فصلنامه مواد پیشرفته و پوشش های نوین
پیاپی 37 (تابستان 1400)

Today, air pollution is one of the biggest problems of different societies due to the development of various industries around the world, especially in industrialized countries. Therefore, solving the problems of air pollution, the environment, disease, and toxicity caused by air pollution has attracted the attention of many researchers. This has led to the rapid development of nanotechnology in the field of air filtration. In this regard, various nanofibrous filters have been produced and studied for the absorption and removal of air pollutant particles. Nanofibers have a high potential for many environmental applications, including nanofilters and membranes, due to their high specific surface area, high porosity, high flexibility, and ease of production at different scales of different materials. Studies show that metal-organic frameworks (MOFs), as a new class of nanosorbents, are suitable for storing and separating gases, separating membranes, and various types of air pollution filters. Characteristics such as low density, adjustable pore size and their high surface area, selective adsorption of small molecules, and most importantly, reversible adsorption, make these compounds suitable for use in nanofibrous filters. In this paper, after introducing metal-organic frameworks and the performance of nanofibrous filters, a comprehensive review of the research performed on the nanofibrous filters and expressing the potential of metal-organic frameworks in improving the performance of nanofibrous filters in the filtration of air pollutants are given.

In this study, polyester resin has been synthesized using linear and cyclic monomers. In the next step, the synthesized resin was neutralized with amine and diluted with water to reach the water reducibility. All products were adjusted to a solid percentage of about 45, which was close to the solid percentage of common commercial resins, and then evaluated. Resin identification was performed using Fourier transform infrared (FTIR), Gel permeation chromatography (GPC) and Differential scanning calorimetry (DSC) tests. By the way, the Thermal gravimetric analysis (TGA) test was used to analyze the thermal degradation of the resin. The highest stability was obtained at pH=7. The synthesized resins were mixed with melamine resin in a weight ratio of 1:4 respectively then applied to the steel sheet for further detailed study of their performance in a coating system. To evaluate the anti-corrosion properties, a salt spray test was done while a commercial polyester resin was used as a reference. The results of the salt spray test showed that despite the hydrophilic nature of the synthesized resin, it shows good water resistance in the coating system.

For decades, aluminum alloys have been known as one the most vital materials utilized in diverse fields of industry. In spite of significance, Al alloys can be easily exposed to corrosion. In this study, it has been tried to investigate anodic oxide coating made by hard anodizing of 5083 aluminum alloy in sulfuric acid at the temperature of 0 ºC and different voltages (20, 27 and 35 V). Subsequently, all samples were characterized using X- Ray Diffraction (XRD), Scanning Electron Microscope (SEM) and Field Emission Scanning Electron Microscope (FESEM). Low angle XRD results showed that the amorphous alumina coatings were formed in the surface of the samples. SEM images showed that the coatings are porous which is directly related and affected by anodizing voltage. FESEM images of fracture surfaces were indicant of formation and growth of oxide nano-cells in the cross section of the coatings. In order to investigate the properties of the coatings, micro-hardness, roughness and thickness measurement was carried out. Results showed that micro-hardness, roughness and thickness of the coatings increase by increasing the anodizing voltage. Furthermore, potentio dynamic polarization and electrochemical impedance spectroscopy (EIS) tests were performed. Electrochemical analysis proved that by increasing the anodizing voltage, corrosion resistance of the samples declined due to increasing the porosities on the surface of the coatings.

In the present study, Ag (silver) and ZnO (zinc oxide) nanolayers were grown on Cu (copper) substrates by electrodeposition method. After deposition of layers, photocatalystic behavior of Ag and ZnO thin layers were studied and compared together. Crystalline structures of nanolayers were studied by means of diffraction pattern X-ray diffraction (XRD), and average of crystallite size was calculated by debye scherrer formula. The morphology of layers was investigated by scanning electron microscopy (SEM). The Energy Dispersive X ray (EDX) analysis determined the precent of elements existed in electrodeposited thin films. Kinetic roughening of surface of both thin layers were studied by using atomic force microscope (AFM). Finally, photocatalytic properties, and the effect of ZnO and Ag were investigated on the degradation of acid violet and methyl orange azo dyes. The photocatalytic behaviors of Ag and ZnO thin films on acid violet and methyl orang under UV radiation were investigated by UV-Vis spectra.

There are different types of suspended metal materials in wastewater and municipal water, and high-cost coagulants must be used to remove them in water refinery. polyaluminum chloride (PAC) is one of the newest coagulants. Due to the high cost and long preparation time of PAC, it is more economical to use simulation methods instead of experimental tests. In this paper, the adsorption process of copper, zinc and cadmium on PAC coagulants has been studied using the density functional theory (DFT) by Quantum Espresso calculation code. The calculations are based on the flat wave method with quasi-potential using the generalized gradient approximation (GGA). The pseudopotential used is also generated by the ultra-soft method. Analysis of the band structure and density of electron states showed that the PAC materals are semiconductor with an energy gap of 5.4 eV. Also, the results obtained from adsorption calculations showed that copper, zinc and cadmium metals are adsorbed with PAC coagulant adsorption energy of -4.56, -8.79 and -13.25, respectively. According to these results, increasing the conductivity of the PAC compound, which is the result of reducing the energy gap during the adsorption process, can be a factor in identifying suspended metals in water.

In this study, the factors affecting the reflection characteristics of traffic lines in different climatic conditions, the effect of different types of glass grains used in traffic colors in terms of dimensions and shape, the role of rainfall on the reflection properties of applied lines and the effect of additives in the paint industry be checked. Based on the results obtained from the evaluation of traffic lines on highways in Tehran, it was found that the dirtiness of traffic lines plays a significant role in the characteristic of reflection.In the first part of this study, the effect of silicone additives to reduce the surface tension of traffic paint and consequently reduce the dirtiness of traffic paints was studied and an increase of 30 units in the reflection characteristic at night was observed. In another part of this study, the effect of rainfall was examined from two perspectives; Rainfall improves the reflection characteristics of day and night in terms of washing traffic lines. But on the other hand, during the rainy season, due to the creation of a layer of water on the lines and the difference in the refractive index of the car's headlights, the night visibility of the traffic lines decreases.In the final part of this study, the effect of glass grain size and their spatial shape, the effect of modifying the surface of coated glass beads and the effect of changing the type of traffic paint from cold thermoplastic to two-part thermostat were investigated and analyzed

In this research, the thermal stability and thermal degradation of epoxy resin in the presence of different amounts (0,0.5,11.5) by weight percent of elastomeric nanoparticles have been investigated using Thermal Gravimetric Analysis. The results of derivative thermogravimetrically analysis (DTG), showed that at constant heating rate, by adding 0.5 and 1 wt% of elastomeric nanoparticles to the epoxy resin matrix, the maxi- mum degradation temperature increases and the mechanism of thermal degradation of epoxy resin and epoxy nanocomposites was single step. 1% nanocomposite sample showed highest maximum degradation temperature and also with increasing the heating rate, the temperature of 95% degradation (T95)of pure epoxy resin and epoxy nanocomposite samples increased . On the other hand ,this temperature for 1.5% and 0.5 and 1% nanocomposites was decreased at first and then increased. The activation energy was evaluated with the models of Augis, Ozawa, Horowitz-Metzger, and Friedman, and the results showed that the models of Augis and Ozawa behave similarly to each other. Examination of the master curve of epoxy nanocomposites showed that by adding 0.5 and 1 wt% of elastomeric nanoparticles to the epoxy resin matrix, the degradation reaction mechanism becomes A4.