar solutions of a block copolymeric amphiphile

We report observations of cloudy–clear transitions, triggered by electric fields, in micellar solutions of a poly(oxy ethylene/propylene)–poly(dimethylsiloxane) based triblock amphiphile dissolved in silicone oil (DC245). Initial studies showed complete clarification of a cloudy 2% solution at ambient temperature when subjected to a uniform electric field of ∼5 kV cm−1. Static Light Scattering measurements showed that the clarification was associated with a significant reduction in the size of the micellar aggregate from ca. 200 nm to 50 nm. Field strength studies at varying temperatures established the potency of the effect at 1 kV cm−1 field equivalent to a 1 K decrease in temperature. The observed effect was qualitatively different from the electric field induced macroscopic pattern formations, or self assembled domain rotations or mesogen alignment phenomena; and quantitatively far more impactful than the minor shifts in phase boundaries reported earlier. Although the mechanistic underpinning of the observed field effect has yet to be established, the optical switchability of the solutions could be exploited for various electro-optical applications such as displays, and optical filters. The work also opens up the possibilities of using electric fields for manipulating micellar solubilization or creating tunable templates for nano-material synthesis.