Defect and Diffusion Forum Vol. 428

Abstract: In this paper, we have studied the electron-donor atom diamagnetic susceptibility confined in a hemi-cylindrical quantum dot (QD). It is analyzed specifically how the impurity location affects diamagnetic susceptibility. The 3D Schrödinger equation in hemi-cylindrical QD was solved using the finite difference method within the effective mass approximation. This is accomplished by performing our system's Hamiltonian in hemi-cylindrical geometry. We have demonstrated that the hemicylindrical size and impurity position have a significant impact on the diamagnetic susceptibility. When the impurity is localized in the center of the nanostructure for the hemi-cylindrical QD, the diamagnetic susceptibility reaches its greatest value.

Abstract: This work describes a theoretical and analytical study of a temperature and pressure sensor based on II-VI semiconductors with a simple multi-quantum wells (MQWs) structure. The proposed sensor operates by detecting changes in the intensity (transmission coefficient) and energy of localized electronic states inside gaps under external perturbations of hydrostatic pressure and temperature. Specifically, the proposed MQWs structure is ZnO/Zn_1-XMg_XO with 10 cells, each containing two materials that form the wells and barriers, respectively. The structure is perturbed by a staircase defect consisting of three defects of the same material or geomaterial. The Green function method is used to study the transmittance of the structure, with cleavage and coupling operators employed. The objective of the work is to explore a new type of defect for use in sensing applications such as multi-quantum well sensors. Key parameters for evaluating the sensor's performance include full width at half maximum (FWHM), sensor sensitivity (S), quality factor (QF), detection limit (DL), signal-to-noise ratio (SNR), dynamic range (DR), detection accuracy (DA), the figure of merit (MF), and standard deviation. These parameters can be optimized by adjusting structural parameters such as the thickness of the staircase or material concentration. The study found that a geomaterial staircase defect provides higher sensitivity to pressure and temperature changes. Additionally, the step (δx) of the staircase defect influences the sensitivity of the localized states: with increasing steps, δx improves sensitivity to temperature and decreases sensitivity to pressure.

Abstract: Taking into account the effective mass approximation and the two-band model, we have studied the combined effects of hydrostatic pressure and temperature on the unbound excitonic properties of a cylinder-shaped quantum dot. The two finite confinement potentials along the radial direction and one finite confinement potential along the axial direction have been considered. We have calculated the electronic energy with and without light hole effect as a function of the core radius, hydrostatic pressure and temperature. The numerical results show that the effect of the confinement potential is dominant over the effect of the hydrostatic pressure and the temperature. Also, the light hole effect on the electronic properties has a significant influence mainly under the external perturbation

Abstract: Float-type g-C₃N₄ microtubes were created by hydrothermal method and calcination using g-C₃N₄. Substances after hydrothermal synthesis and float-type g-C₃N₄ microtubes were investigated by XRD and SEM. The photocatalytic activity of float-type g-C₃N₄ microtubes was evaluated by methylene blue decomposition. According to these results, the substance, such as a needle, was found to have the same crystal structure as g-C₃N₄. In addition, it was confirmed that the needle-like substance was hollow inside, according to the SEM result. This substance can float on water. Therefore, Float type g-C₃N₄ microtubes can receive more light, and the decomposition rate has increased compared to g-C₃N₄.

Abstract: Photocatalysts that can utilize sunlight energy have attracted attention. In this study, g-C₃N₄ and mesoporous SiO₂@TiO₂ particles were mixed by hydrothermal synthesis. g-C₃N₄ was made by a simple method of directly heating melamine. Mesoporous SiO₂@TiO₂ was prepared using the stover method. These two types of particles were then mixed by hydrothermal synthesis. Hydrothermal synthesis reduced the size of the g-C₃N₄ particles, and they bound more closely with the TiO₂ particles. The degradation of methylene blue dye by visible light was performed to evaluate the organic degradation of the mixed particles. In addition, the mixed particles were formed into a thin film by the spin-coating method. The film's methylene blue degradation performance and the film's power generation performance in a battery were evaluated. The film showed high convenience in the practical application of photocatalytic degradation of organic pollutants because it can be easily separated from the treated liquid after organic matter degradation.

Abstract: In this manuscript, a new concept of power generation from thermoelectric generators TEGs using the sun irradiation and two oil tanks, one hot and one cold, is proposed. It consists of two oil tanks separated by a plate covering several TEGs in series. The oil tank at the bottom of the system constitutes a cold convection condition for the TEGs plate; on the other hand, the upper oil tank accounts for a hot convection condition since its upper surface is transparent and therefore subjected to the sun irradiation that will heat up the oil. To test the feasibility of this concept, an appropriate thermal modeling is developed and associated parametric analysis was carried out. It shows that powers up to 242 W can be generated with a system having a hot oil tank height of 0.2 m along with a width and length of 2 m each.

Abstract: The process of welding is prone to many defects and these defects can cause the formation of many defective regions. It is necessary to identify the regions of defects as these may cause problems and breakages. In this work, we have proposed a method to detect and identify the defects that are commonly seen in seam welds. Manually identifying the detects is not only error prone and time consuming, most of the defects are not visible to the human eyes. In recent days, X-ray images of weld seam are used for this purpose. In this paper we have applied computer vision techniques and proposed an image processing pipeline to generate a binary segmentation of the image to identify the regions of slag and porosity defect seen in weld seams. From the experimental results on the publicly available dataset, GDX-ray images, it could be observed that, there is a significant improvement in detecting various defects with the proposed approach.

Abstract: This study presents the results of visual and infrared (IR) inspection of photovoltaics (PV) technologies installed at the Qatar environment and energy research institute (QEERI) outdoor test facility (OTF) at Qatar Foundation (Doha, Qatar). Silicon based PV technologies which have been operational in the field since 2014, have been investigated for various failure modes. The visual inspections were carried out for all the PV modules from the backside however, the inspection from the front side was not possible for some modules due to heavy soiling. The visual defects which were identified during this study include, cracking of the back glass, yellowing of the encapsulant material, cracks formation in the back sheet, and pits formation in the back sheet. The visual inspection revealed that around 19 % of the total modules have back sheet cracking and discoloration, 8 % have yellowing of the encapsulant, and around 4 % were having pits in the back sheet. Moreover, one module was detected with back glass cracking. The IR inspection was also done both from front and backside for all the silicon PV modules to detect hot spots. The IR inspection has revealed that hot spots were generated at different locations of the PV modules. 39 % of the modules have hot spots at the location of junction boxes, around 6 % of the modules have hot spots in junction boxes and around 1 % have hot spots at the locations away from junction boxes. The visual and IR inspection has revealed that the dominant failure modes which have been observed for silicon-based technologies at OTF are the hot spots generation at junction boxes and the back sheet cracking, and its yellowing.