Effect of B 2 O 3 content on crack resistance was investigated by indentation tests of glass samples with various compositions of B 2 O 3 . The ternary SiO 2 B 2 O 3 Na 2 O glass system (SBN series) and non-alkaline aluminoborosilicate glass system (SAB series). When B 2 O 3 is substituted with SiO 2 in the SBN system ("SBN1" series), crack resistance has a relationship with density. In a series of the SBN system where density did not change with B 2 O 3 content ("SBN2" series), crack resistance decreased with increasing B 2 O 3 content. On the other hand, crack resistance increased with increasing B 2 O 3 content in the SAB series, where density did not change. According to the results of NMR measurement, boron in 4-cordination state ([4] B) increased in the SBN2 series while boron in 3-cordination state ([3] B) increased in the SAB series with increasing B 2 O 3 content. Therefore, crack resistance increases with increasing [3] B and decreases with increasing[4] B. The difference in structure between [3] B and [4] B containing glasses leads to different effect on residual stress around the indentation, resulting in difference in crack resistance.
The stacking order of graphite layers in mesocarbon microbeads (MCMB5) heat-treated between 700 and 3000°C was examined by analyses of x-ray diffraction measurements, and lithium insertion into the MCMBs has been observed using solid-state ti-nuclear magnetic resonance (7Li-NMR) spectroscopy. In MCMTBs heat-treated above 2000°C, the fully lithiated MCMBs showed two bands at ca. 45 ppm (vs. LiC1) and ca. 27 ppm in their 7Li-NMR spectra. The profile of the band at 45 ppm was very close to that for the first-stage lithium graphite intercalation compound (Li-GIC), though the other band at 27 ppm could not be assigned to any phases of Li-GICs. From these results, it is suggested that the structures of the MCMBs heat-treated above 2000°C for lithium insertion are classified as graphitic structure, which has the AB stacking order of graphite layers, and turbostratic structure with a random stacking sequence of graphite layers; the fully lithiated compositions of both structures were estimated as LiC6 and ca. Li,2C6, respectively. Although MCMB heat-treated at 700°C gave a higher capacity than LiC6, the line shift in the 7Li-NMR spectra indicated that lithium stored in the MCMB displayed an ionic character. Capacity change of the MCMBs during charge-discharge cycling up to 20 cycles and capacity loss at higher current densities (< 200 mA g') were also examined.) unless CC License in place (see abstract). ecsdl.org/site/terms_use address. Redistribution subject to ECS terms of use (see 128.122.253.228 Downloaded on 2015-02-06 to IP
Transparent fluorescence oxide glass with high emission yields has been prepared. Porous glass was impregnated with rare-earth and transition-metal ions and consequently sintered at 1100°C into a compact nonporous glass. Reduction sintering is indispensable for obtaining fluorescence glass with high emission yield. Sintering of glass impregnated with Eu ions in a reducing atmosphere enhances the emission intensity by about 15 times than that sintered in air. The Eu 2+ and Ce 3+ ions and Sn 2+ and Cu + ions incorporated in SiO 2 glass obtained by reduction sintering exhibit intense fluorescence in the near-ultraviolet and visible ranges, their emission yields are 97%, 70%, 100%, and 90%, respectively.
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