sio2

In this research, core-shell SiO2/SnO2, SnO2/SiO2 composite nanofibers, and SnO2 nanofibers were synthesized by electrospinning method and were calcined in an electric furnace at temperature of 500 degrees Celsius for 2 hours. Photocatalytic degradation ability of synthesized nanofibers was studied on Crystal violet, methylene blue and methyl orange dyes under ultraviolet light. Structural characteristics of core-shell SnO2/SiO2 nanofibers, SiO2/SnO2 and SnO2 nanofibers were investigated using field emission scanning electron microscope (FESEM), transmission electron microscope (TEM), X-ray diffraction spectroscopy (XRD), and Fourier transform infrared spectroscopy (FT-IR), energy diffraction X-ray spectroscopy (EDX) and Xmap analysis. TEM images clearly show the core-shell structure of SiO2/SnO2 and SnO2/SiO2 nanofibers with an average diameter of 550 nm. XRD analysis shows the amorphous structure of nanofibers before thermal treatment and the formation of the dominant crystalline phase after thermal treatment. Uniform distribution of elements was observed by Xmap analysis. The comparison of photocatalytic decomposition of methylene blue, methyl orange and crystal violet dyes in the presence of SnO2 single layer nanofibers, core-shell SnO2/SiO2 nanofibers and SiO2/SnO2 shows that core-shell SiO2/SnO2 nanofibers with 40.58 percent decomposition in methylene blue, 44/44 in methyl orange and 12/31 in crystal violet had the most effect in destroying colors.

In this research Cr2O3-SiO2 and Cr2O3-TiO2 green pigments have been fabricated using a mixture of Cr2O3-SiO2 and Cr2O3-TiO2 powder by ceramic method. The samples have been homogenized using planetary mill in a solvent with a ratio of 1:4 for 5 h and then printed on the ceramic using screen printing method and heated in the industrial condition. The crystal structure of samples, the shape and the size of the particles and their optical properties have been characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and UV-Vis spectroscopy and CIE L*a*b* colorimetric methods. The XRD results show two-phase structure has been created in both samples. The average of crystallite size for Cr2O3-SiO2 and Cr2O3-TiO2 were measured 40 and 34 nanometers, respectively. The SEM images show that the average size of Cr2O3-SiO2 and Cr2O3-TiO2 are 290 and 143 nanometers, respectively. The physical properties of printed ceramic were investigated by SEM and colorimetric methods. The average particle size for printed samples, Cr2O3-SiO2 and Cr2O3-TiO2, on the ceramic were measured 131 and 106 nm respectively.

In this study, an appropriate coating was prepared by increasing ultraviolet reflectance of cotton-nylon 66 fabric for camouflage of military targets in the snowy areas. For this purpose, first several highly UV reflective compounds such as BaSO4, SiO2 and Polytetrafluoroethylene (PTFE) were applied on the fabric by using citric acid and sodium hypophosphite (SHP) and then grafted by heat treatment. The effects of the effective parameters including type and amount of compounds, amount of citric acid and SHP and temperature of heat treatment were investigated. Reflectance behavior and surface morphology of the fabric were studied by UV-Vis reflectance spectroscope and SEM, respectively. Results indicated that UV and visible reflectance increases up to 85% with applying of BaSO4 particles on the fabric. Thus a suitable fabric coating has been achieved for camouflage in the snowy areas. Excellent rubbing and washing durability of grafted BaSO4 particles on the fabric demonstrated that these particles have been attached on the fibers of the fabric with chemical bands, especially on the cotton fibers. Moreover, the used method in this study does not have any significant effect on the cotton and nylon 66 fibers structure. Parameters such as citric acid and SHP concentration and heat treatment temperature have an optimum amount and thus, using them more than this amount leads to decreasing UV and visible reflectance of applied fabric.

In this report، various compositions were selected based on wollastonite in CaO-SiO2-MgO system. XRD analysis revealed that wollastonite was the main crystalline phase in the sintered glass-ceramics. Sinterability and crystallization of glass ceramics were analyzed at various temperatures. 830 oC، was selected as the optimum sinterability temperature. Finally dielectric properties of glass-ceramic samples at 830 oC، in 12-8 GHz frequency were reported. Dielectric constant and dielectric loss of glass ceramics are 6. 7-7. 5 and 0. 0028-0. 0034 respectively.

In this paper، the microstructural characteristics of ternary ceramic powders Al2O3-SiO2-ZnO system prepared by sol-gel method، in order to increase surface area of ZnO nanocrystals supported on silica-alumina matrix، have been studied. Values of 20، 50 and 70 weight percents of zinc oxide with an equal weight ratio of SiO2-Al2O3، using simultaneous reaction of zinc nitrate (Zn(NO3) 2. 6H2O)، tetraethyl orthosilicate، (TEOS) and aluminum nitrate (Al(NO3) 3. 9H2O) were synthesized. The nanostructure of prepared composites were characterized by X-ray diffraction، SEM/EDS and BET studies. The results showed that crystaline phase zinc oxide has been formed in amorphous silica-alumina matrix، which led to reducing zinc oxide particles size، preventaing of aglomeration and increasing specific surface.

The traditional picture of the interfacial transition zone (ITZ) in concrete involves an approximately 30 μm zone around each aggregate, within which the porosity increases as the aggregate interface is approached. The ITZ microcracks in concrete will grows to visible cracks, thus they are very important to be studied. Effect of nano-SiO2 on cracks width in ITZ was studied in this research. For investigation of crack width, SE signals of SEM were used. The samples were cut from edges and middle of 5×5×5 cm cubic specimens. It was seen that nano-SiO2 could less the crack width. It is for the first time that SE use for ITZ imaging. Finally it was shown that adding nano-SiO2 could reduce the width of ITZ cracks.

In this paper, effect of particle concentration on the erosion -corrosion behavior of AISI 420 stainless steel was investigated. Erosion-corrosion tests were conducted using an impingement jet apparatus containing a solution of 3.5% NaCl and 30, 60 and 90 g /lit of SiO2 particles and weight loss of samples were measured. Tafel polarization test was carried out to study the static corrosion behavior of steel samples. Scanning electron microscope was used to study the synergy between erosion and corrosion of th e alloy. The results showed that by increasing the sand concentration from 30 to 90 g/lit, erosion and erosion corrosion rates increased 73 and 153%, respectively. The results also showed that the increase of sand concentration the synergy rate between erosion and corrosion also increased.