Fumed Nanosilica Research Articles

Fumed nano-silica modified PVA-chitosan composite hydrogel with Janus structure for solar-driven interfacial evaporation

Solar-driven interfacial evaporation (SIE) receives much attention nowadays. At present, efficient thermal management and salt resistance during operation are still the difficulties of SIE technology. In this work, a new composite hydrogel for SIE has been reported. This composite hydrogel uses polyvinyl acetate (PVA) and chitosan (CS) as the framework, carbon nanoparticles (CB) as the photothermal material, modified with hydrophilic/hydrophobic fumed nano-silica. The addition of fumed nano-silica reduces the thermal conductivity and effectively immobilizes heat energy on the evaporator’s top surface, which reduces heat loss and improves the evaporation rate. The CSPC (CB/Nano-silica PVA-CS) evaporator modified with hydrophobic nano-silica exhibits Janus structure with transition from a hydrophobic top to a hydrophilic bottom. The Janus-structured CSPC evaporator has the characteristics of excellent salt resistance, simple preparation process, low heat loss with self-floating property. The CSPC evaporator containing 0.5 g hydrophobic fumed nano-silica has a maximum evaporation rate of 1.58 kg/(m2·h), about 1.6 times higher than the evaporator without fumed nano-silica, which proves that the introduction of fumed nano-silica can effectively improve the evaporation performance of hydrogel. The overall efficiency of CSPC evaporator in simulated seawater is 88.63 %. The evaporation rate of CSPC evaporator has reached a high level in the evaporators using carbon black as photothermal material which was prepared by simple and low-cost method. It should be a promising category of material to be employed for solar desalination.

Influence of Fumed Nanosilica on Ballistic Performance of UHPCs

This research delves into the potential use of fumed nanosilica in ultra-high performance concrete for ballistic protection. First, the mechanical properties, slump flow, and specific gravity of UHPC with different contents of Aerosil 200 were determined. Then, calorimetric studies were conducted on these cement composites. Lastly, the differential efficiency factor and spalling area of UHPC with fumed nanosilica were determined. It was found out that the slump flow, the mechanical properties, and differential efficiency factor are slightly decreased by the addition of fumed nanosilica. However, the addition of the fumed nanosilica is beneficial in terms of the spalling area decrease and it is highly reactive during the induction period. Some of the results are supported by BSEM imaging.

Feasibility of Valorization of Post-Consumer Recycled Flexible Polypropylene by Adding Fumed Nanosilica for Its Potential Use in Food Packaging toward Sustainability.

The food industry has a current challenge of increasing the recycling of post-consumer plastics to reduce plastic waste towards a circular economy, especially flexible polypropylene, which is highly demanded in food packaging. However, recycling post-consumer plastics is limited because service life and reprocessing degrade their physical-mechanical properties and modify the migration of components from the recycled material to the food. This research evaluated the feasibility of valorization of post-consumer recycled flexible polypropylene (PCPP) by incorporating fumed nanosilica (NS). For this purpose, the effect of concentration and type (hydrophilic and hydrophobic) of NS on the morphological, mechanical, sealing, barrier and overall migration properties of PCPP films was studied. Incorporating NS improved Young's modulus and, more significantly, tensile strength at 0.5 wt% and 1 wt%, where a better particle dispersion was confirmed by EDS-SEM, but it diminished elongation at breakage of the films. Interestingly, NS tended to increase the seal strength of PCPP nanocomposite films more significantly at higher NS content, showing a seal failure of the adhesive peel type which is preferred for flexible packaging. NS at 1 wt% did not affect the water vapor and oxygen permeabilities of the films. Overall migration of PCPP and nanocomposites exceeded the limit value of 10 mg dm-2 allowed by European legislation at the studied concentrations of 1% and 4 wt%. Nonetheless, NS reduced the overall migration of PCPP from 17.3 to 15 mg dm-2 in all nanocomposites. In conclusion, PCPP with 1 wt% of hydrophobic NS presented an improved overall performance of the studied packaging properties.

Effect of geometric modification of fumed nanoscale silica for medical applications on adsorption of human serum albumin: Physicochemical and surface properties

The influence of the geometric modification (GM) of fumed nanoscale silica A300 (NS) on the adsorption capacity of human serum albumin (HSA) as well as the physicochemical and textural properties of the protein/nanosilica system was analyzed. An effective medical enterosorbent based on fumed nanosilica was designed and produced in the Chuiko Institute of Surface Chemistry, National Academy of Sciences of Ukraine. To design an effective nanomaterial for biomedical applications as a wound-healing material, the adsorption, physicochemical and surface properties of the initial nanosilica (NS), nanosilica after geometric modification (GM-nanosilica), and HSA/nanosilica biocomposites were characterized. The differences in sorption capacities, acid-base, textural, and surface properties of the obtained materials were monitored using the diffuse UV–vis reflectance spectroscopy, the potentiometric titration of suspension, the nitrogen adsorption/desorption isotherms, the scanning electron microscopy with the energy dispersive X-ray microanalysis and the digital optical microscope. For a deeper understanding of the nature of immobilized HSA molecules on the nanosilica and GM-nanosilica, the surface functional groups were characterized by the FTIR spectroscopy. It was found that the adsorption properties, physicochemical and textural characteristics of fumed nanoscale silica depend on the mechanical treatment time (tMT) and bulk density (db). In fact, as the tMT increases, the db of initial fumed nanosilica increases, and the protein adsorption capacity decreases, however, it remains at an acceptable level: 0.075 g/g, 0.056 g/g, 0.032 g/g for GM-nanosilica after 1, 4, and 7 h of mechanical treatment, respectively. HSA adsorption significantly changes the surface morphology, acid-base character, and structure of both unmodified and modified nanosilica.

Nano Silica application for inducing rice resistance and the possibility for Ytterbium Rare Earth Elements green mining

There is a growing interest and recognition of Silicon (Si) in plants to increase growth, productivity, and plant resistance. This research examines the role of Nano Silica to increase yield and resistance. This study set out to assess the effect of hydrophilic fumed Nano Silica application with the frequency of 1×, 2×, 3×, and 4× applications respectively with three replications using RCBD as well as SEM-EDX and XRF analysis. Nano Silica frequencies showed a distinctive decrease of damage intensity at the 3× and 4× applications. The rice husk increases of metal-like surface appearance as more Nano Silica frequency was applied. It is proposed that Nano Si induced plant resistance through the modification of surface layer and stronger plant tolerance against environmental stress. The most unexpected observation to emerge was the Ytterbium (Yb) concentration known as a Rare Earth Elements at the 3× and 4× Nano Si applications. This indicates that Nano Silica application provides insights and opportunities to Nano Si application on Rice for the purpose of acquiring Ytterbium from farmland. Nano Silica can play an important role as a new method in addressing the Ytterbium green mining.

Effects of Nano-Ceramic Particle Addition for Cold Sprayed Fluoropolymer Coatings

Semi-crystalline polymers such as fluoropolymers are extremely difficult to coat with using solid-state deposition technique such as cold spray (CS) due to its high viscoelastic-viscoplastic behavior. Generally, fluoropolymers solid-state deposition using CS are characterized by a relatively low deposition efficiency (DE) as compared to metallic materials using this deposition technique. In this article, the study on the effect of hydrophobic fumed nanosilica (FNS) and fumed nanoalumina (FNA) in Perfluoroalkoxy (PFA) solid-state deposition using CS has been studied. This study incorporated certain parameters related to the CS process. In addition, powder modification technique using hydrophobic FNS and FNA as additive to feedstock has been studied as well. The results show a number of parameters affected the DE; particle size, traverse speed, gas temperature, and addition of hydrophobic fumed nanoparticles, indicated a better DE. Moreover, PFA coating produced in this manner, retained its hydrophobicity.

Synthesis and properties of self-assembled ultralong core-shell Si3N4/SiO2 nanowires by catalyst-free technique

Self-assembled ultralong Si3N4/SiO2 nanowires (SiNNWs) with core-shell structure are prepared by air jet-spinning followed by high-temperature calcination employing low-cost fumed nano silica and industrial polyacrylonitrile as raw materials. Without using metal catalysts or reductive atmosphere, Si3N4/SiO2 nanowires are generated through autocatalysis and self-assembly. The ultralong SiNNWs are uniform and continuous throughout the entire length with a 3–4 nm amorphous SiO2 shell layer on surface of the Si3N4. The diameter of the SiNNWs is about 80–200 nm with the length being at centimeter level and the main component of the SiNNWs is the standard hexagonal cell of α-Si3N4. Moreover, the photoluminescence spectrum of SiNNWs exhibits an intense blue-green light emission at room temperature. The self-assembly mechanism of the SiNNWs is discussed.

Thermomechanical behavior and thermal stability of polyurethane rigid nanocomposite foams containing binary nanoparticle mixtures

Polyurethane (PU) rigid nanocomposite foams containing binary nanoparticle mixtures were prepared via reactive foaming process by using the synergy of mixing based on H-bonding interactions between nanofillers and polymer matrix. Using a very high surface area hydrophilic fumed nanosilica with a primary particle size of 7 nm and a concentration of less than 0.2 wt% in addition to carboxylic acid functionalized multiwalled carbon nanotubes (MWCNTs-COOH) in PU rigid foams leads to improved thermal stability, thermomechanical and mechanical properties. Particularly, the system containing both 0.4 wt % CNT and 0.1 wt% nanosilica has a much higher value in terms of T g , storage modulus value at T g , reduced compressive strength, thermal stability and cell density compared to the sample containing only 0.5 wt% CNT. Based on FT-IR results, favorable and enhanced H-bonding interactions of N–H and carbonyl functional groups of the urethane linkage in PU chains with surface silanols of hydrophilic nanosilica particles and carboxylic acid functional groups of MWCNT-COOH were shown to be the main reasons for the reinforcement effect in PU rigid foams. • H-bonding interactions induced synergy of mixing between nanoparticles and PU rigid foam. • The addition of 0.4 wt % CNT and 0.1 wt % nanosilica maximized H-bonding. • The addition of 0.4 wt % CNT and 0.1 wt % nanosilica improved thermomechanical properties. • The addition of 0.4 wt % CNT and 0.1 wt % nanosilica improved reduced compressive strength, thermal stability. • The addition of CNT and more than 0.2 wt % nanosilica decreased thermomechanical properties, thermal stability.

Study on the Low and High Strain Rate Behavior of Fumed Nano Silica Dispersions

Shear Thickening Fluids (STFs) are a special class of field responsive non-Newtonian fluids which exhibit transition from low viscosity to high viscosity state when they are subjected to shearing deformation above the critical shear rate (CSR). Due to this unique characteristic of STFs, these have found application in ballistics, especially in the development of special class of body armors called Liquid Body Armors (LBAs) which are lighter in weight and more flexible as compared to conventional heavy armours. Fumed silica (FS) is a rheologically significant material as it is a well known viscosity modifier owing to its fractal structure, and is generally used in paints, coatings, sealants, printing inks etc. In this study, two different grades of FS (A-130 and A-150) were used for the synthesis of STFs. The low strain rate studies were conducted on cone and plate rheometer and high strain rate experiments were accomplished on split Hopkinson pressure bar (SHPB) set up. The colloidal dispersions in PPG-400 (Poly Propylene Glycol 400) were synthesized using ultrasonic homogenization technique. From the experiments it was observed that A-150 fumed silica dispersion exhibited higher severity in shear thickening in the low strain rate domain, whereas A-130 fumed silica dispersion exhibited higher specimen stress and compressional strain rate under high strain rate dynamic compressive loading. Thus, it can be inferred that the same material may exhibit different behaviors in the low and high strain rate regimes. Therefore, both the studies play a vital role to completely characterize the material, especially when the material has to be subjected to ballistic applications.

Anti-aging behavior of amino-containing co-condensed nanosilica in polyethylene

Physical loss of stabilizers by migration and extraction accelerates the degradation of polymer materials. In this work, amino-containing nanosilica with anti-aging properties was prepared simply by the co-condensation of tetraethoxysilane and N-(2-aminoethyl)-3-aminoproply-trimethoxysilane (AEAPS). AEAPS was used to introduce amino groups into silica nanoparticles and to act as a catalyst in this process. The co-condensed nanosilica (CCS) showed agglomerate structure similar to the typical fumed nanosilica (FS). The amino groups were distributed both on the surface and inside the nanoparticles. HDPE/CCS and HDPE/FS composites were prepared by melt blending. Thermogravimetric analysis and oxidative induction time showed that CCS has effectively improved the thermo-oxidative stability of HDPE. In the long-term accelerated thermo-oxidative aging and UV aging tests, HDPE/CCS composite showed superior stability to neat HDPE and HDPE/FS composite. The results of infrared spectroscopy and electron paramagnetic resonance suggested that the HDPE/CCS composite manifested a special degradation mechanism involving the nucleophilic addition of amino groups to carbonyl species as well as the oxidation of amino groups on CCS by peroxides. The amino groups on CCS consumed carbonyl species and peroxides, and generated hydroxylamines and nitroxide radicals which were able to eliminate free radicals, thus restrained the degradation of HDPE.

Mesoporous Li2FeSiO4/C nanocomposites with enhanced performance synthesized from fumed nano silica

Mesoporous Li2FeSiO4/C nanocomposites (LFS-FNS and LFS-NS) were prepared from fumed nano silica (FNS) and nano silica (NS) through facile solid-state reactions, respectively. XRD analysis indicates that the crystalline structures of LFS-FNS and LFS-NS are indexed to monoclinic Li2FeSiO4 of P21. SEM results prove that the particle size of LFS-FNS and FNS (25~40 nm) is smaller than that of LFS-NS and NS, revealing the particle size of Li2FeSiO4/C nanocomposites can be tuned by choosing different silica. TEM further indicates Li2FeSiO4 nanoparticles are uniformly dispersed in the amorphous carbon networking of LFS-FNS. Pore structure analysis indicates the external surface areas of LFS-FNS as well as LFS-NS are 51.4 and 36.1 m2 g−1, indicating the pore properties of mesoporous Li2FeSiO4/C nanocomposites can be controlled by using different silica as silicon resource. The reduced particle size and high external surface area shorten the lithium-ion diffusion path and make LFS-FNS possess better electrochemical performance over LFS-NS. The discharge capacity of LFS-FNS is as high as 172 mA h g−1 at 0.1 C.

Photo- and thermo-oxidative aging of polypropylene filled with surface modified fumed nanosilica

Fumed nanosilica (FS) was treated separately by different silane coupling agents, including n-dodecyl-trimethoxyl silane (DTMS), aminoethylaminopropyl-trimethoxyl silane (AEAPS), aminopropyl-trimethoxyl silane (APS) and methacryloxypropyl-trimethoxyl silane (MAPS). Their influences on photo- and thermo-oxidative aging of polypropylene were evaluated by Fourier transform infrared spectroscopy (FTIR), differential scanning calorimetry (DSC) and thermal gravimetric analysis (TGA). The photoaging of polypropylene was accelerated by the MAPS-modified FS but delayed by the neat FS and other modified FS. On the other hand, the thermal and thermo-oxidative stability of polypropylene were improved with the incorporation of the nanoparticles, independent of the modification. The AEAPS-modified FS and the APS-modified FS revealed simultaneously noticeable enhancement in both photo-stability and thermo-oxidative stability of polypropylene. The possible mechanism was discussed.

Effect of silane coupling agents with different non-hydrolytic groups on tensile modulus of composite PDMS crosslinked membranes

In this paper, four silane coupling agents with different non-hydrolytic groups were used to treat a kind of hydrophilic fumed nanosilica to investigate the influence of different silane coupling agents on the mechanical properties of PDMS composite matrix. The four coupling agents were ethyl triethoxysilane (ETES), octyl triethoxysilane (OTES), phenyl triethoxysilane (PTES), and 3-aminopropyl triethoxysilane (APTES) which exhibited the same hydrolytic groups. For each coupling agent/nanosilica system, six modified nanosilica samples were prepared at different addition contents of the coupling agent; six corresponding PDMS composite crosslinked membranes were also prepared. It was found that compared with pure PDMS membrane, the addition of modified nanosilica to PDMS increased the tensile modulus of the composite membranes. The miscibility strongly influenced the tensile modulus of the composite membranes when the HSP (Hansen solubility parameter) difference Ra was adopted to characterize the miscibility between the non-hydrolytic groups of the four coupling agents and the solvent (n-hexane). A better miscibility induced a larger tensile modulus. When the length of the non-hydrolytic groups was larger than the distance between two adjacent hydroxyl groups, the sheltered hydroxyl groups by the non-hydrolytic groups would be prevented to couple with other coupling agent molecules, thereby reducing the available hydroxyl groups. When all of the potentially available hydroxyl groups at the nanosilica surface reacted with the coupling agent molecules, the tensile modulus of the composite membranes would reach a maximum value. In addition, according to the results of equilibrium swelling in ethanol and water, it was found that a membrane with large tensile modulus possessed strong resistant capability to swelling. From the results of ethanol and water pervaporation experiments, connection between ideal ethanol/water permeation selectivity or ideal ethanol/water diffusion selectivity and the tensile modulus was also observed.

Cyanuric chloride functionalized silica nanoparticles for covalent immobilization of lipase

AbstractBACKGROUNDIn this work, fumed nano‐silica (FNS) was chemically modified to amino (AFNS) and subsequently to cyanuric chloride (CCAFNS) modified silica and tested for the immobilization of lipase from Candida rugosa (CRL). The effects of the initial enzyme concentration, immobilization time and buffer ionic strength on immobilization were investigated in order to optimize utilization of the support and determine the mechanism of immobilization. The most active preparations were used to examine thermal and operational stability.RESULTSThe amount of immobilized enzyme increased with increasing enzyme concentration, achieving loadings of 121.3, 104.8 and 61.2 mg per g of FNS, CCAFNS and AFNS, respectively. Lipase immobilized on CCAFNS carrier in 0.1 mol L−1 buffer expressed the highest lipolytic activity (1320 IU g−1 support), while more stable preparations were obtained in 1 mol L−1 buffer.CONCLUSIONSuccessful modification of silica was confirmed with Fourier transform infrared spectroscopy and thermogravimetric analysis. Activity results showed that, depending on the support, immobilization was governed by different interactions. On FNS and AFNS immobilization was exclusively by adsorption, while on CCAFNS after the initial adsorption lipase molecules reoriented and amino groups of the enzyme formed a covalent bond with the chlorine atom of the modified carrier. Improved thermal and operational stability of lipase immobilized on CCAFNS in 1 mol L−1 buffer led to the conclusion that electrostatic interactions have a great role in the immobilization. © 2014 Society of Chemical Industry

Assessment of Nanoparticle Exposure in Nanosilica Handling Process: Including Characteristics of Nanoparticles Leaking from a Vacuum Cleaner

Nanosilica is one of the most widely used nanomaterials across the world. However, their assessment data on the occupational exposure to nanoparticles is insufficient. The present study performed an exposure monitoring in workplace environments where synthetic powders are prepared using fumed nanosilica. Furthermore, after it was observed during exposure monitoring that nanoparticles were emitted through leakage in a vacuum cleaner (even with a HEPA-filter installed in it), the properties of the leaked nanoparticles were also investigated. Workers were exposed to high-concentration nanosilica emitted into the air while pouring it into a container or transferring the container. The use of a vacuum cleaner with a leak (caused by an inadequate sealing) was found to be the origin of nanosilica dispersion in the indoor air. While the particle size of the nanosilica that emitted into the air (during the handling of nanosilica by a worker) was mostly over 100 nm or several microns (µm) due to the coagulation of particles, the size of nanosilica that leaked out of vacuum cleaner was almost similar to the primary size (mode diameter 11.5 nm). Analysis of area samples resulted in 20% (60% in terms of peak concentration) less than the analysis of the personals sample.

Influence of nano-silica agglomeration on fresh properties of cement pastes

The influence of nano-silica agglomeration on fresh properties of the cement paste was investigated by using precipitated nano-silica (PS) with very large agglomerates and fumed nano-silica (FS) with much smaller ones as nano-strengthening admixtures. The rheologic tests revealed that addition of PS showed a greater influence on rheological behavior of the paste than that of FS, because the very large agglomerates in PS cannot act as fillers to release free water in the void space originally contributing to fluidity, but absorb free water originally contributing to fluidity in paste. Through monitoring the heat evolution, it is interestingly found that addition of PS accelerated cement hydration more significantly than that of FS though the latter provides much more seeds than the former, implying that the acceleration may have nothing to do with the so-called seeding effect. The calcium-adsorption tests confirmed that the accelerating effect is probably caused by the rapid calcium adsorption of nano-silica, which can keep a low under-saturation of calcium ions in paste, enabling a higher dissolution rate of calcium and thus an increase of heat evolution.

Photo‐curable highly water‐repellent nanocomposite coatings

Modification and use of natural products have gained a lot of interest in recent years due to their environmental friendliness and their availability from different sources. In this study, (castor oil)‐based photo‐curable highly hydrophobic coatings were prepared and characterized. Castor oil was first modified with 3‐isocyanatopropyltriethoxysilane and then hydrolyzed prior to the coating preparation. The resulting precursor was mixed with norbornyl acrylate and hexanediol diacrylate, and highly roughened hydrophobic coatings were prepared with the aid of fluorinated/nonfluorinated alkoxysilane coupling agents and hydrophobic fumed nanosilica particles. The coatings were applied on borofloat glass. The addition of fluorine and nanosilica showed a significant impact on the properties of the coatings. As the fluorine and nanosilica contents were increased in the formulations, flame retardancy and the contact angle values of the coatings increased. The surface roughness of the coatings increased with the addition of hydrophobic fumed nanosilica particles. Also, the relation between the surface energy and the contact angle values of the coatings was investigated. J. VINYL ADDIT. TECHNOL., 19:31–38, 2013. © 2013 Society of Plastics Engineers

Adhesion of dry nano-coated microparticles to stainless steel: A physical interpretation

During the manufacture of pharmaceuticals, it is desirable to modify the surface of powder particles to alter their adhesion characteristics without changing their dissolution rates or their chemical or biological characteristics. In this study, dry silica nanoparticle coatings were applied to spheroidal micron-scale aluminum host particles to alter their surface morphology and adhesion behavior. The host particles were coated with either hydrophobic or hydrophilic fumed nanosilica using a magnetically assisted impact coating technique. The adhesion between polished or unpolished stainless steel and all three particle types, including uncoated aluminum and aluminum coated with either hydrophobic or hydrophilic nanosilica, was examined at 30% relative humidity. On both steel surfaces, the measured adhesion force towards the uncoated aluminum was greater than towards either type of coated aluminum. The uncoated aluminum adhered more strongly to the polished substrate than to the unpolished one. The hydrophobic- and hydrophilic-coated particles adhered to both substrates with roughly the same force, such that there was no effect of either the substrate type or the coating type on the adhesion. To confirm that capillary forces had no influence on the measured adhesion, the adhesion behavior between the uncoated aluminum particles and the steel was measured at 15 and 30% RH, and no change in adhesion force was observed.

Preparation and properties of melt‐mixed metallocene polyethylene/silica nanocomposites

AbstractMetallocene polyethylene (mPE)/silica nanocomposites were prepared via melt mixing. Two types of commercial fumed nanosilica, bare silica (A200) and organic modified silica (R974), were incorporated to improve the mechanical properties of the nanocomposites. Transmission electron microscopy, atomic force microscopy, and scanning electron microscopy revealed that the modified silica was dispersed slightly better within the mPE matrix. No distinct effects on the thermal behaviors of the fast‐crystallizing mPE matrix were observed with variations in both the silica dosages and types. Thermal stability was enhanced through the addition of nanosilica, with or without surface treatment. The surface‐modified silica system showed slightly higher tensile strength and Young's modulus compared with the bare silica system, as evidenced by a rheological study using a Cole‐Cole plot to assess enhanced polymer matrix‐dispersed silica interactions, especially for high dosages of organic modified silica. A limited increment in the dynamic storage modulus for modified silica cases, completely opposite of that observed for bare silica cases, was due to the low‐aspect ratio of smaller agglomerates from highly dispersed organic modified silica within the mPE matrix. POLYM. ENG. SCI., 2011. © 2010 Society of Plastics Engineers.