International Journal of Mechanical and Materials Engineering最新文献

This paper delves into the innovative synthesis of various morphologies of CeO₂, including flower-like, spherical, quasi-spherical, and rod-shaped, as well as AgI/CeO₂ composites. Utilizing cold coprecipitation and one-pot hydrothermal methods, a range of CeO₂ and highly efficient photocatalytic AgI/CeO₂ composites were successfully prepared. These composites were, for the first time, applied to bamboo scrimber for antimicrobial research, significantly enhancing its antibacterial properties. Advanced characterization techniques such as XRD, SEM, TEM, and FT-IR were employed to analyze the prepared materials’ structural characteristics systematically. Under visible light irradiation, the photocatalytic activity of AgI/CeO₂ composite catalysts with varying AgI loadings was evaluated using levofloxacin (LVF) as a model pollutant. The results indicated that the 20%AgI/CeO₂ composite exhibited a unique mesoporous structure, high-specific surface area, and optimal photocatalytic degradation efficiency for LVF, achieving a degradation rate of up to 94.06%. Additionally, this composite significantly bolstered the antibacterial efficacy of the bamboo scriber under visible light conditions. It was securely anchored onto the surface of the bamboo scriber through a specific surface treatment process, forming a durable and practical antibacterial protective layer. In conclusion, AgI/CeO₂ composites demonstrate exceptional performance in both photocatalytic degradation and bamboo scrimber modification, making significant contributions to environmental protection and the development of green building materials.

The primary objective of this study is to examine the impact of incorporating boron carbide (B₄C) and zirconium oxide (ZrO₂) on the mechanical characteristics of AA7075 composites. Different weight fractions of B₄C and ZrO₂ were used to fabricate the composites via powder metallurgy, and mechanical tests, including hardness and compression strength, were performed to assess their properties. Microstructural analysis was conducted to evaluate the dispersion and interfacial bonding of the reinforcements within the matrix. The results revealed a significant enhancement in mechanical properties, with a maximum compression strength of 252 MPa, representing a 165% increase compared to the unreinforced alloy. This improvement is attributed to key strengthening mechanisms, including strain hardening induced by dislocation-particle interactions, grain boundary strengthening through refinement, effective load transfer between the matrix and reinforcements, and Zener pinning that stabilized the microstructure during sintering. The addition of ZrO₂ as a secondary reinforcement further enhanced these effects, leading to optimized mechanical performance. These findings provide valuable insights into the design and development of advanced hybrid composites for industrial applications.

Dynamic transformation in a 9% Cr steel is shown to improve the room-temperature workability through microstructural modification. The dynamically transformed microstructure contains 10–18% of ductile ferrite in a brittle martensitic matrix. The two-phase microstructure results in 40% higher uniform elongation and 25% lower tensile strength, which facilitate cold working. Further, the presence of ductile ferrite is shown to increase the strain hardening exponent, further enhancing the workability. It is also shown that the dynamic transformation alters the martensitic matrix, and creates a secondary source of softening. These softening effects and overall mechanical response are accurately modelled by a robust modified rule-of-mixtures formulation with prediction error of ~ 0.3%. This investigation reveals the potential of dynamic transformation to create intermediate microstructures suitable for cold working during the manufacturing process and establishes the limits within which deformation can be safely imparted.

Carbon quantum dots (CQDs) have emerged as promising organic nanomaterials due to their unique physicochemical properties and versatile applications. In recent years, there has been a growing interest in exploring the role of CQDs in improving the performance of construction and building materials, including cement, concrete, and asphalt. This paper presents a comprehensive literature review of recent articles focusing on the synthesis methods of CQDs and graphene quantum dots (GQDs), their characteristics, and their effects on the mechanical, thermal, and durability properties of cement-based materials. Furthermore, the potential challenges and future research directions in this field towards carbon capture, utilization, and storage (CCUS) direction are also discussed. The mechanisms behind these improvements are analyzed, focusing on the interfacial bonding between CQDs, seeding nucleation of the cement hydration process, and filling effect. Additionally, the review addresses the challenges associated with CQD implementation, such as cost-effectiveness and large-scale implementation. Finally, a suggested outline for optimizing CQDs used in construction materials in many research directions is discussed, suggesting novel ways for high-performance, functional, and sustainable construction materials for smart applications.

Graphical Abstract

The search for advanced materials has been growing, and high entropy alloys (HEAs) are emerging as promising candidates for application in the fusion domain. This work investigates the effect of Cr on the FeTaTiW medium entropy alloy to form (CrFeTaTi)₇₀W₃₀ high entropy alloy, comparing the experimental production and characterization with the simulation (molecular dynamics and hybrid molecular dynamics-Monte Carlo) of the phases formed. The alloys were produced by mechanical alloying and sintered by spark plasma sintering. Both simulations have shown that a body-centered cubic structure is formed for both compositions. Monte Carlo simulation provides a more precise prediction of microstructural formation and element segregation. Microstructural examination of the consolidated material revealed the presence of a W-rich phase and a Ti–rich phase, consistent with the phase separation observed in the MC simulations. Moreover, X-ray diffraction analysis of the milled powder for FeTaTiW and (CrFeTaTi)₇₀W₃₀ confirmed the formation of a bcc (body-centered cubic)-type structure with a low fraction of intermetallic phases. Mechanical testing showed ductile behavior at 1000 °C where (CrFeTaTi)₇₀W₃₀ showed a stress magnitude almost double that of FeTaTiW. Additionally, the thermal diffusivity between 20 and 1000 °C of both alloys increases as the temperature rises. (CrFeTaTi)₇₀W₃₀ exhibits an increase from 3 to 5 mm²/s, while FeTaTiW increases from 4 to 9 mm²/s. Still, both system’s thermal diffusivity values are lower than those of CuCrZr and pure tungsten. Despite this, the study underscores the promising attributes of HEAs and highlights areas for further optimization to enhance its suitability for extreme conditions.

Acrylonitrile–Butadiene–Styrene (ABS) material known for its mechanical strengths and versatility in industrial applications deteriorates physically, chemically, and mechanically due to prolonged environmental exposure and loses its effectiveness over time, thus necessitating research into methods for rejuvenation and property restoration. This degradation impacts critical properties like impact resistance, tensile strength, and thermal stability, limiting ABS’s usability in manufacturing. This study explores advanced techniques for restoring aged ABS, including physical methods like reprocessing and thermal treatments, chemical restoration using solvents and additives, and mechanical enhancement through fibre or filler reinforcement. Each technique extends the lifespan of ABS materials, aligning with sustainable practices and the circular economy by reducing raw material consumption and minimising waste, enabling its reuse in industrial applications. Case studies on successful additive integration demonstrate the recycling process yielding 20% and 59% enhanced tensile and impact strength, improving material performance and durability after restoration. It was observed that the chain extenders in rABS boost the tensile and impact strength to 34.7 MPa and 6.3 kJ/m² from 20 MPa and 2.1 kJ/m² in aged ABS (almost 90% and 30% boost compared to virgin ABS). Studies also reflect that the effect of UV exposure reduces the impact and tensile strength by 50% and 25% after 6 and 12 months respectively. Stabilisers and plasticisers are observed to increase the service life and flexibility by 25% and 20% respectively in rABS. These findings demonstrate the significance of using mechanical and chemical stabilisers and mechanical reinforcement in ABS. The challenges include the cost-effectiveness, technical limitations, and regulatory concerns surrounding the use of restored ABS. Investing in biodegradable additives and smart materials for ABS restoration will drive sustainable innovation and enhance industrial circularity practices.

Graphical Abstract

The synthesis by precipitation method of a ZnS hybrid photocatalyst functionalized with monoethanolamine in a MEA-water solution for its application in photocatalytic hydrogen production was investigated in this research work. The functionalization of ZnS with MEA as an organic component in the hybrid photocatalyst greatly modified the structural, textural, and optical properties of ZnS. With different MEA ratios in the reaction medium, these properties were enhanced. The specific surface area is augmented up to 150 m²/g, and the hybrid photocatalyst exhibited an optical response in the visible spectrum. Moreover, the crystallite size was affected by the incorporation of the MEA molecule. However, the photocatalytic efficiency is significantly improved due to the role of the MEA molecule in facilitating electron transfer, which favors electron–hole separation and consequently reduces the recombination rate. The most active photocatalyst showed a hydrogen evolution rate of almost 7900 μmol g_cat⁻¹ h⁻¹. The high photocatalytic performance was attributed to its large surface area, crystallite size, and the incorporation of MEA molecules as the organic component in the hybrid photocatalyst.

The carbon spheres (CSs) have been identified as a potentially valuable addition to agricultural practices, because they capacity to enhance the germination and growth of domestic and forest plants through the introduction of innovative techniques that facilitate sustainable agriculture. The objective of the present study was to assess the impact of CSs on the in vitro germination and greenhouse growth of Pinus devoniana seeds. The research was conducted in two phases. The initial phase of the study involved the synthesis and characterization of the CSs. The subsequent phase of the study involved the treatment of seeds with CSs and a 50% reduced dose of a mineral solution (MS). The response variables encompassed days of emergence and percentage of germination in vitro, in addition to phenology and biomass of the seedlings under greenhouse conditions. The experimental data were validated through ANOVA/Tukey (P < 0.05). The characterization of CSs by microscopic and spectroscopic techniques revealed the presence of CSs with a diameter of less than 500 nm, predominantly composed of carbon and oxygen, with the notable presence of polar functional groups. The data demonstrated that the response of P. devoniana seeds exposed to 10 ppm CSs and 50% MS exhibited statistically significant differences from the data obtained for untreated P. devoniana seeds across all response variables. These findings substantiate the assertion that CSs exert a beneficial effect on the germination and growth of P. devoniana seeds, with could be an option in reforestation projects.

Background

Calcification is the primary cause of bioprosthetic material degradation, triggered by various factors. Although many studies have proposed different anti-calcification methods, most of them focus on a single target and modify it, while the treated tissue is still stored in glutaraldehyde, re-exposing them to calcification-prone environments, thus failing to achieve ideal clinical application.

Methods

Decellularization was performed using surfactants Triton X-100, sodium dodecyl sulfate (SDS), and sodium deoxycholate (SDC) to remove cellular membrane phospholipid fragments. Sodium bisulfite (SBS) was then used to neutralize unbound aldehyde groups. Finally, the treated tissue was stored in a 75% glycerol solution. A series of biomechanical properties of the treated bovine pericardium were evaluated in vitro, and its anti-calcification properties were assessed through a 6-month in vivo implantation study using a sheep model.

Results

Compared with the glutaraldehyde-treated control group, the tissues treated with the new comprehensive anti-calcification method showed no significant changes in tensile strength or elongation at break. Additionally, no adverse effects on coagulation or hemolysis were observed, and the use of surfactants showed no significant cytotoxicity. Subcutaneous implantation in rats and mitral valve implantation in sheep model showed significantly improved anti-calcification performance compared to the glutaraldehyde control group.

Conclusion

This study proposes a comprehensive anti-calcification treatment method, which includes removing cellular debris, reducing phospholipids, neutralizing residual aldehyde groups, and storing the tissue in glycerol. This approach offered a new avenue for further research in the field and significant potential for clinical application.