Concentration Of SiO2 Nanoparticles Research Articles

Preparation and thermal properties of novel eutectic salt/nano-SiO2/ expanded graphite composite for thermal energy storage

This paper presents a novel shape-stable phase change material (PCM) composite for thermal energy storage applications. The formulation of the material consists of the components: eutectic nitrate (NaNO3-KNO3) as thermal storage material, expanded graphite (EG) for improving structural stability and thermal conductivity, and SiO2 nanoparticles for improving specific heat. The material was successfully prepared by the mechanical dispersion method. The effects of EG and SiO2 nanoparticles additives on the thermophysical properties of the composite were investigated by SEM, STA, and LFA. The results showed that EG, SiO2 nanoparticles and eutectic nitrate have excellent chemical compatibility. The specific heat of the composite was 3.92 J/(g·K), which was 2.58 times higher than that of eutectic nitrate when the content of EG and SiO2 nanoparticles was 15 wt% and 1 wt%, respectively. The latent heat of the composite decreased with the increase of EG mass fraction, but overall an increase in energy storage density was found due to the addition of SiO2 nanoparticles. The thermal conductivity of the composite with 15 wt% EG and 1 wt% SiO2 nanoparticles was significantly increased by about 16.2 times compared with that of eutectic nitrate. Furthermore, thermal cycle stability was tested. The NaNO3-KNO3/1 wt% nano-SiO2/15 wt% EG composite showed no obvious specific heat change after 100 thermal cycles and 100 h high-temperature test, respectively. The prepared NaNO3-KNO3/nano-SiO2/EG composite has a promising application prospect in the high-temperature energy storage.

Scattering Effect on Optical Performance of Quantum Dot White Light-Emitting Diodes Incorporating SiO₂ Nanoparticles

The scattering effect plays an important role in improving the optical performance of the quantum dot (QD) white light-emitting diodes (LEDs). A majority of the previous studies have focused on the planar packaging structure only with respect to total internal reflection (TIR). In this study, SiO2 nanoparticles are incorporated into QD-silicone encapsulation of LEDs with semi-spherical lens packaging (SSLP) to exploit their scattering effect. The results show that the radiant efficacy (31.35%@100 mA) and luminous efficacy (87.56 lm/W@100 mA) of QD white LEDs can be optimized using SiO2 nanoparticle concentration (0.1 wt%) and that they increase by 5.04% and 11.08%, respectively, as compared to the conventional structure. A comprehensive ray-tracing simulation validates that the nanoparticles in the SSLP structure lead to severe loss of chip light. On the contrary, the fluorescence light increases due to the enhancement of conversion by QDs. The transmission electron microscopy images and the finite-difference time-domain simulation have been introduced to investigate the surface adsorption of SiO2 nanoparticle. This study indicates that SiO2 incorporation is an effective method to improve the efficiency of QD white LEDs, and provides a better understanding on the scattering effect based on TIR, color conversion, and surface adsorption.

Study the Effect of SiO2 Nanofluids on Heat Transfer in Double Pipe Heat Exchanger

In this paper the effect of nanofluid is studied in the double pipe heat exchanger counter current flow, the viscosity of nanofluids are measured at different temperatures and different particle sizes. SiO2 nanoparticles are dispersed at different concentrations (0.2-2) % with different particle sizes of (50-25) nm in base fluid of water. The friction factor and heat transfer coefficient are calculated at different nanoparticle sizes, the results showed that the viscosity was increased as nanoparticle concentration increased. The friction factor is increased as SiO2 nanoparticles concentration and increased as nanoparticles size decreased. The heat transfer coefficient increased as nanoparticle concentration increased and particles size decrease.

Influence of SiO2 nanoparticles on morphology, optical, and conductivity properties of Poly (ethylene oxide)

In this work, a detailed insight to the microstructure, morphology, surface topography, electrical and optical properties in visible and terahertz range was presented for polyethylene oxide (PEO)/silicon dioxide SiO2 nanocomposites. PEO-filled with various contents of SiO2 nanoparticles were synthesized via the solution cast technique. The polycrystalline nature of PEO/SiO2 films was affirmed by the selected area electron diffraction pattern (SAED) recorded by HRTEM measurement and it was found to nearly conformable with X-ray diffraction data. The energy-dispersive X-ray analysis (EDAX) proved the existence of SiO2 with wt% ranged from 0 to 5% as starting fillers. The high-resolution scanning electron microscope planar images indicated uniform distribution of SiO2 nanoparticles within the PEO films. The atomic force microscope 3D images depicted the surface changed from rough to smooth upon the filling with SiO2. The composite samples exhibit absorption spectra that extended from UV–Vis to near infrared regions. Based on Tauc's formula, it was found that the absorption edge shifted from 4.90 to 3.20 eV as the filler fraction increased from 0 to 5 wt%. The analysis of reflective index in the UV–Vis–NIR regions displayed decrement with increasing filler content. Moreover, the refractive index in Vis–NIR regions is good extension to that in THz region expressing the optical quality of studied films. The optical dispersion parameters were analyzed in the view of Wemple-Didomenico single oscillator and Sellmeier model. The values of nonlinear optical parameters (nonlinear susceptibility χ(3) and nonlinear refractive index (n2) were influenced by the filler fractions. Upon the rise of filler content, the conductivity values show slightly decrement.

Preparation and optimization of antifouling PPSU/PES/SiO2 nanocomposite ultrafiltration membranes by VIPS-NIPS technique

In this paper, the preparation of PPSU/PES/Nano silica composite ultrafiltration membranes by a combined vapor induced phase separation (VIPS) and non-solvent induced phase separation (NIPS) techniques were successfully investigated. For this purpose, the effect of VIPS time from 0 to 60s, the blending ratio of PPSU:PES from 0 to 100%, polymer concentration from 16 to 24wt.%, and SiO2 nanoparticles concentration from 0 to 5wt.% as an additive to dope solution on the performance and characteristics of ultrafiltration membranes were studied. As the number of parameters is high, the response surface methodology (RSM) was applied for designing the experiments for obtaining the optimum condition for the fabrication of a high flux ultrafiltration membrane. Liquid-liquid displacement porosimetry (LLDP), scanning electron microscope (SEM), pure water flux (PWF), and bovine serum albumin (BSA) retention were used for characterization of the fabricated membranes. The results are shown different trends for the effect of SiO2 nanoparticles concentration at the low and high polymer concentrations in dope solution. When the polymer concentration in the dope solution is low, the increase of SiO2 nanoparticles concentration resulted in lower fluxes, but at high polymer concentrations, the increase of the nanoparticles caused an increase in permeate flux. At optimum condition, the highest PWF of 76.65L/m².h (15.33L/m².h.bar), and a BSA retention of 82.01% was obtained.

Structural, thermal, and linear optical properties of SiO2 nanoparticles dispersed in polyvinyl alcohol nanocomposite films

AbstractIn the present work, polyvinyl alcohol (PVA) films were prepared for polymer optoelectronic applications, in which the SiO2 nanoparticles were incorporated through a sonication technique followed by a solution casting method. The structure of PVA/SiO2 films was evaluated using the experimental results attained by X‐ray diffraction (XRD), Fourier transform infrared (FTIR), and scanning electron microscope (SEM) examinations. A thermal stability study of the nanocomposite films was performed. UV‐vis spectra were used to investigate the optical properties of PVA/SiO2 nanocomposite films. The XRD results confirmed the semicrystalline nature of the PVA. The SEM results ascertained the homogeneity of the SiO2 nanoparticles in the polymer matrix. From the study, a simultaneous increase of SiO2 nanoparticle content decreased the direct optical band gap and Urbach energy; however, the refractive index and extinction coefficient were increased. The acquired nanocomposite films could be utilized in polymer optoelectronic applications.

Biogenic silicon dioxide nanoparticles processed from natural sources

The main purpose of this study is to obtain the biogenic silica nanoparticles from selected types of plants and thorough characterization. Plants create SiO2 nanoparticles while growing from the colloidal solution of orthosilicic acid contained in the soil. Together with acid, they absorb additional ions that are essential for their growth, which was found using SEM and EDX analysis. The organic part of the plants was removed using a two-step method. Firstly, the plants were purified in 10% HCl in order to remove undesirable ions. Next, the optimal degradation temperatures were determined according to TGA results that varies between 500–650 °C. After the above-mentioned processes silica was studied using ICP-OES, FTIR, TEM, and N2 adsorption. The nanoparticles obtained from the investigated kinds of plants showed an amorphous structure, differed in size (from 8 to 20 nm) and are not purely symmetrical in any of the investigated samples. Estimated content of SiO2 nanoparticles was in the range 11.5–25.3% depending on the sample. The specific surface area was measured using the BET method.

Hepatic toxicological responses of SiO2 nanoparticle on Oreochromis mossambicus

The present study was carried out to investigate the impact of various concentrations of SiO2 nanoparticles (SiO2 NP) on the commonly available freshwater fish Oreochromis mossambicus. The 96 h median lethal concentration (LC50) of SiO2 NP was found to be between 270−280 ppm. This novel study has demonstrated histological alterations in the hepatic tissues and a dose-dependent depletion of tissue protein content and an elevated transaminases activity in the treated fish, which has facilitated understanding of the impact of SiO2 NP in O. mossambicus.

In tube convection heat transfer enhancement: SiO2 aqua based nanofluids

Abstract In this paper, an experimental investigation is carried out on internal convective heat transfer of SiO2/water nanofluids in a copper tube for a fully turbulent regime. Nusselt number and convective heat transfer coefficients of nanofluid at three different volumetric concentration (0.001%, 0.003%, 0.007%) of nanoparticles were estimated. Local convective heat transfer coefficient at different locations along the tube at varying Reynolds number was also observed. With volumetric concentration of 0.001% of SiO2 nanoparticles, maximum enhancement observed was 8–9%. Whereas at 0.007% volumetric concentration of SiO2 nanoparticles, a 27% enhancement in convective heat transfer coefficient was observed. The decrease in the heat transfer rate was observed in axial direction. Particle migration, chaotic movement of the nanoparticles and fluctuations in the fluid and increased thermal conductivity of the nanofluid are considered the possible reasons for this enhancement.

Enhancement in Nanomechanical, Thermal, and Abrasion Properties of SiO2 Nanoparticle-Modified Epoxy Coatings

Epoxy formulations containing 1%, 3%, and 5% SiO2 nanoparticles (SNPs) were produced and applied to mild steel substrates in order to improve their thermal, nanomechanical, and abrasion resistance. Field emission scanning electron microscopy (FE-SEM) was used to analyze the dispersion of nanoparticles in the final coating samples, and Energy-dispersive X-ray spectroscopy (EDX) was used to confirm the presence of nanoparticles. Thermogravimetric analysis (TGA) was employed to measure the thermal resistance of the prepared coatings. Conventional techniques were used to measure the impact and scratch resistance. For nanomechanical testing, nanoindentation was performed using a Berkovich-type indenter. Using a taber abraser, the abrasion properties of the coatings were measured. The FE-SEM images indicated good dispersion of the nanoparticles at all three different loading levels. The scratch, impact, and hardness of coatings improved with the addition of the SNPs. Nanomechanical properties, such as hardness and elastic modulus, improved when compared to the unmodified coatings. The thermal and abrasion resistances of the coatings improved with the increase in the SNPs content of the coatings. The highest mechanical, thermal, and abrasion properties were obtained for the coatings with 5% SNP content.

Brazing YSZ ceramics by a novel SiO2 nanoparticles modified Ag filler

Yttria-stabilized zirconia (YSZ) ceramics are soundly brazed in air using a novel amorphous SiO2 nanoparticles (NPs) modified Ag filler. Scanning electron microscopy, transmission electron microscopy and X-ray diffraction are employed to characterize the interfacial microstructure of YSZ joints. A uniform amorphous SiO2 layer is observed on the YSZ substrate surface. Micro-sized SiO2 clusters are dispersed in the Ag braze matrix, which forms the brazing seam. The content of SiO2 NPs and the brazing temperature exert significant effects on the formation of YSZ joints. The maximum shear strength of YSZ joints reaches 47 MPa under the optimized brazing conditions (Ag–2SiO2, 1050 °C/30 min, 2 MPa load pressure).

Effect of SiO2 Nanoparticles Addition on Tribological and Electrochemical Behaviors of Ni–P–MoS2 Multi-Component Coatings after Heat Treatment

The tribological and electrochemical properties of various nanocomposite coatings of Ni–P–MoS2–SiO2 have been investigated. Such coatings were made by the electroless method and then heated at 400°C for 1 h. The amount of SiO2 nanoparticles was a factor which changed Ni–P–MoS2 coatings characteristics. In addition to microstructure evaluations and the phase detection, the microhardness, the friction coefficient, and wear behavior were studied for various coatings. Field emission scanning electron microscopy images demonstrated that SiO2 nanoparticles were distributed uniformly in the Ni–P–MoS2 matrix. The obtained results showed that when the concentration of SiO2 nanoparticles in the deposition bath increased from 5 to 20 g/L, then the microhardness and the wear resistance increased as well. Besides, the friction coefficient reached the lowest value of 0.05. For nanocomposite coatings, the ratio of the friction coefficient to the square hardness was a proper parameter which could predict the wear behavior. Additionally, energy dispersive spectroscopy results showed that the content of SiO2 nanoparticles in such coatings increased from 4.9 to 11.4 wt %. Corrosion tests demonstrated that the best corrosion resistance was observed for the nanocomposite coating when the concentration of SiO2 nanoparticle was 20 g/L.

Silicon dioxide nanoparticles have contrasting effects on the temporal dynamics of sulfonamide and β-lactam resistance genes in soils amended with antibiotics

Nanoparticles (NPs) and antibiotic resistant genes (ARGs), as emerging environmental contaminants, have been reported to be accumulated in the soil environment. The use of NPs have raised increasing concerns about their environmental impacts, but the combined effect of NPs and antibiotics on ARGs remains less understood. Here, we established laboratory microcosms to explore the impacts of different concentrations of SiO2 NPs on β-lactam and sulfonamide resistance genes in soils amended with β-lactam or sulfonamide. Illumina sequencing and quantitative PCR revealed that the addition of NPs increased the bacterial community diversity but had no significant effects on the bacterial abundance. Moreover, NPs and sulfonamide jointly increased the abundances of sulfonamide resistance genes, while the exposure of NPs and β-lactam decreased β-lactam resistance genes. The detected ARGs were associated closely with two mobile genetic elements (MGEs, the tnpA and intI1 genes), indicating that MGEs may contribute to the dissemination of ARGs. Correlation analysis indicated the shifts in potential bacterial hosts and the frequency of horizontal gene transfer were important factors explaining the patterns of ARGs. Furthermore, structural equation models indicated that NPs exposure decreased the abundances of β-lactam resistance genes by driving changes in bacterial community and MGEs, whereas the increased abundances of sulfonamide resistance genes were mainly associated with the bacterial community, diversity and MGEs mediated by NPs and antibiotics. These results suggested that the combined effects of NPs and antibiotics on soil bacterial resistance were different due to the types of antibiotics.

Influence of SiO2 Content and Exposure Periods on the Anticorrosion Behavior of Epoxy Nanocomposite Coatings

Epoxy coating formulations containing 1%, 3%, and 5% SiO2 nanoparticles were produced and applied on a mild steel substrate to achieve the objective of high performance corrosion resistance. The electrochemical impedance spectroscopy (EIS) technique was employed to measure the anticorrosive properties of coatings. The corrosion tests were performed by exposing the coated samples in a solution of 3.5% NaCl for different periods of time, varied from 1 h and up to 30 days. Fourier transform infrared spectroscopy (FT-IR) and X-ray diffraction (XRD) analyses revealed the presence of nanoparticles in the final cured samples. Establishing the incorporation of the nanoparticles in the coating formulations was confirmed by employing both of XRD and FT-IR techniques. The FT-IR spectra have proved to be satisfactory indicating that there was a complete reaction between the epoxy resin with the hardener. EIS measurements confirmed that the presence and the increase of SiO2 nanoparticles greatly improved the corrosion resistance of the epoxy coating. The highest corrosion resistance for the coatings was obtained for the formulation with 5% SiO2 nanoparticles content, particularly with prolonging the immersion time to 30 days.

Investigation of tribological and compressive behaviors of Al/SiO2 nanocomposites after T6 heat treatment

The aim of this paper is to present experimental results of tribological and compression properties of aluminum nanocomposites after T6 heat treatment. This heat treatment contained three stages: solutionizing at 500°C for 5 h, quenching in water, and ageing 180°C for 9 h. The method of nanocomposite production was the stir casting process. The SiO2 nanoparticles in 0.5 and 1% wt were added to the aluminum melt as the reinforcement agent. The microstructural evaluation was conducted by the optical microscopy (OM) and the field emission scanning electron microscopy (FESEM) methods. The results of the wear test revealed that the specific wear rate of specimens comprising SiO2 nanoparticles was lower than that of specimens without nanoparticles. Thus, the formation of the holes, wear debris and cracks decreased obviously for nanocomposite surfaces during wear testing. Moreover, the wear rate reduced obviously for nanocomposites fabricated by the pre-heating process compared to others. It was noticeable that the ball-milling process was an effective method to decrease the friction coefficient value to 0.15 for nanocomposites. Such observations were due to higher hardness and lower micro-porosity content. The elastic modulus for various nanocomposites improved by 8–19% compared to the aluminum alloy. In addition, when the content of SiO2 nanoparticles increased from 0.5 to 1% wt, the ultimate compressive strength decreased about 11–13% due to the presence of more micro-porosities.

Optical properties of PMMA/ZnO/SiO2 composite thin film

The properties of the polymeric composite thin films highly depends on the nature of the additives. Usually, nanoparticles of different kinds are added in various concentrations to tune the properties of the composite thin film. In this paper, we studied the effect of a mixture of ZnO and SiO2 nanoparticles on optical properties of PMMA/ZnO/SiO2 composite thin film. We have fabricated composite thin films of 50 µm thickness by solution casting method. The concentration of SiO2 nanoparticles is kept constant at 0.5%, while the concentration of ZnO nanoparticles is varied from 0.5 wt% to 2 wt%. It is observed that the opticalbandgap of the composite thin films decreases with an increase in the ZnO concentration.

High Velocity Impact Response of Aluminum- Carbon Fibers-Epoxy Laminated Composites Toughened by Nano Silica and Zirconia

This research work investigated the effects of SiO2 and ZrO2 nanoparticles type and content incorporated into an epoxy matrix on the high velocity impact behavior of carbon fiber reinforced aluminum laminates (CARALL). CARALL specimens consisted of a 0/90/90/0 stacking sequence of a carbon-epoxy composite containing 0, 1, 3, 5 and 7 wt% of each of nanoparticles sandwiched between two layers of aluminum 2024-T3. To observe the toughening effects of the nanoparticles on the fracture surface of the impacted CARALL, a typical field emission scanning electron microscope (FESEM) was employed. Impact energy absorption of CARALL was at most increased by 18 % and 12 % with the nanoparticles content of 5 wt% SiO2 and 3 wt% ZrO2, respectively. Overloading of the nanoparticles content up to 7 wt% resulted in the creation of nanoparticles aggregated sites associated with loss in the energy absorption capacity. FESEM fractography procedure also showed that the crack deflection and pinning were the most recognizable toughening mechanisms exhibited by nanoparticles. Overall, the controlled addition of SiO2/ZrO2 rigid nanoparticles to CARALL was found to be a promising method for improving the high velocity impact energy absorption of CARALL.

Multilayer Polymeric Nano composite Membrane for Oxygen Separation

Air separation is a process of separating primary components from the atmospheric air. Development of membrane technologies plays a key role in air separation. Multi-layer polymeric nanocomposite membranes have been developed by a novel technique using Polyacrylonitrile (PAN) and cellulose acetate (CA) along with nano silica particles (SiO2) to obtain a higher oxygen selectivity and permeability. For the construction of the multilayer membrane, the Box-Behnken design has been used by employing three independent variables namely PAN Electro spinning time, the SiO2 percentage in the PAN polymer and CA/PEG polymer concentration. The developed membranes have been characterized for its surface morphology and physical properties. Along with the analysis of compound desirability, the results were also subject to statistical analysis in order to form regression equations. The electro spun fiber diameter increases along with the concentration of SiO2 nanoparticles and the range is from 50 nm to 400 nm. Moreover, the maximum pore size on the surface of the membrane lies between 200 to 400 nm whereas the maximum percentage of oxygen purity obtained is 48 with the permeate flux of 5.45 cm3/cm2/min.

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.