In direct contact membrane distillation (DCMD), heat and mass transfers occur through the porous membrane. Any model developed for the DCMD process should therefore be able to describe the mass transport mechanism through the membrane, the temperature and concentration effects on the surface of the membrane, the permeate flux, and the selectivity of the membrane. In the present study, we developed a predictive mathematical model based on a counter flow heat exchanger analogy for the DCMD process. Two methods were used to analyze the water permeate flux across one hydrophobic membrane layer, namely the log mean temperature difference (LMTD) and the effectiveness-NTU methods. The set of equations was derived in a manner analogous to that employed for heat exchanger systems. The obtained results showed that the permeate flux increases by a factor of approximately 220% when increasing the log mean temperature difference by a factor of 80% or increasing the number of transfer units by a factor of 3%. A good level of agreement between this theoretical model and the experimental data at various feed temperatures confirmed that the model accurately predicts the permeate flux values for the DCMD process.

In this study, we investigated the fabrication, properties, and sensing applications of TiO₂ nanotubes. A pure titanium metal sheet was used to demonstrate how titanium dioxide nanotubes can be used for gas-sensing applications through the electrochemical anodization method. Subsequently, X-ray diffraction indicated the crystallization of the titanium dioxide layer. Scanning electron microscopy and transmission electron microscopy then revealed the average diameter of the TiO₂ nanotubes to be approximately 100 nm, with tube lengths ranging between 3 and 9 µm and the thickness of the nanotube walls being about 25 nm. This type of TiO₂ nanotube was found to be suitable for NO₂ gas sensor applications. With an oxidation time of 15 min, its detection of NO₂ gas showed a good result at 250 °C, especially when exposed to a NO₂ gas flow of 100 ppm, where a maximum NO₂ gas response of 96% was obtained. The NO₂ sensors based on the TiO₂ nanotube arrays all exhibited a high level of stability, good reproducibility, and high sensitivity.

This study explored advancements in photovoltaic technologies by enhancing the electronic quality of multicrystalline silicon (mc-Si) through silicon nitride (SiN_x) and hydrogen (H₂) plasma deposition via plasma-enhanced chemical vapor deposition (PECVD). This innovative approach replaced toxic chemical wet processes with H₂ plasma and SiN_x. The key parameters of silicon solar cells, including the effective lifetime (τ_eff), diffusion length (L_diff), and iron concentration ([Fe]), were analyzed before and after this sustainable solution. The results show significant improvements, particularly in the edge region, which initially exhibited a low τ_eff and a high iron concentration. After the treatment, the τ_eff and L_diff increased to 7 μs and 210 μm, respectively, compared to 2 μs and 70 μm for the untreated mc-Si. Additionally, the [Fe] decreased significantly after the process, dropping from 60 ppt to 10 ppt in most regions. Furthermore, the treatment led to a significant decrease in reflectivity, from 25% to 8% at a wavelength of 500 nm. These findings highlight the effectiveness of the PECVD-SiN_x and H₂ plasma treatments for improving the optoelectronic performance of mc-Si, making them promising options for high-efficiency photovoltaic devices.

In this study, we investigated and compared the influence of alumina nanoparticles (Al-NPs) and silicon nitride (SiN_x) layers individually deposited on multi-crystalline silicon (mc-Si) on mc-Si’s structural, optical, and optoelectronic characteristics to improve surface quality. Alumina nanoparticle-covered multi-crystalline silicon, immersion in HF/H₂O₂/HNO₃, and porous silicon (PS) covered with a silicon nitride structure are key components in achieving high electronic quality in multi-crystalline silicon. Surface reflectivity decreased from 27% to a minimum value of 2% for alumina nanoparticles/PS and a minimum value of 5% for silicon nitride/PS at a wavelength of 930 nm. Meanwhile, the minority carrier diffusion length increased from 2 µm to 300 µm for porous silicon combined with silicon nitride and to 100 µm for alumina nanoparticles/porous silicon. Two-dimensional current mapping further demonstrated a considerable enhancement in the generated current, rising from 2.8 nA for untreated mc-Si to 34 nA for Al-NPs/PS and 66 nA for PS/SiN_x. These results confirm that the surface passivation of mc-Si using Al-NPs or PS combined with SiN_x is a promising and efficient method to improve the electrical quality of mc-Si wafers, contributing to the development of high-performance mc-Si-based solar cells.

By solving the three-dimensional Schrödinger equation with a second-order implicit Finite Difference Method (FDM), the combined effects of temperature, morphology, hydrostatic pressure, and transverse electric field on the nonlinear optical rectification (NOR) of GaAs/Al_εGa_1−εAs elliptical quantum rings are examined. The NOR amplitude is twelve times enhanced and a noticeable blue shift is induced in the THz region when the electric field is increased. Consequently, with the electric field of 1 × 10⁵ V/m, the NOR magnitude achieves its maximum value of 17.116 × 10⁵ m/V. Additionally, when the electric field is aligned along one side of the system’s in-plane cross-section, the strongest amplification takes place. However, with corresponding spectrum shifts, the NOR intensity rises with temperature and falls with hydrostatic pressure. Additionally, changing the transverse profile of the quantum ring from triangular to parabolic broadens the carrier wave functions and has a considerable impact on the NOR coefficient. These findings provide important information for the construction of high-performance, tunable THz optoelectronic devices by demonstrating effective external and structural tuning of NOR.