الفهرس 
Chapter 1Only 14 pages are availabe for public view
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Abstract
The radioactive materials emit different types of ionizing radiation like X-rays, gamma-rays and neutrons do great harm to nearby instruments, humans, and living creatures, especially γ rays in the case of an external radiation hazard. In order to avoid undesired hazards from these kinds of radiation, a variety of shielding materials that have good attenuation properties were used to attenuate or absorb the radiations in addition to two other very important parameters time and distance. Among them, high Z materials usually have been employed to attenuate high-energy radiation such as X-rays and γ-rays. In modern radiotherapy the new shielding material should meet so characteristics. First, the shielding ability of the material should meet the requirement of application in radiotherapy. Second, the new material should be flexible enough to be conveniently customized into arbitrary shapes. Last, the material should be environmentally friendly and easily recycled. In order to provide safe operating conditions for radiation workers and the public at large, the radiation shielding for radiotherapy treatment rooms will have to be determined by an expert physicist according to the applicable radiation control regulations. Because of the rapid economic developments in Egypt, the field of radiotherapy has in recent years experienced exponential growth. Due to the inherent hazards of radiation production near humans, hospitals and radiotherapy facilities must adhere to local radiation regulations and are required to protect personnel and the public by providing appropriate shielding and protection. The main objective of this study was to enhance and evaluate attenuation properties of new environmentally friendly radiation shielding materials to use in nuclear medicine applications.So, because Pb toxicity is an important environmental disease and its effects on the human body are devastating. Thus, there is an urgent need to find sustainable radiation shielding material to safeguard humans and the environment from destructive impact of radiation. For this study, we prepared three groups as follows: Chemical composition of all-as prepared melt-spun process alloys and weight percent of each element.Alloy Composition Bi (Wt. %) Pb(Wt. %) Sn (Wt. %) Zn (Wt. %)Sb (Wt. %) Bi-Pb-Sn (First group)
50 50 - -
50 40 10 -
50 30 20 -
50 20 30 -
50 10 40 -
Sn-Bi-Zn
(Second group) 50 - 50 -
45 - 50 5
40 -50 10
35 - 50 15
30 -50 20
50 - 50
Sn-Bi-Sb
(Third group) 50 50
48 50 2
46 50 4
44 50 6
42 50 8
In this study we investigate the structure, microstructure, mechanical and gamma radiation shielding properties of some melt-spun process binary and ternary alloys reinforced with some metallic elements such as Sn, Zn and Sb have chemical compositions Bi-Pb50-x-Snx(x=0,10,20,30,and 40wt.%), Sn-Bi50-x-Znx (x=5,10,15, and 20 wt.%) in addition to Sn-Bi50-x-Sbx (x=2,4,6 and 8 wt.%) using rapid solidification processing technology. The structure, microstructure, mechanical, microhardness and shielding parameters of all as-prepared samples was investigated and examined by x-ray diffraction analysis, scanning electron microscopy, tensile test machine, Vickers microhardness technique as well as FH 40 G dose rate measuring unit respectively. The structural analysis indicated that crystallite size decreased by increasing doping elements Sn, Zn and Sb contents in the Sn matrix which enhances the mechanical properties of shielding alloys. The x-ray diffraction revealed that appearance of different phases such as Bi, Sn as well as different intermetallic compounds such as Bi0.05Sn0.95, Bi0.3Pb0.7, Sn0.85Zn0.15, SbSn and SbBi. It is observed that from results the mechanical properties and microhardness are enhanced due to strong interactions by alloying elements additions such as Sn, Zn and Sb elements act as hard inclusions and make precipitations from IMCs in the matrix. Fine recrystallized grains and an increase of grain boundaries was found in the matrix alloy with high additions predicting higher micro-hardness and strength. Because of fine precipitates and fine grains structure, the matrix alloy with high additions is associated with plastic deformation. The lead-free alloys are reported to exhibit maximum shielding efficiency. This current work focused on the study and development of new lead-free shielding materials in nuclear medicine. Results from this study show that these materials are very useful for gamma ray shielding and the best candidate for lead-based shielding material.The calculated mass attenuation coefficient MAC μm, linear attenuation coefficient LAC μl, half-value layer HVL, tenth-value layer TVL, mean free path MFP, are performed theoretically by using Phy-X/PSD computer programs in the energy range from 15 keV to 15 MeV. A comparative study was conducted to find the optimum shielding parameters for the fabricated shielding alloys. This work aimed to obtain evidence shielding improvement lead-based materials by lead-free replacement. The outcomes from this work can lead a way for advanced investigations of lead and lead-free based alloys structures in design of new generation shielding materials.To contribute with the national and international research society about solving the many problems related to shielding materials by trying to produce a new friendly-environmentally radiation shielding materials have enhanced shielding properties using lead based and lead-free based alloys.• Design and investigation of newly developed radiation shielding materials for radiation protection.•To attenuate or absorb gamma rays and protect the workers in medical hospitals, and nuclear reactors from harmful effects.•To obtain newly developed shielding materials for medical applications.• To obtain environmentally friendly and easily recycled materials. • To obtain low cost and economic materials.•To study the effect of rapid solidification technology and small traces nanoparticles additions on shielding materials properties.•To develop the structure, mechanical, thermal and attenuation properties of shielding materials.•Substitution of lead and cadmium elements with non-toxic materials.