Effect Of Nanosilica Content Research Articles

Research on mechanical properties and microscopic mechanism of multi-based geopolymer concrete under combined action of pre-curing and nano-silica

In order to study the combined action of curing conditions and nano-silica (NS) on geopolymer concrete (GPC), the multi-based geopolymer concrete (FSSGC) was prepared with fly ash (FA), slag (SG) and steel fiber (SF), the experiments were carried out in three stages. Firstly, the mechanical properties of FSSGC was tested by monofactor analysis, with pre-curing temperature (20, 40, 60, 80, and 100 °C) and pre-curing time (6, 12, 18, 24, 30, and 36 h) as parameters. The compressive strength and splitting tensile strength initially increased and then decreased with the increase of parameters, and there was an optimal value for subsequent experimental research (80 °C and 18 h). Secondly, the effects of NS content (0, 0.5, 1.0, 1.5, and 2.0 wt%) on the mechanical properties of FSSGC under different curing conditions were analyzed. The results indicated that the mechanical properties of the FSSGC exhibited a trend of initially increasing and then decreasing with the increase of NS content, with the optimal mechanical performance observed under the combined action of high-temperature pre-curing conditions and the incorporation of NS (1.0 wt%). Thirdly, X-ray diffraction, scanning electron microscopy, image analysis, and microhardness tests had been conducted, and the results were consistent with the mechanical properties. The pre-curing temperature affected the rate of geopolymerization, while the pre-curing time influenced the degree of geopolymerization by maintaining this rate. The small particle size and high Young's modulus of the NS effectively filled pores and inhibited the propagation of microcracks. High-temperature pre-curing enhanced the nucleation effect and pozzolanic effect of NS, resulting in a combined action that formed a denser microstructure in the matrix and interfacial transition zone (ITZ).

Effects of nano-silica on fracture properties and mechanism analysis of basalt fiber reinforced concrete

The reinforcing effect of basalt fibers (BFs) on the performance of concrete mainly relies on the bridging effect of fibers, while recently, it has been shown that nano-silica (NS) may further enhance this effect. In this paper, three-point bending fracture tests were carried out on BF reinforced concrete (BFRC) to determine the optimal BF condition (i.e. volume content and length). Based on this optimal condition, the effect of NS content on the fracture performance of BFRC was examined from macroscopic and microscopic perspectives. The results indicate that the optimal BF condition for yielding the best concrete performance was 0.2 % volume content and 6 mm fiber length. Based on this condition, NS at 1 % mass content could improve its fracture performance to the best extent. Specifically, the crack initiation toughness, unstable fracture toughness and fracture energy were 1.83 MPa·m0.5, 3.35 MPa·m0.5 and 364.42 N/m, respectively, which were improved by 5.58 %, 15.93 % and 4.97 % compared to BFRC. NS mainly affects the crack propagation mode of BFRC by enhancing the fiber bridging effect or altering the way BFs play a bridging role. NS at an appropriate mass content can delay the occurrence of cracks and improve the deformation ability of BFRC.

The relationship between cellular microstructure and the mechanical properties of styrene/methyl methacrylate copolymer‐silica nanocomposite foams prepared by a supercritical CO2 blowing agent

AbstractStyrene/methyl methacrylate (St/MMA) copolymer‐silica nanocomposite foams were prepared using supercritical CO2 as blowing agent, and the relationships between their cellular microstructure and mechanical properties were investigated. The effects of nanosilica content, size, and surface chemistry on the foam's microstructure and properties were examined. Dispersion and distribution of silica nanoparticles with different surface chemistry in St/MMA copolymer nanocomposites were discussed. To determine the most suitable copolymer composition for incorporating silica nanoparticles, some operating conditions such as temperature and pressure were primarily examined to study their effects on the microstructure of resulting foams. In compressive mechanical properties of final foams, a considerably high value was obtained for the compressive strength of the foams of up to 9.5 MPa. The prepared low‐density (below 0.2 g/cm3) St/MMA copolymer microcellular foams can be used in green lost foam iron casting processes.Highlights Styrene/methyl methacrylate copolymer‐silica nanocomposite foams were prepared via supercritical CO2. Foams' cell size was changed by changing silica nanoparticle surface chemistry and size. The uniform cellular microstructure was achieved by nanosilica size increment. Increasing nanoparticle size improved the foam's mechanical properties. Low‐density foams were achieved for potential application in lost foam casting.

UV accelerated aging of RTV/SiO2 nanocomposites: Study on surface microstructure, hydrophobicity, and electrical properties

RTV-SiR coatings are widely used to preserve ceramic insulators in high voltage power lines. These coatings enhance insulators’ resistance to environmental factors, such as contamination and moisture, as well as UV irradiation. The functional lifespan of RTV-SiR could be improved via addition of different nanoparticles such as SiO2. In this research, the effect of nano silica content on surface microstructure, hydrophobicity, and electrical properties of RTV-SiR before and after UV irradiation was studied by FESEM, AFM, surface roughness, contact angle, hydrophobicity transfer ability, dielectric parameters, and electric resistance. Results demonstrated that the optimal percentage of filler in the composite could make an appropriate surface roughness and increases hydrophobicity. Also, the excessive destruction of the RTV-SiR caused by UV irradiation is prevented by nano silica. Moreover, the contact angle of the coating reached the first level in a shorter period of time after applying pollution thanks to the presence of nano silica. Eventually, composite samples illustrated better performance than pure RTV-SiR, and the best properties were observed in samples containing 3 wt% silica.

Investigating the properties of asphalt binder modified by high- and low-density polyethylene polymer and nano-silica

This paper describes nano-silica (NS) reinforcement effects on the properties of an asphalt binder modified by 5% of low density polyethylene (LDPE) and high density polyethylene (HDPE) polymers. NS was added at 0, 2, 4 and 6% of modified asphalt weight and some physical, rheological, chemical and microstructure of the binders were evaluated. Results show adding NS into the polymer modified binder (PMB) results in better dispersion of polymer in the binder, improvement of elastic recovery and storage stability, decrease of temperature susceptibility, decrease of ductility, and slightly improvement in rutting resistance. Statistical analysis revealed that the polymer type has significant effect on SHRP rutting parameter at 76°C, elastic recovery and storage stability. It was also found that the effect of NS content is significant on the penetration, penetration index, viscosity temperature sensitivity (VTS) and storage stability.

Study on Visible Light Catalysis of Graphite Carbon Nitride-Silica Composite Material and Its Surface Treatment of Cement

Cement-based composite is one of the essential building materials that has been widely used in infrastructure and facilities. During the service of cement-based materials, the performance of cement-based materials will be affected after the cement surface is exposed to pollutants. Not only can the surface of cement treated with a photocatalyst degrade pollutants, but it can also protect the cement-based materials from being destroyed. In this study, graphite carbon nitride-silica composite materials were synthesized by thermal polymerization using nanosilica and urea as raw materials. The effect of nanosilica content and specific surface area were investigated with the optimal condition attained to be 0.15 g and 300 m2/g, respectively. An X-ray diffractometer, thermogravimetric analyzer, scanning electron microscope, a Brunauer–Emmett–Teller (BET) specific surface area analyzer and ultraviolet-visible spectrophotometer were utilized for the characterization of as-prepared graphite carbon nitride-silica composite materials. Subsequently, the surface of cement-based materials was treated with graphite carbon nitride-silica composite materials by the one-sided immersion and brushing methods for the study of photocatalytic performance. By comparing the degradation effect of Rhodamine B, it was found that the painting method is more suitable for the surface treatment of cement. In addition, through the reaction of calcium hydroxide and graphite carbon nitride-silica composite materials, it was found that the combination of graphite carbon nitride-silica composite materials and cement is through C-S-H gel.

The effects of nanosilica on charpy impact behavior of glass/epoxy fiber reinforced composite laminates

Desire to improve the efficiency of composite materials for engineering applications has led to the use of nano-sized additives or fillers such as nanoclay, nanosilica, nano-graphene, carbon nanotubes. The effect of nanoparticle inclusion on mechanical properties of fiber reinforced composite materials has been investigated by many researchers and crucial effects have been reported in several papers. In this work, the effects of nanosilica content on the low velocity impact behaviors of glass/epoxy fiber reinforced composite laminates are determined using Charpy impact tests. The composite laminates are fabricated via hand lay-up followed by hot press molding. The nanosilica particles with different weight percentages are dispersed in epoxy resins using mechanical stirring. The absorbed impact energy values of flatwise-unnotched and edgewise-notched beam specimens, and impact damages are analyzed as a measure of impact behavior. The results show that the incorporation of nanosilica particles have significant effects on the Charpy impact behavior.

Effect of nanosilica content on the corrosion inhibition of composite coatings of a filled epoxy resin grafted with a hydrophobic fluoroalkylsilane: a dual critical concentrations interpretation

Hydrophobic epoxy-resin composite coatings uniquely display double corrosion-inhibition extrema at nanosilica dual critical concentrations of 0–0.5 and ∼3 wt%.

Mechanical performance of woven carbon fabric reinforced pCBT composites with nanosilica particles

The effect of nanosilica content (0, 0.5, and 2 wt%) on mechanical performance of carbon fabric woven cloth reinforced polymerized poly(butylene terephthalate) resin composites (CF/pCBT) is investigated. The catalyst and nanosilica particles are added on the prepreg surface, and hot‐press processing is adopted in order to manufacture CF/pCBT composites. The experimental results reveal that nanosilica could enhance the mechanical performance of CF/pCBT composites. After adding nanosilica in the composites, elastic modulus enhances 23.96%, and Mode‐II fracture toughness increases 380.43%. Scanning electron microscope observation shows that dispersity of nanoparticles in composites plays an important role on the overall mechanical performance of the obtained composites. Furthermore, failure mechanism has been analyzed according to the damage morphology. POLYM. COMPOS., 38:2528–2535, 2017. © 2015 Society of Plastics Engineers

Effect of water absorption on the wear behavior of sol-gel processed epoxy/silica hybrids

The aim of this study is to investigate the wear behavior of epoxy-silica hybrids. These hybrids were obtained through the addition of sol-gel prepared silica nanoparticles to epoxy resin. In this study, the effect of nanosilica content on the mechanical properties and wear behavior of epoxy-silica hybrid materials was investigated. Tensile strength, impact strength, hardness, water absorption and wear tests were conducted on the epoxy-silica hybrid specimens. The results demonstrated that the composition of hybrids was of significant importance on mechanical, water uptake and wear properties. Water absorption was found to be highly effective on the wear behavior of hybrids.

Effect of nanosilica content on properties of polyurethane/silica hybrid emulsion and its films

AbstractPolyurethane/silica hybrid emulsion (PUSi) was synthesized by the reaction of isophorone isocyanate, polyether polyol, hydrophilic nanosilica (A200), dimethylol propionic acid, trimethylol propane, and 3‐aminopropyltriethoxysilane (KH550). The films of the waterborne polyurethane (WPU) were prepared. The structure of the polyurethane was characterized by Fourier transform infrared spectrometer (FTIR), thermogravimetry (TG), and differential scanning calorimetry (DSC). The particle size distribution and morphology of emulsion were examined. Influence of nanosilica content on the mechanical properties and solvent absorption of the cast films were also measured quantificationally. FTIR indicates that NH2 of KH550 reacted with NCO of polyurethane. TG analysis indicates that nanosilica can improve thermal stability of polyurethane. There is no clear effect of nanosilica on the glass transition of soft segments. It was found that greater mechanical properties of WPU were obtained when chemical networks were formed by sol‐gel process. As the nanosilica content increases, water absorption and ethanol absorption decreased. The particle size increases with increase of A200 content. PUSi hybrid emulsions are endowed with pseudoplasticity. The apparent viscosity of emulsions increased and then decreased with addition of A200. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011

Modeling and characterization of viscoelasticity of PI/SiO 2 nanocomposite films under constant and fatigue loading

In this paper, the viscoelastic behavior of PI/SiO 2 nanocomposite thin films under constant and fatigue tensile loading was studied. The cyclic hardening and viscous dissipation of PI/SiO 2 nanocomposite thin films during the fatigue process were experimentally investigated and analyzed by storage modulus, loss modulus and phase lag. The time-dependent deformation under constant and fatigue loading was simulated based on two viscoelastic models known as Burger model and Findley power law. Standard parameter analysis methodology was employed to interpret the structure–property relationship and deformation mechanisms of this kind of nanocomposites. In addition, the effects of nano-silica content, stress level and loading pattern (constant or fatigue loading) on the creep resistance of materials were discussed as well.

Influence of Nano-Silica on Microstructure and Mechanical Properties of SiO<sub>2</sub>/BN Ceramics

In this paper, nano-silica particles were incorporated to a fused silica-boron nitride dual phase ceramics originally using micrometer sized particles as starting powders. Effects of nano-silica content on density, sintering behavior, mechanical properties and microstructure of the dual phase ceramics were investigated. It was found that with the addition of nano-silica particles, the density and mechanical properties of the dual phase ceramics increased. Flexural strength and fracture toughness of them attained to 51.4MPa and 0.8MPa·m1/2, respectively. The increased density and spatial network structure of fused silica attribute to the improvement of the mechanical properties of the dual phase ceramics.