Nanosilica Surface Research Articles

ENHANCED BIOGAS (CO2/CH4) SEPARATION PERFORMANCE OF HYBRID MIXED MATRIX MEMBRANE BY INCORPORATING NANOSILICA PARTICLES INTO POLYETHERSULFONE

This paper studies the gas transport properties of PES-nanosilica hybrid mixed matrix membrane for biogas purification. Problem statement: The hybrid mixed matrix membrane was produced to improve the membrane separation performance for biogas purification. The membrane was produced via dry-wet phase inversion method, in which the nanosilica was incorporated into polyethersulfone membranes and the prepared membrane was performed on biogas separation experimental test. Quantitative result: The SEM images analysis confirmed that nanosilica surface had taken important role in gas transport properties. Moreover, the nano-gaps (voids) between polymer and nanosilica particles were disappeared in the polyethersulfone hybrid mixed matrix membrane. The results revealed that the good nano-silica dispersion leads to enhance the properties of gas permeation up to 200% and slighly increased the selectivity about 0.9% of the nanosilica concentration 8 wt-%. Conclusion: It can be concluded that incorporation of nanosilicas particles into the matrix of polyethersulfone polymer significantly enhanced the membrane structure and separation properties.

Interfacial Hydrogen Bonds and Their Influence Mechanism on Increasing the Thermal Stability of Nano-SiO₂-Modified Meta-Aramid Fibres.

For further analysis of the effect of nano-doping on the properties of high polymers and research into the mechanism behind modified interfacial hydrogen bonds, a study on the formation probability of nano-SiO2/meta-aramid fibre interfacial hydrogen bonds and the strengthening mechanism behind interfacial hydrogen bonds on the thermal stability of meta-aramid fibres using molecular dynamics is performed in this paper. First, the pure meta-aramid fibre and nano-SiO2/meta-aramid fibre mixed models with nanoparticle radiuses of 3, 5, 7 and 9 Å (1 Å = 10−1 nm) are built, and then the optimization process and dynamics simulation of the models are conducted. The dynamics simulation results indicate that the number of hydrogen bonds increase due to the doping by nano-SiO2 and that the number of interfacial hydrogen bonds increases with the nanoparticle radius. By analysing the hydrogen bond formation probability of all the atom pairs in the mixed model with pair correlation functions (PCFs), it can be observed that the hydrogen bond formation probability between the oxygen atom and hydrogen atom on the nanoparticle surface is the greatest. An effective way to increase the number of interfacial hydrogen bonds in nano-SiO2 and meta-aramid fibres is to increase the number of hydrogen atoms on the nano-silica surface and oxygen atoms in the meta-aramid fibre. By using the radial distribution function (RDF), the conclusion can be further drawn that the hydrogen bond formation probability is at a maximum when the atomic distance is 2.7–2.8 Å; therefore, increasing the number of atoms within this range can significantly increase the formation probability of hydrogen bonds. According to the results of chain movement, the existence of interfacial hydrogen bonds effectively limits the free movement of the molecular chains of meta-aramid fibres and enhances the thermal stability of meta-aramid fibres. The existence of interfacial hydrogen bonds is one of the important reasons for formation of the stable interface structure between nanoparticles and meta-aramid fibres. In addition, a nanoparticle with a small radius improves the interfacial hydrogen bond energy density and interfacial interaction energy density, enhancing the stability of the mixed model interface.

Effect of Thermoplastic Polyurethane-Modified Silica on Melt-Blended Poly(Lactic Acid) (PLA) Nanocomposites

3-aminopropyltriethoxysilane (APTES) was used as a coupling agent to graft thermoplastic polyurethane (TPU) onto a nanosilica surface. The modification of TPU on the surface of silica nanoparticles was confirmed by FTIR, NMR, ESCA and TGA assessment. The grafting degree of TPU onto the silica was about 7.3%. The incorporation of surface-modified silica (TAS50) into poly(lactic acid) (PLA) induced the nucleation of PLA, giving a higher crystallisation peak temperature, which would be advantageous for fast processing cycles in the commercial moulding process. With pristine silica incorporated into PLA, the variation in the cold crystallisation and melting temperatures was limited. However, for the surface-modified silica filled PLA, a lower cold crystallisation temperature at 112.1 °C and a shift of melting temperature from Tm1 to Tm2 at 167.7 °C were observed. The cooling rate also played an essential role in the derived crystalline forms. The tensile strength of the composite containing modified silica was slightly higher than that with the pristine silica, even though both showed similar degrees of silica dispersion from the morphology observation. For the surface-modified silica composite, the optical transmittance was higher than that of unmodified silica case. This finding implies the significance of the surface modification.

Mechanical performance of nanosilica filled quartz fiber/polyimide composites at room and elevated temperatures

The polyimide (PI) composites reinforced with silanized nanosilica (SNS) and/or quartz fabrics had been fabricated. Influences of the SNS dispersion on morphology, Vickers hardness, thermal stability and mechanical properties of these composites were studied. The uniform dispersion of SNS in PI resulted from the crosslink of silane pretreated on the surface of nanosilica and PI chains. The measurement results indicated that density, Vickers hardness and flexural strength were enhanced due to the addition of SNS into the PI matrix and the optimum content of SNS was 2 wt%. The thermal stability of the SNS reinforced PI composites increased with an increase in weight fraction of SNS, compared with the neat PI resin. The effects of quartz fabric on the mechanical properties of quartz fabric-reinforced PI composites with different volume fractions and effects of post-curing on the flexural strength were also investigated. Results also showed that better mechanical properties of quartz fabric-reinforced PI composites were obtained when the volume fraction of quartz fabric was 50%. The quartz fabric-reinforced PI composites containing 2 wt% SNS after post-curing exhibited the highest flexural strength and elasticity modulus by virtue of good fiber-matrix interface, and flexural strength was almost 500 MPa at 300 °C. It is pointed that the composites have a great application prospect as one of engineering materials with high strength and high temperature resistance.

Enhanced Drag Reduction Performance of Nanocomposites: The Effects of Surface Modification of Nano Silica

In this paper, nanocomposite was synthesized with nano silica and poly-α-olefin, and the effects of surface modification to the nano silica on its drag reduction performance were investigated. The dosage coupling agent, Y-aminopropyltriethoxysilane, and the modification temperature were studied intensively through surface hydroxyl and oil adsorption analysis. The test results indicated that the hydroxyl number of the silica was decreased by Y-aminopropyltriethoxysilane modification, with improved lipophilicity and oil adsorption. At 50°C, the optimum Y-aminopropyltriethoxysilane dosages were 15% for Nano-Si-10, 5% for Nano-Si-20, and 10% for Degussa-R972. The modification significantly changed the nano silica surface properties and enhanced the interaction with poly-α-olefin. Through drag reduction and shear resistance tests by rotating disk 40 mins degradation and testing loop 2 times shearing, it was shown that the nanocomposite possessed good drag reduction and excellent shear resistance properties.

Water-Dispersible Reactive Nanosilica and Poly(2-acrylamido-2-methyl-1-propanesulfonic acid sodium) Nanohybrid as Potential Oil Displacement Agent for Enhanced Oil Recovery

2-acrylamido-2-methyl-1-propanesulfonic acid sodium (AMPS) was grafted onto the surface of reactive nanosilica (RNS-D) by free radical polymerization to afford RNR-D/PAMPS inorganic–polymer nanohybrid with good water dispersibility, which can serve as a potential oil displacement agent for enhanced oil recovery. The RNS-D/PAMPS nanoparticles were characterized by transmission electron microscopy and Fourier transform infrared spectrometry, and the oil displacement performance of the RNS-D/PAMPS nanohybrid solution was evaluated by static and dynamic oil displacement tests. Results showed that the RNS-D/PAMPS nanohybrid as the potential oil displacement agent could obviously reduce the interfacial tension between crude oil and water, increase the hydrophilicity of rock surface, and dramatically decrease the adhesion work of crude oil and rock. When the RNS-D/PAMPS solution is introduced at a mass fraction of 5.0% under static and dynamic oil displacement tests, the tested crude oil can be recovered at a to...

Biocompatible nanocomposites based on semi-interpenetrating polymer networks and nanosilica modified by bioactive amino acid tryptophan: Morphology, dynamics and properties

The nanocomposites based on polyurethane and poly(2-hydroxyethyl methacrylate) (PU-PHEMA) semi-IPN matrices with 17 or 37wt.% PHEMA, containing from 3 to 15wt.% nanosilica (NS), were synthesized aiming at the biomedical applications. NS surface was modified using the mechanosorptive method, with formation of basically monomolecular layer of biologically active substance – amino acid tryptophan. The AFM analysis of morphology of the nanocomposites and the complex DSC-TSDC-DMA-CRS analysis of their thermal, relaxation and elastic properties over the broad temperature range, from −150 to 200°C, were performed. Satisfactory nanofiller dispersion and the pronounced changes in matrix morphology were observed at 17wt.% PHEMA in the matrix, whereas nanofiller submicro- and microaggregates prevailed in the nanocomposites with 37wt.% PHEMA. As a result, just in the first case the most substantial “constrained dynamics” effect (e.g., increasing Tg by 20–30°C) was observed in the nanocomposites.

Boric acid incorporated on the surface of reactive nanosilica providing a nano‐crosslinker with potential in guar gum fracturing fluid

ABSTRACTSmall molecule borate crosslinker widely used in hydraulic fracturing treatment has a low crosslinking efficiency of less than 1%. Thus boric acid was introduced onto the surface of reactive nanosilica (denoted as nano‐SiO2; size: about 20 nm) containing NH2 group to obtain a nanosilica‐based crosslinker (denoted as nano‐crosslinker) with increased crosslinking efficiency, thereby broadening the application of nano‐SiO2 in guar gum fracturing fluid. Moreover, the influence of the as‐prepared nano‐crosslinker on the rheological behavior of guar gum gel was investigated with borate crosslinker as a reference. Results show that boric acid chemically reacts with the amino group of the reactive nano‐SiO2 to form NB bond, which is beneficial to the formation of the network structure of guar gum gel. The guar gum gel crosslinked with the 57 ppm of borate based on the carrier of nano‐SiO2 exhibits better temperature tolerance and shear resistance as well as breaking behavior than the counterpart crosslinked with 200 ppm of borate. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017, 134, 45037.

Temperature and pH Dual-Responsive Core-Brush Nanocomposite for Enrichment of Glycoproteins.

In this report, we present a novel modular approach to the immobilization of a high density of boronic acid ligands on thermoresponsive block copolymer brushes for effective enrichment of glycoproteins via their synergistic multiple covalent binding with the immobilized boronic acids. Specifically, a two-step, consecutive surface-initiated atom transfer radical polymerization (SI-ATRP) was employed to graft a flexible block copolymer brush, pNIPAm-b-pGMA, from an initiator-functionalized nanosilica surface, followed by postpolymerization modification of the pGMA moiety with sodium azide. Subsequently, an alkyne-tagged boronic acid (PCAPBA) was conjugated to the polymer brush via a Cu(I)-catalyzed azide-alkyne cycloaddition (CuAAC) click reaction, leading to a silica-supported polymeric hybrid material, Si@pNIPAm-b-pBA, with a potent glycol binding affinity. The obtained core-brush nanocomposite was systematically characterized with regard to particle size, morphology, organic content, brush density, and number of immobilized boronic acids. We also studied the characteristics of glycoprotein binding of the nanocomposite under different conditions. The nanocomposite showed high binding capacities for ovalbumin (OVA) (98.0 mg g-1) and horseradish peroxidase (HRP) (26.8 mg g-1) in a basic buffer (pH 9.0) at 20 °C. More importantly, by adjusting the pH and temperature, the binding capacities of the nanocomposite can be tuned, which is meaningful for the separation of biological molecules. In general, the synthetic approach developed for the fabrication of block copolymer brushes in the nanocomposite opened new opportunities for the design of more functional hybrid materials that will be useful in bioseparation and biomedical applications.

The effect of gas-wetting nano-particle on the fluid flowing behavior in porous media

The effect of gas-wetting on the liquid-blocking effect near a wellbore region is significant. Here, we functionally modified nano-silica particles with a size of approximately 40nm each by using a fluorosurfactant and obtained a super gas-wetting nano-silica particles, which could improve the contact angles of brine and hexadecane from 23° and 0° to 152° and 140°, respectively, and decrease the surface free energy of rock surface from 72 to 1.6mN/m. The decrease in the gas displacement was approximately 30%. FT-IR, SEM and EDS were employed to determine the morphological change in the rock surface before and after gas-wetting alteration. Results indicate that when the fluorosurfactant molecules are joined to the nano-silica surface, and CF bond is recognized. The grape-like particles forming a multi-adsorption on the rock surface, which play an important role in super gas-wetting by decreasing surface free energy and increasing roughness on the rock surface. The data of EDS was consistent with the results of FT-IR and SEM. To further understand the influence of gas-wetting alteration on the flow and distribution of fluids in porous media, visualization flooding was conducted. The results show that the initial liquid saturation in the micromodel decreased sharply from 33.23% to 20.77% after the gas-wetting treatment, and the contact angle of isolated brine droplet on the treated pore-wall was approximately 125°, which also verifies that pore wettability can be altered to gas-wetting. The analytical data of the oil displacement experiment demonstrates that the substantial decrease in oil saturation may contributes to enhancing oil recovery. Furthermore, the mobility of oil trapped in micro channels can also be enhanced significantly after gas-wetting alteration due to the presence of methane.

Self-healing hybrid nanocomposite anticorrosive coating from epoxy/modified nanosilica/perfluorooctyl triethoxysilane

Abstract Self-healing hybrid nanocomposite was successfully prepared from epoxy resin containing self-healing microcapsules and organosilane modified nanosilica to enhance the anticorrosion performance of an epoxy coating. Nanosilica surface was modified with (3-glycidoxypropyl)trimethoxysilane (GPTMS) and (3-aminopropyl)trimethoxysilane (APTES) to accomplish well dispersion in the polymer matrix. Perfluorooctyl triethoxysilane (POT), ethanolamine (ETA), and diethanolamine (DEA) as self-healing agents were encapsulated by polymer shell and incorporated into the epoxy coating along with modified nanosilica to form anticorrosion barrier of organic and inorganic coating on a cold-rolled steel surface (CRS). The results revealed that the self-healing hybrid nanocomposite containing 3 wt% of GPTMS-modified silica (GMS) and 10 wt%POT microcapsules possessed the best corrosion performance with the corrosion rate of 0.09 mm/year (I corr of 0.01 mA/cm 2 ), corrosion rating number of 9 and oxygen permeability about 0.14 barrer. The addition of modified silica (GMS) and self-healing agent microcapsules (POT) effectively increased the length of the diffusion pathways, as well as decreased the O 2 permeability of the nanocomposite film.

지환식 에폭시/표면개질된 마이크로-나노실리카 콤포지트의 유전특성

The surface of nanosilica and microsilica was modified in order to develop a high voltage insulation material for outdoor application. The modified silicas were well dispersed in an aliphatic cyclic epoxy resin. Dielectric properties were studied for 8 kinds of specimens: 1 kind of neat epoxy, 3 kinds of epoxy/microsilica composites, and 4 kinds of epoxy/microsilica/nanosilica composites. Complex dielectric constants were measured in the range of 10-2~1.2 Hz at room temperature.

Encapsulation of NiO nanoparticles in mesoporous carbon nanospheres for advanced energy storage

Abstract A facile encapsulation of NiO nanoparticles in mesoporous carbon nanospheres (NiO/MCNs) is demonstrated. Silicate-ion groups on nanosilica surface can react with Ni 2+ ions to generate nickel silicate in situ around the SiO 2 cores. Such hybrids are introduced into polymer nanospheres prepared by extended Stober strategy, followed by calcination and template removal to fabricate NiO/MCNs. The typical NiO/MCNs have spherical morphology (∼280 nm in diameter), uniform mesopores (5.9 nm), high specific surface area (714 m 2 g −1 ), and well-dispersed NiO nanoparticles (7.20 wt.%). Package mesoporosity among the carbon spheres reduces ion diffusion distance, and the mesopores benefit fast ion transportation. Besides, the introduction of NiO nanoparticles not only provides pseudocapacitance, but also increases the graphitization degree of the carbons and improves crystalline structure. As a result, NiO/MCNs as supercapacitor electrodes show a high specific capacitance of 406 F g −1 at 1.0 A g −1 in 6 M KOH electrolyte, and it still maintains 315 F g −1 at a high loading current density of 20.0 A g −1 . Besides, NiO/MCN electrode retains ∼91.0% of the original capacity at 3.0 A g −1 after 10,000 cycles, exhibiting outstanding cycle stability. The easy prepared, well-structured, and high-performance NiO/MCNs provide great potential to support advanced energy storage systems.

Thermal degradation and flammability of nanocomposites composed of silica cross-linked to poly(methyl methacrylate)

The effect of polymer cross-linkages on thermal degradation of silica/poly (methyl methacrylate) (PMMA) nanocomposites is investigated using a single novel nanoparticle. Nanosilica surface treated with KH570, an organic surface treatment capable of free-radical polymerisation, was used to cross-link PMMA via an in situ method. Scanning electron microscopy was used to characterise nanosilica before use, while X-ray diffraction confirmed silica was well dispersed in PMMA. Thermogravimetric analysis (TGA) results showed that thermal degradation of silica cross-linked nanocomposites was significantly stabilised compared to PMMA, with a 30% reduction in the peak mass loss rate. Kinetic studies revealed the degradation of nanocomposites in this work abide by first-order kinetics, with an increase in the degradation activation energy of approximately 100 kJ mol−1. This is nearly double the improvement compared to conventional PMMA-silica nanocomposites in literature, showing dramatic enhancements to thermal stability. Analysis of high-temperature residuals from TGA tests suggest that cross-linked silica have increased char yields when compared with both PMMA and traditional silica nanocomposites. Cone Calorimetry results showed the materials in this work have reduced heat release rates compared to PMMA and traditional silica-PMMA nanocomposites.

Features of Fischer–Tropsch synthesis in the presence of an iron-containing catalyst supported on the surface of spherical nanosilica

Features of Fischer–Tropsch synthesis in the presence of an iron-containing catalyst supported on spherical nanosilica (the average sizes of spherical SiO2 and iron-containing particles on the silica surface are 250 and 14 nm, respectively) are studied. The catalyst exhibits high activity in the conversion of syngas, viz., 7.6 times higher than the activity of a 20% Fe/silica gel catalyst. A distinctive feature of a catalyst supported on spherical silica is higher selectivity for liquid products, which decreases only slightly with increasing temperature. Reduction characteristics are studied using the temperature-programmed reduction method; the specific surface area is measured and the phase composition of the synthesized catalyst systems is determined by X-ray diffraction analysis.

Modified Nano Silica by Acrylate for High Performance Hard Coating

The surface modification of nano silica was carried out with acrylate and then organic/inorganic hybrid coating material was prepared using commercially available acrylic hard coating material with the modified nano silica. UV curing was carried out for the prepared coating material on poly(ethylene terephthalate) (PET) film and physical properties were evaluated. FTIR results show that the hydroxyl groups on the surface of nano silica were successfully modified with acrylate. It was found that inorganic/organic UV curing between acrylate and acrylate modified nano silica resulted in the improvement of surface hardness and anti-scratching behavior with maintaining optical transmittance but the increase of haze was noticed due to the increase of light scattering on the rough surface by nano silica.

One-Pot Preparation of Nano-SiO2 Using a Silane Derivative as a Coupling Agent

Abstract The nano-silica particles were prepared by one-pot method using absolute ethanol as solvent. After the nano-silica derived from TEOS was synthesized, the coupling agent was added into the above suspension without any filtration or purification processes to modify the nano SiO2. The optimum modification conditions were determined based on the degree of oil affinity and water sorption ratio. The size and morphology of SiO2 before and after modification were observed using Transmission Electron Microscopy. The introductions of the organic chains to their surfaces were measured using Ultraviolet and Visible Spectrophotometry, Fourier Transform Infrared Spectroscopy and 13C solid-state Nuclear Magnetic Resonance. The influences of the hydrophobicity of the organic functional group on the nano-silica particles were tested by the water contact angle. The results show that the organic chains had been grafted on the surface of nano-silica.

On the Effect of Nanoparticle Surface Chemistry on the Electrical Characteristics of Epoxy-Based Nanocomposites.

The effect of nanosilica surface chemistry on the electrical behavior of epoxy-based nanocomposites is described. The nanosilica was reacted with different volumes of (3-glycidyloxypropyl)trimethoxysilane and the efficacy of the process was demonstrated by infrared spectroscopy and combustion analysis. Nanocomposites containing 2 wt % of nanosilica were prepared and characterized by scanning electron microscopy (SEM), AC ramp electrical breakdown testing, differential scanning calorimetry (DSC) and dielectric spectroscopy. SEM examination indicated that, although the nanoparticle dispersion improved somewhat as the degree of surface functionalization increased, all samples nevertheless contained agglomerates. Despite the non-ideal nature of the samples, major improvements in breakdown strength (from 182 ± 5 kV·mm−1 to 268 ± 12 kV·mm−1) were observed in systems formulated from optimally treated nanosilicas. DSC studies of the glass transition revealed no evidence for any modified interphase regions between the nanosilica and the matrix, but interfacial effects were evident in the dielectric spectra. In particular, changes in the magnitude of the real part of the permittivity and variations in the interfacial α′-relaxation suggest that the observed changes in breakdown performance stem from variations in the polar character of the nanosilica surface, which may affect the local density of trapping states and, thereby, charge transport dynamics.

Investigation the effect of nanocomposite material on permeation flux of polyerthersulfone membrane using a mathematical approach

Integrally skinned asymmetric membranes based on nanocompositepolyethersulfone were prepared by the phase separation process using the supercritical CO2 as a nonsolvent for the polymer solution. In present study, the effects of temperature and nanoparticle on selectivity performance and permeability of gases has beeninvestigated. It is shown that the presence of silica nanoparticles not only disrupts the original polymer chain packing but also alters the chemical affinities of penetrants in polyethersulfone matrices. Because, in the presence of hydrophilic silica, CO2 affinity filler, hydrogen-bond interactions between the oxygen atoms of carbon dioxide and the hydrogen atoms of hydroxyl group on the nanosilica surface would take place at the interface and thus solubility and consequently permeability towards CO2 are higher in comparison with CH4 for the membranes. Furthermore, in present study, a novel mathematical approach has been proposed to develop a model for permeation flux and selectivity performance of the membrane using Support Vector Machine. SVM is employed to develop a model toestimateprocess output variables of a nanocomposite membrane including permeation flux and selectivity performance. Model development that consists of training, optimization and test was performed using randomly selected 80%, 10%, and 10% of available data respectively.

A facile and green preparation of nanosilica-supported antioxidant and its reinforcement and antioxidation effect on styrene-butadiene rubber

ABSTRACTA novel solid-phase method has been proposed to prepare a nanosilica-supported antioxidant by the reaction of nanosilica with 2-mercaptobenzimidazole (MB) and silane coupling agent γ-chloropropyltriethoxysilane. Fourier transform-infrared spectroscopy and other characterization methods confirmed that MB was chemically bonded onto the surface of nanosilica. Silica-s-MB was homogeneously dispersed in a styrene-butadiene rubber (SBR) matrix with strong filler-rubber interaction, leading to enhanced mechanical performance of SBR/silica-s-MB composites compared with SBR/m-silica composites. Based on the results of thermo-oxidation testing of SBR/silica-s-MB and SBR/m-silica/MB composites containing equivalent antioxidant component, silica-s-MB showed better antioxidative efficiency than the corresponding low-molecular-weight MB owing to its lower migration and volatility at high temperature.