Glasse hydrous

FIuorosihca.tes, Compared to the simple sUicates, these crystals have more complex chain and sheet stmctures. Examples from nature iaclude hydrous micas and amphiboles, including hornblende and nephrite jade. In glass-ceramics, fluorine replaces the hydroxyl ion fluorine is much easier to iacorporate ia glass and also makes the crystals more refractory. Eour commercial fluorosUicate glass-ceramic compositions and thek properties are Usted ia Table 2. 

A gel is defined as a hydrous metal aluminosihcate prepared from either aqueous solutions, reactive soflds, colloidal sols, or reactive aluminosihcates such as the residue stmcture of metakaolin and glasses. 

Rutile. It is unlikely that rutile will incorporate any U-series cations other than U, Th and Pa. Au and Aph can be estimated from Api, Azr and Anr, using the experimental data of Foley et al. (2000). In three experiments on a doped natural tonalite under hydrous conditions at 1.8 to 2.5 GPa, Foley et al. (2000) measure Azr and Anr by LA-ICP-MS. Unfortunately they do not report Api. However, we can estimate the Ti02 content of the melt from the glass analysis in Tenner et al. (1993) for the same tonalite starting material at similar P and T, which gives Api = 84. The Api/Azr and Anf/Azr ratios for the three experiments in Foley et al. (2000) can be fitted (using Vl-fold ionic radii) with =... 

Crowe and Crowe [3.39] proved that it is sufficient for certain liposomes, e. g. egg phosphatidyl-choline (DPPC), to be vitrified by trehalose or dextran during freezing and freeze drying. In trehalose the retention rate was almost 100 %, and in dextran more than 80 %. This did not apply to egg PC-liposomes Dextran as CPA alone led to an almost total loss of the CF-indicator, but addition of dextran into a trehalose solution (Fig. 3.20) also reduced the retention rate of CF substantially, e. g. from 90 % in a pure trehalose to approx. 45 % if trehalose and dextran were in equal amounts in the solution. Since T of dextran is approx. -10 °C and Tg- of trehalose is -30 to -32 °C, dextran should form a glass phase at much higher temperatures than trehalose. Therefore the stabilization of egg- PC with trehalose cannot be related with the vitrification. Crowe showd with IR spectroscopy that egg-PC freeze dried with 2 g trehalose/g lipid had almost the identical spectrographic characteristics as the hydrous lipid Trehalose molecules replaced the water molecules, and hydrogen... 

Behrens, H. and Stuke, A. (2003). Quantification of H20 contents in silicate glasses using IR spectroscopy - a calibration based on hydrous glasses analysed by Karl-Fischer titration. Glass Science and Technology 76 176-189. 

Figure 2-6 An FTIR spectrum of hydrous rhyolitic glass in the near-IR region of 600- to 375-mm wavenumbers. The absorbance A is defined as -log(7/7o), where Iq is the infrared beam intensity without the sample, and I is the intensity with the sample in the beam path. This sample contains about 0.8 wt% H20t. Both 523-and 452-mm peaks are combination modes. There are more hydrous peaks outside the region The fundamental stretch of OH (the strongest peak) is at 355 mm and the absorbance is usually off the scale. The overtone of the fundamental stretch is at 710mm, which is weak. As H20t content increases, the ratio of 523-mm peak height to 452-mm increases.

If the compositional difference along the diffusion direction is primarily in one component, and the difference in other components is due to the dilution effect, then diffusion of this component (not necessarily the other components) may be treated as effective binary, and the EBDC can be applied reliably to similar situations. Some examples are a diffusion couple made of dry rhyolite on one half and hydrous rhyolite on the other half, the hydration or dehydration of a silicate melt, and adsorption of a gas component by a glass. 

Infrared measurement of a hydrous obsidian glass gives the band intensities as 0.040/mm for the 523- mm band and 0.12/mm for the 452-cm band. Find the cooling rate of the obsidian glass when it was at the temperature of T e-... 

Silica makes up 12.6 mass-% of the Earth s crust as crystalline and amorphous forms. It was found that both modifications show similar main luminescence bands, namely a blue one centered at 450 nm ascribed to which substitutes for Si, red centered at 650 nm linked with non-bridge O, and dark-red at 700-730 nm linked with Fe. Time-resolved luminescence of hydrous volcanic glasses with different colors and different Fe, Mn, and H2O contents were measured and interpreted (Zotov et al. 2002). The blue band with a short decay time of 40 ns was connected with T2( D)- Ai ( S) and Ai C G)- Ai ( S) ligand field transitions of Fe " ", the green band with a decay time of approximately 250 ps with a Ti( G)- Ai( S) transition in tetrahedrally coordinated Mn ", while the red band with a much longer decay time of several ms with T1 (4G)- Ai( S) transitions in tetrahedrally coordinated Fe ". We detected Fe " " in the time-resolved luminescence spectrum of black obsidian glass (Fig. 4.43d). 

S. C. Kohn, R. Dupree and M. E. Smith, A multinuclear magnetic resonance study of the structure of hydrous albite glasses. Geochim. Cosmochim. Acta, 1989, 53,2925-2935. 

The most general feature of the adsorption behavior of metal ions at solid-aqueous solution interfaces is the abrupt rise in adsorption over a narrow pH range. This has been illustrated, for example, for manganese adsorption on glass (2), cobalt on hydrous ferric oxide (8), manganese on hydrous manganese oxide (12), protactinium on glass (14), and... 

Kohn, S. C., Chamock, J. M., Henderson, C. M. B. Greaves, G. N. (1990) The structural environment of trace elements in dry and hydrous silicate glasses A manganese and strontium K-edge X-ray absorption spectroscopic study. Contrib. Mineral. Petrol., 105, 359-68. 

Property Calcium carbonate Kaolin Talc Mica Glass microballoons Hydrous alumina Silica Wood flour... 

---