Rheological Experiments Research Articles

Exploring Self‐Assembly and Viscoelastic Behavior of Pyrene‐Based Fluorescent Hydrogel: Designing Paper Sensors for Water‐Soluble Explosives

AbstractRecently organic‐doped polyethyleneimine based hydrogels have emerged as smart responsive materials for optical sensing applications. To this end, herein we have designed and synthesized a biocompatible fluorescent hydrogel based on polyethyleneimine (PEI), incorporating pyrene as the polyaromatic signaling moiety. The self‐assembly properties of the composite materials were primarily influenced by the nature of the organic dopant, the degree of substitution, and the microenvironment. The presence of the polyaromatic scaffold, such as pyrene, not only affects the fluorescence properties of the molecules but also modulates the extent of cross‐linking by controlling π‐π stacking interactions. The hydrogel formation was observed in a methanol‐water (3 % v/v) mixture. Additionally, the pyrene‐attached hydrogel demonstrated promising potential for the highly sensitive detection of trinitrophenol (TNP), a toxic, water‐soluble explosive. Spectroscopic investigations revealed that the electrostatic interaction between the ammonium units of PYR‐PEI and picrate anions in aqueous medium facilitated charge transfer from pyrene to the picrate anion, resulting in a fluorescence turn‐off response. Along with fluorometric response, using rheological experiments we show that the viscoelastic behaviour of the polymer gels also varied significantly upon addition of TNP. To determine the viscoelastic parameters, a two‐term Maxwell model was used to fit the angular frequency‐dependent storage and loss moduli measurements. Additionally, hydrogel‐coated, highly robust, and reusable paper strips were also developed for on‐field detection of TNP.

Software package for automated processing of rheological experiment results

Software package for automated processing of rheological experiment results

Metal Ion Cross-Linked Cellulose/Lignin Nanocomposite Films: A Pathbreaking Approach toward High-Performance Sustainable Biomaterials.

Inspired by the reinforcement mechanisms observed in biomaterials, cellulose/lignin composite membranes are prepared successfully by mixing nanolignin and nanocellulose and impregnating them with metal ion solution. Metal ion cross-linking and hydrogen bonds between cellulose and lignin create a robust cross-linking network. The composite films achieve a tensile strength of 223.8 MPa, more than twice that of pure nanocellulose films (104 MPa), and surpass commonly used commercial petroleum-based plastics. Through investigation utilizing dynamic rheological experiments and density functional theory, the interactions between cellulose fibers and lignin are elucidated, showcasing the synergistic effects of Ca2+ cross-linked oxygen-containing functional groups and hydrogen bonding. These interactions enhance the strength and toughness of the composite films. Capitalizing on the hydrophobic nature of nanolignin and the strong interactions between metal ions and oxygen-containing functional groups, the wet strength of the composite films reached 33.3 MPa. Moreover, the composite material demonstrates optical properties, electromechanical stability, and thermal stability, including the UV blocking rate. Compared to petroleum-based plastics such as polyethylene and poly(vinyl chloride), cellulose-based films completely degrade within 30 days. With its inherent biodegradability, the composite films have the potential to replace conventional plastics in various applications, advancing sustainable and environmentally friendly materials.

Synergistic stabilization of oil-in-water emulsion gels by pea protein isolate and cellulose nanocrystals: Effects of pH and application to 3D printing.

Synergistic stabilization of oil-in-water emulsion gels by pea protein isolate and cellulose nanocrystals: Effects of pH and application to 3D printing.

Transport of Fe‐Based Nanoparticles in Porous Media Facilitated by Xanthan Gum: Non‐Monotonic Relation Between Transport Efficiency and Flow Velocity

AbstractThe transport of Fe‐based nanoparticles (Fe‐NPs) in porous media is of vital importance for application of Fe‐NPs in groundwater remediation, yet their low mobility remains an open question. Here, we conducted column and microfluidic transport experiments combined with rheology experiments and model simulations to investigate the effect of xanthan gum (XG) on the transport of two types of Fe‐NPs (nanoparticles of Fe3O4 (nFe3O4) and zero‐valent iron (nZVI)) in quartz sand at different input concentrations and flow velocities. We observed that the rheological modification of water by XG significantly enhanced the transport of both Fe‐NPs, and the transport of nZVI was better than that of nFe3O4. With the increase of input concentration of Fe‐NPs, the transport of nZVI slightly declined, whereas the transport of nFe3O4 initially increased and then decreased. The different responses of transport of nFe3O4 and nZVI to input concentrations were attributed to the unique shear‐thinning rheological properties of XG suspensions with each type of Fe‐NPs. We observed a novel non‐monotonic relation between transport efficiency and flow velocity, where the transport of both Fe‐NPs initially weakened and then enhanced as pore‐water velocity rose within a certain range. We demonstrated that the formation of a non‐flowing layer of XG on the surface of the porous medium was identified as the mechanism responsible for the non‐monotonic transport behavior. These findings provide new insights into transport behavior of Fe‐NPs in porous media under the rheological remediation of XG, and have practical implications for application of Fe‐NPs in groundwater remediation.

Numerical Simulation of Acid Diversion and Wormhole Propagation Mechanism of Nanoparticle VES Acid in High-Temperature Carbonate Reservoirs

Uniform acid distribution is a critical challenge and a key factor for the successful acidizing of carbonate reservoirs. Previous experimental studies have shown that nanoparticles can enhance the viscosity and thermal resistance of viscoelastic surfactant (VES) fracturing fluids. However, there has been limited research on the effects of nanoparticles on the wormhole propagation and diversion performance of VES acid. This paper establishes a nanoparticle VES acid rheological model based on rheology experiments, and introduces a porous medium temperature field and nanoparticle adsorption model into a two-scale continuum model to establish a mathematical model for the expansion of wormholes in nanoparticle VES acid. The accuracy of the wormhole model is verified through laboratory experiments. The effects of permeability contrast, initial acid temperature, and nanoparticle adsorption on the diversion performance and wormhole propagation of nanoparticle VES acid are analyzed. The results indicate that nanoparticle VES acid differs from conventional VES acid, with its invaded zone divided into high-viscosity and low-viscosity zones. The presence of the high-viscosity zone allows nanoparticle VES acid to improve wormhole propagation in low-permeability cores by 16.2% compared to conventional VES acid. At 393 K, nanoparticle VES acid has a better diversion effect in carbonate cores with permeability contrast of 10, as the acid fluid flows faster in high-permeability cores, resulting in wormhole shapes with more branches. Numerical model results show that when the permeability contrast is 8, increasing the injection temperature of the acid solution from 293 K to 368 K improves the ability of low-permeability cores by 33.3%. This study establishes a mathematical model for nanoparticle VES acid based on laboratory experiments and numerical simulations, investigates the effects of nanoparticles on VES rheological properties under acidic conditions, and clarifies the wormhole propagation and acid diversion behavior of nanoparticle VES acid, providing guidance for future field applications of this acid.

The Numerical Analysis of the Fractional Maxwell Fluid in Porous Rock Formations

ABSTRACTFractional derivatives are global operators in which the time and space fractional derivatives represent temporal memory and spatial nonlocality, respectively. It is confirmed that the fractional Maxwell fluid model is more suitable for describing crude oil constitutive relation by the rheological experiment. In this paper, an investigation of the magnetohydrodynamic (MHD) flow and heat transfer of crude oil nanofluid in porous rock formations is presented. The fractional governing equations with the time and space fractional derivatives have been established. Numerical solutions are obtained by the finite difference method with the L1 algorithm and L2 algorithm to discrete the fractional derivatives. The numerical solution is verified by comparing with the exact solution constructed by introducing a source term. The effects of the involved parameters on the velocity and temperature distributions are analyzed and discussed in detail. It is noteworthy that the velocity profiles decrease significantly with the increasing while the temperature profiles increase with the increasing .

The Role of FeO/SiO2 Ratio in Valorizing Iron Silicate Slags as Supplementary Cementitious Materials

Pyrometallurgical copper production is associated with high slag rates, typically ranging from 2.2 to 3.0 tons of slag per ton produced copper. Therefore, slag valorization is necessary to maintain a resource-efficient operation. An attractive application for these iron silicate slags is as supplementary cementitious materials (SCMs), which effectively lowers the CO2 emissions per ton of concrete. Although utilizing iron silicate slags as SCMs has been studied in previous work, the scientific literature has limited data on the isolated effect of composition on the inherent reactivity in cementitious systems. In particular, no reports on the impact of the FeO/SiO2 ratio have been presented in previous publications. Therefore, the present study aimed to isolate this parameter in a synthetic FeO–SiO2–Al2O3–CaO–MgO–Cr2O3 system. Since the amorphous content is a pertinent parameter for SCMs, a hot-stage confocal laser scanning microscope was utilized to assess the crystallization behavior at continuous cooling conditions. Furthermore, high-temperature rheological experiments were conducted to measure the viscosities of the slags in relation to the crystallization behavior. The experiments highlighted that depolymerizing the slag by increasing the FeO/SiO2 ratio poses increased demands on the cooling rate to avoid crystallization, which was consistent with the rheological data on the impact of temperature on structural changes in the slags. Furthermore, Rapid Reliable Relevant (R3) isothermal calorimeter experiments, assessing the inherent reactivity as an SCM, showed that increasing FeO/SiO2 ratios improves early reactivity at the expense of seven-day reactivity, i.e., a balance between the degree of polymerization and contribution of silicon to the reactions.Graphical

Highly Extensible Physically Crosslinked Hydrogels for High-Speed 3D Bioprinting.

Hydrogels have emerged as promising materials for bioprinting and many other biomedical applications due to their high degree of biocompatibility and ability to support and/or modulate cell viability and function. Yet, many hydrogel bioinks have suffered from low efficiency due to limitations on accessible printing speeds, often limiting cell viability and/or the constructs which can be generated. In this study, a highly extensible bioink system created by modulating the rheology of physically crosslinked hydrogels comprising hydrophobically-modified cellulosics and either surfactants or cyclodextrins is reported. It is demonstrated that these hydrogels are highly shear-thinning with broadly tunable viscoelasticity and stress-relaxation through simple modulation of the composition. Rheological experiments demonstrate that increasing concentration of rheology-modifying additives yields hydrogel materials exhibiting extensional strain-to-break values up to 2000%, which is amongst the most extensible examples of physically crosslinked hydrogels of this type. The potential of these hydrogels for use as bioinks is demonstrated by evaluating the relationship between extensibility and printability, demonstrating that greater hydrogel extensibility enables faster print speeds and smaller print features. The findings suggest that optimizing hydrogel extensibility can enhance high-speed 3D bioprinting capabilities, reporting over 5000 fold enhancement in speed index compared to existing works reported for hydrogel-based bioinks in extrusion-based printing.

Supramolecular gel with enhanced immunomodulatory effects presents a minimally invasive treatment strategy for eosinophilic chronic rhinosinusitis.

Supramolecular gel with enhanced immunomodulatory effects presents a minimally invasive treatment strategy for eosinophilic chronic rhinosinusitis.

Modified Herschel–Bulkley–Papanastasiou model considering particle size distribution to debris flow rheological properties

Debris flow, a typical non-Newtonian fluid, exhibits rheological behavior significantly influenced by particle size distribution. Traditional rheological models often struggle with applicability and predictive accuracy in complex particle systems. This study proposes a modified Herschel–Bulkley–Papanastasiou (HBP) model, incorporating particle size distribution parameters to dynamically adjust yield stress and shear viscosity, enhancing its accuracy in describing debris flow behavior under varying particle gradations. The model distinguishes the roles of fine and coarse particles: fine particles reduce shear resistance through lubrication effects, while coarse particles enhance yield stress and viscosity via interlocking effects. To validate the model, a series of rheological experiments were conducted on 14 particle gradation conditions. Results showed the modified HBP model achieved fitting coefficients between 0.933 and 0.990, significantly outperforming traditional models and demonstrating superior adaptability across different particle distributions. The model was further integrated into the OpenFOAM framework for three-dimensional simulations of a flume experiment. These simulations considered wall friction and dynamic free surface changes. Comparative analysis with physical experiments revealed the modified HBP model accurately captured debris flow behavior, free surface dynamics, and pressure field distributions under varying channel bed conditions. In summary, the modified HBP model overcomes limitations of traditional models by incorporating particle size distribution parameters, offering a more precise and versatile framework for debris flow rheology. This work provides a robust theoretical and numerical tool for advancing the prediction and mitigation of debris flow in engineering applications.

Rheological experiments on dense silty sediments under steady shear loadings

Rheological experiments on dense silty sediments under steady shear loadings

Supramolecular Gelation Based on Native Amino Acid Tyrosine and Its Charge-Transfer Complex Formation.

Self-assembly of amino acids and short-peptide derivatives attracted significant curiosity worldwide due to their unique self-assembly process and wide variety of applications. Amino acid is considered one of the important synthons in supramolecular chemistry. Self-assembly processes and applications of unfunctionalized native amino acids have been less reported in the literature. In this article, we are first-time reporting the self-assembly process of tyrosine (Tyr), an aromatic amino acid, in dimethyl sulfoxide (DMSO) solvent. Most of the studies related to Tyr self-assembly were reported in different aqueous solutions. In our work, we studied the self-assembly in several common organic solvents and found that Tyr could self-assemble into a supramolecular gel in dimethyl sulfoxide (DMSO) solvent. The self-assembly process was investigated by several techniques, such as UV-vis, fluorescence, FTIR, and NMR spectroscopy. Morphological features on the nanoscale were investigated through scanning electron microscopy (SEM). SEM images indicated the formation of nanofibrils with high aspect ratios. The supramolecular gel property was investigated by different rheological experiments. Computational study on the self-assembly process of Tyr in DMSO medium suggested that noncovalent interactions like hydrogen bonding and π-π stacking among the Tyr molecules played a prominent role. Finally, the charge-transfer complex formation ability of electron-rich Tyr with electron-deficient 2,3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ) was studied. In the presence of DDQ due to the charge-transfer complex formation, the supramolecular gel converted into a reddish color solution, and their fibrillar nanoscale morphologies collapsed.

Representing Structural Isomer Effects in a Coarse-Grain Model of Poly(Ether Ketone Ketone).

Carbon-fiber composites with thermoplastic matrices offer many processing and performance benefits in aerospace applications, but the long relaxation times of polymers make it difficult to predict how the structure of the matrix depends on its chemistry and how it was processed. Coarse-grained models of polymers can enable access to these long-time dynamics, but can have limited applicability outside the systems and state points that they are validated against. Here we develop and validate a minimal coarse-grained model of the aerospace thermoplastic poly(etherketoneketone) (PEKK). We use multistate iterative Boltzmann inversion to learn potentials with transferability across thermodynamic states relevant to PEKK processing. We introduce tabulated EKK angle potentials to represent the ratio of terephthalic (T) and isophthalic (I) acid precursor amounts, and validate against rheological experiments: The glass transition temperature is independent to T/I, but chain relaxation and melting temperature is. In sum we demonstrate a simple, validated model of PEKK that offers 15× performance speedups over united atom representations that enables studying thermoplastic processing-structure-property-performance relationships.

Exploring novel aspects of designed macromolecular structures on their interactions with cement and nano/microsilica particles and rheological properties

Various copolymers and novel branched terpolymers with different sulfonate ion and amine groups were prepared and characterized. Zeta potentials of cement slurries increased following the addition of synthesized polymers, indicating the effects of molecular weight, sulfonate ion and polyethylene glycol (PEG) branch. The rheology experiments revealed that it is possible to control the viscosity of cement slurries by varying the molecular structures of the resulting polymers. The formation of different networks through interactions between nano/microsilica and various polymer chains was accounted for the diversity in viscosity. The viscosity behavior of polymer-modified cement slurries was fit by the Generallized Newtonian Power-Law model. The results of SEM showed that polymer structures have an effect on the microstructure and morphology of cement, such as the dispersion, shape and size of hydrated calcium silicate (CSH) gels, as well as the dispersion of nano/microsilica particles. The presence of nano/microsilica particles along with various copolymers increased the hardness of the 1 and 7-day hydration cement. These results provide new ideas to control cement slurries properties using novel functional and branched polymers and nano/micro silica.

Fine-tuning the architecture of microgels by varying the initiator addition time.

Poly-N-isopropylacrylamide (PNIPAM) microgels are versatile colloidal-scale polymer networks that exhibit unique responsiveness to external stimuli, such as temperature. While the synthesis of PNIPAM microgels is well-documented, there is limited exploration of how their structural properties can be modified by subtle changes in the polymerization process. In this work, we carefully investigate how varying the time of addition of a common initiator, such as potassium persulfate, during the polymerization process allows a precise control over microgel architecture. Our findings, based on a combination of numerical simulations, scattering, and rheology experiments, reveal that delayed initiator addition results in a more heterogeneous network, characterized by a less extended corona. In contrast, more homogeneous microgels are obtained by adding the initiator all at the start of the synthesis. In this way, the internal mass distribution of the particles can be tuned, highlighting the importance of synthesis timing for optimizing microgel conformation and functionality in tailored applications.

Study of the Rheological Properties of Rubberized Asphalt Mortar: Mechanisms of Action of Rubber Powder and Filler–Binder Ratio

Rubber asphalt mortar is widely utilized in road engineering for its excellent high-temperature stability and low-temperature crack resistance, but the influence mechanisms of the rubber powder’s mesh size, content, and filler-to-binder ratio on its performance remain unclear. This study systematically evaluated these factors through viscosity testing, rheological experiments, and viscoelastic analysis. The results indicate that the rubber powder content and filler-to-binder ratio significantly affected the viscosity and rheological properties of the mortar, with the 40-mesh rubber powder demonstrating optimal stability. The grey correlation analysis revealed that the filler-to-binder ratio is the most critical factor, followed by the rubber powder content and mesh size. The findings suggest that optimizing the filler-to-binder ratio and rubber powder content, along with appropriate temperature control during construction, can significantly enhance the mortar’s performance, providing a scientific basis for road engineering applications.

Screen Printing Catalyst Inks With Enhanced Process Stability for PEM Fuel Cell Production

ABSTRACTCurrent state‐of‐the‐art coating techniques for PEM fuel cell electrode manufacturing such as slot‐die coating use closed ink reservoirs, allowing low boiling point solvents as the dispersion matrix for solid components of the catalyst ink. Applying such low boiling point inks to printing methods that expose catalyst inks to air, like flatbed screen printing, results in an instable and nonscalable production process due to the successive evaporation of these solvents. Within this study, a total of 12 different solvents are examined for process stability and electrochemical performance when applied with flatbed screen printing. Ink characteristics, such as contact angle, rheology, and sedimentation experiments, are quantified to reveal the most suitable set of solvents, enabling the use of open‐reservoir printing methods like flatbed screen printing. Additionally, electrochemical in situ characterization of catalyst‐coated membranes showed that 1,2‐propanediol and 1‐heptanol are solvents that combine process stability with high fuel cell performance.

Study on Fluidity and Deposition Characteristics of Air-Containing Filling Slurry.

With the continuous exploitation of global mineral resources, backfill technology for gob areas has become a crucial aspect of mine safety and sustainable development. As a primary method of gob area backfill, slurry backfill directly relates its flow properties and filling height to the efficiency and safety of mine extraction. To enhance the flow properties of the slurry and increase its filling height, a research study on the flow and deposition characteristics of a gas-containing filling slurry was conducted using a combination of theoretical analysis, laboratory experiments, and field tests. Experiments on the gas content were conducted using a concrete gas content tester, rheological property experiments were performed using a paddle rheometer, slump flow tests were carried out using a slump cone, and slurry deposition experiments were conducted using gob area similarity models. Analysis of viscosity characteristics revealed that the slurry gas content increased with the addition of air-entraining agents and the yield stress of the slurry decreased by 49.27% with an increase in the gas content at the same mix ratio, resulting in a 48% reduction in slurry viscosity. By analyzing the mechanism of gas phase enhancement on slurry flow, it was found that the anionic strength of bubbles generated by adding air-entraining agents was greater than the anionic strength within the slurry, changing the original particle arrangement and disrupting the tailings flocculation, thereby increasing the distance between floccules and enhancing the slurry's fluidity. Based on field tests, a semiindustrial flow and deposition experimental platform was established based on similarity theory, which found that the settlement rate of filling slurry with air-entraining agents decreased, improving the expansion ratio. This research is of significant importance for improving the effectiveness of the slurry backfill.

Rheology of polyacrylamide-based fluids and its impact on proppant transport in hydraulic fractures

Rheological experiments and measurements of particle settling velocity under static conditions were conducted for two types of polyacrylamide (PAA-based) fluids. The flow behavior of the viscoelastic fluids is described by a simplified, three-parameter model that integrates a constant viscosity at low shear rates with a power-law viscosity dependency at higher shear rates. The estimated dependencies of the rheological parameters and particle settling velocity on PAA concentration align with the classical power-law scaling for semi-dilute polymer solutions. The identified scaling offers valuable insight for optimizing the chemical composition of fracturing fluids, thereby improving the efficiency of hydraulic fracturing technology. By applying the lubrication approximation to the Navier–Stokes equations, a set of equations for the suspension flow in a vertical plane channel, characterized by the three-parameter rheology model, was derived. In typical fracturing conditions, the conventional power-law viscosity model used in current fracturing simulators significantly overestimates the gap-averaged apparent fluid viscosity compared to the proposed model. The novel model of the suspension flow aims to enhance the accuracy of proppant transport models applied in hydraulic fracturing simulators. Based on the three-parameter rheology model, a new model of particle settling in the studied PAA-based fluids is developed. It is based on smart Stokes' law, where viscosity is calculated according to either the plateau or power-law region, depending on the self-induced shear rate. The new model more accurately approximates experimentally determined settling velocity of proppant under static conditions across a broad range of PAA concentrations than existing models.