Toshinori Okura
Abstract
This review article describes a series of studies on the glass-ceramic Na + superionic conductors with Na5YSi4O12 (N5)-type structure synthesized using the composition formula of Na3+3x-yR1-xP < em>ySi3-yO9 for a variety of rare earth elements, R, under the appropriate composition parameters. Recent ...
Read More
This review article describes a series of studies on the glass-ceramic Na + superionic conductors with Na5YSi4O12 (N5)-type structure synthesized using the composition formula of Na3+3x-yR1-xP < em>ySi3-yO9 for a variety of rare earth elements, R, under the appropriate composition parameters. Recent researches on structural control of the Na + superionic conducting glass-ceramics are also introduced. The optimum conditions for crystallization were discussed with reference to the conduction properties and the preparation of crack-free N5-type glass-ceramics. The effects of Si substitution with the various elements with tetrahedral oxygen coordination structure and Y substitution with the various R elements were also discussed on ionic conductivity of N5-type glass-ceramics, respectively.
A. Dussan; Heiddy P. Quiroz
Abstract
In this work, we fabricated samples of titanium dioxide nanotube arrays via electrochemical anodization by using titanium foils as anode and cathode. A solution of water, ethyleneglycol, and ammonium fluoride (NH4F) at room temperature was used for the samples synthesis process. Different times and anodizing ...
Read More
In this work, we fabricated samples of titanium dioxide nanotube arrays via electrochemical anodization by using titanium foils as anode and cathode. A solution of water, ethyleneglycol, and ammonium fluoride (NH4F) at room temperature was used for the samples synthesis process. Different times and anodizing voltages were used during reaction. From X-ray diffraction (XRD) and micro-diffraction (mXRD) measurements, rutile and anatase phases were identified as function of deposition parameters. The Ti3O5 phase was observed by deconvolution of Debye-Scherrer rings of the microdiffraction spectra. Annealing processes were performed for all samples in the range between 273 and 723 K, without changes in the material’s morphological properties, while the crystalline structure was affected. Nanotube diameters varying between 30 and 42 nm were observed from SEM micrographs, when NH4F concentration was changed from 0.25 to 0.50 wt%. An alternating anodizing voltage generates the formation of nanotubes evenly spaced on the surface with nodes in bamboo-type form, while a smooth form for nanotubes was observed with constant applied voltage. From stereoscopic 3D micrographs, a reconstruction of the topographic surface of the TiO2 nanotubes was conducted. A correlation between synthesis parameters and morphological properties is presented.
)