Materials Science and Engineering: R: Reports最新文献

Electromagnetic (EM) absorbers drive the development of EM technology and advanced EM equipment. The utilization of EM energy conversion of the EM absorber to design a variety of devices is attractive and promising, especially in personal protection and healthcare. In this review article, wearable EM materials are reviewed, ranging from design strategies, EM response mechanism, EM performance improvement, to the construction of smart EM devices. For EM response mechanism, the relaxation and charge transport associated with radiation energy conversion are dissected. For wearable EM devices, two main functions are highlighted, including EM sensors to replace of human senses, as well as EM absorbers to block transmission radiation. Furthermore, the current issues and potential opportunities of the wearable EM devices are pointed out, and new directions for future prospects are proposed.

The spin-orbit coupling field, an atomic magnetic field inside a Kramers’ system, or discrete symmetries can create a topological torus in the Brillouin Zone and provide protected edge or surface states, which can contain relativistic fermions, namely, Dirac and Weyl Fermions. The topology-protected helical edge or surface states and the bulk electronic energy band define different quantum or topological phases of matters, offering an excellent prospect for some unique device applications. Device applications of the quantum materials rely primarily on understanding the topological properties, their mutual conversion processes under different external stimuli, and the physical system for achieving the phase conversion. There have been tremendous efforts in finding new topological materials with exotic topological phases. However, the application of the topological properties in devices is still limited due to the slow progress in developing the physical structures for controlling the topological phase conversions. Such control systems often require extreme tuning conditions or the fabrication of complex multi-layered topological structures. This review article highlights the details of the topological phases, their conversion processes, along with their potential physical systems, and the prospective application fields. A general overview of the critical factors for topological phases and the materials properties are further discussed to provide the necessary background for the following sections.

Natural biomaterials have benefited the human civilisation for millennia. However, in recent years, designing of natural materials for a wide range of applications have become a focus of attention, spearheaded by sustainability. With advances in materials science, new ways of manufacturing, processing, and functionalising biomaterials for structural specificity has become feasible. Our review is focused on bacterial cellulose (BC), an exceptionally versatile natural biomaterial. BC is a unique nanofibrillar biomaterial extruded by microscopic single- cell bacterial factories utilising the chemical energy harvested from renewable substrates. BC is extracellular and is intrinsically pure, unlike other biopolymers that require extraction and purification. BC fibres are 100 times thinner than plant-derived cellulose and exist in a highly porous three-dimensional network that is highly biocompatible. Macro fibres fabricated from BC nanofibrils are stronger and stiffer, have high tensile strength values and can be used as substitutes for fossil fuel-derived synthetic fibres. The increased surface area to volume ratio allows stronger interactions with the components of composites that are derived from BC. The reactive hydroxyl groups on BC allows various chemical modifications for the development of functionalised BC with a plethora of ‘smart’ applications. In this review we consolidate the current knowledge on the production and properties of BC and BC composites, and highlight the very recent advancements in bulk applications, including food, paper, packaging, superabsorbent polymers and the bio-concrete industries. The process simplicity of BC production has the potential for large scale low-cost applications in bioremediation. Furthermore, the emerging high value applications of BC will be in electrochemical energy storage devices as a battery separator, and in transparent display technologies will be explored. Finally, the extensive biomedical applications of BC are discussed including, wound healing, controlled drug delivery, cancer treatment, cell culture and artificial blood vessels. In a further development on this, additive manufacturing considers enhancing the capabilities for manufacturing complex scaffolds for biomedical applications. An outlook on the future directions of BC in these and other innovative areas is presented.

Personal protective equipment (PPE) is crucial for ensuring occupational safety when handling toxic chemicals or in close contact with biological pathogens. The increased poisoning and infection cases outside the working scenario have attracted public attention, which drove the development and application of PPE for the professionals and the public. The use of PPE can effectively lower the risk of acute and chronic diseases caused by pesticide exposures and significantly reduce the spread of infectious diseases. However, conventional PPE mostly only functions as physical blocking or electrostatic repulsion materials, which still poses potential risks caused by cross- and post-contamination from the PPE. Although sensors are not usually considered as a necessary component of PPE, the detection of health threats in the environment could benefit preparations for unprepared risks promptly, especially in non-occupational situations, thus improving the protection of human safety. In this review, we discuss the needs of novel PPE by surveying some insufficient protection cases and threats that occurred during conventional PPE applications. Then, we summarize recent progress in developing single-functional decontamination and colorimetric sensing PPE, mostly fiber-based media against agricultural toxicants and microorganisms, with intension to inspire the future design of novel PPE with the integrated “decontamination-and-sensing” property. Some recently developed conventional dual-functional materials against either pesticide or microorganism exposures are highlighted. Finally, strategies and limitations of developing decontamination and sensing material using unique interactions and reactions of targets with functionalized fibrous substrates are discussed by comparing the successful approaches and practical challenges in PPE applications.

The prevalence of bacterial infections and resistance to existing antibiotics make new effective antibacterial strategies urgently needed. Photocatalytic antibacterial, an effective strategy relying on exogenous excitation, has drawn increasing attention over the past decades, owing to its controllable, safe, and non-invasive characteristics. Many photoresponsive agents have been developed. With exceptional features of abundance, facile synthesis, suitable band structure, high stability, and low toxicity, metal-free polymeric two-dimensional nanomaterial graphitic carbon nitride (g-C₃N₄) is an attractive photosensitizer for antibiotic-free antibacterial application. In this review, the basic structural characteristics and preparation methods of g-C₃N₄ are summarized. The photocatalytic antibacterial mechanism of g-C₃N₄ through reactive oxygen species (ROS) generation is also discussed. In order to achieve more precise and efficient antibacterial effects, we pay special attention to two aspects: (1) how to increase the utilization of visible light and reduce the recombination of electron-hole pairs, thereby enhancing the production of ROS; and (2) how to obtain effective bacteria-killing activity while maintaining good biocompatibility and environmental friendliness, which determines the practical applications of materials. Several significant modification strategies are thus introduced, including structure design, surface modification, element doping, and construction of g-C₃N₄-based heterojunctions. Furthermore, various typical examples of combining the photocatalytic antibacterial effect of g-C₃N₄ with other strategies to exert good synergistic effects are summarized. Lastly, the potential challenges and perspectives are offered. This review is expected to inspire more follow-up work to design high-performance g-C₃N₄-based materials for photocatalytic antibacterial application.

Bulk metallic glasses (BMGs) being metallic materials without long-range order have attracted a considerable amount of interest from academia and industry in the past three decades due to their unique and outstanding properties. However, the manufacturing of glassy components with large dimension and complex geometries has remained a considerable challenge. The main obstructions in this regard arise from the oftentimes limited glass-forming ability (GFA) of most metallic systems, which requires extremely fast quenching of the corresponding melts and, consequently, limits the obtainable dimensions. In addition, BMGs generally have a poor machinability due to their intrinsic high hardness and extreme brittleness. The emerging 3D printing technology (also called additive manufacturing), as an advanced bottom-up manufacturing process, seems to be a viable route to circumvent these deficiencies inherent to conventional processing routes. Additive manufacturing theoretically allows the fabrication of large-sized BMGs and components with complex geometries, greatly extending the range of applications of BMGs as both structural and functional materials. The 3D printing technology has given fresh impetus to the field of BMGs and represents an approach, which is intensely explored in the BMG’s scientific community at the moment. In this review, we present a comprehensive overview of the state-of-the-art research on various aspects related to 3D printing of BMGs. It covers various 3D printing techniques for manufacturing BMGs, the microstructures (e.g. structural heterogeneities and fused-related defects) found in 3D-printed BMGs, the crystallization behavior in additively manufactured glasses and the associated alloy selection criterion, the observed mechanical properties and deformation mechanisms, and finally the functional properties and potential applications of 3D-printed BMGs and BMG matrix composites, in terms of catalysis, wear, corrosion, and biocompatibility. This article also identifies a number of key questions to be answered in the future in this important research direction in order to successfully bridge the gap from fundamental research to large-scale application of additively manufactured bulk metallic glasses.

As one of the most complex structures in nature, butterflies have attracted wide interest over the past few decades. Inspired by these delicate structures and the marvelous derived properties, scientists have investigated and biomimetic fabricated several designs to replicate the structure and to apply the functional features. Here, we present up-to-date researches concerning butterfly-inspired functional materials in different fields. After introducing the basic properties and corresponding structures, the bio-mimic fabrication methods are clarified and concluded. We then concerned about the applications, combining the modified butterfly wing and the fabricated replicas. The challenges and prospects of the further development of the butterfly inspired functional materials are conclusively presented.

Additive manufacturing of industrially-relevant high-performance parts and products is today a reality, especially for metal additive manufacturing technologies. The design complexity that is now possible makes it particularly useful to improve product performance in a variety of applications. Metal additive manufacturing is especially well matured and is being used for production of end-use mission-critical parts. The next level of this development includes the use of intentionally designed porous metals - architected cellular or lattice structures. Cellular structures can be designed or tailored for specific mechanical or other performance characteristics and have numerous advantages due to their large surface area, low mass, regular repeated structure and open interconnected pore spaces. This is considered particularly useful for medical implants and for lightweight automotive and aerospace components, which are the main industry drivers at present. Architected cellular structures behave similar to open cell foams, which have found many other industrial applications to date, such as sandwich panels for impact absorption, radiators for thermal management, filters or catalyst materials, sound insulation, amongst others. The advantage of additively manufactured cellular structures is the precise control of the micro-architecture which becomes possible. The huge potential of these porous architected cellular materials manufactured by additive manufacturing is currently limited by concerns over their structural integrity. This is a valid concern, when considering the complexity of the manufacturing process, and the only recent maturation of metal additive manufacturing technologies. Many potential manufacturing errors can occur, which have so far resulted in a widely disparate set of results in the literature for these types of structures, with especially poor fatigue properties often found. These have improved over the years, matching the maturation and improvement of the metal additive manufacturing processes. As the causes of errors and effects of these on mechanical properties are now better understood, many of the underlying issues can be removed or mitigated. This makes additively manufactured cellular structures a highly valid option for disruptive new and improved industrial products. This review paper discusses the progress to date in the improvement of the fatigue performance of cellular structures manufactured by additive manufacturing, especially metal-based, providing insights and a glimpse to the future for fatigue-tolerant additively manufactured architected cellular materials.

Fire safety has become a major concern due to the ubiquitous use of polymers. The development of flame retardant polymer materials has consequently experienced a huge growth in market size. New strategies and legislation have also been proposed to save lives and property. The science and economics of flame retardancy, fire regulations, and new technologies are under permanent evolution. This review paper focuses on revisiting and classifying recent developments in the knowledge and technology of flame retardant polymer materials and demonstrating the qualitative and quantitative analyses carried out on their flame retardant properties. In particular, it comprehensively addresses the progress made and the future prospects for designing precise structures via innovative technologies, particularly 3D printing - as the state-of-the-art manufacturing methodology providing innovative features in this realm of research - and their flame retardancy performances. Indeed, the strategies driving the technologies of innovative flame retardant polymer materials and 3D printing technology are approaching a practical juncture in the near future.

The engineering applications of thermoelectric (TE) devices require TE materials possessing high TE performance and robust mechanical properties. Research on thermal and electrical transport properties of TE materials has made significant progress during the last two decades, developing TE materials on the threshold of commercial applications. However, research on mechanical strength and toughness has lagged behind, restricting application of TE materials. Mechanical failure in these materials involves multi-scale processes spanning from atomistic scale to macro scale. We have proposed an integral stress-displacement method to estimate fracture toughness from intrinsic mechanical behavior. In this review, we summarize our recent progress on fracture toughness of TE materials. This is in three parts:

(1) Predicting fracture toughness of TE materials from intrinsic mechanical behavior;

(2) Intrinsic mechanical behavior and underlying failure mechanism of TE materials; and

(3) Nanotwin and nanocomposite strategies for enhancing the mechanical strength and fracture toughness of TE materials.

These findings provide essential comprehensive understanding of fracture behavior from micro to the macro scale, laying the foundation for developing reliable TE devices for engineering applications.