International Journal of Mechanical and Materials Engineering最新文献

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.

Heat transfer studies have been conducted for cooling systems with coatings made of natural materials, depending on the parameters of the detonation flame of a thermal tool and the thermophysical properties of natural materials. Cooling systems with porous coatings of mineral media powders (quartzites, granites, teschenites, tuffs, marbles) had been developed, which were applied on a metal surface at temperatures up to (2500 ÷ 3500) °C and flow rates up to 2500 m/s by hot flames emanating from combustion chambers and nozzles. The holography and high-speed filming method has been used in the studies. The cost impact per one thermal tool is at least 200–300 dollars. The phenomenon of spin detonation of a flame at an oxidant excess coefficient of less than one has been recorded; the spraying process was intensified by 2 to 6 times. The coatings have shown high reliability compared to other boosted systems. The maximum specific heat flows on the coating are (from 2 to 20 × 10⁶ W/m²) and the oscillation frequency are up to 200 Hz. The overheating range of the coating was 20 ÷ 75 K. The thermodynamic characteristics of thermal tools have been established in the model and experimentally; the granulometric composition of materials has been obtained; the hydrodynamic operating modes of the burners have been selected (fuel combustion method, jet length, jet angle). The flight time of the particles, the optimal thickness of the coatings, the diameter of the powder, and the limiting compression and tensile stresses of the coating have been determined. Dependences of displacements for coatings under thermal influence have been obtained, which is important for diagnostics and forecasting of plants and prolongation of service life.

In this study, the physical and structural properties of Mn₄Si₇ silicide crystals synthesized using Hot Isostatic Pressing (HIP) and Spark Plasma Sintering (SPS) methods were analyzed using X-ray diffraction (XRD) techniques. In the samples obtained by the HIP method, 11 diffraction peaks were identified, with crystal sizes ranging from 8.8∙10⁻⁹ m to 3.6∙10⁻⁸ m, and the lattice strain index varied from 0.01 to 0.41. These results reflect the microstructural characteristics and the deformation of the crystals, providing insight into how these structural features influence the mechanical, thermal, and electronic properties of the material. In the SPS method samples, 13 diffraction peaks were observed, with crystal sizes ranging from 3.8∙10⁻⁹ m to 3.6∙10⁻⁸ m, and lattice strain varied from 0.002 to 0.19, indicating that the crystals maintain structural equilibrium and geometric integrity. The dislocation density, measured in the HIP samples (ranging from 3.5∙10¹⁰ to 3.2∙10¹²) and SPS samples (ranging from 7.4∙10¹¹ to 7.9∙10¹⁴), plays a crucial role in determining the crystals' plasticity and mechanical strength. The degree of crystallinity was found to be 6.4% for the HIP method and 7% for the SPS method, reflecting the structural purity and perfection of the crystals. IR transmission spectra revealed structural changes in the crystals, demonstrating their direct influence on the material's electronic and optical properties. These analyses provide valuable insights into enhancing the thermoelectric properties and mechanical stability of materials, as well as improving the performance of technological devices under high-temperature and high-pressure conditions. This study lays the foundation for future research aimed at optimizing material properties for advanced technological applications.

The surging demand for innovative components in the aerospace, biomedical, and automotive sectors has prompted extensive research on the 3D printing of titanium parts. Among various additive manufacturing techniques, electron beam melting has attracted increased attention owing to its high-density components produced per unit of time. However, the surface finishing of powder bed-based additive manufacturing methods is generally poor; that is, their mechanical performance is wanting and does not meet all the industrial standards. Higher surface finishing can be achieved by post-processing. The quality of the surface, having a substantial impact on the fatigue behavior, will give insights into the influence of chemical machining, and it cannot be ignored for an experimental trial. The rotating fatigue beam testing method was selected for this experimental campaign because of its inherent capability to stress sample surfaces more uniformly, emphasizing the effects of surface finishing.

Inconel 625 alloy exhibits high strength, fabricability, and resistance to corrosion. Cladding processes including laser cladding, arc welding-based cladding, and plasma arc cladding have been applied to deposit the Inconel 625 layer with metallurgical bonding for surface protection. In this work, we developed a dual-constricted (DC) plasma arc cladding process to fabricate Inconel 625 coating. A numerical model was used to understand the arc thermal distribution, and the microstructure and corrosion resistance of the deposited layers were analyzed. It shows that in the DC plasma arc cladding process, the arc has a narrower column with increased energy density, and it can generate a higher arc pressure on the processing area. The deposited single track is narrower and thicker, and the melt pool penetration is deeper. In the Inconel 625 layer deposited by the DC-plasma arc, the microstructure is refined, and the Laves and MC precipitates are observed. The corrosion test indicates that the corrosion resistance in the 3.5% NaCl solution of the coating fabricated by DC plasma arc cladding is increased compared to conventional plasma arc cladding.