SiO2 Particle Size Research Articles

The Effect of Nano SiO2 Particle Size Distribution on Rheological Behaviour of Shear Thickening Fluids

Abstract In present work the influence of particle size distribution on the dilatant effect of shear thickening fluid was investigated. As a ceramic powder a mixture of silicas 200 and 7 nm in ratio 95:5, 90:10, 85:15, 80:20, 75:25, 50:50 was used. A dispersing agent was poly (propylene glycol) of a molecular weight of 425 g/mol. The as prepared slurries were examined on a rotational rheometer Kinexus Pro with a plate-plate measuring system at room temperature, where the viscosity as a function of shear rate was investigated. The measurement showed that by partially replacing greater particle size by smaller one, it is possible to shift the onset of shear thickening to the higher value of shear rate, however, the decreases of dilatant effect is observed. The influence of particle size distribution on a maximum volume fraction also was investigated. The maximum volume fraction which was passible to obtain was 35 vol%.

Synthesis of amorphous silica and sulfonic acid functionalized silica used as reinforced phase for polymer electrolyte membrane

In this work silica (SiO2) and sulfonic acid-functionalized silica (sul-SiO2) were synthesized by sol–gel method from tetraethoxysilane (TEOS) and 3-mercatopropyltrimethoxysilane (MPTMS) with various ratios between them. The synthesized materials were characterized by x-ray diffraction (XRD) for crystalline structure, Brunauer–Emmet–Teller (BET) specific surface area analysis, transmission electronic microscopy (TEM) and dynamic light scattering (DLS) for particle size analysis, and ion exchange capacity (IEC) for determining sulfur content in Sul-SiO2 materials. The initial results showed that the average particle size of amorphous SiO2 and Sul-SiO2 at different TEOS: MPTMS ratios are in narrow distribution with average diameter about 20–30 nm. The particle size of Sul-SiO2 is almost unaffected by the content of MPTMS while IEC depends strongly on it. Composite membranes of 60 μm thickness were successfully prepared from blending of poly(vinylidene fluoride) (PVDF) and synthesized amorphous SiO2. It was shown that the latter may be used as a reinforced phase for composite membrane electrolytes based on PVDF.

Super-liquid-repellent coating on the carbon steel surface

In this study, the spray coating method was used to fabricate a superamphiphobic coating with extremely high contact angles of 170°, 159.7° and 124° and low sliding angles of 1°, 4° and 10° for DI water, ethylene glycol and fuel oil droplets, respectively. The superamphiphobic coatings were fabricated on the carbon steel surface by the creation of hierarchical structures and lowering the surface energy. The hierarchical structure was fabricated by silica multilayer coatings and controlling the particle size of SiO2 in each layer. The surface energy was decreased by perfluorodecyltriethoxysilane. The prepared coatings maintained their superamphiphobicity after 768h of immersion in DI water. In the potentiodynamic polarization test, the highest protection efficiency of fabricated films was more than 94%. Also, the scratch hardness number of the prepared coatings reached as high as 6.89GPa. These satisfied results and the simplicity of the coating method confirmed that this superamphiphobic coating can be fabricated on the large scale surfaces with any shape and material.

Properties of Natural Rubber Vulcanizates/Nanosilica Composites Prepared Based on the Method of In-situ Generation and Coagulation

Using the characteristics of silica sol dispersing well in water and easy formation of silica gel when the silica sol is heated, by mixing a system of concentrated natural rubber latex and silica sol, the silica sol can in-situ generate SiO2 particles when heated. After coagulation of the mixed system, natural rubber/nanosilica composites C(NR/nSiO2) were obtained. The composites C(NR/nSiO2) and their vulcanizates were studied using a rubber processing analyzer (RPA), dynamic mechanical analysis (DMA), and scanning electron microscopy (SEM). The influence of silica contents on the C(NR/nSiO2) vulcanizates mechanical properties, cross-linking degree, Payne effect, dissipation factor (tanδ), and the particle size and dispersion of SiO2 in NR were investigated. The results obtained were compared with the NR/SiO2 composites based on traditional dry mixing of bale natural rubber and precipitated silica (white carbon black). The results showed that when using a sulfur curing system with a silica coupling agent ...

Relationship between activity of silica thin films and density of cells occupation

The SiO2 thin films (STFs) were deposited on the surfaces of stainless steel tapes and their activity was particularly investigated from the aspect of the number density of hydroxyl groups on their surfaces. The calculation procedure of density of active OH groups includes determination of average length of silica chains that constitute silica sol particles with almost uniform size, on the base of thermogravimetric analysis. The size of SiO2 particles is analyzed by transmission electron microscopy and dynamic light scattering method. Fibroblast (L929) cell densities on the surfaces of these films were investigated using phase contrast microcopy. It was shown that there is a relationship between OH group densities and density of attached cells. Besides, the cytotoxicity effect was studied and compared for various thermally treated STFs.

Study on antireflection SiO2 coatings fabricated by layer-by-layer deposition

Multifunctional (poly(diallyldimethyl ammonium chloride)/ sodium poly(4-styrene sulfonate))n((PDDA/PSS)n) thin films were fabricated by layer-by-layer assembled on the glass substrate. The monolayer silica nanoparticles were prepared on the (PDDA/PSS)n films. The SiO2-polyelectrolyte coatings exhibit antireflection properties with low refractive index (as low as 1.22). Interestingly, wavelengths of maximum transmittance could be well tailored by simply changing the particle size of SiO2. A maximum transmittance of 97.03% in the visible spectral range is achieved for the particle size of 100 nm SiO2 films. The coatings also show excellent mechanical stability and good adhesion to substrates. The easy availability of the raw materials and simplicity of the fabrication method for such films might make them be potentially useful for various applications.

Characterization and Properties of UV-Curable Hyperbranched Polyurethane Acrylate-Polyurethane Diacrylate/SiO2 Hybrid Coatings

A series of new UV-curable hybrid coatings were prepared with hyperbranched polyurethane acrylate-polyurethane diacrylate (HBPUA-PUDA) and organic SiO2 as formation, and 2-hydroxyl-2-methyl-l-phenyl-1-propanone (Darocur 1173) was used as photo-initiator. The effect of organic SiO2 content on the thermal stability and conversion of C=C bonds of the UV-cured HBPUA-PUDA/SiO2 films were evaluated using thermal gravimetric analysis (TGA) and Fourier transform infrared spectroscopy (FTIR). The morphology of SiO2 were observed by using transmission electron microscopy (TEM), field emission scanning electron microscopy (FESEM), and the elemental composition of SiO2 was tested by energy dispersive spectrometer (EDS). The results revealed that when organic SiO2 content was less than 30 wt%, the average particle size of SiO2 was about 95 nm and the particles were well-dispersed in the organic phase. The mechanical properties, abrasion resistance and transmittance of the films were also investigated. The results showed that with the increase of organic SiO2 content, the adhesive force and pendulum hardness were increased obviously, while the transmittance and flexibility were decreased. When the content of the organic SiO2 was 30 wt%, the film of HBPUA-PUDA/SiO2 showed the optimal comprehensive performance as follows: pendulum hardness was 0.74, transmittance was 93.1%, adhesion was 0 grade, flexibility was 2 mm, impact strength was 43 Kg x cm and mass loss of 300 cycles was 12.9 mg.

Effect of SiO<sub>2</sub> Particle Size on Optical Properties of TiO<sub>2</sub>-SiO<sub>2</sub> Nanocomposite Thin Films

TiO2-SiO2thin film system is known to be very attractive to use for photocatalytic and display applications. In this study, TiO2-SiO2nano-composite solutions were prepared by adding colloidal solutions consisted of different SiO2nano-particle sizes (7-50 nm) into TiO2powder-dispersed solutions. TiO2-SiO2thin films on glass substrates were fabricated by the dip-coating technique and their crystal structure, surface morphology and photocatalytic properties were investigated as a function of SiO2particle size. While the SiO2particle size had little influence on the crystal structure of thin films, the photocatalytic activity and anti-reflectance (anti-glare) characteristics were found to be dependent on the SiO2particle size. This result could be explained in terms of surface characteristics and the order of degradation of methylene blue under UV light irradiation.

Fundamental Study on Reduction Rate for Electrolytic Reduction of SiO2 Powder in Molten CaCl2

Direct electrolytic reduction of powdery SiO2 has been investigated in molten CaCl2 at 1123 K aiming at a low cost and mass production of solar-grade Si. SiO2 powder was set on a Si plate which was installed at the bottom of the crucible and connected to a graphite rod used as a current lead. SiO2 powder was reduced to Si by cathodic polarization of the Si plate. The reduction rate was evaluated by the magnitude of the reduction current, in which three parameters were varied: electrode potential, SiO2 layer thickness, and SiO2 particle size. As a result, the rate-determining step of the reduction is suggested to be the diffusion of O2- ions inside the reduced porous Si particles filled with the electrolyte. During the reduction process, however, other factors such as contact resistance between Si particles and porosity of SiO2 particles possibly influence the reduction rate.

Failure analysis on the economisers of a biomass fuel boiler

The premature failure of the economiser in a biomass fuel boiler was studied. On the internal oxide surface, three morphologies of iron oxides – aggregate oxide (Fe3O4), flower oxide (Fe3O4) and spherical oxide (FeO) have been discovered using ESEM/EDS. The oxidation and pitting occurred on the internal surface was trivial in comparison to the erosion–corrosion rate at outer surface of the economiser. The dominant abrasive SiO2 particles were partially cemented by the calcium compound particles in the biomass fly ash. The individual sharp abrasive SiO2 particles had been revealed with filtergram by dissolved the calcium compound particles in acid solution. The average size of SiO2 particles was approximately 100μm. Some SiO2 particles were up to 500μm. Study on the external scale found different oxide morphologies and the compositions, the flower-like oxide (Fe3O4) at the top and “mud-crack” FeO oxide at the flat sides. The wastage profile of ‘V-shaped thickness thinning’ can be explained by the mechanism proposed in this paper; the oxidation acting simultaneously with two-body abrasive wear by fly ash particle impingement.

Preparation of silica antireflective films for solar energy application

Antireflective films were fabricated by an acid-catalyzed sol-gel process using cetyltrimethylammonium bromide (CTAB) as template. Size of SiO2 particles in the sol was measured to be in the range of 10–30nm. The films were coated on glass substrates by dip-coating method then baked at 180°C and tempered at 720°C for different times. The template CTAB can be removed completely by tempering, which shortens the baking time and reinforces the bonding strength between the film and the substrate. The adhesion of the tempered films all reaches 5B and their hardness is 3H or above. The maximum light transmittance of 97.7% was obtained which increased about 6.0% compared with its glass substrate.

Anticorrosives, encapsulates, catalytic supports and other novel nanostructured materials

A phenolic-formaldehydic resin (PFR) of the Novolac-type and modified through the attachment of carboxylic end groups (MPR), is used to tailor the morphological and optical properties of sol–gel synthesized silica materials. Silica microparticles are produced from alkoxide precursors in the presence of PFR or MPR resins, leading to a final material consisting of SiO2 globules entangled inside a polymerized resin matrix. Under appropriate experimental conditions, chemical bonds can be established between the SiO2 silanol surface groups and the MPR carboxylic chains, to render SiO2/MPR core-shell-type compounds. The presence of PFR or MPR resins during the sol–gel production of silica microspheres allows to control: (i) the sizes of final SiO2 particles and (ii) the transparency or opacity properties of the final hybrid products. In this way, either opaque or transparent solid substrates can be obtained, depending on the amounts of reactants used to prepare the hybrid specimens. Solid MPR and SiO2/MPR samples were characterized by infrared spectroscopy, thermogravimetric analysis and scanning electron microscopy to determine chemical and textural properties of the hybrid substrates. Under appropriate experimental conditions, chemical bonds could be established between the SiO2 silanol surface groups and the MPR carboxylic chains, to render SiO2/MPR core-shell-type compounds.

Deformation investigation on iPP/SiO2 composites: Influence of stretching temperature and particle size on morphology evolution and crystalline structure of thin films

In the present work, structure changes during stretching of isotactic polypropylene (iPP) and iPP/silicon dioxide (SiO2) composites have been investigated systematically. The α-form crystal structure of both iPP and iPP/SiO2 composites is destroyed and transforms into the mesophase as the samples are stretched at a low temperature (35°C), while stretching at high temperatures (90°C and 120°C) can restrain the appearance of defects and keep the perfection of crystal structure. FTIR results reveal that the stretching temperatures show no obvious difference of the effect on the orientation of pure iPP, however, the orientation of iPP/SiO2 composites is greatly changed by the tensile temperature. In the case of micron-sized SiO2 particles (average particle diameter d > 1 μm), the orientation of the composites is lower than that of pure iPP at all stretching temperatures. The above results suggest that the stretching temperature and the SiO2 particle size have great influence on the structure variation and orientation behavior of iPP/SiO2 composites.

Influence of Poly (Ethylene Glycol) and Oleylamine on the Formation of Nano to Micron Size Spherical SiO<sub>2</sub> Particles

We report an eco-friendly synthesis of well–controlled, nano-to-micron-size, spherical SiO2particles using non-hazardous solvent and a byproducts-producing system. It was found that the morphology and size of spherical SiO2particles are controlled by adjusting the concentration of PEG and oleylamine, ethanol solvent selection, and reaction temperature. The SEM images show spherical-shaped silica particles with homogeneous particle-size distribution. Structural and optical properties of the silica particles were investigated by FT-IR absorption spectroscopy and photoluminescence. The resultant SiO2particles from the synthesis system were easily dispersed in both water and organic solvent.

Superhydrophobic SiO2 micro-particle coatings by spray method

In nature, numerous biological surfaces depict hierarchical micro- and nano-structures with low energy surfaces that offer the superhydrophobic properties with low water adhesion. The superhydrophobic coatings were prepared using sol–gel derived SiO2 micro-particles by spray method. A methyltrimethoxysilane (MTMS) was used as a sol–gel precursor to prepare a coating sol. The entire spray coating process is a single-step and takes place at 70°C temperatures. The surface morphological studies showed that the size of SiO2 particles were between 8 and 14μm in diameter. These different diameter SiO2 micro-particles form hierarchical micro-structure which facilitates to reduce solid/water interface. The prepared superhydrophobic coatings showed static water contact angle (θ) of 162°±2° and roll-off angle of 6°±1°. The wetting properties and surface morphology of the coatings were investigated by static and dynamic water contact angle measurements and scanning electron microscopy, respectively. The characterization of the coatings by Atomic Force Microscopy and Fourier transformation infrared spectroscopy was also made. The resulting hierarchical surface morphology can be easily tuned over large areas by simple spray method.

Experimental investigation of in-flight melting by hybrid heating of multi-phase alternating current arc with oxygen burner for alkali-free glass raw materials

An innovative in-flight glass melting technology was developed for a purpose of energy saving and environmental protection. Granulated glass raw materials with small diameter were treated by hybrid heating of multi-phase AC arc combined with an oxygen burner. A multi-phase AC arc and hybrid plasma were compared to study the in-flight melting efficiency of the granulated raw materials. The effects of the input energy and the primary size of SiO2 in the glass raw materials on the characteristics of the in-flight melted particles were investigated. The reaction rate inside the individual in-flight particles was enhanced with decreasing the primary size of SiO2 particles, resulting in the more effective in-flight melting by the hybrid plasma.

Foaming Behavior and Mechanical Properties of Microcellular PP/SiO2 Composites

Abstract Microcellular foamed polypropylene (PP)/SiO2 composites were prepared by using micro-SiO2 and nano-SiO2 particles. The effects of the particle size of SiO2 on the foaming behavior and mechanical properties of the composites were studied based on heterogeneous nucleation theory. The results showed that the silica facilitated the cell nucleation to some extent. The average cell size of 16.3 μm and the cell density of 4.46 × 107 cells/cm3 were achieved for the composite foam at the silica content of 4 wt.%. The plastic deformation of the PP was strongly constrained due to the presence of the nano-silica. The tensile and impact strength of the nano-SiO2 composite foam are larger than those of the micro-SiO2 composite foam due to the high crack propagation resistance in the microcellular PP/nano-SiO2 composite.

Numerical Simulation and PIV Test on Flow-Field Character of Zinc-Silica Composite Electrolyte

Composite electrodeposition is one of the most important metallic material surface finishing technology and metal-based composite material preparation technology. Electric field and flow field are the two main influence factors during electrodeposition process of composite coatings. In this paper, numerical simulation of flow-field of zinc-silica composite electrolyte is finished by FLUENT software and the actual flow state is recorded by Particle Image Velocimetry (PIV). The research work is also focused on influence of current and stirring intensity on flow character of electrolyte. The electrolyte composition and plating conditions are: ZnCl280 g/L, KCl 220 g/L, H3BO325 g/L, brightening agent 0.5 g/L, pH value of electrolyte 5.5, temperature 25°C, mass concentration of SiO2particles in electrolyte 1 g/L. The average particle size of SiO2particle is 11.07 μm. The stirring intensity is controlled between 0 and 3000 rpm, and current is controlled between 0 and 0.5 A. The results show that influence degree of stirring on flow field is much greater than current, and the numerical simulation of flow field finished by FLUENT software is approximately similar to the actual flow charactor recorded by PIV.

Hydrophilicity/porous structure-tuned, SiO2/polyetherimide-coated polyimide nonwoven porous substrates for reinforced composite proton exchange membranes

Porous substrate-reinforced composite proton exchange membranes have drawn considerable attention due to their promising application to polymer electrolyte membrane fuel cells (PEMFCs). In the present study, we develop silica (SiO2) nanoparticles/polyetherimide (PEI) binders-coated polyimide (PI) nonwoven porous substrates (referred to as “S-PI substrates”) for reinforced composite membranes. The properties of S-PI substrates, which crucially affect the performance of resulting reinforced composite membranes, are significantly improved by controlling the hygroscopic SiO2 particle size. The 40nm S-PI substrate (herein, 40nm SiO2 particles are employed) shows the stronger hydrophilicity and highly porous structure than the 530nm S-PI substrate due to the larger specific surface area of 40nm SiO2 particles. Based on the comprehensive understanding of the S-PI substrates, the structures and performances of the S-PI substrates-reinforced composite membranes are elucidated. In comparison with the 530nm S-PI substrate, the hydrophilicity/porous structure-tuned 40nm S-PI substrate enables the impregnation of a large amount of a perfluorosulfonic acid ionomer (Nafion), which thus contributes to the improved proton conductivity of the reinforced Nafion composite membrane. Meanwhile, the reinforced Nafion composite membranes effectively mitigate the steep decline of proton conductivity with time at low humidity conditions, as compared to the pristine Nafion membrane. This intriguing finding is further discussed by considering the unusual features of the S-PI substrates and the state of water in the reinforced Nafion composite membranes.

One-step electrophoretic deposition for the preparation of superhydrophobic silica particle/trimethylsiloxysilicate composite coatings

SiO2 particle/silicone resin (trimethylsiloxysilicate (TMSS)) composite coatings were prepared by electrophoretic deposition (EPD), and their wettability was examined. SiO2 coatings prepared by EPD baths without TMSS were hydrophilic, while superhydrophobicity was observed for SiO2/TMSS composite coatings. IR spectra and EDS analyses revealed that not only SiO2 particles but also TMSS electrophoretically moved toward a cathode; as a result, hydrophilic SiO2 particles turned into superhydrophobic composite coatings by one-step EPD. SEM and AFM images of the superhydrophobic SiO2/TMSS composite coatings showed the presence of both nanometer- and micrometer-sized roughness in their surfaces. Particle size of SiO2 had a great influence on the wettability of the composite coatings. The superhydrophobic SiO2/TMSS composite coatings showed excellent water repellency; they repelled running water continuously. In addition, by controlling the amount of deposited SiO2 particles and TMSS, transparent superhydrophobic SiO2/TMSS composite coatings were prepared.