Shear Thinning Behavior Of Fluid Research Articles

Radial displacement patterns of shear-thinning fluids considering the effect of deformation

Radial injection of shear-thinning fluids into rock fractures is ubiquitous in subsurface engineering practices, including drilling, hydraulic fracturing, and rock grouting. Yet, the effect of injection-induced fracture deformation on radial displacement behavior of shear-thinning fluids remains unclear. Through radial injection experiments of shear-thinning fluids displacing an immiscible Newtonian fluid in a Hele–Shaw cell, we investigate the fracture deformation behavior during injection and the fluid–fluid displacement patterns under this impact. A mixed displacement pattern is observed where the invasion front gradually evolves from unstable (viscous fingering) to stable (compact displacement) as the injection proceeds. We demonstrate that the combined effect of shear-thinning property and radial flow geometry plays a controlling role in the evolution of the patterns. At high flow rates, the fracture dilation induced by high injection pressure tends to reduce the displacement efficiency in stages. Based on linear stability analysis, we propose a theoretical criterion for the transition of interfacial stability considering the viscosity of injected fluids and fracture deformation, which agrees well with the experimental observations. This research underscores the importance of rock deformation on two-phase flow dynamics in fractured media.

Biotechnological Effects of Advanced Smart-Bile Acid Cyclodextrin-Based Nanogels for Ear Delivery and Treatment of Hearing Loss.

Inner ear delivery requires safe and effective drug delivery vehicles incorporating high-viscosity formulations with permeation enhancers. This study designs novel thermoresponsive-smart polymer-bile acid and cyclodextrin-based nanogels for inner ear delivery. Nanogels are examined for their rheological and physical properties. The biocompatibility studies will be assessed on auditory and macrophage cell lines by investigating the impact of nanogels on cellular viability, mitochondrial respiration, glycolysis, intracellular oxidative stress, inflammatory profile, and macrophage polarization. Novel ther nanogels based on bile acid and beta-cyclodextrin show preserved porous nanogels' inner structure, exhibit non-Newtonian, shear-thinning fluid behavior, have fast gelation at 37°C and minimal albumin adsorption on the surface. The nanogels have minimal impact on cellular viability, mitochondrial respiration, glycolysis, intracellular oxidative stress, and inflammatory profile of the auditory cell line House Ear Institute-Organ of Corti 1 after 24h incubation. Nanogel exposure of 24h to macrophage cell line RAW264.7 leads to decreased viability, mitochondrial dysfunction, and increased intracellular ROS and inflammatory cytokines. However, polarization changes from M2 anti-inflammatory to M1 pro-inflammatory macrophages are minimal, and inflammatory products of RAW264.7 macrophages do not overly disrupt the survivability of HEI-OC1 cells. Based on these results, thermoresponsive bile acid and cyclodextrin nanogels can be potential drug delivery vehicles for inner ear drug delivery.

Effect of topographical pattern on vortex shedding and heat transfer phenomena in power-law fluid flow around a rotating cylinder

The present numerical investigation studies the momentum and heat transfer phenomena from a heated rotating patterned cylinder in the vortex shedding regime. In particular, the effect of surface patterns ( ω , δ ), fluid behavior ( 0.4 ≤ n ≤ 1.6 ), cylinder rotation speed ( 0.5 ≤ α ≤ 2 ), and Prandtl number ( 1 ≤ Pr ≤ 100 ) at Reynolds number 100 on the force coefficients and Nusselt number are studied. Vorticity and isotherm profiles demonstrate the flow dynamics and heat transfer characteristics. According to the findings of this study, the formation of the vortex (including its size, shape, and number of vortices) and the time period during which the vortex shedding pattern repeats itself demonstrates a dependency on the shape of the cylinder, fluid behavior, and rotating speed. It has been noted that a significant decrease in the frequency of vortex shedding occurs on adding topographical patterns. Additionally, it has been noticed that on increasing rotational speed, vortex shedding can be suppressed for all fluid behaviors. Numerical simulation results reveal that the average drag coefficient ( C ¯ D ) for a rotating patterned cylinder decreases with increasing rotational speed ( α ), and it further reduces on increase in pattern frequency ( ω ) and amplitude ( δ ) compared to a smooth circular cylinder. The shear-thinning fluid behavior helps to dissipate the heat from the cylinder to the surrounding fluid. Conversely, shear-thickening fluid behavior exhibits the opposite trend.

Effect of different oleogelation mechanisms on physical properties and oxidative stability of macadamia oil-based oleogels and its application

In this study, macadamia oil-based oleogels were prepared with four low molecular weight oleogelators: beeswax (BW), monoglyceride stearate (MG), rice bran wax (RBW), and a mixture of γ-oryzanol and β-sitosterol (SO). The physicochemical properties of these oleogels were evaluated by polarized light microscopy, Fourier transform infrared spectroscopy, differential scanning calorimetry, X-ray diffraction, texture and rheological analysis. Results indicated that the van der Waals force and hydrogen bond interaction existed mainly in MG- and SO-based oleogels, while only van der Waals force interaction observed in RBW- and BW-based oleogels. SO-based oleogels presented superior hardness, oil binding ability and oxidative stability, attributed to the formation of strong polymer network structure. Additionally, all four oleogels demonstrated stable crystal structures and solid-state shear-thinning fluid behavior, with SO-based oleogels displaying higher viscosity. Meanwhile, the feasibility of oleogel as a substitute for cocoa butter (CB) was explored, found that all of oleogels proved effective substitutes for CB in chocolate preparation. The rheological parameters of the oleogel-based chocolates, except for 50%BW oleogel, fell within the range of Casson plastic viscosity and yield stress for chocolate, and exhibited excellent heat tolerance. The results provide a novel strategy for utilization of macadamia oil and the development of heat-resistant chocolate.

Application of Taro (Colocasia esculenta) Mucilage as a Promising Antimicrobial Agent to Extend the Shelf Life of Fresh-Cut Brinjals (Eggplants).

Taro rhizomes are a rich source of polysaccharides, including starch and mucilage. However, mucilage has excellent anti-microbial efficacy, and unique gel-forming and techno-functional properties. Therefore, this study aimed to extract and utilize taro mucilage (TM), which is viscous and has a gel-like texture, for the shelf-life enhancement of fresh-cut brinjals (eggplants). Mucilage was extracted using hot-water extraction and the yield was calculated to be 6.25 ± 0.87% on a dry basis. Different formulations of coating gel solutions were prepared: 1, 2, 3, 4, 5, 6, and 7%. The selection of the coating gel solution was carried out based on particle size. The smallest particle size was observed in treatment T5 (154 ± 0.81 nm) and zeta potential -27.22 ± 0.75 mV. Furthermore, cut brinjals were coated with the prepared mucilage gel solution and this showed a significant effect on the overall physicochemical properties of cut brinjals. Maximum weight loss occurred on the 10th day (12.67 ± 0.24%), as compared with coated brinjals (8.99 ± 0.42%). Minor changes were observed in pH, for the control sample significantly decreased from 4.58 ± 0.45 to 2.99 ± 0.75 on the 0th day to the 10th day, respectively. Titrable acidity of coated and uncoated cut brinjals was found to be at 0.31 ± 0.44% on the 0th day, which increased up to 0.66 ± 0.20% for the control and 0.55 ± 0.68% for coated brinjals on the 10th day. The taro mucilage coating gel (TMCG) solution showed pseudo-plastic behavior or shear-thinning fluid behavior. FTIR data confirmed the existence of several functional groups including various sugars, proteins, and hydroxylic groups. Antioxidant activity of coated and uncoated cut brinjals was found to be 22.33 ± 0.37% and 22.15 ± 0.49%, respectively. The TMCG solution showed effective results towards the various food pathogenic microorganisms. Overall, it is a natural, renewable resource that is biodegradable. This makes it an environmentally friendly alternative to synthetic additives or thickeners. It is cost effective, easily available, eco-friendly, and non-toxic. This can be an attractive feature for consumers looking for sustainable and eco-friendly options.

Effects of dielectric barrier discharge plasma modification on structure, physicochemical and functional properties of watermelon peel pectin

Dielectric barrier discharge (DBD) plasma is a simple and green method for biomacromolecule modification, and watermelon peel pectin (WMP) has broad application prospect in food industry. This study investigated the effects of DBD plasma under different voltage (20 V, 40 V) and treatment time (1 min, 3 min, 5 min) on the structural, physicochemical and functional properties of WMP. The DBD plasma treatment (40 V, 5 min) exhibited the lowest molecular weight (Mw, 199.06 ± 8.05 kg/mol), average molecular weight (Mn, 27.15 ± 1.75 kg/mol), degree of methylation (DM, 36.18 ± 0.65%) and acetylation (DA, 2.33 ± 0.09%) of WMP. Moreover, DBD plasma treatment could degrade the main chain of WMP, and had less effect on the side chain. The microstructure of WMP changes from dense block structures to porous and thin fibrous, while pectin molecules are degraded and oxidized after DBD plasma treatment. Compared with the native WMP, DBD plasma treatment at different modes effectively increased the thermal stability, antioxidant ability, solubility and emulsifying properties of WMP, but lowered its shear thinning fluid behavior and liquid-like property. Conclusively, our results show that DBD plasma is a promising way to modified and improve functional properties of WMP.

Investigation of flocculation and rheological properties of microalgae suspensions cultivated in industrial process wastewater

Microalgae harvesting at an industrial scale remains a techno-economic bottleneck for large-scale microalgae production that can account for up to 30% of the total cost ofbiomass production. A wide range of harvesting techniques have been applied commercially, among which, coagulation-flocculation techniques prove to be both convenient and cost-effective as pre-treatment techniques used in conjunction with other methods. In this study, process wastewater acquired from onshore natural gas facilities in Qatar was utilized to cultivate freshwater microalgae specie Scenedesmus sp. for simultaneous pollution abatement and biomass harvesting applications. Scenedesmus sp. was cultivated in two growth phases (fast and slow growth phases) to examine the influence of the microalgae growth phase on the flocculation process and rheological behavior. Effective flocculation was achieved using a commercial high charge density and high molecular weight cationic polyacrylamide-based flocculant. Flocculation efficiencies exceeded 97% for both fast and slow growth phase suspensions at an optimum flocculant dose of 10 mg/L. Optimum conditions were well corroborated by residual turbidity and zeta potential measurements. For fast growth phase suspensions, the optimum PAM dose coincided with a minimum residual turbidity of 2.35 NTU and a zeta potential of −0.52 mV. Similarly, the optimum PAM dose was fixed based on a minimum residual turbidity of 2.30 NTU and a zeta potential of +0.63 mV for slow growth phase suspensions. Large, easily settleable and compact flocs were obtained with average D50 values of 70.7 μm and 142.0 μm recorded for fast and slow growth phase suspensions, respectively, at optimum PAM dose. Moreover, based on rheological characterization studies, the flocculated suspensions demonstrated an overall non-Newtonian pseudoplastic (shear thinning) fluid behavior. Introduction of cationic PAM significantly improved the viscosity and yield stress of the flocculated suspensions around the optimum PAM dose range. At the optimum PAM dose, the initial viscosities were recorded as 10.37 and 39.19 mPa.s with yield stresses of 12.84 and 16.59 N/m2 for fast and slow growth phase suspensions, respectively. The flocculated biomass further displayed a viscoelastic solid (gel) behavior, characterized by high gel strength and resistance to shearing around optimum flocculant doses. At the optimum PAM dose, the storage moduli were recorded as 886.2 and 1068.6 mPa for fast and slow growth phase suspensions, respectively.

Direct dissolution of unbleached pulp from corncob and wheat straw in N-methylmorpholine-N-oxide

Lignocellulose, as a kind of abundant natural resource, continuously developed to convert high value-added biological products is of great significance. Herein, we report a N-methylmorpholine-N-oxide (NMMO) solvent system to completely dissolve unbleached pulp to prepare a renewable lignin-containing cellulose film. The viscosity of the completely dissolved cellulose solution was measured using a high-pressure rotary rheometer. The shear viscosity exceeded 85 Pa·s at a shear rate of 1.62 s−1. It exhibited shear-thinning non-Newtonian fluid behavior with increasing shear rate. CF-WS had excellent tensile strength (>73 MPa), and exhibited unique optical properties of high transmittance in the visible region and high shielding performance in the ultraviolet region. When the thickness is only 0.016 mm, the UV shielding rate exceeds 75 % (λ < 380 nm). The structure of the bioplastic was revealed by SEM, XPS, and Raman spectroscopy. Directly dissolving lignocellulose in NMMO aqueous solution is expected to yield bioplastics with high strength and biodegradability. It is a potential substitute for petrochemical plastics and provides a possible way for the utilization of agricultural waste.

Effect of power law on viscous fingering behavior of shear-thinning fluid in a lifted hele-shaw cell

Effect of power law on viscous fingering behavior of shear-thinning fluid in a lifted hele-shaw cell

Ultrasonication for preparing high-performance phase change material nano-emulsions: Optimization and characterization

This work was aimed to optimize the formulation of phase change material nano-emulsions by ultrasonic emulsification that has not been investigated systematically. The optimization was performed using response surface methodology on two response parameters, average droplet size and apparent viscosity, and three independent variables including ultrasonic amplitude (X1), treatment time (X2), and surfactant content (X3). The significance of three variables on both droplet size and apparent viscosity followed the order of X3 > X1 > X2. At the optimal variable levels (X1 = 58 %; X2 = 9 min; X3 = 8 wt%), the droplet size of 118.2 nm and apparent viscosity of 7.3 mPa·s were predicated by the regression model and also well verified by experiments. The 25 wt% phase change nano-emulsion formed by ultrasonication exhibited the best emulsion stability and the lowest apparent viscosity compared with those formulated by high-energy rotor-stator homogenizer and low-energy method of phase inversion temperature. In addition, the rheological behavior associated with the average droplet size and the solid/liquid state of phase change material was illustrated numerically for the first time. In general, a threshold of 170–180 nm was found for the transition of liquid-in-water emulsions from a shear-thinning non-Newtonian fluid to a Newtonian fluid in the shear rate range of 0.6–73 s−1. All solid-in-water suspensions showed shear-thinning fluid behavior, though the shear-thinning degree was dramatically reduced to a flow behavior index of about 0.95 as the particle size was below 100 nm. These findings may be useful for designing high-performance phase change material nano-emulsions with long service life, high energy storage capacity, and low pumping power consumption for applications.

Novel high energy media mill produced macadamia butter: Effect on the physicochemical properties, rheology, nutrient retention and application

A novel high energy media mill (HEMM) was used to prepare macadamia butter (MB). The effect of grinding time on the properties of MB was investigated. Results showed that with the grinding time increased from 0 min to 65 min, the D[3,2], D[4,3], D50 and D90 value of the MB samples were gradually decreased from 24.03, 68.48, 59.50, and 124.67 μm to 4.37, 14.25, 8.82, and 34.07 μm, respectively, and the release of volatile flavor compounds gradually increased. Moreover, it did not adversely impact the color and chemical composition. Rheological analysis showed that the viscosity and yield stress of MB gradually decreased with the increasing of grinding time and the non-Newtonian shear thinning fluid behavior (flow behavior index, n < 1) was observed. In addition, HEMM treatment result in more oil separation and poor spreadability of MB. The maximum oil separation rate reached 49.46 g/100 g after 65 min of grinding. However, the addition of 1–3 g rice bran wax/100 g can significantly improve its oil separation and spreadability in toast. The results can provide a support for the application of HEMM in MB processing, and new insights for the development of multi-purpose MB.

On enhancing interfacial mass transport through microextraction in dispersed droplet systems

The physio-chemical hydrodynamics and the solute transport around a translating dispersed drop are often multicomponent and multiphase systems. When such a dispersed droplet system is out of the thermodynamic equilibrium, steep momentum and concentration gradients are developed around the interface leading to rapid flow and solute transport. In broader perspectives, the dispersed droplet system has direct/indirect relevance to addressing the technological challenges in the 21st century, namely, energy storage, hydrogen production, CO2 capture, biofuel production, chemical analysis, diagnosis extraction, and drug delivery. Environmental engineering challenges include flotation and separation technology, inkjet printing, coatings, and paints. The most challenging issue in such applications is enhancing the transport rate from the droplet to the bulk of the fluid. In this work, we have proposed a novel method to foster the transport of solute from the drop to the bulk fluid by altering the viscosity of the bulk fluid. We have exploited the shear-thinning behavior of the fluid in bulk to reduce the viscous losses and resistances to the mass transfer. A linear thermodynamic equilibrium relation at the fluid-fluid interface is considered. The scant prior experimental results were observed to agree with the present findings. Therefore, the extensive numerical findings are presented for the ranges of pertinent parameters such as Reynolds number, (1≤Re≤75) Peclet number, (10≤Pe≤103), internal to external fluid diffusivity ratio, (0.5≤dratio≤4), dispersed to continuous fluid viscosity ratio, (0.25≤μratio≤4) and power-law index, (0.4≤n≤1). The drag coefficient exhibits an increase of 180% with the increase in the μratio as well as with the n at the maximum convective regime. The Sherwood number exhibits a positive dependence on the Reynolds number, Peclet number, and the diffusivity ratio. On the contrary, the viscosity ratio lowers the transport of species from the droplet to the fluid due to the reduced internal circulations inside the droplet. Shear-thinning fluid behavior offers a higher extraction efficiency than the Newtonian fluid (upto 30% increase in at low Pe). Finally, simple predictive correlative equations have been proposed for the drag coefficient and the average Sherwood number over the conditions considered here.

Experimental Study on a Superstable Nano-TiO2 Deep Eutectic Solvent Nanofluid for Solar Energy Harvesting

Nanofluids have emerged as an important working fluid for various heat transfer and thermal energy transportation demands thanks to its promising thermal conductivity. While, poor static stability brought by segregation of nanoparticle heavily hinders its wide practical utilization. In this work, a novel “one-pot one-step” strategy was realized to generate a superior stable nanofluid which can stand uneventfully for at least 2 months without observation of any sedimentation with tetrabutyl titanate as a TiO2 precursor in glycerol/chlorine chloride deep eutectic solvents. Mechanism study reveals that the good stability of this nanofluid is mainly attributed to in situ formation protocol for which the inherent aggregation of TiO2 can be theoretically avoided. Meanwhile, thermophysical properties, such as viscosity, thermal conductivity, and rheological behavior, were comprehensively studied, which indicates that the obtained nanofluids exhibit a non-Newtonian shear thinning fluid behavior with a thermal conductivity enhancement ratio up to 9.0%. More importantly, photothermal conversion efficiency of the nanofluid could reach 51.2%, and the efficiency enhancement is 181.9% over the pristine deep eutectic solvents. This work paves a novel avenue for fabricating nanofluids with super static stability and gives a supplementary idea for “one-step” nanofluids preparation process.

Oxidized yeast β-glucan: Rheological behaviors and the formation of entanglement network at different oxidation degree

This work investigated the rheological properties of oxidized yeast β-glucans (OYG) with three different oxidation degrees (15.2%, 47.3% and 71.2%). Firstly, the intrinsic viscosities of OYG2 and OYG3 calculated by Huggins and Kraemer equations were 104 and 214 mL/g, respectively. Steady-state shear test showed that the OYG solutions exhibited shear-thinning behavior of pseudoplastic non-Newtonian fluid when concentration (c) was greater than 5 mg/mL and OYG1 had the highest apparent viscosity. By fitting viscosity data to the Cross model, the critical overlap concentration (c*) were determined to be 4.69, 3.79 and 2.25 mg/mL for OYG1, OYG2 and OYG3, respectively. From the results of dynamic frequency sweep test, the storage modulus (G′) and the loss modulus (G″) were greatly dependent on frequency and concentration, and OYG solutions represented the feature of structural fluid, an entanglement network at c ≥ 5 mg/mL. Micro-rheological test revealed that the OYG1 solutions were dominated by viscoelasticity at c ≥ 13 mg/mL and the Fluidity Index (FI) decreased with increasing concentration, indicating the increase in elasticity and viscosity. Meanwhile, as the concentration increased from 13 to 20 mg/L, shorter time and lower temperature were required for OYG1 to form a gel, as indicated as they decreased from 53′21″ and 78.60 °C to 41′34″ and 67.40 °C, respectively. Results of temperature ramp test illustrated a thermo-irreversible characteristic of OYG1/water system. The findings suggest that OYGs can be potentially employed in food or cosmetic products for various applications as thickener, stabilizer and so on.

Impact of Non-Newtonian Fluids' Rheological Behavior on Double- Diffusive Natural Convection in an Inclined Square Porous Layer

In the current study, natural convection is numerically simulated in a shallow, porous, square cavity that is filled with a non-Newtonian fluid. In terms of temperature and concentration gradients (heat and mass fluxes), the active wall was seen as uniform and constant, whereas the other walls are adiabatic and impermeable. To analyze the behavior of shear-thinning fluids, a Carreau-Yasuda model is utilized, which is suitable for many non-Newtonian fluids. It is presummated that the fluid will fulfill the Boussinesq approximation, be laminar, and be incompressible.

High-pressure induced structural modification of porcine myofibrillar protein and its relation to rheological and emulsifying properties

Here, we investigated the effects of high-pressure homogenization (HPH) on the physicochemical, rheological, and emulsifying properties of myofibrillar proteins (MFPs). The mean particle size of MFPs treated by HPH with different pressures (0–150 MPa) decreased from 886.0 ± 120.2 nm to 172.6 ± 13.7 nm with increasing HPH pressure. In addition, more uniform and homogeneous protein particles were obtained as the HPH pressure was increased. In SDS-PAGE, the band intensities of high molecular weight proteins (200 kDa) decreased and the intensities of some of the smaller molecular fractions (70–120 kDa) increased when the MFPs were subjected to HPH treatment at more than 60 MPa owing to the fragmentation of high molecular weight proteins, such as myosin heavy chains. The surface hydrophobicity of MFPs increased with increasing HPH pressure owing to the exposure of buried hydrophobic groups by protein unfolding. In the rheological study, the MFP dispersions exhibited shear thinning fluid behavior, but the MFP dispersion homogenized at high pressure (120–150 MPa) presented close to Newtonian fluid behavior with low viscosity. The emulsifying activity (EA) and emulsion stability index (ESI) of MFPs improved with increasing HPH pressures. The MFPs treated with HPH at different pressures were used for o/w emulsion preparation, and their dispersion stabilities were investigated during storage. The emulsion systems stabilized with MFPs pressurized at more than 60 MPa showed comparatively less cream formation in the top layer, indicating high dispersion stability.

Deacetylation and Desuccinylation of the Fucose-Rich Polysaccharide Fucopol: Impact on Biopolymer Physical and Chemical Properties.

FucoPol is an acylated polysaccharide with demonstrated valuable functional properties that include a shear thinning fluid behaviour, a film-forming capacity, and an emulsion forming and stabilizing capacity. In this study, the different conditions (concentration, temperature, and time) for alkaline treatment were investigated to deacylate FucoPol. Complete deacetylation and desuccinylation was achieved with 0.02 M NaOH, at 60 °C for 15 min, with no significant impact on the biopolymer's sugar composition, pyruvate content, and molecular mass distribution. FucoPol depyruvylation by acid hydrolysis was attempted, but it resulted in a very low polymer recovery. The effect of the ionic strength, pH, and temperature on the deacetylated/desuccinylated polysaccharide, d-FucoPol, was evaluated, as well as its emulsion and film-forming capacity. d-FucoPol aqueous solutions maintained the shear thinning behaviour characteristic of FucoPol, but the apparent viscosity decreased significantly. Moreover, contrary to FucoPol, whose solutions were not affected by the media's ionic strength, the d-FucoPol solutions had a significantly higher apparent viscosity for a higher ionic strength. On the other hand, the d-FucoPol solutions were not affected by the pH in the range of 3.6-11.5, while FucoPol had a decreased viscosity for acidic pH values and for a pH above 10.5. Although d-FucoPol displayed an emulsification activity for olive oil similar to that of FucoPol (98 ± 0%) for an oil-to-water ratio of 2:3, the emulsions were less viscous. The d-FucoPol films were flexible, with a higher Young's modulus (798 ± 152 MPa), a stress at the break (22.5 ± 2.5 MPa), and an elongation at the break (9.3 ± 0.7%) than FucoPol (458 ± 32 MPa, 15.5 ± 0.3 MPa and 8.1 ± 1.0%, respectively). Given these findings, d-FucoPol arises as a promising novel biopolymer, with distinctive properties that may render it useful for utilization as a suspending or emulsifier agent, and as a barrier in coatings and packaging films.

Ultrasonic effects on molecular weight degradation, physicochemical and rheological properties of pectin extracted from Premna microphylla Turcz

The high molecular weight and poor solubility of pectin extracted from Premna microphylla Turcz (PEP) limits its application. Therefore, in this paper, the degradation effects of PEP under ultrasound irradiation and the influences of ultrasonic on the PEP processing characteristics were investigated. The results indicated that the Mw of PEP decreased significantly with a narrow distribution after ultrasonic treatment. The degradation kinetics of PEP at different ultrasound intensities were sufficiently described by the 2nd-order kinetics eq. X-ray diffraction (XRD) and scanning electron microscopy (SEM) analysis suggested that ultrasonic treatment destroyed the ordered structure inside the PEP, resulting in a looser microscopic morphology. Compared with the control, the thermal stability of PEP was significantly boosted after ultrasonic treatment. Rheological analysis illustrated that the sonicated PEP presented lower apparent viscosities than the original PEP. While the elasticity and thermal reversibility of the degraded products was enhanced. Ultrasonic treatment prominently weakened its shear thinning fluid behavior and thixotropy, thus improved its processing quality. Therefore, desirable PEP can be prepared by ultrasonic irradiation. The results can provide a reference for the development and application of PEP.

Highly stable GO/formamide based GOLLCs for free standing film fabrication and their photodegradation applications against organic dyes

In this context, formamide is explored as an efficient solvent for the dispersion of GO sheets and preparation of graphene oxide lyotropic liquid crystals (GOLLCs). Polarizing optical microscopy (POM) studies confirm that GO/formamide dispersion shows smectic phase at lower concentration (< 2 mg/mL) and nematic phase up to 300 mg/mL. GOLLCs are found stable for up to 24 months. Probably it is the first report on the formation of GOLLCs in formamide and their long-term stability up to 24 months. GOLLCs are studied for steady and dynamic rheological behavior at room temperature. All the GOLLCs exhibit shear-thinning fluid behavior under the shear rate 1–100 s−1. Dynamic rheology reveals that GOLLCs follow solid viscoelastic behavior till 20 mg/mL concentration and then depict long range viscoelastic behavior at higher concentrations. Complex moduli behavior of GOLLCs has been studied to predict their elasticity. The scaling analysis of tunable viscoelastic GOLLCs is computed from Er=Ax−xc4.43. The free-standing film is prepared via thermal treatment method from 2 mg/mL GOLLCs and studied for structural and photocatalytic degradation behavior. rGO film shows 99.18% and 97.87% degradation efficiency for malachite green and methyl orange organic dyes respectively under UV light and is found stable up to 3 cycles.

Electroosmotic transport and current rectification of viscoelastic electrolyte in a conical pore nanomembrane

Nanomembranes have received a wide range of applications in water treatment, gas separation, molecular and supramolecular separations. Nanopores offer the separation of the components even at nano- or picomolar concentrations. In addition, DNA translocation, DNA sequencing of nucleotides, single molecular analyses for biomedical nanoscopic devices are perhaps the unique feature of nanomembranes that convectional membranes may not achieve. Despite such an overwhelming application, the theoretical understanding of electroosmotic transport in nanopores is still in infancy and it is limited to simple Newtonian-like fluids. This work has numerically investigated the ionic current rectification (ICR) in a conical nanopore filled with viscoelastic electrolyte. ICR quantifies the unequal upstream and downstream ionic flow rates during the forward and reverse potential bias. This is similar to a semiconductor transistor’s current potential (I−V) response. The ICR exhibits several potential applications in the design of biosensors for the measurement and analysis of biofluids such as blood, lymph, and plasma, micro-scale pumping devices, ion-selective membranes, etc. The electroosmotic flow (EOF) in the conical nanopore of Carreau fluid is investigated by solving a set of Poisson, Nernst–Planck, and momentum equations to account for the electric potential, transport of ionic species, and velocity field. The behaviors of ICR in Carreau fluid are examined by varying the shear-thinning index (0.6≤n≤1), Debye length (1≤κRt≤50), Deborah number (1≤De≤100), and applied electric potential (−50≤V≤50). The electroosmotic flow is observed to be significantly stronger in shear-thinning fluids. All else being equal, the volumetric flow rate increases several folds in shear-thinning fluids. Shear-thinning fluid behavior enhances the magnitude of the current in the conical nanopore.