Experimental study on the rheological behavior of nanolubricant-containing MCM-41 nanoparticles with viscosity measurement

In this study, the rheological behavior and viscosity of a stable nanofluid, which is prepared with the suspension of MCM-41 nanoparticles in SAE40 engine oil as base fluid, would be presented. Two-step method has been used to stabilize the nanoparticles in engine oil. To obtain structural and morphological properties of the synthesized nanoparticles, small-angle X-ray scattering, N₂ adsorption/desorption analysis and scanning electron microscopy have been done. Then, viscosity of nanofluids has been measured in temperature range of 25–55 °C, shear rates up to 13,000 s^?1 and different concentrations (0 mass%, 0.5 mass%, 1 mass%, 3 mass% and 5 mass% of MCM-41 nanoparticles). For all the samples, the shear stress versus shear rate diagrams showed that SAE40 oil has Newtonian behavior, in which adding mesoporous silica nanoparticles causes non-Newtonian or pseudoplastic behavior. The results declared that viscosity decreases with increasing temperature and increases with an enhancement in concentration. Furthermore, based on experimental results, an accurate correlation has been proposed to predict the viscosity of SAE40/MCM-41 nanolubricants.

     

Synthesis of a novel comb-like copolymer used as dispersant in organic solvent and influence of free comb-like copolymer on CaCO3 suspension

A novel comb-like copolymer poly (1e)-graft-poly (ε-caprolactone) (SMA-g-PCL, SP), which can be used as an effective CaCO₃ dispersant in organic solvent, was prepared via the esterification reaction between SMA and PCL. The structures and compositions of the graft copolymer were determined by Fourier transform infrared spectrometry (FTIR), H-nuclear magnetic resonance (¹H NMR), and gel permeation chromatography (GPC), respectively. The influences of free comb-like copolymer on CaCO₃ suspension viscosity and rheological behavior were investigated. It was found that the particle-binding bridge generated among CaCO₃ particles through hydrogen bonding and/or electrostatic interactions increased the suspension viscosity as well as the depletion flocculation. On the other hand, it was noteworthy that the free comb-like copolymer could make the CaCO₃ suspension evolve from shear-thinning fluid or nearly Newtonian fluid into shear-thickening fluid. It was attributed to the formation of a transient network through intermolecular associations between the adsorbed SP and the free polymer chains under the action of shear. Finally, the fitting parameters from the Herschel–Bulkley model were in good agreement with the evolution of the rheological behavior of CaCO₃ suspension.     

Synthesis and characterization of cubic cobalt oxide nanocomposite fluids

Narrow size distribution cubic Co₃O₄ nanoparticles were synthesized and rheological properties of suspensions of the cubes in oligomeric polyethylene glycol (PEG) were explored over a range of particle volume fractions and rotational shear flow conditions. At low and high particle volume fractions, the relative viscosity of the suspensions is described by a Krieger–Dougherty formula with an intrinsic viscosity consistent with expectations for suspensions of ideal cuboids. At intermediate to high particle loadings, the suspensions manifest complex rheological behavior, including shear thinning and shear-thickening features. These observations are discussed in terms of the charge carried by the cubes and the shear rate/volume fraction dependency of the transition from shear thinning to shear thickening.     

Rheological properties of surface-modified nanoparticles-stabilized CO2 foam

This study investigates the rheological properties of surface-modified nanoparticles-stabilized CO₂ foam in porous media for enhanced oil recovery (EOR) applications. Due to the foam pseudo-plastic behavior, the foam apparent viscosity was estimated based on the power law constitutive model. The results show that foam exhibit shear-thinning behavior. The presence of surface-modified silica nanoparticles enhanced the foam bulk apparent viscosity by 15%. Foam apparent viscosity in the capillary porous media was four times higher than that in capillary viscometer, and foam apparent viscosity increased as porous media permeability increases. The high apparent viscosity of the surface-modified nanoparticles-stabilized foam could result in effective fluid diversion and pore blocking processes and enhance their potential applications in heterogeneous reservoir.     

Dispersion stability and rheological behavior of suspensions of polystyrene coated fumed silica particles in polystyrene solutions

Polystyrene coated silica（SiO₂@PS） core-shell composite particles with averaged diameter of about 290 nm were prepared by in situ emulsion polymerization of styrene on the surface ofγ-methacryloxypropyltrimethoxysilane grafted SiO₂ nanoparticles of 20-50 nm in diameter.Rheological behavior and dispersion stability of SiO₂@PS suspension in 10 wt%PS solution were compared with suspensions of untreated SiO₂ and silane modified SiO₂ nanoparticles.Suspensions of the untreated and the silane modified SiO₂ exhibited obvious shear thinning.The SiO-2@PS suspension exhibits shear viscosity considerably smaller than suspensions of untreated and silane modified SiO₂ at low shear rates.Transmission electron microscopy showed that the composite particles can uniformly and stably disperse in PS solution compared to other suspensions,implying that the PS shell can effectively enhance the particle compatibility with PS macromolecules in solution.     

A Study of the Influence of Nanoparticles on the Properties of Drilling Fluids

The effect of nanoparticles with different compositions and sizes on the rheological properties, filtration losses, and lubricating ability of drilling fluids has been experimentally studied. Nanoparticles of silicon, aluminum, and titanium oxides have been examined, while an aqueous bentonite suspension with a solid phase mass fraction of 5% has been used as a basic model of a drilling fluid. The concentrations and sizes of nanoparticles in the drilling fluids have been varied from 0.25 to 2 wt % and from 5 to 100 nm, respectively. It has been shown that the addition of nanoparticles substantially changes the properties of the drilling fluids. In contrast to suspensions of particles with macro- and microscopic sizes, the rheological parameters, filtration losses, and lubricating and sticking abilities of the suspensions containing nanoparticles depend on the size and nature of the latter and vary markedly already at low nanoparticle concentrations.     

Phase state and rheology of organosilicon nanocomposites with functionalized hyperbranched nanoparticles

The phase equilibrium in a system of linear polydimethylsiloxane–functionalized nanoparticles 1.2–2.2 nm in size with a core made of hyperbranched silica and a periphery of decyl groups has been studied by laser interferometry method. Phase diagrams of the studied systems fit the amorphous phase equilibrium with UCST increasing with the nanoparticle size. The mixtures present nanoparticle solutions in the linear polymer or emulsions of a saturated solution of one component in a saturated solution of other component depending on the components ratio. Dilute, concentrated, or highly concentrated dispersions show individual features of the rheological behavior. For each colloid chemical and phase states of mixtures, the viscosity and viscoelastic properties have been investigated in a wide temperature range. The obtained results have been compared with the previous data for mixtures of decylated nanoparticles and polyisobutylene.     

Molecular architecture and rheological characterization of novel intramolecularly crosslinked polystyrene nanoparticles

Novel polystyrene nanoparticles were synthesized by the controlled intramolecular crosslinking of linear polymer chains to produce well‐defined single‐molecule nanoparticles of varying molecular mass, corresponding directly to the original linear precursor chain. These nanoparticles are ideal to study the relaxation dynamics/processes of high molecular mass polymer melts, as the high degree of intramolecular crosslinking potentially inhibits entanglements. Both the nanoparticles and their linear analogs were characterized by measuring their intrinsic viscosity, hydrodynamic radius (R_h), and radius of gyration (R_g). The ratio R_g/R_h was computed to characterize the molecular architecture of the nanoparticles in solution, revealing a shift toward the constant density sphere limit with increasing crosslink density and molecular mass. Further, confirming particulate behavior, Kratky plots obtained from neutron scattering data show a shift toward particle‐like nature. The rheological behavior of the particles was found to be strongly dependent on both the extent of intramolecular crosslinking and molecular mass, with a minimal viscosity change at low crosslinking levels and a gel‐like behavior evident for a large degree of crosslinking. These and other results suggest the presence of a secondary mode of polymer relaxation/movement besides reptation, which in this case, is influenced by the total number of crosslinked loops present in the nanoparticle. © 2006 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 44: 1930–1947, 2006     

Viscoelasticity of Shear Thickening Fluid Based on Silica Nanoparticles Dispersing in 1-butyl-3-methylimidizolium Tetrafluoroborate

The viscoelasticity of shear thickening fluid (STF), a crucial property in the protective composite applications, with different silica nanoparticle concentrations in ionic liquid, 1-butyl-3-methylimidizolium tetrafluoroborate ([C₄min]BF₄), was studied at different temperatures and with shear frequencies through oscillatory shear, respectively. All STFs present strain thickening behavior. With increasing silica nanoparticle concentration, the critical shear strain for the onset of strain thickening decreased, while the complex viscosity, storage modulus, and loss modulus increased significantly. The critical shear strain increased with an increase of temperature, while the complex viscosity, storage modulus, and loss modulus decreased notably. The critical shear strain was constant with increasing the frequency of strain, while the complex viscosity decreases slightly. The storage modulus and loss modulus were independent with frequency in the strain thickening region. Nanoparticle clusters leading to strain thickening were demonstrated. The viscoelastic response of STFs to varying silica nanoparticle content, temperature, and frequency investigated here will help to design the specific application of STFs in soft protective composites and damping devices.     

Influence of cellulose nanofibers on the rheological behavior of silica-based shear-thickening fluid

In this work, the influence of cellulose nanofibers (CNFs) on the rheological behavior of silica-based shear-thickening fluid (STF) is investigated. CNFs of 150–200 nm in diameter were extracted from cotton fibers using a supermasscolloider. CNF-reinforced STF of different concentrations (0.1–0.3 wt.%) was prepared via an ultrasonication technique. The presence of CNFs and their interaction with the silica nanoparticles in the STF were analyzed using SEM and FTIR. The addition of a minute quantity of CNF to the STF (0.3% CNF-reinforced STF) caused a marked increase in the peak viscosity, from 36.8 (unmodified STF) to 139.0 Pa s (0.2% CNF-reinforced STF), and a concomitant decrease in the critical shear rate from 33.45 to 14.8 s^?1 . The presence of a large number of hydroxyl groups on the CNFs enhanced their interaction with the nanoparticles via hydrogen bonding, which induced shear thickening. The mechanism of the interaction between silica nanoparticles and CNF was also demonstrated. Oscillatory dynamic rheological analysis showed that the addition of even a small amount of CNF led to higher elastic behavior in the system at lower shear rates. In contrast, a more viscous nature was demonstrated at higher angular frequencies. As the concentration of  nanofibers in the STFs increased, the crossover point between storage and loss modulus shifted to higher angular frequencies, implying stronger interaction between the constituents of the STF. The dynamic viscosity profile of all samples also exhibited shear-thickening behavior.     

Rheological and electrical properties of polypropylene/MWCNT composites prepared with MWCNT masterbatch chips

Melt compounded PP/MWCNT (polypropylene/multi-walled carbon nanotube) composites were prepared by diluting highly concentrated masterbatch chips. Maleic anhydride grafted polypropylene (PP-g-MAH) was used as a compatibilizer to promote dispersion and interaction of MWCNTs. Rheological properties were investigated with respect to the MWCNT and compatibilizer loadings, and related to morphological and electrical properties. As the MWCNT loading was increased, shear viscosity and yield stress were increased at low shear rate region because of increased interaction between MWCNT particles. When the MWCNT loading was low, MWCNT dispersion was improved by the PP-g-MAH compatibilizer because MWCNTs were wetted sufficiently due to the presence of the compatibilizer. However, rheological and electrical properties of highly concentrated MWCNT composites with the compatibilizer were not improved compared with PP/MWCNT composites without the compatibilizer because the compatibilizer did not provide sufficient wrapping of MWCNT particles. Electrical and morphological properties of PP/MWCNT composites were correlated with the rheological properties in steady and dynamic oscillatory shear flows.     

Rheological Properties of Silica Particle Suspensions in Mineral Oil

The rheological properties of particles suspended in a non‐polar mineral oil have been investigated as a function of volume fraction of particles, particle size, surface properties and shear rate. Three different types of particles were investigated; glass microspheres, monodisperse silica particles and fumed silica. The suspensions showed shear thinning behavior at higher volume fractions, and the viscosity increased with decreasing particle size. The hydrophobic particles display lass shear thinning effects. The relative viscosity of all the suspensions was well fitted to the Krieger and Dougherty model.     

Nanofluid in Hydrophilic State for EOR Implication Through Carbonate Reservoir

More than 50% of oil is trapped in petroleum reservoirs after applying primary and secondary recovery methods for removal. Thus, to produce more crude oils from these reservoirs, different enhanced oil recovery (EOR) approaches should be performed. In this research, the effect of hydrophilic nanoparticles of SiO₂ at 12 nm size, in (EOR) from carbonate reservoir is systematically investigated. Using this nanoparticle, we can increase viscosity of the injection fluid and then lower the mobility ratio between oil and nanofluid in carbonate reservoirs. To this end, a core flooding apparatus was used to determine the effectiveness and robustness of nanosilica for EOR from carbonate reservoirs. These experiments are applied on the reservoir carbonate core samples, which are saturated with brine and oil that was injected with nanoparticles of SiO₂ at various concentrations. The output results depict that, with increasing nanoparticle concentration, the viscosity of the injection fluid increases and results in decreased mobility ratio between oil and nanofluid. The results confirm that using the nanoparticle increases the recovery. Also, increasing the nanoparticle concentration up to 0.6% increases the ultimate recovery (%OOIP), but a further increase to 1.0 does not have a significant effect.     

Pickering emulsion polymerization of core–shell-structured polyaniline@SiO2 nanoparticles and their electrorheological response

We synthesized semiconducting polyaniline (PANI) nanoparticles through a solid-stabilized Pickering emulsion route using silica nanoparticles. Specific morphologies of the silica nanoparticle wrapped PANI particles were observed using both scanning electron microscope and transmission electron microscope, which showed the emulsifiability of silica nanoparticles in the emulsion system. Electrorheological (ER) behavior of this novel particle-based ER fluid dispersed in silicone oil was measured by a controlled shear stress rheometer and analyzed with a flow curve equation of Cho-Choi-Jhon model, which fitted well the flow curves measured in the exposed electric field.     

Antiwettability enhancement of PVDF-HFP membrane via superhydrophobic modification by SiO2 nanoparticles

Pore wetting is undesirable in the membrane gas–liquid separation process as it deteriorates the gas removal flux. To alleviate the affinity of a membrane surface toward a liquid solvent, its hydrophobicity needs to be enhanced. In this study, a superhydrophobic polyvinylidene fluoride-co-hexafluoropropylene membrane was synthesized via a simple and facile nonsolvent-induced phase inversion process. Hydrophobic nano-SiO₂ particles were used as solvent additives to improve the wetting resistance of the membrane. The results revealed that blended nano-SiO₂ membranes exhibited enhanced surface hydrophobicity in terms of water contact angle. Such improvement was attributed to the enhancement of surface roughness via the formation of hierarchical multilevel protrusions. Besides, the embedment of nanoparticles in polymer spherulitic globules also contributed to the reduction in surface energy of the membrane. As a result, the blended nano-SiO₂ membrane achieved superhydrophobicity with a water contact angle of up to 151°.     

Synthesis and characterization of poly1-hexene/silica nanocomposites

SiO₂ nano particles, with particle size of 12 nm, were first modified by substituting surface OH groups with O-hexyl moiety. Then, poly1-hexene/modified-SiO₂ composites with various nano-SiO₂ weight fractions were prepared by three different methods: in situ, solution, and melt methods and designated as PH-SiO₂/Insitu, PH-SiO₂/Sol and PH-SiO₂/Melt, respectively. PH-SiO₂/Insitu samples showed highly uniform particle dispersion up to 30 wt. % of silica while in PH-SiO₂/Sol and PH-SiO₂/Melt samples agglomeration of the silica nanoparticles occurred for filler contents ≥5 wt. % (i.e. 5, 10, 20 and 30 wt%). In the synthesized composites, the storage modulus significantly increased as high as 20.7 times when compared with neat poly1-hexene. Maximum decomposition temperature (T_max) and char yield at 600 °C increased with increasing silica level. Rheological results showed that G^ʹ> G^ʺ over the frequency range, illustrating the elastic behavior of the composite samples. In fact, samples showed the characteristic of a non-Newtonian fluid with a strong shear thinning effect in which η* increased with increasing filler weight fraction. From the results, it can be expected that modified silica could replace silica nanoparticles in polyolefin nanocomposite reinforcement.     

Pickering-stabilized emulsion gels fabricated from wheat protein nanoparticles: Effect of pH,NaCl and oil content

A novel Pickering-stabilized emulsion gel with controlled rheological properties was derived from wheat gliadin nanoparticles-stabilized emulsions by altering preparation conditions (pH, ionic strength or oil content). The formed nanoparticles were relatively small uniform spheres particles (d?相似文献   

Improving titanium dioxide dispersion in water through surface functionalization by a dicarboxylic acid

In this work, we show evidence of improving the dispersion of titanium dioxide particles in water. This is observed in the titanium dioxide-water colloid by the shear-thinning flow behavior in rheological measurements induced by the functionalization of a glutaric acid layer on the surface of titanium dioxide particles. The characterization of the layer was achieved by using infrared spectroscopy and ^13?C nuclear magnetic resonance. Rheological measurements corroborated that functionalization of TiO₂ particles decreases the rheological properties such as viscosity measurements at a constant shear rate in two orders of magnitude compared with the pure TiO₂ in suspensions. We present the results as a novel strategy to limit the formation of agglomerates in these colloidal suspensions, and this will be of great use in applications in the paints field and printing technologies.     

Experimental investigation toward obtaining a new correlation for viscosity of WO3 and Al2O3 nanoparticles-loaded nanofluid within aqueous and non-aqueous basefluids

In this study, the effect of temperature and mass fraction of Al₂O₃ and WO₃ nanoparticles dispersed in deionized water and liquid paraffin was investigated on dynamic viscosity of nanofluid. The results of the TEM tests showed that the size of Al₂O₃ and WO₃ nanoparticles was ranged from 10 to 60 nm, and the results showed that nanoparticles were semi-spherical. Also the results of DLS and zeta potential tests, respectively, exhibited the uniform size and high stability of the nanoparticles in the basefluid environment. The findings showed that adding a certain amount of nanoparticles to water and liquid paraffin increases dynamic viscosity, and in the case of various shear rates, the viscosity is constant for the water-based nanofluids, which indicates the Newtonian behavior of the nanofluid. In addition, for those prepared by liquid paraffin as a basefluid, the viscosity does not remain constant at different shear rates and at low amount of shear rate the viscosity achieves higher value, indicating non-Newtonian behavior of liquid paraffin-based nanofluids. The results showed that by increasing the temperature in liquid paraffin-based nanofluid the uniformity and linearity of the viscosity curve at various shear rates could be observed, which represents an approach for Newtonian behavior of nanofluid at higher temperatures. These results also showed that with increasing the mass fraction of nanoparticles in water and liquid paraffin, the viscosity increases at different shear rates. Finally, the correlation presented in this study shows that for nanofluid viscosity as a function of nanoparticles load and temperature, the deviation of correlated data from experimental values is less than 10%.

     

Effect of polyethylene oxide on the viscosity of dispersions of charged silica particles: interplay between rheology, adsorption, and surface charge

In this study a systematic investigation on the adsorption of polyethylene oxide (PEO) onto the surface of silica particles and the viscosity behavior of concentrated dispersions of silica particles with adsorbed PEO has been performed. The variation of shear viscosity with the adsorbed layer density, concentration of free polymer in the solution (depletion forces), polymer molecular weight, and adsorbed layer thickness at different salt concentrations (range of the electrostatic repulsion between particles) is presented and discussed. Adsorption and rheological studies were performed on suspensions of silica particles dispersed in solutions of 10⁻² M and 10⁻⁴ M NaNO₃ containing PEO of molecular weights 7,500 and 18,500 of different concentrations. Adsorption measurements gave evidence of a primary plateau in the adsorption density of 7,500 MW PEO at an electrolyte concentration of 10⁻² M NaNO₃. Results indicate that the range of the electrostatic repulsion between the suspended particles affects both adsorption density of the polymer onto the surface of the particles and the viscosity behavior of the system. The adsorbed layer thickness was estimated from the values of zeta potential in the presence and absence of the polymer and was found to decrease with decreasing the range of the electrostatic repulsive forces between the particles. Experimental results show that even though there is a direct relation between the viscosity of the suspension and the adsorption density of the polymer onto the surface of the particles, variation of viscosity with adsorption density, equilibrium concentration of the polymer, and range of the electrostatic repulsion cannot be explained just in term of the effective volume fraction of the particles and needs to be further investigated. Received: 15 February 2000/Accepted: 26 June 2000