Search Results (1,632)

To investigate the shear behavior of rock mass joint surfaces with varying roughness and lithology, this study introduces a novel experimental framework that combines high-precision 3D printing and direct shear testing. Ten artificial joint surfaces were fabricated using Barton standard profiles with different joint roughness coefficients (JRC) and were cast using two representative rock-like materials simulating soft and hard rocks. The 3D printing technique employed significantly reduced the staircase effect and ensured high geometric fidelity of the joint morphology. Shear tests revealed that peak shear strength increases with JRC, but the underlying failure mechanisms vary depending on the lithology. Experimental results were further used to back-calculate JRC values and validate the empirical JRC–JCS (joint wall compressive strength) model. Numerical simulations using FLAC3D captured the shear stress–displacement evolution for different lithologies, revealing that rock strength primarily influences peak shear strength and fluctuation characteristics during failure. Notably, despite distinct lithologies, the post-peak degradation behavior tends to converge, suggesting universal residual shear mechanisms across rock types. These findings highlight the critical role of lithology in joint shear behavior and demonstrate the effectiveness of 3D-printing-assisted model tests in advancing rock joint characterization. Full article

This study examined cast AZ31 magnesium alloy and its variant containing micro-alloying elements of Y and Ca (AZXW alloy), evaluating their potential as anode materials in magnesium–air batteries. The AZXW alloy was fabricated via two manufacturing techniques: casting and extrusion. The synergistic influence of Y and Ca, in conjunction with the production procedure, on the microstructure, electrochemical characteristics, and anodic discharge behavior of the examined alloys was investigated. The addition of Y and Ca results in the formation of secondary phases that affect grain size, particle size, and distribution, as well as the electrochemical performance and discharge properties of the Mg–air battery constructed for this study, over 24 h or until fully discharged. This work demonstrates the potential to enhance discharge performance and electrochemical behavior by adjusting the aqueous electrolyte solution in the battery through the incorporation of Citric Acid (C.A) at varying concentrations. The incorporation of citric acid into the aqueous electrolyte improves battery stability and specific energy as long as citric acid is present in the solution. Magnesium hydroxide (Mg(OH)₂) begins to form on the anode surface as its concentration progressively decreases due to complexation with dissolved magnesium ions. This diminishes the effective anode area over time, ultimately resulting in the distinctive “knee-type” collapse characteristic of electrolytes containing citric acid. Full article

Magnetotactic bacteria (MTB) have attracted interest in recent years, mainly due to their natural ability to form intracellular magnetic nanocrystals with potential for biomedical and environmental applications. In this study, we focused on the morphological analysis of the Paramagnetospirillum magnetotacticum MS-1 strain, trying to keep the bacteria as close to their natural state as possible. An important element of this work is the use of untreated bacterial cells, without conductive coating or chemical fixation, using a simple and low-cost support. This choice was made intentionally to avoid changes induced by metallization and to allow direct observation of characteristics that may be relevant in applications where the interaction of the bacteria with the environment plays an important role, such as biosensors. In addition, the analysis was performed on a bacterial suspension stored for approximately 10 months at 4 °C to assess whether the morphology specific to the MS-1 strain is maintained over time. The obtained results show that the general cell morphology and magnetosome organization can be clearly and reproducibly observed even after long-term storage. Without attempting to replace studies based on conventional sample preparation methods, this work provides a complementary perspective and suggests that magnetotactic bacteria may represent a natural and effective alternative to synthetic magnetic nanoparticles, with potential applications in the biomedical and environmental fields. Full article

The seeding technique is the only way to precisely control the crystal orientation of single-crystal superalloy castings. However, an inevitable assembly gap exists between the seed and the mold cavity in practice, whose role in defect formation remains insufficiently understood. To elucidate the mechanism and impact of this gap, superalloy seeds were machined to different extents, aiming to create varying gaps with the mold. After the seeding experiment, the chilled layers formed on the perimeter of the pre-processed seeds were detected, exhibiting two distinct microstructural zones: a eutectic aggregation region at the bottom and an equiaxed grain at the top. The thicker the layer, the more pronounced the differences in microstructure between these two regions. This can be explained by the fact that during preheating, the γ/γ′ eutectic-rich interdendritic region (enriched with Al + Ti + Ta) in the original seed melted first due to its lower melting point. The molten fluid flowed downward into the gap, solidifying rapidly into the chilled layer. The leading portion of the fluid, melting from the interdendritic zone, formed the eutectic zone in the lower part of the chilled layer. The subsequently poured charge alloy melt (non-enriched with Al + Ti + Ta) generated the upper equiaxed zone with only a little γ/γ′ eutectic. These equiaxed grains in the chilled layer subsequently grew upward and potentially developed into stray grains of the casting. Full article

Some expressway emergency lanes adopt simplified pavement structures that fail to meet load-bearing requirements after reconstruction. To address the issue of subgrade reinforcement without excavation, a finite element method was employed to analyze the effects of enlarged-borehole grouting (EBG), considering variations in grouting depth and inter-pile subgrade modulus, on pavement load-bearing capacity. Furthermore, field experiments were conducted to evaluate grouting techniques, including enlarged-borehole micro-expansive cement casting (EB-MECC) and enlarged-borehole steel flower pipe split grouting (EB-SFPSG), and three composite grouting schemes. Results indicated that EBG effectively improved the fatigue cracking life of the semi-rigid base layer. Reinforcement effectiveness was positively correlated with grouting depth and subgrade modulus, with the latter exhibiting a more significant influence. Therefore, a 1.5 m grouting depth combined with splitting or compaction is recommended to enhance subgrade stiffness. Field experiments showed that EB-SFPSG effectively enhanced pile–subgrade interaction and mitigated stress concentration around the pile–pavement interface. Comparison of the three composite grouting schemes revealed that both the scheme employing only EB-SFPSG and the hybrid scheme using EB-SFPSG in the middle row with EB-MECC in the side rows exhibited favorable mechanical performance. The latter, however, was achieved at a lower construction cost. Another hybrid scheme that further replaced the middle row with enlarged-borehole conventional pressure grouting (EB-CPG) provided limited reinforcement and poorer uniformity. Full article

Marine plants are a rich source of bioactive compounds with unique properties. The Mediterranean seagrass Posidonia oceanica is particularly abundant in phenolics and flavonoids, which exhibit antioxidant and anti-inflammatory activities. In this study, a phenolic-rich extract (POS) was obtained from beach-cast P. oceanica leaves using supercritical fluid extraction (SFE), an eco-friendly technique that preserves thermolabile compounds and avoids organic solvents. POS was incorporated into a base cream (POS-enriched cream) to evaluate its bioactive potential in topical applications. The antioxidant capacity of POS and the cream formulation was firstly evaluated using the DPPH radical scavenging assay, confirming strong radical scavenging activity for the POS (IC₅₀ = 2.32 ± 0.33 mg/mL) and significant activity for the POS-enriched cream (IC₅₀ = 16.76 ± 0.58 mg/mL) compared to a base cream as control (IC₅₀ = 37.62 ± 1.27 mg/mL). The antioxidant and photoprotective effects of POS were investigated in human skin fibroblasts (HS-68) exposed to oxidative stress and UV-induced damage, while anti-melanogenic activity was assessed in human epidermal melanocytes (HEM) by measuring tyrosinase activity and melanin content. POS significantly reduced ROS accumulation and modulated key molecular pathways involved in apoptosis (p-JNK), inflammation (NF-κB), energy balance (p-AMPK), and collagen synthesis (Col1A1) in fibroblasts. In melanocytes, both POS pure extract and POS-enriched cream effectively inhibited tyrosinase activity while maintaining unaltered basal melanin levels, indicating a modulatory rather than fully suppressive effect. These findings highlight the potential of P. oceanica SFE extracts as sustainable natural marine-derived products for photoprotection and anti-melanogenesis, thereby bridging the gap between marine waste stream management and applications in skin health and anti-aging strategies. Full article

This work presents an approach to water-dispersible polylactide (PLA) particle fabrication and their application in low-temperature film formation using a combination of mechanical dispersion and ultrasonication techniques. Stable PLA dispersions were obtained after removal of surfactant and allowed for thin-film preparation, exhibiting a significantly reduced minimum film formation temperature (MFFT) from 128 °C to 80 °C after reducing the characteristic particle size from ~2.2 µm to ~140 nm. To tailor the interfacial behavior and mechanical flexibility of the resulting coatings, a set of conventional and bio-based plasticizers was evaluated, including epoxidized fatty acids, PEG-400, and several hydrophobic deep eutectic solvents (HDESs) synthesized from menthol and carboxylic acids. Compatibility between PLA and each plasticizer was predicted using Hansen solubility parameters. The efficiency of plasticization was assessed through glass transition temperature suppression in solvent-cast films. The combination of submicron PLA particles and selected plasticizers enabled film formation at temperatures as low as 48 °C, confirming the potential of these systems for energy-efficient coating technologies. Furthermore, composite coatings incorporating micro-sized cellulose fibers (L/D ≈ 10.5–11.5) regenerated from agricultural residues were successfully obtained, demonstrating the feasibility of integrating bio-derived fillers into waterborne PLA formulations. In this study, the use of water-insoluble deep eutectic solvents type plasticizers for PLA coatings from water dispersions was reported for the first time. This establishes a foundation for developing sustainable, low-VOC, and low film formation temperature PLA-based coating materials. Full article

Non-destructive evaluation techniques are increasingly recognised as effective alternatives to destructive testing for estimating the compressive strength of lightweight aggregate concrete (LWAC). Among these, ultrasonic pulse velocity (UPV) is a well-established and widely employed method, characterised by its speed, non-invasiveness, and relative simplicity of implementation. In this study, an experimental dataset comprising 640 core segments from 160 cylindrical specimens, provided for analysis, was investigated. Each segment was described by physical and processing variables or features, including lightweight aggregate (LWA) and concrete densities, casting and vibration times, experimental dry density, and P-wave velocity obtained through UPV testing. A segregation index, derived from UPV measurements and defined as the ratio of local to mean P-wave velocity within each specimen, was also considered, following approaches previously suggested in the literature. A range of machine learning techniques was applied to assess the predictive capacity of local P-wave velocity and segregation index. Most ensemble-based methods and support vector regression (SVR) achieved the highest predictive performance when the segregation index was excluded, suggesting that its inclusion did not improve the predictive ability of the models. By contrast, Gaussian process regression (GPR) showed slight improvements when the segregation index was included. The results confirmed that the P-wave velocity measured by UPV testing is a reliable non-destructive predictor of compressive strength in LWAC. At the same time, the added value of the segregation index remained negligible under conditions of low segregation, as reflected by segregation index values above 0.8. These findings highlight the practical potential of integrating UPV-based measurements with data-driven modelling to enhance the reliability of concrete characterisation and quality control. Full article

With the rise in additive manufacturing in construction, particularly 3D printing using extrusion-based mortars, there is an increasing need to optimize material properties. This study compares the mechanical performance of mortar specimens produced by traditional casting and 3D printing, with a focus on flexural behavior. A high-durability mortar with very low chloride and sulfate content, which produces less CO₂ than standard Portland cement, was used. This study also explores the impact of varying water–cement (w/c) ratios to obtain a valid mix for both fabrication methods. The results show that the samples obtained by traditional processes and those produced through 3D printing exhibit distinctly different behaviors under bending stresses. In the case of the molded samples, the maximum stress ranged from 1.23 to 1.78 MPa, indicating good strength and uniformity within these materials. In contrast, the 3D-printed samples showed higher values but with greater variation, ranging between 2.77 and 3.76 MPa. This variation highlights the influence of the fabrication technique in 3D printing, which may contribute to either the superiority or limitations of these samples. In terms of deformation, molded specimens exhibited brittle failure with limited post-peak energy dissipation (0.11–0.22 kN.mm), whereas 3D-printed samples displayed a mixed brittle–ductile response and enhanced energy absorption (1.70–2.82 kN.mm). These findings suggest that traditionally obtained specimens are suitable for applications requiring predictable stiffness, while 3D-printed mortars are advantageous for applications demanding greater flexibility and energy absorption. Full article

The paper presents a follow-up on the subject of the use of thermal analysis for the generation of fraction solid evolution in cast alloys, particularly in aluminum—silicon alloys. It discusses in detail the importance of correctly determining the characteristic temperatures of the cooling curve, including the beginning of solidification, the eutectic temperature, and the end of solidification. It demonstrates the importance of the smoothing techniques applied to the experimentally recorded temperature (cooling curve). Newtonian and Fourier analyses are used to generate the evolution of fraction of solid and the latent heat on cups of different diameters, to assess the effect of cooling rate for Al-7.5%Si alloys. Calculation results are compared with the literature data. It was found that the maximum temperature of the alloy in the cup affected the overall results. Full article

In Al–Fe alloys, the mechanical properties are determined by the morphology of iron-rich phases. In this work, AA8176(Al-1Fe)-nY (n = 0, 0.3, 0.5, 0.7, and 0.9 wt.%) alloys were prepared by the cast method. The effects of yttrium (Y) addition on the microstructure and mechanical properties of AA8176 alloy were studied using various techniques including optical microscopy (OM), scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), cooling curve analysis and tensile tests. The results revealed that the optimal refinement effect was achieved when the amount of Y content was 0.5 wt.%. When the Y content increased from 0 to 0.5 wt.%, the coarse needle-like Al₁₃Fe₄ phases were gradually transformed into short rod-like morphology and some fine Al₁₀Fe₂Y phases were formed around the Al₁₃Fe₄ phases. The average length of iron-rich phases was decreased from 10.01 μm to 2.65 μm. Additionally, as the Y content increased from 0 to 0.5 wt.%, the secondary dendrite arm spacing (SDAS) of AA8176 alloy was reduced from 31.33 μm to 20.24 μm. Furthermore, the mechanical properties of the AA8176 alloy were improved due to the modified microstructure. With the addition of 0.5 wt.% Y, the ultimate tensile strength, yield strength, elongation, and Vickers hardness were improved to 96.86 MPa, 57.21 MPa, 23.1%, and 30.55 HV, respectively, compared to 84.47 MPa, 50.71 MPa, 18.6%, and 27.28 HV for the unmodified AA8176 alloy. It is proposed that the growth of α-Al dendrite and Al₁₃Fe₄ phases were effectively inhibited by segregation of Y atoms around α-Al dendrite and Al₁₃Fe₄ phases during solidification. And the Al₁₀Fe₂Y phases were formed by these Y atoms with Al and Fe elements. However, the formation of coarse Al₁₀Fe₂Y phases was promoted by excessive Y content, resulting in a substantial degradation in mechanical properties. Full article

The construction industry is moving forward with the aim to maintain process sustainability. In this aspect, the role of life cycle assessment is essential in determining the appropriate material or method. Hence, this study aims to compare the environmental impacts of a concrete frame office structure, built with different construction techniques, including cast in situ, precast, and semi-precast methods of construction. The analysis adopts the CML 2001 characterisation method to present and compare the environmental impacts from cradle to gate and, therefore, the extraction and production of raw materials, manufacturing, and construction phases of these technologies. Results show that the total energy consumption for the three methods of construction is similar, with a variation of less than 5%. The highest energy consumption phase is associated with the extraction and production of cement. In fact, the precast and semi-precast methods were found to have almost 30% higher global warming potential (CO₂ equation) than the cast in situ method per functional unit due to the utilisation of higher cement content in the mix. Hence, the environmental impacts associated with each phase will help the concrete construction industry to develop and improve its efficiency while adopting more sustainable measures. Full article

As industrial technology advances at an accelerated pace, the demands on the performance characteristics of aluminum alloys are becoming more stringent. Researchers have enhanced the casting process of aluminum alloys through a range of innovative methods, thereby significantly improving the overall performance of these materials. This advancement better equips aluminum alloys to meet the increasingly stringent requirements in the aerospace, new energy, and automotive industries. This paper reviews the current development status of casting aluminum alloys using directional solidification technology, details the process parameters and simulation techniques, and summarizes studies on the corrosion performance of directionally solidified aluminum alloys as evaluated by electrochemical testing. Additionally, this paper elaborates on the current research status regarding the enhancement of directionally solidified aluminum alloys through the application of magnetic fields, providing a valuable reference for future studies on directional solidification technology in casting aluminum alloys. Full article

The integration of molecular imprinting technology with electrochemical methods has become fundamental in the development of next-generation sensors. This study explores two different strategies for developing a dopamine-based molecularly imprinted polymer (MIP) for the electrochemical sensing of levofloxacin. In the first case, the MIP is developed by electropolymerization on a screen-printed carbon electrode (SPCE) surface using cyclic voltammetry, while in the second, the MIP is obtained by an oxidation process, and the resulting dispersion is drop-cast on the SPCE surface. The same approach is used for a non-imprinted polymer. The physicochemical properties of the synthesized materials and the surface morphology of the modified electrodes are investigated by several techniques. Differential pulse voltammetry is used to evaluate the performance of the modified electrodes, assessing their linear concentration range, limit of detection, and limit of quantification, together with repeatability and selectivity. MIP-based SPCEs obtained with these two fabrication strategies exhibited comparable imprinting factor values and linear concentration ranges, along with comparable limits of detection and quantification. The MIP-based SPCE obtained by electropolymerization showed greater repeatability, whereas the MIP-based SPCE produced by drop-casting provided higher sensitivity in levofloxacin detection. Full article

In order to address the urgent demand for high-performance materials in the field of automotive lightweighting, there is a need for solutions to the interface instability and performance degradation of traditional reinforcing phases (e.g., SiC, CNT) at elevated temperatures. The present study prepared BNNTs/Al composites via the stirred casting method for automotive connecting rods. The microstructure, interface characteristics, phase evolution, and high-temperature wettability were systematically characterised using a range of analytical techniques, including SEM, TEM, XRD, and DSC. A study was conducted to assess the mechanical properties of the composites in comparison to those of conventional 40Cr steel. This investigation enabled an evaluation of the material’s comprehensive performance for use in automotive connecting rods. The study successfully achieved uniform dispersion of BNNTs within the aluminium matrix, forming tightly bonded, semi-coherent interfaces such as Al/AlN and Al/AlB₂. It was found that complete wetting was achieved at 675 °C, with interface reactions generating AlN and AlB₂ phases that significantly enhanced performance. The prepared connecting rod demonstrates a specific strength that significantly exceeds that of 40Cr steel. The experimental investigation conducted in a controlled setting yielded notable outcomes. The empirical evidence demonstrated a 6.5% enhancement in braking performance and a 5.8% reduction in fuel consumption. Through the optimisation of interface design and process control, the BNNTs/Al composite achieves a balanced compromise between high strength, low density, and excellent thermal stability. The material’s potential for use in lightweight automotive connecting rods is significant, offering a novel approach to the eco-friendly manufacturing of related components. Full article