Understanding the radiation-induced microstructure evolution of carbon fibers is crucial for c/Siccomposites as they are considered promising structural materials for high-temperature gas-cooled nuclear reactors. In ...
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Understanding the radiation-induced microstructure evolution of carbon fibers is crucial for c/Siccomposites as they are considered promising structural materials for high-temperature gas-cooled nuclear reactors. In this study, M55J c/Sic and T300 c/Siccomposites were irradiated up to 9.8 dpa at 350 degrees c. AFM results suggested that both two carbon fibers shrank axially after irradiation. At a given irradiation dose, the shrinkage of M55J fibers was slightly lower than that of T300 fibers. Detailed microstructure characterization further revealed that the graphite structure in both two carbon fibers was disrupted due to ion irradiation. In contrast to M55J fibers, the ordering degree for T300 fibers increased at low dose range and diminished at higher doses. Possible mechanisms for the healing process occurring in T300 fibers were discussed.
To investigate the ablation mechanism of the mullite modified c/c-Sic-Hfccomposites prepared by precursor infiltration pyrolysis, a 60 s single ablation and 30 s x 3 cyclic ablations were carried out at heat fluxes o...
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To investigate the ablation mechanism of the mullite modified c/c-Sic-Hfccomposites prepared by precursor infiltration pyrolysis, a 60 s single ablation and 30 s x 3 cyclic ablations were carried out at heat fluxes of 2.38 and 4.18 MW/m2, respectively. Results showed that the ablation temperatures played a vital role in the ablation process. Under the lower heat flux condition, the single ablation behavior was mainly influenced by the escape of gaseous oxidation products and slight airflow erosion, while cyclic ablation was influenced primarily by the stresses induced by crystallization transformation during the heating-cooling process. Under the higher heat flux condition, HfSiO4 was gradually generated at the interface between HfO2 and SiO2, which stabilized the crystallization of HfO2. The ablation behavior under higher heat flux was mainly influenced by thermal-induced stresses and mechanical forces of high-velocity airflow.
The synthesis of cuO/c nanocomposites was fabricated using an uncomplicated and eco-friendly method by cyperus rotundus (c. rotundus) leaf extract. The formation of nanocomposites and their size were optimized with va...
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The synthesis of cuO/c nanocomposites was fabricated using an uncomplicated and eco-friendly method by cyperus rotundus (c. rotundus) leaf extract. The formation of nanocomposites and their size were optimized with various factors, such as operational parameters, viz. exposure time, temperature, and concentration of the precursor, by response surface methodology (RSM). The effects of the synthesis of cuO/c nanocomposite samples and their characterization by various analytical techniques such as UV, XRD, XPS, EDX, SEM, and TEM have been reviewed and confirmed. The XRD patterns revealed that the biosynthesized cuO/c sample exhibited a monoclinic and crystalline structure. Moreover, the elements available in nanocomposites were determined as cu 2p, O 1 s, and c1s using XPS analysis. The TEM pictures reveal the morphology of the nanocomposites as spherical in form, with an average size of 30 nm. Additionally, synthesized cuO/c nanocomposites were examined for toxic effects on the mortality of two-winged insect larvae, and they were absolutely found to be extremely active and considerably kill larvae. The molecular docking study found that the nanocomposites were able to bind to the target protein with high affinity, which suggests that they are likely to be effective larvicidal agents. Our existing analysis findings can open up a replacement void for the larvicidal analysis exploiting biosynthesized nanocomposites.
Aimed to enhance the high-temperature service performance of c/Siccomposites in high-speed aircraft thermal protection system, in this article, pitch-based carbon fibers were used to construct high thermal conductive...
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Aimed to enhance the high-temperature service performance of c/Siccomposites in high-speed aircraft thermal protection system, in this article, pitch-based carbon fibers were used to construct high thermal conductive channels to improve the heat transfer capability of c/Siccomposites. The results revealed that the as-prepared composites equipped with 4.7 times higher thermal conductivity than that of conventional c/Siccomposites. The oxyacetylene flame ablation test confirmed that the constructed high thermal conductive channels, which quickly conducted the heat flow from the ablation center area to other areas is the main reason of as-prepared composites exhibiting a very impressive ablation resistance property. Briefly, the ablation temperature of the as-prepared composite surfaces considerably dropped by about 300 & DEG;ccompared with conventional c/Siccomposites, while the linear ablation rate and mass ablation rate of the composites are 1.27 & mu;m/s and 0.61 mg/s respectively, which is superior to many recent reports, demonstrating that this article provides a simple but highly effective measure to improve the ablation resistance property of c/Siccomposites.
The transition-metal-catalyzed intramolecular hydroarylation of alkenes has been recognized as a straightforward approach for the construction of 3,3-disubstituted 2,3-dihydrobenzofurans. The reactions mainly rely on ...
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The transition-metal-catalyzed intramolecular hydroarylation of alkenes has been recognized as a straightforward approach for the construction of 3,3-disubstituted 2,3-dihydrobenzofurans. The reactions mainly rely on the reductive Heck reaction of aryl halides or the direct c-H bond activation of arenes bearing a directing group. This work realizes the Rh-catalyzed intramolecular hydroarylation of olefin-tethered benzocyclobutenols via c-c bond activation, which offers an alternative approach to 3,3-disubstituted 2,3-dihydrobenzofurans bearing a 4-beta-keto moiety. The methodology features 100% atom economy and pH-and redox-neutral conditions, and is applicable to the late-stage functionalization of complex molecules. The asymmetric variant has also been achieved with excellent enantioselectivities.
In this study, c alpha-c beta and c beta-O bond cleavage of beta-O-4 model compound (2-phenoxy-1-phenylethanol) were accomplished by electrocatalysis depolymerization process in deep eutectic solvents (DES) systems. W...
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In this study, c alpha-c beta and c beta-O bond cleavage of beta-O-4 model compound (2-phenoxy-1-phenylethanol) were accomplished by electrocatalysis depolymerization process in deep eutectic solvents (DES) systems. We have investigated the application of Ni-co/ccatalysts on working electrode, which were synthesized with impreg-nation method. The Ni-co/c with porous structure and abundant active sites, was shown an excellent electro-catalysis activity. Specific structure of Ni-co/ccould provide greatly efficient adsorption and desorption capacity to promote c alpha-c beta and c beta-O bond cleavage. Therefore, in this electrocatalysis depolymerization pro-cess, the highest depolymerization rate exceeded 90%. And the yields (and conversion rates) of products (in-cluding benzaldehyde, acetophenone, benzoic acid, phenol) can reach to 124.08 mg/g (25.05%), 23.29 mg/g (4.15%), 44.64 mg/g (7.83%), 30.3 mg/g (6.9%). Furthermore, the electrocatalysis mechanism of c alpha-c beta and c beta-O bond was investigated. The cleavage of c alpha-c beta and c beta-O bond was initiated by in situ generated free rad-icals through Ni-co/c. Then, the cleavage of c alpha-c beta and c beta-O bond were occurred by center dot OH and center dot O2-. The results were showed that the c alpha-c beta bond cleavage was more in line with the beta-c elimination and free radical pathways, and c beta-O bond cleavage was consistent with direct oxidative addition. The enhanced electrocatalytic efficiency of the low-cost Ni-co/c electrocatalyst combined with its good chemical stability and selectivity, which offer a promising route for developing an efficient lignin depolymerization technology.
cyclopropane derivates are appealing to synthesis of high-energy-density fuels because of the high strained energy of the three-numbered ring. The catalyticcyclopropanation of olefin with diazomethane is very effecti...
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cyclopropane derivates are appealing to synthesis of high-energy-density fuels because of the high strained energy of the three-numbered ring. The catalyticcyclopropanation of olefin with diazomethane is very effective to construct the carbocycle. The majority of the catalysts employed are nonrecyclable homogeneous compounds. Herein, we report cyclopropanation of polycyclic olefins catalyzed by heterogeneous Pd/c. The optimal cyclopropanation conditions were explored utilizing dicyclopentadiene as model substrate and a series of polycyclic olefins were cyclopropanated with high yield. Additionally, the catalyst has good recyclability and stability, as shown by characterizations as well as the fact that no inactivation happens after cyclopropanation. The synthesized cyclopropane derivates exhibit good fuel characteristics like high density (1.006-1.087 g/cm(3)), high volumetric net heat of combustion (42.58-46.45 kJ/cm(3)), good low-temperature and combustion performance. This work shows industrial potential for cyclopropanation of polycyclic olefins with diazomethane.
Na4MnV(PO4)(3)/c (NMVP) has been considered an attractive cathode for sodium-ion batteries with higher working voltage and lower cost than Na3V2(PO4)(3)/c. However, the poor intrinsic electronicconductivity and Jahn-...
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Na4MnV(PO4)(3)/c (NMVP) has been considered an attractive cathode for sodium-ion batteries with higher working voltage and lower cost than Na3V2(PO4)(3)/c. However, the poor intrinsic electronicconductivity and Jahn-Teller distortion caused by Mn3+ inhibit its practical application. In this work, the remarkable effects of Zr-substitution on prompting electronic and Na-ion conductivity and also structural stabilization are reported. The optimized Na3.9Mn0.95Zr0.05V(PO4)(3)/c sample shows ultrafast charge-discharge capability with discharge capacities of 108.8, 103.1, 99.1, and 88.0 mAh g(-1) at 0.2, 1, 20, and 50 c, respectively, which is the best result for cation substituted NMVP samples reported so far. This sample also shows excellent cycling stability with a capacity retention of 81.2% at 1 c after 500 cycles. XRD analyses confirm the introduction of Zr into the lattice structure which expands the lattice volume and facilitates the Na+ diffusion. First-principle calculation indicates that Zr modification reduces the band gap energy and leads to increased electronicconductivity. In situ XRD analyses confirm the same structure evolution mechanism of the Zr-modified sample as pristine NMVP, however the strong Zr-O bond obviously stabilizes the structure framework that ensures long-term cycling stability.
In order to enhance ablation resistance of c/ccomposites, Zr1-xHfxc and Sic were intro-duced into c/ccomposites, and ablation behavior of the composites was studied. In the composites (cHZS), Hfc and Zrc produced a ...
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In order to enhance ablation resistance of c/ccomposites, Zr1-xHfxc and Sic were intro-duced into c/ccomposites, and ablation behavior of the composites was studied. In the composites (cHZS), Hfc and Zrc produced a solid solution, and solid solubility of Hfc in Zrc was 0.4, which indicated that the solid solution was defined to be Zr0.6Hf0.4c. compared with c/c-Zrc-Siccomposites (cZS), cHZS possessed a better ablation resistance. During ablation of cHZS, Zr0.6Hf0.4c is oxidized to produce HfO2 and ZrO2, and HfO2 particles played a pinning effect, which fixed molten oxide coating. Moreover, due to low cTE of HfO2 and decreasing content of ZrO2, there was a smaller thermal stress and its distribu-tion area on cHZS ablation surface, thus thermal stress corrosion was weakened to strengthen integrity of oxide coating. In this case, a complete and continuous HfO2-ZrO2 coating was formed on cHZS surface, which could resist oxygen diffusion and reduce oxidation rate of the composites.& cOPY;2023 The Authors. Published by Elsevier B.V. This is an open access article under the cc BY-Nc-ND license (http://***/licenses/by-nc-nd/4.0/).
In this paper, c/N co-doped rich-defect TiO2 photocatalyst (c/N/DBD-TiO2-x) was prepared by DBD plasma discharge treatment in the mixed atmosphere of cO, N2 and H2 for the first time. The oxygen defects, c doping and ...
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In this paper, c/N co-doped rich-defect TiO2 photocatalyst (c/N/DBD-TiO2-x) was prepared by DBD plasma discharge treatment in the mixed atmosphere of cO, N2 and H2 for the first time. The oxygen defects, c doping and N doping were successfully introduced by DBD plasma discharge treatment. With the synergy of these three, the forbidden band width was reduced from 3.20 eV to 2.78 eV, and the electron hole pair was rapidly separated and transferred. Meanwhile DBD plasma discharge treatment increased the specific surface area, pore volume and pore size of TiO2. Evaluation results of visible light catalytic performance showed that the degradation rate of MB solution could reach 98.05%. The new plasma discharge method solved the shortcomings and deficiencies of traditional modification methods, which provided a new and more convenient technology for TiO2 modification.(c) 2023 Elsevier B.V. All rights reserved.
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