الفهرس 
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Abstract
Molybdenum trioxide nanoparticles have been prepared via three different techniques, those were: 1) Laser ablation from consolidated molybdenum trioxide powders. Both fundamental and second harmonic of Nd: YAG pulsed laser (i.e. wavelengths = 1064 nm and 532 nm ) were used to achieve the ablation experiment. The consolidated disk was submerged in ethanol as a liquid medium for ablation process, and this method well known as pulsed laser ablation in liquid media ( PLA-LM). 2) Sol-gel method has been employed to produce molybdenum trioxide nanoparticles by the hydrolysis of ammonium molybdate in the presence of citrate as a capping material. The concentration of the precursor solutions was the more efficient parameter to control the size of the obtained nanoprticles. 3) High energy ball milling was carried out at room temperature using a planetary ball mill. Both dry and wet milling have been used at which the dry milling was achieved in the ambient atmosphere. On the other hand, the wet milling process has been employed using deionized water, ethanol, and butanol as milling environments. The morphological characteristics of the prepared nanoparticles (i.e. size and shape) have been investigated using transmission electron microscope (TEM). On the other hand, the structural characteristics (i.e. crystal structure and the degree of crystallinity) have been investigated using X-ray diffraction (XRD) and electron diffraction ( ED) analysis. It is worth to mention that the molybdenum trioxide nanoparticles were successfully produced in different crystal structures (i.e. single crystal, polycrystalline and super lattice structure) via high energy ball milling and sol-gel techniques. With high energy milling specially wet milling and further drying step after wet milling process; molybdenum trioxide nanoparticles were successfully designed at which size and shape and crystal structure were controlled depending on the type of liquid environment. On the other hand, pulsed laser ablation in ethanol produced colloidal suspensions include different crystal structures of molybdenum nanocomposites. With controlling the experimental parameters of sol-gel method specially the concentration of the precursor solution; the size of the obtained nanoparticles has been controlled. In comparison between the previously mentioned techniques for preparation of molybdenum trioxide nanoparticles, the different characteristics (i.e. size, shape, size distribution, uniformity and crystallinity) have been demonstrated and the obtained results have been statistically represented. The largest nanoparticles have been produced via dry milling and laser ablation at which the average sizes were 55 nm and 50 nm subsequently. The smallest nanoparticles have been produced via sol-gel and wet milling using butanol at which the average sizes were 20 nm and 13 nm subsequently. The most uniform nanoparticles have been prepared via laser ablation, the high degree of crystallinity was obtained via sol- gel method. Finally the ball milling technique confirmed its ability to produce molybdenum oxide nanoparticles with achieving the mass production and maintaining the crystallinity and size reduction.