International Journal of Mechanical and Materials Engineering最新文献

Herein, we report the oxalic acid and cetyl trimethyl ammonium bromide (CTAB) assisted co-precipitation synthesis of nanocrystalline tungsten oxide (WO₃). Different annealing temperatures were selected systematically based on the thermo-gravimetric analysis (TGA) of the precursors. The high crystallinity of the samples was revealed from the intense and narrow X-ray diffraction (XRD) peaks. Oxalic acid-assisted WO₃ showed a considerable reduction in crystallite size. The increase in crystallite size with annealing temperature was also evident in both samples. The change of surfactant and annealing temperature resulted in a modification of surface morphology that was identified using high-resolution resolution-scanning electron microscopy (HR-SEM). The formation of WO₃ was further established by the Raman spectra of the samples. Size strain plot (SSP) analysis of the samples showed a decrease of microstrain with an increase in annealing temperature. The bandgap energy obtained from the diffused reflectance spectra of the samples showed a red shift with an increase in annealing temperature. The X-ray photoelectron spectroscopy (XPS) analysis confirmed the existence of a pure oxidation state of W⁶⁺ in oxalic acid-assisted WO₃ and mixed oxidation states of W⁶⁺ and W⁵⁺ in CTAB-assisted WO₃ samples. The mesoporous nature and specific surface area of the samples are inferred from Brunauer–Emmett–Teller (BET) analysis. The reduced crystallite size, stable oxidation state, and higher specific surface area of the oxalic acid-assisted WO₃ samples suggest its possible use as a supercapacitor and photocatalyst.

Graphical Abstract

Mainly in the new era, there is a need to accelerate chemical reactions, which is made possible by advanced nanocatalysts, whose magnetic nanocatalysts are highly efficient in controlling chemical reactions such as Sonogashira coupling and alcohol oxidation. Magnetic nanocatalysts are made of magnetite nanoparticles under the chemical co-precipitation method. Their structure was identified by analysis such as EDX (energy-dispersive X-ray) and XRD (X-ray diffraction). The Sonogashira carbon–carbon coupling reaction was performed twice consecutively, and the product efficiency was more than 97%. Oxidation of alcohols to produce aldehyde products is up to 99%. The structure of the magnetic nanocomposite was analyzed after several reuses, and the results showed that it was unchanged, and its performance, structure, and magnetic properties were fully preserved. The reaction conditions are at the lowest possible temperature, harmless solvents, and the highest efficiency percentage, which creates green conditions. The products obtained from the Sonogashira double coupling reaction have two triple bonds. Also, the products with the oxidation of alcohols, which are used as the main precursors in the chemical and medical industries for chemical and pharmaceutical production, are very important.

The article presents the results of a study on the effect of a dispersed filler, produced by thermal synthesis from a mixture of titanium hydride, ferrosilicomanganese, and boron carbide powders on the tribological characteristics of a polymer composite based on ED-20 epoxy diane oligomer. The filler was incorporated into the resin at concentration ranging from 5 to 40 parts of composite powder per 100 parts (by weight) of the epoxy oligomer. At a sliding speed of 0.5 m/s, the highest friction coefficient (µ) in the range of 0.55–0.6 was noted for the epoxy polymer without a filler, while an increase in the filler concentration in the epoxy polymer led to a noticeable decrease in the friction coefficient values. The lowest values of µ (0.32–0.35) were observed in composites with 5 and 10 wt.% filler. With an increase in the sliding speed up to 1 m/s at the stage of constant friction, the friction coefficient for unreinforced polymer and the composite with 5% filler reached values of 0.55–0.65 followed by a transition to catastrophic wear. For polymers with 10, 20, and 40 wt.% filler, composites with a higher content of the dispersed component were characterized by lower values of µ. The specific wear of composites decreased with the incorporation of cermet particles into the polymer and with an increased in its concentration in the polymer from 5 to 20%. However, when the filler content increases to 40%, the level of specific wear increases slightly.

This study aims to evaluate the destructive and non-destructive strength parameters of bacterial concrete with different grades (M20, M25, M30) and cell counts (10^5 and 10^6 cells/ml) using Bacillus subtilis. Additionally, cost analysis and cost–benefit comparisons were conducted for each mix. The effectiveness of B. subtilis in resisting high temperatures was also examined. Findings indicate a 25–40% increase in strength parameters in bacterial concrete compared to conventional concrete. Bacterial mixes consistently showed velocities above 4.45 km/s, indicating excellent quality, surpassing conventional concrete. Notably, bacteria with a cell count of 10^5 cells/ml exhibited greater strength than 10^6 cells/ml across all grades. Cantabro loss tests revealed a 15–25% reduction in wear and tear for bacterial concrete. The bacterial specimens also showed significantly lower strength loss at higher temperatures. This study underscores the potential of bacterial-based self-healing concrete for specific construction applications, offering high temperature resistance, increased strength, and reduced wear and tear.

Polymer matrix composites (PMCs) have emerged as critical materials in lightweight engineering applications due to their excellent mechanical properties and design versatility. However, their inherent limitations in electrical and thermal conductivity necessitate metallization, particularly for applications such as lightning strike protection (LSP) and electromagnetic interference (EMI) shielding. Cold spraying, a low-temperature metallization technique, addresses the shortcomings of conventional methods by enabling the deposition of dense, oxide-free, and highly conductive coatings with minimal damage to the composite substrate. This review provides a comprehensive overview of advancements in metallization techniques, with a focus on cold spraying, to enhance the electrical and thermal performance of PMCs for LSP and EMI shielding. The combination of PMCs with conductive materials presents an innovative approach to achieving lightweight, corrosion-resistant, and efficient LSP and EMI shielding solutions, offering significant advancements in surface functionalization. Future research directions include the exploration of hybrid metallization strategies and the integration of cold spraying with additive manufacturing, highlighting their potential to create multifunctional and high-performance PMC-based systems. Additionally, emerging trends such as novel or smart materials, optimization of cold spray processes through advanced modeling, and the translation of these innovations into industrial applications are discussed.

In the present study, the mesoporous TiO₂ that was supported on graphitic carbon nitride (g-C₃N₄) was decorated with Au. The nanocomposite (Au-m-TiO₂/g-C₃N₄) has been successfully synthesized by combining sono-chemical and EISA methods and was subsequently used in photocatalytic oxidative desulfurization of dibenzothiophene (DBT) in n-octane as a model fuel and under visible illumination. The Au-m-TiO₂/g-C₃N₄ photocatalyst was characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), UV–Vis diffusive reflectance spectra (UV–Vis DRS), high-resolution transmission electron microscopy (HR-TEM), Fourier transform infrared spectra (FT-IR), and nitrogen adsorption measurements. The removal efficiency of DBT was 98.7% under the optimized reaction conditions and under visible-light irradiation (λ > 400 nm).

The primary aim of this study is to examine the rheological attributes of graphene oxide (GO)-reinforced gum ghatti-cl-poly(AA)/GO (GGAAGO) hydrogels, with the intent of improving their mechanical and thermal properties. Thermal gravimetric analysis (TGA) was employed to assess the thermal stability of the synthesized hydrogels, revealing the interaction between GO, gum ghatti, and acrylic acid. This investigation centers on the swelling behavior and rheological assessments of the hydrogels. Various experiments were conducted on nanocomposite particle gels to scrutinize the impact of graphene oxide (GO) microparticle concentration (ranging from 0 to 5 mg) on network topology, swelling, and mechanical characteristics of the gels. The rheological analysis also indicates a reduction in viscosity.

Furthermore, the rheological examination of hydrogels indicates that the storage modulus (G′) consistently surpasses the loss modulus (G″) within the linear viscoelastic zone across the entire frequency spectrum. This dominance of the storage modulus over the loss modulus suggests continuous covalent crosslinking, accounting for the solid-like and elastic nature (G′ > G″) of the hydrogels. All rheological parameters highlight commendable mechanical properties, rendering the composite hydrogel suitable for applications such as drug administration and various environmental uses.

The engineering of the architecture of the quantum wires has shown a real challenge in the scientific community owing to their fascinating and auspicious application potential in the field of optoelectronics. The modulation of the morphology and structure of the quantum wires may give rise to the modulation of the energy levels and band offset positions to enhance the charge carriers transfer through any electronic device and improve the overall performance for the future application in the field of spintronics and photonics. Here, we proposed, for the first time, a novel rectangular architecture based Al_xGa_1-xAs and Ga_xIn_1-xAs quantum wires to engineer the electron energy spectrum according to a wide range of applications in electronics and optical devices. The electron energy levels in rectangular Al_xGa_1-xAs and Ga_xIn_1-xAs quantum wires with infinite potential barrier were calculated at different x values and different cross-section areas to explore the role of dopant and compared with the cylindrical shape. The calculations of the electron confinement energy in the first and second energy levels indicate that the energy value in cylindrical quantum wire is less than its value in rectangular one while for E₃ the energy value in cylindrical quantum wire is larger than its value in rectangular one for all values of x. The confinement energy was found to be inversely proportional to the ratio of the doped material. The electron energy dispersion in Al_xGa_1-xAs and Ga_xIn_1-xAs quantum wires of 100 nm² cross-section area, x = 0.4 for E₁, E₂ and E₃ with the wave vector value has been investigated. The calculations of the first and second energy levels indicated that the energy value in cylindrical quantum wire is less than its value in rectangular one for E₁ and E₂ while for E₃ the energy value in cylindrical quantum wire is larger than its value in rectangular with a distinct value for each wave vector value for all x values. These unique features of the proposed novel architecture may open a new avenue for the future applications in photonics, spintronics and waveguides.

Polylactic acid (PLA) and polyvinyl alcohol (PVA) are promising biocompatible and biodegradable materials for biomedical uses, yet they have limitations. Similarly, lignin is a precursor for carbon fiber but requires plasticizers to be spun into fibers. This hampers their use in areas like carbon fiber production and tissue engineering, thus the reason for this study. Lignin was extracted from the plantain stem, and a lignin blend with PLA and PVA was made and electrospun into fibers. Thereafter, the physiochemical properties of the composite fibers were analyzed. The XRD spectra revealed increased crystallinity in PLA/Lignin fiber. When 0.75 wt.% of lignin was added to PVA, a new peak and peak shift were formed in the composite fiber, indicating strong interaction. The crystallinity of PVA/lignin decreased from 71.5 to 60.1% when 0.25 wt. % of lignin was added. DSC showed miscibility of polymers and improved melting temperatures from 155 to 228 °C, for PLA/lignin (0.5wt.%) fiber, but a reduction in melting temperatures of PVA, with higher lignin content (149–143 °C). FTIR showed notable functional groups, typical of PLA, PVA, and lignin, such as the OH group between 3800 and 3459 cm⁻¹. The minor peak shift in PLA/lignin showed that the level of molecular interaction is less than that of PVA/lignin. PLA/lignin displayed better fiber morphology compared to PVA/lignin, where fibers became sheet-like with higher lignin content. The addition of lignin improved the tensile strength of PVA (0.7 to 2.7 MPa). Conversely, PLA/lignin’s tensile strength decreased, due to reduced load transfer efficiency. Overall, PVA/lignin and PLA/lignin composites exhibit potential as reinforcement materials for biopolymers and carbon fiber precursors, with PVA showing more promise for carbon fiber production due to robust polymer-lignin interaction.

Hydrogen is crucial for decarbonization efforts due to its abundance, environmental friendliness, and versatility. To maximize its potential, an efficient transportation infrastructure is essential. While utilizing the natural gas pipeline network for transporting hydrogen is cost-effective, hydrogen embrittlement (HE) poses a significant challenge. When hydrogen enters the metal, it significantly compromises its fracture toughness. This study investigates the impact of high-pressure hydrogen on the mechanical properties of API 5L X65 carbon steel through a combined experimental and computational approach. To quantify the extent of HE, tensile tests were performed on identical specimens, one set pre-exposed to high-pressure hydrogen and another set kept in an inert environment for comparison. Finite element modelling, employing the Bai-Wierzbicki material model (BWMM), was used to simulate the material behaviour under large plastic deformations and correlate with experimental results. This synergistic approach integrates experimental data with simulations, creating a framework for predicting and preventing catastrophic failures.