mohammad moarrefi romeileh

In this research, nanoparticles of copper ferrite was synthesized by hydrothermal method and nanoparticles of copper hydroxide was synthesized by ultrasonic method. Then, to check the properties of these nanoparticles, analyzes such as X-ray diffraction pattern (XRD), scanning electron microscope (SEM), vibrating sample magnetometry (VSM) and infrared spectroscopy (IR) were taken. The results of analyzes showed that the nanoparticles were prepared in a completely uniform, fine and homogeneous manner and no agglomeration was seen in them. In addition, these nanoparticles had good magnetic properties and the peaks of the X-ray diffraction pattern were consistent with the standard peaks. In the next step, 5% by weight of copper ferrite and copper hydroxide nanoparticles were added to the epoxy resin and then mixed together by a stirrer. In the next step, the epoxy resin was subjected to ultrasonic waves and after the complete distribution of nanoparticles in the field, it was placed in the vacuum chamber for bubble removal and finally poured into the mold. Finally, various tests were taken from the composites, such as: thermal properties test (TGA) and flame resistance test (UL-94).

The hydrothermal method synthesized the first cobalt ferrite and cobalt oxide nanoparticles in this article. The synthesized nanoparticles were then subjected to various analyzes such as X-ray diffraction patterns, scanning electron microscopy images, infrared spectroscopy, and vibration sample magnetometer to ensure their properties and prepare the nanoparticles for the next step. Then, 6% by weight of nanoparticles were added to the epoxy resin as a reinforce, and a polymer matrix composite was made. After making the composites according to the ASTM D638 standard, they were subjected to a tensile test. The results showed that the nanoparticles were prepared very fine, uniform, high purity, and had good magnetic properties. Also, hydrothermal was a suitable method for the synthesis of these nanoparticles. Furthermore, samples made using cobalt ferrite nanoparticles offer better tensile properties than samples made with cobalt oxide. However, in general, the tensile properties of composites have improved compared to pure polymers.

In this research, we investigate the effects of pressure and enthalpy on the composition of molybdenum disulfide in the framework of the density functional theory and with the Espresso quantum code with flat waves and the exchange potential of the generalized slope approximation of the stationary charge. The lattice constants of the hexagonal structure of molybdenum disulfide compound were calculated and compared with other works and we have seen the agreement of the results. The electronic properties of the compound were plotted and calculated for comparison with pressure application. The band structure of molybdenum disulfide shows the semiconducting nature with a gap of about 2.27 electron volts, which is larger than the results of other researches. The density of states is plotted for the molybdenum disulfide compound and confirms the semiconducting nature of the compound. The gap obtained from the density of states is more consistent with the results of other works and its value is about 1.3 electron volts. It draws the density of partial states and shows the role of d orbital of molybdenum atom and p of sulfur atom in the overall state density. In the following, we apply different pressures, by applying constant positive pressures, the network increases, and first the bandgap decreases, then increases a little in energy, and then decreases again until the structure changes from a semiconducting nature to a metal, and by applying pressures. The lattice constant negativity is reduced and the bandgap is reduced, and in the same application of the initial pressures, it is out of the semiconducting nature and tends towards the metallic property. 

In this article, nickel oxide and nickel ferrite nanoparticles were first synthesized using an ultrasonic method as a simple, fast, eco-friendly, and cost-effective method. To ensure the properties of the nanoparticles and to avoid problems in the following steps, the nanoparticles are synthesized under various analyzes such as scanning electron microscopy (SEM) images, infrared spectroscopy (IR), an X-ray diffraction pattern (XRD), and Vibrating sample magnetometry (VSM). In the next step, using these nanoparticles and epoxy resin, a polymer matrix composite was made. Then, the composites were tested for corrosion against acid and hardness tests based on the ASTM D2583-13 standard. The results showed that the structure of the manufactured nanoparticles is very uniform and homogeneous. In addition, the hardness of composites made from nickel ferrite and nickel oxide nanoparticles was improved compared to pure polymer, and composites made from nickel ferrite had better hardness than composites made from nickel oxide. Also, the acid corrosion test results showed that creating a composite layer around aluminum can protect it against acid corrosion.

In this study, the effect of integer Hall effect on nanoribbons of boron nitride at the presence of impurity function concerning magnetic resistance in terms of filling ratio was investigated. First, a dopant will be applied to the system in the form of Dirac Delta function, at the presence of this dopant, Landau levels will be divided into extended and localized levels giving rise to Hall step. In this model, the Aharanov-Boehm fluctuations are observed and impurity eradicates stagnation in energy levels. In fact, by increasing the width and height of the quantum dot destroys the step, and finally, the quantum-hall effect vanishes Then, another dopant will be applied to the system in the form of quantum dot. By increase of the width and height of quantum dot, the Hall step will fade and quantum Hall effect will disappear. The more the increase of quantum hall domain, the faster the Hall step and therefore quantum effect will fade.