Properties Of Suspensions Research Articles

On-line coupling of hollow-fiber flow field-flow fractionation and depolarized multi-angle static light scattering (HF5/D-MALS). Proof of principle

Introduced here is the on-line coupling of hollow-fiber flow field-flow fractionation (HF5) to depolarized multi-angle static light scattering (D-MALS). HF5 is a size-based separation alternative to size-exclusion and hydrodynamic chromatography and asymmetric flow field-flow fractionation. HF5 can separate larger sizes than its chromatographic counterparts and provides several advantages over its fractionation counterpart, including reduced sample consumption and greater ease of operation. D-MALS is a variant of MALS in which the depolarized scattering from the analyte solution is measured at a variety of angles simultaneously. Measurements of depolarized scattering have previously been employed in studying the optical properties of solutions or suspensions, to determine the length of rod-like analytes, and to gain increased accuracy in the determination of analyte molar mass. The coupling HF5/D-MALS allows for the depolarization ratio of a solution or suspension to be measured continuously across the fractogram. This is demonstrated here for a Teflon latex the size range of which extends beyond that accessible to commercial size-exclusion columns. The results presented provide the first reported on-line HF5/D-MALS coupling, showing the feasibility of the technique as well as its realized potential for providing continuous depolarization measurements, inter alia.

Unravelling the emulsifying properties of unfractionated plant powders: From interface to bulk

Crude plant-based by-product powders can stabilise emulsions. Their chemical composition varies substantially depending on both the source plant and the manufacturing process, resulting in different emulsifying properties. This diversity was assessed by studying the emulsifying properties of three chemically different by-products (apple seed cake: protein-rich, apple pomace: non-protein soluble-rich, and liquorice root: mostly water-insoluble) ground into fine and coarse powders. The properties (droplet size, particle anchoring ratio, rheological properties) of the powder-stabilised emulsions were monitored for one month and linked to powder suspensions properties assessed in the presence and absence of solid particles. The interfacial scale was emphasized as the primary location to study the interactions between mixed emulsifiers. The interfacial properties of the powders, and especially the competition between solid particles and soluble compounds, were successfully linked to emulsions properties. Protein-rich powder-stabilised emulsions contained smaller droplets, whose diameter varied slightly with particle size, confirming soluble macromolecules dominance at interfaces. With the soluble powder, particles and soluble macromolecules acted synergistically at both interfacial and bulk scales, indicating mixed interfaces. Particle size determined the properties of the emulsions stabilised with insoluble powder, suggesting interfaces mostly composed of solid particles. Solid particles ensured the gravitational and thermodynamic stability of all powder-stabilised emulsions.

Mild extraction of faba bean (Vicia faba L.) proteins against conventional methods: Impact on physicochemical and thermal characteristics

Faba bean (high- and low-tannin) protein isolates were water extracted followed by dialysis or micellization in comparison to concentrates from conventional alkali extraction + acid precipitation, and salt-based extraction (1% NaCl) + dialysis. Protein fractions were characterised for secondary structure conformational changes, crystalline structure, particle size distribution in aqueous suspension and thermal properties. Mild water or salt extraction did not influence particle size distribution. Based on XRD, FTIR and CD, β-sheet structures were the most abundant secondary structures and water extraction + dialysis had minimal impact on their native conformation. DSC results showed an association between protein purity, glass transition temperature and endothermic enthalpy. High melting temperature above glass transition confirms the suitability of faba bean proteins for thermal/extrusion processing. Fractionation method was a more significant determinant of physicochemical characteristics compared to the cultivar. Further exploration of the techno-functional characteristics of faba bean proteins is essential for value-added food applications.

Rheological study of hybrid aqueous suspension of TEMPO-oxidized cellulose nanofibrils and graphene oxide

The incorporation of graphene oxide (GO) into a nanocellulose matrix has attracted considerable attention due to the unique advantages of both components. This study focuses on investigating the viscoelastic and flow properties of hybrid aqueous suspensions (2.00 w/v%), composed of TEMPO-oxidized cellulose nanofibrils (TOCNF) and GO at different TOCNF/GO weight ratios. To adjust the elastic properties of the hybrid suspensions, calcium ions are introduced, varying the concentration systematically to study their effects on the hybrid network structure. All blends exhibit shear-thinning behaviour and demonstrate elastic, gel-like properties. Notably, in the absence of calcium ions, the enhancement of elastic properties is more pronounced at higher GO fractions. Conversely, with the introduction of calcium ions, the enhancement of elastic properties becomes particularly important at higher TOCNF fractions. For the quantitative evaluation of these enhancements, we employ the logarithmic mixing rule. Significant positive deviations from the predictions of the logarithmic mixing rule are ascribed to the complex, concentration-dependent arrangement of cellulose nanofibrils and GO liquid crystals in the aqueous suspension, coupled with ionic crosslinking induced by calcium ions. The study aims to contribute to the understanding of the rheological behaviour of the TOCNF/GO hydrogel, showing potential advancements in various applications.Graphical abstract

Low temperature effects on the rheological properties of aqueous cellulose nanofiber suspensions

Low temperature effects on the rheological properties of aqueous cellulose nanofiber suspensions

Modeling microgel swelling: Influence of chain finite extensibility.

Microgels exhibit the ability to undergo reversible swelling in response to shifts in environmental factors that include variations in temperature, concentration, and pH. While several models have been put forward to elucidate specific aspects of microgel swelling and its impact on bulk behavior, a consistent theoretical description that chains throughout the microscopic degrees of freedom with suspension properties and deepens into the full implications of swelling remains a challenge yet to be met. In this work, we extend the mean-field swelling model of microgels from Denton and Tang [J. Chem. Phys. 145, 164901 (2016)] to include the finite extensibility of the polymer chains. The elastic contribution to swelling in the original work is formulated for Gaussian chains. By using the Langevin chain model, we modify this elastic contribution in order to account for finite extensibility effects, which become prominent for microgels containing highly charged polyelectrolytes and short polymer chains. We assess the performance of both elastic models, namely for Gaussian and Langevin chains, comparing against coarse-grained bead-spring simulations of ionic microgels with explicit electrostatic interactions. We examine the applicability scope of the models under a variation of parameters, such as ionization degree, microgel concentration, and salt concentration. The models are also tested against experimental results. This work broadens the applicability of the microgel swelling model toward a more realistic description, which brings advantages when describing the suspensions of nanogels and weak-polyelectrolyte micro-/nanogels.

Analysis of fluid flow and heat transfer in CNT-infused spiraling disk

This study investigates the fluid flow and heat transfer characteristics influenced by the thermophysical properties of carbon nanotube suspension in engine oil over a stretching-spiraling disk. The surface comprises Homan stagnation point flow impinging normal to a rotating, radially stretching disk, which gives velocity a form of logarithmic spiral. Similarity ansatz transformed coupled nonlinear differential equation system is derived and solved numerically using MATLAB’s bvp4c collocation method. Numerical and asymptotic solutions are also obtained against the controlled parameters via graphical representations and tabular data. Findings indicate that the magnetic field enhances temperature distribution while reducing the velocity field. At the same time, stretching increases radial velocity but decreases azimuthal velocity and temperature profiles, regardless of carbon nanotube type. The asymptotic values of skin friction decline with an increase in the spiralisng angle and in the absence of a magnetic field for both SWCNTs and MWCNTs cases.

Jamming Memory into Acoustically Trained Dense Suspensions under Shear

Systems driven far from equilibrium often retain structural memories of their processing history. This memory has, in some cases, been shown to dramatically alter the material response. For example, work hardening in crystalline metals can alter the hardness, yield strength, and tensile strength to prevent catastrophic failure. Whether memory of processing history can be similarly exploited in flowing systems, where significantly larger changes in structure should be possible, remains poorly understood. Here, we demonstrate a promising route to embedding such useful memories. We build on work showing that exposing a sheared dense suspension to acoustic perturbations of different power allows for dramatically tuning the sheared suspension viscosity and underlying structure. We find that, for sufficiently dense suspensions, upon removing the acoustic perturbations, the suspension shear jams with shear stress contributions from the maximum compressive and maximum extensive axes that reflect or “remember” the acoustic training. Because the contributions from these two orthogonal axes to the total shear stress are antagonistic, it is possible to tune the resulting suspension response in surprising ways. For example, we show that differently trained sheared suspensions exhibit (1) different susceptibility to the same acoustic perturbation, (2) orders of magnitude changes in their instantaneous viscosities upon shear reversal, and (3) even a shear stress that increases in magnitude upon shear cessation. We work through these examples to explain the underlying mechanisms governing each behavior. Then, to illustrate the power of this approach for controlling suspension properties, we demonstrate that flowing states well below the shear jamming threshold can be shear jammed via acoustic training. Collectively, our work paves the way for using acoustically induced memory in dense suspensions to generate rapidly and widely tunable materials. Published by the American Physical Society 2024

Effects of confinement-induced non-Newtonian lubrication forces on the rheology of a dense suspension

In this work, we propose a functionalised bi-viscous lubrication model to study the material properties of concentrated non-Brownian suspensions and explore the possible confinement-induced non-Newtonian effects of the lubricant in the rheological response of this type of suspensions. From tribological studies, it is well-known that even macroscopically Newtonian liquids under strong confinement might exhibit properties which deviate significantly from their bulk behaviour. When two surfaces separated by an extremely small gap (still large compared to the molecular size) are sheared, strong shear-thinning of the lubricant viscosity at low shear-rates is observed, in spite of its Newtonian-like bulk response. This is connected to a significant increase of the zero-shear-rate viscosity under extreme confinement. We start from an effective lubrication algorithm recently proposed and develop a new gap-size-dependent interparticle bi-viscous lubrication model, able to capture qualitatively the main phenomenology of confined lubricants. We solve the lubrication interaction between particles iteratively via a semi-implicit splitting scheme. Since the handling of lubrication is made implicitly here, the method copes efficiently with large increases of the inter-particle effective viscosities, which would otherwise lead to simulation blow-up or the use of vanishing time-steps in standard explicit schemes. We analyse the rheological response of the suspension systematically in terms of model parameters. In contrast to pure Newtonian lubrication interactions, distinct shear-thinning and shear-thickening regimes in the relative suspension viscosity are observed, which are discussed in terms of particle microstructure coupled with the complex rheology of the confined lubricant. In addition, normal-stress response is negative in both N1 and N2, which is difficult to achieve with standard contact frictional models.

Preparation of fine suspensions using stirred media bead mill

Preparation of fine suspensions using stirred media bead mill

Rheological properties of magnesium bentonite and sepiolite suspensions after dynamic ageing at high temperatures

Abstract The rheological properties of three Na-activated, trioctahedral Mg-bentonites (hectorite clay from the CMS Source Clay Project repository, saponite clay from Spain and stevensite clay from Rhassoul, Morocco) and a sepiolite clay from Greece were examined after dynamic ageing at temperatures up to 230°C. The 5% w/v suspensions were prepared by dispersing the clay mineral samples in distilled water. The suspensions underwent dynamic, thermal ageing for 16 h before determination of the viscosity, filtration loss, filter cake thickness and pH and the concentration of dissolved Na+ and Mg2+. Thermal ageing contributed to the dispersion of clay particles, with a direct effect on plastic and apparent viscosity, introducing pseudoplastic behaviour. With the exception of the stevensite clay at 230°C that displayed limited dissolution at 230°C and partial conversion to kerolite, the clays were stable at high temperatures. The Na-activation of all clays except for stevensite was not adversely affected by thermal ageing. Thermal ageing of stevensite at 230°C facilitated Na exchange and yielded suspension with high viscosity and low filtrate loss. Only the suspensions of hectorite and those of stevensite aged at 230°C met with American Petroleum Institute specifications. The thermal behaviour and rheological properties of the clays might be interpreted according to the intrinsic properties of the clay minerals, such as layer charge and charge distribution.

Real-time multibody simulation of vehicle wheel suspensions of different topologies with elastokinematic properties

AbstractDriving simulators are becoming increasingly important in vehicle development, as they allow test drivers to evaluate the driving characteristics of a vehicle at an early stage of the development process. Vehicle dynamics models used for such real-time applications are usually simplified to achieve sufficiently low computation times, especially with respect to the elastokinematic properties of the wheel suspension. This contribution introduces a real-time capable multibody simulation model for wheel suspensions taking into account their elastokinematics. The underlying data model allows the parametrization of different suspension topologies. Linear-implicit integration methods enable real-time capable integration of the underlying numerically stiff equation of motion without major model simplifications. It is shown how the computational effort of linear-implicit integration can be reduced by explicitly taking the suspension topology into account. A versatile process for the analytical online-linearization of the equation of motion of arbitrary suspension topologies is presented. Both a double wishbone and a multilink suspension are simulated with very high accuracy in real-time on a standard PC.

Preparation and characterization analysis of modified bentonite-based powder for improving explosion suppression effects

Properties of explosion suppression material have a significant impact on controlling the explosion propagations. Bentonite, with a large surface area and abundant pore structure, can adsorb free radicals during the explosion reactions. It is a kind of ideal explosion suppression materials. However, bentonite can easily absorb moisture and solidify into cakes in a humid environment, which lacks the possibilities of reactions with radicals in explosions and results in a poor suppression effect. To enhance the space suspension property of bentonite, in this paper, three surface modification methods are proposed to prepare the modified bentonite-based powder by using a silane coupling agent modification, silica encapsulation modification, and quaternary ammonium salt insertion modification. Then, changes in the characteristics of modified bentonite are analyzed and characterized using FTIR, SEM, et al. The results show that the pore structures fundamentally changed and surface is poor combination with water, which greatly solves the “Caking” problem.

Innovative DIY drinking water disinfection for underserved communities

Waterborne pathogens threaten 2.2 billion people lacking access to safely managed drinking water services, causing over a million annual diarrheal deaths. Individuals without access to chlorine reagents or filtration devices often resort to do-it-yourself (DIY) methods, such as boiling or solar disinfection (SODIS). However, these methods are not simple to implement. In this study, we introduced an innovative and easily implemented disinfection approach. We discovered that immersing aluminum foil in various alkaline solutions produces alkali-treated aluminum foil (ATA foil) that effectively adsorbs Escherichia coli (E. coli), Salmonella, and Acinetobacter through the generated surface aluminum hydroxide. For example, a 25 cm2 ATA foil efficiently captures all 104E. coli DH5α strains in 100 mL water within 30 min. Using a saturated suspension of magnesium hydroxide, a type of fertilizer, as the alkaline solution, the properties of the saturated suspension eliminate the need for measuring reagents or changing solutions, making it easy for anyone to create ATA foil. ATA foils can be conveniently produced within mesh bags and placed in household water containers, reducing the risk of recontamination. Replacing the ATA foil with a foil improves the adsorption efficiency, and re-immersing the used foil in the production suspension restores its adsorption capacity. Consequently, ATA foil is an accessible and user-friendly alternative DIY method for underserved communities. Verification experiments covering variations in the water quality and climate are crucial for validating the efficacy of the foil. Fortunately, the ATA foil, with DIY characteristics similar to those of boiling and SODIS, is well-suited for testing under diverse global conditions, offering a promising solution for addressing waterborne pathogens worldwide.

Water Structuring Induces Nonuniversal Hydration Repulsion between Polar Surfaces: Quantitative Comparison between Molecular Simulations, Theory, and Experiments.

Polar surfaces in water typically repel each other at close separations, even if they are charge-neutral. This so-called hydration repulsion balances the van der Waals attraction and gives rise to a stable nanometric water layer between the polar surfaces. The resulting hydration water layer is crucial for the properties of concentrated suspensions of lipid membranes and hydrophilic particles in biology and technology, but its origin is unclear. It has been suggested that surface-induced molecular water structuring is responsible for the hydration repulsion, but a quantitative proof of this water-structuring hypothesis is missing. To gain an understanding of the mechanism causing hydration repulsion, we perform molecular simulations of different planar polar surfaces in water. Our simulated hydration forces between phospholipid bilayers agree perfectly with experiments, validating the simulation model and methods. For the comparison with theory, it is important to split the simulated total surface interaction force into a direct contribution from surface-surface molecular interactions and an indirect water-mediated contribution. We find the indirect hydration force and the structural water-ordering profiles from the simulations to be in perfect agreement with the predictions from theoretical models that account for the surface-induced water ordering, which strongly supports the water-structuring hypothesis for the hydration force. However, the comparison between the simulations for polar surfaces with different headgroup architectures reveals significantly different decay lengths of the indirect water-mediated hydration-force, which for laterally homogeneous water structuring would imply different bulk-water properties. We conclude that laterally inhomogeneous water ordering, induced by laterally inhomogeneous surface structures, shapes the hydration repulsion between polar surfaces in a decisive manner. Thus, the indirect water-mediated part of the hydration repulsion is caused by surface-induced water structuring but is surface-specific and thus nonuniversal.

Properties of composite fuel based on pyrocarbon, a product of tire pyrolysis

The possibility of utilizing technical pyrocarbon, produced by the pyrolysis of used automobile tires, in a composite suspension fuel is demonstrated. It has been found that pyrocarbon-based systems without additives are not suitable for use as fuel due to thickening and hydrophobic properties. To improve the properties of the composite suspension fuels, the influence of stabilizer, plasticizer, and dispersant additives on the rheological properties of the composite suspension fuel was investigated. Carboxymethyl cellulose, sodium lignosulfonate, NF, C-3 (a condensation product of -naphthalene sulfonic acid and formaldehyde), and humic acids were used as additives. It was determined that the surface of unmodified pyrocarbon has a positive surface charge in the pH range of 2–10. Addition of reagents induces a change in the surface charge of pyrocarbon and surface recharging. It is shown that the best results in composite suspension fuel compositions are achieved with the addition of C-3 at a concentration of 2 wt.%. The effective viscosity of the obtained suspensions at a shear rate of 9 s–1 does not exceed 0.8 Pas. This allows the use of the obtained systems with additives as liquid suspension fuels.

Rheological Properties of Colloidal Suspensions Affected by Inter-Particle Interactions

Rheological Properties of Colloidal Suspensions Affected by Inter-Particle Interactions

Design of automobile vehicle suspension with combined damping

A new approach to the design of automobile vehicle suspensions is presented by simultaneous use of several damping devices of different types that make up a combined damping system (CDS). A rational combination of the components of the CDS and optimization of their parameters ensure an increase in the smooth running of the vehicle. Calculation and analysis of the damping properties of pneumatic suspension with different combined damping systems made it possible to determine the most effective systems. Keywords:automobile vehicle, pneumatic suspension, combined damping system, dynamic damper, inertial-friction shock absorber, air damper, hydraulic shock absorber nvv_60@mail.ru

The Effects of Organically Modified Lithium Magnesium Silicate on the Rheological Properties of Water-Based Drilling Fluids.

To address the problem of insufficient temperature and salt resistance of existing polymer viscosity enhancers, we designed an organic-inorganic hybrid composite as a viscosity enhancer for water-based drilling fluids, named LAZ, and it was prepared by combining a water-soluble monomer and lithium magnesium silicate (LMS) using an intercalation polymerization method. The composite LAZ was characterized using Fourier transform infrared spectroscopy, transformed target X-ray diffractometry, scanning electron microscopy, and thermogravimetric analysis. The rheological properties of the composite LAZ were evaluated. The composite LAZ was used as a water-based drilling fluid viscosity enhancer, and the temperature and salt resistance of the drilling fluid were evaluated. The results showed that the composite LAZ presented a complex reticulation structure in an aqueous solution. This reticulation structure intertwined with each other exhibited viscosity-enhancing properties, which can enhance the suspension properties of water-based drilling fluids. The aqueous solution of the composite LAZ has shear dilution properties. As shear rate increases, shear stress becomes larger. The yield stress value of the aqueous solution increases as the composite LAZ's concentration increases. The aqueous solution of the composite LAZ exhibits strong elastic characteristics with weak gel properties. The addition of the composite LAZ to 4% sodium bentonite-based slurry significantly increased the apparent viscosity and dynamic shear of the drilling fluid. The drilling fluids containing the composite LAZ had good temperature resistance at 150 °C and below. The rheological properties of brine drilling fluids containing the composite LAZ changed slightly before and after high-temperature aging at 150 °C.

Measurements of the inherent optical properties of aqueous suspensions of microplastics

AbstractLibraries of inherent optical properties (IOPs) of microplastics are sparse, yet they are essential for the development of optical techniques to detect and quantify microplastics in the ocean. In this study, we describe our results and technique for the measurement of the IOPs of microplastic suspensions generated from commonly utilized plastics. The measurements included angle‐resolved polarized light scattering, and spectral absorption and beam attenuation coefficients. We also performed ancillary characterization of particle properties, including size distribution, shape, and mass concentration of suspended matter. We observed several unique optical characteristics regarding absorption, scattering, and polarization properties compared with typical marine particle assemblages. We show that these results are useful for radiative transfer simulations as well as the potential development of novel plastic detection techniques from above‐ or in‐water optical measurements.