ChemInform Abstract: Structure of Phosphorus Oxynitride Glasses

Abstract

005ChemInform Abstract has been investigated using a combination of solid-state 31P, 15N, and 23Na NMR and Raman spectroscopy. The Raman spectra of model phosphazene compounds with different types of P-N bonding have been used for the spectral assignment. The structural results are shown to be consistent with known chemical and physical properties of nitrided NaPO3 glasses. The N atoms replace O in the phosphate glass network both as N bonded to two P atoms via one double and on single bond and as N bonded to three P atoms via single bonds. Nitrogen influences the chemical durability, thermal expansion, and other properties by cross-linking polymeric phosphate chains together in the glass network.

Raman investigation of the structural changes during alteration of historic glasses by organic pollutants

“…2), which suggests that the structure tends to become more polymerised on alteration. Bunker et al 23 have made similar observations for binary soda-silicate glass. However, we note that compared to the spectrum of vitreous silica, that of the altered layer has additional bands in the stretching region.…”

“…3), which suggests that only low concentrations of silanols are present in the glass. The absence of a large concentration of silanols, expected from the extensive ion-exchange reaction, suggests that the condensation process described by Bunker et al 11,23 has taken place. The increase of the 300-500 cm 1 region, associated with the bending vibration of Si-O-Si, confirms that new Si-O-Si bonds have formed by condensation of the silanol species.…”

“…9,22,23 In general, the leaching of alkali silicate and borosilicate glasses causes the decrease or disappearance of the depolymerised structure coordinated to the metal cations (disappearance of non-bridging oxygen (NBO) sites) and the formation of silanols and molecular water in the structure. 23 Next, polymerisation of the silanols in the hydrosilicate structure creates new Si-O-Si linkages and, in the case of an acid leachant, four-fold silicate rings (D 1 ). 11,13,23 With the polymerisation reaction the silicate network is transformed from a homogeneous diffusion barrier to a heterogeneous porous aggregate of colloidal silica particles.…”

“…23 Next, polymerisation of the silanols in the hydrosilicate structure creates new Si-O-Si linkages and, in the case of an acid leachant, four-fold silicate rings (D 1 ). 11,13,23 With the polymerisation reaction the silicate network is transformed from a homogeneous diffusion barrier to a heterogeneous porous aggregate of colloidal silica particles.11 In the case of hydration of sodium silicate glass, in which water is introduced without removal of any element, the Raman spectra display a shift of the major bands. 20 These shifts were attributed to a decrease in the average Si-O-Si angle accompanied by a decrease in the average polymerisation of the silicate unit of the structure.…”

Network structure and thermal stability study of high temperature seal glass

“…The main structural unit is Q 3 ͑chemical shift of ϳ−87 ppm͒. 25 The shoulder near −100 ppm indicates the presence of a small amount of Q 4 species with one or two aluminum as next-nearest neighbors. The 29 Si MAS NMR spectra of SABS-5 to SABS-10 are very similar to that of SABS-0, in spite of the increase in the B 2 O 3 content.…”