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Abstract: In the present paper, we will introduce the synthesis and application of carbon nanotubes as filler for nanocomposite materials. Physical and chemical properties such as mechanical strength, thermal and electrical conductivity, chemical stability, density and affinity with the matrix vary a lot among different types of carbon nanotubes. We first will overview the main component of nanocomposite, carbon nanotube and its synthesis and purification, and introduce some of the nanocomposites and its applications that we have taken part in the development. [Copyright &y& Elsevier]

Lithium-doped K0.5Na0.5NbO3 (KLNN) films were fabricated by chemical solution deposition on Pt/TiO2/SiO2/Si substrates. Homogeneous and stable precursor solutions were prepared by controlling the reaction of starting metal alkoxides. Perovskite KLNN single-phase thin films were successfully synthesized on Pt/TiOx/SiO2/Si substrates. The 0.75-μ m-thick KLNN film annealed at 650°C exhibited ferroelectric polarization hysteresis loops at -250°C. The loop at room temperature was round, indicating the film contained leakage components. The dielectric constant under zero bias was 490 at room temperature. A typical upside-down butterfly DC bias-capacitance curve was obtained in the KLNN film capacitors at room temperature, indicating that polarization reversal occurred in the obtained KLNN films. [ABSTRACT FROM AUTHOR]

Abstract: Here we describe synthesis of very unusual multi-walled carbon nanotubes through a catalytic chemical vapor deposition method using a floating reactant method and subsequent thermal treatment up to 2600°C in a large quantity. Main characteristics of these nanotubes are (1) relatively wide distribution of diameters ranging from 20 to 70nm and linear, long macro-morphology (aspect ratio >100), (2) highly straight and crystalline layers, (3) high purity through removal of metallic impurity, (4) very low interlayer spacing (0.3385nm) and low R value (I D/I G =0.0717), (5) high G′ intensity over intensity of G band (G′/G=0.85) and strongly negative magnetoresistance value of −1.08% at 77K and 1T. The unusual microstructure of thin multi-walled carbon nanotubes with a partially facetted cross-sectional shape caused by thermal treatment is mainly ascribed to abrupt density changes (from 1.89 to 2.1g/cm3) within a confined nanosized space, accompanying with the phase separation. [Copyright &y& Elsevier]

Highly disordered carbon nanotube is obtained through a catalytic thermal chemical vapor deposition method, especially, using the floating reactant method. The results of annealing highly disordered carbon nanotube are (1) removal of metallic compounds, (2) structural conversion into multi-wall carbon nanotube with a little faceted cross-section, and (3) development of a tug morphology in carbon nanotubes. The characteristic observed in annealed multi-wall carbon nanotubes make them useful as a filler in advanced composite. [Copyright &y& Elsevier]

Cone-stacked nanotubes with thick layers of deposited carbon obtained by a catalytic chemical vapor deposition method are annealed at high temperature. Phase separation between cone-stacked nanotubes and amorphous carbon layers occurs during annealing due to different structural transformation behaviors, resulting in the formation of multi-wall carbon nanotubes containing a cone-type multi-shell arrangement. The apex angles of the nanocones are about 40°. This type of carbon nanotube shows different physical and electrical properties. [Copyright &y& Elsevier]

Very different types of straight and long multiwalled carbon nanotubes, ranging from semi-crystalline to highly crystalline, are obtained using a floating reactant method, by merely changing the flow rate of the carrier gas. Graphitization behaviors of these nanotubes are studied comparatively in terms of their microstructure and morphology, showing a large change in structure for the semi-crystalline nanotubes, but little change in the highly crystalline nanotubes with heat treatment. © 2001 American Institute of Physics. [ABSTRACT FROM AUTHOR]

Abstract: We present a high temperature heat treatment study of CVD-grown graphene nanoribbons annealed up to 2800°C, demonstrating a progressive annihilation of lattice defects as the heat treatment temperature is raised. Starting at 1500°C, single and multiple loop formation were observed on the ribbons edges as the temperature was increased. The structural changes of the samples are documented by X-ray diffraction, Raman spectroscopy, TGA, SEM, and HRTEM. This work indicates that nanoribbon annealing eventually leads to defect-free samples, through graphitization and edge loop formation. The annealed material exhibits structural differences that could be tailored for a variety of specific applications. [Copyright &y& Elsevier]

Abstract: Hydrogenated microcrystalline silicon (µc-Si:H) films were prepared by inductive coupled plasma chemical vapor deposition (ICP-CVD) system using internal low inductance antenna (LIA) units on various under layer composed of Si, O, and N. The resultant changes in the crystallinity of the µc-Si:H films were investigated using Raman scattering spectroscopy and the details of the interface structure were observed by high resolution transmission electron microscope. We had found that µc-Si:H film on the SiN x layer treated by O2 plasma has good interface quality. The highly crystallized µc-Si:H films with no amorphous incubation layer at interface of Si/SiN x could be directly deposited on the SiN x layer. [Copyright &y& Elsevier]

Abstract: Compositional changes of the residual iron compounds in isothermally treated catalytic chemical vapor deposition derived multi-walled carbon nanotubes have been monitored using 57Fe transmission Mössbauer spectroscopy and X-ray fluorescence. The iron phases entrapped in the as-synthesized carbon nanotubes consist of γ-iron, α-iron, Fe3C and Fe1−x S. The Fe1−x S phase decomposes completely around 1500°C while the iron carbide phase decomposes in the temperature range of 1500–2400°C. The obtained apparent activation energy of ca. 76kcal/mol suggests that the entrapped iron was removed via a diffusion process during thermal treatment. [Copyright &y& Elsevier]

Abstract: Systematic isothermal annealing has been carried out on catalytic chemical vapor deposition-derived highly disordered multi-walled carbon nanotubes in order to understand the structural evolution of carbon nanotubes kinetically. After specified isothermal time the crystallographic parameters strongly depend on annealing temperature, and can be divided into three stages. Rapid structural enhancement in the range from 1800 to 2200°C originates from the abrupt evolution of the residual catalytic compounds and is seen as partially aligned small fringes along the tube length. The lack of further structural ordering at temperatures above 2400°C and the low activation energy (ca. 90kJ/mol) are thought to be the result of the limited space available for further structural development considering the nano-sized multi-walled carbon nanotubes. [Copyright &y& Elsevier]