Junya Matsuno

Formation mechanism of metal embedded amorphous silicate nanoparticles by induction thermal plasmas

The purpose of this paper was to synthesize metal embedded amorphous silicate nanoparticles by induction thermal plasmas. Powder of Fe, Ni, Sn, and Zn were used as precursor as well as SiO2 and MgO. In the case of Fe, Ni, and Sn, metal embedded nanoparticles were successfully synthesized. While most of Zn nanoparticles were attached on the surface of the amorphous silicate nanoparticles. Internal rate of each metal in the synthesized nanoparticles and nucleation temperature were evaluated to understand the formation mechanism of the metal embedded amorphous silicate nanoparticles. Results indicated that the relationship between the nucleation temperature of silicon and the melting temperature of each metal has important role on the metal embedded nanoparticles formation.

Reduction experiment of FeO-bearing amorphous silicate: application to origin of metallic iron in GEMS

Glass with embedded metal and sulfides (GEMS) are amorphous silicates included in anhydrous interplanetary dust particles (IDPs) and can provide information about material evolution in our early solar system. Several formation processes for GEMS have been proposed so far, but these theories are still being debated. To investigate a possible GEMS origin by reduction of interstellar silicates, we synthesized amorphous silicates with a mean GEMS composition and performed heating experiments in a reducing atmosphere. FeO-bearing amorphous silicates were heated at 923 K and 973 K for 3 hr, and at 1023 K for 1-48 hr at ambient pressure in a reducing atmosphere. Fe grains formed at the interface between the silicate and the reducing gas through a reduction. In contrast, TEM observations of natural GEMS show that metallic grains are uniformly embedded in amorphous silicates. Therefore, the present study suggests that metallic inclusions in GEMS could not form as reduction products and that other formation process such as condensation or irradiation are more likely.