Dispersed Liquid Phase Research Articles

“Fast-charging” mechanism of Li3VO4 from the perspective of material science for lithium-ion battery

“Fast-charging” lithium-ion batteries enjoy extensive attention as energy storage devices for portable electronic devices and new energy vehicles. Regrettably, high safety could not be effectively ensured while the batteries undergo fast-charging process. Li3VO4 could be recognized as a high-safety “fast-charging” anode material considering its appropriate Li-insertion voltage and fast kinetic characteristics. Currently, notwithstanding the fact that Li3VO4 has been extensively investigated as an anode material for lithium-ion batteries and the encouraging research results have been accomplished, the distinction between ion diffusion mechanisms during fast-charging and slow-charging has not been well elucidated. Unlike previous reports, Li+ fast/slow diffusion mechanisms in Li3VO4 are investigated in detail in this work. Specifically, Li+ tends to diffuse along path a due to rather fast Li-insertion/deinsertion processes. Correspondingly, Li+ undergoes diffusion along path a and path b during slow-charging. Unlike the conventional view that Li+ prefers to diffuse along path a under all conditions. Additionally, the lattice changes of Li+ insertion into different sites are predicted. The findings could facilitate to comprehend the mechanism of doping, nanosizing, and other modification methods, and the fast-charging issue could be addressed in a targeted way. For instance, the optimal fast diffusion paths are modified at both atomic and lattice scales, inducing that Li+ could be inserted into the lattice of material faster during fast-charging and the power densities could be increased. Accordingly, understanding the fast diffusion mechanism of Li+ in Li3VO4 is crucial to addressing the “fast-charging” of these materials. Unfortunately, the inferior electronic conductivity restricts its Li-storage capacity in “fast-charging” devices. Herein, a Li3VO4 based anode material is prepared thorough a one-step hydrothermal method and liquid-phase dispersion technique in the existence of polyvinyl pyrrolidone, which demonstrates exceptional discharging and charging specific capacities, maintaining 273 mAh g−1 at 0.1 A g−1. It also presents considerably higher “fast-charging” performance even at 1.0–4.0 A g−1. Electrochemical kinetic studies indicate that the thin coating could improve the conductivity of Li3VO4. The Li-insertion sites and diffusion paths during fast-charging and slow-charging processes are predicted computationally. And the in-situ XRD is adopted to insight into the structural changes of composites during Li-insertion/deinsertion processes. The data furnishes a theoretical basis for comprehending the fast lithium storage mechanism of Li3VO4 and offers a new method for searching for “fast-charging” anode materials.

Ion-irradiation effect on swelling and microstructure of BN particle dispersed liquid phase sintering SiC

The boron nitride (BN) particle dispersed silicon carbide (SiC) materials were fabricated by liquid phase sintering (LPS) with Al2O3 and Y2O3 sintering additives as the reference matrix material for SiC composites. They were irradiated to 0.1/1/3/10 dpa by 5.1 MeV Si2+ ions at 800 °C. Raman spectra indicated that the pure h-BN structure was partially destroyed following irradiation, while yttrium aluminum garnet (YAG) structure at grain boundaries formed from the sintering additives wasn’t destroyed. TEM images and diffraction patterns indicated that the mechanism of microstructure evolution of SiC after irradiation up to high fluence at 800 °C was defect clusters induced by irradiation.

A novel thermal-tailored strategy to mitigate thermal cracking of cement-based materials by carbon fibers and liquid-metal-based microencapsulated phase change materials

Massive concrete structures are susceptible to thermal cracking due to the large surface-to-internal temperature gradients induced by the exothermic cement hydration, threatening their durability and safety. This study explored a novel thermal-tailored strategy to mitigate thermal cracking of cement-based materials by incorporating carbon fibers (CF) and liquid-metal-based microencapsulated phase change materials (MEPCM). Specifically, spherical MEPCM composed of In-Bi-Sn alloy cores coated by polyvinyl alcohol shells was prepared through a high-speed liquid-phase dispersion method, with average diameters of 36.26 μm and a high volumetric latent heat of 214 MJ/m3. The synergistic effect of CF and MEPCM on the microstructure, mechanical and thermal properties of cement mortars was further investigated. Upon adding 0.3 wt% of CF and 3.2 vol.% of MEPCM, the flexural strength of cement mortars exhibited a significant increase of 30.3 %. Microanalysis revealed that the molten MEPCM could flow to fill the pores and microcracks within its surrounding matrix and form a network skeleton with well-dispersed CF, imparting flexibility to the typically rigid cement hydrates. By this way, the thermal conductivity of cement mortars was increased by 21.7 % and internal temperature rise was decreased by 12 ℃ by adding 4.8 vol.% of MEPCM, contributing to the mitigation of risks associated with thermal cracking. The research outcomes will provide valuable insights into the development of thermal cracking-resistant cement-based materials in a highly efficient way.

The Thermophysical Aspects of the Transformation of Porous Structures in Versatile Nanostructured Materials

The technology of obtaining porous nanostructures is based on ecological organosilicon materials and their uses in some spheres of human life, for example, for medical preparations, for thermal insulation of building structures and industrial equipment, and for cleaning. The purpose of this study was to establish correlations between various experimental parameters (shear stress, speed pulsations, temperature, viscosity, and processing time) and the rheological characteristics of suspensions obtained by the method of liquid-phase dispersion; it was a study of hydrodynamic effects and the processes of heat and mass exchange in liquid systems during the liquid-phase dispersion of hydrogel monoliths by means of discrete-pulse activation in a special rotary apparatus. The dehydration of hydrogels was carried out by two methods: convective drying in a layer and spraying in the coolant flow. Experiments have shown that the key parameters for obtaining stable homogeneous suspensions are a synergistic combination of concentration factors and processing time. To obtain adsorbents in the form of pastes with specified adsorption properties and a monolith size of up to 300 μm, the optimal parameters were a hydrogel concentration of 70% and a processing time in the double-recirculation mode. Xerogels obtained by convective drying are a polydisperse mixture of strong monoliths and fragile aggregates. In contrast, xerogel monoliths obtained by spray drying show great homogeneity in terms of dispersion and strength characteristics. The rheological parameters of the hydrogel dispersions, which depend on the concentration and hydrodynamic treatment modes, are the dominant factors affecting the moisture extraction during drying. This study marks the first investigation into the resilience of porous organosilicon structures against the influence of intense turbulence fields and mechanical stresses experienced within the rotor apparatus during suspension production.

Rational design of cationic starch with high purification performance and insight into the working mechanism

The utilization of starch to treat sewage that received widespread attention has become one of the promising ways to purify water due to the advantages of low cost and biodegradability. However, the poor purification capacity for wastewater and difficult liquid phase dispersion of natural starch severely hindered its application in wastewater treatment and limited the development of starch materials. Hence, a series of cationic starches with different particle sizes were fabricated by controlling the acidification time and combining starch with N-2,3-epoxy-propyl trimethyl ammonium chloride to improve the dispersion and purification effect of starch in water. Acid hydrolysis could destroy the spatial structure of starch, which improved the etherification property to enhance the purification property of starch to different pollutants and the dispersed stable state in water. The maximum adsorption capacities of the optimal functional agents were 43.2 mg/g (methyl orange), and 236.8 mg/g (acid black) and the optimal penetration rate of the treated kaolin solution was 94.6%. The working behavior of cationic starch could be composed of rapid, stable, and equilibrium stages, and the working process of HS-g-GTA conformed to the pseudo-second-order dynamic model. This work provides a simple and low-energy pretreatment method for preparing cationic starch, which has important application value in removing anionic substances from wastewater.

Strength-plasticity-matched (GNPs+GFs)/Mg–3Zn-0.1Ymagnesium matrix composites with high modulus through liquid-phase dispersion and multistep deformation

This paper explores the production of high-modulus 3 wt%(GNPs + GFs) composites through high-energy ultrasonics-assisted semisolid stirring followed by combining multidirectional forging (MDF) and extrusion (EX) techniques. Compared to EX-alloy, the yield strength of the MDF + EX composite material was increased to ∼313 MPa, and the modulus was increased from ∼44 Gpa to ∼56.5 Gpa while retaining a higher plasticity of ∼9 %. The mechanical properties of the composites are significantly improved due to several factors. These include the grain boundary strengthening effect caused by refinement and high recrystallization rate, the Orowan strengthening effect due to dynamically precipitated nano-MgZn2 phases, and the homogeneous dispersion of GNPs and GFs.

Machine learning enhanced droplet microfluidics

Machine learning has recently been introduced in the context of droplet microfluidics to simplify the process of droplet formation, which is usually controlled by a variety of parameters. However, the studies introduced so far have mainly focused on droplet size control using water and mineral oil in microfluidic devices fabricated using soft lithography or rapid prototyping. This approach negated the applicability of machine learning results to other types of fluids more relevant to biomedical applications, while also preventing users that do not have access to microfluidic fabrication facilities to take advantage of previous findings. There are a number of different algorithms that could be used as part of a data driven approach, and no clear comparison has been previously offered among multiple machine learning architectures with respect to the predictions of flow rate values and generation rate. We here employed machine learning to predict the experimental parameters required for droplet generation in three commercialized microfluidic flow-focusing devices using phosphate buffer saline and biocompatible fluorinated oil as dispersed and continuous liquid phases, respectively. We compared three different machine learning architectures and established the one leading to more accurate predictions. We also compared the predictions with a new set of experiments performed at a different day to account for experimental variability. Finally, we provided a proof of concept related to algae encapsulation and designed a simple app that can be used to generate accurate predictions for a given droplet size and generation rate across the three commercial devices.

Current Limitations for Predicting Liquid Dispersion in Continuous Flow Bubble Columns Using CFD

Liquid-phase dispersion in a continuous flow bubble column was studied using computational fluid dynamics (CFD) and different combinations of turbulence and biphasic models. The results were compared with the experimental data obtained by the stimulus-response method in an air-water pilot-scale bubble column (2 m tall, 0.234 m internal diameter). Two flow combinations were examined: high flow rates of 3.2 m3 h−1 and 4.5 m3 h−1 and low flow rates of 1.98 m3 h−1 and 0.954 m3 h−1 for water and air, respectively. The objective was to evaluate commercial CFD 16.1 software to predict flow behavior beyond macroscale parameters such as hold-up or mixing time. The turbulence models that best replicated the experimental tracer dispersion were large eddy simulation-type models: scale-adaptive simulation (SAS) and shear stress transport-SAS. The simulations qualitatively predicted the tracer concentration with time but were unable to reveal the small-scale perturbations in the biphasic system. The predicted tracer residence time was double or triple the measured times for low and high flow, respectively.

Three-Dimensional Imaging of Emulsion Separation through Liquid-Infused Membranes Using Confocal Laser Scanning Microscopy.

The removal of emulsified oils from water has always been a challenge due to the kinetic stability resulting from the small droplet size and the presence of stabilizing agents. Membrane technology can treat such mixtures, but fouling of the membrane leads to dramatic reductions in the process capacity. Liquid-infused membranes (LIMs) can potentially resolve the issue of fouling. However, their low permeate flux compared with conventional hydrophilic membranes remains a limitation. To gain insight into the mechanism of transport, we use 3D images acquired by confocal laser scanning microscopy (CLSM) to reconstruct the sequence of events occurring during startup and operation of the LIM for removal of dispersed oil from oil-in-water emulsions. We find evidence for coalescence of oil droplets on the surface of and formation of oil channels within the LIM. Using image analysis, we find that the rate at which oil channels are formed within the membrane and the number of channels ultimately govern the permeate flux of oil through the LIMs. Oil concentration in the feed affects the rate of coalescence of oil on the surface of the LIM, which, in turn, affects the channel formation dynamics. The channel formation dynamics also depend on the viscosity of the infused liquid and the operating pressure. A higher affinity to the pore wall for infused liquid than permeating liquid is essential to antifouling behavior. Overall, this work offers insight into the selective permeation of a dispersed liquid phase through a LIM.

Boundary element method for modeling droplet deformation in secondary atomization

A droplet deformation model based on the combination of an axisymmetric Boundary Element Method (BEM), Viscous Potential Flow (VPF) theory, and a simplified heuristic model for the action of aerodynamic forces is presented. The model predicts droplet distortion and interface shape up to the point of initial droplet break-up. To address liquid viscosity a previously introduced Generalized Viscous Pressure Correction was employed after its extension to 3D axisymmetric cases. Assumed are thin boundary layers within the droplet phase, a high density ratio between the two phases and moderate Reynolds numbers. The model requires at most around 200 flow variables to properly predict droplet deformation and distortion. The overall model produces results comparable to those of the Taylor Analogy Breakup model and its nonlinear version in the vibrational regime. However, it requires a calibration factor of 1.36 for the aerodynamic local pressure, in order to obtain the correct critical Weber number of around 12. In the bag and bag-stamen regimes, the droplet shape and distortion parameters are in good agreement with experimental data. Overall, the results indicate that the present modeling approach might be used as sub-grid model for droplet dynamics in multiphase flow simulation with a highly dispersed liquid phase.

Lightweight chopped carbon fiber/carbon composites with low thermal conductivity fabricated by vacuum filtration method

Lightweight carbon fiber/carbon composites (CFC) are widely used in solar silicon furnace, semiconductor long crystal furnace and other high-temperature equipment due to its superior low thermal conductivity, low expansion coefficient, high purity, good mechanical properties, and high temperature resistance. In this paper, the lightweight chopped CFC was prepared by the method of liquid phase dispersion of chopped carbon fibers-vacuum filtration-curing molding-high temperature carbonization and graphitization. The thermal conductivity of lightweight chopped CFC with different densities (0.12, 0.16 and 0.18 g/cm3) was studied, and the thermal conductivity of lightweight chopped CFC at high temperature was also studied. The results show that the thermal conductivity (1000 °C) of the chopped CFC gradually increases with the increasing density from 0.179 W/(mK) (0.12 g/cm3) to 0.190 W/(mK) (0.16 g/cm3), 0.282 W/(mK) (0.18 g/cm3), indicating that with the increasing density, the thermal conduction path of the carbon fiber increases, the thermal conductivity of the CFC material increases, and then the thermal insulation performance decreases. In addition, with the increasing temperature, the phonon vibration increases, the thermal conductivity of the CFC material also increases, and then the thermal insulation performance decreases.

Investigation of the extraction of natural alkaloids in Karr reciprocating plate columns: Fluid dynamic study

Previous work found that 0.2 M Cyanex® 923 in xylene has potential to extract natural alkaloids such as morphine. In this work, pilot scale fluid dynamic tests using 0.2 M Cyanex® 923 in xylene as a dispersed phase and water as a continuous phase in a reciprocating plate Karr column were conducted at different flowrates of both phases and reciprocating frequencies. The results show that the dispersed phase liquid holdup increases with the increase of dispersed phase velocity and reciprocating frequency, and the Sauter-mean drop diameter is independent of the velocity of both phases, and it slightly reduces with increasing reciprocating frequency. The results were used to regress an empirical model. In addition, morphine extraction using the same solvents were also studied in two different Karr columns. The results were consistent with those of fluid dynamic tests, and further used to investigate the regressed model within 30 % deviation.

Experimental Investigation on Spray Evaporation and Dispersion Characteristics of Impinged Biodiesel-Butanol Blends

Abstract The objective of the investigation is to explore the spray evaporation and dispersion characteristics of impinged biodiesel-butanol blends at various n-butanol ratios (0, 10%, 30%, 50%) and ambient conditions. A total of 180 experimental cases were performed in a constant-volume combustion chamber. The liquid- and vapor-phase sprays were captured by backlight imaging technique and Schlieren imaging technique, respectively. Several macroscopic parameters were measured and discussed, including impinged spray structure, width, height, and area. Some novel parameters are derived to analyze spray evaporation and dispersion. Results show that biodiesel blended with 30% n-butanol transits better from liquid-phase to vapor-phase compared with other blends, displaying rapid liquid-phase evaporation an steady vapor-phase dispersion. After wall impingement, an increase in the ambient pressure or temperature hinders the liquid-phase dispersion in the vertical direction significantly, leading to a rapid decrease in the height of the impinged spray. The vapor-phase diffusion rate in the horizontal direction is about four times the rate in the vertical direction, and the rate ratio is slightly affected by ambient conditions and injection pressure. Compared with the free jet, the impinged spray is not beneficial for liquid-phase evaporation and vapor-phase dispersion, presenting larger liquid-phase area and smaller vapor-phase area. However, impinged biodiesel blended with 30% n-butanol displays better spray evaporation and dispersion.

Influence of Co on the Microstructure, Electrochemical and Pseudocapacitive Properties of Amorphous Manganese Dioxide

Manganese dioxide is a cathode material for zinc-ion batteries which is low in cost and high in performance, whereas, traditional manganese dioxide materials have poor cycle stability and poor conductivity. In response to this problem, many researchers have carried out related research, such as the preparation of various crystal forms of manganese dioxide, element doping (Co, Sn, V, etc.) and so on. However, the research on doping amorphous materials to solve the above problems is in scarcity. In this paper, amorphous manganese oxide and Co doping were combined for the first time, and Co-doped amorphous manganese dioxide was prepared by in-situ liquid phase dispersion coprecipitation method. The influence of Co doping on the microstructure and electrochemical properties of amorphous manganese dioxide were also investigated for the first time. As can be observed from the results, despite that Co doping preserves the abundant structural defects in amorphous manganese dioxide, it transforms the amorphous manganese dioxide particles from spherical to nano-sheet shape, significantly increases the particular area of surface and pore size of amorphous manganese dioxide, and stabilizes its crystal structure. Furthermore, Co doping can not only reduce the impedance of the amorphous manganese dioxide cathode, but also extremely boost the pseudocapacitive performance of amorphous manganese dioxide, thereby greatly improving its discharge specific capacity, the rate performance and the cycle stability. The prepared Co-doped amorphous manganese dioxide cathode has a maximum discharge specific capacity of 325 mAh g−1, and a capacity retention rate of 64% at 600 cycles under a current density of 1 A g−1.

Droplet formation under wall slip in a microfluidic T-junction

Although no slip is a universally accepted condition for wall-bounded flows, velocity slip occurs due to lubricating action by stable air pockets sandwiched between the fluid and solid surface asperities when a flow takes place along a superhydrophobic surface. The effects of velocity slip on single-phase flow systems have been reported by several researchers. However, its impact on the two-phase flow system has been less investigated. The present work investigates the effect of velocity slip at the wall during droplet formation in a microfluidic T-junction. The presence of velocity slip exhibited by the dispersed phase liquid on the channel wall has been experimentally measured with micro-PIV, and numerical simulations have been performed for investigating the effects of continuous phase fluid slip length on the two-phase flow system. We have also developed an analytical model to establish the effect of wall slip on the droplet length for various properties. All the results (numerical, experimental, and analytical) produce a satisfactory agreement. The effect of slip length on the shear stress at a lower flow rate is more pronounced than at a higher flow rate ratio. An increase in the slip of the continuous phase liquid enhances the vorticity inside the droplet, which resists the droplet detachment, increasing the droplet length.

Destruction of polymers under the action of laser radiation

Laser ablation is one of the main mechanisms of polymers destruction under the action of laser radiation. In this paper, the basic information on laser ablation of polymers is presented. Under the action of laser radiation on the polymer, processes of thermal, thermo-oxidative, and mechanical degradation occur simultaneously, resulting in the evaporation of macromolecules fragments (up to oligomers), and in some cases, separation of polymer particles and filler by a gas or plasma jet is observed. In addition, a substance ablation is accompanied by a large number of concomitant effects: vapor condensation and liquid phase dispersion.

Boosting the electrochemical performance of Li4Ti5O12 anode modified by Ag2V4O11

In this study, Ag2V4O11 was employed as an additive to boost the electrochemical performance of Li4Ti5O12. A series of Li4Ti5O12/Ag2V4O11 composites with different Ag2V4O11 mass ratios of 3 wt.%, 5 wt.% and 8 wt.% were prepared using liquid-phase dispersion method to yield compounds abbreviated as Li4Ti5O12/Ag2V4O11 (3 wt.%), Li4Ti5O12/Ag2V4O11 (5 wt.%) and Li4Ti5O12/Ag2V4O11 (8 wt.%), respectively. Among them, Li4Ti5O12/Ag2V4O11 (5 wt.%) composite displayed a considerable initial discharge specific capacity of 252.4 mAh g−1 at 30 mA g − 1 which still maintained at 152.0 mAh g−1 over 500 cycles. At 1200 mA g−1, a capacity of 69.0 mAh g−1 was retained over 5,000 cycles. The electrode kinetic studies revealed that the introduction of Ag2V4O11 phase boosted the transport rate of lithium ion and the electronic conductivity of Li4Ti5O12. In-situ XRD tests related that Ag2V4O11 was decomposed to in situ produce metallic Ag on Li4Ti5O12 after cycle. In a word, Li4Ti5O12/Ag2V4O11 (5 wt.%) composite was a promising as the electrode material in lithium-ion batteries. The data also provided a fire-new method to enhance the electrochemical property of Li4Ti5O12.

Computational Protocol for Spray Flow Simulations Including Primary Atomization

Abstract Primary atomization is the key element in spray flow simulations. We have, in our previous work, used and validated the integral form of the conservation equations, leading to the “quadratic formula” for determination of the drop size during spray atomization in various geometry. A computational protocol has been developed where this formulation is adapted to existing computational frameworks for continuous and dispersed (droplet) liquid phase, for simulations of pressure-atomized sprays with and without swirl. In principle, this protocol can be applied to any spray geometry, with appropriate modifications in the atomization criterion. The preatomization continuous liquid motion (e.g., liquid column or sheet) is computed using volume-of-fluid (VOF) or similar methods, then the velocity data from this computation is input to the quadratic formula for determination of the local drop size. This initial drop size, along with the local liquid velocities from VOF, is then used in a Lagrangian tracking algorithm for the postatomization dispersed droplet calculations. This protocol can be implemented on coarse-grid, time-averaged simulations of spray flows, and produces convincing results when compared with experimental data for pressure-atomized sprays with and without swirl. This approach is general, and can be adapted in any spray geometries for complete and efficient computations of spray flows.

Oil-Water Interfacial-Directed Spontaneous Self-Assembly of Natural Quillaja Saponin for Controlling Interface Permeability in Colloidal Emulsions.

Assembly of amphiphiles at the interface of two immiscible fluids is of great scientific and technological interest in offering efficient routes to smart vehicles for functional deliveries. Natural Quillaja saponin (QS) has gathered widespread interest within the scientific community as a result of its unique interfacial properties. Herein, spontaneously interface-driven self-assembly (SIDSA) of QS at the oil-water interface was systematically studied by morphology and spectroscopy. It was found to self-assemble into a micrometer-scale network in helical fibers by combined intermolecular π-π stacking and hydrogen bonding among saponins at the liquid-liquid interface. From SIDSA, multilayer films on the surfaces of dispersed droplets were formed and enhanced emulsion stability. Interfacial QS-based films on droplet surfaces were also shown to confine interfacial diffusion processes by serving as transport barriers. Furthermore, they can be exploited to control the release of volatiles from the dispersed liquid phase by regulating the interface film, which is shown by molecular dynamics to occur through a hydrogen-bonded mechanism. These results provide new insight into the interfacial assembly structure that can enable unique controllable release in a broad range of applications in food, beverages, pharmaceuticals, and cosmetics.

Numerical study of multicomponent spray flame propagation

A computational study of one dimensional multicomponent laminar Jet-A/air spray flames is presented. The objective is to understand the effect of various spray parameters (diameter, droplet velocity, liquid loading) on the spray flame structure and propagation. Simulation of the Eulerian gas phase is coupled with a Lagrangian tracking of the dispersed liquid phase. Jet-A surrogate of n-dodecane, methyl-cyclohexane and xylene is considered. A discrete multicomponent model for spray vapourisation is used along with an analytically reduced chemistry for computing the gas phase reactions. Both overall lean and rich cases are examined and compared with existing literature for single component spray flames. The preferential evaporation effect, unique to multicomponent fuels causes a variation of fuel vapour composition on both sides of the flamefront and this has a direct impact on the spray flame structure and propagation speed. In the rich cases, multiple flame structures exist due to the staged release of vapours across the reactive zone. Spray flame speed correlations proposed for single component fuels are extended to the multicomponent case, for both zero and high relative velocity between the liquid and the gas. The correlations are able to accurately predict the effective equivalence ratio at which the flame burns and hence the laminar spray flame speeds of multicomponent fuels for all cases studied in this work.