Single-phase α''-Fe16N2 nanoparticles have been synthesized with high reproducibility in gram amounts for the first time. The nanoparticles were obtained through the various kinds of successive procedure starting from the reduction of Fe-oxides, followed by nitriding in an atmosphere with very low moisture and oxygen contents of less than 1 ppm through the entire process. The single-phase α''-Fe16N2 nanoparticles exhibited saturation magnetization (Ms) of 234 emu/g at 5 K and a magnetocrystalline anisotropy constant (Ku) of 9.6×106 erg/cm3. These magnetic properties of this α''-Fe16N2 nanoparticles suggest that a new path for a possible candidate of the rare-earth-free permanent magnet material with a high Ms.

Carboxylated SiO2-coated α-Fe nanoparticles have been successfully prepared via CaH2-mediated reduction of SiO2-coated Fe3O4 nanoparticles followed by surface carboxylation. These α-Fe-based nanoparticles, which are characterized by ease of coating with additional functional groups, a large magnetization of 154 emu per g-Fe, enhanced corrosion resistivity, excellent aqueous dispersibility, and low cytotoxicity, have potential to be a versatile platform in biomedical applications.

Nanoparticles of R-Fe, an excellent soft magnet, have been successfully made corrosion-resistant and dispersible in polar and nonpolar solvents by coating these with inner and outer layers of amorphous silica and organics like poly(ethylene glycol), respectively. The double coating was facilitated by using stable and easy-to-handle oxide particles as the core to be subsequently metallized at temperatures low enough to keep the organic layer intact. Use of CaH 2 as a reductant lowered the working temperature down to 200-300 °C, where thermal particle adhesion did not take place, formation of impurities like iron silicates was suppressed, and the overall morphological features of the starting particles were preserved. The feasibility of organo-functionalization of the surface will open a way for this nanomagnet toward bioscientific and medical applications.

The e#ect of the continuous flow of supercritical CO, microbubbles (the SC-CO, method) on the inactivation of both Escherichia coli in model water and coliform bacteria in water prior to treatment at a municipal water filtering plant were studied as a way to produce safe drinkable tap water. The number of surviving cells in both samples drastically decreased above a certain concentration of dissolved CO, (gῌ,/). When treated for +-.-min, cells were not detected at concentrations over gῌ-*. The dependences of the number of surviving cells on the concentration of dissolved CO, were similar in both the treatments for 0.1 and +-.-min. Therefore, it was suggested that e#ective inactivation could be achieved by minimizing the treatment time. From these results, it was proposed that the SC-CO, method might be e#ective in inactivating E. coli and coliform bacteria for the production of public drinking water.