Magnetic and electromagnetic characterization of barium hexaferrite ceramics and their polymer matrix composites /

Kaya, Seray
In this study, BaHF-based polymer matrix composites were prepared as potential EM wave absorbing materials. Firstly, BaHF powders and platelets were synthesized by mixed oxide method and by molten salt synthesis (MSS) technique, respectively, which were further used as additives in the EM wave absorbing composites. The effect of molten salt composition on the amount of BaHF phase formation, as well as, on the morphology and magnetic properties of the final products were discussed according to the characterization results. Quantitative XRD results showed that with the increase in NaCl flux content, BaHF formation was enhanced and the highest conversion (97.8 wt%) was obtained in the case of 100 wt% NaCl flux. Corners of the BaHF platelets in NaCl flux were rounded, while KCl flux produced sharp edge platelets. Increasing NaCl content in the flux improved the coercivity and remnant magnetization of BaHF, leading to a more pronounced hard magnetic behavior. vi In the second part of the study, BaHF-based polymer matrix composites were prepared by tape casting method, and their electromagnetic wave absorption potentials were investigated within 18-40 GHz frequency range by free-space measurement method. Effect of BaHF content and alignment on the EM wave properties was investigated. To enhance the EM wave absorption potential of the resulting composites, graphite or nickel flakes were incorporated into polymer matrix, and multilayered composites were produced. BaHF-Ni flake containing composites revealed 50-75% EM wave absorption in 18-40 GHz range with the synergistic effect of the magnetic and ohmic loss effective in the structure.


Magnetic monitoring approach to nanocrystallization kinetics in Fe-based bulk amorphous alloy
Duman, Nagehan; Akdeniz, Mahmut Vedat; Mehrabov, Amdulla (2013-12-01)
Much of the recent metallic glass research is devoted to controlling the crystallization of amorphous precursors with the purpose of obtaining amorphous matrix nanocrystalline alloys which combine unmatched soft magnetic properties with good mechanical properties. Therefore, it is crucial to have better understanding of crystallization mechanisms and thermal dependence of nanocrystals that are formed by annealing. This study deals with the nanociystallization kinetics of Cu-modified Fe-Co-Ni-B-Si-Nb bulk am...
Magnetic Fe3O4-chitosan micro- and nanoparticles for wastewater treatment
ŞAHBAZ, DENİZ AKIN; YAKAR, ARZU; Gündüz, Ufuk (2019-08-18)
In this study, first, magnetic nanoparticles (MNP) were synthesized using a coprecipitation method and the synthesized particles were characterized using Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), dynamic light scattering (DLS), and vibrating sample magnetometry (VSM). According to DLS and VSM analyses results, it was seen that the size of the MNP was smaller than 10 nm and they exhibited superparamagnetic properties, respectively. Then, magnetic Fe3O4-chitosan micro/n...
Nanoscale Thermal Transport in Single, Bilayer Graphene, and Graphite
Gholivand, Hamed; Donmezer, Nazli (2016-10-12)
In this study, ab-initio calculations were performed to obtain phonon dispersions of single, bilayer graphene, and graphite structures. Using these dispersions single mode relaxation times, thermal conductivities, and mean free paths (MFPs) have been calculated. Finally, calculated variables were used to understand the effects of additional layers to thermophysical properties, phonon mode contributions to thermal conductivity, and the limits for ballistic-diffusive heat transfer of single, bilayer graphene,...
Inclusive Search for Supersymmetry Using Razor Variables in pp Collisions at root s=7 TeV
Chatrchyan, S.; et. al. (2013-08-01)
An inclusive search is presented for new heavy particle pairs produced in root s = 7 TeV proton-proton collisions at the LHC using 4.7 +/- 0.1 fb(-1) of integrated luminosity. The selected events are analyzed in the 2D razor space of M-R, an event-by-event indicator of the heavy particle mass scale, and R, a dimensionless variable related to the missing transverse energy. The third-generation sector is probed using the event heavy-flavor content. The search is sensitive to generic supersymmetry models with ...
Conducting polymer composites of polypyrrole and polyimide
Selampinar, F; Akbulut, Ural; Toppare, Levent Kamil (1997-01-01)
A conducting composite of polypyrrole with a polyimide as the insulating matrix polymer was prepared via electrochemical methods. The characterization of the composite was done by FTIR, SEM and TGA studies. Conductivity and solubility studies together with spectroscopic methods reveal that a chemical interaction between the two polymers exists.
Citation Formats
S. Kaya, “Magnetic and electromagnetic characterization of barium hexaferrite ceramics and their polymer matrix composites /,” M.S. - Master of Science, Middle East Technical University, 2014.