Presence Of SiO2 Nanoparticles Research Articles

Catalytic graphene formation in coal tar pitch- derived carbon structure in the presence of SiO2 nanoparticles

A simple and effective way to manufacture graphene from a coal tar pitch (CTP) is demonstrated. Silica (SiO2) nanoparticles were used to modify the CTP as carbon precursor. A silica nanofiller introduced into the CTP matrix underwent carboreduction during heat treatment to 2000°C, resulting in the formation of silicon carbide. Surfaces of SiC grains were sites for graphene formation. The influence of SiO2 on the structure and microstructure of CTP- based carbon matrix, after annealing up to 2800°C, was studied. Carbon samples were analyzed using X- ray Diffraction (XRD), Transmission Electron Microscopy (TEM) and Raman Spectroscopy. Crystallite sizes (La, Lc) and interplanar distance (d002) were determined. The presence of SiO2 in CTP carbon precursor favored the crystallites’ growth in the ‘a′ crystallographic graphite direction, and inhibited their growth on the ‘c′ axis. The crystallites composing of graphene layers, were characterized by an elongated dimension in the ‘a′ axis direction. Above 2000°C silicon carbide decomposed, followed by the sublimation of silicon from the carbon matrix.

Experimental investigation of minimization in surfactant adsorption and improvement in surfactant-foam stability in presence of silicon dioxide and aluminum oxide nanoparticles

Foams stabilized by a mixture of nanoparticles and surfactants are presently being considered for improving the poor macroscopic sweep efficiency of gas enhanced oil recovery (EOR) methods. The stability of these foams is influenced by the adsorption and foaming properties of the nanoparticles-surfactant mixtures. This study investigates the influence of silicon dioxide (SiO2) and aluminum oxide (Al2O3) nanoparticles on sodium dodecyl sulfate (SDS) adsorption on kaolinite and SDS-foam stability at static and dynamic conditions. The adsorption experiments were conducted by surface tension and two-phase titration methods. Adsorption data were analyzed by fitting with Langmuir, Freundlich and Temkin adsorption isotherms. Influence of salt on foam performance was investigated from bulk stability experiment conducted using KRÜSS dynamic foam analyzer. The pore scale visualization experiments were carried out with etched glass micromodels to study foam stability in porous media. Results show that SDS adsorption on kaolinite reduced by 38% in presence of Al2O3 nanoparticles and 75% in presence of SiO2 nanoparticles. The Langmuir isotherm model suits the equilibrium adsorption of sole SDS and Al2O3-SDS onto kaolinite while the Freundlich isotherm model suits the adsorption of SiO2-SDS onto kaolinite. Foam stability decreased in presence of salts until the transition salt concentration. Beyond the transition salt concentration, foam stability generally increased with the increasing salt concentrations. The presence of Al2O3 and SiO2 nanoparticles increased the foam half-life and decreased the transition salt concentrations. The dominant mechanisms of foams flow process were identified as lamellae division and bubble-to-multiple bubble lamellae division. The dominant mechanisms of residual oil mobilization and displacement by foam were found to be direct displacement and emulsification of oil. The identified pore scale mechanisms were independent of the pore geometry of the etched glass micromodels. There was lamellae detaching and collapsing during the flow process of SDS-foam in presence of oil which resulted in poor microscopic displacement efficiency. The SiO2-SDS and Al2O3-SDS foams propagated successfully in porous media in presence of oil with almost 100% microscopic displacement efficiency due to the enhanced films interfacial elasticity. The findings of this research provide an insight into surfactant adsorption minimization and pore-scale mechanisms of foam stability improvement by nanoparticles.

Preparation and performance evaluation of high-density polyethylene/silica nanocomposite membranes in membrane bioreactor system

In this study, in order to improve the antifouling properties of high-density polyethylene (HDPE) membrane in the membrane bioreactor (MBR) system, HDPE/SiO2 nanocomposite membrane was developed and evaluated for its physicochemical changes with different contents (0, 0.25, 0.5, and 1wt.%) of SiO2 nanoparticles (NPs). Flat sheet membranes were fabricated via thermally induced phase separation (TIPS) method and characterized by field emission scanning electron microscopy (FESEM), contact angle, energy dispersive X-ray analysis (EDX), tensile test and pure water flux. The filtration experiments and FESEM confirmed that certain dosages of SiO2 NPs (0.5wt.%) can increase the membrane porosity. Fouling analysis revealed that the presence of SiO2 NPs in the membrane matrix results in respectively 27% and more than 70% reduction in the total fouling ratio (TFR) and irreversible fouling ratio (IFR) and a little bit increase (16%) in the reversible fouling ratio (RFR). The obtained results showed high efficiencies of chemical oxygen demand (COD) removal rates like more than 95% for both membranes coupled biological filtration tests. In order to identify the most likely fouling mechanism, Hermia’s model was used and the obtained results revealed the existence of two fouling phases; in the first phase, cake filtration is the main fouling mechanism for both membranes, while complete blockage model is the prevailing fouling mechanism in the second phase.

Desulfurization efficiency of polydimethylsiloxane/silica nanoparticle nanocomposite membranes: MD simulations

The effect of SiO2 nanoparticles on the efficiency of polydimethylsiloxane membranes to separate n-octane from benzothiophene was investigated using molecular dynamics simulations. The non-bond energies were more negative (by∼4000kcal/mol) compared with their corresponding potential energies. Further, adding 2–10vol% silica particles to the membrane led to increase in the potential and non-bond energies so that the 10vol% SiO2 membrane had the greatest negative potential as well as non-bond energies of nearly −35,000 and −39,000kcal/mol, respectively. It was found that the free volume was increased from 82764.23Å3 in the pure polydimethylsiloxane membrane to 99362.47–208186.38Å3 in 2–10vol% SiO2 nanocomposite membranes. The X-ray diffraction patterns of all membranes exhibited one peak at about 23° proving the presence of amorphous silica structures. Increasing the silica content into the polymeric matrix caused enhancement in the surface area so that it was changed within the range of 37421.00–43812.95Å2 which may be related to the presence of greater accessible surfaces on the total molecules by increasing amount of the SiO2 particles. The radial distribution function analysis revealed the interactions of benzothiophene molecules with SiO2, n-octane and polydimethylsiloxane were strong, moderate and weak, respectively suggesting the benzothiophene molecules would diffuse and transfer more easily within the polydimethylsiloxane membrane in the presence of SiO2 nanoparticles. The lowest n-octane diffusion coefficient (0.0037×10−4 cm2/s) was measured for the 6vol% SiO2 membrane while the largest BT diffusion coefficient was obtained for the 6vol% SiO2 membrane (0.0071×10−4 cm2/s) confirming this membrane was the most appropriate nanocomposite to separate benzothiophene from n-octane (desulfurization process).

Study of the Effects of SiO<sub>2</sub> Nanoparticles Concentration on the TiO<sub>2</sub> Nanoparticles Suspensions Stabilization

TiO2 nanoparticles (NPTiO2) suspensions are in several ecosystems and residue treatment processes or disposal systems due to their large industrial use and handling. The interactions of the NPTiO2 with NPSiO2 have special interest due to their strong ability to maintain high TiO2 nanoparticles concentration in suspension and promote nanoparticles clustering. These characteristics are used either in cleaning systems or in production of nanoparticles solution for several applications in the food industry or medicine. In this study, suspensions of NPTiO2 and NPSiO2 are synthetized and their stabilizations are discussed. A base TiO2 nanoparticles suspension was synthetized and the initial concentrations of SiO2 nanoparticles (NPSiO2) were changed in order to determine the effects of presence of SiO2 nanoparticles on the stabilization and clustering size. Zeta potential and concentrations measurements were carried out throughout the time and correlated with the initial concentrations of the base suspensions. In this study, the concentrations, zeta potential and pH are measured to estimate the stability of the suspensions. The clustering size, obtained by nanoparticle tracking analysis (NTA), are also monitored and discussed. Results of column soil experiments are discussed and compared under similar conditions with literature data.

Use of vitamin B1 for the surface treatment of silica (SiO2) and synthesis of poly(vinyl chloride)/SiO2 nanocomposites with advanced properties

In this study, silica (SiO2) nanoparticles (NP)s were used as fillers for the preparation of nanocomposite (NC) films. SiO2 NPs have a strong tendency to agglomerate. Therefore, the surface modification of SiO2 NPs was performed by vitamin B1 (VB1) as a biodegradable modifier. To obtain better dispersion into the polymer matrix, the process was accomplished under ultrasonic as a green route. After that, modified SiO2 NPs with different contents, incorporated into poly(vinyl chloride) (PVC) matrix and PVC/SiO2-VB1 NCs were prepared. TGA results indicated that the incorporation of SiO2-VB1 into the polymer matrix enhanced the thermal stability of pure PVC. Microscopic observations showed that SiO2-VB1 was homogeneously dispersed into the PVC matrix. According to UV–Vis spectra, the absorption of pure PVC increased in the presence of SiO2 NPs. The mechanical tensile test showed more flexibility for NC films in comparison to the pure PVC. Also, water contact angle analysis showed that the hydrophilicity of PVC increased in the presence of SiO2-VB1 NPs.

Study of the BZ oscillating system in the presence of silica nanoparticles containing NiO using a new approach: Conductometry

Oscillating chemical reactions are complex systems involving a large number of chemicalspecies such as ionic, radical and molecular intermediates, which exhibit fluctuation in their concentration with time. One of the oscillating chemical reactions is BZ {---}System. In this work for the first time a new, simple and appropriate method, i.e.conductometry, have applied for the investigation of BZ oscillating system.Furthermore, presence of SiO2 nanoparticles containing NiO apparently affected the intensity and period of BZ system. The effect of varying concentrationof , , and on the conductance of BZ oscillating chemical system at 20 (±0.1)°C was also investigated. The obtained results of this work indicated that rather than potential and color of the BZ system, the conductance of system is also oscillates during the reaction and is also proportional to the reactants concentration as well. The intensity, intensity and period of the oscillation are strongly depending on the concentration of reactants.

Synergistic effect of silica nanoparticles in the matrix of a poly(ethylene glycol) diacrylate coating layer for the surface modification of polyamide nanofiltration membranes

ABSTRACTIn this study, a commercial polyamide nanofiltration membrane was modified by a combination of poly(ethylene glycol) diacrylate (PEGDA) in situ polymerization and silica (SiO2) nanoparticles. The PEGDA layer was polymerized on the surface of the membranes alone or mixed with SiO2 nanoparticle. The surface modification influence on the water flux, salt rejection, and antifouling behavior was investigated. The effects of the nanoparticles and PEGDAylation on the membrane properties were characterized by Fourier transform infrared spectroscopy, contact angle measurement, and scanning electron microscopy analyses. The membranes that were in contact with 30 wt % PEGDA and then treated with ultraviolet light for 5 min had a better water flux than the unmodified membrane. The fouling resistance of the membranes to a foulant solution containing bovine serum albumin, humic acid, and sodium sulfate were studied, and the results show that the membrane with 30 wt % PEGDA had better antifouling properties. After the weight percentage of PEGDA for the prepolymerization solution was optimized (30 wt % was the best), the SiO2 nanoparticle concentration in the prepolymerization matrix was optimized. The presence of SiO2 nanoparticles in the PEGDA layer increased the membrane flux. The maximum water flux and good antifouling properties were obtained for 0.5 wt % SiO2 nanoparticles in a 30 wt % PEGDA layer. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016, 133, 43793.

Electro-codeposition of Ni-SiO2 nanocomposite coatings from deep eutectic solvent with improved corrosion resistance

Electro-codeposition of nano-sized SiO2 particles into the metal matrix in aqueous solution is generally difficult. In this paper, the nano-sized SiO2 particles were successfully codeposited in the Ni matrix from a choline chloride (ChCl)/ethylene glycol (EG) based deep eutectic solvent (DES) by pulse electro-codeposition. The effects of nano-sized SiO2 particles on electrochemical behaviour of Ni(II) were investigated. The microstructure, composition and corrosion resistance of pure Ni and Ni-SiO2 nanocomposite coatings were explored. Results showed that the SiO2 nanoparticles exhibited excellent dispersion stability in ChCl:2EG DES without any stabilizing additives and the presence of SiO2 nanoparticles have significant effects on the nucleation mechanism of Ni. The maximum content of SiO2 nanoparticles in composite coatings can achieve 4.69wt.%, which closes to the level of co-deposition micro-sized SiO2 particles from aqueous solution. The Ni-SiO2 nanocomposite coatings exhibit much better corrosion resistance than pure Ni coating, and the corrosion resistance performance increases with increasing SiO2 content in the composite coatings.

Growth and Physiological Responses of Wheat Seedlings to Cadmium Alone and in Combination with SiO2 Nanoparticles

Heavy metals are the major environmental pollutants, mainly in areas with high anthropogenic activities. In this study, the effects of three cadmium (Cd) concentrations (30, 60, and 120 mg-1l) alone and in combination with two concentrations of SiO2 nanoparticles (10 and 100 mg-1l) on growth and some physiological parameters of wheat (Triticum aestivum) seedlings were investigated. Cadmium treatments decreased the fresh and dry weight of roots, shoots, chlorophyll, carotenoid and total protein contents of the leaf tissues significantly. It also increased the amount of proline, lipid peroxidation and catalase activity of wheat seedling. The toxic effects of cadmium ions on growth and physiological activities of wheat seedlings were reduced in the presence of SiO2 nanoparticles.

Low driving voltage characteristics of polyaniline–silica nanocomposites as hole-injection material of organic electroluminescent devices

Polyaniline–fumed silica (PANI–SiO2) nanocomposites were synthesized through in-situ chemical oxidative polymerization of the aniline in the presence of SiO2 nanoparticles by using ammonium peroxydisulphate (APS) as an oxidant. The resulting PANI–SiO2 nanocomposites with different SiO2 contents were characterized using FT-IR, XRD, FE-SEM and UV–vis techniques. The influence of SiO2 contents on the sheet resistance of the nanocomposite was investigated by four-point probe system. The optical properties of poly [2-methoxy-5-(2′-ethylhexyloxy)-1,4-phenylenevinylene] (MEH-PPV) in toluene solution studied by UV–vis and photoluminescence (PL) measurements at room temperature. For the first time, the application of the prepared PANI–SiO2 nanocomposites as a hole-injection layer (HIL) of electroluminescent (EL) devices was examined and the device performance (e.g., turn-on voltage and current density–voltage (J–V) characteristics) was investigated. The Fowler–Nordheim (FN) field-emission tunneling model was used to explain the J–V characteristics of the fabricated devices. The hole-injection barrier height (φ) values for the devices were obtained and reported.

Influence of SiO2 nanoparticles on morphological, thermal, and dielectric properties of PVDF

The morphology, crystalline structure, and thermal stability in a system of SiO2 nanoparticles dispersed in PVDF matrix are investigated. SEM/TEM indicated that SiO2 nanoparticles present in PVDF matrix have been homogeneously dispersed. The spherulite texture of PVDF was significantly disrupted by the presence of SiO2 nanoparticles as observed by optical micrographs. The XRD pattern shows that the intensity decreases, while full width at half maximum increases with the increasing nanoparticles content, which is ascribed to the significant decline in crystallinity. DSC also shows that the crystallinity is influenced by the SiO2 nanoparticles in the PVDF matrix. The thermal properties of nanocomposites directly reflect the morphological and structural changes induced by SiO2 nanoparticles. TG shows that the nanocomposites have higher decomposition temperatures in comparison with the PVDF. The increase in thermal stability with the addition of SiO2 nanoparticles is mainly attributed to interfacial interactions between the organic polymer and inorganic nanoparticles. The investigation of the dielectric properties at different frequencies and temperature revealed that the relaxation mechanism, which controls the movement of the charge carriers in the nanocomposites, is strongly related to the morphology of the system.

Nano-SiO2 Enriched Biocompatible Powder Coatings

The success/failure of implants largely depends on their osseointegration with the surrounding bone, which in turn a strong function of their biocompatibility and surface roughness. Therefore, nanoparticles of metal oxides are recently being extensively used into composites in order to enhance their topographical and biological properties. Hence, the objective of this study is to develop biocompatible polymeric powder coatings enriched with nano-SiO2 by using ultrafine powder coating technology and to grow HEPM cell on them. The coating technique involves a pre-processing of the powder mixture with the nanoparticles that ensures the homogeneous dispersion of nanoparticles into the coating ingredients. As a consequence, the presence of SiO2 nanoparticles into the polymeric materials facilitates fabrication of nano topographies onto the coated surfaces. An experimental set up was designed and executed to evaluate the adhesion/ bond strength of the coating and to measure the load bearing capacity that the coatings can withstand before being detached from the substrate. Coating's topographical features and cells’ morphology were analyzed by using SEM.

Investigation of characteristic velocity in a pulsed packed column in the presence of SiO2 nanoparticles

This study examined effects of pulse intensity, mass transfer and nanoparticles on characteristic velocity in a pulsed packed column. Distilled water and kerosene were used as continuous phase and dispersed phase respectively. Mass transfer took place from the dispersed phase to the continuous one. Acetic acid (4.6wt%) and silica's H2O nanoparticles (0.06wt%) were used in dispersed phase to investigate the effects of mass transfer and nanoparticles on characteristic velocity. The results showed that the more the pulse intensity increased in water–kerosene and water–acetic acid–kerosene systems, the more the characteristic velocity decreased and increased respectively as regards pulse intensities lower than 1.2cm/s and pulse intensities higher than 1.2cm/s. Furthermore, mass transfer increased the characteristic velocity. Other findings revealed that an increase in pulse intensity in water–acetic acid–kerosene–nanoparticles system led to reduction in characteristic velocity in pulse intensity span of 0.8–2cm/s. The statistical-derived equation in this paper indicated highly precise results for predicting characteristic velocity in pulsed packed column.

In situ 18F-γ-ray-induced Ag nanoparticle formation in the presence of SiO2 nanoparticles under air

The in situ 18F-γ-ray irradiation of SiO2 nanoparticles in an aqueous solution containing Ag+ led to the reduction of Ag+ to Ag0 aggregates or Ag0 nanoparticles in a small volume (0.1 ml) under air. 18F was used in the form of 18F-fluorodeoxyglucose, produced by a cyclotron at our University hospital. The in situ average absorbed dose at the distance of 1 µm in the solution volume (0.1 ml) was calculated to be 12.2 kGy equivalent to a point source of 20 MBq. The SiO2 nanoparticles had two effects; they enhanced the reduction of Ag+ to Ag0 aggregates and they acted as reaction sites to prevent aggregation. When Ag+ adsorbed on the surface of the SiO2 nanoparticles, Ag nanoparticles were formed by 18F γ-rays. The absorption spectra of Ag nanoparticles and Ag0 aggregates were markedly different.

Corrosion Protection of Steel 316 Using Coatings Based on Epoxy and Poly p-Phenylendiamine–SiO2 Nanocomposite

Poly p-phenylendiamine–SiO2 nanocomposite (PSC) was prepared by oxidative polymerization of p-phenylendiamine in hydrochloric acid with ammonium persulfate in the presence of SiO2 nanoparticles. The results of atomic force microscopy confirm that the surface is smoother for the case of epoxy/PSC/steel. The smoothness of epoxy/PSC/steel is due to the formation of a compact protective coating that inhibit the corrosion of steel. The coatings on steel were evaluated using potentiodynamic polarization and electrochemical impedance spectroscopy in 1 M HCl solution. Results indicated that the coating having PSC can protect the steel more efficiently than the coating containing sole poly p-phenylendiamine.

Influence of SiO<sub>2</sub> Nanoparticle Codeposition on Homogeneity of Zinc-Nickel Alloy Plating from an Acid Sulphate Bath

Zinc-nickel-SiO2 electrodeposits have been produced from an acid sulphate bath. Thecodeposition behavior of SiO2 and the homogeneity of platings were examined. The presence ofSiO2 nanoparticles in the plating bath appears to change the alloy deposition behavior. Rate ofnickel deposition was considerably decreased with SiO2 nanoparticles in the bath. The homogeneityof platings between zinc and nickel were improved by adding the SiO2 nanoparticles in the bath. Atan early stage of electrodeposition, it seems that the SiO2 nanoparticle acts as a nucleus of theprecipitation. The SiO2 nanoparticle has not uniformly dispersed in a plating film, but distributedonly in the SiO2 rich layer with about 50 nm in thickness formed beneath the surface. In addition,this SiO2 rich layer can improve the anticorrosive performance. Therefore, the zincic use can besuppressed, because film thickness can be more thinned, compared with zinc and zinc-nickel alloyelectroplating.

Radiation Processing of Formamide and Formamide:Water Ices on Silicate Grain Analogue

Lyman-α (121.6 nm) photon and 1 keV electron-beam irradiation of pure HCONH2 (FA) ice and H2O:HCONH2 ice mixtures on high-surface-area SiO2 nanoparticles have been investigated with FT-IR spectroscopy and temperature programmed desorption (TPD). Lyman-α photolysis of pure amorphous FA ice grown at 70 K and crystalline FA ice produced by annealing to 165 K gives spectral signatures between 2120 and 2195 cm(-1) that we assign primarily to OCN(-) and CO. The OCN(-) and CO yields are ∼25% less abundant for crystalline FA ice. Photon and electron processing also produces H2 that is released from the ice between ∼90 and 140 K. A decrease in the H2 TPD peak is seen for irradiated crystalline HCONH2 ice. Lyman-α photolysis of H2O:HCONH2 mixed ices increases OCN(-) and CO production, suggesting a catalytic role of H2O. Also, for pure FA, 1 keV electron irradiation slightly increases the yield of OCN(-), while CO decarboxylation is selectively prevented. CO is also not produced in H2O:HCONH2 ices upon electron irradiation. Dissociative ionization, direct dissociative excitation, and dissociative electron attachment (DEA) channels are accessible in the Lyman-α (121.6 nm) photon and 1 keV electron-beam energy range. DEA energetically favors OCN(-) and H(-) formation, with the latter leading to H2 formation. The FA fragment product identities, yields, and branching ratios are considerably different relative to the gas phase and depend upon the radiation type, ice structure, and the presence of SiO2 nanoparticles. The latter may increase ion-electron recombination and radical recombination rates. The main products observed suggest very different condensed-phase dissociation channels from those reported for gas-phase dissociation. Formation of ions/products from FA is not negligible upon Lyman-α photolysis or electron irradiation, both of which could process ices in interstellar regions as well as in Titan's atmosphere.

Fabrication and characterization of gold/acrylic polymer nanocomposites

We report the method of incorporation of preformed gold nanoparticles (AuNPs) into the acrylic polymer (AP) matrices and optical, TEM characterization of AuNP/AP bulk and film composite. It was shown that incorporation of dodecanethiol-covered AuNP can be enhanced in the presence of SiO2 nanoparticles, enabling at the same time a wider range of tailoring of composite properties for optical processing.

Increased rubber content in high impact polypropylene via a sirius ziegler‐natta catalyst containing nanoparticles

AbstractHigh impact polypropylene was produced in a two‐reactor polymerization process operating in series using two different Ziegler‐Natta catalysts (referred to as catalysts A and B) that had been prepared by Sirius emulsion technology in the absence and presence of SiO2 nanoparticles, respectively. The homo polypropylene matrix was produced in liquid bulk and the ethylene/propylene rubber in gas phase under industrial conditions. Catalyst B was prepared with the same emulsion technology as catalyst A, except that SiO2 nanoparticles (average particles size 80 nm) were added during catalyst preparation. Scanning electron microscopy studies showed that the nanoparticles were fairly evenly distributed within catalyst B particles, although there was some agglomeration. It was shown that the nanoparticles in catalyst B increased the internal porosity in the homo polypropylene matrix particles and this enabled a significant increase in the rubber content. Maximum rubber content, before running into stickiness problems, was approximately 25 wt % for catalyst A without nanoparticles, whereas the maximum rubber content for catalyst B was almost doubled to 45 wt % due to the beneficial transformation of the internal catalyst morphology by the nanoparticles. In addition, it was also found that the reaction was not mass transfer limited during the ethylene/propylene rubber polymerization stage, even at very high rubber contents where all pores and cavities were filled with rubber. © 2013 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2013