الفهرس 
Chapter One: IntroductionOnly 14 pages are availabe for public view
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Abstract
In this work, three polymeric mixtures were prepared to be used as a gamma – ray shields. The first system was polyvinyl chloride doped with different ratios of basalt rocks added in its powder form 1.0 up to 20.0 wt%. This composite was prepared via the solution casting method using tetra hydro furan (THF) as a solvent for the polymer. The crystal structure, optical, and gamma-ray attenuation properties of the undoped and the doped polymeric samples which were coded as PB0.0 – PB50.0, where x = 0.0, 5.0, 10.0, 15.0, 20.0, and 50.0 wt% were investigated. The density of the prepared samples increased from 1.38 to 2.18 g/cm3 with increasing basalt nanoparticle concentrations. Scanning electron microscope (SEM) of the prepared samples showed a good dispersion in the small ratios of dopant and some agglomerations in the high basalt ratios in the mixture. Values of the direct optical energy gap varied from 3.0 to 3.5 eV, while refractive index changed from 2.39 to 2.27. The gamma-ray shielding parameters were evaluated using the Phy-X/PSD software program as well as the MCNP – code. The most critical results showed that the linear-attenuation coefficient (μ) increased from 14.421 to 23.862 cm-1 (at 0.015 MeV), and from 0.030 to 0.048 cm-1 (at 15 MeV) for PB0.0 and PB50.0 samples, respectively. Moreover, the evaluation of other gamma - ray attenuation parameters showed an enhancement with the addition of the basalt nanoparticles.
The second system was polyethylene doped with different ratios of the basalt powder with chemical formula (100-x) polyethylene + x basalt, where x = 0, 1, 3, 5, 10, and 20 wt.%. This system was prepared via the melt blending technique which is preferable in the large-scale production processes. The measured density varied from 0.945 to 1.33 g/cm3, for B0 to B20 respectively. Besides, dominant peaks at 21o, 24o, and 28o for HDPE and basalt were investigated. The FTIR spectroscopy was done on the prepared samples, and good evidence of adding the filler to the pure polyethylene was obtained. The optical bandgap reduced from 3.5 to 2.0 eV for indirect allowed transition and from 4.4 to 3.0 eV for direct allowed transition as basalt concentration increased in the prepared samples. The linear attenuation coefficient μ of each prepared set of samples was measured using a gamma-ray spectrometer including High Purity Germanium detector (HPGe) at energies 662.5, 1173.24, and 1332.51 keV. Based on the measured values of (μ) and sample density, other effective shielding parameters were calculated. Values of μ showed an increase with increasing the dopant ratios from 0.0 up to 20.0 wt.%. In addition, μ values decreased with the photon’s energy. The μ values were found 0.0847 up to 0.1175 cm-1, 0.0571 up to 0.0855 cm-1, and 0.0543 up to 0.075 cm-1 at 662, 1173, and 1332 keV for B0 up to B20, respectively. To define the accuracy of the measurements, these values were estimated by both Phy-X/PSD and MCNP codes and the relative difference was calculated and found around 10%. The Zeff values were determined and found equal to 2.995, 3.023, 3.079, 3.136, 3.287, and 3.624 for 0.015 MeV and 4.403, 4.915, 5.854, 6.695, 8.453, and 10.974 for B0, B1, B3, B5, B10, and B20, respectively. These results ensured that the insertion of basalt with high ratios increased the attenuation properties of the prepared samples.
The third system was also prepared by melt blending technique without the need for polymer solvent. This system chemical formula (95-x) polyethylene + 5.0 basalt + x Bi2O3, where x = 0, 5, 10, 15, 20, 25, and 30 wt.% with samples coded as Bi.0.0 – Bi30.0. The density of the samples increased from 0.976 to 1.431 g/cm3. The μ values was linearly increased with the increase in the sample’s density, while decreased with increasing the incident photon energy.
The measured linear attenuation coefficient and the other calculated parameters introduced Bi30.0 sample as the best sample from the attenuation properties point of view with HVL equal to 4.938, 7.246, 7.683 cm when compared to Bi0.0 sample with HVL equal to 7.615, 10.809, 12.261 cm at 0.662, 1.173, 1.332 MeV, respectively. In conclusion, regrading to the three prepared systems, the μ values of system 1 increased by 49% than the pure polymer at 662 keV. While for System 2, the μ values increased by 39%, 50%, and 40% than the pure polymer at 662, 1173, and 1332 keV. Finally, for System 3, the μ values increased by 57%, 45%, and 48% than the pure polymer at 662, 1173, and 1332 keV.