The Structure And Phase Transition Of Metal Nanoparticles In Carbon Nanotubes

Use the nano-space of carbon nanotube cavity,we can fill nano materials into the carbon nanotube in a variety of ways.Metal nanoparticles limited by the carbon nanotube may have new structure and properties.All calculations were adopted molecular dynamics method and rigid immobile single-walled carbon nanotubes(SWNTS)are the basic model.Cu and Ag metal nanoparticles in different proportions were imported into the carbon nanotubes.Then we studied the structure,potential energy and phase transformation properties of the metal atoms under different temperature condition,and some meaningful conclusions are obtained.Studies have shown that:(1)Under the limited space(n,n)and(n,0)carbon nanotubes,nanoparticles(Cu0.5 Ag0.5)256 all form a fan-shaped layered structure,and the smaller the diameter of carbon nanotube,the more obvious fan-shaped structure.We can infer that as the increase of metal particles imported into the inside of the carbon nanotube,Cu and Ag atoms will form surface deposition in the part of the tubes,then gradually gathered along the axis direction and showed pyramidal sector development.Finally metal atoms will form a cylindrical laminated structure filled with the internal space of the carbon tube.The structure stability of Ag-Cu alloy particles is improved by the inner space,when the size of the inner space is large enough than the size of Ag-Cu alloy particles,the chirality and size of the carbon tube have no significant influence on the thermodynamic characteristics of the alloy particles.(2)We need to find ways to increase the strength of the interaction between the carbon atoms and the metal atoms or to precisely control the temperature of the system,so that the metal particles are in a liquid state and are sucked into the carbon tube by capillarity to make the metal atomic energy outside the carbon tube stable adsorption in the space inside the tube.The arrangement structure of carbon atoms on the wall of carbon tube and the size of the space inside the tube are the factors affecting the arrangement structure of metal atoms.The arrangement of metal atoms outside the tube is generally consistent with the arrangement orientation of carbon atoms in the tube wall.In addition to the chirality of the carbon tube,the size of the restricted space is a more important factor determining the arrangement structure of metal atoms inside the tube.(3)Cylindrical lamellar structure is formed in the carbon tube after annealing with sufficient(CuxAg1-x)N particles in the inner space.The inner space of the carbon tube determines the number of layers in the laminar structure.The distance between the outermost metal atomic ring and the wall of the tube and between adjacent layers is basically unchanged,which is independent of the diameter of the carbon tube.Whether there is an atomic chain in the axis of the carbon tube is determined by the radius of the carbon tube.In the shell structure formed by(Cu)N nanoparticles,the structure of each layer of metal atoms on the cylinder is arranged in a triangular dense pile,which is a planar dense pile structure.(4)The restricted space improves the thermal stability of Cu particles.With the increase of the size of Cu particles,the potential energy curve of the restricted Cu particles tends to saturate rapidly,indicating that the molecular dynamics calculation of the behavior of Cu particles with larger sizes in carbon tubes will no longer be urgently needed.If the space inside the tube is more restrictive,the phase transition of Cu particle structure will be transformed from discontinuous to continuous,which is conducive to the preparation of atomic disordered metallic glassy state.Whether or not the metal particles are limited,the phase transition temperature of(CuxAg1-x)N alloy particles is generally close to or lower than that of Ag elemental particles with the same atomic number.