Improved Dispersion Stability Research Articles

Engineering-safer-by design ZnO nanoparticles incorporated cellulose nanofiber hybrid for high UV protection and low photocatalytic activity with mechanism

Cellulose nanofiber (CNF) is a well-known biocompatible polymer with various versatile characteristics. In recent years, nano-sized materials with high flexibility and biocompatibility that exhibit ultraviolet (UV) blocking properties with maximum dispersion have attracted increasing attention, particularly, materials with photocatalytic activity. In this study, zinc oxide nanoparticle (ZnO NP) was synthesized on the surface of CNF to form a hybrid material by an environmentally friendly sol-gel reaction, and the UV blocking properties of the hybrid were systematically explored. The size of the ZnO NP on the CNF surface was optimized to improve the UV-blocking performance and the transmittance. The optimized safer-by-design structured hybrid exhibited the following features: 1) improved dispersion stability, 2) low whitening effect and 3) high UV blocking performance (i.e., 3.05 a.u. and 2.80 a.u. in UVB and UVA area, respectively). Moreover, only 8.8% rhodamine B (Rh-B) dye degraded through photocatalytic oxidation process (negligible photocatalysis activity). The synthesis strategy of the ZnO-CNF hybrid proposed in this study is a promising approach that can be implemented practically for high value-added applications in the field of cosmetics.

Generation of stable thermal gradient by solar energy harvesting in porous cobalt oxide based nanofluid

Tailored nanoforms of cobalt oxide were synthesized to prepare water based nanofluid system for developing stable and significantly large thermal gradient within nanofluid column. The decisive impact of morphological growth on both optical and thermal properties of the dispersed nanomaterial has been elaborately studied. Morphological evolution from rod to flower induces significant enhancement in optical absorption within VIS-NIR region whereas, the thermal conducting property of flower nanoform is found inferior to rod. The morphological growth implements 48% enhancement in thermal gradient for ultralow concentration around 0.005 wt% at sunlit condition. The highly porous flower nanoform exhibiting an enhanced optical absorption and improved dispersion stability but inferior thermal conducting property leads to the formation of thermal gradient ~43 °C stable for >3 h at a filler fraction of 0.011 wt% in sunlit condition (800 W/m2). The optimum concentrations for maximum thermal gradient for each system have been investigated. Due to the significant heat localization, proposed nanofluid system is promising in field of solar driven evaporation. Employing the stable and significantly large thermal gradient within the nanofluid column the possibility of thermo-emf generation with known thermoelectric materials has also been proposed.

Sustainable exploitation of macroalgae species from Chilean coast: Characterization and food applications

The use of macroalgae has been always linked to direct consumption, however, current trends have increased the applications of algae in the formulation of foods to replace animal proteins. Hence, we must ensure the safety of the increasing food products based on macroalgae. In this regard, and due to the worldwide variability of its composition, we determined the nutritional characterization of Durvillaea Antarctica, Macrocystis pyrifera, and Lessonia nigrescens to evaluate their potential at nutritional level. Also, as they are accumulating organisms, we characterized their minerals and heavy metals content, to determine its potential applications and consumption risks. The results indicated that the content total As is into the safe range to be consumed (16.92 and 60.75 mg/kg dw), but Cd (between 3.97 and 6.15 mg/kg dw) is higher than 0.5 mg/kg of final product (regarding Chilean Normative), and in this case, we have two possibilities: To add no more than 12.5% of M. pyrifera and no more than 8% of D. antarctica or L. nigrescens flour in the final product; or avoid the heavy metals by the extraction of alginates to enhance applications in food such as increasing the viscosity or improving dispersion stability. From the last point of view, we have compared the alginates extracted from D. antarctica, M. pyrifera, and L. nigrescens through the use of two methodologies to obtain calcium alginate (10.55–16.75% extraction yield) and sodium alginate (12.45–20.8% extraction yield), where the methodology to extract sodium alginate showed the best perform for the three macroalgae. The results showed that viscosities at 20 °C and alginate concentration of 40 g/L were: 1201.4 cP, 544.0 cP and 722.4 cP for D. antarctica, M. pyrifera, and L. nigrescens respectively. With these results we can conclude that the macroalgae D. antarctica is the one with both the highest extraction yield and technological potential as it generates a higher viscosity.

Direct Organometallic Synthesis of Carboxylate Intercalated Layered Zinc Hydroxides for Fully Exfoliated Functional Nanosheets

AbstractIntercalation of organic anions into 2D materials can enable exfoliation, improve dispersion stability, increase surface area, and provide useful functional groups. In layered metal hydroxides, intercalation of bulk structures is commonly achieved by cumbersome and typically incomplete anion exchange reactions. In contrast, here, a series of carboxylate‐intercalated layered zinc hydroxides (LZH‐R) are synthesized directly, at room temperature, by reacting an organozinc reagent with a precise sub‐stoichiometric quantity of the desired carboxylic acid and water. A range of carboxylic acids are used to make new LZH‐R materials which are crystalline, soluble, and functionalized, as established by X‐ray diffraction, spectroscopic, and microscopy techniques. When R is an alkyl ether carboxylate, this direct synthesis method results in the spontaneous exfoliation of the LZH‐R into monolayer nanosheets with high yields (70–80%) and high solubilities in alcohols and water of up to 180 mg mL−1. By altering the carboxylate ligand, functional groups suitable for post‐synthetic modification or for detection by fluorescence are also introduced. These examples demonstrate a versatile synthetic route for functional exfoliated nanosheets.

TiO2 nanoparticle-induced Xanthan Gum Polymer for EOR: Assessing the underlying mechanisms in oil-wet carbonates

This work systematically investigates the potential of Anatase TiO 2 nanoparticles-induced Xanthan-gum polymer as a Nano-polymer suspension for enhanced oil recovery (EOR) in carbonates. For this purpose, initially, viscosity of Xanthan gum polymer with and without the nanoparticles (NPs) was examined at different conditions. The stability of the suspensions was determined qualitatively and quantitatively. The capability of the Nano-polymer suspensions for wettability alteration was explored using contact angle measurement aided by a mathematical approach. Interfacial tension measurement was performed. Finally, oil displacement experiments were conducted to examine EOR efficiency of the Nano-polymer suspension. We found that while increasing temperature and adding salt to polymeric solutions caused a reduction in shear viscosity, the addition of NPs to the solutions could relatively recover the viscosity. The presence of polymers in the nanofluids improved dispersion stability of NPs. Also, the Nano-polymer suspensions could extend the ability of the NPs for wettability alteration and faster equilibrium states obtained than the polymer-free nanofluids. The mathematical model derived based on the equation of kinetic adsorption could describe the wettability alteration process well and successfully captured contact angle profiles. Results of the oil displacement tests revealed that whereas TiO 2 nanofluid and polymer solution showed additional oil recovery values of 12 and 19% of OOIP, respectively, 25% additional oil was produced using Anatase TiO 2 -induced Xanthan gum polymer flooding. • EOR potential of Anatase TiO 2 Nanoparticles-induced Xanthan Gum Polymer was investigated systematically. • TiO 2 nanoparticles relatively compensated the viscosity reduction of the polymer for thermal breakage and salt effect. • Xanthan gum polymer was helpful for nanofluids to remain stable for a long time range. • The performance of nanoparticles for rock wettability alteration was fortified by Xanthan gum polymer. • An extra oil recovery of 25% of OOIP was recovered using the Nano-polymer suspension.

An experimental study and mechanism analysis on improving dispersion stability performance of Al2O3 nanoparticles in base synthetic oil under various mixing conditions

An experimental study and mechanism analysis on improving dispersion stability performance of Al2O3 nanoparticles in base synthetic oil under various mixing conditions

Electrophoretic Deposition of Carbon Nanotubes onto Zinc Substrates for Electrode Applications

Carbon nanotubes (CNTs) as nanostructured materials have been widely used to improve electrochemical performance of electrode materials for various batteries and electrolyzers. The purpose of this work was to investigate the electrophoretic deposition (EPD) of multi-walled CNTs (MWCNTs) onto Zn plates for application in aqueous Zn ion batteries. The effects of MWCNTs on Zn oxidation and reduction were assessed using cyclic voltammetry. Before EPD, the MWCNTs were modified using H2 SO4 /HNO3 under reflux to improve dispersion stability in water. Acid modification shortened the MWCNTs but did not cause significant changes in crystallinity, tube diameter, and interlayer spacing. In a second step, the acid modified MWCNTs were homogeneously deposited onto a conductive Zn plate by EPD. Cyclic voltammetry data indicate that the coating of Zn with MWCNTs does not affect the Zn oxidation and reduction potential. Oxidation of Zn eventually leads to formation of a ZnO film, protecting the Zn surface from corrosion. When the protective ZnO film is dissolved, the underlying Zn is oxidized, leading to unfavorable loss of Zn. The presence of MWCNTs reduces oxidation during the cathodic sweep, implying that the MWCNT coating partially protects the underlying Zn surface from oxidation during charging. In addition, the MWCNT coated electrodes also facilitate hydrogen formation and show less oxygen limitation reaction, and could thus be envisaged as possible electrode materials for energy storage devices such as bifunctional electrodes for electrolyzers or air cathodes for batteries or fuel cells.

Polymerization and coordination synergistically constructed photothermal agents for macrophages-mediated tumor targeting diagnosis and therapy

Developing an ideal photothermal agent is one of the challenges for effective photothermal therapy (PTT). Herein, a green and simple yet versatile method is developed to construct a novel poly-(iron-dopamine coordination complexes) nanoparticles (P[Fe-DA]-NPs) based on polymerization and coordination synergistically by using Fe3+ ions and dopamine (DA) in aqueous solution, and simultaneously poly(vinylpyrrolidone) (PVP) is applied to improve dispersion stability. P[Fe-DA]-NPs can be laden into macrophages directly with no further purification required to target tumor tissue to perform cell-mediated strategy. P[Fe-DA]-laden macrophages as an ideal photothermal agent has the advantages of good biocompatibility, simple preparation process, high photothermal performance, and effective tumor targeting. Furthermore, the P[Fe-DA]-laden macrophages possess excellent photoacoustic imaging (PAI) capacity for guiding the precise PTT. The results show that the tumors are significantly suppressed after PTT with the help of the accurate PAI diagnosis. This cell-mediated strategy may be the most promising avenue for the future clinical cancer therapy.

Coupled hybrid nanoparticles for improved dispersion stability of nanosuspensions: a review

Dispersion stability of nanosuspensions attracts increasing attention in the past decades due to its significant effect on the thermal performance and phase behaviors of suspensions applied in various areas. The review of DLVO, steric stability, and depletion theories along with the detailed analysis of intermolecular forces was provided to elucidate the stability mechanism of hybrid nanoparticles in nanosuspensions. On this basis, mixed approach and coupled approach for achieving superior dispersion stability of hybrid nanosuspensions were specifically introduced. By using the coupled approach, the performance of phase behaviors can be largely promoted, preventing the nanoparticle aggregation as a result of the chemical bond formed in the fabrication process. The improved stability of coupled hybrid nanosuspensions enables the feasibility of the applications in heat and mass transfer and phase behavior–related fields, which are extensively reviewed in the current study. It is revealed that the thermal conductivity and phase behavior of hybrid nanoparticles are the dominant factors that need to be examined to improve abilities in heat transfer and colloidal control. With the development of fabrication techniques, it is promising that highly stabilized nanosuspensions such as GO nanoplatelets could be incorporated with drugs or genes for achieving targeted delivery, controlled release of drugs, and DNA transfer in complicated conditions. This indicates the value of stability promotion of nanosuspensions composed by coupled hybrid nanoparticles.

Cellulose Nanowhisker/Silver Nanoparticle Hybrids Sterically Stabilized by Surface Poly(ethylene glycol) Grafting.

Sterically stabilized hybrids of cellulose nanowhiskers (CNWs) and silver nanoparticles (AgNPs) were prepared via poly(ethylene glycol) (PEG) grafting and subsequent reduction of Ag+ counterions by sodium borohydride (NaBH4) for improved dispersion stability after hybridization. The preparation scheme includes surface carboxylation of CNWs using a 2,2,6,6-tetramethyl-1-pyperidinyloxy radical (TEMPO), grafting of monomethoxy PEG (mPEG) via amidation mediated by 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochloride or 4-(4,6-dimethoxy-1,3,5-triazin-2-yl)-4-methylmorpholinium chloride, exchange of countercation of residual carboxyls to Ag+, and deposition of AgNPs via reduction with NaBH4. UV-vis spectroscopy and electron microscopy analyses confirmed the successful deposition of AgNPs. Most of the mPEG-grafted hybrids were stable under the presence of an electrolyte, although some of them were precipitated by the addition of 0.1 M CaCl2. The addition of CaCl2 was also found to trigger discoloration of the hybrids, suggesting the partial dissolution of AgNPs and the formation of water-insoluble AgCl.

Modification of the physicochemical and structural characteristics of zein suspension by dielectric barrier discharge cold plasma treatment.

Owing to the strong hydrophobicity of zein, improved solubility is required to enhance the recovery of bioactive peptides. Using a zein suspension prepared by the antisolvent precipitation method, the impact of varying the voltage during dielectric barrier discharge (DBD) treatment on the physicochemical and conformational properties of zein in water was investigated. Analysis of the particle size, specific surface area, and free sulfhydryl content indicated that the protein solubility was maximized by treatment at 70V for 70 s. DBD treatment destroyed covalent bonds and introduced some hydrophilic groups onto the zein surface, thus enhancing the contact area with water molecules and leading to a more uniform dispersion. A decrease in the hydrodynamic radius of zein micelles indicated that intermolecular interactions were disrupted, thus improving dispersion stability. A more hydrophilic microenvironment was formed owing to the reduction in hydrophobic interactions. Additionally, evaluation of the secondary structure demonstrated that DBD treatment broke hydrogen bonds, resulting in a loose conformation with more exposed sites of action for water. These results are expected to facilitate the development of technologies for improving utilization of zein. PRACTICAL APPLICATION: Strong hydrophobicity limits the application of zein in the food industry. The study indicated that DBD treatment could promote loose structure, and improve dispersion stability and hydrophilicity of zein suspension prepared by antisolvent precipitation method. This work revealed the potential of cold plasma treatment for modifying zein and other insoluble proteins, which would expand their scope of application.

Encapsulation of vitamin D3 in gum arabic to enhance bioavailability and stability for beverage applications.

Delivery of vitamin D3 (VD3 ) in foods should exhibit desirable physicochemical characteristics and improves absorption. In this study, gum arabic (GA) was investigated as a VD3 carrier to encapsulate VD3 . VD3 dissolved in 5mL ethanol corresponding to 0.3 to 6.0% mass of GA, was blended in 5.0% w/v GA solution, followed by freeze drying. The encapsulation efficiency decreased while loading capacity increased with an increased amount of VD3 . At the highest VD3 level, the loading capacity (3.47%) was the highest, and the encapsulation efficiency (61.24%) was satisfactory, and the treatment was further studied. The magnitude of negative zeta-potential increased from 3.1 to 31.0mV at pH 2.0 to 7.4. During the 100-day storage at 3 °C of capsules reconstituted at pH 2.0 to 7.4, the hydrodynamic diameter decreased at all pH conditions, most evident for reduction to 81.3nm at pH 7.4, and no precipitation was observed, indicating the significance of steric repulsion on capsule stability. Bioaccessibility of VD3 in capsules (95.76%) was significantly higher than the nonencapsulated VD3 (68.98%). The in vivo pharmacokinetic study in Sprague-Dawley rats after a single-dose of 300µg VD3 showed the area-under-curve of serum 25(OHD) level in 48 hr of the encapsulation treatment was 4.32-fold of the nonencapsulated VD3 and more than twice higher than the VD3 -GA physical mixture. During 2-week supplementation of 60µg VD3 /d, rats receiving capsules or physical mixture had 25(OH)D levels of at least 81ng/mL higher than that of the nonencapsulated VD3 group. The studied encapsulation system holds great potential as a value-added ingredient to supplement VD3 in beverages with a wide pH range. PRACTICAL APPLICATION: The findings of this study demonstrated the improved dispersion stability and absorption of vitamin D3 after encapsulation in gum arabic. The capsules exhibited good dispersion stability across a pH range between 2.0 and 7.4, showing potential application in beverages. Furthermore, the enhanced absorption of VD3 after encapsulation highlights the nutritional benefits of the studied encapsulation system.

Increased Adsorption of Heavy Metal Ions in Multi-Walled Carbon Nanotubes with Improved Dispersion Stability.

In recent years, carbon nanotubes (CNTs) have been intensively studied as an effective adsorbent for the removal of pollutants from wastewater. One of the main problems for its use corresponds to the agglomeration of the CNTs due to the interactions between them, which prevents using their entire surface area. In this study, we test the effect of dispersion of oxidized multi-walled carbon nanotubes (MWCNTs) on the removal of heavy metals from acidic solutions. For this, polyurethane filters were dyed with a well-dispersed oxidized MWCNTs solution using chemical and mechanical dispersion methods. Filters were used in column experiments, and the sorption capacity increased more than six times (600%) compared to experiments with suspended MWCNTs. Further, kinetic experiments showed a faster saturation on MWCNTs in column experiments. These results contribute to a better understanding of the effect of dispersion on the use of CNTs as heavy metal ions adsorbent.

Immobilization of nano-zero-valent irons by carboxylated cellulose nanocrystals for wastewater remediation

Nano-zero-valent irons (nZVI) have shown great potential to function as universal and low-cost magnetic adsorbents. Yet, the rapid agglomeration and easy surface corrosion of nZVI in solution greatly hinders their overall applicability. Here, carboxylated cellulose nanocrystals (CCNC), widely available from renewable biomass resources, were prepared and applied for the immobilization of nZVI. In doing so, carboxylated cellulose nanocrystals supporting nano-zero-valent irons (CCNC-nZVI) were obtained via an in-situ growth method. The CCNC-nZVI were characterized and then evaluated for their performances in wastewater treatment. The results obtained show that nZVI nanoparticles could attach to the carboxyl and hydroxyl groups of CCNC, and well disperse on the CCNC surface with a size of ~10 nm. With the CCNC acting as corrosion inhibitors improving the reaction activity of nZVI, CCNC-nZVI exhibited an improved dispersion stability and electron utilization efficacy. The Pb(II) adsorption capacity of CCNC-nZVI reached 509.3 mg·g–1 (298.15 K, pH = 4.0), significantly higher than that of CCNC. The adsorption was a spontaneous exothermic process and could be perfectly fitted by the pseudo-second-order kinetics model. This study may provide a novel and green method for immobilizing magnetic nanomaterials by using biomassbased resources to develop effective bio-adsorbents for wastewater decontamination.

Stable Dispersion of Coal Fines during Hydraulic Fracturing Flowback in Coal Seam Gas Reservoirs—An Experimental Study

In subterranean coal seam gas (CSG) reservoirs, massive amounts of small-sized coal fines are released during the production and development stages, especially during hydraulic fracturing stimulation. These coal fines inevitably cause mechanical pump failure and permeability damage due to aggregation and subsequent pore-throat blockage. This aggregation behavior is thus of key importance in CSG production and needs to be minimized. Consequently, such coal fines dispersions need to be stabilized, which can be achieved by the formulation of improved fracturing fluids. Here, we thus systematically investigated the effectiveness of two additives (ethanol, 0.5 wt % and SDBS, 0.001 and 0.01 wt %) on dispersion stability for a wide range of conditions (pH 6–11; salinity of 0.1–0.6 M NaCl brine). Technically, the coal suspension flowed through a glass bead proppant pack, and fines retention was measured. We found that even trace amounts of sodium dodecyl benzene sulfonate (SDBS) (i.e., 0.001 wt %) drastically improved dispersion stability and reduced fines retention. The retention was further quantified by fractal dimensional analysis, which showed lower values for suspensions containing SDBS. This research advances current CSG applications and thus contributes to improved energy security.

Facile preparation PCL/ modified nano ZnO organic-inorganic composite and its application in antibacterial materials

Due to its good biodegradability and biocompatibility, polycaprolactone (PCL) has attracted widespread attention in the field of biomedical materials. Incorporation of Zinc oxide (ZnO) into PCL has been proved an effective way to improve its antibacterial properties. However, the interfacial compatibility of the organic-inorganic system needs to be improved due to the agglomeration of nanoparticles and phase separation of ZnO and PCL matrix affect its antibacterial efficiency. In this research, the ZnO surface was modified with citric acid monohydrate (CA) to improve the interfacial properties of ZnO-PCL system. The surface modification of ZnO was analyzed by DLS, TEM, TGA, and XPS. The results suggest that CA coating process can significantly reduce the agglomeration of ZnO nanoparticles and improve dispersion stability. The uniform PCL/ZnO-CA membranes with various nanofiller contents were fabricated through the solvent casting method. DSC and TGA analysis showed that the presence of ZnO-CA nanoparticles slightly decreased the crystallinity and thermal stability of the polymer. And ZnO-CA loaded improved the mechanical properties and wettability of the composite PCL membranes. Moreover, the composite PCL membranes showed good antibacterial activity against both E. coli and S. aureus while exhibiting good cytocompatibility, which indicated that the antibacterial and no cytotoxicity biomaterials had promising application in the biomedical field.

Stable SiO2–TiO2 composite-based nanofluid of improved rheological behaviour for high-temperature oilfield applications

ABSTRACTNanofluid synthesis in pure water is associated with premature settlement resulting in least dispersion stability. Therefore, in this study, polyacrylamide (PAM) is used as viscosity enhancer to improve dispersion stability of nanofluid stabilized by composites of silica and titania. Different techniques such as dynamic light scattering measurements, electrical conductivity, scanning electron microscopy, and rheological studies are used to support the analysis. The use of silica and titania nanoparticles together with PAM has additional advantage over particle agglomeration, and thus, the dispersion stability improved. Further, nanofluid stabilized by composites of silica and titania was tested for rheological measurements at 90°C to find nanotechnology applicability in high-temperature applications. The shear-thinning behaviour of nanofluids at high temperature (90°C) was least affected by shear deformation and reduced to 0.48 mPa.s at higher shear rate (4200 s−1), while shear thinning of PAM solution seriously varied with increasing shear deformation and takes the edge of 0.0005 mPa.s at higher shear rate (4200 s−1). In addition, the thermal stability of nanofluids was better due to slight decrease in viscosity with increasing temperature, which makes them suitable to be utilized at high-temperature applications in widespread industrial areas including oilfield where the temperature becomes a major factor.

Surface characterization of silicon nitride powder and electrokinetic behavior of its aqueous suspension

The dispersion stability of aqueous suspensions containing silicon nitride nanopowder prepared by direct nitridation had been studied. The Si3N4 powder was calcined at 200 °C, 400 °C and 600 °C, respectively. It was aimed to improve dispersion stability of Si3N4 suspension, and the effects were evaluated by measuring the median diameters of the samples taken from the slurries after settling experiments. The relationship between the median diameter and the viscosity of the slurry was discussed on the basis of Stoke's law. High resolution transmission electron microscopy (HRTEM) clearly revealed that the calcined Si3N4 particles were covered by an amorphous surface layer, which was mainly composed of silica. It can also be easily verified according to the results of X-ray photoelectron spectroscopy (XPS) analyses and diffuse reflectance Fourier transform infrared spectroscopy (DRTIFT) measurements. The formation of oxide layer also led to an increase in the total oxygen content of Si3N4 powder. Inductively coupled plasma atomic emission spectrometry (ICP-OES) analyses showed that the soluble impurities decreased after thermal oxide process, which also contributed to the lower of viscosity according to Jones-Dole expression. Electrokinetic behavior of suspensions also indicated that the absolute value of ζ-potential increased after powder calcination.

Aggregate Morphology and Aqueous Dispersibility of Spray-Dried Powders of Cellulose Nanocrystals

Spray drying is the most cost-efficient technology to produce bulk quantities of dry cellulose nanocrystals (CNCs) from acid hydrolyzed CNC suspensions. Spray drying results in the aggregation of CNC particles in granular material which is difficult to redisperse in water to individual particles. In this research, we investigated cospray drying of CNC suspensions with nonionic surfactant (10-mol ethoxylated octylphenol) at different concentrations and the role of this nonionic surfactant on the redispersion of spray-dried granular CNC particles. Dispersions of spray-dried CNC powder samples in water were investigated under static, mechanically stirred, and ultrasound-assisted mixing conditions. The granular morphology of spray-dried CNCs was affected by the concentration of nonionic surfactant. Overall, the formations of hollow and blistered particles in the presence of 5 and 10 mM OPE-100 were attributed to interactions between nonionic surfactant and CNCs which cause a reduction in the repulsion of nanoparticles during the shrinking of spray drying droplets. Higher light transmission properties, improved dispersion stability, and narrower particle size distribution of spray-dried CNC suspensions were achieved with the incorporation of nonionic surfactant at 5 and 10 mM prior to spray drying. These results are explained by the presence of hollow particles and by the increased interparticle interaction distance of CNCs due to weak and reversible adsorption of nonionic surfactant. Therefore, the addition of a nonionic surfactant is an attractive approach to control granular particle morphology and aqueous redispersion of CNC granular powder. Such results are of particular significance in the commercialization and process optimization for the manufacture of CNCs.

Experimental evaluation of dispersion behavior, rheology and thermal analysis of functionalized zinc oxide-paraffin oil nanofluids

The dispersion of nanomaterials in oils can improve the thermal storage and energy conversion capabilities of nano-synthetic oils. The zinc oxide (ZnO)-oil nanofluids can explore extensive industrial applications, especially in heat transfer processes, the food industry, and medicine. The zinc oxide nanoparticles are functionalized with oleic acid using surface-modification non-polarization approach to improve the stability of nanofluids. Different surface characterizations of the functionalized zinc oxide (f-ZnO) nanoparticles are presented. The presence of the carboxylic group on the surface of f-ZnO nanoparticles is analyzed by Energy Dispersive X-ray (EDX) and Fourier Transform Infrared (FTIR) spectroscopy. The f-ZnO nanoparticles are dispersed in highly refined paraffinic mineral oil at different concentrations (0–1 wt%) using the two-step method and ultrasonication. The dispersion stability is examined by sedimentation and Dynamic Light Scattering (DLS) methods for pure ZnO-oil- and f-ZnO-oil nanofluids and improved dispersion stability of the f-ZnO-oil nanofluids is observed. The thermal properties of the stabilized f-ZnO-oil nanofluids at different temperatures and concentrations are experimentally measured. These thermophysical properties include effective density, rheological behavior, and effective thermal conductivity. The effective coefficient of thermal expansion for different concentrations of nanofluids is obtained from density measurements using the conventional model. The rheological studies suggest that the nanofluids show higher viscosity than pure oil and exhibit shear-thickening behavior. Improvement in thermal conductivity of up to 18% is observed for 0.5 wt% of f-ZnO-oil nanofluid. The experimental data for thermophysical properties are compared with the existing conventional models of nanofluids to check the effectivity of theoretical models in the case of f-ZnO-oil nanofluids. The multi-variable new generalized correlations for effective density and effective viscosity of f-ZnO-oil nanofluids are proposed.