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

Abstract

The effect of the average ionic potential ξ = Ze/r of the network modifier cations on crack initiation resistance (CR) and Young's modulus E has been measured for a series of alkaline‐earth aluminoborosilicate glasses with the compositions 60SiO2–10Al2O3–10B2O3–(20−x)M(2)O–xM’O (0 ≤ x ≤ 20; M, M’ = Mg, Ca, Sr, Ba, Na). Systematic trends indicating an increase of CR with increasing ionic potential, ξ, have been correlated with structural properties deduced from the NMR interaction parameters in 29Si, 27Al, 23Na, and 11B solid state NMR. 27Al NMR spectra indicate that the aluminum atoms in these glasses are essentially all four‐coordinated, however, the average quadrupolar coupling constant <CQ> extracted from lineshape analysis increases linearly with increasing average ion potential computed from the cation composition. A similar linear correlation is observed for the average 29Si chemical shift, whereas the fraction of four‐coordinate boron decreases linearly with increasing ξ. Altogether the results indicate that in pure alkaline‐earth boroaluminosilicate glasses the crack resistance/E‐modulus trade‐off can be tailored by the alkaline‐earth oxide inventory. In contrast, the situation looks more complicated in glasses containing both Na2O and the alkaline‐earth oxides MgO, CaO, SrO, and BaO. For 60SiO2–10Al2O3–10B2O3–10MgO–10Na2O glass, the NMR parameters, interpreted in the context of their correlations with ionic potentials, are consistent with a partial network former role of the MgO component, enhancing crack resistance. Altogether the presence of MgO in aluminoborosilicate glasses helps overcome the trade‐off issue between high crack resistance and high elasticity modulus present in borosilicate glasses, thereby offering additional opportunities for the design of glasses that are both very rigid and very crack resistant.

Physico‐chemical properties of international simple glass (ISG) nuclear waste simulants: Luminescence baseline study

“…26 Nevertheless, elucidating the coordination environment of magnesium and differences in bonding becomes more difficult for glasses containing other modifiers such as sodium cations as well as other network formers such as boron. 27 In the present work, the dissolution data in Figure 4 point to Mg 2+ cations acting most likely as network modifiers in the multicomponent ISG-2 with fairly complex composition (Table 1). In addition, ISG-2 being more prone to dissolution is also consistent with the Raman deconvolution results (vide supra) indicating a lower Q 3 /Q 2 ratio implying a weaker network F I G U R E 5 Dilatometric profiles obtained for the various international simple glass (ISG) samples.…”

Impact of magnesium on the structure of aluminoborosilicate glasses: A solid‐state NMR and Raman spectroscopy study

“…Another 9% decrease in the B[IV] proportion was observed when 7.5% of the calcium was substituted by magnesium in the same proportion (N19M8). This has also been seen in different compositions by Backhouse et al 14 or Logrado et al 12 Quintas et al 100,101 noticed that the cation MFS (see Equation ) affects its ability to charge‐compensate for boron atoms. A higher MFS induces a decrease in the charge‐compensating abilities 56,58,79,102 …”

“…Some studies suggest that magnesium can be found in both tetrahedral and octahedral forms in glasses, even if the calculation gives a mean coordination number value of approximately 5 20,46 . The presence of tetrahedral magnesium indicates that it could behave similar to an intermediate cation: between a network former and modifier 12,15,21,24,107 . Watts et al 21 suggested that this behavior is more often seen in a highly disrupted glass.…”

“…In bioactive glasses used for bone repair, magnesium appears to enhance crystallization and apatite formation in the early stages, favoring contact with living tissues 4‐7 . From a technological point of view, adding magnesium to glasses intrinsically changes their properties such as viscosity, 8 glass transition temperature, 4 mechanical properties, 8‐12 and chemical durability 13 . Furthermore, some of the vitrified high‐level waste (HLW) from nuclear facilities in the United Kingdom (Magnox) 14‐16 and France (AVM) 17,18 contains relatively high magnesium proportions (around 5.90 wt% and between 2.5 and 7.5wt%, respectively 17 ).…”

Compositional Effects on Indentation Mechanical Properties of Chemically Strengthened TiO2-Doped Soda Lime Silicate Glasses

“…The understanding of CR is of high interest. There are many studies trying to elucidate the underlying parameters affecting crack resistance [6,22,52,[60][61][62][63][64][65][66][67][68][69][70][71][72]. Their purpose is to advance the understanding of glass science and provide the possibility of modeling CR with the aim of developing more crack-initiation-resistant glasses [3,73,74].…”