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Magnetic transitions in graphene derivatives

Nano Research 2014年第10期7卷 1507-1518页

作者： Pengzhan Sun Kunlin Wang Jinquan Wei Minlin Zhong dehai wu Hongwei Zhu School of Materials Science and Engineering State Key Laboratory of New Ceramics and Fine Processing Key Laboratory of Materials Processing Technology of MOE Tsinghua University Beijing 100084 China Department of Mechanical Engineering Tsinghua University Beijing 100084 China Center for Nano and Micro Mechanics Tsinghua University Beijing 100084 China

The magnetic transitions in graphene oxide （GO） have been investigated experimentally. Micron-sized GO flakes exhibit dominant diamagnetism accompanied by weak ferromagnetism at room temperature. However, when the lateral dimensions of GO flakes are reduced from micron-size to nano-size, a clear transition from dominant diamagnetism to ferromagnetism is observed. After reducing the GO chemically or thermally, the dominant magnetic properties are not altered markedly except for the gradual enhancement of ferromagnetic components. In contrast, at 2 K, significant paramagnetism is present in both the micron-sized and nano-sized GO sheets. The effects of different functional groups on magnetic transitions in graphene derivatives have been further investigated using on hydroxyl-, carboxyl-, amino- and thiol- functionalized graphene. The results reveal that significant diamagnetism with weak ferromagnetism is present at room temperature in all of these functionalized graphene derivatives and the ability of different functional groups to introduce magnetic moments follows the order -SH 〉 --OH 〉 -COOH, -NH2. Notably, at 5 K, diamagnetism, paramagnetism and ferromagnetism coexist in thiol-, hydroxyl- and carboxyl-functionalized graphene, while amino-graphene exhibits dominant paramagnetism, analogous to the low-temperature magnetism in GO. These results indicate that diamagnetism, paramagnetism and ferromagnetism can coexist in graphene derivatives and magnetic transitions among the three states can be achieved which depend on edge states, vacancies, chemical doping and the attached functional groups. The results obtained may help settle the current controversy about the magnetism of graphene-related materials.

关键词： graphene derivatives defects functionalization magnetic transition

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Provenance of Uranium Mineralization of the Yuqia Area,Northwest China:Constraints from Detrital Zircon U-Pb Geochronology and Hf Isotopes

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Journal of Earth Science 2022年第6期33卷 1549-1570页

作者： Guangwen Huang Jiayong Pan Fei Xia Jie Yan Chengyong Zhang dehai wu Ying Liu State Key Laboratory of Nuclear Resources and Environment East China University of TechnologyNanchang330013China Key Laboratory of the Northern Qinghai-Tibet Plateau Geological Processes and Mineral Resources Xining810012China School of Resources Environment and JewelryJiangxi College of Applied TechnologyGanzhou341000China

Many sandstone-type uranium mineralization sites have been identified along the northern margin of the Qaidam Basin in North *** tectonism and multistage magmatism that occurred there have restricted the use of conventional techniques(petrogeochemistry)to deduce the sources of detritus and uranium in these sediments,and to further explore the sandstone-type uranium *** this study,U-Pb geochronological and Hf isotopic analyses were conducted on detrital zircon grains collected from Jurassic to Paleogene sandstones exposed in the Yuqia area of the Qaidam *** results indicate that the U-Pb ages of the analyzed zircon grains are clustered into four groups,285–229,498–401,999–806,and 2520–2305 ***ε_(Hf)(t)of the analyzed zircon grains ranges from-21.9 to+10.5,with two-stage Hf model ages(T_(DM2))concentrated between 2.1 and 1.3 *** on paleocurrent studies and results of petrological,detrital zircon geochronology,and Hf isotopic analyses,the Jurassic sediments in the Yuqia area were likely derived from the tectonic belt along the northern margin of the Qaidam Basin,such as the Qilian Mountains and the Quanji *** contrast,the Paleogene sediments were probably sourced from the northern margin of the Qaidam Basin and the Qilian *** uranium and thorium content and Th/U value of the rock mass and sedimentary strata in the source area show that the Indosinian Early Paleozoic uranium-rich granites and the Middle Jurassic uranium-rich strata of the northern margin of the Qaidam tectonic belt in the source area provide dual uranium sources for the Yuqia sandstone-type uranium ***,the study area appears to be favorable for sandstone-type uranium mineralization and may have potential for uranium prospecting.

关键词： uranium zircon U-Pb dating Hf isotope paleocurrent sandstone-type uranium deposit Qaidam Basin

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Preparation of alumina supported on carbon nano-tubes and its application in fluoride adsorption from an aqueous solution

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Chinese Science Bulletin 2002年第9期47卷 722-724页

作者： WANG Shuguang LI Yanhui ZHAO Dan XU Cailu LUAN Zhaokun LIANG Ji wu dehai State Key Laboratory of Environmental Aquatic Chemistry Research Center for Eco-Environmental SciencesChinese Academy of SciencesBeijing 100085China Department of Mechanical Engineering State Key Laboratory of Automotive Safety and EnergyTsinghua UniversityBeijing 100084China Department of Chemistry Northeast UniversityShenyang 110004China

A novel material, alumina supported on carbon nanotubes (Al2O3/CNT), was prepared from carbon nano-tubes and A1(NO3)3. X-ray diffraction (XRD) spectra demonstrate that alumina is amorphous, and scanning electron microscope (SEM) images show that CNT and alumina are homogeneously mixed. Furthermore, the fluoride adsorption behavior on the surface of Al2O3/CNT has been investigated and compared with other adsorbents. The results indicate that Al2O3/CNT has a high adsorption capacity, with a saturation adsorption capacity of 39.4 mg/g. It is also found that the adsorption capacity of Al2O3/CNT is 3.0-4.5 times that of γ-Al2O3 while almost equal to that of IRA-410 polymeric resin at 25°C . The adsorption isotherms of fluoride on Al2O3/CNT fit the Freundlich equation well, and optimal pH ranging from 5.0 to 9.0.

关键词： carbon nanotube alumina fluoride removal composite material.

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Interconnected graphene/polymer micro-tube piping composites for liquid sensing

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Nano Research 2014年第6期7卷 869-876页

作者： Tingting Yang Hongze Zhang Yan Wang Xiao Li Kunlin Wang Jinquan Wei dehai wu Zhihong Li Hongwei Zhu School of Materials Science and Engineering State Key Laboratory of New Ceramics and Fine Processing Key Laboratory of Materials Processing Technology of MOE Tsinghua University 8eijing 100084 China Center for Nano and Micro Mechanics Tsinghua University Beijing 100084 China National Key Laboratory of Science and Technology on Micro/Nano Fabrication Institute of Microelectronics Peking University Beijing 100871 China Department of Physics and Nanoscience and Nanotechnology Laboratory Institute for Advanced Study Nanchang University Nanchang 330031 China Department of Mechanical Engineering Tsinghua University Beijing 100084 China

Detection and analysis of volatile organic compounds （VOCs） as pollutants in the atmosphere and liquids are of great significance because of the detrimental effects of VOCs. A polymer-coated graphene micro-tube piping （GMP） structure with a cross-linked and interconnected channel network was synthesized for liquid sensing. By virtue of their unique cross-linked and interconnected channel network configuration, polycrystalline conformation, and the support of a polymer layer, the resistivity of the 3D hollow micro-tubing GMPs was sensitive to strain, ensuring high sensitivity of the liquid sensor （R/Ro of -4 × 10^3% for pure acetone and R/Ro of -105% for 0.01 wt.% acetone solution）. Due to the capillary force, the interfaces of the 3D structures can speed up the penetration of solvents into the polymer, thus promote distinct selectivity within seconds and significantly decrease the response time. Owing to their good selectivity, high sensitivity, rapid response and flexibility, and the ease of use of the sensors and the simplicity of the fabrication processes, the GMP/polymer composites should be a good candidate for liquid sensing.

关键词： liquid sensing graphene micro-tube piping flexible devices high sensitivity

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Carbon nanotube-polypyrrole core-shell sponge and its application as highly compressible supercapacitor electrode

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Nano Research 2014年第2期7卷 209-218页

作者： Peixu Li Enzheng Shi Yanbing Yang Yuanyuan Shang Qingyu Peng Shiting wu Jinquan Wei Kunlin Wang Hongwei Zhu Quan Yuan Anyuan Cao dehai wu Department of Mechanical Engineering Tsinghua University Beijing 100084 China Department of Materials Science and Engineering College of Engineering Peking University Beijing 100871 China Key Laboratory of Analytical Chemistry for Biology and Medicine (Ministry of Education) College of Chemistry and Molecular Sciences Wuhan University Wuhan 430072 China Key Laboratory for Advanced Materials Processing Technology and School of Materials Science and Engineering Tsinghua University Beijing 100084 China

A carbon nanotube （CNT） sponge contains a three-dimensional conductive nano- tube network, and can be used as a porous electrode for various energy devices. We present here a rational strategy to fabricate a unique CNT@polypyrrole （PPy） core-shell sponge, and demonstrate its application as a highly compressible supercapacitor electrode with high performance. A PPy layer with optimal thickness was coated uniformly on individual CNTs and inter-CNT contact points by electrochemical deposition and crosslinking of pyrrole monomers, resulting in a core-shell configuration. The PPy coating significantly improves specific capacitance of the CNT sponge to above 300 F/g, and simultaneously reinforces the porous structure to achieve better strength and fully elastic structural recovery after compression. The CNT@PPy sponge can sustain 1,000 compression cycles at a strain of 50% while maintaining a stable capacitance （〉 90% of initial value）. Our CNT@PPy core-shell sponges with a highly porous network structure may serve as compressible, robust electrodes for supercapacitors and many other energy devices.

关键词： carbon nanotube sponge polypyrrole core-shell configuration compressible electrode supercapacitor

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Microwave absorbing properties and magnetic properties of different carbon nanotubes

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Science China(Technological Sciences) 2009年第1期52卷 227-231页

作者： XuChun Gui KunLin Wang JinQuan Wei RuiTao Lü QinKe Shu Yi Jia Chen Wang HongWei Zhu dehai wu Key Laboratory for Advanced Manufacturing by Materials Processing Technology Department of Mechanical Engineering Tsinghua University Beijing 100084 China Department of Materials Science and Engineering Tsinghua University Beijing 100084 China

The microwave absorbing properties and magnetic properties of as-grown Fe-filled carbon nanotubes (CNTs), annealed Fe-filled CNTs, and multi-walled CNTs were studied. Vibrating sample magnetometer results showed that the annealed Fe-filled CNTs have the weakest coercivity and strongest saturation magnetization among the three types CNTs, due to the presence of more ferromagnetic α-Fe nanowires. After annealing, the values increased to 291.0 Oe and 28.0 emu/g and the samples showed excellent microwave absorbing properties. The reflection loss was over 5 dB between 11.6 GHz and 18 GHz with a maximum value of 10.8 dB for annealed Fe-filled CNTs (1.1 wt%)/epoxy composite.

关键词： carbon nanotubes microwave absorbing properties magnetic properties

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Effects of structure and sur-face properties on carbon nanotubes' hydrogen storage characteristics

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Chinese Science Bulletin 2001年第16期46卷 1358-1360页

作者： LI Xuesong ZHU Hongwei CI Lijie XU Cailu MAO Zongqiang WEI Bingqing LIANG Ji wu dehai Department of Mechanical Engineering State Key Laboratory ofAutomobile Safety and EnergyTsinghua UniversityBeijing 100084China Institute of Nuclear Energy Technology Tsinghua UniversityBeijing 100084China

Hydrogen adsorption experiments were carried out in special stainless steel vessels at room temperature (298K) and under 10 MPa using self-synthesized multi-walled carbon nanotubes. In the experiments, carbon nanotubessynthesized by the seeded catalyst method were pretreatedby being soaked in chemical reagents or annealed at hightemperature before they were used to adsorb hydrogen, but their capacity for hydrogen storage was still poor. Carbonnanotubes synthesized by the floating catalyst method were found to be able to adsorb more hydrogen. They have ahydrogen storage capacity of over 4% after they wereannealed at high temperatures, which suggested that theycould be used as a promising material for hydrogen storage.

关键词： carbon nanotube hydrogen storage adsorption surface functional group heat treatment.

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Light emission of double-walled carbon nanotube filaments doped with yttrium and europium

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Science China(Technological Sciences) 2009年第1期52卷 252-255页

作者： SHU QinKe WANG KunLin WEI JinQuan ZHU HongWei LI XinMing CHEN Xi JIA Yi GUI XuChun XU ErYang wu dehai Key Laboratory for Advanced Manufacturing by Materials Processing Technology Department of Mechanical EngineeringTsinghua UniversityBeijing 100084China

As the potential applications of carbon nanotubes in the field of electroluminescence, elements yttrium and europium were introduced to modify the emission properties of double-walled carbon nanotubes (DWNTs) to obtain higher efficacy and other properties. The light emission spectrum of the Y-Eu-doped DWNT filament is suppressed in the near-infrared range, while enhanced in the mid-infrared range. The doped DWNT filament can reach higher efficacy than that of the pure DWNT filament at the same input power and can work stably as long as 5000 h at 12 V. These filaments could be useful for the light sources with special functions, such as infrared light sources operated at low input power.

关键词： carbon nanotubes electroluminescence efficacy yttrium europium

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Deposition of the platinum crystals on the carbon nanotubes

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Chinese Science Bulletin 2000年第2期45卷 134-137页

作者： CHEN Guiru XU Cailu MAO Zongqiang LI Yubao ZHU Jie CI Lijie WEI Bingqing LIANG Ji wu dehai Department of Mechanical Engineering.Tsinghua University Beijing 100084China Institute of Nuclear Enefgy Technology Tsinghua UniversityBeijing 100084China

A new technique and the affecting factors for depositing platinum on the carbon nanotubes were investigated. The results show that the deposited platinum crystals in the atmosphere of hydrogen or nitrogen have a small size and a homogeneous distribution on the surface of the carbon nanotubes. The pretreatment would decrease the platinum particles on the carbon nanotubes

关键词： carbon nanotubes scauning electron microscopy transmission electron microscopy platinum.

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Three-dimensional porous graphene sponges assembled with the combination of surfactant and freeze-drying

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Nano Research 2014年第10期7卷 1477-1487页

作者： Rujing Zhang Yachang Cao Peixu Li Xiaobei Zang Pengzhan Sun Kunlin wang Minlin Zhong Jinquan Wei dehai wu Feiyu Kang Hongwei Zhu School of Materials Science and Engineering State Key Laboratory of New Ceramics and Fine Processing Key Laboratory of Materials Processing Technology of MOE Tsinghua University Beijing 100084 China Department of Mechanical Engineering Tsinghua University Beijing 100084 China Advanced Materials Institute Graduate School at Shenzhen Tsinghua University Shenzhen 518055 China Center for Nano and Micro Mechanics Tsinghua University Beijing 100084 China

With the combination of surfactant and freeze-drying, we have developed two kinds of graphene spongy structures. On the one hand, using foams of soap bubbles as templates, three-dimensional porous graphene sponges with rich hierarchical pores have been synthesized. Pores of the material contain three levels of length scales, including millimeter, micrometer and nanometer. The structure can be tuned by changing the freezing media, adjusting the stirring rate or adding functional additives. On the other hand, by direct freeze-drying of a graphene oxide/surfactant suspension, a porous framework with directionally aligned pores is prepared. The surfactant gives a better dispersion of graphene oxide sheets, resulting in a high specific surface area. Both of the obtained materials exhibit excellent absorption capacity and good compression performance, providing a broad range of possible applications, such as absorbents, storage media, and carriers.

关键词： graphene sponge hierarchical freezing media porous foams

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