Journal of Materials Research and Technology-JMR&T
·
2025
·
IF 6.6
Yuanming Zhou,Zhenxiao Tang,Ruizhi Liu,Zhe Zhou,Maozhong Yi,Ke Peng
To further enhance the ablation resistance of C/C composites, solid solution ceramic Ta 0.2 Zr 0.8 C was used to replace traditional ultra-high-temperature ceramic carbides for matrix modification of C/C composites. The C/C-Ta 0.2 Zr 0.8 C-SiC composite was fabricated by a high-solid-loading slurry impregnation combined with the precursor infiltration and pyrolysis process. The comparative samples of C/C-ZrC-SiC and C/C-TaC-SiC were also prepared using these same technologies. The microstructure, flexural properties, and ablation performance of the composite were investigated. Results showed that the C/C-Ta 0.2 Zr 0.8 C-SiC exhibited excellent overall flexural properties. During the ablation test under an oxyacetylene flame with high heat flux, the ablation resistance of C/C-Ta 0.2 Zr 0.8 C-SiC improved with prolonged ablation time, reaching mass and linear ablation rates of 0.67 mg/s and 0.18 μm/s after 120 s of ablation. Compared to the C/C-ZrC-SiC and C/C-TaC-SiC, the mass ablation rate of the composite was reduced by 49.24% and 68.70%, and the linear ablation rate was reduced by 97.22% and 97.71%, respectively. The enhanced ablation resistance was primarily attributed to the formation of the Ta-Zr-O oxide layer, composed of TaZr 2.75 O 8 , ZrO 2 , and Ta 2 O 5 , on the composites surface. In the oxide layer, the Ta-rich oxides served as a binder, filling gaps in the interface. Meanwhile, the Zr-rich oxides formed the skeleton that pinned the molten liquid oxides. The combined effects of Ta-rich and Zr-rich oxides made the Ta-Zr-O oxide layer more compact and strongly bonded to the matrix.
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Surfaces and Interfaces
·
2024
·
IF 5.7
Wenhao Du,Fanhao Zeng,Yafang Gao,Ziwei Wang,Meiyan Chen,Zhi Li
Increasing the high-temperature anti-oxidation time of Carbon/carbon(C/C) composites faces significant challenges for conventional coatings. Herein, a unique bi-layer coating of HfC-TaC-B 4 C-SiC(HTBS)/ZrSiO 4 -glass(ZA) was proposed and prepared through slurry sintering method, and their oxidation behavior and mechanism were investigated. The results show that after oxidation at 1673 K in air for 750.5 h, the mass loss of the coated C/C was only 3.48% with about 720 h of weight gain oxidation, indicating that the anti-oxidation time has increased by two or three times compared to traditional coatings. The improved oxygen resistance performance was mainly attributed to the hinder layer of Si/Hf-Ta-Si-O during oxidation, which grew with the simultaneous carbothermal reduction reaction of SiO near matrix and oxidation reaction of HTBS. This is beneficial to lowering the thermal mismatch of coating system, reducing the connected thermal stress cracks as oxygen permeation channels. Our findings provide a new insight on improving the long-time thermal protection performance of C/C composites.
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ACS Applied Nano Materials
·
2024
·
IF 5.3
Fei-Feng Mao,Yi-An Wang,Yan Zhou,Ming-Shuai Sun,Wei Hui,Duan-Jian Tao
The efficient and selective conversion of biomass-derived vicinal diols into high-value-added chemicals represents a pivotal area of research that has garnered substantial interest within the scientific community. In this work, three ultralow loading Fe supports on N-doped carbon nanosphere catalysts (Fe@NC-T) were successfully prepared using the hard template method with acid etching. The selective conversion of vicinal diols into aldehydes, ketones, and amines over the Fe@NC-800 nanosphere catalyst was achieved through an anaerobic cleavage of C–C bonds and successfully utilized autologous hydrogen resources. The exceptional catalytic activity of the Fe@NC-800 nanosphere catalyst may be credited to the presence of highly dispersed Fe species at the active sites, which has been verified through several characterization techniques, control tests, and density functional theory calculations. In addition, the Fe@NC-800 nanosphere catalyst also demonstrated its wide applicability and excellent reusability under the operating conditions. We believe that this study presents an auspicious scheme for the highly selective conversion of vicinal diols into high value-added carbonyl compounds and amine products.
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BIOMASS & BIOENERGY
·
2024
·
IF 5.8
Yong Liu,Jirong Long,Zhijiao Huang,Lungang Chen,Chenguang Wang,Xinghua Zhang,Longlong Ma
Direct production of 2,5-dimethylfuran (DMF) from fructose is crucial for developing biomass-derived fuels, yet it presents significant challenges due to the need for multifunctional active sites for dehydration and hydrodeoxygenation. Meanwhile, the disposal of wine lees, a major winemaking by-product, incurs substantial costs. Herein, a hybrid catalyst system of sulfonated wine lees carbon (WLC-SO 3 H) and PtFe/C was introduced, achieving a DMF yield of 66.4 % directly from fructose. WLC-SO 3 H, with enhanced Brønsted acidity, demonstrated high activity in dehydrating fructose to 5-hydroxymethylfurfural (HMF) with a 98.2 % yield. PtFe/C effectively catalyzed the hydrodeoxygenation of HMF to DMF, driven by the strong interaction between Pt and Fe species. This interaction was confirmed through in situ DRIFTS and theoretical calculations, highlighting the system's superior catalytic performance.
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VACUUM
·
2025
·
IF 3.9
Penggen Chen,Jianhao Wang,Xingyue Lu,Li-An Ma,Qiong Liu,Lizhen Liu,Xiaoyun Ye,Qianting Wang
To address the growing need for high-performance microwave absorbing materials in modern communication and radar technologies, this study proposes a hierarchical heterostructured engineering strategy to integrate multiple loss mechanisms and optimize electromagnetic wave absorption. The hierarchical heterostructured C/TiO 2 /Ni@C composites were constructed via in situ hydrothermal synthesis combined with high-temperature calcination. The microwave absorption properties of the composite can be tuned by adjusting the MXene doping level and pyrolysis temperature. The TiO 2 /C framework derived from MXene and porous Ni@C microspheres derived from Ni-MOF enhance dielectric losses (interfacial polarization and dipole relaxation). The precipitated Ni magnetic nanoparticles improve magnetic losses. Compared with traditional microwave absorbing materials such as single-phase carbon or metal oxides, the C/TiO 2 /Ni@C-2 composite thermally decomposed at 600 °C exhibits excellent microwave absorption properties with an optimal reflection loss of −57 dB at a thickness of 4.26 mm and a frequency of 7.1 GHz. Upon optimization to a thickness of 2.16 mm, its effective absorption bandwidth (EAB) extends to 5.34 GHz (12.43–17.77 GHz), thereby fully encompassing the Ku band. The exceptional microwave absorption performance is attributed to its distinctive magnetic-dielectric layered architecture, heterointerface synergy, and optimized impedance matching, offering critical insights for designing next-generation broadband microwave absorbers.
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Nanoscale
·
2025
·
IF 5.1
Junhao Hu,Mengzhu Liu,Yuqi Zhai,Yongpeng Wang
C nanofibers dotted with square Fe@C crystals derived from metal–organic frameworks (MOFs) with a novel 3D hierarchical architecture were successfully prepared through electrospinning, hydrothermal processing, and high-temperature pyrolysis. The introduction of carbon nanofibers endowed the particles with directional action and mechanical support, inhibiting local agglomeration and the collapse of the Fe@C crystals. The unique overall 3D porous structure with micro-concavities on its surface provided sufficient paths for electromagnetic wave transmission, abundant heterostructured interfaces for interfacial polarization and a connected network for conductive loss. The appropriate combination of the magnetic Fe@C crystals with dielectric carbon nanofibers optimized the impedance matching. Benefitting from the ingenious design, the composites exhibited excellent electromagnetic wave absorption (EWA) performances. FC1–30 was found to exhibit a minimum reflection loss (RLmin) of −28.09 dB at a thickness of 5.5 mm and a widest effective absorption bandwidth (EAB) of 1.1 GHz at a thickness of 2.5 mm. FC1–10 showed a RLmin of −20.82 dB at a thickness of 3.0 mm and a broadest EAB of 3.8 GHz at a thickness of only 1.5 mm. The preparation process was optimized, and the influence of the filler loading ratio on EWA performance was investigated. The EWA mechanism has been discussed in detail. The study provides an opportunity for the development of advanced electromagnetic devices with integrated structure and function.
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PubMed
高影响因子
ASTRONOMISCHE NACHRICHTEN
·
2007
·Vol. 328
·期 6
·451-474
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IF 1.399
K. G. Strassmeier,K. Agabi,L. Agnoletto,A. Allan,M. I. Andersen,W. Ansorge,F. Bortoletto,R. Briguglio,J.-T. Buey,S. Castellini,V. Coudé du Foresto,L. Damé,H. J. Deeg,C. Eiroa,G. Durand,D. Fappani,M. Frezzotti,T. Granzer,A. Gröschke,H. J. Kärcher,R. Lenzen,A. Mancini,C. Montanari,A. Mora,A. Pierre,O. Pirnay,F. Roncella,F.-X. Schmider,I. Steele,J. W. V. Storey,N. F. H. Tothill,T. Travouillon,L. Vittuari,M. Weber
This article reviews the situation for robotization of telescopes and instruments at the Antarctic station Concordia on Dome C. A brain-storming meeting was held in Tenerife in March 2007 from which this review emerged.We describe and summarize the challenges for night-time operations of various astronomical experiments at conditions “between Earth and Space” and conclude that robotization is likely a prerequisite for continuous astronomical data taking during the 2000-hour night at Dome C. (© 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)
研究领域:
天文学
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科学机器人技术
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极地天文学
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观测天体物理学
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MOLECULES
·
2024
·Vol. 29
·期 18
·4336
·
IF 4.2
Yan Liao,Dashuang Wang,Wenrui Zhu,Zhilan Du,Fanbo Gong,Tuo Ping,Jinsong Rao,Yuxin Zhang,Xiaoying Liu
Transition metal oxides have been widely used in microwave-absorbing materials, but how to improve impedance matching is still an urgent problem. Therefore, we introduced urea as a polymer carbon source into a three-dimensional porous structure modified by Co3O4nanoparticles and explored the influence of different heat treatment temperatures on the wave absorption properties of the composite. The nanomaterials, when calcined at a temperature of 450 °C, exhibited excellent microwave absorption capabilities. Specifically, at an optimized thickness of 9 mm, they achieved a minimum reflection loss (RLmin) of −97.3 dB, accompanied by an effective absorption bandwidth (EAB) of 9.83 GHz that comprehensively covered both the S and Ku frequency bands. On the other hand, with a thickness of 3 mm, the RLminwas recorded as −17.9 dB, with an EAB of 5.53 GHz. This excellent performance is attributed to the multi-facial polarization and multiple reflections induced by the magnetic loss capability of Co3O4nanoparticles, the electrical conductivity of C, and the unique three-dimensional structure of diatomite. For the future development of bio-based microwave absorption, this work provides a methodology and strategy.
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PubMed
高影响因子
ADVANCED ENGINEERING MATERIALS
·
2024
·Vol. 26
·期 14
·2400527
·
IF 3.4
Rongjuan Zhang,Qi Hu,Shaobo Yang,Song Yan,Yaxin Gu,Jiawei Ji,Zheng Zhou,Chaoze Liu,Xinran Li,Zihao Wang,Chengchun Tang
The arrival of the 5 G era has brought great benefits to our lives, but it has also brought problems such as electromagnetic radiation. Therefore, the demand for lightweight, high-performance microwave absorbing materials with wide effective bandwidth is increasing. Herein, MIL-53/g-C 3 N 4 is first synthesized from precursors of ferric chloride, terephthalic acid, and g-C 3 N 4 , and then thermally annealed at different temperatures to generate MOF-Fe@C nanocomposites. Heat treatment can effectively carbonize g-C 3 N 4 to amorphous carbon and reduce iron in MIL-53 to magnetic Fe and Fe 3 O 4 nanoparticles through carbon-thermal reduction reaction. The synergistic effect of dielectric loss of amorphous carbon and magnetic losses of magnetic particles enhances attenuation and improves impedance matching, enhancing microwave absorption. The RL min of MOF-Fe@C(4)-700 is as low as -72.78 dB at 9.44 GHz at a thickness of 3.18 mm and its effective absorption bandwidth is as broad as 4.88 GHz, covering most of X-band frequency range. The research introduces a novel technique for synthesizing absorbers with controllable electromagnetic characteristics by incorporating g-C 3 N 4 as carbon sources into MOF materials.
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ACS Sustainable Chemistry & Engineering
·
2021
·
IF 8.198
Changzhou Chen,Peng Liu,Haihong Xia,Jianchun Jiang,Xiaohui Yang,Minghao Zhou
Lignin is an abundant source of aromatics with low effective hydrogen-to-carbon ratio (H/Ceff), and the depolymerization of lignin provides significant potential for producing liquid products with an improved H/Ceff value. In this work, the catalytic conversion of lignin monomers, dimer, trimers, and realistic lignin over spherical MOF-derived NiMo@C catalysts was well established, to get liquid fuels with a higher H/Ceff. The optimal ratio of the Ni4Mo1@C catalyst exhibited good hydrodeoxygenation activity and stability for the hydrotreatment of lignin model compounds and lignin. The addition of Mo facilitated the decrease of the particle size of a spherical structure, strengthened the electron-transfer capability between metals Mo and Ni, and enhanced the acid strength. All of these factors contributed to higher hydrodeoxygenation activity in the hydrotreatment process. Up to 100% conversion and 90% yields of ethylcyclohexane and cyclohexanol with H/Ceff values of 2.0 and 1.667, respectively, were obtained. The Ni4Mo1@C catalyst achieved a decrease of the oxygen element and an increase of H/Ceff and HHV values. The physicochemical characterizations were performed by various means including X-ray diffraction (XRD), scanning electronic microscopy (SEM), transmission electron microscopy (TEM), H2-temperature-programmed reduction (H2-TPR), NH3-temperature-programmed desorption (NH3-TPD), pyridine-infrared spectroscopy (Py-IR), inductively coupled plasma emission spectrometer (ICP), and Raman and X-ray photoelectron spectroscopy (XPS) analyses, which definitely elucidated the formation of a synergistic effect between metals Mo and Ni. Additionally, a control experiment also illustrated the synergistic effect that facilitated the occurrence of the hydrotreatment process under lower temperatures after the addition of metal Mo. Based on the optimal reaction condition (240 °C, 4 h, 2.0 MPa H2), both lignin and its monomers/dimers/trimers could be effectively hydrotreated to afford liquid products with improved H/Ceff value compared to raw lignin.
研究领域:
能源化学
·
催化化学
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高影响因子
HIGH PERFORMANCE POLYMERS
·
2017
·
IF 1.179
Lala Rukh Sidra,Nafeesa Mushtaq,Guofei Chen,Xingzhong Fang
A series of poly(N-arylene benzimidazole ether imide) copolymers PEIBIs were prepared from 1H,3′H-5,5′-bis-benzimidazole, bisphenol-A and 4,4′-bis(4-fluorophthalimido)diphenyl ether by nucleophilic displacement polymerization. The resulting copolymers PEIBI(10–90) demonstrated moderate to good solubility in polar aprotic solvents and high glass transition temperatures (Tgs) of 228–336°C, good thermal stability with 10% weight loss temperatures in the range of 503–548°C. All copolymer films showed good mechanical properties with tensile strengths of 101–130 MPa, tensile moduli of 3.3–4.0 GPa, elongations at break of 5–7%, and also presented low water uptake (0.15–0.34%). The wide-angle X-ray diffraction results revealed the amorphous nature of copolymers. The copolymer PEIBI-80 showed good balance in solubility, thermal and mechanical properties.
研究领域:
材料科学
·
高分子化学
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高影响因子
Science China-Chemistry
·
2021
·Vol. 64
·期 5
·770-777
·
IF 9.445
Qiao Xiaofeng,Lin Yuhan,Li Jiazhen,Ma Wanhong,Zhao Jincai
Both β- and γ- hydroxyketone structures are important units in biologically active molecules, synthetic drugs and fine chemicals. Although there are some routes available for their manufacture from pre-functionalized groups on one or two matrix molecule(s), the approaches to simply and simultaneously deposit two oxygen atoms from dioxygen into two specific C(sp 3 ) positions of pure saturated hydrocarbons have rarely succeeded because they are involved in the targeted activation of three inert C-H σ bonds all at once. Here, we show that a TiO 2 -CH 3 CN photocatalytic suspension system enables the insertion of dioxygen into one C(sp 3 )-C(sp 3 ) bond of strained cycloparaffin derivatives, by which difunctionalized hydroxyketone products are obtained in a one-pot reaction. With the cleavage event to release strain as the directional driving force, as-designed photocatalytic reaction systems show 21 examples of β-hydroxyketone products with 31%–76% isolated yields for three-membered ring derivatives and 5 examples of γ-hydroxyketone products with 30%–63% isolated yields for four-membered ring substrates. 18 O isotopic labeling experiments using 18 O 2 , Ti 18 O 2 and intentionally added H 2 18 O, respectively, indicated that both oxygen atoms of hydroxyketone products were exclusively from dioxygen, suggesting a previously unknown H + /TiO 2 -e − catalyzed arrangement pathway of the hydroperoxide intermediate to convert dioxygen into hydroxyketone units.
研究领域:
有机化学
·
光催化化学
·
药物化学
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危险品化学品经营许可证（带存储）