| 1. |
- Karaoglu, E., et al.
(författare)
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Effect of Hydrolyzing Agents on the Properties of Poly (Ethylene Glycol)-Fe3O4 Nanocomposie
- 2011
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Ingår i: Nano-Micro Letters. - 2150-5551. ; 3:2, s. 79-85
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Tidskriftsartikel (refereegranskat)abstract
- Poly (ethylene glycol) (PEG) assisted hydrothermal route has been used to study the influence of the hydrolyzing agent on the properties of PEG-iron oxide (Fe3O4) nanocomposites. Iron oxide nanoparticles (NPs), as confirmed by X-ray diffraction analysis, have been synthesized by a hydrothermal method in which NaOH and NH3 were used as hydrolyzing agents. Formation of PEG-Fe3O4 nanocomposite was confirmed by Fourier transform infrared spectroscopy (FTIR). Samples exhibit different crystallite sizes, which estimated based on line profile fitting as 10 nm for NH3 and 8 nm for NaOH hydrolyzed samples. The average particle sizes obtained from transmission electron microscopy was respectively 174 +/- 3 nm for NaOH and 165 +/- 4 nm for NH3 gas hydrolyzed samples. Magnetic characterization results reveal superparamagnetic characteristics despite a large particle size, which indicate the absence of coupling between the nanocrystals due to the presence of polymer in the nanocomposites. The conductivity curve demonstrates that sigma(DC) is strongly temperature dependent.
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| 2. |
- Karaoglu, E., et al.
(författare)
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Hydrothermal Synthesis and Characterization of PEG-Mn3O4 Nanocomposite
- 2011
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Ingår i: Nano-Micro Letters. - 2150-5551. ; 3:1, s. 25-33
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Tidskriftsartikel (refereegranskat)abstract
- Here, we report on the synthesis of PEG-5/Mn3O4 nanocomposite (NP's) via a hydrothermal route by using Mn(acac)(2), ethanol, NH3 and PEG-400. The crystalline phase was identified as Mn3O4. The crystallite size of the PEG-Mn3O4 nanocomposite was calculated as 12 +/- 5 urn from X-ray line profile fitting and the average particle size from TEM was obtained as 200 nm. This reveals polycrystalline character of Mn3O4 NP's. The interaction between PEG-400 and the Mn3O4 NP's was investigated by FTIR. Temperature independent AC conductivity of PEG-Mn3O4 nanocomposite beyond 20 kHz provides a strong evidence of ionic conduction through the structure. The conductivity and permittivity measurements strongly depend on the secondary thermal transition of nanocomposite beyond 100 degrees C. Above that temperature, Mn3O4 particles may interact with each other yielding a percolated path that will facilitate the conduction. On the other hand, the relatively lower activation energy (E-a=0.172 eV) for relaxation process suggests that polymer segmental motions of PEG and electrons hopping between Mn2+ and Mn3+ may be coupled in the sample below 100 degrees C. Room temperature magnetization curve of the sample does not reach to a saturation, which indicates the superparamagnetic character of the particles. As the temperature increases, the frequency at which (epsilon '') reaches a maximum shifted towards higher frequencies. The maximum peak was observed at 1.4 kHz for 20 degrees C while the maximum was detected at 23.2 kHz for 90 degrees C.
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| 3. |
- Karaoglu, E., et al.
(författare)
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Synthesis and characteristics of poly(3-pyrrol-1-ylpropanoic acid) (PPyAA)-Fe(3)O(4) nanocomposite
- 2011
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Ingår i: Journal of Alloys and Compounds. - : Elsevier BV. - 0925-8388 .- 1873-4669. ; 509:33, s. 8460-8468
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Tidskriftsartikel (refereegranskat)abstract
- Poly(3-pyrrol-1-ylpropanoic acid) (PPyAA)-Fe(3)O(4) nanocomposite was successfully synthesized by an in situ polymerization of 1-(2-carboxyethyl) pyrrole in the presence of synthesized Fe(3)O(4) nanoparticles. Evaluation of structural, morphological, electrical and magnetic properties of the nanocomposite was performed by XRD, FT-IR, TEM, TGA, magnetization and conductivity measurements, respectively. XRD analysis reveals the inorganic phase as Fe(3)O(4) and TGA shows about 90 wt% loading of Fe(3)O(4) in the nanocomposite. FT-IR analysis indicates a successful conjugation of Fe(3)O(4) particles with polypyrrole acetic acid. Magnetization measurements show that polypyrrole acetic acid coating decreases the saturation magnetization of Fe(3)O(4) significantly. This reduction has been explained by the pinning of the surface spins by the possible adsorption of non-magnetic ions during the polymerization process. The conductivity and dielectric permittivity measurements strongly depend on the thermally activated polarization mechanism and thermal transition of PPyAA in the nanocomposite structure. Large value of dielectric permittivity (epsilon') of the nanocomposite at lower frequency is attributed to the predominance of species like Fe(2+) ions and grain boundary defects (interfacial polarization).
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