فصلنامه مواد پیشرفته در مهندسی
سال چهل و دوم شماره 3 (پاییز 1402)

One of the major challenges in natural gas sweetening plants is the corrosion of components in amine solution during the CO2 removal process. In this study, electrochemical tests (Tafel polarization and electrochemical impedance spectroscopy) were employed to evaluate the corrosion performance of carbon steel and stainless steel 316 in the aMDEA solution present in the CO2 absorption/desorption process of hydrogen generation unit in Isfahan refinery, including the absorber (rich) and regenerator (lean), as well as freshly made solution. The tests were performed at a constant temperature of 65 °C. Passive behavior was observed for both carbon and 316 stainless steels in the absence of CO2. The lowest corrosion resistance of these steels was observed in the rich solution due to the lowest pH and the highest specific conductivity compared to the lean and freshly made solutions. The carbon steel corroded actively by the purging of CO2 at a temperature of 65 °C while the passive behavior of 316 stainless steel was maintained. Both steels exhibited lower corrosion resistance in the rich solution.

This research used multi-walled carbon nanotubes with a 30 to 50  nm diameter and an approximate length of 6  µm to store hydrogen gas by the volumetric method. Carbon nanotubes' structure, shape, and physical properties were investigated by X-ray diffraction analysis, transmission electron microscopy, and infrared spectroscopic analysis. To investigate the hydrogen storage capacity in carbon nanotubes, the effect of two parameters, namely acid washing and YAG: Nd laser irradiation, were studied. The results showed that acid washing and laser irradiation increased the specific surface area of carbon nanotubes by 59%  and 100%, respectively. Studies also showed that purified carbon nanotubes stored 0.3 wt.% hydrogen, which revealed a 75% increase compared to the original nanotubes. Also, laser irradiation with different times changed the storage capacity of nanotubes. The optimal value of laser irradiation was obtained to be 90  minutes, which increased the storage capacity of hydrogen gas in nanotubes to 1.1 wt.%.

In this research, α-MnO2 nanorod was synthesized by a novel morphology controlled hydrothermal method in the absence of mold for electrochemical energy storage. Graphite oxide (GO) was synthesized using the modified Hummers method. The oxygenated groups of GO were eliminated by the use of hydrazine to produce the reduced graphene oxide (RGO). Nanocomposites with different percentages were made with reduced graphene oxide (G) and manganese dioxide (M) (G20M80, G40M60, G80M20) and were characterized successfully with appropriate methods. To investigate the electrochemical capacitor behavior of various samples, cyclic voltammetry (CV) and galvanostatic charge/discharge (GCD) experiments were performed in a three-electrode system containing 0.5 M Na2SO4 solution as the electrolyte. Electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV) study in 10 mM K4Fe(CN)6 containing 0.1 M KCl also investigated to evaluate the surface properties of the electrodes. The results of the electrochemical experiments showed that the G40M60 electrode had the lowest resistance to charge transfer and ionic diffiution. The results of electrochemical tests revealed excellent supercapacitor behavior of G40M60 nanocomposite and high stability of 91% after 50 charge-discharge cycles at 5 Ag-1 current density. The specific capacitance for the G40M60 nanocomposite was higher than that of other samples and was calculated as 179.72 F.g-1 in current density of 0.6 A.g-1.

In this study, the effect of partial addition of silicon on the structural behavior and electromagnetism of TiC/Ti3AlC2 ceramic matrix composites has been investigated. In this regard, the mechanical alloying and annealing processes were used for the synthesis of the desired composite. Structural and phase investigations were performed using scanning electron microscope, differential thermal analysis, and X-ray diffractometer, and electromagnetic behavior was investigated by network analyzer. The results showed that it was possible to synthesize TiC/Ti3AlC2 composite structure with in-situ partial addition of silicon. 2TiC-Al-Ti-0.2Si system showed the best absorption behavior of electromagnetic waves with reflection loss of about -30.10 dB at matching frequency of 15.1 GHz. It was found that the TiC/Ti3AlC2 composite structure obtained from the mechanical alloying was stable after annealing at 1400 °C. However, the electromagnetic absorption behavior was affected. Thus, the reflection loss of the annealed samples was obtained about -1dB.

In this research, creative techniques have been applied on the surface of polymer optical fiberto observ new optical effects in the production of luminous textiles and their further application in designing luminous clothing. Accordingly, optical fibers of three different thicknesses (0.25, 0.5, and 0.75 mm) were subjected to secondary operations using techniques such as knotting, pulling, grinding the surface with sandpaper, melting, and creating scratches with a cutter, and were exposed to LED to evaluate their luminescence. The result showed that the light emitted from fibers with greater thickness shined more than the similar samples in fibers with less thickness. Additionally, a thicker fiber has been proven to be less flexible than a thinner fiber. Thinner plastic fibers revealed faster melting and weremore fragile and more sensitive to heat. In the knotting and melting methods, the obtained light was appeared in the form of a three-dimensional spotlight. In the melting method, the resulting light was appeared brighter than other samples due to the formation of a spherical shape in the fiber tip. On the other hand, the light emitted from the samples exposed to sanding and pulling scatter appeareduniformly due to the fiber transparency and linear processing. The conducted research declaredthe high potential of optical fibers for the production of luminous textiles with unique design capabilities and their high efficiency in the fashion and clothing industry.

The purpose of this research was to produce Meso Carbon Micro Beads (MCMB) using mesophase pitch as a raw material by suspension method. The effect of pyridine solvent and also carbonization processes in the production of MCMBs were investigated. Finally, the structural and chemical properties of MCMBs were evaluated. The results showed that extraction with pyridine solvent and the carbonization process had a great effect on the morphology and removal of impurities in mesophase pitch and production efficiency. According to the obtained results, the presence of x-ray patterns located at 2θ equal to 26 and 43 degrees confirmed the formation of a graphite hexagonal network. Also, the existence of bands bands and G bands confirmed the existence of regular hexagonal bonds (G) and incomplete bonds (D) in carbon mesophase spheres. At the end of the process, all mesophase pitch particles were converted into carbon mesophase spheres with a particle size distribution of 80 nm to 12 µm.