On the Surface and Beyond. Degradation Morphologies Affecting Plant Ash-Based Archaeological Glass from Kafir Kala (Samarkand, Uzbekistan)

The study focuses on an assemblage of glass finds from the citadel of Kafir Kala, Uzbekistan, located along one of the major Eurasian branches of the “Silk Roads” with a consistent occupation between the 8th and 12th century CE. Glass fragments for this study were selected based on marked surface alterations they showed, with stratified deposits of different thickness and colours. Starting from a preliminary observation under Optical Microscope, fragments were clustered into four main groups based on the surface appearance of the alterations; Scanning Electron Microscopy investigations of the stratigraphy of the alteration products were then carried out, to evaluate micro-textural, morphological and compositional features. Data from the analyses allowed identifying preferential patterns of development of the various degradation morphologies, linkable to compositional alterations of the glass due to burial environment and the alkali leaching action of the water. Iridescence, opaque weathering (at times associated with black stains), and blackening were identified as recurring degradation morphologies; as all but one sample were made of plant ash-based glass, results show no specific correlation between glass composition and the occurrence of one or the other degradation pattern, often found together. Framed in a broad scenario, the paper aims to set the basis for the development of a study approach dedicated to the degradation morphologies affecting archaeological glasses, a topic still lacking systematisation and in-depth dedicated literature.

Forty years of durability assessment of nuclear waste glass by standard methods

Standard methods to assess the durability of vitrified radioactive waste were first developed in the 1980’s and, over the last 40 years, have evolved to yield a range of responses depending on experimental conditions and glass composition. Mechanistic understanding of glass dissolution has progressed in parallel, enhancing our interpretation of the data acquired. With the implementation of subsurface disposal for vitrified radioactive waste drawing closer, it is timely to review the available standard methodologies and reflect upon their relative advantages, limitations, and how the data obtained can be interpreted to support the post-closure safety case for radioactive waste disposal.

INVESTIGATION OF THE INFLUENCE OF MICROWAVE RADIATION ON THE PROPERTIES OF GRANULAR HEAT INSULATION MATERIALS BASED ON LIQUID GLASS

The main methods of improving the performance of granular thermal insulationmaterials based on liquid glass are chemical methods of their modification, which are based onchanging their structure through the use of special ingredients. At the same time, there is a need to introduce often a large number of components and individual technological operations, which is notalways technological. One of the promising methods of changing the physical state of substancesunder the action of an electromagnetic field is non-thermal treatment of microwave radiation. Theadvantages of using microwave radiation in comparison with the generally accepted methods ofmodification of materials are the transformation of their structure without significant changes in thetechnological process and the need to use additional components. Due to volumetric heating and themechanism of non-thermal action of microwave radiation on processing objects the duration of theirheating considerably decreases. When microwave heating of a liquid glass composition part of theenergy of electromagnetic radiation is converted into heat, which contributes to the intense swellingof the material, and the other part is aimed at structural changes in the material, which improve itsproperties due to the non-thermal effect of microwave radiation. Studies show that the best set ofperformance properties have granular materials obtained under the action of microwave radiationat a power of 650 W, which corresponds to a temperature of 110-120 0C. The required duration ofsuch heat treatment is 6-7 minutes. The closest to them in terms of coefficient of swelling are materialsobtained by convective heating at a temperature of 200 0C for 1 hour, but their physical andmechanical properties are much lower. Thus, it can be noted that the use of microwave radiationallows to obtain granular thermal insulation materials with a better set of performance properties atlower energy costs for their production.

Trivalent Ions and Their Impacts on Effective Conductivity at 300 K and Radio-Protective Behaviors of Bismo-Borate Glasses: A Comparative Investigation for Al, Y, Nd, Sm, Eu

We aimed to determine the contribution of various trivalent ions like Al and rare-earths (Y, Nd, Sm, Eu) on resistance behaviors of different types of bismo-borate glasses. Accordingly, eight different bismuth borate glasses from the system: 40Bi2O3–59B2O3–1Tv2O3 (where Tv = Al, Y, Nd, Sm, and Eu) and three glasses of (40Bi2O3–60B2O3; 37.5Bi2O3–62.5B2O3; and 38Bi2O3–60B2O3–2Al2O3) compositions were extensively investigated in terms of their nuclear attenuation shielding properties, along with effective conductivity and buildup factors. The Py-MLBUF online platform was also utilized for determination of some essential parameters. Next, attenuation coefficients, along with half and tenth value layers, have been determined in the 0.015 MeV–15 MeV photon energy range. Moreover, effective atomic numbers and effective atomic weight, along with exposure and energy absorption buildup factors, were determined in the same energy range. The result showed that the type of trivalent ion has a direct effect on behaviors of bismo-borate glasses against ionizing gamma-rays. As incident photon energy increases, the effective thermal conductivity decreases rapidly, especially in the low energy range, where photoelectric effects dominate the photon–matter interaction. Sample 8 had the minimum heat conductivity at low photon energies; our findings showed that Eu-reinforced bismo-borate glass composition, namely 40Bi2O3–59B2O3–1Eu2O3, with a glass density of 6.328 g/cm3 had superior gamma-ray attenuation properties. These outcomes would be useful for the scientific community to observe the most suitable additive rareearth type and related glass composition for providing the aforementioned shielding properties, in terms of needs and utilization requirements.

Study on the Optical Properties of High Refractive Index TeO2-PbO-ZnO-BaF2 Glass System

The tellurite 60TeO2-20PbO-(20-x)ZnO-xBaF2 (x = 1, 3, 5, 6, 7, 9, and 11) series glass samples were prepared. The samples’ SEM, XRD, DSC, density, refractive index, and absorption spectra were tested. A self-made optical platform was used to measure and calibrate the refractive index. The relationship between glass composition and crystallinity was discussed. The effects of density, molar refractive index, and metal standard value on the refractive index of glass samples were studied. The results showed that TPZBF glass has a high refractive index, and the refractive index increases with the increase in BaF2 content.

Dissolution of Amorphous S53P4 Glass Scaffolds in Dynamic In Vitro Conditions

The silicate-based bioactive glass S53P4 is clinically used in bone regenerative applications in granule form. However, utilization of the glass in scaffold form has been limited by the high tendency of the glass to crystallize during sintering. Here, careful optimization of sintering parameters enabled the manufacture of porous amorphous S53P4 scaffolds with a strength high enough for surgical procedures in bone applications (5 MPa). Sintering was conducted in a laboratory furnace for times ranging from 25 to 300 min at 630 °C, i.e., narrowly below the commencement of the crystallization. The phase composition of the scaffolds was verified with XRD, and the ion release was tested in vitro and compared with granules in continuous flow of Tris buffer and simulated body fluid (SBF). The amorphous, porous S53P4 scaffolds present the possibility of using the glass composition in a wider range of applications.