Search Results (833)

The design of functional paper coatings with excellent barrier properties, including water repellence, anti-microbial properties, and recyclability, is highly demanded in view of the sustainable use of paper as flexible substrates for various industrial applications such as packaging. The enhanced coating functionalities should be incorporated through a combination of selected bio-based materials and the creation of appropriate surface textures enhancing coating performance. The bio-inspired approaches through the replication of hierarchical surface structures with multi-scale dimensional features in combination with selection of appropriate bio-based functional groups offer new concepts for coating design. In this short perspective paper, concepts in the field are illustrated with a focus on the combination of hydrophobic and anti-microbial properties. Based on long-term work with the available toolbox of bio-based building blocks and nanoscale architectures, they can be processed into applicable aqueous suspensions for sprayable paper coatings. The macroscopic roughness profile of paper substrates can be complemented through the decoration of nanoscale bio-based polymer particles of polyhydroxybutyrate or vegetable oil capsules with dimensions in the range of 20–50 nm or 100–500 nm depending on the synthesis conditions. The anti-microbial properties can be provided by the surface modification of nanocellulose with biologically active molecules sourced from nature. Besides the more fundamental issues in design and synthesis, the industrial application of the bio-inspired coatings through spray-coating becomes relevant. Full article

The recycling of lithium iron phosphate (LiFePO₄) batteries from electric and hybrid vehicles was investigated, by applying mechanical pretreatment and hydrometallurgical methods. The aim was to extract lithium (Li) into the aqueous solution and precipitate iron (Fe) in the form of ferric iron phosphate (FePO₄). Samples of lithium iron phosphate (LFP) batteries from small electric vehicles provided by the company BEEV were used in this study. Initially, the black mass was isolated using mechanical crushing, screening, and sink–float separation methods, avoiding the need for costly chemical or thermal treatments. The cathodic material was then leached with sulfuric acid (H₂SO₄) and hydrogen peroxide (H₂O₂) to oxidize ferrous to ferric iron, resulting in the precipitation of iron phosphate, which was collected in the solid residue from the leaching process. Leaching tests were conducted by varying the concentrations of sulfuric acid and hydrogen peroxide, as well as the leaching time. It has been indicated that by using a sulfuric acid concentration equal to the stoichiometric requirement, and hydrogen peroxide at four times the stoichiometric amount, Li extraction of greater than 98% was achieved within the first few minutes of leaching, while iron extraction remained below 0.5%. Full article

Geothermal energy is typically produced from underground reservoirs using water as the working fluid to transfer heat energy to surface and eventually to the delivery point. CO₂ has been proposed as an alternative working fluid due to its improved mobility, density and its supercritical phase state, leading thus to so-called CPG (CO₂ Plume Geothermal) systems. As a positive side effect, the injected CO₂ mass circulation in the reservoir can be considered a CO₂ storage mechanism, which, depending on the size of the porous medium, may account for few millions of CO₂ tons. Moreover, the thermosiphon effect, owned to the significant change of fluid density between the injection (cold) and the production wells (hot) as well as to its change along the wells, significantly reduces the need for pumping, hence the operating costs. In this work, we setup a mathematical model that fully describes flow in the production/injection wells doublet as well as in the geothermal reservoir. Subsequently, the model is used to evaluate the sensitivity of the beneficial effects of circulating CO₂ rather than water. Parameters such as reservoir properties, injection temperature and thermal effects, are tweaked to demonstrate the sensitivity of each one to the system performance. The results can be utilized as a guideline to the design of such systems and to the emphasis needed to be paid by the engineers. Full article

A computational fluid dynamics-based study of a corrugated wing section inspired by the dragonfly wing was performed for a low Reynolds number (10’000), focusing on gliding flight. The aerodynamic characteristics are compared to those of a typical technical aerofoil (NACA 0009). The objective of this study is to develop a simulation tool for the design and development of corrugated wings for aerospace applications and to gain a better understanding of the flow over corrugated wing sections. The simulation results were verified using a convergence study and validated by an angle of attack study and comparison with experimental results. The results demonstrated the simulations capability of predicting key flow features but there were some discrepancies from the experimental observations, mainly the prediction of the critical angle of attack. Overall, the simulation results demonstrated a comparable, if not better, aerodynamic performance compared to the technical aerofoil. Full article

In line with Sustainable Development Goal 9 (sustainable industrialisation and innovation), environmentally responsible engineering designs in modern robotics should consider factors such as renewability, sustainability, and biodegradability. The robotics sector is growing at an exponential rate and, as a consequence, its contribution to e-waste is a growing concern. Our work contributes to the technological development of caninoid necro-robots, robots that are built from the skeletons of deceased dogs. The already formed skeletal structures of deceased dogs (and other animals) are ideal natural material replacements for synthetic robotic architectures such as plastics, metals, and composites. Since dog skeletons are disarticulated, simple but effective methods need to be developed to rearticulate their bodies. The canine head is essentially a large end effector, but its mandible is held together by a fibrocartilaginous joint (symphysis) that degrades at a higher rate than the bone itself. The degradation of the symphysis would ordinarily negate the utility of a canine head as a necro-robotic end effector; however, in this research, we consider simple methods of mandible reinforcement to circumvent this problem. Our research uses 3D scans of a real canine head, which is modelled using the finite element method to ascertain optimal geometrical reinforcements for the mandible. The full head structures and their reinforcements are printed and adhesively connected to determine the most effective reinforcing strategy of the mandible. Here, we elucidate geometrically selected reinforcement designs that are evidenced through mechanical testing, to successfully increase the stiffness of a disarticulated mandible. Full article

While commercially available lightweight “stab-proof” apparel exists, it offers little resistance to true stabbing as it is primarily designed to withstand slash attacks. Yet, crimes involving the use of a knife or sharp instrument have consistently been rising in the UK over several decades. For the most part, the various proposed solutions to stab-proofing are based on speciality textiles and while these have shown success in slash-proofing, their utility for stab-proofing is still somewhat of a misnomer. Nature showcases a plethora of puncture-resisting materials and structures. At the macro-scale, these include carapaces, egg cases, toughened skin, and more. One of the most effective protective mechanisms known comes through surface scaling, present on animals such as reptiles and fish. Scaled protective armours present in extant fish species include overlapping elasmoid scales, interlocking ganoid scales, placoid scales, tessellating carapace scutes, and interlocking plates. Here, we research overlapping and interlocking scaled structures to ascertain the stab penetration resistance of biomimetic scaled structures against continuum material to obtain the force–time relationship of the impact event as well as ascertaining the penetration depth. We use additive manufacturing methods to manufacture biomimetic armour made of nylon, a common protective artificial material used in slash-proofing textiles. Stab testing to the closely replicated HOSDB body armour standard 2017, we find that biomimetic scales made of nylon offer greater protection against direct stabbing than continuum nylon material sheets. This can be attributed to (a) the heightened flexibility in an interlocked fish scale structure that does not exist in a continuum sheet of the same material; (b) the effect of overlapping of the fish scales, resulting in a greater penetration depth requirement before the structure undergoes perforation; and (c) segmentation into smaller armour plates (of the same thickness) rather than continuum sheets provides a lower span-to-depth ratio, therefore leading to a smaller deflection of the plate upon impact and a greater deceleration and, hence, a greater impact force. Full article

This study investigates the dynamic response and damage characteristics of cornstalk-inspired lightweight structures. Specimens were fabricated via 3D printing using Acrylonitrile Butadiene Styrene (ABS) as the chosen thermoplastic due to its toughness and resistance to impact. Low-velocity impact tests were conducted at varying incident energies, with subsequent damage analyses performed using X-ray CT scans. The effect of geometrical variations in the constituents on energy-absorbing capability was also investigated. The results demonstrate a ~14% increase in specific energy absorption (SEA) compared to quasi-static measurements. This research is built upon the authors’ previous work on the quasi-static response of the cornstalk-inspired design. Full article

This paper investigates the impact performance of a hybrid scale–tissue structure inspired by elasmoid fish scales. Acrylonitrile butadiene styrene (ABS) acted as the hard scales, whereas thermoplastic polyurethane (TPU) mimicked the soft tissue. Low-velocity impact scenarios were investigated using a commercially available software, ANSYS LS-Dyna. The effect of indenter shape (conical, hemispherical, and flat head) was studied at three impact energy levels (50 J, 75 J, and 100 J). The specific energy absorbed for the conical indenter was the highest. The peak force for the conical, hemispherical, and flat-head indenters at an impact energy of 100 J was 6.0 kN, 5.4 kN, and 4.5 kN, respectively. The primary failure modes were shear failure and tensile breaking of the scales. The present study highlights the effect of indenter shape on the impact behaviour of a fish scale-inspired structure. Full article

Electronic skin (e-skin) is an innovative technology characterized by its flexibility, stretchability, and self-healing properties, designed to biomimic the functionalities of human or animal skin. This technology is well-suited for applications in robotics, prosthetics, and health monitoring since it can sense a wide range of tactile signals, such as humidity, pressure, temperature, and stress. Developing e-skin for wearable devices faces several challenges. One major challenge is the need for soft and stretchable electronic materials, as conventional materials are brittle. Furthermore, the development of skin-like hydrogel devices for wearable electronics faces challenges such as limited functionality, low ambient stability, poor surface adhesion, and relatively high power consumption. Innovation in this area has the potential to pay off. Organizations that invest in and develop innovative e-skin technologies based on biomimetic hydrogels can secure intellectual property rights through patents. This study is dedicated to reviewing the state of the art by presenting what has been patented concerning biomimetic-hydrogel-based e-skin. At the end, a section presents relevant patents to demonstrate the innovation and formulation of such hydrogels as biomimetic materials for e-skin applications. A market overview of e-skins is also presented. This contextualizes the significance of research in biomimetic-hydrogel-based e-skins within the broader commercial landscape. Full article

The demand for green hydrogen (H₂) and related technologies is expected to increase in the coming years, driven by climate changes and energy security of supply issues, amid the European and global energy crises. The European Green Deal and REpowerEU Plan have identified H₂ as a key pillar for reaching climate neutrality by 2050 and for the intensification of hydrogen delivery targets, bringing the large-scale adoption of hydrogen production and applications, and stressing the need for a skilled workforce in emergent H₂ markets. To that end, the H2Excellence project will establish a Platform of Vocational Excellence in the field of fuel cells and green hydrogen technologies, with an educational and training scheme to tackle identified skill gaps and to implement life-long learning opportunities. This project aims to become a European benchmark in training and knowledge transfer, incorporating the entire hydrogen value chain. The work is supported by the Knowledge Triangle Model, integrating education, research, and innovation efforts to build a dynamic ecosystem in the green hydrogen sector. In this work, activities conducted so far by LNEG as a project partner and expected impacts are highlighted. Those activities are based on a stakeholder needs assessment conducted by project partners and on the knowledge and experience accumulated in research activities developed in the Materials for Energy research area. Full article

Commercial NdFeB magnets are often coated with different thin layers to increase corrosion resistance. Fast and reliable test methods are being developed, especially for the automotive industry. Since corrosion test methods can inadequately describe the operating conditions of the e-motor, magnets are usually only tested in the demagnetized state. Corrosion tests close to sintered NdFeB magnet e-motor application conditions have been applied. Corrosion tests for sintered NdFeB magnets are usually demagnetized and performed in aqueous solutions or vapor environments instead of organic substances such as oil. In this study, sintered NdFeB magnets were immersed in a pre-saturated water-based salt solution and placed in gearbox oil. The test conditions have been specially selected to test the suitability of the magnets for e-motor applications (e.g., in hybrid vehicles). The microstructural effect of magnetic properties and corrosion resistance on the NdFeB magnets have been systematically studied. The aim of the study is the realization of the coating on the sintered NdFeB magnet, which provides high corrosion resistance and significantly reduces the thickness of the coating and ensures maximum efficiency in the use of magnets. The results of these studies are thought to play an important role in determining and optimizing the usage strategy of coated NdFeB magnets. Full article

Urban noise is considered a growing problem in major cities around the world. This paper explores the development of a nanomembrane-based material for noise attenuation. The experimental results show that a combination of acoustic foam and nanomembranes can act as a Helmholtz resonator. The average sound absorption coefficient was around 90%, with peak frequencies varying from 2400 Hz to 4000 Hz. The average thickness of the nanomembranes was approximately 5.0 µm, while the acoustic foam was 13 mm thick. The mean noise reduction, around 10 dB, depends on the morphology of the nanomembranes, their thickness, and their pore size. Full article

Carbon nanofiber mats can be applied for diverse energy applications. Usually, they should be freestanding and show sufficient structural stability. Poly(acrylonitrile) (PAN) is often used as the base material for electrospinning due to its high carbon yield during carbonization. Carbonized PAN nanofiber mats, however, may be brittle and break under mechanical load. Here, we report a study of the impact of ZnO and tetraethyl orthosilicate (TEOS) as nanoparticle additives on the stabilization, carbonization and resulting morphology of the respective nanofiber mats. By comparing morphological, mechanical, and chemical properties of these mats, it is shown that carefully tailoring nanoparticular additives and spinning parameters enables the production of flexible freestanding carbon nanofiber mats for possible applications as electrodes in energy storage devices. Full article

This study investigates the synthesis and characterization of SiO₂-Gd₂O₃-Eu₂O₃ nanomaterials. The sol–gel method was employed using tetraethoxysilane (TEOS), gadolinium nitrate, and europium nitrate as precursors. The influence of rare earth oxide concentration on the hydrolysis kinetics and activation energy was evaluated. Additionally, the acid-base properties of the synthesized materials were examined using the Hammett indicator adsorption method. The results revealed that the addition of Gd₂O₃ and Eu₂O₃ oxides to the system accelerated the hydrolysis process and reduced the activation energy. The formation of a layered structure, consisting of a central Si(OH)₄ nucleus, a Si-O-Si polymer layer, and hydrated metal ion layers, was observed. The acid-base properties of the synthesized nanomaterials were influenced by the drying method and the composition of the system. The findings provide valuable insights into the synthesis and properties of SiO₂-Gd₂O₃-Eu₂O₃ nanomaterials, which have potential applications in various fields such as optoelectronics and catalysis. Full article