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Ivan Stijepović

Faculty of Technology, University of Novi Sad, Novi Sad, Serbia

Aim of the STSM was to use facilities and available equipment at the Institute Jožef Stefan to investigate ferrite and silica coated ferrite particles synthesised at the Faculty of Technology, Novi Sad, in order to determine their structural and functional properties. Nickel and zinc ferrite nanoparticles were synthesised using co-precipitation method and stabilised with citric acid (CA), poly(diallyl dimethylammonium)chloride (PDDA) and tetramethylammonium hydroxide. Then core/shell structure was made by adjusting zeta potential of as-synthesised particles by choosing appropriate stabilization compound. The other method was to synthesise nickel ferrite and then add zinc and iron nitrate salts in the reaction mixture and continue the synthesis. In this way, zinc ferrite shell would form on the core particles of nickel ferrite. Additionally, ferrite core particles with silica layer on top of them were obtained using Stöber process. All together, 16 different samples were used for magnetic measurements using vibrating sample magnetometry (VSM). Magnetization was measured in the range from -16 kG to 16 kG. Five samples were used for TEM investigations to determine structural characteristics of the synthesised nanoparticles. TEM results showed that samples mainly consisted of non-crystalline nickel ferrite with the presence of FeOOH secondary phase. This was consistent with magnetic measurements which showed that as-synthesised samples were paramagnetic. On the contrary, sample with NiFe2O4 core/ZnFe2O4 shell showed superparagnetic S-curve of magnetization. This indicates that prolonged synthesis time enables crystallization of NiFe2O4. All samples with silica shell were also paramagnetic.