Complex Phase Separation Research Articles

High-Temperature Superconductivity in a Hyperbolic Geometry of Complex Matter from Nanoscale to Mesoscopic Scale

While it was known that High Temperature Superconductivity appears in cuprates showing complex multiscale phase separation due to inhomogeneous charge density wave (CDW) order, the spatial distribution of CDW domains remained an open question for a long time, because of the lack of experimental probes able to visualize their spatial distribution at mesoscale, between atomic and macroscopic scale. Recently scanning micro X-ray Diffraction (SmXRD) revealed CDW crystalline electronic puddles with a complex fat-tailed spatial distribution of their size. In this work we have determined and mapped the anisotropy of the Charge Density Waves (CDW) puddles in HgBa2CuO4+y (Hg1201) single crystal. We discuss the emergence of high temperature superconductivity in the interstitial space with hyperbolic geometry, that opens a new paradigm for quantum coherence at high temperature where negative dielectric function and interference between different pathways can help to raise the critical temperature.

Edible double-network gels based on soy protein and sugar beet pectin with hierarchical microstructure

The sugar beet pectin/soy glycinin (SBP/SG) double network (DN) gel was synthesized by a two-step enzymatic-induced sequential cross-linking strategy. Laccase and microbial transglutaminase (mTGase) were successively employed to the SBP/SG dispersion, so as to induce the formation of the covalent cross-links among the SBP and SG molecules. Uniaxial compression measurements indicated that the DN gels exhibited greater mechanical toughness than the gels with corresponding single network which was only cross-linked by mTGase. Confocal laser scanning microscope (CLSM) and scanning electron microscopy (SEM) observation demonstrated that the phase separation behavior of the two biopolymers at different length scales resulted in the formation of a highly heterogeneous and hierarchical microstructure in the DN gel. The higher structural complexity and mechanical integrity derived from this architecture might be mainly responsible for the enhancement of the gel toughness. A significant decrease of the gel toughness and the disappearance of the hierarchical microstructure were observed in the DN gel prepared by SG and the modified SBP which was subjected to an acidic protease treatment to remove the protein components in SBP. This suggested that the amphiphilic property and the structural heterogeneity of SBP might be the dominant factor in the formation of the unique microstructure in the enzymatic cross-linked protein/polysaccharide DN gel system. These results suggested that the DN principle could widen the texture range of gel-like foods and offer food industry an attractive strategy for developing hierarchical gel architectures via manipulating complex phase separation behavior of protein and polysaccharide.

Phase transition in orthorhombic perovskite Sm1−xLuxMnO3: Evidenced by the emergence of ferroelectric polarization

A series of polycrystalline orthorhombic manganites Sm1−xLuxMnO3 have been synthesized in order to study the magnetism-induced ferroelectricity. Detailed measurements of the magnetic and electric properties of Sm1−xLuxMnO3 (0 ≤ x ≤ 0.3) compounds have been performed. The obtained Mn-O-Mn bond angle and the Néel temperature decrease with increasing x, indicating the strengthened frustration of original A-type antiferromagnetic (A-AFM) order of Mn spins. For lower x concentrations, no ferroelectricity is detected, implying the stability of the A-AFM ordering. Further increasing x, a dielectric anomaly begins to develop at 28 K since x = 0.15 which is not observed in SmMnO3. Coinciding with this dielectric anomaly, a ferroelectric polarization emerges, implying the multiferroicity. For intermediate compositions, a possible complex phase separation exists.

CDW and Similarity of the Mott Insulator-to-Metal Transition in Cuprates with the Gas-to-Liquid-Liquid Transition in Supercooled Water

New advances in X-ray diffraction, extended X-ray absorption fine structure (EXAFS), and X-ray absorption near edge structure (XANES) using synchrotron radiation have now provided compelling evidence for a short-range charge density wave phase (CDW) called striped phase in the CuO2 plane of all cuprate high-temperature superconductors. The CDW is associated with a bond order wave (BOW) and an orbital density wave (ODW) forming nanoscale puddles which coexist with superconducting puddles below T c . The electronic CDW crystalline phase occurs around the hole doping 0.125 between the Mott charge transfer insulator and the 2D metal. The Van der Waals (VdW) theoretical model for a liquid of anisotropic extended objects proposed for supercooled water is used to describe the following: (a) the underdoped regime as a first spinodal regime of a “slightly doped charge transfer Mott insulator puddles coexisting with the striped polaronic CDW puddles;nd (b) the optimum doping regime as a second spinodal regime where striped polaronic CDW puddles coexist with the normal 2D metal puddles. This complex phase separation with three competing phases depends on the strength of the anisotropic electron-phonon interaction that favours the formation striped polaronic CDW phase.

Determination of arsenic species in rice samples using CPE and ETAAS

A highly sensitive and selective procedure for the determination of arsenate and total arsenic in food by electrothermal atomic absorption spectrometry after cloud point extraction (ETAAS/CPE) was developed. The procedure is based on the formation of a complex of As(V) ions with molybdate in the presence of 50.0mmolL−1 sulfuric acid. The complex was extracted into the surfactant-rich phase of 0.06% (w/v) Triton X-114. The variables affecting the complex formation, extraction and phase separation were optimized using factorial designs. Under the optimal conditions, the calibration graph was linear in the range of 0.05–10.0μgL−1. The detection and quantification limits were 10 and 33ngL−1, respectively and the corresponding value for the relative standard deviation for 10 replicates was below 5%. Recovery values of between 90.8% and 113.1% were obtained for spiked samples. The accuracy of the method was evaluated by comparison with the results obtained for the analysis of a rice flour sample (certified material IRMM-804) and no significant difference at the 95% confidence level was observed. The method was successfully applied to the determination of As(V) and total arsenic in rice samples.

Multiple superconducting transition and phase separation in melt-textured YBa2Cu3O7−d

We report on careful measurements of the temperature derivative of the resistivity, dρ/dT, in the region encompassing the superconducting transition of melt-textured samples of the YBa2Cu3O7−d cuprate superconductor. Measurements were carried out in orientations parallel and perpendicular to the Cu−O2 atomic planes in the presence of small magnetic fields applied parallel to the current orientation. The dρ/dT results reveal the occurrence of complex multi-peak structures that were analyzed with a new method based on the assumption that a simple series association of conductivities is adequate for describing the resistive transition of multiphased superconductors. We ascribe the multi-peak structure observed in the derivative measurements to a subtle and complex phase separation phenomenon leading to the stabilization of domains having slightly different electronic properties that are related to the ordering of labile oxygen atoms in the YBa2Cu3O7−d chain sub-structure.

Molecular Self-Assembly Assisted Liquid–Liquid Phase Separation in Ultrahigh Molecular Weight Polyethylene/Liquid Paraffin/Dibenzylidene Sorbitol Ternary Blends

Dibenzylidene sorbitol (DBS) was chosen as an in situ forming nucleating agent to study ultrahigh molecular weight polyethylene (UHMWPE)/liquid paraffin (LP) physical gel and complex phase separation. The experimental results indicated that DBS self-assembled into fibrils first and the solution became a physical gel before liquid–liquid phase separation (LLPS) and crystallization during thermally induced phase separation (TIPS) of UHMWPE/LP/DBS solution. The temperature of DBS self-assembly and viscoelasticity of UHMWPE/LP/DBS gel show a strong dependence on DBS concentration, temperature, and time. By controlling the relative quenching depth and annealing time, the grow rate of the characteristic length showed a crossover from LLPS to crystallization, which was further justified by differential scanning calorimetry (DSC) and wide-angle X-ray diffraction (WAXD). With decreasing temperature further, crystallization occurred with the aid of DBS fibrils. Those interactions were affected mutually, showed comp...

Core–shell structured electrospun biomimetic composite nanofibers of calcium lactate/nylon-6 for tissue engineering

In this work, core-shell structured nylon-6/lactic acid (LA) nanofibers have been produced via single-spinneret electrospinning from the simple blending of LA and nylon-6 solution. The low evaporation rate and plasticizer property of LA was found to be responsible for the formation of point-bonded morphology whereas solvent degradation of nylon-6 with complex phase separation mechanism could give spider-wave-like architecture of the mat and core–shell structure of the composite fibers. The core–shell nanostructure and existence of LA on the shell layer of the fiber were confirmed by TEM and XPS analysis. These fibers were further treated with calcium base to convert surface LA into calcium lactate (CL) which could increase the biocompatibility of composite mat. The SBF incubation test not only confirmed the nucleation capacity of CL to accelerate the deposition of calcium compound on the surface of nanofibers but also facileated the formation of hollow calcium phosphate particles at biomimetic conditions. The adhesion, viability and proliferation properties of osteoblast cells on the composite nanofibers were analyzed by in vitro cell compatibility test. This study demonstrated the non-cytotoxic behavior and good proliferation capacity of calcium lactate/nylon-6 (CL/nylon-6) composite mat. Therefore, the novel nanofibrous composite mat may become a potential candidate for bone tissue engineering.

A micellar improved method for trace levels selenium quantification in food samples, alcoholic and nonalcoholic beverages through CPE/FAAS

A useful preconcentration and determination method was proposed for trace selenium in food samples. The procedure is based on complex formation of Pyronine B with Se(IV) ions in the presence of sodium dodecyl sulphate (SDS) and Ponpe 7.5. The variables affecting complex formation, extraction and phase separation were studied and optimised. Under the experimental conditions used, the calibration graph was linear in the range of 20–1700μgL−1 for Se(IV) ions. The limit of detection was 3.81μgL−1 of Se(IV) and the relative standard deviation for 5 replicate determinations at 250μgL−1concentration level was 2.45%. Recovery values were obtained between 97.8% and 102.8% for spiked samples. The method was successfully applied to the determination of total selenium in some food samples and alcoholic and nonalcoholic beverages. Its validity was checked by the analysis of four certified reference materials. The results obtained by the proposed method were quantitatively in good agreement with the certified values.

Anomalous surface segregation profiles in ferritic Fe-Cr stainless steel

The iron-chromium alloy and its derivatives are widely used for their remarkable resistance to corrosion, which only occurs in a narrow concentration range around 9 to 13 atomic percent chromium. Although known to be due to chromium enrichment of a few atoms thick layer at the surfaces, the understanding of its complex atomistic origin has been a remaining challenge. We report an investigation of the thermodynamics of such surfaces at the atomic scale by means of Monte Carlo simulations. We use a Hamiltonian which provides a parameterization of previous ab initio results and successfully describes the alloy's unusual thermodynamics. We report a strong enrichment in Cr of the surfaces for low bulk concentrations, with a narrow optimum around 12 atomic percent chromium, beyond which the surface composition decreases drastically. This behavior is explained by a synergy between (i) the complex phase separation in the bulk alloy, (ii) local phase transitions that tune the layers closest to the surface to an iron-rich state and inhibit the bulk phase separation in this region, and (iii) its compensation by a strong and non-linear enrichment in Cr of the next few layers. Implications with respect to the design of prospective nanomaterials are briefly discussed.

Complex phase separation of ternary Co–Cu–Pb alloy under containerless processing condition

The macrosegregation and solidification processes of ternary Co43Cu40Pb17 alloy have been investigated under the containerless processing condition in drop tube. The addition of Pb element is found to be quite effective to promote the phase separation of Co–Cu alloy, resulting in a macroscopic segregation pattern in ternary Co43Cu40Pb17 alloy. The rapidly solidified alloy droplets are characterized by core–shell structures due to the combined effects of reduced gravity and containerless state during free fall. When the droplet diameter is smaller than 450μm, a kind of three-layer core/shell structure is formed, which consists of a Co-rich core, a Cu-rich intermediate layer and a Pb-rich surface shell. EDS analyses show that the Pb solute has a stronger affinity with Cu-rich liquid and a repulsive interaction with Co-rich liquid. The solidification process of Co43Cu40Pb17 ternary alloy involves two successive phase separation events, a subsequent peritectic transformation and a final monotectic transformation.

Optimization of Pr0.9Ca0.1MnO3thin films with varying in-situ oxygen annealing treatments

The influence of in situ oxygen annealings on narrow electronic bandwidth Pr0.9Ca0.1MnO3 films are investigated in the complex phase separation region. Measurements by x-ray di!ractometry and SQUID magnetometry reveal that relatively high deposition temperature at 700 ! C relaxes the lattice by twin boundaries while the lower deposition temperature at 500 ! C with higher post-annealing temperature of 700 ! C relaxes the substrate induced strain via oxygen absorption and makes the film structure more homogeneous. This behaviour is clearly supported by the decrease of ferromagnetic ordering due to decrease of Mn 3+ ions in films oxygen annealed at high temperatures and this phenomenon is widely discussed with the models of double-exchange interaction, trapping of carriers in the oxygen vacancies and formation of magnetic polarons. The results show unambiguously that because the oxygen content tailors many physical properties dramatically, the annealing treatments are in very important role when optimizing these materials for future applications.

Superstripes and Complexity in High-Temperature Superconductors

While for many years the lattice, electronic and magnetic complexity of high-temperature superconductors (HTS) has been considered responsible for hindering the search of the mechanism of HTS now the complexity of HTS is proposed to be essential for the quantum mechanism raising the superconducting critical temperature. The complexity is shown by the lattice heterogeneous architecture: a) heterostructures at atomic limit; b) electronic heterogeneity: multiple components in the normal phase; c) superconducting heterogeneity: multiple superconducting gaps in different points of the real space and of the momentum space. The complex phase separation forms an unconventional granular superconductor in a landscape of nanoscale superconducting striped droplets which is called the "superstripes" scenario. The interplay and competition between magnetic orbital charge and lattice fluctuations seems to be essential for the quantum mechanism that suppresses thermal decoherence effects at an optimum inhomogeneity.

Phase Separation in Electron Doped Iron-Selenide K0.8Fe1.6Se2 Superconductor by Scanning X-ray Nano-Diffraction

A new family of high temperature superconductors, the heavily electron doped iron-selenides, like K0.8Fe1.6Se2, has been attracting high interest since they show both 30 K superconductivity, with missing hole pockets questioning the s± pairing model, and unusually high magnetic moments. The hot debate is between coexistence versus phase separation and on the possible divergence of surface from bulk structure. Here, we provide direct evidence for a nanoscale phase separation in a single crystal of K0.8Fe1.6Se2, where a first magnetic phase, with superlattice modulation $(\sqrt{5}\times\sqrt{5})$ , coexists with a second nonmagnetic phase, with a second superlattice modulation ( $\sqrt{2} \times\sqrt{2}$ ), below 520 K using transmission X-ray diffraction. The mapping of the spatial distribution of the two phases is measured by scanning X-ray nanodiffraction using a 300×300 nm2 X-ray spot. The complex spatial phase separation clarifies the coexistence of superconductivity and magnetism in the same sample.

Viscoelastic effects in thermoplastic poly(styrene-acrylonitrile)-modified epoxy–DDM system during reaction induced phase separation

The viscoelastic phase separation of a poly(styrene-co-acrylonitrile) (SAN) modified epoxy system based on the diglycidyl ether of bisphenol A (DGEBA) cured with 4,4′-diaminodiphenylmethane (DDM) has been monitored in situ using rheometry, optical microscopy (OM) and small angle laser light scattering (SALLS). The amount of SAN in the epoxy blends were 3.6, 6.9, 10, and 12.9 wt%. The relationship between rheological properties and phase separation was carefully explored. The evolution of storage modulus, loss modulus, and tan δ were found to be closely related to the evolution of complex phase separation. From the rheological profile, two gel points are identified, corresponding to physical gelation and chemical gelation, the first one because of viscoelastic phase separation and the second one related to crosslinking of the epoxy resin, these depend on the cure temperature and amount of thermoplastic. Further SALLS investigations investigated the mechanism of phase separation. The time-dependent peak scattering vector was simulated with a Maxwell-type viscoelastic relaxation equation. Relaxation times obtained at different temperatures for the blends could be described by the Williams–Landel–Ferry equation. Moreover, the development of light scattering profile follows the Tanaka model of viscoelastic phase separation.

Rheology and pressure–volume–temperature behavior of the thermoplastic poly(acrylonitrile-butadiene-styrene)-modified epoxy-DDS system during reaction induced phase separation

The rheology and volume shrinkage characteristics of an epoxy matrix based on diglycidyl ether of bisphenol-A (DGEBA) cured with 4,4′-diaminodiphenylsulfone (DDS) and those containing poly(acrylonitrile-butadiene-styrene) (ABS) at compositions ranging from 0 to 12.9 wt% were monitored in situ using rheometry and pressure–volume–temperature (PVT) analysis. This investigation has focused on the importance of cure rheology on microstructure formation, using rheometry. The relationship between rheological properties and the phase separation process was carefully explored. The evolution of storage modulus, loss modulus, and tan δ was found to be closely related to the evolution of complex phase separation. It was found that complex viscosity profiles follow an exponential growth with curing at various temperatures. The characteristic relaxation time of viscosity growth can be described by the WLF equation. In the second part of this manuscript PVT measurements carried out to understand the volume shrinkage of the blend matrix with respect to cure are described. Volume shrinkage is highest for a neat epoxy system, the volume shrinkage decreased linearly up to 6.9 wt% ABS then it shows a different trend for the 10 and 12.9 wt% ABS modified epoxy blend. Investigation of the volume shrinkage behavior in these blends by various techniques confirms that the shrinkage behavior is influenced by thermoplastic phase separation during cure.

Emulsification through Surfactant Hydration: The PIC Process Revisited

We have performed sudden composition changes on a (surfactant + oil + water) system by adding water to a (surfactant + oil) solution. This composition change quenches the system into a metastable oil-in-water emulsion with a population in the 100 nm range. The conditions for a successful quench are as follows: the initial water content should be below a boundary called the "clearing boundary" (CB), the final water content should be sufficiently beyond CB, and the quench should be fast. We have used high purity components to avoid the complex phase separation patterns that occur with low purity ingredients: the surfactant is octaethylenehexadecyl ether (C(16)E(8)) and the oil is hexadecane (C(16)). Under these conditions, we show that the pathway for this type of quench proceeds through the swelling of the reverse micellar phase by the added water and the formation of a sponge phase. Then, further water addition causes the nucleation of oil droplets in this sponge phase, with a size that matches the spontaneous curvature of the sponge phase. Part of the surfactant remains adsorbed on these droplets, and the rest is expelled as micelles that coexist with the droplets. It is concluded that a PIC emulsification will always lead to a bimodal size distribution with surfactant "wasted" in small micelles. This is in contrast with the more efficient PIT emulsification.

Vertical (La,Sr)MnO3 Nanorods from Track‐Etched Polymers Directly Buffering Substrates

AbstractA novel and general methodology for preparing vertical, complex‐oxide nanostructures from a sol–gel‐based polymer‐precursor solutions is developed using track‐etched polymers directly buffering substrates. This method is able to develop a nanostructure over the entire substrate, the dimensions and localization of the vertical nanostructures being preset by the polymeric nanotemplate. Thereby, nanostructures with lateral sizes in the range of 100 to 300 nm and up to 500 nm in height have been grown. Two examples are presented herein, the latter being the evolution of the initial, metastable nanostructure. Specifically, La0.7Sr0.3MnO3 polycrystalline rods are grown at mild temperatures (800 °C); upon strong thermal activation (1000 °C) they suffer a profound transformation into vertical, single‐crystalline (La,Sr)xOy nanopyramids sitting on a La0.7Sr0.3MnO3 epitaxial wetting layer. The driving force for this outstanding nanostructural evolution is the minimization of the total energy of the system, which is reached by reducing the grain‐boundary, total‐surface, and strain‐relaxation energies. Finally, advanced electron‐microscopy techniques are used to highlight the complex phase separation and structural transformations occurring when the metastable state is overcome.

Mixed System of Eudragit S-100 with a Designed Amphipathic Peptide: Control of Interfacial Elasticity by Solution Composition

We report an interfacially active system based on an informational peptide surfactant mixed with an oppositely charged polyelectrolyte. The 21-residue cationic peptide, AM1, has previously been shown to respond reversibly to pH and metal ions at fluid interfaces, forming elastic films that can be rapidly switched to collapse foams or emulsions on demand. Here we report the reversible association of AM1 with the methacrylate-based anionic polymer Eudragit S-100. The strength of the association, in bulk aqueous solution, is modulated by added metal ions and by ionic strength. Addition of zinc ions to the peptide-polymer system promotes complex formation and phase separation, while addition of a chelating agent reverses the association. The addition of salt weakens peptide-polymer interactions in the presence or absence of zinc. At the air-water interface, Eudragit S-100 forms an elastic mixed film with AM1 in the absence of metal, under conditions where the peptide alone does not show interfacial elasticity. When zinc is present, the elasticity of the mixed film is increased, but the rate of interfacial adsorption slows due to formation of peptide-polymer complexes in bulk solution. An understanding of these interactions can be used to identify favorable foam-forming conditions in the mixed system.

Dissipative particle dynamics simulation study on the binary mixture phase separation coupled with polymerization

The influence of polymerization on the phase separation of binary immiscible mixtures has been investigated by the dissipative particle dynamics simulations in two dimensions. During polymerization, the bulk viscosity increases, which consequently slows down the spinodal decomposition process. The domain size growth is monitored in the simulations. The absence of 23 exponent for inertial hydrodynamic mechanism clearly reflects the suppressing effect of polymerization on the phase separation. Due to the increasing viscosity, the individual phase may be trapped in a metastable stage instead of the lamellar morphology identified for symmetric mixtures. Moreover, the polymerization induced phase separation in the binary miscible mixture has been studied. The domain growth is strongly dependent on the polymerization probability, which is naturally related to the activation energy for polymerization. The observed complex phase separation behavior is attributed to the interplay between the increasing thermodynamic driving force for phase separation and the increasing viscosity that suppresses phase separation as the polymerization proceeds.