International Journal of Mechanical and Materials Engineering最新文献

Bio-additives, generally composed of alcohol or esters, are sustainable substances added to fuels to enhance their properties and reduce CO₂ emissions. In Mexico, there is a lack of regulations on bio-additive-gasoline mixture composition and effects this composition on the mechanical properties of the tanks is not clear. This study investigates the impact of the quantity of a bio-additive added to gasoline on metallic automotive and motorcycle tanks. Two experimental setups were developed: immersion tests in gasoline-bio-additive mixtures at varying concentrations of a sheet of automotive tanks, and exposure of motorcycle metallic tanks to ambient pressure–temperature conditions over 14 months. Corrosion signs and sediment accumulation appeared within 2 weeks, particularly in the 30% bio-additive mixture, pointing to compatibility issues. Characterization methods, including Raman spectroscopy, gas chromatography-mass spectrometry (GC–MS), Electron microscopy (SEM/EDS), and metallography, revealed methanol in the bio-additive composition. Methanol increases corrosion of the automotive sheets, also, it causes the removal of lead from the anticorrosion coating that covers the motorcycle tanks. This results, emphasize the compatibility challenges between bio-additives and all components of the metallic tanks.

In contemporary dental practice, there is a significant demand for materials that not only exhibit superior mechanical strength and durability but also offer excellent biocompatibility and aesthetic appeal. Zirconia (ZrO₂) has emerged as a leading biomaterial addressing these needs, owing to its exceptional properties such as high fracture toughness, resistance to corrosion and wear, and tooth-like translucency. These characteristics make zirconia ideal for various dental prosthetics, including crowns, bridges, and abutments. Advancements in zirconia composites, particularly yttria-stabilized zirconia (YSZ) and zirconia-toughened alumina, have further enhanced its mechanical properties and stability. YSZ, for instance, is widely utilized in dental ceramics due to its increased strength and fracture toughness. To optimize zirconia’s performance, especially in terms of corrosion resistance and osseointegration, various surface modification techniques have been developed. These techniques encompass acid etching, coating, polishing, biofunctionalization, sandblasting, ultraviolet light exposure, and laser treatments. These modifications significantly improve bone integration by altering surface texture, structure, wettability, chemical resilience, and antibacterial characteristics. In summary, zirconia’s combination of mechanical strength, biocompatibility, and aesthetic appeal, along with ongoing advancements in composite formulations and surface treatments, solidify its role as a leading biomaterial in implant applications.

The photocatalysis process using sunlight as an energy source is a promising alternative to produce hydrogen from the decomposition of water. For this purpose, the reduced graphene oxide (rGO) was synthesized by the Hummers method to increase the electronic transport. In the effort to create a composite with different energy levels, WO₃ was used as a support that can absorb the sunlight and copper ions to induce effects (energetic sublevels) on the photocatalytic activity. Composites with different contents of rGO and WO₃ were obtained by the hydrothermal process, and Cu¹⁺ ions were coupled by the impregnation method. The resulting materials were characterized by spectroscopies Raman, ultraviolet visible (UV–Vis), and X-ray photoelectron (XPS) as well as scanning electron microscopy (FESEM), nitrogen sorption, and X-ray diffraction (XRD). From the parameters analyzed, the Raman results indicate that the highest content of reduced graphene oxide is associated with the strongest intensities in the 2D and G bands, which suggests the formation of a multilayered material. Incorporating 0.5% copper ions reduced the FWHM value of WO₃, indicating higher crystallinity. The reduced graphene oxide enhances electronic transport on the photocatalytic surface. Additionally, copper ions serve as sites for electron capture, which prevents charge recombination. This process is reflected in an increase in interfacial charge transfer. The experimental results from a solar concentrator demonstrated that the composite material containing 0.5 wt.% copper and 6 wt.% reduced graphene oxide on tungsten trioxide (0.5Cu-6rGO-WO₃) achieved the highest yield, producing 349 µmol/g after a reaction time of 5 h. In comparison, the bare WO₃ produced only 272 µmol/g. The enhanced photocatalytic activity of the composite materials is attributed to their increased ability to absorb visible light, which stimulates the reduction reactions, as confirmed by optical analysis. The research reveals that utilizing a specific photocatalyst under a parabolic cylindrical solar concentrator offers a pathway for the generation of molecular hydrogen.

The synergy between a semiconductor, such as CdS, and an insulator, such as MgO, was approached to improve the photocatalytic H₂ evolution. Commercial MgO, nitrate magnesium and carbonate magnesium as Mg precursor of MgO were evaluated in the obtaining of CdS/MgO nanocomposites and their photocatalytic activity. The synthesis of CdS/MgO nanocomposites and its photoactivity as a function of the Mg precursor were sensitive to the MgO structure. A dependence on the mixture of MgO and Mg(OH)₂ phases, and the crystallite size in [2 0 0] (D_{(2 0 0)}) and [2 2 0] (D_{(2 2 0)}) crystallographic directions, in the MgO cubic phase, was discovered after X-ray diffraction (XRD) analyses. HR-TEM images revealed the formation of a composite of CdS nanofibres over MgO and their distribution by mapping elemental analysis. Photoactivation was attributed to CdS under blue light, demonstrated by diffuse reflectance spectroscopy (DRS). The photoactivity increased as a function of the MgO support: MgO commercial (~ 3 mmol_H2 g⁻¹ _CdS h⁻¹) < MgO nitrate (~ 8 mmol_H2 g⁻¹_CdS h⁻¹) < MgO carbonate (~ 28 mmol_H2 g⁻¹_CdS h⁻¹). The photocatalytic activity as a function of the MgO precursor was correlated with the mixture of MgO/Mg(OH)₂ phases as well as the D_{(2 0 0)} and D_{(2 2 0)} crystallite size of the MgO cubic phase.

Developing efficient and sustainable energy storage devices is crucial for advancing mobile electronics and electric vehicles. While lithium-ion batteries currently dominate the market, their limitations have prompted the exploration of alternative technologies. This study investigates the potential of CuMoO₄ spinel nanomaterials as cathodes for aqueous zinc-ion batteries. By combining the unique properties of copper and molybdenum oxide into spinel form, we aim to enhance charge transfer kinetics and stability, thereby overcoming the limitations of traditional CuO–MoO₃ composite electrodes. The CuMoO₄ electrode delivered a specific capacity of 873 mAhg⁻¹ at 1 A/g and maintained 612 mAhg⁻¹ even at a high current density of 10 Ag⁻¹ Additionally, the spinel electrode retained 94% of its initial capacity after 2000 cycles at 1 Ag⁻¹, demonstrating remarkable stability.

In the construction sector, diverse microorganisms have the ability to form biofilms on constructed surfaces affecting the health of the inhabitants. In this sense, diverse nanomaterials of titanium oxide (TiO₂), copper oxide (CuO), and CuO/TiO₂ were synthesized by the sol–gel method, Pechini method, and a mechanical synthesismethod. The influence of the thermal treatment (425–575 °C) on the formation of crystalline phases in the compounds, as well as their antibacterial activity on Escherichia coli and Staphylococcus aureus was investigated. X-ray diffraction technique(XRD) results displayed the formation of anatase, rutile, and tenorite phases on the as-synthesized samples. The Rietveld refinement analysis estimated the composition of phases, as well as the crystal size for each crystalline phase in the specimens (from ~ 16 up to ~ 165 nm). The Fourier Transform Infrared (FTIR) spectroscopy showed the characteristic M–O vibrations of the TiO₂ and CuO compounds. No relevant signals of the precursors were detected. RAMAN spectroscopy confirmed the formation of anatase and rutile phases in the TiO₂ nanomaterials. Scanning electron microscopy (SEM) micrographs revealed the morphology of the compounds and dynamic light scattering (DLS) and electrophoretic light scattering (ELS) analysis showed the particle sizes (from ~ 225 to ~ 750 nm) with Z-potentials between − 11 mV and − 21 mV. Nitrogen adsorption/desorption isotherms results revealed pore sizes between ~ 0.2 and ~ 12.4 nm as well as surface area values up to ~ 158 m²/g. Finally, the minimum inhibitory concentration (MIC) evaluation revealed that the compounds that CuO-based compounds exhibit good antibacterial activity, with MIC values starting at 0.625 mg/mL, and the CuO/TiO₂ sample at 475 °C showed the highest efficacy at 0.312 mg/mL. These results suggest that the as-synthesized compounds could be used as disinfection agents on construction surfaces and in sick buildings, as well as they could to reduce the health risks associated with exposure to bacteria.

Oxidative stress is a process caused by excess-free radicals and reactive oxygen species (ROS), which contribute to the onset and progression of various chronic degenerative diseases. Consequently, interest has grown in studying natural and synthetic antioxidant compounds that restore normal ROS metabolism, alleviating the damage in affected tissues. Despite the above, several preclinical and clinical studies evaluating these therapies have shown some contradictory results since sometimes the use of these molecules has not shown the desired therapeutic efficacy, or in some cases, the use of these antioxidants has been related to the appearance of harmful effects due to their lack of specificity, to the associated adverse effects, in addition to the fact that some ROS are essential for normal physiological functions. On the other hand, nanotechnology is one of the most widely used technological advances in the drug industry. Targeted delivery of active ingredients combines knowledge of pharmacology, pharmaceutical development, polymer sciences, conjugate chemistry, and molecular biology to improve the pharmacokinetics of active ingredients, decreasing their toxicity, immunogenicity, and biorecognition. Cerium oxide nanoparticles (CeO₂-NPs) have emerged as a novel therapeutic alternative with high antioxidant capacity, demonstrating beneficial effects in both in vivo and in vitro studies for treating chronic degenerative disorders. CeO₂-NPs are only activated when ROS levels reach a harmful threshold, which protects healthy cells from unwanted effects. Their therapeutic potential has been demonstrated in multiple fields of medicine, including oncology, neurology, ophthalmology, cardiology, and hepatology. Therefore, this review addresses the potential applications of CeO₂-NPs evaluated in animal and in vitro models of chronic degenerative diseases, which help visualize and position them as an effective and safe therapeutic alternative for treating this condition.

This investigation introduces a novel method for the fabrication of ZnSe thin films on glass substrates through the spin coating technique which employs thiol-amine cosolvents. The thiol-amine co-solvent system efficiently dissolves several metal and metal chalcogenide precursors, facilitating cost-effective, and low-temperature solution-based deposition compatible with flexible substrates. The synthesized ZnSe thin films underwent air annealing at temperatures between 250 and 350 °C, thereby improving their structural and optical characteristics. The polycrystalline nature of ZnSe was elucidated via X-ray diffraction (XRD) analysis, while scanning electron microscopy (SEM) assured the rise of surface smoothness and uniformity with annealing temperature. Energy-dispersive spectroscopy (EDS) analysis indicated near-stoichiometric ZnSe composition, and Fourier-transform infrared (FTIR) spectroscopy identified Zn–Se stretching vibrations in the 960–1120 cm⁻¹ range. The optical data demonstrated high transmittance with an optical bandgap of 3.32–3.85 eV. Furthermore, optical data of ZnSe were embarked for computation of Ge-on-ZnSe waveguide with SiO₂ cladding for long-wave infrared (LWIR) light. The waveguide showed a remarkable power confinement factor (PCF) of ~ 0.99 with nearly 1 dB/cm loss at a laser wavelength of 8 μm. These outputs are highly optimistic for the fabrication of solution-processed ZnSe for LWIR photonic integration.

The Di barium magnesium Di-silicate Ba2MgSi2O7 (BMSO) with single-doped Tb3 + , Eu3 + phosphors, and co-doped Tb3 + /Eu3 + phosphors were prepared by the combustion method. The structural characterisation was studied by X-ray diffraction (XRD) technique, and an optical property (PL, ML) and luminescence decay curves were utilised to describe each phosphor’s properties. Profound green emission due to the Tb3 + 5D4-7F5 transition was optically canvassed in the Tb3 + single-doped Ba2MgSi2O7 sample, and it was determined that the appropriate concentration quenching process involved a diople-diople interaction. A huge overlap between Tb3 + emission and Eu3 + excitation spectra has consequences for strength transfer from Tb3 + to Eu3 + . Based on the concentration quenching approach, it was found that the energy transfer mechanism is a quadrupole–quadrupole interaction, and the energy transfer critical distance from Tb3 + to Eu3 + ions is predicted to be (6.7). Additionally, by altering the ratio of Tb3 + and Eu3 + concentrations in Ba2MgSi2O7:Tb3 + Eu3 + phosphors, white light emission was produced. According to all the findings, the single-component white light-producing phosphor BMSO: Tb3 + Eu3 + is a promising one.