Phase Separation Characteristics Research Articles

Phase separation characteristics in biphasic solvents based on mutually miscible amines for energy efficient CO2 capture

One of the challenges with regard to the aqueous amine-based CO2 capture process is the considerable energy requirement for solvent regeneration. To overcome this challenge, a biphasic solvent was employed in this study. Here, the phase separation behavior of amine blends depending on the characteristic structures of the solvent component was investigated using a turbidity measurement apparatus. Amines were classified as (1) primary/secondary amines or tertiary/sterically hindered amines depending on the CO2 reaction species, such as carbamate and bicarbonate (2) alkyl and alkanolamines, depending on the presence of a hydroxyl group, (3) chain and cyclic amines, and (4) mono- and polyamines depending on the molecular structure. Easy phase separation occurred in solvent blends containing polyamines such as DETA (diethylenetriamine), TETA (triethylenetetramine), and DEEA (2-(diethylamino) ethanol). The types with the greatest potential were the DETA/DEEA blended solvents. A phase separation could be determined based on the difference in the reaction rate with CO2 and the low solubility between the carbamate species of DETA and DEEA.

Accelerating Cell Dynamics Simulations of Soft Materials using CUDA-GPU

Soft materials are a highly demanded class of research for predicting the characteristics of phase separation and self-assembly into nanoscale structures. One of the most well-known methods to demonstrate and simulate dynamic behavior of particles, such as particle tracking, and to consider different effects of simulation parameters is cell dynamic simulation. In fact, cell dynamic simulation as a cellular computerization can be used to investigate different aspects of morphological topographies of soft material system. To achieve accurate and efficient computational results for cell dynamic simulation method, two factors are essential and vital: first, computing/calculating time-scale; and second, simulation system size. Consequently, finding available computing algorithms and resources such as sequential algorithm for implementing a complex technique and achieving precise results is critical and expensive. Therefore, it is very important to consider a parallel algorithm and programming model to solve time-consuming and massive computational processing. This paper presents a novel GPU-based parallel acceleration approach to cell dynamics simulations (CDS) for a spherical phase diblock copolymer under a shear flow. A new achievement is based on a commodity NVIDIA Quadro K5000 graphic card and Compute Unified Device Architecture (CUDA) C language.

Preparation and characterization of a naphthalene-modified poly(aryl ether ketone) and its phase separation morphology with bismaleimide resin

Poly(aryl ether ketone) (PAEK) is a kind of thermoplastic resin that can be used for toughening thermoset resins. In this work, we modified PAEK by introducing naphthalene group into the polymer chain. The physicochemical properties of the prepared thermoplastic resin were investigated by a few methods. The molecular weight was determined by gel permeation chromatography (GPC), and the glass transition temperature was measured by differential scanning calorimetry (DSC). The microstructure of the blends doping with bismaleimide resin was examined by scanning electron microscopy (SEM). The SEM micrographs show obvious phase separation structures, which are typical characteristics of reaction-induced phase separation. The present results may provide information for designing thermoplastic polymers used for toughening bismaleimide resins.

Inkjet-Printed Organic Transistors Based on Organic Semiconductor/Insulating Polymer Blends.

Recent advances in inkjet-printed organic field-effect transistors (OFETs) based on organic semiconductor/insulating polymer blends are reviewed in this article. Organic semiconductor/insulating polymer blends are attractive ink candidates for enhancing the jetting properties, inducing uniform film morphologies, and/or controlling crystallization behaviors of organic semiconductors. Representative studies using soluble acene/insulating polymer blends as an inkjet-printed active layer in OFETs are introduced with special attention paid to the phase separation characteristics of such blended films. In addition, inkjet-printed semiconducting/insulating polymer blends for fabricating high performance printed OFETs are reviewed.

Thermally induced vertical phase separation and photovoltaic characteristics of polymer solar cells for P3HT/PCBM composites

The occurrence of vertical phase separation has been reported for various spin-cast polymer films, including bulk-heterojunction films of polymer solar cells (PSCs). Focusing on real-space analysis, we conducted a study on the relationship between the morphology and processing conditions of PSCs for typical poly(3-hexylthiophene) (P3HT) and [6,6]-phenyl-C61-butyric acid methyl ester (PCBM) cells. Our results demonstrated that spin-casting caused a localized reduction in the P3HT concentration in the bulk center. Thermal annealing after cathode formation enhanced the unevenness in concentration and created a multilayered vertical phase-separated morphology in which the P3HT domains were gathered near the electrodes, leaving only PCBM domains at the center of the film. Cells with this morphology had good power conversion efficiency (∼3%).

Phase separation of polymer blends in solution: A case study

The phase behavior and phase separation features of the quaternary system poly-l-lactide (PLLA)/poly-rac-lactide (PLA)/dioxane/water were investigated. Experiments were performed with fixed total polymer concentration of 6wt%, by varying the PLLA/PLA weight ratio. Blend weight compositions examined were 100/0, 80/20, 50/50, 20/80 and 0/100, at fixed dioxane/water weight ratio (87/13). Cloud point measurements reported that the demixing temperatures of blends are close to PLLA in the same mixed solvent, in line with the calculated spinodals. As regards to foam preparation, above the PLA cloud point, morphology is similar to pure PLLA foams; conversely, below PLA cloud point, the morphology resulted highly inhomogeneous. This behavior could be related to a change in equilibrium conditions occurring close to PLA cloud point. The equilibrium measurements performed gave out results in line with this hypothesis.

Simulation of liquid–vapour phase transitions and multiphase flows by an improved lattice Boltzmann model

An improved lattice Boltzmann (LB) model with a new scheme for the interparticle interaction force term is proposed in this paper. Based on the improved LB model, the equation-free method is implemented for simulating liquid–vapour phase change and multiphase flows. The details of phase separation are presented by numerical simulation results in terms of coexistence curves and spurious currents. Compared with existing models, the proposed model can give more accurate results in a wider temperature range with the spurious currents reduced and less time consumed. Characteristics of phase separation can be quickly and accurately reflected by the proposed method. Then, the contact angle of the solid surface is numerically investigated based on the proposed model. The proposed model is valid for steady flow with near zero velocity; unsteady cases will be investigated in further studies. This work will be helpful for our long-term aim of multi-scale modelling of convective boiling.

Investigations on zwitterionic alkylsulfobetaines and nonionic triton X-100 in mixed aqueous solutions: Effect on size, phase separation and mixed micellar characteristics

Zwitterionic sulfobetaine surfactants are widely applied in industries dealing with personal care products, mainly due to an advantage of minimal irritating effects to skin as compared to ionic surfactants. We investigate on the aqueous solution behaviour of zwitterionic surfactant, namely alkyl N,N-dimethyl-3-ammonio-1-propanesulfonate (CnPS, n=10, 12, 14, 16) in pure and mixed state with Triton X-100 (non-ionic surfactant) by using surface tensiometry, dynamic light scattering (DLS) and cloud point measurements. The critical micelle concentration (CMC) for aqueous CnPS solutions decreases with corresponding increase in alkyl chain length and is also accompanied by an increase in aggregation number. The calculated interfacial parameters for binary mixed aqueous systems involving zwitterionic surfactant and TX-100 depict almost independent behaviour of πCMC and Γmax, indicating a non-associative ideal mixing. The calculated interaction parameter (βm) for TX-100+CnPS mixed system reveals insignificant deviation from ideal behaviour as confirmed by calculated values in proximity to zero. As concluded from size measurements using DLS, the apparent hydrodynamic size of the mixed micelles decreases with gradual addition of alkylsulfobetaines due to demicellization of formerly present ellipsoidal aggregates of TX-100. The clouding temperature of formed mixed micelles increases on gradual addition of CnPS due to corresponding increase of ionic charge and accordingly improved solubility. It is assumed that electrically neutral nature of sulfobetaines confines its electrostatic interactions with non-ionic TX-100 and accordingly deters feasible interactions leading to synergism.

Thickness-dependent electrical properties of soluble acene–polymer blend semiconductors

This study examined the electrical properties of 2,8-difluoro-5,11-bis(triethylsilylethynyl)anthradithiophene (diF-TES-ADT)/poly(methyl methacrylate) (PMMA) blend semiconductors for fabricating high-performance organic field-effect transistors (OFETs). The phase-separation characteristics were investigated over a range of blend solution concentrations. Regardless of the concentration, diF-TES-ADT crystal-top/PMMA-bottom bilayer structures were formed onto SiO2/Si substrates owing to the surface energy difference between diF-TES-ADT and PMMA. The phase-separated interfaces between diF-TES-ADT and PMMA provided efficient pathways for charge transport. Consequently, a high field-effect mobility of 0.1cm2/Vs and a current on/off ratio of 107 were achieved at the optimum concentration of 20mg/ml where thickness of phase-separated diF-TES-ADT crystal is 20nm. When the concentration was too low (e.g., 10mg/ml) or too high (e.g., 30, 40, and 50mg/ml), field-effect mobility was reduced significantly. It can be concluded that this is due to the homogeneity and thickness of the phase-separated diF-TES-ADT crystals.

Systematic Phase Separation Analysis of Surfactant-Containing Systems for Multiphase Settler Design

The handling of multiphase systems applied in mixer–settler processes, in which phase separation characteristics are exploited, is to date still a challenge for the chemical industry. Approaches for analyzing the influencing parameters on these systems can be of use, especially regarding equipment design and technical applicability. In this contribution, a guideline is presented and applied in a case study for a surfactant-containing multiphase system implemented in a hydroformylation mini-plant. Herein, the most relevant investigated parameters such as temperature, concentrations of reactants, system pressure, and stirrer characteristics are analyzed. This is followed by an analysis of various internal fittings including their influence on the temperature profile within the settler. The results of the systematic analysis are used to design a highly flexible, modular, and efficient settler for the separation of up to three liquid phases.

Effect of geometric parameters of liquid-gas separator units on phase separation performance

Five liquid-gas separator units were designed and constructed based on a new concept of a validated high-performance condenser. Each separator unit consiss of two united T-junctions and an apertured baffle. The separator units have different header diameters or different baffles with different diameters of the liquid-gas separation hole. The phase separation characteristics of the units were investigated at inlet air superficial velocities from 1.0 m/s to 33.0m/s and water superficial velocities from 0.0015 m/s to 0.50 m/s. The experimental results showed that the liquid height, liquid flow rate through the separation hole, and liquid separation efficiency increased with increased header diameter and decreased diameter of the separation hole. The geometric structures of the separator units affected the phase separation characteristics by influencing the liquid height in the header and the liquid flow rate through the separation hole.

Liquid phase separation and rapid dendritic growth of highly undercooled ternary Fe62.5Cu27.5Sn10 alloy

The phase separation and dendritic growth characteristics of undercooled liquid Fe62.5Cu27.5Sn10 alloy have been investigated by glass fluxing and drop tube techniques. Three critical bulk undercoolings of microstructure evolution are experimentally determined as 7, 65, and 142 K. Equilibrium peritectic solidification proceeds in the small undercooling regime below 7 K. Metastable liquid phase separation takes place if bulk undercooling increases above 65 K. Remarkable macroscopic phase separation is induced providing that bulk undercooling overtakes the third threshold of 142 K. With the continuous increase of bulk undercooling, the solidified microstructure initially appears as well-branched dendrites, then displays microscale segregation morphology, and finally evolves into macrosegregation patterns. If alloy undercooling is smaller than 142 K, the dendritic growth velocity of γFe phase varies with undercooling according to a power function relationship. Once bulk undercooling exceeds 142 K, its dendritic growth velocity increases exponentially with undercooling, which reaches 30.4 m/s at the maximum undercooling of 360 K (0.21TL). As a comparative study, the liquid phase separation of Fe62.5Cu27.5Sn10 alloy droplets is also explored under the free fall condition. Theoretical calculations reveal that the thermal and solutal Marangoni migrations are the dynamic mechanisms responsible for the development of core-shell structure.

Ionic liquids as stationary phases in gas chromatography--an LSER investigation of six commercial phases and some applications.

The separation properties of six novel stationary phases for gas chromatography, commercially available from Sigma-Aldrich (Supelco) and based on ionic liquids (ILs), were investigated. The linear solvation energy relationship model (LSER) was used to describe the molecular interactions between these stationary phases and 30 solutes. The solutes belong to different groups of compounds, like haloalkanes, alcohols, ketones, aromatics, aliphatics, and others. A good description of different interactions, as described by the LSER model, could be achieved. The calculated values of system constants for the ionic liquid phases were compared with constants of commonly used standard phases like a 5% phenyl/95% dimethyl siloxane and a polyethylene glycol phase. The solute descriptors are in good agreement with those found by previous authors who have used the LSER model for 44 different ionic liquids as stationary phase. The experiments were carried out at two temperatures to evaluate the influence on the phase parameters and separation characteristics. The interactions of different functional groups with the IL phases are discussed. These novel IL phases are a promising replacement of or an addition to common polar phases. Based on the evaluated phase properties, several possibilities for applications of these novel phases are shown.

Phase separations in aerosol OT reverse micellar solutions in dodecane: A curious case of polar domain composition driven transition from lower consolute temperature (LCT) to upper consolute temperature (UCT) regime

AOT-based microemulsions have been studied quite extensively on account of their numerous industrial applications and their existence as simple ternary phases. Properties of these microemulsions with higher alkanes as the oil continuous phase are governed by the presence of a strong inter micellar attractive interaction. In water in oil (w/o) microemulsions the inter micellar attraction strengthens with increase in temperature and leads to the observation of critical behavior on approaching the lower consolute temperature (LCT). In this manuscript we show that the phase behavior of AOT-based reverse micellar solutions in dodecane transforms dramatically when the polar domain is changed from water to formamide (FA) and even to aqueous solution of urea and NaCl. In all these cases the temperatures dependence of the microemulsion properties undergo complete reversal, which brings about a transition in their phase separation characteristics from lower consolute temperature (LCT) to upper consolute temperature (UCT) regime. Such systematic transformation in the phase behavior as a function of polar domain composition, which has been explained based on the influence of the polar domain on the properties of the interfacial AOT layer, is first of its kind in any reverse micellar system.

Phase Separation Characteristics of Ammonium Alum Hydrates with Poly Vinyl Alcohol

Phase Separation Characteristics of Ammonium Alum Hydrates with Poly Vinyl Alcohol

Morphology, Mineralogy, and Solid–Liquid Phase Separation Characteristics of Cu and Zn Precipitates Produced with Biogenic Sulfide

The morphology, mineralogy, and solid-liquid phase separation of the Cu and Zn precipitates formed with sulfide produced in a sulfate-reducing bioreactor were studied at pH 3, 5, and 7. The precipitates formed at pH 7 display faster settling rates, better dewaterability, and higher concentrations of settleable solids as compared to the precipitates formed at pH 3 and 5. These differences were linked to the agglomeration of the sulfidic precipitates and coprecipitation of the phosphate added to the bioreactor influent. The Cu and Zn quenched the intensity of the dissolved organic matter peaks identified by fluorescence-excitation emission matrix spectroscopy, suggesting a binding mechanism that decreases supersaturation, especially at pH 5. X-ray absorption fine structure spectroscopy analyses confirmed the precipitation of Zn-S as sphalerite and Cu-S as covellite in all samples, but also revealed the presence of Zn sorbed on hydroxyapatite. These analyses further showed that CuS structures remained amorphous regardless of the pH, whereas the ZnS structure was more organized at pH 5 as compared to the ZnS formed at pH 3 and 7, in agreement with the cubic sphalerite-type structures observed through scanning electron microscopy at pH 5.

Passive control of gas–liquid flow in a separator unit using an apertured baffle in a parallel-flow condenser

A transparent separation unit with an apertured baffle for liquid–gas separation was constructed using acrylic resin. The phase-separation characteristics were examined using air and water as working fluids. The drain limit, flooding limit, and liquid level in the header of the unit were determined under different inlet liquid and gas superficial velocities. The performances of the unit were evaluated by analyzing the effects of pressure, gravity, and capillary force. The liquid-separation efficiency of the separator was determined by the inlet flow patterns. The unit showed strong liquid–gas separation effects at optimal inlet conditions. The liquid-separation efficiency was higher than 45% for an annular flow inlet, higher than 80% for a slug flow inlet at low liquid inlet superficial velocities, and approached 100% for a stratified flow inlet. The flow distribution in the header was visually observed using a high-speed camera to determine the effects of the inlet flow patterns on the drain limit as well as on the liquid-separation efficiency.

Phase separation characteristics of the Bunsen reaction when using HIx solution (HI–I2–H2O) in the sulfur–iodine hydrogen production process

To continuously operate an integrated sulfur–iodine (SI) hydrogen production process, the HIx solution (HI–I2–H2O) could be recycled from the HI decomposition section as a reactant in the Bunsen reaction section. In this study, the temperature, iodine content and water content were varied to identify the phase separation characteristics of products from the Bunsen reaction using the HIx solution with SO2. Increasing the temperature increased the volume of the H2SO4 phase solution and decreased the impurity content in each phase. Increasing the iodine feed concentration somewhat decreased the volume of the H2SO4 phase solution, although the density difference between the phases increased. The amount of H2SO4 that separated into the H2SO4 phase was very small under most of these conditions, which significantly hindered the continuous operation of the integrated SI process. The feed of additional water in the separation step was suggested to improve the separation performance of the H2SO4 phase solution while minimizing side reactions.

Influence of the initial HI on the multiphase Bunsen reaction in the sulfur–iodine thermochemical cycle

In the sulfur–iodine cycle flowsheet, HI may exist in the feeds of Bunsen reaction. The effects of the initial HI and the operating temperature on the kinetic process and thermodynamic equilibrium of the multiphase Bunsen reaction were investigated. Increasing initial HI concentration (HI/H2O = 0–1/18) or temperature (303 K–358 K) amplified the reaction kinetic rate, and led to the earlier appearance of liquid–liquid separation and less time to reach the thermodynamic equilibrium. But the separation became difficult for further increase of the initial HI content. The liquid–liquid equilibrium (LLE) phase separation was enhanced with rising temperature. An increase in the initial HI content slightly weakened the LLE phase separation at a lower temperature, while at 345 K and 358 K, the LLE phase separation characteristics showed little variation in the HI/H2O molar ratio range of 0–1/18. A hyper-azeotropic HI concentration in the HIx phase was obtained with feeding HI. The conversion of SO2 lowered as the initial HI content and the temperature increased.

Phase separation characteristics of (U,Nd)O2 solid solutions by high temperature oxidation

The phase separation characteristics of the Nd element from SIMFUEL (simulated spent fuel) by high temperature oxidation was investigated in terms of the temperature range between 1,150 and 1,300 °C and the initial concentration of Nd (x) in the pellets of (U1−x Nd x )O2 with x = 0.03, 0.037 and 0.09. The XRD and SEM results indicate that an increase of the heat treatment temperature increases the amount of the Nd-rich (U1−y Nd y )O2+v phase, while decreasing that of the Nd-poor (U1−z Nd z )3O8−w phase after heat treatment. Since the solubility of Nd in the (U1−z Nd z )3O8−w phase was almost constant regardless of the heat treatment temperature, the decrease of the Nd concentration in the Nd-rich (U1−y Nd y )O2+v phase with increasing heat treatment temperature seems to be due to a diffusion of the U ions from the Nd-poor (U1−z Nd z )3O8−w phase to the Nd-rich (U1−y Nd y )O2+v phase. The phase separation ratio of Nd was not nearly affected by the heat treatment temperature, but was increased with an increase in the initial concentration of Nd (x) in the pellets of (U1−x Nd x )O2.00. However, the phase separation ratio of U was slightly decreased with an increase in the heat treatment temperature and was strongly decreased with an increase in the initial concentration of Nd (x) in the pellets of (U1−x Nd x )O2.00.