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  • Coupling halide perovskites with different materials: from doping to nanocomposites, beyond photovoltaics
    Prog. Mater. Sci. (IF 23.725) Pub Date : 2020-01-23
    Marcello Righetto; Daniele Meggiolaro; Antonio Rizzo; Roberto Sorrentino; Zhubing He; Gaudenzio Meneghesso; Tze Chien Sum; Teresa Gatti; Francesco Lamberti

    Lead halide perovskites (LHPs) have been for a decade and still remain the rising stars in current materials science research. After ten years of incessant work, researchers have reached important results in LHP photovoltaics, overcoming the 25% power conversion efficiency threshold and thus closely approaching silicon performance. On the other hand, challenges are now open for finding other useful applications for LHPs, going beyond the prevalent use in low-cost solar cell technologies. To this goal, the multiple possibilities which can be explored rely on the modification of the lattice structure of LHPs, creating libraries of different compounds with different peculiar properties. In this review, we conducted a deep and comprehensive examination of the recent literature reporting on two main strategies for making alterations at the native LHP structure. We defined them, namely, the endogenous and exogenous strategies. The first one accounts for all the compositional engineering methodologies that were applied during the last 10 years for the internal modification of the LHP lattice, while the second one refers to the realization of nanocomposites, in which LHPs and other materials are combined together. The review encompasses historic, theoretical, spectroscopic, electrical and technological contents, in order to provide a comprehensive starting point for defining a new era in LHP research.

  • A MACEing Silicon: Towards single-step etching of defined porous nanostructures for biomedicine
    Prog. Mater. Sci. (IF 23.725) Pub Date : 2019-12-26
    Hashim Alhmoud; Daniel Brodoceanu; Roey Elnathan; Tobias Kraus; Nicolas H. Voelcker

    Metal-assisted chemical etching (MACE) affords porous silicon nanostructures control over size, shape, and porosity in a single step. Simplicity and flexibility are potential advantages over more traditional silicon bulk micromachining techniques. MACE porous micro- and nanostructures are suitable as biomaterials through their length scales and biocompatibility. This work provides a comprehensive overview of the MACE reaction mechanism that yields biomedically relevant silicon nanostructures – from nanowires, nanopillars, to sub-micrometer holes and pores. We discuss their biomedical applications in biosensors, cell capture and transfection arrays, and drug delivery vectors. We assess the reported benefits of the various nanostructures and discuss whether MACE provides clear and distinct advantages over other techniques. The flexibility and simplicity of MACE comes at a cost. The reaction parameters are many and inter-related, and we lack a full model of the etching mechanism. While the cathode reaction is well understood, the anode reaction involving dissolution of the silicon remains controversial. Such uncertainties impede rational design of specific structures that address biomedical requirements. We summarize current understanding to provide design guidelines for structures used in biomedicine and review the effects of key parameters on the morphological attributes of the etched features.

  • Metal oxides based electrochemical pH sensors: Current progress and future perspectives
    Prog. Mater. Sci. (IF 23.725) Pub Date : 2019-12-16
    Libu Manjakkal; Dorota Szwagierczak; Ravinder Dahiya

    Electrochemical pH sensors are on high demand in numerous applications such as food processing, health monitoring, agriculture and nuclear sectors, and water quality monitoring etc., owing to their fast response (<10 s), wide pH sensing range (2–12), superior sensitivity (close to Nernstian response of 59.12 mV/pH), easy integration on wearable/flexible substrates, excellent biocompatibility and low cost of fabrication. This article presents an in-depth review of the wide range of MOx materials that have been utilized to develop pH sensors, based on various mechanisms (e.g. potentiometric, conductimetric, chemi-resistors, ion sensitive field effect transistor (ISFET) and extended-gate field effect transistor etc.). The tools and techniques such as potentiometric and electrochemical impedance spectroscopic that are commonly adopted to characterize these metal oxide-based pH sensors are also discussed in detail. Concerning materials and design of sensors for various practical application, the major challenges are toxicity of materials, interfernce of other ions or analytes, cost, and flexibility of materials. In this regard, this review also discusses the metal oxide-based composite sensing (active) material, designs of pH sensors and their applications in flexible/wearable biosensors for medical application are examined to present their suitability for these futuristic applications.

  • The materials science of skin: Analysis, characterization, and modeling
    Prog. Mater. Sci. (IF 23.725) Pub Date : 2019-12-16
    Andrei Pissarenko; Marc A. Meyers

    Skin is the outermost layer of the body and acts as a primary protective barrier against external agents such as heat, light, infection, and injury. Additionally, skin regulates the temperature of the body and the exchange of fluids. Skin contains a vast network of nerves, glands, and vessels that enable sensing of heat, touch, pressure and pain, and is also a crucial interface that regulates our body temperature and stores water and lipids to maintain a healthy metabolism. In order to fulfill such a broad range of functions throughout life, skin must be able to withstand and recover from significant deformation as well as mitigate tear propagation that can occur during growth, movement, and injuries affecting its integrity. Hence, characterizing the mechanical behavior of skin and understanding the underlying mechanisms of deformation at different spatial scales is essential in a large spectrum of applications such as surgery, cosmetics, forensics, biomimetics and engineering of protective gear or artificial grafts, among others. The present review draws a comprehensive list of experimental techniques that have been developed over the years to test skin’s nonlinear elastic, viscoelastic, and dissipative properties. To identify parameters affecting its behavior, a significant number of models have been developed, some of which are detailed here; they range from macroscopic constitutive laws to structurally-based formulations, involving nonlinear, dynamic, or damage-inducing processes. The principal structural elements within the dermis, and especially the arrangement and orientation of the collagen fibrils and fibers, are presented; their incorporation into the constitutive models is discussed. Future challenges and perspectives in implementing more accurate structural models are highlighted. Major efforts at developing and using synthetic skin are described.

  • Layered Intercalation Compounds: Mechanisms, New Methodologies, and Advanced Applications
    Prog. Mater. Sci. (IF 23.725) Pub Date : 2019-12-10
    Minwang Laipan, Lichen Xiang, Jingfang Yu, Benjamin R. Martin, Runliang Zhu, Jianxi Zhu, Hongping He, Abraham Clearfield, Luyi Sun

    The structural characteristics of two-dimensional (2-D) materials result in unique physical, electronic, chemical, and optical properties, making them potentially useful in a wide range of applications. These unique properties can be fine-tuned and enhanced via intercalation, expanding the applications of various 2-D intercalation compounds to a much wider scope. This article aims to provide an overview of innovations in the field of intercalation chemistry of 2-D intercalation materials, as well as to highlight their leading applications. A brief perspective on the intercalation of 2-D layered compounds is provided, focusing on mechanisms, approaches, and influential factors involving intercalation. Insights into the potential applications, challenges, and future opportunities of 2-D intercalated materials are discussed.

  • FeO-based nanostructures and nanohybrids for photoelectrochemical water splitting
    Prog. Mater. Sci. (IF 23.725) Pub Date : 2019-12-10
    S. Kment, K. Sivula, A. Naldoni, S.P. Sarmah, H. Kmentova, M. Kulkarni, Y. Rambabu, P. Schmuki, R. Zboril

    The need to satisfy the growing global population’s enormous energy demands is a major challenge for modern societies. Photoelectrochemical (PEC) water splitting (WS) is seen as a leading strategy for producing an extremely promising renewable store of energy - hydrogen (H2). However, PEC-WS is a complex process involving several sequential physicochemical reaction steps including light absorption, separation of photoexcited charges, and surface redox reactions. At present, FeO-based semiconductors represent a unique class of materials known to exhibit very high performance in all these processes. This review summarizes and critically discusses the major components of PEC-WS systems incorporating FeO-based light harvesting systems, and outlines the progress that has been made, particularly over the last decade. Emphasis is placed on materials used as photoanodes (including hematite and nonhematite iron oxides, spinel iron ferrites, and pseudobrookite iron titanates) as well materials used as cocatalysts and passivation layers – notably iron hydroxyoxides and their composites. We discuss strategies for overcoming the main limitations of the aforementioned materials via nanostructuring, elemental doping, surface decoration, and the formation of advanced hybrid nanoarchitectures. Finally, we use this knowledge to present a critical overview of the field and the future prospects of Fe-O semiconductors in PEC-WS applications.

  • Solid-state cold spraying of Ti and its alloys: a literature review
    Prog. Mater. Sci. (IF 23.725) Pub Date : 2019-12-10
    Wenya Li, Congcong Cao, Shuo Yin

    Compared to conventional high temperature processes, e.g. arc additive manufacturing, thermal spraying and laser/electron-beam cladding/additive manufacturing, coatings of Ti and its alloys with cold spraying (CS) are increasingly attracting attention from researchers and industries, because of the low temperature and high velocity characteristics of sprayed particles, which strictly restrict the oxidation of the sprayed powder and bring about prominent metallurgical benefits. However, coatings of Ti and its alloys by CS have found limited industrial applications compared to other materials (e.g. Cu and Al), partly due to the specific particle deposition behavior of Ti and its alloys and the lack of comprehensive knowledge of its control. This review therefore focuses on the deposition characteristics of Ti and its alloys during CS in an effort to shed light on it and expand its applications. The first part presents a brief introduction of CS and the basic characteristics of Ti and its alloys coatings by CS. The second part describes the effects of CS process parameters on the deposition characteristics of Ti and its alloys. The third part discusses the bonding mechanisms of Ti and its alloys particles during CS. The fourth part discusses in depth the strengthening methods to use like in-situ shot peening and laser-assisted CS. The coatings properties can also be improved with post-spray treatment, such as heat treatment, laser treatment, hot rolling, hot isostatic pressing and friction stir processing. In addition, further uses are suggested, such as protective coatings, biocompatible coatings, and additive manufacturing. Finally, the summary and prospects for the deposition of Ti and its alloys are presented.

  • The Fate and Role of in situ Formed Carbon in Polymer-Derived Ceramics
    Prog. Mater. Sci. (IF 23.725) Pub Date : 2019-11-30
    Qingbo Wen, Zhaoju Yu, Ralf Riedel

    Polymer-derived ceramics (PDCs) have been intensively studied for nearly 50 years due to their unique advantages to produce ceramic fibers, coatings, foams, nanocomposites and additive manufacturing. A phenomenon associated with the polymer-to-ceramic transformation process using organo-substituted silicon polymers as the starting material has been widely reported, namely, in situ formation of carbon within the generated silicon-based ceramic matrix. Interestingly, the precipitation of carbon depends to a great extent on the molecular structure of preceramic polymer and significantly affects the composition, crystallization and decomposition behavior, microstructural evolution as well as the related structural and functional properties of PDCs. Thus, this review article highlights the recent progress in the PDC field with the focus on the fate and role of the in situ formed carbon. Firstly, a brief summary of the synthesis and processing of PDCs is provided, followed by the microstructural characterization of the formed ceramics. The in situ formation of carbon, precursor-carbon-morphology relation and high-temperature evolution of the carbon will be summarized. Secondly, the influence of the segregated carbon on the microstructure and its associated properties of the PDCs will be comprehensively highlighted. Finally, potential advanced structural and functional applications of the PDCs related to the carbon are evaluated.

  • Flexible CIGS, CdTe and a-Si:H based thin film solar cells: A review
    Prog. Mater. Sci. (IF 23.725) Pub Date : 2019-11-29
    Jeyakumar Ramanujam, Douglas M Bishop, Teodor K Todorov, Oki Gunawan, Jatin Rath, Reza Nekovei, Elisa Artegiani, Alessandro Romeo

    Flexible thin film solar cells such as CIGS, CdTe, and a-Si:H have received worldwide attention. Until now, Si solar cells dominate the photovoltaic market. Its production cost is a major concern since Si substrates account for the major cost. One way to reduce the module production cost is to use the low-cost flexible substrates. It reduces the installation and transportation charges also, thereby reducing the system price. Apart from metallic foils, plastic films and flexible glass, paper substrates such as cellulose papers, bank notes, security papers and plain white copying papers are also used as substrates for flexible solar cells. In this review, recent developments in flexible CIGS, CdTe and a-Si:H solar cells are reported. Progress on various flexible foils, fabrication and stability issues, current challenges and solutions to those challenges of using flexible foils, and industrial scenario are reviewed in detail. Encapsulation issues and solutions related to water vapor transmission rate are discussed.

  • A Review on the Advancements in Phosphor-converted Light emitting diodes (pc-LEDs): Phosphor Synthesis, Device Fabrication and Characterization
    Prog. Mater. Sci. (IF 23.725) Pub Date : 2019-11-29
    Govind B. Nair, H.C. Swart, S.J. Dhoble

    This article puts emphasis on the role of phosphors in the advancement of Light-emitting diodes (LEDs). The increasing use of phosphors in LEDs, consequently, led to the nomenclature of phosphor-converted LEDs (pc-LEDs). This article makes a thorough discussion about the various methods employed for the synthesis of phosphors and the materials involved in the fabrication of pc-LEDs. A review on the various color-emitting phosphors has been exclusively made to understand the combinations of host materials with luminescent ion dopants that are essential to produce a specific color-emission of interest. There is a brief outlook on the various characteristics and indexes associated with the color quality and performance of pc-LEDs. The challenges faced by pc-LEDs and the advances made to overcome them have also been discussed. On the parallel, other variants of LEDs have started to show up with more promising features than pc-LEDs; but those are yet to accomplish a place in the LED industry due to the lackluster observed in their stability and lifetime. This article will brief the records on such new variants of LEDs assuming that these issues will be resolved in the near future and establish them as the next-generation of LEDs.

  • Geopolymer foams: an overview of recent advancements
    Prog. Mater. Sci. (IF 23.725) Pub Date : 2019-11-27
    Rui M. Novais, Robert.C. Pullar, João A. Labrincha

    Geopolymer foams (highly porous materials) have emerged as one of the most exciting materials over the past few years due to their remarkable properties, low cost and green synthesis protocol, enabling their use in various high added-value applications. Review papers on porous geopolymers are uncommon, and the emphasis has been given to materials processing and properties, while the applications were only briefly addressed. This review aims to fill this gap by presenting a comprehensive literature survey and critical analysis of the most recent and exciting research carried out on geopolymer foams. Up to now, these bulk-type (not powders) materials have been mainly considered as thermal and acoustic insulators. However, besides addressing their use as building material, this review also shows that their use in less investigated, but environmentally and economically relevant applications (e.g. bulk-type adsorbents, pH buffering agents and catalysts), is feasible and might ensure performance and technical advantages over their powdered counterparts. The limitations, challenges and future prospects associated with the different applications are presented. This review shows the remarkable potential of geopolymer foams in high added-value applications, far beyond their historical use as Portland cement replacement, which may encourage the widespread technological use of these materials.

  • Nanoporous TiO2 Spheres with Tailored Textural Properties: Controllable Synthesis, Formation Mechanism, and Photochemical Applications
    Prog. Mater. Sci. (IF 23.725) Pub Date : 2019-11-27
    Yong Ding, In Seok Yang, Zhaoqian Li, Xin Xia, Wan In Lee, Songyuan Dai, Detlef W. Bahenmann, Jia Hong Pan

    Nanoporous TiO2 spheres have emerged recently as a new class of TiO2 nanomaterials for photochemical applications. Compared with conventional TiO2 nanoparticles, the spherical assemblies consisting of low-dimensional nanocrystallites present significant advantages in terms of structural isotropy, monodisperse nature, structural diversity on nano- and (sub)micro-scales, structural stability, light harvesting property, interconnected nanobuilding blocks with less grain boundary, and easy reclaim. Superior performances have been demonstrated in the fields of photoelectrocatalysis and photovoltaics. Research efforts have been devoted to the rational design of a synthetic strategy for the facile preparation of nanoporous TiO2 spheres. The last decade has witnessed rapid progress in developing a synthesis strategy of nanoporous TiO2 spheres for optimal photochemical applications. Both chemical and physical routes have been extensively developed aiming to ease control over the self-assembly of nanobuilding blocks and, thus, the resultant textural properties and physicochemical performances of the nanoporous TiO2 spheres. In this review, a comprehensive description of different synthetic strategies is first presented, with a special emphasis on the formation mechanism, in particular, the pathway followed by nanocrystallites to self-assemble into a spherical structure. Notable experimental parameters are also discussed for the reproducible and controllable preparation of nanoporous TiO2 spheres with well-defined hierarchical structure, tunable porous microstructure from assembled nanobuilding blocks, and optimal physicochemical properties. Important applications in environmental photocatalysis, solar fuel synthesis, dye-sensitized solar cells (DSCs), and perovskite solar cells (PSCs) are summarized, and the synthesis-component-structure-property relationship in nanoporous TiO2 spheres is highlighted. Finally, perspectives in this rapidly developing field are offered.

  • PAN precursor fabrication, applications and thermal stabilization process in carbon fiber production: Experimental and mathematical modelling
    Prog. Mater. Sci. (IF 23.725) Pub Date : 2019-06-17
    Hamid Khayyam, Reza N. Jazar, Srinivas Nunna, Gelayol Golkarnarenji, Khashayar Badii, Seyed Mousa Fakhrhoseini, Satish Kumar, Minoo Naebe

    Polyacrylonitrile (PAN) is a versatile man-made polymer and has been used in a large array of products since its first mass production in the mid 40s. Among all applications of PAN the widely used application is in manufacture of precursor fiber for fabrication of carbon fibers. The process of PAN-based carbon fiber production comprises fiber spinning, thermal stabilization and carbonization stages. Carbon fiber properties are significantly dependent on the quality of PAN precursor fiber and in particular the process parameters involved in thermal stabilization. This paper is the first comprehensive review that provides a general understanding of the links between PAN fiber structure, properties, and its stabilization process along with the use of mathematical modelling as a powerful tool in prediction and optimization of the processes involved. Since the promise of the mathematical modelling is to predict the future behaviour of the system and the value of the variables for the unseen or unmeasured domain of variables; and in the era of industry 4.0 rise, this review will be valuable in further understanding of the intricate processes of carbon fiber manufacture and utilising the advanced mathematical modelling using machine learning techniques to predict and optimize a range of critical factors that control the quality of PAN and resultant carbon fibers.

  • X-ray photoelectron spectroscopy: Towards reliable binding energy referencing
    Prog. Mater. Sci. (IF 23.725) Pub Date : 2019-07-30
    G. Greczynski, L. Hultman

    With more than 9000 papers published annually, X-ray photoelectron spectroscopy (XPS) is an indispensable technique in modern surface and materials science for the determination of chemical bonding. The accuracy of chemical-state determination relies, however, on a trustworthy calibration of the binding energy (BE) scale, which is a nontrivial task due to the lack of an internal BE reference. One approach, proposed in the early days of XPS, employs the C 1s spectra of an adventitious carbon layer, which is present on all surfaces exposed to air. Despite accumulating criticism, pointing to the unknown origin and composition of the adventitious carbon, this is by far the most commonly used method today for all types of samples, not necessarily electrically insulating. Alarmingly, as revealed by our survey of recent XPS literature, the calibration procedure based on the C 1s peak of adventitious carbon is highly arbitrary, which results in incorrect spectral interpretation, contradictory results, and generates a large spread in reported BE values for elements even present in the same chemical state. The purpose of this review is to critically evaluate the status quo of XPS with a historical perspective, provide the technique’s operating principles, resolve myths associated with C 1s referencing, and offer a comprehensive account of recent findings. Owing to the huge volume of XPS literature produced each year, the consequences of improper referencing are dramatic. Our intention is to promote awareness within a growing XPS community as to the problems reported over the last six decades and present a guide with best practice for using the C 1s BE referencing method.

  • Metal-organic framework-derived nanocomposites for electrocatalytic hydrogen evolution reaction
    Prog. Mater. Sci. (IF 23.725) Pub Date : 2019-11-13
    Ziliang Chen, Huilin Qing, Kun Zhou, Dalin Sun, Renbing Wu

    The rapid development of hydrogen energy is strongly dependent on the economic and efficient production of hydrogen. The electrocatalytic splitting of water to molecular hydrogen via the hydrogen evolution reaction (HER) provides an appealing solution for producing high-purity hydrogen, but low-cost and highly active electrocatalysts are required for HER. Among currently investigated HER electrocatalysts, metal-organic framework (MOF)-derived nanocomposites constructed from transition metals (TMs)/TM compounds (TMCs) and carbon materials offer extremely promising and attractive HER activities because of their unique properties, such as tunable compositions, readily regulated electronic structures, controllable morphologies, and diverse configuration. Herein, this article provides a comprehensive overview of MOF-derived nanocomposites as HER electrocatalysts for water splitting. It begins with the introduction of the fundamentals of electrocatalytic HER. Afterwards, various of ingeniously designed strategies for improved MOF-derived HER electrocatalysts are meticulously summarized and discussed, with special emphasis on the component manipulation of the TMs/TMCs, carbon matrix modifications, morphology tuning and electrode configuration engineering. Finally, future perspectives on the development of these nanocomposites as HER electrocatalysts are proposed.

  • Recent progress on flexible and stretchable piezoresistive strain sensors: from design to application
    Prog. Mater. Sci. (IF 23.725) Pub Date : 2019-11-11
    Lingyan Duan, Dagmar R. D'hooge, Ludwig Cardon

    Flexible and stretchable piezoresistive strain sensors which can translate mechanical stimuli (strain changes) into electrical signals (resistance changes) provide a simple and feasible detection tool in the field of health/damage monitoring, human motion detection, personal healthcare, human-machine interfaces, and electronic skin. Herein a detailed overview is presented on both strategies for sensing performance improvement and progress to medium or large-scale fabrication. A broad range of matrices/substrates and incorporated nanomaterials is covered and attention is paid to the current state-of-the-art of feasible but low-cost manufacturing methods. The sensor design parameters include sensitivity (gauge factor), stretchability, linearity, hysteresis, biocompatibility, and self-healing potential. Starting from fundamental sensing mechanisms, i.e. the tunneling effect, the disconnection mechanism, and the crack propagation mechanism, examples are provided from lab to application scale.

  • Progress in understanding structure and transport properties of PEDOT-based materials: a critical review
    Prog. Mater. Sci. (IF 23.725) Pub Date : 2019-11-02
    Magatte N. Gueye, Alexandre Carella, Jérôme Faure-Vincent, Renaud Demadrille, Jean-Pierre Simonato

    Since the late ’80s, a highly stable conductive polymer has been developed, that is poly(3,4-ethylene dioxythiophene), also known as PEDOT. Its increasing conductivity throughout the years combined with its intrinsic stability have aroused great attention both in the academic and industrial fields. The growing importance of PEDOT, can be easily acknowledged through the numerous applications in thermoelectricity, photovoltaics, lighting, sensing, technical coatings, transparent electrodes, bioelectronics, and so forth. Although its high electrical conductivity is strongly established in the literature, the wide range of data shows that disorder, as the limiting factor in charges’ transport, hinders the design of materials with optimal performances. The aim of this article is to review and discuss recent progresses dealing with the electrical conductivity and transport properties in PEDOT materials, with special attention on morphological and structural features. Particular emphasis is given to the commercial PEDOT:PSS as well as other PEDOT-based materials stabilized with smaller counter-anions. It appears that the electrical conductivity and the transport mechanisms are closely related to the fabrication process, the crystallinity of the material and the choice of the counter-anions. With the tunable electrical properties, new functionalities appear accessible and add up to the already existing applications that are concisely highlighted.

  • Application of Materials as Medical Devices with Localized Drug Delivery Capabilities for Enhanced Wound Repair.
    Prog. Mater. Sci. (IF 23.725) Pub Date : 2017-11-14
    Esther J Lee,Beom Kang Huh,Se Na Kim,Jae Yeon Lee,Chun Gwon Park,Antonios G Mikos,Young Bin Choy

    The plentiful assortment of natural and synthetic materials can be leveraged to accommodate diverse wound types, as well as different stages of the healing process. An ideal material is envisioned to promote tissue repair with minimal inconvenience for patients. Traditional materials employed in the clinical setting often invoke secondary complications, such as infection, pain, foreign body reaction, and chronic inflammation. This review surveys the repertoire of surgical sutures, wound dressings, surgical glues, orthopedic fixation devices and bone fillers with drug eluting capabilities. It highlights the various techniques developed to effectively incorporate drugs into the selected material or blend of materials for both soft and hard tissue repair. The mechanical and chemical attributes of the resultant materials are also discussed, along with their biological outcomes in vitro and/or in vivo. Perspectives and challenges regarding future research endeavors are also delineated for next-generation wound repair materials.

  • Piezoelectric films for high frequency ultrasonic transducers in biomedical applications.
    Prog. Mater. Sci. (IF 23.725) Pub Date : 2011-07-02
    Qifa Zhou,Sienting Lau,Dawei Wu,K Kirk Shung

    Piezoelectric films have recently attracted considerable attention in the development of various sensor and actuator devices such as nonvolatile memories, tunable microwave circuits and ultrasound transducers. In this paper, an overview of the state of art in piezoelectric films for high frequency transducer applications is presented. Firstly, the basic principles of piezoelectric materials and design considerations for ultrasound transducers will be introduced. Following the review, the current status of the piezoelectric films and recent progress in the development of high frequency ultrasonic transducers will be discussed. Then details for preparation and structure of the materials derived from piezoelectric thick film technologies will be described. Both chemical and physical methods are included in the discussion, namely, the sol-gel approach, aerosol technology and hydrothermal method. The electric and piezoelectric properties of the piezoelectric films, which are very important for transducer applications, such as permittivity and electromechanical coupling factor, are also addressed. Finally, the recent developments in the high frequency transducers and arrays with piezoelectric ZnO and PZT thick film using MEMS technology are presented. In addition, current problems and further direction of the piezoelectric films for very high frequency ultrasound application (up to GHz) are also discussed.

  • Advantages and Challenges of Relaxor-PbTiO3 Ferroelectric Crystals for Electroacoustic Transducers- A Review.
    Prog. Mater. Sci. (IF 23.725) Pub Date : 2014-12-23
    Shujun Zhang,Fei Li,Xiaoning Jiang,Jinwook Kim,Jun Luo,Xuecang Geng

    Relaxor-PbTiO3 (PT) based ferroelectric crystals with the perovskite structure have been investigated over the last few decades due to their ultrahigh piezoelectric coefficients (d33 > 1500 pC/N) and electromechanical coupling factors (k33 > 90%), far outperforming state-of-the-art ferroelectric polycrystalline Pb(Zr,Ti)O3 ceramics, and are at the forefront of advanced electroacoustic applications. In this review, the performance merits of relaxor-PT crystals in various electroacoustic devices are presented from a piezoelectric material viewpoint. Opportunities come from not only the ultrahigh properties, specifically coupling and piezoelectric coefficients, but through novel vibration modes and crystallographic/domain engineering. Figure of merits (FOMs) of crystals with various compositions and phases were established for various applications, including medical ultrasonic transducers, underwater transducers, acoustic sensors and tweezers. For each device application, recent developments in relaxor-PT ferroelectric crystals were surveyed and compared with state-of-the-art polycrystalline piezoelectrics, with an emphasis on their strong anisotropic features and crystallographic uniqueness, including engineered domain - property relationships. This review starts with an introduction on electroacoustic transducers and the history of piezoelectric materials. The development of the high performance relaxor-PT single crystals, with a focus on their uniqueness in transducer applications, is then discussed. In the third part, various FOMs of piezoelectric materials for a wide range of ultrasound applications, including diagnostic ultrasound, therapeutic ultrasound, underwater acoustic and passive sensors, tactile sensors and acoustic tweezers, are evaluated to provide a thorough understanding of the materials' behavior under operational conditions. Structure-property-performance relationships are then established. Finally, the impacts and challenges of relaxor-PT crystals are summarized to guide on-going and future research in the development of relaxor-PT crystals for the next generation electroacoustic transducers.

  • Piezoelectric single crystals for ultrasonic transducers in biomedical applications.
    Prog. Mater. Sci. (IF 23.725) Pub Date : 2014-11-12
    Qifa Zhou,Kwok Ho Lam,Hairong Zheng,Weibao Qiu,K Kirk Shung

    Piezoelectric single crystals, which have excellent piezoelectric properties, have extensively been employed for various sensors and actuators applications. In this paper, the state-of-art in piezoelectric single crystals for ultrasonic transducer applications is reviewed. Firstly, the basic principles and design considerations of piezoelectric ultrasonic transducers will be addressed. Then, the popular piezoelectric single crystals used for ultrasonic transducer applications, including LiNbO3 (LN), PMN-PT and PIN-PMN-PT, will be introduced. After describing the preparation and performance of the single crystals, the recent development of both the single-element and array transducers fabricated using the single crystals will be presented. Finally, various biomedical applications including eye imaging, intravascular imaging, blood flow measurement, photoacoustic imaging, and microbeam applications of the single crystal transducers will be discussed.

  • Relaxor-based ferroelectric single crystals: growth, domain engineering, characterization and applications.
    Prog. Mater. Sci. (IF 23.725) Pub Date : 2014-07-26
    Enwei Sun,Wenwu Cao

    In the past decade, domain engineered relaxor-PT ferroelectric single crystals, including (1-x)Pb(Mg1/3Nb2/3)O3-xPbTiO3 (PMN-PT), (1-x)Pb(Zn1/3Nb2/3)O3-xPbTiO3 (PZN-PT) and (1-x-y)Pb(In1/2Nb1/2)O3-yPb(Mg1/3Nb2/3)O3-xPbTiO3 (PIN-PMN-PT), with compositions near the morphotropic phase boundary (MPB) have triggered a revolution in electromechanical devices owing to their giant piezoelectric properties and ultra-high electromechanical coupling factors. Compared to traditional PbZr1-x Ti x O3 (PZT) ceramics, the piezoelectric coefficient d33 is increased by a factor of 5 and the electromechanical coupling factor k33 is increased from < 70% to > 90%. Many emerging rich physical phenomena, such as charged domain walls, multi-phase coexistence, domain pattern symmetries, etc., have posed challenging fundamental questions for scientists. The superior electromechanical properties of these domain engineered single crystals have prompted the design of a new generation electromechanical devices, including sensors, transducers, actuators and other electromechanical devices, with greatly improved performance. It took less than 7 years from the discovery of larger size PMN-PT single crystals to the commercial production of the high-end ultrasonic imaging probe "PureWave". The speed of development is unprecedented, and the research collaboration between academia and industrial engineers on this topic is truly intriguing. It is also exciting to see that these relaxor-PT single crystals are being used to replace traditional PZT piezoceramics in many new fields outside of medical imaging. The new ternary PIN-PMN-PT single crystals, particularly the ones with Mn-doping, have laid a solid foundation for innovations in high power acoustic projectors and ultrasonic motors, hinting another revolution in underwater SONARs and miniature actuation devices. This article intends to provide a comprehensive review on the development of relaxor-PT single crystals, spanning material discovery, crystal growth techniques, domain engineering concept, and full-matrix property characterization all the way to device innovations. It outlines a truly encouraging story in materials science in the modern era. All key references are provided and 30 complete sets of material parameters for different types of relaxor-PT single crystals are listed in the Appendix. It is the intension of this review article to serve as a resource for those who are interested in basic research and practical applications of these relaxor-PT single crystals. In addition, possible mechanisms of giant piezoelectric properties in these domain-engineered relaxor-PT systems will be discussed based on contributions from polarization rotation and charged domain walls.

  • Multifunctional nanoplatforms for subcellular delivery of drugs in cancer therapy
    Prog. Mater. Sci. (IF 23.725) Pub Date : 2019-08-26
    Xing Guo, Xiao Wei, Zi Chen, Xiaobin Zhang, Guang Yang, Shaobing Zhou

    To achieve highly effective treatment to diseases, successful delivery of drugs with a carrier into the specific organelles (nucleus, mitochondria, lysosomes, etc.) is of great importance. Targeted delivery based on nanoparticle (NP)-based drug delivery systems (NDDSs) is mainly focused on cell-membrane targeting. In this review we summarize researches on organelle-specific drug delivery with multifunctional NPs. Many effective strategies are introduced for functionalizing these NPs by altering their chemical composition or by grafting functional groups onto their surface for improving organelle-targeting ability. Only when the concentration of released drugs becomes high enough will they interact with molecular targets on specific organelles to induce tumor cell apoptosis. Organelle-specific delivery will become one of the primary goals for targeted drug delivery research.

  • Revisiting fundamental welding concepts to improve additive manufacturing: From theory to practice
    Prog. Mater. Sci. (IF 23.725) Pub Date : 2019-08-01
    J.P. Oliveira, T.G. Santos, R.M. Miranda

    Additive manufacturing technologies based on melting and solidification have considerable similarities with fusion-based welding technologies, either by electric arc or high-power beams. However, several concepts are being introduced in additive manufacturing which have been extensively used in multipass arc welding with filler material. Therefore, clarification of fundamental definitions is important to establish a common background between welding and additive manufacturing research communities. This paper aims to review these concepts, highlighting the distinctive characteristics of fusion welding that can be embraced by additive manufacturing, namely the nature of rapid thermal cycles associated to small size and localized heat sources, the non-equilibrium nature of rapid solidification and its effects on: internal defects formation, phase transformations, residual stresses and distortions. Concerning process optimization, distinct criteria are proposed based on geometric, energetic and thermal considerations, allowing to determine an upper bound limit for the optimum hatch distance during additive manufacturing. Finally, a unified equation to compute the energy density is proposed. This equation enables to compare works performed with distinct equipment and experimental conditions, covering the major process parameters: power, travel speed, heat source dimension, hatch distance, deposited layer thickness and material grain size.

  • Modular Fabrication of Intelligent Material-Tissue Interfaces for Bioinspired and Biomimetic Devices
    Prog. Mater. Sci. (IF 23.725) Pub Date : 2019-07-17
    John R. Clegg, Angela M. Wagner, Su Ryon Shin, Shabir Hassan, Ali Khademhosseini, Nicholas A. Peppas

    One of the goals of biomaterials science is to reverse engineer aspects of human and non-human physiology. Similar to the body’s regulatory mechanisms, such devices must transduce changes in the physiological environment or the presence of an external stimulus into a detectable or therapeutic response. This review is a comprehensive evaluation and critical analysis of the design and fabrication of environmentally responsive cell-material constructs for bioinspired machinery and biomimetic devices. In a bottom-up analysis, we begin by reviewing fundamental principles that explain materials’ responses to chemical gradients, biomarkers, electromagnetic fields, light, and temperature. Strategies for fabricating highly ordered assemblies of material components at the nano to macro-scales via directed assembly, lithography, 3D printing and 4D printing are also presented. We conclude with an account of contemporary material-tissue interfaces within bioinspired and biomimetic devices for peptide delivery, cancer theranostics, biomonitoring, neuroprosthetics, soft robotics, and biological machines.

  • A review of biomimetic surface functionalization for bone-integrating orthopedic implants: Mechanisms, current approaches, and future directions
    Prog. Mater. Sci. (IF 23.725) Pub Date : 2019-07-12
    Callum Stewart, Behnam Akhavan, Steven G. Wise, Marcela M.M. Bilek

    Orthopedic implants are increasing in global prevalence, with hundreds of thousands of operations performed annually. However, a significant proportion of these operations experiences failure due to poor bone integration. Many avenues of investigation have been explored to address this issue and improve the biocompatibility of orthopedic devices by modifying the biological response to the implant surface. Biomimetic functionalization of orthopedic surfaces enables control over the biological response by signaling through immobilized proteins and other biomolecules. This approach seeks to promote osteoblast differentiation and bone formation at the implant surface, leading to integration between the orthopedic surface and the local bone tissue. This review commences by highlighting the need for biomimetic functionalization from a materials and biological perspective. The surface properties that govern protein-surface interactions are subsequently explained. Progress in biomolecule functionalization of orthopedic surfaces performed via adsorption, chemical covalent immobilization, and physical covalent immobilization are discussed and reviewed. The immobilization mechanisms for each approach are examined and the strategies are evaluated according to their complexity, efficacy, reproducibility, and scalability. Emerging and prospective avenues for the transition from 2D to 3D substrates and the multi-functionalization of biomimetic surfaces are then explored.

  • PMSP Aboulkhair 3D printing of Aluminium alloys
    Prog. Mater. Sci. (IF 23.725) Pub Date : 2019-07-10
    Nesma T. Aboulkhair, Marco Simonelli, Luke Parry, Ian Ashcroft, Christopher Tuck, Richard Hague

    Metal Additive Manufacturing (AM) processes, such as selective laser melting (SLM), enable the fabrication of arbitrary 3D-structures with unprecedented degrees of freedom. Research is rapidly progressing in this field, with promising results opening up a range of possible applications across both scientific and industrial sectors. Many sectors are now benefiting from fabricating complex structures using AM technologies to achieve the objectives of light-weighting, increased functionality, and part number reduction, among others. AM also lends potential in fulfilling demands for reducing the cost and design-to-manufacture time. Aluminium alloys are of the main material systems receiving attention in SLM research, being favoured in many high-value applications. However, processing them is challenging due to the difficulties associated with laser-melting aluminium where parts suffer various defects. A number of studies in recent years have developed approaches to remedy them and reported successful SLM of various Al-alloys and have gone on to explore its potential application in advanced componentry. This paper reports on recent advancements in this area and highlights some key topics requiring attention for further progression. It aims to develop a comprehensive understanding of the interrelation between the various aspects of the subject, as this is essential to demonstrate credibility for industrial needs.

  • Recent Progress in Fundamental Understanding of Halide Perovskite Semiconductors
    Prog. Mater. Sci. (IF 23.725) Pub Date : 2019-07-09
    Kai Wang, Dong Yang, Congcong Wu, Mohan Sanghadasa, Shashank Priya

    The rapid progress in the field of organic-inorganic halide perovskite (OIHP) has led to not only >24% power conversion efficiency for photovoltaics, but also provided breakthroughs in processing of materials with tailored functional behavior. This ability to design and synthesize engineered OIHP materials has opened the possibility to develop various other optoelectronic applications. In addition to that of photovoltaics, this includes photodetector, laser, light emitting diode, X-ray and gamma detector, photocatalyst, memory, transducer, transistor, and more. At this stage, the emphasis is on fundamental understanding of the underlying physics and chemistry of OIHP materials, which will assist the evaluation of device performance and provide explanations for some of the contradictory results reported in literature. This review discusses the theoretical and experimental analysis of the OIHP materials reported from various sources and considers the chemical and structural origin of their unique optoelectronic properties, correlated microstructures, and newly discovered extraordinary properties. In the first few sections, we summarize and discuss the crystallography, chemical bonding, and substitutional effects, followed by the discussion of correlated photophysics including the optical, electronic, excitonic, charge transport, and ion migration characteristics. Next, we revisit and discuss the in-depth behavior of films with unique defect structure, structural disorder, morphology, and crystallization thermodynamics. Novel thermal-electrical-optical properties including ferroelectricity, hot-carrier contribution, spin-orbit coupling effect, terahertz time response, edge-state discovery, etc., are rationalized considering the results debated in the community. We elaborate on the opportunities and challenges regarding stability, toxicity, and hysteresis. The viewpoint on commercialization of OIHP based solar module is presented with the goal of identifying near-term opportunities. Throughout this review, the overarching goal is to provide a simplified explanation for the complex physical effects and mechanisms, underlying interconnections between different mechanisms, uncertainties reported in literature, and recent important theoretical and experimental discoveries.

  • [email protected] Framework Hybrid Materials: A Critical Survey
    Prog. Mater. Sci. (IF 23.725) Pub Date : 2019-07-09
    Samir El Hankari, Mosto Bousmina, Abdelkrim El Kadib

    Metal organic frameworks (MOFs) are a class of pervasive nanostructured materials that generate annually an incredible amount of work in different fields, spanning from separation, adsorption, sensing and catalysis to health care and nanomedicine. The combination in their framework of isoreticular ligands and metallic clusters have resulted in a library of confined organic-inorganic hybrid materials with high specific surface area, tunable multimodale porosity and a versatile chemical reactivity. In addition, their processing with synthetic polymers has been recognized as a milestone of their real implementation in everyday life technologies and practices. A step further toward sustainable MOF-based materials has been recently performed by the integration of bio-based precursors in their synthetic procedures either directly as polytopic ligands within the material framework or indirectly as coating reagents or functional surface-modified polymeric materials. This imparted to the resulting MOF-based bio-hybrid materials a set of additional advantages, including hydrophilicity, easy-processing, flexibility, shape-controlled ability, multifunctionality and most importantly, improved biocompatibility. This review article spotlights the fashionable trend in bridging the field of MOF-based materials through the use of bio-based precursors (mainly biopolymers) and discusses how the holistic association of the MOF crystals and the biopolymer matrices resulted in promising materials with prominent properties.

  • Extraterrestrial Construction Materials
    Prog. Mater. Sci. (IF 23.725) Pub Date : 2019-06-28
    M.Z. Naser

    In recognition of the 50th anniversary of the first manned lunar landing, the National Aeronautics and Space Administration (NASA), together with the European Space Agency (ESA), revealed plans to resume manned exploration missions and to establish permanent human presence in outposts (habitats) on the Moon and Mars by 2040. In order to promote feasible and sustainable space exploration, these habitats are envisioned to be built from lunar and Martian in-situ resources. Our understanding of such indigenous resources, from materials science, construction and structural engineering points of view, is lacking and continues to hinder further development of Earth-independent habitats. In order to bridge this knowledge gap, a comprehensive assessment on the physical features and property characteristics of extraterrestrial construction materials such as those exploited from the Moon and Mars, mined from near-earth objects (NEOs), or cultured through modern technologies is presented herein. This review explores the suitability of construction materials derived from lunar and Martian regolith along with concrete derivatives, space-native metals and composites, as well as advanced and non-traditional materials for interplanetary construction. This review also identifies processing techniques suitable to produce non-terrestrial construction materials in the alien environment of space (i.e. vacuum, low gravity etc.) and highlights emerging trends and future directions to stimulate further research in this area.

  • A review of catalytic performance of metallic glasses in wastewater treatment: Recent progress and prospects
    Prog. Mater. Sci. (IF 23.725) Pub Date : 2019-06-17
    Lai-Chang Zhang, Zhe Jia, Fucong Lyu, Shun-Xing Liang, Jian Lu

    Metallic glasses (MGs), with their unique disordered atomic packing structure and superior catalytic capabilities, have gradually begun to emerge in the field of catalysis. As a new type of promising catalyst, recent reports have demonstrated that MGs exhibit many excellent catalytic properties in wastewater treatment, such as ultrafast catalytic efficiency and reliable stability with a reduced metal leaching effect, etc. This review introduces, for the first time, recent developments in using MGs with various atomic components and excellent catalytic performance as environmental catalysts. In terms of the unique properties of MGs, this article provides a full discussion of several effects of their physical characteristics on catalytic reactivity, such as structural relaxation, crystallization, and rejuvenation, electronic structure, atomic configuration, thermophysical property, atomic composition, surface roughness, residual stress, and porosity by dealloying. The catalytic performance, including decolorization, mineralization, metal leaching, sustainability and reusability, as well as the effects of different chemical parameters, is systematically reviewed. This review also delivers several important prospects in further developing MG catalysts, offering new research opportunities into the study of their novel functional applications and providing new insights into the synthesis of novel catalysts.

  • Earth-Abundant Transition Metal and Metal Oxide Nanomaterials: Synthesis and Electrochemical Applications
    Prog. Mater. Sci. (IF 23.725) Pub Date : 2019-06-05
    Govindhan Maduraiveeran, Manickam Sasidharan, Wei Jin

    Earth-abundant transition metal and metal oxide (EATM&MO) nanomaterials offer numerous positive attributes such as catalytic activity, selective enzyme-mimicking catalysis, energy harvesting and storage, green chemistry and atom economy guided by size and morphology induced intrinsic properties at the nanoscale. Noble metal nanomaterials have long been played a central role and highly efficient for various electrochemical applications but their high cost and least abundance unfortunately make them less attractive towards industrial applications. In this perspective, the design and development of EATM&MO nanomaterials with unique features are imperative in the fabrication of potential electrochemical devices. This review gives an account of the various emerging synthesis of EATM&MO nanomaterials and their nanocomposites using numerous chemical strategies for the state-of-the-art electrochemical applications. A variety of synthetic strategies for the production of diverse size-, morphology-, and composition- controlled EATM&MO nanomaterials has been described for emerging applications such as sensing and biosensing, fuel cells, photovoltaics, water electrolyzer, photo-electrochemical water electrolyzer, and energy storage systems (Lithium Ion Batteries, LIBs). Recent progress, important approaches, structure property relations, and future outlook towards the EATM&MO nanomaterials fabrication for diverse electrochemical devices are highlighted.

  • Production of large-area 2D materials for high-performance photodetectors by pulsed-laser deposition
    Prog. Mater. Sci. (IF 23.725) Pub Date : 2019-06-03
    J.D. Yao, Z.Q. Zheng, G.W. Yang

    Our review provides a comprehensive overview on the latest progress in pulsed-laser deposition (PLD) of 2D layered materials (2DLMs), and its application in photoelectric detection. We begin with a retrospective overview on various 2DLMs and their development in photoelectric detection. Then we present the fundamentals of PLD and its unique advantages compared with the traditional growth methods. Subsequently, the PLD growth of 2DLMs and the influence of various parameters are discussed. After this, we describe the current metal-semiconductor-metal and vertical heterojunction photodetectors that incorporate the PLD-grown 2DLMs. This leads into a summary of the strategies used to improve the photosensitivity and in-depth insights into the working mechanism. We then present the PLD-fabricated transparent and flexible 2DLM photodetectors. Finally, we highlight the unresolved issues and propose the future directions in this emerging research field.

  • Flexoelectricity in Solids: Progress, Challenges, and Perspectives
    Prog. Mater. Sci. (IF 23.725) Pub Date : 2019-05-31
    Bo Wang, Yijia Gu, Shujun Zhang, Long-Qing Chen

    The flexoelectricity describes the contribution of the linear couplings between the electric polarization and strain gradient and between polarization gradient and strain to the thermodynamics of a solid and represents the amount of polarization change of a solid arising from a strain gradient. Although the magnitude of the flexoelectric effect is generally small, its contribution to the overall thermodynamics of a solid may become significant or even dominant at the nanometer scale. Recent experimental and computational efforts have led to significant advances in our understanding of the flexoelectric effect and its exploration of potential applications in devices such as sensors, actuators, energy harvesters, and nanoelectronics. Here we review the theoretical development and experimental progress in flexoelectricity including the types of materials systems that have been explored and their potential applications. We discuss the challenges in the experimental measurements and density functional theory computations of the flexoelectric coefficients including understanding the order of magnitude discrepancies between existing experimentally measured and computed values. Finally, we offer a perspective on the future directions for research on flexoelectricity.

  • Phase-field modeling of crystal nucleation in undercooled liquids – A review
    Prog. Mater. Sci. (IF 23.725) Pub Date : 2019-05-30
    László Gránásy, Gyula I. Tóth, James A. Warren, Frigyes Podmaniczky, György Tegze, László Rátkai, Tamás Pusztai

    We review how phase-field models contributed to the understanding of various aspects of crystal nucleation including homogeneous and heterogeneous processes, and their role in microstructure evolution. We recall results obtained both by the conventional phase-field approaches that rely on spatially averaged (coarse grained) order parameters in capturing freezing, and by the recently developed phase-field crystal models that work on the molecular scale, while employing time averaged particle densities, and are regarded as simple dynamical density functional theories of classical particles. Besides simpler cases of homogeneous and heterogeneous nucleation, phenomena addressed by these techniques include precursor assisted nucleation, nucleation in eutectic and phase separating systems, phase selection via competing nucleation processes, growth front nucleation (a process, in which grains of new orientations form at the solidification front) yielding crystal sheaves and spherulites, and transition between the growth controlled cellular and the nucleation dominated equiaxial solidification morphologies.

  • Dynamic Relaxations and Relaxation-Property Relationships in Metallic Glasses
    Prog. Mater. Sci. (IF 23.725) Pub Date : 2019-05-25
    Wei Hua Wang

    Dynamic relaxation is an intrinsic and universal feature of glasses and enables fluctuation and dissipation to occur, which induces plentiful behaviour, maintains equilibrium, and achieves evolution in glass systems. Relaxation covers a broad time, frequency, and temperature ranges and determines the functions, behaviour, properties and applications of glassy system. Investigations of dynamic relaxation are significant for understanding the nature of glasses, liquids, and the critical issues of glass formation and transition, dynamic and structural heterogeneities, flow behaviour and flow units, various crossover temperatures, deformations, aging and rejuvenation, stability, crystallization, and the mechanical and physical properties of glasses. Metallic glasses (MGs) with unique microstructure and mechanical and functional properties, offer a simple but effective system for study of relaxation and related issues in glass science. In this review, a panoramic view of the state of the art of various aspects of dynamic relaxation in metallic glassy system, as well as a comparison with other glassy systems, is presented. The features and mechanisms of each known relaxation mode including primary α-relaxation, slow and fast 7 β -relaxations, nearly constant loss, and boson peak, as well as their coupling in MGs, are reviewed and summarized. Emphasis is presented to the microstructural origin of these dynamic relaxation modes and their connection with the dynamic and structural heterogeneities in MGs. The factors which determine and affect the relaxation modes and behaviour in low-dimensional MGs are also introduced. It is shown that the relaxation in MGs is connected with their structural characteristics, heterogeneity, formation, glass transition, flow behaviour, physical and mechanical properties, crystallization, stability, and the localized atomic diffusion. The roles and the importance of dynamic relaxation in understanding many crucial issues in glassy physics are demonstrated. The correlations between dynamic relaxation and various properties of MGs are established and summarized. With this review on dynamic relaxation in metallic glasses, relaxation in MG can provide an effective perspective for understanding nearly all issues in metallic glasses. It is demonstrated that the relationship of relaxation to various properties, similar to the relationship of structure-property of crystalline materials, can be applied to control and design of new glassy materials with multiple functionalities, superior mechanical performance, and other extraordinary physical and chemical properties. Finally, the key unsolved questions regarding dynamic relaxation in metallic glasses are listed, and several emerging research directions in this still-evolving field are highlighted for future investigations.

  • Multiple and two-way reversible shape memory polymers: Design strategies and applications
    Prog. Mater. Sci. (IF 23.725) Pub Date : 2019-05-25
    Kaojin Wang, Yong-Guang Jia, Chuanzhuang Zhao, X.X. Zhu

    Shape memory polymers (SMPs) are capable of changing their shapes in a pre-defined manner under a stimulus, and have gained considerable interest in the past decades. Although a number of stimulus-responsive SMPs have been developed, thermally-induced SMPs are still the most common. This review presents the concepts, the programming procedures, the molecular mechanism, classification, design strategies and the recent progress of thermally-induced SMPs, including dual, triple, multiple SMPs and two-way reversible SMPs (2W-SMPs) activated by direct and indirect heating method. Examples of the applications of these types of SMPs are also presented and discussed.

  • Bioprocess-inspired fabrication of materials with new structures and functions
    Prog. Mater. Sci. (IF 23.725) Pub Date : 2019-05-21
    Jingjing Xie, Hang Ping, Tiening Tan, Liwen Lei, Hao Xie, Xiao-Yu Yang, Zhengyi Fu

    Strategies that attempt to mimic the well-defined structures or unique functions of natural biological materials have succeeded in designing and synthesizing bio-inspired materials in the past twenty years. Furthermore, natural structure-forming processes in biological systems can efficiently and accurately fabricate biomaterials under environmentally benign conditions, in contrast to our anthropogenic technologies wherein harsh conditions are commonly prerequisites. Hence, natural structure-forming processes are well worth studying in pursuit of new techniques for fabricating advanced materials with novel structures and functions, a new research direction, called “bioprocess-inspired fabrication” has been proposed in recent years. In this review, we systematically introduce and evaluate the advance of bioprocess-inspired fabrication of materials for the first time. We describe advances in the exploration and development of bioprocess-inspired fabrication technology and related exquisite materials. We summarize in detail the advances in biomineralization, photosynthesis and other bioprocess-inspired fabrication methods, and have finally discussed some new ideas and directions that need to be emphasized in the future. Bioprocess-inspired fabrication of materials will convey far-reaching implications for materials science, life science, biology, chemistry and other related interdisciplinary fields.

  • Stimuli directed alignment of self-organized one-dimensional semiconducting columnar liquid crystal nanostructures for organic electronics
    Prog. Mater. Sci. (IF 23.725) Pub Date : 2019-03-29
    Hari Krishna Bisoyi, Quan Li

    Electronic devices are ubiquitous and inorganic semiconductors generally serve as their active components. Recently, organic semiconductors, i.e., conjugated polymers, oligomers and small molecules with delocalized π-electron clouds, have been employed in electronic and optoelectronic devices and their performances are being constantly improved. In this context, the columnar phases of discotic liquid crystals have been investigated as a new generation of organic semiconductors in organic field-effect transistors (OFETs), organic light emitting diodes (OLEDs), organic photovoltaic (OPV) solar cells, etc. These self-organizing and soft materials possess the necessary charge carrier mobility and anisotropic conduction characteristics for employment in semiconductor devices, however little control over the desired molecular orientation in device architectures has been a major roadblock in the exploration of the full potential of these fascinating functional materials. Since spontaneous alignment capability of these intriguing materials is poor, various methods and techniques have been developed to direct their molecular orientation with suitable configuration using different stimuli to demonstrate their optimal performance in device structures. Accordingly, a variety of physical and chemical methods have been used to obtain highly ordered columns with desired orientation on single substrates as open supported films and in-between two substrates as confined flat films. Moreover, their controlled organizations in micro and nano grooves, trenches and pores have also been demonstrated. This article deals with the different methods involving various stimuli used for the large area alignment control of discotic columnar phases both parallel (uniaxial planar) and perpendicular (homeotropic) to the substrates. Various strategies utilizing one or more stimulus to control the alignment have been described. The applications of achieved alignment control over the supramolecular columnar nanostructures in the fabrication optoelectronic devices have been highlighted. The article concludes with a brief perspective on the challenges and opportunities in this area of research and development involving these intriguing self-healing materials.

  • Nanocalorimetry: Door opened for in situ material characterization under extreme non-equilibrium conditions
    Prog. Mater. Sci. (IF 23.725) Pub Date : 2019-04-05
    Yulai Gao, Bingge Zhao, Joost J. Vlassak, Christoph Schick

    The past two decades have witnessed the rapid development of nanocalorimetry, a novel materials characterization technique that employs micromachined calorimetric sensors. The key advances of this technique are the ultrahigh scanning rate, which can be as high as 106 K/s, and the ultrahigh heat capacity sensitivity, with a resolution typically better than 1 nJ/K. Nanocalorimetry has attracted extensive attention in the field of materials science, where it is applied to perform quantitative analysis of rapid phase transitions. This paper reviews the development of nanocalorimetry over the last three decades and summarizes its applications to various materials ranging from polymers to metals. The glass transition and crystallization of non-crystalline materials, melting and solidification of metallic droplets, and solid-state phase transitions of thin films are introduced as typical examples. Furthermore, nanocalorimetry coupled with structural characterization techniques, such as transmission electron microscopy and synchrotron X-ray diffraction, is presented. Finally, current challenges and future outlooks for the technique are discussed. Given the unique attributes of the technique, we expect nanocalorimetry to attract increasing attention, especially with regard to characterization of fast phase transitions and evaluation of size effects.

  • One-dimensional SiC nanostructures: Designed growth, properties, and applications
    Prog. Mater. Sci. (IF 23.725) Pub Date : 2019-04-15
    Shanliang Chen, Weijun Li, Xiaoxiao Li, Weiyou Yang

    Silicon carbide (SiC) is recognized as one of the shining stars of third generation semiconductors, because of its preeminent characteristics, for instance, outstanding mechanical behavior, exceptional chemical inertness, high thermal stability, and high thermal conductivity, which represent its unique advantage and importance to be serviced under high-power/high-temperature/high-voltage harsh environments. In this review, we firstly present a comprehensive overview on the designed growth of one-dimensional (1D) SiC nanostructures in fruitful morphologies with tailored doping, followed by a detailed discussion to highlight a range of intriguing properties. Subsequently, the state-of-the-art research activities regarding their extensive applications are systematically summarized, including field emitters, supercapacitors, field-effect transistors, photocatalysts, pressure sensors, microwave absorption, superhydrophobic coating, and so forth. Finally, the future prospects and research directions of 1D SiC nanostructures are proposed.

  • Catalytic materials based on silica and alumina: Structural features and generation of surface acidity
    Prog. Mater. Sci. (IF 23.725) Pub Date : 2019-04-12
    Guido Busca

    The structural, surface chemical and catalytic properties of the materials belonging to the SiO2Al2O3 system are reviewed critically. In particular, amorphous silicas, transitional aluminas, different silica-aluminas (silica-rich and alumina-rich) and protonic zeolites are taken into consideration. The nature of the acid sites, of the Lewis and of the Brønsted type, over these surfaces is discussed and rationalized, based on the fundamental chemistry and structural chemistry of silicon and aluminum compounds.

  • Structural heterogeneities and mechanical behavior of amorphous alloys
    Prog. Mater. Sci. (IF 23.725) Pub Date : 2019-04-24
    J.C. Qiao, Q. Wang, J.M. Pelletier, H. Kato, R. Casalini, D. Crespo, E. Pineda, Y. Yao, Y. Yang

    Although the atomic structure of amorphous alloys, which lacks long-range translational symmetry, may appear homogeneous at the macroscopic scale, their local dynamic and/or static properties however vary significantly according to the recent experimental and simulation results. In the literature of amorphous alloys, the nature of such local heterogeneities is currently an issue under debate. More importantly, since amorphous alloys are in a thermodynamically nonequilibrium state, their local structures constantly evolve during structural relaxation, physical aging and mechanical deformation. As such, local structural heterogeneities, which vary with the thermal and mechanical history of amorphous alloys, could provide a key to understand the structural origin of their mechanical behavior, such as anelasticity, viscoelasticity, plasticity and fracture. In this review article, we first review mechanical spectroscopy or dynamic mechanical analyses as an important tool to study the relaxation dynamics in amorphous alloys, with a focus on the possible correlation between the secondary (also called β) relaxation and the local structural heterogeneities of amorphous alloys. After that, we discuss the recent advances on the understanding of structural heterogeneities in metallic supercooled liquids and the influence of the structural heterogeneities on the overall mechanical properties of the corresponding amorphous alloys. Finally, we briefly discuss the further development of research on this subject.

  • Two-/multi-wavelength light excitation effects in optical materials: From fundamentals to applications
    Prog. Mater. Sci. (IF 23.725) Pub Date : 2019-05-14
    Zhi Chen, Guoping Dong, Hanwei Gao, Jianrong Qiu

    Probing the nature of two-/multi-wavelength light excitation effects in optical materials, such as its mechanisms, materials composition, opt-electronic behaviors, is crucial for observing photophysical and photochemical performances for their applications. Recently this research area has stimulated extensive attention owing to its remarkable optical performances; capable of tunable fluorescence emission, tailorable photochemical reaction, controllable electrons population, and driving novel photophysical and photochemical phenomena, which are promising for emerging applications in broad areas of spectroscopy, photophysics, photochemistry, opt-electronics, biophysics, environment, and materials science. In this work, we will review recent progresses in the interdisciplinary studies on photoluminescence mechanisms, emitting centers, host materials system, optical setups and characterization techniques, and application fields for the optical materials by two-/multi-wavelength light excitation effects. In the first part, we will introduce latest progress of two-/multi-wavelength light excitation effects in optical materials from fundamentals to applications. In the second part, we will present dominating two-/multi-wavelength excited photoluminescence mechanisms, including excited state absorption, stimulated emission depletion (STED), ground state depletion, and more on STED-inspired models. Moreover, we will outline the recent progress in the optically active centers and host materials classifications; their intrinsic connections between tunable microstructures and applications for different materials systems based on two-/multi-wavelength light excitation effects. Optical measurements setups and characterization techniques for broad application fields were review and summarized. By emphasizing on the progress of emerging photoluminescence properties in optical materials and its application prospects based on the two-/multi-wavelength light excitation effects, involving three-dimensional displays, lasers, STED super-resolution nanoscopies, photolithography and optical data storage, ultraviolet bacteriostatic, solar cells, and optical switches were explained. At the end, we discussed the present achievements, the existing questions, and provide perspectives for future researches directions.

  • Particle-Reinforced Metal Matrix Nanocomposites Fabricated by Selective Laser Melting: A State of the Art Review
    Prog. Mater. Sci. (IF 23.725) Pub Date : 2019-04-24
    W.H. Yu, S.L. Sing, C.K. Chua, C.N. Kuo, X.L. Tian

    Significant progress has been made in understanding selective laser melting (SLM) process as well as fabrication of various materials using this technology. This paper covers the emerging research on particle reinforced metal matrix nanocomposites (MMNCs) with SLM and provides a comprehensive overview of the underlying scientific topics behind them. In order to provide a thorough basis for understanding and controlling of the SLM processing of MMNCs fabrication, the state of the art research from the perspective of materials and SLM processing parameters is reviewed. Feedstock preparation methods for MMNCs are emphasized and compared in detail. Mechanical properties of nanocomposites and the enhancing mechanisms due to reinforcement are discussed in depth, highlighting strength, microhardness and fatigue properties. Thereafter, defects, especially those associated with SLM processing, are also elucidated by discussing their classification, mechanisms of formation and tendency in MMNCs. Applications in aerospace, automobile, electronics and electronic packaging, and biomedical industry are illustrated. Summary of findings from this review and trends for future research in the development of MMNCs by SLM are addressed in the final part.

  • Protective polymeric films for industrial substrates: A critical review on past and recent applications with conducting polymers and polymer composites/nanocomposites
    Prog. Mater. Sci. (IF 23.725) Pub Date : 2019-04-17
    Saviour A. Umoren, Moses M. Solomon

    Corrosion defined as the deterioration of a material when it interacts with its environment is a global problem. Among the different strategies employed to combat corrosion, use of coatings and corrosion inhibitors are the most popular. Coatings or corrosion inhibitors form a layer over the metallic substrate and protect it against corrosion. Polymers, both naturally occurring and synthetic have been tested for metal corrosion protection as replacement for the toxic inorganic and organic corrosion inhibitors. Interest in them stems from their availability, cost effectiveness, and eco-friendliness (especially for natural polymers) in addition to the inherent stability and multiple adsorption centers. However, it is found that most polymeric materials studied are moderate corrosion inhibitors. Several attempts such as copolymerization, addition of substances that exert synergistic effect, cross linking, blending, and most recently incorporation of inorganic substances in nano size into the polymer matrix have been made to improve the inhibition ability of polymers. In this review, the application of conducting polymers, polymer composites and nanocomposites for corrosion protection of different industrial metal substrates are explored based on reported experimental data and their mechanism of inhibition explained. Some identified drawbacks and future direction in this area have also been highlighted.

  • Mechanical properties characterization of two-dimensional materials via nanoindentation experiments
    Prog. Mater. Sci. (IF 23.725) Pub Date : 2019-03-15
    Guoxin Cao, Huajian Gao

    Nanoindentation has been widely adopted for mechanical properties characterization of two-dimensional (2D) materials, where one typically starts with measuring the indentation load-displacement relationship of a selected 2D material, either free-standing or on a substrate, and then fits the result to an analytical model to extract the elastic modulus and strength of the material. However, the existing indentation models were not originally intended to be used for atomically thin materials, which has led to some controversies and confusion in the field. There is now an urgent need to develop new analytical models capable of describing the indentation response of 2D materials for accurate characterization of their mechanical properties. Here, we review recent progress in this field to identify existing issues and opportunities for future studies.

  • High temperature materials for heavy duty diesel engines: Historical and future trends
    Prog. Mater. Sci. (IF 23.725) Pub Date : 2018-10-24
    Dean Pierce, Allen Haynes, Jeff Hughes, Ron Graves, Phil Maziasz, Govindarajan Muralidharan, Amit Shyam, Ben Wang, Roger England, Claus Daniel

    Heavy duty (HD) vehicles are projected to be the largest fuel-use subsector in transportation, with current demand for diesel fuel projected to grow 30% by 2040. Historically, a primary strategy for increasing diesel engine efficiency has been to increase peak cylinder pressure (PCP). However, increasing PCP imparts greater mechanical and thermal loads on engine components and materials. In recent years, the material property limits for many components have been reached and further increases in PCP above ∼20 MPa have been difficult, while still maintaining the necessary affordability and longevity of on-road HD diesel engines. This paper reviews the historical evolution and major metallurgical advancements of high temperature materials in HD on road diesel engines (10–15 L displacement) up to the current state of the art, focusing on materials in the engine block, cylinder heads, pistons, valves, and exhaust components. These components cover a wide range of material classes, including cast iron, ferritic steel, austenitic steel, titanium alloys, nickel based super-alloys, and high temperature coatings. The microstructural degradation and failure mechanisms of the materials associated with the complex mechanical and thermal loading during service are discussed and key areas for future materials research are suggested that overcome technical barriers.

  • Icephobic materials: fundamentals, performance evaluation, and applications
    Prog. Mater. Sci. (IF 23.725) Pub Date : 2019-03-07
    Yizhou Shen, Xinghua Wu, Jie Tao, Chunling Zhu, Yuekun Lai, Zhong Chen

    Ice accretion may cause malfunction or serious performance degradation in outdoor facilities and structures, such as aircraft, ship, locks and dams, offshore platforms, solar panels, wind turbines, power transmission towers and lines, and sports facilities, leading to huge economic loss or even loss of human lives. Icephobic materials, typically applied in the form of coatings, have received growing attention in the last decade. This review focuses on recent research progress in water wetting state, ice nucleation, and ice adhesion from both theoretical and application perspectives. After a short introduction, static and dynamic water wetting behaviors are reviewed, with an emphasis on reducing the water adhesion at low temperatures. Ice nucleation theories have been applied to investigate how the surface texture affects the ice nucleation behavior, which in turn could be used to explain various observed icing delays. Icephobic performance tests at lab scale are then introduced, before several application examples of icephobic materials are illustrated. This review ends up with discussions of some outstanding issues and challenges faced by this research community, keeping in mind the complexity of different environment in which practical applications are taking place.

  • Dendrimer-entrapped gold nanoparticles as promising nanocarriers for anticancer therapeutics and imaging
    Prog. Mater. Sci. (IF 23.725) Pub Date : 2019-03-07
    Prashant Kesharwani, Hira Choudhury, Jaya Gopal Meher, Manisha Pandey, Bapi Gorain

    Theranostic nanotherapeutic strategy has been widely emphasized now a day to develop next generation nanomedicine. Dendrimer entrapped gold nanoparticles (DE-Au-NP) have acquired emerging application in therapeutic, imaging as well as in theranostics sciences. DE-Au-NP decorated with specific ligand for cancer cells could deliver contrast agents at target sites for imaging as well as chemotherapeutics for anticancer activity. Entrapped Au in DE-Au-NP complex could serve as an excellent contrast agent for CT imaging with better signal intensity to identify initial stages of cancer, whereas its photothermal effect can kill cancerous cells effectively. Although, reported nonspecific binding of DE-Au-NP due to free amine groups and associated toxicities of dendrimer complex could be minimized through PEGylation or acetylation of such surface amines. Recent research on gene delivery also revealed DE-Au-NP as an active tool to deliver plasmids to cancer cells to express/supress particular protein(s) to combat against cancer.

  • Cobalt oxide-based nanoarchitectures for electrochemical energy applications
    Prog. Mater. Sci. (IF 23.725) Pub Date : 2019-03-05
    Jun Mei, Ting Liao, Godwin A. Ayoko, John Bell, Ziqi Sun

    Cobalt oxide nanostructures have been considered as promising electrode materials for various electrochemical applications, especially for batteries, supercapacitors, and electrocatalysis, owing to their unparalleled advantages of high theoretical capacity, highly-active catalytic properties, and outstanding thermal/chemical stability. If hybridized with property-complementary nanomaterials, such as nanocarbon, CNTs, graphene, metal oxides/sulfides, conductive polymers, etc., their electrochemical properties can be further enhanced in terms of specific reversible capacity/capacitance, rate capability, cycling stability, and catalytic activity. In this review, we first give a comprehensive overview on recent progress in both monolithic cobalt oxide nanostructures and their hybrid nanomaterials for batteries, supercapacitors, and electrocatalysis applications. Then, structure-property relationships of the cobalt oxide based nanomaterials and current challenges in both nanoarchitectures design and their applications in electrochemical energy devices are proposed, and an outlook on future research of this family of materials in electrochemical energy applications are brought forward. This understanding on the relationships of synthesis-nano/microstructure-property-performance of cobalt oxide-based nanomaterials is expected to lay a good foundation for pushing this promising class of materials to the practical application in energy conversion and storage devices and to provide a good reference for the readers in the fields of materials, chemistry, sustainable energy, and nanotechnology.

  • Recent advances in carbon-based polymer nanocomposites for electromagnetic interference shielding
    Prog. Mater. Sci. (IF 23.725) Pub Date : 2019-02-07
    Hooman Abbasi, Marcelo Antunes, José Ignacio Velasco

    Carbon-based nanoparticles have recently generated a great attention, as they could create polymer nanocomposites with enhanced transport properties, overcoming some limitations of electrically-conductive polymers for high demanding sectors. Particular importance has been given to the protection of electronic components from electromagnetic radiation emitted by other devices. This review considers the recent advances in carbon-based polymer nanocomposites for electromagnetic interference (EMI) shielding. After a revision of the types of carbon-based nanoparticles and respective polymer nanocomposites and preparation methods, the review considers the theoretical models for predicting the EMI shielding, divided in those based on electrical conductivity, models based on the EMI shielding efficiency, on the so-called parallel resistor-capacitor model and those based on multiscale hybrids. Recent advances in the EMI shielding of carbon-based polymer nanocomposites are presented and related to structure and processing, focusing on the effects of nanoparticle’s aspect ratio and possible functionalization, dispersion and alignment during processing, as well as the use of nanohybrids and 3D reinforcements. Examples of these effects are presented for nanocomposites with carbon nanotubes/nanofibres and graphene-based materials. A final section is dedicated to cellular nanocomposites, focusing on how the resulting morphology and cellular structures may generate lightweight multifunctional nanocomposites with enhanced absorption-based EMI shielding properties.

  • Biomaterials Used in Stem Cell Therapy for Spinal Cord Injury
    Prog. Mater. Sci. (IF 23.725) Pub Date : 2019-02-06
    Akon Higuchi, S. Suresh Kumar, Giovanni Benelli, Qing-Dong Ling, Hsing-Fen Li, Abdullah A. Alarfaj, Murugan A. Munusamy, Tzu-Cheng Sung, Yung Chang, Kadarkarai Murugan

    Spinal cord injury (SCI) is a common, severe damage to the central nervous system. Here, we discuss the use of biomaterials for stem cell transplantation in preclinical and clinical studies for the treatment of patients with SCI, because cell culture materials could influence the differentiation fate of stem cells, and not act only as carriers or scaffolds for delivery of stem cells and their differentiated cells. Therefore, the effects of cell culture materials on stem cell differentiation fate have been discussed. A direct injection of stem cells is the easiest method to transplant stem cells into the site of SCI. However, the stem cell solution tends to leak out from the injection site. Biomaterials such as fibrin have been used to reduce scarring at the transplantation site and facilitate the integration of transplanted stem cells or progenitor cells in animal models of SCI. Transplantation of stem cells using biomaterials (scaffolds or hydrogels) has been reported to be effective for the treatment of SCI in animal models. It would be necessary to investigate the optimal chemical structure, porosity, and morphology of biomaterials used for the transplantation of stem cells.

  • Trap-controlled mechanoluminescent materials
    Prog. Mater. Sci. (IF 23.725) Pub Date : 2019-02-05
    Jun-Cheng Zhang, Xusheng Wang, Gerard Marriott, Chao-Nan Xu

    Mechanoluminescence (ML) is generated during exposures of certain materials to mechanical stimuli. Many solid materials produce ML during their fracturing, however, the irreversibility of fracto-induced ML limits the practical applications of these materials. In 1999, Chao-Nan Xu discovered an intense and reproducible ML from trap-controlled materials, including ZnS:Mn2+ and SrAl2O4:Eu2+, and introduced the principles and applications of hybrid inorganic/organic mechanoluminescenct (ML) composites, and related sensors to visualize stress/strain in target structures. This discovery has triggered intense research interest in trap-controlled ML materials and composites over the past 2 decades. Notable achievements of this research include the development of trap-controlled materials that exhibit bright ML emission from the ultraviolet to the near infra-red, and multiscale mechano-optical sensitivities. This research has also increased our understanding of the mechanisms of ML phenomena, enabling the rational design of trap-controlled ML materials. Practical applications of ML are also being driven by the discovery that ML composites can serve as “mechano-optical sensitive skin” for structural health diagnosis, stress sensors for biomechanics, and mechanically-activated light sources. This review focuses on the design, synthesis, characterization, optimization and application of trap-controlled ML materials, finally concludes with discussions on the future direction of ML research and specific challenges.

  • Emerging natural and tailored materials for uranium-contaminated water treatment and environmental remediation
    Prog. Mater. Sci. (IF 23.725) Pub Date : 2019-01-29
    Yi Xie, Changlun Chen, Xuemei Ren, Xiangxue Wang, Haiyan Wang, Xiangke Wang
  • Ascendant Bioinspired Antireflective Materials: Opportunities and Challenges Coexist
    Prog. Mater. Sci. (IF 23.725) Pub Date : 2019-01-23
    Zhiwu Han, Zhibin Jiao, Shichao Niu, Luquan Ren

    In the past decades, antireflective (AR) materials have drawn more and more attention owing to its promising and wide applications such as photovoltaic industry, optical devices, and flexible display. However, there are also some critical challenges remaining. Fortunately, natural creatures have exhibited diversified well-organized micro/nanostructures and near-perfect functional materials, which provide design principles for development of the bioinspired materials. In terms of the advantages of biological strategies, the ascendant bioinspired AR materials with micro/nanostructure arrays have been developing rapidly, which can effectively suppress light reflection and improve light transmittance as well as absorption, determining the performances of related optical devices. This review highlights recent advances of the bioinspired AR materials. Firstly, the fundamental principles of achieving antireflection are briefly addressed. Next, some typical organisms with sophisticated AR nanostructures are described in detail. After that, recent progress in the optimized design and large area manufacturing is emphasized. Afterwards, the optical performance of the bioinspired AR materials with distinct pattern arrays are reviewed with particular emphasis on bioinspired nanostructure arrays. In addition, the advantages and disadvantages of these manufacturing techniques as well as their limitations are also analyzed in depth. Then, the practical applications and its potential value of micro/nanostructure arrays-based AR materials in solar cells, light-emitting diodes and organic light-emitting diodes, flexible mobile display devices, infrared stealthy camouflage, agricultural greenhouse, as well as display components of transportation means are briefly discussed. Finally, the remaining grand challenges and future development trend of the ascendant bioinspired AR materials are also presented: opportunities and challenges coexist.

  • Fe-based bulk metallic glasses: glass formation, fabrication, properties and applications
    Prog. Mater. Sci. (IF 23.725) Pub Date : 2019-01-19
    H.X. Li, Z.C. Lu, S.L. Wang, Y. Wu, Z.P. Lu

    The invention of bulk metallic glasses has stimulated extensive interest, due to their possible technological applications in a variety of industrial fields and their scientific importance in understanding related condensed matter physics. Among all types of BMGs, Fe-based BMGs are a unique yet important family due to their high mechanical strength, good thermal stability, strong corrosion resistance, excellent soft magnetic properties, and relatively low production costs. Since the first synthesis of the Fe-Al-Ga-P-C-B BMG reported in 1995, a vast body of literature regarding Fe-based BMGs has been published. However, until now, a full and systematic description of the development status and future prospects of Fe-based BMGs has been missing. Therefore, this article presents the research development and achievements of Fe-based BMGs in the past few decades, including their preparation, glass-forming ability, crystallization characteristics, mechanical properties, corrosion behaviors, soft and hard magnetic properties, and industrial applications. In addition, future developments of Fe-based BMGs are also proposed.

  • Structural architectures with toughening mechanisms in Nature: A review of the materials science of Type-I collagenous materials
    Prog. Mater. Sci. (IF 23.725) Pub Date : 2019-01-10
    Wen Yang, Marc A. Meyers, Robert O. Ritchie

    The structural constituents of tissues in organisms are composed primarily of minerals and proteins. Collagen is the most common protein used to construct such natural materials in vertebrates; among these structures, a wide variety of hierarchical architectures with structural and property gradients have evolved to induce desired combinations of stiffness, strength, ductility and toughness for a diverse range of mechanical functionalities. The soft collagen provides biological materials the ability to resist tensile tractions and to dissipate energy under mechanical deformation. Here we seek to understand the structure, deformation and toughening mechanisms of collagenous materials from the perspective of the hierarchical assembly of individual collagen molecules, fibrils, fibers, as well as the other nature-designed hierarchical structural elements. This review summarizes the structural designs of collagenous materials focusing on Type-I collagen, the most abundant extracellular protein that forms linear arrays, as well as examining its deformation and toughening mechanisms by illustrating how nature uses hierarchical structures and gradients, at nano-, micro- to macro-levels, to confer different functions to its organisms. The organization of collagen is discussed for different structures in order to illustrate the broad range of its functional and mechanical properties: specifically, skin, arteries, eye cornea, fish scales, bone, ligaments and tendons. We conclude by highlighting important developments in tissue engineering where synthetic and natural collagen has been incorporated into the architecture of the body. We trust that such insight may provide guidance for the design of the next-generation of synthetic structural materials with unprecedented functionality.

  • Electrophoretic Deposition of Chitosan-based Composite Coatings for Biomedical Applications: A Review
    Prog. Mater. Sci. (IF 23.725) Pub Date : 2019-01-06
    Egemen Avcu, Fatih E. Baştan, Hasan Z. Abdullah, Muhammad A. Ur Rehman, Yasemin Yıldıran Avcu, Aldo R. Boccaccini

    Chitosan is one of the most widely used natural biopolymers for a great variety of biomedical applications owing to its excellent biocompatibility, non-toxicity, biodegradability, and antibacterial activity. It can be employed as a dispersant, binder, and surface charge agent for particles in suspension. Electrophoretic deposition (EPD) of chitosan, especially in combination with other materials, is receiving increasing attention for biomedical applications. This article presents a comprehensive review of the field of EPD of chitosan-based composite coatings by highlighting their microstructural, mechanical, surface, and biological properties. Since suspension characteristics have significant influences on the deposition mechanisms, kinetics, and overall properties of the electrophoretically deposited coatings, suspension parameters such as concentration, viscosity, and zeta potential are discussed including chitosan-based suspensions with hydroxyapatite, bioactive glass, carbonaceous materials and other inorganic and organic materials. The deposition mechanisms proposed for each composite system are highlighted. Moreover, effects of key process parameters of EPD on the microstructural homogeneity, mechanical properties as well as surface and biological characteristics of these coatings are emphasised, and specific approaches for future research are proposed based on the state-of-the-art and considering EPD chitosan-based coatings in applications such as tissue engineering and drug delivery systems.

  • Flax (Linum usitatissimum L.) fibre reinforced polymer composite materials: A review on preparation, properties and prospects
    Prog. Mater. Sci. (IF 23.725) Pub Date : 2018-12-23
    M. Ramesh

    History is often marked by the materials and technology that reflect human capability and understanding. The increasing needs on bio-degradable and eco-friendly nature for consumer goods, the usage of bio-based materials is on demand. Flax has attracted attention since Stone Age as one of a few plants from which highly valued products are made. Fibres from flax plants are cost-effective, bio-degradable and exhibited good mechanical properties. This review focuses on the preparation, properties and prospects of flax fibres and its composites. The plant growth, harvesting, fibre structure, properties, effect of chemical treatments, influence of various factors such as fibre length, diameter, fibre location, influence of fibre orientation on properties of composites, and processing-structure-property relationships have been reviewed. Then the effect of fibre configuration, manufacturing processes, fibre quantity, matrix selection, ecological effects, mechanical properties, life cycle assessment, failure studies and fibre/matrix interface parameters on the characteristics of flax fibre composites have also been analyzed. Many open issues and ideas for further improvement are also analyzed, and more emphases are given for the development of environment-friendly bio-inspired material. Focusing on the summary of the review and the effects of the flax fibres on the finished products are also presented in this review.

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上海纽约大学William Glover