Journal of Nano Research Vols. 18-19

Abstract: Poly(vinyl butyral)-polyaniline-sodium montmorillonite nanocomposites were prepared via polymerization of aniline between clay mineral platelets at two different pH levels (2.0 and 5.0), followed by dispersion of the polyaniline-sodium montmorillonite nanocomposite in a poly(vinyl butyral) solution. A comparison was made of the effect of the pH levels and the polyaniline-sodium montmorillonite nanocomposite precursor on the final structures of the poly(vinyl butyral) nanocomposites and their electrical conductivities. X-ray diffraction patterns revealed the formation of nanocomposites at both pH levels. UV-Vis spectra indicated that the polyaniline formed at both pH levels was conductive, with the UV-Vis spectra presenting a band at 420 nm corresponding to the polaronic form and the beginning of a new band at 600 nm indicating the presence of polaronic segments. FTIR spectra revealed the peaks of the groups present in polyaniline and poly(vinyl butyral) nanocomposites. The electrical conductivities of the polyaniline and poly(vinyl butyral) nanocomposites prepared at pH 2.0 were lower than those of the same nanocomposites prepared at pH 5.0, probably due to the lower formation of polyaniline chains in a more acidic dispersion and to the final configuration of polyaniline in the nanocomposites.

Abstract: Barium Strontium Titanate Ba_0.8Sr_0.2TiO₃ (BST) thin films have been deposited on Pt/Ti/SiO₂/Si substrates by pulsed laser deposition technique. The X-ray diffraction (XRD) shows that the films crystallize in a perovskite phase. XRD and Atomic Force Microscopy (AFM) characterization reveal that the grains are nano-sized. Rutherford Backscattering Spectrometry (RBS) analysis shows the stoichiometry of the films to be close to the stoichiometry of the target. The Raman spectroscopy shows that the films exhibit the tetragonal structure by the presence of the Raman active modes at 301 cm^-1 and 729 cm^-1, at room temperature. Leakage current measurements of Au/ Ba_0.8Sr_0.2TiO₃/Pt capacitors have been done, at room temperature, to investigate the conduction mechanisms of the films. We found that there are two different conduction regions in the capacitors, namely, an ohmic behavior at low voltages and a Schottky emission mechanism at high voltages. The Schottky barrier height has been estimated to be 0.99 eV.

Abstract: Focused-ion-beam (FIB) milling is a modern fabrication technique by using focused energetic ions to ablate material and generate features with nanometer resolution. FIB system with Ga ion source was used in our lab to make moulds for laser-based micro/nano lithography. For FIB milling on glassy carbon, particles in the range of tens of nanometers up to 400 nm can often be found around the area subject to milling, with the composition of carbon and gallium. As the laser-based micro/nano lithography involves thermal process, it is important to identify the dynamic process of those compound nanoparticles during heat treatment. Glassy carbon moulds after FIB milling have been heated in air from room temperature up to 550 oC with temperature ramp rate of 10 oC/min. Scanning Electron Microscope (SEM) was used to record the morphology of the machined surface after heat treatments. Energy dispersive X-ray spectroscopy (EDS) was used for elemental analysis. Particles increase their size before the heating temperature reaches 200 oC. With further temperature increase, new particles nucleate, and grow at the neighbouring of the existing particles via coalescence and Ostwald ripening. When the temperature is over 400 oC, the morphology of nanoparticles changes, due to the evaporation of gallium. When the in air heating reaches 525 oC, cracking starts on the surface of glassy carbon. It is suggested that for in air lithographic application, heating temperature should not exceed 500 oC.

Abstract: Single wall carbon nanotube reinforced yttria stabilized zirconia ceramic materials have been obtained by means of spark plasma sintering technique. Single wall carbon nanotubes were treated in an acid solution before mixing with zirconia powders to obtain a uniform distribution of both powders. This method allows obtaining ceramic materials with a grain size between 200 nanometers and 1 micron and with a grain size distribution which depends on processing conditions. This new route opens a new perspective for new ceramic composites tailoring with enhanced mechanical properties as structural materials