Search Results (38,924)

Enhancing the thermal conductivity of fluids by using nanoparticles with outstanding thermophysical properties has acquired significant attention for heat-transfer applications. Nanofluids have the potential to optimize energy systems by improving heat-transfer efficiency. In this study, cobalt ferrite nanoparticles clusters with controlled mean sizes ranging from 97 to 192 nm were synthesized using a solvothermal method to develop novel nanofluids with enhanced thermal conductivity. These clusters were comprehensively characterized using transmission electron microscopy, X-ray diffraction, Raman spectroscopy, vibrating-sample magnetometry, and nitrogen physisorption. The CoFe₂O₄ cluster nanofluids were prepared using the two-step method with various base fluids (water, propylene glycol, and a mixture of both). Dynamic light scattering analyses of the average Z-size of the dispersed nanoadditives over time revealed that the stability of the dispersions is influenced by cluster size and the proportion of glycol in the base fluid. The thermal conductivity of the base fluid and nine different 0.5 wt% CoFe₂O₄ cluster nanofluids was measured using the transient hot wire method at temperatures of 293.15, 303.15, and 313.15 K, showing different temperature dependencies. The study also explores the relationships between the thermal conductivity, cluster size, and specific surface area of the nanoadditives. A maximum thermal conductivity enhancement of 4.2% was reported for the 0.5 wt% nanofluid based on propylene glycol containing 97 nm CoFe₂O₄ clusters. The findings suggest that the specific surface area of nanostructures is a more relevant parameter than size for describing improvements in thermal conductivity. Full article

Bismuth (Bi) can be considered for use as a green substitute for lead in bearing applications. However, accelerated Bi oxidation can occur during operation, creating a brittle surface and resulting in premature seizure failure. Thus, the aim of this study was to evaluate the influence of engine oil degradation, especially nitration processes, on the oxidation of Bi. Tailor-made artificially aged oils with different degrees of nitration were produced and utilized in static bearing oxidation tests. By means of X-ray photoelectron spectroscopy (XPS), the Bi surfaces were analyzed regarding their chemical compositions after the tests. The results were correlated with the respective oil conditions determined via conventional parameters as well as high-resolution mass spectrometry. The findings obtained revealed a direct correlation between the amount of Bi-oxide and the nitration values of the oil, proving there was a positive impact of nitration products on the oxidation of the Bi surfaces. A comparison with the Bi content in the oils demonstrated a protective effect of the oxide layer as the Bi content declined with an increase in nitration. Overall, valuable insight into understanding the impact of oil condition on engine parts is given, and the importance of testing engine parts with aged lubricants is emphasized. Full article

In this study, a catalyst composed of zinc, ferrocyanide, and carbon nanotubes (CNTs) was synthesized and used to enhance the methanolysis of sodium borohydride (NaBH₄). The structural characteristics of Zn₃[Fe(CN)₆]²-CNT catalysts were investigated utilizing X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM) analyses and transmission electron microscopy (TEM). The catalytic activity was studied by measuring the volume of hydrogen produced versus time. The results demonstrated a hydrogen generation rate of 51,480 mL min⁻¹ g⁻¹ for methanolysis of 250 mg NaBH₄ at 298 K using 10 mg of the catalyst. Varying the catalyst weight for the methanolysis reaction of NaBH₄ showed a high generation rate when a weight of 10 mg was used. The impact of the catalyst on the methanolysis reaction resulted in a lower activation energy (Ea) compared to other works, which is 24.14 kJ mol⁻¹. Moreover, other activation parameters, namely enthalpy (ΔH) and entropy (ΔS), were calculated to be 21.641 kJ mol⁻¹ and −98.986 J mol⁻¹, respectively. The catalyst reusability study showed the stability of the hydrogen generation rate over four cycles. Full article

A dense monolithic SiC/(Hf_0.25Ta_0.25Zr_0.25Nb_0.25)C/C high-entropy ceramic nanocomposite was prepared using a polymer-derived ceramic (PDC) method combined with spark plasma sintering (SPS). The microstructural evolution and mechanical properties of the obtained nanocomposites were characterized by X-ray diffractometer (XRD), transmission electron microscope (TEM), scanning-electron microscope (SEM), and nanoindentation. The results indicate that the phase composition of SiC/(Hf_0.25Ta_0.25Zr_0.25Nb_0.25)C/C can be adjusted by modifying the metal content of the single-source precursor (SSP) through molecular design. The resulting precursor exhibits an exceptionally high ceramic yield, with mass retention of over 90% at 1100 °C, which guarantees the densification of the final SiC/(Hf_0.25Ta_0.25Zr_0.25Nb_0.25)C/C composites. The PDC route facilitates the in situ formation of a high-entropy phase within the ceramic matrix under low temperature pyrolysis conditions. Combined with SPS, a dense monolithic SiC/(Hf_0.25Ta_0.25Zr_0.25Nb_0.25)C/C nanocomposite was obtained, exhibiting an open porosity of 0.41 vol%, nano-hardness of 27.47 ± 0.46 GPa, elastic modulus of 324.00 ± 13.60 GPa, and fracture toughness of 3.59 ± 0.24 MPa·m^0.5, demonstrating excellent mechanical properties. Full article

Background/Objectives: Reports on type V FDP tendon avulsions and their treatment are rare. Furthermore, they are not always classified in a consistent manner in the literature. The purpose of our retrospective data analysis was to evaluate and present jersey finger type V injury characteristics, primary radiological findings, treatment options and subsequent patient outcomes, as well as potential complications. Methods: We reviewed all patients treated for a fracture of the distal phalanx at an academic Level 1 trauma center over a period of 19 years. By reviewing the patients’ charts and their initial X-rays, we identified 44 patients with injuries matching the criteria for classification as jersey finger type Va and type Vb. All clinical records and radiologic images were reviewed to gather data on the mechanism of trauma, injury characteristics, type of treatment and subsequent outcomes in both subtypes. Results: Direct blows represented the most common mechanism of trauma, accounting for 23 cases. Among 44 jersey finger type V injuries, 31 showed minor displacement and were treated conservatively with a good outcome. Six patients undergoing surgery showed a poor outcome, except for one. Conclusions: Jersey finger type V differs considerably from the remaining types of jersey finger injuries regarding the predominant trauma mechanism. Therefore, its inclusion in this classification should be reevaluated. Established surgical techniques for refixation did not show a satisfying outcome, thus the implementation of alternative surgical techniques seems advisable when better therapeutic results are sought. Full article

Photocatalytic degradation is a leading technology for complete mineralization of organic dyes in the ocean. In this work, a new viologen-bearing silver-thiocyanate-based photocatalyst, i.e., {(i-PrV)[Ag₂(SCN)₄]}_n (i-PrV²⁺ = isopropyl viologen) has been synthesized and structurally determined, with results showing that it can exhibit excellent degradation performance on rhodamine B (RhB) in artificial seawater. The planar i-PrV²⁺ dications are confined in the free voids of the [Ag₂(SCN)₄]_n²ⁿ⁻ layer with a two-dimensional (6,3) mesh, and strong C-H···S hydrogen bonds contribute to its structural stabilization. This photocatalyst was further characterized by powder X-ray diffraction (PXRD), UV-Vis, fluorescence, and photo/electrical responsive measurements, pointing to its application in visible-light-driven catalysis. Interestingly, using this photocatalyst, good photocatalytic degradation performance on rhodamine B in artificial seawater could be observed. The dye pollutant could be degraded with a high degradation ratio of 87.82% in 220 min. This work provides a promising catalyst for organic dye-type ocean pollutant treatments. Full article

Two tetranuclear Co(II) complexes, [Co₄(pmab)₄Cl₄] (1) and [Co₄(pmab)₄(OBz)₂]Cl₂ (2) [Hpmab = 2-{(p-pyridinylmethylene)amino}benzenemethanol], have been synthesized and characterized through single-crystal X-ray diffraction, IR and UV-VIS spectroscopy, and magnetic measurements. Structural analysis revealed that both complexes possess a [Co₄O₄] cubane-like metal core connected by μ₃-alkoxo bridges. Magnetic measurements of Complex 1 indicate weak ferromagnetic interactions (J ~ +0.75 cm⁻¹) within the tetranuclear core, while Complex 2 exhibits antiferromagnetic behavior due to the presence of syn-syn bridging benzoate ligands. Alternating current (AC) magnetic measurements suggest that Complex 1 exhibits slow magnetic relaxation behavior. Full article

The silicon carbide (SiC) Schottky diode (SBD) detector in a SiC hybrid photomultiplier tube (HPMT) generates signals by receiving photocathode electrons with an energy of 10 keV. So, the performance of the SiC SBD under electron irradiation with an energy of 10 keV has an important significance for the application of the SiC-HPMT. However, studies on 10 keV radiation effects on the SiC SBDs were rarely reported. In this paper, the performance degradation of the SiC SBDs irradiated by 10 keV electrons at different fluences was investigated. After the irradiation, the forward current of the SiC SBDs increased, and the turn-on voltage decreased with the irradiation fluences until 1.6 × 10¹⁶ cm⁻². According to the capacitance–voltage (C-V) curves, the effective doping concentration increased slightly after the irradiation, and an obvious discrepancy of C-V curves occurred below 5 V. Moreover, as a radiation detector, the peak position of the α-particles’ amplitude spectrum changed slightly, and the energy resolution was also slightly reduced after the irradiation due to the high collection charge efficiency (CCE) still being larger than 99.5%. In addition, the time response of the SiC SBD to the 50 ns pulsed X-ray was almost not affected by the irradiation. The results indicated that the performance degradation of the SiC SBD irradiated at the fluence of 1.5 × 10¹⁷ cm⁻² would not result in a deterioration of the properties of the SiC-HPMT and showed an important significance for the supplement of the radiation resistance of the SiC SBD radiation detector. Full article

Trace mercury contamination in groundwater poses a serious threat to ecological systems and human health. The kinetics and isotherms of MoS₂ (MS) for Hg removal were studied in batch tests under an unfavorable high salinity and low mercury environment. Flower-like MS with nanosheets can effectively remove Hg in the groundwater matrix, with a shorter equilibrium time (3 h), superior removal efficiency (94.26%), excellent distribution coefficient (5.69 × 10⁶ mL g⁻¹), and higher maximum adsorption capacity (926.10 ± 165.25 mg g⁻¹). Furthermore, the Adams-Bohart model (R² = 0.9052–0.9416) can accurately describe the dynamic interception process of the initial stage (≤40 PVs), and the Yan model (R² = 0.9765−0.9941) depicts the whole process (140 PVs) of MS in a fixed column well. A higher dosage of m, but lower C₀ and ν_p facilitate the interception efficiency in column tests. Based on the characterizations of X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM), which were used to simultaneously consider the species of Hg and the groundwater matrix, surface complexation, electrostatic attraction, ion exchange, and precipitation is a plausible interfacial adsorption mechanism of MS for mercury. The excellent performance demonstrates that MS with nanosheets is a promising candidate for the PRB remediation of trace Hg in saline groundwater. Full article

The continuous development of biomedical materials necessitates exploring new solutions to enhance implant performance. This study investigates the impact of titanium dioxide nanoparticles on calcium phosphate coatings applied to VT1-0 titanium substrates using micro-arc oxidation. Titanium, widely recognized for its excellent mechanical properties and compatibility, serves as an ideal substrate for implants. The coatings were synthesized in an electrolyte with varying titanium dioxide concentrations to examine their influence on surface morphology, wettability, roughness, hardness, and tribological characteristics. Characterization techniques, such as scanning electron microscopy, X-ray diffraction, and profilometry, were employed to analyze the coatings’ structural and mechanical properties. The results demonstrate that increasing titanium dioxide concentrations leads to enhanced uniformity, reduced pore sizes, and higher hardness. Furthermore, the coatings showed improved wear resistance and reductions in friction coefficients at optimal nanoparticle levels. The inclusion of titanium dioxide significantly enhances the mechanical and tribological performance of the calcium phosphate coatings, making them suitable for biomedical applications, especially in implants requiring long-term durability and enhanced compatibility. Full article

Soluble aluminum alloy materials used in underground operational tools are synthesized via a high-temperature smelting process. The microstructure and composition distribution of the alloy were analyzed using X-ray diffraction, metallographic microscopy, and scanning electron microscopy with energy-dispersive X-ray and electron backscatter diffraction techniques. The mechanical properties were evaluated using a universal testing machine and hardness tester, while solubility assessments were conducted in a constant-temperature water bath. This study focuses on the plasticity and dissolution characteristics of Al-Mg-Ga-Sn-In alloys with varying Mg contents. The tensile strength (σ_b) of the alloy was 181.99 MPa, with an elongation (δ) of 27.49% and cross-sectional shrinkage (φ) of 11.67% at a magnesium content of 3.0 wt.%. Additionally, in the compressive test, the compressive yield strength (σ_sc) was recorded at 188.32 MPa, while the compression rate (δ) was 27.06% and the section expansion rate (φ) was 138.66%. Furthermore, the alloy demonstrated the ability to dissolve spontaneously in water at 90 °C, exhibiting an average dissolution rate of 1.0 g·h⁻¹cm⁻² and a maximum dissolution rate of 3.25 g·h⁻¹cm⁻² after 12.0 h. Consequently, this alloy composition not only satisfies the requirements for rapid solubility but also exhibits favorable plasticity, providing a novel reference for the selection of soluble aluminum alloy materials. Full article

Currently, industrial water pollution represents a significant global challenge, with the potential to adversely impact human health and the integrity of ecosystems. The continuous increase in global consumption has resulted in an exponential rise in the use of dyes, which have become one of the major water pollutants, causing significant environmental impacts. In order to address these concerns, a number of wastewater treatment methods have been developed, with a particular focus on physicochemical approaches, such as adsorption. The objective of this study is to investigate the potential of a bio-based material derived from olive oil pomace (OOP) as an environmentally friendly bio-adsorbent for the removal of methylene blue (MB), a cationic dye commonly found in textile effluents. The biobased material was initially characterized by determining the point of zero charge (pHpzc) and using scanning electron microscopy (SEM), X-ray diffraction (XRD), and Fourier transform infrared spectroscopy (FTIR). Subsequently, a comprehensive analysis was conducted, evaluating the impact of specific physicochemical parameters on MB adsorption, which included a thorough examination of the kinetic and thermodynamic aspects. The adsorption process was characterized using Langmuir, Freundlich, Brunauer-Emmett-Teller (BET), and Dubinin Radushkevich (D-R) isotherms. The results suggest that the equilibrium of adsorption is achieved within ca. 200 min, following pseudo-second-order kinetics. The optimal conditions, including adsorbent mass, temperature, bulk pH, and dye concentration, yielded a maximum adsorption capacity of ca. 93% (i.e., 428 mg g⁻¹) for a pomace concentration of 450 mg L⁻¹. The results suggest a monolayer adsorption process with preferential electrostatic interactions between the dye and the pomace adsorbent. This is supported by the application of Langmuir, BET, Freundlich, and D-R isotherm models. The thermodynamic analysis indicates that the adsorption process is spontaneous and exothermic. This work presents a sustainable solution for mitigating MB contamination in wastewater streams while simultaneously valorizing OOP, an agricultural by-product that presents risks to human health and the environment. In conclusion, this approach offers an innovative ecological alternative to synthetic adsorbents. Full article

The structure and magnetic properties of epitaxial Heusler alloy films (Co₂FeGe) deposited on MgO (100) substrates were investigated. Films of 60 nm thickness were prepared by magnetron co-sputtering at different substrate temperatures (T_S), and those deposited at room temperature were later annealed at various temperatures (T_a). X-ray diffraction confirmed (001) [110] Co₂FeGe || (001) [100] MgO epitaxial growth. A slight tetragonal distortion of the film cubic structure was found in all samples due to the tensile stress induced by the mismatch of the lattice parameters between Co₂FeGe and the substrate. Improved quality of epitaxy and the formation of an atomically ordered L2₁ structure were observed for films processed at elevated temperatures. The values of magnetization increased with increasing T_S and T_a. Ferromagnetic resonance (FMR) studies revealed 45° in-plane rotation of the easy anisotropy axis direction depending on the degree of the tetragonal distortion. The film annealed at T_a = 573 K possesses the minimal FMR linewidth and magnetic damping, while both these parameters increase for another T_S and T_a. Overall, this study underscores the crucial role of thermal treatment in optimizing the magnetic properties of Co₂FeGe films for potential spintronic and magnonic applications. Full article

This paper explores the historical and geological background of the refectory of the Manzana Jesuítica in the city of Córdoba (Argentina), as a basis for characterising some of the building materials used in it. The aim is to gain a better understanding of the raw materials, labour, and production methods employed by the Jesuits in the seventeenth and eighteenth centuries. To this end, six fragments containing brick, render, and paint layers were studied by X-ray diffraction and using optical and scanning electron microscopies. Our results show that the ceramics differed solely in terms of their firing temperature, while the mortars were either air lime- or gypsum-based. The paints, mainly lime-based with clays, have similar mineralogical compositions, with some differences in colour due to the presence of goethite. This study demonstrates that the Jesuits, through their strategically situated settlements in the province of Córdoba, developed an economic system for the extraction and transport of raw materials, centred around the use of local resources. This, combined with construction techniques imported from Spain and adapted to local circumstances, was a sign of the adaptability of the Jesuit Order and their lasting influence on the region. Understanding the materials and techniques used by the Jesuits provides valuable insight into the methods of construction employed in historical buildings, offering key perspectives for their conservation. Moreover, it highlights the significance of local resource management in the longevity and preservation of these architectural works. Full article

Thorium is a weak radioactive element, but the control of its concentration in natural aqueous systems is of great interest for health, because it is a toxic heavy metal. The present paper presents the recovery of thorium from diluted synthetic aqueous systems by nanofiltration. The membranes used for the nanofiltration of systems containing thorium species are composites containing 4′-Aminobenzo-15-crown-5 ether (ABCE) and sulfonated poly–etherether–ketone (sPEEK). The composite membranes (ABCE–sPEEK) were characterized by scanning electron microscopy (SEM), energy-dispersive X–Ray spectroscopy (EDAX), thermal analysis (TG and DSC), and from the perspective of thorium removal performance. To determine the process performance, the variables were the following: the nature of the composite membrane, the concentration of thorium in the aqueous systems, the rotation speed of the stirrer, and the pressure and the pH of the thorium aqueous system. When using pure water, a permeate flux value of 12 L·m⁻² h⁻¹ was obtained for the sPEEK membrane, and a permeate flux value of up to 15 L·m⁻² h⁻¹ was obtained for the ABCE–sPEEK composite membrane. The use of mechanical stirring, with a propeller stirrer, lead to an increase in the permeate flux value of pure water by about 20% for each of the studied membranes. Depending on the concentration of thorium and the pH of the feed solution, retentions between 84.9% and 98.4% were obtained. An important observation was the retention jump at pH 2 for the ABCE–sPEEK composite membrane. In the paper, a thorium ion retention mechanism is proposed for the sPEEK membrane and the ABCE–sPEEK composite membrane. Full article