Surface-treated Silica Nanoparticles Research Articles

Effect of Silica Nanoparticles On Flexural Strength And Surface Hardness Of Heat Polymerized Acrylic Resin.

Statement of problem. Various studies are present to increase the strength and surface hardness of heat polymerized acrylic resin by addition of material or surface treatments. The present study to evaluate an effect of silica nanoparticles on flexural strength and surface hardness of heat polymerized acrylic resin. Purpose. The purpose of this study was effect of silica nanoparticles, incorporated into Polymethyl Methacrylate, on flexural strength and surface hardness. The present study compared the effect of silanated and non silanated silica nanoparticles on the flexural strength and surface hardness of heat polymerized acrylic resin. Material and Methods. A total of 270 acrylic bars were fabricated, in two batches of 135 each, for testing flexural strength by universal testing machine and surface hardness determined using a digital micro Vickers hardness tester. The control group and subgroups had a sample size of 15 each with varied concentrations of nanoparticles by weight. The fabricated samples were tested for flexural strength and surface hardness. Results. Flexural strength was highest for PMMA (Polymethyl methacrylate) with 0.5% silanated silica nano particles as fillers. In both the groups, the flexural strength decreased with increase in filler concentration. Surface hardness was highest in the PMMA group with non-silanated nano particles as fillers at 5% concentration. In both groups the surface hardness improved with an increase in filler concentration. ANOVA and TUKEY’s HSD test were used. P<0.05 was considered statistically significant. Conclusion. Lower concentrations of surface-treated silica nanoparticles should be used as fillers to enhance the flexural strength of commercially available heat polymerized acrylic resin. Bangladesh Journal of Medical Science Vol.23 (Special Issue) 2024 p.S79-S86

Role of Surface-Treated Silica Nanoparticles on the Thermo-Mechanical Behavior of Poly(Lactide)

Surface-treated fumed silica nanoparticles were added at various concentrations (from 1 to 24 vol%) to a commercial poly(lactide) or poly(lactic acid) (PLA) matrix specifically designed for packaging applications. Thermo-mechanical behavior of the resulting nanocomposites was investigated. Field Emission Scanning Electron Microscopy (FESEM) micrographs revealed how a homogeneous nanofiller dispersion was obtained even at elevated filler amounts, with a positive influence of the thermal degradation stability of the materials. Modelization of Differential Scanning Calorimetry (DSC) curves through the Avrami–Ozawa model demonstrated that fumed silica nanoparticles did not substantially affect the crystallization behavior of the material. On the other hand, nanosilica addition was responsible for significant improvements of the storage modulus (E′) above the glass transition temperature and of the Vicat grade. Multifrequency DMTA tests showed that the stabilizing effect due to nanosilica introduction could be effective over the whole range of testing frequencies. Sumita model was used to evaluate the level of filler dispersion. The obtained results demonstrated the potential of functionalized silica nanoparticles in improving the thermo-mechanical stability of biodegradable matrices for packaging applications, especially at elevated service temperatures.

Evaluating the potential of surface-modified silica nanoparticles using internal olefin sulfonate for enhanced oil recovery

Recently, nanoparticles have proven to enhance oil recovery on the core-flood scale in challenging high-pressure high-temperature reservoirs. Nanomaterials generally appear to improve oil production through wettability alteration and reduction in interfacial tension between oil and water phases. Besides, they are environmentally friendly and cost-effective enhanced oil recovery techniques. Studying the rheological properties of nanoparticles is critical for field applications. The instability of nanoparticle dispersion due to aggregation is considered as an unfavorable phenomenon in nanofluid flooding while conducting an EOR process. In this study, wettability behavior and rheological properties of surface-treated silica nanoparticles using internal olefins sulfonates (IOS20–24 and IOS19–23), anionic surfactants were investigated. Surface modification effect on the stability of the colloidal solution in porous media and oil recovery was inspected. The rheology of pure and surface-treated silica nanoparticles was investigated using a HPHT rheometer. Morphology and particle size distributions of pure and coated silica nanoparticles were studied using a field emission scanning electron microscope. A series of core-flood runs was conducted to evaluate the oil recovery factor. The coated silica nanoparticles were found to alter rheological properties and exhibited a shear-thinning behavior as the stability of the coated silica nanoparticles could be improved considerably. At low shear rates, the viscosity slightly increases, and the opposite happens at higher shear rates. Furthermore, the surface-modified silica nanoparticles were found to alter the wettability of the aqueous phase into strongly water-wet by changing the contact angle from 80° to 3° measured against glass slides representing sandstone rocks. Oil–water IFT results showed that the surface treatment by surfactant lowered the oil–water IFT by 30%. Also, the viscosity of brine increased from 0.001 to 0.008 Pa s by introducing SiO2 nanoparticles to the aqueous phase for better displacement efficiency during chemical-assisted EOR. The core-flood experiments revealed that the ultimate oil recovery is increased by approximately 13% with a surfactant-coated silica nanofluid flood after the conventional waterflooding that proves the potential of smart nanofluids for enhancing oil recovery. The experimental results imply that the use of surfactant-coated nanoparticles in tertiary oil recovery could facilitate the displacement efficiency, alter the wettability toward more water-wet and avoid viscous fingering for stable flood front and additional oil recovery.

Nanoparticles as Foam Stabilizer for Steam-Foam Process

Summary Steam foams have been considered effective additives for unconventional oil-recovery processes. Conventionally, for steam-foam applications, chemical additives are injected with steam. However, this procedure can have serious challenges because of poor thermal stability of additives and high volume of additives loss caused by adsorption to the rock surface. To overcome these limitations, nanoparticles can be used as novel additives to improve generation and stabilization of the foams for steam-foam applications. In this study, silica nanoparticles in synergy with surfactants have been used as steam additives. Dynamic light scattering (DLS), a foam-height test using N2 at reservoir conditions, and thermal-stability analysis were designed to measure nanoparticle size distribution in brine, foamability, and thermal stability of the additive solutions, respectively. Subsequently, coreflooding tests were performed to evaluate the synergistic effect of nanoparticles and surfactants on the foam performance and oil recovery. We observed an optimal ratio of nanoparticle and surfactant that yields the best foam-generation performance in bulk medium. Herein, surface-treated silica nanoparticles have been tested with two of our candidate surfactants. The nanoparticles alone generate a small amount of foam, whereas each surfactant generates a small-to-moderate amount of foam. Synergy is demonstrated by the system that contains 0.1-wt% nanoparticles (the optimal concentration) and 0.5-wt% surfactant solution at neutral pH (≈7), as it leads to approximately 67 and 50% greater foam height, respectively, for Surfactants A and B than foam height observed in tests with surfactants only, in bulk medium. Corefloods with coinjected steam and water containing nanoparticles and surfactant confirm the synergy, exhibiting measurable improvement in mobility-reduction factor (MRF) and steam control, compared with coinjection of steam and water containing only surfactant.

Surface Degradation and Nanoparticle Release of a Commercial Nanosilica/Polyurethane Coating Under UV Exposure.

Many coatings properties such as mechanical, electrical, and ultra violet (UV) resistance are greatly enhanced by the addition of nanoparticles, which can potentially increase the use of nanocoatings for many outdoor applications. However, because polymers used in all coatings are susceptible to degradation by weathering, nanoparticles in a coating may be brought to the surface and released into the environment during the life cycle of a nanocoating. Therefore, the goal of this study is to investigate the process and mechanism of surface degradation and potential particle release from a commercial nanosilica/polyurethane coating under accelerated UV exposure. Recent research at the National Institute of Standards and Technology (NIST) has shown that the matrix in an epoxy nanocomposite undergoes photodegradation during exposure to UV radiation, resulting in surface accumulation of nanoparticles and subsequent release from the composite. In this study, specimens of a commercial polyurethane (PU) coating, to which a 5 mass % surface treated silica nanoparticles solution was added, were exposed to well-controlled, accelerated UV environments. The nanocoating surface morphological changes and surface accumulation of nanoparticles as a function of UV exposure were measured, along with chemical change and mass loss using a variety of techniques. Particles from the surface of the coating were collected using a simulated rain process developed at NIST, and the collected runoff specimens were measured using inductively coupled plasma-optical emission spectroscopy (ICP-OES) to determine the amount of silicon released from the nanocoatings. The results demonstrated that the added silica nanoparticle solution decreased the photodegradation rate (i.e., stabilization) of the commercial PU nanocoating. Although the degradation was slower than the previous nanosilica epoxy model system, the degradation of the PU matrix resulted in accumulation of silica nanoparticles on the nanocoating surface and release to the environment by simulated rain. These experimental data are valuable for developing models to predict the long-term release of nanosilica from commercial PU nanocoatings used outdoors and, therefore, are essential for assessing the health and environmental risks during the service life of exterior PU nanocoatings.

Polyethersulfone Ultrafiltration Membranes Containing Surface Treated Silica Nanoparticles for Improvement of Antibacterial Activity and Hydrophilicity

To overcome drawbacks of polyethersulfone (PES) ultrafiltration membranes such as hydrophobicity and bacteria growth on the membrane surface, PES membranes containing silica nanoparticles grafted with poly(1-vinylpyrrolidone) (silica-PVP) and those garfted with poly(sulfadiazine acrylamide) (silica-PSA) were fabricated. PES membranes containing silica-PVP exhibited better water flux than PES membrane, and the solute rejection of the former was similar with that of the latter when PES membrane contains less than or equal to 3 wt% of silica-PVP. PES membranes exhibiting antibacterial activity and improved water flux were fabricated by adding more than 3 wt% of silica-PSA.

Aggregation of silica nanoparticles and its impact on particle mobility under high-salinity conditions

Abstract CO 2 foams that are stabilized with nanoparticles are being considered to improve volumetric sweep efficiency for CO 2 enhanced oil recovery (EOR) processes. To better understand the nanoparticle retention/transport under high salinity conditions often associated with typical hydrocarbon reservoirs, the aggregation of the surface-treated silica nanoparticles was studied as a function of salinity and nanoparticle concentration. At pH 8.5, an enhancement in aggregation kinetics occurred with increasing calcium and particle concentration. However, when the pH was reduced to ca. 3, close to the CO 2 saturated condition, the aggregation was insignificant regardless of the salinity and the particle concentration over 10 days. In the transport test of silica nanoparticles in the sandpack column, a negligible amount of nanoparticles was retained with non-aggregated nanoparticles and for aggregates less than 235 nm regardless of flow rate. However, the retention of larger aggregates (>ca. 1000 nm) was enhanced as Darcy velocity decreased. Modeling based on a modified version of clean-bed filtration theory was able to explain experimental breakthrough curves only for the non-aggregated and slightly aggregated particles, suggesting that further considerations are essential to understand the physical effect of aggregation on the transport of larger aggregates. These results suggest a possible breakdown of the aggregates due to the hydrodynamic forces, hence retrieving the mobility of silica nanoparticles in the porous media. These observations demonstrate that silica nanoparticle aggregation can be prevented by increasing flow rate and lowering pH. The findings of this study would provide an insight on the behavior of nanoparticle in the reservoirs and a guideline for the application of the nanoparticles in enhanced oil recovery operations.

Mobility control through spontaneous formation of nanoparticle stabilized emulsions

[1] We report on measurements of the flow pattern and in-situ saturations whenn-octane displaces a brine in which surface treated silica nanoparticles are dispersed. The nanoparticles are known to stabilize octane-in-water emulsions. We find that the displacement front is more spatially uniform, and with a later breakthrough when compared to a control displacement with no in-situ nanoparticles. Pressure measurements during the displacement are consistent with generation of a viscous phase such as an emulsion. These observations suggest that a nanoparticle stabilized emulsion is formed during the displacement which acts to suppress the viscous instability. We argue that generation of droplets of nonwetting phase occurs at the leading edge of all drainage displacements. The droplets rejoin the bulk phase in the absence of stabilizing agents, but are preserved when nanoparticles adhere to the fluid/fluid interface.

Influence of various surface treated silica nanoparticles on the electrochemical properties of SiO 2/polyurethane nanocoatings

Various organosilane-treated SiO 2 nanoparticles were dispersed in a 2-pack polyurethane coating. The influence of surface modification and silica content on the electrochemical behaviour of the resultant nanocoatings was investigated. Electrochemical impedance spectroscopy (EIS) and open circuit potential (OCP) variations were examined. The surface chemistry of nanoparticles and its effect on the resultant nanocoating morphology were also studied utilising FTIR, and TEM analyses. The results reveal that the presence of more hydrophobic groups and longer-lengthed hydrophobic chains on the surface of nanoparticles, greatly improves the interfacial interactions at the polymer/filler interfaces resulting in a better corrosion performance.

Fabrication of nearly monodispersed silica nanoparticles by using poly(1-vinyl-2-pyrrolidinone) and their application to the preparation of nanocomposites

To fabricate dental nanocomposites containing finely dispersed silica nanoparticles, nearly monodispersed silica nanoparticles smaller than 25 nm were synthesized without forming any aggregates via a modified solgel process. Since silica nanoparticles synthesized by the Stober method formed aggregates when the particle size is smaller than 25 nm, the synthetic method was modified by changing the reaction temperature and adding poly(1-vinyl-2-pyrrolidinone) (PVP) to the reaction mixture. The size of the formed silica nanoparticles was reduced by increasing the reaction temperature or adding PVP. Furthermore, the formation of aggregates with primary silica nanoparticles smaller than 25 nm was prevented by increasing the amount of PVP added to the reaction mixture. To enhance the dispersion of the silica particles in an organic matrix, the synthesized silica nanoparticles were treated with 3-methacryloxypropyltrimethoxysilane (γ-MPS). A dental nanocomposite containing finely dispersed silica nanoparticles could be produced by using the surface-treated silica nanoparticles.

Size Control of Silica Nanoparticles and Their Surface Treatment for Fabrication of Dental Nanocomposites

Nearly monodispersed silica nanoparticles having a controlled size from 5 to 450 nm were synthesized via a sol-gel process, and then the optimum conditions for the surface treatment of the synthesized silica nanoparticles with a silane coupling agent (i.e., 3-methacryloxypropyltrimethoxysilane (gamma-MPS)) were explored to produce dental composites exhibiting enhanced adhesion and dispersion of silica nanoparticles in the resin matrix. The particle size was increased by increasing amounts of the catalyst (NH4OH) and silica precursor (tetraethylorthosilicate, TEOS) and by decreasing the amount of water in the reaction mixtures regardless of solvents used for the synthesis. The particle size prepared by using ethanol as a solvent was significantly larger than that prepared by using methanol as a solvent when the composition of the reaction mixture was fixed. The nanosized particles in the 5-25 nm range were aggregated. The amount of grafted gamma-MPS on the surface of the synthesized silica nanoparticles was dependent on the composition of the reaction mixture when an excess amount of gamma-MPS was used. When surface treatment was performed at optimum conditions found here, the amount of the grafted gamma-MPS per unit surface area of the silica nanoparticles was nearly the same regardless of the particle size. Dispersion of the silica particles in the resin matrix and interfacial adhesion between silica particles and resin matrix were enhanced when surface treated silica nanoparticles were used for preparing dental nanocomposites.

Nanocomposite resist systems for next generation lithography

A novel nanocomposite resist system was developed for sub-100 nm resolution e-beam lithography by dispersing surface-treated silica nanoparticles in a commercial ZEP520 ® resist. At 4.0 wt.% loading of silica nanoparticles, the system exhibited a much higher resolution than ZEP520 ® without sacrificing the intrinsic sensitivity and contrast of the starting polymer. The first major result is that 46 nm-wide isolated lines were obtained in the nanocomposite system (∼250 nm-thick layer), whereas comparatively 130 nm-wide lines were obtained in ZEP520 ® under the same experimental conditions. Contrary to standard e-beam resists, this important reduction of line broadening already occurred at 20 keV while higher energy e-beams (up to 100 keV) did not lead to further line broadening reduction. Moreover, it was shown that the addition of silica nanoparticles resulted in a higher resistance of the nanocomposite to plasma etching with O 2 gas. Subjecting this nanocomposite resist to 75-keV Xe + ion irradiation showed that it is also particularly suitable for ion projection lithography as a preliminary resolution of 114 nm (l/s) was obtained while the sensitivity increased by a factor of 40 compared to 30-keV electrons. Extending the nanocomposite approach to KRS-XE ®, a chemically amplified resist, led to both enhanced resolution and mechanical stability for electron beam lithography. The major resolution and etch resistance improvements in both resist systems indicate that nanocomposite systems are promising candidates not only for sub-100 nm resolution e-beam lithography but also for ion projection lithography. Supported by preliminary Monte Carlo simulations a tentative mechanism highlighting the electron–nanocomposite interactions as the explanation for line broadening reduction is proposed.

Nanocomposite resists for electron beam nanolithography

A novel nanocomposite resist system was developed for sub-100 nm resolution e-beam lithography by dispersing surface-treated silica nanoparticles in a commercial ZEP520 ® resist. At 4.0 wt % loading of silica nanoparticles, the system exhibited a much higher resolution than ZEP520 ® without sacrificing the intrinsic high sensitivity and contrast of the starting polymer. The first major result is that 46 nm-wide isolated lines were obtained in the nanocomposite system, whereas comparatively 130 nm-wide lines were obtained in ZEP520 ® under the same experimental conditions. Moreover, it was shown that the addition of silica nanoparticles resulted in a higher resistance of the nanocomposite to plasma etching with O 2 gas. The major resolution improvement indicates that the nanocomposite is a promising candidate resist for sub-100 nm resolution e-beam lithography.