Concentration Of SiO2 Nanoparticles Research Articles

Effects of embedded SiO2 nanoparticles on the moisture barrier performance of inorganic/organic laminates

Thin-film encapsulation (TFE) is essential and challenging for flexible organic/quantum dot light-emitting diodes (OLEDs/QLEDs). In this work, SiO2 nanoparticles were added into the NEA 121 polymer (s-NEA) to prolong the permeation pathways, showing good barrier property and high optical transparency. With increasing the concentration of SiO2 nanoparticles up to 20 mg/ml, the value of water vapor transmission rate (WVTR) decreased. A single s-NEA layer with silica concentration of 20 mg/ml and thickness of ~ 75 µm exhibited WVTR of 2.5 × 10−3 g/m2/day and light transmittance of above 80%. Al2O3 thin films fabricated using atomic layer deposition were inserted between s-NEA layers to form dyad-style Al2O3/s-NEA multilayers. The Al2O3 (60 nm)/s-NEA (20 µm) multilayers with 3 units exhibited WVTR of 2.6 × 10−5 g/m2/day and consistently demonstrated a significantly extended QLED lifetime.

The effect of SiO2 nanoparticles content in engine oil on tribological properties of valvetrain chain transmission components

The drive from the crankshaft to the camshaft in an internal combustion engine is usually carried out by means of a cogged belt transmission or a chain transmission when high millage is required without service operations. The valvetrains in CI engines sometimes use the gear transmissions, and the historical rather bevel gear can be found in old cars of collectors or in some motorcycle engines. The chain gear used in SI engines has a two- or three-row chain with high strength, due the unevenness of loads that additionally induce chain pulling and valve timing deregulation. The chain transmission requires the use of pre-tensioners, usually self-acting and driven by springs or oil pressure. The vibrations and chain runout are limited using plastic guides placed on the outside of the long straight sections of the chain. The model of the chain transmission developed with the use of the Finite Elements Method, which operates under oil lubrication conditions, was analyzed. Such the model allowed obtaining weight and mass inertial moments of components. The aim of the study was to evaluate the effect of SiO2 nanoparticles content in engine oil on the friction between chain transmission components. The resulted values of the friction torque in the chain transmission operating in different conditions of lubrication have been presented in the paper.

Systematic experimental investigation of filtration losses of drilling fluids containing silicon oxide nanoparticles

This paper presents the results of silicon oxide nanoparticles-incorporated drilling fluid filtration through a porous medium with different permeability. A water-based clay suspension was used as a basic model for creating investigated fluid samples. AlN (aluminium nitride) particles were used as a dispersed phase. The concentration of microparticles varied from 0.5 to 4.00 wt%, while the microparticles size varied from 1 to 10 μm. The concentration of SiO2 nanoparticles was changed within the range of 0.25 and 4.00 wt%, while the nanoparticles size varied from 5 to 100 nm. It was shown that filtration of drilling fluids with nanoparticles inclusions depends on their concentration, size and material, the concentration and size of microparticles and the pore sizes of ceramic filters. The addition of the nanoparticles leads to a significant reduction in filtration of a microsuspension and affects the structure and thickness of a cake formed on the surface of a filter. The main novelty of this work lies in the fact that the effect of the addition of nanoparticles on filtration losses depends on the ratio between nano and microparticles. It was shown that the positive effect of nanoparticle additives on filtration losses is determined not only by the properties of nanoparticles (size and concentration), but also by the properties of microparticles contained in the drilling fluid, as well as the characteristics of the rock (pore size).

Influence of SiO2 nanoparticles on the dielectric properties and anchoring energy parameters of pure ferroelectric liquid crystal

In this study, we have investigated the electrical and anchoring energy of ferroelectric liquid crystal (FLC) with the dispersion of SiO2 nanoparticles (NPs). Due to their higher average spontaneous polarization and helical arrangement of FLC molecules, the molecules strongly interacted to SiO2 NPs which increased the value of dielectric permittivity and anchoring energy parameters as demonstrated by the dielectric and electro-optic properties measurement. This two-dimensional array of molecules has been exploited through the study of dielectric permittivity and dielectric loss in presence of silica NPs from low frequency regime to high frequency region in deep smectic phase. In present work we reported dielectric and electro-optical parameters for pristine FLC and SiO2+FLC composites (0.5% and 1.0% wt/wt concentrations of SiO2 NPs). The dielectric permittivity and dielectric loss have been calculated from the measurement of capacitance and conductance with variation of frequency and concentration of NPs as well. The dispersion and polarization anchoring energy coefficients have been calculated from electro-optic properties measurement with the function of applied voltage for pure and SiO2+FLC composites. The dielectric permittivity has increased with the dispersion of SiO2 NPs in pure FLC matrix and relaxation frequency shifted towards high and low frequency region for low (0.5%) and high (1.0%) concentrations of NPs. The spontaneous polarization of SiO2+FLC composites is increased as compared to pure FLC. The experimental results are explained on the basis of different intermolecular interactions arising between FLC molecules and SiO2 NPs.

Investigation of tribological properties of lithium grease with SiO2 nanoparticles

The aim of the work was to investigate the effect of the SiO2 nanoparticles concentration in the lithium grease and of contact pressure on the spinning friction coefficient in the contact zone between a steel plate and a ball. The invvestigations were carried out using the a tribotester for the spinning friction torque in the contact between the ball and the plate. Ball rotated relative to the plate axis at a constant speed and was loaded by the a force increasing in a stepwise manner for the consecutive series. The contact zone was lubricated with a pure lithium grease - pure or with the grease with suspended SiO2 nanoparticles. The friction coefficient decreased with the increase of contact pressure for the pure lithium grease. For the concentration □ = 6wt.% of SiO2 nanoparticles in the grease friction coefficient decreased and for the other concentrations it increased with the increase of the contact pressure. If the values of average contact pressure were below 550 MPa, the friction coefficient values for pure lithium grease were higher than those for lithium grease with suspended SiO2 nanoparticles. For higher values of the contact pressure, the values of the friction coefficient for the pure lithium grease could be lower, equal or higher than those for lithium grease containing SiO2 nanoparticles depending on the value of SiO2 the concentration.

Photocurable Poly(ethylene glycol) Diacrylate Resins with Variable Silica Nanoparticle Loading

Photocurable nanocomposites have tremendous potential in tissue engineering, advanced manufacturing, and structural, multifunctional materials. This project investigates the effect of silica (SiO2) nanoparticle loading content on the thermal, mechanical, physical, and morphological characteristics of the nanocomposite. An increased concentration of SiO2 nanoparticles causes a decrease in the gel fraction of the nanocomposite, which, at low nanoparticle loading, degrades the thermal and mechanical properties. However, further addition (>3.8 wt %) causes an increase in the glass-transition temperature, Young’s modulus, and ultimate compressive strength. The addition of the nanoparticles had no significant effect on the hydrophilicity according to water uptake experiments. Small-angle X-ray scattering experiments, in conjunction with scanning electron microscopy and transmission electron microscopy, indicated a multimodal particle size distribution and the presence of large-scale aggregates.

Cooperative surface‐enhanced Raman spectroscopy enhancement in Au nanorod/SiO2 nanoparticle solutions

AbstractSurface‐enhanced Raman spectroscopy (SERS) signals in liquid state are significantly enhanced by utilizing cooperative interaction between metal surface plasmon and dielectric resonance. Raman signals from the diluted solutions are very weak even if they are amplified by SERS using Au nanorods. When SiO2 nanoparticles are added together with Au nanorods, however, Raman intensity increased by three order comparing with that of system containing only Au nanorods. Finite‐difference time‐domain simulations show that SiO2 nanoparticles exhibit dipolar electric resonance, which is strongly enhanced by interacting with the surface plasmon of Au nanorods. The size and concentration of SiO2 nanoparticles are optimized to 354 nm in diameter and 4.5 vol%. Under the optimized condition, SERS intensity decrease with concentration of analyte (rhodamine 6G or crystal violet) is much slower for the system containing both Au nanorods and SiO2 nanoparticles than that of the system containing only Au nanorods. The detection limit is 10−10 M for both aqueous rhodamine 6G and crystal violet solutions.

A molecular investigation into the interaction of SiO2 nanoparticles with elastase by multispectroscopic techniques and kinetic studies

The increasing use of nanoparticles in various industries has triggered the need to study their interconnection with biological macromolecules. The goal of this study was to survey the SiO2-nanoparticles efficacy on the thermal denaturation, conformation and activity of elastase at three temperatures of 303, 313 and 323K in the Tris buffer at pH of 8.5. In this work, distinct techniques such as UV–vis Spectrophotometry, Spectrofluorometry, and circular dichroism were employed. The fluorescence studies showed that SiO2 nanoparticles extremely reduced the intensity of elastase with the static mechanism. Thermodynamic parameter analysis also indicated that the process of binding of SiO2-nanoparticles to elastase was spontaneous, thereby suggesting that van der Waals forces or hydrogen bonding interactions played a key role in determining the complex stability. Far-UV circular dichroism studies further revealed that SiO2 nanoparticles could cause 9.79% reduction in the content of the α-helix and 3.24% increase in the content of the β-sheet.Furthermore, kinetic parameters (Vmax and Kcat/Km) indicated that SiO2 nanoparticles had an activation effect on the elastase activity. Melting temperature studies at the selected concentration of SiO2 nanoparticles also showed that by adding SiO2 nanoparticles, elastase thermal stability was slightly increased. Overall, these nanoparticles modified the structure of the elastase, ultimately changing the activity and stability of this enzyme.

Superhydrophobic surface by SiO2 particle modified SiO2-Ni/a-C:H film deposition and superior corrosion protection

A superhydrophobic surface was constructed by a simple method of one-step electrochemical deposition in which methanol was used as carbon source and SiO2 nanoparticles/nickel were used as dopant. Carbon-based films doped with SiO2 nanoparticles and nickel (SiO2-Ni/a-C:H films) were fabricated for comparison experiments at various SiO2 nanoparticle concentrations. It was turned out that the maximum contact angle of SiO2-Ni/a C:H film with SiO2 nanoparticle concentration of 0.006 mg ml−1 (sample-3 film) is 162.4 degrees, and the minimum sliding angle is 1.2 degrees, showing excellent superhydrophobicity. Furthermore, dynamic potential polarization and electrochemical impedance spectroscopy (EIS) measurements indicated that the superhydrophobic film exhibited excellent anti-corrosion performance. It is very important for the industrial manufacture of corrosion-resistant superhydrophobic films and has broad prospects for expanding the application of carbon-based films.

Simultaneous mapping of single bubble dynamics and heat transfer rates for SiO2/water nanofluids under nucleate pool boiling regime

Dependence of single vapor bubble dynamics and heat transfer rates on varying concentration of SiO2 nanoparticles for a range of subcooled conditions (0–9 °C) has been experimentally studied under nucleate pool boiling configuration. Non-invasive measurements have been carried out using rainbow schlieren deflectometry. Results on bubble dynamics showed that the bubble diameter and aspect ratio decrease with increasing subcooling levels as well as concentration of nanofluids. The frequency of bubble oscillations was found to increase first and then decrease with increasing subcooling levels while it decreases monotonically with increasing nanofluid concentration. Bubble departure frequency increased significantly for nanofluids, while it decreased with increasing subcooling levels. Condensation effects at the bubble interface were reflected in the form of redistribution of colors around it. Schlieren images clearly revealed a spread in the spatial extent of the thermal boundary layer region caused by the suspended nanoparticles around the vapor bubble as well as near the heated substrate. This phenomenon has been considered as one of the factors that tends to alter the condensation effects and, in turn, affects the bubble dynamics. Quantitative analysis of schlieren images revealed that the natural convective heat flux increases with increasing subcooling levels, while it decreases with increasing nanoparticle concentration. Deterioration in the natural convection phenomenon in the presence of suspended nanoparticles has been attributed to the reduced strength of thermal gradients adjacent to the heater substrate. On the other hand, evaporative heat flux was observed to decrease with increasing subcooling levels and increase with increasing concentration of nanofluids.

Study of Sedimentation Process in Nanofluids with Various Concentrations of SiO2 and Al2O3 Nanoparticles

This work focuses on the preparation of nanoliquids with application of nanoparticles in order to study sedimentation processes in suspensions chosen. Nanoliquids on the basis of SiO2 and Al2O3 nanoparticles with sizes of 50 nm are prepared at their various concentrations using water as a basic liquid. The sedimentation process of the suspension in a steady state and for a long time has been monitored. In accordance with preliminary tests, sedimentation in SiO2-based nanoliquids is slower than that in nanoliquids on the basis of Al2O3 nanoparticles. The monitoring for 72 h of sedimentation of nanoliquids prepared using a two-step method with application of two types of SiO2 nanoparticles with sizes of 12 nm and 16 nm, as well as Al2O3 with a size of 50 nm, reveals that sedimentation and agglomeration processes in the considered nanoliquids depend to a large extent on the size and concentration of nanoparticles. The optimal sizes of particles and their concentrations in the suspension result in a very weak sedimentation.

The influence of SiO2 nanoparticles addition into electrolyte on the wear resistance of oxide layers formed by PEO on aluminum-silicon alloy

Scanning electron microscopy, X-ray spectral microanalysis, X-ray diffraction analysis, and instrumental indentation were used for studying of oxide layers formed by plasma electrolytic oxidation (PEO) on the eutectic aluminum-silicone alloy A04130 in electrolyte with the addition of SiO2 nanoparticles of different concentrations. The optimum concentration of SiO2 nanoparticles in the electrolyte (3 g/l) was found, for achieving maximum microhardness and wear resistance of the oxide layer, exceeding the value obtained in the electrolyte without adding SiO2 nanoparticles by 1.6 and 3.5 times, respectively.

Superhydrophobic Coating Polymer/Silica Nanocomposites: Enhancing Water Vapor Barrier Properties of Packaging Paper with Ultra-Thin PS/silica nanocomposite polymer Coating

Regardless, the advantages of packaging paper and paperboards they lose their marketing share to the plastics because of their inadequate barrier properties due to their porous structure. They have no resistance against gases, moisture, and vapors. For that reason, the aim of this study is imparting roughening to cellulose fiber surface by applying ultra-thin coating of PS /silica nanocomposite. The effect of hydrophobic coating on surface morphology (SEM), contact angel, water vapor permeability (WVP), water sorption isotherm, and mechanical properties were investigated. The maximum contact angel >120o was obtained at SiO2 nanoparticle concentration (4%). WVP results revealed remarkable sharp decline in WVP of coated paper compared with uncoated one with increasing coating thickness beyond ( 4% ) SiO2 nanoparticle content attained WVP (0.0003 g Pa-1 s-1 m-1) compared with uncoated sample (0.0126 g Pa-1 s-1 m-1 ). The sorption isotherm of PS/ silica nanocomposite coated paper results have been fitted using BET model. The curves exhibited the characteristic sigmoid-shaped type II isotherm. The monolayer water content values (M0) range between 0.00005 - 0.00280 g water/g dry film. The applied PS/silica nanocomposite on mechanical properties showed enhancement in each of burst, short span, tensile strength. However, roughness and elongation decreased further than (4%) SiO2 nanoparticle content.

Application of SiO2 nanoparticles as pretreatment alleviates the impact of drought on the physiological performance of Prunus mahaleb (Rosaceae)

We studied the physiological responses of Prunus mahaleb (Mahaleb) seedlings to drought stress when previously irrigated (or not) with different concentrations of SiO2 nanoparticles (SNPs). SNPs were applied at four concentrations (0, 10, 50 and 100 mg L-1) for 45 days, and then seedlings were subjected to three watering treatments including low (300 mL water every 3 d), moderate (150 mL water every 3 d) and severe drought stress (no irrigation) for 19 days. Results showed that gas exchange – photosynthesis, stomatal conductance, and transpiration rate – were significantly less impacted by severe drought stress when seedlings were pretreated with SNPs at high concentrations. Beneficial effects of SNPs pretreatment were evident in the nutritional status of the plants as the concentration of N, P and K, were maintained at similar levels than in well-watered seedlings. Pretreated seedlings were able to maintain the root length and to reduce the impact of severe drought on root dry mass accumulation. Therefore, application of SNPs as pretreatment should be considered as a promising agronomic practice in sites prone to suffer from water deficit.

Effect of SiO2 nanoparticles on compression behavior of flexible polyurethane foam

In the current study, flexible polyurethane foam was reinforced with different contents of SiO2 nanoparticles (0.5–2 wt%). Compression test was performed in a range of strain rates (1–20 min−1), and compression set test was also done at different temperatures. Results showed that addition of SiO2 nanoparticles improved compression properties of PU foam and the sample with 0.5 wt% SiO2 nanoparticles exhibited the highest mechanical performance with about 180 and 40% improvements in the compressive plateau and densification stress. Strain rate was showing a positive effect on these parameters with the enhancements of 360 and 90%. It was also shown that the temperature had a remarkable effect on compression set behavior of nanocomposite as the values change from 0.5% at − 20 °C to near 79% at 100 °C. Finally, microscopy micrographs confirmed the appearance of larger cell pores and a greater tendency for incomplete cell opening with increasing SiO2 content.

Fungistatic Activity of Engineered Nanoparticles

The influence of various concentrations of Ag, TiO2, and SiO2 nanoparticles on conidia germination of the phytopathogenic fungus Bipolaris sorokiniana and mycelium growth of the xylotrophic fungi Pleurotus ostreatus and Neonothopanus nambi was analyzed. It is established that a decrease in conidia germination of phytopathogenic fungus and mycelium growth of the xylotrophic fungi occurs at relatively high silver nanoparticle concentrations. The appropriate ЕС50 values for Bipolaris sorokiniana, Pleurotus ostreatus, and Neonothopanus nambi are found to be 30, 14, and 31 mg/dm3, respectively. No effect of various concentrations of TiO2 and SiO2 nanoparticles on the studied cultures of fungi is highlighted. Thus, the negative impact of nanosilver on the growth of fungi at a high concentration which is untypical for objects of the environment and a lack of this influence of titanium dioxide and silica nanoparticles testifies to the high resistance of mycelial forms of organisms to engineered nanoparticles.

Preparation of microcapsules containing double-component lubricant and self-lubricating performance of polymer composites

Double-component microcapsules containing lubricant oil and SiO2 nanoparticles were prepared by solvent evaporation method. The synthesized microcapsules have the regular spherical structure with the mean diameter of 105 μm and wall thickness of 15 μm. The synthesized microcapsules have excellent thermal stability, and the lubricant oil content was 71.4 wt%. Self-lubricating polymer composites were fabricated by incorporating double-component microcapsules into epoxy matrix. When the SiO2 nanoparticles content was 3 wt% relative to the lubricant oil, 10 wt% microcapsules brought 60.8% and 93.3% decrease for epoxy composites in the friction coefficient and specific wear rate, respectively. The synergetic effect between lubricant oil and SiO2 nanoparticles play a positive role in improving the triboligical properties of polymer composites.

SiO2 nanoparticle and KCl salt effects on filtration and thixotropical behavior of polymeric water based drilling fluid: With zeta potential and size analysis

Abstract Maturity of conventional and shallow reserves and demand of energy force the drilling industry to drill deeper and more complicated wells. The nanoparticles initiated revolution in different aspects of science and engineering. Utilizing these particles can lead to a more efficient drilling in deep and troublesome environments. In this study the polymeric water based drilling fluid was set as base fluid. Effects of SiO2 nanoparticles and KCl salt on different aspects of polymeric water based drilling fluid filtration and thixotropical behavior in different concentrations and temperatures were investigated. Mostly, the SiO2 nanoparticle addition improved the drilling fluid performance however, the addition of SiO2 nanoparticles in higher concentrations was not so effective. The concentration of SiO2 nanoparticles for effective and justifiable usage should be carefully selected. The KCl also had impact on SiO2 nanoparticles behavior in drilling fluid. It is shown by measuring zeta potential and particles size, the SiO2 nanoparticles in different temperatures, SiO2 and KCl concentrations have different properties. The high KCl concentration affected the effectiveness of SiO2 nanoparticles in filtration behavior improvement. Moreover, presence of KCl changed the thixotropical behavior of SiO2 contained drilling fluid.

Effects of SiO2 nano-particles on tribological and mechanical properties of aluminum matrix composites by different dispersion methods

This study has been presented with mechanical properties of aluminum matrix composites, reinforced by SiO2 nano-particles. The stir casting method was employed to produce various aluminum matrix composites. Different composites by varying the SiO2 nano-particle content (including 0.5 and 1 weight percents) and two dispersion methods (including ball-milling and pre-heating) were made. Then, the density, the hardness, the compression strength, the wear resistance and the microstructure of nano-composites have been studied in this research. Besides, the distribution of nano-particles in the aluminum matrix for all composites has been also evaluated by the field emission scanning electron microscopy (FESEM). Obtained results showed that the density, the elongation and the ultimate compressive strength of various nano-composites decreased by the presence of SiO2 nano-particles; however, the hardness, the wear resistance, the yield strength and the elastic modulus of composites increased by auditioning of nano-particles to the aluminum alloy. FESEM images indicated better wetting of the SiO2 reinforcement in the aluminum matrix, prepared by the pre-heating dispersion method, comparing to ball-milling. When SiO2 nano-particles were added to the aluminum alloy, the morphology of the Si phase and intermetallic phases changed, which enhanced mechanical properties. In addition, the wear mechanism plus the friction coefficient value were changed for various nano-composites with respect to the aluminum alloy.

Measurement of Low Concentration of Nanosized Objects Suspended in a Liquid Medium

Abstract The new optical scheme of refractometer with temperature stabilisation 10−2 °C is developed, which allows measuring a refractive index of the sample with accuracy not worse than 10−5; dependence of refraction index on concentration of SiO2 nanoparticles in liquid suspension is obtained within the framework of the research.