Phase Separation Process Research Articles

Simultaneous Single Crystal Growth and Segregation of Ni-Rich Cathode Enabled by Nanoscale Phase Separation for Advanced Lithium-Ion Batteries

A novel nanoscale phase separation process has been discovered to promote the growth and segregation of single-crystal LiNi0.8Mn0.1Co0.1O2 (NMC811). This process occurs directly during high-temperature calcination without significant agglomeration. The key lies in converting transition metal hydroxide (TM(OH)2) precursors with well-controlled morphology into transition metal oxide (TMO) intermediates before reacting them with lithium salt. The nanoscale redistribution of Ni in TMO, resulting from the concurrent formation of spinel and rock salt phases, helps to deagglomerate the clusters of later-formed NMC811 crystals. The as-prepared single-crystal NMC811 is further validated in a 2Ah pouch cell, demonstrating 1,000 stable cycles. The fundamentally new reaction mechanism of single-crystal growth and segregation provides a new direction for large-scale synthesis of a broad range of single crystals for advanced energy storage.

Adaptive isogeometric phase-field modeling of the Cahn–Hilliard equation: Suitably graded hierarchical refinement and coarsening on multi-patch geometries

We present an adaptive scheme for isogeometric phase-field modeling, to perform suitably graded hierarchical refinement and coarsening on both single- and multi-patch geometries by considering truncated hierarchical spline constructions which ensure C1 continuity between patches. We apply the proposed algorithms to the Cahn–Hilliard equation, describing the time-evolving phase separation processes of immiscible fluids. We first verify the accuracy of the hierarchical spline scheme by comparing two classical indicators usually considered in phase-field modeling, for then demonstrating the effectiveness of the grading strategy in terms of accuracy per degree of freedom. A selection of numerical examples confirms the performance of the proposed scheme to simulate standard modes of phase separation using adaptive isogeometric analysis with smooth hierarchical spline constructions.

The Influence of Physical Properties on the Membrane Morphology Formation during the Nonisothermal Thermally Induced Phase Separation Process.

The physical properties of a polymer solution that are composition- and/or temperature-dependent are among the most influential parameters to impact the dynamics and thermodynamics of the phase separation process and, as a result, the morphology formation. In this study, the impact of composition- and temperature-dependent density, heat capacity, and heat conductivity on the membrane structure formation during the thermally induced phase separation process of a high-viscosity polymer solution was investigated via coupling the Cahn-Hilliard equation for phase separation with the Fourier heat transfer equation. The variations of each physical property were also investigated in terms of different boundary conditions and initial solvent volume fractions. It was determined that the physical properties of the polymer solution have a noteworthy impact on the membrane morphology in terms of shorter phase separation time and droplet size. In addition, the influence of enthalpy of demixing in this case is critical because each physical property showed a nonhomogeneous pattern owing to the heat generation during phase separation, which in turn influenced the membrane morphology. Accordingly, it was determined that investigating spinodal decomposition without including heat transfer and the impact of physical properties on the morphology formation would lead to an inadequate understanding of the process, specifically in high-viscosity polymer solutions.

A simple and low-energy strategy for the separation of water and acetonitrile.

As acetonitrile is a widely used solvent for the chemical industry, the recovery of acetonitrile from acetonitrile wastewater is significant for both industrial cost reduction and environmental protection. In this article, a simple, low-energy, and low-cost strategy is proposed for the effective separation of acetonitrile from high-concentration acetonitrile wastewater. The approach is based on a sequential combination of two steps: salt-induced phase separation and hydrophobic filtration. The acetonitrile wastewater was first induced to split into two phases by salt, that is, the acetonitrile-rich phase and the water-rich phase, then the above two phases were poured into the hydrophobic filter paper funnel for the separation. It was shown that NaCl is a suitable salting-out reagent, and that hydrophobic filter papers-obtained from modification by butyltrichlorosilane and octyltrichlorosilane were the optimal choice for hydrophobic filtration. The salt-induced phase separation process is able to increase the volume fraction of acetonitrile in the acetonitrile-rich phase up to 92%. The acetonitrile-rich phase can pass through the hydrophobic filter paper, whereas the water-rich phase was intercepted. The hydrophobic filter paper retained strong hydrophobicity and high acetonitrile-separating capacity after 3 months storage, or upon immersion in acetonitrile-water mixtures for 12h, or applied for 25 consecutive separations.

Mechanism of Low-Frequency Oscillation When Electric Multiple Units Pass Neutral Zone, and Suppression Method

This article addresses the problem of the contact voltage increase caused by the low-frequency oscillation of the train-grid system in the phase-separation process of EMUs. The article establishes the EMU-contact line-traction substation model, reveals the mechanism of low-frequency oscillation, and ascertains the relationship between the phase angle when the pantograph leaves the line, and low-frequency oscillations. Methods to suppress overvoltage during the low-frequency oscillation are proposed. The research indicated that a significant voltage amplitude was observed in the neutral zone, when the phase angle of the pantograph to the contact line separation power supply fell within the range of 60–90° and 240–270°. The maximum voltage amplitude reached 69.75 kV, and there was an occurrence of low-frequency oscillation in the neutral zone, where electrical phase separation takes place. During this oscillation, the voltage of the contact network in the neutral zone mainly operated at one-third of the power frequency (16.7 Hz). However, after installing an RC suppression device in the neutral zone, when low-frequency oscillation occurred, the absolute value of the peak voltage dropped below 37 kV as soon as the EMU entered electric phase separation. Furthermore, compared to situations without a connected suppression device, there was nearly a 30% reduction in the absolute value of the peak voltage. The study provides a basis for the design of the neutral zone of the contact line, and the selection of high-voltage equipment for the EMU.

Pollen wall development in Impatiens glandulifera: exine substructure and underlying mechanisms.

The aim of this study was to investigate in detail the pollen wall ontogeny in Impatiens glandulifera, with emphasis on the substructure and the underlying mechanisms of development. Sporopollenin-containing pollen wall, the exine, consists of two parts, ectexine and endexine. By determining the sequence of developing substructures with TEM, we have in mind to understand in which way the exine substructure is connected with function. We have shown earlier that physical processes of self-assembly and phase separation are universally involved in ectexine development; currently, we try to clear up whether these processes participate in endexine development. The data received were compared with those on other species. The ectexine ontogeny of I. glandulifera followed the main stages observed in many other species, including the late tetrad stage named "Golden gates". It turned out that the same physico-chemical processes act in endexine development, especially expressed in aperture sites. Another peculiar phenomenon observed in exine development was the recurrency of micellar sequence at near-aperture and aperture sites where the periplasmic space is widened. It should be noted that, in the whole, the developmental substructures observed during the tetrad and early post-tetrad period are similar in species with columellate exines. Evidently, these basic physical processes proceed, reiterating again and again in different species, resulting in an enormous variety of exine structures on the base of a relatively modest number of genes. Granular and alveolar exines emerge on the base of the same basic processes but are arrested at spherical and cylindrical micelle mesophases correspondingly.

The stability of NPM1 oligomers regulated by acidic disordered regions controls the quality of liquid droplets.

The nucleolus is a membrane-less nuclear body that typically forms through the process of liquid-liquid phase separation (LLPS) involving its components. NPM1 drives LLPS within the nucleolus and its oligomer formation and inter-oligomer interactions play a cooperative role in inducing LLPS. However, the molecular mechanism underlaying the regulation of liquid droplet quality formed by NPM1 remains poorly understood. In this study, we demonstrate that the N-terminal and central acidic residues within the intrinsically disordered regions (IDR) of NPM1 contribute to attenuating oligomer stability, although differences in the oligomer stability were observed only under stringent conditions. Furthermore, the impact of the IDRs is augmented by an increase in net negative charges resulting from phosphorylation within the IDRs. Significantly, we observed an increase in fluidity of liquid droplets formed by NPM1 with decreased oligomer stability. These results indicate that the difference in oligomer stability only observed biochemically under stringent conditions has a significant impact on liquid droplet quality formed by NPM1. Our findings provide new mechanistic insights into the regulation of nucleolar dynamics during the cell cycle.

Novel low energy mixed amine biphasic solvent for carbon dioxide capture in biogas upgrading

A low energy consumption aqueous mixed amine biphasic solvent consisting of monoethanolamine, N-methyldiethanolamine and 1-butyl-3-methylimidazolium tetrafluoroborate (BF) was prepared for CO2 capture in biogas upgrading process. The solvent could be divided into two phases after biogas upgrading: rich liquid phase and lean liquid phase, the rich liquid phase would enter the regeneration tower for regeneration, and the lean liquid phase could directly enter the absorber tower for biogas upgrading without regeneration, the methane purity of the upgraded biogas could reach 100 %, the energy consumption of regeneration would be lower than that of 30 wt% MEA by 44.07 %, and the carbon enrichment rate of the rich liquid phase could reach more than 98 % after the phase separation. A comprehensive study of the influence of the BF addition on CO2 capture and mass transfer was carried out Amplified by analyzing the physical parameters of mixed system and a beneficial conclusion was reached. In addition, the added BF could effectively reduce the free energy during the reaction and improve the efficiency of the reaction. The higher dipole moment of the BF also provided an effective impetus for the phase separation process to take place. Finally, an amplified phase separator was used to simulate the whole process of phase separation in real conditions and it was found that high CO2 loadings were effective in accelerating the rate of phase separation. This study provided a theoretical basis for the subsequent research of biphasic solvents in the field of biogas upgrading, as well as technical guidance for the wide application of biogas upgrading in industry, which had a broad research prospect.

Phase separation and ripening in a viscoelastic gel

The process of phase separation in elastic solids and viscous fluids is of fundamental importance to the stability and function of soft materials. We explore the dynamics of phase separation and domain growth in a viscoelastic material such as a polymer gel. Using analytical theory and Monte Carlo simulations, we report a domain growth regime in which the domain size increases algebraically with a ripening exponent [Formula: see text] that depends on the viscoelastic properties of the material. For a prototypical Maxwell material, we obtain [Formula: see text], which is markedly different from the well-known Ostwald ripening process with [Formula: see text]. We generalize our theory to systems with arbitrary power-law relaxation behavior and discuss our findings in the context of the long-term stability of materials as well as recent experimental results on phase separation in cross-linked networks and cytoskeleton.

Fractal feature analysis based on phase transitions of the Allen–Cahn and Cahn–Hilliard equations

This paper explores the fractal characteristics of phase value time series in phase field models. The phase value time series are obtained from the corresponding phase separation process. Phase field models, such as the conservative Allen–Cahn (CAC) and Cahn–Hilliard (CH) equations, are adopted. The fractal features are calculated by the multifractal detrend fluctuation analysis (MF-DFA) model. We observe that during the phase separation evolution of the CAC and CH models, the Hurst exponent H(2) of the time series of phase values gradually increases from 0.5 of the sequence under random walk, until the evolution tends to stabilize, and H(2) also becomes stable. Additionally, we find that the curve behaviors of 2−H(2) for both phase field models are consistent with the energy dissipation curves in the phase separation process. The characteristics of H(2) show that the sequence of phase values exhibits fractal characteristics, and the persistence of self-similarity increases with the number of numerical simulation iterations. Our study can provide time series with a specified Hurst exponent for the research field of unstable series. Furthermore, our research finds that the energy dissipation system in the phase field evolution process is closely related to self-similarity.

Successful preparation of polyaniline‐modified polystyrene novel composite membrane

AbstractThis work describes the polyaniline (PANI) nanoparticles' impregnation into the polystyrene (PS) membrane and its impact on the different membrane properties for the first time. PANI nanoparticles were synthesized separately using the oxidative polymerization technique and then impregnated into the polystyrene‐DMF matrix solution. Membranes were cast via the Non‐Solvent Induced Phase Separation (NIPS) process. The surface and structural properties of the fabricated membranes were thoroughly characterized using contact angle measurement (CA), x‐ray diffraction (XRD), Fourier‐transform infrared spectrometer (FTIR), and scanning electron microscopy (SEM). Thermal gravimetric analysis (TGA) and the mechanical characteristics of the membrane were also investigated. According to the CA results, the addition of PANI in the matrix improved the polystyrene membrane's hydrophilicity from 65° to 54.5°. The FTIR spectra revealed that the PANI nanoparticles were successfully impregnated into the PS matrix. SEM images illustrated that the porosity of the PANI‐modified membrane was enhanced by 50% compared to the pristine PS membrane. Furthermore, adding PANI to the PS membrane significantly reduced the average pore size. The filtration experiment showed that PANI modified membrane had 81% rejection of MO dye as compared to the pristine PS membrane which had 60%. Therefore, The PANI added to the PS membrane greatly enhanced the PS membrane's structural properties.

Constructing and validating ternary phase diagrams as basis for polymer dissolution recycling

One of the recycling methods for polymer waste is the dissolution-precipitation process, which is based on dissolving the polymer in a suitable solvent followed by contaminant removal by, optionally filtration, and polymer precipitation through the addition of a nonsolvent. As showcased for poly(vinyl chloride) (PVC), a polymer used in the construction sector and for packaging, the current work makes clear that the less studied ternary phase diagrams are a very promising tool for the ideal solvent-nonsolvent selection. Such ternary phase diagrams provide compositional information concerning the phase separation process pushing forward the dissolution-precipitation recycling technology. It is demonstrated that these diagrams can be constructed by connecting the Flory-Huggins theory, Hansen solubility parameters and UNIQUAC activity coefficients. Model validation is performed via cloud point measurements for which one can utilize labour-intensive visual inspection or, as demonstrated in this work, one can also apply dynamic light scattering and turbidimetry, with the latter as the preferred method that is cheaper and faster. Ternary phase diagrams for multiple solvent-nonsolvent systems are theoretically constructed and experimentally validated, considering cyclohexanone-ethanol and THF-ethanol as solvent-nonsolvent pairs. It follows that PVC phase diagrams are inherently different compared to other, more commonly studied polymers, such as polyethersulfone (PES) and that for PVC the addition of a ternary interaction parameter might be required.

Effect of air gap induction on the morphological microstructure of polyether sulfone hollow fiber membrane

AbstractPolyether sulfone hollow fiber membrane was prepared via nonsolvent‐induced phase separation process using dimethylacetamide (DMAc) as a solvent, Polyvinylpyrrolidone (PVP‐K30) and water as additives. The mechanism of air gap environment in the membrane structure formation was studied. The scanning electron microscope microstructure morphology revealed that the air gap environment induced the microstructure formation of membranes. The low humidity air gap environment was not conducive to the surface pore formation and hard to obtain surface pores until lowering the dope solution temperature. The high humidity can easily induce the formation of large out surface pore structure along with the decreases of the surface pore uniformity. As air gap humidity and distance increased, the membrane cross section structure near the outer surface tends to be looser and that near the inner surface became denser, while the proportion of finger‐like pores in the cross section initially increased and stabilized. At 100 RH, the average outer surface pore size increased from 0.192 μm at an air gap distance of 20 cm to 0.351 μm at 50 cm, the corresponding pore density decreased from 2.66 to 1.13 pores/μm2, and the percentage of the inner skin layer thickness increased from 3.26% to 7.69%.

Metal-Organic Framework-Manipulated Dielectric Genes Inside Silicon Carbonitride toward Tunable Electromagnetic Wave Absorption.

Heterointerface engineering for different identifiable length scales has emerged as a key research area for obtaining materials capable of high-performance electromagnetic wave absorption; however, achieving controllable architectural and compositional complexity in nanomaterials with environmental and thermal stabilities remains challenging. Herein, metal-containing silicon carbonitride (SiCN/M) nanocomposite ceramics with multiphase heterointerfaces were in situ synthesized via coordination crosslinking, catalytic graphitization, and phase separation processes using trace amounts of metal-organic frameworks (MOFs). The results reveal that the regulation of dielectric genes by MOFs can yield considerable lattice strain and abundant lattice defects, contributing to strong interfacial and dipole polarizations. The as-prepared SiCN/M ceramics demonstrate excellent microwave absorption performance: the minimum reflection loss (RLmin ) is -72.6dB at a thickness of only 1.5mm and -54.1dB at an ultralow frequency of 3.56GHz for the SiCN/Fe ceramics and the RLmin is -55.1dB with a broad bandwidth of 3.4GHz at an ultralow thickness of 1.2mm for the SiCN/CoFe ceramic. The results are expected to provide guidance for the design of future dielectric microwave absorption materials based on heterointerface engineering while offering a paradigm for developing MOF-modified SiCN nanocomposite ceramics with desirable properties.

Fabrication of PVDF ultrafiltration membrane using modified thermally induced phase separation: The role of amphiphilic and hydrophilic non-solvents

The use of amphiphilic pore formers and hydrophilic non-solvents has demonstrated its effectiveness in improving the surface porosity and permeability of polyvinylidene fluoride (PVDF) ultrafiltration (UF) membranes through the nonsolvent induced phase separation (NIPS) process in literatures. However, in the thermally induced phase separation (TIPS) process, few reports illustrated how the amphiphilic pore-former and water-soluble non-solvent interact with water-insoluble diluents. In this study, water-insoluble dimethyl phthalate (DMP) was used as the main diluent to rule out the effect of diluent outflow. The amphiphilic pore former polyethylene glycol 400 (PEG400) failed to open pores on the outer surface of the membranes because of its amphiphilic nature. On the contrary, UF membranes with a mean pore size of 55 nm could be obtained by adding hydrophilic triethylene glycol (TEG) to the dope with a satisfactory pure water permeability (PWP) of 262.6 L m−2 h−1 bar−1. Moreover, PEG400 can serve as a stabilizer for the TEG droplets during the phase separation if both were added to the polymer dope solution. The addition of both PEG400 and TEG could significantly increase the membrane's PWP to 645.4 L m−2 h−1 bar−1 with moderate enlargement of the mean pore size of the membrane to 84 nm. Additionally, the well-connected membrane structure resulted in the tensile strength of the membranes ranging from 3.07 to 6.65 MPa. This study expands the range of additives used in the TIPS process and demonstrates the different roles of amphiphilic and hydrophilic non-solvents in the TIPS process.

Dilution-Induced Deposition of Concentrated Binary Mixtures of Cationic Polysaccharides and Surfactants.

This work investigates the effect of dilution on the phase separation process of binary charged polysaccharide-surfactant mixtures formed by two cationic polysaccharides and up to four surfactants of different nature (anionic, zwitterionic, and neutral), as well as the potential impact of dilution-induced phase separation on the formation of conditioning deposits on charged surfaces, mimicking the negative charge and wettability of damaged hair fibers. The results obtained showed that the dilution behavior of model washing formulations (concentrated polysaccharide-surfactant mixtures) cannot be described in terms of a classical complex precipitation framework, as phase separation phenomena occur even when the aggregates are far from the equilibrium phase separation composition. Therefore, dilution-enhanced deposition cannot be predicted in terms of the worsening of colloidal stability due to the charge neutralization phenomena, as common phase separation and, hence, enhanced deposition occurs even for highly charged complexes.

Kinetic control of shape deformations and membrane phase separation inside giant vesicles.

A variety of cellular processes use liquid-liquid phase separation (LLPS) to create functional levels of organization, but the kinetic pathways by which it proceeds remain incompletely understood. Here in real time, we monitor the dynamics of LLPS of mixtures of segregatively phase-separating polymers inside all-synthetic, giant unilamellar vesicles. After dynamically triggering phase separation, we find that the ensuing relaxation-en route to the new equilibrium-is non-trivially modulated by a dynamic interplay between the coarsening of the evolving droplet phase and the interactive membrane boundary. The membrane boundary is preferentially wetted by one of the incipient phases, dynamically arresting the progression of coarsening and deforming the membrane. When the vesicles are composed of phase-separating mixtures of common lipids, LLPS within the vesicular interior becomes coupled to the membrane's compositional degrees of freedom, producing microphase-separated membrane textures. This coupling of bulk and surface phase-separation processes suggests a physical principle by which LLPS inside living cells might be dynamically regulated and communicated to the cellular boundaries.

Thermodynamic Theory of Phase Separation in Nonstoichiometric Si Oxide Films Induced by High-Temperature Anneals

High-temperature anneals of nonstoichiometric Si oxide (SiOx, x < 2) films induce phase separation in them, with the formation of composite structures containing amorphous or crystalline Si nanoinclusions embedded in the Si oxide matrix. In this paper, a thermodynamic theory of the phase separation process in SiOx films is proposed. The theory is based on the thermodynamic models addressing various aspects of this process which we previously developed. A review of these models is provided, including: (i) the derivation of the expressions for the Gibbs free energy of Si oxides and Si/Si oxide systems, (ii) the identification of the phase separation driving forces and counteracting mechanisms, and (iii) the crystallization behavior of amorphous Si nanoinclusions in the Si oxide matrix. A general description of the phase separation process is presented. A number of characteristic features of the nano-Si/Si oxide composites formed by SiOx decomposition, such as the local separation of Si nanoinclusions surrounded by the Si oxide matrix; the dependence of the amount of separated Si and the equilibrium matrix composition on the initial Si oxide stoichiometry and annealing temperature; and the correlation of the presence of amorphous and crystalline Si nanoinclusions with the presence of SiOx (x < 2) and SiO2 phase, respectively, in the Si oxide matrix, are explained.

Advancing Nanofiber Research: Assessing Nonsolvent Contributions to Structure Using Coaxial Electrospinning.

In this study, we explored the influence of molecular interactions and solvent evaporation kinetics on the formation of porous structures in electrospun nanofibers, utilizing polyacrylonitrile (PAN) and polystyrene (PS) as model polymers. The coaxial electrospinning technique was employed to control the injection of water and ethylene glycol (EG) as nonsolvents into polymer jets, demonstrating its potential as a powerful tool for manipulating phase separation processes and fabricating nanofibers with tailored properties. Our findings highlighted the critical role of intermolecular interactions between nonsolvents and polymers in governing phase separation and porous structure formation. Additionally, we observed that the size and polarity of nonsolvent molecules affected the phase separation process. Furthermore, solvent evaporation kinetics were found to significantly impact phase separation, as evidenced by less distinct porous structures when using a rapidly evaporating solvent like tetrahydrofuran (THF) instead of dimethylformamide (DMF). This work offers valuable insights into the intricate relationship between molecular interactions and solvent evaporation kinetics during electrospinning, providing guidance for researchers developing porous nanofibers with specific characteristics for various applications, including filtration, drug delivery, and tissue engineering.

Improvement of persistent hydrophilicity and pore uniformity of polyvinyl chloride ultrafiltration membranes by in-situ crosslinking reaction assisted phase separation

A novel in-situ crosslinking reaction assisted phase separation strategy was proposed for persistent hydrophilization and pore size regulation of polyvinyl chloride (PVC) membranes. In-situ cross-linking between PVC molecular chains was achieved through grafting of 3-aminopropyltrimethoxysilane (APTMS) during the dissolution process and cross-linking reactions between siloxanes in APTMS molecules initiated by the coagulation bath (water). The effect of in-situ crosslinking reaction on the structure, separation and anti-fouling performance of the PVC membranes was studied. Through in-situ crosslinking reaction induced phase separation, the migration and curing of polymer molecular chains in the phase separation process were regulated, which endowed the modified membrane with improved hydrophilicity, higher porosity and narrow pore size distribution. The pure water flux of the obtained membrane increased 3.5 times as much as that of the pure PVC membrane. In addition, the flux recovery rate (FRR) of the obtained membrane was increased by 15.9% and the strength was also increased slightly at the same time. The stability of the membranes was also improved, without chemical agents leaching during filtration, avoiding secondary pollution to our environment.