Using traditional weight-loss tests, as well as different electrochemical techniques (potentiodynamic polarization and electrochemical impedance spectroscopy), we investigated the corrosion-inhibition performance of 2,2′-(1,4-phenylenebis(methanylylidene)) bis(N-(3-methoxyphenyl) hydrazinecarbothioamide) (PMBMH) as an inhibitor for mild steel in a 1 M hydrochloric acid solution. The maximum protection efficacy of 0.0005 M of PMBMH was 95%. Due to the creation of a protective adsorption layer instead of the adsorbed H₂O molecules and acidic chloride ions, the existence of the investigated inhibitor reduced the corrosion rate and increased the inhibitory efficacy. The inhibition efficiency increased as the inhibitor concentration increased, but it decreased as the temperature increased. The PMBMH adsorption mode followed the Langmuir adsorption isotherm, with high adsorption-inhibition activity. Furthermore, the value of the $∆G_{ads}^o$ indicated that PMBMH contributed to the physical and chemical adsorption onto the mild-steel surface. Moreover, density functional theory (DFT) helped in the calculation of the quantum chemical parameters for finding the correlation between the inhibition activity and the molecular structure. The experimental and theoretical findings in this investigation are in good agreement.

The thermal conductivity and stability of any nanofluid are essential thermophysical properties. These properties are affected by many parameters, such as the nanoparticles, the base fluid, the surfactant, and the sonication time used for mixing. In this study, multi-walled carbon nanotubes (MWCNTs) were selected as additive particles, and the remaining variables were tested to reach the most suitable nanofluid that can be used to cool photovoltaic/thermal (PVT) systems operating in the harsh summer conditions of the city of Baghdad. Among the tested base fluids, water was chosen, although ethylene glycol (EG), propylene glycol (PG), and heat transfer oil (HTO) were available. The novelty of the current study contains the optimization of nanofluid preparation time to improve MWCNTs’ PVT performance with different surfactants (CTAB, SDS, and SDBS) and base fluids (water, EG, PG, and oil). When 1% MWCNT mass fraction was added, the thermal conductivity (TC) of all tested fluids increased, and the water + nano-MWCNT advanced all TC (EG, PG, and oil) by 119.5%, 308%, and 210%, respectively. The aqueous nanofluids’ stability also exceeded the EG, PG, and oil at the mass fraction of 0.5% MWCNTs by 11.6%, 20.3%, and 16.66%, respectively. A nanofluid consisting of 0.5% MWCNTs, water (base fluid), and CTAB (surfactant) was selected with a sonication time of three and quarter hours, considering that these preparation conditions were practically the best. This fluid was circulated in an installed outdoor, weather-exposed PVT system. Experiments were carried out in the harsh weather conditions of Baghdad, Iraq, to test the effectiveness of the PVT system and the nanofluid. The nanofluid-cooled system achieved an electrical efficiency increase of 88.85% and 44% compared to standalone PV and water-cooled PVT systems, respectively. Additionally, its thermal efficiency was about 20% higher than that of a water-cooled PVT system. With the effect of the high temperature of the PV panel (at noon), the electrical efficiency of the systems was decreased, and the least affected was the nanofluid-cooled PVT system. The thermal efficiency of the nanofluid-cooled PVT system was also increased under these conditions. This success confirms that the prepared nanofluid cooling of the PVT system approach can be used in the severe weather of the city of Baghdad.

The development of modern photovoltaic thermal systems (PV/T) is one of the most important steps in the application of using solar energy to produce both electricity and heat. Studies have shown that a system consisting of a heat-collecting tank the is most efficient system, in which the phase change materials (PCMs) are mixed with nanoparticles inside the system that are cooled by a cooling fluid (preferably a nanofluid). The PCMs have a high capacity to store energy in the form of latent heat. Nanoparticles are added to PCMs to treat and improve the low thermal conductivity of these materials. In this experimental study, nano-iron oxide III (Fe₂O₃) was added to paraffin wax in multiple mass fractions to evaluate the thermophysical changes that can be occur on the wax properties. Four samples of paraffin–nano-Fe₂O₃ were prepared with mass fractions of 0.5%, 1%, 2% and 3%, and their thermophysical properties were compared with pure paraffin (without nano additives). The results from this study showed that adding nano-Fe₂O₃ at any mass fraction increases the viscosity and density of the product. Thermal conductivity is improved by adding nano-Fe₂O₃ to paraffin wax by 10.04%, 57.14%, 76.19%, and 78.57% when adding mass fractions of 0.5%, 1%, 2%, and 3%, respectively. Stability tests showed that the prepared samples have excellent thermal stability (especially for 0.5% and 1% added nano-Fe₂O₃) to acceptable level of stability when adding 3% of nano-Fe₂O₃. The nano-Fe₂O₃ paraffin PV/T system was tested outdoors to ensure its ability to operate in the harshest weather conditions of Baghdad city. The current experimental results indicated clear evidence of the success of the examined nano-PCM.

Iraq is characterized by hot and sunny weather with high radiation intensity. These conditions are suitable to produce photovoltaic electricity, on the one hand, but on the other hand are not suitable for photovoltaic modules whose efficiency decreases with increasing temperature. In this study, a photovoltaic module was practically cooled by two PV/T systems, one cooled by water and the other by nanofluid and nano-paraffin. Iraqi-produced paraffin was used in this study for its cheap price, and because its melting and freezing temperature (46 °C) is close to the operating range of photovoltaic modules. Nano-TiO₂ was adopted as an additive to water and paraffin. The study results showed an obvious enhancement of the thermal conductivity of both water and paraffin, by up to 126.6% and 170%, respectively, after adding a 2% mass fraction of nano-TiO₂. The practical experiments were carried out outdoors in the city of Baghdad, Iraq. A fluid mass flow rate of 0.15 kg/s was selected for practical reasons, since at this rate the system operates without vibration. The PV panel’s temperature, in the PV/T system (nano-fluid and nano-paraffin), decreased by an average of 19 °C when the tested systems operated during the peak period (12 PM to 3 PM). The decrease in temperatures of the PV module caused a clear improvement in its electrical efficiency, as it was 106.5% and 57.7% higher than the PV module (standalone) and water-cooled PV system, respectively. The thermal efficiency of this system was 43.7% higher than the case of the water-cooled PV/T system. The proposed system (nano-fluid and nano-paraffin) provides a greater possibility of controlling the heat capacity and increasing both efficiencies (electrical and thermal), when compared to a standalone PV module, in harsh Iraqi weather.

It is well known that three-dimensional (3D) printing is an emerging technology used to produce customized implants and surface characteristics of implants, strongly deciding their osseointegration ability. In this study, Ti alloy microspheres were printed under selected rational printing parameters in order to tailor the surface micro-characteristics of the printed implants during additive manufacturing by an in situ, controlled way. The laser path and hatching space were responsible for the appearance of the stripy structure (S), while the bulbous structure (B) and bulbous–stripy composite surface (BS) were determined by contour scanning. A nano-sized structure could be superposed by hydrothermal treatment. The cytocompatibility was evaluated by culturing Mouse calvaria-derived preosteoblastic cells (MC3T3-E1). The results showed that three typical microstructured surfaces, S, B, and BS, could be achieved by varying the 3D printing parameters. Moreover, the osteogenic differentiation potential of the S, B, and BS surfaces could be significantly enhanced, and the addition of nano-sized structures could be further improved. The BS surface with nano-sized structure demonstrated the optimum osteogenic differentiation potential. The present research demonstrated an in situ, controlled way to tailor and optimize the surface structures in micro-size during the 3D printing process for an implant with higher osseointegration ability.