Structural Origins of Crack Resistance on Magnesium Aluminoborosilicate Glasses Studied by Solid-State NMR

Abstract

The beneficial effect of magnesium oxide upon the performance of crack-resistant oxide glasses has been explored in a series of aluminoborosilicate glasses with the compositions 60SiO2–(20 – x)­Al2O3–xB2O3–20Na2O and 60SiO2–(20 – x)­Al2O3–xB2O3–10Na2O–10MgO. The simultaneous presence of both boron and aluminum oxides in these glasses produces a synergetic effect upon crack resistance (CR), whose structural origins are being explored by detailed 11B, 23Na, 27Al, and 29Si single and double resonance solid-state NMR studies. Aluminum is exclusively four-coordinated, whereas boron is found in both three- and four-coordination. Substitution of B2O3 with Al2O3 and Na2O with MgO leads to a dramatic reduction of N 4, the fraction of four-coordinate boron, accompanied by an increase in CR. 11B/27Al double resonance NMR studies show only weak interactions between the boron oxide and aluminum oxide components, giving no evidence of the formation of new structural units not already realized in the ternary aluminosilicate and borosilicate glass systems. Rather, the effect of magnesium can be related to a dramatic reduction of the fraction of four-coordinate boron species compared to the analogous sodium-based system. This reduction results from a preference of the sodium ions to charge-compensate anionic AlO4/2 – species, combined with an unfavorable interaction of four-coordinate boron with Mg2+. Overall, the results give important insights into the Mg-driven structural network changes in this four-component glass system, providing a structural rationale for the dramatic effect of magnesium upon the mechanical properties of these glasses.

Structure‐property relations in crack‐resistant alkaline‐earth aluminoborosilicate glasses studied by solid state NMR

“…9 Overall, the trends observed in the present study are in excellent agreement with previous results obtained on other aluminoborosilicate glasses. [9][10][11][12][13][14][15][16][17][18][19][20][21][22][23] Figure 8a shows the relationship between ( 27 Al) and  of all the glasses of the present study. Except for the Na-Ca and Na-Mg 〈 〉 glasses (yellow symbols), there seems to be a good correlation.…”

“…As previously shown the only related glass revealing significant concentrations of higher-coordinate aluminum in both the TQMAS-and the SATRAS data is the purely MgO containing sample 60SiO 2 -20Al 2 O 3 -20MgO. 9 In that sample, the amount of higher-coordinated aluminum is estimated at 16±2% Al(V) and 2±2% Al(VI). Minor amounts of Al(V) have also been detected in 60SiO 2 -20Al 2 O 3 -10MgO-10Na 2 O glass.…”

“…This article is protected by copyright. All rights reserved 10Al 2 O 3 -10B 2 O 3 -10Na 2 O-10MO (M = Mg, 9 and M = Ca, Sr, Ba) and 60SiO 2 -10Al 2 O 3 -10B 2 O 3 -(20-x)MO-xMgO (M = Ca, Sr, Ba), combining results from 11 B, 27 Al, and 29 Si solid state NMR with physical property measurements. 116 pm (crystal ionic radii as listed in ref, 29 ) we calculate ionic potentials of 3.72, 2.81, 2.42, 2.15, and 1.38 ×10 -9 C/m, for Mg 2+ , Ca 2+ , Sr 2+ , Ba 2+ , and Na + , respectively.…”

“…To monitor the structural origins of this evolution, nuclear magnetic resonance has already provided some important insights into this matter. [4][5][6]8,9 In aluminosilicate and aluminoborate glasses, crack initiation resistance was shown to increase with increasing average coordination number (presence of higher-coordinated aluminum species). 5,7 In the alkaline-earth aluminoborate glasses of reference 8 exactly these structural changes have been monitored.…”

Transition in deformation mechanism of aluminosilicate glass at high pressure and room temperature

“…These observations could explain the difference in the mechanical property between MAS and NAS. That is, MAS has much higher CR than that of NAS (ie, MAS: 2,200 gf and NAS: 300 gf) 2 . In addition, at initial deformation stage, MAS flows significantly comparing with NAS at the same shear stress condition (eg, 0.08-and 0.5-hour dwell of S1.1 + M0.25 in Table 1).…”