الفهرس 
INTRODUCTION AND LITERATURE REVIEWOnly 14 pages are availabe for public view
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Abstract
Cellulose acetate (CA) and cellulose acetate–ZnO blended materials were successfully prepared via the casting technique. The hybrid materials were prepared by casting of cellulose acetate solutions with dispersed ZnO at concentrations varying between 0.125 wt% and 1.0 wt%. The influence of ZnO concentration on the molecular structure of the polymer material was examined by means of Fourier Transform Infrared Spectroscopy (FTIR) and X-Ray Diffraction (XRD). FTIR shows the main characteristic bands of pure cellulose acetate. These bands shift to new position upon the addition of ZnO. A new band is appearing around 472 cm⁻¹ which indicate the presence of ZnO. This band shifts to lower wavenumber by increasing the concentration of ZnO in cellulose acetate which indicates the formation of hydrogen bond between CA and ZnO.
XRD results indicate that the material is amorphous even after the addition of different concentration of ZnO. except at 1.0 wt% where three peaks are observed at two theta ranging from 30 to 40 degree.
Also the effect of addition of ZnO at different concentration on the optical properties of cellulose acetate is examined as a function of wavelength in the range from 200 - 1500 nm using spectrophotometric measurements of the transmittance, T(λ), and reflectance, R(λ), at nearly normal incidence. The data of transmittance and reflectance were analyzed to determine the optical constants (the refractive index, n, and the absorption coefficient α). The dispersion analysis has been carried out on the samples of pure cellulose acetate and cellulose acetate blended with different concentration of ZnO to obtain the dispersion energy, oscillator energy, the high frequency dielectric constant and the lattice dielectric constant. The absorption analysis has been performed to determine the type of transitions and the optical energy gaps of CA and CA/ZnO blended material. The type of transition was found to be indirect allowed in pure and blended samples. The values of optical gaps were found to be 2.54 and 3.59 eV respectively. The values of optical energy gaps decrease by the addition of ZnO and reached to 1.69 and 2.33 eV at the highest concentration of ZnO. The Urbach energy was determined and was observed to increase with increasing ZnO concentration.
The ac conductivity and dielectric properties of the samples were studied in temperature range (303-363 K) and frequency range (0.042-5000 KHZ). The ac conductivity, real and imaginary part of dielectric constant were found to increase with increasing the temperature. Also they were found to increase with increasing the ZnO concentration. The experimental results of the ac conductivity have been analyzed with reference to various theoretical models. The analysis showed that the correlated barrier hopping model (CBH) is the most appropriate mechanism for the electron transport. The maximum barrier height was calculated according to CBH model and reveals that the electronic conduction takes place via single polaron hopping processes. The activation energy was calculated and was found to decrease with increasing the frequency as it was found to decrease with increasing ZnO concentration. The study of the frequency dependence of both dielectric constant and dielectric loss showed that they decrease with increasing frequency.