François O. Méar’s research while affiliated with Artois University and other places

The ICG Spring School 2024 will bring together glass experts from industry and academia under one roof to discuss the grand challenges essential for (1) making glass production sustainable and (2) glass as a material for a sustainable future. The five-day event will be organized in a school format, where the lectures by experts from industry and academia will focus on (1) problems/challenges of reducing carbon footprint in the glass industry with emphasis on furnace design, raw materials, redox and viscosity of melt and recycling, and their possible scientific and industrial solutions; (2) applications of glass/glass-ceramics in the production of clean energy; (3) composition – structure – property relationships in glasses; and (4) the use of modeling approaches and artificial intelligence in the design of new glass formulations. The overarching goal of the school is to (1) educate students about the latest developments in glass science and technology and (2) enable progress toward a sustainable future for the glass industry. A call for abstracts will be made for a poster session covering all the topics addressed in the ICG Spring School. Topics  Industrial issues roadmap to reduce CO2  Glass and glass-ceramic synthesis  Current furnace technologies and issues  Physico-chemical properties of molten glass and optimization  Primary raw material issues  Technical solutions to reduce CO2 emission  Modeling approaches  In situ characterization techniques to track the behavior of molten glass (structure, crystallization, bubbling, etc.)

The effect of V2O5 addition on sealing properties of glasses with nominal composition (29-x)SiO2-23SrO-32BaO-4Al2O3-10B2O3-2P2O5-xV2O5 (where x = 2; 4; 6 mol.%) is reported. The glass transition temperature (Tg) decreases, and flow temperature increases with an increase in V2O5 content. ²⁹Si and ³¹P MAS-NMR indicate that silicates are present mainly as Q² groups, while phosphates are present as Q⁰ groups. ²⁷Al MAS-NMR data shows that Al is 4-coordinated with oxygens, and¹¹B NMR spectra show the presence of both BO3 and BO4 units. Composite materials were prepared by mixing glasses and vanadium di-boride VB2 (15 vol.%). Sealing with Crofer-22 alloy was carried out with composite and revealed good bonding and tight interfaces.

Sodium-calcium-lead phosphate glasses having a mol.% composition (25-z/2)Na2O-(25-z/2)CaO-zPbO-50P2O5 (0 ≤ z ≤ 50) were prepared by using the melt-quench technique. Some physical properties have been measured and their structure has been studied by IR and Raman spectroscopies. Density of the glass increases linearly with the substitution of Na2O and CaO by PbO. Glass molar volume vary slightly with the substitution, and a non-linear increase of PbO molar volume and a non-linear decrease of P2O5, Na2O and CaO ones is observed. Glass transition temperature increases non-linearly with PbO substitution. FTIR and Raman spectra reveal the formation of P–O–Pb bonds, which replace P–O–Na and P–O–Ca bonds, and no modification of the network polymerization is observed with substitution by PbO. However, Raman spectra exhibit shoulder’s peak due to (PO3)²⁻ terminal groups, which seemingly results from disproportionation of species in the glass melts. PbO is assumed to play a network modifier role like Na2O and CaO, but it reticulates the phosphate network, which causes an increase of Tg and a slight effect on molar volume.

The effect of the process atmosphere composition on the foam formation of cathode-ray tube (CRT) glass containing graphite and MnO2 was studied using in situ environmental scanning electron microscopy at high temperature (HT-ESEM). When compared to He+4% H2, O2 or air, water steam facilitates glass grain sintering. This is probably due to the formation of hydroxyl groups at the glass grain surface that locally decrease the glass viscosity. We have shown that increasing the steam pressure from 50 Pa to 750 Pa decreases both sintering and foaming onset temperatures by approximately 100°C, favouring the formation of closed pores in viscous glass. At high temperature, the presence of water steam or oxygen promotes foam formation, while the presence of a reducing atmosphere (He+4%H2) limits glass melt foaming. A synergetic effect of O2 and H2O on the onset temperature of glass sintering and foam formation is evidenced.

A study of the high temperature (up to 1200 °C) degradation of aluminum metaphosphate Al(PO3)3 has been carried out to evaluate the stability of this compound used for many purposes. For the preparation of Al(PO3)3, an aluminum dihydrogen-phosphate Al(H2PO4)3 solution has been heated at 700 °C. Thermal degradation of Al(PO3)3 has been followed through the measurement of weight loss on isothermal mode at 1000 and 1200 °C and by thermogravimetric analysis coupled with mass spectroscopy (TGA-MS). Structural data have been obtained by ²⁷Al, ³¹P and ¹H MAS NMR spectroscopy. NMR analyses have shown that [A] and [B] allotropic forms of Al(PO3)3 are formed after the preparation procedure. In addition, NMR revealed that hydroxyls groups are also present in the sample, and they form P-OH groups. TGA-MS showed that they are decomposed at a temperature of 875 °C, while the decomposition of Al(PO3)3 into AlPO4 and P2O5 begins at 1000 °C.

Silver phosphate glasses have been investigated for the conditioning of radioactive iodine 129. Their disposal in a deep geological repository requires high chemical durability, and to improve this property, two crosslinking agents were examined here: Nb2O5 and Bi2O3. In addition, for some of these glasses, 50 % of phosphorus was replaced by molybdenum to assess the role of glass former entities. The effect of these modifications on the glass chemical durability was studied in pure water, at 50°C. Given the very long half-life of iodine 129 (15.7 × 10⁶ years), only long-term alteration tests were carried out, in order to check if a passivating alteration layer could be formed in these conditions. Alteration rates were then calculated following various methods and compared. Results showed that the use of elemental releases in solution alone leads to an underestimation of the alteration rate, as there is no tracer element in the glass composition. For phospho-molybdate glasses, the addition of Nb2O5 had a significant effect on their chemical durability, i.e. their ability to form a passivating layer that retains most of the elements that are part of the pristine glass. For phosphorus, the more mobile element, release rates decreased by two orders of magnitude compared to phosphate-only glasses, and this trend depends on the Nb2O5 concentration.

The structural role of V in 28Li2O–72SiO2 (in mol%) lithium silicate glass doped with 0.5 mol% V2O5 was assessed using ²⁹Si and ⁵¹V Nuclear Magnetic Resonance (NMR), Fourier‐transform infrared (FTIR), and X‐ray photoelectron (XPS) spectroscopy techniques. Despite the low amount of V2O5 used, the structural information obtained or deduced from the statistical analysis of the NMR data could explain the evolution of glass properties after V2O5 addition. The XPS results indicated that all vanadium exists in 5+ oxidation state. Both the ²⁹Si NMR and FTIR data point toward an increase in the polymerization of the silicate network, caused by the V2O5 acting as network former, capable to form various QVn tetrahedral units (for n = 0, 1, and 2) in the glasses. These QVn units, which are similar to phosphate units, scavenge the Li⁺ ions and cause the silicate network to polymerize. However, in an overall balance, the entire glass network is depolymerized due to the additional nonbridging oxygens contributed by the vanadium polyhedra. The addition of vanadium causes the network to expand and increases the ionic conductivity.