Nature of Alumina in Phosphate Glass: I, Properties of Sodium Aluminophosphate Glass

Abstract

Glasses along four compositional tie lines, I: xAI(PO,),.(lx)NaPO, 11: xAIPO,.(l -x)NaPO,, 111: xAl,O,.(lx)NaPO,, and I V xNaAlO,.(l -x)NaPO,, have been prepared and a number of their properties evaluated. In general, AI,O, additions increase the glass transition temperature, decrease thermal expansion, and improve aqueous durability. However, the composition/property relationships are strongly influenced by relative cation ratios and thus the overall O/P ratio. The nature of these glasses undergoes significant transformations at both the pyrophosphate (O/P = 3.5) and the orthophosphate (O/P = 4.0) compositions, producing significant changes in the property behavior. Spectroscopic analyses of glass structure, described in part I1 of this report, reveal that changes in A1 coordination coincide with the breaks in the property behavior.

Simultaneous aluminum, silicon, and sodium coordination changes in 6 GPa sodium aluminosilicate glasses

“…In the NS4 series, at both 1 atm and 6 GPa, as the Al content increases, there is a decrease in mean Al coordination, similar to the decrease for Si discussed above. The NS3 glass with Al/(Al+Si) = 0.013 has an average Al coordination number of 5.49, which is apparently higher than has been previously reported for any alumina-bearing oxide glass synthesized up to 10 GPa (possibly excepting glasses very rich in phosphorus, Brow et al 1993). This extreme value is clearly related to the low Al content, although the mean Al coordination of the NS4 glass with even lower Al content is somewhat less, indicating a complex relationship between composition and this aspect of the network structure.…”

Thermal properties of 60P2O5–20Fe2O3–20Al2O3 glass for salt waste immobilization

“…. With the Al 2 O 3 content increase, the content of alumina in coordination 4 and orthophosphate [PO 4 ] groups increases accordingly [31]. When the ratio Al 2 O 3 /P 2 O 5 exceeds 0.63, glass network is made up mainly by the [AlO 4 ] and [PO 4 ] tetrahedra, joined each other by the bridging oxygen's-mixed alumino-phosphate network [32].…”

Identification of the hydrate gel phases present in phosphate-modified calcium aluminate binders

“…Here, the application of 31 P{ 1 H} CP/MAS NMR provides the possibility to establish whether phosphate environments are related to hydrogen atoms, which is essential in accurately characterising the gel phase present in the phosphate-modified CAC binder. The MAS spectrum of the polyphosphate precursor, Figure 6A, shows three broad responses at 1, -7 and -20 ppm, attributed to Q 0 , Q 1 and Q 2 phosphate structural units respectively [43,44], and the CP/MAS spectrum, Figure In both sets of spectra (MAS and CP/MAS) for the hydration products of the phosphate-modified CAC, two broad main bands are identifiable at 1.1 (shoulder) and -4.1 ppm (main peak), indicating the presence of multiple relatively disordered hydrated phosphorus environments. The similar line shapes of the 31 P MAS and 31 P CP/MAS spectra indicate that all of the phosphorus environments in these samples are protonated to some extent, and thus the phosphorus environments are related to hydrate phases forming in these binders.…”