Differential scanning calorimetry (DSC) is a powerful tool to address some of the most challenging issues in glass science and technology, such as the nonequilibrium nature of the glassy state and ...the detailed thermodynamics and kinetics of glass-forming systems during glass transition, relaxation, rejuvenation, polyamorphic transition, and crystallization. The utility of the DSC technique spans across all glass-forming chemistries, including oxide, chalcogenide, metallic, and organic systems, as well as recently discovered metal–organic framework glass-forming systems. Here we present a comprehensive review of the many applications of DSC in glass science with focus on glass transition, relaxation, polyamorphism, and crystallization phenomena. We also emphasize recent advances in DSC characterization technology, including flash DSC and temperature-modulated DSC. This review demonstrates how DSC studies have led to a multitude of relevant advances in the understanding of glass physics, chemistry, and even technology.
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The objective of this communication is to clarify the meanings of solid and liquid, to dwell on the ultimate fate of glass in the limit of infinitely long time, and to propose a modern, improved ...definition of glass. We review the four characteristic states of matter related to vitrification: the stable equilibrium liquid (L), the metastable supercooled liquid (SCL), the unstable nonequilibrium glass (G), and the stable crystal (C). We also discuss some relevant terms and phenomena, including glass transition, crystallization, non-crystalline, amorphous, solid, and frozen. We review several previously published definitions of glass and finally propose an improved definition in two alternative forms. The first improved definition is: “Glass is a nonequilibrium, non-crystalline state of matter that appears solid on a short time scale but continuously relaxes towards the liquid state.” This is an intuitive description for the general public and young students. An alternative, more detailed definition to be understood and used by advanced students, researchers, and professors is: “Glass is a nonequilibrium, non-crystalline condensed state of matter that exhibits a glass transition. The structure of glasses is similar to that of their parent supercooled liquids (SCL), and they spontaneously relax toward the SCL state. Their ultimate fate, in the limit of infinite time, is to crystallize.” This definition is for experts who understand the meaning of glass transition.
•The glassy state appears solid on a short time scale but continuously relaxes toward the liquid state.•A new definition of glass is proposed as a unique nonequilibrium state of matter.•The ultimate fate of a glass is to crystallize, i.e., to solidify.
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In this review we critically analyze 28 theses and dissertations and over 30 scientific papers that tested Biosilicate®, a highly bioactive glass-ceramic, in a number of applications throughout the ...past 20years. Biosilicate® presents a combination of positive features for bone tissue regeneration: it is highly bioactive, osteoconductive, osteoinductive, non-cytotoxic, non-genotoxic and has antibacterial properties. In addition, in the monolithic form, it is quite strong and tough. Its in vitro bioactivity is similar to that of the gold standard Bioglass 45S5. Biosilicate® has shown to be a very versatile, multipurpose biomaterial. It can be applied in powder, monolithic and 3D scaffold forms that could be easily machined during surgical procedures. This material has been successfully tested in a number of in vitro, in vivo and clinical studies, and several trials are ongoing. Biosilicate® is indeed a great option for a wide range of tissue engineering applications.
•Biosilicate®, a highly bioactive glass-ceramic, is reviewed.•Bio and mechanical properties are described.•Applications in powder, monolithic and 3D scaffolds are described.•In vitro, in vivo and clinical tests are critically reviewed.
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The glass transition temperature (Tg) is a kinetic property of major importance for both fundamental and applied glass science. In this study, we designed and trained an artificial neural network to ...induce a model that can predict the Tg of multicomponent oxide glasses. To do this, we used a dataset containing more than 55,000 inorganic glass compositions and their respective experimental values of Tg. These compositions contain from 3 to 21 of the 45 chemical elements studied here. We implemented an optimization procedure to find artificial neural network hyperparameter values that were able to induce a model with high predictive performance. The resulting neural network model can correctly predict, with 95% accuracy, the published Tg value within less than ±9% error, whereas 90% of the data are predicted with a relative deviation lower than ±6%. This level of uncertainty is equivalent to the level present in the original dataset and allows a very satisfactory description of the Tg for multicomponent oxide glasses containing combinations of the 45 studied chemical elements. The prediction uncertainty does not depend on the number of elements in the glass composition. However, it is larger for glasses having very high Tg (above 1250 K). The most important aspect is the algorithm's ability to predict the Tg of glasses that are not included in the experimental dataset used for training, thus showing a high generalization ability. Besides, the procedure used here is general and can be easily extended to predict several other properties as a function of the glass composition. This handy feature will most probably help to develop new multicomponent glass compositions having remarkable properties.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
Here we review and summarize the groundbreaking scientific researches of the late Professor Larry L. Hench, including several of his key discoveries in materials science and engineering. First, we ...provide a statistical overview of his exceptional scientific performance using Scopus, Web of Science, and other Web sites to extract statistical data on his scientific publications and patents. Professor Hench achieved an exceptionally high
h
-index of 77 (Scopus) for the field of materials science and engineering, which resulted from his 340 research papers, 210 conference papers, 41 patents, 24 books, 4 editorial notes, and 3 biographies starting in 1967. Then, we summarize and highlight his seminal articles, books, and patents in several research areas, such as bioactive glasses, optical gel glasses, biocomposites/coatings, glass–ceramics, biophotonics, advanced ceramics, semiconducting and ionic conducting glasses, glass corrosion, and nuclear waste disposal. Prof. Hench not only discovered the first man-made material to form a chemical bond with bone and initiated a whole new field—bioactive glasses and glass–ceramics—but also made several other important scientific discoveries. It is quite clear that he was one of the most influential materials scientists/engineers of all time! We hope that this review is not only useful for all persons interested in materials science and engineering but also encourages students and younger investigators to make use of this accumulated knowledge to design novel materials and discover new applications for glasses and ceramics.
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DOBA, EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, IZUM, KILJ, KISLJ, MFDPS, NLZOH, NUK, OBVAL, OILJ, PILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, SIK, UILJ, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
The
Field Weighted Citation Index
(FWCI) is an article age- and field-normalized metric to evaluate scientific visibility and impact. The
Topic Prominence Percentile
(TPP) is another parameter that ...allegedly measures an article’s “momentum.” Both are available at SciVal and are thought-provoking but have been scarcely used by the community, partially because it is very time-consuming to collect these parameters, paper by paper. In this article, we created and tested a computer code that can efficiently harvest the FWCI and TPP of articles of any chosen researcher, research group, or institution from the Scopus database. After collecting the desired data, our algorithm computes the sum, mean and standard deviation, mode, and median. It also calculates an alternative metric, proposed here, i.e., a normalized parameter that divides each FWCI by the number of authors of that article and then produces similar metrics. We first used the new algorithm to collect an article dataset from a selected researcher, used as an example, who has published 226 articles since 2000. The automated data collection task took 35 min versus 4 h manually. To demonstrate the power of this approach, we present the most relevant results. For instance, 20% of this researcher’s papers have achieved very high visibility, an FWCI ≥ 2. Surprisingly, however, his articles of the highest FWCI are not the most cited. His 20 oldest papers have a similar FWCI to the 20 newest, showing that his scientific output reached a steady-state long ago. Moreover, we discovered that the papers of the highest FWCI have a higher share (65%) of international collaborators than the articles of the lowest FWCI (< 40%). These results corroborate the well-known trend that international collaboration increases scientific visibility. To generalize these findings, we also successfully compared the FWCI statistics of several senior researchers and young investigators who work in diverse fields, revealing significant differences. This way, we demonstrated that the proposed computer code and resulting metrics provide a new scientometric tool. However, a drawback is that a significant fraction of the “topics” defined by SciVal does not perfectly fit the article’s field, which leads to errors in the computation of the FWCI. Therefore, while the FWCI is a handy parameter to evaluate and compare the scientific visibility and impact of researchers of any age and science field, reliable analyses will only be possible using an improved choice of topics.
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EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, KILJ, KISLJ, MFDPS, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
Strong glass‐ceramics (GCs) have been envisaged and widely researched for various applications, including large architectural panels, ballistic impact protection, bioactive medical implants, and ...odontological prostheses. Here, we report on the development and characterization of a novel hard, strong and tough enstatite‐zirconia (MgSiO3‐ZrO2) glass‐ceramic derived from a 51SiO2–35MgO–6Na2O–4ZrO2–4TiO2 (mol%) glass. The best GC was developed by treating glass samples for nucleation at 700°C for 12 hours, followed by crystal growth at 1090°C for 3 minutes. It was characterized by X‐ray fluorescence (XRF), differential scanning calorimetry (DSC), X‐ray diffraction (XRD), scanning electron microscopy (SEM), and high‐resolution transmission electron microscopy (HR‐TEM), and contained plate‐like enstatite, zirconia, and Ti‐containing crystals. We investigated the nucleating ability of ZrO2 and TiO2 in inducing internal nucleation. In the early stage of crystallization, enstatite spherulites were observed, which were precipitated by heterogeneous nucleation on previously nucleated ZrO2 nano‐crystals. At more advanced stages, at high temperatures, they transformed into plate‐like crystals. The ball‐on‐three‐balls strength, elastic modulus, and Vickers micro‐hardness of the GC are 323 ± 26 MPa, 146 ± 13 GPa, and 6.9 ± 0.1 GPa (load = 5N), respectively. The indentation (KC), single‐edge notched beam bending (KIC), and crack tip (Ktip) fracture toughness are 2.8 ± 0.6 MP.m0.5, 2.2 ± 0.3 MP.m0.5, 1.9 ± 0.3 MP.m0.5, respectively. The crack propagation profile after a controlled Vickers indentation was quite intricate. The enstatite and zirconia crystals enhanced crack deflection, bridging and branching, hindering crack propagation. According to the ISO 6872 for dental materials, the chemical solubility of our GC is 80 ± 5 μg/cm2. Due to this positive combination of high strength, toughness, hardness, and chemical durability, this new glass‐ceramic is envisioned as a candidate for several applications and could be further developed for memory disc substrates, architectural cladding and tiles, ceramic glazes, and dental materials.
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BFBNIB, DOBA, FZAB, GIS, IJS, IZUM, KILJ, NLZOH, NUK, OILJ, PILJ, PNG, SAZU, SBCE, SBMB, UILJ, UKNU, UL, UM, UPUK
The validity of the classical nucleation theory (CNT), the most important tool to describe and predict nucleation kinetics in supercooled liquids, has been at stake for almost a century. Here, we ...carried out comprehensive molecular dynamics simulations of the nucleation kinetics of a fast quenched supercooled germanium using the Stillinger–Weber potential at six temperatures, covering a supercooling range of T/T m = 0.70–0.86, where T m is the equilibrium melting temperature. We used the seeding method to determine the number of particles in the critical crystal nuclei at each supercooling, which yielded n * = 150–1300 atoms. The transport coefficient at the liquid/nucleus interface and the melting point were also obtained from the simulations. Using the parameters resulting directly from the simulations, the CNT embraces the experimental nucleation rates, J(T), with the following fitted (average) values of the nucleus/liquid interfacial free energy: γ = 0.244 and 0.201 J/m2, for the experimental and calculated values of thermodynamic driving force, Δμ(T), respectively, which are close to the value obtained from n *(T). Without using any fit parameter, the calculated nucleation rates for the experimental and calculated values of Δμ(T) embrace the experimental J(T) curve. Therefore, this finding favors the validity of the CNT.
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Glass‐forming ability (GFA) is a measure of the easiness to vitrify a given substance. Theoretically, it is possible to make a glass from any liquid provided it is quenched from its liquidus ...temperature with a cooling rate above a critical value Rc to avoid crystallization. However, measuring GFA is a laborious and time‐consuming task. Moreover, predicting the GFA of substances that have never been vitrified is of greater interest. Here, we propose and evaluate a new parameter that can predict the glass forming ability of oxide mixtures. We derived a mother parameter, GFA = 1/Rc ∝ U(Tmax) × TL−1, where U(Tmax) is the maximum crystal growth rate, and TL is the liquidus temperature, which strongly correlates with the experimental critical cooling rates of oxide glass‐formers. A simplified version derived from the mother parameter—which does not need (scarce) crystal growth rate data and only relies on viscosity η and TL, GFA ∝ η(TL)/TL2—also correlates well with the Rc of several oxide compositions. This new GFA parameter, dubbed Jezica, works when heterogeneous nucleation prevails. It corroborates the widespread concept that substances having high viscosity at TL, and a low TL can be easily vitrified, and provides a powerful tool for the quest and design of novel glasses.
Proposed predictor Jezica (y‐axis) vs Rc in Log scale to cover 8 o.m. (■) Stoichiometric glasses and (●) Nonstoichiometric glasses, both with calculated Rc; (▲) Experimental Rc data; (○) Al2O3 = calculated Jezica. The continuous line represents the expected slope (−1) for the linear regression between logη(TL)/T2L and log(Rc)
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Abstract
Understanding the conditions that favour crystallisation and vitrification has been a longstanding scientific endeavour. Here we demonstrate that the extremely high glass-forming ability of ...unseeded supercooled Na
2
O·Al
2
O
3
·6SiO
2
(Albite) and B
2
O
3
—known for decades as “crystallisation anomaly”—is caused by insufficient crystal nucleation. The predicted temperatures of the maximum homogeneous nucleation rates are located well below their glass transition temperatures (T
g
), in a region of very high viscosity, which leads to extremely long nucleation time-lags and low nucleation rates. This behaviour is due to the remarkably small supercoolings where the glass transition occurs for these liquids, which correspond to a very small driving force for crystallisation at and above the T
g
, where crystallisation is normally observed. This meagre nucleation ability is caused by the significant difference in the structures of the supercooled liquids and their isochemical crystals. These findings elucidate the cause behind the crystallisation anomaly, and could be used for the design of other oxide glasses that are extremely stable against crystallisation.
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