Effect of air annealing on properties of maghemite nanoparticles produced by radiation-chemical method

• Published in: Ceramics international 2023-08, Vol.49 (15), p.25414-25426
• Main Authors: Ilves, V.G., Pizúrová, N., Korusenko, P.M., Sokovnin, S. Yu, Balezin, M.E., Gerasimov, A.S., Uimin, M.A., Zuev, M.G., Vasin, A.A.
• Format: Article
• Language: English
• Subjects: Annealing in air; DSC-TG; Maghemite and hematite nanoparticles; Magnetism; Photocatalysis; Photoluminescence; Radiation-chemical method; XPS
• ISSN: 0272-8842
• DOI: 10.1016/j.ceramint.2023.05.080

Amorphous-crystalline nanoparticles (NPles) of maghemite (γ-Fe2O3) were successfully prepared by a radiation-chemical method using a precursor-heptahydrate of iron (II) sulfate. Synthesized NPles were quasi-spherical agglomerates 200–300 nm in size with an uneven surface covered with thin, porous, randomly oriented, elongated plates of irregular shape, with sharp vertices. The amorphous component of NPles included ultra-fine NPles maghemite about 2 nm in size. Stepwise annealing of the original nanopowder (NP) in air showed a phase transformation of NPles along the following path: maghemite + amorph (RT-150 °C) →amorph (200–500 °C) →hematite (570–1050 °C). The hematite NP produced after annealing at a temperature of 575 °C showed good texture characteristics: the specific surface area (SSA) increased from 21 to 36.8 m2/g, the pore volume increased from 0.04 to 0.15 cm3/g, while maintaining the particle nanosize of not more than 38 nm. X-ray photoelectron spectroscopy (XPS) showed the presence of the following elements on the surface of the synthesized NPles –S, C, O, Fe and N (N only in the original sample S0) and increased O–Fe bond with an increase in annealing temperature. The paramagnetic properties of the studied NPles indicate the prospect of their use as contrast agents in magnetic resonance imaging (MRI). •The amorphous-crystalline NPles maghemite with protuberances were produced by means of radiation-chemical method.•After annealing at 200 °C, the amorphous crystalline NP became completely amorphous and maintained it up to 500 °C.•Under dynamic heating, the phase transformations were carried out according to the following scheme: [Display omitted] •Hematite NPles size after annealing at 575 °C did not exceed 38 nm•Paramagnetic, photoluminescent and photocatalytic properties of the produced NPles indicate their high potential in medicine and catalysis