Organic compounds, such as polyvinylidene fluoride (PVDF), have been widely used as a binder in battery electrode preparations. While such an approach does not have a significant impact on the ...performance of the batteries that utilize low valence ions, such as the Li ion battery (LIB), the diffusion of high valence ions (such as Zn2+) will be severely impaired. This will be especially pronounced if the polymeric binder contains highly electronegative atoms, such as fluorine. The high charge density ions, such as Zn2+, tend to adsorb onto these electronegative atoms, thus the mobility of these ions across the material is inevitably affected. As such, it becomes highly necessary to consider the binder-free electrode architecture when designing a high rate performing and cycling-stable zinc ion battery (ZIB) cathode. Herein, this work demonstrates an improved Zn ion battery by adopting a freestanding electrode. The obtained V2O5/CNT paper electrode delivers a specific capacity of 312 mA h g−1, while achieving a respectable 75% retention in capacity after increasing the current density by 10-fold. Furthermore, excellent cycling stability is recorded with 81% capacity retention after 2000 cycles at 1.0 A g−1. Thus, this work clearly demonstrated that the freestanding electrode is a promising approach for high valence ion batteries.
Display omitted
•Additives made the cellulose film more transparent.•Highly stretchable film was achieved.•Film remains amorphous after the addition of crystalline additives.•Glass transition ...temperature decreases after the addition of additives.
Developing natural products to replace synthetic plastics is necessary due to the serious environmental problem of non-biodegradable plastic waste. Cellulose is the most abundant natural material that is from all plants. This paper reports our success in achieving the most stretchable and transparent cellulose-based films through a very green process. The films are highly transparent, with 90% transparency per 100 μm at 550 nm wavelength. The films are very flexible, able to be twisted and folded greatly without breaking. The film can reach an unprecedented maximum of 233% elongation at break. The success in such highly stretchable and transparent films sheds light on the great promise of cellulose for potential applications to replace synthetic plastics, such as transparent and stretchable substrates for flexible and stretchable electronics, transparent and stretchable films and various products. The mechanisms in achieving high transparency, flexibility and stretchability of the cellulose-based films are discussed.
Conformability, lightweight, consistency and low cost due to batch fabrication in situ on host structures are the attractive advantages of ultrasonic transducers made of piezoelectric polymer ...coatings for structural health monitoring (SHM). However, knowledge about the environmental impacts of piezoelectric polymer ultrasonic transducers is lacking, limiting their widespread use for SHM in industries. The purpose of this work is to evaluate whether direct-write transducers (DWTs) fabricated from piezoelectric polymer coatings can withstand various natural environmental impacts. The ultrasonic signals of the DWTs and properties of the piezoelectric polymer coatings fabricated in situ on the test coupons were evaluated during and after exposure to various environmental conditions, including high and low temperatures, icing, rain, humidity, and the salt fog test. Our experimental results and analyses showed that it is promising for the DWTs made of piezoelectric P(VDF-TrFE) polymer coating with an appropriate protective layer to pass various operational conditions according to US standards.
While the active ultrasonic method is an attractive structural health monitoring (SHM) technology, many practical issues such as weight of transducers and cables, energy consumption, reliability and ...cost of implementation are restraining its application. To overcome these challenges, an active ultrasonic SHM technology enabled by a direct-write transducer (DWT) array and edge computing process is proposed in this work. The operation feasibility of the monitoring function is demonstrated with Lamb wave excited and detected by a linear DWT array fabricated in situ from piezoelectric P(VDF-TrFE) polymer coating on an aluminum alloy plate with a simulated defect. The DWT array features lightweight, small profile, high conformability, and implementation scalability, whilst the edge-computing circuit dedicatedly designed for the active ultrasonic SHM is able to perform signal processing at the sensor nodes before wirelessly transmitting the data to a remote host device. The successful implementation of edge-computing processes is able to greatly decrease the amount of data to be transferred by 331 times and decrease the total energy consumption for the wireless module by 224 times. The results and analyses show that the combination of the piezoelectric DWT and edge-computing process provides a promising technical solution for realizing practical wireless active ultrasonic SHM system.
This paper presents a method for measuring surface cracks based on the analysis of Rayleigh waves in the frequency domain. The Rayleigh waves were detected by a Rayleigh wave receiver array made of a ...piezoelectric polyvinylidene fluoride (PVDF) film and enhanced by a delay-and-sum algorithm. This method employs the determined reflection factors of Rayleigh waves scattered at a surface fatigue crack to calculate the crack depth. In the frequency domain, the inverse scattering problem is solved by comparing the reflection factor of the Rayleigh waves between the measured and the theoretical curves. The experimental measurement results quantitatively matched the simulated surface crack depths. The advantages of using the low-profile Rayleigh wave receiver array made of a PVDF film for detecting the incident and reflected Rayleigh waves were analyzed in contrast with those of a Rayleigh wave receiver using a laser vibrometer and a conventional lead zirconate titanate (PZT) array. It was found that the Rayleigh waves propagating across the Rayleigh wave receiver array made of the PVDF film had a lower attenuation rate of 0.15 dB/mm compared to that of 0.30 dB/mm of the PZT array. Multiple Rayleigh wave receiver arrays made of the PVDF film were applied for monitoring surface fatigue crack initiation and propagation at welded joints under cyclic mechanical loading. Cracks with a depth range of 0.36-0.94 mm were successfully monitored.
Flexible and recyclable zinc-based batteries have been hot research topics due to their high discharge platform, safety, and low cost. However, most research on zinc-based batteries put their ...attention on metal oxides as the cathode, such as manganese dioxide (MnO2), cobaltosic oxide (Co3O4), nickel oxide (NiO), etc. Very few studies use metal sulfides as electrode materials and focus on its mechanism based on theoretical analysis. Hence, in this work, we firstly used cobaltosic sulfide (Co3S4) nanosheets grown on Ni foam (CSNSs/NF) as an electrode material for zinc-based batteries. Both first-principles calculations and experimental results reveal that S plays a crucial role in the capacitive activity and electrical conductivity enhancement for Co-based materials. The Zn//CSNSs/NF battery provides a high specific capacity of 317 mA h g−1 at a current density of 1 A g−1. Furthermore, it also displays an impressive energy density of 507 Wh kg−1 and a long cycling performance. Impressively, the Zn//CSNSs/NF battery has high flexibility and can work well under different deformations. This work not only provides a new member of cathode materials in zinc-based batteries, but also opens new opportunities for powering portable and wearable electronics.
The Zn//CSNSs/NF battery displays an impressive energy density of 507 Wh kg-1 and a long cycling performance (no decay after 5000 cycles). Impressively, the Zn//CSNSs/NF battery has high flexibility and can still work while under different deformations. This work not only provides a new member as cathode material in zinc-based batteries, but also opens new opportunities for powering portable and wearable electronics. Display omitted
•The Zn//CSNSs/NF battery provides a high specific capacity of 317 mA h g−1 at current density of 1 A g−1.•The device displays an impressive energy density of 507 Wh kg−1 and a maximum power density of 19.2 kW kg−1.•Impressively, the Zn//CSNSs/NF battery has high flexibility and can still work while under different deformations.
Shear mode guided waves are highly demanded for underwater structural health monitoring (SHM) applications due to their simplified non‐dispersive feature and minimal acoustic energy loss in the ...presence of liquid. Excitation and detection of pure shear wave are challenging using conventional piezoelectric materials used in the current ultrasonic transducers because they have complex piezoelectric responses mixed with multiple longitudinal, transverse, and shear modes. They also suffer from aging issue due to depoling. Here, conformable shear mode ultrasonic transducers are designed and made of flexible piezoelectric poly (L‐lactic acid) (PLLA) fibers on both flat and tubular structures. The electromechanical responses over a macroscopic area of the transducers are evaluated in a wide frequency range up to 500 kHz. The PLLA fiber‐based shear mode ultrasonic transducers exhibit a consistent sensitivity of detecting defects in liquid and air. In addition, the only shear mode in PLLA fibers originates from crystal structure without requiring electrical poling to render piezoelectricity, thus does not depole due to aging. The theoretical analyses including ab initio calculations and experimental results on both flat and tubular structures show the great potential of PLLA material and significant advantage of PLLA fiber‐based shear mode ultrasonic transducers for underwater SHM applications.
Pure shear mode and conformable ultrasonic transducers are designed and produced from flexible piezoelectric poly (L‐lactic acid) (PLLA) fibers with molecular chain orientation. The PLLA‐fiber transducers exhibit unique directivity for non‐dispersive shear wave, and no substantial change in the ultrasonic signals for operation in water. The theoretical analysis and experimental demonstration show great value for underwater ultrasonic structural health monitoring applications.
Shear mode‐guided ultrasonic waves are highly regarded for submerged or subterranean structural health monitoring (SHM), owing to their non‐dispersive feature and minimized acoustic energy loss when ...in contact with liquid or solid. High‐performance shear mode ceramic ultrasonic transducers with robustness and cost‐effectiveness are highly demanded for underwater or underground SHM applications, especially in harsh environments. However, the implementation of discrete shear mode piezoelectric ceramic ultrasonic transducers is hindered by the inconsistency with manual installation, lack of conformability on curved surfaces, and unreliable acoustic coupling between the transducers and the structure. Here, direct‐write conformable shear mode ultrasonic transducers made from piezoelectric lead‐free ceramic coatings, which are in situ produced on steel structures by a scalable thermal spray process, are proposed. The obtained lead‐free lithium‐doped potassium sodium niobate (KNN‐LN) ceramic coatings exhibit a high effective shear piezoelectric strain coefficient (d24, f) above 60 pm V−1 in a broad frequency range from 100 Hz to 200 kHz. The resulting conformable shear mode KNN‐LN ceramic coating transducers successfully showcase the functions of exciting and detecting stable shear mode ultrasonic wave signals with operation temperature exceeding 200 °C and demonstrate reliable capability in defect detection in both air and liquid environments.
Direct‐write conformable shear mode ultrasonic transducers are designed and produced from lead‐free piezoelectric potassium sodium niobate (KNN) ceramic coatings. These coating transducers ensure consistent, non‐dispersive shear wave transmission and stable ultrasonic signals across various temperatures and underwater conditions. Such reliability and robustness highlight their potential for monitoring the health of submerged or subterranean structures, especially in harsh environments.
Zero-group-velocity (ZGV) Lamb waves are usually excited and detected using non-contact laser ultrasonic systems, as contact techniques such as using conventional bulky discrete piezoelectric ...transducer may cause interferences and errors in identifying the ZGV Lamb waves due to the large mass and stiffness introduced. Nevertheless, contact transducers have many advantages over the laser ultrasonic method, including cost, sensitivity, safety, and efficiency. Here, a contact technique is explored by using lightweight and low-profile direct-write piezoelectric ultrasonic transducer (DWT) made of piezoelectric polymer coating to generate and detect the ZGV Lamb waves. The frequency shift and wave attenuation of the ZGV Lamb waves, and their ability for monitoring adhesive bonded structure are investigated with both numerical modeling and experimental testing, with comparison between the DWT and discrete piezoelectric transducer. The potential of the DWT for generating and detecting ZGV Lamb waves for ultrasonic nondestructive evaluation is demonstrated by overcoming the drawbacks of discrete piezoelectric transducers.
