Yuzhen Lv

TiO2 nanoparticle induced space charge decay in thermal aged transformer oil

TiO2 nanoparticle with good dispersibility and stability in transformer oil was prepared and used to modify insulating property of aged oil. It was found that space charge decay rate in the modified aged oil can be significantly enhanced to 1.57 times of that in the aged oil at first 8 s after polarization voltage was removed. The results of trap characteristics reveal that the modification of nanoparticle can not only greatly lower the shallow trap energy level in the aged oil but also increase the trap density, resulting in improved charge transportation via trapping and de-trapping process in shallower traps.

Low temperature synthesis and optical properties of small-diameter ZnO nanorods

Small-diameter ZnO nanorods (∼10nm) with lengths of 80–100nm were synthesized by a simple solution route at low temperature (61.2°C). X-ray diffraction and high-resolution transmission electron microscopy analyses confirmed that the nanorods are hexagonal single crystals with a growth direction along [001]. Room temperature photoluminescence (PL) measurement showed a strong ultraviolet (UV) emission peak at 382nm with weak deep level emission. Quantum confinement effect in the ZnO nanorods was clearly revealed by low temperature PL. The complex origin of the UV peak has been discussed based on the temperature-dependent photoluminescence measurements.

Nanostructured stars of ZnO microcrystals with intense stimulated emission

We demonstrate the synthesis of single-crystalline star-shaped ZnO microcrystals with six arms by a simple solution method. Microscopic and diffraction data reveal that the as-grown products have a wurtzite structure. Each arm of the ZnO microstars has a sharp tip of several nanometers. Under moderate optical excitation, stimulated emission was observed at 388.4nm with a full width at half-maximum (FWHM) of less than 3nm and a threshold of 318kW∕cm2.

Effect of nanoparticles on charge transport in nanofluid-impregnated pressboard

Transformer pressboard impregnated in mineral oil modified by nanoparticles (nanofluid) exhibits substantially higher AC and DC breakdown voltage than that of the pure oil-impregnated pressboard (OP). Charge transport and decay characteristics of both pressboards were measured by pulse electroacoustic technique. It reveals that nanofluid-impregnated pressboard (NP) has a more uniform internal electric field and a higher charge decay rate compared to OP, which is caused by an increase of shallow trap density in NP related to the difference of internal structures, based on the test results of thermally stimulated current and Fourier transformed infra-red spectroscopy.

Shape Evolution of ZnO Nanostructures Modified by Trioctylphosphine Oxide

Beijing University of Aeronautics and Astronautics, Beijing 100080, China 2 Max-Planck-Institute for Chemical Physics of Solids, Dresen, 01187, Germany sunny@mse.buaa.edu.cn, jiyunliang@163.com, licp@buaa.edu.cn, guolin@buaa.edu.cn, xuhb@buaa.edu.cn, simon@cpfs.mpg.de

MORPHOLOGY CONTROLLING AND OPTICAL CHARACTERIZATION OF ZnO NANOMATERIALS

Wurtzite ZnO nanomaterials including nanoparticles, nanocolumns and nanorods were successfully synthesized by a solution route. Concentrations of modifying reagent and differences of solvent employed in the synthetic process can effectively adjust the morphologies of the as-grown products. Photoluminescence measurements of the ZnO nanocolumns and nanorods have been carried out at room temperature. A sharp Ultraviolet emission at 386 nm and a weak visible emission centered at 515 nm were observed in the PL spectrum of the nanocolumns, while a UV emission of the nanorods was observed at 377 nm.