Search Results (215)

This study addresses the need for thermomechanically robust materials for high-temperature environments by investigating fabric-reinforced composites produced through polymer infiltration and thermal pressing using phenol-formaldehyde (PF) and epoxy (ER) resins. Experimental validation was required due to the lack of comparative data across different textile reinforcements under identical conditions. Seven technical fabrics—carbon, aramid, basalt, silica, fiberglass, asbestos, and a carbon/aramid hybrid—were used as reinforcements. Mechanical testing revealed that carbon- and hybrid fiber composites exhibited the highest tensile (up to 465 MPa) and compressive strengths (up to 301 MPa), particularly when combined with ER. Conversely, the use of PF generally resulted in a 30–50% reduction in mechanical strength. However, PF-based composites demonstrated superior thermal resistance, with the silica/PF combination showing the lowest back-face temperature (401 °C), up to 37% lower than other pairings. Thermal conductivity ranged from 0.041 to 0.51 W/m·K, with PF-based systems offering 6–12% lower values on average compared to ER-based analogs. Morphological analysis confirmed better interfacial bonding in ER composites, while PF systems showed higher structural integrity under thermal loading. Overall, the results emphasize the trade-offs between mechanical strength and thermal protection depending on the fabric–resin combination. Among all variants, the silica fabric with PF demonstrated the most balanced performance, making it a promising candidate for thermomechanical applications. Full article

Quinoline, a heterocyclic scaffold of paramount importance in medicinal and industrial chemistry, has garnered significant attention due to its versatile applications. Traditional synthetic methods, dating back over a century, have evolved into innovative strategies leveraging catalytic C–H bond activation, transition-metal-free protocols, and photo-induced oxidative cyclization. Recent advancements highlight the synergistic roles of catalysts, oxidants, and solvents in enhancing molecular reactivity and reaction efficiency. This review systematically summarizes state-of-the-art oxidative annulation techniques for quinoline synthesis, emphasizing mechanistic insights and practical applications. Full article

The enhancement of proppant conductivity in shale gas fracturing can be effectively achieved through the implementation of coated proppants. After soaking, non-curable viscous resin-coated proppants exhibit progressive viscosity development and spontaneous agglomeration during the transportation phase. Furthermore, upon fracture closure, the formed proppant agglomerates demonstrate significant stability and do not flow back with the fracturing fluid through the wellbore. While contemporary research has mostly focused on proppant coating methodologies, the transportation process of these proppants remains insufficiently investigated. To fill this knowledge gap, a sophisticated migration two-phase flow coupling model was developed utilizing the computational fluid dynamics–discrete element method (CFD-DEM) approach. This model incorporates the bond contact forces between film-coated proppant particles, accounting for their distinctive cementing characteristics during transport. Through comprehensive numerical simulations, the transport properties of film-coated proppants were systematically analyzed. Field application indicated that compared with conventional continuous sand fracturing, the amount of proppant after treatment with viscous resin film was reduced by 35% and the production was increased by about 25–30%. Additionally, the optimization of the field-scale coated proppant transport processes was achieved through the implementation of a lower fracturing displacement combined with staged sand addition. Full article

Certain fixed-income securities, such as callable bonds and mortgage-backed securities subject to prepayment, typically exhibit negative convexity at low yields and cannot be adequately immunized through duration and convexity-matching alone. To address this residual risk, we examine the concepts of bond tilt and bond agility. We provide explicit calculations and derive several approximation formulas that incorporate higher-order terms. With the help of these methods, we are able to track the price-yield dynamics of callable bonds remarkably well, achieving mean absolute errors below 2.5% across a wide variety of callable bonds for parallel yield shifts of up to ±200 basis points. Full article

Circular RNA is a type of noncoding RNA with a special covalent bond structure. As an endogenous RNA in animals and plants, it is formed through RNA splicing. The 5′ and 3′ ends of the exons form circular RNA at the back-splicing sites. Circular RNA plays an important regulatory role in diseases by interacting with the associated miRNAs. Accurate identification of circular RNA can enrich the data on circular RNA and provide new ideas for drug development. At present, mainstream circular RNA recognition algorithms are divided into two categories: those based on RNA sequence position information and those based on RNA sequence biometric information. Herein, we propose a method for the recognition of circular RNA, called circ2LO, which utilizes the LucaOne large model for feature embedding of the splicing sites of RNA sequences as well as their upstream and downstream sequences to prevent semantic information loss caused by the traditional one-hot encoding method. Subsequently, it employs a convolutional layer to extract features and a self-attention mechanism to extract interactive features to accurately capture the core features of the circular RNA at the splicing sites. Finally, it uses a fully connected layer to identify circular RNA. The accuracy of circ2LO on the human dataset reached 95.47%, which is higher than the values shown by existing methods. It also achieved accuracies of 97.04% and 72.04% on the Arabidopsis and mouse datasets, respectively, demonstrating good robustness. Through rigorous validation, the circ2LO model has proven its high-precision identification capability for circular RNAs, marking it as a potentially transformative analytical platform in the circRNA research field. Full article

Silver (Ag) is a precious and valuable metal, and it has many carrier minerals. Through LA-ICP-MS analysis, it was found that jamesonite not only contains lead (Pb) and antimony (Sb) as precious metals but also trace amounts of Ag. In practice, the flotation method is generally used to recover these metals. This paper employs density functional theory calculations to demonstrate that after Ag doping in jamesonite, the Ag atoms exist in the lattice channels of jamesonite, and they form strong covalent bonds with the S atoms, resulting in strong interactions. When Ag is doped in the channels, the adsorption of sodium diethyldithiocarbamate (DDTC) as a collector on the Ag-doped jamesonite surface is the strongest, while that of butyl xanthate is the weakest. The adsorption interactions on the Ag-doped jamesonite surface are also stronger than on pure jamesonite. Coordination chemistry studies reveal that Ag⁺ undergoes a transition from a d¹⁰ to a d⁹s¹ electronic configuration when incorporated into jamesonite, which increases its reactivity by generating unpaired electrons available for π-backbonding with collector molecules. Furthermore, owing to the high polarizability of Ag, the presence of Ag atoms alters the electronic environment of the surrounding Pb atoms, which enhances the π-backbonding interactions between the adsorbate reagent molecules and the Ag active sites. The research results are of great significance for the efficient recovery of Ag-containing jamesonite and provide a reference for the study of the properties of Ag-doped minerals. Full article

Additive manufacturing (AM) has the potential to produce novel high-performance electrical machines, enabling the direct printing of complex shapes and the simultaneous processing of multiple feedstocks in a single build. We examined the properties and functional performance of Fe-3 wt.% Si materials that were printed via selective laser melting, machined down to thin laminates, and stacked to form a stator core of a prototype brushless permanent-magnet electrical motor. Big Area Additive Manufacturing of Nd₂Fe₁₄B (NdFeB)–polyphenylene sulfide (PPS) bonded magnets was performed, with them then being magnetized and used for the rotor. The magnetic, mechanical, and electrical properties of the as-printed and various heat-treated thin laminates and the back electromotive force (EMF) of the electrical motors at different rotational speeds were measured. The thin laminates exhibit a maximum relative permeability of 7494 at an applied field of 0.8 Oe and a core loss of about 20 W/lb at 60 Hz with the maximum induction of 15 kg. In addition to the demonstration of AM printing, motor assembly, and complete characterization of printed Fe-3 wt.% Si, this report highlights the areas of improvement needed in printing technologies to achieve AM built electrical motors and the need for isotropic microstructure refinements to make the laminates appropriate for high-mechanical-strength and low-loss rotational electrical devices. Full article

To address the insufficient interlayer bonding performance and high preparation costs associated with conventional prime coat materials for semi-rigid base asphalt pavement, in this study, we utilized waste bio-oil to enhance asphalt–aggregate separation in recycled asphalt pavement (RAP) and collected the filtrate after separation. The RAP–bio-oil filtrate acts as a diluent, which is reintroduced into the asphalt to form a novel prime coat material: RAP–bio-oil filtrate cut-back asphalt (RFCA). The optimal proportions of each component in RFCA were determined through penetration tests, interlayer shear tests, and interlayer tensile tests. Subsequently, interlayer shear strength tests were conducted to evaluate the bond strength of RFCA compared to traditional prime coat materials, such as PC-2 emulsified asphalt (PC-2 EA) and kerosene cutback asphalt (KCA). Additionally, interlayer shear fatigue tests were performed to assess the durability of the bond provided by RFCA between the surface and base layers. The experimental results indicate that the optimal formulation for RFCA comprises 60% asphalt by mass of the RAP–bio-oil filtrate and 10% penetrant agent by mass of the RAP–bio-oil filtrate. Under conditions of 15 °C, 40 °C, and 15 °C water immersion, the interlayer shear strength of RFCA demonstrates an enhancement compared to PC-2 EA and KCA. Compared to PC-2 EA, the interlayer shear fatigue life of RFCA improved by 39.7% at a stress ratio of 0.2, 40.8% at 0.3, 51.2% at 0.4, and 40.3% at 0.5. The application of RFCA as a prime coat material significantly enhances interlayer durability. Based on the cost analysis, the application cost per square meter for RFCA is lower than that of PC-2A. Consequently, RFCA presents a viable option as a green, renewable, low-cost, and high-performance prime coat material for application on semi-rigid base asphalt pavement. Full article

In this work, we report the properties of molybdenum disulfide (MoS₂) thin films deposited on the p-type silicon substrate using RF magnetron sputtering. The structural, vibrational and morphological properties of MoS₂ thin films were investigated using the Raman spectroscopy, X-ray diffraction technique (XRD), atomic force microscope (AFM) and scanning electron microscope (SEM). Raman spectroscopy result showed the appearance of broad E¹_2g and A_1g Raman peaks even without DC biasing the substrate and becomes sharp and distinct when the substrate is DC biased at 60 V. Post-deposition annealing in sulfur ambient resulted in sharp and distinct Raman E¹_2g and A_1g peaks confirming the formation of MoS₂ thin film and improved Mo-S bonding on the top surface. X-ray diffraction spectra of the samples validates the formation of MoS₂ thin film with the appearance of [002] XRD peak, when the substrates are biased. Improved morphological effects with the reduction in nano-sized defects, advent of continuous film and low surface rms roughness value of 0.872 nm, were observed on samples deposited with substrate biasing and post sulfur annealing. A back-gated thin film transistor was fabricated with Al as source-drain contacts and MoS₂ as the semiconducting channel. The fabricated transistor exhibited p-type transfer characteristics with threshold voltage of −3.8 V. As a result of annealing and ambient exposure, MoO₃ fragments on the top of thinned MoS₂ layer resulted in extraction of hole from MoS₂, resulting in the p-type behavior in the fabricated thin film transistor. The combination of XRD analysis, Raman measurements and EDS data of the film confirmed MoO₃ inclusions in the MoS₂ thin film. Full article

The interfacial bonding properties of stainless steel clad (SSC) rebars determine whether they can be widely used. In the industrial production of SSC rebars, the process of intermediate and finish rolling of the microstructure evolution, element diffusion behavior, and interfacial bonding properties of bimetallic interfaces are investigated. In this paper, 316L seamless stainless steel (SS) tube and HRB400E carbon steel (CS) bar were prepared by a vacuum oxidation-free composite round billet, and the industrial emergency stopping of SSC rebars’ hot rolling was carried out. The metallographic results showed that the thicknesses of the carburized austenite zone (CAZ) varied greatly (832–238 μm) and showed a parabolic downward trend, while the thicknesses of the decarburized ferrite zone (DFZ) varied little (85–99 μm). The elemental line scans showed that Fe and Cr had the same parabolic downward trend. The intermediate-rolling had a great influence on element diffusion, and, in S6–9, the diffusion distance of Fe and Cr decreased significantly. The diffusion distances of the elements in the intermediate-rolling back stage and finishing-rolling front stage (S9–12) were basically balanced. The elemental diffusion distances and interfacial bonding strength were not consistent. Among them, the shear strength (τ) of S13 was 410.7 MPa. Compared with ordinary rebars, the yield strength (Re) and tensile strength (Rm) of finished SSC rebars were increased by 7.05% (30.9 MPa) and 7.10% (43.0 MPa), respectively. The tensile properties exceed those of mixture effects. The paper provides a theoretical basis for the improvement of the interfacial bonding strength and optimization of the rolling process system for the industrial production of SSC rebars. Full article

Bonded Nd-Fe-B magnets have greater freedom of shape than sintered Nd-Fe-B magnets. The ring structure is one of the typical structures of bonded Nd-Fe-B materials. In this paper, we analyzed the generation and spread of demagnetization fault (DMF) and changes in motor performance. Meanwhile, a BLDC fitted with a bonded Nd-Fe-B magnet ring was analyzed for DMF under actual overload conditions. DMF occurred with obvious localization and variability, which was mainly concentrated on the side of each pole opposite to the direction of the motor’s operation, near the weak magnetic zones. The experimental results show that back electromotive force (EMF) and its harmonic had the same variation trends as the surface radial flux density of the magnet ring. The analysis with the EMF waveform and total harmonic distortion (THD) were proposed as a method for diagnosing the DMF. Finally, this paper presents a modified magnet ring. The anti-demagnetization capability of the modified magnet ring is effectively improved. This research can provide a reference for the design analysis of BLDCs using bonded Nd-Fe-B magnet rings. Full article

Carbon catalysts have shown promise as an alternative to the currently available energy-intensive approaches for nitrogen fixation (NF) to urea, NH₃, or related nitrogenous compounds. The primary challenges for NF are the natural inertia of nitrogenous molecules and the competitive hydrogen evolution reaction (HER). Recently, carbon-based materials have made significant progress due to their tunable electronic structure and ease of defect formation. These properties significantly enhance electrocatalytic and photocatalytic nitrogen reduction reaction (NRR) activity. While transition metal-based catalysts have solved the kinetic constraints to activate nitrogen bonds via the donation-back-π approach, there is a problem: the d-orbital electrons of these transition metal atoms tend to generate H-metal bonds, inadvertently amplifying unwanted HER. Because of this, a timely review of defective carbon-based electrocatalysts for NF is imperative. Such a review will succinctly capture recent developments in both experimental and theoretical fields. It will delve into multiple defective engineering approaches to advance the development of ideal carbon-based electrocatalysts and photocatalysts. Furthermore, this review will carefully explore the natural correlation between the structure of these defective carbon-based electrocatalysts and photocatalysts and their NF activity. Finally, novel carbon-based catalysts are introduced to obtain more efficient performance of NF, paving the way for a sustainable future. Full article

Millions of tonnes of plastic and glass waste are generated worldwide, with only a marginal amount fed back into recycling with the majority ending at landfills and stockpiles. Excessive waste production calls for additional recycling pathways. The technology being investigated in this study is based on recycled glass fines encapsulated in a high-density polyethylene (HDPE) matrix. Laboratory tests are performed on specimens at different manufacturing conditions using compression moulding, determining an optimised manufacturing method. The performance of composites prepared under different formulations is tested to identify an optimised mix design by means of statistical analysis. At this optimum ratio, flexural, tensile, and compressive strengths of 33.3 MPa, 19.6 MPa, and 12.8 MPa, are, respectively, recorded. Upon identifying the optimum dosage levels, the potential for employing HDPE from diverse origins are investigated. The microstructure, pore structure, and chemistry of optimised composite specimens are analysed to interpret the composite performance. The effective stress transfer in the composite is attributed to strong hydrogen bonds created by maleic anhydride leading to 37.6% and 8.5% improvements in compressive and flexural strengths, respectively. These research findings can facilitate the pathway for utilising plastic and glass waste in landfills/stockpiles for sustainable polymeric composites towards structural applications. Full article

In the process of a systematic study of the bis-chelate oxime-amide ligands with different polymethylene spacers and their transition metal complexes, two new Ni(II) and Cu(II) complexes of the mhiea₂poh ligand have been isolated, and their molecular and crystal structures determined by single crystal X-ray diffraction. Potentiometric titrations were performed on a range of aqueous solutions in both systems, which allowed the identification of various complex species and afforded their stability constants. ESR spectra of samples with optimised concentrations of complexes in Cu(II)–L–H system were recorded. A distinguishing feature of both systems is the dimerization of anionic pseudo-macrocyclic complexes. The latter is caused either by centrosymmetric hydrogen bonding of the hydroxy group on the propane spacer to the oximato oxygen of the opposing unit or by back-to-back π-stacking of planar complex units. ESR measurements indicated likely coupling of Cu-Cu paramagnetic centres in the dimers. Full article

Chalcogen bonds (ChBs) involving selenium have attracted substantial scholarly interest in past years owing to their fundamental roles in various chemical and biological fields. However, the effect of the valency state of the electron-deficient selenium atom on the characteristics of such ChBs remains unexplored. Herein, we comparatively studied the σ-hole-type Se∙∙∙O ChBs between SeF₂/SeF₄ and a series of oxygen-bearing Lewis bases, including water, methanol, dimethyl ether, ethylene oxide, formaldehyde, acetaldehyde, acetone, and formic acid, using ab initio computations. The interaction energies of these chalcogen-bonded heterodimers vary from −5.25 to −11.16 kcal/mol. SeF₂ participates in a shorter and stronger ChB than SeF₄ for all the examined heterodimers. Such Se∙∙∙O ChBs are closed-shell interactions, exhibiting some covalent character for all the examined heterodimers, except for SeF₄∙∙∙water. Most of these chalcogen-bonded heterodimers are predominantly stabilized through orbital interactions between the lone pair of the O atom in Lewis bases and the σ*(Se–F) antibonding orbitals of Lewis acids. The back-transfer of charge from the lone pair of selenium into the σ* or π* antibonding orbitals of Lewis bases is also observed for all systems. Energy decomposition analysis reveals that the electrostatic component significantly stabilizes the targeted heterodimers, while the induction and dispersion contributions cannot be ignored. Full article