12For the first time, the influence of glass composition on the vapor hydration kinetics of the French AVM 13 nuclear waste glass simulants was investigated. Three complex borosilicate glasses (> 20 oxides) along 14 with three simplified Na/(Ca, Na)/(Mg, Na)-alumino-borosilicate glasses with four or five oxides were 15 altered at 50°C in water vapor (95% RH) for up to 557 days. The solid characterization of the altered 16 samples (by SEM, TEM, XRD, ToF-SIMS, SAXS) revealed that the rate-controlling vapor hydration 17 mechanism is composition dependent. The vapor hydration rate of the more durable glasses, whose 18 molar ratio of Al 2 O 3 /(CaO or MgO) is ≥1, seems to be limited by network-hydrolysis, whereas the overall 19 glass alteration rate of the less durable glasses, whose Al 2 O 3 /MgO ratio is <1, seems to be driven by the 20 precipitation of Mg-rich secondary phases. All the vapor hydrated glasses show the presence of a 21 homogeneous gel layer of a few tens of nm thickness. The more durable glasses have a smaller quantity 22 of secondary phases precipitated on their surface. The less durable glasses have a relatively significant 23 quantity of secondary phases precipitated above the gel layer and irregularly shaped, scattered and 24 highly porous altered zones formed beneath the gel layer. The overall alteration rate of the less durable 25 glasses was 10-20 times faster than the more durable glasses. For all glasses, FTIR spectroscopy indicated 26 an inflexion in the vapor hydration rate after 120-200 days of alteration, likely due to a passivating effect 27 of the altered layer formed under unsaturated conditions. The average pore size of the altered layer in 28 50°C [34]. The vapor hydration of SON68 (French inactive reference nuclear waste glass) at high 58 temperatures (90-200°C, activation energy (E a )=43-47 KJ/mol) [28] and lower temperatures (35-90°C, 59 by studying the behavior of three AVM (Atelier de Vitrification de Marcoule) glasses in contact with water 87 vapor. The AVM glasses are complex borosilicate glasses containing more than 20 oxides including fission 88 products issued from the UNGG (Uranium Naturel Graphite-Gaz) reactor at Marcoule. The range in the 89 AVM glasses composition is extensive due to the variation in the composition of fission products 90The synthesis of the AVM glasses has already been described by Thien [46]. The glass samples for this 113 study were retrieved from the same batch. Q, QCa and QMg were prepared using the oxide precursors 114

While glass alteration in liquid water has been widely studied for decades, glass alteration in unsaturated atmosphere (relative humidity, RH < 100%) has been far less examined. However, the understanding of the mechanisms involved in the reactions between glass and water in vapor state is fundamental to several fields such as glass industry, conservation of glasses of the cultural heritage and long-term assessment of nuclear waste glasses. This paper outlines the issues raised by the atmospheric alteration of glass in these fields and attempts to summarize the scientific approaches and findings of the three communities. This short review reveals that atmospheric alteration should not be confused with liquid alteration at high S/V (S = exposed surface of glass and V = volume of solution), because the kinetics and the nature of the alteration products are distinct. Notably, alkalies and non-bridging oxygens may be significantly retained in glass hydrated in unsaturated atmosphere, depending on the glass composition. Future lines of research are drawn to progress in the understanding of the specificities of atmospheric glass alteration.

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Alumina ceramics were joined by a transient liquid phase (TLP) bonding method at relatively lower temperatures, using mixed powders of Bi2O3 and ZnO with different weight ratios as interlayers between the ceramic components. Bonding was achieved at 750 °C for several of the prepared interlayer mixtures, which makes the applied approach attractive due to the relatively lower joining temperature and potentially low fabrication costs. Measurements by SEM and EDX were used to study the microstructure and chemical analysis of the obtained joints. It also allowed us to investigate the diffusion mechanism occurring in the systems, which resulted in the hypothesis that Zn2+/ZnO diffuses through the ceramics. XRD and Raman spectra were acquired to examine the reaction products that formed during the thermal treatment. The results showed that both ZnO and Bi2O3 react with each other as well as with alumina to form spinel and other products.

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A Na-alumino-borosilicate glass and its Ca-doped counterpart were altered in vapor phase (98% relative humidity) and aqueous medium at 90 °C. Both the alteration media were enriched in 17O. Characterization of the altered samples pointed out some differences between glass alteration in aqueous medium and vapor phase in terms of the alteration kinetics, the effect of Ca-doping on glass chemical durability, the behavior of elements in the gel layer, and the structure of the gel layer. Some of the key results are the recondensation of boron in the gel layer formed in the vapor phase and the utility of Rotation Echo DOuble Resonance Nuclear Magnetic Resonance spectroscopy to qualitatively distinguish between signals from the pristine glass and hydrated gel layer within a sample that was not altered to the core. The results gave rise to inferences about glass alteration mechanisms in both the alteration media and the differences between them.