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Flexible and densified graphene/waterborne polyurethane composite film with thermal conducting property for high performance electromagnetic interference shielding

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Nano Research 2022年第11期15卷 9926-9935页

作者： wang Yang Hengxuan Bai Bo Jiang Chaonan wang Weimin Ye Zhengxuan Li Chong Xu Xiaobai Wang Yongfeng Li State Key Laboratory of Heavy Oil Processing China University of PetroleumBeijing 102249China Department of Materials Application Research AVIC Manufacturing Technology InstituteBeijing 100024China

High-performance electromagnetic interference(EMI)shielding materials with flexibility,excellent mechanical property,and thermal conductivity are highly desired for fifth-generation communications devices.Graphene exhibits tremendous potential due to its high electrical conductivity and unique lamellar structure.However,the construction of densified graphene structure in polymer matrix is still challenging.Herein,we develop a graphene/waterborne polyurethane(G/WPU)flexible film with densified and ordered layer-structure for using as an EMI shielding material.By virtue of the polyvinylpyrrolidone modified strategy and facile liquid phase ball-milling treatment,the graphene nanosheets can be efficiently dispersed into the WPU substrate and tightly connected between each other via internal interactions.Benefiting from the relatively low defects and densified structure of graphene,the resultant G/WPU film yields a high electrical conductivity of 1,004.5 S/m,and a tensile strength of around 48.5 MPa.As a consequence,it achieves an average EMI shielding effectiveness of over 30 dB in the X-band with a thickness of merely 0.15 mm and the value is further enhanced to 73.4 dB at 0.9 mm with a low density of 1.4 g/cm^(3),offering over 99.99999%shielding of incident electromagnetic waves.More importantly,this G/WPU film also exhibits a high cross-plane thermal conductivity of about 1.13 W/(m·K).Thus,this work develops a high-performance EMI shielding material with both good capacity of heat transmission,but also provides a facile strategy for designing next-generation advanced,lightweight,flexible,and multifunction shielding materials.

关键词： electromagnetic interference shielding graphene densification flexible thermal conductivity

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Multiscale structure and interface engineering of Fe/Fe_(3)C in situ encapsulated in nitrogen-doped carbon for stable and efficient multi-band electromagnetic wave absorption

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Journal of Materials Science & Technology 2023年第27期158卷 9-20页

作者： Bo Jiang wang Yang Hengxuan Bai Chen Zhang Siyuan Li Shaoxiong Du Ye wang Li Sun Xiaobai Wang Yongfeng Li State Key Laboratory of Heavy Oil Processing China University of Petroleum(Beijing)Changping 102249China Department of Materials Application Research AVIC Manufacturing Technology InstituteBeijing 100024China

Most reported electromagnetic wave absorption(EWA)materials show significant effective absorption in a certain frequency range,but their performances deteriorate dramatically as the frequency changes.As the range of working frequencies for electronic devices is gradually widening,it is of great interest to explore frequency-insensitive EWA materials that can achieve efficient absorption in every waveband by simply changing the absorption thickness.To this end,a multi-scale absorber(Fe/Fe_(3) C@NC)is rationally synthesized by chemical foaming and in-situ growth strategy.By controlling the growth of carbon nan-otubes,the Fe/Fe_(3) C@NC-2 exhibits a well-constructed 3D multi-scale architecture.Thanks to dipole po-larization,interface polarization and magnetic-dielectric energy conversion,the Fe/Fe_(3) C@NC-2 overcomes the frequency dispersion behavior and keeps a stable dielectric attenuation capability across the entire frequency range.Consequently,it delivers a superb full-band absorption of-50.1,-59.83,-55.87 and-51.91 dB in the S,C,X and Ku bands,respectively.The maximum radar cross-sectional reduction reaches 35.44 dB m^(-2) when the incidentθis 20°,testifying its impressive performance.Surprisingly,this EWA material also shows a remarkable resistance to oxidation and corrosion derived from the tightly coated carbon layers.This work provides new insight into the design of multi-band and stable EWA materials for practical application.

关键词： Multi-scale structure Heterogeneous interface Multiple bands Magnetic-dielectric composites Electromagnetic waves absorption

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Chemical synthesis and coercivity enhancement of Nd2Fe14B nanostructures mediated by non-magnetic layer

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Nano Research 2020年第4期13卷 1141-1148页

作者： Kai Zhu Junjie Xu Xiaobai Wang Wei Li Kesong Tian Yanglong Hou Beijing Key Laboratory for Magnetoelectric Materials and Devices(BKLMMD) Beijing Innovation Centre for Engineering Science and Advanced TechnologyDepartment of Materials Science and EngineeringCollege of EngineeringPeking UniversityBeijing 100871China Academy for Advanced Interdisciplinary Studies Peking UniversityBeijing 100871China

High-performance Nd2Fei4B magnets have been widely required in various fields recently due to the lightweight and miniaturization of devices.In this work,we synthesize Nd2Fei4B nanostructures with tunable magnetic properties through surfactant-assisted high energy ball milling(SAHEBM)process,achieving prominently enhanced coercivity by forming non-magnetic layers as grain boundary phase.When the reduction annealing process was carried out as pellet with Ca,the coercivity increased from 0.8 kOe to over 3 kOe as Nd2Fei4B powder,which is proved to be the contribution of the chemical diffusion of Nd elements and the formation of Nd-rich layer as magnetic insulating medium.In addition,two-dimensional graphene oxide(GO)was employed to build extra grain boundary,by which the coercivity of the core@dual-shell structure can achieve up to 8 kOe,tenfold of the original sample.The intrinsic mechanism indicated that the Nd-diffusion induced Nd-rich phase along with the reduced GO in the system could form non-magnetic layer as grain boundary and magnetically isolate the adjacent grains,significantly enhancing the exchange coupling effect.This work markedly opens up an effective approach for the chemical preparation of high-performance Nd2Fe14B nanostructured magnets,especially after post treatment,and gives an insight on the interactions at nanoscale.

关键词： Nd2Fei4B nanostructures chemical reduction diffusion process grain boundary graphene oxide coercivity enchantment

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Lignin-derived dual-function red light carbon dots for hypochlorite detection and anti-counterfeiting

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Frontiers of Chemical Science and Engineering 2023年第7期17卷 966-975页

作者： Yixuan Chang Fanwei Kong Zihao Zhu Ziai wang Chunxia Chen xiaobai Li Hongwei Ma Key Laboratory of Forest Plant Ecology Ministry of EducationEngineering Research Center of Forest Bio-PreparationCollege of ChemistryChemical Engineering and Resource UtilizationNortheast Forestry UniversityHarbin 150040China State Engineering Laboratory of Bio-Resource Eco-Utilization Northeast Forestry UniversityHarbin 150040China Collaborative Innovation Center for Development and Utilization of Forest Resources Harbin 150040China

The efficient utilization of natural lignin,which is the main by-product of the cellulose industry,is crucial for enhancing its economic value,alleviating the environmental burden,and improving ecological security.By taking advantage of the large sp2 hybrid domain of lignin and introducing amino functional groups,new lignin-derived carbon dots(SPN-CDs)with red fluorescence were successfully synthesized.Compared with green and blue fluorescent materials,red SPN-CDs have desirable anti-interference properties of short-wave background and exhibit superior luminescence stability.The SPN-CDs obtained exhibited sensitive and distinctive visible color with fluorescence-dual responses toward hypochlorite.Considering this feature,a portable,low-cost,and sensitive fluorescence sensing paper with a low limit of detection of 0.249μmol∙L^(–1) was fabricated using the SPN-CDs for hypochlorite detection.Furthermore,a new type of visible-light and fluorescence dual-channel information encryption platform was constructed.Low-concentration hypochlorite can be employed as an accessible and efficient information encryption/decryption stimulus,as well as an information“eraser”,facilitating a safe and diversified transmission and convenient decryption of information.This work opens new avenues for high-value-added applications of lignin-based fluorescent materials.

关键词： alkali lignin red light carbon dots hypochlorite encryption and anti-counterfeiting

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Residues of organochlorine pesticides in surface soils from college school yards in Beijing, China

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Journal of Environmental Sciences 2008年第9期20卷 1090-1096页

作者： Xiaofei wang[a], Dianzhong wang[b], Xiaofei QIN[a] xiaobai XU[a] [a]State Key Laboratory of Environmental Chemistry Ecotoxicology Research Center for Eco-Environmental Sciences Chinese Academy of Sciences Beijing 100085 China [b]State Key Laboratory of Remote Sensing Science Institute of Remote Sensing Applications Chinese Academy of Sciences Beijing 100101 China

Organochlorine pesticides (OCPs) have been a major environmental issue, attracting much scientific concern because of their nature of toxicity, persistence, and endocrine disrupting effects. Soil samples were collected from ten college school yards in Beijing in 2006 and analyzed to determine fifteen OCPs. Dichlorodiphenyltrichloroethanes (DDTs) were found to be the main pollutants, accounting for 93.70% of total OCPs, followed by hexachlorohexanes (HCHs) (2.25%) and hexachlorobenzene (HCB) (1.82%). Content...

关键词： organochlorine pesticides （OCPs） pollution soil college school yards

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汉语二语写作线上同伴互评行动研究

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国际汉语教学研究 2023年第4期 83-93页

作者：王佳王晓白南京大学海外教育学院

本研究基于线上汉语二语写作课堂,以两个班共65名留学生为研究对象,开展同伴互评行动研究,旨在考察汉语学习者同伴评语的特点、学习者对同伴互评的认可度及其影响因素。研究发现:(1)同伴评语以称赞类为主,而能够促进作文修改的建议类评... 详细信息

本研究基于线上汉语二语写作课堂,以两个班共65名留学生为研究对象,开展同伴互评行动研究,旨在考察汉语学习者同伴评语的特点、学习者对同伴互评的认可度及其影响因素。研究发现:(1)同伴评语以称赞类为主,而能够促进作文修改的建议类评语比例偏低;(2)汉语学习者整体上对同伴互评持认可态度,认为互评对其汉语写作能力发展有一定帮助;(3)二语水平、评语质量、跨文化语境以及互评观念和动机等因素影响学习者对同伴互评的认可度。

关键词：汉语二语写作线上教学同伴互评行动研究

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Progress in study on endocrine disrupting pesticides (EDPs) in aquatic environment

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Chinese Science Bulletin 2005年第20期50卷 2257-2266页

作者： XUE Nandong wang Hongbo XU xiaobai State Key Laboratory of Environmental Chemistry and Ecotoxicology Research Center for Eco-Environmental Sciences Chinese Academy of Sciences Beijing 100085 China Department of Environmental Sciences and Engineering Hunan Agricultural University Changsha 410128 China

Background on the generation of the problems of endocrine disrupting pesticides (EDPs) in aquatic environment, characteristics of EDPs, adverse effects and their effect mechanism of EDPs on human and wildlife, the transportation and degradation pathways of EDPs in water and analysis methods of EDPs in water were reviewed. The importance of EDPs in water should be attached to adverse effects on wildlife and human health. It was advised to estab- lish research programs on EDPs in aquatic environment es- pecially in water supply source.

关键词：水生环境内分泌紊乱杀虫剂 EDPs 人类健康化学物质

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急性应激对精神疾病患者的影响

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中华精神科杂志 2020年第3期53卷 204-207页

作者：王奇李晓白沈阳医学院第二医院心理科 110001 中国医科大学附属第一医院精神医学科沈阳110001

当前,新型冠状病毒肺炎(简称新冠肺炎)疫情作为急性应激源,对大众的身心健康产生了不同程度的影响。与健康人相比,精神疾病患者在遭受急性应激刺激后可能会导致更为严重的后果,如精神疾病症状加重、疾病复发和自杀风险增加。我国精神疾... 详细信息

当前,新型冠状病毒肺炎(简称新冠肺炎)疫情作为急性应激源,对大众的身心健康产生了不同程度的影响。与健康人相比,精神疾病患者在遭受急性应激刺激后可能会导致更为严重的后果,如精神疾病症状加重、疾病复发和自杀风险增加。我国精神疾病的发病率较高,疫情对精神疾病患者的影响需引起业界及社会的广泛重视。为了解急性应激对精神疾病患者的影响,我们检索了近年来国内外发表的相关文献并予以综述,探讨急性应激对精神疾病患者的影响,有助于精神科医生及时评估患者病情的变化并制定合理的临床治疗方案。

关键词：应激障碍,创伤性,急性新型冠状病毒肺炎精神病

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Spin-orbit torque efficiency enhancement to tungsten-based SOT-MTJs by interface modification with an ultrathin MgO

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Science China(Information Sciences) 2024年第1期67卷 316-317页

作者： Shiyang LU xiaobai NING Hongchao ZHANG Sixi ZHEN Xiaofei FAN Danrong XIONG Dapeng ZHU Gefei wang Hong-Xi LIU Kaihua CAO Weisheng ZHAO Fert Beijing Institute School of Integrated Science and EngineeringBeihang University Truth Memory Corporation

Spin-orbital torque (SOT) based three-terminal magnetic tunnel junctions (MTJs) have attracted much interest as the next generation magnetic random-access memory (MRAM)key device both in the academy and the industry. This is because SOT-MTJs feature high endurance and fast switching speed, benefiting tremendously from the separation of read/write current paths and less incubation time during the write in contrast to the spin-transfer torque (STT) MTJs [1].

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Effect of annealing on the characteristics of Au/Ni_(50)Fe_(50) bilayer films grown on glass

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Journal of University of Science and Technology Beijing 2007年第2期14卷 160-166页

作者： Hao Qian Hong Qiu xiaobai Chen Yue Tian Ping Wu Fengping wang Liqing Pan Applied Science School University of Science and Technology Beijing Beijing 100083 China Department of Mathematics and Physics Beijing Technology and Business University Beijing 100037 China

Sputter-deposited Au/NisoFeso bilayer films were annealed in a vacuum of 5×10^-4 Pa at 523 to 723 K for 30 or 90 min. The characteristics of the bilayer films were determined by Auger electron spectroscopy, field emission scanning electron microscopy, X- ray diffractometry, a four-point probe technique, and an alternating gradient magnetometer. When the annealing temperature and time reached 723 K and 90 min, Ni and Fe atoms markedly diffused into the Au layer. The grain size of the Au layer did not change markedly with the annealing condition. As the annealing time was 30 min and the annealing temperature exceeded 573 K, the resistance of the bilayer film increased with increasing the annealing temperature. Furthermore, the resistance of the bilayer film annealed at 723 K for 90 ,nin was lower than that of the bilayer film annealed at 723 K for 30 min. All the bilayer films showed magnetic hysteresis loops. The as-deposited bilayer film showed a hard magnetization. The bilayer film represented an easy magnetization with increasing the annealing temperature. The Au/Ni50Fe50 film that annealed at 723 K for 90 min had the lowest saturation magnetization.

关键词： Au/Ni50Fe50 bilayer film annealing diffusion characteristic

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