Water aluminosilicate glasses

Zeng et al. (1999) employed H- Al and H- Na TRAPDOR in combination with H mas to investigate the proton distribution in 4 hydrous aluminosilicate glasses. Peaks at 6 and 2.9 ppm correspond to 2 different water environments while others at 5-6, 3.5 and 1.5 ppm arise from 3 different hydroxyls. Rapid exchange occurs at room temperature between the 2 water environments. The data reveal the complexity of the proton speciation in these materials. All the resonances show a TRAPDOR effect to some extent. One of the groups identified is AlQ -OH, implying that the aluminosilicate framework is depolymerised by the water. This conclusion does not agree... 

Hartree Fock level calculations were made of the vibrational wavenumbers of A1(H20)63+.115 High-pressure Raman spectroscopy was used to follow the course of the C2/c to P2j/c phase transition at 3.2 GPa for LiAlSi2Oe (spodu-mene).116 IR and Raman spectra were used to follow the effects of water dissociation on the structure of boron-bearing aluminosilicate glasses based on albite, NaAlSi308.117... 

Make microelectrodes—we use 1.2-mm diameter, thin-walled aluminosilicate glass with internal filament (A-M Systems, Everett, WA). Electrode tip should have a nice constant taper and be fine but not wispy. When back-filled with dextran and 1M potassium chloride, they should have a resistance of between 50 and 150MQ. In practice, the precise electrode resistance does not matter if the electrode penetrates a cell, records a stable membrane potential, and passes sufficient dye, then it is a good electrode (see Notes 7 and 8). Electrodes should first be back-fiUed with approx 0.5 0L of fluorescent dextran (lOOmg/mL in distilled water. Molecular Probes cat. no. D-3308 and D-3306 for tetramethylrhodamine and fluorescein fluorescence, respectively) and then with a little 1M potassium chloride. Don t worry about air bubbles. The capillary action of the internal filament will deal with them. 

Many barium aluminosilicate-based compositions will eventually react with the chromium oxide or aluminum oxide scales on the metal interconnect or metal edge rails to form barium chromate or a celsian phase at the interface [6], This can cause a mechanical weakness that is easily delaminated. Also, compositions that contain boron can react over time with water (steam) to produce B2(OH)2 or B(OH)3 gas. This can decompose the glass and greatly limit the lifetime of the seal. Thus many of the new investigations have emphasized low or no boron glass compositions. 

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