Concentration Of SiO2 Nanoparticles Research Articles

Effect of low concentrations of SiO2 nanoparticles on the physical and chemical properties of sodium alginate-based films

This work investigated the effect of adding low concentrations of nano-SiO2 (0.5, 1.0 and 1.5%) in the properties of films based on sodium alginate, to identify lower thresholds in the proportion of the reinforcing agent. It was found that, even in the smallest proportion, thermal stability of the nanocomposites improved significantly (with degradation onset increased by almost 15% compared with the control film). The surface morphology showed pronounced roughness at nano-SiO2 concentrations greater than 1.0%, indicating agglomeration of part of the nanomaterial. Mechanical properties were reduced for the samples with concentrations equal to 1.0 and 1.5%, however, without significant differences between them. Conversely, water vapor and light barrier properties have not undergone significant changes in any formulation. Therefore, the use of 0.5% nano-SiO2 in alginate films would be an easy and economically interesting way to improve thermal stability, without significantly reducing mechanical properties of the pure material.

Nejayote biopolyelectrolytes multifunctionality (glucurono ferulauted arabinoxylans) in the separation of hazardous metal ions from industrial wastewater

The scarcity and contamination of water by suspended nanoparticles and hazardous metal ions demand more performant technologies to reduce space, time and cost of wastewater treatment. For example, it is desirable to find eco-friendly chemicals that warranty simultaneous separation of colloidal particles and hazardous metallic contaminants for a more sustainable recovery of water quality.As the second part of a series of physicochemical studies about multifunctional biopolyelectrolytes (BPEs), in this paper, we present three of the main features of the glucurono ferulauted arabinoxylans (GFAXs) from nejayote: simple extraction, physicochemical characterization and multifunctional performance when used in a wastewater treatment unit. The polyelectrolytic and macrochelating properties of the GFAXs were studied through zeta potential measurements to predict and understand the multifunctional performance of GFAXs in a conventional coagulation-flocculation unitary operation. Two real cases were approached: the wastewater from silicon wafer cutting process (SWCP) and the wastewater from electroplating baths (EPB). Nejayote GFAXs showed high coagulant, flocculant and macrochelating activity in the simultaneous separation of Si4+, Al3+, Cr3+, Ni2+, Mg2+, Ca2+, Ni2+, Cd2+, Pb2+, Cu2+, Zn2+ and Fe2+. The water treatment tests demonstrate the high performance of the GFAXs in the coagulation-flocculation of the wastewater according to the following parameters: EPB wastewater at pH = 5.0 (optimal dose = 55–65 mg GFAXs/L, clarification = 380 T%/h and sedimentation kinetics = 110.4 mm/h); SWCP wastewater at pH = 5.5 (optimal dose = 30.0–32.5 mg GFAXs/L, clarification = 295 T%/h and sedimentation kinetics = 89.4 mm/h). With these results, nejayote GFAXs showed to be a sustainable solution for the wastewater treatment from semiconductor and metal finishing industry with high content of hazardous metal ions and SiO2 nanoparticles.

Effect of modifying TiO2 powdert with SiO2 and ZrO2 nanoparticles on its composition, structure, optical properties, and on the alteration of these parameters under solar spectrum quanta

The authors examined the effect of solid-state modification of titanium dioxide powder with the nanoparticles of zirconia and silica on the composition, structure, and diffuse reflectance spectra (ρλ) of the powder and on their alteration (Δρλ) under influence of solar spectrum quanta. It was established that when the concentration of SiO2 nanoparticles is 3 wt% and ZrO2 is 5 wt%, the reflectance coefficient undergoes a 10% decrease in visible spectrum and increases by 9.5% in the near-IR region. After the irradiation of non-modified and modified powders with intensity three times higher than solar irradiation, the wide absorption bands appeared in Δρλ spectra with the peaks at 420 nm and 800–1200 nm. With increasing the irradiation time from 5 to 40 h, the bands’ intensity increases as well. It was established that photostability of modified powders is two times higher than that of non-modified powders. Modification with SiO2 nanoparticles provides a more significant effect in comparison with ZrO2 nanoparticles.

Influence of Ionizing Radiation on the Corrosion Resistance of ZnNi/SiO2 Composite Coatings

The influence of x-ray radiation on the protective properties of ZnNi/SiO2 composite coatings has been investigated experimentally, and the optimal regimes of their electrodeposition on irradiation by the method of complete factor experiment have been revealed. It is shown that the action of x-ray radiation on the electrolytes used for electrodeposition of ZnNi/SiO2 leads to an increase in their dispersive power, which makes it possible to form composite coatings with the metal uniformly distributed over the surface and, correspondingly, with elevated corrosion resistance. It has been found that the action of x-ray radiation on the process of electric deposition of ZnNi/SiO2 coatings promotes formation of layers with enhanced anticorrosion properties. Based on experimental data and according to the method of complete factor experiment, the influence of variations in the x-ray radiation exposure dose power and concentration of SiO2 nanoparticles in the electrolyte on the dispersive power of electrolytes and corrosion resistance of ZnNi/SiO2 coatings has been considered. Regression equations have been obtained, an analysis of the coefficients of which allowed the conclusion that a maximum increase in the dispersive power and a decrease in the rate of appearance of corrosion products on ZnNi/SiO2 coatings are achieved on combination of two factors: addition of SiO2 nanoparticles to the electrolyte and irradiation of the electrolyte by x-ray radiation in the process of coating deposition. The developed statistical model allows one to adequately determine the optimal concentrations of SiO2 nanoparticles in an electrolyte and the regime of x-ray irradiation for obtaining coatings with enhanced anticorrosive properties.

Enhanced thermal insulation properties of PI nanofiber membranes achieved by doping with SiO2 nanoparticles

At present, energy consumption is a worldwide topic and it is an urgent requirement for the development of energy-saving materials. Thermal insulation materials with a low thermal conductivity show a significant potential to reduce energy waste. In this study, polyimide (PI) and silica/polyimide (SiO2/PI) nanofiber membranes (NFMs) with low thermal conductivity were prepared by electrospinning. The effect of different content of SiO2 nanoparticles (SiO2 NPs) on the thermal insulation properties of PI NFMs and the thermal insulation mechanism were studied. SiO2/PI NFMs has the lowest thermal conductivity of 0.033 W/(m·K) when the content of SiO2 NPs was 2 wt%. The experimental results reveal that when the addition of SiO2 NPs was low, the dominant factor of the increasing thermal insulation is the interfacial thermal contact resistance between the SiO2 NPs and PI nanofibers. Moreover, the SiO2 NPs can improve the thermal stability and hydrophobic of SiO2/PI NFMs. This study indicates the SiO2/PI NFMs has the potential applications in thermal insulation.

Study of nano-SiO2 reinforced CO2 foam for anti-gas channeling with a high temperature and high salinity reservoir

CO2 flooding has been widely applied in lots of low permeability reservoirs. After extensive CO2 injection, some reservoirs began to show serious gas channeling problems. CO2 foam had been successfully used to solve gas channeling problems due to its advantages of water selective plugging features (not plugging oil). In this paper, a novel CO2 foam system was developed for high temperature and high salinity(HTHS) (85℃, 60,000mg/L) aiming at solving the gas channeling in Changqing Oilfield. Taking the foam half-life as the evaluation standard, the optimum foam system (0.5wt% EC-1+1wt% SiO2) for the target reservoir was determined. The influences of temperature, salinity and pressure on the CO2 foam performance were studied by high temperature and high pressure(HTHP)method. The ability and mechanism of anti-gas channeling were studied by experiments of sand packed tube and microscopic displacement, respectively. The results showed that the foam system possessed good foam properties at HTHS with pressure. As the concentration of SiO2 nanoparticles increased, the resistance factor of the foam system increased. However, temperature showed an adverse effect on foam stability, the resistance factor decreased with the increase of temperature. The Jamin superposition and emulsion plugging mechanism of foam system was revealed by microscopic displacement experiments.

PH-sensitive soluble soybean polysaccharide/SiO2 incorporated with curcumin for intelligent packaging applications.

In the present work, the effect of various concentrations of SiO2 nanoparticles (5, 10, and 15%) on physicochemical and antimicrobial properties of soluble soybean polysaccharide (SSPS)‐based film was investigated. Then, the migration of SiO2 nanoparticles to ethanol as a food simulant was evaluated. Subsequently, curcumin was added to the nanocomposite formulation to sense the pH changes. Finally, the cytotoxicity of the developed packaging system was investigated. With increasing nanoparticle concentration, the film thickness, water solubility, and water vapor permeability decreased and mechanical performance of the films improved. SSPS/SiO2 nanocomposite did not show antibacterial activity. SEM analysis showed that SiO2 nanoparticles are uniformly distributed in the SSPS matrix; however, some outstanding spots can be observed in the matrix. A very homogeneous surface was observed for neat SSPS film with R a and R q values of 3.48 and 4.26, respectively. With the incorporation of SiO2 (15%) into SSPS film, R a and R q values increased to 5.67 and 5.98, respectively. Small amount of SiO2 nanoparticles was released in food simulant. The nanocomposite incorporated with curcumin showed good physical properties and antibacterial activity. A strong positive correlation was observed between TVBN content of shrimp and a* values of the films during storage time (Pearson's correlation = 0.985).

Synthesis and Properties of Polyimide Silica Nanocomposite Film with High Transparent and Radiation Resistance.

In order to prepare flexible glass cover sheet materials suitable for space solar cells, fluorinated diamine 2,2’-bistrifluoromethyl benzidine (TFDB) and fluorinated dianhydride 4,4’ (hexafluoroisopropyl) diphthalic dianhydride (6FDA) as the monomer, polyimide (PI)/SiO2 composite film was synthesized by in situ polymerization, and the influence of coupling agent and SiO2 nanoparticle content on the film structure and properties was studied. The results show that PI synthesized from fluorine-containing monomers has better light transmittance, and the highest transmittance can reach 91.4%. The average visible light transmittance of the composite film decreases with the increase of SiO2 content, and the transmittance of the film decreases less in the high-wavelength region and greatly decreases in the low-wavelength region. The tensile strength and elastic modulus of PI/SiO2 composite film increase with the increase of SiO2 content, first increase and then decrease, reaching the maximum when the content is 10%; while the elongation at break of the composite film gradually increases with the increase of SiO2 content reduce. The thermal stability of PI/SiO2 composite film increases with the increase of SiO2 content. The doping of nano-SiO2 significantly suppresses the influence of irradiation on the mechanical properties of the film.

Enhancement of the PL Intensity of Silica Based Polymer Electret after Electro-Thermo-Polarization

In this study, the influence of electro-thermo-polarization (ETP) on the charge state and luminescence properties of polymer nanocomposites based on PP and nanoparticles of amorphous silicon dioxide nanoparticles were investigated. By comparing the results of the charge state and the intensity of the PL spectra of nanocomposites, it was determined that polarized composites with a 3% mass content of SiO2 nanoparticles have relatively high luminescence. For the same composites PP + 3% SiO2, relatively high values of the spatial space charge density, the intensity of the internal local field, and the thickness of the interphase layer are observed. Space charges create a large internal local field that stimulates the already existing oxygen deficiency centers in amorphous silica nanoparticles. This leads to the activation of the luminescence centers, which is the cause of the increase in the PL emission intensity in this nanocomposite after the ETP.

Experimental investigation of convective heat transfer using ethylene glycol-based nano-fluid

Coolant plays important characteristic in automobile industry to prevent failure and damage by balancing the temperature. Due to this approach, coolants are being used as new thermal fluid to study the heat transfer coefficient performance. This study consists of an experimental investigation of internal convective heat transfer of 50:50 Water-Ethylene Glycol based Nano-fluid through a copper tube of 18mm external diameter and 16.5mm internal diameter and a test section of 1m in a fully turbulent regime. Total convective heat transfer coefficient of Nano fluid at three different volumetric concentrations of nanoparticles is estimated. Local convective heat transfer at eight different points along the tube at varying Reynolds number is also determined. At 0.15% volumetric concentration of SiO2 Nanoparticles (NPS) 29% increment in convective heat transfer coefficient (CHT) is observed. The decrease in the heat transfer rate is observed with changing distance axially. Particles disorganized movement of NPs and undulation in the fluid and increased in thermal conductivity of Nano fluid can be possible reason for extra ordinary change in heat transfer.

Tuning charge transport in organic semiconductors with nanoparticles and hexamethyldisilazane

In this study, we showcase the use of silicon dioxide (SiO2) nanoparticles and hexamethyldisilazane (HMDS) treatment to regulate the thin film morphology and manipulate charge transport of solution-processed, small-molecular, organic semiconductors. 6,13-Bis(triisopropylsilylethynyl) pentacene (TIPS pentacene) was blended with SiO2 nanoparticles as an exemplary organic semiconductor. A higher concentration of SiO2 nanoparticles were observed near the edge of TIPS pentacene crystals and enlarged the width of crystal edges. This greatly reduced the dendritic crystal growth pattern of TIPS pentacene and contributed to its enhanced orientation uniformity. In addition, the HMDS treatment effectively passivated the silanol groups on the hydrophilic gate dielectrics. As a result, bottom-gate, top-contact TIPS pentacene/SiO2 nanoparticle-based organic thin-film transistors boosted a performance consistency enhancement (defined by the ratio of average mobility to the standard deviation of mobility). The combinational approach to employ SiO2 nanoparticles and HMDS treatment as demonstrated in this work sheds light on important applications in high-performance organic electronics devices on flexible substrate.

Heat transfer study on flowing liquid film of SiO2‐water nanofluid with surfactant confined by metallic foam

SummaryTo solve the urgent issue of rapid heat dissipation in narrow spaces of electronic devices, the nanofluid as coolant is an effective way, in the cases that the thermo‐physical properties and stabilities of coolant solution can be improved by the dispersion of nanoparticles and surfactant in the base fluid, and scattering sodium dodecyl benzene sulphate (SDBS) as the surfactant and SiO2 nanoparticles, respectively, at different concentration ratios into the base fluid of water to form SiO2‐SDBS‐water (SSW) nanofluid in current research. In the liquid film of SSW nanofluid flowing across heating surface confined by porous metal foam, the effects of the concentration ratios of nanoparticles and surfactant on heat transfer and mechanism of heat transfer enhancement are analyzed in gradual heating and rapid cooling. The boiling and cooling performances can be improved in the SSW nanofluids with the proper concentrations of SiO2 nanoparticles as well as matching surfactant, and the deterioration in heat transfer occurs with the mentioned concentrations exceeding the critical values. In the cooling process, the variation of critical heat flux happens with the concentrations of SiO2 nanoparticles and sodium dodecylbenzene sulfonate in the SSW nanofluids, and the concentration ratio of SiO2 nanoparticles to surfactant should be optimized to enhance heat transfer. Specifically at constant SDBS concentration of 50 ppm, and the relative better heat transfer performances can be obtained at SiO2 concentration of ωSiO2 = 100 ppm, in which the removed heat flux increased by 19%, the cooling time shortened from 8.1 to 5.7 seconds and the critical heat flux increased by 18% in comparison with deionized water. The optimized concentration ratio of SiO2 nanoparticles to SDBS to benefit heat transfer changes with variation of SiO2 nanoparticles in nanofluid at the relatively higher superheat temperature.

Process synthesis and optimization of SiO2/PVDF mixed-matrix membrane for oil-water emulsion separation

In this study, and optimized silicon oxide (SiO2)/polyvinyledene fluoride (PVDF) mixed-matrix membrane formulation was developed using response surface methodology (RSM). SiO2 nanoparticles (NPs) concentration (1-3%), silane solution concentration (1:100-3:100 ratio of silane to ethanol) and duration of silanization process (240-600 s) were identified as the factor in affecting the membrane performance, both permeate flux and rejection. The synthesized membranes were characterized in terms of membrane pore size, porosity, surface roughness, and surface wettability. The optimum SiO2/PVDF mixed-matrix membrane formulation was obtained with 2.9% SiO2 NPs concentration, 2.22:100 ratio of silane to ethanol, with 496 seconds of salination process duration. The optimum SiO2/PVDF mixed-matrix membrane formulation exhibited an extraordinarily high oil droplets rejection (92.01%) with 27.57 L/m2 h of permeate flux at 1 bar of operating pressure.

Phenomenological study of the micro- and macroscopic mechanisms during polymer flooding with SiO2 nanoparticles

The incorporation of SiO2 nanoparticles in polymer solutions for oil recovery has generated considerable interest in recent research. Although this approach improves the polymer performance, little evidence is available about the recovery mechanisms that intervene in the polymeric nanofluid suspension or polymer nanofluid. Therefore, the purpose of this study is to describe the microscopic and macroscopic mechanisms involved during oil recovery with polymeric nanofluid flooding. Changes in the rheology and capillary forces (contact angle and interfacial tension) in the polymeric solution due to the incorporation of SiO2 nanoparticles were evaluated. Coreflooding tests were made to evaluate the retention, apparent viscosity, and impact on the relative permeability. Finally, macroscopic oil recovery was measured by displacement tests in a quarter 5-spot system, and microscopic displacement was evaluated by a microfluidic test. Results indicated that the conservation of a favorable mobility ratio in polymeric nanofluids along the porous medium is the phenomenon that most impacts macroscopic oil recovery. This behavior was associated with a reduction in loss retention and the conservation of the apparent viscosity in the porous medium. A direct relationship was observed between the concentration of SiO2 nanoparticles and the viscoelastic behavior of the polymer and the water-wet condition on the surface exposed to the nanofluid. Moreover, residual oil distribution in microscopic displacement revealed that the reduction in residual oil mainly originated from the decrease in the size of the oil clusters. Consequently, the evidence suggests that microscopic oil displacement in polymeric nanofluid is attributed to the reduction in the capillary forces and increases in the viscoelastic nature of the polymer. Results in this work indicated that the additional oil recovery obtained by polymeric nanofluid flooding is generated by the improvement of macroscopic recovery mechanisms and the activation of microscopic mechanisms.

Experimental investigation of Sio2 nanolubricants for R410A vapour compression refrigeration system

Abstract In this paper Sio2 nanoparticles is dispersed in lubricating oil of R410A refrigeration system. Experimental investigation was carried using 0 g/L, 0.2 g/L, 0.4 g/L and 0.6 g/L of Silicon dioxide (Sio2) nano particle concentrations in Polyolester (POE) lubricating oil by varying the mass of refrigerant R410A as 30, 40, 50, 60 and 70 g. The performance of the refrigeration system was investigated using the important parameters like Coefficient of performance, refrigerating effect and compressor work and pull down test. From the experiment it has been concluded that 0.4 g/L Sio2 nano-lubricant and 40 g refrigerant mass gave more refrigerating effect and it was found to be 160 W when compared with system without nanolubricants and with 0.2 g/L and 0.6 g/L nanolubricant with various refrigerant mass charges. Addition of Sio2 nanolubricants results in reduced compressor work of 80 W with 0.4 g/L and 40 g of refrigerant. Dispersion of Sio2 nanolubricants leads to enhanced C.O.P value of 1.7 for 0.4 g/L nanolubricants when compared to system without nanolubricants and with 0 g/L, 0.2 g/L and 0.6 g/L nanolubricants. From the pull down test, the obtained evaporator temperature is reduced very quickly while using 0.4 g/L nanolubricants with 40 and 60 g refrigerant mass charges.

The Role of Interfacial Interactions on the Functional Properties of Ethylene-Propylene Copolymer Containing SiO2 Nanoparticles.

In this paper, the mechanical properties, thermal stability, and transparency of ethylene–propylene copolymer (EPC) elastomer modified with various weight percentages (1, 3, and 5 wt.%) of SiO2 nanofillers have been studied. The nanocomposites were prepared via a simple melt mixing method. The morphological results revealed that the nanofillers were uniformly dispersed in the elastomer, where a low concentration of SiO2 (1 wt.%) had been added into the elastomer. The FTIR showed that there are interfacial interactions between EPC matrix and silanol groups of SiO2 nanoparticles. Moreover, by the addition of 1 wt.% of SiO2 in the EPC, the tensile strength and elongation at break of EPC increased by about 38% and 27%, respectively. Finally, all samples were optically transparent, and the transparency of the nanocomposites reduced by increasing the content of SiO2 nanoparticles.

Enhancement of thermophysical coefficients in nanofluids: A simulation study

Molten salts constitute one kind of PCMs (Phase Change Materials) widely used in concentrating solar power facilities for heat storage and heat transfer. This paper aims to simulate nanofluid PCMs with molecular dynamics method. Concretely, the thermophysical properties of a nanofluid of KNO3 doped with SiO2 nanoparticle are investigated by equilibrium and nonequilibrium molecular dynamics simulations. For the first time, these properties of a nanofluid in the family of PCMs are calculated. The density, thermal expansion coefficient, specific heat capacity, thermal conductivity, and viscosity are characterized as functions of the SiO2 nanoparticle concentration. The effect of the SiO2 nanoparticle size on the nanofluid’s properties is also investigated. The simulation results present an enhancement of the thermophysical properties, especially for the specific heat capacity, in good agreement with the existing experimental results on a representative nanofluid PCM, and open prospects for the understanding of microscopic mechanism leading to such enhancements.

Effect of hydrophilic silica and dual coagulation bath on structural and mechanical properties of PVDF membrane for membrane distillation

The water scarcity threatens environmental health and human development. Membrane distillation (MD) is one of the most applicable processes for purifying water using a hydrophobic membrane. In this study, the synergetic effect of SiO2 nanoparticles as well as employing the dual coagulation bath on physical and mechanical properties of Polyvinylidene Fluoride (PVDF) flat-sheet membranes produced by dry-wet phase inversion (DIPS) technique has been investigated. The results of microstructural analysis using Scanning Electron Microscope (SEM) demonstrated that by adding nanoparticles while the pore size decreased noticeably, the percentage of porosity significantly increased. Also, it has been revealed that by utilizing isopropanol as the first coagulation bath the finger-like macro-voids became smaller in size, and the share of sponge-like structures rose remarkably. The membrane performance was tested by Vacuum Membrane Distillation (VMD) for measuring the flux and Liquid Entry Pressure (LEPw) laboratory setup. It can be seen that by increasing the content of SiO2 nanoparticles to 6 wt.% while the LEPw approximately halved, the flux soared to about 10000 g/m2h. Moreover, mechanical testing showed that although the tensile strength of nanocomposite samples fabricated in isopropanol dual coagulation bath was improved by up to 66%, their ductility slightly declined. Furthermore, the hydrophobicity of each membrane was examined via contact angle measurements. Finally, it was found that all membranes completely rejected the NaCl in rejection test. Graphical abstract.

Evaluation of the Nanoparticle Dispersion and the Thermal Behaviors of Polyamide-6/Silica Composites

Polyamide-6 (PA6)/silica (SiO2) composites with different sizes and concentrations of SiO2 nanoparticles were prepared via in situ anionic ring opening polymerization. An electron probe microanalyzer was used for visual examination to analyze the distribution of SiO2 nanoparticles in PA6/SiO2 composites. In addition, the thermal behavior of PA6/SiO2 composites was evaluated using thermogravimetric analysis and differential scanning calorimetry. As a result, the SiO2 nanoparticles were found to be well dispersed in the ϵ-caprolactam monomer with a watery viscosity. The sizes and the concentrations of the nanoparticles could affect both the polymerization and the crystallization behaviors of the composites.

Insights into Nanoscale Wettability Effects of Low Salinity and Nanofluid Enhanced Oil Recovery Techniques

In this study, enhanced oil recovery (EOR) techniques—namely low salinity and nanofluid EOR—are probed at the nanometer-scale using an atomic force microscope (AFM). Mica substrates were used as model clay-rich rocks while AFM tips were coated to present alkyl (-CH3), aromatic (-C6H5) and carboxylic acid (-COOH) functional groups, to simulate oil media. We prepared brine formulations to test brine dilution and cation bridging effects while selected concentrations (0 to 1 wt%) of hydrophilic SiO2 nanoparticles dispersed in 1 wt% NaCl were used as nanofluids. Samples were immersed in fluid cells and chemical force mapping was used to measure the adhesion force between polar/non-polar moieties to substrates. Adhesion work was evaluated based on force-displacement curves and compared with theories. Results from AFM studies indicate that low salinity waters and nanoparticle dispersions promote nanoscale wettability alteration by significantly reducing three-phase adhesion force and the reversible thermodynamic work of adhesion, also known as adhesion energy. The maximum reduction in adhesion energy obtained in experiments was in excellent agreement with existing theories. Electrostatic repulsion and reduced non-electrostatic adhesion are prominent surface forces common to both low salinity and nanofluid EOR. Structural forces are complex in nature and may not always decrease total adhesion force and energy at high nanoparticle concentration. Wettability effects also depend on surface chemical groups and the presence of divalent Mg2+ and Ca2+ cations. This study provides fresh insights and fundamental information about low salinity and nanofluid EOR while demonstrating the application of force-distance spectroscopy in investigating EOR techniques.