Function Of Nanoparticle Concentration Research Articles

Mesoscale simulations of diffusion and sedimentation in shape-anisotropic nanoparticle suspensions.

We determine the long-time self-diffusion coefficient and sedimentation coefficient for suspensions of nanoparticles with anisotropic shapes (octahedra, cubes, tetrahedra, and spherocylinders) as a function of nanoparticle concentration using mesoscale simulations. We use a discrete particle model for the nanoparticles, and we account for solvent-mediated hydrodynamic interactions between nanoparticles using the multiparticle collision dynamics method. Our simulations are compared to theoretical predictions and experimental data from existing literature, demonstrating good agreement in the majority of cases. Further, we find that the self-diffusion coefficient of the regular polyhedral shapes can be estimated from that of a sphere whose diameter is the average of their inscribed and circumscribed sphere diameters.

Evaluation and prediction of rise velocity and drag coefficient of an ascending bubble affected by the impurity in continuous and discrete phases, distinctly and concurrently

Obtaining a deep knowledge about the bubbly flow systems, which are widely applied in various chemical and industrial processes, is crucial for scholars and engineers to achieve more accurate equipment design and processes control. This paper is dedicated to experimentally investigate the distinctly and concurrently effects of fumed silica nanoparticles (NPs) and hexane vapor molecules as impurities in continuous and discrete phases, respectively, on the terminal velocity and drag coefficient of a single rising bubble in aqueous solutions. The obtained experimental data were compared to the calculated data by derived correlations in literatures. As a result, none of those can predict the experimental data and a new correlation for considering the SiO2 NPs as an impurity in liquid is required. As a novelty, this work proposed two new correlations for prediction of terminal velocity and drag coefficient of a rising bubble in NPs solutions as a function of NPs concentration in aqueous solutions. The proposed correlations of terminal velocity and drag coefficient are in excellent agreements with the experimental data over the range of Re <310 and We <1.8, and with the maximum average relative errors of about 0.5% and 1.3%, respectively. Moreover, an interesting synergistic effect at the bubble interface was shown, due to creation of hexane oily layer at the interface and its interaction with rotational and vibrational effects of NPs in 200 ppm solution, where the exerted drag force on the rising bubble was reduced by 12.5% in comparison to the pure water (Air) case.

Viscosity of CuO nanofluids: Experimental investigation and modelling with FFBP-ANN

The current work examines the viscosity of nanofluids as a function of nanoparticle concentration, size, and temperature. CuO nanoparticles with an average size of 15 nm, 45 nm, and 75 nm have been used in this study. Viscosity measurements of volume concentrations of 1% to 4% are carried out in the temperature range of 293 K to 353 K. The results show a maximum increase of 23% in effective viscosity due to the addition of nanoparticles. However, the viscosity decreases by about 80% as the temperature increases from 293 K to 353 K. Furthermore, a maximum increase of 0.5% in viscosity is observed with the particle size increment. Based on present experimental data and literature data, a correlation is developed to predict the effective viscosity. Furthermore, ANN modelling is carried out to predict the effective viscosity of nanofluids and compared with the developed correlation. The results demonstrate that ANN modelling outperforms hypothesised correlation in estimating the effective viscosity. The R-squared values for the ANN model and correlation model are 0.95 and 0.90, respectively.

Structural and electrical behaviours of PEDOT:PSS thin films in presence of negatively charged gold and silver nanoparticles: A green synthesis approach

Negatively charged gold and silver nanoparticles are prepared using the dry leaf of Annona reticulata and are used to prepare thin films of PEDOT:PSS nanocomposites. Significant changes in structure, morphology and electrical behaviours of nanocomposite thin films are observed depending upon the type and concentration of nanoparticles. The composite nature of the films are evidenced from the X-ray diffraction, Fourier transform infrared and Raman spectroscopy, while the surface morphology and film thickness are obtained from the analysis of atomic force microscopy. The in-plane DC conductivity of the composite films is enhanced by a moderate value with increase in nanoparticle concentration. Electrical responses obtained from the impedance spectroscopy over a broad frequency range show that both the real and imaginary parts of the impedance vary as a function of nanoparticles concentration and applied frequency. Structural changes after composite formation and the corresponding modifications in electrical behaviors are explained.

Multi-axis alignment of Rod-like cellulose nanocrystals in drying droplets

HypothesisRadial capillary flow in evaporating droplets carry suspended nanoparticles to its periphery where they are deposited and form a coffee-ring. Rod-like nanoparticles seeking to minimize their capillary energy will align with their long-axis parallel to the contact line. Particles exhibiting electrostatic repulsion, such as cellulose nanocrystals (CNCs), establish a competition between capillary flow-induced impingement against a growing coffee-ring and entropic minimization leading to enhanced particle mobility. Therefore, balancing these effects by manipulating the local particle concentration in drying droplets should result in deposition with a controlled orientation of CNCs. ExperimentsThe dynamic local order in aqueous suspensions of CNCs in evaporating sessile droplets was investigated through time-resolved polarized light microscopy. The spatial distribution of alignment in deposited CNCs was explored as a function of nanoparticle concentration, droplet volume, initial degree of anisotropy, and substrate hydrophobicity. Computational analysis of the rotational Péclet number during evaporation was also investigated to evaluate any effects of shear-induced alignment. FindingsMultiple modes of orientation were identified suggesting local control over CNC orientation and subsequent properties can be attained via droplet-based patterning methods. Specifically, high local particle concentrations led to tangential alignment and lower local particle concentrations resulted in new evidence for radial alignment near the center of dried droplets.

The influence of SiO2 and Al2O3 nanofluids based on seawater on IFT reduction: EOR

Water injection is a widespread technique used in the oil production sector to enhance the oil recovery and expand the production life of a well. Using nanoparticles to further enhance the recovery by reducing interfacial tension (IFT) and altering wettability is a new trend adopted in the water injection application due to the low risk of formation damage, also for their cost-effectiveness. However, water salinity and suspended particles are significant challenges as they affect the behaviour of nanoparticles in the water saline media. The objective of this study is to evaluate the effect of two types of nanofluids with nano-SiO2 and Al2O3 on reducing IFT for water injection application. In this work, a 1:1 mix of seawater and effluent water is, respectively, examined based on an interfacial step change. The technique of mixing seawater with effluent water is being used to reduce the salinity of the effluent water for the selected reservoir. The mixed water was prepared under elevated temperature and 1000 Psi to resemble downhole conditions and then evaluated by inductively coupled plasma and energy-dispersive spectroscopy, where for thermal stability prediction of the water mix the OLI Studio was used. Then selected nanoparticles were then added at different concentrations to the mixed water to form the required nanofluid. IFT was measured as a function of nanoparticle concentration by a Drop Shape Analyzer—DSA100 apparatus using an optical pendant drop method to evaluate the effect of the nanoparticles within the prepared mix in terms of interfacial tension between crude oil and the prepared water, as IFT is an essential variable for oil recovery. The study revealed that 0.025 and 0.05 wt% of SiO2 concentration had reduced the IFT of the crude effectively for the selected seawater mix ratio. In addition, when R2 values for the collected data were compared, Al2O3 concentration of 0.025% showed more cost-effectiveness over other concentrations. The study concludes that the prepared water mix is compatible with nanoparticles and causes the desired reduction in IFT at a low concentration which can be considered as an advantage in terms of cost-effectiveness and rock pore plugging.

Effects of nanoscale fuel additives on properties and non-reacting spray performance of alternative, conventional and blended jet fuels at elevated ambient conditions

The dispersion of nanoscale metal particles in liquid hydrocarbon fuels, or nanofuels, has recently garnered interest owing to its positive influence on fuel emission characteristics. Physical properties of the fuel are altered due to the addition of nanoparticles, which in turn can affect its atomization, combustion, and emission characteristics. Therefore, a better understanding of the atomization phenomena is essential to recognize its influence on the combustion process. The objective of this work is to investigate the impact of alumina nanoparticles on the non-reacting spray characteristics of conventional Jet A-1, an alternative gas-to-liquid (GTL) fuel, and a 50–50% by-volume blend of these, each at elevated ambient conditions that are relevant to industrial applications. First, the influence of the nanoparticle addition on the fuel properties relevant to atomization is investigated. Then, the macroscopic spray characteristics, such as spray cone angle, liquid sheet dynamics, and liquid sheet velocity, are determined as a function of nanoparticle concentration, fuel type, and ambient pressure. For this purpose, an aviation-based pressure-swirl nozzle is used to generate the fuel spray with nanoparticle weight concentrations at 0, 2%, and 4%. The spray characteristics are measured at different ambient pressures of 100, 500, and 900 kPa, while the ambient temperature is maintained at an elevated 400 K for all the cases. The spray features of the above fuels with and without the dispersion of nanoparticles are compared. The macroscopic spray results demonstrate that the nanoparticle dispersion, even at low concentrations, can affect the spray in the near-nozzle region. The earlier disruption of the liquid sheet occurring with nanofuels indicates the influence of nanoparticles on the spray liquid sheet dynamics. Also, the results show that ambient pressure has a significant effect on the spray features for all three fuels studied.

A Novel Supercritical CO2 Foam System Stabilized With a Mixture of Zwitterionic Surfactant and Silica Nanoparticles for Enhanced Oil Recovery.

In order to improve the CO2 foam stability at high temperature and salinity, hydrophilic silica nanoparticles (NPs) were added into a dilute zwitterionic surfactant solution to stabilize supercritical CO2 (SC-CO2) foam. In the present paper, the foaming capacity and stability of SC-CO2 foam were investigated as a function of NP concentration at elevated temperatures and pressures. It was observed that the drainage rate of SC-CO2 foam was initially fast and then became slower with NPs adsorption at the gas-liquid interface. The improved foam stability at high temperature was attributed to the enhanced disjoining pressure with addition of NPs. Furthermore, an obvious increase in the foam stability was noticed with the increasing salinity due to the screening of NP charges at the interface. The rheological characteristics including apparent viscosity and surface elasticity, resistance factor, and microstructures of SC-CO2 foam were also analyzed at high temperature and pressure. With addition of 0.7% NPs, SC-CO2 foam was stabilized with apparent viscosity increased up to 80 mPa·s and resistance factor up to 200. Based on the stochastic bubble population (SBP) model, the resistance factor of SC-CO2 foam was simulated by considering the foam generation rate and maximum bubble density. The microstructural characteristics of SC-CO2 foam were detected by optical microscopy. It was found that the effluent bubble size ranged between 20 and 30 μm and the coalescence rate of SC-CO2 foam became slow with the increasing NP concentration. Oscillation measurements revealed that the NPs enhanced surface elasticity between CO2 and foam agents for resisting external disturbances, thus resulting in enhanced film stability and excellent rheological properties.

Stability, Thermal Conductivity, Viscosity, and Tribological Characterization of Zirconia Nanofluids as a Function of Nanoparticle Concentration

Commercially prepared spherical zirconia (ZrO2) nanoparticles with an average particle diameter of 5 nm and functionalized with a hydrocarbon ligand were dispersed in a polyalphaolefin (PAO) base oil, producing a 10-nm stabilized zirconia nanofluid. The resulting nanofluid’s properties were characterized, including thermal conductivity and viscosity. A preliminary study of the nanofluid’s ability to generate protective tribofilms was conducted. Long-term stability was verified using dynamic light scattering (DLS) and average particle size was quantified as a function of time. A 10 wt% ZrO2 nanofluid maintained a 10-nm average particle size over 25 months, with no signs of agglomeration or sedimentation, and redispersion was not necessary before analysis. The tribological performance of several concentrations of ZrO2 nanofluids wasdisc characterized with a ball-on-disc tribometer. Tribofilm growth over time was collected via optical interference imaging. Friction data collected over time are also reported. Nanoparticle concentration was varied to understand its effect on tribofilm growth. The ZrO2 tribofilm morphology and chemistry were characterized using scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), and transmission electron microscopy (TEM).

Investigation of flexible polymer-Tl2O3 nanocomposites for x-ray detector applications

We report on the synthesis and characterization of composite semiconducting polymer – nanoparticle membranes for X-ray detection applications. The membranes are made of poly(vinyl alcohol) (PVA) organic polymer that is doped with ionic liquid (IL) to control its electrical conductivity. Tl2O3 nanoparticles with different weight concentrations are added to the polymer, and membranes are produced using solution casting method. The nanoparticles are synthesized using a microwave assisted technique under controlled temperature and pressure, and their average size is 13.0 ∓ 1.9 nm. Structural and compositional tests confirm the fabrication of homogeneous polymer-nanoparticle films. Electrical impedance tests are conducted as a function of nanoparticle concentration and temperature for the membranes, and they reveal that the dc electrical resistance of the membranes decreases with increasing both nanoparticle concentration and temperature. The activation energy was found to increase with increasing nanoparticle concentration. The membranes are utilized as conductometric X-ray sensors, and their response increases with increasing X-ray generator voltage. The fabricated composite membranes exhibit semiconducting properties, easy to fabricate, low cost, and qualify practical device utilization in the X-ray dosimetry sector.

Production and characterization of flexible semiconducting polymer-nanoparticle composites for x-ray sensors

Fabrication and characterization of flexible semiconducting polymer-nanoparticles composite membranes for x-ray sensor device applications are presented in this work. Poly(vinyl alcohol) (PVA) polymer was initially doped with glycerol ionic liquid (IL) that permitted the control of its electrical resistivity. Metal-oxide Bi2O3 nanoparticles were prepared by a modified sol-gel method. The average nanoparticle size was found to be 39 ± 10 nm. Thin films of flexible polymer membranes with different nanoparticle concentrations were prepared using a solution casting method. Compositional characterizations revealed the formation of homogeneous polymer-nanoparticle membranes. Electrical impedance measurements of the membranes were performed for the membranes in a form of capacitor structure as a function of temperature and nanoparticle concentration. The measurements demonstrated that the membranes could be modeled with a pair of parallel resistor and capacitor that were assigned to the contributions of grain boundaries as well as the region of electron depletion in the membrane. As nanoparticle concentration increases, the resistivity and activation energy decrease. Current-voltage measurements demonstrated that the produced membranes function as x-ray sensors, and their response increases as a function of nanoparticle concentration. The produced membranes exhibit semiconducting properties that qualify them as potential candidates for device applications in the field of x-ray dosimeter.

Ablation of Hepatic Tumors through the Use of a Novel Magnetic Nanocomposite Probe: Magnetic Characterization and Finite Element Method Analysis

The authors recently proposed a novel system for thermoablation—based on nanoheating—that can potentially overcome limitations associated with previously reported techniques. The aim of this study was to evaluate the therapeutic performance of the system in the ablation of hepatic tissue, the most frequently ablated. A model nanocomposite system, maghemite nanoparticle-filled polydimethylsiloxane, was prepared, and its magnetic properties were studied as a function of nanoparticle concentration. On the basis of measured magnetic properties, a 3D finite element method (FEM) model was used to explore the development of temperature and thermal damage in nonperfused and fully perfused tissue using alternating magnetic field (AMF) parameters that are acceptable for human use. The FEM model was tested for its validity using an analytical model. The saturation magnetization increased to about 9% of the value of pure maghemite nanoparticles over the range of volume fraction (vol. %) between 1 and 5%. Lesion sizes were shown to be greatly affected by tissue perfusion and time. FEM predictions showed good agreement with results obtained with an analytical model to within 7%. Probes fabricated with magnetic nanocomposite can potentially be used to achieve reasonable lesion sizes in hepatic tissues using human-safe AMF parameters.

Controlling boundary layer separation in stretching sheet flow

The effects of non-uniform nanoparticle concentration within the boundary layer flow due to stretching surface are analyzed by employing a non-homogeneous model of nanofluid which passively controls the concentration of nanoparticles at the surface. All fluid properties are simulated as function of nanoparticle concentration. For such a consideration a self-similar solution exists and its worth mentioning influence is to control the boundary layer separation which is subsequently found to depend upon diffusion parameter and nanoparticle concentration. Furthermore the results show that the behavior of nanoparticles distribution across the boundary layer is highly dependent upon variation of different parameters. For instance, Shmidt number leads to decrease the concentration layer thickness and nanoparticle concentration at the sheet but hydrodynamic and thermal boundary layers remained unaffected. The heat transfer and drag coefficient enhancement are also directly affected by the non-uniform behavior of nanoparticle is also an important observation towards the understanding of role of nanoparticle in momentum and thermal transport.

A Tribological Study of γ-Fe2O3 Nanoparticles in Aqueous Suspension

In this work, the nano- and macroscale tribological properties of maghemite (γ-Fe2O3) nanoparticles in aqueous solution are compared and contrasted for alumina contacts as a function of nanoparticle concentration. A quartz crystal microbalance (QCM) technique was used for nanotribology measurements and a ball-on-disk method was used to measure macroscale friction coefficients. Statistical methods were employed to identify significant associations between the QCM and ball-on-disk measurements, employing selected candidate performance factors for each system. In particular, the macroscale response was parameterized by % reduction in the friction coefficient while candidate QCM “bulk” and “surface” performance factors were selected from functions of the frequency f and resistance Rm shifts upon addition of nanoparticles to the water surrounding the QCM. Incremental increases in concentration were performed and reductions in friction and drag forces were observed for concentrations up to 0.6 wt%, after which further reductions were not observed. The factor δRfilm/δffilm exhibited a linear correlation with the reduction in macroscale friction coefficient, defined as the ratio of the shift in resistance to the shift in frequency attributable to interfacial effects and changes in the glide plane location. Atomic force microscopy was also utilized to both qualitatively and quantitatively determine surface roughness before and after particle uptake, leading to the observations that particles are easily removed from the surface and do not significantly alter surface morphology.

Influence of surface roughness and nanoparticles concentration on the friction and wear characteristics of PAO base oil

Surface roughness plays a significant important role in deciding the tribological behavior of different materials. The aim of the study is to evaluate the effect of surface roughness and nanoparticles concentration on the lubricating performance of synthetic oil. In the present study, diamond nanoparticles have been used as additives in the PAO oil. The nanoparticles were used in varying concentrations from 0–0.8 wt%. The effect on seven surface roughness values has been studied. The testing conditions were selected in such a way so that boundary lubrication regime can be ensured. The results were obtained for steel/steel contacts using pin on disc tribometer. A 3D profilometer was used to quantify the different surface roughness parameters. Optical microscopy was used to find out wear scar diameter, in order to calculate the wear volume. Scanning Electron Microscopy (SEM) was used to analyze the wear behavior of worn out samples. It can be observed that for the oil containing diamond nanoparticles, the COF is a function of nanoparticles concentration and size. For rough surfaces, the higher concentration of nanoparticles reduces the COF by a larger amount and for the smooth surfaces a small concentration of nanoparticles is enough to lower the COF. The minimum COF was obtained for 0.4 wt% concentration of nanoparticles for 0.120 μm surface. This is because of the nanoparticles size, which is in the range of the Ra value of the disk samples as a small amount of nanoparticles is sufficient to fill the valleys and polish the sharp asperities. However, the increased concentration of nanoparticles acts as abrasives, thereby resulting in a slight increase in COF.

How to accurately predict solution-phase gold nanostar stability.

Unwanted nanoparticle aggregation and/or agglomeration may occur when anisotropic nanoparticles are dispersed in various solvents and matrices. While extended Derjaguin-Landau-Verwey-Overbeek (DLVO) theory has been successfully applied to predict nanoparticle stability in solution, this model fails to accurately predict the physical stability of anisotropic nanostructures; thus limiting its applicability in practice. Herein, DLVO theory was used to accurately predict gold nanostar stability in solution by investigating how the choice of the nanostar dimension considered in calculations influences the calculated attractive and repulsive interactions between nanostructures. The use of the average radius of curvature of the nanostar tips instead of the average radius as the nanostar dimension of interest increases the accuracy with which experimentally observed nanoparticle behavior can be modeled theoretically. This prediction was validated by measuring time-dependent localized surface plasmon resonance (LSPR) spectra of gold nanostars suspended in solutions with different ionic strengths. Minimum energy barriers calculated from collision theory as a function of nanoparticle concentration were utilized to make kinetic predictions. All in all, these studies suggest that choosing the appropriate gold nanostar dimension is crucial to fully understanding and accurately predicting the stability of anisotropic nanostructures such as gold nanostars; i.e., whether the nanostructures remain stable and can be used reproducibly, or whether they aggregate and exhibit inconsistent results. Thus, the present work provides a deeper understanding of internanoparticle interactions in solution and is expected to lead to more consistent and efficient analytical and bioanalytical applications of these important materials in the future. Graphical abstract ᅟ.

Investigation of an Optimum Concentration for Nano-Silica Used as an Adhesive Bonding Strength Enhancer

In this paper, the effect of silica nanoparticles (nano-silica) on the bonding strength of reinforced adhesive joints was experimentally studied in five concentrations. A two-part epoxy-based adhesive (Araldite 2015) was used to bond the adherends as well as silica nanoparticles for strengthening purposes. Nano-silica was added into the adhesive by 1, 1.5, 2, 2.5 and 3 wt.%. Some adhesive joints with and without nanoparticles were tested under uniaxial loading to obtain their bonding strength. The results showed that the change in the bonding strength is a function of nanoparticles concentration. Furthermore, it was concluded that the addition of silica nanoparticles has a suitable effect on the joint strength at an optimum point, in which the joint strength takes its maximum value, and a further increase in the nanoparticles weight fraction causes the joint strength to decrease.

Tribological Investigation of Graphene as Lubricant Additive in Vegetable Oil

In this study, the tribological behaviours of graphene nanoparticles as lubricant additive in vegetable oil were investigated as a function of nanoparticle concentration. Graphene nanoparticles were added at 25 ppm, 50 ppm and 100 ppm as additive into vegetable oil as lubricant through hydrodynamic and acoustic cavitation as homogenising mechanism. The tribological properties of each homogenised solution were tested using a four-ball machine according to ASTM D4172. Wear scar diameter and friction coefficient were the determining parameters in this study. The results showed that 50 ppm is the optimum concentration that recorded the lowest wear scar diameter and friction coefficient as compared to control sample.

A local effect model-based interpolation framework for experimental nanoparticle radiosensitisation data

A local effect model (LEM)-based framework capable of interpolating nanoparticle-enhanced photon-irradiated clonogenic cell survival fraction measurements as a function of nanoparticle concentration was developed and experimentally benchmarked for gold nanoparticle (AuNP)-doped bovine aortic endothelial cells (BAECs) under superficial kilovoltage X-ray irradiation. For three different superficial kilovoltage X-ray spectra, the BAEC survival fraction response was predicted for two different AuNP concentrations and compared to experimental data. The ability of the developed framework to predict the cell survival fraction trends is analysed and discussed. This developed framework is intended to fill in the existing gaps of individual cell line response as a function of NP concentration under photon irradiation and assist the scientific community in planning future pre-clinical trials of high Z nanoparticle-enhanced photon radiotherapy.

Effect of nanoparticles/nanofluids on the rheology of heavy crude oil and its mobility on porous media at reservoir conditions

In this work, we evaluate the effect of nanoparticles and nanofluids as viscosity reducers for heavy crude oil (HO). The effect of alumina, silica and acidic silica nanoparticles was evaluated through n-C7 asphaltene adsorption and aggregation tests using UV–vis spectrophotometry and dynamic light scattering. The nanoparticles of acidic silica were used to prepare a water-based nanofluid at different concentrations in distilled water, and also with the addition of 2.0wt% of a non-ionic surfactant. The shear rheological response was obtained as function of nanoparticle concentration, temperature (from 298 to 323K) and shear rate (ranging from 0 to 100s−1). Experimental results indicate that increasing the concentration of nanoparticles in the mixture, up to 10,000ppm, leads to a viscosity reduction of approximately 90% in comparison with the nanoparticle-free crude oil. At higher concentration of nanoparticles, the effectiveness of the heavy-oil viscosity reduction diminishes. Rheological tests showed a non-Newtonian behavior for the mixtures tested at 298K. However, as the temperature reaches 323K the specimens behave in a Newtonian fashion. Coreflooding tests were conducted under typical reservoir conditions of pore and overburden pressures, i.e. 2600 and 3600psi, respectively, and at 360K. Results indicate that the addition of nanoparticles increases the heavy oil mobility and leads to an improvement in oil recovery of roughly 16%.