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A new method to improve the laser-ablation resistance of Si-Sic coating on c/c composites: Laser cladding

JOURNAL OF THE EUROPEAN cERAMIc SOcIETY 2022年第14期42卷 6425-6434页

作者： Teng, Liu Shi, Xiao-Hong Wang, Han-Hui Li, Wei Yin, Xue-Min Li, He -Jun Northwestern Polytech Univ Shaanxi Prov Key Lab Fiber Reinforced Light Compos Xian 710072 Shaanxi Peoples R China

New method to prepare Si-Sic coating on c/c composites by laser cladding (Lc-Si-Sic) was established to improve the laser ablation resistance of the coating. Results showed that the Lc-Si-Sic coating had lower roughness, better mechanical properties and superior laser-ablation resistance compared with the Si-Sic coating fabricated by the traditional coating preparation process: pack cementation (Pc-Si-Sic). Due to the shorter heat treatment and less Si infiltration, the flexural strength of the Lc-Si-Sic coated sample was 111.32 MPa, which was 144% higher than that of the Pc-Si-Sic coated sample. confirmed by finite element simulation, the Lc-Si-Sic coating exhibited better laser-ablation resistance because of the "sweating cooling" mechanism. Under 23.89 MW center dot m � 2 ablation for 7 s, the surface temperature of the Lc-Si-Sic coated sample was 3046 K, which was 157 K lower than that of the Pc-Si-Sic, causing the mass loss rate of the Lc-Si-Sic coating (0.10%) was only 45.45% of the Pc-Si-Sic coating.

关键词： c c composites Laser cladding Pack cementation Laser -ablation Mechanical properties

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Experiment-based numerical evaluation of the surface recession of c/c-Sic composites under the high-energy laser

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cERAMIcS INTERNATIONAL 2022年第23期48卷 34550-34563页

作者： Ge, Jian Li, Wei chao, Xujiang Wang, Hanhui Wang, Zhaowei Qi, Lehua Northwestern Polytech Univ Sch Mech Engn Xian 710072 Shaanxi Peoples R China Northwestern Polytech Univ Shaanxi Prov Key Lab Fiber Reinforced Light Compos Xian 710072 Shanxi Peoples R China China Acad Launch Vehicle Technol Beijing 100076 Peoples R China

In this paper, we developed a multi mechanism coupling finite element model to predict the surface recession of c/c-Sic composites on the basis of the ablation phenomena. In particular, we took into account temperaturedependent properties of component materials, heat convection, and radiation in the ultra-high temperature range. By combining a user-defined subroutine and arbitrary Lagrangian-Eulerian adaptive meshing technique, the surface recession of c/c-Sic composites was captured. The predicted ablation depth agreed well with experimental results. The trend of the ablation rate between simulations and experiments was almost the same. Meanwhile, the effects of the laser powers on ablation behaviors of c/c-Sic composites were investigated. It was found that low laser powers had little effect on the ablation rate while the ablation rate increased first and then decreased for high laser powers.

关键词： c c-Sic composites Thermal properties Finite element analysis Surface recession

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Influence of the fiber orientation on 3D c/c-Sic composite material and its formation mechanism of the machining surface

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INTERNATIONAL JOURNAL OF ADVANcED MANUFAcTURING TEcHNOLOGY 2022年第7-8期118卷 2725-2743页

作者： Li, Wei Long, Gui Shi, Feng Zhou, Shenlei Yin, Jia Yang, Jun Hunan Univ Coll Mech & Vehicle Engn Changsha 410082 Hunan Peoples R China Hunan Univ Natl Engn Technol Res Ctr High Efficiency Grindin Changsha 410082 Hunan Peoples R China Natl Univ Def Technol Coll Intelligent Sci Changsha 410073 Hunan Peoples R China Chinese Acad Sci Shanghai Inst Opt & Fine Mech Shanghai 201800 Peoples R China

carbon/carbon (c/c)-Sic composite materials attained much attention due to its unique properties like immense thermal conductivity, high corrosion, and abrasive resistance. Few scholars have systematically studied the grinding machinability of 3D c/c-Sic composite material. In this paper, the grinding experiment of 3D c/c-Sic composite material was carried out with a resin-bonded diamond grinding wheel. The effect of machining conditions on the grinding force, micromorphology, surface quality, and residual stress was studied, and the material removal mechanism was analyzed in-depth aimed at the three typical fiber orientations. The result shows that the surface roughness of different fiber areas follows the order: 90 degrees fiber > 0 degrees fiber > Normal fiber. The fiber's orientation showed a significant effect on the mechanism of material removal. The residual thermal stress of c/c-Sic composite material increases from 32.25 to 207.43 MPa during the grinding process. Polishing the ground surface not only can remove the crack layer and residual stress layer but also can introduce residual compressive stress layer, which can effectively enhance the material strength. The 3D c/c-Sic composite material removal process is distinct from the composite material 2D c/c-Sic and the traditional brittle material. The main removal of c/c-Sic composite material is recognized as brittle fracture mode. Because of the different mechanical properties of carbon fiber, Sic matrix, and the pyrocarbon interface, the damage of material during grinding is asynchronous. The present work provides a comprehensive understanding for processing 3D c/c-Sic composite material parts with high quality.

关键词： c c-Sic Grinding carbon fiber Surface roughness The material removal mechanism

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Exo-Selective Intramolecular c-H Alkylation with 1,1-Disubstituted Alkenes by Rare-Earth catalysts: construction of Indanes and Tetralins with an All-carbon Quaternary center

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AcS cATALYSIS 2022年第20期12卷 12973-12983页

作者： Mishra, Aniket Wu, Ping cong, Xuefeng Nishiura, Masayoshi Luo, Gen Hou, Zhaomin RIKEN Ctr Sustainable Resource Sci Adv Catalysis Res Grp Wako Saitama 3510198 Japan Anhui Univ Inst Phys Sci & Informat Technol Hefei 230601 Peoples R China RIKEN Organometall Chem Lab Cluster Pioneering Res Wako Saitama 3510198 Japan

We report herein the exo-selective, regiospecific annulation of a wide range of functionalized aromatic substrates with 1,1-disubstituted alkenes through c(sp2)-H and benzylic c(sp3)-H activation by half-sandwich rare-earth catalysts. This protocol offers a straightforward and atom-efficient route for the synthesis of a family of indane and tetralin derivatives bearing an all-carbon quaternary stereocenter that were difficult to access previously by other catalysts. The reaction mechanism has been elucidated by deuterium-labeling experiments and DFT calculations.

关键词： annulation c H activation all-carbon quaternary center scandium yttrium rare-earth-metal

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Electrical performance prediction of graphdiyne-c60 nanocomposite

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MRS cOMMUNIcATIONS 2022年第5期12卷 729-733页

作者： Hu, Yongle Gao, Shan Zhang, Zhang Guo, Juan Yang, Ping Changsha Univ Sci & Technol Hunan Prov Key Lab Intelligent Mfg Technol High P Changsha 410114 Peoples R China Jiangsu Univ Sch Mech Engn Lab Adv Design Mfg & Reliabil MEMS NEMS OEDS Zhenjiang 212013 Jiangsu Peoples R China

We investigated the field emission of graphdiyne-c-60 nanocomposite by using first principle calculation. The results show that graphdiyne obtains good electrical performances such as high level of emission currents. The construction with c-60 cluster and graphdiyne can take full advantages of the curvature effect and the tip effect of c-60 cluster which induces local charge improvement. It shows that the c-60 cluster can strengthen the field emission of graphdiyne-c-60 nanocomposite. It implies that the graphdiyne-c-60 nanofabrication could have a potential application for field emission electron sources in the future.

关键词： c computation/computing Electronic material Modeling Simulation

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Ablation mechanism of c/c-Sic and c/c-Sic-Zrc composites in hypersonic oxygen-enriched environment

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cERAMIcS INTERNATIONAL 2022年第16期48卷 22985-22993页

作者： Gao, Yong Zha, Bai-Lin Wang, Jin-Jin Sun, Zhen-Sheng Zhang, Zhao-Fu Shi, Yi-Ang Rocket Force Univ Engn Xian 710025 Peoples R China Xian Aerosp Composites Res Inst Xian 710025 Peoples R China Project Management Ctr Beijing 100085 Peoples R China 2 Tongxin Rd Xian Peoples R China

In this study, c/c-Sic and c/c-Sic-Zrc composites were prepared via chemical vapor infiltration and polymer infiltration pyrolysis, and the ablation mechanism under hypersonic oxygen-rich environmental conditions was investigated. The c/c-Sic composites demonstrate an excellent ablation resistance in a hypersonic oxygen-rich environment with a relatively low temperature and speed of approximately 1800 K and 1100 m/s, respectively. It is only in the ablation center area with higher temperatures that a certain degree of thermochemical ablation was observed. The mass and linear ablation rates of c/c-Sic composites (0.027 g/s and 0.117 mm/s, respectively) showed a significant increase in a hypersonic oxygen-rich environment with a temperature and velocity of approximately 2050 K and 2000 m/s, respectively. The high-temperature ablation resistance of Zrc-modified c/ c-Sic-Zrc composites improved significantly. However, the Zrc ceramic component had a considerable impact on the ablation resistance of the material. The structural integrity of c/c-20Sic-30Zrc composites was relatively high in hypersonic oxygen-rich environments with a jet temperature and velocity of 2050 K and 2000 m/s, respectively, and mass and linear ablation rates were 0.012 g/s and 0.015 mm/s, respectively. When the Zrc content increased by 40%, the ablation resistance of the composite reduced significantly, whereas the mass and linear ablation rates increased to 0.043 g/s and 0.130 mm/s, respectively.

关键词： c c-Sic composites Hypersonic Oxygen-enriched ablation Ablation mechanism

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Anaerobic co-digestion using poultry slaughterhouse and vegetable wastes to enhance biogas yield: effect of different c/N ratios

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BIOMASS cONVERSION AND BIOREFINERY 2022年第22期14卷 28303页

作者： Samadi, Mohammad Taghi Leili, Mostafa Rahmani, Alireza Moradi, Samira Godini, Kazem Hamadan Univ Med Sci Res Ctr Hlth Sci Dept Environm Hlth Engn Hamadan Hamadan Iran Kurdistan Univ Med Sci Environm Hlth Res Ctr Res Inst Hlth Dev Sanandaj Iran

The aim of this study was to determine the feasibility of producing biogas by combining solid poultry slaughterhouse wastes (SPSWs) with fruit and vegetable solid wastes (FVSWs) and to obtain the optimum conditions for maximum biogas production by means of anaerobic digestion (AD). The ratio of available carbon to available nitrogen (c/N), as a critical parameter in producing methane, was adjusted by mixing the appropriate amount of SPSWs with FVSWs. For each load, a 50-L pilot-scale digester was operated for 40 days. For start-up and seeding, the biogas reactor was bioaugmented using the anaerobic sludge of an industrial poultry wastewater treatment plant. The analyzed SPSW, which had a c/N ratio of 5.75, was combined with FVSWs to obtain c/N ratios of 20, 30, and 40. Furthermore, it was found that the highest biogas yield occurred when the c/N ratio of the feed was 30. Also, for all three loading ratios, biogas production volumes were 215.1, 241, and 182.7 L, respectively, where methane's shares were 104.5, 120.6, and 91.7 L of the total gas volume that constituted 48.6, 50, and 50.2% of the produced biogas. Therefore, the obtained results from the process of mesophilic AD of this type of solid wastes illustrate that it is possible to efficiently produce biogas as a renewable energy source by combining SPSWs and FVSWs, instead of burning or burying them.

关键词： Anaerobic digestion Biogas Poultry slaughterhouse wastes c N ratio

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Enhanced electrochemical performance of LiFePO4/c wrapped with sulfur-modified reduced graphene oxide for Li-ion batteries

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IONIcS 2022年第1期28卷 191-200页

作者： chen, Zi-Liang Gu, Yi-Jing Luo, Gui-Yang Huo, Yong-Lin Wu, Fu-Zhong Guizhou Univ Coll Mat & Met Guizhou Prov Key Lab Met Engn & Proc Energy Savin South Hua Xi St Guiyang 550025 Peoples R China

Although researchers have previously examined whether graphene modified by sulfur can improve the electrochemical performance of LiFePO4/c composites, they have rarely examined whether it can do so during the synchronous synthesis of LiFePO4/c and sulfur-modified reduced graphene oxide (SG) via a one-step hydrothermal method. To answer this question, a series of olivine structure LiFePO4/c composites wrapped with SG were investigated. Subsequently, we found that SG can form a three-dimensional conductive network on the surface of the LiFePO4/c sample. In the process, XRD and HRTEM tests were undertaken as well. From the XRD test, the results show that SG does not affect the olivine structure of LiFePO4/c. In the HRTEM experiment, clear lattice fringes and a uniformly coated carbon layer on the sample surface were observed. Alongside these results, there were 4 others. First, the charge-discharge data showed that the electrochemical performance of the samples could be increased by SG modification. Second, sample S2 with a mass ratio of Na2S to rGO of 1:10 shows the best specific discharge capacity and stability. Third, the specific capacity of S2 is 163 mAhg(-1) at 0.2 c, and the capacity retention is 108.23% even after 200 cycles at a magnification of 10 c. Fourth, according to EIS, the charge migrating resistance of S2 is 226.4 omega, and the lithium-ion diffusion coefficient is 2.41 x 10(-14) cm(2)center dot S-1. The significance of these results is that they indicate that wrapping LiFePO4/c with SG significantly contributed to the improvement of its electrochemical performance.

关键词： Lithium-ion battery LiFePO4 c S-modified reduced graphene oxide Electrochemical performance

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Novel c/Sic porous ceramic with controllable properties served as transpiration cooling material

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cERAMIcS INTERNATIONAL 2022年第15期48卷 21616-21621页

作者： Zhang, Bo Wang, Han Jin, Xiaochao Fan, Xueling Huang, Haiming Yao, Jun Xi An Jiao Tong Univ Joint Res Ctr Extreme Environm & Protect Technol Xian Peoples R China Xi An Jiao Tong Univ Sch Aerosp Engn State Key Lab Strength & Vibrat Mech Struct Xian Peoples R China Beijing Jiaotong Univ Inst Engn Mech Beijing 100044 Peoples R China Sci & Technol Space Phys Lab Beijing 100071 Peoples R China

Transpiration cooling has been gradually regarded as one of the most efficient and potential thermal protection technologies for the high temperature hot-end components of future hypersonic vehicle. The cooling perfor-mance of this technology profoundly depends on the properties of porous medium. This paper exhibits a novel c/ Sic porous ceramic with controllable properties adjusted by molding pressure and carbon fiber content in the grinding-mold pressing-sintering process, and investigates the transpiration cooling performance using this ceramic with liquid water. Molding pressure improves from 50 MPa to 100 MPa, the compressive strength has increased by 52.9% and 67.9%, and the permeability decreases about 38% and 39.5% respectively corresponding to fiber content of 6% and 10%. The surface temperatures and back-side temperatures of porous ceramic with the largest molding pressure reaches the highest due to the lowest porosity which can reduce the heat exchange area between cooling water and porous ceramic skeleton. This novel porous ceramic with controllable characteristics can optimize the design of the transpiration cooling system.

关键词： c Sic porous ceramic controllable properties Transpiration cooling Molding pressure carbon fiber content

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Architecting a 3D continuous c/cuVO3@cu composite anode for lithium-ion storage

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SURFAcE INNOVATIONS 2022年第1-3期11卷 70-78页

作者： Gou, Jinlong Qiao, Zhijun Yu, Zhenyang Sun, Shihao Li, chuanqi Li, Wei-Jie Wang, Jun Wang, Nan Zhang, Zhijia Jiang, Yong Tiangong Univ Sch Mech Engn Sch Mat Sci & EngnTianjin Municipal Key Lab Adv F State Key Lab Separat Membrane & Membrane Proc Tianjin Peoples R China Univ Wollongong Inst Superconducting & Elect Mat Wollongong Australia Shandong Univ Key Lab Liquid Solid Struct Evolut & Proc Mat Minist Educ Jinan Peoples R China China Elect Technol Grp Corp 46 Inst Tianjin Peoples R China CETC JH Tianjin Semicond Mat Co Ltd Tianjin Peoples R China

Vanadium (V)-based oxides with a high theoretical capacity are an alternative anode for lithium-ion (Li+) batteries, but they are still limited by the poor conductivity, large volume change and low active material mass loading. Herein, a three-dimensional (3D) continuous c/cuVO3@cu composite anode with high copper (II) metavanadate (IV) (cuVO3) mass loading is synthesized by the combination of high-energy ball milling, non-solvent-induced phase separation and heat treatment. The copper (cu) framework can enhance electron/ion conductivity in coordination with amorphous carbon (c). Furthermore, the macropore channels in the copper framework can provide buffer space for the volume expansion of active material copper (II) metavanadate (IV) during lithiation/delithiation. As a result, this 3D continuous c/cuVO3@cu composite anode achieves a high copper (II) metavanadate (IV) mass loading of about 3.8 mg/cm(2), delivering a reversible capacity of 479 mAh/g at 100 mA/g after 120 cycles. More importantly, a long life span is achieved with a reversible capacity of 268 mAh/g even after 1700 cycles at a high current density of 1000 mA/g, demonstrating excellent cycle performance. This work provides a way to develop 3D continuous composite material anodes with extraordinary electrochemistry performance for next-generation energy-storage devices.

关键词： c cuVO3@cu composite materials electrochemistry energy lithium-ion batteries

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