Browsing by Author "Zhang, Jiangnan"

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    Fracture toughness of the sidewall fluorinated carbon nanotube-epoxy interface
    (AIP Publishing LLC., 2014) Ganesan, Yogeeswaran; Salahshoor, Hossein; Peng, Cheng; Khabashesku, Valery; Zhang, Jiangnan; Cate, Avery; Rahbar, Nima; Lou, Jun
    The effects ofﾠcarbon nanotubeﾠ(CNT)ﾠsidewall fluorination on theﾠinterfaceﾠtoughness of theﾠCNTﾠepoxyﾠinterfaceﾠhave been comprehensively investigated. Nanoscale quantitative single-CNT pull-out experiments have been conducted on individual fluorinatedﾠCNTsﾠembedded in an epoxy matrix,ﾠin situ, within aﾠscanning electron microscopeﾠ(SEM)ﾠusing an InSEMﾮﾠnanoindenter assisted micro-device. Equations that were derived using a continuum fracture mechanics model have been applied to compute theﾠinterfacialﾠfracture energy values for the system. Theﾠinterfacialﾠfracture energy values have also been independently computed by modeling the fluorinated graphene-epoxyﾠinterfaceﾠusingﾠmolecular dynamics simulationsﾠandﾠadhesionﾠmechanisms have been proposed.
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    Nanotribological and Nanomechanical Investigation of Nanomaterials
    (2013-09-16) Zhang, Jiangnan; Lou, Jun; Ajayan, Pulickel M.; Li, Qilin
    This dissertation primarily documents the quantification of the interfacial behavior of carbon based nanomaterials, which includes two categories, one is the nanofriction properties evaluation of aligned carbon nanotube carpets, few-layer graphene as well as three types of functionalized graphene nanoribbons, the second is the mechanical characterization of individual functionalized carbon nanofibers and the interfacial fracture toughness quantification in carbon nanotube/polymer derived ceramics nanocomposite. The aligned carbon nanotube carpets have a highly anisotropic friction behavior, which means the friction force are lower for transversely aligned CNTs side than for vertically aligned CNTs surface. We can also tune the friction properties of graphene ribbons by grafting different functional groups. In addition, two narrow angular regions with high friction, separated by a wide angular interval with low friction, were identified between graphene and highly oriented pyrolytic graphite. The distance between the two friction peaks is 61◦, which corresponds well with the 60◦ symmetry of individual atomic layers in the graphite lattice. The technique that involves the usage of mcirodevices and nanoidenter was used to conduct tensile tests on pristine, fluorinated and amino-functionalized carbon nanofibers, which were found to exhibit varied load-bearing abilities and unique fracture modes. The technique was also used to perform single fiber pullout experiments to study carbon nanotube/polymer derived ceramic interface.