Solid State Phenomena Vols. 121-123

Abstract: Bamboo-shaped carbon nanotubes (BCNTs) have been synthesized by chemical vapor deposition method. The activated BCNTs after simple ball milling and KOH etching are used as polarizable electrodes in electric double layer capacitor (EDLC). Our results show that the specific capacity of BCNTs can be improved by the activation treatment.

Abstract: The carbon-nanofibers carrying Ag nanoparticles (Ag/CNF) have been successfully obtained via electrospinning followed by calcination. For it, AgNO3/polyacrylonitrile (PAN) fibers were firstly prepared as an intermediate and then the intermediate was calcined at 600°C for 4h to transit the PAN nanofibers to the CNF and reduce AgNO3 to the Ag nanoparticles. Transmission electron microscope (TEM), Fourier transform infrared (FTIR) spectroscopy and X-ray diffraction (XRD) were used to characterize their morphologies and structures. The results show that the diameters of the Ag nanoparticles and CNF are 5 nm and 180 nm on the average, respectively. Most of the Ag nanoparticles were located on the surface of carbon nanofibers.

Abstract: In-doped ZnO nanodisks were successfully fabricated by thermal evaporation Zn, In2O3 and graphite powder mixture without catalyst. Morphology, structures and components of ZnO nanodisks were investigated by SEM, HRTEM, EDS and X-Ray diffraction. ZnO nanodisks have perfect hexagonal shape, with 1~3μm size and 40~100 nm in thickness. The nanodisks are single-crystalline ZnO with wurtzite structure and In content of nanodisks reaches 2.2%. The growth along [0001] is suppressed leading to the formation of ZnO nanodisks. Room temperature photoluminescence spectra of the nanodisks shows that the UV emission peak blueshifts and becomes broader after doping.

Abstract: A highly uniform Fe antidot array with a density up to 1.2×1010/cm2 was fabricated by RF magnetron sputtering deposition of Fe film on porous anodic aluminum oxide (AAO). Scanning electron microscopy (SEM) images show the deposited Fe film was well patterned by AAO template with antidots arranged in a hexagonal manner. Further investigation by transmission electron microscopy (TEM) reveals that the deposited Fe film has polycrystalline microstructure with random orientation. The patterned Fe film with antidots exhibits peculiar magnetic reversal features in both the increasing of coercive field (Hc) and the decreasing of remanent magnetization in comparison with the continuous Fe film of the same thickness on glass substrate. A dramatically large out of plane Hc of 280Oe which might be caused by the cylindrical Fe structures formed in AAO channels was observed.

Abstract: In this article stable multi-walled carbon nanotubes (MWNTs) aqueous suspension with a 1.0 wt.% concentration was obtained with a very small quantity of dispersant. Precursor of ceramics were synthesized in the suspension and densely deposited on the surface of MWNTs successfully by a simple and effective in-situ precipitation method. The most important advantage for the in-situ composite method is to make MWNTs homogeneously distributed in the matrix. The fully dense compacts were obtained by spark-plasma-sintering (SPS) the in-situ precipitated composite powders at temperature 200 oC lower than that of composite powders made from the traditional mixing method. Furthermore, the microstructure and the mechanical property of the composites are much better than that of traditional method. The in-situ precipitation could be a promising method to fabricate CNTs composites of ceramics matrix especially those hard to sinter.

Abstract: A safe, common, and low-cost method was proven to be effective for the synthesis of high quality CdSe nanocrystals. Cd(Ac)2 and Lauric acid were found to be the excellent cadmium precursor and solvent/ligand, respectively. The size and shape of CdSe nanocrystals synthesized by this route can be varied in a controllable manner in a broad size range, from about 2.0 nm to 4 nm. The growth kinetics of CdSe nanocrystals nucleated from TOPSe and cadmium acetate was also investigated in Lauric Acid. The rate constant for steady-state CdSe growth was found to be 4.15×10─8 m s─1 at 260°C.

Abstract: Many preparations of carbon nanotubes have been developed in the last decade, such as arc discharge, plasma-enhanced chemical vapor deposition, simple thermal chemical vapor deposition by pyrolysis of ethyl alcohol, etc. Here we present a simple growth technique of carbon nanotubes by combustion of ethyl alcohol. Pt filament can be employed as substrate, ethyl alcohol as carbon source, and iron nitrate as catalyst precursor. We have characterized the morphology of carbon nanotubes at the different synthesis conditions by both SEM and TEM. In our experiment, we also use other metal as substrate, such as Cu, top of pin, and other catalyst precursor of different concentration, such as nickel nitrate. This technique has some advantages, such as low cost, large production, and flexible reaction conditions, etc. We can use this technique to synthesize carbon nanotubes on metal substrate directly. So this technique has protential applications for fabricating nano-electrical devices.

Abstract: By adding methyl alcohol/water solution with certain concentration into sol to hydrolysis directly and sintering the fresh sol directly, lead titanate(PbTiO3) ceramics doped with magnesium are prepared by using magnesium acetate as doper to prohibit the disadvantages contained in conventional sol-gel method, such as low hydrolytic rate, high sintering temperature, long preparation period. The changes of structure, microstructure, synthesis process and electric properties of modified ceramics are studied in detail. The sizes and morphology of high purely and high density magnesium doped lead titanate nanocrystals thus obtained are observed by TEM photographs and the structures and affection of sintering temperature of to lattice constant and sizes of nanocrystals are detected by XRD. Electric properties detection results show that doped lead titanate ceramics exhibite excellent dielectric, ferroelectric and pyroelectric properties compare with pure lead titanate.

Abstract: GNFs with fish-bone structure were first produced by a simple method. To optimize the growth conditions, different hydrogen treatment of the catalyst, different growth time and growth temperature, as well as different gas flow rate were employed. The effects of these growth conditions on the morphology and yield of GNFs were studied in details. It is found that fish-bone GNFs with high yield and high purity can be produced under the optimized conditions.

Abstract: WC-10Co nanocomposite powders prepared by spray pyrogenation-continuous reduction and carburization technology were consolidated by vacuum sintering plus hot isostatic pressing (HIP). Influences of ball-milled time on properties and microstructure of ultrafine WC-10Co cemented carbide were investigated. The results show that ultrafine WC-10Co cemented carbides can reach 99.79% relative density, and transverse rupture strength is more than 3750MPa, Rockwell A hardness is more than 92.6, the average grain size is less than 440 nm, when ball-milled time is 48 hours, ultrafine WC-10Co cemented carbide with excellent properties and fine microstructure is obtained. The optimum ball-milling time is 48 hours.