Development of magnesium‐aluminum‐silicate glass‐ceramics nucleated with Nb₂O₅

Abstract

The influence of nucleating agents and heat‐treatments on magnesium‐aluminum‐silicate (MAS) glass‐ceramics was studied. MAS precursor glasses were melted in oxidant (air) and reducing atmospheres. Nb2O5, MoO3 and TiO2+ZrO2 were added as nucleating agents at the same molar proportion (1.0%). MAS glass‐ceramics nucleated with Nb2O5 are strike face candidates for security windows when relevant outputs are taken into account, such as transparency, crack resistance, hardness and feasibility. Nb2O5‐doped MAS can achieve up to 20% crystalline volume fraction, while keeping the visible transparency close to 70%. Knoop hardness was raised up to 7.4 GPa in comparison to precursor glass (6.2 GPa), considering the indentation size effect. The crack resistance reached 4 N.

Machine learning predictions of Knoop hardness in lithium disilicate glass‐ceramics

“…A common conclusion from these studies is that the Vickers hardness ( H V ) increased with an increasing volume fraction of crystals within the microstructure 19,20 . Some works have measured the H K in addition to the H V , consistently observing that the H K values were lower than the H V values, which is consistent with other materials 21,22 . In addition to the systems previously mentioned, hardness values have been acquired on lithium disilicate (LD) systems using either the nanoindentation 23 or Vickers microindentation 24 .…”

“…19,20 Some works have measured the H K in addition to the H V , consistently observing that the H K values were lower than the H V values, which is consistent with other materials. 21,22 In addition to the systems previously mentioned, hardness values have been acquired on lithium disilicate (LD) systems using either the nanoindentation 23 or Vickers microindentation. 24 To our knowledge, our previous work 4 was the first to measure H K on an LD system, and our system contained lithium tantalate (LT) as a secondary phase.…”

Nanocrystalline microstructure in Sm3+ and Gd3+ doped K2O–MgO–Al2O3–SiO2–F glass-ceramic sealant (SOFC)

“…The crystalline peaks shown in Fig. 2 15 During the heat-treatment, Mg 2+ and F À ions tend to form MgF 2 precipitates at B600-650 1C. 16 The tiny particles of MgF 2 then mix with magnesium silicates to form the additive compound i.e., norbergite crystallites.…”

“…2) is associated with the crystallite size and high concentration of the fluorophlogopite phase. 15,17 Mica belongs to the monoclinic system with the co-existence of several types of atoms, where the volume fraction, crystallinity and grain size of the crystalline phase is controlled by the heat-treatment as well as the doping agents. 5,17 In the present report, the controlled nucleation in the SiO 2 -MgO-Al 2 O 3 -B 2 O 3 -K 2 O-MgF 2 glass is performed under two selected parameters: (i) heat-treatment at 950 1C for 2 h and (ii) the addition of 5 mol% Sm 2 O 3 and Gd 2 O 3 .…”