C. Tang

Morphology-?and composition-controlled synthesis of aluminium borate nanowires without catalysts

To depress evaporation of boron oxide during the high-temperature synthesis of borates, a sol?gel route followed by calcination was used to grow various aluminium borate nanowires. The morphology and structure of Al4B2O9 and Al18B4O33 nanowires could be controlled by adjusting the boron oxide content in the sol?gel derived precursors and the calcined temperature. Fine Al4B2O9 nanowires with an average diameter of ~20?nm were obtained by the calcination of Al2O3?2B2O3 xerogel at 1100??C, whereas heat treatment at the same temperature for Al2O3?B2O3 xerogel gave rise to Al18B4O33 nanowires with an average diameter of ~30?nm. The morphology and composition dependence were investigated by x-ray diffraction, thermogravimetric and Brunauer?Emmett?Teller surface area analyses, and various microscopy techniques. A possible growth mechanism was also proposed based on high-resolution transmission electron microscopy observations.

Synthesis of BN nanobamboos and nanotubes from barium metaborate

Abstract Nanobamboo and nanotube structures of BN have been controllably synthesized by reaction of barium metaborate with ammonia. The gallium addition plays an important role in the formation of nanotubes. The experimental results indicate that, without the gallium additive, the reaction results in the growth of nanobamboo structure. Gallium addition, probably as a catalyst within the framework of vapor–liquid–solid growth, promotes the growth of nanotubes. High-solution transmission electron microscopy research indicates that rhombohedral stacking order is the dominant atomic arrangement for BN nanobamboos; whereas hexagonal stacking is the dominant arrangement for BN nanotubes.

From Al4B2O9 nanorods to AlOOH (boehmite) hierarchical nanoarchitectures

Complex hierarchical nanoarchitectures of AlOOH (boehmite) have been synthesized from the prefabricated Al4B2O9 nanorods based on a hydrothermal self-assembled process without employing any templates/substrates or surfactants. XRD patterns, SEM and TEM images were used to characterize the products. The boehmite nanostructures which exhibit two hierarchies are built by small crystal strips that contain even smaller one-dimensional nanorods. The length of the small crystal strips is about 2 µm and their diameter is about 100 nm in the middle section. Our investigation shows that the Al4B2O9 nanorods could separate the process of nucleation and growth, which is favoured for the formation of the hierarchical self-assembled nanoarchitectures. The growth mechanism has been proposed by the detailed microscopy observations. The thermal stability of the Al4B2O9 nanorods under hydrothermal conditions has also been discussed.

Characterization and photoluminescence properties of aluminum borate nanorods doped with Eu

Aluminum borate (Al18B4O33) nanorods doped with Eu3+ and Eu2+ were synthesized via a simple calcination method. Both nanorods are of straight morphology and smooth surface, with the average diameter of ∼80nm. The structural and compositional characteristics have been investigated by x-ray diffraction, infrared spectra, and various microscopy techniques. A possible growth mechanism was proposed for the synthesis of the doped Al18B4O33 nanorods. Photoluminescence measurements indicate that Al18B4O33:Eu3+ nanorods exhibit emission peaks at 590, 595, 612, and 617nm, and Al18B4O33:Eu2+ nanorods display a broad green emission band centered at ∼540nm.

A novel method for preparing carbon-coated germanium nanowires

Single-crystalline Ge nanowires covered with amorphous carbon were synthesized by using GeO2 as the Ge source and reacting it with a mixed gas of C2H4 and NH3 at 750 °C. Electron microscopy studies show that the nanowires have a diameter distribution ranging from 15 to 50 nm and a length up to tens of micrometres. The growth mechanism of the Ge nanowires could be attributed to the well known vapour–liquid–solid (VLS) catalytic growth process promoted by nanoparticles attached at the end of the nanowires.