ABSTRACTIn the last two decades nanogels have emerged as very promising and versatile biomaterials suitable for a wide range of applications. Their features such as large surface area, ability to hold molecules, flexibility in size and water-based formulations have ensured them great recognition as drug delivery systems with various in vivo applications which have confirmed their potential. On the other handnanogels have been investigated in recent years for applications in various fields other than biomedicine. Clear examples of this are represented by the possibility of employing nanogels as sensing materials, as catalysts or as adsorbents for environmental applications. In view of this variety of possible applications, in this work we extend our knowledge on the topic of their possible uses described in literature, taking stock of the state of the art for all possible nanogel employment and their synthesis methods.

ABSTRACTAdvancements in electrochemical energy storage devices such as batteries and supercapacitors are vital for a sustainable energy future. Significant progress has been made in developing novel materials for these devices, but less attention has focused on developments in electrode and device manufacturing. While electrodes are traditionally made through slurry casting of electrochemically active material, advanced manufacturing techniques enable patterning of novel electrode architectures and control of device geometries in real-time, which can potentially result in electrodes with increased loading, improved electrochemical performance, and added functionality, such as flexibility and wearability. These inexpensive methods are particularly suited for lab-scale research and start-up companies, as they enable rapid prototyping without a full device production line. The present review describes three main methods of advanced manufacturing (inkjet printing, direct ink writing, and laser-induced graphene techniques) and evaluates the performance of batteries and supercapacitors fabricated via these methods in comparison to traditionally manufactured devices.

ABSTRACTBinary polymer systems provide significant advantages in the preparation of materials used in biomedical applications. To highlight the importance and need of binary polymer systems in biomedical applications; utilisations of nano-carrier and fibre are discussed in detail in terms of their use as biomaterial, and their potential for further development with focus on dual and sequential drug delivery applications. On the other hand, in fibre technology, creation of binary polymer systems have been investigated using spinning processes such as electrospinning and even more recently innovated pressurised gyration. How these methods can be used to promote the mass production of binary polymer systems with various morphologies and characteristics are elucidated. The effects of different polymer materials, including solvents, mechanical properties, and the rate of degradation of polymers, are discussed. Current polymer blending systems and manufacturing processes are analysed, and technologies for biomaterials are carefully considered with up to date details.

ABSTRACTThis review critically examines the current understanding of calcia–magnesia–alumina–silicate (CMAS) degradation mechanisms and mitigation approaches in thermal and environmental barrier coatings. First, the review introduces case studies of field returned engine components exposed to CMAS attack, followed by fundamental aspects of CMAS-induced degradation. Understanding CMAS adhesion, infiltration, spallation mechanics, and thermochemical attack mechanisms is crucial to designing materials approaches to mitigate CMAS attack. CMAS mitigation strategies have focused on reactive approaches aimed at crystallising molten CMAS at the earliest stage possible to inhibit infiltration. Promising approaches are presented, starting with fundamental reaction kinetics studies, followed by the effects of microstructure in actual coatings systems. Salient results on coating systems tested in various burner rigs and a full engine test are presented to benchmark the success of various mitigation strategies. Lastly, several key future research areas are presented in order to provide a roadmap towards ‘sandphobic’ thermal and environmental barrier systems.

ABSTRACTIn the current review, an exceptional view on the multi-scale integrated computational modelling and data-driven methods in the Additive manufacturing (AM) of metallic materials in the framework of integrated computational materials engineering (ICME) is discussed. In the first part of the review, process simulation (P-S linkage), structure modelling (S-P linkage), property simulation (S-P linkage), and integrated modelling (PSP and PSPP linkages) are elaborated considering different physical phenomena (multi-physics) in AM and at micro/meso/macro scales (multi-scale modelling). The second part provides an extensive discussion of a data-driven framework, which involves extracting existing data from databases and texts, data pre-processing, high throughput screening, and, therefore, database construction. A data-driven workflow that integrates statistical methods, including ML, artificial intelligence (AI), and neural network (NN) models, has great potential for completing PSPP linkages. This review paper provides an insight for both academic and industrial researchers, working on the AM of metallic materials.

ABSTRACTLatest advancements in transparent ceramics development have ensured a mainstream research interest in this family of materials. Crystallization of glass into transparent ceramics has emerged recently as an alternative but complementary trajectory for obtaining transparent ceramics, which circumvents some of the long-standing technical difficulties associated with traditional transparent ceramics processing. The full bulk glass crystallization allows for the synthesis of high-density/low-porosity transparent ceramics of stable and metastable phases or even non-cubic structures, which are difficult to obtain using the traditional processing methods. This article presents a brief survey of the science of the transparency of ceramics and a detailed overview of the materials systems and techniques used for the preparation of transparent ceramics through the glass crystallization route. Finally, the review provides authors' insights into the future trends and research directions aimed to encourage a widespread application of glass crystallization into transparent ceramics in the fabrication of next-generation materials.

ABSTRACTMetal–air batteries have been considered as promising battery prototypes due to their high specific capacity, energy density and easily available nature of air. Al can be regarded as an attractive candidate because of its abundant reserve (the most abundant metal element in the earth's crust), low price (1.9 USD·kg–1), high theoretical capacity density of 2.98 Ah·g−1 and high energy density of 8.1 Wh·g−1. For meeting the level of commercialization, nevertheless, there are still many scientific and technical challenges to overcome in the Al–air batteries. In this review, a comprehensive overview of Al–air batteries is initially provided, along with highlighting recent progresses in high-performance Al anodes, advanced air cathodes and improved electrolytes for Al–air batteries. The analysis and discussion on the progresses and challenges for Al–air batteries here are expected to provide a meaningful guide for future efforts to boost Al–air batteries.

ABSTRACTAmongst the many additive manufacturing (AM) techniques, directed energy deposition (DED) is a prominent one, which can also be used for the repair of damaged components. In this paper, we provide an overview on it, with emphasis on the typical microstructures of DED alloys and discuss the processing-microstructure-mechanical property correlations. Comparison is made with those manufactured using the conventional techniques and those obtained with laser beam powder bed fusion (LB-PBF). The characteristic solidification rates and thermal histories in DED result in distinct micro- and meso-structural features and mechanical performance, which are succinctly summarized. The potential of DED for manufacturing graded materials and for component repair is elaborated while highlighting the key-associated challenges and possible solutions. Modelling and simulation studies that facilitate an in-depth understanding of the DED technique are summarized. Finally, some critical issues and research directions that would help develop DED further and extend its application potential are identified.

ABSTRACTElectrophoretic deposition (EPD) is a powerful technique to assemble carbon nanotube (CNT) coatings and composite films with controlled architectures. This comprehensive review of the EPD of CNTs and CNT-containing composites focuses on achievements within the last 15 years and ongoing challenges. Stable CNT suspensions are a pre-requisite for successful EPD and have been prepared by a variety of strategies, discussed here. The resulting film microstructure is determined by the initial feedstock, the suspension, and the EPD approach applied, as well as a variety of EPD processing parameters. Nanocomposites can be prepared via co-deposition, sequential deposition, or post-deposition treatments, to introduce metallic, ceramic or polymeric phases. There are numerous potential applications for both homogeneous and patterned CNT films, including as structural reinforcements for composites, as field emission, energy storage and conversion devices, as well as in biomedical applications. The advantages and disadvantages of EPD processing in these contexts are discussed.

ABSTRACTAmong various materials available for alleviating the corrosion-related degradation, thermal sprayed Fe-based metallic glass coatings (MGCs) have received huge attention from the scientific community due to the exceptional combination of mechanical and corrosion properties, along with commercially attractive low material cost of this particular alloy system. Emerging reports on the thermal sprayed Fe-based MGCs outperforming conventional corrosion-resistant materials and coatings have accelerated further exploration of this domain, resulting in an immense increase of research activities over the last few decades producing fascinating results. This review takes a holistic approach encompassing an in-depth assessment of all the relevant salient work till date, including corrosion properties, corresponding degradation mechanisms, metallurgical and environmental factors with reference to passive film dynamics and/or formation of corrosion products. Moreover, various strategies for improved corrosion properties and recent research progress have been reviewed with an attempt to identify the present knowledge gaps and the future research directions.

ABSTRACTLiquid crystalline epoxy networks (LCENs) are a class of materials that combine the useful benefits of both liquid crystals and epoxy networks exhibiting fascinating thermal, mechanical, and stimuli-responsive properties. They have emerged as a new platform for developing functional materials suitable for various applications, such as sensors, actuators, smart coatings and adhesives, tunable optical systems, and soft robotics. This article provides an overview of LCENs and their composites as functional materials, including their synthesis and characterisation, focusing on structure-processing–property relationships. We provide objective analyses on how materials engineers can use these relationships to develop LCENs with desired functionalities for targeted applications. Emerging areas, including advanced manufacturing and multi-functional design of LCENs are covered to show the overall progress in this field. We also survey the forward-looking status of LCEN research in designing novel materials for future technologies.

ABSTRACTAdditive Manufacturing (AM) has the potential to completely reshape the manufacturing space by removing the geometrical constraints of commercial manufacturing and reducing component lead time, especially for large-scale parts. Coupling robotic systems with direct energy deposition (DED) additive manufacturing techniques allow for support-free printing of parts where part sizes are scalable from sub-metre to multi-metre sizes. This paper offers a holistic review of large-scale robotic additive manufacturing, beginning with an introduction to AM, followed by different DED techniques, the compatible materials and their typical as-built microstructures. Next, the multitude of robotic build platforms that extend the deposition from the standard 2.5 degrees of freedom (DOF) to 6 and 8 DOF is discussed. With this context, the decomposition and slicing of the computerized model will be described, and the challenges of planning the deposition trajectory will be discussed. The different modalities to monitor and control the deposition in an attempt to meet the geometrical and performance specifications are outlined and discussed. A wide range of metals and alloys have been reported and evaluated for large-scale AM parts. These include steels, Ti, Al, Mg, Cu, Ni, Co–Cr and W alloys. Different post-processing steps, including heat treatments, are discussed, along with their microstructures. This paper finally addresses the authors' perspective on the future of the field and the largest knowledge gaps that need to be filled before the commercial implementation of robotic AM.

ABSTRACTResearch on thermoelectric materials – with their vast potential for applications in solid-state cooling or energy-conversion devices – has so far mainly focused on enhancing their conversion efficiency. However, understanding and tailoring the mechanical performance of thermoelectric modules and devices is crucial for their long-term use, as they are subjected to spatially-complex and time-varying thermomechanical stresses – both internal and external – which may lead to plastic, fatigue and/or creep deformation. This leads to changes in thermoelectric performance, dimensions (via strain accumulation) and mechanical integrity (via crack and pore formation, leading to failure). This review addresses the current understanding of various modes of stress-induced deformation that can take place during extended operation of thermoelectric materials and their impact on the strain (elastic, plastic, and creep), and the associated damage (bloating, fatigue, and fracture). Finally, some new areas of research straddling mechanical and thermoelectric behaviour are identified.

ABSTRACTSteels with medium manganese (Mn) content (3∼12 wt-%) have emerged as a new alloy class and received considerable attention during the last decade. The microstructure and mechanical response of such alloys show significant differences from those of established steel grades, especially pertaining to the microstructural variety that can be tuned and the associated micromechanisms activated during deformation. The interplay and tuning opportunities between composition and the many microstructural features allow to trigger almost all known strengthening and strain-hardening mechanisms, enabling excellent strength-ductility synergy, at relatively lean alloy content. Previous investigations have revealed a high degree of microstructure and deformation complexity in such steels, but the underlying mechanisms are not adequately discussed and acknowledged. This encourages us to critically review and discuss these materials, focusing on the progress in fundamental research, with the aim to obtain better understanding and enable further progress in this field. The review addresses the main phase transformation phenomena in these steels and their mechanical behaviour, covering the whole inelastic deformation regime including yielding, strain hardening, plastic instability and damage. Based on these insights, the relationships between processing, microstructure and mechanical properties are critically assessed and rationalized. Open questions and challenges with respect to both, fundamental studies and industrial production are also identified and discussed to guide future research efforts.

ABSTRACTThe photocatalytic oxidation of volatile organic compounds (VOCs) has been extensively investigated. With respect to water treatment, photocatalytic degradation of air pollutants is still less understood, but this has not prevented photocatalytic building materials and air purifiers to reach the market. Here, we provide a selective overview of the current understanding on VOC photocatalytic oxidation, focusing on ethanol, acetaldehyde, and acetic acid. Among the main indoor pollutants, these molecules are also oxidation intermediates of numerous VOCs. Their adsorption at the photocatalyst surface is first presented, based on theoretical and experimental evidence. Reaction intermediates are discussed, comparing proposed reaction mechanisms. The role of the photocatalyst features in directing adsorption and oxidation phenomena is highlighted, encompassing both TiO2 and emerging photocatalysts. We then critically discuss gaps in our knowledge, such as the effect of air humidity, multi-pollutant interactions and deactivation pathways. Finally, attempts to model VOC degradation in realistic conditions are reviewed.

ABSTRACTUltra-high molecular weight polyethylene (UHMWPE) materials have played a significant role in the field of reconstructive surgery, particularly as acetabular liners/sockets for total hip joint replacement (THR), and tibial inserts for total knee joint replacement (TKR). This review aims to provide a perspective on key elements regarding the processing–structure–property relationship of UHMWPE and derivatives. Much emphasis will be provided to discuss the clinically relevant properties of UHMWPE blend/composite formulation, Vitamin-E reinforced or highly crosslinked variants. In addition, we provide clinical insights into the role of wear debris in inflammation and osteolysis. The relatively unexplored domain of UHMWPE additive manufacturing. Finally, the relatively unexplored domain of UHMWPE additive manufacturing and the opportunities associated with the next generation of UHMWPE implants are highlighted.

ABSTRACTIn recent years, the hydrogen economy has been strongly favoured by governmental and industrial bodies worldwide. A tremendous number of papers are published every year on different aspects of protonic ceramic electrochemical cells (PCECs) due to their lower operation temperature, easier reversible operation, and brighter prospects for further development. While new progress is being made continuously, many critical challenges remain. The effort on PCEC investigation could be more aligned for greater collective impact, e.g. the academic community could devote more effort to overdue critical problems but less to incremental improvements. This review aims to provide some insightful perspectives on critical challenges facing the development of PCECs, to sort out priorities in future effort, and to suggest promising directions to pursue. In this way, it is hoped that the technical readiness level of PCECs might advance more quickly, toward field demonstrations and commercialization for a clean and sustainable energy era.

ABSTRACTMechanical actuators are defined as mechanical devices that convert an input energy into motion. Since the 1990s, advancements in the fields of robotics and automation have produced a critical need for the development of lightweight and efficient actuators capable of human-like motion. In the past few decades, extensive research activities in the fields of materials science and smart materials have led to the development of a novel type of actuator known as artificial muscles. This review paper describes the evolution of mechanical actuators from conventional technologies such as electric, hydraulic, and pneumatic actuators, to bioinspired artificial muscles. The working mechanism, manufacturing process, performance, and applications of different artificial muscles are described and compared with those of conventional actuators. Details on the cost, input sources, activation modes, advantages, and drawbacks of each artificial muscle technology are also provided to guide the reader through the intricate selection process of the best-suited actuator for a specific application.

ABSTRACTBioceramics are in high demand due to their biocompatibility and bone-regenerative properties, representing a multibillion-dollar industry with orthopaedic and dental implant applications. However, traditional manufacturing methods have limitations in producing complex geometries tailored to match patient-specific bone defects. Vat-photopolymerization 3D printing has emerged as a precise and high-resolution technique to fabricate complex bioceramic parts, generating strong, ultralight, energy-absorbing, and tough materials. Despite their promise, the clinical translation of 3D-printed bioceramic implants is hampered by regulatory and reimbursement hurdles. This review analyses recent advances in vat-photopolymerization printing of bioceramics, highlighting the technical challenges and the potential of nanoscale printing to enhance the mechanical and biological functions of implants. The review also provides recommendations for regulatory frameworks, envisioning a future with the successful clinical translation of advanced 3D architectures.

ABSTRACTCyanide-based baths are generally used industrially to produce silver and gold coatings via electroplating. Baths containing ([Au(CN)2]−) and ([Ag(CN)2]−) are used for the deposition of gold and silver coatings, respectively. However, due to the severe toxicity, the technical personnel involved in work are at risk. Additionally, the disposal of cyanide-containing wastes poses a significant threat to the environment as they pollute various natural resources. The coatings produced from alkaline cyanide-based baths cause embrittlement of electronic circuit patterns. Due to these reasons, many cyanide-free baths have started to replace the existing cyanide-based baths. In the cyanide-free baths, the primary cyanide complexing agent is replaced with eco-friendly alternative compounds like sulphite, thiosulphate, thiourea, DMH, EDTA, and ionic liquids (ILs). This review article provides an overview of the various cyanide-free electroplating baths available for electroplating silver and gold that are either used for commercial practice or are developed for laboratory-scale use.