ABSTRACT Borosilicate glasses are often used in conditions where they are exposed to irradiation, whether as nuclear waste forms, radiation shields, or in space applications. This has motivated an extensive body of work examining how these materials respond to that irradiation, both at the fundamental scale where the short‐ and medium‐ranged atomic structure can change, and at the macroscopic scale where functional properties are changed. This review surveys the literature to summarise what is known about how radiation damage impacts structure and properties in these glasses. We focus on insights that have been gained over the last 20 years, including from computer simulations. We also provide some outlook regarding open questions that need to be addressed to provide a more complete picture of the radiation damage response of these materials.
ABSTRACT Triply periodic minimal surface (TPMS) structures have been rapidly adopted in engineering applications due to their superior mechanical properties, geometric continuity, and suitability for additive manufacturing. This study investigates the influence of the unique morphologies in four representative TPMS unit cells (Primitive, Gyroid, Neovius, and IWP) on brittle crack propagation. Two geometry‐driven concepts are proposed: (1) the prediction of crack propagation along geodesic lines on the surface and (2) the evaluation of damage localization through the distribution of cross‐sectional area along the loading direction. A mathematical framework is developed to compute analytical geodesics on curved surfaces and to compare them with numerically obtained crack paths. In addition, the areas of irregular cross‐sectional shapes in each TPMS unit cell are analyzed to assess how cross‐sectional variation influences compressive resistance. The base material of the TPMS structures is alumina ceramic modeled in finite element (FE) analysis using the Johnson–Holmquist II constitutive model. The results demonstrate that the numerical crack propagation paths are highly consistent with the analytical geodesics and that damage localization is governed by regions with small cross‐sectional areas. This approach provides a robust geometric basis for predicting fracture in complex lattice topologies.
ABSTRACT Hydroxyapatite (HA)‐based bioceramics are widely used as collagen biostimulators and dermal fillers. This study provides a direct comparative characterization of two commercially available HA‐based injectable products, identified in this work as Product 1 (Revita Absorbable Implant) and Product 2 (Radiesse Duo). A multimodal analytical framework was employed to assess chemical composition, microstructure, rheology, pH, and osmolality. Methods included Fourier‐transform infrared spectroscopy (FTIR) with ATR, thermogravimetric analysis (TGA), X‐ray diffraction (XRD), scanning electron microscopy (SEM), complemented by particle‐size analysis, rheological measurements, and standard pH and osmolality assays. FTIR and TGA indicate a HA‐dominated composition with auxiliary constituents (water, Na‐CMC, and glycerol) consistent with the reported formulations. XRD patterns are consistent with hydroxyapatite as the predominant crystalline phase, with no detectable secondary phases under the adopted experimental conditions in either product. SEM and laser‐diffraction analyses show spherical HA microstructures with average diameters near 30 µm (33.9 µm for Revita and 35.2 µm for Radiesse). Rheological measurements reveal closely similar complex viscosities, and the measured pH values under the adopted dilution conditions are 7.66 (Revita) and 7.76 (Radiesse), that is, near the physiological range. Osmolality values are elevated relative to isotonic targets: ∼1250 mOsm/kg for Revita and ∼1300 mOsm/kg for Radiesse. Overall, the two products show highly similar chemical composition, predominant crystalline phase, and particle microstructure, with differences primarily arising from the gel matrix, possibly related to differences in Na‐CMC molecular characteristics, which may contribute to differences in rheology and tonicity. The results indicate substantial physicochemical similarity between the two products.
ABSTRACT HfC–SiC is one of the leading thermal insulation ceramics that has the potential to perform well under high thermomechanical loads. In this study, we explore the use of pressureless sintering to produce this material at relatively low temperatures (2100°C) and focus on understanding the effect of adding WC, in the 0 to 20 wt.% range, on its ablation resistance. The sintered samples were evaluated for their relative density, phase composition, morphology, microstructure, Vickers hardness, and bending strength. The relative density and the Vickers hardness increased from 89% to 97% and from 13.0 to 18.4 GPa, respectively, when the WC content increased from 0 to 20 wt.%. A relatively high value of 480 MPa for the bending strength was measured for the sample with 10 wt.% WC, which was attributed to the more refined microstructure. Oxyacetylene torch testing in tandem with cross‐section micrographs and elemental composition mapping revealed that the addition of WC increased protection in an ablative environment. The observed enhanced oxidation protective ability of these UHTCs is linked to the retention of Si during the ablation process to form an amorphous Hf–Si–W–O overlayer. The retention of Si ensures that a glassy and viscous silicate phase is formed on the surface of the sample. This protective oxide phase restricts volatile oxide phase formation and thus reduces surface porosity and oxygen diffusion. In addition, the viscous tungsten‐silicate phase provides self‐healing of surface defects and improves bending strength.
ABSTRACT Glass‐ceramic composites are promising heterogeneous materials for the immobilization of high‐level nuclear waste. In this study, a composite containing a monazite‐type rare‐earth phosphate dispersed within a borosilicate glass (BG) matrix was synthesized using the ceramic method by first mixing all of the precursors needed to form the phosphate and glass, followed by annealing. The phosphate phase, La0.5Gd0.5PO4, was selected due to its high chemical durability and capacity to incorporate actinides. Gd is a neutron absorber, which is a good attribute for a nuclear waste form. Characterization of the composite materials was performed using powder X‐ray diffraction (XRD), X‐ray absorption near‐edge spectroscopy (XANES), scanning electron microscopy (SEM), and energy‐dispersive X‐ray spectroscopy (EDX). XRD analysis confirmed the formation of a novel co‐substituted monazite phase (i.e., La0.5Gd0.5PO4) dispersed in a glass matrix. XANES analysis provided insight into the local chemical environment of the rare‐earth elements, while SEM and EDX mapping revealed the distribution of the La0.5Gd0.5PO4 crystallites within the borosilicate glass matrix.
