Effect Of Phase Separation Research Articles

Phase Separation and Multibody Effects in Three-Dimensional Active Brownian Particles.

Simulation studies of the phase diagram of repulsive active Brownian particles in three dimensions reveal that the region of motility-induced phase separation between a high and low density phase is enclosed by a region of gas-crystal phase separation. Near-critical loci and structural crossovers can additionally be identified in analogy with simple fluids. Motivated by the striking similarity to the behavior of equilibrium fluids with short-ranged pairwise attractions, we show that a direct mapping to pair potentials in the dilute limit implies interactions that are insufficiently attractive to engender phase separation. Instead, this is driven by the emergence of multibody effects associated with particle caging that occurs at sufficiently high number density. We quantify these effects via information-theoretical measures of n-body effective interactions extracted from the configurational structure.

Study of dual-phase functionalisation of NiCoFeCr-Alx multicomponent alloys for the enhancement of magnetic properties and magneto-caloric effect

We have studied the effect of phase separation on the magnetic and magneto-caloric properties of the CoFeNi0.5Cr0.5-Alx (x = 0.0, 1.0 and, 1.5) system. Results show that a collaborative behaviour among FeCr-rich segregated nanoparticles (NPs) increases the saturation magnetisation (Ms) while the Curie temperature (Tc) is controlled by the amount of added Al. With a strong ferromagnetic coupling between segregated FeCr-NPs, the CoFeNi0.5Cr0.5-Al1.0 sample shows the highest Ms (100 Am2 kg−1) with an increase of 61% over the Al-free CoFeNi0.5Cr0.5 sample. It is argued that as the ferromagnetic interaction increases in a degenerated superspin-glass-like state of the NPs the field induced phase transition is broadened while the magnetic entropy decreases. In turn, the CoFeNi0.5Cr0.5-Al1.0 sample shows the highest refrigerant capacity (17.1 J kg−1 at μ0ΔH = 1.0 T), and the smallest measured magnetic entropy change (ΔSmpeak = 0.22 J kg−1 K−1). We found that the enhanced magnetic and refrigerant capacity by mean of phase separation and NPs clustering are among the highest reported for the multicomponent alloys being investigated for energy applications in the high temperature range.

Phase separation affects the rheological properties of starch dough fortified with fish actomyosin.

Starch and protein are common polymers in food, and their phase separation often occurs during food processing. Protein-fortified starch dough can be considered as a triple phase separation system, and the effect of phase separation on dough rheology warrants further research. In this study, starch doughs fortified with fish actomyosin were used, and their rheological properties were researched and explained with respect to phase separation. The results suggested that the phase separation of actomyosin-binder-starch granules in the raw dough affected the quality of dough. The addition of actomyosin significantly decreased stiffness and shear sensitivity but increased the fluidity of the blended dough. Moreover, it was found that the interaction between mung bean starch and actomyosin was very weak. The polymer molecules were connected by physical links. Owing to phase separation, it was presumed that “wall slip” occurred between the binder, starch granule, and actomyosin. The blended dough containing 30% of the added actomyosin (R3) showed the best recovery ability and the weakest molecular interaction (interaction type Z′ = 0.40 for storage modulus G′ and 0.31 for loss modulus G′′). Additionally, the phase structure of the model doughs was investigated. It was found that the starch network played a dominant role when 10% (R1) actomyosin was added. With the addition of actomyosin, the protein network formed gradually. A bicontinuous phase structure with interpenetrating network was observed in R3 (actomyosin = 30%). In summary, our findings demonstrate the feasibility to make blended doughs by mixing fish actomyosin and mung bean starch. Moreover, in terms of use in traditional noodle making, the blended R3 dough was found to be the best in terms of recovery ability and flow characteristics.

Effect of Static Magnetic Field on Nucleation of Cobalt Nitrate Hexahydrate

Abstract Freezing of cobalt nitrate hexahydrate (CoNHH) under a static magnetic field was studied at three different magnetic field intensities. The results show that the magnetic field has a significant effect when the sample enters the solid phase and reduces the stochastic behaviour of the nucleation. Thermal properties investigated using thermogravimetric and differential thermal analysis revealed the shift to a lower temperature for the onset of decomposition and melting temperature after the freeze-thaw in a magnetic field. Besides that, we observed a significant change in the FT-IR peaks that might indicate the emergence of cobalt nitrate with a lower hydrate number, a phase separation effect, and the evaporation of NO3- ions. Refinement of the XRD spectra shows a single phase of CoNHH with a slight lattice parameter change after the freezing-thawing in a magnetic field. The freezing behaviour of CoNHH was compared to that observed previously for water, a salt solution, and an ethylene glycol solution. We investigated the relationship of the freezing behaviour with hydrogen bonding and magnetic properties and its impact on the change in the Gibbs free energy. The results of this study are important to optimise the performance of CoNHH as latent thermal energy storage.

Dilution refrigerator and its heat transfer problems

In the research of cryogenic physics and quantum information science, it is essential to maintain a steady low temperature of millikelvin regime continuously. Dilution refrigerator is a widely used refrigeration device to achieve extremely low temperature. It utilizes the phase separation effect of superfluid <sup>4</sup>He and its isotope <sup>3</sup>He mixed solution at ultra-low temperatures. The performance of heat exchanger is the key factor to determine the performance of continuous cycle refrigerating machine. At extremely low temperatures, there appears a huge interfacial thermal resistance between helium and metal (Kapitza resistance), and the problem of heat exchange can be effectively solved by using the porous sintered metal particles to increase the contact area. Therefore, it is of significance to study the heat exchange between metal particles and liquid helium at extremely low temperature and to develop the relevant high-performance sintered Ag powder heat exchanger.

Moringa oleifera gum/poly(vinyl alcohol) blend solutions: Phase separation and rheological properties

Moringa oleifera Gum (MOG) is a plant-based gum, which is mainly composed of polysaccharides and Polyvinyl Alcohol (PVA) is a biodegradable synthetic polymer. This paper reports investigation carried out regarding the potential use of a novel material based on a blend of MOG and PVA. Blend solution of MOG/PVA showed phase-separation at room temperature which was observed under an optical microscope. Heat treatment at 50 °C and continuous stirring for 72hrs reduced the phase-separation effect. Rheological studies were carried out to see the effect of MOG and PVA on their blend solutions at various concentrations. Viscosity was measured as a function of shear rate. At shear rate of 10 s−1, viscosity values of 6% pure MOG, 6% MOG/PVA and 6% pure PVA blend solution were found to be 983.18, 962.41 and 343.05 mPa·s respectively.

Phase separation and histone epigenetics in genome regulation

Liquid-liquid phase separation is increasingly recognized as a phenomenon that affects cell behavior. For example, phase separation of transcription factors and coactivators has been shown to drive efficient transcription. For many years, phase separation of intracellular components has been observed; however, only recently have researchers been able to garner functional significance from such events. Inspired from recent literature that describes phase separation of chromatin in a histone-dependent manner, we review the role and effect of phase separation and histone epigenetics in regulating the genome and discuss how these phenomena can be leveraged to control cell behavior.

Processing Optimization for Metal Injection Molding of Orthodontic Braces Considering Powder Concentration Distribution of Feedstock

Metal injection molding (MIM) utilizes a compound consisting of metal powder particles and a binding agent as the feedstock material. The present study combines MIM mold flow simulations with the Taguchi method to clarify the individual and combined effects of the main MIM process parameters on the metal powder concentration distribution in the final sintered product. The results show that the molding process should be performed using a short filling time, a high melt temperature, a low packing pressure, a low mold temperature, and a small gate size. Given these process settings, the powder concentration uniformity and phase separation effect are significantly improved; giving rise to a better aesthetic appearance of the final sintered product and an enhanced mechanical strength.

Structural properties and Faraday effect of arc melted magnesia transparent polycrystal

Abstract This experimental investigation focuses on the preparation of polycrystalline magnesium oxide transparent ceramics via arc-melting technique. Dense and compact transparent ceramics with interesting magneto-optical properties, and good transparency over 60% are proposed as a promising material for window and a magneto-optical device. Surface micro-morphology of the arc-melted MgO ceramics revealed the well-developed regular grains of several micrometers in diameter. The XRD results confirmed the cubic structure of MgO. The polycrystalline synthetic MgO contain homogenously distributed, silica-rich phase caused by secondary phase separation effect. The segregation of impurities to grain boundaries affects the optical and magneto-optical properties of this material. Optical band gap energy was calculated as 3.03 eV and decreased with the increasing temperature. The Verdet constant achieves values from +380 to +100 deg/T·m in the 350–1070 nm range at room temperature. The Verdet constant decreased with increased temperature. CIE 1931 chromaticity diagram was used to determine color of the emission light.

Phase separation effects on a partially miscible viscous fingering dynamics

Classical viscous fingering (VF) instability, the formation of finger-like interfacial patterns, occurs when a less viscous fluid displaces a more viscous one in porous media in immiscible and fully miscible systems. However, the dynamics in partially miscible fluid pairs, exhibiting a phase separation due to its finite solubility into each other, has not been largely understood so far. This study has succeeded in experimentally changing the solution system from immiscible to fully miscible or partially miscible by varying the compositions of the components in an aqueous two-phase system (ATPS) while leaving the viscosities relatively unchanged at room temperature and atmospheric pressure. Here, we have experimentally discovered a new topological transition of VF instability by performing a Hele-Shaw cell experiment using the partially miscible system. The finger formation in the investigated partially miscible system changes to the generation of spontaneously moving multiple droplets. Through additional experimental investigations, we determine that such anomalous VF dynamics is driven by thermodynamic instability such as phase separation due to spinodal decomposition and Korteweg convection induced by compositional gradient during such phase separation. We perform the numerical simulation by coupling hydrodynamics with such chemical thermodynamics and the spontaneously moving droplet dynamics is obtained, which is in good agreement with the experimental investigations of the ATPS. This numerical result strongly supports our claim that the origin of such anomalous VF dynamics is thermodynamic instability.

Two-stage anaerobic process benefits removal for azo dye orange II with starch as primary co-substrate.

Two-stage anaerobic system (S1: R1 (acidogenic phase) + R2 (methanogenic phase)) and the one-stage control (S0) were established to investigate the effect of phase separation on the removal of an azo dye orange II, i.e., Acid Orange 7 (AO7), with starch as the primary co-substrate. Although final AO7 removal from two systems showed no statistical differences, the first-order rate constants for AO7 removal (kAO7-) and sulfanilic acid (SA) formation (kSA) were higher in S1. Kinetic analysis showed that kAO7- and kSA in S1 were 2.7-fold and 1.7-fold of those in S0, respectively, indicating the benefit of phase separation to the AO7 reduction. However, this benefit only appeared in the period with influent AO7 concentrations higher than 2.14 mM. Otherwise, this advantage would be hidden due to the longer HRT (5 d) and sufficient electron donor (1.0 g starch L-1). Within S1, R1 only contributed about 10% of the entire AO7 removal, and kAO7- in R1 (0.172 h-1) was much lower than in R2 (0.503 h-1). The methanogenic phase rather than acidogenic phase was the main contribution to AO7 removal, because the influent of R2 had more available electron donors and suitable pH condition (pH 6.5-7.0) for the bio-reduction process.

Alteration of Protein Binding Affinities by Aqueous Two-Phase Systems Revealed by Pressure Perturbation

Interactions between proteins and ligands, which are fundamental to many biochemical processes essential to life, are mostly studied at dilute buffer conditions. The effects of the highly crowded nature of biological cells and the effects of liquid-liquid phase separation inducing biomolecular droplet formation as a means of membrane-less compartmentalization have been largely neglected in protein binding studies. We investigated the binding of a small ligand (ANS) to one of the most multifunctional proteins, bovine serum albumin (BSA) in an aqueous two-phase system (ATPS) composed of PEG and Dextran. Also, aiming to shed more light on differences in binding mode compared to the neat buffer data, we examined the effect of high hydrostatic pressure (HHP) on the binding process. We observe a marked effect of the ATPS on the binding characteristics of BSA. Not only the binding constants change in the ATPS system, but also the integrity of binding sites is partially lost, which is most likely due to soft enthalpic interactions of the BSA with components in the dense droplet phase of the ATPS. Using pressure modulation, differences in binding sites could be unravelled by their different volumetric and hydration properties. Regarding the vital biological relevance of the study, we notice that extreme biological environments, such as HHP, can markedly affect the binding characteristics of proteins. Hence, organisms experiencing high-pressure stress in the deep sea need to finely adjust the volume changes of their biochemical reactions in cellulo.

Quantitative Determination of the Vertical Segregation and Molecular Ordering of PBDB-T/ITIC Blend Films with Solvent Additives

The vertical component distribution of bulk heterojunction (BHJ) active film shows a significant impact on determining the device performance in polymer solar cells (PSCs). Processing solvent additives are well known for regulating the BHJ active layer morphology; however, there are few reports regarding the quantitative evaluation of the effect. Herein, a study of the quantitative determination of the vertical segregation in combination of molecular ordering of PBDB-T/ITIC blend films with various 1,8-diiodooctane (DIO) contents is provided. A 0.5% (volume ratio) DIO-added blend film achieves the highest power conversion efficiency of 10.75%. The reduced performance of the PSCs resulted from the excessive vertical component segregation and overcrystallization investigated by various techniques. X-ray photoelectron spectroscopy indicates that DIO aggravates the PBDB-T enrichment region at the air side. Neutron reflectivity further quantitatively figures out the phase separation effect. Although increased crystallinity of ITIC and a higher face-on ratio of PBDB-T in active layer were obtained with increased DIO content approved by grazing-incidence wide-angle X-ray scattering (GIWAXS), the enhanced vertical distribution along with the enhanced crystal size of ITIC leads to the reduced performance of the PSCs due to the reduced carrier transportation paths between donor and acceptor.

Effect of Microphase Separation Conditions in a Resol Resin/Ethylene Glycol System on the Properties of Its Pyrolysates

We have studied the effect of polymerization-induced phase separation (PIPS) step conditions in a resol phenol-formaldehyde resin–ethylene glycol system on the physicochemical properties of carbon samples obtained after post-curing and pyrolysis. The results demonstrate that raising the PIPS step temperature leads to a decrease in macropore size and increase in the total mesopore volume. Pyrolysis of cured samples obtained at a PIPS step duration shorter than or equal to the gelation time leads to a “collapse” of the pore structure formed in the microphase separation step. Pyrolysis of cured samples after a PIPS step whose duration considerably exceeds the gelation time leads to shrinkage of the samples, without changes in their density or pore structure. PIPS step conditions have an insignificant effect on the structure of the carbon skeleton, which consists of X-ray amorphous carbon containing crystalline graphite inclusions.

Cooperative phase transitions in a system of photons and dye molecules

Bose condensed light can form new phases [1] in a dye filled cavity due to the presence of the orientational disorder created by dye molecules which are essentially frozen on the time scale of the photonic thermalization (few ps). At longer times (few ns) molecular degrees of freedom -- orientations and positions -- become important. Including them on equal footing with photons can change the nature of the photonic condensation -- it can proceed as Ist order phase transition which can also result in the mutual phase separation effect -- for photons and dye. The analysis is conducted within the mean field approach in the thermodynamic limit. Recommendations for the experimental detection of the transition nature are formulated.

Effect of phase separation and supercooling on the storage capacity in a commercial latent heat thermal energy storage: Experimental cycling of a salt hydrate PCM

• Experimental study of a novel latent cold storage design in a laboratory unit. • Phase separation and supercooling has been determined to cause a significant storage capacity decrease as soon as after the first cycle. • The phase separation and supercooling effects in the storage is reversible and repeatable results are presented. • A sample analysis only on material scale is not enough to predict this storage decrease. Latent heat storage technologies offer process benefits like daily peak shaving. In this work a commercial storage design for storing cold thermal energy has been studied using a laboratory prototype containing 168 kg of a commercial salt-hydrate phase change material (PCM). The storage was charged and discharged with subsequent cycles at different mass flow rates over a fixed temperature range and duration. It was found that the PCM TES design exhibits phase separation and increased supercooling with continuous cycling. Both phenomena lead to a gradual decrease of the effective storage capacity. With later cycles only the bottom part stores latent heat, while the top and middle parts of the storage remain liquid. The results were repeatable and are consistent with T-History measurements of samples from the PCM TES before and after cycling. It is likely that the PCM itself does not suffer from incongruent melting. Instead, the phase separation is likely to occur due to a segregation of different liquid phases across the height of the storage. It was found that T-History measurements alone are not able to predict this behavior. Moreover, it is shown that phase separation in the storage can be reversed by increasing the PCM temperature and mechanical mixing of the liquid phase. This phase separation has to be prevented in future work in order to achieve stable performance with the studied storage design.

Tailored disorder: a self-organized photonic contact for light trapping in silicon-based tandem solar cells.

We present a process development leading to efficient rear side light trapping structures with the purpose of enhancing the infrared response of a silicon-based tandem solar cell. To this end, we make use of phase separation effects of two immiscible polymers, polystyrene and poly(methyl methacrylate), resulting in a non-periodic polystyrene structure on silicon with a well-defined size distribution. Onto this pattern, we evaporate silver as a scattering rear side mirror and contact layer. Average feature sizes and periods can be tuned by varying material properties (e.g. molar weights or ratios of the polymers) as well as processing conditions during the spin coating. This way a favorable pseudo period of approx. 1 µm for these disordered structure features was realized and successfully implemented into a silicon solar cell. The structure shows a ring-shaped scattering distribution which is beneficial for light trapping in solar cells. External quantum efficiency measurements show that a gain in short circuit current density of 1.1 mA/cm2 compared to a planar reference can be achieved, which is in the same range as we achieved using nanoimprint lithography in a record triple-junction III/V on a silicon device.

Simulation study of the effects of phase separation on hydroxide solvation and transport in anion exchange membranes.

Anion exchange membranes (AEMs) can be cheaper alternatives than proton exchange membranes, but a key challenge for AEMs is to archive good ionic conductivity while maintaining mechanical strength. Diblock copolymers containing a mechanically strong hydrophobic block and an ion-conducting hydrophilic block have been shown to be viable solutions to this challenge. Using our recently developed reactive hydroxide model, we investigate the effects of block size on the hydroxide solvation and transport in a diblock copolymer (PPO-b-PVBTMA) in its highly hydrated state. Typically, both hydroxide and water diffusion constants decrease as the hydrophobic PPO block size increases. However, phase separation takes place above a certain mole ratio of hydrophobic PPO to hydrophilic PVBTMA blocks and we found it to effectively recover the diffusion constants. Extensive analyses reveal that morphological changes modulate the local environment for hydroxide and water transport and contribute to that recovery. The activation energy barriers for hydroxide and water diffusion show abrupt jumps at the same block ratios when such recovery effects begin to appear, suggesting transformation of the structure of water channels. Taking the advantages of partial phase separation can help optimize both ionic conductivity and mechanical strength of fuel cell membranes.

A pressure-based solution framework for sub- and supersonic flows considering real-gas effects and phase separation under engine-relevant conditions

The present study describes a pressure-based solution framework suitable for the numerical investigation of sub- and supersonic injection processes under high-pressure conditions. The focal point is put on the introduction of a fully consistent and rigorous thermodynamic closure based on the cubic equation of state. Hereby, both real-gas effects as well as phase separation processes can be considered resulting in a more thorough investigation of physical phenomena and an increased solver stability as the inadvertently penetration of unphysical states, i.e., the crossing of the spinodal, is prevented. To demonstrate the advantage of the numerical framework, recent experimental investigations of an underexpanded argon jet showing both real-gas and phase separation effects are used. The agreement between the experiment and the Large-Eddy Simulation is good. In particular, the phase separation process shows excellent agreement and is studied thoroughly based on the numerical results.

Possible universal behavior of magnetoresistance and resistivity isotherms in magnetic materials

In the present communication, we propose a simple phenomenological model in order to describe the magnetic field dependence of negative magnetoresistance (MR) and resistivity isotherms. Our model is founded on the decomposition of MR into two distinct components: low field and high field MR. The model was successfully tested on several magnetic specimens and the evolution of the fitting parameters was discussed in detail. The present model works even for samples showing complicated behavior like charge ordering, magnetic phase separation and training effect. The validity of our proposed model indicates the presence of a universal behavior controlling the evolution of MR and resistivity isotherms as a function of the applied magnetic field. This model allows also the comparison of samples performances for magnetic field sensing and spintronics applications.