Papers by Keyword: Nanotube

Abstract: In this paper, we report the structural and optical properties of bamboo-like silicon-doped boron nitride nanotubes. The morphologies and structures of the nanotubes were characterized using electron microscopy and FTIR spectroscopy. Three strong broad peaks centered at 1.76ev, 2.20ev, 2.40ev were observed from the room-temperature PL spectrum of the nanotubes. The spectrum suggested the existence of multifold energy levels within the band gap.

Abstract: TiO₂ nanotube arrays were fabricated by anodic oxidation. It was studied that the influences of the parameters for the preparation of TiO₂ nanotube arrays on the micrograph of the material, such as anodizing potential, annealing temperature. Then it is used in the dye sensitized solar cell (DSSC).The microstructures and morphologies of the TiO₂ nanotubes were investigated by scanning electron microscopy (SEM) and x-ray diffraction (XRD). The results show that TiO2 nanotubes arrays were fabricated when anodizing voltage is 20V. The photoelectric conversion efficiency _{Subscript text}of DSSC made by this structure is 1.53%, the open voltage is 0.734V, short-circuit current is 4.52mA, fill factor is 0.460.

Abstract: Using Zn nanowires as a self-sacrificed template, hierarchical tubes constructed by zinc oxide (ZnO) nanoflakes and ZnO nanotubes have been successfully fabricated by two different thermal-oxidation modes. The products were characterized by the X-ray powder diffraction, transmission electron microscopy and field-emission scanning electron microscopy. The experimental results show that the formation processes of ZnO nanostructures are sensitive to the growth temperature, which is lower or higher the melting point of Zn (419 °C). Our method provides an easy and convenient way to prepare metal oxides tubular nanostructures with different morphologies through self-sacrificed template method via adjusting the heat-treatment process.

Abstract: Copper sulfide (CuS) nanotubes assembled by nanoparticles were successfully synthesized by reaction thiourea with Cu(OH)₂ nanowire precursor which was obtained using CuCl₂ and NaOH as raw materials in the solvent ethylene glycol at 80 °C by a facile microwave-assisted solvothermal method. The forming influencing factors of CuS nanotubes were investigated. One of the advantages of this method is that the preparation of CuS nanotubes can well duplicate the shape of the nanowire precursor, thus the simplicity and low cost can be achieved. The products are characterized by X-ray powder diffraction (XRD) and transmission electron microscopy (TEM). The photocatalytic property of the CuS samples was also investigated.

Abstract: Field emission property of Ga-doped carbon nanotube (CNT) film has been studied and compared with those of un-doped, N-doped as well as B and N co-doped CNT films. It is found that the Ga-doped CNT film exhibits superior field emission property to the other films. The turn-on field for Ga-doped CNT film is well below 1.0 V/μm, lower than those for un-doped (2.22 V/μm), N-doped (1.1 V/μm), B and N co-doped (4.4 V/μm) CNT films. Its current density reaches 5000 μA/cm² at 2.6 V/μm which is well above those for un-doped (1400 μA/cm²), N-doped (3000 μA/cm²) as well as B and N co-doped (2) CNT films at applied electric field of 5.7 V/μm. First principles calculations were carried out to obtain the binding energy and electronic nature altering of a CNT by Ga doping. It is shown that Ga-doped CNT (8,0) alters from semiconductor to intrinsic metal and a binding energy of 2.7527 eV is obtained. The field emission property can not simply be explained by the defect concentration, but can be understood by significant altering in the local density of states near the Fermi level introduced by dopants.

Abstract: In the present work, we demonstrated a facile process to prepare an open-ended high aspect-ratio TiO2 nanotube films through separating the anodic TNT array from the Ti substrate by a small reverse bias and opening the tube bottom by a chemical etching. The possible mechanisms of film detachment and pore opening processes have been briefly discussed. Such a process allows controlling the open-ended morphology by the straightforward chemical etching, which shows great potential in many applications, such as flow-through photocatalytic reactions, biofiltration, and diffusion controlling, and so on. An example using the open-ended TNT films is finally given as a flow-through photocatalytic reactor. The photocatalytic film has been shown to have multiple functions such as physical separation of contaminants, filtration, and decomposition of organic pollutants during diffusion.

Abstract: Carburization of silicon nanowires (NWs), with diameters of about 800 nm and lengths of about 10 µm, under methane at high temperature in order to obtain silicon carbide (SiC) nanostructures is reported here. The produced SiC nanostructures display a tubular shape and are polycrystalline. The as-prepared silicon carbide nanotubes (NTs) were characterized and studied by scanning electron microscopy (SEM), dual focused ion beam – scanning electron microscope (FIB-SEM), transmission electron microscopy (TEM) and Raman spectroscopy. The formation of nanotubes can be explained by the out-diffusion of Si through the SiC during the carburization process.

Abstract: Au supported titania composite photocatalyst was prepared by one-pot synthesis method where titanate nanotubes as supports and which was subsequently transformed into anatase TiO₂ during the water vapor treatment. The composite was characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM) and N₂ isothermal adsorption-desorption. Au nanoparticles in the crystallite size of 10-15 nm were uniformly deposited onto the surface of titanate nanotubes or anatase TiO₂ nanoparticles. Some nanotubes were kept even at 120 °C and the composite had specific surface areas ranged from 163 to 310 m².g¹ depending on the vapor temperature. The photocatalytic activity of the composite photocatalyst was evaluated in the degradation of dyes acid red G (ARG) and methylene blue (MB) under UV irradiation. Au supported TiO₂ had good adsorption ability to dyes, and showed an enhanced photocatalytic efficiency compared to the pristine titanate nanotubes.

Abstract: Carbon coated N-doping of TiO₂ nanotube films were successfully prepared by a two-step process of anodization and gas thermal penetration. The morphologies and structures of composites were characterized by SEM, XRD, XPS and Raman spectroscopy analyses, respectively. The results show that graphitized carbon deposited on the surface of TiO₂NTs nanotubes under gas thermal penetration conditions, by which N atoms are incorporated into the lattice of TiO₂NTs through substituting the site of oxygen atoms. Such Carbon coated N-doping of TiO₂ nanotube films presents the enhance absorption in visible region. The photo catalytic tests show that the prepared films at 600°C reveal higher photocatalytic activity for splitting of water than other samples.

Abstract: In this work, the effect of water content from < 1 to 100 vol% on the electrochemical anodization of titanium in ethylene glycol-based electrolyte was investigated. The samples were characterized using X-ray diffraction (XRD) and their dimensional change was monitored by field emission scanning electron microscopy (FE-SEM). It was found that the microstructure and morphology of TiO2 varies dramatically with the water content. Nanotubes become less ordered with increasing water content up to 50 vol%. At 75 vol% water, only porous structure could be observed. Most importantly, at fixed applied voltage, smoother but relatively longer tubes can be grown with lower water content. Varying water content has no effect on the crystalline phase of the resulted nanotubes. However, the intensity of anatase (101) peak increases with increasing water content, indicating better crystallinity of samples. Nanotubes obtained in 50 vol% water exhibit the highest photoresponse when tested using linear sweep photovoltammetry due to enhanced microstructure and crystallinity.