Through high-temperature X-ray diffraction, the thermal expansion of two varieties of transition alumina were measured for the first time, between 20 and 900 °C: η-Al2O3 (6.3 × 10-6 °C-1), ω-Al2O3 (7.1 × 10-6 °C-1), along with the structurally-related transient spinel phase issued from the firing of kaolinite (6.8 × 10-6 °C-1). Their lower expansion, compared to α-Al2O3 (8.7 × 10-6 °C-1) and the inflection on the ω-Al2O3 plots probably result from the lower structure compactness and oxygen coordination.

Bi2O3-based glazes were developed to replace toxic PbO-based glazes from a ternary PbO-B2O3-SiO2 reference industrial composition bearing about 70 wt % PbO for ceramic applications, with the aim of keeping very similar properties and retaining the same glazes deposition process at 840 degrees C. Compositions in the SiO2-B2O3-Bi2O3 system melted at 1100 degrees C showed a higher tendency to phase separation and crystallization than the PbO-based reference, probably due to the higher field strength of Bi3+ ion, but the addition of 5-10 mol% Al2O3 led to homogeneous glasses, even after slow cooling. The physical properties of these quaternary glasses (thermal expansion, glass transition temperature, viscosity, density, hardness, elastic modulus) were evaluated, proving comparable to those of the reference PbO-based glass. Coloring pigments (ZnAl2-xCrxO4, 0 <= x <= 2) incorporated at 840 degrees C in a Bi2O3-based glaze also showed similar interactions as with the PbO-based glass according to XRD-Rietveld and SEM-EDX analyses. This work leads to conclude that a quaternary SiO2-B2O3-Bi2O3-Al2O3 glass bearing about 78 wt% Bi2O3 can advantageously replace the more toxic PbO-based formulation for glazing purposes without modifying the firing process.

Glass curators often question how their treatments affect the long-term stability of historical glass. While damp cotton swabs are commonly used to remove surface salts and dust, the use of water remains controversial, particularly for heavily altered glass, due to concerns about worsening hydration. This study investigates the effect of water rinsing on an unstable soda-lime glass altered for six months (monoliths) and fifteen months (powders) at 35 °C and 85% relative humidity. Samples were then rinsed with Milli-Q water at 20 °C or 50 °C, and the monolithic glass was subsequently subjected to an additional 15 months of alteration under the same conditions. The glass surface was characterized by optical and scanning electron microscopy (SEM) as well as Raman spectroscopy to identify the nature of the salts. The evolution of the hydrated layer was assessed using transmission FTIR, Raman and solid-state NMR spectroscopies, ToF-SIMS, and thermogravimetric analysis (TGA). The results show that rinsing effectively removes surface salts—primarily sodium carbonate—and induces structural changes in the hydrated layer, promoting silicate network polymerization. Upon resuming alteration, rinsed monolithic samples exhibit no further degradation after the additional 15 months of alteration. These findings offer promising insights for conservation practices and may help curators refining their treatment strategies for altered glass.

The original electronic structure of the Pb$^{2+}$ ion explains its particular structural role in crystalline phases and silicate glasses. After a description of the structural role of lead in crystalline phases (PbO, silicates), this chapter presents a summary of the main structural studies carried out on glasses from the SiO$_2$-PbO, SiO$_2$-PbO-R$_2$O (R: alkaline) and SiO$_2$-PbO-Al$_2$O$_3$ systems, using various spectroscopic and simulation techniques.

This chapter reviews the physical bases of the main optical properties. It presents an overview of the optical properties and applications of transparent SiO 2 -PbO-M 2 O glasses that are often said to take a yellow color. When traveling through a material medium such as glass, light is partly reflected, partly refracted and transmitted, and partly absorbed if absorbing species are present in the glass. The visible domain corresponds to the energies of the valence electrons. The absorptions in the visible are therefore always related to resonant electron excitations at the level of the most external electrons. SiO 2 -PbO-M 2 O glasses form a very ancient family of transparent glasses used in optics, referred to as "flint". Lead glazes have warm and intense colors, unlike their soda lime colored with the same transition ions.

Colourless glass particles are found in oil painting layers from the fifteenth-seventeenth centuries. Several historical sources mention the use of finely ground glass powder as a solid drier. In order to assess the siccative effect of glass particles added to paint, this research focused on red lake reconstructions and followed their natural drying using Fourier transform infrared (FTIR) analysis. Three glasses with different sodium-potassium and manganese contents were studied. Significant differences in drying rates were observed in each of the samples, indicating a relationship between both the composition - either enriched with or without manganese - and the size of the glass particles added as siccatives. This FTIR approach highlights several complex mechanisms involved in the drying effect of glass powders mixed in paint layers.

This work focuses on the effect of adding increasing amounts of P2O5 (0-10 mol%) on the microstructure and crystallization tendency of a Na2O-rich aluminoborosilicate simplified nuclear glassy matrix obtained after melt quenching or controlled cooling from 1100degree celsius. Above 2 mol% P2O5 , phase separation followed by crystallization of Na3PO4 occurred, then followed by NaCaPO4 and even Na(4)P(2)O(7 )when P2O5 content reached 10 mol%. The Na2O and CaO depletion induced in the residual glass by phosphate phases crystallization is responsible for an important increase of its glass transition temperature due to a significant increase of the silicate network polymerization as confirmed by Si-29 MAS NMR.

Microscopic particles of transparent colourless silicate glass have been found in numerous oil paintings dating from the fifteenth and sixteenth centuries. The widespread occurrence of such powdered glass has been demonstrated in combination with various pigments and within different pictorial layers in works by artists belonging to the Italian, German, Netherlandish, French, Spanish and Portuguese schools. The aims of this paper are to evaluate the multiple current hypotheses for its use, which include modification of transparency, siccative effects and rheology, and through reconstruction experiments, to gain a better understanding of the modifications of the physical and chemical properties of the paint induced by the addition of glass powder. Experimental works have been carried out using lead white based oil paint mixtures, since this pigment is one of those most frequently mixed with crushed glass in Italian paintings. Optical (reflectance and transmittance), rheological and Fourier transform infrared spectroscopy measurements were carried out on pure lead white paint as well as on paint mixtures containing varying amounts of crushed glass. These experiments indicated that the addition of crushed glass increases the transparency and siccative effect of paint films, without significantly altering rheological properties.

In this study, the well-preserved glazes of 13 colored bricks representative of the decoration of the palaces of Sargon II (Khorsabad, 8th century BC) and of Darius I (Susa, 6th century BC) were examined. The purpose of this research is to gather information about the ancient brick manufacturing processes by examining the colored glazes and, in particular, black glazes using a combination of methods that included optical microscopy, SEM-EDX, synchrotron µ-XRD, and µ-Raman spectroscopy. The results revealed different coloring techniques for producing black glazes in the Neo-Assyrian and Persian Achaemenid periods. Regarding the black glazes of Susa, it is particularly interesting to note that their chemical composition varies according to the function of the glazes on the bricks: manganese oxide (for colored fields of glaze) and iron-rich compounds (for raised lines separating glazed areas). In comparison, the black glazes from Khorsabad are characterized by the presence of spherical copper sulfide and galena nanoparticles (ranging from less than 100 nm to about 1 µm) for both the glazed areas and the separating lines. This coloring technique to obtain black glazes is very rarely described in the literature, as well as the mechanism of formation of these spherical nanoparticles.

La structure électronique originale de l’ion Pb2+ permet d’expliquer son rôle structural particulier au sein des phases cristallines et des verres silicatés. Après une description du rôle structural du plomb dans les phases cristallines (PbO, silicates), ce chapitre présente une synthèse des principales études structurales réalisées sur les verres des systèmes SiO2-PbO, SiO2-PbO-R2O (R : alcalin) et SiO2-PbO-Al2O3 en s’appuyant sur des techniques spectroscopiques et de simulation variées.

Les propriétés optiques particulières des verres de silicates de plomb sont expliquées en considérant les absorbances très fortes dans le proche UV induites par la présence de la paire libre 6s2 du plomb. Le déplacement vers le visible de la bande de transfert de charge en présence d’ions métalliques apporte une composante jaune à la couleur de ces verres.

Following an industrial process to protect manufactured glass windows against atmospheric corrosion during their storage and transport, this research is focused on the possibility that a surface deposit of a small amount of zinc salts may efficiently reduce the atmospheric alteration kinetics of ancient glasses (soda, potash, and mixed alkali silicates). To this end, the chemical action of zinc salts was investigated by means of aging experiments (with temperature and relative humidity (RH) control) on three glass models, of which compositions are representative of the cultural heritage. When the treatment was performed on pristine glass (about 1 mu g/cm(2) of deposited Zn2+ ions), treated glass plates developed a significantly thinner hydrated layer than the untreated ones at 80 degrees C or at 40 degrees C (85 RH%). The formation of alkali and Ca-carbonates salts on the surface was also considerably reduced. The state of the glass surface undergoing the Zn treatment and the temperature of the treatment seem critical regarding the efficacy of the protection.

Because of their flexible structure, oxide glasses (borosilicates, phosphates) can easily dissolve the majority of the numerous elements (radioactive or not) present in highly radioactive nuclear waste solutions from commercial (spent commercial reactors fuel) and defense sources. Depending on their charge and size, the different elements present in waste mainly play the role of modifiers or charge compensators (alkalis, alkaline-earths, lanthanides, actinides) while the ones with the highest field strengths may act as reticulating agents (Zr4+) or may be present as oxoanionic species non-connected to the glassy network (P5+,Mo6+,Tc7+). Industrial vitrification processes have been implemented for many years to prepare glassy wasteforms able to resist to alteration for tens of thousands of years (geological disposal) in spite of strong internal irradiation due to fission products and actinides. To increase waste loading or to isolate specifically and more efficiently long-lived radionuclides (actinides), partially crystallized wasteforms such as glass-ceramics are also envisaged.

To investigate the origin of the protection effect of zinc salts against glass atmospheric alteration, the speciation of Zn2+ ions on glass according to the deposit protocol and the Zn2+ surface concentration, and its change over time, was investigated in the light of the respective performances of the treatments. In that respect, a combination of various characterization methods of the glass surface and near-surface was used before and after aging experiments (temperature, relative humidity (RH) control) of the Zn-treated glass. Different Zn-species could be observed on the surface of the treated glass: chemisorbed species, physisorbed species and precipitated hydroxide phases, their respective distribution being highly dependent on the nature of the treatment and on the Zn2+ surface concentration. GI-XAS (Zn K-edge) and ToF-SIMS experiments pointed out the conversion by thermal activation of these surface species into chemisorbed species inserted in the glass network in the near-surface. The chemisorbed species appear to be the most effective ones for the glass protection, possibly by making the surface less soluble, less hydrophilic and even by acting as a diffusion barrier.

Dismantling nuclear facilities leads to radioactive waste less active but which may have highly variable compositions compared to the high-level radioactive wastes recovered after the reprocessing of spent nuclear fuel. In this work, we studied the ability of an alkali-rich glass matrix belonging to the SiO2-B2O3-Al2O3-Fe2O3-Na2O-Li2O-CaO system to solubilize P2O5, MoO3, ZrO2 and Cs2O by melting at 1100 degrees C. Phosphorus, molybdenum, zirconium and cesium are present as a mixture of complex compounds in the real radioactive dismantling waste containing Cs-137 considered here. To determine the capacity of the matrix to accept a wide range of variations of waste composition and the solubility limits of P2O5, MoO3, and ZrO2, several glass series were prepared by melting mixtures of raw materials (oxides, carbonates, phosphates) and by increasing the total amount of oxides representing the waste and varying their relative proportions. Their incorporation in the melt was studied by analyzing the microstructure of quenched glasses by XRD and SEM-EDS. In addition, the phase separation and crystallization tendencies during cooling were studied by analyzing the microstructure of glasses cooled at 1 degrees C.min(-1) from 1100 degrees C (representative of cooling in industrials steel canisters). It is shown that the glass can accept a wide range of waste compositions without exhibiting heterogeneities. For all compositions the melt remained homogeneous (study of quenched samples). However, during slow cooling, P2O5 and MoO3 may lead to phase separation and crystallization of Na2MoO4, CsLiMoO4, NaCaPO4, NaLi2PO4, and Li3PO4. Cs can be partially incorporated into the molybdenum-rich phase CsLiMoO4 when MoO3 content is higher than 1.3wt%. ZrO2 never lead to phase separation or crystallization, possibly because of the existence of strong connections between Zr and Si through Zr-O-Si bonds whereas P and Mo would be present as PO43- and MoO42- mobile entities. The increasing order of oxides solubility in the glass is the following: MoO3<P2O5<ZrO2. (C) 2020 Elsevier B.V. All rights reserved.

The glass composition is a determining parameter that influences the glass chemical durability, particularly in atmospheric conditions (defined by the relative humidity, RH, < 100%). This is obvious in the field of the cultural heritage (CH), where some glass compositions qualified as unstable show advanced signs of degradation under atmosphere, while others seem, on the contrary, stable. This study investigates the differences between stable and unstable glass compositions regarding the phenomenology of the atmospheric glass alteration, by means of accelerated ageing of three glass replicas followed by the characterization of their alteration layers at different scales. Over the same ageing period and experimental conditions, the two glass compositions qualified as unstable develop thick hydrated layers and a thin top layer of carbonate precipitates. Their hydrated layers are depolymerized, and they remarkably retain alkalis and non-bridging oxygens in a dense network of hydrogen bonds, as demonstrated by 29Si and 1H MAS NMR. On the contrary, the stable glass composition shows a considerably thinner hydrated layer and, relatively, a higher amount of carbonates on the surface. In unstable glasses, the retention of a significant proportion of alkalis and NBOs, probably by maintaining a basic character to the hydrated layer, seems comparatively a destabilizing factor sustaining hydration by fast network hydrolysis.

GdVO4 crystals doped with different erbium and ytterbium concentrations have been grown in order to study their spectroscopic and kinetic properties and identify the nature of active centres in them. Their polarised transmission and luminescence spectra have been used to construct energy level diagrams of the Er3+ ion. The lifetime of the lower level of the 4I11/2 excited-state multiplet has been shown to decrease markedly with increasing ytterbium concentration. Inequivalent erbium centres have been observed to form in the crystals with increasing ytterbium concentration.

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.