ZY（朱志远） Zhu

Nanocrystalline diamond from carbon nanotubes

Structural phase transformation from multiwalled carbon nanotubes to nanocrystalline diamond by hydrogen plasma post-treatment was carried out. Ultrahigh equivalent diamond nucleation density above 1011 nuclei/cm2 was easily obtained. The diamond formation and growth mechanism was proposed to be the consequence of the formation of sp3 bonded amorphous carbon clusters. The hydrogen chemisorption on curved graphite network and the energy deposited on the carbon nanotubes by continuous impingement of activated molecular or atomic hydrogen are responsible for the formation of amorphous carbon matrix. Diamond nucleates and grows in the way similar to that of diamond chemical vapor deposition processes on amorphous carbon films.

Large-area fabrication of periodic Fe nanorings with controllable aspect ratios in porous alumina templates.

Highly uniform Fe nanoring arrays in porous anodic alumina templates are fabricated by physical vapour deposition and grazing ion milling techniques. The nanorings have aspect ratios ranging from 0.8 to 4, depending on the deposition conditions. The outer diameter of the individual nanorings, and the area density and distribution patterns are completely determined by the template used. Selected-area electron diffraction reveals that these nanorings have a polycrystalline microstructure. The nanoring fabrication method demonstrated here can be extended to other materials.

Synthesis of carbon nanotube arrays using ethanol in porous anodic aluminum oxide template

Carbon nanotube (CNT) arrays confined by porous anodic aluminum oxide (AAO) template were synthesized using ethanol as reactant carbon source at low pressure. Images by scanning electron microscope (SEM) and low magnification transmission electron microscopy (TEM) show that these CNTs have highly uniform outer diameter and length, absolutely controlled by the diameter and depth of nano-channel arrays of the AAO. High resolution transmission electron microscopy (HRTEM) imaging indicates that the graphitization of the CNT walls is better than the results reported on this kind of template-based CNT arrays, although it is not so good as that of multiwalled carbon nanotubes (MWCNTs) synthesized by catalysis. CNTs synthesized using acetylene as reactant gas show much less graphitization than those prepared using ethanol by comparing the results of HRTEM and Raman spectroscopy. The etching effects of decomposed OH radicals on the amorphous carbon and the roughness of AAO nano-channel arrays on the CNTs growth were employed to explain the graphitization and growth of the CNTs.

RMF calculation and phenomenological formulas for the rms radii of light nuclei

The RMF (Relativistic Mean Field) calculations are performed systematically for light isotopes (A < 40) with NL-SH parameter set. The calculated binding energies and root mean square (rms) radii of light nuclei are discussed. On the basis of the theoretical calculations and the experimental data, we have suggested a group of phenomenological formulas for the neutron, proton and matter rms radii for nuclei with A < 40, including the drip-line nuclei. In these formulas, the effects of binding energies, isospin and separation energies are considered. These formulas not only agree to the experimental data for stable nuclei well, but also reproduce the abnormal large radii of nuclei near the drip-line that the previous empirical models fail to reproduce them

Enhanced field emission from nano-graphite coated carbon nanotubes

An effective method by low energy carbonhydrogen ion treatment to enhance field emission of the carbon nanotubes (CNTs) is demonstrated. Comparing with control, field emission (FE) currents of the CNTs by carbonhydrogen ion irradiation increased, and the turn-on field and the threshold field decreased significantly. The structure characteristic revealed by transmission electron microscopy demonstrates that CNTs are coated by nano-graphite particles after being treated with low energy carbonhydrogen ion and that there are large quantities of defects and grain boundaries in the coated layer. It is considered that the coating layer can decrease the effective surface work function of CNTs and correspondingly increase field emission. In addition, die defects, the grain boundaries and the C-H dipoles forming in the process of the low energy ions irradiation can effectively enhance the field emission.

Optical conductivity of single walled nanotube films in the terahertz region

A theoretical investigation for the conductivity of single walled nanotube films is carried out with an effective medium model in the Terahertz region. The results are compared with the recent experiment and a decrease of the real conductivity with increasing frequency is predicted. Meanwhile, the off-diagonal components of the dielectric function of single-walled carbon nanotube films based on the magnetooptical effects are also shown.

Study of thermal stability of fullerenes by molecular dynamics

The thermal stability of fullerene C20, C26, C36 and C60 is studied using Molecular Dynamics (MD) simulation based on Brenner potential in this work. Lindemanns relative root-mean-square (rms) bond-length fluctuation is used to monitor the behavior of the structural and thermal properties. The results show that the rms bond-length fluctuation becomes scattered points at relative high tempereture, which is caused by different isomerization transitions. Larger fullerenes are found to be more stable than small ones. The results are compared with those from MD simulation based on TLHT potential. Mechanic stability of fullerene C20 is also studied.