Papers by Author: Zahari Ibrahim

Abstract: Quantum dots (QDs) semiconductors exhibit size-dependent Opto-electronic properties and customizable bandgaps that can be engineered to match the solar spectrum [. Organometallic synthetic approach relies on the injection of organometallic precursor into a pyrolyphic mixture at elevated temperature sufficient enough to initiate particle growth. This approach entails precise control of temperature gradient [. Organometallic reagents injected into a heated non-coordinating octadecene (ODE) were compatible with oleic acid (OA) that was used to protect the CdSe QDs against oxidation and emission loss. ODE is stable in air and has a low melting point (below 20 oC) making it easier to be handled at room temperature. Its high boiling point (about 360 oC) coupled with its inert nature, less toxicity, low cost and good dissolving power makes it an ideal solvent for the growth of CdSe QDs [3,4,5 and 6]. However, QDs synthetic methods differ and relies on how the thermodynamic properties of the reactant mixtures are varied. QDs nucleation growth depicted the underlying processes occurring in aqueous solution and the need to control thermodynamic variables such as reaction time and temperature of the reactants as well as non-thermodynamic variable such as stirring speeds.

Abstract: We report the room temperature thermal conductivity κ and thermal diffusivity α of polycrystalline La0.7Ca0.3-xSrxMnO3 for x = 0 to 0.1. The samples were prepared by heating at 1220 and 1320oC. The insulator-metal transition temperature, TIM and thermal diffusivity increased with Sr content. Phonon was the dominant contributor to thermal conductivity and the electronic contribution was less than 1%. Enhancement of electrical conductivity σ and thermal diffusivity for x ≥ 0.08 was observed in both series of samples. The grain size of the samples (28 to 46 µm) does not show any affect on the thermal and electrical properties.