International Journal of Mechanical and Materials Engineering最新文献

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.

Every manufacturing process alters the state of a surface, endowing it with new attributes that engineers use to enhance the performance of the finished products. When these surfaces come into contact with the human body, they exert specific influences depending on their condition affecting medical device biocompatibility. This study shows how a titanium alloy surface, characterized by standard measurement parameters such as roughness and contact angle, specifically influences the response of osteoblast-like cells in terms of proliferation and morphology. This relationship is quantified by comparing different machine learning techniques.

More in detail, the impact of the milling process on Ti6Al4V substrates on the growth of the human osteosarcoma cell line MG63 has been investigated. By varying the technological parameters such as the cutting speed and depth and, consequently, the surface condition, the number of cells after a 72-h culture was measured to correlate cell proliferation with the process parameters. Ultimately, it is conceivable that with further research, surfaces could be designed to elicit varying cellular responses by appropriately combining manufacturing processes and their technological parameters.

CdS(en)/Mg(OH)₂-MgO photocatalysts were easily synthesized using a one pot synthesis, the resulting materials were obtained with an excellent dispersion of the hybrid CdS(en) on the surface. Their structural, optical, and morphological properties were characterized by X-ray diffraction, UV–vis spectroscopy, FTIR spectroscopy, nitrogen physisorption, and scanning electron microscopy (SEM). These supported materials were used as photocatalysts in the hydrogen evolution reaction (HER), using water as the raw material, and methanol as a sacrificial molecule under visible (blue) light irradiation. CdS(en)/Mg(OH)₂-MgO materials presented high performances in the HER reaction. When Mg(OH)₂-MgO support was obtained by ammonia pre-treatment of MgO, an improvement in the electronic-optical and textural properties was observed, resulting in an enhancement in the H₂ yields. Notably, in comparison to previously reported CdS-supported materials which achieved H₂ production rates of 64–300 μmol/gh, the photocatalysts presented in this study exhibit significantly superior performance. Specifically, CS/Mg5H is almost 5 times more active, producing exceptional H₂ yields while requiring only a small amount of catalyst (50 mg containing just 4.2 wt.% CdS). Furthermore, this remarkable performance is achieved under visible light irradiation using low-intensity 12 W LED lamps.