جستجوی مقالات مرتبط با کلیدواژه « Nano Silica » در نشریات گروه « مهندسی شیمی، نفت و پلیمر »

Nanotechnology improves the mechanical properties of polymer and metal compounds in the form of nanocomposites. The presence of nanometer-sized secondary phases in polymer coatings can increase the physical and mechanical properties more than conventional reinforcements. The nanosilica particles are used as an efficient filler in polymer matrix. In this research, polypropylene/ nanosilica nanocomposite fibers were prepared to investigate their properties. For this purpose, after surface modification of nano-silica and adding polypropylene maleic as a compatibilizer to the polypropylene matrix of obtained nanocomposite fibers, they were meltspinined with different percentages of nanosilica. Investigation of rheological and viscoelastic properties showed that due to the increase of nanoparticles up to 0.5%, it had no significant effect on rheological behavior and melt spinning process. The results of TGA test showed that the onset temperature of degradation decreased with increasing percentage of nanosilica. SEM and EDAX images showed that the particle distribution in nanocomposites containing lower amounts of nanosilica was uniform and almost free of particle aggregation, but with an increase of nanosilica by 1.5%, there was particle aggregation at different points. The main objective of this research is study of Rheological properties of nanocomposite along side of morphological behaviours.

This study demonstrates a synthetic strategy for the preparation of porous SiO2 for adsorption applications using natural and waste materials from rice husks which are functionalized with polymer dendrimer molecules and surface amino groups as the source of biosilica and were investigated to remove divalent cadmium ions from aqueous solutions.

Porous silica nanoparticles with a mean diameter of 45 nm were successfully fabricated from rice husk (RH) biomass via a multistep method. During the first step, sodium silicate is extracted from rice husks. Then, cetyltrimethylammonium bromide, HCl, and acetic acid were added to the sodium silicate solution, and the resulting mixture was sonicated. After the hydrothermal reaction, the collected samples were calcinated to obtain silica nanoparticles. These synthetic nanoparticles were identified using various techniques such as Fourier-transform infrared spectroscopy, thermogravimetric analysis, transmission electron microscopy, field emission scanning electron microscopy, nitrogen adsorption-desorption analysis and dynamic light scattering analysis. Then, the adsorption kinetics and the effects of synthetic nanoadsorbents dosage on the removal of divalent cadmium ions were investigated. The effect of contact time on cadmium adsorption and recyclability of adsorbent was also investigated.

The results show that there is no significant reduction in the performance and activity of this nanosorbent in the adsorption of metal ions after 6 times of recycling and reuse. The excellent performance of this nanosorbent in the removal of metal ions is due to its high porosity, active surface amine groups and high surface-to-volume ratio.

Research subject: 

In this research we studied the anti-corrosion properties of epoxy coating containing anti-corrosion pigment zinc phosphate with hydrophobic nano silica with different percentage also for determine the optimal conditions for preparation of nanocomposite Taguchi experimental design method was used.

Research approach: 

Anti-corrosion properties of epoxy coating under the influence of very important factors such as the percentage of nano silica, anticorrosive pigment and pigment to resin ratio according to model L9 taguchi method was studied and analyzed. Anti-corrosion properties of epoxy coatings were studied by electrochemical impedance spectroscopy test (EIS) in 3/5% NaCl aqueous solution and salt fog test (salt spray). To investigate the distribution of nano silica particles in epoxy resin were analyzed by transmion electron microscope (TEM) and scanning electron microscope (SEM). The results show that using from zinc phosphate and nano-silica was able to improve the corrosion resistances.

Results shows that addition of zinc phosphate and nano silica to epoxy resin caused a decrease in number of blisters and corrosion products after exposure to corrosion test based on the results in Nyquist and Bode plots, also the similarity in results was observed for the epoxy coating loaded according to the optimum conditions with 8% zinc phosphate, 3% nano silica and pigment to resin ratio of one according to salt spary. The significance levels of the experimental parameters, which indicate how the factors affect the compressive addition of zinc phosphate and nano silica to epoxy resin, were determined by using variance (Anova) method.

The gas flooding is one of the most common methods for enhancing oil recovery. However, some problems; such as, gas uptake reduces this method’s efficiency. The foam formation reduces the relative permeability of the gas and improves this technique. However, the generated foam by the combination of water and gas does not have enough stability. Thus, surfactant is used for many years. However, the foam stabilized by surfactants is problematic in high temperatures and salt content. The studies have shown that the foam stabilized with Nanoparticles can endure the harsh conditions. Since the presence of oil in the reservoir is inevitable, investigating the effects of crude oil on the foam is of special importance. In this project, the foam generated by Nano-silica and SDS is studied. Then the differences between this foam and the foam generated by only surfactant is discussed. The effect of different kinds of crude oils with different viscosities on foam structure is discussed too. For studying the foam ability and foam stability in the presence of different concentration of these crude oils, the static method called “mixing” is used by the setup that is designed for this job. The results show that nanoparticles do not effect foam ability but increase the foam stability significantly. Regarding the effect of crude oil, it was also determined that the presence of crude oil reduces foam stability and by increasing oil concentration, the stability reduces more. It also turned out that with increasing oil viscosity, foam stability and properties will be improved.

A practical method to measure the energy dissipation in rubber vulcanization under rolling condition has been considered. For this purpose, a modified rolling pendulum device was designed and constructed to eliminate the shortcomings of an initial design by Gent. This modified device has a working table, heated rolling plate, symmetric pendulum, and ultrasonic sensor for accurate measurement of the roller traveled distance and calculation of rolling resistance parameters for rubber. Performance of this new device was evaluated by measurement of the rolling resistance force and coefficient for rubber vulcanization containing un-modified and Silane- modified nano-Silica under different conditions. The device could successfully show the effects of strain, temperature, and silica surface modification on rubber rolling resistance parameters, as reported by other researchers.

In this work, nano silica was modified by Glycidoxy propyl trimethoxy silane at different pH conditions. In order to study the surface treated particles, some testes on particles and poly urethane clear coat containing nano particles were performed. To characterize the particles some tests such as pH, density, FT-IR, elemental analysis and zeta potential were performed.Also in order to study surface chemistry of treated particles, Turbidity of particle in two solvents with different solubility parameters was implemented. The results show that the pH of treating bath, highly affects on amount of grafting. Maximum grafting content was obtained at isoelectric point of silane (4.7) and above isoelectric point of silica (5-6). Grafting silane on silica Surface causes the density of particles decrease and the isoelectric point increases. Sample with higher grafting has better dispersion stability in solvents with higher hydrogen bonding parameter (δH) and lower polar parameter (δP).This phenoma is because of increasing hydrophobisity of treated particles and decrease of polarity. Inorder to quantify interaction of particles with poly urethane matrix, Tensile strength, DMTA and Buchhol Hardness, were performed. The results were representative chemical and physical interaction between treated particles and poly urethane matrix which is increase considerably mechanical properties of nano composite.

In order to modify the nanosilica surface from hydrophilic to hydrophobic one, and to have a better. dispersion of nanosilica in a non-polar media, nano silica surface treatment using methacryloxy propyl trimethoxy silane was performed. In this study three independent variables were explored. These factors included silane coupling agent concentration, bath pH and hydrolysis ratio. Particle analysis was performed to investigate the surface behavior of the treated nanosilica. pH of particles was determined in a mixture of water and ethanol. Apparent densities were measured using a Helium Pycnometer. FTIR Spectroscopy was used to study the surface chemistry of the treated nanosilica. Thermogravimetric analysis (TGA) and elemental analysis were employed to illustrate the quantitative amounts of grafted silane on the surface. It was revealed that pH of particles changed from 3.8 for pristine silica to 4.9 and 6.9 for the lowest and the highest grafted particles respectively. The results indicated that the silane/silica concentration had a strong effect on the grafting of silane on the silica surface. Based on the elemental analysis, carbon content of treated silica in different condition of experiments changed between 1.2.

In this research optimization of water -based overprint clear coat on printed substrate (flexography) was investigated and optimized by the Design Expert 7 software. the nano silica، Tinuvin 400 and water were the components in composition of overprint clear coat، which affect properties of clear coat. So these components were considered as variable factors in a mixture experimental design and their effects on clear coat properties were studied. Measurements of some physical and mechanical properties such as light fastness، gloss، abrasion resistance and adhesion were carried out on samples. These factors and their interactions effects were determined analysing the results and finally، the optimized regeons on the contour diagrams were obtained. J. Color Sci. Tech. 6 (2012)، 1-8© Institute for Color Science and Technology.

In this work nano silica was treated by an amin silane at different pH conditions and analysed using different techniques. It was found that the pH of treating bath highly affected the grafting of silane on the surface leading to grafting ratios between 29 and58 percent. The zeta potentials changed from -7.1 mv for pristine silica to +5.5 mv and +18.01 mv for the lowest and the highest grafted particles respectively. The results showed that, the sample with higher grafting has better dispersion stability in solvents with higher hydrogen bonding parameter and lower polar parameter. The higher mechanical properties of the nano clear coats using a polyurethane filled with these particles may confirm the better dispersion and possibility of a physicochemical interaction between the surface modified silica and the matrix. The tensile strength, elongations at yield and break and micro indentation hardness as well as the Young modulus were used to show the improvement achieved in properties of modified particles containing resin. J. Color Sci. Tech. 4(2010), 71-82© Institute for Color Science and Technology.