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1.
《Journal of Non》2005,351(8-9):650-655
Aluminate glasses containing 45–71.5 mol% alumina, 10–40 mol% rare earth oxide, and 0–30 mol% silica were synthesized from precursor oxides. The glass transition and crystallization temperatures were determined by differential scanning calorimetry; the structural and mechanical properties were investigated by Raman and Brillouin spectroscopy. The range of the supercooled liquid region varies from ∼40 °C to 200 °C, providing a useful working range for compositions with 5–30 mol% silica. Raman scattering showed the presence of isolated SiO4 species that strengthen the network-forming structure, enhance glass formation, and stabilize the glass even when they are present at fairly low concentrations. Sound velocities were measured by Brillouin scattering. From these and other values, various elastic moduli were calculated. The moduli increased with both aluminum and rare earth content, as did the hardness of the glasses. Young’s modulus was in the range 118–169 GPa, 60–130% larger than that for pure silica glass. 相似文献
2.
A simple IR reflection method was used in a previous study to determine the fictive temperature of silica glasses and a soda-lime glass. The IR method is based upon the fact that the silica structural band of a glass takes a unique wavenumber at a particular fictive temperature. When this method was applied to an alumino-silicate glass in this study, however, the IR reflection peak wavenumber of the glass surface was found to be strongly affected by the reaction of the glass with water vapor in the atmosphere. Still, it was possible to measure the fictive temperature of the alumino-silicate glass using IR spectroscopy by taking an IR reflection of the bulk sample after eliminating the surface layer affected by the reaction with water vapor. The IR peak wavenumber of the silica structural band decreased with increasing fictive temperature for the alumino-silicate glass, similar to silica glass. 相似文献
3.
Calcium aluminosilicate and calcium fluoro-aluminosilicate glasses have been characterized by 29Si, 27Al and 19F MAS-NMR. The two calcium aluminosilicate glasses examined were based on the composition 2SiO2 · Al2O3 · 2CaO (ART1) and the mineral anorthite 2SiO2 · Al2O3 · CaO (ART2). The observed chemical shifts for 29Si and 27Al agreed with previous studies. The fluorine containing glasses were based on 2SiO2 · Al2O3 · (2−X)CaO · XCaF2. The 29Si chemical shift moved in a negative direction with increase fluorine content indicating a progressive reduction in the average number of non-bridging oxygens, NBO, attached to a silicon. The 27Al spectra indicated the presence of four coordinate aluminium in the glasses with X=0.0-0.75, but aluminium was present in Al(IV), Al(V) and Al(VI) coordination states in the highest fluorine content glass with X=1.0. The 19F spectra indicated the presence of F-Ca(n) in low fluorine content glasses and both F-Ca(n) and Al-F-Ca(n) in high fluorine content glasses. We speculate here that the Al-F-Ca(n) species are oxyfluorides [AlOxFy]n−, where x=1-6, y=1-6 and n is the charge on the total complex when aluminium is in Al(IV), Al(V) and Al(VI) coordinate states. The reduction in the average number of NBO per silicon with increasing fluorine content is explained by fluorine converting Ca2+ to F-Ca(n). 相似文献
4.
The elastic constants of 7 phosphate/vanadate glasses, containing TiO2, Na2O and a range of concentrations of CuO, have been measured from 4.2 to 300 K. The pressure variation of the elastic constants has also been measured and has been used to calculate the low temperature value of the Grüneisen parameter γO for these glasses. Analysis of the results and other data has been used to show how TiO2, Na2O and CuO may be incorporated in the structure of these P2O5/V2O5 glasses. 相似文献
5.
《Journal of Non》2006,352(50-51):5301-5308
A detailed analysis of the reflectance and transmittance spectra of a set of glasses allowed retrieval, besides the optical functions, of quantitative information on the structural changes occurring in the calcium silicate glass system. The occurrence of a threshold around 46% of CaO content is confirmed and is connected to the appearance in the glass structure of a new configuration of calcium cations. It was also shown that the calcium cations that exceeds the compositional threshold does not act as modifiers of the silicate network since they form Ca–O–Ca bonds in the glass structure. Obvious changes occurring at the threshold in the physical or chemical properties can be understood in the light of the structural changes observed in the system. 相似文献
6.
The elastic moduli and their variation with pressure have been determined for three glass compositions in the K2OSiO2 glass system. The results may be summarized:
Property/Composition | 0.15K2O–0.85SiO2 | 0.25K2O–0.75SiO2 | 0.33K2O–0.67SiO2 |
Shear modulus | 266 | 241 | 231 |
Bulk modulus | 310 | 283 | 273 |
Young's modulus | 620 | 564 | 540 |
( | ?5.1 | ?4.4 | ?3.9 |
( | ?2.8 | ?2.6 | ?2.5 |
Poisson's ratio σ | 0.167 | 0.168 | 0.170 |
() | |||
(kb?1) | ?1.5 | ?1.2 | ?0.95 |