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International Journal of Minerals,Metallurgy and Materials 2023年第7期30卷 1398-1406页

作者： Zeli Jia xiaomeng fan Jiangyi He Jimei Xue fang Ye Laifei Cheng Science and Technology on Thermostructural Composite Materials Laboratory Northwestern Polytechnical UniversityXi’an 710072China Xi’an Xinyao Ceramic Composite Materials Co. Ltd.Xi’an 710117China

A polymer-derived ZrC ceramic with excellent electromagnetic interference(EMI)shielding performance was developed to meet ultra-high temperature requirements.The thermal decomposition process of ZrC organic precursor was studied to reveal the evolution of phase composition,microstructure,and EMI shielding performance.Furthermore,the carbothermal reduction reaction occurred at 1300℃,and the transition from ZrO_(2) to ZrC was completed at 1700℃.With the increase in the annealing temperature,the tetragonal zirconia gradually transformed into monoclinic zirconia,and the transition was completed at the annealing temperature of 1500℃ due to the consumption of a large amount of the carbon phase.The average total shielding effectiveness values were 11.63,22.67,22.91,22.81,and 34.73 dB when the polymerderived ZrC was annealed at 900,1100,1300,1500,and 1700℃,respectively.During the thermal decomposition process,the graphitization degree and phase distribution of free carbon played a dominant role in the shielding performance.The typical core–shell structure composed of carbon and ZrC can be formed at the annealing temperature of 1700℃,which results in excellent shielding performance.

关键词： ZrC ceramics polymer-derived ceramic phase composition electromagnetic interference shielding

Post-synthesis and structural evolution of hollow titanium silicalite-1 with solvent-free method

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Nano Research 2023年第1期16卷 1740-1747页

作者： Yaqi fan Xianchen Gong xiaomeng Si Changjiu Xia Peng Wu Yanhang Ma Shanghai Key Laboratory of High-resolution Electron Microscopy ShanghaiTech UniversityShanghai 201210China School of Physical Science and Technology ShanghaiTech UniversityShanghai 201210China Shanghai Key Laboratory of Green Chemistry and Chemical Processes School of Chemistry and Molecular EngineeringEast China Normal UniversityShanghai 200062China State Key Laboratory of Catalytic Materials and Reaction Engineering Research Institute of Petroleum ProcessingSINOPECBeijing 100083China Institute of Eco-Chongming Shanghai 202162China

Generating hollow structure inside titanium silicalite-1(TS-1)is a widely used method to improve its liquid-phase oxidation catalytic performance in industry.However,traditional dissolution-recrystallization method usually required a large amount of aqueous solution of organic template,leading to unfavorable polluted waste,low production efficiency,and high manufacture cost.Here,a facile and environmental friendly strategy was proposed for the post-synthesis of hollow TS-1 zeolite with a solventfree method utilizing NH4HCO3 and tetrapropylammounium bromide as selective etching agents,which reduced the usage of organic template and avoided the liquid waste.The high crystallinity,the microporous structure,and the active Ti sites were preserved at a high product yield(>93%).The formation mechanism of hollow structure was also investigated by exploring effects of different reactants and experimental parameters.Meanwhile,the obtained hollow TS-1 showed an outstanding performance in the epoxidation of 1-hexene in comparison to the parent zeolite.

关键词： hollow structure zeolite post synthesis method solvent-free structural evolution TS-1

Kinetics and corrosion products of aqueous nitrate reduction by iron powder without reaction conditions control

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Journal of Environmental Sciences 2009年第8期21卷 1028-1035页

作者： FAN XiaoMeng GUAN Xiaohong MA Jun AI Hengyu School of Municipal and Environmental Engineering Harbin Institute of Technology Harbin 150090 China College of Chemical and Environmental Engineering Harbin University of Science and Technology Harbin 150080 China

Although considerable research has been conducted on nitrate reduction by zero-valent iron powder (Fe0), these studies were mostly operated under anaerobic conditions with invariable pH that was unsuitable for practical application. Without reaction conditions (dissolved oxygen or reaction pH) control, this work aimed at subjecting the kinetics of denitrification by microscale Fe0 (160–200 mesh) to analysis the factors affecting the denitrification of nitrate and the composition of iron reductive products coating upon the iron surface. Results of the kinetics study have indicated that a higher initial concentration of nitrate would yield a greater reaction rate constant. The reduction rate of nitrate increased with increasing Fe0 dosage. The reaction can be described as a pseudo-first order reaction with respect to nitrate concentration or Fe0 dosage. Experimental results also suggested that nitrate reduction by microscale Fe0 without reaction condition control primarily was an acid-driven surface-mediated process, and the reaction order was 0.65 with respect to hydrogen ion concentration. The analyses of X-ray diffractometry and X-ray photoelectron spectroscopy indicated that a black coating, consisted of Fe2O3, Fe3O4 and FeO(OH), was formed on the surface of iron grains as an iron corrosion product when the system initial pH was lower than 5. The proportion of FeO(OH) increased as reaction time went on, whereas the proportion of Fe3O4 decreased.

关键词：硝酸盐浓度反应pH值还原铁粉条件控制水动力学涂料产品腐蚀产物 X射线光电子能谱

Diversity of culturable alginate lyase-excreting bacteria associated with Sargassum

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Acta Oceanologica Sinica 2023年第6期42卷 70-77页

作者： xiaomeng Sun Zhao Xue Cui Chen Shoujin fan Huihui Fu Peng Wang Life Science College Shandong Normal UniversityJinan 250014China College of Marine Life Sciences/Frontiers Science Center for Deep Ocean Multispheres and Earth System Ocean University of ChinaQingdao 266003China

Large numbers of bacteria live on the surface of various brown algae and can produce alginate lyases to consume alginate,an important component of the cell wall of brown algae.Sargassum is a genus of the largest canopyforming brown algae of more than 150 species,which are widely distributed in tropical and subtropical environments.However,our knowledge about the epiphytic bacteria and the alginate lyase-excreting bacteria from Sargassum is still primitive.Here,we investigated the diversity of the culturable epiphytic bacteria and alginate-degrading bacteria from Sargassum samples collected from the coastal seawaters of Shandong Province,China.In total,37 strains belonging to 21 genera in 3 phyla were isolated,including 15 previously unreported genera,of which Vibrio(6/37)and Pseudoalteromonas(5/37)are the dominant genera.Eight strains,mainly Vibrio and Pseudoalteromonas species,were further identified as alginate lyase-excreting strains that can utilize alginate for growth.The extracellular alginolytic activity of the 8 strains was determined,and strains Vibrio sp.C42and Pseudoalteromonas sp.M9 showed the highest activity.These results provide a better understanding of brown algae epiphytes and alginate-degrading bacteria,and are fundamental for further studies on the interactions between brown algae and their epiphytes.

关键词： Sargassum epiphyte alginate lyase-excreting bacteria alginolytic activity

Effect of pyrolytic carbon interphase on mechanical properties of mini T800-C/SiC composites

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Journal of Advanced Ceramics 2021年第2期10卷 219-226页

作者： Donglin Zhao Tong Guo xiaomeng fan Chao Chen Yue Ma Science and Technology on Thermostructure Composites Materials Laboratory Northwestern Polytechnical UniversityXi’an710072China Innovation Academy for Microsatellites of Chinese Academy of Sciences Shanghai201203China

The effect of pyrolytic carbon(PyC) thickness on the tensile property of mini T800 carbon fiber reinforced SiC matrix composites(C/SiC) was studied. PyC interphase was prepared by chemical vapor infiltration(CVI) process using C3H6–Ar as gas source, the PyC thickness was adjusted from 0 to 400 nm, and then the SiC matrix was prepared by CVI process using methyltrichlorosilane(MTS)–H2–Ar as precursor and gas source. The results showed that the tensile strength of mini T800-C/SiC increased first and then decreased with the increase of the PyC thickness. When the thickness of PyC was 100 nm, the average strength reached the maximum value of 393 ± 70 MPa. The Weibull modulus increased from 2.0 to 8.06 with the increase of PyC thickness, and the larger the Weibull modulus, the smaller the dispersion, which indicated that the regulation of PyC thickness was conducive to improve tensile properties.

关键词： T800 carbon fiber C/SiC pyrolytic carbon(PyC)interphase tensile strength Weibull modulus

A novel lightweight metamaterial with ultra broadband electromagnetic wave absorption induced by three-dimensional CNTs conductive-coated arrays

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Science China(Technological Sciences) 2023年第3期66卷 881-888页

作者： ZHOU Qian SHI TianTian XUE Bei GU ShengYue REN Wei YE fang FAN XiaoMeng ZHANG YuXin QI ChenXi DU LiFei College of Science Xi’an University of Posts and TelecommunicationsXi’an 710121China College of Materials Science and Engineering Xi’an University of Science and TechnologyXi’an 710054China Science and Technology on Thermostructural Composite Materials Laboratory Northwestern Polytechnical UniversityXi’an 710072China

Lightweight metamaterials for broadband electromagnetic wave absorption have become a significant requirement for electromagnetic interference and stealth technologies.In this study,a novel lightweight metamaterial absorber with three-dimensional(3D)carbon nanotubes(CNTs)conductive-coated arrays is designed and fabricated through 3D printing and dipping process,which realized less than-10 dB reflection loss in the frequency range of 7.0–40 GHz.The effect of the sheet resistance of CNTs conductive coatings and geometric parameters of meta-structure on the frequency-dependent absorption properties is investigated,and the improved absorbing efficiency is discussed based on the synergy effect of multiscale structures of 3D conductive-coated arrays.Moreover,the volume of the proposed ultra broadband absorber is reduced by approximately 60.5%compared with that of the dense plate structure,indicating a significant lightening with efficient absorbing capacities.Additionally,the absorption bandwidth and intensity of the proposed absorber have insensitive changes with the variation of incident angle.Therefore,an ultra broadband electromagnetic absorption is designed and realized,indicating a promising lightweight ultra broadband electromagnetic absorbing candidate for lightweight metamaterial absorbers.

关键词： 3D conductive coating lightweight absorber metamaterials broadband absorption

Low Infrared Emissivity and Strong Stealth of Ti-Based MXenes

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Research 2022年第4期2022卷 147-153页

作者： Xinliang Li Minghang Li Xin Li xiaomeng fan Chunyi Zhi Department of Materials Science and Engineering City University of Hong Kong83 Tat Chee AvenueKowloonHong Kong 999077China Science and Technology on Thermostructural Composite Materials Laboratory Northwestern Polytechnical UniversityXi'an710072China

Advanced scenario-adaptable infrared(IR)stealth materials are crucial for creating localized closed thermal environments.Low emissivity over the broadest possible band is expected,as is superior mechanical deformability.Herein,we report a series of Ti-based MXenes with naturally low emissivity as ideal IR shielding materials.Over a wavelength ranging from 2.5 to 25μm,Ti_(3)C_(2)T_(X) film delivers an average emissivity of 0.057 with the lowest point of 0.042.Such a low emissivity coupled with outstanding structural shaping capability is beyond the current grasp.The reflection-dominated mechanism is dissected.Also,some intriguing scenarios of IR stealth for wearable electronic devices and skin thermal control are demonstrated.This finding lights an encouraging path toward next-generation IR shielding by the expanding MXene family.

关键词： wear Infrared Strong

Co-aromatization of methane and hexane over Pt encapsulated in ZSM-5 zeolite and the electronic effect of K promoters

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Science China Chemistry 2024年第3期67卷 1017-1027页

作者： Bei Liu fan Wang xiaomeng Dou Pengfei Li Hongwei Xiang Yong Yang Peng He State Key Laboratory of Coal Conversion Institute of Coal ChemistryChinese Academy of SciencesTaiyuan 030001China Department of Chemistry Tsinghua UniversityBeijing 100084China National Energy R&D Center for Coal to Liquid Fuels Synfuels China Technology Co.Ltd.Beijing 101407China University of Chinese Academy of Sciences Beijing 101408China Leibniz-Institut für Katalyse e.V.an der Universitat Rostock Rostock 18059Germany

The co-aromatization of methane with higher hydrocarbons represents a promising route to valorize methane, an abundant but underexploited carbon resource. In this study, we elucidate a novel approach to enhance the catalytic co-aromatization of hexane and methane by confining Pt within zeolite catalysts and modulating its electron density. Our findings show that encapsulating Pt within MFI structure is pivotal for activating the feedstock and fostering the formation of aromatic products. Interaction between K atoms and the silanol nest forms siloxy groups which are critical for the stabilization of Pt species. Tuning the K content in PtSn@MFI catalysts adeptly alters the electronic configuration of Pt clusters. This modification is corroborated by infrared and X-ray photoelectron spectroscopy analysis, and density functional theory calculations. Remarkably, the catalyst with 0.8 wt% K exhibits an optimal Pt electron density, driving its superior efficacy in the co-aromatization reaction, converting 0.78 mol of methane for each mole of hexane processed. By employing ~(13)C isotopic labeling and solid-state NMR studies, we demonstrate the participation of methane in the adsorbed species inside the zeolite channel and its incorporation to the benzyl site of the substitute group and phenyl rings in aromatic compounds, underscoring the importance of Pt encapsulation.

关键词： Pt encapsulation MFI zeolite methane activation co-aromatization ^(13)C solid-state NMR

Failure behavior of interfacial domain in SiC-matrix based composites

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Journal of Materials Science & Technology 2021年第29期88卷 1-10页

作者： Jinxue Ding Xiaokang Ma xiaomeng fan Jimei Xue fang Ye Laifei Cheng Science and Technology on Thermostructural Composite Materials Laboratory Northwestern Polytechnical UniversityXi'an710072China

In this work,the microstructure,failure behavior and interfacial properties with respective to the interfacial domain in SiCf/BN/SiC and C_(f)/PyC/SiC composites were studied via the fiber push-in test.The differences in the mechanical response of the interfacial domain were observed.During the fiber push-in test for SiCf/BN/SiC,the interface debonding accompanied with interphase fracture occurred,resulting in an obvious sign of the onset of debonding on loading-displacement(P-u)curves.While the good continuity of P-u curves can be observed for Cf/PyC/SiC,which is due to that the failure is in the form of interface debonding along with interphase lateral slipping caused by the extension of buckled carbon fiber,without any interphase fracture.The interfacial properties calculated from the fiber push-in test show that Cf/PyC/SiC possesses a weaker interfacial domain compared with SiC_(f)/BN/SiC.The interfacial shear stress of SiCf/BN/SiC and C_(f)/PyC/SiC composites amounts 94.2 and 48.1 MPa,respectively.

关键词： SiC-matrix based composites Interfacial domain Fiber push-in test Failure behavior Interfacial mechanical properties

A SiC nanowires/Ba_(0.75)Sr_(0.25)Al_(2)Si_(2)O_(8) ceramic heterojunction for stable electromagnetic absorption under variable-temperature

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Journal of Materials Science & Technology 2022年第30期125卷 29-37页

作者： Xin Li Xiaoke Lu Minghang Li Jimei Xue fang Ye xiaomeng fan Yongsheng Liu Laifei Cheng Litong Zhang Science and Technology on Thermostructural Composite Materials Laboratory Northwestern Polytechnical UniversityXi’an 710072China State Key Laboratory of Solidification Processing School of Materials Science and EngineeringNorthwestern Polytechnical UniversityXi’an 710072China

The application of semiconductor materials was limited as electromagnetic absorption materials,due to the unstable absorption performance caused by the temperature sensitivity.In this work,a structurally controllable ceramic heterojunction was developed by assembling structural units of SiC nanowires(SiCnws)and Ba_(0.75)Sr_(0.25)Al_(2)Si_(2)O_(8)(BSAS).Benefiting from the optimization of the energy gap and the construction of heterogeneous interfaces,the ceramic heterojunction can achieve stable electromagnetic absorption from room temperature to 600℃,the effective absorption bandwidth is almost unchanged.And the minimum reflection loss value reached-63.6 dB at 600℃.Meanwhile,the SiCnws/BSAS ceramic heterojunction shows stable electromagnetic absorption performance in various simulated outdoor environments,including acid rain,seawater,high temperature and water vapor corrosion.This result provides a fire-new idea to realize the environmental adaptability of electromagnetic absorption materials and largely broadens its application prospect.

关键词： Ceramic heterojunction Energy gap regulation Polarization effect Stable electromagnetic absorption Variable-temperature Environment adaptability