Papers by Author: Nor Diyana Abdul Aziz

Abstract: Titanium dioxide powders were synthesized via a sol-gel method using titanium nitride as the precursor. The structure and morphology of the synthesized powders were investigated and characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM). XRD results indicate that pure single phase titanium dioxide of rutile structure had been obtained. It was also revealed that annealing temperature plays an important role in the formation of single phase titanium dioxide powders. Increasing heat treatments also modified the shape and surface morphology from chunks and rock-like morphology to a mixture of flaky aggregates. Conductivity studies using a.c. impedance technique was used. The conductivity of the sample annealed at 400 °C is 89 % higher than that annealed at 800 °C and attributed to the phase and morphology of the samples.

Abstract: Fe₂O₃ was synthesized via a sol-gel method. Pure, single phase materials were obtained at 300 °C and 800 °C heated for 24 hours. The conductivies of the materials were investigated using a.c. impedance spectroscopy. It was found that the material annealed at a lower temperature gives better conductivity value of about two orders of magnitude higher.

Abstract: Poly [2-methoxy, 5-(2-ethyl-hexyloxy)-p-phenylene-vinylene] (MEH-PPV) is a conjugated polymer that exhibit excellent luminescence properties in the visible spectrum. The fundamental absorption edge in the film is formed by the direct allowed transitions. In this work, free-standing films of MEH-PPV and MEH-PPV/MCMB were obtained by a solvent casting method. Mesocarbon Microbead (MCMB), a type of carbon, is added to the polymer producing composite films. The films were characterized by using the UV-Vis-NIR spectrophotometer. The film samples exhibited an absorption band in the red visible region. This is due to the electron transition between the non-localized bands. However, when MCMB is doped into the polymer matrix, the band absorption edge is red-shifted compared to that of the MEH-PPV pure film. Therefore, the optical band gaps of the composite films have decreased due to the presence of MCMB.

Abstract: The diffusion of charged species in solids is a very important part of the study of the electrical properties of materials. Electrical measurements using alternating current (ac) impedance is a powerful technique to study diffusing species in metal oxides as well as polymers. Three case studies are being presented here whereby the electrical properties of LiTaO3, Poly[2-methoxy-5-(2’-ethylhexyloxy)-(p-phenylenevinylene)] (MEH-PPV) and its composite are being studied using the same ac impedance technique. LiTaO3 is a metal oxide while MEH-PPV is a polymer. They are very different and therefore present very good examples for the versatility and power of ac impedance method. Electrical parameters such as conductivity and conduction behaviours of the conducting species can be extracted from the studies. The kinetics of the diffusing species can be elucidated by using proper analytical techniques.