Structure And Thermostability Of Ni Nanowires Encapsulated By Carbon Nanotubes

Carbon nanotube (CNT) with special structure and nanometer scale are found tohave many outstanding characteristics, such as high rigidity, excellent electronic,mechanic properties and high surface-volume ratio. Therefore it’s predicted to be apotential material for light and hydrogen absorption. Besides, CNT can be filled withvarious kinds of matters including metals such as semiconductor material,metallics,organic polymer because of its capsule-like structure, for the purpose of preparation ofhybrid materials with different functions. Up to now, metals have been successfullyencapsulated into CNT experimentally. Furthermore, theoretical research predicts thatmetals filled in CNT will possess unique features such as preventing metals fromoxidization，making efficient and multi-functional catalysts, as well as realizingcompound materials with special electronic, magnetic mechanic properties. In fact,the interface interaction existing in the hybrid material will affect its structuralconfiguration, and consequently results in different physical characteristics. Therefore,in this thesis，by the means of molecular dynamic simulation and quenched annealingmethod, we studied the structural features of nickel nanowires encapsulated bysingle-wall carbon nanotubes and discussed the mechanism lying in the process offorming those structures.Molecular dynamics simulations were used to study the composite structure ofNi nanowires packaged CNT. There are two kinds of interatomic interaction in thecomposite structures. The carbon-carbon interaction, carbon-nickel interaction andnickle-nickel interaction were described by Tersoff potential, Lennard-Jones Potentialand Tight Binding potential, respectively.Firstly, the structures of armchair carbon nanotubes encapsulating Ni nanowiresand their helicity and thermal stability are discussed. We find that Ni nanowires aremultiple helical tubular structures and each layer is composed of several Ni atomchains. Different layers of Ni nanowires have different helicity and the helicity of Ninanowires in the inner layer is greater than that of the outer one. Moreover, thehelicity will be the greatest when the number of the Ni atom chains is an integermultiple of three. As the increase of the diameters of the CNT, the helicity of Ninanowires changes periodically. The structure and helicity only have tiny alteration even at high temperature as the CNT can protect the Ni nanowire.Secondly, periodic structure of Ni nanowires encapsulated by (9,9)CNT wasdiscussed through the atomic potential energy distribution. The Ni nanowires haveperiodic structure that atomic potential energy of high and low alternative distribution.Each periodic unit has six layer atomic, and each layer has six Ni atoms. The atomicpotential energy of the fifth and the sixth layers is higher. Ni nanowires in handednesscarbon nanotube have similar structure all the same,but the Ni nanowires have sameother periodic structure, some of Ni nanowires have non-standard periodic structure.