Processing of Bulk Metallic Glass Schroers, Jan
Advanced materials (Weinheim),
April 12, 2010, Volume:
22, Issue:
14
Journal Article
Peer reviewed
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.
We report the fast growth of high-quality millimeter-size monolayer MoSe2 crystals on molten glass using an ambient pressure CVD system. We found that the isotropic surface of molten glass suppresses ...nucleation events and greatly improves the growth of large crystalline domains. Triangular monolayer MoSe2 crystals with sizes reaching ∼2.5 mm, and with a room-temperature carrier mobility up to ∼95 cm2/(V·s), can be synthesized in 5 min. The method can also be used to synthesize millimeter-size monolayer MoS2 crystals. Our results demonstrate that “liquid-state” glass is a highly promising substrate for the low-cost growth of high-quality large-size 2D transition metal dichalcogenides (TMDs).
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.
Porous glasses from metal–organic frameworks (MOFs) represent a new class of functional inorganic–organic materials, which have been proposed for applications ranging from solid electrolytes to ...radioactive waste storage. So far, just a few zeolitic imidazolate frameworks (ZIFs), a subset of MOFs, have been reported to melt and the structural and compositional requirements for MOF melting and glass formation are poorly understood. Here, we show how the melting point of the prototypical ZIF-4/ZIF-62(M) frameworks (composition M(im)2–x (bim) x ; M2+ = Co2+, Zn2+; im– = imidazolate; bim– = benzimidazolate) can be controlled systematically by adjusting the molar ratio of the two imidazolate-type linkers im– and bim–. By covering the entire range from x = 0 to 0.35, we unveil a delicate transition from ZIF materials showing sequential amorphization/recrystallization to derivatives exhibiting coherent melting and a liquid phase that is stable over a large temperature window. The melting point of this ZIF system is a direct function of x and can be lowered from ca. 430 °C to only 370 °C, by far the lowest melting point reported for a three-dimensional porous MOF. On the basis of our results, we postulate compositional requirements for ZIF melting and glass formation, which may guide the search for other meltable ZIFs. Moreover, gas physisorption experiments establish that the ZIF glasses adsorb technologically relevant C3 and C4 hydrocarbons. Importantly, the adsorption kinetics are much faster for propylene compared to propane and are also dependent on the im–:bim– ratio, thus demonstrating the potential of these ZIF glasses for applications in gas separation.
•MBG acts as a carrier for Ag to impart sustained antibacterial activity to the polymer scaffold.•Polydopamine acts as a green reducing agent to obtain in situ grown Ag nanoparticles in MBG.•The ...novel antibacterial scaffold was constructed by additive manufacturing technology.•The composite scaffold releases silver ions in a sustained release manner.•The composite scaffold exhibits strong antibacterial activity and good cytocompatibility.
An antibacterial scaffold is highly desirable to prevent bacterial infection in orthopedic treatment. In this work, silver was in situ grown in mesoporous bioactive glass (MBG) to endow a polymer scaffold with sustained antibacterial activity. In detail, MBG was firstly modified by the oxidative self-polymerization of dopamine (denoted as pMBG). Then, pMBG was used to capture silver ions into the mesoporous channel via coordination reaction and further in situ reduce silver ions to metallic silver by the redox reaction of the catechol groups. Finally, the Ag loaded pMBG (Ag@pMBG) was introduced into polymer matrices to construct composite scaffold by additive manufacturing technology. The antibacterial tests showed that the composite scaffold exhibited robust antibacterial activity with an inhibition ring of 24.2 mm and bacterial inhibition rate more than 99% against Escherichia coli. Moreover, ion release behavior demonstrated that the composite scaffold could continually release Ag over 28 days. Besides, the composite scaffold also showed good cytocompatibility in facilitating osteoblast adhesion and proliferation.
Cancer poses a significant threat to life due to its aggressive nature, high potential for metastasis, and heterogeneity. Globally, both the men and women are mostly affected by lung and colon (LC) ...cancer. Early and accurate detection is essential to enhance the well-being of patients facing LC cancer. The traditional techniques face challenges such as low accuracy and high execution time. This work combines the pre-trained deep learning (DL) models like ResNet-50, InceptionV3, and DenseNet with Kernel Extreme Learning Machine (KELM) for the accurate and fast diagnosis of LC cancer using histopathology images. The pre-trained DL models provide a strong foundation for feature extraction, capturing intricate patterns indicative of cancerous tissues. Feature fusion combines the complementary strengths of multiple pre-trained models, enhancing the method's ability to capture diverse features and improve classification accuracy. KELM efficiently handles the high-dimensional feature space generated by the DL models, ensuring fast and accurate classification. Mutation Boosted Dwarf Mongoose Optimization Algorithm (MB-DMOA) further optimizes the model parameters, mitigating the risk of getting stuck in local optima and facilitating better convergence towards the global optimum. By leveraging the advantages of each technique and integrating them into a cohesive framework, the proposed approach achieves superior performance in diagnosing LC cancer, ultimately improving patient outcomes. The proposed study attains accuracy (98.9%), F1-score (97.6%), specificity (96.5%), precision (96.7%) and sensitivity (95.8%). The results illuminate the efficacy of this approach within therapeutic environments.
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