International Journal of Mechanical and Materials Engineering最新文献

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.

The current research focuses on the fabrication of polymer-ceramic composite materials by the solution casting process of multi-faceted titanium ferrite, TiFe₂O₄ (TFO). We experimented with different proportions of TFO composition, ranging from 5 to 15 wt%, in the polymer matrix of PVDF. Various characterization methods were employed to study the mechanical, spectroscopic, morphological, and dielectric properties affected by TFO load. X-ray diffraction (XRD) was used to identify both non-polar alpha- and polar beta-phases in the composites. Samples from scanning electron microscopy (SEM) revealed a spherulite-like morphology and uniform distribution of TFO particles. Our main goal was to increase the ferroelectric properties of the polyvinyl-HFP by increasing the percentage of TFO filler to increase the β-fraction. The enhanced attributes of our materials hint at potential applications in polymer-ceramic capacitor technology, a topic we delve into extensively.

Cellulosic natural fibers play an important role as reinforcement in polymer composites due to their biodegradability, lightweight and non-toxicity. Grewia ferruginea (GF) fiber is a type of natural fiber containing cellulosic fiber that is inexpensive and readily available in sub-Saharan Africa. In this study, the GF fibers collected from Central Ethiopia were extracted and its physical, chemical and mechanical properties such as density, diameter, cellulose, hemicellulose, lignin, tenacity and tensile strength were experimentally characterized. The findings reveal that the raw GF fiber exhibited a mean fineness of 90.55 Tex, an average cross-sectional area of 0.0096 mm², and density values of 1.43 g/cm³ at 20 °C. Chemical analysis indicates the GF fiber contains 2.413% extractive,65.6% cellulose, 13.25% hemicellulose, and 18.74% lignin. It was observed that the raw GF fiber exhibits a relatively high cellulose content compared to most plant fibers and demonstrated GF suitable for applications that demand strength and durability. A tensile strength of 309.3 MPa was recorded for the raw GF fiber. Based on these results, it can be concluded that this study has briefly demonstrated that raw GF fiber is positioned as a viable and sustainable alternative to other natural fiber for composite reinforcement, with properties that can be further improved through fiber treatment optimization.

Using traditional resistance spot welding with a novel bulged double-helix electrode, 5182 aluminum alloy and DP780 galvanized steel were welded under two different current parameters. After baking, both samples exhibited a similar average peak load of 3.30 kN, while defect locations showed significant differences. In the low-current sample, defects remained near the nugget center (11.64 μm), whereas in the high-current sample, defects shifted farther away (1490.3 μm). Crack initiation in both cases started along interfacial compounds at the weld edge. In the low-current sample, the crack propagated along interfacial defects on the aluminum side until complete fracture. In contrast, the high-current sample exhibited crack deflection into the aluminum, leading to a pullout fracture. The findings highlight the influence of post-welding baking on the durability and performance of welded joints. This study provides valuable insights for optimizing aluminum-steel resistance spot welding in industrial applications, particularly for reliability after baking.

This study presents a cost-effective strategy to enhance supercapacitor performance using ZnO/reduced graphene oxide (ZnO/rGO) nanocomposites synthesized via a microwave-assisted method. The nanocomposites exhibit pseudocapacitive behavior, enabling improved charge storage. A PVA/KOH gel polymer electrolyte and a Nafion-117 film were integrated to enhance ionic conductivity and structural stability. Structural and morphological characterizations (XRD, FTIR, SEM, and TGA) confirmed the successful formation of uniformly distributed ZnO nanoparticles (average size: 22.44 ± 0.09 nm) on rGO sheets. Electrochemical testing revealed a high specific capacitance of 812.23 F·g⁻¹, an energy density of 28.20 Wh·kg⁻¹, and a power density of 4,060.80 W·kg⁻¹. Moreover, the composite retained 99.97% of its capacitance after 5,000 cycles. These results demonstrate the potential of ZnO/rGO–Nafion hybrid electrodes for next-generation high-performance supercapacitors.

The rapid demands of the engine industry for greases that can perform under a wide range of operating conditions focused on developing environmentally friendly, inorganic lubricating greases free from soap-based components. Utilizing bentonite clay as an innovative porous thickener, combined with two base oils blend with soft and hard paraffin wax additives, seeks to economically synthesize greases that are versatile and suitable for a wide range of service conditions. Acid post-treatment of raw bentonite was undertaken to activate the bentonite clay and alter its surface from hydrophilic to organophilic, enhancing its dispersion in organic base oil. The activated bentonite exhibited significant modifications in surface area, porosity, and crystal morphology, which directly influenced the grease's physical properties and performance. Notably, activated bentonite treated by nitric acid showed superior efficacy in homogeneously integrating with both base oil types and paraffin waxes compared to other acid post-treatments, producing greases with higher dropping points similar to lithium complex and organic clay grease, lower working penetrations as normal grease as classified by National Lubricating Grease Institute (NLGI) consistency grade. This study contributes to the development of inorganic grease formulations by systematically evaluating the rheological and thermal performance of modified bentonite. On the other hand, it highlights the flexibility of modified bentonite as a universal thickener for lubricating greases, demonstrating its efficiency as a multifunctional thickener that meets the evolving demands of various industrial engines.

Ti6Al4V and 316L stainless steel alloys have been extensively utilized as conventional implant materials. However, there are always concerns regarding the biocompatibility of these alloys. Recently, high-entropy alloys have been introduced as new biomaterials due to their unique properties. In this investigation, a Ti₃₅Nb₂₅Zr₁₅Mo₁₅V₁₀ bio-high entropy alloy was developed utilizing thermodynamically parameters and calculations to fabricate a high efficiency biomaterial. Microstructural evolutions were characterized using X-ray diffraction (XRD), scanning electron microscope as well as energy-dispersive X-ray spectroscopy (EDS) techniques. Studies conducted on this alloy demonstrated the formation of a BCC solid solution without the presence of any intermetallic compounds. The results showed that the developed high entropy alloy exhibited the lowest elastic modulus compared to the control samples, which was reported as 115 GPa. The results of the nano-scratch test indicated a lower scratch depth and friction coefficient compared to the control samples for the bio-high entropy alloy. In addition, the Ti₃₅Nb₂₅Zr₁₅Mo₁₅V₁₀ alloy exhibited lower corrosion rate in three environments of PBS, NaCl, and H₂SO₄, in comparison to the control samples. The results of the shear punch test suggested better mechanical properties of the studied bio-high entropy alloy compared to the control samples. Overall, the investigation regarding the mechanical properties, corrosion resistance, and wear characteristics showed that the developed Ti₃₅Nb₂₅Zr₁₅Mo₁₅V₁₀ alloy has the significant potential to be used as a new metallic biomaterial, serving as a substitute for conventional Ti6Al4V and 316L SS alloys.

This study evaluated microfibrillated adsorbents obtained from kraft pulp (PC) cellulose of Moringa oleifera (M. oleifera). In this research, Cd (II) adsorption was evaluated on unmodified microfibrillated cellulose (PMC) and hematite-modified microfibers (SN-PMC) on kraft pulp as starting material cooked for 10 min. This cellulose pulp as a starting material was also used in a previous work from our research group but with a 20-min pulping cooking to obtain a composite of nanofibers and maghematite, obtaining less favorable results in terms of cadmium adsorption capacity, with a qt = 12 mg/g.

PMC and SN-PMC were characterized by SEM–EDS, XRD, zeta potential and FTIR. The experimental kinetic and equilibrium results on PMC and SN-PMC were modeled, obtaining a pseudo-first-order kinetic fit result on SN-PMC and an Elovich approach on the PMC adsorbent. Regarding the equilibrium in both materials, the adsorption isotherms were fitted to the Langmuir model. The maximum adsorption capacities (Qo) were 27.3 mg/g and 33.8 mg/g for PMC and SN-PMC, respectively, obtained from isothermal data at 25 °C and pH 5, which were the conditions with the highest adsorption in isotherms. The main adsorption mechanism is chemisorption; however, it was concluded that SN-PMC was dominated by physisorption and chemisorption, which gives rise to a hybrid mechanism. On the other hand, both adsorbents presented spontaneous and exothermic process. These materials, especially SN-PMC, have potential in the removal of cadmium from industrial effluents. Their low cost, biocompatibility, and efficiency can contribute to the development of sustainable adsorbents, with the role of iron oxide highlighted in the removal. Future research could evaluate the material to improve its adsorption capacity in multicomponent mixtures or evaluate its regeneration and reuse.

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