Search Results (393)

In this study, a Z-scheme Ho₂InSbO₇/Ag₃PO₄ (HAO) heterojunction photocatalyst was successfully fabricated for the first time by ultrasound-assisted solvothermal method. The structural features, compositional components and morphological characteristics of the synthesized materials were thoroughly characterized by a series of techniques, including X-ray diffraction, Fourier transform infrared spectroscopy, Raman spectrum, X-ray photoelectron spectroscopy, transmission electron microscopy, scanning electron microscopy and energy-dispersive X-ray spectroscopy. A comprehensive array of analytical techniques, including ultraviolet-visible diffuse reflectance absorption spectra, photoluminescence spectroscopy, time-resolved photoluminescence spectroscopy, photocurrent testing, electrochemical impedance spectroscopy, electron paramagnetic resonance, and ultraviolet photoelectron spectroscopy, was employed to systematically investigate the optical, chemical, and photoelectronic properties of the materials. Using oxytetracycline (OTC), a representative tetracycline antibiotic, as the target substrate, the photocatalytic activity of the HAO composite was assessed under visible light irradiation. Comparative analyses demonstrated that the photocatalytic degradation capability of the HAO composite surpassed those of its individual components. Notably, during the degradation process, the application of the HAO composite resulted in an impressive removal efficiency of 99.89% for OTC within a span of 95 min, along with a total organic carbon mineralization rate of 98.35%. This outstanding photocatalytic performance could be ascribed to the efficient Z-scheme electron-hole separation system occurring between Ho₂InSbO₇ and Ag₃PO₄. Moreover, the adaptability and stability of the HAO heterojunction were thoroughly validated. Through experiments involving the capture of reactive species and electron paramagnetic resonance analysis, the active species generated by HAO were identified as hydroxyl radicals (•OH), superoxide anions (•O₂⁻), and holes (h⁺). This identification provides valuable insights into the mechanisms and pathways associated with the photodegradation of OTC. In conclusion, this research not only elucidates the potential of HAO as an efficient Z-scheme heterojunction photocatalyst but also marks a significant contribution to the advancement of sustainable remediation strategies for OTC contamination. Full article

This paper presents a numerical simulation study evaluating carbon dioxide capture and storage (CCS) feasibility for the Turceni Power Plant in Oltenia, Romania, using the nearby depleted Bibești-Bulbuceni gas reservoir. A comprehensive reservoir model was developed using Petrel software, integrating geological and reservoir engineering data for the formations of the Bibești-Bulbuceni structure, which is part of the western Moesian Platform. The static model incorporated realistic petrophysical inputs for the Meotian reservoirs. Dynamic simulations were performed using Eclipse compositional simulator with Peng–Robinson equation of state for a CH4-CO₂ system. The model was initialized with natural gas initially in place at 149 bar reservoir pressure, then produced through depletion to 20.85 bar final pressure, achieving 80% recovery factor. CO₂ injection simulations modeled a phased 19-well injection program over 25 years, with individual well constraints of 100 bar bottom-hole pressure and 200,000 Sm³/day injection rates. Results demonstrate successful injection of a 60 Mt CO₂, with final reservoir pressure reaching 101 bar. The modeling framework validates the technical feasibility of transforming Turceni’s power generation into a net-zero process through CCS implementation. Key limitations include simplified geochemical interactions and relying on historical data with associated uncertainties. This study provides quantitative evidence for CCS viability in depleted hydrocarbon reservoirs, supporting industrial decarbonization strategies. The strategy not only aligns with the EU’s climate-neutral policy but also enhances local energy security by repurposing existing geological resources. The findings highlight the potential of CCS to bridge the gap between current energy systems and a sustainable, climate-neutral future. Full article

Multi-hop routing over low-power wide-area networks (LPWANs) has emerged as a promising technology for extending network coverage. However, existing protocols face high transmission disruption risks due to factors such as dynamic topology driven by stochastic events, dynamic link quality, and coverage holes induced by imbalanced energy consumption. To address this issue, we propose a failure risk-aware deep Q-network-based multi-hop routing (FRDR) protocol, aiming to reduce transmission disruption probability. First, we design a power regulation mechanism (PRM) that works in conjunction with pre-selection rules to optimize end-device node (EN) activations and candidate relay selection. Second, we introduce the concept of routing failure risk value (RFRV) to quantify the potential failure risk posed by each candidate next-hop EN, which correlates with its neighborhood state characteristics (i.e., the number of neighbors, the residual energy level, and link quality). Third, a deep Q-network (DQN)-based routing decision mechanism is proposed, where a multi-objective reward function incorporating RFRV, residual energy, distance to the gateway, and transmission hops is utilized to determine the optimal next-hop. Simulation results demonstrate that FRDR outperforms existing protocols in terms of packet delivery rate and network lifetime while maintaining comparable transmission delay. Full article

In the present study, the coaxial waterjet-assisted nanosecond laser drilling of micro-holes in C_f/SiC composites, coupled with nanosecond laser drilling in air for fabricating micro-holes with high aspect ratios, were investigated. The surface morphology, reaction products, and micro-hole shapes were thoroughly examined. The results reveal that, for the coaxial waterjet-assisted nanosecond laser drilling of micro-holes in the C_f/SiC composite, the increasing of waterjet velocity enhances the material removal rate and micro-hole depth, but reduces the micro-hole diameter and taper angle. The coaxial waterjet isolates the laser-ablated region and cools down the corresponding region rapidly, leading to the formation of a mixture of SiC, SiO₂, and Si on the surface. As the coaxial waterjet velocity increases, the morphology of residual surface products changes from a net-like structure to individual spheres. Coaxial waterjet-assisted nanosecond laser drilling, with a waterjet velocity of 9.61 m/s, achieves micro-holes with a good balance between efficiency and quality. For the fabrication of micro-holes with a high aspect ratio in C_f/SiC composites, micro-holes fabricated by nanosecond laser drilling in air exhibit obvious taper features, which should be ascribed to the combined effects of spattering slag, plasma, and energy dissipation. The application of coaxial waterjet-assisted nanosecond laser drilling on micro-holes fabricated by laser drilling in air effectively expands the hole diameter. The fabricated micro-holes have very small taper angles, with clean wall surfaces and almost no reaction products. This approach, combining nanosecond laser drilling in air followed by coaxial waterjet-assisted nanosecond laser drilling, offers a promising technique for fabricating high-quality micro-holes with high aspect ratios in C_f/SiC composites. Full article

Impact Drilling Technology is one of the most effective methods for enhancing the penetration rate and efficiency in hard rock formations. Downhole axial vibration impact tools can provide a stable impact load, but they also increase the complexity of the Bottom Hole Assembly (BHA) motion. Addressing the problem of vibration fatigue in the lower BHA when subjected to high-frequency impact stresses during impact drilling, this study utilizes finite-element impact modules and Design-Life fatigue analysis software to establish a nonlinear dynamic model of the drill string assembly under axial excitation. It investigates the influence patterns of control parameters, such as the impact energy and impact frequency, on BHA vibration damage and rock-breaking efficiency. The results show that the vibration characteristics of the BHA are significantly affected by the impact tool’s control parameters. Increasing the input impact energy intensifies the amplitude of alternating stress in the drill string system. Meanwhile, the equivalent stress fluctuation of the drill string tends to stabilize at high frequencies above 100 Hz, indicating that high-frequency impacts are beneficial for mitigating vibration damage and prolonging the service life of the BHA. This study provides a theoretical basis for reducing the drill string fatigue damage and optimizing the drilling parameters for an improved performance. Full article

Highly efficient photocatalysts for solar energy conversion require effective charge carrier separation and rapid interfacial transport kinetics to maximize electron availability. Two-dimensional Ti₃CNT_x, a novel conductive material in the MXene family with exceptional electrical conductivity, has emerged as an ideal electron transfer mediator due to its large specific surface area and abundant active terminal groups. In this work, we strategically integrated the 2D multi-metal sulfide Cu-Zn-In-S (CZIS) with 2D Ti₃CNT_x nanosheets through physical mixture, constructing a heterostructured 2D/2D CZIS/Ti₃CNT_x composite photocatalyst for the hydrogen evolution reaction. The unique architecture significantly accelerates electron migration from CZIS to Ti₃CNT_x, while synergistically promoting the spatial separation and directional transfer of photogenerated electron–hole pairs (e⁻/h⁺). When the hydrogen evolution reaction is carried out under identical conditions, the hydrogen yield rate is 4.3 mmol g⁻¹ h⁻¹ with pristine CZIS but is improved dramatically to 14.3 mmol g⁻¹ h⁻¹ when the composite containing an adequate amount of 2D Ti₃CNT_x is used. This study offers new insight into the rational design and controllable synthesis of Ti₃CNT_x-based composite photocatalytic systems for efficient photocatalytic hydrogen production. Full article

The drilling machinability of glass fiber G₁₄, basalt fiber B₁₄, and two hybrid laminates (B₄G₆B₄, G₄B₆G₄) was evaluated through 36 full-factorial experiments employing an HSS-G drill, three spindle speeds (715, 1520, 3030 rpm), and three feed rates (0.1–0.3 mm rev⁻¹). Peak thrust force varied from 65.8 N for B14 at 0.1 mm rev⁻¹ to 174.3 N for G₁₄ at 0.3 mm rev⁻¹; hybrids occupied the intermediate range of 101–163 N. Infra-red thermography recorded maximum drill temperatures of 110–120 °C for G₁₄, almost double those of B₁₄, while both hybrids attenuated hotspots to below 90 °C. ANOVA attributed 73.4% of thrust force variance to feed rate, with material type and spindle speed contributing 15.5% and 1.7%, respectively; for temperature, material type governed 41.5% of variability versus 17.0% for speed. Dimensional quality tests revealed that the symmetric hybrid G₄B₆G₄ maintained entrance and exit diameters within ±2% of the nominal 6 mm, whereas B₄G₆B₄ over-expansion exceeded 8% at the lowest feed and G₁₄ exit diameters grew to 6.1 mm at 0.3 mm rev⁻¹. Integrating basalt compliance with glass stiffness, therefore, halves thrust force relative to G₁₄, suppresses delamination and overheating, and offers a practical strategy to prolong tool life and improve hole quality in multi-material composite structures. These insights guide parameter selection for lightweight hybrid composites in aerospace, renewable-energy installations, and marine components worldwide. Full article

Compared to the traditional flip-chip bonded focal plane array, in high-density vertically integrated photodiode (HDVIP) focal plane technology, the thickness of the mercury cadmium telluride (MCT or Hg_1−xCd_xTe) layer serves as a more critical parameter. This parameter not only influences the efficiency of photon energy absorption but also defines the pn junction area, thereby affecting the magnitude of the dark current. Furthermore, it significantly impacts the manufacturability of via-hole etching and formation processes. This paper investigated the photonic crystal resonances and coherent perfect absorption (CPA) effect of a thin MCT layer in HDVIP by using COMSOL Multiphysics^® 4.3b and optimized the structure of the loop-hole photodiode device. The CPA, which is formed by this structure, achieves high absorption of illumination in a very thin MCT film. It is demonstrated that an absorption rate of infrared radiation of more than 95% with a wavelength during the 8 µm–10 µm range can be achieved in Hg_1−xCd_xTe (x = 0.225) with a thickness of only 1.5 µm–3 µm. The benefit of thinner MCT film is that it decreases the dark current of pn junction and reduces the technical difficulty of etching and metallization of the loop-hole photodiode. Full article

ZnO/WO₃ coatings were synthesized by the plasma electrolytic oxidation of zinc in an alkaline phosphate electrolyte (supporting electrolyte, SE) with the addition of WO₃ particles or tungstosilicic acid (WSiA, H₄SiW₁₂O₄₀) at concentrations of up to 1.0 g/L. These coatings were intended for the decomposition of methyl orange (MO) through photocatalysis. The morphology, chemical composition, crystal structure and absorption properties of the coatings were investigated using scanning electron microscopy, energy dispersive X-ray spectroscopy, wavelength-dispersive X-ray spectroscopy, X-ray diffraction, photoelectron spectroscopy and diffuse reflectance spectroscopy. Under artificial sunlight, the PA of the coatings was investigated using MO decomposition. The photocatalytic activity (PA) of the ZnO/WO₃ coatings was higher than that of the ZnO obtained in SE. The decrease in the recombination rate of photo-generated electron/hole pairs due to the coupling of ZnO and WO₃ is related to the increased PA. The PA for ZnO and the most photocatalytically active ZnO/WO₃ was around 72% and 96%, respectively, after 8 h of irradiation. A mechanism for MO photo-degradation by the ZnO/WO₃ photocatalyst was also proposed. Full article

Bismuth oxide (β-Bi₂O₃) is a promising visible-light-driven photocatalyst due to its narrow direct bandgap, but its practical application is hindered by rapid electron–hole recombination and limited surface active sites. This study demonstrates a sol-gel synthesis approach to tailor β-Bi₂O₃ nanoparticles through magnesium (Mg) doping, achieving remarkable enhancements in the photocatalytic degradation of organic pollutants and hydrogen evolution. The structural analysis through XRD, SEM, and EDX confirmed Mg-doping concentrations of 0.025 to 0.1 M led to crystallite size reduction from 79 nm to 13 nm, while the UV–Vis bandgap measurement showed it decreased from 3.8 eV to 3.08–3.3 eV. The photodegradation efficiency increased through Mg doping at a 0.1 M concentration, with the highest rate constant value of 0.0217 min⁻¹. The doping process led to VB potential reduction between 3.37 V (pristine) and 2.78–2.91 V across the doped samples when referenced to SCE. The photocatalytic performance of Mg_0.075Bi_1.925O₃ improved with its 3.2 V VB potential because the photoelectric band arrangement enhanced both light absorption and charge separation. The combination of modifications through Mg doping yielded an enhanced photocatalytic performance, which proves that magnesium doping is a pivotal approach to modifying β-Bi₂O₃ suitable for environmentally and energy-related applications. Full article

This study systematically investigates the combustion behavior and kinetic characteristics of oil shale semi-coke. Thermogravimetric analysis (TGA) experiments, combined with both model-free and model-based methods, were used to explore the thermal characteristics, kinetic parameters, and reaction mechanisms of the combustion process. The results show that the combustion process of oil shale semi-coke can be divided into three stages: a low-temperature stage (50–310 °C), a mid-temperature stage (310–670 °C), and a high-temperature stage (670–950 °C). The mid-temperature stage is the core of the combustion process, accounting for approximately 28–37% of the total mass loss, with the released energy concentrated and exhibiting significant thermal chemical activity. Kinetic parameters calculated using the model-free methods (OFW and KAS) and the model-based Coats–Redfern method reveal that the activation energy gradually increases with the conversion rate, indicating a multi-step reaction characteristic of the combustion process. The F2-R3-F2 model, with its segmented mechanism (boundary layer + second-order reaction), better fits the physicochemical changes during semi-coke combustion, and the analysis of mineral phase transformations is more reasonable. Therefore, the F2-R3-F2 model is identified as the optimal model in this study and provides a scientific basis for the optimization of oil shale semi-coke combustion processes. Furthermore, scanning electron microscopy (SEM) and X-ray diffraction (XRD) analyses were conducted on oil shale semi-coke samples before and after combustion to study the changes in the combustion residues. SEM images show that after combustion, the surface of the semi-coke sample exhibits a large number of irregular holes, with increased pore size and a honeycomb-like structure, indicating that the carbonaceous components were oxidized and decomposed during combustion, forming a porous structure. XRD analysis shows that the characteristic peaks of quartz (Q) are enhanced after combustion, while those of calcite (C) and pyrite (P) are weakened, suggesting that the mineral components underwent decomposition and transformation during combustion, particularly the decomposition of calcite into CO₂ at high temperatures. Infrared spectroscopy (IR) analysis reveals that after combustion, the amount of hydrocarbons in the semi-coke decreases, while aromatic compounds and incompletely decomposed organic materials are retained, further confirming the changes in organic matter during combustion. Full article

With the continuous growth of global energy demand and the increasingly severe environmental issues, the extensive utilization of traditional fossil fuels has led to serious energy crises and environmental pollution problems. In this study, a hydrothermal method was employed, and by adding ethanolamine and controlling different temperatures, pink zinc sulfide with zinc vacancies was synthesized. UV-Vis DRS analysis indicated that the sample exhibited significant visible light absorption characteristics within the wavelength range of 500–550 nm. The presence of zinc vacancies was confirmed through XPS. Due to the existence of zinc vacancies, the sample demonstrated excellent photocatalytic hydrogen evolution activity without the need for co-catalysts, with the optimal sample achieving a hydrogen evolution rate of 7631.70 μmol h⁻¹ g⁻¹. Zinc vacancies can provide additional active sites, enhance catalytic efficiency, and promote the separation of photogenerated electrons and holes. Furthermore, the introduction of vacancies effectively reduces the bandgap of the material, significantly broadening its visible light absorption range. This work provides a new approach for enhancing hydrogen evolution in pure ZnS and offers novel strategies for the further design of ZnS-related photocatalysts. Full article

Direct liquid cooling technology has the potential to enhance the thermal management performance of electric motors with continuously increasing energy density. However, direct liquid cooling technology has practical limitations for full-scale commercialization. In addition, the conventionally used indirect liquid cooling imposes higher thermal resistance to cope with the increased thermal management performance of high power density electric motors. Therefore, this study proposes a hybrid direct–indirect oil cooling system as a next-generation cooling strategy for the enhanced thermal management of high power density electric motors. The heat transfer characteristics, including maximum winding, stator and motor housing temperatures, heat transfer coefficient, friction factor, pressure drop, and performance evaluation criteria (PEC), are investigated for different spray hole diameters, coolant oil volume flow rates, and motor heat loss levels. The computational model was validated with experimental results within a 5% error developed to evaluate heat transfer characteristics. The results show that spray hole diameter significantly influences cooling performance, with a larger diameter (1.7 mm) reducing hydraulic resistance while causing a slight increase in motor temperatures. The coolant oil volume flow rate has a major impact on heat dissipation, with an increase from 10 to 20 L/minute (LPM) reducing winding, stator, and housing temperatures by 22.05%, 22.70% and 24.02%, respectively. However, higher flow rates also resulted in an increased pressure drop, emphasizing the importance of the selection of a suitable volume flow rate based on the trade-off between cooling performance and energy consumption. Despite the increase in motor heat loss level from 2.6 kW to 8 kW, the hybrid direct–indirect oil cooling system effectively maintained all motor component temperatures below the critical threshold of 180 °C, confirming its suitability for high-performance electric motors. These findings contribute to the development and commercialization of the proposed next-generation cooling strategy for high power density electric motors for ensuring thermal stability and operational efficiency. Full article

With global energy demand surging and traditional energy resources diminishing, the solar absorber featuring optimized design shows substantial potential in areas like power generation. This study proposes a solar absorber that is insensitive to wide-angle incidence and polarization. It has a cylindrical structure with square holes, which is constructed from titanium nitride (TiN). The calculation results indicate that, for plane waves, the average absorption of this solar absorber across the wavelength range of 300–2500 nm reaches 92.4%. Moreover, its absorption rate of the solar spectrum corresponding to AM1.5 reaches 94.8%. The analysis of the characteristics within the electric and magnetic field profiles indicates that the superior absorption properties arise from a cooperative resonance effect. This effect originates from the interaction among surface plasmon resonance, guided-mode resonance, and cavity resonance. In this study, the geometric parameters of the solar absorber’s structure significantly influence its absorption performance. Therefore, we optimized these parameters to obtain the optimal values. Even at a large incident angle, this absorber maintains high absorption performance and shows insensitivity to the polarization angle. The findings expected from this study are likely to be of considerable practical importance within the realm of solar photothermal conversion. Full article

Tetracycline hydrochloride pollution poses a serious environmental threat; however, it is difficult to deal with by conventional methods. In this study, the Z-scheme BiOCl/Bi₂WO₆ composite was hydrothermally synthesized and evaluated for its ability to decompose tetracycline hydrochloride under visible light. The composite material was systematically characterized by XRD, SEM, TEM/HRTEM, XPS, FTIR, BET, PL, UV-Vis DRS, and EPR to analyze its structure, morphology, and optical/electrochemical properties. Characterization revealed that the composite featured a flower-ball structure with broader light absorption and higher solar energy efficiency. A narrow bandgap further facilitated charge separation, boosting photocatalytic performance. Among the synthesized materials, the 20% BiOCl/Bi₂WO₆ composite exhibited the best performance, removing 94% of tetracycline hydrochloride in 60 min, which was 5.2 times and 1.4 times higher than pure BiOCl and Bi₂WO₆, respectively. The rate constant was 10.8 times and 2.5 times higher than that of pure BiOCl and Bi₂WO₆. After five cycles, it maintained the 88.7% removal rate, with X-ray diffraction analysis confirming its structural stability and well mechanical properties. Electron paramagnetic resonance and radical scavenging experiments identified photogenerated holes (h⁺) and superoxide radicals (·O₂⁻) as the primary active species. This work highlights the fact that the prepared Z-scheme BiOCl/Bi₂WO₆ composite exhibited excellent photocatalytic performance in the degradation of tetracycline hydrochloride, demonstrating promising potential for practical applications. Full article