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In this study, the influence of grafting 198Au radioisotope on functionalized silica nanoparticles with a the biodistribution of this radioisotope compare to pure gold nanoparticles, was investigated. The Au radioisotope was prepared using neutronic bombardment of a highly pure metallic gold. The prepared radioisotope was coated on silica through an interface ligand. The biodistribution suggested that the hydrophilicity of the 198Au@MCM-41 nanosilica compare to pure gold nanoparticles was higher. Through the SPECT images and %ID/g measurement, it was found that the excretion of radiotracer from the body compare to pure gold nanoparticles became faster. The Au@MCM-41 nanocomposite could potentially be used in diagnosis and therapy of cancer.

Silica is a valuable compound with very high performance in various fields. The aim of this study was to investigate the sites of silica accumulation in corn to prepare SBA-15 and its use in the removal of chromium and fluoride from aqueous solutions. First silica nanoparticles and then functionalized SBA-15 nanoparticles were synthesized. Afterwards the effect of pH, adsorbent amount, initial concentration of ions and contact time on the removal of heavy metals chromium and fluoride were tested. To measure the samples, colorimetric method was performed using spectrophotometers at 540 and 570 nm. The amount of silica in corn was determined using X-ray fluorescence (XRF). The results showed that the highest percentage of silica was related to corn leaves with 93.8%. X-ray diffraction (XRD) and Fourier transform infrared (FT-IR) indicated the formation of silica particles with amorphous structure and siloxane bonds (Si-O-Si). The results of scanning electron microscopy (SEM) represented a size of about 8-15 nm. Transmission electron microscopy (TEM) images displayed that the SBA-15 has been successfully synthesized with hexagonal symmetry and regular channels, a large pore volume, and an average pore diameter of 10 nm. The results pointed that the maximum adsorption time for chromium was 60 min and in 80 min for fluorine. The amount of adsorption per adsorbent unit increased by 53% for chromium and by 41% for fluorine. This study demonstrated that corn agricultural waste can be a good source for the production of silica and SBA-15 nanoparticles, which can also be effective as a cheap and useful way to eliminate water pollution.

Hypothesis: Proper dispersion of silica nanoparticles in epoxy resin leads to promising improvements in mechanical and thermal properties of nanocomposite. A comparative s‌tudy of dispersion between GPOSS-modified silica nanoparticles and neat silica nanoparticles shows a measure of GPOSS efficiency in dispersion of silica nanoparticles.Methods: Nanoparticle dispersion was inves‌tigated through polymer cumulative behavior such as rheological parameters and viscosity measurement. Using the ultrasonic technique, a pre-dispersed compound containing 20 %wt silica nanoparticles and GPOSS was firs‌t prepared. The pre-dispersed compound was then diluted to a final percentage of silica nanoparticles of 2, 5 and 10 %wt. An atomic force microscope (AFM) was also used to further inves‌tigate the dispersion of silica nanoparticles in the pre-dispersed compound.Findings: According to the rheometry tes‌t results, all samples with pre-dispersed compound showed lower viscosity than their corresponding counterparts. It seems that the GPOSS is able to lower the composition viscosity through minimizing interfacial interactions between silica nanoparticles as well as possible interactions between epoxy chains and silica nanoparticles. In comparison with the sample prepared without pre-dispersed compound, the viscosity of the composition containing 10% (wt) silica nanoparticles was dras‌tically reduced, i.e. from 246000 cP to 39000 cP. AFM surface images of the pre-dispersed compound represent the presence of particles with a s‌tatis‌tical accuracy of 95% in the range of 12 nm to 20 nm, proving that the silica nanoparticles are well dispersed in GPOSS. The interes‌ting finding of this s‌tudy was that a pre-dispersed compound of GPOSS and silica nanoparticles not only improves the dispersion of silica nanoparticles and hence the final mechanical properties, but also improves the easy use through reducing the viscosity of the epoxy-based composition.

Background and Aims: Poly methyl methacrylate (PMMA) is still the most commonly used material in prosthetic dentistry. However, there are problems with the mechanical properties of this type of material including low flexural strength. Addition of nanoparticles into the polymer is one way to improve the mechanical properties of acrylic resin. In the present study, the effect of silicon dioxide (SiO2) nanoparticles addition into the heat-cured acrylic resin in different concentrations was investigated. Because of the controversy had been observed in previous articles, the aim of this study was to investigate the mechanical properties of PMMA/SiO2 nanoparticle obtained from different percentages of SiO2. Materials and Methods: In this in-vitro study, acrylic resin specimens containing 0, 1, 3 and 5% silicon dioxide (SiO2) were prepared. The specimens were placed inside the gypsum molds and placed under pressure for three times. The mold cured in boiling water for 30 min. A trimmer was used to remove the additives. Sandpapers with 180, 320 and 600 grains of silicon-carbide were used for final finishing and polishing. Finally, the flexural strengths were measured using a universal testing machine. Data were finally analyzed by ANOVA and Tukey tests at a significant level of 5% using SPSS software. Results: The mean flexural strengths and standard deviations of control group, 1% filler, 3% filler, and 5% filler, were 57.24±8.30, 69.98±7.26, 60.16±9.18, and 61.59±9.28 MPa, respectively. After comparing significant values between each group with the control group, a significant difference was observed between the control and 1% filler group (P=0.021). However, no significant difference was observed between 3 and 5% fillers with the control group or each other. The significant differences (P-value) between 3% filler and control group were 0.892 and between 5% filler and control group was 0.975. Conclusion: The results of the present study showed that the use of low percentage of silicone dioxide (SiO2) nanofiller could improve the flexural strength of poly methyl methacrylate acrylic resin.

Background and Objective: With increasing water pollution, serious water shortages and increased pressure to save water, recycling and reuse of water has attracted more attention in various industries. Removal of silica from cooling water is essential for recycling and reuse of water. The aim of this study was to remove silica from water using magnesium oxide nanoparticles (MgO) synthesized by chemical deposition method. Materials and Methods: Synthetic nanoparticles were successfully determined using field emission scanning electron microscopy (FE-SEM), Fourier transform infrared (FTIR) and X-ray diffraction (XRD). To determine the optimal adsorption conditions the batch system, the effect of important parameters such as pH (2-8), contact time (0-150 min), initial concentration of silica solution (50-1000 mg/L), adsorbent amount (0.01-0.14 g) and temperature (25-60 ˚C) were studied. Results: Under optimal conditions, an almost removal of 200 mg/L silica solution was achieved in 60 min reaction time. Equilibrium data were analyzed using the Langmuir and Freundlich isotherms. The adsorption process can be well described by the Langmuir model, and the maximum adsorption capacity was calculated as 75.76 mg/g. Synthetic data were analyzed using pseudo-first-order and pseudo-second-order equations. The pseudo-second-order model showed good agreement with the obtained data (R² = 0.9949). Conclusion: Due to the high potential of magnesium oxide nanoparticles in silica removal, it can be a good candidate for the removal of silica and industrial wastewater treatment. [ABSTRACT FROM AUTHOR]

In this study, the effect of silica nanoparticles and heat treatment of beech (Fagus orientalis), walnut (Juglans regia) and spruce (Picea abies) woods on adhesion strength and drop contact angle of clear coating lacquer were studied. For this purpose, samples with 8% moisture and 200 × 100 × 20 mm dimension were prepared. The wood samples were heat treated in oven at different temperatures of 160 and 180 °C for 3 hours. After treatment, the surface of the specimens was finished using 120 and 180, sand papers. Transparent lacquer folders containing 0, 0.5, 1 and 1.5% silica nanoparticles were used to cover the samples. The results showed that heat treatment increased the drop contact angle and the adhesion strength of the coating and increased the temperature of the drop contact angle treatment and the adhesion strength as well. Thermal treatment at 180 °C with coating containing 1% nano and lowest drop contact angle was observed in control samples. Wood samples treated with walnut at 160 ° C and containing 1% nano coating had the highest adhesion resistance. The water uptake of treated wood samples decreased compared to the untreated samples in all three species and this trend continued with the increase of nanoparticles in the coating so that the walnut control samples had the highest water uptake at 180 °C. and 1% nano coatings were the lowest water absorption in spruce. [ABSTRACT FROM AUTHOR]

Mortar is suitable for utilizing in compressed parts such as columns and arches due to its considerable compressive strength. However, despite this advantage, the relatively low tensile strength and brittleness of the mortar limit its use for components that are under tensile loads. Using fibers and nano-particles can be a way to reduce these problems. In this research work, various fiber reinforced and nano-engineered cement mortars have been successfully prepared through the addition of nanosilica into plain and fiber reinforced mortars. In this way, effects of nano-SiO2 on the mechanical properties of cement mortars with polypropylene fibers and also without it have been evaluated. Polypropylene fibers were used in lengths of 6-18 mm and aspect ratios of 300-900. The effect of fibers in two different percentages of 0.1% and 0.2%, and the influence of nano-silica in various percentages of 1, 2, 3, 4 and 5% on mortars with a water-to-binder weight ratio of 0.485 were evaluated and compared. A total of 108 cubic mortar samples with a dimension of 5×5×5 cm3 and 108 rectangular cubic samples with a dimension of 16×4×4 cm3 were made according to ASTM standards, and compressive and flexural strength tests were carried out on samples at the ages of 7 and 28 days. The results of the experiments indicated a significant enhancement in the mechanical properties of the prepared mortars, as the values of 7-day and 28-day compressive strength of the sample containing 0.1% fiber and 3% nano-SiO2 were increased by 51% and 61%, respectively, compared to the control sample. Besides, the values of 7-day and 28-day flexural strength of the sample containing 0.2% fiber and 3% nano-SiO2 were increased by 48% and 55%, respectively, compared to the control sample. A noticeable increase in mechanical properties indicated the suitable performance of this type of mortar.

The membrane technology has experimentally and theoretically attracted much attention by researchers as a way to reduce the increasing emission of carbon dioxide to the atmosphere due to the high competitiveness in separation performance and economics. In this work, the modified Maxwell model and modified Lewis-Nielsen model are developed to predict the experimental gas separation performance of polyimide/silica nanoparticles and polysulfone/silica nanoparticles mixed matrix membranes. The developed modified models consider the crucial role of interfacial voids between inorganic nanoparticles and the polymer matrix. The prediction accuracy of developed models is evaluated and compared with that of conventional models such as the Maxwell model, Bruggeman model, Lewis-Nielsen model and Pal model. The modified Maxwell model, developed in this work, considering the role of interfacial voids, can accurately predict the experimental gas permeability data of MMMs with error values lower than 6%. However, the error is obtained around 30% for conventional models. [ABSTRACT FROM AUTHOR]

In this research, mathematical modeling for the absorption process of carbon dioxide and hydrogen sulfide gases using silica-water nanofluid has been performed in a packed bed column. A laboratory apparatus consisting of two towers packed with plastic Raschig rings was prepared for the absorption and desorption process. Experimental tests were performed for three flow rates of 3, 7 and 15 LPM for gas and 0.35, 0.50 and 1 LPM for liquid and the molar fraction of CO2 and H2S in two phases of gas and the liquid are measured. The modeling of the process was done using the overall and partial mass balance equations. Comparison of the obtained model results with the experimental results shows a close correlation between the experimental data and the model and the average relative error was about 10%. Using the obtained model, the component concentration, transferred molar flux and mass flux for liquid and gas are plotted along the column. The results show that with increasing the gas flow rate, both the rate of mass transfer and the slope of the molar fraction gas components were increased. On the other hand, the mass transfer flux in higher gas flow rates achieved to more than twofold. Also, the mass transfer of carbon dioxide was higher than that of hydrogen sulfide, which is due to the higher concentration of carbon dioxide in the inlet gas. [ABSTRACT FROM AUTHOR]

Hypothesis: In recent years, with the shortage of conventional energy resources, there has been a great advancement in the study of fuel cells particularly hydrogen-methanol types as an important energy alternative. One of the main components in such fuel cells is an electrolyte membrane whose main function is to carry protons and capture methanol. The electrolyte membrane must have a high chemical and electrochemical stability plus mechanical resistance. In addition, high proton conductivity is required to support better fuel cell performance.Methods: In this research, novel nanocomposite membranes were prepared as electrolyte for application in fuel cells. For this purpose, two types of membranes, including sulfonated polyethersulfone (SPES) and its blend with polyurethane (PU), were chosen as base membranes. At first, polyethersulfone was sulfonated by using sulfonic acid and blended with PU. Then, silica nanoparticles with different percentages (3, 5, and 8 wt%) were added to blend membrane (SPES/PU/SiO2). The prepared membranes properties were studied by Fourier transform spectroscopy (FT-IR), X-ray diffraction analysis, thermogravimetry (TGA), water and methanol uptake test, proton conductivity test and scanning electron microscopy (SEM).Findings: The results suggested that there was a proper distribution of PU into the prepared membrane through forming hydrogen bonds between polar groups of SEPS and PU. Hence, by the mechanism of increasing polarity, the conductivity in SPES/PU blend membrane was increased (74%), comparing to its pure samples without intense increase in water and ethanol uptake. Additionally, by adding the silica nanoparticles to a SEPS/PU blend membrane and forming SPES/PU/SiO2 nanocomposite membrane, these particles formed a higher adhesion between the phases by forming covalent bonds with sulfonic acid groups of SPES and forming hydrogen bond with polar groups of PU and SPES. As a result, the morphology was modified by the mechanism of decreasing cavities and voidages. Finally, the conductivity of SPEC/PU/SiO2 nanocomposite membrane compared to that of the SPES pure sample increased by 53.13% only by an increase of 11% and 8% in water and methanol uptake, respectively.

Background and Aims: Poly methyl methacrylate (PMMA) is still the most commonly used material in prosthetic dentistry. However, there are problems with the mechanical properties of this type of material including low flexural strength. Addition of nanoparticles into the polymer is one way to improve the mechanical properties of acrylic resin. In the present study, the effect of silicon dioxide (SiO2) nanoparticles addition into the heat-cured acrylic resin in different concentrations was investigated. Because of the controversy had been observed in previous articles, the aim of this study was to investigate the mechanical properties of PMMA/SiO2 nanoparticle obtained from different percentages of SiO2. Materials and Methods: In this in-vitro study, acrylic resin specimens containing 0, 1, 3 and 5% silicon dioxide (SiO2) were prepared. The specimens were placed inside the gypsum molds and placed under pressure for three times. The mold cured in boiling water for 30 min. A trimmer was used to remove the additives. Sandpapers with 180, 320 and 600 grains of silicon-carbide were used for final finishing and polishing. Finally, the flexural strengths were measured using a universal testing machine. Data were finally analyzed by ANOVA and Tukey tests at a significant level of 5% using SPSS software. Results: The mean flexural strengths and standard deviations of control group, 1% filler, 3% filler, and 5% filler, were 57.24±8.30, 69.98±7.26, 60.16±9.18, and 61.59±9.28 MPa, respectively. After comparing significant values between each group with the control group, a significant difference was observed between the control and 1% filler group (P=0.021). However, no significant difference was observed between 3 and 5% fillers with the control group or each other. The significant differences (P-value) between 3% filler and control group were 0.892 and between 5% filler and control group was 0.975. Conclusion: The results of the present study showed that the use of low percentage of silicone dioxide (SiO2) nanofiller could improve the flexural strength of poly methyl methacrylate acrylic resin. [ABSTRACT FROM AUTHOR]

Hypothesis: Gas-liquid membrane contactors have been considered as one of the potential alternatives for CO2 removal compared to conventional technologies. However, membranes wetting with liquid absorbents during this process limits membrane contactors application, which indicates the need for the use of hydrophobic membranes in these systems. In recent years, the use of nanoparticles to increase the hydrophobicity of polymer membrane surfaces and fabrication of nanocomposite membranes has been considerably investigated by researchers.Methods: In order to reduce the wetting problem of membranes, in the present work, methyl grafted silica nanoparticles (CH3SiO2 NPs) were used to increase surface hydrophobicity of the polypropylene (PP) hollow fiber membranes, which were synthesized by the sol-gel method. Prepared membranes were characterized by ATR-FTIR, XRD, FE-SEM, contact angle, mechanical strength and breakthrough pressure. Findings: The obtained results from ATR-FTIR analysis confirmed the presence of methyl grafted silica NPs on the surface of PP membrane. The results of the contact angle measurement showed that for nanocomposite membranes by increasing the MTES/TEOS molar ratio from 1 to 4, the contact angle increased from 125° to 164°; however, the contact angle decreased with further increase in the molar ratio of MTES/TEOS. Also, with the precision in the results of mechanical strength measurement, it can be seen that the synthesis of NPs on the membrane surface as well as in the cross-section increased the tensile strength of the membrane to 12.8 MPa. Finally, the performance of membranes was investigated in the membrane contactors for CO2 absorption, which results in a significant decrease in the flux for pure membranes compared with nanocomposite membranes.

Cancer is one of the main causes of death worldwide. Chemotherapy is the most common method for cancer therapy which represent non-specific side effects on normal cells and tissues and drug resistance in cancer cells. There are two main mechanisms for Multi Drug Resistance (MDR) in cancer cells including: drug efflux pump and activation of anti-apoptotic pathways. Cancer chemotherapy disadvantages can be overcome by using nanoparticulate drug delivery systems like Mesoporous Silica Nanoparticles (MSNs) that have been used as drug delivery system since 2001. The present review included synthesis, targeted (active or passive) drug delivery to cancer cells, co-delivery of anticancer drugs and siRNA by MSNs and its toxicity. This review revealed that MSNs are good candidate for drug delivery to cancer cells due to its unique properties including: controllable pore and particle sizes, thermal and chemical stability, modifications of outer and inner surfaces of nanoparticles for drug and siRNA loading, attachment of ligand for targeted drug delivery, high drug loading capacity and controlled drug release, biocompatibility and biodegradation in aqueous medium. [ABSTRACT FROM AUTHOR]

Solar pond is the one of the important ways for collecting and storing solar energy in the world. The salinity gradient solar ponds included the three layers of water-salt with different densities. In this study, the effect of the silica nanoparticles in the middle layer of the salt gradient solar pond was investigated for four different solar radiation zones in Iran. The nanoparticles volume concentrations, which were used in this study, were 1, 2, 5 and 10%. The results showed that nanoparticles improved solar pond efficiency and it increased with nanoparticles concentration. The temperature of the lower layer and efficiency of solar pond increased by 10% and 18 %, respectively. The nanoparticles were more efficient at cold zone.

In this study, silica nanoparticles (SNPs) were prepared by sol-gel technique. Chlorpyrifos (40.8% EC) was loaded on the SNPs by immersion loading method. The Specific surface area (SBET) of nanosilica was characterized by BET and recorded 102.24 m2/g. Loading efficiency of chlorpyrifos-loaded in silica nanoparticles (Ch-SNPs) was measured 86.79% using UV-VIS spectrophotometer. According to FT-IR results, chlorpyrifos properties remained intact after loading on nanosilica because of physical adsorption process of the insecticide in the pores. The residual toxicity of Ch-SNPs was assessed against two stored product insect species, Rhyzopertha dominica F. and Tribolium confusum Jacquelin du Val. on Petri dish, galvanized steel, mosaic and concrete surfaces. Residual toxicity was evaluated 7, 15, 30, 45 and 60-day post treatment. For each post treatment, the mortality was counted after 6, 24, 48 and 72 h of exposure. The mortality increased with increasing concentration of insecticide and time exposed to each concentration. According to the results, the Ch-SNP was effective against the both pest species, but the toxicity varied depending on the surface material. Ch-SNPs provided long-term protection on petri dishes against the pests, whilst concrete followed by mosaic surfaces with less protection. For instance, R. dominica mortality percentage after 24 h exposure to Petri dish, galvanized steel, mosaic and concrete treated with 0.2 mg cm-2 Ch-SNPwas 100, 82.8, 40 and 1.4%, whereas the mortality was 100, 97.1, 20 and 18.5 % for T. confusum at 60-day post-treatment, respectively.

An epoxy resin was modified by silica nanoparticles and cured with an anhydride. The particles with different batches of 12, 20, and 40 nm sizes were each distributed into the epoxy resin ultrasonically. Electron microscopy images showed that the silica particles were well dispersed throughout the resin. Tensile test results showed that Young’s modulus and tensile strength increased with the volume fraction and surface area of the silica particles. The simultaneous use of two average sizes of 20 and 40 nm diameter silica particles still increased these mechanical properties but other combinations of silica particles were unsuccessful. A three-point bending test on each pre-cracked specimen was performed to measure the mode I fracture toughness energy. The fracture energy increased from 283 J/m2 for the unmodified epoxy to about 740 J/m2 for the epoxy with 4.5 wt% of 12 nm diameter silica nanoparticles. The fracture energy of smaller particles was greater because of their higher surface to volume ratio. The fracture energy results showed also that the combined nanoparticles has a synergic effect on the fracture toughness of nanocomposites. Simultaneous use of 10 and 20 nm particles increased the fracture energy to about 770 J/m2. Finally, crack-opening displacement was calculated and found to be in the range of several micrometers which was much larger than the sizes of particles studied. Thus, the toughening mechanisms of crack pinning and crack deflection have a negligible effect on improvement of toughness, nevertheless, the plastic deformation and plastic void growth are dominant mechanisms in epoxy toughening by nanoparticles.

Because most contaminants in water create strong interactions with hydrophobic surfaces, there are usually problems such as flux decline and pore blocking in polyethylene (PE) membranes due to irreversible adsorption of foulants on their intrinsic hydrophobic surface. Therefore, in this work, attempts were made to improve the properties of PE membranes in terms of water flux and membrane fouling resistance by dispersion of silica nanoparticles (NPs). First, NPs were synthesized by sol-gel method at two concentrations of ammonia (0.5 and 1 mol/L). The synthesized NPs with smaller size were used to fabricate the mixed matrix PE membranes containing 0, 0.5, 1 and 2 wt% NPs. FE-SEM and EDX analyses were employed to evaluate the morphology and structure of the fabricated membranes and confirmed the presence of NPs in the membranes matrix. The results of pure water flux test revealed that the membrane containing 1 wt% NPs displayed the maximum flux of 30 L/m2.h. Furthermore, the performance and fouling behaviors of membranes during filtration of humic acid solution, one of the most important contaminants of water resources, were studied using a classical fouling model. Fouling mechanism analysis showed that for neat and NPs-embedded membranes containing 0.5 and 2 wt% NPs, the best fit of the data was obtained by cake layer formation as well as the intermediate blocking mechanisms. However, the best fit of the experimental data of NPs-embedded membrane containing 1 wt% occurred with only cake layer formation mechanism. The investigation on membrane fouling resistance showed that 1 wt% NPs-embedded membrane displayed 58% maximum flux recovery and 52% reversibility to total fouling ratio, respectively.

Background and aims: Silica oxide nanoparticles (SiO2-NPs) have attracted a great interest in biotechnology and medicinal fields. It has been documented SiO2-NPs can induce cytotoxicity in normal cells. However, until now, the cytotoxicity of SiO2-NPs against nervous system cells did not examine. Methods: In this in vitro study, the activities of caspase-8 and 6 were analyzed in the PC12 cells treated with different concentrations of silica oxide nanoparticles, and was assessed by Elisa plate reader. Data were analyzed using SPSS software, and by One-way ANOVA and Student t-test. Results: The results showed that the caspase-8 and 6 activities increased in a concentration dependent manner. Indeed, the activity of caspase-8 and 6 was induced after exposure to 1-100 μM of SiO2-NPs. However, the SiO2-NPs showed only slight toxicity in the concentration of 0.1 μM (P<0.05). Conclusion: A mitochondrial-dependent pathway activated by caspase-8 and 6 mediated by SiO2-NPs may be involved in apoptosis induced by NPs, and therefore, cell cytotoxicity plays a role in PC12 cells. [ABSTRACT FROM AUTHOR]

Silica nanoparticles were modified with titanium tetraisopropoxide (TTIP) via atwo-step sol-gel route. The modified silica nanoparticles were characterized using FTIR spectroscopy, thermal gravimetric analysis (TGA) and EDAX elemental analysis. Photocatalytic activity of the modified nanocomposites was evaluated by photo-activated degradation of Rhodamine B (Rh.B) dyestuff, as a colorant model, in distilled water. Reduction in Rh.B concentration in aqueous solution was evaluated by UV-visible spectroscopy and with the aid of visual observations. The FTIR spectroscopy results confirmed the formation of Ti-O-Si chemical bond on the surfaceof silica nanoparticles. TGA test results showed that the weight loss of the modified sample is due to deterioration of the alkoxy groups of the SiO2 surface. According to the results of EDAX elemental analysis, the presence of carbon and titanium in the structure of the modified samples and also reduction in oxygen levels are attributed to the chemical interactions due to surface chemical modification. Carbon detection in the composition can be attributed to the presence of isopropoxide in titanium tetraisopropoxide compound. The results also revealed that, with TiO2 grafting on the silica nanoparticles surface, absorption in UV region is increased and that the silica nanoparticles modified with titanate compound show photocatalytic characteristics and degradation ability of Rh.B dyestuff under UV light irradiation. It became also evident that the photocatalytic activity of the modified nanoparticles is less than TiO2 nanoparticles. However, by inclusion of modified silica nanoparticles into the polymeric coating, the photocatalytic properties of the coating can be established. Although modified silica nanoparticles have less photocatalytic activity compared to TiO2 nanoparticles, but they cause less damage to the polymer matrix.

The aim of the present study is to study the effects of adding diopside (CaMgSi2O6) as well as silica sulfuric acid nanoparticles to ceramic part of glass ionomer cement (GIC) in order to improve its mechanical properties. To do this, firstly, diopside (DIO) nanoparticles with chemical formula of CaMgSi2O6 were synthesized using sol-gel process and then, the structural and morphological properties of synthesized diopside nanoparticles were investigated. The results of scanning electron microscopy (SEM) and particle size analyzing (PSA) confirmed that synthesized diopside are nanoparticles and agglomerated. Besides, the result of X-ray diffraction (XRD) analyses approved the purity of diopside nanoparticles compounds. Silica sulfuric acid (SSA) nanoparticles are also prepared by chemical modification of silica nanoparticles by means of chlorosulfonic acid. Fourier transform infrared spectroscopy (FTIR) technique was used to find about the presence of the (SO3H) groups on the surface of silica sulfuric acid nanoparticles. Furthermore, various amounts (0.1, 3 and 5 wt.%) of diopside and silica sulfuric acid nanoparticles were added to the ceramic part of GIC (Fuji II GIC commercial type) to produce glass ionomer cement nanocomposites. The mechanical properties of the produced nanocomposites were measured using the compressive strength, three-point flexural strength and diametral tensile strength methods. Fourier transform infrared spectroscopy technique confirmed the presence of the (SO3H) groups on the surface of silica nanoparticles. The compressive strength, three-point flexural strength and diametral tensile strength were 42.5, 15.4 and 6 MPa, respectively, without addition. Although adding 1% silica solfonic acid improved nanocomposite mchanical properties by almost 122%, but maximum increase in nanocomposite mechanical properties was observed in the nanocomposites with 3% diposid, in which 160% increase was seen in the mechanical properties. [ABSTRACT FROM AUTHOR]

In this research, effect of adding silica nano-particles on the mode II interlaminar fracture toughness of epoxy matrix composites reinforced with glass fibers was experimentally studied. Hand lay-up method has been used to manufacture nanocomposites withl8 layers of 2D woven glass fibers with 40% fiber volume fraction. The nano-epoxy resin system is made of diglycidyl ether of bisphenol A (epon 828) resin with jeffamine D400 as the curing agent. Nanosilica particles are dispersed with 0, 0.5, 1 and 3 wt.% (of epoxy resin) to study the effect of nanosilica content on fracture toughness. Also, a series of nanocomposites with 1 wt.% nanosilica content and containing 55 vol.% glass fibers were fabricated to investigate the effect of fiber volume fraction on results. End notch flexure (ENF) test was adopted for the measurement of mode II interlaminar fracture toughness. The results show that high loading of nanosilica has no significant effect on the interlaminar fracture toughness of nanocomposites while the addition of 0.5 wt% nanosilica enhanced the interlaminar fracture toughness about 36% compared to the neat composites. Decreasing fiber volume fraction improved interlaminar fracture energy. [ABSTRACT FROM AUTHOR]

In this study, a three-dimensional micromechanics-based analytical model is developed to study the effects of regular and random distribution of silica nanoparticles on the thermo-elastic and viscoelastic properties of polymer nanocomposites. The Representative Volume Element (RVE) of nanocomposites consists of three phases including silica nanoparticles, polyimide matrix and interphase. Since the polymer in the vicinity of the nanoparticles shows distinct properties from those of the bulk matrix, due to nanoparticle--polymer matrix interactions this region as interphase is considered in micromechanical modeling with specific thickness and properties. In order to simulate random distribution of silica nanoparticles into polyimide matrix, the RVE is extended to cxrxh cubic nano-cells in three dimensions. Perfect bonding conditions are applied between the constituents of RVE. It is assumed that all three phases of the RVE are homogeneous and isotropic to obtain the thermo-elastic response of nanocomposite. The extracted thermo-elastic properties by the micromechanical model with random distribution of silica nanoparticles are closer to the experimental data. To predict the effective viscoelastic properties of the nanocomposites, silica nanoparticles are modeled as a linear elastic material, while polyimide matrix and interphase are assumed to be as a linear viscoelastic material. The model is also used to examine the influence of varying interphase properties and silica nanoparticle size on the effective nanocomposite behavior. The overall creep behavior of the nanocomposite for several stress levels is also presented. [ABSTRACT FROM AUTHOR]