采用放电等离子体烧结技术(SPS)构筑三维共价结构碳纳米管网络
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摘要
单根碳纳米管在轴向维度上具有无比优异的导电、导热以及机械性能,然而在把这些优异的材料性能向三维方向拓展时,却遇到了难以克服的阻碍。由碳纳米管构成的三维集合体,其材料性能远低于单根碳纳米管相应的材料性能,造成这种情况的主要原因,是目前三维碳纳米管集合体中,碳纳米管之间是以一种较弱的范德华力相连接的。为此本文采用化学气相沉积法,在碳纳米管上覆盖一层无定形碳,通过SPS烧结,形成由强的C-C共价键连接的三维碳纳米管网络,极大提高了材料的导电性和机械性。实验结果表明,采用先覆盖无定形碳,再在30MPa、1400℃条件下烧结而制备的碳纳米管网络,其最优电导率约为133 S·cm~(-1),其杨氏模量约为16.5 MPa。
Single carbon nanotube(CNT) had the excellent electrical conductivity, thermal conductivity and mechanical properties along the axial direction. However, it came to huge difficulties when we tried to get the outstanding material properties of carbon nanotube along other two directions. The material properties of 3 dimensional CNT collector was far poor compared with corresponding part of single CNT. The main reason for this was due to the molecular bonding between the neighboring CNTs inside of the CNT collector, which was Vander Waals bonding. To solve this problem, here we proposed a method based on the spark plasma sintering(SPS) technology. The surface of CNTs used in this study were pre-deposited a thin layer of amorphous carbon layer in a chemical vapor deposition chamber, before subjected to the following SPS process. By adjusting the parameters of the SPS process,the atomic structure on CNT surface could be tuned. Under suitable experimental conditions, the amorphous carbon on the surface of CNTs was transformed to graphitic carbon layer and the junction points located at neighboring CNTs were covered with graphitic carbon layer. 3 D covalently bonded carbon nanotube network could be built, which could significantly improved the electrical conductivity and mechanical properties of the CNT network. The best sample prepared under 1400℃ sintering temperature and 30 MPa pressure, had the highest electrical conductivity～133 S/cm, and the highest young's modulus was 16.5 MPa.
Single carbon nanotube(CNT) had the excellent electrical conductivity, thermal conductivity and mechanical properties along the axial direction. However, it came to huge difficulties when we tried to get the outstanding material properties of carbon nanotube along other two directions. The material properties of 3 dimensional CNT collector was far poor compared with corresponding part of single CNT. The main reason for this was due to the molecular bonding between the neighboring CNTs inside of the CNT collector, which was Vander Waals bonding. To solve this problem, here we proposed a method based on the spark plasma sintering(SPS) technology. The surface of CNTs used in this study were pre-deposited a thin layer of amorphous carbon layer in a chemical vapor deposition chamber, before subjected to the following SPS process. By adjusting the parameters of the SPS process,the atomic structure on CNT surface could be tuned. Under suitable experimental conditions, the amorphous carbon on the surface of CNTs was transformed to graphitic carbon layer and the junction points located at neighboring CNTs were covered with graphitic carbon layer. 3 D covalently bonded carbon nanotube network could be built, which could significantly improved the electrical conductivity and mechanical properties of the CNT network. The best sample prepared under 1400℃ sintering temperature and 30 MPa pressure, had the highest electrical conductivity～133 S/cm, and the highest young's modulus was 16.5 MPa.
引文
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[2]Treacy MM,Ebessen TW,Gibson JM.Exceptionally high Young’s modulus observed for individual carbon nanotubes[J].Nature,1996,381:678-680.
[3]Marinho B,Ghislandi M,Tkalya E,et al.Electrical conductivity of compacts of graphene,multi-wall carbon nanotubes,carbon black,and graphite powder[J].Powder Technology,2012,221(none):351-358.
[4]Kis A,Csányi G,Salvetat J P,et al.Reinforcement of singlewalled carbon nanotube bundles by intertube bridging[J].Nature Materials,2004,3(3):153.
[5]Jing L,Papadopoulos&Amp C,Xu J.Nanoelectronics:Growing Y-junction carbon nanotubes[J].Nature,1999,402(6759):253-254.
[6]Hashim D P,Narayanan N T,Romo-Herrera J M,et al.Covalently bonded three-dimensional carbon nanotube solids via boron induced nanojunctions[J].Scientific Reports,2012,2(4):363.
[7]Fu Y,Carlberg B,Lindahl N,et al.Templated Growth of Covalently Bonded Three-Dimensional Carbon Nanotube Networks Originated from Graphene[J].Advanced Materials,2012,24(12):1576-1581.
[8]Gui X C,Wei J Q,Wang K L,et al.Carbon nanotube sponges.[J].Advanced Materials,2010,22(5):617-621.
[9]GROZA,J.R,RISBUD,et al.Plasma activated sintering of additive-free AlN powders to near-theoretical density in 5minutes[J].Journal of Materials Research,1992,7(10):2643-2645.
[10]Yang K,He J,Su Z,et al.Inter-tube bonding,graphene formation and anisotropic transport properties in spark plasma sintered multi-wall carbon nanotube arrays[J].Carbon,2010,48(3):756-762.
[11]Elastic improvement of carbon nanotube sponges by depositing amorphous carbon coating[J].Carbon,2014,76:19-26.