فصلنامه مواد پیشرفته در مهندسی
سال چهل و دوم شماره 1 (بهار 1402)

Magnetic cobalt ferrite nanoparticles have been widely employed in various applications, such as medical applications due to their desirable characteristics. Although generally magnetic nanoparticles are appropriate for such employments, their applications are restricted due to their toxic properties. Hence, it is tried to decrease the toxic damages by using a biocompatible coating layer. For this purpose, in the present study, it was tried to synthesize Ca2+ and Gd3+ doped cobalt ferrite nanoparticles by the sol-gel auto-combustion method and coat them with chitosan and polyethylene glycol polymers. X-ray diffraction (XRD) pattern along with the Rietveld refinement results confirmed the formation of pure cobalt ferrite nanoparticles with the average crystallite size of 27 nm. Moreover, the results of both thermogravimetry (TGA) test and Fourier transform infrared (FTIR) spectroscopy confirmed the formation of a coated layer of chitosan and polyethylene glycol polymers on the surface of nanoparticles. Magnetic characterization of the synthesized nanoparticles indicated that the formation of the coating layer can affect the magnetic properties, so that the saturation magnetization (Ms) increased from 67.93 to 74.61 emu/g. However, the coercivity (Hc) decreased from 982.86 to 908.13 Oe as a result of the formation of the coating layer.

In the present study, the effect of magnetic field and electrospray on the orientation of carbon nanotubes (CNT), stabilized with COOH, in the obtained alginate/CNT adsorbent’s matrix, as well as the adsorption of methylene blue, were investigated. FE-SEM and UV-visible spectroscopy were used to determine the characteristics and performance of absorbents. The images showed that the CNTs were significantly oriented in the polymer matrix by placing alginate-CNTs colloid in a magnetic field with an average strength of 318 mT for 2 h. While the spraying of colloidal droplets under the electric field had a negligible effect on the alignment of CNTs, it led to the size reduction of the droplets and an increase in the specific surface area of particles. By combining magnetic and electric fields in the presence of CNT, 92.2% of the methylene blue adsorption was obtained, which was higher than electrospray only (71%), and electrospray only without CNTs (59%). This research revealed that the orientation of carbon nanotubes under magnetic and electric fields was effective in increasing the adsorption efficiency of environmental pollutants and can lead to the production of more economical adsorbents.

The present research has aimed to investigate the effect of Ti3AlC2 reinforcing MAX phase on the electromagnetic behavior of TiC matrix composites. In this case, the milling process and secondary heat treatment were used for the synthesis of the composite. The resulting structures were examined by scanning electron microscope, differential thermal analysis, and X-ray diffractometer. Electromagnetic behavior was investigated by vector network analyzer. The investigations showed that it is possible to create a TiC/Ti3AlC2 composite structure in situ after milling. Electromagnetic investigations revealed that the electromagnetic absorption behavior of TiC/Ti3AlC2 ceramic matrix composite was improved compared to the original TiC. So that the lowest reflection loss of the milled composite was equal to -19.46 dB in the frequency range of 1 to 18 GHz band. After annealing at 1400 °C, it was found that the Ti3AlC2 phase resulting from the milling process was not stable and turned into the single phase solid solution of TiCx. Electromagnetic investigations of the annealed sample showed that after removing the MAX phase, the electromagnetic absorption behavior was weakened. Thus, the lowest reflection loss of the annealed sample was equal to -9.82 dB.

In this study, Mg-3Zn nanocomposite powder was produced using planetary ball mill under argon atmosphere. The aim of this work was to study the effect of milling time (2.5, 5, 7.5, and 10 h) on the crystallographic features and microstructure of Mg-3Zn. X-Ray diffraction (XRD) was used to investigate phase analysis of various milled powders. Also, the morphology of different samples were observed by scanning electron microscopy (SEM). The crystallographic features of the composite powders such as crystallite size, strain, and lattice parameter were thoroughly characterized by Rietveld and Williamson-Hall methods. The effect of milling time on the mechanical properties of the powders was evaluated using microhardness test. The results declared that crystallite size, lattice parameter, and microhardness of Mg-Zn powder decreased with increasing milling time.

In this research, Cu/Ag core-shell nanoparticles were synthesized by laser ablation in liquid using a nanosecond Nd:YAG laser. The synthesis of Cu/Ag core-shell nanoparticles by the laser ablation in liquid method was done in a single step by setting the process parameters at 450 mj/pulse energy, 1064 nm wavelength, 3 Hz frequency and 6 mm/s scanning speed in an acetone environment. Characterization of the synthesized nanoparticles using ultraviolet visible spectroscopy (UV-Vis), atomic absorption spectroscopy (AAS), dynamic light scattering (DLS), field emission scanning electron microscopy (FESEM), high resolution transmission electron microscopy (HRTEM), and X-ray diffraction (XRD) were performed. The investigations confirmed that CACS nanoparticles had nanometric size, spherical morphology, and core-shell structure of pure copper/silver.

Nowadays, roller plates are used in the steel industry and pellet making unit in order to classify iron ore pellets. Roller plates or screen rolls are a type of screening device, which are used to determine size, granulation, and transfer of materials. In this research, the corrosion behavior of these rolls was evaluated in two different water environments including fresh water (drinking) and return water (C60). First, the spark spectrometry test was performed to measure the chemical composition, and then the electrochemical corrosion tests were performed on steel parts A+, A, B at a temperature of 25 °C. The open circuit potential test was performed to measure the open circuit potential and study the general behavior of the components. Then electrochemical impedance spectroscopy test was performed to evaluate corrosion resistance and surface conditions, potential dynamic polarization test to determine corrosion rate and, pitting test to evaluate pitting corrosion conditions. The results of these tests showed that the A+ part had the highest corrosion resistance and the A part had the highest corrosion rate in both environments due to the presence of a larger amount of molybdenum element in the structure of A+ part compared to A. Also, the results showed that the corrosion of all parts in fresh water was less than the corrosion in C60 water. The main reason for this difference was related to less aggressive ions such as chlorine in fresh water compared to C60 water. In addition to uniform corrosion and pitting corrosion, galvanic corrosion between phases in the microstructure was also determined as one of the main causes of alloy corrosion. According to the metallographic images of the parts and the hardness measurement results, the microstructure of all three parts was martensitic, which was observed in parts A, B, and delta ferrite phase in the martensitic field.