2021 年 31 巻 1 号 p. 18-25
In this article, spinel structure MFe2O4 (M = Ni, Cu, Zn) nanoparticles from Fe(NO3)3 and M(NO3)2 (M = Ni, Cu, Zn) aqueous solutions could be synthesized continuously with a flow reactor at 673 K, 30 MPa, and 0.35 - 2.00 s residence time. The particles were characterized by TEM, XRD, and XRF to obtain sizes, crystal structures, lattice parameters, and molar ratios, respectively. Solid solution nanoparticles of MFe2O4 with a cubic spinel structure and an average particle size under 20 nm were obtained. M/Fe molar ratio of the obtained particles evaluated by XRF analyses was lower than the ratio in the stating solution. This result suggests the formation of nonstoichiometric MFe2O4 particles. Further, minimal M/Fe molar ratio of the particle to maintain stable phase at 673 K was investigated by calcination at 673 K for 3 h and it was found to be about 0.35 for Zn/Fe.
