Dispersion Stability Of Nanoparticles Research Articles

Innovative Role of Magnesium Oxide Nanoparticles and Surfactant in Optimizing Interfacial Tension for Enhanced Oil Recovery

Enhancing oil recovery efficiency is vital in the energy industry. This study investigates magnesium oxide (MgO) nanoparticles combined with sodium dodecyl sulfate (SDS) surfactants to reduce interfacial tension (IFT) and improve oil recovery. Pendant drop method measurements revealed a 70% IFT reduction, significantly improving nanoparticle dispersion stability due to SDS. Alterations in Zeta Potential and viscosity, indicating enhanced colloidal stability under reservoir conditions, were key findings. These results suggest that the MgO-SDS system offers a promising and sustainable alternative to conventional methods, although challenges such as scaling up and managing nanoparticle–surfactant dynamics remain. The preparation of MgO nanofluids involved magnetic stirring and ultrasonic homogenization to ensure thorough mixing. Characterization techniques included density, viscosity, pH, Zeta Potential, electric conductivity, and electrophoretic mobility assessments for the nanofluid and surfactant–nanofluid systems. Paraffin oil was used as the oil phase, with MgO nanoparticle concentrations ranging from 0.01 to 0.5 wt% and a constant SDS concentration of 0.5 wt%. IFT reduction was significant, from 47.9 to 26.9 mN/m with 0.1 wt% MgO nanofluid. Even 0.01 wt% MgO nanoparticles reduced the IFT to 41.8 mN/m. Combining MgO nanoparticles with SDS achieved up to 70% IFT reduction, enhancing oil mobility. Changes in Zeta Potential (from −2.54 to 3.45 mV) and pH (from 8.4 to 10.8) indicated improved MgO nanoparticle dispersion and stability, further boosting oil displacement efficiency under experimental conditions. The MgO-SDS system shows promise as a cleaner, cost-effective Enhanced Oil Recovery (EOR) method. However, challenges such as nanoparticle stability under diverse conditions, surfactant adsorption management, and scaling up require further research, emphasizing interdisciplinary approaches and rigorous field studies.

Covalent vs. Non covalent chemical modification of multiwalled carbon nanotubes based-nanofluids: Stability and thermal conductivity steadiness over temperature

Thermal conductivity enhancement coupled to nanoparticle dispersion stability over time are the two main conflicting requirements to overcome to develop carbon nanomaterial-based nanofluids. Both covalent and non-covalent approaches, having their own advantages and disadvantages, are commonly used for carbon nanotube based nanofluids development. However, they are rarely compared regarding their impact on stability and thermal conductivity performances for the same kind of nanofluid. In this work, multiwalled carbon nanotubes have been chemically modified by both covalent and non-covalent functionalization. For the covalent functionalization, a simple oxidation method is applied. It consists of refluxing the powdered MWCNTs in H2SO4/HNO3 at 5 M concentration. For the non-covalent approach, both an anionic (sodium dodecyl sulfate) and a non-ionic (Pluronic P123, comprising poly(ethylene oxide) (PEO) and poly(propylene oxide) (PPO) in an alternating linear fashion, PEO-PPO-PEO) surfactants were employed at a concentration of 1 wt%. Nanofluids were prepared with multiwalled carbon nanotubes at a fixed concentration of 0.2 wt% for both chemical modification approaches. The oxidation reaction occurs without significant structure damaging as shown by transmission electron microscopy, Raman spectroscopy, Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy. UV–visible spectrophotometry analysis shows a remarkable stability with temperature in the 293.15–303.15 K range over one-week and for a longer period of 49 days for all the three types of nanofluids. Their thermal conductivity has been investigated in the same temperature range. For all the three nanofluid series prepared with a fixed concentration of carbon nanomaterials, a thermal conductivity enhancement compared to that of the base fluid has been observed. The thermal conductivity evolution with temperature is different for each type of nanofluid. The covalently oxidized multiwalled carbon nanotube based nanofluids showed the better thermal conductivity enhancement steadiness (around 7 %) with temperature. The discussion on the surfactant-based nanofluid behavior proposes the possible involved mechanisms as temperature increases for each surfactant.

Assembly of Zinc‐Single‐Site‐Containing Silica Nanoparticles to Supraparticle Powders with Destructibility to Serve as Filler and Vulcanization Activator in Rubbers

AbstractThe vulcanization process is widely used in industry for tire manufacturing. Therefore, zinc oxide is commonly utilized as an activator material, but unreacted zinc oxide remains in the final products and can be released into the environment with a significant impact. To reduce the amount of required zinc and to prevent leaching from tire material, zinc single site‐containing silica fillers are interesting candidates. In these materials, zinc sites are anchored on the surface of silica nanoparticles through their complexation with functionalized aminosilanes. Based on these, a novel powder sample is prepared via spray‐drying. The obtained supraparticles allow for a homogeneous distribution of the filler nanoparticles in the rubber matrix via their disintegration during the incorporation process. All synthesis steps are carried out in ethanol and water, respectively, at very mild temperatures to account for sustainability demands. As core of this study, the role of zinc ions and their amino‐complexation in nanoparticle dispersion stability and in supraparticle formation during spray‐drying is elucidated. Additionally, the superior performance of supraparticles as activator in rubber vulcanization is demonstrated. These show a higher curing efficiency, leading to lower curing time (−70%), higher torque values (+15%), and improved dynamic mechanical properties compared to the conventional ZnO activator.

A high temperature resistance and hyper‐dispersed nanoparticle grafted by multi‐monomer via in‐situ polymerization: Preparation, characterization, and its imbibition performance

AbstractIn recent years, the excellent cleaning‐oil capacity of nanofluid has attracted extensive attention and it has been widely used in oilfields as an imbibition agent. To solve the poor dispersion stability of nanoparticles in high‐temperature and high‐salt reservoir, this paper has prepared a hyper‐dispersed nanoparticle, polymer grafted nanosilica (PNS) that is anti‐salt monomer and anti‐temperature monomer simultaneously grafting on the surface of nanosilica via in‐situ polymerization reaction. Its imbibition performance has been discussed. Results show that (1) The two monomers are all successfully grafted on the surface of nanosilica via optimization of in‐situ polymerization reaction conditions. This hyper‐dispersed nanoparticle has 14.5% final grafting rate, approximately 18 nm in particle size, and −41.2 mV of zeta potential; (2) PNS fluid has excellent dispersion stability and its grain size has no obvious change in 20 wt.% of NaCl or 4 wt.% of CaCl2 fluids at room temperature (25°C), as well as in 18 wt.% of NaCl or 4 wt.% of CaCl2 fluids at 130°C after 1 week; (3) Crude oil–water interface tension can be decreased and the hydrophilicity is significantly boosted by this PNS fluid. Meanwhile, the 10−3 mN/m of interface tension can be obtained and the contact angle of water phase is decreased to 12.8° by surfactant erucamide propyl hydroxysulfobetaine (EHSB) synergizing with PNS fluid; (4) Oil recovery efficiency replaced by PNS in surfactant fluid has reached 39.3%. That is mainly because the hyper‐dispersed nanoparticle provides a stronger spreading force to enhance the efficiency of cleaning oil.

Dispersion stability and tribological behavior of nanocomposite supramolecular gel lubricants and molecular dynamic simulation

The poor dispersion stability of nanoparticles in oils limited their application. To address this problem, diverse of nanoparticles were introduced to supramolecular gels to fabricate a new lubricant (Nano-Gel). The results of molecular dynamics simulation show that gelators adsorbed onto the surface of nanoparticles at the non-covalent interaction. Besides, the intricate networks of supramolecular gels show spatial confinement to nanoparticles, which improved the dispersion stability of nanoparticles. Compared with supramolecular gels lubricant, Nano-Gel shows good anti-friction and anti-wear properties. The excellent tribological properties would be contributed to the self-repairing and tribo-film formed by nanoparticles and gelators. The Nano-Gels provide effective solution to the application of nanoparticles in lubricating oil, which have great values to prolong the life of mechanisms.

Surface modification boosts dispersion stability of nanoparticles in dielectric fluids

Achieving stable dispersion of nanoparticles in dielectric fluids is a challenging task, as there are complex and diverse influencing factors, requiring molecular-level understanding of the nanoparticle aggregation. In this paper, we conducted long-time molecular simulations of dielectric nanofluids containing fifteen SiO2 nanoparticles, systematically varying the length of alky chains grafted onto their surface to explore their impact on the aggregation process. Our results reveal that appropriate surface modification can dramatically increase the dispersion stability of nanoparticles in dielectric fluids. SiO2 nanoparticles lacking alkyl chains exhibit a strong tendency to approach each other, and form aggregates in natural esters, because of the Coulombic energy from heteroatoms of SiO2 nanoparticles. Despite the differences in the length of grafted alkyl chains on the surface of SiO2 nanoparticles, all of them, regardless of their length, are capable of effectively shielding the Coulombic interactions and increasing the van der Waals interaction with natural esters, thereby reducing the aggregation tendency of nanoparticles. Furthermore, the smaller diffusion ability, caused by the steric hindrance effect, of surface-modified SiO2 nanoparticles also inhibits their collision and subsequent aggregation.

Nanofluids as a coolant for polymer electrolyte membrane fuel cells: Recent trends, challenges, and future perspectives

In this comprehensive review, we critically examine the application of nanofluids as coolants in PEMFCs, explicitly focusing on elucidating their thermal efficiency enhancement mechanisms. In addition to the existing research, the significant areas critically reviewed include the influence of nanoparticle size and concentration, surface modification techniques, characterization methods, nanofluid stability under different conditions, nanofluid behavior in various flow regimes, and the impact of nanofluids on system performance and efficiency. A meticulous analysis of the most recent studies involving single nanofluids (Al2O3, SiO2, TiO2, ZnO, BN) and hybrid nanofluids (CuFeAl, Al2O3:SiO2, Bio glycol+Al2O3:SiO2, TiO2:SiO2) underscores their potential to revolutionize PEMFC cooling systems. Findings reveal that nanofluids exhibit remarkable enhancements in heat transfer, offering a 20–27% reduction in radiator size compared to traditional coolants. The science underpinning this enhancement is multifaceted, characterized by self-deionization phenomena, nanoparticle dispersion stability via Brownian motion, and unprecedented inter-atomic interactions. Notably, nanofluids effectively eliminate particle sedimentation and coagulation, ensuring sustained heat transfer performance over extended operational periods. However, several challenges are observed, such as the limited exploration of electrical conductivity, which occurred because of the correlation between the net-charge influence of the suspended particle and electrical double layer (EDL) behavior. Furthermore, understanding and utilizing smart nanofluids and nanobubbles demand rigorous investigation for optimal cooling strategies. Future research should focus on standardizing nanofluid synthesis and characterization protocols, elucidating the underlying heat transfer mechanisms, addressing cost and scalability issues, and ensuring nanofluids’ durability in PEMFCs. The review’s timeliness lies in its relevance to the current advancements and challenges in the field, offering valuable insights for researchers and practitioners working in the thermal management of PEMFC.

The effect of the degree of sulphenylation on the stability of reduced graphene oxide nanofluids

Dispersion stability of nanoparticles in nanofluids is a prerequisite for allowing the nanofluids to act as convection heat transfer working fluids. This research prepared multiple types of sulfophenylated graphene (PSG) nanoparticles. Two samples subjected to different degrees of sulfophenylation were chosen to formulate different nanofluids with varying sulfophenylated particle concentrations. The nanofluids’ measured Zeta potential, electric conductivity, and thermal conductivity coefficients were used to investigate the stability. The research indicates the increase in the degree of sulfophenylation can improve the stability of nanofluids while exerting little influence on thermal conductivity; on the premise of ensuring stability, the number of nanoparticles added in base fluids can increase thermal conductivity. After that, high-sulfophenylated particle concentration nanofluids (2 mg/mL) were formulated using sulfonated-reduced graphene oxide (s-rGO) nanoparticles prepared to demonstrate excellent stability, and their thermal conductivity reached 0.773 W/m. K (55 °C).

Influence of Polymer Concentration on Drying of SPION Dispersions by Electrospinning.

To improve the physical stability of nanoparticle dispersions, several methods for their transformation into stable and easily dispersible dry products have been investigated thus far. Recently, electrospinning was shown to be a novel nanoparticle dispersion drying method, which addresses the crucial challenges of the current drying methods. It is a relatively simple method, but it is affected by various ambient, process, and dispersion parameters, which impact the properties of the electrospun product. The aim of this study was, thus, to investigate the influence of the most important dispersion parameter, namely the total polymer concentration, on the drying method efficiency and the properties of the electrospun product. The formulation was based on a mixture of hydrophilic polymers poloxamer 188 and polyethylene oxide in the weight ratio of 1:1, which is acceptable for potential parenteral application. We showed that the total polymer concentration of prior-drying samples is closely related to their viscosity and conductivity, also affecting the morphology of the electrospun product. However, the change in morphology of the electrospun product does not affect the efficiency of SPION reconstitution from the electrospun product. Regardless of the morphology, the electrospun product is not in powder form and is therefore safer to handle compared to powder nanoformulations. The optimal total polymer concentration in the prior-drying SPION dispersion, which enables the formation of an easily dispersible electrospun product with high SPION-loading (65% (w/w)) and fibrillar morphology, was shown to be 4.2% (w/v).

Development of a rapid method to detect and to monitor bacteriophage amplification in contact with viable but non-culturable bacteria

ABSTRACT We propose in this study to develop a rapid, reliable, and non-culture method to detect and estimate bacteriophage (phage) titre as an alternative to the routine use of the double agar overlay assay (DLA). The present method is based on the analysis of nanoparticle (NPs) dispersion/aggregation dynamic in interaction with the phage. Titanium dioxide nanoparticles (TiO2-NPs) were used as nanosensors to detect and monitor virions’ titres in aqueous samples. Dispersion stability of TiO2-NPs in aqueous suspension was investigated using a UV-Visible spectrophotometer. The comparison of NP spectral profiles with and without phage elucidated the impact of phage’s titre on NP dispersion/aggregation behaviour in an aqueous solution. Indeed, the increase of nanoparticle dispersion stability is correlated with the increase of phage titre. Thus, based on this result, the phage was considered as a bio-dispersant agent. The determination of area under spectral profiles limiting the UV region [200–400 nm] was allowed to quantify, and compare the NPs bio-dispersion rate, in relation with added phage at different titres. In this study, this method was applied to monitor the phage amplification cycle for the detection of bacteria in viable but non-culturable (VBNC) state after water treatment by photocatalysis. The analysis of NP bio-dispersion rate shows an increase of TiO2-NP dispersion stability correlated with an increase of free phage titration, mainly after the entry of target bacteria in VBNC state underestimated using a conventional method. Thus, this method could allow the establishment of new recommendations of wastewater treatment and assessment.

The Colloidal Stability of Apolar Nanoparticles in Solvent Mixtures

Solvent engineering is a powerful and versatile method to tune colloidal stability. Here, we link the molecular structure of apolar ligand shells on gold nanoparticles with their colloidal stability in solvent mixtures. The agglomeration temperature of the particles was measured with small-angle X-ray scattering. It depended on solvent composition and changed linearly for hexane-hexadecane mixtures, but nonlinearly for cyclohexane-hexadecane and hexanol-hexadecane mixtures. Molecular dynamics (MD) simulations indicate that agglomeration is dominated by temperature-dependent ligand order in the alkane mixtures and that the temperature at which the ligand shell orders depends on the solvent composition near the ligands, which can differ substantially from the bulk composition. Small-angle neutron scattering confirmed that, at intermediate solvent compositions above the agglomeration temperature, the fraction of cyclohexane near the ligands was larger than in the bulk. The enrichment of cyclohexane near the ligands stabilized their disordered state, which, consequently, led to the experimentally observed nonlinear trend of the agglomeration temperature. In contrast, hexanol was depleted from the ligand shell at all temperatures. This again stabilized the disordered state. Furthermore, we found that agglomeration at high hexanol fractions was driven by a solvophobic effect that exceeded the influence of ligand order. The results show that strong nonlinearities in the colloidal stability of nanoparticle dispersions in solvent mixtures are directly linked to the molecular details of ligand-solvent and solvent-solvent interactions, which can be used to precisely tune stability.

Effects of the polymer glass transition on the stability of nanoparticle dispersions.

In addition to the repulsive and attractive interaction forces described by Derjaguin-Landau-Verwey-Overbeek (DLVO) theory, many charged colloid systems are stabilized by non-DLVO contributions stemming from specific material attributes. Here, we investigate non-DLVO contributions to the stability of polymer colloids stemming from the intra-particle glass transition temperature (Tg). Flash nanoprecipitation is used to fabricate nanoparticles (NPs) from a library of polymers and dispersion stability is studied in the presence of both hydrophilic and hydrophobic salts. When adding KCl, stability undergoes a discontinuous decrease as Tg increases above room temperature, indicating greater stability of rubbery NPs over glassy NPs. Glassy NPs are also found to interact strongly with hydrophobic phosphonium cations (PR4+), yielding charge inversion and intermediate aggregation while rubbery NPs resist ion adsorption. Differences in the lifetime of ionic structuration within mobile surface layers is presented as a potential mechanism underlying the observed phenomenon.

Colloidal Systems in Concentrated Electrolyte Solutions Exhibit Re-entrant Long-Range Electrostatic Interactions due to Underscreening.

Surface force measurements have revealed that at very high electrolyte concentrations as well as in neat and diluted ionic liquids and deep eutectic solvents, the range of electrostatic interactions is far greater than the Debye length. Here, we explore the consequences of this underscreening for soft-matter and colloidal systems by investigating the stability of nanoparticle dispersions, the self-assembly of ionic surfactants, and the thickness of soap films. In each case, we find clear evidence of re-entrant properties due to underscreening at high salt concentrations. Our results show that underscreening in concentrated electrolytes is a general phenomenon and is not dependent on confinement by macroscopic surfaces. The stability of systems at very high salinity due to underscreening may be beneficially applied to processes that currently use low-salinity water.

Experimental investigation on the effect of TiO2 nanoparticles on the performance of NH3 – H2O - LiBr absorption refrigeration system

The newly NH3 – H2O – LiBr working fluid can decrease the power wasted in the generator, thus improves the COP of the ammonia absorption refrigeration system. But the applying of NH3 – H2O – LiBr working fluid decreases the ammonia absorption efficiency, so the COP of the system is still unsatisfactory. To further enhance the COP of the NH3 – H2O - LiBr absorption refrigeration system, TiO2 nanoparticles are added to the NH3 – H2O - LiBr working fluid in this study. And the effects of TiO2 nanoparticles concentration on the performances of the generator, absorber, evaporator, condenser, and solution heat exchanger are tested in an ARS experimental system. The experimental results indicate that the addition of TiO2 nanoparticles increases the Pg, Pe, Pa, and Pc, meaning that the value of ammonia produced in the generator increases. Therefore, the COP and iCOP of the system are improved by adding TiO2 nanoparticles, and the COP is maximum improved by 18.96% compared with the ammonia-water absorption refrigeration system. When the xTiO2 is increased from 0.3% to 0.5%, the increase rate of the COP decreases because the newly added nanoparticles do not disperse well. So 0.3% is a better choice for the TiO2 nanoparticles concentration when comprehensively considering the dispersion stability of nanoparticles and the COP.

Tribological analysis of blended vegetable oils containing CuO nanoparticles as an additive

In view of environmental issues, petroleum-based oils are required to be replaced by vegetable oil-based nanolubricants. The key aim of the present work is to investigate the lubrication efficiency of neat blended oil and blended oil (rice bran: sunflower oil) containing copper oxide (CuO) nanoparticles in 0.01 %, 0.02 %, 0.03 %, and 0.04 % volume fraction. Also, to investigate the dispersion stability of nanoparticles having two different volume fraction (0.01% and 0.05%) in blended oil (rice bran oil: sunflower oil) with different nanoparticle to surfactant mass ratios (1:1, 1:2, and 1:3). The tribological properties of blended oil with four different volume fractions of CuO nanoparticles has been investigated on four ball tribotester by using ASTM D 4172B standards. The results showed that better dispersion stability of nanolubricant has been observed at optimum nanoparticle to surfactant mass ratio of 1:3. The minimum coefficient of friction and wear scar diameter has been observed at 0.04% volume fraction of CuO nanoparticles.

About the influence of the colloidal magnetic nanoparticles coating on the specific loss power in magnetic hyperthermia

The current magnetic hyperthermia with nanoparticles is a method of destroying cancer cells, increasingly studied theoretically and experimentally. The colloidal magnetic nanoparticle systems used in this method have a pronounced agglomeration tendency that leads to the blocking of blood vessels in the case of intravenous administration of the nanoparticles. For nanoparticle dispersion stability and biocompatibility, the particles are covered with an organic layer. The influence of nanoparticle coating on the generation of heat by magnetic hyperthermia is very little studied. In this paper, we theoretically study, by numerical simulation, the way in which the nanoparticle coating affects the agglomeration tendency of the nanoparticles, as well as the specific loss power which characterises the nanoparticle performance in the generation of heat by magnetic hyperthermia. For this purpose, we propose a theoretical model. The self-organisation of colloidal nanoparticles will be simulated using a Langevin dynamics stochastic method based on an effective Verlet-type algorithm, then the magnetic relaxation time used in the specific loss power (SLP) relation, obtained based on the theory of magnetic fluid losses from Rosensweig.

Effect of pH and surfactants on the electrokinetic properties of nanoparticles dispersions and their application to the PET fibres modification

This paper presents the effect of surfactants, pH and electrolyte (0.1 × 10−3 M KCl) on the stability of the aqueous dispersions of commercial ZnO and AgCu nanoparticles. As the surfactants cationic hexadecyltrimethylammonium bromide (CTAB), anionic sodium dodecyl sulfate (SDS), and nonionic 4-(1,1,3,3-tetramethylbutyl)phenyl polyethylene glycol (Triton X-100) at concentrations of 0.5 × 10−3, 1.0 × 10−3, and 0.1 × 10−3 M, respectively, were used. The zeta potential values, z-average hydrodynamic diameter and long-term stability of ZnO and AgCu nanoparticles were examined by means of the dynamic light scattering (DLS) technique. It was found that the presence of ionic surfactants reduced the tendency of nanoparticles for agglomeration/aggregation and improved their colloidal stability. They were characterized by high (>|70| mV) and pH-independent zeta potential values. In addition, ZnO nanoparticles in the presence of ionic surfactants showed a better long-term stability than AgCu nanoparticles. Their z-average hydrodynamic diameters in CTAB and SDS were 195 ± 2 nm and 295 ± 5 nm, respectively, and remained almost unchanged for 5 days. The addition of KCl improved the stability of aqueous and containing nonionic surfactant dispersions of nanoparticles, what was reflected in the zeta potential values > 30 mV in almost the entire pH range. The stability of nanoparticles dispersion significantly affects the uniformity of nanoparticles distribution on the fibres surface. The uniformity of distribution of the ZnO and AgCu dispersion on the surface of polyester (PET) fibres was carried out by means of microscopic methods (SEM/EDS).

Influence of the magnetic nanoparticle coating on the magnetic relaxation time.

Colloidal systems consisting of monodomain superparamagnetic nanoparticles have been used in biomedical applications, such as the hyperthermia treatment for cancer. In this type of colloid, called a nanofluid, the nanoparticles tend to agglomeration. It has been shown experimentally that the nanoparticle coating plays an important role in the nanoparticle dispersion stability and biocompatibility. However, theoretical studies in this field are lacking. In addition, the ways in which the nanoparticle coating influences the magnetic properties of the nanoparticles are not yet understood. In order to fill in this gap, this study presents a numerical simulation model that elucidates how the nanoparticle coating affects the nanoparticle agglomeration tendency as well as the effective magnetic relaxation time of the system. To simulate the self-organization of the colloidal nanoparticles, a stochastic Langevin dynamics method was applied based on the effective Verlet-type algorithm. The Néel magnetic relaxation time was obtained via the Coffey method in an oblique magnetic field, adapted to the local magnetic field on a nanoparticle.

Dual modified nanosilica particles as reinforcing fillers for dental adhesives: Synthesis, characterization, and properties

A facile procedure has been devised to develop a novel dentin bonding system containing poly (acrylic acid)-grafted-silanized fumed silica particles as reinforcing filler, with high stability of nanoparticle dispersion and enhanced bond strength and mechanical properties. In the first step, the silanization of fumed silica nanoparticles was performed in the following conditions: (i) ethanol-water solution with a pH of 5 and (ii) cyclohexane with a pH of 9 using trimethoxysilylpropyl methacrylate (γ–MPS) as a reactive silane coupling agent. FTIR and TGA analyses confirmed the presence of silane in the resultant structure and enhanced dispersion stability of modified particles was proved by a separation analyzer and also zeta potential analyses. In the second step, free radical polymerization of acrylic acid monomers in the presence of silanized nanoparticles was carried out and poly (acrylic acid) -grafted- silanized fumed silica were acquired. The flexural strength and fracture toughness of the adhesive containing 0.2 wt.% of the dual modified filler reached maximum of 70.4 MPa and 1.34 MPa m1/2, respectively, showing average improvements of 74% and 179%, respectively, in comparison with the adhesive without filler. Flexural modulus values did not significantly change with increasing the filler content except the adhesive containing 5 wt.% having the lowest flexural modulus. The highest microtensile bond strength was also observed at 0.2 wt.% filler content showing the average improvements of 197% as compared with the neat adhesive. Energy dispersive X-ray (EDX) mapping confirmed a homogenous and uniform distribution of the fillers in the adhesive matrix containing 0.2 wt.% and 0.5 wt.% of filler while incorporation of 5 wt.% led to large particle aggregates. SEM images of the fracture surface of the adhesive with different filler contents subjected to fracture toughness test showed rougher surface and longer crack path by increasing filler concentration. The adhesive containing 0.2 wt.% of filler perfectly penetrated into the dentin tubules proved by the SEM micrographs in microtensile bond strength test.

Thermal Conductivity of Multiwalled Carbon Nanotubes‐Kapok Seed Oil‐Based Nanofluid

AbstractThe synthesis of a nanofluid from multiwalled carbon nanotubes (MWCNTs) and Kapok seed oil by a one‐step method is reported. The nanofluid showed excellent stability of nanoparticle dispersion in the base fluid. Furthermore, this study deals with the prediction of the thermal conductivity of the MWCNTs‐kapok seed oil nanofluid. To improve the prediction of the thermal conductivity of the nanofluid, the artificial neural network (ANN) computing approach was used with different algorithms including the back‐propagation, Levenberg‐Marquardt, and genetic algorithm (GA). Finally, the ANN‐GA model is recommended for the prediction of thermal conductivity with higher accuracy.