الفهرس 
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Abstract
Iron oxides nanoparticles play an important role in a variety of disciplines including: industrial chemistry, engineering, physics, chemistry, environment and materials science. The nano dimension of iron oxide, revealed a new physical properties of matter which are intermediate between atoms and bulk materials that trigger iron oxide to several specific nanotechnological applications. Much research has been developed to find reliable convenient preparative methods for synthesizing the major iron oxides at controlled nanometer level with varieties suitable for application in numerous fields.
In order to attain this purpose, the work in the thesis was oriented to search for suitable techniques and conditions for the preparation of iron oxide nanoparticles having different nano-sizes and morphologies with different molecular absorption spectra and colour shades. Sol-gel, micro-emulsions/ reverse micelles and co-precipitation were the techniques used throughout the work to achieve such a goal.
The first chapter was devoted to introduce some terms describing some nanotechnological concepts, definitions and types of products such as: nanoscience, nanostructure, nanomaterial, nanocomposite and nanoparticles.
The review of literature in this thesis (chapter 2) was directed to throw the light on the occurrence of iron in the earth`s crust and the ores bearing iron minerals. The last ones include: hematite, Fe2O3; pyrite, Fe2S2; ilmenite, FeTiO3; magnetite, Fe3O4; siderite, FeCO3; and limonite FeO(OH). The different types of iron oxides and their applications in the industrial and biomedical fields were also discussed in this chapter. The literature survey was extended to include different chemical and physical methods used in the synthesizing of nanoparticles.
The third chapter contains the description of the procedures followed in the preparation of α-Fe2O3 nanoparticles using three different methods: sol-gel, co-precipitation and micro-emulsion. This chapter was also pointed out to explain the basic principles and techniques used for characterization of the prepared samples such as: transmission electron microscopy (TEM), X-ray Diffraction (XRD), infrared (FTIR) spectroscopy, thermal gravimetric analysis (TGA) and diffuse reflectance spectroscopy (DRS).
The fourth chapter was intended to discuss the results obtained from the different characterization techniques.
In regard to the samples prepared using sol-gel method, effects of changing: type of chelating agent, type of ferric ion precursor, ferric salt: chelating agent molar ratio, calcination temperature on structure, morphology and size of the prepared α-Fe2O3 nanoparticles were studied. The results revealed that the α-Fe2O3 nanoparticles prepared using the sol-gel method showed little aggregation. They also appeared to be well-dispersed with a fairly narrow size distribution. The size of the primary particles is on the nano-scale and the particles have regular shape with roundness of the edges. The sample prepared using tartaric acid as the chelating agent recorded the smallest particles size and the best thermal stability. It was found also that the particles tend to aggregate and consequently, have larger size as the molar ratio of the ferric salt to the chelating agent increases. The α-Fe2O3 sample prepared using 2:1 molar ratio demonstrated the largest aggregation and has the largest particles size (37-53 nm). While those prepared using 1:2 and 1:1 molar ratio showed less particles aggregation and the particles sizes laid in the ranges 17-23 nm and 34-41nm, respectively.
For the α-Fe2O3 samples prepared using co-precipitation method, the effects of changing type and concentration of ferric ion precursors, calcinations temperature on the structure, crystalline phase and particles size of the prepared samples were studied. Most of the prepared samples appeared as aggregated particles with a wide size distribution with a diameter varied between 15-130 nm, and 41-95nm for the samples prepared from ferric chloride and ferric sulfate respectively. Some of these particles were spherical while others had tube-like shape. It was observed also that the concentration of the ferric ion precursor is a determining factor in controlling the particle size in such a way that when the concentration increases, the average particle size is significantly increased. It was found also that the α-Fe2O3 nanoparticles prepared using 0.2M of the ferric ion precursor measured the largest particle size while those prepared using 0.1, 0.05M recorded smaller particle size.
Regarding the samples prepared using microemulsion method, the prepared α-Fe2O3 nanoparticles recorded the smallest particle size among all the prepared samples. They also showed the narrowest range of particle size variation, with grains size in the ranges of 7-9 nm and 8-11nm for the α-Fe2O3 samples prepared using 0.2M of ferric sulfate and ferric chloride respectively. Effect of changing ferric salt concentration was also studied; it was observed that the particles size increased with elevating the ferric salt concentration. The results showed also that changing surfactant concentration affected on the prepared α-Fe2O3 nanoparticles size. It was observed that as the concentration of surfactant increases, the α-Fe2O3 particles size tend to increase.
The thermogravimetric analysis of the precursors performed to study the thermal stability of the prepared samples and to optimize the calcinations temperatures required to obtain the desired product showed that the optimum calcination temperature was 700 ºC. The results obtained from X-ray powder diffraction characterization revealed that all the prepared samples adopted the hexagonal structure (R3c space group). The results showed also that the sizes of the prepared α-Fe2O3 particles estimated from the XRD patterns with the aid of the Scherrer’s formula lie in the nano-scale. Both the diffraction peaks and lattice parameters (a and c) of all synthesized α-Fe2O3 were in good agreement with those of standard hematite. Infrared spectra confirmed the formation of α-Fe2O3 and the removal of organic matter at 700 °C. The diffuse reflectance spectra showed that reflectance in the red color range increases as the particle size decreases.
In the fifth chapter, the α-Fe2O3 nanoparticles produced according to three three methods were used in preparation of different red pigments and were evaluated as pigments according to the ASTM standard methods for evaluation of pigments.
The prepared pigments were found to possess reasonable hiding and tinting power as well as a high degree of fastness towards water, organic solvents, acids, alkalis, light and heat. They showed also low oil absorption. These outstanding physical and chemical properties of the prepared pigments make them to be used satisfactorily as suitable pigments for coating applications.