نشریه تحقیقات در علوم مهندسی سطح و نانو مواد
پیاپی 3 (پاییز 1401)

The solar cells based on perovskite materials have attracted a lot of attentions in recent years. These technologies, have been the subject of numerous researches due to their ability to achieve high efficiency with low cost. Based on this, relying on existing knowledge and to gain a deeper insight into this field of technology, this research has a comprehensive review of the effective factors on the production processes and the intrinsic challenges of halide perovskite solar cells (HPSCs) and monitors stepwise the background of scientific research conducted on solutions to improve performance, increase stability and reduce toxicity of these types of devices. Investigations showed that, in addition to the type of deposition method and the architecture of the components, the most important issues to achieve a perovskite solar cell with high photovoltaic performance include improving the morphology, reducing the energy barrier for nucleation, controlling the uniform growth of perovskite crystals and reducing the hysteresis effect. These parameters can be optimized by using the engineering of solvents and additives, adjusting the coating variables such as processing and post-processing temperatures, and managing the reaction time. Also, research on the replacement of lead element with other less toxic elements shows that until now, the most promising results for tin-based perovskite solar cells have been obtained with a power conversion efficiency (PCE) of about 9-12%. This efficiency compared to lead-based perovskites, which is about 26% to 2023, is still not competitive and requires more effort in this field of research. 

In recent years, following the attention of the automobile industry to reduce the weight of cars, the use of alternative materials with lower weight and better mechanical properties has been the focus of these companies. In particular, hot-stamped boron steel has been considered as an alternative material due to its good mechanical properties. This material is used to reduce the weight of the frame due to its reduced thickness, excellent performance and good performance. Considering that hot stamping of boron steel causes oxidation and carbon deposition on the surface, the use of surface coating is necessary to prevent these cases. This coating layer itself causes side problems such as the narrowing of the weldable range and also the reduction of mechanical properties during resistance welding. Therefore, in this study, we introduce research performed to improve the weldability of Al-Si coated hotstamped boron steel in terms of the material and process.

Currently, aluminum is widely used in various industries due to its low density and good corrosion resistance. In this research, the simulation of the effect of friction stir welding process on the mechanical strength of aluminum sheet with aluminum multilayer background and carbon fiber or glass composite with aluminum background is discussed. First, the aluminum sheet in specific dimensions with Ensys finite element software for dam simulation. Then, friction stir welding was performed on aluminum alloy using one of the research parameters such as speed or penetration depth of the tool. According to the results of the research, when the pin starts moving, the amount of stress applied to the plate decreases. Therefore, reducing the speed of the linear movement of the pin and increasing its rotational speed makes the friction stir welding process go through a better process, and when the pin moves, the displacement of the plate particles decreases. By examining the particles, it was seen that the movement of the pin along the plate creates a turbulent area in the plate. It has been observed that with the application of stress by the pin, the particles in the HAZ area are also displaced and enter from the upper surface of the welding area and exit from the lower surface according to the direction of movement. It was observed that the aluminum composite participates favorably in the friction stir welding process and the part is not damaged in this process. 

In this research, the structural and phononic properties of the combination of cerium carbide and lanthanum carbide have been investigated using first principle calculations based on density functional theory by Espresso quantum. The results of density of states calculations showed that both cerium carbide and lanthanum carbide compounds have metallic properties. The structural calculations performed using the LDA approximation for both compounds showed almost the same compressibility and hardness. The results of phonon calculations did not show any frequency gap for cerium carbide composition, while similar calculations in the range of 229 cm-1 to 261 cm-1 show a frequency gap for lanthanum carbide composition. The results show that there is no acoustic oscillation in the range of the observed gap and light and heat will not pass through the crystal. 

Due to the presence of initial cracks in gas pipelines and to prevent the increase in replacement and repair costs, the use of composite patches in cracks areas has become popular in recent decades. In this research, the role and performance of composite patch to prevent with fatigue crack growth in steel pipes used in gas pipelines under cyclic internal pressure is investigated. . For this purpose, the method of intelligent growth of a semi-elliptical surface crack has been used for simulation using Ansys software. The findings of the research indicate the predominance of the peripheral sliding separation mode over the normal separation mode, which leads to the separation of the patch from the pipe. The internal crack of the pipe has more critical conditions in terms of stress and stress intensity factor than the external crack. The crack growth in the pipe depends on the type of loading and if the angle of the composite fibers is in the direction of the crack growth, the best reinforcement is provided. Also, with the increase of the internal pressure, the load cycles for crack growth are greatly reduced, and the use of glue between the pipe and the patch leads to a better transfer of strains from the pipe to the outer layers of the composite. 

Currently, with the growth and development of new heat transfer technologies, it has been used to reduce the time of heat transfer, reduce the size of heating equipment and finally increase the thermal efficiency. In this research, the validity of the organizations of alumina water and titania water converter with separator, shape and middle fin is done in this field. An international solidwork design has been done and a grid has been made in the Ansys network. The input for this purpose is from the input external union and to get out of the external pressure compliance. Out of compliance in software. In the following, taking into account the volume ratio and diameter of nano particles, a continuity equation and an incompressible Navier-Stokes equation for a coordinate system corresponding to the object have been solved using the control volume method. The results indicate the reduction of the friction coefficient with the increase of the Reynolds number. By comparing the heat transfer coefficient between water-alumina nanofluid and water-titanium dioxide nanofluid, it can be seen that the average value of this coefficient is 14% higher for water-alumina nanofluid. On the other hand, the transformation of the heat transfer coefficient of waterdioxatnium nanofluid compared to water-Al nanofluid is more intense than the changes of Reynolds number. Also, with the increase in diameter from 40 to 60 mm in the range of Reynolds number from 3000 to 8000, an increase in Nusselt number was observed. By examining the performance index, it is evaluated that with the increase in the average diameter, a 19.3% increase in the performance index is observed.