Investigation Of Microstructure Characterizations And The Properties Of The Carbon Nano-materials With Novel Structures

As one of the most investigated elements,carbon,which consists multifarious composites,has been a lasting hotspot in materials science and engineering.While the nano materias usually refer to the materials whose size is in the nano scale in at least one dimension and this ultra small feature endow them with excellent properties which do not exsist in the bulk material although the compositions are same.Thanks to the continuous progress in techonology,carbon nanomaterial has been attracting increasing attention for its unique acoustic,optic and electromagnetic properties and has made great contributions in catalyzing,medicine,energy,etc.Unfortunately,the abundant researches on the properties and application didn't bring equivalent researches on structure and the relation between the structure and property still remain ambiguous.In this dissertation,this relation is investigated,by endeavouring to discover the structure of the novel carbon nanomateirals through electromicroscopy,the properties through the macro spectroscopies.The relation between properties and structure would be discussed more thoroughly.Our major work are as following:The emerging 0-dimensional carbon nanomaterial,carbon quantum dot?CQD?has made great contribution in many areas.Because of the multifarious sysnthesis methods,CQD has different kinds of structures,but most of them were hypothesis and not substantiated,especially the face centered cubic?FCC?structure,which has been controversial for long periods of time.In the first part,we use critric to synthesize the CQDs with fcc structure,through the hydrothermal metod.The CQDs have good crystallinity and the average size is about 3.2 nm.The SAED result shows that the CQDs have intact fcc structure and the lattice parameter is about 3.63?.The HRTEM and STEM images manifest the atomic structure and lattice infringe of the CQDs,consistent with the simulation.Abundance of five-fold twins,which usually exsist in the metal with fcc structure,are also observed.The XPS and IFRT spectrum show that the CQDs have the hydroxy and carboxyl and the core is pure carbon.The EELS spectrum displays the electronic structure different from the graphite and diamond,which may represent the new s²p² hybridization.This novel structure may give the CQD unique property like metal,such as antifricitonal property,and good thermal-stability,which can be demonstrated through the result of in-situ heating experiment.As a typical kind of two-dimensional carbon nanomaterials,graphene,which is widely applied in the fields of catalysm,energy,etc.,also attracted much research interest.There is a unique defect structure in graphene,topological defect.Unfortunately,few researches focused on the influence the topological defect had on the properties,just like the structure of carbon quantum dots we mentioned above.Hence,taking Proanthocyanin as ingredient,a series of graphene catalysts with abundant topological defects were synthesized through the method of pyrolysis under different temperature,hoping to discover how these defects affect the properties of the graphene.According to the results,OPC-900 has the best catalytic performance.The electron microscopy image shows that there are numerous topological defects exsisting in the periphery of the catalysm,much more than those synthesized under different temperature,leading to several redox states,full absorption of visible light and suitable band edges for overall water splitting.Under stirring in dark or visible light,the catalyst can help water be split into H₂ and O₂ in low conductivity medium,best performance reaching 106.97?mol·h^-1g^-1 and 47.65?mol·h^-1g^-1 respectively with mechanical energy conversion efficiency of 7.01%.