Кафедра технології неорганічних речовин та екології (КТНРтаЕ)

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ENG: Department of Inorganic Substances and Ecology

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Influence of Synthesis pH on Structural, Dielectric and Magnetic Properties of MnFe2O4
(Oles Honchar Dnipro National University, Dnipro, 2025) Frolova, Liliya A.; Saltykov, Dmytro Yu.; Holub, Iryna V.; Bila, Оlena V.
ENG: Dispersed manganese ferrite particles were obtained by a combined co-precipitation method at different pH of the initial solution (7–12). The structural, morphological, optical and magnetic properties of the synthesized nanoparticles were characterized using X-ray diffraction, scanning electron microscopy, and vibrational magnetometry. The XRD results showed that MnFe2O4 has a cubic spinel crystal structure with an average crystallite size of 14–65 nm. The presence of additional phases is observed at low pH and pH greater than 12. Ferritization significantly depends on pH, which affects the phase composition of the products and the size of the crystallites. In addition, with an increase in pH from 7 to 12, the percentage of microstresses and the density of dislocations decreases. The obtained MnFe2O4 samples exhibit ferrimagnetic properties, the highest saturation magnetization value of 56.8 Emu/g is achieved at pH 10. In addition, the coercive force changes from 5 to 50 Oe with increasing pH due to the increase in crystallite size.
PVA-CoFe2O4-Biochar Composites: Structure and Properties
(Oles Honchar Dnipro National University, Dnipro, 2025) Frolova, Liliya A.; Saltykov, Dmytro Yu.; Kushnerov, Oleksandr I.; Olkhov, Kostyantin V.; Nikitin, Maksim O.; Rodin, Dmytro O.
ENG: PVA-CoFe2O4-biochar composites were synthesized by a two-stage combined method. The resulting composites were characterized by X-ray diffraction, scanning electron microscopy, UV-visible absorption spectroscopy, vibrational magnetometry, and vector microwave analysis. The results of electron microscopy show that biochar has a block structure with large pores, so this structure can be used in the creation of composites. The magnetic properties depend on the content of cobalt ferrite in the composite. The results of the study of photocatalytic properties showed that the rate of destruction of methylene blue (MB) is 50–98% after 60 min of UV radiation. It was established that the reaction of photocatalytic decomposition of MB obeys pseudo-first-order kinetics. Among these catalysts, biochar showed the highest rate constant of 0.085 min−1, PVA/CoFe2O4-biochar composites – 0.05 min−1. When studying the absorption of electromagnetic radiation in the radar range from 8 GHz to 12 GHz by PVA/CoFe 2O4- biochar composites, it was found that with an increase in the ratio of CoFe2O4-bichar components to 0.67 wt. parts CoFe2O4, the absorption losses of the composite reach –14.15 dB/mm at a frequency of 8 GHz and –12.37 dB at a frequency of 12 GHz.