Secondary re-crystallization is one of the most important processes in hydrothermal synthesis. In this process individual nanoparticles rapidly grow at the expense of the other particles. The process makes the control of the particle size very difficult or even impossible. In the article, the new synthesis procedure was published. The procedure is based on the complete blocking of the secondary re-crystallization using the addition of oleic acid. The nanoparticles synthesized in the presence of oleic acid were hydrophobic and can be dispersed in nonpolar carrier liquids to prepare ferrofluids.
COBISS.SI-ID: 22768167
The article explains the mechanisms that enable control of the nanoparticle size during the hydrothermal synthesis of barium hexaferrite. The particle size crucially depends on the temperature and the concentration of the reactants. High concentrations of hydroxyl ions result in the formation of iron-rich complexes, which significantly decrease the formation temperature of the product. The developed knowledge related to the chemistry involved in the crystallization of barium hexaferrite enabled the synthesis of nanoparticles of controlled size.
COBISS.SI-ID: 20843303
The formation of Ba hexaferrite generally requires high temperatures, typically around 700 oC. However, using the hydrothermal method, the hexaferrite can be synthesized at much lower temperatures. Knowledge related to the crystallization of the hexaferrite enabled us to decrease its synthesis temperature and be the first in the world to synthesize ultrafine superparamagnetic nanoparticles. Moreover, the synthesis temperature was decreased below 100 oC, meaning that even simple co-precipitation can be used instead of the hydrothermal method.
COBISS.SI-ID: 23430183
In the article, the relations between the experimental conditions applied during the hydrothermal synthesis and the properties of the synthesized Ba-hexaferrite nanoparticles were presented.
COBISS.SI-ID: 20748839
Our procedure for the preparation of ferrofluids with the dispersion of superparamagnetic, barium-hexaferrite nanoparticles in nonpolar liquids was presented. These ferrofluids were prepared for the first time. The procedure is based on the addition of the surfactant oleic acid to the reaction mixture during the hydrothermal synthesis of the nanoparticles. The addition of the surfactant has two roles: first, it prevents secondary re-crystallization of the nanoparticles during the synthesis; and second, the surfactant absorbed at the nanoparticles’ surfaces prevents their agglomeration.
COBISS.SI-ID: 22216743