Search

Via molecular dynamics simulations, we study kinetics in aVicsek-like phase-separating active matter model. Quantitative results, for isotropic bicontinuous pattern, are presented on the structure, growth, and aging. These are obtained via the two-point equal-time density-density correlation function, the average domain length, and the two-time density autocorrelation function. Both the correlation functions exhibit basic scaling properties, implying self-similarity in the pattern dynamics, for which the average domain size exhibits a power-law growth in time. The equal-time correlation has a short distance behavior that provides reasonable agreement between the corresponding structure factor tail and the Porod law. The autocorrelation decay is a power-law in the average domain size. Apart from these basic similarities, the overall quantitative behavior of the above-mentioned observables is found to be vastly different from those of the corresponding passive limit of the model which also undergoes phase separation. The functional forms of these have been quantified. An exceptionally rapid growth in the active system occurs due to fast coherent motion of the particles, mean-squared-displacements of which exhibit multiple scaling regimes, including a long time ballistic one. [ABSTRACT FROM AUTHOR]

The interactions of molecules and particles in solution often involve an interplay between isotropic and highly directional interactions that lead to a mutual coupling of phase separation and selfassembly. This situation arises, for example, in proteins interacting through hydrophobic and charged patch regions on their surface and in nanoparticles with grafted polymer chains, such as DNA. As a minimal model of complex fluids exhibiting this interaction coupling, we investigate spherical particles having an isotropic interaction and a constellation of five attractive patches on the particle's surface. Monte Carlo simulations and mean-field calculations of the phase boundaries of this model depend strongly on the relative strength of the isotropic and patch potentials, where we surprisingly find that analytic mean-field predictions become increasingly accurate as the directional interactions become increasingly predominant. We quantitatively account for this effect by noting that the effective interaction range increases with increasing relative directional to isotropic interaction strength. We also identify thermodynamic transition lines associated with self-assembly, extract the entropy and energy of association, and characterize the resulting cluster properties obtained from simulations using percolation scaling theory and Flory-Stockmayer mean-field theory. We find that the fractal dimension and cluster size distribution are consistent with those of lattice animals, i.e., randomly branched polymers swollen by excluded volume interactions. We also identify a universal functional form for the average molecular weight and a nearly universal functional form for a scaling parameter characterizing the cluster size distribution. Since the formation of branched clusters at equilibrium is a common phenomenon in nature, we detail how our analysis can be used in experimental characterization of such associating fluids. [ABSTRACT FROM AUTHOR]

The stability limits of the isotropic state of melt of rod-rod AB polydisperse diblock copolymer have been studied within weak segregation theory. The number of units in A block is assumed to be a random variable distributed by the Schulz-Zimm distribution. Inspection of the spinodal curves shows that the copolymer melt with polydisperse rigid blocks is less stable with respect to formation of the nematic and microphase separated states than the monodisperse melt. The values of ratios between strengths of isotropic and anisotropic interactions in the system strongly influences the forms of isotropic-nematic boundary curves. [ABSTRACT FROM AUTHOR]

In many colloidal suspensions, the micrometer-sized particles behave like hard spheres, but when non-adsorbing polymers are added to the solution a depletion attraction (of entropic origin) is created. Since 60 years the Asakura-Oosawa model, which simply describes the polymers as ideal soft spheres, is an archetypical description for the statistical thermodynamics of such systems, accounting for many features of real colloid-polymer mixtures very well. While the fugacity of the polymers (which controls their concentration in the solution) plays a role like inverse temperature, the size ratio of polymer versus colloid radii acts as a control parameter to modify the phase diagram: when this ratio is large enough, a vapor-liquid like phase separation occurs at low enough colloid packing fractions, up to a triple point where a liquid-solid two-phase coexistence region takes over. For smaller size ratios, the critical point of the phase separation and the triple point merge, resulting in a single two-phase coexistence region between fluid and crystalline phases (of "inverted swan neck"-topology, with possibly a hidden metastable phase separation). Furthermore, liquid-crystalline ordering may be found if colloidal particles of non-spherical shape (e.g., rod like) are considered. Also interactions of the particles with solid surfaces should be tunable (e.g., walls coated by polymer brushes), and interfacial phenomena are particularly interesting experimentally, since fluctuations can be studied in the microscope on all length scales, down to the particle level. Due to its simplicity this model has become a workhorse for both analytical theory and computer simulation. Recently, generalizations addressing dynamic phenomena (phase separation, crystal nucleation, etc.) have become the focus of studies. [ABSTRACT FROM AUTHOR]

Lithium chloride aqueous solutions (LiClaq solutions) below 10 mol.% are vitrified by cooling from room temperature to 77 K at 0.3 GPa. We examine the solvent state of the glassy sample and its transformation by heating at 1 atm using low-temperature differential scanning calorimetry and Raman spectroscopy. This experimental study suggests strongly that the solvent state of the glassy LiClaq solution closely relates to the state of high-density amorphous ice. Moreover, we reconfirm that the separation into the low-density amorphous ice and the glassy highly concentrated LiClaq solution occurs in the glassy dilute LiClaq solution at ∼130 K, not the glass-to-liquid transition which is commonly observed in the glassy LiClaq solution above ∼10 mol.%. In order to interpret the sudden switchover between the glass-to-liquid transition and the phase separation at ∼10 mol.%, we propose a state diagram of LiClaq solution which connects with a polyamorphic state diagram of pure water and discuss a possibility that the electric field induces a polyamorphic transition of water. [ABSTRACT FROM AUTHOR]

Structures of small mixed krypton-xenon clusters of different compositions with an average size of 30-37 atoms are investigated. The Kr 3d5/2 and Xe 4d5/2 surface core level shifts and photoelectron intensities originating from corner, edge, and face/bulk sites are analyzed by using soft x-ray photoelectron spectroscopy. Structural models are derived from these experiments, which are confirmed by theoretical simulation taking induced dipole interactions into account. It is found that one or two small Xe cores are partly embedded in the surface of the Kr clusters. These may grow and merge leading to a phase separation between the two rare gas moieties in mixed clusters with increasing the Xe content. [ABSTRACT FROM AUTHOR]

The capping of GaN quantum dots (QDs) with an Al0.5Ga0.5N layer is studied using transmission electron microscopy and atomic force microscopy in combination with theoretical calculations. The capping process can be divided into several well-distinguishable stages including a QD shape change and a local change of the Al0.5Ga0.5N capping layer composition. The phase separation phenomenon is investigated in relation with the capping layer thickness. Amount of the chemical composition fluctuations is determined from separate analysis of scanning transmission electron microscopy and high-resolution transmission electron microscopy images. The local distortion of atomic lattice in the QD surroundings is measured by high-resolution electron microscopy and is confronted with theoretically calculated strain distributions. Based on these data, a possible mechanism of alloy demixing in the Al0.5Ga0.5N layer is discussed. [ABSTRACT FROM AUTHOR]

Partially wet granular medium is a mouldable material due to capillary cohesion and its behavior plays key roles in geophysics. However, completely wet nanogranules may also demonstrate mouldable properties via van der Waals attraction and they exhibit colloidal glass or gel characteristics, depending on the solvent. As solvent-enhanced attractions prevail, phase separation is observed and nanogranular gel can be obtained. In contrast, as cage effects dominate, the stable slurry is seen and the nanogranular glass can be prepared. Upon surfactant addition, however, the arrested glass state changes into colloidal gel due to the formation of hydrogen bonds between nanogranules. [ABSTRACT FROM AUTHOR]

The structure and dynamics of early stage kinetics of pressure-induced phase separation of compressible polymer solutions via spinodal decomposition is analyzed using a linear Euler-Cahn-Hilliard model and the modified Sanchez Lacombe equation of state. The integrated density wave and Cahn-Hilliard equations combine the kinetic and structural characteristics of spinodal decomposition with density waves arising from pressure-induced couplings. When mass transfer rate is slower that acoustic waves, concentration gradients generate density waves that cycle back into the spinodal decomposition dynamics, resulting in oscillatory demixing. The wave attenuation increases with increasing mass transfer rates eventually leading to nonoscillatory spinodal demixing. The novel aspects of acousto-spinodal decomposition arise from the coexistence of stable oscillatory density dynamics and the unstable monotonic concentration dynamics. Scaling laws for structure and dynamics indicate deviations from incompressible behavior, with a significant slowing down of demixing due to couplings with density waves. Partial structure factors for density and density-concentration reflect the oscillatory nature of acousto-spinodal modes at lower wave vectors, while the single maximum at a constant wave vector reflects the presence of a dominant mode in the linear regime. The computed total structure factor is in qualitative agreement with experimental data for a similar polymer solution. [ABSTRACT FROM AUTHOR]

Molecular dynamics simulations have been employed to study the formation of a physical gel by semiflexible polymer chains. The formation of a geometrically connected network of these chains is investigated as a function of temperature and rate of cooling. The stiffness of the molecules is controlled via a potential between beads separated by two bonds. As the temperature is lowered, a percolated homogeneous solution phase separates to form a high-density, non-percolated nematic fluid and a low-density gas phase. On further decreasing the temperature, the chains are dynamically arrested preventing the completion of the vapor-liquid (VL) phase separation. As a result, the chains are stuck in a three-dimensional network of nematic bundles forming a percolated gel. Apart from temperature, the rate of cooling also plays an important role in the formation of the gel. Cooling the system at a faster rate yields gel while slower rates result in complete VL phase separation. [ABSTRACT FROM AUTHOR]

We report a study of aqueous solutions of poly(vinylalcohol) and its hydrogel by thermal conductivity, κ, and specific heat measurements. In particular, we investigate (i) the changes in the solution and the hydrogel at 0.1 MPa observed in the 350-90 K range and of the frozen hydrogel at 130 K observed in the range from 0.1 MPa to 1.3 GPa, and (ii) the nature of the pressure collapse of ice in the frozen hydrogel and kinetic unfreezing on heating of its high density water at 1 GPa. The water component of the polymer solution on cooling either first phase separates and then freezes to hexagonal ice or freezes without phase separation and the dispersed polymer chains freeze-concentrate in nanoscopic and microscopic regions of the grain boundaries and grain junctions of the ice crystals in the frozen state of water in the hydrogel. The change in κ with temperature at 1 bar is reversible with some hysteresis, but not reversible with pressure after compression to 0.8 GPa at 130 K. At high pressures the crystallized state collapses showing features of κ and specific heat characteristic of formation of high density amorphous solid water. The pressure of structural collapse is 0.08 GPa higher than that of ice at 130 K. The slowly formed collapsed state shows kinetic unfreezing or glass-liquid transition temperature at 140 K for a time scale of 1 s. Comparison with the change in the properties observed for ice shows that κ decreases when the polymer is added. [ABSTRACT FROM AUTHOR]

In this paper, we study the evolution of phase-separating binary mixtures which are subjected to alternate cooling and heating cycles. An initially homogeneous mixture is rapidly quenched to a temperature T1Tc. These cycles are repeated to create a domain morphology with multiple length scales, i.e., the structure factor is characterized by multiple peaks. For phase separation in d = 2 systems, we present numerical and analytical results for the emergence and growth of this multiple-scale morphology. [ABSTRACT FROM AUTHOR]

We report on the first observation of the macroscopic (long-range) Si[Single_Bond]SiO2 phase separation in Si-rich oxide SiOx (x<2) obtained by continuous-wave laser annealing of free-standing SiOx films. The effect is analyzed by a unique combination of microscopic methods (Raman, transmission, photoluminescence, and infrared spectroscopy, transmission electron microscopy, electron energy loss spectroscopy, and x-ray photoelectron spectroscopy). Three regions can be distinguished on a SiOx free-standing film after 488 nm laser annealing at intensities above ∼104 W cm-2: central spot, ring around the central spot, and pristine film outside the irradiated area. In the pristine SiOx material, small Si nanocrystals (Si-nc) (diameters of a few nanometer) are surrounded by SiO2 with an addition of residual suboxides, the Si-nc being produced by annealing at 1100 °C in a furnace. The central spot of the laser-annealed area (up to ∼30 μm wide in these experiments) is practically free of Si excess and mainly consists of amorphous SiO2. The ring around the central spot contains large spherical Si-nc (diameters up to ∼100 nm) embedded in amorphous SiO2 without the presence of suboxides. Laser-induced temperatures in the structurally modified regions presumably exceed the Si melting temperature. The macroscopic Si[Single_Bond]SiO2 phase separation is connected with extensive diffusion in temperature gradient leading to the Si concentration gradient. The present work demonstrates the advantages of high spatial resolution for analysis in materials research. [ABSTRACT FROM AUTHOR]

Structural, magnetic, and electronic transport properties of Bi0.6-xLaxCa0.4MnO3 (0≤x≤0.6) manganites have been studied systematically. The parent compound exhibits robust charge ordered antiferrromagnetic (COAFM) phase with TCO∼293 K and AFM Néel temperature TN∼149 K. The sample with x=0.1 show a M(T) curve of 'arch bridge' form between 142 and 253 K, which is attributed to the AFM peak embedded in the broad transition of the CO. For the middle doping samples (0.2≤x≤0.4), although the CO peaks disappear as a result of the suppression of the long range CO state, AFM superexchange coupling has been strengthened with the increasing of La doping level. The Bi0.1La0.5Ca0.4MnO3 sample shows interesting phenomena such as magnetization steps and magnetic memory effect. The resistivity of the samples exhibits insulating behavior in our measured temperature range for x≤0.4. While both x=0.5 and x=0.6 compounds exhibit metal-insulator transition. Furthermore, large low field magnetoresistance (MR) and hysteresis appears only in the MR(H) curve of x=0.5 sample. These results are discussed in terms of the charge localization caused by the lattice distortion due to the character of the 6s2 lone pair of Bi3+ ions. [ABSTRACT FROM AUTHOR]

Structural, magnetic, and electronic transport properties of Bi0.6-xLaxCa0.4MnO3 (0≤x≤0.6) manganites have been studied systematically. The parent compound exhibits robust charge ordered antiferrromagnetic (COAFM) phase with TCO∼293 K and AFM Néel temperature TN∼149 K. The sample with x=0.1 show a M(T) curve of 'arch bridge' form between 142 and 253 K, which is attributed to the AFM peak embedded in the broad transition of the CO. For the middle doping samples (0.2≤x≤0.4), although the CO peaks disappear as a result of the suppression of the long range CO state, AFM superexchange coupling has been strengthened with the increasing of La doping level. The Bi0.1La0.5Ca0.4MnO3 sample shows interesting phenomena such as magnetization steps and magnetic memory effect. The resistivity of the samples exhibits insulating behavior in our measured temperature range for x≤0.4. While both x=0.5 and x=0.6 compounds exhibit metal-insulator transition. Furthermore, large low field magnetoresistance (MR) and hysteresis appears only in the MR(H) curve of x=0.5 sample. These results are discussed in terms of the charge localization caused by the lattice distortion due to the character of the 6s2 lone pair of Bi3+ ions. [ABSTRACT FROM AUTHOR]

Polarization microscopy was used to study the behavior around the isotropic-nematic interface of colloidal goethite dispersions in a magnetic field. It has been found before that the nematic phase is favored in an external field. In the case of goethite this was also observed; nematic droplets formed inside the isotropic phase and coalesced with the nematic phase. However, the behavior was found to be much richer because of the particle rotation around a certain critical field strength. The simultaneous occurrence of (parallel)nematic-(perpendicular)nematic phase separation under the influence of a magnetic field also plays a role here. [ABSTRACT FROM AUTHOR]

The phase separation of Nd0.5Ca0.5-ySryMnO3, for 0≤y≤0.5, is studied via electron spin resonance (ESR) in the temperature range 80–400 K. Two types of magnetic phases are found to coexist in the samples with y>0 below a phase separation temperature T*. The ESR line width exhibits a minimum near the charge order transition temperature TCO for samples with y<0.25, and near T* for y≥0.25. A systematic decrease in line width is observed as y increases from 0 to 0.5. The g factors increase slightly and the ESR intensities increase exponentially when the temperature decreases in the paramagnetic region. Our results demonstrate presence of two local magnetic structures due to the intrinsic phase separation. [ABSTRACT FROM AUTHOR]

The phase separation of Nd0.5Ca0.5-ySryMnO3, for 0≤y≤0.5, is studied via electron spin resonance (ESR) in the temperature range 80–400 K. Two types of magnetic phases are found to coexist in the samples with y>0 below a phase separation temperature T*. The ESR line width exhibits a minimum near the charge order transition temperature TCO for samples with y<0.25, and near T* for y≥0.25. A systematic decrease in line width is observed as y increases from 0 to 0.5. The g factors increase slightly and the ESR intensities increase exponentially when the temperature decreases in the paramagnetic region. Our results demonstrate presence of two local magnetic structures due to the intrinsic phase separation. [ABSTRACT FROM AUTHOR]

Using high-speed visualization we demonstrate that ultrasound irradiation of pressurized carbon dioxide (CO2) induces phenomena that do not occur in ordinary liquids at ambient conditions. For a near-critical mixture of CO2 and argon, sonication leads to extremely fast local phase separation, in which the system enters and leaves the two-phase region with the frequency of the imposed sound field. This phase transition can propagate with the speed of sound, but can also be located at fixed positions in the case of a standing sound wave. Sonication of a vapor-liquid interface creates a fine dispersion of liquid and vapor, irrespective whether the ultrasound horn is placed in the liquid or the vapor phase. In the absence of an interface, sonication of the liquid leads to ejection of a macroscopic vapor phase from the ultrasound horn with a velocity of several meters per second in the direction of wave propagation. The findings reported here potentially provide a tunable and noninvasive means for enhancing mass and heat transfer in high-pressure fluids. [ABSTRACT FROM AUTHOR]

The phase behavior of physically associating polymer solutions, where the polymer chain contains a small fraction of “stickers” regularly placed along the backbone, is studied using self-consistent field lattice model. Two inhomogenous morphologies are observed. One is a microfluctuation homogenous (MFH) morphology, where the mean-field values of the local average concentrations of polymers [lowercase_phi_synonym]P(r) and stickers [lowercase_phi_synonym]st(r) slightly fluctuate around their respective bulk average values [lowercase_phi_synonym]P and [lowercase_phi_synonym]st and regularly from site to site. The other is a randomly close-packed micelle (RCPM) morphology. The structure of the micelle in RCPM morphology is similar to that of the “flower micelle” in the telechelic associative polymer system, where stickers are located in the core of the micelle and nonsticky groups in the corona. When [lowercase_phi_synonym]P>=0.08, if homogenous associating polymer solutions are cooled, MFH morphology appears, and the system entirely changes from homogenous solutions (HS) to MFH morphology; If the solutions are cooled further, RCPM morphology appears. When [lowercase_phi_synonym]P<0.08, however, RCPM morphology appears immediately. If [lowercase_phi_synonym]P<0.53, a macroscopic phase separation, where the polymer rich phase is RCPM morphology, occurs. If [lowercase_phi_synonym]P>=0.53, only RCPM morphology is found in the system. A peak appears in the temperature-dependent specific-heat curve CV(χ) at each transition point. For the HS-MFH transition, CV(χ) has an abrupt increase and a slow decrease, whereas for the MFH-RCPM transition, both the increase and the decrease in CV(χ) are slow. Furthermore, the system with only MFH morphology may be trapped in one of the two energy basins in a experimental time scale. However, the appearance of RCPM morphology means that the system is trapped in one of a series of “deeper” energy basins, and it is very difficult to jump off this deep basin into the one of MFH morphology or one of the other RCPM morphologies through thermal fluctuations. [ABSTRACT FROM AUTHOR]

Treating the repulsive part of a pairwise potential by the hard-sphere form and its attractive part by the effective depletion potential form, we calculate using this model potential the colloidal domains of phase separation. Differing from the usual recipe of applying the thermodynamic conditions of equal pressure and equal chemical potential where the branches of coexisting phases are the ultimate target, we employ the free energy density minimization approach [G. F. Wang and S. K. Lai, Phys. Rev. E 70, 051402 (2004)] to crosshatch the domains of equilibrium phases, which consist of the gas, liquid, and solid homogeneous phases as well as the coexistence of these phases. This numerical procedure is attractive since it yields naturally the colloidal volume of space occupied by each of the coexisting phases. In this work, we first examine the change in structures of the fluid and solid free energy density landscapes with the effective polymer concentration. We show by explicit illustration the link between the free energy density landscapes and the development of both the metastable and stable coexisting phases. Then, attention is paid to the spatial volumes predicted at the triple point. It is found here that the volumes of spaces of the three coexisting phases at the triple point vary one dimensionally, whereas for the two coexisting phases, they are uniquely determined. [ABSTRACT FROM AUTHOR]

Phase separation (PS) in hole-doped cobaltites (La1-xSrxCoxO3) is drawing renewed interest recently. In particular, the magnetic behavior of La0.85Sr0.15CoO3 has been subjected to a controversial debate for the past several years; while some groups show evidence for magnetic PS, others show spin glass (SG) behavior. Here, an attempt is made to resolve the controversy related to “PS versus SG” behavior in this compound. We present the results of a comprehensive investigation of the dc magnetization, ac susceptibility, and the magnetotransport properties of La0.85Sr0.15CoO3 samples. We contemplate that the magnetic PS in La0.85Sr0.15CoO3 is neither intrinsic nor inherent, but it is a consequence of the preparation conditions. It is realized that a low temperature annealed (LTA) sample shows PS whereas the high temperature annealed (HTA) sample shows SG behavior. The Brillouin-like behavior of field cooled dc magnetization and apparently no frequency dependent peak shift in ac susceptibility for the LTA sample characterize it to be of ferromagneticlike whereas a kink in field cooled dc magnetization and a considerable amount (∼3 K) of frequency dependent peak shift in the ac susceptibility for the HTA sample characterize it to be of SG state. The magnetotransport properties show that the HTA sample is more semiconducting as compared to the LTA sample. This is interpreted in terms of the presence of isolated as well as coalescing metallic ferromagnetic clusters in the case of LTA sample. The magnetoresistance (MR) at 10 K for the HTA sample exhibits a huge value (∼65%) as compared to the LTA sample, and it monotonically decreases with the rise in temperature. Such a high value of MR in the case of HTA sample is strongly believed to be due to the spin dependent part of random potential distribution. Further, the slow decay of remnant magnetization with progress of time and the existence of hysteresis at higher temperatures (up to 200 K) in the case of LTA sample as compared to the HTA sample clearly unveil different magnetic states associated with them. [ABSTRACT FROM AUTHOR]

Semiconductor nanospheres were efficiently synthesized by the pulsed-laser-ablation-in-liquid technique applied to suspensions of certain powders. The nanosphere formation is demonstrated to follow a solid phase separation mechanism and take place in a low-temperature zone of the laser-irradiated volume, while the high temperature and rapid cooling rate generated by pulsed laser are crucial for the particle shape. The synthetic route is applied to different material systems and proved to be a general way for manufacturing various high-quality nanostructures with spherical shape. [ABSTRACT FROM AUTHOR]

Indium-rich AlInN are grown by metal-organic (MO) chemical vapor deposition using trimethylaluminum, trimethylindium, and ammonia. Under the conservation of MO influx, the effects of gas flow in the MO route on AlInN growth and Al-related parasitic reaction are investigated. With an increase in this gas flow, the suppression of Al-related parasitic reaction, i.e., enhancement in Al content incorporation and improvement of crystalline quality, is satisfactorily shown until the occurring of severe phase separation. Accordingly, Al content x in AlxIn1-xN can be tuned from x=0.02 to 0.26. The Raman spectra of those AlInN samples with phase separation are analyzed by the resonant excitation effect and two-mode behavior for A1(LO). Finally, we propose a phase diagram to interpret the phase separation and Al content evolution under the influence of gas flow. [ABSTRACT FROM AUTHOR]

The macroscopic phase separation of undercooled liquid Fe50Sn50 immiscible alloy was investigated by both drop tube experiment and the modified Model H. Core-shell structures with two, three, and five layers were formed during experiment. The concentric shells comprised of Fe-rich phase and Sn-rich phase distribute periodically in the solidified droplet, and the Sn-rich phase is always located at the sample surface owing to its smaller surface tension. The simulated results of modified Model H reproduce core-shell structures with the same layers, which justifies the prediction of this model. If the fluidity parameter Cf and solute concentration [lowercase_phi_synonym] satisfy the physical conditions of both Cf<1 and 0<[lowercase_phi_synonym]<0.45 or Cf≥1, the phase separation morphology exhibits the double-layer core-shell structure, whereas the multilayer core-shell structure is expected to form under the conditions of both Cf<1 and 0.45≤[lowercase_phi_synonym]<0.5. The forming ability of core-shell structure for various immiscible alloys can be predicted accordingly. [ABSTRACT FROM AUTHOR]

We have investigated the details of phase separation in the electron-doped manganites Sm1-xCaxMnO3 (0.8≤x≤0.92) by using temperature dependent x-ray diffraction. The lattice of the low-temperature orthorhombic phase is distorted to various extents according to the strength of the coexisting monoclinic phase. Meanwhile, the room-temperature lattice becomes more distorted due to the increasing Jahn–Teller active Mn3+ ions by Sm3+ doping. On the other hand, the substitution of Ca2+ with Sm3+ introduces the Mn3+–Mn4+ pairs, which favor the double exchange ferromagnetism. As a result of the competition between the lattice distortion and electron doping level, the modified phase diagram have been presented, including the high-temperature Griffiths phase and the ground state with competing multiphases. [ABSTRACT FROM AUTHOR]

Both La0.375Pr0.25Ca0.375MnO3 (LPCMO) and La0.625Ca0.375MnO3 (LCMO) were found to exhibit coexistence of competing orders (phase separation) over a wide temperature range. However, substantial hysteretic behaviors in both of the temperature-dependent resistance [R(T)] and magnetization [M(T)] [also known as the persistent magnetic memory effect (PMME)] are only displayed in LPCMO. The results indicate that, in LPCMO, the size distribution of the coexisting charge-ordered insulating and metallic ferromagnetic (FM) phases plays a determinant role in the PMME effects in different temperature regimes. Moreover, due to the direct competition between the two coexisting phases, the system is most susceptible to the external applied field in the hysteretic temperature region. On the other hand, in LCMO, the phase transition between paramagnetic and FM is more like an isomorphic transition in pure materials, and thus does not show significant hysteresis. [ABSTRACT FROM AUTHOR]

Systematic studies of magnetic, electrical, and thermal transport properties have been performed on a single crystal of La0.98Pb0.02Mn0.74Co0.25O3. From 5 to 500 K, the material system shows three distinct magnetic states, a low-temperature glassing state (from 5 to 185 K), a Griffiths-like ferromagnetic state (from 185 to 326 K), and a single paramagnetic phase above 326 K. The sample shows a semiconducting electrical transport behavior in the whole studied temperature range. With decreasing temperature, magnetoresistance increases rapidly from 290 K and reaches a maximum at 185 K and then decreases continuously with a broad peak in the vicinity of 100 K. Magnetothermopower also presents obvious anomalies at these characteristic temperatures. Both the magnetic and transport properties suggest an intrinsic phase separation in the single crystal. [ABSTRACT FROM AUTHOR]

Systematic studies of magnetic, electrical, and thermal transport properties have been performed on a single crystal of La0.98Pb0.02Mn0.74Co0.25O3. From 5 to 500 K, the material system shows three distinct magnetic states, a low-temperature glassing state (from 5 to 185 K), a Griffiths-like ferromagnetic state (from 185 to 326 K), and a single paramagnetic phase above 326 K. The sample shows a semiconducting electrical transport behavior in the whole studied temperature range. With decreasing temperature, magnetoresistance increases rapidly from 290 K and reaches a maximum at 185 K and then decreases continuously with a broad peak in the vicinity of 100 K. Magnetothermopower also presents obvious anomalies at these characteristic temperatures. Both the magnetic and transport properties suggest an intrinsic phase separation in the single crystal. [ABSTRACT FROM AUTHOR]

The magnetic, resonance, and electric properties of LaxMnO3+δ (0.815≤x≤1.0) polycrystalline samples have been studied in the temperature range of 77–370 K and at high pressures of up to 11.5 kbar. It is shown that the increase in the La/Mn ratio gives rise to a change in the low temperature magnetic state from ferromagnetic to cluster spin glass, as well as to a drastic transformation of electric properties. A peculiar double-peaked shape is characteristic of the resistivity versus temperature curves for the intermediate range of x values. Within this range, the application of high pressures drastically changes both the value of resistivity and the character of its temperature dependence. It is shown that the approach, which regards the state of LaxMnO3+δ polycrystals as a mixture of interpenetrating paramagnetic insulating and ferromagnetic metallic phases, is able to successfully describe the peculiarities of the temperature dependence of total resistivity, as well as the features of its transformation under hydrostatic compression. It is demonstrated that the formation of a low temperature resistance peak is a result of a wide-temperature-region coexistence of the phases, which exhibits opposite trends in the temperature dependences of resistivity. The conclusion is made that not only does hydrostatic compression result in drastic changes in the relative volume fractions of the coexisting phases, but it also affects the intrinsic parameters of each of the phases. [ABSTRACT FROM AUTHOR]

We study the morphology of spinodal decompositions (SDs) in mixtures of a liquid crystal and a colloidal particle by solving time-dependent Landau–Ginzburg equations for a conserved order parameter (concentration) and two nonconserved order parameters (orientation and crystallization). We numerically examine the coupling between concentration, nematic ordering, and crystalline ordering in two dimensional fluid mixtures, coexisting a nematic and a crystalline phase. On increasing the concentration of colloidal particles, we have three different SDs: a nematic order-induced SD, a phase-separation-induced SD (PSD), and a crystalline-order-induced SD (CSD). In NSD, the phase ordering can lead to fibrillar and cellular networks of the minority colloidal-particle-rich phase in early stages. In the PSD, we find a bicontinuous network structure consisting of a nematic phase rich in liquid crystal and a crystalline phase rich in colloidal particles. In the CSD, nematic droplets can be formed in a crystalline matrix. Asymmetric mixtures of a liquid crystal and a colloidal particle lead to rich varieties of morphologies. [ABSTRACT FROM AUTHOR]

The spinodal phase decomposition of an immiscible binary polymer blend system is investigated with numerical models in two-dimensional and three-dimensional (3D). The effect of the elastic energy is included. The mechanism of the evolution of the phase separation is studied and the characteristic length R(t) is shown to be proportional to t1/3. In the case when the phase separation is directed by a heterogeneously functionalized substrate, the increase in the characteristic length is divided into two stages by a critical time. The R(t)∼t1/3 diagram can be fitted with a straight line in both the first and second stages. The slope of the fitting line significantly decreases after the critical time. The compatibility of the resulting pattern to the substrate pattern is also measured by a factor CS. It is observed that there is also a critical time in the evolution of the compatibility for the cases with and without elastic energy. The critical time of CS is identical with the respective critical time of R(t). The lateral and vertical composition profiles functionalized substrate is observed with the 3D model. The difference mechanism of the cases with and without elastic energy is discussed. [ABSTRACT FROM AUTHOR]

Lamellar structure via two-step surface-directed phase separation in polymer blend films is numerically investigated in three-dimensional (3D) space, which is more physically appropriate for the experimental situation than that in two-dimensional (2D) space [L.-T. Yan and X. M. Xie, J. Chem. Phys. 128, 034901 (2008)]. The 3D phase morphology and its evolution dynamics in both critical and off-critical conditions have been studied. The wetting layer formation mechanism during the second quench has been concerned. The effects of noise on the ordered phase structures have also been examined. The simulated results in 3D space give a more certain evidence that the lamellar structure can be induced by the surface or interface when the system is in the equilibration state with very shallow quench depth first and then imposed on a further quench depth in the unstable region of the phase diagram. It is found that the lamellar structure can also be induced in the polymer blends with off-critical condition. The simulated results demonstrate that the formation of the lamellar structure can present two basic processes and obey logarithmic growth law at the initial and metaphase stages. The results also show that a stronger thermal noise corresponds to a smaller region with the lamellar structure. [ABSTRACT FROM AUTHOR]

Abstract We present a phase-field model of thermally-induced phase separation in polymer solutions, calibrated for the polyvinylidene fluoride (PVDF)/diphenyl carbonate (DPC) system. Large-scale three-dimensional computer simulations were performed for isotropic and anisotropic thermal quenches, and the evolution and structure of the resulting two-phase morphology is analyzed. Isotropic quenches, in which the temperature is uniformly reduced below the binodal temperature, were conducted to understand the initiation and coarsening of the polymer-rich and polymer-poor phases throughout time. Anisotropic quenches, in which the system is cooled from one particular surface, were also conducted to understand how gradients in the characteristic domain size develop for varying conditions. In these anisotropic quenches, we observe the formation of a dense skin layer adjacent to the cooling surface, the thickness of which depends on several parameters including the polymer volume fraction, the assumed bath temperature that is maintained at the cooling surface, and the rate of thermal conduction through the polymer solution. The model here can be adapted to other polymer/solvent systems by modifying the thermodynamic and kinetic parameters specific to the two species. [ABSTRACT FROM AUTHOR]

Graphical abstract Abstract Mixed matrix membranes blended with graphene-based nanomaterials have great potential in water and wastewater treatment on account of their multiple functionalities. To solve the complicated biofouling problem and diversify the applications of membranes, novel synergistic antibacterial guanidyl-functionalized graphene/polysulfone (GFG/PSF) mixed matrix ultrafiltration membranes were prepared by a non-solvent induced phase separation method. The guanidyl-functionalized graphene nanosheets were achieved by a two-step grafting process consisting of amination and guanidination and exhibited high dispersibility in the casting solution, which showed good compatibility with the polymer matrix. Besides the advantages of partially reduced graphene oxide (GO) nanosheets in creating a stronger interaction with the bacterial cell membrane to destroy the bacteria, the induced bidendate binding between guanidyl groups and phosphate groups on the cell wall can make high sterilization rate even at low concentrations. Different techniques including XRD, FTIR, XPS, SEM, TEM, EDX, contact angle meter, filtration and antibacterial experiments were employed to characterize and investigate the performance of nanosheets and membranes. Compared with pure PSF membrane, the GFG/PSF mixed matrix membranes not only exhibited superior permeability and prominent antifouling property performance toward bovine serum albumin (BSA), but also displayed excellent antimicrobial activity and long-term duration toward Escherichia coli and Staphylococcus aureus. [ABSTRACT FROM AUTHOR]

The solubility of drugs is a crucial physicochemical property in the drug discovery or development process and for improving the bioavailability of drugs. There are various methods for evaluating the solubility of drugs including manual measurement methods, mathematical methods, and smart methods. Manual measurement and mathematical methods have some defects which make the smart systems more reliable and important in this field. In this review, various instruments used for the solubility determination, along with the smart systems, have been discussed. Mechanism and applications of each method have been elaborated in detail. Moreover, unique characteristics as well as some limitations of discussed methods are also described. [ABSTRACT FROM AUTHOR]

In this paper we report a study of phase separation in bulk InxGa1-xN films grown by metal organic chemical-vapor deposition using mid-UV Raman spectroscopy. Evidence of phase separation is observed by the occurrence of low frequency shoulders identified as minority phase in the A1(LO) Raman mode. A phase transition in the alloy from the metastable to unstable region was found to be occurring at an indium concentration of about 25%. Raman spectroscopic results also indicate that the compositional inhomogenity in our samples increase, as would be expected, with depth in the film. A direct correspondence is also found between the percentage of indium concentration in the film and the amount of compositional inhomogenity. [ABSTRACT FROM AUTHOR]

ABSTRACT: In this study, poly(vinylidene fluoride) (PVDF) membranes were prepared using two different solvents with various polymer concentrations to investigate the predominant kinetic or thermodynamic aspects of membrane preparation in a phase separation process. For this purpose, dimethyl sulfoxide (DMSO) as a weak solvent and N‐2‐methylpyrrolidone (NMP) as a strong solvent were used with polymer concentrations between 8 and 15 wt %. Scanning electron microscopy and water content, contact angle, and pore size measurements were used to assess the factors affecting the physicochemical properties of the prepared membranes. The results showed that in the case of NMP, the membrane structure is mainly controlled by thermodynamic parameters, while when using DMSO, kinetic parameters are predominant. According to the results, the prepared PVDF‐based membranes with DMSO exhibited a relatively denser top layer and less permeation compared to the NMP/PVDF membranes. The difference between the viscosities of the casting solutions with equal polymer concentrations in DMSO and NMP was considered to be the main effective factor in solvent/nonsolvent exchange, resulting in denser top layers in the DMSO/PVDF membranes. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018, 135, 46419. [ABSTRACT FROM AUTHOR]

ABSTRACT: Self‐assembled block polymer membranes are rising to the fore of next‐generation separations technologies, and a particular fabrication process of significant interest is the self‐assembly and non‐solvent induced phase‐separation (SNIPS) method. This is because the SNIPS process allows for the facile manipulation of independent variables to produce simultaneously size‐ and chemically‐selective membranes in a scalable manner. Despite significant advances in the SNIPS membrane fabrication procedure, the early‐stage solution behavior of many of the polymer–solvent systems employed is still poorly understood. This work addresses the challenges posed by these systems and illuminates guiding relationships for the optimization of SNIPS membrane casting solutions. Specifically, polymer aggregate structures and critical micelle concentration (CMC) values are determined for an A‐B‐C triblock polymer dissolved in 1,4‐dioxane using a combination of scattering and atomic force microscopy techniques. The CMC of this system ranges from 20 to 80 μM and shows a strong dependence on the polymer composition and solution processing method. Additionally, the shape of the self‐assembled structures in solution can be altered by varying these parameters. These studies establish the relationships between polymer solution properties (i.e., the block polymer composition and the processing method) and assembly behavior as they impact membrane fabrication through SNIPS processing. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018, 135, 45531. [ABSTRACT FROM AUTHOR]

Common conversion point stacking or migration of receiver functions (RFs) and H-k (H is depth and k is Vp/Vs) stacking of RFs has become a common method to study the crust and upper mantle beneath broad-band three-component seismic stations. However, it can be difficult to interpret Pds RFs due to interference between the Pds, PPds and PSds phases, especially in the mantle portion of the lithosphere. We propose a phase separation method to isolate the prominent phases of the RFs and produce separate Pds, PPds and PSds 'phase specific' receiver functions (referred to as PdsRFs, PPdsRFs and PSdsRFs, respectively) by deconvolution of the wavefield rather than single seismograms. One of the most important products of this deconvolution method is to produce Ps receiver functions (PdsRFs) that are free of crustalmultiples. This is accomplished by using H-k analysis to identify specific phases in the wavefield from all seismograms recorded at a station which enables development of an iterative deconvolution procedure to produce the above-mentioned phase specific RFs. We refer to this method as wavefield iterative deconvolution (WID). The WID method differentiates and isolates different RF phases by exploiting their differences in moveout curves across the entire wave front. We tested the WID by applying it to synthetic seismograms produced using a modified version of the PREM velocity model. The WID effectively separates phases from each stacked RF in synthetic data. We also applied this technique to produce RFs from seismograms recorded at ARU (a broad-band station in Arti, Russia). The phase specific RFs produced using WID are easier to interpret than traditional RFs. The PdsRFs computed using WID are the most improved, owing to the distinct shape of its moveout curves as compared to the moveout curves for the PPds and PSds phases. The importance of this WID method is most significant in reducing interference between phases for depths of less than 300 km. Phases from deeper layers (i.e. P660s as compared to PP220s) are less likely to be misinterpreted because the large amount of moveout causes the appropriate phases to stack coherently if there is sufficient distribution in ray parameter. WID is most effective in producing clean PdsRFs that are relatively free of reverberations whereas PPdsRFs and PSdsRFs retain contamination from reverberations. [ABSTRACT FROM AUTHOR]

Superhydrophobic and superoleophilic porous reduced graphene oxide/polycarbonate (RGO/PC) monoliths with novel micro-nanoscale binary structure were first fabricated by thermally impacted nonsolvent induced phase separation (TINIPS) method. Owing to the unique pore structure, the porous monoliths possessed high specific surface area (137.19 m 2 /g) and porosity (91.3%). The superhydrophobic RGO/PC monoliths exhibited excellent capability to selectively adsorb a wide range of oils and organic solvents from water. Furthermore, the monoliths could keep a stable repellency against corrosive mediums (e.g., acidic and alkali solutions). Based on these superior properties, porous RGO/PC monoliths will be a promising candidate for high-efficiency oil/water separation to deal with water pollution. [ABSTRACT FROM AUTHOR]

Highly-priced rubidium (Rb) can be effectively extracted from seawater using potassium cobalt hexacyanoferrate (KCoFC) and ammonium molybdophosphate (AMP) adsorbents in the membrane adsorption hybrid system (MAHS). KCoFC (<0.075 mm), KCoFC (0.075–0.15 mm), and AMP (<0.075 mm) had Langmuir adsorption capacities of 145, 113, and 77 mg/g at pH 6.5–7.5, respectively. When KCoFC (<0.075 mm) at a dose of 0.2 g/L was initially added to 4 L of a solution containing 5 mg Rb/L in the MAHS and 25% of the initial dose was repeatedly added every hour, the amount of Rb removed remained steady at 90–96% for the experiment’s 26 h duration. The removal of Rb by AMP under similar conditions was 80–82%. The cumulative Rb removed by KCoFC (<0.075 mm) in MAHS was only 33% reduced in the presence of high concentrations of other cations in synthetic seawater compared to that in solution containing only Rb. Approximately 30% of the adsorbed Rb was desorbed using 1 M KCl. When the desorbed solution was passed through a column containing resorcinol formaldehyde (RF), 35% of the Rb in the desorbed solution was adsorbed on RF. Furthermore 50% of the Rb adsorbed on RF was recovered by 1 M HCl leaching of the column. This sequence of concentration and separation of Rb in the presence of other cations in synthetic seawater is an efficient method for recovering pure Rb from real seawater and seawater reverse osmosis brine. [ABSTRACT FROM AUTHOR]

It is known that Fluoride ions strongly affect bone mineralization and formation. In the present study, the engineered bone tissue scaffolds are fabricated using silk fibroin (SF) and flouridated TiO 2 nanoparticles. TiO 2 nanoparticles are modified by fluoride ions, and different levels (0, 5, 10, 15 and 20 wt%) of the fluoridated TiO 2 nanoparticles (TiO 2 -F) were subsequently added to the SF matrix through phase separation method to prepare silk fibroin/flouridated TiO 2 nanocomposite scaffolds (SF/TiO 2 -F). Phase structure, functional groups, morphology and mechanical properties of the obtained scaffolds were evaluated by X-ray diffraction method (XRD), Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM) and compressive testing, respectively. In vitro degradation studies of scaffolds were performed by incubating the samples in phosphate buffered saline (PBS) at 37 °C and pH 7.4 for 30 days. Additionally, the bioactivity of scaffolds was estimated in a simulated body fluid (SBF) buffered at 37 °C and pH 7.4 for 28 days. Moreover, MTT assay was used to confirm the biocompatibility of the scaffolds using human like SaOS-2 osteoblast cell line for 1, 3 and 5 days. The obtained results indicated that the mechanical properties of scaffolds have been improved by increasing the TiO 2 -F amount up to 15 wt%. However, a detrimental effect was observed by a further increase in the TiO 2 -F content. The bioactivity of SF/TiO 2 -F nanocomposite scaffolds was promoted by flouridation of TiO 2 . Furthermore, cell cytotoxicity results demonstrated that the SF/TiO 2 -F nanocomposite scaffolds are nontoxic to osteoblasts. The cell fixation results after 3 days of incubation revealed that the cell attachment and spreading on SF/TiO 2 -F nanocomposite scaffolds are improved with respect to SF/TiO 2 nanocomposite scaffolds control sample. [ABSTRACT FROM AUTHOR]

Iron oxide supported oxygen carrier (OC) is regarded to a promising candidate for chemical looping combustion (CLC). However, phase separation between Fe2O3 and supports often occurs resulted from the severe sintering of supports during calcination, which leads to the sintering and breakage of Fe2O3 thus the decrease of redox reactivity. In this article, La-promoted Fe2O3/α-Al2O3 were used as OCs for CLC of CH4 and for the first time found that the OC with the addition of 18 wt % La exhibited outstanding reactivity and redox stability during 50 cycles of CLC of CH4. Such a superior performance originated from the formation of LaAl12O19 hexaaluminate (La-HA) phase with not only small particle size but also excellent thermal stability at CLC conditions, which worked as a binder to prevent the phase separation thereby the sintering and breakage of active species α-Fe2O3 were avoided during reaction. © 2017 American Institute of Chemical Engineers AIChE J, 63: 2827-2838, 2017 [ABSTRACT FROM AUTHOR]

Phase separation processes following high-rate extension in unentangled polymer solutions are studied theoretically. The flow-induced demixing is associated with the coil-stretch transition predicted in high-molecular-weight polymer solutions at high-enough Weissenberg numbers. The developed mean-field theory is valid in the dilute/semidilute solution regime, where the stretched coils overlap strongly. We elucidate and discuss the main kinetic stages of the polymer/solvent separation process including (i) growth of concentration fluctuations and formation of oriented protofibrils by anisotropic spinodal decomposition; (ii) development of well-defined highly oriented and stiff fibrils forming an anisotropic network (cross-linked fiber); (iii) microphase separation and lateral collapse of the network yielding dense oriented fiber. These novel predictions are in qualitative agreement with the experimental data. [ABSTRACT FROM AUTHOR]

We present an extension of the Stefan-type solution method applicable to multi-component, multi-phase 1D porous flows, and illustrate the method by applying it to phase separation dynamics in an NaCl- $$\hbox {H}_2\hbox {O}$$ -saturated hydrothermal heat pipe. For this example, three mathematical models are constructed. The first two models concern the rate of progression of two interfaces, one separating brine from two-phase fluid and another separating two-phase fluid from single-phase liquid at seawater salinity. The brine layer model shows that the layer may reach quasi-steady-state thickness even while the salt content of the layer continues to increase; the two-phase layer model shows how variable heat flux at the top of the layer leads to departure from the linear growth rate predicted by a simpler model. The third model concerns the temperature profile in the entire column. The governing advection-diffusion equation has highly variable coefficients, with no negligible terms in it in the region of parameter space considered. We present a method to solve this type of equation by constructing a propagator and a corresponding Green's function. Finally, we show how to use the developed framework to test the internal consistency of numerical simulations, again using the 1D heat pipe as an example. [ABSTRACT FROM AUTHOR]

In the present study, rice bran stearin was used to improve the physical stability and encapsulation efficiency of water-in-oil (W/O) emulsions fabricated from rice bran oil and polyglycerol polyricinoleate ester (PGPR). In the absence of rice bran stearin, the emulsions were highly unstable to phase separation with an oil layer forming on their surfaces. Phase separation was delayed by increasing the PGPR concentration because this reduced the water droplet size. Phase separation could be completely inhibited by replacement of 30 to 45 wt% of rice bran oil with rice bran stearin due to the formation of a semi-solid fat crystal network that prevented droplet movement. Moreover, addition of rice bran stearin delayed the release of ferrous sulfate from the W/O emulsions. These results demonstrate that rice bran stearin can be used to improve the stability and encapsulation efficiency of W/O emulsions and reduce the level of PGPR required to stabilize them. [ABSTRACT FROM AUTHOR]

Atmospheric icing problem is considered as one of the major hazards to the aviation industry and the existing anti-icing system has numerous disadvantages within it. The recent studies on the super hydrophobic surfaces inspired from lotus leaf are found to be an emerging trend in the ice protection system because of its resistance to the ice formation. But the experimental procedure for creating those surfaces is expensive and it requires specialised equipments. The work of Erbil et al. is identified to be a cost-effective and simple method for creating those surfaces based on the process called phase separation. The experimental investigation of this alternate coating method is scheduled and conducted by creating the polypropylene coating on the aluminium sheet metal. The coated aluminium surface is then tested for its ice repelling property by spraying the super-cooled liquid droplets similar to Rime ice formation. It has shown few excellent results by repelling the water and the ice formation under various atmospheric conditions. Further, the wing model and the coated layer are designed using computer software to analyse the influence of anti-icing coating on the basic stress–strain and flow properties. This novel approach provides significant cost and weight savings through a roadmap for replacing the existing ice protection systems. [ABSTRACT FROM AUTHOR]