By using the in situ thermal analysis-mass spectroscopic technique, combined with transmission electron microscopic characterization of the carbon nanotube (CNT) product, we have studied the chemical vapor deposition (CVD) growth of CNTs with Fe-Co/Á-Al2O3 catalyst and benzene precursor in the range of room temperature to 700℃. The growth process has been clearly illuminated, which starts from the reduction of catalyst around 645℃ followed by the dissociation of carbon-hydrogen bonds of benzene and the sequential growth of CNTs. A surprising fact is that no possible hydrocarbon species derived from benzene was detected, indicating that the carbon-carbon bond was not broken under our experimental conditions. All of the experimental results strongly reinforce the six-membered-ring-based growth model, and a schematic elucidation is presented accordingly. This in situ study not only reveals the unique and convincing information directly related to the growth mechanism from the involved chemistry, but also provides a powerful way to clarify the mechanism of CVD synthesis of CNTs with other precursors.

Aluminum nitride nanostructures are attractive for many promising applications in semiconductor nanotechnology. Herein we report on vapor-solid growth of quasi-aligned aluminum nitride nanocones on catalyst-coated wafers via the reactions between AlCl3 vapor and NH3 gas under moderate temperatures around 700℃, and the growth mechanism is briefly discussed. The as-prepared wurtzite aluminum nitride nanocones grow preferentially along the c-axis with adjustable dimensions of the sharp tips in the range of 20-60nm. The photoluminescence spectrum reveals a broad blue emission band with a fine photon structure while the field emission study shows a notable emission current with a moderate turn-on field as expected, suggesting their potential applications in light and electron emission nanodevices.

Periodic spindle-unit boron nitride (BN) nanotubes with buglelike open-end tips have been found in the product by nitriding Fe-B nanoparticles at 1100℃ with a mixture of nitrogen and ammonia gas. The microstructure was well-characterized by high-resolution transmission electron microscopy (HRTEM) and energy-dispersive X-ray spectroscopy (EDX). The diameter of this BN nanotube shows a decreasing tendency along the growth direction. For each spindle unit, the outer diameter decreases steeply and then increases gradually, accompanied by thinning of the wall thickness along the growth direction. Some spindle units are partially occupied by the iron-containing catalyst particles at the hemispherical-like ends. An improved stress-induced sequential growth model has been reasonably deduced accordingly, with which the formation process of this novel BN nanostructure could be well understood.

A chemical method has been developed for synthesizing boron nitride nanowires through the reaction of a mixture gas of nitrogen (N2) and ammonia (NH3) over nanoscale a-FeB particles at 1100℃. Boron content in the product comes from the a-FeB catalyst itself. Transmission electron microscopic image indicates an abundant quantity of BN nanowires with diameter about 20nm and length up to several tens of microns. The product has also been characterized by high-resolution electron microscopy and electron energy loss spectrometer. The perfectly straight lattice fringes with an interlayer spacing of about 0.333nm corresponding to d0002 spacing of h-BN indicate that the BN nanowires are well crystallized. Also, a growth mechanism has been speculated.

Gallium phosphide nanotubes with zinc blende structure were synthesized for the first time. The as-prepared GaP nanotubes are polycrystalline with diameters of 30-120nm and occasionally partially filled. The growth has been reasonably proposed to follow vapor-liquid-solid (VLS) mechanism. The integration of the nanotubular structure with the unique intrinsic semiconducting properties of GaP might bring GaP nanotubes some novel optical and electronic properties and applications.