2016 年 124 巻 1 号 p. 23-28
The synthesis conditions of a nano-sized magnetite powder using a reverse coprecipitation method were studied in order to control the particle size and the heat generation ability in an AC magnetic field for thermal coagulation therapy. A low temperature reaction and high concentration of the mixed irons as the starting materials in solution increased the particle size of the magnetite powder. The particle size decreased with an increase in the concentration of the coexisting Na+ and Cl− ions. The particle size was enhanced with an increase in the R = Fe2+/(Fe2+ + Fe3+) molar ratio of the divalent iron, and the maximum heat generation ability was obtained at the R = 0.33 molar ratio. The maximum heat generation ability of 0.25–0.28 W·g−1 in the AC magnetic field (370 kHz, 1.77 kA·m−1) was obtained for the magnetite having an ca. 13–14 nm particle size.