Hongbo Huang

Crystalline nanotubes of γ-AlOOH and γ-Al2O3: hydrothermal synthesis, formation mechanism and catalytic performance

Crystalline nanotubes of gamma-AlOOH and gamma-Al(2)O(3) have been synthesized. An anionic surfactant-assisted hydrothermal process yields gamma-AlOOH nanotubes, and appropriate calcination treatment of the gamma-AlOOH nanotubes yields gamma-Al(2)O(3) nanotubes. The nanotubes were characterized by XRD, SEM, TEM, TG-DSC, FTIR and nitrogen adsorption-desorption techniques. Both the gamma-AlOOH and gamma-Al(2)O(3) nanotubes are crystalline, with a representative length of approximately 500 nm and diameters of 20-40 nm. The gamma-Al(2)O(3) nanotubes exhibit a very high mesoporous specific surface area (SSA) of 201.0 m(2) g(-1) and a high mesopore volume of 0.68 cm(3) g(-1) with an average mesopore size of 27.7 nm, as well as a high microporous SSA of 186.0 m(2) g(-1) and a micropore volume of 0.08 cm(3) g(-1) with an average micropore size of 0.53 nm. The formation process was discussed and a possible mechanism was proposed, in which a lamellar phase was first formed by camphorsulfonic anions and Al(III) species, and then rolled up to form the crystalline nanotubes under the hydrothermal condition. The catalytic performance of the obtained gamma- Al(2)O(3) nanotubes was tested by using the dehydration of ethanol to ethylene as a probe reaction and it was shown that the obtained gamma- Al(2)O(3) nanotubes catalyst possesses a higher catalytic activity compared with the gamma- Al(2)O(3) nanoparticles.

Metal nanotubes prepared by a sol?gel method followed by a hydrogen reduction procedure

A sol?gel method followed by a hydrogen reduction procedure was proposed in this work for the preparation of metal nanotubes. The tube length, diameter, wall thickness and, most importantly, the chemical components can be adjusted conveniently. Several examples of metal nanotubes (Fe, Ni, Pb and CoFe) were prepared by using anodic aluminium oxide (AAO) templates. The fabricated nanotubes are uniform in diameter and wall thickness through the entire tubes. The length of the nanotubes is about 100??m, with an aspect ratio of about 1000.

Multiform structures of SnO2 nanobelts

Multiform SnO2 microstructures were synthesized by a facile thermal evaporation of tin grains. The product was characterized with a variety of techniques to obtain the structural and optical information. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) images showed a large percentage of acute angle zigzag nanobelts with perfectly periodic morphology. High resolution transmission electron microscopy (HRTEM) images and selected area electron diffraction (SAED) patterns revealed that the zigzag nanobelts were single crystalline and their zone axis was along the [010] crystal direction. The growth mechanism of zigzag nanobelts was proposed based on TEM characterization and thermodynamic analysis. The zigzag nanobelts were deduced to be formed by changing the growth direction from to [101] or vice versa. The photoluminescence (PL) spectroscopy of the nanobelts showed a broad and strong luminescence emission centred at 550?nm.

Zinc nanoplates synthesized by a micro-jet under electron-beam irradiation

Zinc nanoplates with interesting shapes have been successfully synthesized by irradiating Zn/ZnS core/shell microballs with electron beams in a transmission electron microscope. The structure characterization reveals that the nanoplates present a wurtzite phase covered with a thin ZnO layer. A systematic study on the microballs has been performed and a formation mechanism for these nanoplates has been proposed. The e-beam radiation technique provides a novel approach for fabrication of novel nanostructured materials.

Mössbauer Studies on High Temperature Solution Grown Pb(Fe 1/2 Nb 1/2 )O 3 Single Crystals

Single crystals of Pb(Fe 1/2 Nb 1/2 )O 3 (PFN) are grown from high temperature solution with PbO as flux. Mössbauer study on the powder samples of Pb(Fe 1/2 Nb 1/2 )O 3 single crystals has been made. It proves that the ferromagnetic phase transition temperature is below 150 K. The temperature dependence of the quadrupole splitting of the PFN samples shows the iron ions in PFN single crystals is in Fe 3+ high spin state. The calculation proved that the B site niobium ions and iron ions are randomly distributed.

Layered tin dioxide microrods

Single-crystalline layered SnO2 microrods were synthesized by a simple tin?water reaction at 900??C. The structural and optical properties of the sample were characterized by x-ray powder diffraction, energy-dispersive x-ray spectroscopy, scanning electron microscopy, high resolution transmission electron microscopy, Raman scattering and photoluminescence (PL) spectroscopy. High resolution transmission electron microscopy studies and selected area electron diffraction patterns revealed that the layered SnO2 microrods are single crystalline and their growth direction is along [1 1 0]. The growth mechanism of the microrods was proposed based on SEM, TEM characterization and thermodynamic analysis. It is deduced that the layered microrods grow by the stacking of SnO2 sheets with a (1?1?0) surface in a vapour?liquid?solid process. Three emission peaks at 523, 569 and 626?nm were detected in room-temperature PL measurements.