This book is an interdisciplinary exploration of archaeological glass in which technological, historical, geological, chemical, and cultural aspects of the study of ancient glass are combined. The ...book examines why and how this unique material was invented some 4,500 years ago and considers the ritual, social, economic, and political contexts of its development. The book also provides an in-depth consideration of glass as a material, the raw materials used to make it, and its wide range of chemical compositions in both the East and the West from its invention to the seventeenth century AD. Julian Henderson focuses on three contrasting archaeological and scientific case studies: Late Bronze Age glass, late Hellenistic-early Roman glass, and Islamic glass in the Middle East. He considers in detail the provenances of ancient glass using scientific techniques and discusses a range of vessels and their uses in ancient societies.
Processing of Bulk Metallic Glass Schroers, Jan
Advanced materials (Weinheim),
April 12, 2010, Letnik:
22, Številka:
14
Journal Article
Recenzirano
Bulk metallic glass (BMG) formers are multicomponent alloys that vitrify with remarkable ease during solidification. Technological interest in these materials has been generated by their unique ...properties, which often surpass those of conventional structural materials. The metastable nature of BMGs, however, has imposed a barrier to broad commercial adoption, particularly where the processing requirements of these alloys conflict with conventional metal processing methods. Research on the crystallization of BMG formers has uncovered novel thermoplastic forming (TPF)‐based processing opportunities. Unique among metal processing methods, TPF utilizes the dramatic softening exhibited by a BMG as it approaches its glass‐transition temperature and decouples the rapid cooling required to form a glass from the forming step. This article reviews crystallization processes in BMG former and summarizes and compares TPF‐based processing methods. Finally, an assessment of scientific and technological advancements required for broader commercial utilization of BMGs will be made.
Bulk metallic glass permits a unique processing method based on thermoplastic forming. Within thermoplastic forming some bulk metallic glasses, which are high‐strength metals, can be processed like plastics. These processing methods enable to net‐shape bulk metallic glasses on multiple length scales including tens of nanometers to tens of centimeters into shapes that were previously unachievable with any metal processing method (see figure).
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Whereas 3D printing of thermoplastics is highly advanced and can readily create complex geometries, 3D printing of metals is still challenging and limited. The origin of this ...asymmetry in technological maturity is the continuous softening of thermoplastics with temperature into a readily formable state, which is absent in conventional metals. Unlike conventional metals, bulk metallic glasses (BMGs) demonstrate a supercooled liquid region and continuous softening upon heating, analogous to thermoplastics. Here we demonstrate that, in extension of this analogy, BMGs are also amenable to extrusion-based 3D printing through fused filament fabrication (FFF). When utilizing the BMGs’ supercooled liquid behavior, 3D printing can be realized under similar conditions to those in thermoplastics. Fully dense and amorphous BMG parts are 3D printed in ambient environmental conditions resulting in high-strength metal parts. Due to the similarity between FFF of thermoplastics and BMGs, this method may leverage the technology infrastructure built by the thermoplastic FFF community to rapidly realize and proliferate accessible and practical printing of metals.
Sol‐gel route has shown its enormous potential in tissue engineering applications as an advantageous method for the production of bioactive glasses aimed at regenerating both hard and soft tissues. ...This review discusses the chemical aspects of the method with emphasis on the morphological, chemical, mechanical, and biological properties of sol‐gel derived materials. The attention will be particularly focused on sol‐gel bioactive glasses and sol‐gel foam scaffolds for bone regeneration. The advantages deriving from the versatility of the sol‐gel method compared to the traditional melt‐quenching route will be underlined in terms of bioactivity, compositions, and processing parameters.
Glass containing optically active nanoparticles have been manufactured for centuries. However, only in the early 1900s, the invention of ultramicroscope and development of Mie theory paved the way to ...discovering the occurrence of nanoparticles in glass and their special role in imparting unique optical properties to glass. This groundbreaking insight inspired scientists to extensively research such nanoparticles‐in‐glass hybrid optical materials, which led to a series of fundamental breakthroughs (e.g., invention of glass ceramics, discovery of quantum dots) and commercial successes (e.g., photosensitive glass, photochromic glass, dichromic polarizer). Over the past decades, a new wave of research in this area has been initiated by opportunities of incorporating a large variety of synthetic nanoparticles in glass, which promises the development of advanced functional devices for lighting, display, smart window, data storage, and sensing applications. Recent development of various approaches of fabricating nanoparticles‐in‐glass hybrid optical materials and postmodifying nanoparticles that are embedded in glass is reviewed. The state‐of‐the‐art techniques relevant to controlling the dispersion, distribution, orientation, and nanostructure of nanoparticles in glass, as well as manipulating the macroscopic performance of the hybrid materials are discussed. Examples of applications with promising pathway to commercially viable devices based on hybrid optical materials are outlined.
The integration of optically active nanoparticles within a glass matrix is reviewed to provide a comprehensive discussion on the various techniques that are widely used to embed and postmodify nanoparticles in glass, and state‐of‐the‐art applications of their prototype devices that have been developed.
When a spatially uniform temperature change is imposed on a solid with more than one phase, or on a polycrystal of a single, non-cubic phase (showing anisotropic expansion-contraction), the resulting ...thermal strain is inhomogeneous (non-affine). Thermal cycling induces internal stresses, leading to structural and property changes that are usually deleterious. Glasses are the solids that form on cooling a liquid if crystallization is avoided--they might be considered the ultimate, uniform solids, without the microstructural features and defects associated with polycrystals. Here we explore the effects of cryogenic thermal cycling on glasses, specifically metallic glasses. We show that, contrary to the null effect expected from uniformity, thermal cycling induces rejuvenation, reaching less relaxed states of higher energy. We interpret these findings in the context that the dynamics in liquids become heterogeneous on cooling towards the glass transition, and that there may be consequent heterogeneities in the resulting glasses. For example, the vibrational dynamics of glassy silica at long wavelengths are those of an elastic continuum, but at wavelengths less than approximately three nanometres the vibrational dynamics are similar to those of a polycrystal with anisotropic grains. Thermal cycling of metallic glasses is easily applied, and gives improvements in compressive plasticity. The fact that such effects can be achieved is attributed to intrinsic non-uniformity of the glass structure, giving a non-uniform coefficient of thermal expansion. While metallic glasses may be particularly suitable for thermal cycling, the non-affine nature of strains in glasses in general deserves further study, whether they are induced by applied stresses or by temperature change.
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It has long been recognized that the relaxation spectrum of glassy solids is intrinsically connected to their disordered structural features and deformation behaviors. However, such ...connections still remain elusive for metallic glasses. Here, through the extensive study of a variety of metallic glasses over a wide range of temperatures, we provide the compelling evidence for the existence of a universal fast secondary relaxation process, which occurs at a temperature far below the glass transition point with a low activation energy (0.3–0.6eV). Furthermore, it is demonstrated that the initiation of plasticity in metallic glasses is strongly correlated with the fast relaxation process. By exciting the fast relaxation process, multiple shear banding is triggered as opposed to single shear banding in the metallic glasses, which leads to an unusual brittle-to-ductile transition in malleability, being fundamentally different from the ordinary one commonly observed in crystalline alloys. Furthermore, our results shed the quantitative insights into the atomistic mechanisms that differentiate brittle from plastic metallic glasses at different temperatures.
This article reports the first robocasting of a sol–gel based glass ceramic scaffold. Sol–gel bioactive glass powders usually exhibit high volume fractions of meso– and micro–porosities, bad for ...colloidal processing as this adsorbs significant portion of the dispersing medium, affecting dispersion and flow. We circumvent these practical difficulties, to achieve pastes with particle size distributions, high solids loading and appropriate rheological properties for extrusion through fine nozzles for robocasting. Scaffolds with different macro-pore sizes (300–500 μm) with solid loadings up to 40 vol.% were robocast. The sintered (800 °C, 2 h) scaffolds exhibited compressive strength of 2.5–4.8 MPa, formed hydroxyapatite after 72 h in SBF, and had no cytotoxicity and a considerable MG63 cells viability rate. These features make the scaffolds promising candidates for tissue engineering applications and worthy for further in vivo investigations.
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•A novel fiber reinforced fly ash based geopolymer was developed for large scale 3D printing application.•Effect of short glass fiber (different fiber lengths and percentages) on ...mechanical properties was investigated.•Mechanical properties are found to be improved on fiber addition up to 1% and mostly dependent of loading directions.
Around the globe, ground breaking projects and case studies are being presented to showcase the potential of digital fabrication with concrete, better known as 3D printing of concrete. With these explorations, underway, the key quest in 3D concrete printing is for structural stability by means of high strength and ductility. This need could be avoided by designing printable fiber reinforcement concrete or concrete with in-process ‘printed’ reinforcement. Therefore, in this paper, an experimental investigation was carried out by reinforcing short glass fiber (GF) of different lengths (3mm, 6mm and 8mm) and percentages (0.25%–1%) in a custom-made sustainable construction material developed for 3D printing application. Thixotropic GF/geopolymer mortar was printed using a 4-Axis gantry system and later loaded in different directions for measuring the mechanical properties. Our experimental results revealed, improved properties of the printed specimens with increase in fiber percentage up to 1% and an obvious directional dependency behaviour, caused by the layer wise deposition.
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