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Title: Synthesis and analysis of physical properties of iron oxides based nanocomposites.
Authors: Ali, Kashif
Keywords: Physical Sciences
Issue Date: 2020
Publisher: International Islamic University, Islamabad.
Abstract: Nanosized magnetic composites have attained excessive consideration and importance over the last few decades. Nanocomposites materials are one of the main subjects of the present-day research and development. The physical properties of magnetic nanocomposites materials are different as compared to their monocomponent counterparts, and their properties can be tuned by increasing the contents of the host material. The aim of this research study focuses on the synthesis of Copper Ferrite (CuFe2O4) and selected metal oxides (MOs) nanocomposites in nanocrystalline form and studies their magnetic, dielectric and electromagnetic absorption (EM) properties. The response of CuFe2O4 magnetic nanoparticles (MNPs) with MOs (ZnO, MgO, WO3, SnO2 and NiO) nanostructures towards EM radiation absorption at Microwave (MW) frequency enhances the effective absorption bandwidth. These MOs nanostructures behave like dielectric loss fillers and alter the electrical conductivity, dielectric permittivity, and interfacial polarization. Moreover, the synergistic behavior between the dielectric and magnetic components also plays a vital role for strong MW absorption. In this research work, MOs nanostructures, CuFe2O4 MNPs, and their nanocomposites have been prepared by facile wet chemical route and characterized by different experimental techniques. The obtained results are interpreted and discussed in this thesis which consists of nine chapters. The first chapter is a brief introduction of ferrites, MOs nanostructures, magnetic nanocomposites, and the approaches to minimize the EM reflection. The second chapter discusses the literature review and the theory of EM absorption. The third chapter introduces the synthesis method applied and working principles of characterization techniques used to obtain the results. xi The detailed studies on the required physical properties of MOs nanostructures are briefly described in the fourth chapter. The fifth chapter describes the synthesis and MW absorption characteristics of (ZnO)x/(CuFe2O4)1-x nanocomposites. The XRD analysis confirms the formation of the required composite with crystallite size ranges from 30-81nm. The SEM images depict the nanodiscs like morphology and Transmission Electron Microscopy (TEM) analysis confirms that CuFe2O4 MNPs are embedded in ZnO matrix. The saturation magnetizations (Ms) of superparamagnetic (SPM) nanoparticles in composite sample decreases with ZnO contents. The higher content of ZnO ≥ 40% in composite sample enhances the effective absorption in a required frequency band (2-10 GHz). The sixth chapter deals with the improvement in MW absorption characteristics of CuFe2O4 MNPs with MgO nanostructures. The structural analysis confirms the formation of nanocomposites in which both phases are present. The MgO contents transform the spherical morphology of CuFe2O4 into an irregular shape as depicted from TEM images. All samples show the same ferromagnetic behavior with decrease in Ms value with MgO weight fractions. The RL properties show an enhancement in effective absorption bandwidth at 40 wt. % of MgO content. The seventh chapter also focuses on structural, vibrational, magnetic and MW absorption characteristics of novel WO3- CuFe2O4 nanocomposites. The structural investigation confirms the formation of nanocomposites. The TEM micrographs demonstrate that the addition of WO3 weight fraction leads to the growth of WO3 grains with an irregular plate-like structure. This irregular structure offers high value of shape anisotropy which leads to an enhancement in coercivity (Hc) as depicted from M-H loops. The MW absorption study also demonstrates a shift in RL towards higher frequency at an elevated concentration of WO3 in the composite. xii The eighth chapter briefly explain the MW absorption properties of (SnO2)x/(CuFe2O4)1-x nanocomposites. The structural study reveals that the composite sample exhibit the single phase up to 30 wt.% of SnO2 due to thermodynamically solubility of Sn4+ ion in CuFe2O4. The TEM images demonstrate that the SnO2 wt. fractions in composite samples alter the shape and particle size from spherical to flatter plate like. The M-H loops of composite samples show the SPM behavior with systematic decrease in Ms values due to the substitution of magnetic ions (Cu2+ and Fe3+) with non-magnetic ion Sn4+. The MW absorption study display the maximum absorption for 10 and 20 wt. % of SnO2. Finally, the ninth chapter also describes the MW absorption properties of NiO/CuFe2O4 nanocomposites. The structural investigation demonstrates the formation of NiO/CuFe2O4 phase and TEM micrographs display the spherical morphology of particles for all composition. The M H loops show a decreasing trend in Ms and Hc which is ascribed to the increase in mass fractions of nonmagnetic samples and particle size respectively. The RL measurement shows a shift in absorption peaks towards higher frequency regime with NiO contents. Moreover, the maximum absorption -47.07 dB at 8.2 G Hz frequency with 30 wt. % of NiO has also been observed.
Gov't Doc #: 21954
Appears in Collections:PhD Thesis of All Public / Private Sector Universities / DAIs.

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