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Structural and magnetic properties of cobalt ferrites synthesized using sol-gel techniques

100%

Hunyek A. , Sirisathitkul C. , Harding P. , Harding D. J.

tom Vol. 30, No. 3

278--281

Cobalt ferrite (CoFe2O4) was synthesized using sol-gel techniques from cobalt nitrate: iron nitrate: polyvinyl alcohol (PVA) gel in a ratio of 1:2:12. Variations in the amount of PVA in water (5 %, 10 % and 15 %) influenced the crystallite size and phases of the ferrite products, which in turn controlled their magnetic properties. X-ray diffraction studies indicated single phase CoFe2O4 with larger crystallite size and with the hysteresis loops displaying an increase in both coercive field and squareness as the PVA content was increased. Differential scanning calorimetry (DSC) showed that desorption of water and combustion of excess gel were clearly observed in CoFe2O4 prepared from 10 % and 15 % PVA in water. In the case of 5 % PVA in water, two other ratios of cobalt nitrate: iron nitrate: PVA solution were also tested and it was found that the 1:2:10 ratio led to the smallest coercive field and squareness.

FePt3 nanosuspension synthesized from different precursors – a morphological comparison by SAXS, DLS and TEM

63%

Sarmphim P. , Soontaranon S. , Sirisathitkul C. , Harding P. , Kijamnajsuk S. , Chayasombat B. , Pinitsoontorn S. , Chingunpitak J.

tom Vol. 65, nr 1

79--84

Annealed iron-platinum (FePt) is ferromagnetic in a nanoscale regime which is necessary for energy and data storage, whereas the as-synthesized form of FePt-based nanoparticles exhibits superparamagnetism useful for biomedical applications. In this study, as-synthesized nanosuspensions from the reaction of Pt(acac)2 with Fe(acac)3 and Fe(hfac)3 are compared. X-ray diffraction (XRD) peaks for both samples are assigned to the FePt3 phase. As shown by transmission electron microscopy (TEM) and small angle X-ray scattering (SAXS), nanoparticles synthesized by using Fe(acac)3 have a smaller average diameter, but larger polydispersity index and particle agglomerations. On the other hand, the nanoparticles synthesized by using Fe(hfac)3 can self-assemble into a longer range of patterned monolayer. Dynamic light scattering (DLS), measuring the size of cluster of nanoparticles as well as oleic acid and oleylamine at their surface, confirms that larger agglomerations in the sample were synthesized by using Fe(acac)3. In addition to the size distribution, magnetic properties were influenced by the composition of these nanoparticles.

FePt3 nanosuspension synthesized from different precursors – a morphological comparison by SAXS, DLS and TEM

63%

Sarmphim P. , Soontaranon S. , Sirisathitkul C. , Harding P. , Kijamnajsuk S. , Chayasombat B. , Pinitsoontorn S. , Chingunpitak J.

nr 1