Search

The pore shape and size of MCM-41 are studied analytically by comparing the observed powder X-ray diffraction intensities with that derived from the MCM-41 crystal structure models, with two different pore shapes, a hexagon and a circle. The pore size and boundary obtained from this approach has agreed well with those obtained from an [N.sub.2] gas adsorption measurement combined with the Fourier synthesized density map.

Author(s): Shunai Che (corresponding author) [1]; Zheng Liu [2, 3]; Tetsu Ohsuna [3]; Kazutami Sakamoto [4]; Osamu Terasaki [3]; Takashi Tatsumi [5] Chirality is widely expressed in organic materials, perhaps [...]

Fourier reconstruction is developed for high resolution transmission electron microscopy (HRTEM) images and enhancement of the atomic positions in blurred potential map obtained by the reconstruction with a support of Patterson map are presented. A Fourier reconstruction method for making a 3d-potential map for HRTEM images might be a more robust way to retrieve the crystal structure when several HRTEM images are taken with high resolution and correction is available.

Author(s): Shinji Inagaki (corresponding author) [1]; Shiyou Guan [1, 2]; Tetsu Ohsuna [3]; Osamu Terasaki [4] Surfactant-mediated synthesis strategies are widely used to fabricate ordered mesoporous solids [1, 2, 3, [...]

The synthesis of novel organic-inorganic hybrid mesoporous materials has led to the homogeneous distribution of organic and inorganic oxide moieties at the molecular level in the framework, forming a covalently bonded network. These materials are highly ordered at the mesoscale, with two- and three-dimensional hexagonal symmetries and well-defined external morphologies. A uniform pore-size distribution with pore diameters of 31 and 27 angstroms, and high surface areas of 750 and 1170 square meter/g was shown by nitrogen adsorption measurements.

The crystal structures, compression behaviors, and electronic properties of Sn3N4 polymorphs were investigated by means of high-pressure in situ measurements, transmission electron microscopy, and DFT ab initio calculations. The direct nitridation of tin above a pressure of 29.5 GPa by using a laser-heated diamond anvil cell resulted in the synthesis of highly crystalline monoclinic Sn3N4 which so far is consistent with the reported one. On the other hand, it was newly discovered that the monoclinic Sn3N4 undergoes phase transition twice along with decompression at ambient pressure. Advanced synchrotron X-ray powder diffraction measurements and TEM analyses on the recovered sample demonstrate that the newly recovered Sn3N4 crystallizes with orthorhombic symmetry and consists of irregularly shaped SnN5 and SnN6. DFT ab initio calculations reveal that this newly recovered orthorhombic Sn3N4 is an indirect band gap semiconductor having a narrower electronic energy gap than that of cubic spinel-type Sn3N4. The present results demonstrate that high-pressure nitridation is a powerful method to synthesize highly crystalline Sn3N4 polymorphs and reveal the new crystal chemistry of group IVA nitrides with respect to the variety of crystal structures and electronic properties. [ABSTRACT FROM AUTHOR]

We fabricated bilayer silicene (BLSi) from an epitaxial CaSi2 thin film grown on a Si (111) substrate followed by treatment with BF−4-based ionic liquid. First, a 6R-CaSi2 thin film was grown from simultaneously supplied Ca and Si sources. After reacting the CaSi2 thin film with BF−4-based ionic liquid, the BLSi was formed. The reaction proceeded laterally along the CaSi2 layer. The rearrangement of the Si and Ca atomic layers in the CaSi2 thin film was investigated by high-angle annular dark-field scanning transmission electron microscope images. [ABSTRACT FROM AUTHOR]

A study to report a unique structural transformation process for a new nanostructured titania film consisting of a high-density anatase nanopillars with open-spaced, perpendicular, and continuous porosity, referred as inverse mesospace is performed. The mesostructures reported have included 2D hexagonal with mesochannels running parallel to substrate and 3D cubic structures and these exhibit ordered pore size and high surface area, the lack of perpendicular porosity greatly reduces the merit of the films.

A novel self-assembly route to ordered silica-organic hybrids using well-defined siloxane oligomers with alkoxy functionality and covalently attached alkyl chains are investigated. The results provide a deeper understanding of the present self-assembly process that is strongly governed by the molecular packing of oligosiloxane precursors.