No abstract

To investigate the sorption mechanism of cesium (Cs) into clay minerals, high-resolution (scanning) transmission electron microscopy (TEM/STEM) imaging of Cs in mica (phlogopite) has been conducted. Platy phlogopite powders were immersed in a cesium chloride (CsCl) solution to achieve Cs(+)-K(+) ion-exchange at the interlayer regions in phlogopite. To observe many phlogopite particles with the incident electron beam parallel to the mica layers, cross-sectional thin specimens were prepared from sedimented particles using a focused ion beam. High-angle annular dark-field imaging with STEM is superior to conventional high-resolution TEM (HRTEM) for visualizing Cs at interlayer sites even in thicker crystal regions and/or at lower magnification due to the intense Z-contrast of Cs. However, HRTEM is also practical for estimating the concentration of Cs at the interlayer site from the thickness dependence of the contrast at the interlayer region. Cs sorption of micas was previously thought to be localized mainly at the frayed-edge sites of mica crystals. However, the present observations indicate that Cs substitution of K occurs not around crystal edges but deep inside the crystals along specific interlayer regions.

Ultrafast demagnetization in magnetic nanoparticles using pulsed laser has attracted considerable attention because of its potential applications in spintronics, such as data storage.In such applications, it is necessary to control magnetization using low-energy laser pulses; however, this poses the problem of increasing the amount of energy from the excitation laser pulses to the spin subsystem. We take advantage of the phenomenon known as localized surface plasmon resonance (LSPR) to enhance the energy transfer from laser pulses to the spin subsystem. To induce LSPR, hybrid nanoparticles consisting of noble metal nanoparticles with LSPR absorption and magnetic metal nanoparticles are prepared using a novel method. Specifically, Ag-Co hybrid nanoparticles are prepared by a self-assembly method using pulsed laser deposition. We performed measurements of the static Faraday and time-resolved Faraday effects using a pump-probe technique on the Ag-Co hybrid nanoparticles with various Ag-Co ratios. The data suggest that the LSPR absorption and demagnetization amplitude increase with the increasing Ag-Co ratio. The results indicate that the amount of energy transferred from the laser pulses to the spin system of magnetic nanoparticles can increase via LSPR absorption.

High-resolution structure analyses using electron beam techniques have been performed for the investigation of subgrain boundaries (SGBs) in deformed orthopyroxene (Opx) in mylonite from Hidaka Metamorphic Belt, Hokkaido, Japan, to understand ductile deformation mechanism of silicate minerals in shear zones. Scanning electron microscopy (SEM) and electron backscatter diffraction (EBSD) analysis of Opx porphyroclasts in the mylonitic rock indicated that the crystal orientation inside the Opx crystals gradually changes by rotation about the b-axis by SGBs and crystal folding. In order to observe the SGBs along the b-axis by transmission electron microscopy (TEM) or scanning TEM (STEM), the following sample preparation protocol was adopted. First, petrographic thin sections were slightly etched with hydrofluoric acid to identify SGBs in SEM. The Opx crystals whose b-axes were oriented close to the normal of the surface were identified by EBSD, and the areas containing SGBs were picked and thinned for (S) TEM analysis with a focused ion beam instrument with micro-sampling system. High-resolution TEM imaging of the SGBs in Opx revealed various boundary structures from a periodic array of dissociated (100) [001] edge dislocations to partially or completely incoherent crystals, depending on the misorientation angle. Atomic-resolution STEM imaging clearly confirmed the formation of clinopyroxene (Cpx) structure between the dissociated partial dislocations. Moreover, X-ray microanalysis in STEM revealed that the Cpx contains a considerable amount of calcium replacing iron. Such chemical inhomogeneity may limit glide motion of the dislocation and eventually the plastic deformation of the Opx porphyroclasts at a low temperature. Chemical profiles across the high-angle incoherent SGB also showed an enrichment of the latter in calcium at the boundary, suggesting that SGBs are an efficient diffusion pathway of calcium out of host Opx grain during cooling.

Asymmetric sulfenylations of 4-alkylcyclohexanones (6a,b) with chiral sulfenamides (1–5) were achieved in the presence of a catalytic amount of triethylamine hydrochloride to give 4-alkyl-2-phenylthiocyclohexanones (7a,b), which were transformed into optically active 4-alkyl-2-phenylthiocyclohexenes (10a,b) and 3-alkylcyclohexanones (11a,b) in fairly good chemical and optical yields. The influences of chiral sulfenamides and the reaction conditions on this asymmetric induction are described.