Open Access

The quasi-nearest atom (QNA) parameter has shown promise in characterizing packing disorder in metallic glasses, yet its application has so far been limited to multicomponent alloys, where compositional complexity obscures the purely geometric nature of the defects it identifies. Here, we use QNA to identify structural defects in monoatomic metallic glasses produced by molecular dynamics simulations and assess their impact on mechanical behavior. We show that loosely packed atoms share similar structural signatures, including disrupted medium-range order, unusual ∼90° bond angles, reduced five-fold symmetry, and a preference for energetically unfavorable 2- and 4-atom connection modes. When subjected to uniaxial tension, glasses with a lower density of loosely packed atoms exhibit superior mechanical properties. Regions with few QNA per atom constitute load-bearing backbones supporting high von Mises stress with limited shear strain, while high-QNA regions accommodate greater plastic deformation at lower stress and serve as preferential sites for shear transformation zones. The normalized QNA distributions collapse onto a single curve across the four FCC and BCC monoatomic glasses studied, with consistent spatial correlations and connection-mode fractions (within ±4%) at each NQ level, suggesting that the packing topology is dominated primarily by geometry rather than by element-specific bonding. These results confirm that QNA is a promising structural descriptor for capturing important trends linking local packing geometry to mechanical behavior in monoatomic MGs.

As a minor component of bioactive glasses (BG), copper can stimulate the proliferation of human endothelial cells, improve the differentiation of mesenchymal stem cells, and promote in vivo angiogenesis. At higher concentrations, copper can cause cytotoxic effects, but still offers antibacterial, antifungal, and antiviral properties, which are promising, e.g., for wound healing applications. Enhanced cell proliferation was found for the copper-doped BG F3-Cu 44.8SiO2-2.5P2O3-35.5CaO-6.6Na2O-6.6K2O-3.0CaF2-1.0CuO (mol%). Sintered powder compacts showed in vitro cytocompatibility and supported the proliferation of MC3T3-E1 pre-osteoblast cells. During the initial incubation stage, however, BG F3-Cu samples proved to be temporarily cytotoxic. This can be explained by the formation of superficial CuO nanocrystals on heat-treated BG surfaces. A Cu+ ion excess, frozen from the melt-temperature Cu+/Cu2+ redox equilibrium during quenching, acts as the driving force for Cu+ migration to the glass surface and its oxidation to CuO (Cu2+) surface crystals. Consequently, even a low copper content can lead to the undesirable formation of cytotoxic CuO crystals during powder processing. As this effect occurs well below the subsequent surface crystallization of the glass, however, it can be independently tuned without major drawbacks on the BG after processing.

Chronic wounds present alkaline pH commonly associated to frequent infections, making pH monitoring useful to follow the healing process and to guide antibacterial treatments. This work aims to develop a multifunctional natural polymer-based wound dressing embedded with a bioactive glass and a natural dye, enabling healing, antibacterial activity, and colorimetric pH-sensing. Preliminary results confirm mechanical flexibility, bioactivity, and measurable pH-responsive behavior of the dressings.

Hard and transparent glass-ceramics (GCs) from the ZnO-Al2O3-SiO2 (ZAS) system containing TiO2 as a nucleating agent often exhibit a grayish to brownish hue, limiting their use in applications requiring high transmittance and colorless materials. This coloration arises from charge-transfer mechanisms involving Ti ions. To address this issue, the oxidizing agents CeO2, Sb2O3, and As2O3 were incorporated individually into a TiO2-nucleated ZAS base composition to promote the oxidation of Ti3+ ions to Ti4+ ions, as the latter exhibits minimal coloring effects. The experimental characterization of the glasses and GCs comprised the following steps: Differential Scanning Calorimetry, to study the influence of the optical clarifiers on the thermal behavior and crystallization kinetics; UV-Vis Spectroscopy and CIELAB color analysis to evaluate the effectiveness of the oxidizers in mitigating the color; Electron Paramagnetic Resonance to determine the oxidation states of the coloring ions; Rietveld analyses to assess the impact of microstructural factors on light absorption; and Vickers microhardness to evaluate the effect of the composition and heat treatments on the mechanical performance. The results demonstrate that As2O3 and Sb2O3 are more effective than CeO2 in reducing coloration and enhancing the transmittance in the visible range of the ZAS GCs containing TiO2 without affecting their hardness.

As a minor component of bioactive glasses (BG), copper can stimulate the proliferation of human endothelial cells, improve the differentiation of mesenchymal stem cells, and promote in vivo angiogenesis. At higher concentrations, copper can cause cytotoxic effects, but still offers antibacterial, antifungal, and antiviral properties, which are promising, e.g., for wound healing applications. Enhanced cell proliferation was found for the copper-doped BG F3-Cu 44.8SiO2-2.5P2O3-35.5CaO-6.6Na2O-6.6K2O-3.0CaF2-1.0CuO (mol%). Sintered powder compacts showed in vitro cytocompatibility and supported the proliferation of MC3T3-E1 pre-osteoblast cells. During the initial incubation stage, however, BG F3-Cu samples proved to be temporarily cytotoxic. This can be explained by the formation of superficial CuO nanocrystals on heat-treated BG surfaces. A Cu+ ion excess, frozen from the melt-temperature Cu+/Cu2+ redox equilibrium during quenching, acts as the driving force for Cu+ migration to the glass surface and its oxidation to CuO (Cu2+) surface crystals. Consequently, even a low copper content can lead to the undesirable formation of cytotoxic CuO crystals during powder processing. As this effect occurs well below the subsequent surface crystallization of the glass, however, it can be independently tuned without major drawbacks on the BG after processing.