Aluminosilicate glasses structure

The polyelectrolyte cements are modern materials that have adhesive properties and are formed by the cement-forming reaction between a poly(alkenoic acid), typically poly(acrylic acid), PAA, in concentrated aqueous solution, and a cation-releasing base. The base may be a metal oxide, in particular zinc oxide, a silicate mineral or an aluminosilicate glass. The presence of a polyacid in these cements gives them the valuable property of adhesion. The structures of some poly(alkenoic acid)s are shown in Figure 5.1. 

Y. Cao and A.N. Cormack. A structural model for interpretation of an anomaly in alkali aluminosilicate glasses at Al/alkali = 0.2-0.4. In H. Jain and D. Gupta, editors, Diffusion in Amorphous Materials, pages 137-151, Warrendale, PA, 1994. The Minerals, Metals and Materials Society. 

In principle these compounds offer access to materials with AliCh-SiCL and Al203 2Si02 stoichiometries. The latter stoichiometry is equivalent to the Al[OSi(OBu-t)3 (OBu-t)] precursor. The major drawbacks with these materials are their air and moisture sensitivity, and the cost of the starting materials. Although the idealized stoichiometries of the above ceramics products are not those of crystalline aluminosilicates, amorphous aluminosilicate glasses are often important in optical applications or in scratch-resistant coatings. Furthermore, they may offer potential for CVD-type applications. There still remains considerable need for simple precursors to crystalline aluminosilicates, especially for structural applications. Dense, phase pure crystalline ceramic materials are desired for optimal mechanical properties, e.g. ceramic fibers for composite manufacture. 

McMillan, P. F. (1981). A structural study of aluminosilicate glasses by Raman spectroscopy. Unpub. Ph.D. Thesis, Arizona State Univ. 

The spectra of a series of framework aluminosilicate glasses (Oestrike et al. 1987) indicate the presence of only tetrahedral Al, corresponding to the structures of the corresponding crystalline aluminosilicates, but with broadened Al resonances. As with the crystalline framework aluminosilicates, the Al becomes progressively deshielded as the compositional parameter Si/(Si(IV) 3- Al(IV)) decreases, leading to a linear relationship between this parameter and the chemical shift 8... 

Many aluminosilicate glass ceramics are based on framework structures of AIO4 tetrahedra, which, when crystallized, posseses low thermal expansions. This gives the glass ceramics based on them near zero expansions and thus excellent dimensional stability, thermal shock resistance, and mechanical strength. Aluminosilicate glass ceramics are used commercially as telescope mirrors, thermally stable structures for satellites and space probes, gyroscope components, heat-resistant windows, stove tops, and cookware. 

Ab initio calculations have been made of H, O, A1 and Si NMR parameters for sodium aluminosilicate glasses and hydrous silica.331 Two-dimensional 170 3Q MAS-NMR experiments on sodium aluminosilicate glass gave evidence for A1 O Al links.332 27A1 NMR spectra were used to study structural localisation of Al3+ in aluminosilicate clays.333 170 MAS-NMR and MQ MAS-NMR experiments have been carried out on hybrid aluminosilicate xerogels, providing evidence for Si-O-Al and Si O Si sites.334 Several other NMR studies have been made on aluminosilicate glasses and related systems.335 338... 

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... 

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