Dispersive Mixing Research Articles

Characterization of Aqueous Dispersions and Gels Made of Sodium Caseinate and Basil Seed Gum: Phase Behavior, Rheology, and Microstructure

The interactions between sodium caseinate (NaCas) and basil seed gum (BSG) in the presence of calcium chloride (CaCl2) were investigated. The phase behavior of the mixed aqueous dispersions and their gels revealed a homogeneous mixture, obtained at the higher concentrations of both CaCl2 and BSG. The Herschel-Bulkley model sufficiently fitted the flow behavior of the mixture solution data. Apparent viscosity increased significantly (p 0.05). Furthermore, there was an increase in thixotropy due to the higher concentrations of BSG and CaCl2. Based on the frequency sweep test, at the low frequencies, a more gel-like behavior was observed in the case of the higher concentrations of either BSG or CaCl2. The rheological and SEM data suggested that the stronger structure of NaCas-BSG gel in the presence of the higher concentrations of CaCl2 was related to the induction of complex formation between the two biopolymers.

Morphology, thermal behavior, rheological, and mechanical properties of polypropylene/polystyrene blends based on elongation flow

Binary blends comprised of polypropylene (PP) and polystyrene (PS) were prepared by a novel eccentric rotor extruder based on elongation flow. The morphology, thermal behavior, rheological and mechanical properties were investigated. As the enhanced mixed dispersion based on the novel extruder, the dispersed PS phase were uniformly dispersed in the PP matrix when the PS not more than 40%, and a distinct cocontinuous phase structure emerged when the PS content was 50%. The size of the dispersed PS phase related to the PS content and the processing flow filed influenced the crystallization behavior and the thermal stability of the blends. The PS droplet with small size could act as a nucleating agent for PP to improve the crystallinity, and PS droplet with large size could promote the thermal and heat transfer between the PS droplets and PP matrix which decreased the thermal stability. The rheological results showed that the compounding with PS into the PP matrix increased the storage and loss modulus as well as the complex viscosity of the materials. When the PS content not more than 20%, the blends showed good impact resistance, and PP/PS blends 30% PS showed good tensile and flexural properties. This study gives a new perspective for the structure and properties of the binary PP/PS blends prepared based on elongation flow.

Contributions of Pore‐Scale Mixing and Mechanical Dispersion to Reaction During Active Spreading by Radial Groundwater Flow

AbstractSpreading and mixing are complementary processes that promote reaction of two reactive aqueous solutes present in contiguous plumes in groundwater. Spreading reconfigures the plume geometry, elongating the interface between the plumes, while mixing increases the volume of aquifer occupied by each plume, bringing the solute molecules together to react. Since reaction only occurs where the two solute plumes are in contact with each other, local mechanisms that drive flow and transport near the interface between the plumes control the amount of reaction. This work uses local characteristics of the plumes and the flow field near the plume interface to analyze the relative contributions of pore‐scale mixing and mechanical dispersion to instantaneous, irreversible, bimolecular reaction in a homogeneous aquifer with active spreading caused by radial flow from a well. Two solutes are introduced in sequence at the well, creating concentric circular plumes. We allow for incomplete mixing of the solutes in the pore space, by modeling the pore space as a segregated compartment and a mixed compartment with first‐order mass transfer between the two compartments. We develop semi‐analytical expressions for concentrations of the solutes in both compartments. We found that the relative contribution of mechanical dispersion to reaction increases over time and also increases due to increases in the Peclet number, in the relative source concentration of the chasing solute, and in the mass transfer rate from the segregated compartment to the mixed compartment of the pore space.

A transparent superhydrophobic coating with mechanochemical robustness for anti-icing, photocatalysis and self-cleaning

Transparent and conformal superhydrophobic coating with mechanochemical robustness is of great importance for various applications, such as waterproof, self-cleaning, and anti-icing for windows of cars and buildings. However, it remains a daunting challenge to endow the functional surface with programmable wettability. Herein, we propose a hierarchical coating consisting of polydimethylsiloxane (PDMS) nanoparticles (NPs) and PDMS microparticles (MPs) functional NPs through a combination of thermal treatment and spray treatment. The evaporation of PDMS under heat treatment is firstly applied to form a uniform nanoarchitectures, followed by spraying a mixed P25-PDMS dispersion to construct a protective coating with enhanced surface roughness. This resulted coating is conformal and possess reversible wettability on various substrates. In virtue of the light-response property of P25, the reversible wettability between superhydrophobicity and hydrophobicity can be achieved by repetitive UV-light irradiation and dark environment storage. Besides, the coating can maintain superhydrophobicity with high transmittance (76% optical transmittance) after immersion in acid/base solution for 24 h and continuously sand impingement. Furthermore, the coating exhibits mechanochemical robustness against high speed water jet and Elcometer 99 tape peeling test for 30 cycles due to the high adhesion between the robust coating and the glass. For practical application, the coating was demonstrated to have excellent performance in anti-icing, photocatalytic degradation of pollutants and self-cleaning.

Photocatalytic degradation of methylene blue using three-dimensional porous graphene-titania microparticles under UV light

Porous graphene and graphene-silica microparticles containing titania nanoparticles were synthesized by emulsion-assisted self-assembly for the photocatalytic decomposition of methylene blue in an aqueous medium. After the mixed dispersion of graphene nanosheets and titania nanoparticles with or without silicic acid was prepared, the complex fluid was emulsified in a continuous oil phase to form tiny droplets that act as micro-reactors for the synthesis of porous photocatalytic particles, the morphology of which was three-dimensional spherical shapes with a number of irregular-shaped macropores. The three dimensional conductive graphene scaffolds greatly enhanced the photocatalytic activity of the porous particles due to the suppression of the recombination of electron-hole pairs generated from titania under UV light irradiation, and adsorption of dye molecules on graphene-silica scaffolds caused rapid removal of aqueous contaminants. Unlike previous reports, the kinetics of the photocatalytic decomposition reaction could not be explained by Langmuir-Hinshelwood kinetics, but the experimental data could be fitted well by the second- or third-order kinetics. This indicates that the removal rate of the pollutant could be enhanced by the supporting material. The removal efficiency of methylene blue was estimated as more than 95% when sufficient amount of the photocatalytic particles was used, implying that application to water treatment process will be possible.

Lattice Boltzmann simulations of meso-vortex in resonance mixing technology

Resonance dispersion mixing technology is a new process developed in recent years. The main function of the technology is each scale vortex caused by the vibration, which is a multiscale phenomenon that includes macroscopic vortices and mesoscopic vortices. For mesoscopic vortices, due to the lack of sufficient resolution, current commercial software filter and average these vortices, so it is difficult to meet the needs of research. Based on this, the paper proposes a lattice Boltzmann Method (LBM) to simulate the mesoscopic vortices. The LBM is a mesoscale research method, so it has sufficient resolution to study mesoscopic vortices. The paper mainly simulated the process of splitting and evolution of mesoscopic vortices, studied the effects of parameters such as simulation interval, viscosity, vibration frequency on mesoscopic vortices. The results show that the selection of the simulation interval has a certain influence on the evolution of the vortices. The viscosity of the flow field plays a decisive role in the vortices, for there is no vortex generation when the viscosity exceeds a certain threshold. The excitation frequency controls the development process of the vortices, larger frequency can significantly reduce the micro-mixing characteristic time to increase mixing efficiency. Different from the previous theoretical analysis literature, this paper gives visual numerical simulation results.

Effects of crumbed para rubber on permanent deformation resistance of hot mix asphalt

In Thailand, natural para rubber (Hevea Brasiliensis) is gaining application in asphalt pavement construction. The natural rubber element helps extending the life period of asphalt pavement. Currently para rubber in a latex form is slowly added to hot asphalt binder and mixed together using shear mixer. An alternative of adding para rubber into asphalt pavement is applying para rubber crumbs into the hot mix asphalt (HMA) during the batch mixing process which is called “Dry Process”. The dry process has an advantage on its simplicity of quality inspection and less modification in the hot mix plant production process. This study has investigated the effects of adding crumbed para rubber particles on the engineering properties related to permanent deformation resistance of asphalt concrete. In this study, the asphalt mixture is prepared via Marshall Mix design, which contained with limestone and asphalt cement of Pen 60/70 at 5.4% by total weight. Crumbed para rubber at 2% by total volume was added in asphalt mixture via two methods, dispersive mixing method and layer method. The specimens that prepared from each method were compacted to cylinder shape according to the requirement of testing standard using Gyratory compactor. The specimens were tested to find resilient modulus and dynamic creep responses. The results showed that adding crumbed para rubber in aggregate by dispersive mixing method is the most effective method. It has increased significantly the resistance to permanent deformation compared with the conventional mixture.

Noncovalent Functionalization of Few-Layered Antimonene with Fullerene Clusters and Photoinduced Charge Separation in the Composite.

Few-layered antimonene (FLSb) nanosheets were noncovalently functionalized with fullerene C60 clusters by quick addition of a poor solvent (i.e., acetonitrile) into a mixed dispersion of FLSb and C60 in a good solvent (i.e., toluene). In a flash-photolysis time-resolved microwave conductivity (FP-TRMC) measurement, the FLSb-C60 composite, (FLSb+C60 )m , showed a rapid rise in transient conductivity, whereas no conductivity signal was observed in the single components, FLSb and C60 . This demonstrated the occurrence of photoinduced charge separation between FLSb and C60 in (FLSb+C60 )m . Furthermore, a photoelectrochemical device with an electrophoretically deposited (FLSb+C60 )m film exhibited an enhanced efficiency of photocurrent generation, compared to those of the single-components, FLSb and C60 , due to the photoinduced charge separation between FLSb and C60 . This work provides a promising approach for fabrication of antimonene-organic molecule composites and paves the way for their application in optoelectronics.

A Subtidal Box Model Based on the Longitudinal Anomaly of Potential Energy for Narrow Estuaries. An Application to the Guadalquivir River Estuary (SW Spain)

AbstractThe objective of the present study is to demonstrate the informative capacity of the longitudinal anomaly of potential energy (LAPE) in the analysis of the magnitude and spatiotemporal variability of estuarine processes. For this purpose, a LAPE balance equation is formulated. The LAPE integrates and varies with the vertical and longitudinal density distribution. The formulation is applied on a subtidal scale to each box or stretch of the Guadalquivir River estuary, a narrow, highly turbid, weakly stratified, and strongly anthropized estuary. Data recorded by a large network of monitoring stations in 2008 and 2009 are used to quantify advective transports as well as the transports associated with longitudinal dispersion and vertical turbulent mixing in different hydraulic regimes. In low‐river flow conditions, (river flows Q<40 m3s−1), the magnitude of LAPE transports decreases upstream and varies locally, depending on neap‐spring tidal cycles. The direction of the net LAPE transport creates convergence zones that are particularly consistent with maximum levels of estuarine turbidity. During high‐river flows (Q>400 m3s−1), this convergence disappears and the maximum longitudinal density gradient moves towards the mouth. More specifically, tidal pumping ‐induced LAPE governs during these conditions and manages to compensate the sum of the mean nontidal and dispersive and differential advective LAPE transports. However, during the post‐riverflood period, the mechanisms controlling recovery downstream from the mouth are the longitudinal dispersive and differential advective LAPE transports. Furthermore, the convergence zone reappears with a longitudinal gradient of the net LAPE transport that is even greater than in low‐river flow conditions.

Simple and immediate quantitative evaluation of dispersive mixing

A dimensionless mixing number is developed to quantify dispersive mixing in a simple and immediate way. This takes into account number-average diameter, volume-average diameter and interfacial area simultaneously. It is an experimentally determined number, meaning the calculations are performed using microscopy images. This parameter was validated using various polymer blends (droplet morphology) and composite systems and can be used to compare various technologies on the basis of dispersive mixing efficiency.

Shear viscosity as a probe of nodal topology

Electronic materials can sustain a variety of unusual, but symmetry protected touchings of valence and conduction bands, each of which is identified by a distinct topological invariant. Well-known examples include linearly dispersing pseudo-relativistic fermions in monolayer graphene, Weyl and nodal-loop semimetals, biquadratic (bicubic) band touching in bilayer (trilayer) graphene, as well as mixed dispersions in multi-Weyl systems. Here we show that depending on the underlying band curvature, the shear viscosity in the collisionless regime displays a unique power-law scaling with frequency at low temperatures, bearing the signatures of the band topology, which are distinct from the ones when the system resides at the brink of a topological phase transition into a band insulator. Therefore, besides the density of states (governing specific heat, compressibility) and dynamic conductivity, shear viscosity can be instrumental to pin nodal topology in electronic materials.

High-performance and ultraflexible PEDOT/silver nanowires/graphene films for electrochromic applications.

We fabricate a kind of flexible electrochromic (EC) film by spraying the mixed dispersion of silver nanowires (AgNWs) and poly (3, 4-ethylenedioxythiophene) (PEDOT) on the graphene (GR) electrode. AgNWs are embedded in the PEDOT nanoparticles, forming an interlaced conductive network and double electron transport channels; therefore, the disadvantages of poor conductive GR electrodes have been remedied effectively. The subsequent GR-based PEDOT/AgNWs composite films have revealed remarkable optical contrast (63%), high coloration efficiency (${182.8}\;{{\rm cm}^{2}}\;{{\rm C}^{ - 1}}$182.8cm2C-1), and good cycle stability (keeping the optical contrast about 60% after switching cycles of 16,000 s). In addition, the GR-based composite films can keep good EC performance after 2000 cycles of bending tests, while those of the ITO/PET-based composite films decrease dramatically. The ultraflexible GR-based PEDOT/AgNWs composite films with excellent EC properties present an opportunity for fabricating large-area flexible EC devices.

Rheological properties of soy protein isolate – carboxymethyl flaxseed gum mixed dispersions under large amplitude oscillatory shear

Abstract Carboxymethyl flaxseed gum (CMFG) is developed in our laboratory by modifying flaxseed gun through carboxymethylation. The aim of this study is to reveal the rheological properties of soy protein isolate – carboxymethyl flaxseed gum (SPI-CMFG) mixed dispersion in realistic processing conditions by conducting large amplitude oscillatory shear (LAOS) test, with consideration of concentration and degree of substitution (DS) of CMFG. Results showed that increasing CMFG concentration significantly increased storage moduli (Gʹ), loss moduli (Gʺ), and the apparent viscosity of all SPI-CMFG mixed dispersions. LAOS test illustrated that the dispersions experienced a transition from LAOS type IV to type III after increasing the concentration of CMFG, while the behavior converted from LAOS type I to type III by increasing DS. Fourier transform rheology (FTR) exhibited that increasing the concentration or DS of CMFG both induced a conversion from “soft sphere” to “hard sphere” behavior. The strain-stiffening ratio S and the shear-thickening ratio T demonstrated, that all SPI-CMFG dispersions experienced a similar conversion from strain stiffening to strain softening, and from shear thinning to shear thickening behaviors by increasing the concentration of CMFG. Nevertheless, the mixed dispersions presented shear thickening behaviors when DS was no more than 0.520 in the whole range of strain, while a conversion from shear thinning to shear thickening behavior occurred, when DS reached at 0.755 and 0.973.

Laser ablation of silicon monoxide and titanium monoxide in liquid: formation of mixed colloidal dispersion with photocatalytic activity

Silica–titania mixed oxides and composites have been extensively studied, whereas to the titanium monoxide (TiO) –silicon monoxide (SiO) counterparts has been devoted very little attention. Laser ablation of SiO and TiO in liquids is in according with literature completely unexplored. Here we report on Nd:YAG pulse laser ablation of SiO and TiO in ethanol which allows generation of SiO- and TiO-based nanoparticles and their agglomerates.Mixed SiO-TiO colloid has been prepared by simple mixing of ablatively prepared individual colloids in 1:1 volume ratio. Measurement of size distribution by Dynamic Light Scattering (DLS) determines sizes of 24.85 nm and 262.3 nm for SiO colloid, 494.8 nm for TiO colloid and 35.2 nm and 397.5 nm for mixed colloid. Zeta potential values suggest incipient instability for all measured systems. Morphology of the particles captured on Ta substrate by evaporation of ethanol was studied using Scanning Electron Microscopy (SEM). Round-shaped, oval, and sheet-like particles and their agglomerates have been observed. Raman spectroscopy of the mixed SiO-TiO colloid revealed multiphase structure consisting of anatase and/or rutile, crystalline and amorphous silicon and silica and crystalline and amorphous titanium silicide TiSi2. Formation of TiSi2 demonstrates unexpected low temperature disproportionation of SiO and TiO-based species and mutual reducing interactions. Catalytic activity of individual SiO and TiO colloids and of their mixture has been tested in terms of methylene blue (MB) degradation under the daylight. TiO-SiO mixture exhibits higher solar-light catalytic activity compared to individual colloids which could by explain by the presence of highly photocatalytic TiSi2. These results represent potential of SiO and TiO reducing interactions which are favorable for generation of photocatalytic materials for water remediation.

Fabrication of BiOBr-silicone aerogel photocatalyst in an aqueous system with degradation performance by sol-gel method

It is a challenge to endow the material with the ability to pollutants degradation while maintaining the oil/water separation performance. Herein, the mixed dispersion of BiOBr photocatalyst and silicone sol was adsorbed in melamine foam. Superhydrophobic BiOBr-silicone aerogel (WCA=154°) was obtained through the transfer melamine foam to an autoclave and reaction at 80°C for 20 h. The prepared superhydrophobic BiOBr-silicone aerogel can effectively remove the water soluble pollutants which remain within the water phase after oil/water separation. The band gap of the superhydrophobic BiOBr-silicone aerogel was calculated to be 2.71 eV , which shows sensitivity to visible light (458 nm). Through mechanism analysis, it is found that the VB position of BiOBr is at 1.07 eV and the position of CB is at −1.64 eV. Finally, we prepared a superhydrophobic BiOBr-silicone aerogel (5 cm × 5 cm × 3 cm ) for the verification of the large scale preparation.

Implications of hydrodynamics on the design of pulsed sieve-plate extraction columns: A one-fluid multiphase CFD model using the volume of fluid method

Presented is a detailed assessment of dispersive mixing and turbulence characterisation of an industrially representative pulsed sieve-plate extraction column (PSEC) obtained using multiphase CFD modelling. The system consists of a 150 mm diameter column with two perforated plates dispersing a 30 vol% dodecane/tributyl phosphate mixture in 3 M nitric acid. Operational conditions were chosen to examine pseudo steady-state dispersion regime operation. Three-dimensional transient flow calculations were performed using large eddy simulation (LES), coupled with the volume of fluid method. This study finds that LES is effective at capturing the different scales of turbulence present within PSECs, and their operational influence. Explicit analysis of the hydrodynamics established that the sieve-plates drive dispersive mixing through their influence on the resulting turbulent flow and flow structures. Furthermore, the standard round-hole sieve-plate design is found to perform poorly at producing and distributing the types of flow and turbulence beneficial to droplet size reduction.

Particle history from massively parallel large eddy simulations of pulverised coal combustion in a large-scale laboratory furnace

A study on the coal particle history during combustion in a large-scale furnace using large eddy simulation is presented. The massively parallel execution produces a high-resolution representation of the fluid mixing and particle dispersion throughout the whole computational domain. The coal combustion is modelled using well-established, cost-effective combustion models. A specific feature of the devolatilization model is the optimisation of the kinetic constants for the furnace operating condition, which were obtained through an iterative procedure between particle heating rates from full large eddy simulation runs and the advanced model Chemical Percolation Devolatilization. In a previous work, we showed that the classical coal combustion models, when used in a high-resolution massively parallel large eddy simulation, lead to satisfactory predictions of the in-flame gas properties, namely gas temperature and gas species concentrations. In this work, we went beyond the comparisons between gas phase measurements and predictions. Single particles were tracked over time and instantaneous ensambles were collected to obtain a better understanding of the conditions that coal particles are subjected to in the investigated test case. The particles trajectory, combustion history and instantaneous state distribution were analysed. The volatile flame features were related with the characteristic trajectory of different sized particles. The combustion history revealed that particles are subjected to large variations of heating rates, including very short sequential periods alternating between heating and cooling during the early stages of combustion, due to the high turbulence intensity in the near burner region. Finally, the state distribution of the ensamble provided a global picture of the instantaneous coal combustion process.

Enhanced Dispersive Mixing in Twin-Screw Extrusion via Extension-Dominated Static Mixing Elements of Varying Contraction Ratios

Abstract Twin screw extruders (TSE) are widely used in polymer blending and compounding operations, since the relatively high stresses they impart on melts and controllable residence times make the...

Proper Orthogonal Decomposition Analysis and Dispersion Characteristics of Resonant Acoustic Flow

The investigation on the flow field and mixing characteristics of resonant sound mixing is of great significance for the dispersion mixing of superfine materials. In order to simulate the flow field and dispersion characteristics of resonant acoustic mixing, a gas-liquid-solid three-phase flow model based on the coupled level-set and volume-of-fluid (CLSVOF) and discrete particle model (DPM) was established. The CLSVOF model solves the gas-liquid interface, and the DPM model tracks the particle position. Then, the particle image velocimetry (PIV) experiment was performed using a self-made resonance acoustic hybrid prototype under different oscillation accelerations, and the radial velocity distribution between the experiment and simulation was compared. Finally, the proper orthogonal decomposition (POD) is used to decompose the flow field under different oscillation accelerations and fill levels, and the energy distribution law and the energy structure of different scales are extracted. The results show that the energy of the instantaneous flow field of the resonant sound is mainly concentrated in the low-order mode, and a close relationship was revealed between the energy distribution law and dispersion behavior of particles. The larger the small-scale coherent structures distribute, the more energy it has and the more favorable it is for fast and uniform dispersion.

Strong instability of standing waves for a fourth-order nonlinear Schrödinger equation with the mixed dispersions

In this paper, we consider the strong instability of standing waves for a fourth-order nonlinear Schrödinger equation with the mixed dispersions iψt−γΔ2ψ+μΔψ+|ψ|pψ=0,(t,x)∈[0,T∗)×RN,where γ>0 and μ<0. This equation arises in describing the propagation of intense laser beams in a bulk medium with Kerr nonlinearity. We firstly obtain the variational characterization of ground state solutions by using the profile decomposition theory in H2. Then, we deduce that if ∂λ2Sω(uλ)|λ=1≤0, the ground state standing wave eiωtu is strongly unstable by blow-up, where uλ(x)=λN2u(λx) and Sω is the action. This result is a complement to the result of Bonheure et al. (2019), where the strong instability of standing waves has been studied in the case μ>0.