Search Results (2,944)

To overcome limitations of dentin bonding due to collagen degradation at a bonded interface, incorporating bioactive glass (BAG) into dentin adhesives has been proposed to enhance remineralization and improve bonding durability. This study evaluated sol–gel-derived BAGs (BAG79, BAG87, BAG91, and BAG79F) and conventional melt-quenched BAG (BAG45) incorporated into dentin adhesive to assess their remineralization and mechanical properties. The BAGs were characterized by using field-emission scanning electron microscopy (FE-SEM) and transmission electron microscopy for surface morphology. The surface area was measured by the Brunauer–Emmett–Teller method. X-ray diffraction (XRD) analysis was performed to determine the crystalline structure of the BAGs. Adhesive surface analysis was performed after approximating each experimental dentin adhesive and demineralized dentin by using FE-SEM. The elastic modulus of the treated dentin was measured after BAG-containing dentin adhesive application. The sol–gel-derived BAGs exhibited larger surface areas (by 400–600 times) than conventional BAG, with BAG87 displaying the largest surface area. XRD analysis indicated more pronounced and rapid formation of hydroxyapatite in the sol–gel BAGs. Dentin with BAG87-containing adhesive exhibited the highest elastic modulus. The incorporation of sol–gel-derived BAGs, especially BAG87, into dentin adhesives enhances the remineralization and mechanical properties of adhesive–dentin interfaces. Full article

Two types of T800 grade carbon fibers, produced using distinct spinning processes, were utilized to fabricate thermoplastic prepregs via the hot melt method. These prepregs were subsequently employed to produce thermoplastic composites. A universal testing machine was used to assess the tensile, bending, and interlaminar shear properties of the composites, evaluating the impact of the two different spinning processes on their mechanical characteristics. The experimental results indicate that the dry spray wet spinning carbon fiber (T800-DJWS) exhibits a smoother surface, more regular cross-section, and more uniform distribution compared to the wet spinning carbon fiber (T800-WS), enhancing the prepreg preparation via the hot melt method. The T800-DJWS/PAEK composite demonstrates a tensile strength that is 706 MPa higher than the T800-WS/PAEK composite, while the latter exhibits a bending modulus 31 GPa higher than the former. Full article

This work investigated the ₀Cr₁₆Ni₅Mo₁ stainless steel using laser selective melting (SLM) technology and explored the effect of the tempering temperature on the microstructure and properties. After the tempering treatment, the quenched martensite transformed from a metastable to steady state, and residual austenite was formed. The results indicated that the elongation of the transverse specimen showed an upward trend as the tempering temperature increased, while the elongation of the longitudinal specimen first increased and then decreased. The fracture mode was ductile. There was an obvious fiber, radial, and shear lip zone on the fracture surface of transverse specimens. When the tempering temperature was 650 °C, the shear lip area of the fracture surface was the largest. For longitudinal specimens, there was no obvious zoning on the fracture surface. Full article

Itraconazole (ITZ) is a broad-spectrum triazole antifungal agent suitable for the treatment of superficial and systemic mycoses. This study aimed to formulate, characterize, and evaluate the in vitro antifungal performance of single-jet electrospun itraconazole-loaded polyvinylpyrrolidone-based fibers. Fibrous mats were prepared under the following experimental conditions: 10, 12.5, and 15 cm needle–collector distance, 20 kV tension, and 1, 1.5, and 2 mL/hour flow rate. The fibers were characterized by SEM, DSC, FTIR, assays, disintegration tests, dissolution tests, and in vitro antifungal activity. Using a 2² factorial design, the effects of preparation variables on the characteristics of the fibrous sheets were described. The electrospinning process led to smooth-surfaced, randomly oriented, and bead-free fibers. The average fiber diameter ranged from 887 nm to 1175 nm. The scanning calorimetry of pure ITZ revealed a sharp endothermic melting point at a temperature of 170 °C, not present in the curves of the fibers. After 60 min, between 70 and 100% of ITZ was released. The antifungal assay revealed that the fibers inhibited the growth of Candida albicans and Candida parapyilosis. The obtained fiber mats prepared from the hydrophilic polymer presented almost instantaneous disintegration, with potential applications for rapid antifungal delivery in oral or topical pharmaceutical form. Full article

A new method of producing metal powders for additive manufacturing by the atomization of free-falling melt streams using pulsed cross-flow gaseous shock or detonation waves is proposed. The method allows the control of shock/detonation wave intensity (from Mach number 4 to about 7), as well as the composition and temperature of the detonation products by choosing proper fuels and oxidizers. The method is implemented in laboratory and industrial setups and preliminarily tested for melts of three materials, namely zinc, aluminum alloy AlMg5, and stainless steel AISI 304, possessing significantly different properties in terms of density, surface tension, and viscosity. Pulsed shock and detonation waves used for the atomization of free-falling melt streams are generated by the pulsed detonation gun (PDG) operating on the stoichiometric mixture of liquid hydrocarbon fuel and gaseous oxygen. The analysis of solidified particles and particle size distribution in the powder is studied by sifting on sieves, optical microscopy, laser diffraction wet dispersion method (WDM), and atomic force microscopy (AFM). The operation process is visualized by a video camera. The minimal size of the powders obtained by the method is shown to be as low as 0.1 to 1 μm, while the maximum size of particles exceeds 400–800 μm. The latter is explained by the deficit of energy in the shock-induced cross-flow for the complete atomization of the melt stream, in particular dense and thick (8 mm) streams of the stainless-steel melt. The mass share of particles with a fraction of 0–10 μm can be at least 20%. The shape of the particles of the finest fractions (0–30 and 30–70 μm) is close to spherical (zinc, aluminum) or perfectly spherical (stainless steel). The shape of particles of coarser fractions (70–140 μm and larger) is more irregular. Zinc and aluminum powders contain agglomerates in the form of particles with fine satellites. The content of agglomerates in stainless-steel powders is very low. In general, the preliminary experiments show that the proposed method for the production of finely dispersed metal powders demonstrates potential in terms of powder characteristics. Full article

Li-ion batteries are at risk of explosions caused by fires, primarily because of the high energy density of Li ions, which raises the temperature. Battery cases are typically made of plastic, aluminum, or SAF30400. Although plastic and aluminum aid weight reduction, their strength and melting points are low. SAF30400 offers excellent strength and corrosion resistance but suffers from work hardening and low high-temperature strength at 700 °C. Additionally, Ni used for plating has a low current density of 25% international copper alloy standard (ICAS). SAF2507 is suitable for use as a Li-ion battery case material because of its excellent strength and corrosion resistance. However, the heterogeneous microstructure of SAF2507 after casting and processing decreases the corrosion resistance, so it requires solution heat treatment. To address these issues, in this study, SAF2507 (780 MPa, 30%) is solution heat-treated at 1100 °C after casting and coated with Ag (ICAS 108.4%) using physical vapor deposition (PVD). Ag is applied at five different thicknesses: 0.5, 1.0, 1.5, 2.0, and 2.5 μm. The surface conditions and electrochemical properties are then examined for each coating thickness. The results indicate that the PVD-coated surface forms a uniform Ag layer, with electrical conductivity increasing from 1.9% ICAS to 72.3% ICAS depending on the Ag coating thickness. This enhancement in conductivity can improve Li-ion battery safety on charge and use. This result is expected to aid the development of advanced Li-ion battery systems in the future. Full article

The ultrasonic vibration laser cladding method is a material-saving and green method to fabricate super abrasive structured grinding wheels. However, the mechanism of the ultrasonic vibration’s effect on the movement behavior of abrasive grains in the laser cladding process has not been clarified. To address this, the impacts of ultrasonic vibration on the abrasive grain distribution and movement behavior were experimentally studied, and the numerical simulation method was introduced to simulate the ultrasonic vibration laser cladding process. A two-dimensional Gaussian cross-section heat source model was developed, and its energy density conformed to a Gaussian distribution in both space and time. The simulations of the temperature and fluid fields of the melt pool were carried out. The CBN abrasive grains in the melt pool were subjected to gravity, the buoyancy force, the drag force of the metal fluid, and the sonophoretic radiation force of the ultrasonic vibration. Based on them, the effects of ultrasonic vibration on the movement behaviors and trajectories of the CBN abrasive grains were analyzed. The influence of the ultrasonic amplitude on the distribution of abrasive grains was studied. The simulation results revealed that the abrasive grains could be uniformly distributed on the surface of the cladding layer during the ultrasonic vibration laser cladding process. Full article

There are numerous lakes in the Tibetan Plateau (TP) that significantly impact regional climate and aquatic ecosystems, which often freeze seasonally owing to the high altitude. However, the special warming mechanisms of lake water under ice during the frozen period are poorly understood, particularly in terms of solar radiation penetration through lake ice. The limited understanding of these processes has posed challenges to advancing lake models and improving the understanding of air–lake energy exchange during the ice-covered period. To address this, a field experiment was conducted at Qinghai Lake, the largest lake in China, in February 2022 to systematically examine thermal conditions and radiation transfer across air–ice–water interfaces. High-resolution remote sensing technologies (ultrasonic instrument and acoustic Doppler devices) were used to observe the lake surface changes, and MODIS imagery was also used to validate differences in lake surface conditions. Results showed that the water temperature under the ice warmed steadily before the ice melted. The observation period was divided into three stages based on surface condition: snow stage, sand stage, and bare ice stage. In the snow and sand stages, the lake water temperature was lower due to reduced solar radiation penetration caused by high surface reflectance (61% for 2 cm of snow) and strong absorption by 8 cm of sand (absorption-to-transmission ratio of 0.96). In contrast, during the bare ice stage, a low reflectance rate (17%) and medium absorption-to-transmission ratio (0.86) allowed 11% of solar radiation to penetrate the ice, reaching 11.70 W·m⁻², which increased the water temperature across the under-ice layer, with an extinction coefficient for lake water of 0.39 (±0.03) m⁻¹. Surface coverings also significantly influenced ice temperature. During the bare ice stage, the ice exhibited the lowest average temperature and the greatest diurnal variations. This was attributed to the highest daytime radiation absorption, as indicated by a light extinction coefficient of 5.36 (±0.17) m⁻¹, combined with the absence of insulation properties at night. This study enhances understanding of the characteristics of water/ice temperature and air–ice–water solar radiation transfer through effects of different ice coverings (snow, sand, and ice) in Qinghai Lake and provides key optical radiation parameters and in situ observations for the refinement of TP lake models, especially in the ice-covered period. Full article

Titanium aluminides, particularly the Ti-48Al-2Cr-2Nb alloy, have drawn significant attention for their potential in high-temperature aerospace and automotive applications due to their exceptional performances and reduced density compared to nickel-based superalloys. However, their intermetallic nature poses challenges such as limited room-temperature ductility and fracture toughness, limiting their widespread application. Additive manufacturing, specifically Electron Beam Melting (EBM), has emerged as a promising method for producing complex-shaped components of titanium aluminides, overcoming challenges associated with conventional production methods. This work investigates the fracture behavior of Ti-48Al-2Cr-2Nb specimens with different microstructures, including duplex and equiaxed, under tensile and high-cycle fatigue at elevated temperatures. Fracture surfaces were analyzed to distinguish between static and dynamic fracture modes. A novel method, employing confocal microscopy acquisitions, is proposed to correlate surface roughness parameters with the causes of failure, offering new insights into the fracture mechanisms of titanium aluminides. The results reveal significant differences in roughness values between the propagation and fracture zones for all the temperatures and microstructure tested. At 650 °C, the crack propagation zone exhibits lower Sq values than the fracture zone, with the fracture zone showing more pronounced roughness, particularly for the equiaxed microstructure. However, at 760 °C, the difference in Sq values between the propagation and fracture zones becomes more pronounced, with a more substantial increase in Sq values in the fracture zone. These findings contribute to understanding fracture behavior in titanium aluminides and provide a predictive framework for assessing structural integrity based on surface characteristics. Full article

As the density of electronic packaging continues to rise, traditional soldering techniques encounter significant challenges, leading to copper–copper direct bonding as a new high-density connection method. The high melting point of copper presents difficulties for direct diffusion bonding under standard conditions, thus making low-temperature copper–copper bonding a focal point of research. In this study, we examine the sintering process at various temperatures by constructing models with multiple nanoparticles and sintering them under different conditions. Our findings indicate that 600 K is a crucial temperature for direct copper–copper sintering. Below this threshold, sintering predominantly depends on structural adjustments driven by residual stresses and particle contact. Conversely, at temperatures of 600 K and above, the activation of rapid surface atomic motion enables further structural adjustments between nanoparticles, leading to a marked decrease in porosity. Mechanical testing of the sintered samples corroborated the structural changes at different temperatures, demonstrating that the surface dynamic motion of atoms inherent in low-temperature sintering mechanisms significantly affects the mechanical properties of nanomaterials. These findings have important implications for developing high-performance materials that align with the evolving requirements of modern electronic devices. Full article

This study investigates fixed and moving mesh methodologies for modeling liquid metal–free surface deformation during the induction melting process. The numerical method employs robust coupling of magnetic fields with the hydrodynamics of the turbulent stirring of liquid metal. Free surface tracking is implemented using the fixed mesh level set (LS) and the moving mesh arbitrary Lagrangian–Eulerian (ALE) formulation. The model’s geometry and operating parameters are designed to replicate a semi-industrial induction melting furnace. Six case studies are analyzed under varying melt masses and coil power levels, with validation performed by comparing experimentally measured free surface profiles and magnetic field distributions. The melt’s stirring velocity and recirculation patterns are also examined. The comparative analysis determines an improved performance of the ALE method, convergence, and computational efficiency. Experimental validation confirms that the ALE method reproduces the free surface shape more precisely, avoiding unrealistic topological changes observed in LS simulations. The ALE method faces numerical convergence difficulties for high-power and low-mass filling cases due to mesh element distortion. The proposed ALE-based simulation procedure is a potential numerical optimization tool for enhancing induction melting processes, offering scalable and robust solutions for industrial applications. Full article

The hydrosphere is an element of the climate system and changes in the latter are reasonably projected over the river outflow. Climatic changes, however, are unevenly distributed over the Earth, and understanding their regional imprint on the hydrosphere is of great importance. In this study, we have conducted a statistical analysis of the monthly maximum and minimum river discharge recorded in 22 hydrological stations located on 19 of the Bulgarian rivers during the period 1993–2022. We have found that in half of the river basins, the trend of the spring maximum discharge is significantly positive (α = 0.05). In the other half of the stations, the trend is neutral. The stations with a positive trend are not randomly distributed but grouped, forming a pattern crossing the country from northwest to southeast. This pattern of trend distribution raises questions about the causes of the irregular hydrological response to the rising global near-surface temperatures. A comparison of hydrological data with some climatic variables (i.e., temperature, precipitation, and ozone at 70 hPa), combined with neural network analysis results, suggests ozone as a possible reason for the heterogeneous hydrological response. Its effect could be explained by an imposed episodic warming of the near-surface temperature due to fluctuations in the ozone density near the tropopause, which in turn favours the faster melting of ice and snow in the corresponding river basins. Full article

In situ measurements of the chemical identity and quantity of anode gases during electrochemical measurements and rare earth (RE) electrolysis from fluoride-based molten salts composed of different kinds of rare earth oxides (REOs) were performed using FTIR spectrometry. Linear sweep voltammetry (LSV) was carried out to characterize oxidation processes and determine the anodic effect from NdF₃ + PrF₃ + LiF + REO melt. RE complex formation and subsequent reactions on the GC anode surface were discussed to understand the formation pathways of CO/CO₂ and perfluorocarbon gases (PFC), mainly CF₄ and C₂F₆. The LSV shows that increasing the REO content from 1 wt.% up to 4 wt.% in the system, leads to a positive shift in the critical potential for a full anode effect, recorded around 4.50 V vs. W with 4 wt.% REO. The FTIR results from on-line off-gas analysis during LSV measurements indicate that the anode gas products were composed mainly of CO and CO₂, whereas CF₄ can be detected before the full anode effect and C₂F₆ at and after this phenomenon. Compositions of off-gases from electrolysis performed using different kinds of REOs were compared. The main off-gas component was found to be CO in RE electrolysis with REOs as raw materials, while in electrolysis with magnet recycling derived oxides (MRDOs), CO₂ content was slightly higher compared to CO. PFC emissions during RE electrolysis were generally similar: CF₄ was detected periodically, but in negligible concentrations, while C₂F₆ was not detected. Full article

Supraglacial debris cover considerably influences sub-debris ablation patterns and the surface morphology of glaciers by modulating the land–atmosphere energy exchange. Understanding its spatial distribution and temporal variations is crucial for analyzing melting processes and managing downstream disaster mitigation efforts. In recent years, the overall slightly positive mass balance or stable state of eastern Pamir glaciers has been referred to as the “Pamir-Karakoram anomaly”. It is important to note that spatial heterogeneity in glacier change has drawn widespread research attention. However, research on the spatiotemporal changes in the debris cover in this region is completely nonexistent, which has led to an inadequate understanding of debris-covered glacier variations. To address this research gap, this study employed Landsat remote sensing images within the Google Earth Engine platform, leveraging the Random Forest algorithm to classify the supraglacial debris cover. The classification algorithm integrates spectral features from Landsat images and derived indices (NDVI, NDSI, NDWI, and BAND RATIO), supplemented by auxiliary factors such as slope and aspect. By extracting the supraglacial debris cover from 1994 to 2024, this study systematically analyzed the spatiotemporal variations and investigated the underlying drivers of debris cover changes from the perspective of mass conservation. By 2024, the area of supraglacial debris in eastern Pamir reached 258.08 ± 20.65 km², accounting for 18.5 ± 1.55% of the total glacier area. It was observed that the Kungey Mountain region demonstrated the largest debris cover rate. Between 1994 and 2024, while the total glacier area decreased by −2.57 ± 0.70%, the debris-covered areas expanded upward at a rate of +1.64 ± 0.10% yr⁻¹. The expansion of debris cover is driven by several factors in the context of global warming. The rising temperature resulted in permafrost degradation, slope destabilization, and intensified weathering on supply slopes, thereby augmenting the debris supply. Additionally, the steep supply slope in the study area facilitates the rapid deposition of collapsed debris onto glacier surfaces, with frequent avalanche events accelerating the mobilization of rock fragments. Full article

The use of electrospun carbon nanofibers (ECNs) has been the focus of considerable interest due to their potential implementation in sensing. These ECNs have unique structural and morphological features such as high surface area-to-volume ratio, cross-linked pore structure, and good conductivity, making them well suited for sensing applications. Electrospinning technology, in which polymer solutions or melts are electrostatically deposited, enables the production of high-performance nanofibers with tailored properties, including fiber diameter, porosity, and composition. This controllability enables the use of ECNs to optimize sensing applications, resulting in improved sensor performance and sensitivity. While carbon nanofiber mats have potential for sensor applications, several challenges remain to improve selectivity, sensitivity, stability and scalability. Sensor technologies play a critical role in the global sharing of environmental data, facilitating collaboration to address transboundary pollution issues and fostering international cooperation to find solutions to common environmental challenges. The use of carbon nanofibers for the detection of air pollutants offers a variety of possibilities for industrial applications in different sectors, ranging from healthcare to materials science. For example, optical, piezoelectric and resistive ECNs sensors effectively monitor particulate matter, while chemoresistive and catalytic ECNs sensors are particularly good at detecting gaseous pollutants. For heavy metals, electrochemical ECNF sensors offer accurate and reliable detection. This brief review provides in-sights into the latest developments and findings in the fabrication, properties and applications of ECNs in the field of sensing. The efficient utilization of these resources holds significant potential for meeting the evolving needs of sensing technologies in various fields, with a particular focus on air pollutant detection. Full article