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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]

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]

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]

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]

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]

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]

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]

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]

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]

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]

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]

PVDF/PAN blend porous membranes were prepared via thermally induced phase separation (TIPS) and used as separators for lithium ion batteries. TIPS behavior was investigated in detail to control the morphology, pore size, porosity, and mechanical properties of the blend separators as a function of PAN content. Rod-like pores are the typical structure resulted from solid−solid phase separation, while the pore size and porosity decrease with an increase of PAN in the blend. The introduction of PAN enhances the tensile strength and the thermal stability of the blend separator. The electrolyte uptake and the ionic conductivity reduce correspondingly with the decrease of the pore size and the porosity. However, the graphite/polymer electrolyte/LiFePO 4 batteries with the blend separators exhibit higher C-rate performance, and better reversible charge/discharge cycle stability than those with PVDF separators and the commercial Celgard 2400. [ABSTRACT FROM AUTHOR]

The molecular orientation and phase separation of poly(3-hexylthiophene) (P3HT) and poly[[N,N-bis(2-octyldodecyl)-napthalene-1,4,5,8-bis(dicarboximide)-2,6-diyl]-alt-5, 5′-(2,2′-bithiophene)] (N2200) blends are investigated by in situ temperature-resolved two-dimensional grazing incidence X-ray diffraction (2D GIXD) in step-by-step heating and cooling processes. When pristine amorphous films are thermally annealed below the melting temperature of P3HT, only the chain segment of P3HT moves, while P3HT molecule is crystallized, induced by N2200 with face-on orientation (thermodynamics unsteady state). The interpenetrating network forms during the crystallization process of the polymers. When thermally annealed above melting temperature of P3HT, the whole molecular chain of P3HT moves, the space restriction of N2200 could be broken. The P3HT crystallizes with edge-on orientation (thermodynamics steady state) while N2200 crystallizes with face-on orientation. The hierarchical morphology forms by nucleation and growth or liquid phase separation. The P3HT crystallization with face-on or edge-on orientation in different postannealing processes is explained in terms of P3HT chain segment and molecule movement confined or broken out by N2200 crystalline confinement. [ABSTRACT FROM AUTHOR]

Four-arm star-shaped poly(2-isopropyl-2-oxazoline) (PiPrOx) with calix[4]arene core was studied by methods of turbidimetry and light scattering in aqueous solutions at concentrations ranging from 0.0002 to 0.0364 g cm. The role of arm number in thermosensitive behavior was determined by comparing the experimental data with the results for eight-arm PiPrOx star. First of all, it is concerned with the growth of large aggregate fraction in PiPrOx solution and the formation of middle mode particles even at low temperature which causes the decrease phase separation temperatures. At relatively high concentrations ( c >0.01 g cm), the dilution of PiPrOx solutions is accompanied by slow growth of phase transition temperatures, and the width Δ T = (1-2) °C of this interval does not depend on the concentration. In the dilute regime, Δ T rises and reaches 9 °C. It is shown that the changes of thermosensitive stars' behavior with arm number reduction are caused by lower intramolecular density of PiPrOx in comparison with that of PiPrOx. [ABSTRACT FROM AUTHOR]

In this paper, we consider the existence of time periodic solutions to the non-isothermal phase separation models with constraints for the order parameter and the Dirichlet boundary condition for the temperature. We firstly address some approximate problems by the Leray–Schauder fixed point theorem. Then the periodic solutions of the original problem are obtained by establishing some a priori estimates and performing a limiting procedure. [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]

We present a comprehensive phase-field model for simulating diffusion-mediated kinetic phase behaviors near the surface of a solid particle. The model incorporates elastic inhomogeneity and anisotropy, diffusion mobility anisotropy, interfacial energy anisotropy, and Cahn–Hilliard diffusion kinetics. The free energy density function is formulated based on the regular solution model taking into account the possible solute-surface interaction near the surface. The coherency strain energy is computed using the Fourier-spectral iterative-perturbation method due to the strong elastic inhomogeneity with a zero surface traction boundary condition. Employing a phase-separating Li X FePO 4 electrode particle for Li-ion batteries as a model system, we perform parametric three-dimensional computer simulations. The model permits the observation of surface phase behaviors that are different from the bulk counterpart. For instance, it reproduces the theoretically well-established surface modes of spinodal decomposition of an unstable solid solution: the surface mode of coherent spinodal decomposition and the surface-directed spinodal decomposition mode . We systematically investigate the influences of major factors on the kinetic surface phase behaviors during the diffusional process. Our simulation study provides insights for tailoring the internal phase microstructure of a particle by controlling the surface phase morphology. [ABSTRACT FROM AUTHOR]

The subject of previous work on liquid-liquid extraction is complemented in this paper through the research activities in micro distillation. After a detailed literature study comparing the performance, strengths, and weaknesses of published micro distillation methods, critical process parameters based on model studies will be discussed. Apparative approaches to micro distillation are presented, where the capillary module used for distillation can provide a successful phase separation of gas-liquid mixtures up to volume feeds of 10 mL min−1. [ABSTRACT FROM AUTHOR]

In our study, various fast lithium-ion conductors of composition Li 1 + x Al x Ge 2 − x P 3 O 12 (LAGP, 0 ≤ x ≤ 1.2) have been synthesized following a sol–gel process with subsequent annealing. For the annealed, crystallized samples, the subtle structural changes upon exchange of Ge 4 + for Al 3 + and Li + in LiGe 2 P 3 O 12 were followed employing X-ray diffraction and solid-state NMR. Among the samples studied, Li 1.4 Al 0.4 Ge 1.6 P 3 O 12 ( x = 0.4) shows the highest Li mobility at room temperature with an activation energy of approx. 30 kJ mol − 1 . Employing heteronuclear dipolar NMR techniques, i.e., 27 Al{ 31 P}-REDOR NMR and 31 P{ 27 Al}-REAPDOR NMR, allowed us to clearly assign the different 31 P-MAS-NMR signals to P(OAl) n (OGe) 4 − n species with 0 ≤ n ≤ 3 and to show that the tetrahedrally coordinated Al is incorporated in an extra AlPO 4 phase, thus not participating in the NASICON structure. For Al-rich samples with x ≥ 0.7, apart from crystalline impurity phases such as AlPO 4 , Li 4 P 2 O 7 and GeO 2 , an additional phase Li 9 Al 3 (P 2 O 7 ) 3 (PO 4 ) 2 is observed, which replaces the LAGP phase as the dominant phase for x > 1.0, giving rise to a compositional limit of Al content as x ≈ 0.6 in LAGP by the sol–gel route. In addition, the effect of the annealing temperature on the nature of the resulting phases was examined. [ABSTRACT FROM AUTHOR]

The aim of this work was to prepare the scaffolds of pure poly (L-lactic acid) 3% (w/v), pure chitosan 3% (w/v), and PLLA/chitosan blend (1:5) 3% (w/v) using TIPS method and investigate their properties and application in tissue engineering. An in vitro degradation study of scaffolds showed the addition of chitosan to PLLA not only increased its degradation rate, but also slowed down its pH value reduction. Addition of chitosan to PLLA increased hydrophilicity, porosity, compressive properties, and cell viability of the scaffolds. The results indicate that among all scaffolds, the most appropriate candidate for tissue engineering is PLLA/chitosan blend. [ABSTRACT FROM PUBLISHER]

This work presents an approach to extend the period for phase separation, independent of temperature, in ambient phase-separating photopolymerizations based on the copolymerization of structurally similar mono- and di-vinyl monomers. Copolymer resins composed of triethylene glycol dimethacrylate (TEGDMA) and ethylene glycol methyl ether methacrylate (EGMEMA) were modified with a thermoplastic prepolymer, poly(butyl methacrylate). With increasing EGMEMA modification into the bulk TEGDMA resin, there is a decrease in the initial reaction rate, which increases the time for development of compositionally different phases prior to network gelation. The period between phase separation and gelation was probed through optical and rheological measurements, and it was extended from 22 s in a TEGDMA resin to 69 s in a TEGDMA:EGMEMA copolymer, allowing these materials to be processed under a wide range of UV-irradiation intensities (300 μW cm −2 –100 mW cm −2 ), which provided an additional degree of control over the resulting phase separated domain size and morphology. [ABSTRACT FROM AUTHOR]

The gas–solid two phase flow under different operating conditions is visualized in a 19 mm × 114 mm narrow rectangular riser at the fully developed region through a high-speed digital image camera. Based on a calibration between image grayscale and solids holdup, the mean solids holdups under different operating conditions can be calculated from the mean grayscale of the images, the results of which is consistent with previous studies. By using different solids holdup as thresholds to transform the grayscale images into the binary images, the solids holdup distribution under different operating conditions can be clearly visualized. To quantify the solids phase separation, the term “relative dense phase area” is introduced as a parameter to characterize the variation of dense phase. A critical solids holdup value of ε sc = 0.04 is chosen by carefully examining the variation profiles of the relative dense phase area with solids holdup thresholds, to demarcate the dilute and dense cluster phases. The cluster fraction is then obtained and ranges from 1% to 59% under the operating conditions of the present research. With images divided into three regions along the lateral direction, it is found that cluster fraction at the wall region is higher than that of the core and the middle regions. The cluster fraction is also found to increase with the mean solids holdup value. [ABSTRACT FROM AUTHOR]

The detection of trapped atomic and molecular ions of rubidium, by extraction, from our thin-wire electrode-modified spherical Paul trap, is discussed in detail. The compact geometry poses serious challenges and constraints for efficient extraction and reliable detection of ions. The solution to the dual challenge of counting the trapped ions with minimum pileup loss as well as detection that permits reliable mass spectroscopy is experimentally implemented. The details of the ion extraction process are understood by numerical simulation. The experimental and numerical data are compared and found to be in close agreement. The reliability of the technique for future, multi-species experiments, is established, and possible improvements are discussed. [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]

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]

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]

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]

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]

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]

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]

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]