2nd International Conference on Surfaces, Coatings and Nanostructured Materials

9-11 July 2007

Alvor, Algarve, PORTUGAL (www.nanosmat.org)

ABSTRACTS BOOK

Edited by:

Dr Nasar Ali Chairman, NanoSMat 2007

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observed with the swift heavy ion irradiation too. The results will be discussed in terms of energy transfer from the incident ion beam etc. Characterizations of GaN nanowires with Mg ion implantation P. J. Huang1, C. W. Hsu2, C. J. Pan3, S. C. Hung1, C. C. Kuo4, C. P. Chen2, L. C. Chen4,*, K. H. Chen2, and G. C. Chi1 1Department of Physics, National Central University, Jhongli, Taoyuan 32001, Taiwan 2Institute of Atomic and Molecular Sciences, Academia Sinica, Taipei 10617, Taiwan 3Optical Sciences Center, National Central University, Jhongli, Taoyuan 32001, Taiwan 4Center for Condensed Matter Sciences, National Taiwan University, Taipei 10617, Taiwan *E-mail: chenlc@ccms.ntu.edu.tw GaN nanowires were grown by thermal catalytic chemical vapor deposition on Si (100) substrate with Au catalyst [1]. The resulting nanowires have the diameters of 60-150 nm and the lengths of 15-20 μm. An energy of 60 keV Mg ions were implanted into the GaN nanowires with various total flux of 5×1012 cm-2 to 5×1014 cm-2. Subsequent thermal annealing treatment was carried out by a furnace at 800°C for 6 min in N2 ambient. Transmission electron microscopy image shows that cluster with the diameter of about 5 nm were formed in annealing Mg-implanted GaN nanowires. Room temperature photoluminescence (PL) spectra of the annealed Mg-implanted GaN nanowires exhibits near-band-edge (NBE) emission, donor- acceptor pair (DAP) transition emission [2], and yellow luminescence (YL), while the as-grown GaN nanowires exhibits only NBE emission at 3.37 eV. With increasing the dose of implantation from 5×1012 cm-2 to 5×1014 cm-2, NBE and DAP emissions shift from 3.32 eV to 3.29 eV and from 3.05 eV to 2.95 eV, respectively. Similar phenomenon of red shift of NBE emission was also observed in Ar-implanted GaN nanowires with the peak position at 3.32 eV. Thus, the red shift of NBE emission might be due to the damage from ion implantation. The YL band shifts from 2.04 eV to 2.34 eV with increasing the dose of implantation from 5×1012 cm-2 to 5×1014 cm-2. The blue shift of YL band might be attributed to the Mg ion implantation induced cluster [3], which was observed in the TEM image. Research on the processing mechanism of nanostructure nickel prepared by spark plasma sintering Zhao-Hui Zhang, Ying Liu, Fu-Chi Wang, Shu-Kui Li School of Material Science and Technology, Beijing Institute of Technology, Beijing 100081, PR China The sintering process of nano-nickel (Ni) powder compacts was investigated by spark plasma sintering (SPS) with high pressure (800-1000MPa) and low temperature. The behavior and activation energy of the grain growth of the nano-Ni powder during the SPS process were analyzed. The microstructure and grain size were examined by SEM and TEM. The densification mechanism was discussed. The results indicate that the uniform, dense and large-scale (60mm in diameter and 30mm in depth) nanostructured production with good mechanical properties can be obtained under certain processing parameter conditions. It is the effect of the high pressure and pulsed current that improves the activity on grain surface, hence significantly deduces the sintering temperature and the activation energy of grain growth. Synthesis of One-Dimensional Nanostructures by Extended Vapor-Liquid-Solid Growth Kaifu Huo1, 2, 3, Zheng Hu1, Paul K Chu 3*, and Yi Chen1

1Key Laboratory of Mesoscopic Chemistry of MOE and Jiangsu Provincial Laboratory for Nanotechnology, Nanjing University, Nanjing 210093, China, 2Hubei Province Key Laboratory of Ceramics and Refractories, College of Materials and Metallurgy, Wuhan University of Science and Technology, Wuhan 430081,China 3Department of Physics & Materials Science, City University of Hong Kong, Hong Kong Electronic mail: paul.chu@cityu.edu.hk

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Vapor-liquid-solid (VLS) growth is one of the most effective techniques to synthesize one-dimensional (1-D) nanostructures. At an elevated temperature, the catalyst exists in the liquid phase and precursors in the vapor phase decompose preferentially at the vapor-liquid (catalyst) interface depositing the constituent component(s) into the liquid-flux catalyst droplets. Supersaturation then leads to whisker-like growth at the liquid-solid interface yielding the lowest interface energy. In VLS growth, the liquid catalyst acts as a medium to transport the component(s) from the vapor precursor(s) to whisker-like solid product. We have recently extended this traditional VLS growth by introducing alloy particles as the catalyst. Some 1-D nanomaterials such as BN Nanowires and nanotubes, AlN nanowires and Si3N4 nanobelts have been synthesized by simply nitriding Fe-B, Ni-Al and Fe-Si alloy particles at high temperature with NH3/N2, respectively. In the extended VLS technique, the alloy catalyst not only acts as the medium for component transport from vapor to solid as in the case of traditional VLS growth, but also supplies partial component(s) to produce the final solid product. In other words, a chemical reaction between the component(s) from the vapor precursor(s) and the catalyst takes place within the liquid catalyst, and the resulting products precipitate with a whisker-like morphology when supersaturation is reached. Strictly speaking, the alloy particle here is not a catalyst but rather a reactant, because the partial component in the alloy is consumed after the chemical reaction. This extended VLS growth technique provides a versatile means to prepare compound nanostructures and will be described in this presentation. Synthesis of Hierarchical Tree-like and Jellyfish-like Silicon Oxide Nanostructures Kaifu Huo1, 2, 3, Zheng Hu 1, Paul K Chu3*, and Yi Chen1

1Key Laboratory of Mesoscopic Chemistry of MOE and Jiangsu Provincial Laboratory for Nanotechnology, School of Chemistry and Chemical Engineering, Nanjing University, Nanjing 210093, China, 2Hubei Province Key Laboratory of Ceramics and Refractories, College of Materials and Metallurgy, Wuhan University of Science and Technology, Wuhan 430081,China 3Department of Physics & Materials Science, City University of Hong Kong, Tat Chee Avenue, Kowloon, Hong Kong * paul.chu@cityu.edu.hk Hierarchical tree-like and jellyfish-like SiOx nanostructures have been synthesized by annealing a mixture of carbon-coated Ni nanoparticles (Ni@C) and SiO2 powers under argon at 1400 oC. The as-synthesized products are characterized by electron microscopy, energy-dispersive X-ray spectroscopy (EDS) and X-ray photoelectron spectroscopy (XPS). Tree-like SiOx nanostrcutures consisting of trunks and many branches and subbranches with diminishing diameters are first observed and reported. The diameters of the trunks are about 150~1000 nm, and the branches become slender with branching ultimately reaching diameters of 20~40 nm at the ends. The jellyfish-like SiOx nanostructures are constructed by catalyst ‘heads’ of about 1~10 μm and many connected quasi-aligned SiOx nanowires with diameters of about 20~40 nm. The Ni of the Ni@C nanoparticles acts as the catalyst and the surface carbon as the reducing agent in the carbo-thermal reduction of SiO2. Our experimental results suggest that the formation of different SiOx nanostructures mainly depend on the dimensions of the congregated Ni catalyst droplets during the reaction process and the growth mechanism is discussed. Photodegradation of VOCs by C_TiO2 nanoparticles by Flame CVD Process XIE Hongyong Department of Environmental Engineering, Shanghai Second Polytechnic University, 2360 Jin Hai Road, Pudong, Shanghai 201209, China E-mail: hyxie@163.com C_TiO2 nanoparticles with rutile mass fraction about 20% and carbon mass fraction about 5%.are synthesized by industrial propane/air flame CVD process. The size obtained by counting particles from TEM pictures shows that size of C_TiO2 nanoparticles is close to normal distribution with mean