Showing papers in "Journal of Materials Science in 2021"

Recent progress in carbon-based materials for supercapacitor electrodes: a review

Abstract: Increased energy consumption stimulates the development of various energy types. As a result, the storage of these different types of energy becomes a key issue. Supercapacitors, as one important energy storage device, have gained much attention and owned a wide range of applications by taking advantages of micro-size, lightweight, high power density and long cycle life. From this perspective, numerous studies, especially on electrode materials, have been reported and great progress in the advancement in both the fundamental and applied fields of supercapacitor has been achieved. Herein, a review of recent progress in carbon materials for supercapacitor electrodes is presented. First, the two mechanisms of supercapacitors are briefly introduced. Then, research on carbon-based material electrodes for supercapacitor in recent years is summarized, including different dimensional carbon-based materials and biomass-derived carbon materials. The characteristics and fabrication methods of these materials and their performance as capacitor electrodes are discussed. On the basis of these materials, many supercapacitor devices have been developed. Therefore, in the third part, the supercapacitor devices based on these carbon materials are summarized. A brief overview of two types of conventional supercapacitor according to the charge storage mechanism is compiled, including their development process, the merits or withdraws, and the principle of expanding the potential range. Additionally, another fast-developed capacitor, hybrid ion capacitors as a good compromise between battery and supercapacitor are also discussed. Finally, the future aspects and challenges on the carbon-based materials as supercapacitor electrodes are proposed.

Additive manufacturing of steels: a review of achievements and challenges

Abstract: Metal additive manufacturing (AM), also known as 3D printing, is a disruptive manufacturing technology in which complex engineering parts are produced in a layer-by-layer manner, using a high-energy heating source and powder, wire or sheet as feeding material. The current paper aims to review the achievements in AM of steels in its ability to obtain superior properties that cannot be achieved through conventional manufacturing routes, thanks to the unique microstructural evolution in AM. The challenges that AM encounters are also reviewed, and suggestions for overcoming these challenges are provided if applicable. We focus on laser powder bed fusion and directed energy deposition as these two methods are currently the most common AM methods to process steels. The main foci are on austenitic stainless steels and maraging/precipitation-hardened (PH) steels, the two so far most widely used classes of steels in AM, before summarising the state-of-the-art of AM of other classes of steels. Our comprehensive review highlights that a wide range of steels can be processed by AM. The unique microstructural features including hierarchical (sub)grains and fine precipitates induced by AM result in enhancements of strength, wear resistance and corrosion resistance of AM steels when compared to their conventional counterparts. Achieving an acceptable ductility and fatigue performance remains a challenge in AM steels. AM also acts as an intrinsic heat treatment, triggering ‘in situ’ phase transformations including tempering and other precipitation phenomena in different grades of steels such as PH steels and tool steels. A thorough discussion of the performance of AM steels as a function of these unique microstructural features is presented in this review.

Laves phases: a review of their functional and structural applications and an improved fundamental understanding of stability and properties

Abstract: Laves phases with their comparably simple crystal structure are very common intermetallic phases and can be formed from element combinations all over the periodic table resulting in a huge number of known examples. Even though this type of phases is known for almost 100 years, and although a lot of information on stability, structure, and properties has accumulated especially during the last about 20 years, systematic evaluation and rationalization of this information in particular as a function of the involved elements is often lacking. It is one of the two main goals of this review to summarize the knowledge for some selected respective topics with a certain focus on non-stoichiometric, i.e., non-ideal Laves phases. The second, central goal of the review is to give a systematic overview about the role of Laves phases in all kinds of materials for functional and structural applications. There is a surprisingly broad range of successful utilization of Laves phases in functional applications comprising Laves phases as hydrogen storage material (Hydraloy), as magneto-mechanical sensors and actuators (Terfenol), or for wear- and corrosion-resistant coatings in corrosive atmospheres and at high temperatures (Tribaloy), to name but a few. Regarding structural applications, there is a renewed interest in using Laves phases for creep-strengthening of high-temperature steels and new respective alloy design concepts were developed and successfully tested. Apart from steels, Laves phases also occur in various other kinds of structural materials sometimes effectively improving properties, but often also acting in a detrimental way.

Strategies for enhancing thermal conductivity of polymer-based thermal interface materials: a review

Abstract: Thermal management has been considered as a key issue for high-power electronics. Thermal interface materials (TIMs) play an extremely important role in the field of thermal management. Owing to their excellent insulation, mechanical properties and low processing costs, functional polymers have become the popular candidate for preparing TIMs. In order to develop high thermally conductive TIMs, the inorganic fillers with high thermal conductivity are generally composited with polymers. For this purpose, some key technologies are needed to improve the dispersibility of fillers to reduce interfacial thermal resistance and increase thermal conduction channels. This paper reviews recent progresses on effective methods for improving thermal conductivity, which mainly include filler functionalization and processing, filler hybridization and coating, filler orientation and network. After implementing these strategies, the interfacial interaction between fillers and polymers, the synergy effect of different fillers and the thermal conduction pathway inside the matrix can be highly improved, hence enhancing the thermal conductivity of TIMs.

Carbon dots anchored high-crystalline g-C3N4 as a metal-free composite photocatalyst for boosted photocatalytic degradation of tetracycline under visible light

Abstract: Photocatalysts with excellent performance, low cost and innocuity are highly desired for environmental remediation. Zero-dimensional carbon dots with a size of 2–10 nm represent a class of promising co-catalysts due to their excellent photo-induced electron transfer, increased light absorption and thus boosted photocatalytic activity. Herein, carbon dots/high-crystalline g-C3N4 (CDs/H-CN) composites were successfully prepared via a facile calcination method for the degradation of tetracycline (TC) under visible light irradiation. Experimental results reveal that the CDs/H-CN-1 composite displays the optimal photocatalytic degradation of TC (86%, 120 min), and exhibits remarkable photostability (no decrease after 4 cycles of reaction within 480 min). According to the identification of intermediates by liquid chromatography-mass spectrometry (LC–MS) analysis, the degradation pathways of TC were proposed. In addition, the planting experiment of mung beans was performed to further confirm the biotoxicity of TC degraded products. This work underlines the importance of co-catalyst and presents a feasible protocol for the rational construction of H-CN-based photocatalysts for various photocatalytic applications.

Thermal modification of wood—a review: chemical changes and hygroscopicity

Abstract: Thermal modification is a well-established commercial technology for improving the dimensional stability and durability of timber. Numerous reviews of thermally modified timber (TMT) are to be found in the scientific literature, but until now a review of the influence of cell wall moisture content during the modification process on the properties of TMT has been lacking. This paper reviews the current state of knowledge regarding the hygroscopic and dimensional behaviour of TMT modified under dry (cell wall at nearly zero moisture content) and wet (cell wall contains moisture) conditions. After an overview of the topic area, the review explores the literature on the thermal degradation of the polysaccharidic and lignin components of the cell wall, as well as the role of extractives. The properties of TMT modified under wet and dry conditions are compared including mass loss, hygroscopic behaviour and dimensional stability. The role of hydroxyl groups in determining the hygroscopicity is discussed, as well as the importance of considering the mobility of the cell wall polymers and crosslinking when interpreting sorption behaviour. TMT produced under wet processing conditions exhibits behaviour that changes when the wood is subjected to water leaching post-treatment, which includes further weight loss, changes in sorption behaviour and dimensional stability, but without any further change in accessible hydroxyl (OH) content. This raises serious questions regarding the role that OH groups play in sorption behaviour.

Comprehensive review on plant fiber-reinforced polymeric biocomposites

Abstract: The expansion of environment-friendly materials based on natural sources increases dramatically in terms of biodegradable, recyclable, and environmental disputes throughout the world. Plant-based natural fiber, a high potential field of the reinforced polymer composite material, is considered as lightweight and economical products as they possess lower density, significant material characteristics, and extraordinary molding flexibility. The usage of plant fibers on the core structure of composite materials have drawn significant interest by the manufacturers to meet the increasing demand of the consumers for sustainable features with enhanced mechanical performances and functionalities. The plant fiber-based composites have widespread usage in construction, automotive, packaging, sports, biomedical, and defense sectors for their superior characteristics. Therefore, this critical review would demonstrate an overview regarding the background of natural fiber composites, factors influencing the composite properties, chemical interaction between the fiber and matrices, future potentiality, and marketing perspectives for triggering new research works in the field of biocomposite materials.

Materials for lithium recovery from salt lake brine

Abstract: Rapid developments in the electric industry have promoted an increasing demand for lithium resources. Lithium in salt lake brines has emerged as the main source for industrial lithium extraction, owing to its low cost and extensive reserves. The effective separation of Mg2+ and Li+ is critical to achieving high recovery efficiency and purity of the final lithium product. This paper summarizes Mg2+/Li+ separation materials and methods in the field of lithium recovery from salt lake brines. The review begins with an introduction to the global distribution and demand for lithium resources, followed by a description of the materials used in various separation techniques, including precipitation, adsorption, solvent extraction, nanofiltration membrane, electrodialysis, and electrochemical methods. A comparison, analysis, and outlook of such methods are comprehensively discussed in terms of principles, mechanisms, synthesis/operation, development, and industrial applications. We conclude with a presentation of challenges and insights into the future directions of lithium extraction from salt lake brines. A combination of the advantages of various materials is the most logical step toward developing novel methods for extracting lithium from brines with high separation selectivity, stability, low cost, and environmentally friendly characteristics.

Efficient designing of triphenylamine-based hole transport materials with outstanding photovoltaic characteristics for organic solar cells

Abstract: Hole transport materials (HTMs), especially dopant-free hole transport materials, are getting attention in enhancing the power conversion efficiencies and stabilities of organic solar cells (OSCs). Herein, we have designed efficient dopant-free HTMs (DM1–DM5) from an outstanding synthetic DFM molecule (having 20.6% PCE). Photo-physical, photovoltaic, optoelectronic and structural-property relationship of newly designed molecules are extensively studied and compared with DFM (R). Density functional theory (DFT) and time-dependent-density functional theory (TD-DFT) have been employed to investigate the alignment of frontier molecular orbitals (FMOs), optical properties, density of states along with transition density matrix, binding and excitation energy, reorganizational energies and for open-circuit voltages of all newly designed molecules. Red-shifting in absorption spectrum offers high power conversion efficiencies, and our tailored molecules exhibit red-shifting in absorption spectrum (λmax = 391–429 nm) as compared to R (λmax = 396 nm). In addition, our all designed molecules expressed better hole transport ability (λh = 0.0056–0.0089 eV) as compared to R (λh = 0.0101 eV). Similarly, DM1–DM5 disclosed narrow HOMO–LUMO energy gap which causes maximum charge transfer from excited HOMO to excited LUMO. The theoretical study of DM3/PC61BM and DM3/Y6 complexes is also performed in order to understand the shifting of charge between donor and acceptor molecules. Results of all analysis clearly show the efficient designing of dopant-free (DM1–DM5) molecules and their possible potential to fabricate a high performance and stable organic solar cells devices. Therefore, the theoretical proposed molecules are recommended to experimentalists for future highly efficient organic solar cells.

Laser-based additively manufactured polymers: a review on processes and mechanical models

Abstract: Additive manufacturing (AM) is a broad definition of various techniques to produce layer-by-layer objects made of different materials. In this paper, a comprehensive review of laser-based technologies for polymers, including powder bed fusion processes [e.g. selective laser sintering (SLS)] and vat photopolymerisation [e.g. stereolithography (SLA)], is presented, where both the techniques employ a laser source to either melt or cure a raw polymeric material. The aim of the review is twofold: (1) to present the principal theoretical models adopted in the literature to simulate the complex physical phenomena involved in the transformation of the raw material into AM objects and (2) to discuss the influence of process parameters on the physical final properties of the printed objects and in turn on their mechanical performance. The models being presented simulate: the thermal problem along with the thermally activated bonding through sintering of the polymeric powder in SLS; the binding induced by the curing mechanisms of light-induced polymerisation of the liquid material in SLA. Key physical variables in AM objects, such as porosity and degree of cure in SLS and SLA respectively, are discussed in relation to the manufacturing process parameters, as well as to the mechanical resistance and deformability of the objects themselves.

Fabrication of visible-light-response face-contact ZnSnO3@g-C3N4 core─shell heterojunction for highly efficient photocatalytic degradation of tetracycline contaminant and mechanism insight

Abstract: The large-scale consumption and discharge of antibiotic tetracycline (TC) urge us to search for a highly efficient and eco-friendly technology to remove it. In this work, face-contact ZnSnO3@g-C3N4 core–shell heterojunction was successfully constructed via one-step calcination route. The experimental data indicate that the photocatalytic TC removal performance of ZnSnO3@g-C3N4 (1:3) reaches 90.8% within 120 min under the same condition compared with bulk g-C3N4 (32% degradation) and ZnSnO3 (9% degradation). The improved photocatalytic activity is ascribed to the formation of core–shell structure between ZnSnO3 and g-C3N4 which not only enlarges visible light response but also effectively separates electron–hole pairs. Meanwhile, this face-contact ZSO-CN photocatalyst displays much more contact interfaces than the point-contact ZSO-CN photocatalyst, and the contact interfaces could play the part of efficient channels for charge transfer. Finally, the photocatalytic reaction mechanism on ZnSnO3@g-C3N4 was also stated at length through active species capture and electron spin resonance (ESR) tests. And the possible intermediates products were discussed through the liquid chromatography–mass spectrometry (LC–MS) analysis.

Chemical and structural properties of reduced graphene oxide—dependence on the reducing agent

Abstract: Graphene oxide (GO) prepared from graphite powder using a modified Hummers method and reduced graphene oxide (rGO) obtained from GO using different reductants, i.e., sodium borohydride, hydrazine, formaldehyde, sodium hydroxide and L-ascorbic acid, were investigated using transmission electron microscopy, X-ray diffraction, Raman, infrared and electron spectroscopic methods. The GO and rGOs’ stacking nanostructure (flake) size (height x diameter), interlayer distance, average number of layers, distance between defects, elementary composition, content of oxygen groups, C sp3 and vacancy defects were determined. Different reductants applied to GO led to modification of carbon to oxygen ratio, carbon lattice (vacancy) and C sp3 defects with various in-depth distribution of C sp3 due to oxygen group reduction proceeding as competing processes at different rates between interstitial layers and in planes. The reduction using sodium borohydride and hydrazine in contrary to other reductants results in a larger content of vacancy defects than in GO. The thinnest flakes rGO obtained using sodium borohydride reductant exhibits the largest content of vacancy, C sp3 defects and hydroxyl group accompanied by the smallest content of epoxy, carboxyl and carbonyl groups due to a mechanism of carbonyl and carboxyl group reduction to hydroxyl groups. This rGO similar diameter to GO seems to result from a predominant reduction rate between the interstitial layers. The thicker flakes of a smaller diameter than in GO are obtained in rGOs prepared using remaining reductants and result from a higher rate of reduction of in plane defects.

Approaches to design a surface with tunable wettability: a review on surface properties

Abstract: Due to the wide application prospects in energy harvesting, conversion, and emission control technology, wettability has gathered momentum in recent years. Surface wettability alteration by nanomaterial fabrication and coating is of recent interest among researchers to attain desirable wetting surfaces. The wettability of liquid over a surface changes with surface properties such as roughness, surface energy, porosity, capillarity, and structure. Eventually, surface chemistry plays major role in changing surface energy which in turn leads to wettability alteration toward wetting and non-wetting extents. Herein, the dependence of surface properties in wettability alteration has been analyzed with the literature reports. Furthermore, surface pre- and post-treatments such as laser, ozone plasma, and UV irradiation contribute to change of surface energy inducing the liquid to encroach toward superhydrophilicity and superhydrophobicity. This review article analyzes the properties that induces wetting and non-wetting ability of liquids over surfaces. Theoretical models opted for wettability determination has been accounted to study the contribution of roughness, porosity, and surface energy. The article provides a clear idea of properties involved in wettability alteration with respect to wide range of applications in energy conversion, oil–water separation, self-cleaning, bio-adhesion, and bio-molecular immobilization.

Novel yolk–shell Fe3O4@void@SiO2@PPy nanochains toward microwave absorption application

Abstract: A growing number of core–shell structured microwave absorbents have been reported; nevertheless, there are few studies accessible about one-dimensional core–shell electromagnetic nanocomposites as microwave absorption materials. In this work, we have developed two kinds of novel electromagnetic nanocomposites, namely yolk–shell Fe3O4@void@SiO2 nanochains and Fe3O4@void@SiO2@PPy nanochains. Their components and morphologies have been characterized by X-ray diffraction (XRD), X-ray photoelectron spectra, scanning electron microscope and transmission electron microscope. The N2 adsorption–desorption isotherms have demonstrated their specific surface areas and porosity, and the magnetic properties have been recorded by the vibrating sample magnetometer. Investigation of microwave absorbing properties manifests that Fe3O4@void@SiO2@PPy nanochains have stronger absorption capability and broader effective absorption bandwidth than Fe3O4@void@SiO2 nanochains, which is caused by the introduction of polypyrrole shells, giving rise to the addition of conductive loss and the enhancement of dipole polarizations, interfacial polarizations, multiple reflection and absorption. Specifically, the minimum reflection loss value is − 54.2 dB (17.70 GHz) and the maximum effective absorption bandwidth can reach 5.90 GHz (11.49–17.39 GHz); thus, Fe3O4@void@SiO2@PPy nanochains will become promising microwave absorption candidates. This research once more demonstrates that necklace-like core–shell magnetic–dielectric complex benefit to enhancement of microwave absorption performance, and establishes a good foundation for exploiting the high-effective microwave absorbing materials.

Strategies for enhancing the room-temperature stretch formability of magnesium alloy sheets: a review

Abstract: Magnesium (Mg) alloys, as one of the lightest structural metallic materials, have attracted considerable attention in the automotive, aerospace, and microelectronic industries. However, wrought Mg alloys are easy to form a strong basal texture with the basal planes of hexagonal close-packed unit cells being parallel to the processing direction during hot processing. This extremely deteriorates the stretch formability of Mg alloy sheets at room temperature (RT) and limits their widespread industrial applications. To overcome this drawback, many studies have been devoted to controlling microstructures including grain sizes, texture characteristics and precipitates to achieve high-performance Mg alloy sheets via alloying and new processing techniques. In this review, we briefly summarize recent advances in enhancing the stretch formability of Mg alloy sheets at RT from two major aspects: (1) by the design of new alloy systems and (2) by the exploitation of advanced processing techniques. Both strategies hold great promise for developing high-performance and low-cost Mg alloy sheets with a superior combination of strength, ductility and stretch formability. Additionally, future research directions for the development of such high-performance Mg alloy sheets are suggested. We hope that this review can provide some insightful information for researchers who are committed to fabricating high-performance Mg alloys for lightweight structural applications in the transportation industry, so as to improve fuel efficiency and reduce climate-changing and health-compromising emissions.

Significantly enhanced dielectric permittivity and low loss in epoxy composites incorporating 3d W-WO3/BaTiO3 foams

Abstract: With the rapid development of miniaturization and high integration of electronic devices, increasing attention has been paid to the exploration of dielectric composites with further improved dielectric permittivities. Herein, a unique design of high dielectric permittivity composites consisting of three-dimensional porous W-WO3/BaTiO3 foams hosted in epoxy matrix is proposed. It is demonstrated that the introduction of W-WO3/BaTiO3 foams into the epoxy matrix results in substantially improved dielectric permittivities in comparison with the epoxy matrix. Meanwhile, low loss which is comparable to that of the epoxy matrix is well maintained. Interestingly, obviously enhanced dielectric permittivities and greatly depressed loss are concurrently achieved via increasing the oxidation temperature. In particular, the composite with 53.1 wt% W-WO3/BaTiO3 foam oxidized at 1300 °C exhibits a high dielectric permittivity of ~ 536 and a low loss tangent of ~ 0.05@10 kHz which are about 149 and 1.5 times those of the epoxy matrix, respectively. It is believed that the strong interfacial polarization and the numerous equivalent micro-capacitors result in the significantly improved dielectric permittivities. The finite element simulation results reveal that the formation of the WO3 shell on the surface of W can effectively weaken the leakage current density, yielding the sharply depressed loss. This work provides a new strategy to design polymer composites with simultaneous high dielectric permittivity and low loss, and the strategy could also be applicable to the exploration of other high-performance dielectric composites.

Synthesis and visible-light photocatalytic properties of BiOBr/CdS nanomaterials

Abstract: The visible-light-responsive composite photocatalyst is beneficial to improve the solar energy utilization efficiency through the coupling of narrow bandgap materials. In this work, CdS nanowires were prepared by hydrothermal method, and then BiOBr/CdS composite materials with different mass ratios were successfully prepared by a simple two-step sonography-precipitation method using CdS nanowires as a deposition template. The photocatalysts were characterized by XRD, SEM, XPS, TEM, and other methods. Rhodamine B (RhB) was used as a model pollutant to evaluate the photocatalytic activity of BiOBr/CdS catalysts with different mass ratios. The photocatalytic test results show that the composite photocatalyst containing 60% BiOBr has the highest photocatalytic activity, which indicates that it is related to the decrease in photogenerated charge recombination rate. Subsequently, the electrochemical and physical methods were used to illustrate the electron transfer mechanism and the main active center of the as-prepared samples. Free radical capture experiments reveal that holes are the main active species in the photocatalytic process of composite samples. BiOBr/CdS composite photocatalyst was prepared by a simple precipitation method using dispersed one-dimensional CdS nanowires as a template. BiOBr/CdS heterostructure combined adsorption and catalysis to degrade RhB molecules more efficiently. Free radical trapping experiments reveal that holes are the main active species in the photocatalytic process of composite samples.

Hydroxylated boron nitride materials: from structures to functional applications

Abstract: Functionalization of boron nitride (BN) materials with hydroxyls has attracted great attention to accomplish better performances at micro- and nanoscale. BN surface hydroxylation, in fact, induces a change in properties and allows expanding the fields of application. In this review, we have summarized the state-of-the-art in developing hydroxylated bulk and nanoscale BN materials. The different synthesis routes to develop hydroxyl BN have been critically discussed. What emerges is the great variety of possible strategies to achieve BN hydroxylation, which, in turn, represents one of the most suitable methods to improve the solubility of BN nanomaterials. The improved stability of BN solutions creates conditions for producing high-quality nanocomposites. Furthermore, new interesting optical and electronic properties may arise from the functionalization by OH groups as displayed by a wide range of both theoretical and experimental studies. After the presentation of the most significant systems and methodologies, we question of future perspective and important trends of the next generation BN materials as well as the possible areas of advanced research. Hydroxyl functionalization of boron nitride materials is a key method to control and enhance the properties and design new functional applications.

Perspectives on the spark plasma sintering process

Abstract: This Viewpoint paper is written in conjunction with the Journal’s celebration of 1000 at 1000, a milestone of reaching the publication of the 1000th issue and highlighting those papers that have been cited 1000 or more times. One of the authors’ papers is in this category, as indicated in a previous Editorial by one of us. In this Viewpoint, we discuss the phenomenal success of the spark plasma sintering process, providing a historical account, presenting an updated overview of the accomplishments attributed to the process, and highlighting selected examples of these.

Anticorrosive and UV-blocking waterborne polyurethane composite coating containing novel two-dimensional Ti3C2 MXene nanosheets

Abstract: In this work, Ti3C2 MXene, a novel two-dimensional nanosheet, was introduced to waterborne polyurethane (WPU) coatings to prepare a composite coating. First, MAX phase materials were in situ etched by HF acid and further intercalated by water molecules to obtain exfoliated single-layer MXene nanosheet. And then, composite coatings were prepared via solution-blending low addition (0–0.4 wt%) of MXene, self-prepared waterborne polyacrylate emulsion (PAE) and isocyanate hardener, applying on Q235 mild steel. Results of AFM, XRD SEM and SEM–EDS confirm that single-layer MXene nanosheets with large lateral-to-thickness ratio are successfully prepared and achieved homogenous distribution within WPU matrix. With 0.4 wt% MXene incorporated, the WPU/Ti3C2 MXene composite coatings reach a lowest corrosion current of 2.143 × 10–6 A/cm2, a decrease of one order of magnitude compared with blank WPU (1.599 × 10–5 A/cm2) and own an excellent UV-blocking property (almost block the whole UV light).

Polymeric micelles for pulmonary drug delivery: a comprehensive review

Abstract: Respiratory diseases have remained one of the most common diseases worldwide, in which oral and intravenous administration are the most common treatment routes. However, these administrative routes face various difficulties in reaching local pulmonary targets, possessing low efficacy, and have high risk of systemic side effects. To solve these issues, polymeric micelles represent an effective approach. These nano-ranged delivery systems can encapsulate and protect poorly water-soluble drugs, enhance drug targeting to the lung, reduce side effects, and improve drug efficacy via inhalation route. In this review, the importance of rational design was highlighted by summarizing the recent progress on the development of polymeric micelles in pulmonary delivery. Emphasis is also placed on the different types and preparations, as well as ideal properties and advantages of polymeric micelles for pulmonary route.

Biomass applied in supercapacitor energy storage devices

Abstract: The ever-increasing energy demand and fossil energy consumption accompanied by the worsening environmental pollution urge the invention and development of new, environmentally friendly and renewable high-performance energy devices. Among them, the supercapacitor has received massive attention, and the various electrode materials and polymer electrolytes have been exploited. The carbon-based electrodes and electrolytes derived from biomass are highly trusted as idea candidates for supercapacitors due to their attractive structure, abundance, low cost, renewability, and environmentally friendliness. This review will highlight the available characteristics of materials, synthetic strategies, and improvement approach of biomass-derived electrodes and electrolytes for application in supercapacitors. Future relative research trends also will be briefly discussed.

A review on mechanisms and recent developments in p-n heterojunctions of 2D materials for gas sensing applications

Abstract: 2D materials and their heterojunctions have been explored for gas sensing applications due to their tremendous surface-to-volume ratio, active edges with atomic thickness, and tunable electrical properties. Heterostructures of 2D materials exhibit absolutely novel physics and versatility with accelerated device performance by integrating the atomic scale properties of individual materials. Traditional gas sensors use homogeneous materials as the sensing interface in which the surface adsorbed oxygen ion species play an important role in its performance. But the performance of the sensors suffers greatly due to their selectivity and high working temperature leading to poor stability and short-term uses; the van der Waals 2D p-n heterojunction-based gas sensors hold several advantages since both the materials and the depletion layer formed at the junction can actively tune the sensing performance. By choosing 2D materials with different band structures, charge polarity, carrier concentration, and work function, band alignment at the interface can be precisely engineered to achieve the selective gas sensing performance with low operating temperature. Herein, we have reviewed the working principles, recent developments, and future perspectives of p-n heterojunctions of 2D materials for gas sensing applications.

Electrospun TiO2 nanofibers for water and wastewater treatment: a review

Abstract: Water and wastewater treatment is a global challenge that requires innovative solutions. Electrospinning is a versatile and simple technique that allows the generation of ultrathin fibers of numerous compositions. Titanium dioxide is a photocatalyst with applications in several technological fields. Thus, the use of electrospinning to produce TiO2 nanofibers is an approach that may bring new insights for the treatment of contaminated water. In this review, it is aimed to provide a comprehensive overview of electrospinning technique and electrospun TiO2 nanofibers production, as well as their application in water and wastewater treatment. First, it is provided a brief introduction to the development of electrospinning-related processes, followed by a discussion of its principle, apparatus, methods and materials commonly used. In the sequence, it is presented the current and potential methods for electrospun TiO2 nanofibers and some aspects related to experimental conditions, catalysts immobilization, metal and nonmetal doping, characterization techniques and applications. The effects of processing parameters on properties as catalyst band gap, adsorption capacity and catalytic efficiency are also discussed. Afterward, the application of electrospun TiO2 nanofibers for pollutants removal from water through photodegradation is highlighted by focusing on some representative examples. Finally, the perspectives are presented regarding challenges, opportunities, and new directions for the application of electrospun TiO2 fibers.

Fabrication of screen-printed electrodes: opportunities and challenges

Abstract: In recent times, wearable electronics, real-time sensing devices and point-of-care device applications have seen a surge in demand. This demand inherently calls for a more economic and reliable method of mass production. One such robust technique is screen printing that offers advantages in terms of being versatile, economical and easy to use. This technique has been proclaimed to be the best amongst the other additive manufacturing techniques by many research groups. This can be solely attributed to its simple equipment design, requiring a paste for printing purpose, a meshwork for housing the design and a squeegee to carry out printing through an up-and-down motion. This subsequently calls for optimising the parameters such as ink rheology, pore size of the mesh, proper choice of mesh design and motion of the squeeze in order to fabricate electrodes for desired purpose. Due to this technique’s immense potential to open up broad inroads in the domain of flexible electronics, whose concept has radically redefined the perception towards the field of electronics, a review article encompassing an elaborate description on the science and other quintessential parameters involved in this mass printing technique would prove to be extremely useful. In this purview, the review article is compartmentalised into sections encompassing discussion on the manufacturing of different kinds of inks for screen printing applications, substrates used, electrode design and pre-treatment procedures.

A review on recent advances in carbon-based dielectric system for microwave absorption

Abstract: Microwave absorbing materials (MAMs), which have been highly developed in the past two decades, are being regarded as a kind of functional materials to combat electromagnetic (EM) pollution, because they can provide sustainable energy conversion rather than simple reflection of incident EM waves. Although traditional magnetic materials can dissipate EM energy effectively, they always suffer from some intrinsic drawbacks, such as high density, easy corrosion, and skin effect, which make them unpopular in many practical applications. Therefore, the rational design of pure dielectric system without any magnetic components is becoming a new frontier topic for MAMs. Among various candidates, carbon-based dielectric system almost dominates the development of non-magnetic MAMs. This review presents a comprehensive introduction on the recent advances of carbon-based dielectric system composed of carbon materials and other dielectric components, including metal oxides/carbon, metal sulfides/carbon, conductive polymers/carbon, carbides/carbon, carbon/carbon, and various ternary carbon-based dielectric composites. Thanks to the synergistic effects between different components and the elaborate microstructure design, these carbon-based dielectric composites can produce superior microwave absorption performance to traditional magnetic materials. Moreover, the challenges and prospects are also proposed to indicate some new insights for the further research of carbon-based dielectric system.

Recent advances in efficient emissive materials-based OLED applications: a review

Abstract: In the present time, organic light-emitting diode (OLED) is a very promising participant over light-emitting diodes (LEDs), liquid crystal display (LCD), and also another solid-state lighting device due to its low cost, ease of fabrication, brightness, speed, wide viewing angle, low power consumption, and high contrast ratio. The most prominent layer of OLED is the emissive layer because the device emission color, contrast ratio, and external efficiency depend of this layer’s materials. This review ruminates on the basics of OLEDs, different light emission mechanisms, OLEDs achievements, and different types of challenges revealed in the field of OLEDs. This review’s primary intention is to broadly discuss the synthesizing methods, physicochemical properties of conducting polymer polymethyl methacrylate (PMMA), and its polymeric nanocomposite-based emissive layer materials for OLEDs application. It also discusses the most extensively used OLED fabrication techniques. PMMA-based polymeric nanocomposites revealed good transparency properties, good thermal stability, and high electrical conductivity, making suitable materials as an emissive layer for OLED applications.

Research progress of starch-based biodegradable materials: a review

Abstract: With the enhancement of global environmental protection awareness, new eco-friendly packaging materials have gained more and more attention since the new century Starch is one of the most potential natural biodegradable materials due to its abundant source, low price, and completely degradable characteristics Starch-based materials with excellent biodegradability can be widely used by improving their properties This review starts with the structure of starch and summarizes its phase transition during processing related to the packaging materials Then, we expound on the development stage of starch-based biodegradable materials and starch modification This part focuses on the research of starch-based composites formed by starch derivatives, including nano-starch Besides, extrusion molding and other modern molding methods are described in detail Through the systematic elaboration of the above contents, the connection among structure, phase transition, and processing can be found, which can better broaden the application of starch-based biodegradable materials Finally, various applications of starch-based materials and prospects for its future research are discussed It is hoped to provide the basic theory and reference for the research of starch-based biodegradable materials

Photocatalytic MOF fibrous membranes for cyclic adsorption and degradation of dyes

Abstract: Metal–organic frameworks (MOF) have attracted great attention in the field of wastewater treatment. When MOF nanoparticles are used for adsorption applications, the nanoparticles normally have to be separated from the dispersed suspension by filtration or centrifugation for regeneration or recycling. In order to avoid this costly and time consuming process, MOF (NH2-MIL-125) nanofibrous hybrid membranes with photocatalytic properties were successfully fabricated in this study. The MOF membranes were characterized by using XRD, SEM, FTIR, TGA, BET, and UV–Vis. The adsorption (including capacity, mechanism, dynamic, and isotherm) of dyes by the membranes is studied in great detail. The membranes exhibit great adsorption capacity to methylene blue and sodium fluorescein, and the adsorption is dominated by steric hindrance of dye molecule, not the π–π interactions and the zeta potential. Most importantly, the MOF membranes could be easily separated from the dyes solution and regenerated via a visible light catalytic degradation process for recycling, and the photocatalytic mechanism is discussed.

Synthesis and properties of multifunctional microencapsulated phase change material for intelligent textiles

Abstract: Microencapsulated phase change materials (MEPCMs) have been widely used in many fields as thermal energy storage materials. This study reported a novel MEPCM with the functions of thermal energy storage, photothermal conversion, ultraviolet (UV) shielding, and superhydrophobicity, which was particularly suitable for intelligent textiles. The microcapsules based on an n-eicosane core and a CuO-doped polyurea shell with hierarchical structure were fabricated through a one-step interfacial polymerization. The morphology of the capsules and the hierarchical shell structure were identified through scanning and transmission electron microscopy. Thermal analysis indicated that the microcapsules had a high latent heat of 162.3 J/g and demonstrated a high thermal reliability. These microcapsules achieved a good photothermal conversion capability and can reduce UV radiation by approximately 30%. The water contact angle of the MEPCM was over 148° and showed a good superhydrophobic property. Cotton fabric coated with the prepared MEPCM was investigated. Results showed that it achieved a high phase change enthalpy of 36.8 J/g, an effective thermoregulation capability, and a large contact angle of 141.6°.