الفهرس 
Crystal structure of ferritesOnly 14 pages are availabe for public view
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Abstract
This research was conducted in Solid State Laboratory, Physics Department, Faculty of Science, Tanta University. This thesis aims to study the electrical and magnetic properties of rubber ferrite nanocomposites (RFCs). Firstly: The spinel Nanoferrite system NiCrxFe2-xO4 (where x=0.0, 0.2, 0.4, 0.6, 0.8 and 1.0) have been synthesized by flash auto combustion method, then annealed at 400oC for 2hrs. Secondly: RTV silicon rubber was incorporated into annealed ferrite sample (x=0.2) to form Rubber Ferrite Composites (RFCs). The X-ray diffraction (XRD) analysis showed that, the ferrite samples have a single-phase spinel cubic structure and this structure doesn’t change during the stages of processing the (RFCs) with appearance an amorphous peak corresponding to silicon rubber appears at θ=11.56o. The values of lattice constant, crystallite size, X-ray density, bulk density, and porosity were calculated. The FTIR spectra of annealed ferrite samples were reported and the values of the force constant were calculated. Morphological observation which were determined by scanning electron microscopy (SEM) shows agglomerated grains with different shapes and sizes and characterize the homogeneity of magnetic nanofiller in rubber matrix. High resolution TEM employed to confirm the results of XRD studies. DC electrical resistivity of annealed samples has been studied at different temperatures. It was observed that, the value of DC resistivity increased by increasing Cr content, whereas decreased by increasing temperature. The dielectric constant and AC resistivity were measured as a function of temperature and different frequencies (1 kHz and 10 kHz). It was observed that, the value of the dielectric constant decreased by increasing Cr content, decreased by increasing frequency and gradually increased with increasing temperature up to 500 K for 1kHz and to 570 K for 10 kHz. The AC resistivity increases by increasing Cr content and decreases by increasing frequency. All the samples of (RFCs) were exposed to heat treatment at temperatures 100oC, 150oC and 200oC for different curing time 2, 4 and 6 hrs. The dielectric properties and AC resistivity were investigated for the composite samples at different frequencies [100 Hz, 1 kHz and 10 kHz]. Magnetic properties of Ni-Cr ferrite were measured by using vibrating sample magnetometer (VSM) at room temperature. It was found that, with increasing Cr content the saturation magnetization decreased from 28 to 3 emu/g whereas coercivity increased from 188 to 666 (G). The magnetic moment of the system and Curie temperature decreased by increasing Cr substitution. The magnetic measurements of the composite samples show minimum losses and the coercivity has almost the same values. The variation of saturation magnetization is occurred after the ferrites were incorporated into RTV-Silicon Rubber. Thermal Gravimetric Analysis (TGA) and it’s first derivative curves of the rubber ferrite nanocomposites samples were carried in the range from 20-600oC.