Continuous Reactive Crystallization of Metal Oxide Nanoparticles with the Spinel Structure in Hot-Compressed Water Using Microspace

Using Microspace 佐藤 敏幸 Toshiyuki SATO In this article, spinel structure MFe 2 O 4 ( M ＝ Ni, Cu, Zn ) nanoparticles from Fe ( NO 3 ) 3 and M ( NO 3 ) 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 MFe 2 O 4 with a cu-bic 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 for-mation of nonstoichiometric MFe 2 O 4 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 0.35 for Zn / Fe. ［ water, metal oxide,