International Journal of Mechanical and Materials Engineering最新文献

The design and development of metastable β-Ti alloys with non-toxic elements that are used in the manufacturing of orthopedic implants are gaining significant research attention. In this work, two metastable β-Ti alloys, binary alloy of Ti-17Mo wt% (referred as Alloy A) and ternary alloy of Ti-16.5Mo-1.1Fe wt% alloy (referred as Alloy B) were designed with different values of electronic parameters such as the Molybdenum equivalence (Moeq), electron to atom ratio (e/a), and the Bo-Md. The contribution of the electronic parameters in influencing the formation of phases and the elastic modulus is discussed. Phase characterization and tensile properties of the alloys after solution treatment at 1100 °C and quenched in ice-brine were carried out using different techniques. The X-ray diffraction (XRD) patterns and optical microscopy (OM) micrographs showed that with increasing e/a ratio the β phase stability increases. EBSD phase maps showed the decrease in the volume fractions of α″and ω phases upon addition of Fe. With increase in stability of β phase, the ultimate tensile strength (UTS) and elastic modulus decreased from 912 MPa to 540 MPa and 82 GPa to 73 GPa in Alloy A and Alloy B, respectively. On the other hand, the increase in the β phase stability resulted in increased hardness from 366 Hv_0.5 for Alloy A to 428 Hv_0.5 in Alloy B. Using scanning electron microscopy (SEM), a combination of cleavage facets and dimpled structure were observered in both alloys.

Epoxy coatings for stacked electrical steel are of high relevance for renewable energy and electric mobility technologies. Waterborne epoxy varnish systems for electrical steel laminates are still under development. The main objective of this study was to assess the effect of fillers on the crosslinking kinetics of epoxies and the mechanical performance of electrical steel laminates. Model varnishes based on bisphenol-A diglycidyl ether (DGEBA) with an epoxy equivalent weight (EEW) of ~ 500 g/mol were modified with CaCO₃ fillers. The filler content was ranging from 1 to 20 wt%. The onset of gelation for CaCO₃ modified epoxy varnishes was reduced by up to 5 °C. This effect was primarily attributed to enhanced thermal conductivity and reduced heat capacity. Interestingly, no significant effect on the glass transition temperature of the fully cured epoxy was observable. By mechanical testing of electrical epoxy laminates better roll peel strength values were deduced for laminates with CaCO₃ modified epoxies. Moreover, crack growth rates in the stable regime and the threshold strain energy release rate were positively affected.

The pure bismuth oxyiodide (BiOI) nanoflower and BiOI/reduced graphene oxide (rGO) nano composites have been prepared via solvothermal route for supercapacitor application.Various mass ratios of BiOI with rGO were incorporated in this study. Additionally, the electrolyte gel was modified with graphene oxide (GO) to investigate the enhancement in supercapacitive charge storage properties. The structural and morphological properties of the pure BiOI nanoflower and BiOI/rGO hybrids were analysed using X-ray diffraction (XRD), Raman spectroscopy, scanning electron microscopy (SEM) with energy dispersive X-ray analysis (EDAX), Transmission Electron microscopy (TEM), N₂ adsorption–desorption isotherms (BET) and X-ray photoelectron spectroscopy (XPS). The electrochemical performances of pure BiOI nanoflower and BiOI/rGO hybrids with different mass ratio were tested by cyclic voltammetry (CV), galvanostatic charge/discharge (GCD) and electrochemical impedance spectroscopy (EIS). The optimal BiOI/rGO hybrid electrode delivered specific capacitance 235 F/g at scan rate 5 mV/s in PVA/H₂SO₄ gel electrolyte with energy density 8.1 Wh/kg and power density 0.146 kW/kg, also with PVA/H₂SO₄ + GO gel electrolyte 288 F/g at 5 mV/s scan rate with energy density 10 Wh/kg at power density 0.18 kW/kg. The BiOI/rGO hybrid electrode maintained capacitive retention of 79% and 71% after 10,000 successive CV cycles at scan rate 100 mV/s in PVA/H₂SO₄ gel and PVA/H₂SO₄ + GO gel electrolytes respectively.

Electrospun fiber mats, as a class of high-performance nonwoven materials, are widely applied in textiles, filtration, medical, and other fields. However, the precise three-dimensional characterization of their microstructure and quantification of volume fraction face challenges such as low resolution, poor computational efficiency, and reliance on expensive experimental imaging. This study aims to develop a computer modeling method independent of experiments, achieving high-precision reconstruction and performance prediction of fiber mats. Methodologically, by simulating the electrospinning deposition process, a parameterized deposition model is constructed, and a solvent-orientation coupled dynamic contact model is proposed, which integrates solvent residual concentration with von Mises orientation distribution and quantifies fiber cross-penetration behavior through adhesion offset equations. The main work includes developing an efficient voxelization algorithm that analyzes fiber-voxel interactions via multi-level detection (center point-corner point-ray penetration) and tolerance compensation mechanisms, enabling rapid calculation of volume fraction. Experimental results demonstrate that the error rate of this method is below 2%, and it remains robust in high fiber density scenarios. This model not only provides a high-precision tool for studying the relationship between microstructure and performance of electrospun materials but can also be extended to multi-process parameter optimization and multi-scale performance prediction, thereby promoting the intelligent design and application of nonwoven materials.

This study presents a comprehensive computational framework for optimizing energy absorption in nano-engineered zinc oxide varistors through systematic multi-component design. A nine-component varistor system comprising ZnO (96.5 mol%), Bi₂O₃ (1.2%), Sb₂O₃ (0.8%), NiO (0.4%), Ce₂O₃ (0.3%), ZrO₂ (0.25%), SnO₂ (0.2%), Co₃O₄ (0.2%), and SiO₂ (0.15%) was computationally modeled using COMSOL Multiphysics to investigate nanoscale energy dissipation mechanisms. The optimized composition demonstrates exceptional nonlinearity coefficient (α = 48) and energy absorption capacity (195 J cm⁻³), representing 40% enhancement over conventional microstructured designs. Finite element analysis reveals critical electric field concentrations at grain boundaries reaching 6.2 kV cm⁻¹ with current density variations of 18 × between conducting pathways and matrix regions. Multi-physics simulations incorporating coupled electromagnetic-thermal analysis demonstrate superior thermal stability with peak temperature gradients of 15°C mm⁻¹ and recovery time constants of 8.2 s. The computational framework provides unprecedented insights into nanoscale conduction mechanisms, enabling precise optimization of varistor compositions for enhanced surge protection applications.

Plant-sourced biomass is a natural, renewable material that has proven to be a good substitute for fossil fuels in energy. Activated carbon (AC) is a carbonized porous material often synthesized from plant biomass for different energy applications, including hydrogen storage. Considering the components of the corn stover, the potency of corn husk (CH) AC for hydrogen storage via physisorption needs to be evaluated. Two different conventional activation reagents, potassium hydroxide (KOH) and sodium hydroxide (NaOH), are made to interact with carbonized corn husk biochar. Characterizations through scanning electron microscope (SEM), X-ray diffraction (XRD), Raman spectroscopy, and thermogravimetric analysis (TGA) show that the properties of these two ACs are comparable. However, their porous structures as analyzed via Brunauer–Emmett–Teller (BET) technique clarify the difference, as activation with KOH (AKNH) possesses a higher microporous surface area (S_BET) and volume of 904.76 m²/g and 1.00 cm³/g, respectively; 704.80 m²/g and 0.36 cm³/g are characterized by NaOH-activated CH biochar (ANCH). At 77 K and 1.2 bar, 2.84 wt.% hydrogen is adsorbed by AKCH, while the uptake capacity for ANCH is 1.48 wt.%. The higher S_BET and micropore volume displayed by AKCH are attributed to its better hydrogen uptake.

Hydrogen offers a high-energy, carbon-free fuel alternative; however, conventional flame-based hydrogen combustion poses challenges, including NO_x emissions and the risk of flame flashback. Catalytic combustion provides a safer, low-temperature approach to hydrogen utilization, but realizing it within compact, integrated systems have remained a significant challenge. This study introduces an innovative approach to hydrogen catalytic combustion by directly integrating noble metal single quantum-crystallites of Pt and Ru within a porous silica aerogel matrix embedded in a silicon chip. This configuration enables deep nanoparticle (np) penetration throughout the aerogel network, maximizing the catalytic surface area and providing efficient on-chip hydrogen combustion. The np@aerogel systems are systematically synthesized and incorporated within silicon chips equipped with a polyimide membrane and Pt thermal structures. This unique setup allows for direct, real-time characterization of hydrogen catalytic combustion by measuring resistance changes in an embedded thermistor. The Pt@SiO₂ system demonstrates a rapid and substantial temperature increase of up to 40 K upon hydrogen exposure, independent of both preheating and Pt concentration, underscoring its robustness and adaptability for micro-scale hydrogen combustion. This on-chip integration of np@aerogel catalysts marks a significant advancement for hydrogen-based energy applications, offering a compact, scalable platform for efficient catalytic combustion. This approach opens pathways for applications in thermoelectric generators and other micro-reactor technologies where controlled, localized energy generation is critical.

Polycarbonate (PC)-based nanocomposites reinforced with cerium nickelate (CeNiO₃) and graphene nanoplatelets (GNP) were synthesized for enhanced electromagnetic interference (EMI) shielding applications. Morphological analysis through SEM and EDX confirmed uniform dispersion and elemental composition of the nanofillers. The structural and chemical interactions were validated using XRD and FTIR, indicating successful integration of CeNiO₃ and GNP into the polymer matrix. The AC conductivity, dielectric loss tangent, and magnetic loss tangent increased with higher filler loading, promoting effective energy dissipation. Among all compositions, the PC/4wt% CeNiO₃@ 6wt% GNP nanocomposite exhibited the highest shielding effectiveness of 36.32 dB in the X-band (8.2–12.4 GHz), attributed to a synergistic balance between reflection and absorption mechanisms. The results of this study highlight the capabilities of CeNiO₃-GNP hybrid fillers in producing high-performance materials for electromagnetic interference shielding in cutting-edge electronic applications.

In this study, we developed a new process for grain refinement in the A6063 aluminum alloy using extrusion with aluminum billets fabricated by additive manufacturing. The resultant extruded profile exhibited fine grains with an average diameter of 3 μm and displayed a fibrous structure elongated in the extrusion direction. The internal microstructure exhibited the typical texture of a plate-shaped extruded profile, characterized by < 001 > + β-fiber{110} < 112 > . The results obtained using this method were superior to those obtained using the conventional approach, in which cast billets were used for A6063 extruded profiles. Specifically, the tensile strength and elongation values improved by 10% and 40%, respectively. Additionally, we detected the development of a yield point (which is generally not observed in aluminum alloys). This outcome confirmed that uniform fine grains were successfully obtained using this process. In addition, this method facilitated the production of extruded profiles, with complex cross-sectional shapes and fine grains, in an alloy with a low transition-metal concentration, such as the A6063 alloy (whose manufacturing has hitherto remained challenging).

Zinc oxide nanoparticles (ZnO-NPs) are gaining popularity due to their low toxicity, cost-effective production, and environmentally friendly profile. However, their practical use is limited by inherent challenges such as a large energy bandgap, high exciton binding energy, rapid electron–hole recombination, poor absorption of visible light, and low photocatalytic efficiency. To address these issues, our study introduces an innovative approach: incorporating small amounts of transition metal oxides like copper (II) oxide (CuO) along with trace amounts of carbon nanomaterials, specifically carbon dots (C-dots). We demonstrate that adding just 9% CuO nanoparticles and 2% C-dots to ZnO-NPs significantly enhances their properties. This modification reduces the energy bandgap from 3.08 eV to 2.51 eV, improving visible light absorption and boosting photocatalytic activity. In practical application, the optimized composite achieved an impressive 98.7% removal of methylene blue (MB) dye within 60 min under visible light, far surpassing pure ZnO-NPs, which only removed 62% in the same period. Additionally, the modified nanocomposites exhibit markedly improved antibacterial activity. The zones of inhibition against bacteria such as Bacillus Seraus, Escherichia coli, Salmonella typhi, and Staphylococcus aureus increased significantly from 8–13 mm for pure ZnO-NPs to 14–18 mm for the ZnO/CuO@C-dot composites, indicating stronger antimicrobial effects driven by enhanced surface charge and stability. Overall, our findings reveal that even minimal integration of C-dots into ZnO/CuO nanocomposites can dramatically elevate their photocatalytic and antibacterial performance. To our knowledge, this represents one of the most significant improvements achieved through such small additive modifications, opening new avenues for efficient environmental remediation and biomedical applications.