Original Capacity Research Articles

High‐Performance Supercapacitor Electrodes Based on Porosity‐Controllable Carbon Paper by Centrifugal Spinning

Carbon paper is widely utilized in supercapacitors primarily for its notable attributes, including high specific surface area, commendable electrical conductivity, and excellent chemical stability. Then investigate the effect of carbon paper with different porosities as supercapacitor substrates on the electrochemical performance of electrodes. Meanwhile, tungsten oxide is grown on the surface of carbon paper using the hydrothermal method to test the electrochemical performance of the composite electrode. The prepared carbon paper and oxygen‐deficient tungsten oxide (WOx) composite electrode (CP@WOx) exhibit an area‐specific capacitance of 915.8 mF/cm² at a current density of 5 mA/cm². In addition, the electrode exhibits good cycling stability. After 20,000 cycles, the capacitance remains 104.1% of the original capacity at 50 mA/cm² current density. Solid‐state symmetric supercapacitors assembled using CP@WOx electrode exhibit excellent performance in terms of surface energy density of 6.25 µWh/cm2(at a power density of 0.6 mW/cm2) and maintain 100.4% of their original capacity after 7000 charge/discharge cycles. Relying on the higher productivity advantage of centrifugal spinning technology over electrostatic spinning technology and other preparation processes, this study develops a new way of thinking for the large‐scale production of composite electrode materials, which has more considerable potential for large‐scale development.

Analysis and optimization of a high-speed generator’s cooling structure based on Taguchi method

To increase the power density of the original generator, it is desired to boost the generator’s power to 1.2 times its original capacity. However, the cooling structure of the original generator cannot meet the heat dissipation requirements of the upgraded power level. It necessitates a redesign of the cooling structure. For the stator, water pipes through the stator core yoke are added; for the rotor, a novel rotor cooling structure is designed. The structure includes the groove bottom vent beneath the rotor excitation winding and the radial auxiliary grooves on the sides. The airflow passes through the groove bottom vent and then follows the radial auxiliary grooves until it reaches the air gap. It can efficiently remove the heat from the rotor excitation winding. The results of the new scheme are discussed. When comparing the new scheme with the original one, the highest temperature of the stator winding decreases by 20.6k, while the one of the rotor excitation winding does by 23.7K. To further improve the cooling structure, the Taguchi method is employed. The optimization variables include the area of the stator back vent, the number of radial auxiliary grooves, and the height of the groove bottom vent. The optimization objectives are the highest temperature of the stator winding, the highest temperature of the rotor excitation winding, the air friction loss, and the inlet-outlet static pressure difference. By analyzing the variance and range of the results, the improved scheme is obtained. Comparing the improved scheme with the new one, the temperature distribution difference between them is negligible. The improved scheme reduces the air frictional loss by 10.7%, but increases the inlet-outlet static pressure difference by 8.0%.

Electrospinning of Sodium Alginate/Copper Oxide Nanofibrous Composite Membrane and Its Application of Cationic Dye Adsorption

AbstractDye wastewater is becoming one of the most significant sources of water pollution, and its impact on human survival is immeasurable. In this study, we successfully synthesized a nanofiber membrane with environmentally friendly and efficient properties using electrospinning of a mixture of sodium alginate (SA) and copper oxide (CuO) nanoparticles, aimed at effective dye removal. The adsorption performance of the SA/CuO nanofiber membrane was evaluated using the cationic dye methylene blue (MB). The maximum adsorption capacity of the nanofiber membrane was increased significantly with the addition of CuO nanoparticles, reaching a maximum value of 1633.4 mg g−1, almost twice as much as that of pure SA membrane. The adsorption kinetics follows the pseudo‐second‐order model, where chemisorption acts as the rate‐limiting step. The adsorption isotherm data indicate that the adsorption is monolayer. The nanofibrous membranes showed better dye removal under an alkaline environment. After four cycles of adsorption/desorption, the MB removal efficiency remained at 70.1% of the original adsorption capacity. The addition of CuO nanoparticles facilitated the adsorption of MB dyes, while the form of the nanofibrous membrane is easily recoverable and reusable. Therefore, the as‐prepared SA/CuO nanofibrous composite membrane is a potentially favorable adsorbent material for wastewater treatment applications.

Cement-Free Geopolymer Paste: An Eco-Friendly Adhesive Agent for Concrete and Masonry Repairs

This study aimed to investigate the feasibility of using geopolymer paste (GP) as an adhesive agent for (i) anchoring steel bars in concrete substrates, (ii) repairing concrete, and (iii) repairing limestone and granite masonry blocks commonly found in historic buildings. In this investigation, seven cement-free GP mixes were developed with different combinations of binder materials (slag, silica fume, and metakaolin). The mechanical properties, adhesive performance, and production cost of the developed GP mixes were compared to those of a commercially epoxy adhesive mortar (EAM). The results obtained from this study indicated that the use of GPs enhanced the bonding between steel bars and concrete substrates, achieving bonding strengths that were 19.7% to 49.2% higher than those of control specimens with steel bars directly installed during casting. In concrete repairs, the GPs were able to restore about 60.6% to 87.9% of the original capacity of the control beams. Furthermore, GPs exhibited a promising performance in repairing limestone and granite masonry blocks, highlighting their potential suitability for masonry structures. The best adhesive performance was observed when a ternary binder material system consisting of 70% slag, 20% metakaolin and 10% silica fume was used. This combination, compared to the investigated EAM, showed comparable adhesive properties at a significantly low cost, indicating the viability of GPs as a cost-effective, eco-friendly adhesive agent.

Influence of edge scour on lateral responses of monopiles with precast microbial reinforcement

Microbiologically Induced Calcite Precipitation (MICP) technology offers a promising method for stiffness reinforcement of offshore wind turbines (OWTs). However, edge scour around microbial reinforcement raises concerns about potential stiffness degradation. This study examines the effects of edge scour on the lateral responses of rigid piles reinforced with precast microbial reinforcement using a low-pH one-phase grouting method. Results from static tests, validated by numerical simulations, demonstrated that MICP technology bonded loose sand grains with the pile, forming a bio-reinforced pile with a larger diameter in the shallow soil layer, which significantly enhanced the original pile's bearing capacity and stiffness. However, edge scour reduced the embedment depth of the bio-reinforced pile, leading to a decrease in its bearing capacity and stiffness. Geometrically, protection width was found to have a relatively greater influence on stiffness and capacity compared to protection thickness. Additionally, symmetric cyclic loading tests were conducted to evaluate the effects of edge scour on backbone curves, secant stiffness, and damping ratio. Although MICP-based reinforcement notably enhanced both the secant stiffness and damping ratio of the piles, its effectiveness was completely lost once the scour depth reached the reinforcement thickness of the bio-reinforced soil block.

One-pot hydrothermal synthesis of 3D garland BiOI, spherical ZnO, and CNFs onto Ni foam: Supercapacitor performance with enhanced electrochemical properties

This study reported one-pot hydrothermal synthesis of 3D garland BiOI, spherical ZnO, and carbon nanofibers (CNFs) onto Ni foam substrate with improved supercapacitor performance and enhanced electrochemical properties. The synthesized nanocomposites exhibited high specific capacitance (SC) of 1073 g−1 at a current density of 1 A/g and excellent cycling stability with 88.6% retention of original capacity after 5000 cycles in 2M KOH aqueous solution. The findings highlight the potential of 3D materials for use as electrode materials in advanced supercapacitor applications due to their high energy storage capabilities.

Control strategy calibration of a direct-expansion solar-assisted heat pump

As known, the performance of a direct-expansion solar-assisted heat pump (DX-SAHP) is affected by environmental and operational parameters significantly, and the variable capacity system has distinct advantages. The calibration of the control strategy will be very useful for the thermal performance improvement of DX-SAHP systems. Based on the test rig which is used to supply domestic hot water, the original variable capacity control strategy has been calibrated with the quasi-dynamic mathematical model under different conditions. The calibration results show that the optimum range of the degree of superheat is 7–12 °C. For winter and spring/autumn conditions, the optimum range of operation duration are 360–420 min and 300–360 min, and the corresponding optimum range of average compressor speed are 3750–4500 r·min−1 and 2750–3750 r·min−1, respectively. Experiments prove that the actual operation parameters can be maintained at the optimum range well and the average coefficient of performance (COPm) during the whole heating process has been improved further. For winter and spring/autumn, the average operation duration and compressor speed are 395 min and 3970 r·min−1, 345 min and 3066 r·min−1, respectively. Moreover, the values of COPm could reach 3.44 and 4.67, respectively. Even at solar radiation intensity of 577.6 W·m−2 with ambient temperature of −9.1 °C, the COPm could reach 2.38.

Study on increasing load capacity of wooden arch bridge by CFRP strengthening: experimental and numerical Verification

The wooden arch corridor bridge is a typical representative of Chinese wooden bridges, holding significant historical research value. Currently, these bridges face issues of severe component deformation and insufficient load-bearing capacity. To address these problems, this study employs CFRP reinforcement on the components of wooden arch corridor bridges to reduce deformation and enhance load-bearing capacity. Experimental research on CFRP reinforcement has yielded the elastic modulus of the bonding interface. Given the lack of an accurate numerical model for wooden arch corridor bridges, this study establishes a precise numerical model by setting parameters based on load test data from wooden arch corridor bridges. The elastic modulus obtained from the experiments is input into the numerical model for analysis. The results indicate that CFRP exhibits excellent reinforcement performance, with the load-bearing capacity of the reinforced damaged components still reaching 75%–85% of their original capacity, while the load-bearing capacity of the reinforced undamaged components increases to 130%–140% of their original capacity. The failure modes of the CFRP-reinforced wooden components suggest that allowing for some gaps in the bonding of CFRP can enhance overall ductility. The application of CFRP to wooden arch corridor bridges also demonstrates favorable reinforcement effects, increasing the load-bearing capacity of the arch surface by approximately 20%, thereby providing a theoretical basis for the reinforcement of wooden arch bridge frameworks.

Ambient-temperature aqueous electrochemical route for direct Re-functionalization of spent LFP cathodes of lithium-ion batteries

Relithiation is a critical step in the direct recycling process, which is the most promising method for spent LiFeIIPO4 (LFP) batteries recycling. It involves the reduction of FeIIIPO4 (FP) in a Li-ion-rich environment and is generally performed by high-temperature sintering or hydrothermal methods. This study proposes an ambient temperature electrochemical relithiation method in an aqueous solution. It follows a preliminary delithiation step described in our previous publications. The results confirmed that FP can be efficiently relithiated in either Li2SO4 or LiHCO3 electrolyte. The reaction follows mostly a Cottrellian behavior, determined from potentiostatic experiments, indicating that diffusion in solution is a critical mechanism. Application of this electrochemical relithiation process to FP originating from spent LFP resulted in a 96 % relithiation yield at a current efficiency of 91 %. The overall recycling process successfully re-functionalized deeply damaged spent LFP by recovering up to 99 % of the LFP's original discharge capacity, achieving up to 153 mAh g−1 at C/12. Meanwhile, the initial discharge capacity of the re-functionalized LFP at 1C attained 119 mAh g−1, which interestingly increased upon cycling, reaching 131 mAh g−1 after 225 cycles. This increase could be associated with electrochemical activation promoted by cycling-induced LFP crystal annealing and/or by electrochemical milling.

Assessment of Siltation Impact and Mitigation Strategies for Sustaining Storage Capacity in Lwanyo Dam, Tanzania

The ongoing generation, transportation, and deposition of silt in the Lwanyo Dam has significantly reduced the storage capacity of the Lwanyo Reservoir, originally constructed to support irrigation and the surrounding ecosystem. The objective of this paper was to assess the extent of siltation in Lwanyo Dam, evaluate its impact on the dam's storage capacity, and propose measures to mitigate silt accumulation. The upstream catchment area, approximately 39.6 km², includes around 128,991 m² allocated for rain-fed crop cultivation and 5.89 km² for pastoral activities. Frequent overtopping of the reservoir has been observed, largely due to siltation reducing its live storage capacity. In the reservoir trial pits were excavated and assessed, and they indicate that average silt layers range in thickness from 0.54 m to 0.98 m per rainy season. The deposited material consists of a silt layer from 0 to 540 mm, followed by an intermediate clay layer from 540 mm to 3100 mm. The impounded silt depth was measured at 1270 mm, with an estimated siltation volume of 58,349.4644 m³. The reservoir's original storage capacity of 210,153 m³ has been reduced by 27.765% due to siltation. The reservoir’s structural design inadequately addresses silt management, lacking both silt flushing tunnels and upstream silt check dams. The analysis indicates that storage capacity decreases by 3.085% annually, and if this linear trend continues without any intervention measures, the dam will lose all storage capacity within 24 years. The study recommends urgent measures to mitigate silt accumulation.

Photo-Crosslinked Polyurethane-Containing Gel Polymer Electrolytes via Free-Radical Polymerization Method.

Using a novel technique, crosslinked gel polymer electrolytes (GPEs) designed for lithium-ion battery applications have been created. To form the photo crosslink via free-radical polymerization, a mixture of polyurethane acrylate (PUA), polyurethane methacrylate (PUMA), vinyl phosphonic acid (VPA), and bis[2-(methacryloyloxy)ethyl] phosphate (BMEP) was exposed to ultraviolet (UV) radiation during the fabrication process. The unique crosslinked configuration of the membrane increased its stability and made it suitable for use with liquid electrolytes. The resulting GPE has a much higher ionic conductivity (1.83 × 10-3 S cm-1) than the commercially available Celgrad2500 separator. A crosslinked structure formed by the hydrophilic properties of the PUA-PUMA blend and the higher phosphate content from BMEP reduced the leakage of the electrolyte solution while at the same time providing a greater capacity for liquid retention, significantly improving the mechanical and thermal stability of the membrane. GPP2 shows electrochemical stability up to 3.78 V. The coin cell that was assembled with a LiFePO4 cathode had remarkable cycling characteristics and generated a high reversible capacity of 149 mA h g-1 at 0.1 C. It also managed to maintain a consistent Coulombic efficiency of almost 100%. Furthermore, 91.5% of the original discharge capacity was maintained. However, the improved ionic conductivity, superior electrochemical performance, and high safety of GPEs hold great promise for the development of flexible energy storage systems in the future.

Circular economy approach for thermal regeneration of graphene-encapsulated magnetic nanoparticles as an efficient adsorbent for sustainable wastewater management

High-performing nanostructured magnetic adsorbents, featuring enhanced dye adsorption from wastewater at various conditions of pH, and separability through the application of magnetic fields, offer significant technical advantages for streamlined water purification processes. Moreover, the efficient regeneration of exhausted magnetic adsorbents provides additional benefits in terms of the sustainability of adsorption process and promoting circular economy principles. Here, we explore the performance of the graphene encapsulated magnetic adsorbent Ni0.4Fe2.6O4/(Fe,Ni)@graphene (GMA) for decolorization of wastewater containing crystal violet (CV), and its reusability properties through thermal regeneration of the exhausted adsorbent at temperatures ranging from 200 to 600 °C. The graphene layer around GMA provides an enhanced adsorption capacity and stability for the agent. Meanwhile, the application of a straightforward and potentially low-cost thermal treatment offers a rapid regeneration strategy, facilitating efficient recycling of the adsorbent. While maintaining structural and morphological stability up to 400 °C, samples regenerated at this temperature exhibit a BET surface area and pore volume of 207.46 m²/g and 0.44 cm³/g, respectively, closely resembling those of the original adsorbent. The regenerated sample recovers over 92 % of the original adsorption capacity. At the same time, approximately 86 % of the saturation magnetization (Ms) of the sample can also be restored through the thermal regeneration, with magnetic remanence and coercivity remaining nearly unchanged compared to the original adsorbent, ensuring the functionality of the regenerated adsorbent.

One-step rapid prototyping of recyclable ultrathin CNF/MWCNT/Fe-based spinel oxide asymmetric interdigital nanopaper electrodes for high performance flexible supercapacitors

Flexible asymmetric supercapacitors (FASCs) are potential energy storage devices for wearable electronics, considering that these have a wide operating voltage window, high specific capacity, and high energy density. However, achieving high energy density through the optimization of structure and electrode remains a challenge. Herein, two electrode inks with exceptional homogeneity nature and stability are prepared by using in-situ grown Fe-based spinel oxide (MFe2O4 = Fe3O4/MnFe2O4) on multi-walled carbon nanotubes (MWCNT) combined with eco-friendly and renewable cellulose nanofiber (CNF). Meanwhile, ultrathin flexible asymmetric interdigital nanopaper electrodes (NFT@MnFe and NFT@Fe) with customized patterns are fabricated through a one-step mask-assisted vacuum filtration strategy by using the obtained electrode inks. The planar interdigital FASC device based on the NFT@MnFe cathode and the NFT@Fe anode has excellent area specific capacity (309.8 mF cm−2), energy density (110.2 μW h cm−2), and power density (0.47 mW cm−2). The FASC maintain over 95 % of the original capacity after 5000 charge/discharge cycles. Noteworthy, a stacked interdigital FASC can be achieved with an energy density of up to 273.8 μW h cm−2 at 0.47 mW cm−2 power density, combining the structural benefits of planar interdigital and sandwich-type devices.

Performance and mechanism of chitosan-modified La-based MOF nanocomposites for high-efficiency adsorption of azo anion dye Congo red

The impact of organic dye wastewater discharge on the environment cannot be ignored following the development of modern industry. The adsorption method is widely used in wastewater treatment owing to its low cost and environmental friendliness. Improving the application performance of adsorption materials is the key to technical optimization. Herein, a lanthanum-based metal organic framework (La-BDC) and its derivative loaded with chitosan (La-MOF@CS) were synthesized with the solvothermal method, and the adsorption behavior and mechanism of anionic dye Congo red (CR) were studied. The experimental adsorption capacities of La-BDC and La-BDC@CS for 100 mg·L-1 CR at 25 ℃ were 260.46 and 227.82 mg·g−1, respectively, and maintained stable in a wide pH range and under different water quality conditions. The results of adsorption kinetics and adsorption isotherm showed that the adsorption process conformed to the pseudo-second-order kinetics and Langmuir model. The saturated adsorption capacities of the two materials were as high as 2249.56 and 2041.07 mg·g−1, respectively. La-BDC@CS maintained more than 95 % of the original adsorption capacity after ten cycles, which has practical application potential. Mechanism experiments show the adsorption of CR by La-BDC@CS is synergistically caused by various chemical mechanisms, such as hydrogen bonding, electrostatic attraction, and π-π coordination.

Analisis Studi Kelayakan Usaha Briket Limbah Tongkol Jagung

The use of energy resources that are not environmentally friendly is a problem in Indonesia today. Briquettes are also the primary material because they are abundant, and the primary material has yet to be optimally utilized, including corn cobs. The purpose of this study is to analyze the economic feasibility of corn cob waste briquettes in this study using data analysis of technological technical aspects, financial feasibility analysis such as Payback Period (PP), Net Present Value (NPV), Internal Rate of Return (IRR) and Benefit and Cost Ratio (B/C). The results showed that it takes 19,800 kg of corn cobs to produce charcoal, as much as 3,168 kg and 158.4 kg with tapioca starch adhesive material, as much as 5% of the total weight of charcoal powder, requiring four pieces of equipment, namely pyrolyzer machines, Hammer mills, Planetary mixers, and Tray dryers. Furthermore, the feasibility analysis of this corn cob briquette business was declared feasible with the four categories: Payback Period (PP) for 3.1319 years, Net Present Value (NPV) of Rp 28,129,336,212; IRR of 17.77%, and Net B/C of 1.55. The corn cob briquette agro-industry will remain profitable even if the production capacity decreases by 28% from the original capacity. The agro-industry can also still operate despite an 8% decrease in the selling price of briquettes and will remain profitable if raw materials increase by 17%.

Rapid and efficient adsorption of p-nitrophenol over biomass-derived vertically aligned graphene nanosheets fabricated by hydrothermal/molten salt-assisted pyrolysis method

Vertical graphene (VG) is an emerging three-dimensional graphene with unique structure and properties, which is expected to possess outstanding adsorption performance. Nevertheless, the utilization of VG as an adsorbent has not been investigated, and its conventional preparation methods are complex and expensive. Herein, we utilize a facile hydrothermal/ molten K2CO3-assisted pyrolysis method for preparing VG from cost-effective and renewable fir bark. The optimized VG-1.0 achieved a high adsorption capacity (556 mg/g) for p-nitrophenol (PNP) within 10 min, far superior to commercial activated carbon (360 mg/g) and previously reported graphene-based materials. Its excellent performance can be ascribed to high specific surface area (1423 m2/g), open & vertical channels, rich oxygen-containing groups and high graphitization degree, providing sufficient adsorption sites and unhindered mass transfer pathways. VG-1.0 was easily regenerated by rinsing with NaOH solution and showed good reusability, maintaining > 80 % of its original adsorption capacity after 5 cycles of reuse. The adsorption isotherm and kinetic data of PNP over VG were fitted well with Freundlich/Temkin model and pseudo-second-order kinetic model, respectively. Various characterizations and density functional theory (DFT) simulations have confirmed that the adsorption of PNP on VG is a spontaneous and endothermic process, involving pore filling and surface adsorption such as hydrogen bonding and π-π interactions.

Core-shell heterostructure Cu(OH)2@NiCoPO4 nanorod arrays constructed by electrochemical deposition for hybrid supercapacitor electrode material

Electrochemical deposition can be used to make three-dimensional nanoarray core-shell heterostructures that can effectively solve the issues of low rate performance and small capacity caused by agglomeration and morphological collapse. NiCo phosphates synthesized using conventional methods are susceptible to agglomeration and experience inevitable volume collapse during prolonged charging and discharging cycles. Core-shell heterostructures are created by electropositing lamellar NiCoPO4 on arrays of Cu(OH)2 nanorods. This structure shortens the ionic transport distance and preserves the excellent electrical conductivity of NiCoPO4, in addition to offering a greater surface area for the growth of NiCoPO4, increasing the reactive sites. Furthermore, electrodeposition can reduce material aggregation, enabling tight contact between NiCoPO4 and the Cu(OH)2 skeleton. This enhances the material's mechanical stability and successfully avoids the collapse issue. Results showed that the Cu(OH)2@NiCoPO4/CF composite demonstrated an elevated specific capacitance of 208.54 mAh g-1 at 1 A g-1, and it maintained 80.03 % of its original capacity after 10,000 cycles. The Cu(OH)2@NiCoPO4/CF//AC HSC device that was made showed great cycling stability, keeping 119.80 % of its charge after 30,000 charge/discharge cycles at 10 A g-1. It also offers an outstanding energy density of 52.16 Wh kg-1 (800.85 W kg-1). The electrochemical performance of bimetallic NiCo phosphates may be significantly enhanced by their structural design, offering new possibilities for the advancement of phosphates in electrode materials.

Enhanced high-rate and long-cycle performance of Mg2+-Al3+ co-doped spinel LiMn2O4 cathode materials for Li-ion batteries

Spinel LiMn2O4 has the potential to be used as a cathode material in lithium-ion batteries because of its affordability, low toxicity, and excellent charge/discharge capability. However, severe capacity attenuation results from the degradation of its long-cycle and high-rate performance caused by the Jahn-Teller distortion and Mn dissolution. Herein, a simple solid-state combustion process is used to successfully prepare the Mg2+-Al3+ co-doped LiMn2O4 with truncated octahedral morphology. The Jahn-Teller distortion is inhibited by the stable Mn-O framework and the decreased lattice constant, which in turn lowers the dissolution of Mn. Moreover, Mg2+-Al3+ co-doped LiMn2O4 have lower activation energy and greater Li+ diffusion coefficient. As a result, the optimized LiMg0.03Al0.10Mn1.87O4 delivers satisfied initial capacity of 102.1 mAh‧g−1 with a capacity retention of 76.2 % after 1000 cycles at 10 C. Even at the ultra-high rate of 15 C and 20 C, Mg2+-Al3+ co-doped sample also remain desired structure stability and cycling performance, which remains 73.8 % of its original capacity after 1000 cycles at 20 C. This work provides a reference for developing high-performance and stability cathode materials for lithium-ion battery.

The recycling potential of fibre reinforced concrete with 4D Dramix® fibres: Experimental analysis and model verification

This experimental study aims to advance sustainable construction practices by exploring the recycling potential of steel fibre reinforced concrete with 4D Dramix® fibres from the company Bekaert. In this research steel fibres from reinforced concrete specimens with varying fibre quantities of two 4D Dramix® fibre types, more precisely, the 55/50 BG and 65/50 BG fibres are recycled. A jaw crusher at the recycling company AC Materials (Flanders, Belgium) and an impact crusher at the research and development company CTP (Wallonia, Belgium) are employed to optimize the quantity and quality of the recycled fibres. Subsequently, the recycled steel fibres are reintegrated into fresh concrete mixes. The recycling process of the fibres results in a general decrease of the residual tensile strength capacity for the concrete mixtures with recycled fibres (RSFRC) compared to those with new fibres (NSFRC), and the deviation increases with increasing crack mouth opening displacement (CMOD). It was found that fibres recovered by the impact crushing process are (generally) shorter than those obtained from the jaw crusher, which results in a fibre reinforced concrete (FRC) with a somewhat lower post-cracking tensile strength. Nevertheless, most recycled fibres retain 75 % of their original capacity, considering the mean residual tensile strength of the FRC mixtures. Consequently, current findings show promising results for the recycling potential of steel fibres and the residual strength behaviour of RSFRC compared to NSFRC. Additionally, this study highlights the potential for an improved constitutive tensile model for FRC mixtures, where the design parameters ka and kc can be estimated based on the fR3k/fR1k-ratio.

Self-Healing Stretchable Li-Ion Battery Based on a High-Voltage Hydrogel Electrolyte

Safe and deformable soft batteries are desirable for future wearable electronic devices. However, current Li-ion batteries on the commercial market are rigidly packaged and hermetically sealed to prevent moisture penetration and the leakage of toxic and flammable organic electrolytes. Since the modulus of elasticity and gas permeability of materials are inextricably linked, stretchable batteries often experience significant performance degradation over time in the ambient due to inevitable moisture penetration. Furthermore, the polymer-based flexible packaging materials can be easily damaged resulting in electrolyte leakage that poses significant safety concerns. Here we report a non-toxic, aqueous hydrogel electrolyte instead of its organic counterpart that is demonstrated to 1) enable highly safe operations due to its non-toxic and non-flammable nature; 2) alleviate the moisture penetration problem from the outside environment; (3) have a high-voltage working window of ~2.97V; and (4) allow the construction of stretchable batteries by using elastic polymer packaging materials instead of rigid hermetic seals. The prototype batteries have shown good stretchability (50% strain) and flexibility (radius of curvature < 2mm) to enable conformal attachments to a wide range of geometric surfaces. The prototype battery also shows outstanding cyclic stability, retaining ~90% of the original capacity after 100 cycles for over 2 months in the ambient environment without using any rigid hermetic sealing package. Finally, a prototype battery with a self-healing elastomer package remains functional after being punctured by a needle 5 times at different locations in the package. Furthermore, it can recover >90% of its capacity after being cut through by a razor blade and subsequently healed at 70 for 10 minutes. Such safe and highly stretchable batteries would be useful for several wearable electronic applications such as blood glucose monitoring, hearing rate monitoring, temperature monitoring, wireless charging, smart clothing, etc. Figure 1