Papers by Author: Hirohisa Yamada

Abstract: The effect of natural mica on the morphology and properties of polyamide 6 (PA-6) nanocomposites was examined. Natural mica (sericite) acquired from a well-known mine in Shimane, Japan was ion-exchanged with an alkyl amine hydrochloride compound. The resulting organomica was extruded with PA-6 using a twin-screw extruder. Quantitative analysis of TEM photomicrographs of the nanocomposite reveal a fairly large average particle length and a higher degree of platelet exfoliation for the natural mica-based nanocomposite compared to the clay version, thus translating into a higher particle aspect ratio. The resulting nanomica/PA-6 composite exhibits a high degree of mica exfoliation and improved thermal mechanical properties.

Abstract: Silver sodalite crystals with hydroxyl guest anion and silver loading higher than 7.9 per unit cell were investigated. EPR spectra of sodalite, recorded just afer g-irradiation at 77K, shows a 9-line, near isotropic signal with giso=1.987 and hyperfine splitting of 8.3 mT. The signal decays completely above 200K. We assign the multiplet to silver octamer Ag8 n+ cluster and tentatively postulate that the cluster charge is +7.