saeid baghshahi

The power line insulators are permanently exposed to various environmental pollutants such as dust and fine particles. This may lead to flashovers and therefore widespread power blackouts and heavy economic damage. One way to overcome this problem is to make the insulator surface superhydrophobic. In this research, the superhydrophobic properties of the insulators were improved by applying room-temperature cured composite coatings consisting of epoxy and hydrophobic nano-silica particles. Either octadecyl trichlorosilane (ODTS) or hexamethyldisilazane (HMDS) was used to coat the silica nanoparticles and make them hydrophobic. Then, the hydrophobic silica was added to a mixture of epoxy resin and hardener. The suspension was applied on the surfaces of a commercial porcelain insulator and cold cured at ambient temperature. The coating increased the water contact angle from 50° to 149°. Even after 244 h exposure to the UV light, the samples preserved their hydrophobic properties. The adhesion of the coating was rated as 4B according to the ASTM D3359 standard. The coating decreased the leakage current by 40% and increased the breakdown voltage by 86% compared to the uncoated sample and showed promise for making power line insulators self-cleaning.

In this study, a CIGS solar cell with a Mo/Cu(In0.7Ga0.3)Se2(CIGS)/CdS/ZnO/Al-doped ZnO (AZO) structure was simulated by Atlas silvaco-TCAD software. The photovoltaic characteristics of solar cells using CdS and ZnSe buffer layers were calculated and compared. Then, the photovoltaic characteristics were examined with different thicknesses of the ZnSe buffer layer. The 25 nm thickness was selected as the optimum thickness. After optimization of the ZnSe layer thickness, the photovoltaic characteristics of solar cells were evaluated by changing the conduction band offset (CBO). The highest CIGS solar cell conversion efficiency was obtained in the range from -0.5 eV to +0.5 eV for CBO. Finally, graphene was replaced with Al-doped ZnO (AZO) due to its high optical transparency, high carrier mobility, and proper mechanical properties. Graphene was used as a monolayer and multilayer as a transparent conductive oxide (TCO) layer. Simulations predicted the highest efficiency for solar cell structure based on Mo/CIGS/ZnSe/i-ZnO/monolayer graphene and the photovoltaic parameters were Jsc=38.64 mA/cm2, Voc=0.67 V, FF=79.33% and η=20.71%.

Transparent conductive oxides have recently been used in solar cells. Hence, transparent conductive oxide, especially SnO2:F (FTO) is considered promising by researchers for solar cell applications due to its inexpensive and efficiency. In the current research, a sol-gel combustion technique was used to prepare fluorine-doped tin dioxide (FTO) powder. Stannous chloride pentahydrate, ammonium fluoride, and citric acid as fuel were used with various ratios of fuel to salt and different pH values. The structure, morphology, and composition of the synthesized powders were characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), and X-ray photoelectron spectroscopy (XPS). The results revealed that the average particle size increased from 125 nm to 300 nm with morphological transformation as the pH value increased from 1 to 6, respectively and the average particle size decreased from 125 nm to 50 nm with round morphology as the fuel to salt ratio decreased from 2 to 1. The presence of fluorine additive in the optimal sample with 50 nm particle size was determined by XPS and it can be a suitable candidate for use in solar cells.

By controlling the synthesis conditions, hematite particles with different geometric shapes and different optical and magnetic properties can be obtained. In this study, due to its high potential for the synthesis of a wide range of particles with different shapes and sizes, the hydrothermal method was used for the synthesis of hematite. Iron (III) hexahydrate, ethanol, sodium acetate, and polyethylene glycol were used as raw materials. In this study, without using common organic solvents and in contrast with most previous researches that focused on the magnetic properties of hematite, Samples were synthesized at 180 and 250 °C and pHs 5, 7, and 11. The phase composition, particle shape, and optical properties of the particles were investigated by XRD, SEM, FTIR, and DRS methods. Hematite particles synthesized at the temperature of 180 °C at pHs 5, 7, and 11 had particle dimensions 293.47, 95.41, and 83.95 nm and at the temperature of 250 °C at pHs 5, 7, and 11 had particle dimensions 88.29, 73.79, and 59.33 nm respectively. As the pH increased, due to the smaller particle size and thus more light absorption, the color of the hematite powder darkened. By using XRD analysis and Scherer equation, it was found that the pH of the process did not affect the size of the unit cells, and the average size of the unit cells at both synthesis temperatures was 27.8 nm. However, the SEM images showed that by increasing pH the hematite particles became more spherical and smaller.

The goal of the present study is to prepare a room temperature cured hydrophobic and self-cleaning nano-coating for power line insulators. As a result, the installed insulators operating in power lines can be coated without being removed from the circuit and without the need to cut off power. For this purpose, hydrophobic silica nanoparticles were synthesized by sol-gel method using TEOS and HMDS. The synthesized hydrophobic silica nanoparticles were characterized by XRD, FTIR, SEM, and TEM analyses to investigate phase formation, particle size, and morphology. Then the surface of the insulator was cleaned and sprayed by Ultimeg binder solution, an air-dried insulating coating, as the base coating. Then the hydrophobic nano-silica powder was sprayed on the binder coated surface and left to be air-cured at room temperature. After drying the coating, the contact angle was measured to be 149o. Pull-off test was used to check the adhesion strength of the hydrophobic coating to the base insulator. To evaluate the effect of environmental factors, UV resistance and fog-salt corrosion tests were conducted. The results showed that 150 hours of UV radiation, equivalent to 9 months of placing the samples in normal conditions, did not have any significant effect on reducing the hydrophobicity of the applied coatings.

In this research, zinc oxide quantum dots and graphene nanocomposites were synthesized via two different methods; In the first (direct) method, ZnO-graphene Nanocomposites were made mixing the synthesized zinc oxide and graphene. In the second (indirect) method, zinc nitrate, graphene, and sodium hydroxide were used to made ZnO-graphene Nanocomposites. XRD, FTIR and Raman spectroscopy analyses were used for phase and structural evaluations. The morphology of the nanocomposites w::as char::acterized by SEM. The specific surface area and porosity of the samples were characterized by BET analysis. The optical properties of the samples were investigated by photoluminescence and ultraviolet-visible spectroscopy analyses. Results showed that using graphene, increased the photoluminescence property and shifted the photoluminescence spectrum of the composites towards the visible light spectrum. The photoluminescence of the synthesized graphene-zinc oxide composite, in the visible light region, was closer to white light than that of pure zinc oxide. According to the results of BET test, the nanocomposite synthesized by direct method had a higher surface area (25.7 m2.g-1) and a higher porosity (0.32 cm3.g-1) than the nanocomposite synthesized by the indirect method with a specific surface area of (16.5 m2.g-1) and a porosity of 0.23 cm3.g-1).

Cu-substituted 58S bioactive glasses (0-10%mol CuO) were synthesized by sol-gel method and the effect of copper substitution for calcium on their biodegradability, bone-like apatite formation, cell proliferation, alkaline phosphatase activity of M3T3-E1 osteoblast cells and antibacterial efficiency were investigated. The results of x-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR) and surface analysis using SEM confirmed the formation of a layer of bone-like apatite on the BGs after 7 days of immersion in SBF. The surface analysis with SEM indicated that the addition of copper to the structure led to a reduction of the amount of apatite formed on the surface. The evaluation of cellular response by MTT assay and alkaline phosphatase activity showed that the proliferation and differentiation of MC3T3-E1 cells in 58S BG substituted with 5 mol% CuO had the highest value compared to other samples while, the substitution of 10 mol% CuO in composition led to a reduction in cell proliferation and differentiation and induction of cell cytotoxicity. In addition, Cu-substituted glasses showed significant antibacterial effect against Escherchia coli (E.coli) and Staphylococcus aureus (S.aureus) bacteria so that the antibacterial activity coefficient against E.coli in 58S containing 5 mol% CuO has doubled compared to base glass and was more than 99% (p<0.01). Taken together, 58S glass containing 5% mol CuO has been recommended for use in repair of bone defects in tissue engineering due to its in vitro bioactivity, stimulation of MC3T3-E1 cell proliferation and differentiation and excellent antibacterial activity.

Porous nanostructured SnO2 with a sheet-like morphology was synthesized through a simple green substrate-free gelatin-assisted calcination process using Tin tetracholoride pentahydrate as the SnO2 precursor and porcine gelatin as the template. Crystalline phase, morphology, microstructure, and optical characteristics of the as-prepared material were also investigated at different calcination temperatures using X-ray diffraction (XRD), Field emission scanning electron microscopy (FESEM), UV-visible absorption, and Photoluminescence spectroscopy (PL), respectively. XRD patterns of all the samples revealed the presence of a tetragonal crystalline structure with no other crystalline phases. Moreover, the synthesized hierarchical sheets assembled with nanoparticles displayed a large surface area and porous nanostructure. The calculated optical band gap energy varied from 2.62 to 2.87 eV depending on the calcination temperature. Finally, photoluminescence spectra indicated that the nanostructured SnO2 could exhibit an intensive UV-violet luminescence emission at 396 nm, with shoulders at 374, violet emission peaks at 405 and 414 nm, blue-green emission peak at 486 nm, green emission peak at 534 nm and orange emission peak at 628 nm.

Traditional photovoltaic devices for replacing fossil fuels have problems, including high construction and installation costs. Hence, there is now more focus on the new generation of solar cells, including solar tiles with higher efficiency and lower const. Due to the emergence of nanolayers and the extensive advances in the selection of raw materials and devices for the application of this type of layers, in the present study, the preparation and achievement of optimal conditions for the main layer of solar tile has been considered. The best sample containing adsorbent layer film ink was obtained from CZTS and was made by solothermal method at 550 ºC. Using X-ray diffraction (XRD) and Raman spectroscopy analysis, phase studies of the synthesized samples as well as the identification of functional groups in the compounds were performed. Field emission scanning electron microscopy (FESEM) was used to study the surface morphology and the microstructure of the prepared inks. A UV-Vis spectrophotometer was used to analyze the ultraviolet-visible absorption spectrum. XRD analysis showed the formation of pure cassiterite as well as the presence of secondary phases of CZTS in some samples. and the results were confirmed by Raman spectroscopy. In the studies, the sample synthesized at 550 ºC with crystalline structure of cassiterite with suitable peak intensities was selected as the most suitable sample. FESEM microscopy showed that all samples of CZTS nanoparticles had a petal-like shape and with increasing temperature the petals bended. Finally the best conditions for the homogeneity of the morphological particles of the sample were observed at 550 ºC. Also, based on the results of the EDS, the sample with the highest weight percentage of copper and the lowest weight percentage of sulfur had priority in terms of application in solar cell structures, such characteristics were observed in the sample synthesized at 550 ºC. UV-Vis results showed that the optical cleavage band of CZTS nanoparticles in the best sample was 1.49 eV. In general, the results of the studies in this work showed the appropriateness of the solothermal synthesis method and also the effect of temperature on the final characteristics of the thin film, including the type of structure, morphology, transmition and energy bandgap.

Soft ferrites are magnetic materials with a spinel structure that have prominent properties such as high electrical resistance, low hysteresis losses, and high permeability, making them suitable for use in catalysts. In this study, ternary CuNiF and CoMnF ferrite nanoparticles were synthesized by sol-gel autocombustion method using glycine, urea and citric acid as fuels. Moreover, ammonium perchlorate (AP) nanoparticles were prepared by adding dissolved ammonium perchlorate to Hydroxyl-terminated polybutadiene (HTPB), homogenization and solvent distillation. Then, the powder nanomaterials were characterized by Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM), techniques. The average particle size of CuNiF and CoMnF ferrite nanoparticles and ammonium perchlorate nanoparticles were calculated 22.15, 34.12 and 68.2 nm, respectively. The catalytic effect of the synthesized ferrite nanoparticles on the thermal decomposition of nano-AP was investigated by TGA and DTG methods. Also, activation energy was calculated using DSC with three different heating rates by Kissinger equation.

In this paper, the rheological behavior of SiC suspensions, fabricated via gel-casting method, and the influence of this behavior on the mechanical properties of the sintered samples were studied. To prepare castable and stable SiC suspensions, the rheological behaviour of the suspensions was characterized and optimized. To this aim tetramethylammonium hydroxide as dispersant, acrylamide as monomer, methylenebisacrylamide as cross linker, ammonium persulfate as initiator and tetramethylethylenediamine as catalyst were used. The results indicated that for obtaining stable SiC suspensions with suitable viscosity, 0.4 wt% dispersant of tetramethylammonium hydroxide, the pH of 10.5 and mixing time of 24 h were required. It should be noted that this suspension was electrosterically stable and the presence of the monomer acrylamide decreased the viscosity. The results showed that in the optimal ratio of methylenebisacrylamide cross linker to acrylamide monomer the highest strength was obtained. The flexural strength of the gel cast bodies was 231 MPa.

To evaluate the biosynthesis of Ag NPs using plant extract of Melissa officinalis (at the eight leaf stage) grown under in vitro (controlled) condition for the first time.
Biosynthesis of Ag NPs using plant extract was carried out and formation of Ag NPs confirmed by UV-Visible spectroscopy, X-ray diffraction (XRD), Field Emission Scanning Electron Microscope (FESEM) and Dynamic Light Scattering (DLS). The functional groups of compounds adsorbed on the Ag NPs were identified using Fourier Transform Infrared Spectroscop (FTIR) studies. The antibacterial activity of the Ag NPs was investigated by agar disc diffusion method.
The plant extract showed color change in extract from yellow to brown after formation of Ag NPs. The surface Plasmon resonance found at 450 nm confirmed the formation of Ag NPs. FESEM images revealed relatively spherical- shaped of Ag NPs. The biosynthesized Ag NPs were crystalline in nature with mean diameter about 34.64 nm. FTIR results expounded the functional groups of plant extract responsible for the bio-reduction of silver ions and their interaction between them. The obtained nanoparticles showed good inhibitory activity against the Gram positive and Gram negative bacteria.
These results suggested that with changes in plants culture condition it may be possible to obtain nanoparticles with desired characteristics.

Porcelain enamels are widely used as coating on metals and alloys, because of their excellent corrosion resistance against different aggressive media with different pHs at high temperatures up to 600oC. In this regard, the chemical composition of the enamels is very important and TiO2 is introduced as additive to promote the corrosion resistance of the enamels. Therefore, corrosion resistance of TiO2 containing and TiO2 free enamels has been examined by applying standard test method ISO 2742. This test has been done in simulated sour water that is one of the most corrosive solutions which is produced during oil refining in refineries. The test has been performed three times on samples for 2.5h. Then, the attacked surfaces were studied by Scanning Electron Microscope (SEM) and then elemental distribution of surface was investigated by Energy Dispersive Spectroscopy (EDS). Finally, by applying Electrochemical Impedance Spectroscopy (EIS), Nyquist spectra of the samples were obtained and compared. The results showed that adding 3.20%wt TiO2 considerably enhanced the chemical and corrosion resistance of the enamel.