Journal of Non-Crystalline Solids: X最新文献

Borate and boron oxide containing bioactive glasses have drawn attention because of their unique properties and potential biomedical applications. In this paper, we review recent advances in understanding of boron oxide addition on the structures and properties of bioactive glasses from both experimental and simulation studies. After reviewing the synthesis, characterization and applications of these novel bioactive glasses, recent developments of simulation methodologies including the interatomic potentials to model boron oxide containing bioactive glasses are reviewed. Effect of boron oxide to silica substitution on a range of properties such as density, glass transition temperature, coefficient of thermal expansion, diffusion and mechanical properties, as well as crystallization behavior, both from our own studies and those from literature, are summarized. Furthermore, influence of boron oxide on in vitro bioactivity in several bioactive glass series are reviewed and discussed, emphasizing the importance of in vitro testing conditions on the bioactivity evaluation. Lastly, an outlook of future directions of the field has been provided.

Prediction of brittle fracture of amorphous oxide glasses continues to be a challenge due to the existence of multiple fracture mechanisms that vary with loading conditions. To address this challenge, we present a model for all three regimes of crack growth in glasses. Regimes I and III are controlled by Arrhenius processes while regime II is transport controlled along with a simple Arrhenius model for viscoelastic stress relaxation. Through dimensional arguments and physical reasoning, we propose a single mechanism which underlies both regime III subcritical crack growth and near-crack-tip viscoelastic relaxation. By combining the subcritical crack growth and viscoelastic models we obtain a prediction for a threshold stress intensity, $K_{\mathrm{th}}$, below which stresses around the crack relax faster than it propagates. For stress intensity $K_I<K_{\mathrm{th}}$, no subcritical crack growth is predicted to occur, allowing for the design of stable glass systems. The prediction is compared to measured subcritical fracture threshold data for soda-lime silica glasses.

In recent years, molecular dynamics (MD) simulation has been used to study the deformation behaviors of glass under nanoindentation, mainly using ideal geometries like a spherical indenter or a 2.5-D sample geometry to simplify post-analysis and save computational costs. To generate stress/strain fields that can be directly compared with experiments, we developed a 3-D nanoindentation protocol in this work to study the deformation behaviors of a model metallic glass under sharp contact loading in MD. Our studies show that the indenter sharpness controls the shear band formation, and the interaction between shear bands dictates the crack initiation in the model metallic glass. Shear bands and residual stress fields in the model metallic glass from our simulated nanoindentation tests are consistent with observations in soda-lime silicate (SLS) glass from the instrumented indentation in experiments, as both of them favor shear deformation under sharp contact loading.

Mixed modifier effect refers to the nonlinear variations of glass properties when mixing different types of modifier ions. The effect plays an important role since it can be applied to design glasses with controlled properties and it is also related to the raw materials selection. In this review, we will summarize the recent important progress on the mixed modifier effect in oxide glasses. The effect has been found in various properties, but we mainly focus on glass transition temperature (T_g), hardness (H), elastic modulus (E), and coefficient of thermal expansion (α) since these properties are critical in glass manufacture and products performance. Different properties exhibit unique features and many theories are proposed to account for the effect. The compositional dependence of these properties is reviewed and the theories proposed to explain this effect are discussed. Moreover, we suggest some future directions for the further work on the mixed modifier effect.

The viscoelastic behavior of supercooled Se-deficient liquids in the series As_xSe_100-x (40 ≤ x ≤ 60) and P_xAs_4–xSe₃ (0 ≤ x ≤ 2.8) are studied using parallel plate rheometry. The compositional variations in the viscosity and fragility of these liquids are shown to be consistent with the corresponding structural evolution. While the shear relaxation of As_xSe_100-x liquids with 40 ≤ x ≤ 50 is associated with the dynamics of AsSe bond scission/renewal, the As-rich liquids with x ≥ 55 are found to display an additional low-frequency process, which is related to a cooperative interconversion between molecular and network structural moieties. A similar behavior is also exhibited by the As-rich liquids in the P_xAs_4–xSe₃ series. In contrast, the P-rich liquids characterized by high molecule content display a power-law relaxation behavior resulting from a rather broad distribution of relaxation timescales associated with various dynamical modes of single molecules and molecular clusters.

Low melting Li₂O-PbO-B₂O₃, Me₂O-ZnO-B₂O₃, Me = Li, Na, K, Rb and CaO-ZnO-B₂O₃ glasses were studied with Raman and infrared spectroscopies to advance the structural understanding of zinc borate glasses as potential candidates for substitution of lead containing glasses.

Although the effect of type of alkali ions on the number (N₄) of fourfold coordinated boron (B₄) in the glasses is small, the alkali ions direct the type of borate groups, i.e., pentaborate in lithium, sodium, and calcium zinc borate glasses, as well as diborate in potassium and rubidium containing ones. Both groups were simultaneously found in Li₂O-PbO-B₂O₃. Alkali ions are mainly responsible for the formation of B₄-units and metaborate. Zinc ions favorably compensate non-bridging oxygen and partially form ZnO₄.

With decreasing N₄ and field strength of the alkali ions the atomic packing density, glass transition temperature and Young's Modulus also decrease. The coefficient of thermal expansion increases with decreasing N₄.

Fracture and damage ascribed to the intrinsic brittleness of amorphous oxide glasses are crucial problems for the daily use of glass products. Because the latest developments in glass and glass-ceramics technologies have further broadened their applications, the safety issues become increasingly important. Computational modeling and simulation are now indispensable in the design and analysis of glass quality and safety. This review, therefore, provides an overview of the state-of-the-art fracture modeling/simulation techniques ranging from atomistic scale to continuum scale. In addition to the fundamental theories, typical and recent studies using a variety of continuum methods are introduced. This review also covers the application examples of classical molecular dynamics (CMD) simulations and reactive CMD simulations to investigate the fracture and damage evolutions in glass and glass-ceramics. Advanced multiscale modeling techniques that bridge atomistic and continuum method are also introduced for modeling amorphous materials.

The disordered structure of glass has been an attractive research topic. The heterogeneity of the disordered structures depends on probes that include theoretical, mathematical, and experimental approaches. This study presents structural ordering and defect formation observations for glass, glass-ceramics, and activator-doped glasses. The combination of these probes is expected to gain importance in the future given the broader range of perspectives (from microscopic (atomistic) to macroscopic) required to gain a deeper understanding of optically active glasses.

Although scientific journals stand as a reliable peer-reviewed source of data, it is often too tedious to manually extract relevant information from papers. This could be attributed to the unstructured data such as images, text, captions, and non-standard reporting of data in tables. Here, using natural language processing (NLP), we introduce a corpus of around ~100,000 glass science-related research papers and 106,238 images published in them, that allow for easy navigation and query-based searching through the database. We perform a meta-analysis of the literature in the corpus employing NLP tools. Specifically, we analyze the trends in the number of publications based on countries, research areas, and journals, thereby giving a broad overview of the progress in glass science over the last six decades. Further, as a demonstration of information extraction, we extract the structure factor data of ~450 glass compositions, thereby creating the first-ever public repository on the structure factor of glasses.

Developing novel scintillating glass with high density and intense radioluminescence is of critical importance for various radiation-related technologies. In this paper, Tb-doped Gd₂O₃-WO₃-SiO₂ (GWS) scintillating glass was prepared and investigated. The optical and scintillation properties are explored. And the optimal concentration of Tb activators in glass excited by UV-light and X-ray is determined. Moreover, annealing glass enables a unique glass bleaching phenomenon. Benefitting from the increasement in transparency, a notable improvement in photoluminescence (~195% enhancement in intensity) and radioluminescence (~146% enhancement in intensity) could be realized. The optical and structural characterizations reveal a dramatic change of W chemical valance state from W⁵⁺ to W⁶⁺, which is supposed to govern the decoloring process. Our research indicates that Tb-doped GWS scintillating glass can be a potential candidate for X-ray monitoring.