Showing papers in "Advanced Engineering Materials in 2018"
TL;DR: State‐of‐the‐art harvesting materials and structures are presented with a focus on characterization, fabrication, modeling and simulation, and durability and reliability, and some perspectives and challenges for the future development of energy harvesting materials are highlighted.
296 citations
293 citations
293 citations
TL;DR: This paper provides a comprehensive review of the characteristics of commercially pure (CP) Zr and Zr‐based alloys as orthopaedic and dental implant materials and the d‐electron theory for Zr alloy design and novel ZR‐alloys.
Abstract: Zirconium alloys for biomedical applications are receiving increasing attention due to their two unique properties: 1) the formation of an intrinsic bone-like apatite layer on their surfaces in body environments, and 2) better compatibility with magnetic resonance imaging (MRI) diagnostics due to their low magnetic susceptibility, as well as their overall excellent biocompatibility, mechanical properties, and bio-corrosion resistance. In particular, since both of the MRI quality and speed depend on magnetic field strength, there is a compelling drive for use of high magnetic field strength (>3 Tesla) MRI systems. This paper provides a comprehensive review of the characteristics of commercially pure (CP) Zr and Zr-based alloys as orthopaedic and dental implant materials. These include their 1) phase transformations; 2) unique properties including corrosion resistance, biocompatibility, magnetic susceptibility, shape memory effect, and super-elasticity; 3) mechanical properties; 4) current orthopaedic and dental applications; and 5) the d-electron theory for Zr alloy design and novel Zr-alloys. The mechanical properties of Zr-based bulk metallic glasses (BMGs) and their application as implant materials are also assessed. Future directions for extending the use of Zr-alloys as orthopaedic and dental implants are discussed.
272 citations
TL;DR: In this article, a general overview of high entropy alloys (HEAs) as a potential candidate for high-temperature applications is presented, and the need for profound research on the hightemperature properties of HEAs is highlighted.
Abstract: In recent years, high entropy alloys (HEAs) receive wide attention due to its unique alloy design concept and outstanding properties. This review presents a general overview of HEAs as a potential candidate for high‐temperature applications. The need for the profound research on the high‐temperature properties of HEAs is highlighted.
244 citations
158 citations
TL;DR: In this paper, the authors review and summarize on the fabrication methods, characteristics, and applications of low-melting liquid metal materials, including challenges, routes, and related efforts.
Abstract: As new generation functional materials, the recently emerging low-melting liquid metals have displayed many unconventional properties superior to traditional materials. Various methods, such as alloying, oxidizing, adding metals, or non-metallic materials and so on, have been developed to prepare desirable functional materials based on the gallium or more other metals. These methods could not only change the form of the materials, but also endow the original liquid metals with rather diversified performances, which have further expanded the application range of the low-melting liquid metals to meet various needs. This article aims to review and summarize on the fabrication methods, characteristics, and applications of the functional liquid metal materials. Furthermore, the future outlook in this field, including challenges, routes, and related efforts, has also been illustrated and interpreted.
158 citations
156 citations
TL;DR: In this paper, the main properties (surface hardness, tensile, and compression strength, as well as fracture toughness) and their anisotropicand inhomogeneous nature are addressed.
Abstract: Additive manufacturing has multiple advantages over conventional fabricationtechniques, such as the geometrical freedom and, to a great extent, theomission of tooling equipment. Hence, futuristic designs and non-standardtopology-optimized structures can be fabricated without causing noteworthyextra cost, since the geometrical complexity is, exaggeratedly spoken, for free.The manufacturing time and the amount of required raw material are the keycriteria, which determine the expenses. What at first glance appears as anengineer’s dream, introduces its complexity in the description of thematerial’s characteristics and their volatility to the manufacturing conditions.Within this study, the main properties (i.e., surface hardness, tensile, andcompression strength, as well as fracture toughness) and their anisotropicand inhomogeneous nature are addressed. Detailed overviews of the progressto date for aluminum, iron, titanium, cobalt, and nickel based raw materialsare provided. Furthermore, an overview about the state-of-the-art in themedical sector is included, comprising the areas of utilization and severaltrail studies.
134 citations
127 citations
TL;DR: In this paper, the authors present the current range of alloys available for metal additive manufacturing, including titanium, steel, nickel, aluminum, less common alloys (including Mg alloys, metal matrix composites alloys and low melting point alloys), and compositionally complex alloys with a focus on the relationship between compositions, processing, microstructures, and properties of each alloy system.
Abstract: Metal additive manufacturing (AM) is an innovative manufacturing technique, which builds parts incrementally layer by layer. Thus, metal AM has inherent advantages in part complexity, time, and waste saving. However, due to its complex thermal cycle and rapid solidification during processing, the alloys well suit and commercially used for metal AM today are limited. Therefore, it is important to understand the alloying strategy and current progress with materials performance to consider alloy development for metal AM. This review presents the current range of alloys available for metal AM, including titanium, steel, nickel, aluminum, less common alloys (including Mg alloys, metal matrix composites alloys, and low melting point alloys), and compositionally complex alloys (including bulk metallic glasses and high entropy alloys) with a focus on the relationship between compositions, processing, microstructures, and properties of each alloy system. In addition, some promising alloy systems for metal AM are highlighted. Approaches for designing and optimizing new materials for metal AM have been summarized.
TL;DR: In this article, an extensive review of fused deposition modeling and its application in the development of high performance UAVs is presented, including the process methodology, materials, post processing, and properties of its products.
Abstract: Additive Manufacturing (AM) is a game changing production technology for aerospace applications. Fused deposition modeling is one of the most widely used AM technologies and recently has gained much attention in the advancement of many products. This paper introduces an extensive review of fused deposition modeling and its application in the development of high performance unmanned aerial vehicles. The process methodology, materials, post processing, and properties of its products are discussed in details. Successful examples of using this technology for making functional, lightweight, and high endurance unmanned aerial vehicles are also highlighted. In addition, major opportunities, limitations, and outlook of fused deposition modeling are also explored. The paper shows that the emerge of fused deposition modeling as a robust technique for unmanned aerial vehicles represents a good opportunity to produce compact, strong, lightweight structures, and functional parts with embedded electronic.
TL;DR: The potential to scale up production processes to large areas and high volumes by introducing continuous roll-to-roll (R2R) methods on flexible substrates has been the topic of intense studies from both applied research institutes and industry as discussed by the authors.
Abstract: The production of electronic devices using solution based (“wet”) deposition technologies has some decisive technical and commercial advantages compared to competing approaches like vacuum based (“dry”) manufacturing. Particularly, the potential to scale up production processes to large areas and high volumes by introducing continuous roll-to-roll (R2R) methods on flexible substrates has been the topic of intense studies from both applied research institutes and industry already for some years. Decisive steps forward have been achieved during that time, resulting in the dawn of commercial applications for a number of processes, while additional development work is still needed in some other fields. This review summarizes the work published during the last few years on the R2R printing and wet coating of electronic devices. An overview is presented of the basic operational principles for the most commonly used R2R printing and coating methods and techniques for proper web handling in R2R lines. Then, the most commonly used types of flexible substrate materials are introduced, followed by a review of the work published in the application areas of transparent conductor materials, printed electric connections, light emitting devices, photovoltaic energy generation, printed logic, and sensing.
TL;DR: In this article, the authors present an overview of the works related to the development of Si-B-C-N ceramics through the PDC route in the last 30 years.
Abstract: Long term stability of ceramics at high temperatures is one of the great challenges of the contemporary technology developments. Multi‐component ceramics such as Si–B–C–N systems gain a lot of interest for high temperature applications due to the stability of their amorphous inorganic network arising from strong covalent bonding. The polymer derived ceramics (PDC) route enables the synthesis of such materials from preceramic polymers as well as their manufacturing as specific ceramic geometries, which are difficult to obtain otherwise. This review proposes an overview of the works related to the development of Si–B–C–N ceramics through the PDC route in the last 30 years. A particular focus is made on the relation between the chemical structure of the precursors and the properties of the resulting ceramics. The main topics reviewed are related to the synthesis of tailor‐made polymeric precursors, to their processing to ceramic components, and to the characterization of the material properties and functionalities. The various strategies adopted for the development of shaped Si–B–C–N ceramics as functional materials are presented and the trend of nowadays research for future evolution of Si–B–C–N materials is discussed.
TL;DR: In this paper, the authors summarize the recent research works and focus on not only the synthesis techniques, but also the composition strategies of silicon nanostructures, and give some reference for engineering application on Si anodes in lithium ion batteries.
Abstract: Silicon (Si) is promising for high capacity anodes in lithium-ion batteries due to its high theoretical capacity, low working potential, and natural abundance. However, there are two main drawbacks that impede its further practical applications. One is the huge volume expansion generating during lithiation and delithiation progresses, which leads to severe structural pulverization and subsequently rapid capacity fading of the electrode. The other is the relatively low intrinsic electronic conductivity, therefore, seriously impacting the rate performance. In the past decades, numerous efforts have been devoted for improving the cycling stability and rate capability by rational designs of different nanostructures of Si materials and incorporations with some conductive agents. In this review, the authors summarize the exciting recent research works and focus on not only the synthesis techniques, but also the composition strategies of silicon nanostructures. The advantages and disadvantages of the nanostructures as well as the perspective of this research field are also discussed. We aim to give some reference for engineering application on Si anodes in lithium ion batteries.
TL;DR: The authors use this improved model to motivate a novel material design that can be post-processed to be indistinguishable from the polymer at 100% conversion, and employs a dual initiating system in which photo-initiated printing is followed by a thermal post-cure to achieve uniform conversion.
Abstract: Application of 3D printed structures via stereolithography (SLA) is limited by imprecise dimensional control and inferior mechanical properties These challenges is attributed to poor understanding ofpolymerization behavior during the printing process and inadequate post-processing methods The former via a modified version of Jacob's working curve equation that incorporates the resin's sub-linear response to irradiation intensity is addressed by the authors This new model provides a more accurate approach to select 3D printing parameters given a desired z-resolution and conversion profile along the depth of the printed part The authors use this improved model to motivate a novel material design that can be post-processed to be indistinguishable from the polymer at 100% conversion This approach employs a dual initiating system in which photo-initiated printing is followed by a thermal post-cure to achieve uniform conversion The authors show that this approach enables fast printing times (10 s per layer), exceptional horizontal resolution (1-10 microns), precise control over vertical resolution, and decreased surface corrugations on a 10's of microns scale The techniques described herein use an acrylate-based SLA resin, but the approach can be extended to other monomer systems to simultaneously achieve predictable properties and dimensions that are critical for application of additive manufacturing in load-bearing applications
TL;DR: In this paper, the potential of poly(acrylonitrile) electrospun membranes with tuneable pore size and fiber distributions was investigated for airborne fine-particle filtration for the first time.
Abstract: The potential of poly(acrylonitrile) electrospun membranes with tuneable pore size and fiber distributions were investigated for airborne fine-particle filtration for the first time. The impact of solution concentration on final membrane properties are evaluated for the purpose of designing separation materials with higher separation efficiency. The properties of fibers and membranes are investigated systematically: the average pore distribution, as characterized by capillary flow porometry, and thermo-mechanical properties of the mats are found to be dependent on fiber diameter and on specific electrospinning conditions. Filtration efficiency and pressure drop are calculated from measurement of penetration through the membranes using potassium chloride (KCl) aerosol particles ranging from 300 nm to 12 μm diameter. The PAN membranes exhibited separation efficiencies in the range of 73.8–99.78% and a typical quality factor 0.0224 (1 Pa−1) for 12 wt% PAN with nanofibers having a diameter of 858 nm. Concerning air flow rate, the quality factor and filtration efficiency of the electrospun membranes at higher face velocity are much more stable than for commercial membranes. The results suggest that the structure of electrospun membranes is the best for air filtration in terms of filtration stability at high air flow rate.
TL;DR: In this paper, thermal desorption spectroscopy (TDS) was used to analyze hydrogen in 980DP after electrochemical charging, and gaseous charging, indicating an influence of steel chemistry on the hydrogen evolution reaction.
Abstract: Thermal desorption spectroscopy (TDS) is used to analyze hydrogen in 980DP after (i) electrochemical charging, and (ii) gaseous charging. The hydrogen concentration increases with (i) a more negative charging potential and (ii) an increasing hydrogen gas pressure. For charging in 0.1 M NaOH, the hydrogen fugacity for 980DP is similar to that for (i) low interstitial steel, and (ii) MS1500, and is greater than that for the 3.5NiCrMoV steel. This indicates an influence of steel chemistry on the hydrogen evolution reaction. The de-trapping activation energies are 40.5 and 50.2 kJ mol−1, indicating hydrogen traps at boundary defects.
TL;DR: In this paper, the effect of grain growth at elevated temperatures is discussed for a newly developed as-cast Mg-Gd-Al-Zn magnesium alloy, supported by fracture surface observations, texture analysis by Schulz reflection method based on X-ray diffraction (XRD), and work-hardening rate plots.
Abstract: The grain refinement by dynamic recrystallization (DRX), the enhancement of room-temperature strength and ductility by decreasing hot extrusion temperature, and the effect of grain growth at elevated temperatures are discussed for a newly developed as-cast Mg–Gd–Al–Zn magnesium alloy. The results are supported by fracture surface observations, texture analysis by Schulz reflection method based on X-ray diffraction (XRD), and work-hardening rate plots. It is found that by decreasing the extrusion temperature, the ductility of alloys enhances, which is related to the weakening of basal texture by the rare earth element Gd. Moreover, the grain growth annealing resulted in decreasing the strength and increasing the ductility in the conventional manner, where the texture intensity remained unchanged.
TL;DR: In this article, different pathways for improving the electro-mechanical performance of dielectric elastomers are highlighted, with special emphasis placed on the promise each method holds, and the compositing and blending of elastomer are shown to be simple, versatile methods that can solve a number of optimization issues.
Abstract: Dielectric elastomers are possible candidates for realizing products that are in high demand by society, such as soft robotics and prosthetics, tactile displays, and smart wearables. Diverse and advanced products based on dielectric elastomers are available; however, no elastomer has proven ideal for all types of products. Silicone elastomers, though, are the most promising type of elastomer when viewed from a reliability perspective, since in normal conditions they do not undergo any chemical degradation or mechanical ageing/relaxation. Within this review, different pathways for improving the electro-mechanical performance of dielectric elastomers are highlighted. Various optimization methods for improved energy transduction are investigated and discussed, with special emphasis placed on the promise each method holds. The compositing and blending of elastomers are shown to be simple, versatile methods that can solve a number of optimization issues. More complicated methods, involving chemical modification of the silicone backbone as well as controlling the network structure for improved mechanical properties, are shown to solve yet more issues. From the analysis, it is obvious that there is not a single optimization technique that will lead to the universal optimization of dielectric elastomer films, though each method may lead to elastomers with certain features, and thus certain potentials.