University of Lakki Marwat

Carbon dots/poly(methyl methacrylate) composite nanofibers (CDs/PMMA-CNFs) were fabricated via electrospinning for ultraviolet (UV) photoconductive sensing applications. Carbon dots were synthesized through a microwave-assisted method using citric acid and urea precursors and subsequently embedded within a PMMA nanofibrous matrix. Structural and morphological characterization was performed using FTIR, XRD, and SEM analyses, confirming successful incorporation of CDs into uniform nanofibers. Optical investigations using UV–Vis and photoluminescence spectroscopy revealed characteristic π–π* and n–π* transitions and excitation-independent emission centered near 495 nm. The fabricated composite exhibited measurable photoconductive response under UV illumination ( 395 nm), with current increasing from 4.48 × 10−8 A (dark) to 4.83 × 10−8 A (UV), corresponding to approximately 7.8

This work presents a first-principles investigation of the pressure-dependent structural, elastic, thermal, and optical properties of the layered MAX-phase carbides Sc2XC (X=Tl, Pb) using density functional theory under hydrostatic pressures ranging from 0 GPa to 12GPa. The evolution of elastic wave velocities, Debye temperature, melting temperature, and lattice thermal conductivity is systematically analyzed to assess the thermo-mechanical stability of these compounds under compression. At ambient pressure, Sc2TlC exhibits longitudinal, transverse, and average sound velocities of 4725.66, 2653.43, and 2952.76ms-1, respectively, which increase markedly to 5619.72, 3219.24, and 3576.39ms-1 at 12GPa, accompanied by an enhancement of the Debye temperature from 317.99K to 400.93K. Similarly, Sc2PbC shows a substantial rise in Debye temperature from 275.52K to 372.13K over the same pressure range, indicating improved lattice stiffness and phonon stability. The lattice thermal conductivity at 300K increases significantly with pressure, reaching 73.56W/m & sdot;K for Sc2TlC and 60.24W/m & sdot;K for Sc2PbC at 12GPa, reflecting enhanced phonon transport under compression. Optical properties reveal pronounced anisotropy, characterized by exceptionally high extinction coefficients along the xx-direction (Kxx approximate to 58-60 at 0eV) and negative refractive indices along the zz-direction (nzz approximate to-7.5 at 0eV), indicative of metallic and plasmonic behavior. Overall, the results demonstrate that Sc2TlC and Sc2PbC combine excellent mechanical robustness with pressure-tunable thermal transport and strongly anisotropic optical responses, highlighting their potential for high-temperature structural applications, advanced thermal management, plasmonic devices, and anisotropic optoelectronic technologies.

This research focused on entropy generation in the triangular solar still based on a nanofluid of TiO2 under the influences of magnetohydro dynamics (MHD), double-diffusive convection, and the DarcyBrinkman-Forchheimer and Ree-Eyring models. The non-dimensional forms of the governing equations were solved by means of the Galerkin Finite Element Method (FEM) using COMSOL Multiphysics. The analysis of the major parameters with regard to flow, temperature distribution, entropy generation, and their combined effect on heat transfer has been supported with comparative sketches and tables, all validated by grid independence tests to assure computational accuracy. It is found that the flow circulation and hence convective heat transfer increased with increasing values of the Ree-Eyring parameter . It was also found that for high values of the Ree-Eyring parameters eta, the nature of heat transfer progressively changed and became conduction dominant beyond a certain value. Increased Darcy numbers (Da) promote a flow towards convection-dominance in heat transfer processes by allowing a more superior permeability of flow and local Nusselt number. Increased porosity & varepsilon; reduces resistance and on the other hand strengthens convection and temperature uniformity with a graph where the local Nusselt number is taken down to a lower level because of reduced effective thermal conductivity. Magnetic effects (Ha) suppress convection but bring about a considerable increase of 100% in the magnetic entropy generation while reducing the viscous entropy generation by25.77%. These will provide very good guidance in model optimization of nanofluid based solar stills, following the interrelationship of MHD, fluid dynamics, and thermal efficiencies of sustainable energy systems.

Parabolic trough solar collectors (PTSC) are widely used for medium-temperature applications, typically operating within a temperature range of 60-400 degrees C . These systems primarily serve the purpose of heat and power production. In recent years, solar energy has emerged as a significant source of renewable heat energy. This study explores the enhancement of heat transfer efficiency by employing a hybrid nanofluid composed of graphene oxide and alumina alloy (GO-AA7075), analyzing its non-Newtonian characteristics using the Ree-Eyring fluid model. The study applies the Darcy-Forchheimer condition to evaluate pressure drop due to fluid-solid interactions, while also examining the effects of thermal elevation and velocity slip over a curved surface. This study aims to enhance heat transfer effectiveness in parabolic trough solar collectors by utilizing a hybrid nanofluid comprising graphene oxide and alumina alloy under varying thermal and flow conditions. Using all assumptions on the geometry, the momentum and energy equations are reduced to nonlinear partial differential equations. The derived highly coupled and non-linear partial differential equations are non-dimensionalized using dimensionless variables. HAM (Homotopy Analysis Method) is applied to solve the differential equations with the help of Mathematica. The addition of nanoparticles enhanced the thermal conductivity of the fluids, so enhancing the efficiency of heat dissipation. The heat transfer efficiency of the hybrid nanofluid is assessed directly at different concentrations of graphene oxide with alumina alloy, thermal radiation levels, space-dependent heat source, curvature parameters, and flow rates. The Ree-Eyring fluid model precisely predicts the complex flow behavior and heat transfer characteristics, enabling the optimization of operational parameters for improved performance. The finding indicates that the hybrid nanofluid (GO-AA7075) significantly improve heat transfer efficiency. The findings reveal that the graphene oxide combined with alumina alloy in the base fluid is an effective solution for enhancing heat transfer efficiency in various engineering applications. The graphs indicate that for greater values of magnetic parameter the velocity profile declined, while temperature is enhanced.

Lead-free double halide perovskites have been identified as potential substitutes for Pb-based absorbers. However, the major challenge remains to optimize the combination of stability, mechanical flexibility, and good optoelectronic performance. Here, by using first-principles computations (WIEN2k, PBE-GGA with TB-mBJ), we have thoroughly explored the structural stability, electronic properties, and predicted performance of the A2LiNaI6 (A = Ca, Sr) environmentally friendly materials at the device level. Both materials are thermodynamically and thermally stable, as evidenced by their tolerance factors (tau = 0.76, 0.81), negative formation energies (-2.14 to-2.29 eV/atom) and AIMD analysis. Interestingly, the fact that their Young's modulus is very low (13.21, 24.32 GPa) means that they are able to undergo mechanical deformation more easily, which is a great feature for flexible photovoltaic devices. They have direct band gaps of 1.08 and 1.63 eV, so the light absorption from the visible range will be strong. Power conversion efficiency at device level has been calculated as 20.81% and 19.61% for these compounds under AM1.5G light. When performing a detailed comparison with the theoretical maximum efficiency by Shockley, Queisser, it was found that the biggest loss in these materials is due to non-radiative recombination which means that it is very important to focus on defect passivation and interface engineering. Besides that, the band-edge alignment looks quite good which means they could also be used for solar-driven hydrogen production.