Nano-sized Silica Research Articles

Effect of micro/nano-SiO$_{2}$ on mechanical, thermal, and electrical properties of silicone rubber, epoxy, and EPDM composites for outdoor electrical insulations

In this paper the influence of micro-sized (3 $\mu $m) and nano-sized (10 nm) silica (SiO$_{2})$ on mechanical, thermal, and electrical properties of silicon rubber (SiR), epoxy, and ethylene propylene diene monomer (EPDM) composites is presented. The micro- and nano-sized SiO$_{2}$ particle-filled SiR, epoxy, and EPDM composites were formulated with 20% microsilica and 5% nanosilica by weight respectively. Among these composites, SiR-SiO$_{2}$ amalgamation was performed by mixing using an ultrasonication procedure. Epoxy-SiO$_{2}$ was compounded in two steps, i.e. dispersion of fillers and mixing, whereas EPDM-SiO$_{2}$ compounding was performed with a two roll mill technique. With the addition of micro/nano-SiO$_{2}$, the composites showed enhanced tensile strength of $\sim $2.7 MPa, improved hardness, and reduced elongation at break. Further incorporation of micro/nano-sized particles resulted in high thermal stability for SiR-nano composites (SNCs) as compared to epoxy and EPDM composites. Compared to SiR and EPDM composites, epoxy-nano composites showed the highest value of dielectric strength, i.e. 38.8 kV/mm. Meanwhile, the volume and surface resistivity of SNCs were found higher as compared to other investigated samples. Promising properties of SiR nanocomposites among all the investigated samples suggest that their application is more suitable for utilization in outdoor electrical insulations.

Templated synthesis of nano-sized silica in confined amorphous space of polypropylene

A template method is a powerful technique to tailor the morphology of formed nanomaterials. The present paper for the first time demonstrated the sol-gel reaction templated by the higher-order structure of semi-crystalline polymer. Silicon alkoxide was impregnated into the amorphous space of polypropylene (PP) with the aid of supercritical CO2, and subsequently converted into uniformly dispersed silica nanoparticles. The size and anisotropy of silica nanoparticles were controlled through the amorphous thickness of PP that was preliminarily defined through the crystallization process. We also studied the impact of the silica morphology on physical properties of resultant PP/silica nanocomposites. The silica morphology was systematically varied, keeping relatively uniform dispersion. We revealed that the storage modulus of the nanocomposites was well correlated with the size and anisotropy of the nanoparticles.

Size controllable synthesis and multicolor fluorescence of SiO2:Ln3+(Ln=Eu, Tb) spherical nanoparticles

A series of size controllable Tb3+ and/or Eu3+ activated nano-sized silica phosphors have been successfully synthesized through a facile sol-gel method. The structure, morphology, compositions, and luminescence properties of as-prepared samples were well investigated using X-ray diffraction (XRD), scanning electron microscope (SEM), energy dispersive spectrometer (EDS), X-ray photoelectron spectroscopy (XPS), Brunauer-Emmett-Teller (BET) and photoluminescence spectroscopy (PL). The results showed that all as-prepared samples were spherical nanoparticles but the sizes reduced gradually with the temperature increased from 25°C to 65°C, which was contrary to the BET surfaces as well as the luminescence intensity. Under ultraviolet excitation, the SiO2:Ln3+(Ln=Eu, Tb) spherical nanoparticles showed characteristic red and green emissions corresponding to f-f transition of Eu3+ and Tb3+, respectively. Moreover, the luminescence emissions of samples can be tuned from green to yellow, orange and red by co-doping the Tb3+ and Eu3+ ions in different concentration ratio into the SiO2 host due to the efficient dipole–dipole energy transfer mechanism from Tb3+ to Eu3+ under 377nm excitation. These results show that as-prepared phosphors may find potential applications in color display fields.

A partially purified outer membrane protein VirB9-1 for low-cost nanovaccines against Anaplasma marginale

Anaplasma marginale is a devastating tick-borne pathogen causing anaplasmosis in cattle and results in significant economic loss to the cattle industry worldwide. Currently, there is no widely accepted vaccine against A. marginale. New generation subunit vaccines against A. marginale, which are much safer, more efficient and cost-effective, are in great need. The A. marginale outer membrane protein VirB9-1 is a promising antigen for vaccination. We previously have shown that soluble recombinant VirB9-1 protein can be expressed and purified from Escherichia coli and induce a high level of humoral and cellular immunity in mice. In this study, we re-formulated the nanovaccines using the partially-purified VirB9-1 protein as the antigen and hollow nano-size silica vesicles (SV-100) as the adjuvant. We simplified the purification method to obtain the partially-purified antigen VirB9-1 with a six-fold higher yield. The new formulations using the partially-purified VirB9-1 protein achieved higher antibody and cell-mediated immune responses compared to the purified ones. This finding suggests that the partially-purified VirB9-1 protein performs better than the purified ones in the vaccination against A. marginale, and a certain level of contaminants in the protein antigen can be self-adjuvant and boost immunogenicity together with the nanoparticle adjuvant. This may lead to finding a “Goldilocks” level of contaminants. The new nanovaccine formulation using partially-purified antigens along with nanoparticle adjuvants offers an alternative strategy for making cheaper veterinary vaccines.

Silicon-dioxide-polyvinylpyrrolidone as a wound dressing for skin defects in a murine model.

There is a high demand for temporary wound dressings that improve wound healing and regeneration. Silicon (as SiO2) has been shown to support the growth and collagen formation in biological systems. A nanocomposite was made from PVP (polyvinylpyrrolidon), nano-sized silica aggregates and water and served for fabrication of a wet dressing material (SiO2-PVP gel, by cross-linking the gel) and a freeze-dried dressing material (SiO2-PVP fleece). Materials were characterized by SAXS, DSC, EDX and viscosity measurements. A 10mm circular defect was set on both sides of the back of SKH1-hr mice (n=40) and both dressing materials were compared with untreated controls. After 3, 6, 9, 12 and 15 days, the defect regions were explanted and evaluated by histomorphometric measurements and CD31-immunohistochemistry. The microstructure of the compound was composed of fiber like structures. SiO2 nano-aggregates inside the composite remained stable and embedded in a rigid amorphous PVP fraction. In animal experiments, all groups showed a non-irritated defect closure after 9 days. EDX of SiO2-PVP gel and fleeces revealed SiO2-PVP diffusion into the wound. Wound contraction was significantly enhanced after treatment with SiO2-PVP gel followed by SiO2-PVP fleece compared to controls. Re-epithelialization was increased in SiO2-PVP treated wounds and the regenerated epidermis showed a well-differentiated layer structure compared to untreated controls. The results indicate that silica diffuses from the dressing into the wound. Both dressings affect the wound healing. The SiO2-based wound dressing may counteract scarring and might be suitable as a temporary wound dressing.

Performance of silicone rubber composites with SiO2 micro/nano-filler under AC corona discharge

Outdoor insulators are often subject to corona discharges and the problem is becoming more prevalent with the increasing use of higher transmission voltage levels. For polymeric insulators, exposure to such discharges can alter the chemical structure of basic polymer and degrade surface properties. This paper investigates the effect of micro and/or nano fillers in silicone rubber composites in suppressing such damage. Four different types of samples are fabricated: pristine silicone rubber (PR), 30wt% micron-sized silica/silicone rubber (MC), 27.5wt% micron + 2.5wt% nano silica/silicone rubber (NMC), and 5wt% nano silica/silicone rubber (NC) composites. Samples are exposed to AC corona using a needle to ground-plane electrode setup. Experimental results are analyzed based on five different measurement methods: phase-resolved partial discharge (PD), hydrophobicity loss-recovery, Scanning Electron Microscopy (SEM), Surface roughness and Fourier Transform Infrared Spectroscopy (FTIR). Results indicate that NC shows a strong resistance to partial discharges and hydrophobicity loss. In the area below the needle tip, higher hydrophobicity loss and higher recovery are observed as compared to the vicinity region. Variations in surface roughness, appearance of crackles, voids, pits, surface splitting into blocky structures and damages to chemical structure of silicone rubber are appreciably retarded in NC as compared to PR, MC and NMC. Based on NMC results, it is found that addition of nano-sized silica can be an attractive approach to improve the corona resistance of micron-sized silica filled silicone rubber.

High capacity supercapacitor material based on reduced graphene oxide loading mesoporpus murdochite-type Ni6MnO8 nanospheres

Mesoporous materials often deliver a series of attractive properties for low-cost and environmentally-friendly energy storage/conversion technologies. Based on this, we prepared mesoporous murdochite-type Ni6MnO8 nanospheres (NMN) with a uniform morphology by using a template route. Then as-prepared NMN were loaded uniformly on reduced graphene oxide (RGO) sheets via electrostatic interaction to fabricate RGO-NMN composite (RGO-NMN), which combines the advantages of both RGO such as double-layer capacity and NMN such as high pseudocapacitity. By the aid of a nanosized mesoporous silica template, NMN and RGO-NMN display a large specific surface areas and concentrated pore diameter distribution. The large surface area and abundant pores can provide a promising route for easy access of electrolyte in energy storage electrodes and favor the availability of Faradic reaction in electroactive sites greatly. Indeed, following electrochemical analysis uncovered a remarkable value of specific capacitance (862.5Fg−1 and 498.3Fg−1 at 0.5Ag−1 for RGO-NMN and NMN) and a predominant long-term stability with slight decays less than 10% after 9000 cycling test in both NMN and RGO-NMN electrodes.

Effectiveness of potato cultivation using nanosized silica under conditions of Kamchatka krai

The results of trials of nanosized silica and its preparation forms under the conditions of Kamchatka krai are given. The dose and methods of silica usage for potato cultivation were identified. When introduced into the soil, silica improved productivity to 16.1–25.7% (2.8–3.6 t/ha). Treatment of tubers and plants with Miwa agro improved productivity to 12.4–16.9% (2.2–3.0 t/ha), with silica (gel) to 13.5–20.3% (2.4–3.6 t/ha) and silica (powder) to 10.7–16.4% (1.9–2.9 t/ha). We offer effective methods of using silica and Miwa agro to reduce the incidence of Rhizoctonia solani. Silica improves phosphorus-potassium nutrition of plants.

Effect of Ambient Temperature on Insulation Lifetime of Inverter Surge Resistant Enameled Wire Prepared with Organic/Inorganic Hybrid Nanocomposite

Inverter surge resistant enameled wire was prepared with an organic/inorganic hybrid nanocomposite, and the effect of ambient temperature on the insulation lifetime of the enameled wire in the form of twisted pair was studied by a withstanding voltage tester. The organic polymer was Polyesterimide-polyamideimide (EI/AI) and the inorganic material was a Nano-sized silica (average particle size : 15 nm). The enamel thickness was 50 μm and the ambient temperature was 100℃, 150℃, 200℃, and 250℃, respectively. Transmission electron microscopy (TEM) observation showed that Nano-sized Silica were evenly dispersed in EI/AI. There were many air gaps in a twisted pair, therefore, when voltage was applied to the twisted pair, enamel erosion took place in the air gap area because of partial discharge accordi, ng to Paschen's law. As ambient temperature increased, insulation lifetime decreased according to Arrhenius relationship, which was explained by the increasing mobility of polymer chains in EI or AI. And insulation breakdown voltage value at 10 kHz was 1,864.5 sec (31.1 min), which is 1.9 times higher than at 20 kHz, 981.6 sec (16.4 min).

Reciprocating sliding wear behaviour of PEEK-based hybrid composites

The present research deals with the effects of fillers in Polyetheretherketone (PEEK) based hybrid composites from the view point of mechanical and tribological properties. In this background, nano-sized silica (SiO2), short carbon fibre (SCF), graphite, titanium dioxide (TiO2) and zinc sulphide (ZnS) were added as the additives. Reciprocating sliding wear tests (flat-on-flat) against AISI 52100 bearing steel were performed at contact pressures ranging from 4MPa to 10MPa and with sliding velocities of 20mm/s and 50mm/s. Under most test conditions, the nanoparticles reduced the friction coefficient. The morphologies of the worn surfaces and the transfer films, were observed by surface topography (ST), optical microscopy (OM) and scanning electron microscopy (SEM). A dimensional analysis was used to evaluate the influence of nanoparticles on transfer film formation on bearing steel counter surface. It is evident that the effect of nanoparticles on wear rate depended on the contact pressure and sliding speed. Results indicated a limited wear resistance for neat PEEK, but PEEK filled with nano-sized silica exhibited superior wear resistance at the highest contact pressure for both sliding speeds. The nanoparticles seem to have a polishing effect on the steel counter surface. The nanoparticle additives may account for their lower friction coefficient and improved wear resistance in comparison to micro-particle-filled and unfilled PEEK. The output from the dimensional analysis based on transfer layer characteristics is in good agreement with the friction result.

Effects of silica nanoparticles on copper nanowire dispersions in aqueous PVA solutions

In this study, the effects of adding silica nanoparticles to PVA/CuNW suspensions were investigated rheologically, in particular, by small and large amplitude oscillatory shear (SAOS and LAOS) test. Interesting, the SAOS test showed the complex viscosities of CuNW/silica based PVA matrix were smaller than those of PVA/CuNW without silica. These phenomena show that nano-sized silica affects the dispersion of CuNW in aqueous PVA, which suggests small particles can prevent CuNW aggregation. Nonlinearity (third relative intensity ≡ I 3/1) was calculated from LAOS test results using Fourier Transform rheology (FT-rheology) and nonlinear linear viscoelastic ratio (NLR) value was calculated using the nonlinear parameter Q and complex modulus G*. Nonlinearity (I 3/1) results showed more CuNW aggregation in PVA/CuNW without silica than in PVA/CuNW with silica. NLR (= [Q 0(ϕ)/Q 0(0)]/[G*(ϕ)/G*(0)]) results revealed an optimum concentration ratio of silica to CuNW to achieve a well-dispersed state. Degree of dispersion was assessed through the simple optical method. SAOS and LAOS test, and dried film morphologies showed nano-sized silica can improve CuNW dispersion in aqueous PVA solutions.

Modified Capillary Electrophoresis for Highly Sensitive and Selective Detection of Hg2+ in Natural Water

AbstractA novel capillary with high sensitivity and selectivity for mercury ion detection based on modified nanosize silica has been designed and synthesized. The obtained modified capillary was applied to separate and determine mercury ion by capillary electrophoresis with a laser‐induced fluorescence detector. The optimal experimental conditions were determined by evaluating various controlling factors: running buffer hexamine‐HCl 15 mmol L−1, pH=5.2, separation voltage 30 kV and temperature 25 °C. The modified capillary exhibited excellent sensitivity and selectivity for Hg2+ over other coexisting metal ions (K+, Ag+, Ca2+, Mg2+, Ba2+, Ni2+, Cd2+, Pb2+ and Zn2+ increased to 10000 times of Hg2+, Cu2+ increased to 5000 times) in aqueous solution, and was successfully applied to the determination of Hg2+ in natural water samples and displayed satisfactory results.

Laminated altered layers in historical glass: Density variations of silica nanoparticle random packings as explanation for the observed lamellae

One of the most striking but unexplained phenomena in the natural degradation of glass is the transformation of an almost colorless, transparent and homogeneous glass into a colored, opaque and heterogeneous degradation layer. In many cases, the degradation layer consists of numerous lamellae with a thickness between 0.1 and 10μm. However, both internal structure and formation process of laminated degradation layers remain unclear. In this paper, a model is proposed where we assume that transformed (degraded) glass consists of a random packing of nano-sized silica particles while the lamellae are the result of different packing densities. The model is able to connect the texture of numerous lamellae observed by several types of microscopic techniques with the structure at molecular level determined by means of chemical analysis. In addition, the model is able to explain numerous properties such as the parameters responsible for the contrast between lamellae. This contrast can be caused by differences in color, density, elemental composition, or surface roughness.

Spectroscopic and Mechanical Properties of Nano Silica Rubber Composite Material

AbstractTo manipulate the mechanical properties of acrylonitrile butadiene rubber (NBR), addition of nano-sized silica on rubberwas performed and nano-silica NBR composite (NSR) materials were fabricated by press molding. The effect of volumefraction of silica in the NSR on the spectroscopic and mechanical properties has been studied.Keywords: NBR, Nano-silica, Volume Fraction, NSR 1. Introduction Polymer nano-composites (NCs) have been a subjectof interest for their mechanical, chemical, and thermalproperties instead of polymers and conventional com-posites materials. Before the use of polymer NCs to var-ious components, such as rubber seals, bearings, andbelts, in industrial materials [1,2] , the accurate analyses oftheir mechanical and chemical properties are necessary.The Charpy impact test is usually adopted to understandof polymer NCs for a long time, the relationshipbetween the stress and the critical energy release ratehas been considered important recently [3-5] .Among various types of polymers, acrylonitrile buta-diene rubber (NBR) is an attractive material system dueto its excellent resistance to organic solvents

Chiral separation and quantitative analysis of citalopram by modified capillary electrophoresis

A novel capillary for the high efficiency splitting of citalopram based on modified nanosize silica was designed and synthesized. The enantiomers of citalopram were separated within 10 min with a resolution (Rs) of 4.25.

Biosafety comparison on a nano-sized silica and a micro-sized silica with nanopores

Biosafety comparison on a nano-sized silica and a micro-sized silica with nanopores

Immobilized phthalocyanines of magnesium, aluminum, and zinc in photodynamic treatment of mesenchymal stromal cells

Phthalocyanines of magnesium, aluminum, and zinc immobilized on nano-sized silica and poly-N-vinylpyrrolidone in aqueous solutions were synthesized. Photochemical activity of the immobilized metal complexes was assessed by generation of singlet oxygen. Nontoxic concentrations of the new photosensitizers were determined in vitro. A comparative analysis of the efficiency of photodynamic therapy (PDT) was performed for immobilized phthalocyanines using mesenchymal stromal cells as a cell model. Aluminum phthalocyanine immobilized on nano-sized silica displayed the highest cell tropism. Irradiation of phthalocyanine-loaded cells resulted in generation of active singlet oxygen and subsequent apoptotic cell death. The use of immobilized phthalocyanines allowed decreasing the effective concentration (dose) of photosensitizer and enhancing the PDT cytotoxicity.

The Effect of Microporous Polymeric Support Modification on Surface and Gas Transport Properties of Supported Ionic Liquid Membranes.

Microporous polymers based on anionic macroinitiator and toluene 2,4-diisocyanate were used as a support for 1-butyl-3-methylimidazolium hexafluorophosphate ([bmim][PF6]) and 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ([emim][Tf2N]) immobilization. The polymeric support was modified by using silica particles associated in oligomeric media, and the influence of the modifier used on the polymeric structure was studied. The supported ionic liquid membranes (SILMs) were tested for He, N2, NH3, H2S, and CO2 gas separation and ideal selectivities were calculated. The high values of ideal selectivity for ammonia-based systems with permanent gases were observed on polymer matrixes immobilized with [bmim][PF6] and [emim][Tf2N]. The modification of SILMs by nanosize silica particles leads to an increase of NH3 separation relatively to CO2 or H2S.

Combined Situ Polymerization and Thermal Cross-Linking Technique for the Preparation of Ammonium Polyphosphate Microcapsules with Composite Shell

Ammonium polyphosphate (APP) was encapsulated with boron containing phenolic resin (BPF) by in situ polymerization and then modified with nanosize silica gel through thermal cross-linking with the goal of further improving its hydrophobicity, thermal stability, and shell mechanical property. The chemical and physical features of APP microcapsules were characterized by Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), differential scanning calorimetery (DSC), and laser particle sizing. The hydrophobicity was assessed by the water contact angle (WCA). The shell mechanical property was characterized by the change of water contact angle before and after the mechanical property test. The residues from thermogravimetric analyzer and muffle burner were investigated. The results showed that the APP microcapsules with a Si–B containing phenolic resin shell had been produced successfully (Si-BPFAPP). Compared with BPFAPP, the hydrophobicity, shell mechanical property, and therm...

Surface modification to produce hydrophobic nano-silica particles using sodium dodecyl sulfate as a modifier

Hydrophobic silica particles were prepared using the surfactant sodium dodecyl sulfate (SDS) as a modifier by a new route comprising three processes, namely, aqueous mixing, spray drying and thermal treatment. Since SDS dissolves in water, this route is free of an organic solvent and gave a perfect dispersion of SDS, that is, there was excellent contact between SDS and silica particles in the modification reaction. The hydrophobicity of the modified surface was verified by the contact angle of the nano-sized silica particles, which was 107°. The SDS grafting density reached 1.82nm−2, which is near the highest value in the literature. The optimal parameters of the SDS/SiO2 ratio in the aqueous phase, process temperature and time of thermal treatment were determined to be 20%, 200°C and 30min, respectively. The grafting mechanism was studied by comparing the modification with that on same sized TiO2 particles, which indicated that the protons of the Brønsted acid sites on the surface of SiO2 reacted with SDS to give a carbocation which then formed a Si–O–C structure. This work showed that the hydrophilic surface of silica can be modified to be a hydrophobic surface by using a water soluble modifier SDS in a new modification route.