Synthesis of Large Quantity Single—Walled Carbon Nanotubes by Arc Discharge

We report on a new method to prepare large quantity single-walled carbon nanotubes(SWCNTs) with high purity.Using a Y-Ni powder composite graphite rod as an anode,at a given angle with the high-purity graphite cathode rod,a cloth-like deposit can be obtained by dc arc discharge in helium at high temperature,which contains about 60% SWCNTs.In this way,we can obtain a deposit of more than one gram in ten minutes.Transmission electron microscopy and Raman scattering have been used to observe the structure and morphology of the SWCNTs.     

Morphologies and microstructures of carbon nanotubes prepared by self—sustained arc discharging

We have investigated the morphology and microstructure of carbon nanotubes and nanoparticles in cathode deposits prepared by self-sustained arc discharge. Scanning electron microscopy images indicate that there are two regions exhibiting different morphologies on the top surface of the cathode deposits. In the central region, there is a triangular pattern of spots with a diameter up to 100μm, which consists of carbon nanotubes and nanoparticles. In the fringe region, carbon nanotubes and nanoparticles are distributed randomly. In addition, carbon nanotubes in the central region have a larger inner diameter, compared with those in the fringe region. The outer diameter distribution of tubes in the central region is narrower than that of tubes in the fringe region, while the former has a smaller peak value than the latter. For the nanoparticles, they exhibit a different behaviour from the tubes existing in the same region. The difference between the microstructure of tubes or particles in the two regions is attributed to the different temperatures and temperature gradients during their formation.     

Effects of Radius and Orientation of Single-Walled Carbon Nanotubes on Their Nonlinear Tensile Deformation Behaviour

By capturing the atomic information and reflecting the behaviour governed by a nonlinear potential function, an analytical molecular mechanics approach is applied to establish the constitutive relation for single-walled carbon nanotubes （SWCNTs）. The nonlinear tensile deformation curves of zigzag and armchair nanotubes with different radii are predicted, and the elastic properties of these SWCNTs are obtained. A conclusion is made that the nanotube radius has little effect on the mechanical behaviour of SWCNTs subject to simple tension, while the nanotube orientation has larger influence.     

Dependence of Structure and Haemocompatibility of Amorphous Carbon Films on Substrate Bias Voltage

Tetrahedral amorphous hydrogenated carbon (ta-C:H) films on Si(lO0) substrates were prepared by using a magnetic-field-filter plasma stream deposition system. Samples with different ratios of sp^3-bond to sp^2-bond were obtained by changing the bias voltage applied to the substrates. The ellipsometric spectra of various carbon films in the photon energy range of 1.9-5.4eV were measured. The refractive index n and the relative sp^3 C ratio of these films were obtained by simulating their ellipsometric spectra using the Forouhi-Bloomer model and by using the Bruggeman effective medium approximation, respectively. The haemocompatibility of these ta-C:H films was analysed by observation of platelet adhesion and measurement of kinetic clotting time. The results show that the sp^3 C fraction is dependent on the substrate bias voltage, and the haemocompatibility is dependent on the ratio of sp^3-bond to sp^2-bond. A good haemocompatibility material of ta-C:H films with a suitable sp^3 C fraction can be prepared by changing the substrate bias voltage.     

Ab-Initio Study of Cobalt Impurity Effects on Phonon Spectra,Mechanical and Thermal Properties of Single Wall Carbon Nanotube （5,0）

We use density functional perturbation theory based on the pseudo-potential to calculate the phonon spectrum, phonon density of states, specific heat capacity and mechanical properties of pristine and cobalt doped （5,0） single wall carbon nanotube （CNT）. In the calculations, we consider one Co atom in the center of the unit cell of the tube and it is shown that the pristine （5~0） CNT is nonmagnetic while the Co-doped tube becomes magnetic. Young＇s modulus for both systems is about 1 TPa （＇after Co-doping it goes slightly higher） and the Poisson ratio for the pristine tube becomes quite a bit larger than the doped one. On the other hand, the calculated value of radial breath mode for the pristine CNT is in good agreement with the experimental reports while after Co-doping it is increased. In addition, heat capacity of the doped CNT is reduced, which leads to some important empirical applications.     

Influence of High Atomic Hydrogenation on the Electronic Structure of Zigzag Carbon Nanotubes： A First-Principles Study

Using density functional theory, we study high hydrogenated zigzag single-walled carbon nanotubes from （7,0） to （11,0）. Two structure transitions are classified： type A is a metallic transition and type B is a ＂semiconductive transition＂ according to the energy band structure. The charge density transforms only at the C-C bonds without hydrogenated sites. The sp^3 hybridization is mainly enhanced for all the C-C bonds in the vertical axial direction for type-A configurations, and the sp^3 hybridization mainly increases for all C-C bonds along the axial direction for the type-B case.     

Influence of Monomer Types on the Designability of a Protein—Model Chain

In a three-dimensional off-lattice model,the method of Shakhnovich and Gutin for minimizing the Hamiltonian is applied to the design of a protein-model chain.The effect of the number of hydrophobic and hydrophilic monomer types on the designability of a protein-model chain is investigated.The simulation results reveal that the number of hydrophobic monomer types is a much more important factor than that of the polar monomer types in the design of a protein-model chain.     

Dependence of in—tube doping on the radius and helicity of single—wall carbon nanotubes

Using the Lennard－Jones interaction potential between the impurity atom and carbon atom, we have studied the dependence of in-tube impurity doping on the radius of a single-wall carbon nanotube (SWNT), as well as its helicity. The obtained results show that the radius of the most stably doped SWNT is different for different kinds of impurity atoms. This is useful for producing the required doped SWNT. In addition, it is found that the helicity of tube has a strong effect on the potential energy of the atoms doped in the SWNT.