An inorganic anionic polymer filter disc: direct crystallization of a layered silicate nanosheet on a glass fiber filter

An inorganic anionic polymer filter disc was successfully produced from heterogeneous nucleation reactions of layered silicate fine crystals on amorphous silica glass fibers. This hybrid material can be obtained only by immersing the silica fiber filter disc in an aqueous solution containing LiF, MgCl2, and urea at 373 K for 48 h. Silica sol, which was partially dissolved from the silica fibers by hydrolysis of urea, was a source of the layered silicate. Firm immobilization of the layered silicate on the fiber silica was confirmed by immersing in aqueous LiCl solution (12 mM) for three weeks. The layered silicate crystals evenly covered the silica fibers while maintaining the original filter disc shape. Careful design of the layered silicate was performed by changing the molar LiF : MgCl2 : urea : SiO2 ratio. The layered silicate on the fibers became thick on adding increasing amounts of LiF and MgCl2. In addition, by increasing the amount of LiF, the negative charge density of the layered silicate increased, following the trend of caffeine adsorption in water. Furthermore, we found that the amount of urea added to the starting solution was important for preventing a loss in the mechanical strength of the fibers (e.g., fracture due to unnecessary dissolution of the silica fiber) and emerging side-reactions (e.g., polymerization of silica sol to yield spherical silica particles). The resulting layers of silicate on the filter disc acted as adsorption sites for both organic (methylene blue and benzylammonium) and inorganic (sodium, calcium, and europium) cationic species in water, as exemplified by batch and flow tests.ArticleRSC ADVANCES. 6(31): 26130-26136 (2016)journal articl

Influence of Cu2O Addition on Crystallization Process and Microstructure of Transparent Mica Glass-Ceramics

ArticleKey Engineering Materials. 617: 209-212 (2014)journal articl

Preparation and Characterization of Deposited Tetraethylorthosilicate-SiO2/SiC MIS Structure

The SiO2 layer was deposited on the 4H-SiC Si face by the thermal decomposition of tetraethylorthosilicate(TEOS) in N2 atmosphere to from MIS diodes. The post deposition annealing was effective to improve the interface properties. The interface state density of the deposited SiO2/SiC MIS structure was estimated to be the order of 1011 cm-2eV-1 by Terman method. The direct nitridation of SiC surface prior to the deposition of the SiO2 layer was effective to reduce the interface state density.ArticleMaterials Science Forum, Vols. 740-742, pp. 805-808 (2013)journal articl

Tin Oxides as a Negative Electrode Material for Potassium-Ion Batteries

ArticleACS Applied Energy Materials. 1(12): 6865-6870 (2018)journal articl

Preparation and luminescent properties of Eu-doped transparent mica glass-ceramics

Eu-doped transparent mica glass–ceramics were prepared, the influence of Eu-doping on the crystallization of the parent glasses was investigated and the luminescent properties of the parent glasses and the glass–ceramics were estimated. A small additive amount of Eu element was very effective in preparing transparent mica glass–ceramics. However, the excess addition led to the coarsening of phase separation in the glass phase and the separation of unidentified crystal phases and β-eucryptite during heating of the parent glasses, which caused white opaque at lower heating temperatures. When mica crystals were separated, Eu ions entered the interlayers of mica crystals. The observed emission and excitation spectra showed that parts of Eu³⁺ ions which were added as Eu₂O₃ were reduced to Eu²⁺ ions during melting of the starting materials and heating the parent glasses in air and the energy transfer from Eu²⁺ to Eu³⁺ ions occurred.ArticleCeramics International. 36(4):1303-1309 (2010)journal articl

Fabrication and Fracture Toughness of CNTs/Alumina Composites with Fine Microstructures

ArticleKey Engineering Materials. 617: 205-208 (2014)journal articl

Deposition of boehmite on carbon nanofibers using aluminum alkoxide and its thermal transformation

We attempted to prepare carbon nanofibers (CNFs) bonded chemically with alumina particles using acid-treated CNFs and aluminum secbutoxide. The structure and morphology of the boehmite deposited on the CNFs, the boundary between the CNFs and the deposited boehmite, and the thermal transformation of the deposited boehmite were investigated using Raman spectroscopy, X-ray diffraction (XRD) analysis, field-emission scanning electron microscopy (FE-SEM), and transmission electron microscopy (TEM). The boehmite deposited not only particulately on the CNFs but also in a film-like manner on parts of the CNFs. In addition, the boehmite could deposit not only on the disordered inner walls of the CNFs but also on the ordered inner walls. By heating at 1200 degrees C, the boehmite on the CNFs was transformed into alpha-alumina and theta-alumina. At this time, some alumina particles, particularly those formed on the ordered inner walls of CNFs, fell out of the CNFs, and only those alumina particles which might chemically bond with CNFs remained on the CNFs. Finally, CNFs dotted with alumina particles with a size of <50 nm were obtained. (C) 2015 Elsevier Ltd and Techna Group S.r.l. All rights reserved.ArticleCERAMICS INTERNATIONAL. 41(10):13171-13178 (2015)journal articl

Plasma Nitridation of 4H-SiC by Glow Discharge of N2/H2 Mixed Gases

The mixed gas of nitrogen and hydrogen was used for the plasma nitridation of SiC surface.A small amount of hydrogen was effective to activate the nitridation reaction and suppress the oxidationreaction. The interface properties were improved by using nitride layer as an interfacial bufferlayer of SiC MIS structure.ArticleMaterials Science Forum, Vols. 821-823, pp. 504-507 (2015)journal articl

Preparation and Characterization of Nitridation Layer on 4H SiC (0001) Surface by Direct Plasma Nitridation

A nitride layer was formed on a SiC surface by plasma nitridation using pure nitrogen as the reaction gas at the temperature from 800°C to 1400°C. The surface was characterized by XPS. The XPS measurement showed that an oxinitride layer was formed on the SiC surface by the plasma nitridation. The high process temperature seemed to be effective to activate the niridation reaction. A SiO2 film was deposited on the nitridation layer to form SiO2/nitride/SiC structure. The interface state density of the SiO2/nitride/SiC structure was lower than that of the SiO2/SiC structure. This suggested that the nitridation was effective to improve the interface property.ArticleMaterials Science Forum, Vols. 778-780, pp. 631-634 (2014)journal articl

Microstructures and luminescent properties of Ce-doped transparent mica glass-ceramics

Transparent mica glass-ceramics were prepared by heating parent glasses that had been doped with 0.5-15 mol% CeO2. During the melting and heat treatment, Ce4+ ions in the specimens were reduced to Ce3+ ions, and one or both of these ion species were then replaced with Li+ ions in the interlayers of the separated mica crystals. However, scanning transmission electron microscope (STEM) and Z-contrast imaging revealed that the mica crystals did not contain the same amount of Ce. On excitation at 254 nm, the parent glasses and glass-ceramics emitted blue light, which originated from the 5d to 4f transition of the Ce3+ ions. The emission of the glass-ceramic containing a smaller amount of Ce was attributed to the Ce3+ ions in both the glass phase and the mica crystals, whereas that of the glass-ceramics containing a larger amount of Ce was caused mainly by Ce3+ ions in the mica crystals. The dependence of the emission band of the parent glasses on the amount of Ce was a unique feature of the Ce-doped transparent mica glass-ceramics and was not observed in previous studies of Eu-doped parent glasses and mica glass-ceramics.ArticleMATERIALS SCIENCE AND ENGINEERING B-ADVANCED FUNCTIONAL SOLID-STATE MATERIALS. 177(7):504-509 (2012)journal articl