3D printing of ceramics: A review Chen, Zhangwei; Li, Ziyong; Li, Junjie ...
Journal of the European Ceramic Society,
04/2019, Letnik:
39, Številka:
4
Journal Article
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Along with extensive research on the three-dimensional (3D) printing of polymers and metals, 3D printing of ceramics is now the latest trend to come under the spotlight. The ability to fabricate ...ceramic components of arbitrarily complex shapes has been extremely challenging without 3D printing. This review focuses on the latest advances in the 3D printing of ceramics and presents the historical origins and evolution of each related technique. The main technical aspects, including feedstock properties, process control, post-treatments and energy source–material interactions, are also discussed. The technical challenges and advice about how to address these are presented. Comparisons are made between the techniques to facilitate the selection of the best ones in practical use. In addition, representative applications of the 3D printing of various types of ceramics are surveyed. Future directions are pointed out on the advancement on materials and forming mechanism for the fabrication of high-performance ceramic components.
Electromagnetic metamaterials are designer materials made from ‘artificial atoms’ which provide unprecedented control over light matter interactions. Metamaterials are fashioned to yield a specific ...response to the electric and magnetic components of light and have realized a multitude of exotic properties difficult to achieve with natural materials. Having matured over the last decade and a half, researchers now look toward realizing applications of metamaterials. The ability to dynamically control novel responses exhibited by electromagnetic metamaterials would bolster this quest thus ushering in the next revolution in materials.
Additive manufacturing (AM) is a technology which has the potential not only to change the way of conventional industrial manufacturing processes, adding material instead of subtracting, but also to ...create entirely new production and business strategies. Since about three decades, AM technologies have been used to fabricate prototypes or models mostly from polymeric or metallic materials. Recently, products have been introduced into the market that cannot be produced in another way than additively. Ceramic materials are, however, not easy to process by AM technologies, as their processing requirements (in terms of feedstock and/or sintering) are very challenging. On the other hand, it can be expected that AM technologies, once successful, will have an extraordinary impact on the industrial production of ceramic components and, moreover, will open for ceramics new uses and new markets.
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•Strong self-interactions of lignin molecules hinder miscibility with polymers.•Competitive interactions determine the structure and properties of lignin blends.•Interactions can be ...estimated quantitatively by simple models.•Interactions can be controlled by plasticization, chemical modification and coupling.•The value added application of lignin increases continuously.
Lignin is a cheap material available in large quantities, thus the interest in its valorization is increasing both in industry and academia. A possible approach towards value added applications is using it as a component in plastics. However, blending lignin with polymers is not straightforward because of the polarity of lignin molecules resulting in strong self-interactions. The structure and properties of lignin depend on the extraction technology used for its production. The structure of lignin is complex and its characterization difficult. Lignin has been added to various polymers in the last few decades and the resulting material was sometimes called blend, while in other cases composite. Based on arguments we show that lignin forms blends, and these are classified and discussed according to the interactions developing in them, since competitive interactions determine the structure and properties of the blends. Usually even strong interactions are not sufficient to result in complete miscibility. As a consequence, lignin is often modified chemically or by plasticization to improve its dispersion in plastics, or a compatibilizer is added to increase interfacial adhesion. Lignin can be used also as a reactive component in various resins and polymers.
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•The abundance of MPs in WWTP declined sharply with a removal rate of 64.4%•Larger size fraction of MPs in the effluent was reduced compared to that in the influent.•Ellipse was ...abundantly seen in the influent with a percentage of 4.4%, while not observed in the effluent.•Polyamide was the main plastic component in wastewater with 54.8%.
Municipal wastewater treatment plants (WWTP) are considered as a significant point source of microplastics (MPs) in the aquatic environment. The objective of this study was to investigate the transport and fate of MPs particles in one WWTP of China based on the conventional activated sludge process. The results exhibited that the abundance of MPs in wastewater declined sharply, from 79.9 n L−1 in the influent to 28.4 n L−1 in the effluent, with a removal rate of 64.4%. MPs removed were mostly transferred and stored into the sludge, and the abundance of MPs in dewatered sludge was 240.3 ± 31.4 n g−1 (dry sludge) with an average size of 222.6 μm. Larger size fraction of MPs in the effluent was reduced compared to that in the influent due to mechanical erosion and sedimentation into sludge. Fiber and fragment were main MPs particles in four wastewater sampling sites, with the average percentage ranged from 33.5 to 56.7% and 30.4 to 45.6%, respectively. An interesting finding is that the ellipses with the size ranged from 100 to 800 µm (average size of 348.1 µm), seldom reported before, were abundantly seen in the influent with a percentage of 4.4%, but not observed in the effluent. A higher fraction of microbead and foam in sludge (17.1% and 12.9%) indicates MPs with the smaller size (average size of 90.3 and 240.1 µm, respectively) in wastewater are prone to be adsorbed and transferred into sludge. Polyamide (nylon) was found to be the main plastic component in wastewater with 54.8% based on Raman spectra, indicating that the MPs particles are primarily originated from the wastewater discharged by washing clothes and polymer manufacturing and processing industries, followed by personal care products.
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•Lightweight and strong foams with outstanding surface appearance were fabricated using foam injection molding.•Uniform nanocellular foaming was achieved using the mold-opening foam ...injection molding.•Nanocellular PP/PTFE nanocomposite foam shows dramatically enhanced mechanical properties.
Lightweight plastic materials are important for saving resources and energy, reducing environmental pollution, and achieving sustainable development. Foam injection molding is a promising technology for manufacturing lightweight plastic components. However, these plastic components present poor mechanical properties and imperfect surface appearances. Herein, we reported a novel strategy to prepare lightweight and tough polypropylene (PP)/polytetrafluoroethylene (PTFE) nanocomposite parts with defect-free surfaces by combining in situ fibrillation and nanocellular injection molding technologies. The nano-fibrillary PP/PTFE nanocomposite was firstly prepared using an in situ method based on twin-screw compounding. Scanning electron microscopy (SEM), rheological and differential scanning calorimetry (DSC) analysis, combined with online optical microscopy observation, demonstrated the network structure of PTFE nanofibrils and its positive effects on melt strength and promoting crystallization. Using nanofibrillary nanocomposites, we achieved nanocellular foaming, for the first time, using the foam injection molding process. The nanocellular PP/PTFE nanocomposite foam thus obtained significantly enhanced mechanical properties compared to the regular PP foam, and even superior strength and ductility compared to unfoamed PP. In particular, the impact strength of the nanocellular foam was 700% higher than that of the regular foam and 200% higher than that of the unfoamed product. Moreover, unlike regular foam, the nanocellular PP/PTFE nanocomposite foam showed outstanding surface appearance without any silver or swirl marks. More importantly, the whole process was facile, flexible, efficient, and easy to scale-up, and could be easily extended to other materials. The remarkable mechanical performance and surface appearance, combined with the flexible and extendable process, confers nanocellular PP/PTFE nanocomposite foams a promising future in many advanced applications where both lightweight and mechanical integrity are required.
We present a novel method to fabricate SiBCN ceramic components with complex shapes from preceramic polymers by using digital light processing (DLP) 3D printing technology in this research work. The ...photocurable precursor for 3D printing was prepared by blending high ceramic yield polyborosilazane with photosensitive acrylate monomers. The material formulation and printing parameters were optimized to fabricate complicated SiBCN ceramic components with high precision. The printed SiBCN ceramic materials were pyrolyzed at different temperatures, and retained their fine features after pyrolysis. Their microstructures were characterized by FTIR, XRD and TEM respectively. Furthermore, the thermal stability and mechanical properties of the SiBCN ceramic samples were investigated and discussed in detail. The 3D printed SiBCN ceramic material exhibited excellent thermal stability and resistance to high temperature oxidation up to 1500 °C.
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•Plasma dynamics in a packed bed DBD reactor were studied by fluid modelling.•Dielectric constant of packing beads affects plasma-catalyst interaction.•Packing with most suitable ...dielectric constant depends on the application.•Higher dielectric constant may limit catalyst activation due to confined discharge.
A packed bed dielectric barrier discharge (DBD) is widely used for plasma catalysis applications, but the exact plasma characteristics in between the packing beads are far from understood. Therefore, we study here these plasma characteristics by means of fluid modelling and experimental observations using ICCD imaging, for packing materials with different dielectric constants. Our study reveals that a packed bed DBD reactor in dry air at atmospheric pressure may show three types of discharges, i.e. positive restrikes, filamentary microdischarges, which can also be localized between two packing beads, and surface discharges (so-called surface ionization waves). Restrikes between the dielectric surfaces result in the formation of filamentary microdischarges, while surface charging creates electric field components parallel to the dielectric surfaces, leading to the formation of surface discharges. A transition in discharge mode occurs from surface discharges to local filamentary discharges between the packing beads when the dielectric constant of the packing rises from 5 to 1000. This may have implications for the efficiency of plasma catalytic gas treatment, because the catalyst activation may be limited by constraining the discharge to the contact points of the beads. The production of reactive species occurs most in the positive restrikes, the surface discharges and the local microdischarges in between the beads, and is less significant in the longer filamentary microdischarges. The faster streamer propagation and discharge development with higher dielectric constant of the packing beads leads to a faster production of reactive species. This study is of great interest for plasma catalysis, where packing beads with different dielectric constants are often used as supports for the catalytic materials. It allows us to better understand how different packing materials can influence the performance of packed bed plasma reactors for environmental applications.
Lithium–sulfur batteries are among the most promising electrochemical energy storage devices of the near future. Especially the low price and abundant availability of sulfur as the cathode material ...and the high theoretical capacity in comparison to state‐of‐the art lithium‐ion technologies are attractive features. Despite significant research achievements that have been made over the last years, fundamental (electro‐) chemical questions still remain unanswered. This review addresses ten crucial questions associated with lithium–sulfur batteries and critically evaluates current research with respect to them. The sulfur–carbon composite cathode is a particular focus, but its complex interplay with other hardware components in the cell, such as the electrolyte and the anode, necessitates a critical discussion of other cell components. Modern in situ characterisation methods are ideally suited to illuminate the role of each component. This article does not pretend to summarise all recently published data, but instead is a critical overview over lithium–sulfur batteries based on recent research findings.
Promising storage: This review addresses ten crucial questions associated with lithium–sulfur batteries and critically evaluates current research with respect to them. The sulfur–carbon composite cathode is in the particular focus, but its complex interplay with other hardware components, such as the electrolyte and the anode, necessitates a critical discussion as well.
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