PHYSICAL CHARACTERIZATION OF OILSHALE/POLYSTYRENE COMPOSITES

The optical, electrical, and thermal properties of prepared oil shale/polystyrene composites with different concentration: 0, 5, 10, 20, 30 wt. % of oil shale were studied in this research, under various measuring conditions including filler content, wavelength of incident radiation, temperature, and applied electric field frequency.

          The optical spectra were obtained in the wavelength range (300 nm-800 nm) using a spectrophotometer. The absorption coefficient and the optical energy gap (Eopt) have been obtained from direct allowed transitions in k-space at room temperature. The tail widths of localized states in the band gap (ΔE) were evaluated using the Urbach-edges method. It was found that both (Eopt) and (ΔE) vary with the concentration of oil shale in the composite.

        The dependence of AC-electrical properties of oil shale/polystyrene composites on frequency, temperature and filler content were studied using the AC impedance technique. The impedance measurements were performed in the frequency range (100 kHz-1.5 MHz) and its thermal behavior was studied within the temperature range 30ºC - 90ºC. Impedance, dielectric constant and AC-conductivity showed frequency, temperature and filler content dependencies. The relaxation time and activation energy were determined as a function of temperature and filler concentration, respectively.

     The thermal conductivities and thermal resistivities of oilshale/polystyrene composites have been studied as a function of temperature. It was found that the thermal conductivity increases with temperature and oil shale concentration.

     The study includes application of some models to explain the observed results. The universal power law of the AC conductivity behaviour is satisfied for different concentration and at different temperatures.

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