Improved Dispersion Stability Research Articles

Carbonyl Iron Particles' Enhanced Coating Effect Improves Magnetorheological Fluid's Dispersion Stability.

The coating effect of 1,2-bis(triethoxysilyl)ethane (BTES) on carbonyl iron particles (CIPs) was enhanced by etching with hydrochloric acid (HCl) of various concentrations, and magnetorheological fluids (MRFs) with significantly improved dispersion stability were obtained. The microstructures, coating effect, and magnetism of CIPs were examined using scanning electron microscopy (SEM), automatic surface and porosity analysis (BTE), Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), and a vibrating sample magnetometer (VSM), respectively. Furthermore, the rheological properties and dispersion stability of the MRFs were assessed by a rotating rheometer and a Turbiscan Tower. The results show that as the HCl concentration increased, nanopores appeared on CIPs and then disappeared, and the specific surface area of the particles increased and then decreased. When the concentration of HCl was 0.50 mol/L, the number of nanopores and the specific surface area of particles changed sharply. Not only that, the coated mass of BTES increased greatly and the saturation magnetization of particles decreased sharply. As the coated mass increased, without a magnetic field, the viscosity and shear stress of the MRFs increased, especially when the coated mass was more than 2.45 wt.%; while under a magnetic field, the viscosity and shear stress decreased, and the sedimentation rate of the MRFs decreased from 0.13 to 0.01 mm/h. By controlling the concentration of HCl for etching, the coating effect of CIPs was greatly enhanced, and thus an MRF with superior shear stress and excellent dispersion stability was obtained, which is significant in basic research and MRF-related applications.

Encapsulated inorganic pigments in epoxy composite microspheres using emulsion synthesis

Inorganic pigments are a commonly used colorant with various applications and promising prospects. However, the implement of organic pigments is hindered by poor dispersion stability in coatings due to non-uniform morphology and size. Herein, encapsulated pigments of Cobalt Chrome Green CoCr2O4 (PG 26), Cobalt Blue CoAl2O4 (PB 28), Titanium Chrome Yellow TiCrSbO6 (PB 24) in epoxy microspheres are obtained via an oil-in-water emulsion polymerization. The morphology, particle size, thermal properties, glass transition temperature (Tg) and color performance of the composite microspheres were characterized by different analytical techniques. The average particle size varied with pigments types and loadings. When the content of CoCr2O4 and CoAl2O4 is in the range of 15 wt%-30 wt%, and TiCrSbO6 content is between 15 wt%-25 wt%, the composite microspheres exhibit a narrow particle size distribution, regular morphology, and smooth surface. The size followed the rule of CoAl2O4/epoxy (20–26 μm) > CoCr2O4/epoxy (14-16μm) > TiCrSbO6/epoxy (6–9 μm). Besides, according to the aggregation-induced emission (AIE) principle, the relationship between fluorescence intensity and reaction time was investigated, thus deducing the curing process of the epoxy groups with m-xylenol dimethylamine (MXDA). The kinds of three inorganic fillers exhibit varying effects on the diffusion process of MXDA. TiCrSbO6 promotes the progress of the epoxy-amine curing reaction. Notably, CoCr2O4 microspheres exhibited stable green value (a*) and color saturation (C*), TiCrSbO6 microspheres showed increased yellow value (b*) and saturation (C*), and CoAl2O4 microspheres enhanced blue value (b*) with minimal change in lightness (L*). Overall, this study provides a comprehensive understanding of the properties of inorganic pigment/epoxy composite microspheres and highlights their potential for improved dispersion stability in coating applications.

Synthesis and characterization of polyaniline-based composites using cellulose nanocrystals as biological templates

Polyaniline (PANI) is considered as an ideal electrode material due to its remarkable Faradaic activity, exceptional conductivity, and ease of processing. However, the agglomeration and poor cycling stability of PANI largely limit its practical utilization in energy storage devices. To address these challenges, PANI was synthesized via a facile one-pot, two-step process using cellulose nanocrystals (CNCs) as bio-templates in this work. Zeta potential and particle size measurements revealed that the CNC template could impart improved dispersion stability to the synthesized PANI, which exhibited a decrease in average particle size from 1100 nm to 300 nm as a function of 10 % CNCs. Furthermore, the effect of CNC loadings on the performance of PANI was systematically investigated. The results showed that the specific capacitance of PANI/CNC increased from 102.52 F·g−1 to 138.12 F·g−1 with the CNC loading increase from 0 to 10 wt%. Particularly, the PANI/CNC composite film with a 1:9 ratio (C-P-10 %) demonstrated a capacity retention of 84.45 % after 6000 cycles and an outstanding conductivity of 526 S·m−1. This work generally offers an effective solution for the preparation of high-performance PANI-based composites, which might hold great promise in energy storage device applications.

Heat treatment improves the dispersion stability of rice bran milk through changing the settling behavior

Poor dispersion stability of nutritious rice bran milk limits its production. In this study, the dispersion stability of rice bran milk after heating at 95 °C for 0–5 min was investigated. Visual observation revealed improved dispersion stability and changes in settling behavior with heat durations. After heating for 5 min, the serum turbidity increased from 1.86 to 2.95. The centrifugal sedimentation rate unexpectedly rose from 9.25% to 29.18%, indicating an increase in volumetric particle concentration. Fourier transform infrared spectroscopy revealed that heating induced starch gelatinization and protein denaturation in rice bran milk, leading to increased volumetric particle concentration. Rice bran protein aggregates after heating were developed and embedded in the gel-like network composed of swollen starch granules. These results suggested that rice bran milk, due to thermal-induced alteration in biomacromolecules, may behave progressively from free settling to hindered settling to compression settling, resulting in improved dispersion stability.

Surface-Modified LDH Nanosheets with High Dispersibility in Oil for Friction and Wear Reduction.

Surface and interfacial engineering of nanomaterials is essential for improving dispersion stability in liquids. In this study, we report that oleic acid (OA)- and stearic acid (SA)-functionalized layered double hydroxide (LDH) nanosheets as lubricant additives can achieve high dispersion and reduce friction and wear. LDH is a typical layered structure, and OA and SA are long-chain organic molecules that are not only compatible with base oils but also act as friction-reducing agents. The OA and SA molecules were branched onto ZnMgAl LDH nanosheets using dehydration condensation between the exposed OH groups on the surface of LDH and the COOH groups on the OA and SA molecules. Compared with that of the pristine ZnMgAl LDH, the dispersion of OA-ZnMgAl LDH and SA-ZnMgAl LDH was significantly improved. The surface-modified LDH exhibited superior tribological properties and great stability due to the synergistic lubrication effect between OA, SA, and LDH. Even at an ultralow concentration (0.15 wt %), the coefficient of friction and wear volume were reduced by ∼65 and ∼99%, respectively, compared to those of the base oil. Due to the green and simple synthesis method and excellent tribological properties, surface-functionalized LDH has enormous possibilities for future industrial applications.

Preparation and tribological properties of hybrid nanofluid of BNNs and SiC modified by plasma

Aviation superalloy is widely used in aviation parts because of its high temperature strength and good fatigue resistance. Due to its high yield strength and low thermal conductivity, it is easy to produce lots of heat during processing, and its hardening tendency is serious, in the case of insufficient cooling lubrication easy to cause burns and poor processing quality. However, the traditional coolant has insufficient cooling performance, which is difficult to solve the thermal problem of aviation superalloy processing. In order to solve these problems, this paper uses plasma hydroxyl modified hexagonal boron nitride nanosheets (BNNs) and silicon carbide (SiC), and then adds sodium dodecyl benzene sulfonate (SDBS) in deionized water to prepare water-based BNNs/SiC hybrid nanofluid. The method of improving dispersion stability was studied by experimental means, and a single factor experiment was designed to study the influence law of mass ratio, mass concentration and temperature on heat transfer performance. Then the tribological properties of the formula were verified by friction and wear test. The results show that the Zeta potential of the nanofluid prepared by plasma hydroxyl modification is greatly improved, and the nanoparticles are effectively dispersed in the water-based liquid under the action of electrostatic stability mechanism. The viscosity reaches a minimum of 0.36249mPa·s, and the thermal conductivity reaches a maximum of 0.99496 W/(m·K). BNNs and SiC particles produce a synergistic structure like the rolling bearing due to the interface effect, which greatly enhances the anti-wear and anti-friction effect of the base fluid. The average friction coefficient is reduced to 0.068, and the volume wear rate is 37.03%, 30.8% and 69.35% lower than the traditional coolant, BNNs nanofluid and SiC nanofluid, respectively.

Molecular-Level Structural Analysis of siRNA-Loaded Lipid Nanoparticles by 1H NMR Relaxometry: Impact of Lipid Composition on Their Structural Properties.

1H NMR relaxometry was applied for molecular-level structural analysis of siRNA-loaded lipid nanoparticles (LNPs) to clarify the impact of the neutral lipids, 1,2-distearoyl-sn-glycero-3-phosphocholine (DSPC) and cholesterol, on the physicochemical properties of LNP. Incorporating DSPC and cholesterol in ionizable lipid-based LNP decreased the molecular mobility of ionizable lipids. DSPC reduced the overall molecular mobility of ionizable lipids, while cholesterol specifically decreased the mobility of the hydrophobic tails of ionizable lipids, suggesting that cholesterol filled the gap between the hydrophobic tails of ionizable lipids. The decrease in molecular mobility and change in orientation of lipid mixtures contributed to the maintenance of the stacked bilayer structure of siRNA and ionizable lipids, thereby increasing the siRNA encapsulation efficiency. Furthermore, NMR relaxometry revealed that incorporating those neutral lipids enhanced PEG chain flexibility at the LNP interface. Notably, a small amount of DSPC effectively increased PEG chain flexibility, possibly contributing to the improved dispersion stability and narrower size distribution of LNPs. However, cryogenic transmission electron microscopy represented that adding excess amounts of DSPC and cholesterol into LNP resulted in the formation of deformed particles and demixing cholesterol within the LNP, respectively. The optimal lipid composition of ionizable lipid-based LNPs in terms of siRNA encapsulation efficiency and PEG chain flexibility was rationalized based on the molecular-level characterization of LNPs. Moreover, the NMR relaxation rate of tertiary amine protons of ionizable lipids, which are the interaction site with siRNA, can be a valuable indicator of the encapsulated amount of siRNA within LNPs. Thus, NMR-based analysis can be a powerful tool for efficiently designing LNP formulations and their quality control based on the molecular-level elucidation of the physicochemical properties of LNPs.

The Effect of Spherical Hybrid Silica–Molybdenum Disulfide on the Lubricating Characteristics of Castor Oil

Abstract This investigation demonstrates the effect of a structural hybrid of spherical silica and lamellar molybdenum disulfide (MoS2) combined to form a sphere used as an antifriction and antiwear additive in vegetable oil in steel-on-steel tribopair. Hybrids demonstrated improved dispersion stability due to the deposition of lightweight silica on the surface of hydrothermally prepared 2D sheets of MoS2. The concentration of nanohybrid was optimized for optimal lubricant performance, and the best region of test space is presented in this work. At the optimum concentration, the coefficient of friction (COF) was 0.03236, with an average wear volume of 2.16 × 10−12 m3. The synergism of the particles significantly reduces friction and wear. The collision of the hybrid spheres with the surface has an immediate effect on it. The broken sphere of wear debris was observed under scanning electron microscopy. The wear debris analysis indicates that the lubrication mechanism begins with the rolling of hybrid spheres and ends with the rolling and sliding of silica and MoS2.

Effect of Organosilane Functionalization of Kaolinite In Structure and Thermal Properties

The composite homogeneity of polymer and inorganic content is often constrained by the high difference in surface tension of the two components. Inorganic filler surface tension is usually reduced using organosilane modification to improve miscibility. In this study, organosilane was introduced into Kaolinite clay to produce silanated kaolinite (sKal). The modification was carried out by reacting kaolinite with 3-Aminopropyltriethoxy silane (APS) in ethanol media. The products were characterized by Fourier Transform InfraRed (FTIR), X-Ray Diffraction (XRD), and thermal analysis. Successful silanated modification, sKal structure, thermal properties, and dispersion stability under water were reported. The appearance of absorptions demonstrated the success of the Kaolin Aps modification. New spectra from the N-H and CH2 group organosilanes of APS, which bind to kaolinite. The addition of organosilane concentrations can affect the structure of kaolinite, increasingly more organosilanes are added, widening the plate spacing of each layer, and resulting in the breaking of the polymer chains and the exfoliation of platelets between the layers of kaolinite. Thermal stability showed an increase in thermal degradation after modification with Organosilan-APS. Furthermore, modifying Kaolinite with APS can improve dispersion stability in aqueous. Kaolinite-APS modification can accelerate the deposition of colloidal dispersions by lowering the surface tension of kaolinite. The data showed the potential of sKal as a modifier polymer in composite preparation for any application.

Effect of the grafting degree of (3glycidyloxypropyl)trimethoxysilane on the corrosion resistance of waterborne epoxy/Ti3C2 nanocomposite coatings

Modification of MXene is usually necessary for their application in corrosion resistant coatings. Nevertheless, the influence of the grafting degree of modifier is not concerned in the past. In this work, modified Ti3C2 nanosheets (G-Ti3C2) with different grafting degree of (3-glycidyloxypropyl)trimethoxysilane (GPS) were obtained by changing GPS dosage, and further incorporated into waterborne epoxy resin coatings (WEP). GPS modification led to deteriorated dispersion in water but improved dispersion stability of Ti3C2 nanosheets in waterborne epoxy resin at appropriate GPS-grafting degree presumably due to the interaction between the liquid epoxy resin droplet and G-Ti3C2 nanosheets. The GPS grafting degree was also critical to get the corrosion resistant nanocomposite coatings. The best corrosion resistance, i.e., with impedance modulus four orders of magnitude higher than that of pure WEP after 30 days' immersion in salt solution as well as the lightest corrosion in salt spray test, was achieved using the Ti3C2 nanosheets modified at the GPS-to-Ti3C2 mass ratio of 30:1. Better dispersion of G-Ti3C2 nanosheets and stronger interaction between epoxy resin matrix and G-Ti3C2 nanosheets should be responsible for the excellent corrosion resistance of the coatings at optimum GPS grafting degree.

A Review on Recent Progress in Preparation of Medium-Temperature Solar-Thermal Nanofluids with Stable Dispersion.

Direct absorption of sunlight and conversion into heat by uniformly dispersed photothermal nanofluids has emerged as a facile way to efficiently harness abundant renewable solar-thermal energy for a variety of heating-related applications. As the key component of the direct absorption solar collectors, solar-thermal nanofluids, however, generally suffer from poor dispersion and tend to aggregate, and the aggregation and precipitation tendency becomes even stronger at elevated temperatures. In this review, we overview recent research efforts and progresses in preparing solar-thermal nanofluids that can be stably and homogeneously dispersed under medium temperatures. We provide detailed description on the dispersion challenges and the governing dispersion mechanisms, and introduce representative dispersion strategies that are applicable to ethylene glycol, oil, ionic liquid, and molten salt-based medium-temperature solar-thermal nanofluids. The applicability and advantages of four categories of stabilization strategies including hydrogen bonding, electrostatic stabilization, steric stabilization, and self-dispersion stabilization in improving the dispersion stability of different type of thermal storage fluids are discussed. Among them, recently emerged self-dispersible nanofluids hold the potential for practical medium-temperature direct absorption solar-thermal energy harvesting. In the end, the exciting research opportunities, on-going research need and possible future research directions are also discussed. It is anticipated that the overview of recent progress in improving dispersion stability of medium-temperature solar-thermal nanofluids can not only stimulate exploration of direct absorption solar-thermal energy harvesting applications, but also provide a promising means to solve the fundamental limiting issue for general nanofluid technologies.

Noncovalently functionalized boron nitride nanotubes and polymer nanocomposites with water-soluble poly (amic acid) salt

In this study, polyamic acid salt-BNNTs (PAS-BNNTs) were prepared by noncovalently functionalizing water-soluble PAS with improved dispersion stability in organic solvents, and high compatibility with polyimide (PI) nanocomposites. We show that BNNTs functionalized with PAS have enhanced mechanical properties that are influenced by various loadings of PAS-BNNT/PI films through in situ polymerization. Compared with the pure PI film, the tensile strength and tensile modulus increased by about 20% and 37%, respectively. The proposed system also improved the coefficient of thermal expansion (CTE) from 52.6 to 45.7 ppm/oC. The enhanced mechanical properties of the PI nanocomposite were due to the interfacial bond strength enhanced by the reinforcing effect of PAS-BNNTs. Our study demonstrates the potential of PAS-BNNTs for preparing BNNT/PI nanocomposites with various structures.

Thermohydraulic performance investigation of a heat exchanger with combined effect of ribbed insert and Therminol55/MXene+ Al2O3 nanofluid: A numerical two-phase approach

MXene-based nanofluids are novel trends with improved dispersion stability and thermophysical characteristics over previously established nanofluids. In the present work, the thermohydraulic characteristics of a double pipe heat exchanger (DPHEX) with a Therminol55(TH55)/MXene + Al2O3 nanofluid and various geometrically shaped (triangular, rectangular) ribbed twisted tape (TT) inserts are numerically investigated using the ANSYS Fluent interface. A counter flow arrangement with three different types of inserts (RRTT, TRTT, TT) and TH55/MXene + Al2O3 nanofluid at 0.20 wt% are studied inside the heat exchanger. Adding ribbed inserts to the conventional TT insert enhances the turbulence intensity by creating extra vortices. The thermal boundary layer grows thinner due to increased axial and radial velocity. Due to the substantial flow obstruction, adding ribs increases the overall pressure drop between the inlet and outlet. The maximum increase in Nu is 11.04 % using nanofluid instead of water, whereas the combination of insert and nanofluid exhibited up to 105 % enhancement for rectangular-ribbed TT compared to the plain tube. Nevertheless, the pressure decrease is found to be maximum in rectangular-ribbed TT because of significant flow disruption. This was likewise true with triangular-ribbed TT and TT insert. According to the PEC assessment, the RRTT insert had a maximum PEC value of 1.67 greater than TRTT and traditional TT for both TH55 and nanofluid flowing inside the tube. To summarize, the combination of TH55/MXene + Al2O3 RRTT insert may be a promising choice for improving heat exchanger performance in a new generation efficient thermal system.

Reliable assessment of carbon black nanomaterial of a variety of cell culture media for in vitro toxicity assays by asymmetrical flow field-flow fractionation

Carbon black nanomaterial (CB-NM), as an industrial product with a large number of applications, poses a high risk of exposure, and its impact on health needs to be assessed. The most common testing platform for engineered (E)NMs is in vitro toxicity assessment, which requires prior ENM dispersion, stabilization, and characterization in cell culture media. Here, asymmetric flow field-flow fractionation (AF4) coupled to UV–Vis and dynamic light scattering (DLS) detectors in series was used for the study of CB dispersions in cell culture media, optimizing instrumental variables and working conditions. It was possible to disperse CB in a non-ionic surfactant aqueous solution due to the steric effect provided by surfactant molecules attached on the CB surface which prevented agglomeration. The protection provided by the surfactant or by culture media alone was insufficient to ensure good dispersion stability needed for carrying out in vitro toxicity studies. On the other hand, cell culture media in combination with the surfactant improved dispersion stability considerably, enabling the generation of shorter particles and a more favourable zeta potential magnitude, leading to greater stability due to electrostatic repulsion. It was demonstrated that the presence of amino acids in the culture media improved the monodisperse nature and stability of the CB dispersions, and resulted in a turn towards more negative zeta potential values when the pH was above the amino acid isoelectric point (IEP). Culture media used in real cell culture scenarios were also tested, and in vitro toxicity assays were developed optimizing the compatible amount of surfactant.Graphical abstract

Protective effect of pangasius myosin on thermal stability of lycopene and their interaction mechanism

In this study, the influence of extracted pangasius myosin on the thermal stability of lycopene and the mechanism of their interaction were examined. The addition of pangasius myosin positively affected the thermal stability of lycopene. After adding myosin, under heating conditions, the L* value of lycopene increased by 6.2–10.04%, a* value increased by 20–27%, and ΔE decreased by 42–51%. Lycopene inhibited the fluorescence of ovalbumin by static burst. Binding and thermodynamic parameters demonstrated that lycopene bound spontaneously to myosin through hydrophobic interaction with a complex stoichiometry ratio of 1:1. Circular dichroism and Fourier infrared transform spectroscopy were used to examine the secondary structure changes that occurred in myosin after it bound to lycopene. Particle size and electron microscopy analysis showed that the addition of low concentrations of lycopene resulted in smaller particle size and improve dispersion stability; however, high concentrations of lycopene promoted myosin aggregation. This study provides a theoretical foundation for improving the thermal stability of lycopene in minced fish products.

Surface-modified carbon fiber for enhanced electromagnetic interference shielding performance in thermoplastic polyurethane composites

There has been a growing interest in developing carbon-based polymer composites for electromagnetic interference (EMI) shielding materials. To achieve a high EMI shielding performance, the morphology of fillers in composites must be controlled. Although carbon fibers (CFs) have remarkable thermal and electrical properties and low density, their poor dispersion behavior within polymer matrix limits their practical applications as EMI shielding materials. In this study, we report an efficient method to disperse CFs within a thermoplastic polyurethane (TPU) matrix using pyranine-functionalized polyether (polyether–pyranine) as a dispersing agent. polyether–pyranine was grafted on the CF surfaces through π–π interactions between the CF and pyranine groups to produce surface-modified CFs (SCFs). Compared to CFs, the SCFs exhibited an improved dispersion stability within a TPU polymer matrix. Furthermore, a TPU composite with SCFs achieved an enhanced electrical conductivity and EMI shielding performance, which was primarily ascribed to the increased structural connectivity between the SCFs due to excellent dispersion.

Carboxymethyl Chitosan-Modified Graphene Oxide as a Multifunctional Vector for Deltamethrin Delivery and pH-Responsive Controlled Release, Enhanced Leaf Affinity, and Improved Mosquito-Killing Activity.

Traditional deltamethrin (DM) formulations (e.g., emulsifiable concentrates, wettable powders, etc.) have significant disadvantages of poor water dispersion stability, burst release, weak leaf affinity, short duration, poor efficacy, and high environmental toxicity. A nanomaterial-based pesticide delivery system (PDS) has provided effective strategies for green preparation and synergism of pesticide formulations. In this article, we developed carboxymethyl chitosan (CMCS)-modified graphene oxide (GO) as a vector for DM and constructed a pH-responsive PDS for Culex pipiens pallens control. GO-CMCS possesses excellent pesticide loading performance for DM (loading rate 87.76%). After being loading on GO-CMCS, the GO-CMCS-DM has a significantly improved dispersion stability in water. The GO-CMCS-DM exhibits pH-responsive controlled release performance, which can sustain the release of DM into the medium, maintaining an effective long-term concentration. Additionally, the leaf adhesion of GO-CMCS-DM is better than that for free DM, which can improve the pesticide utilization. Therefore, GO-CMCS-DM has a prolonged persistent period and sustained activity against Culex pipiens pallens. Considering the industrialization potential of GO, we believe that GO will play an important role in the pest control and antiepidemic fields.

Effects of residual pectin composition and content on the properties of cellulose nanofibrils from ramie fibers

In this study, a series of pretreatment methods (pectin extraction) were employed to prepare cellulose nanofibrils (CNFs) with different pectin composition and contents from ramie fibers. The comprehensive effects of residual pectin on the final properties of CNFs were investigated. The residual pectin did not have a significant effect on the size distribution of the obtained CNFs. While the presence of pectin led to higher zeta potential value, improved dispersion stability and enhanced storage modulus of the CNF dispersion, with the sodium carbonate extraction method showing the greatest impact. The possible mechanism for enhanced dispersion stability of CNFs is the formation of self-assembled hierarchical pectin-hemicellulose/lignin-cellulose nanostructures, offering abundant electrostatic repulsion and steric hindrance between the nanoparticles. This work provides guidelines for the tailored production of CNFs to meet the requirements for different applications.

Production, deformation and magnetorheological characteristics of the alginate/chitosan hydrogel magnetic microspheres

To improve dispersion stability and magnetorheological (MR) characteristics of carbonyl iron (CI) particles, we proposed novel hydrogel magnetic microspheres (MPs) dual-coated with alginate (AL) and chitosan (CTS) for the first time. The double-network structures formed by biological crosslinking and chelation reactions are capable to enhance its own structural stability and mechanical properties. The structural characterization, MR properties, and dispersion stability for different MPs were investigated. Additionally, the swelling behaviors were studied by swelling the dried MPs in the deionized water and sodium chloride solution, respectively. The results showed that the AL/CTS hydrogel core/shell MPs displayed the advantages of simple manufacturing, superior MR properties and deformability compared to pure micron-sized CI particles, indicating the improved dispersion stability of the MR fluids compared to that of the pure CI particles-based MR fluids. The introduction of double network structures with natural biopolymers will provide a new thought for the development of MR materials.

Dispersion stability of nano additives in lubricating oils – an overview of mechanisms, theories and methodologies

ABSTRACT With the advancement in the field of nanotechnology, various researchers have reported an improvement in the friction and wear behaviour of different lubricating oils by the addition of different nano additives. However, the stability of these nano additives remains a challenge. In this paper, the dispersion stability of various nano additives in lubricating oils has been studied in detail. The paper aims to summarize various dispersion stability theories and several methods reported in the literature to improve dispersion stability. Apart from this, a special focus has been laid to highlight the various surfactants used to improve the dispersion stability, particularly the tribological properties. The literature suggests that although a number of studies have been carried out to study the effect of surfactant addition on dispersion stability, however, future developments could be focused to improve the dispersion stability of the existing mono and hybrid nano fluids and their underlying mechanisms. Abbreviations: SWCNH, single-walled carbon nano-horns; PAO, poly alpha olefin; MoS2, molybdenum di sulphide; H, Hamaker constant, MWCNTs, multi-walled carbon nanotubes; GNF, graphene nanoflakes; DLVO, Derjaguin and Landau Verway and Overbeek; DLS, dynamic light scattering; HLB, hydrophobic lyophilic balance; FERTEM, freeze etching replication transmission electron microscope; SDS, sodium dodecyl sulphate; PTFE, polytetrafluoroethylene; FTIR, Fourier-transform infrared spectroscopy; TBAAc, tetra butyl ammonium acetate; THF, tetrahydrofurane; UV–Vis, ultraviolet visible light; SEM, scanning electron microscope; TEM, transmission electron microscope