Amorphous materials: Properties, structure, and durability: Structure of Mg- and Mg/Ca aluminosilicate glasses: 27Al NMR and Raman spectroscopy investigations

Abstract

The structure and properties of glasses and melts in the MgO-Al 2 O 3 -SiO 2 (MAS) and CaO-MgOAl 2 O 3 -SiO 2 (CMAS) systems play an important role in Earth and material sciences. Aluminum has a crucial influence in these systems, and its environment is still questioned. In this paper, we present new results using Raman spectroscopy and 27 Al nuclear magnetic resonance on MAS and CMAS glasses. We propose an Al/Si tetrahedral distribution in the glass network in different Q n species for silicon and essentially in Q 4 and V Al for aluminum. For the CMAS glasses, an increase of V Al and VI Al is clearly visible as a function of the increase of Mg/Ca ratio in the (Ca,Mg) 3 Al 2 Si 3 O 12 (garnet) and (Ca,Mg)AlSi 2 O 8 (anorthite) glass compositions. In the MAS system, the proportion of V Al and VI Al increases with decreasing SiO 2 and, similarly with calcium aluminosilicate glasses, the maximum of V Al is located in the center of the ternary system.

Environment of titanium and aluminum in a magnesium alumino-silicate glass

“…27 Al 1D NMR experimental spectra and the fitting models obtained with parameters given in table 2 (top) and contour plots of 27 Al MQ-MAS NMR spectra (bottom) for the (a) 2MgO-2Al 2 O 3 -5SiO 2 (COR) glass and for the (b) 2MgO-2Al 2 O 3 -5SiO 2 -TiO 2 (Ti-COR) glass. and [6] Al exist in this glass, as is observed in other Ca-aluminosilicate glasses [35] and Mg-alumino-silicate glasses [36,37]. When introducing titanium in the melts, we observe a slight increase of the chemical shift (δ iso ) and of the quadrupolar coupling constant (C Q ) of each site that can be correlated to an increased distortion of the Al environment.…”

“…27 Al NMR results show a modification of the aluminosilicate network with the formation of highly coordinated aluminum atoms, mainly [5] Al, as TiO 2 is introduced. The presence of highly coordinated aluminum atoms is well established in alkaline-earth alumino-silicate glasses because alkaline-earth cations are less good charge compensators than alkalis [35][36][37]. However, quantitative evaluation of these species gives lower [5] Al and [6] Al content for the COR glass than for the Ti-COR glass.…”

Effect of P2O5 Addition on the Viscosity and Structure of Titanium Bearing Blast Furnace Slags

“…Amongst these vibration modes, the stretching vibration of SiO4 tetrahedral, AlO4 tetrahedral, PO4 groups, and TiO4, Ti2O6 groups have been reported in the relatively high wavenumber region, 23,[29][30][31][32][33][34] whereas the bending vibrations of T-O-T where T denotes Ti, Al, Si or P elements could appear in the lower wavenumber region (400-600 cm -1 range), as reported by some previous studies. 23,26,33) Raman spectra for slag melts are presented in Fig. 9.…”

Effect of Al₂O₃/SiO₂ Ratio on the Viscosity and Structure of Slags

“…Another possible reason is that the substitution of Si 4+ with Al 3+ results in a shift to lower wavenumber of Raman spectra for [SiO4]-tetrahedra. 39) In view of the fact that the Al2O3 content increases and SiO2 decreases simultaneously under the present chemical composition and the strength of Al-O bonding is weaker than Si-O bonding, i.e., the decrease in silicate networks with increasing mAl 2 O 3 / mSiO 2 ratio seems to contribute to the decrease in viscosity. Though it is difficult to determine which factor is the main reason, both two aforementioned factors can lower viscosity of slag.…”

“…As Fig. 5 shows, the primary crystalline regions changed from pyroxene (MgCaSi2O6), forsterite (Mg2SiO4)) phase region 39) and consequently cause the change of activity coefficient from negative deviation to positive deviation. This is consistent with the previous analysis (Figs.…”