Light Weight Research Articles

Design of Acetaldehyde Gas Sensor Based on Piezoelectric Multilayer Microelectromechanical System Resonator.

Acetaldehyde is a volatile organic compound that can cause damage at the cellular and genomic levels. The monitoring of acetaldehyde gas at low concentrations requires fast-response and low-cost sensors. Herein, we propose the design of an acetaldehyde gas sensor based on a low-cost Microelectromechanical System (MEMS) process. This sensor is formed by a single-clamped piezoelectric multilayer resonator (3000 × 1000 × 52.2 µm) with a simple operating principle and easy signal processing. This resonator uses a zinc oxide piezoelectric layer (1 µm thick) and a sensing film of titanium oxide (1 µm thick). In addition, the resonator uses a support layer of 304 stainless steel (50 µm thick) and two aluminum layers (100 nm thick). Analytical and Finite-Element Method (FEM) models are developed to predict the mechanical behavior of the gas sensor, considering the influence of the different layers of the resonator. The analytical results agree well with respect to the FEM model results. The gas sensor has a first bending frequency of 4722.4 Hz and a sensitivity of 8.22 kHz/g. A minimum detectable concentration of acetaldehyde of 102 ppm can be detected with the proposed sensor. This gas sensor has a linear behavior to detect different acetaldehyde concentrations using the frequency shifts of its multilayer resonator. The gas sensor design offers advantages such as small size, a light weight, and cost-efficient fabrication.

ELGO electric motorcycle: Design and analysis of trail-type electric motorcycle frame using finite element analysis

The frame is an important part of the motorcycle as it carries the load of the passenger. Therefore, it is necessary to design a frame that can withstand the load and is lightweight. A lighter motorcycle will reduce the power required to ride it. This research aims to redesign the frame of a trail-type ELGO electric motorbike by considering a reduction in frame weight. The research was carried out using finite element analysis. The data from the analysis were checked based on the maximum stress not exceeding the yield strength of the DIN 1.0030 material and the safety factor greater than 1. The results showed that the newly designed frame has a lighter weight, with a maximum stress less than the yield strength of the DIN 1.0030 material and a safety factor value greater than 1. The simulation results also indicate the potential for further research by showing the maximum and minimum stress areas on the frame.

Deployment Dynamic Modeling and Driving Schemes for a Ring-Truss Deployable Antenna

Mesh reflector antennas are widely used in space tasks owing to their light weight, high surface accuracy, and large folding ratio. They are stowed during launch and then fully deployed in orbit to form a mesh reflector that transmits signals. Smooth deployment is essential for duty services; therefore, accurate and efficient dynamic modeling and analysis of the deployment process are essential. One major challenge is depicting time-varying resistance of the cable network and capturing the cable-truss coupling behavior during the deployment process. This paper proposes a general dynamic analysis methodology for cable-truss coupling. Considering the topological diversity and geometric nonlinearity, the cable network’s equilibrium equation is derived, and an explicit expression of the time-varying tension of the boundary cables, which provides the main resistance in truss deployment, is obtained. The deployment dynamic model is established, which considers the coupling effect between the soft cables and deployable truss. The effects of the antenna’s driving modes and parameters on the dynamic deployment performance were investigated. A scaled prototype was manufactured, and the deployment experiment was conducted to verify the accuracy of the proposed modeling method. The proposed methodology is suitable for general cable antennas with arbitrary topologies and parameters, providing theoretical guidance for the dynamic performance evaluation of antenna driving schemes.

Improved diabetic retinopathy severity classification using squeeze-and-excitation and sparse light weight multi-level attention u-net with transfer learning from xception.

Diabetic Retinopathy (DR) is a significant cause of vision loss in diabetic patients, making early detection and accurate severity classification essential for effective management and prevention. This study aims to develop an enhanced DR severity classification approach using advanced model architectures and transfer learning to improve diagnostic accuracy and support better patient care. We propose a novel model, Xception Squeeze-and-Excitation Sparse Lightweight Multi-Level Attention U-Net (XceSE_SparseLwMLA-UNet), designed to classify DR severity using fundus images from the Messidor 1 and Messidor 2 datasets. The XceSE_SparseLwMLA-UNet integrates several advanced mechanisms: the Squeeze-and-Excitation (SE) mechanism for adaptive feature recalibration, the Sparse Lightweight Multi-Level Attention (SparseLwMLA) mechanism for effective contextual information integration, and transfer learning from the Xception architecture to enhance feature extraction capabilities. The SE mechanism refines channel-wise feature responses, while SparseLwMLA enhances the model's ability to identify complex DR patterns. Transfer learning utilizes pre-trained weights from Xception to improve generalization across DR severity levels. The proposed XceSE_SparseLwMLA-UNet model demonstrates superior performance in DR severity classification, achieving higher accuracy and improved multi-class F1 scores compared to existing models. The model's color-coded segmentation outputs offer interpretable visual representations, aiding medical professionals in assessing DR severity levels. The XceSE_SparseLwMLA-UNet model shows promise for advancing early DR diagnosis and management by enhancing classification accuracy and providing valuable visual insights. Its integration of advanced architectural features and transfer learning contributes to better patient care and improved visual health outcomes.

Human Gait phases recognition based on multi-source data fusion and BILSTM attention neural network

A human gait recognition algorithm with deep learning based on multi-source data fusion is proposed to assist exoskeleton realizing complex human-exoskeleton cooperative motion. A lightweight gait acquisition device simultaneously acquires three different types of sensor signals, i.e., thigh surface electromyography (sEMG), ground reaction force (GRF) of human feet and two joints motion information. The sample data is obtained by many multi-scene gait experiments involving stand still, walk up/down stairs, and walk up/down slope, etc. The proposed algorithm recognizes multiple gait phases (27 classes) in different motion patterns by using short-time gait data, which has two typical advantages: (1) Based on multi-source sensor distributed in human body, this wearable device is constructed for ease of use to address several Subjects (different weights and heights) with low cost and light weight. (2) The critical features of gait data are identified by Bi-directional Long Short-Term Memory (BILSTM) attention neural network with higher recognition accuracy than other state-of-art recognition methods, especially in arbitrary gait switching durations.

Interfacial Study of Steel Joints Prepared with a Catechol-Modified Epoxy Adhesive with Enhanced Bonding Performance and Durability.

Bonding is widely used in aircraft and vehicles due to its light weight and simple process, but its strength decreases sharply in hot and humid environments. Anodization treatment, used for enhancing aging performance, is environmentally harmful and unsuitable for steel. In this study, a catechol-modified epoxy adhesive (CMEA) was prepared on a hectogram scale. Comparative analysis with phenol-modified epoxy adhesive (PMEA) and pristine epoxy adhesive (EA) revealed that the underwater bonding of CMEA (13.0 MPa) on stainless steel (SS) significantly outperformed the two control groups. Moreover, after 32 days of hydrothermal aging at 50 °C, CMEA preserved 73.9% of its initial bonding strength, while PMEA and EA retained 59.8 and 11.4%, respectively. Furthermore, X-ray photoelectron spectroscopy (XPS) etching at different times to analyze the interface between adhesives and the SS substrate indicated a marked increase in the O-H/O2- value at the interface between CMEA and the SS substrate compared to the two control groups. The above results demonstrated that the catechol-modified adhesive enhanced the bonding and aging properties of the adhesive, possibly due to the formation of a higher density of hydroxyl groups at the interface between the adhesive and the SS substrate. These findings contribute to the understanding of the enhancement mechanism of catechol in improving the bonding and aging properties of adhesives and suggest a feasible direction for designing adhesives with high bonding strength and high durability.

Cost-effective preparation of pre-oxygenated PAN fiber composite SiO2 aerogel felt with excellent mechanical and thermal insulation properties

Silica aerogel is an attractive thermal insulation material due to its low thermal conductivity, light weight and non-combustible inorganic properties, but its inherent brittleness and high production cost hinder its practical application on a large scale. Herein, the high-performance pre-oxidized polyacrylonitrile fiber composite silica aerogel felt (PPAF-SiO2) was successfully prepared by a cost-effective combustion drying technique for the first time. The results show that the PPAF-SiO2 has the feature of lightweight, good flexibility, and its heat resistance, hydrophobicity, and specific surface area are significantly improved. Due to the further polymerization of fiber structure molecules caused by combustion, the tensile strength of the PPAF-SiO2 is increased by 81.9 % to 1.71 MPa. More importantly, due to the high proportion of silica aerogel in felt, its thermal conductivity can be reduced to 0.02 W/(m·K), which is lower than most aerogel composite materials. Moreover, the thermal insulation performance of the PPAF-SiO2 was further confirmed by the infrared thermal imager from room temperature to 300 ℃. In addition, the innovative drying mechanism based on the combustion flame model was proposed. Finally, compared with traditional physical drying technologies in terms of drying time and drying conditions, the combustion drying technology shows great advantages in drying efficiency, energy consumption and equipment investment, which greatly reduces production costs. The combustion drying technology opens up a promisingly method for high efficiency, low energy consumption, and low cost preparation of silica aerogel composites.

Experimental and theoretical analysis of mechanical properties of FRP laminated rubber bearing

Fiber reinforced polymer (FRP) laminated rubber bearing is a kind of high-performance isolator with simple structure, low cost, light weight and excellent mechanical properties. The mechanical properties of FRP laminated rubber bearings are investigated by experimental and theoretical methods. Based on the pseudo-static vertical compression test and compression-shear test experiment, the vertical and horizontal mechanical properties of the bearings under different vertical pressures are investigated. According to the deformation compatibility and boundary conditions of elastic composites, the modified calculation equations for the vertical and horizontal stiffness of FRP laminated rubber bearings are derived, and the theoretical analysis is verified by the results of laboratory tests. The influence law of characteristic parameters such as shape factor on the mechanical properties of bearings has been investigated. Tests and theoretical analysis show that the increase of vertical pressure causes a certain degree of increase in the vertical stiffness and a significant reduction in the horizontal stiffness of the bearing. By studying the effect of horizontal and vertical stiffness, the manuscript provides a useful reference for the design of FRP laminated rubber bearings.

Research on AZ31 magnesium alloy tee joint tube with lateral hole by hot extrusion forming with sand mandrel limited by stainless steel gasket

As one of the lightest metals in the world, magnesium alloy can be used to reduce weight and save energy. Magnesium alloy tubes with different shapes can also further direct the transportation of fluid in this light weight. But the tee joint tube is difficult formed because of the complex shapes. In this paper, magnesium alloy tube is applied to form tee joint tube with sand mandrel. During the deformation, the magnesium alloy tube is driven by the sand mandrel pressed by the push. Different from traditional extruding with full tubes without hole on the sidewall, some tube with holes on the sidewalls are also used in the extrusion. All the key parameters such as extrusion depth, temperature, tube length, hole size, and hole location are discussed in both simulations and experiments. After the extrusion results are obtained, the microhardness and microstructures are observed to explain the promotion of the mechanical properties. Based on the results received from both simulations and experiments, deeper extrusion depth, higher temperature, shorter length of tube, larger size of the hole, and the higher location of the hole influence positively on forming results. No matter there are holes or not on the sidewalls, the errors between the results in simulation and experiment are small. Also the simulation and experiment results can be used to investigate the shape of tee joint tubes. The surface quality can be also measured to prove the surfaces in extrusion with sand mandrel acceptable. A novel strategy to sand mandrel extrusion of magnesium alloy tee joint tube by tube with holes on sidewall is provided.

Bimetallic two-dimensional metal-organic frameworks nanosheets derived bimetallic@C composite materials for effective electromagnetic wave absorption

The development of information technology has resulted in serious environmental pollution and health concerns due to electromagnetic wave radiation. There is a necessity to develop electromagnetic wave absorbers with strong absorption, wide bandwidth, thin thickness, light weight, and environmental friendliness. In this study, a series of Ni4Cux@C composite materials was synthesized through a simple coprecipitation and pyrolysis process. The morphology and absorption properties of the composite materials were precisely tuned by adjusting the ratio of the bimetallic Ni and Cu. The Ni4Cux@C two-dimensional nanosheets were designed to possess a high specific surface area and abundant porous structure, thus optimizing impedance matching. Its strong dielectric loss capability is collectively contributed to the excellent graphitization degree and multiple polarizations. Additionally, the dispersion of NiCu alloy nanodisks within the carbon matrix leads to the aggregation of a large number of free space charges at the heterogeneous interface, inducing the formation of interfacial polarization. The well-designed Ni4Cu2@C composite materials exhibit outstanding electromagnetic wave absorption capabilities, with the optimal reflection loss reaching -74.9 dB, and the maximum effective absorption bandwidth reaching 6.8 GHz (2.9 mm). This work provides an important research foundation for the rational design of a new generation of two-dimensional bimetallic electromagnetic waveabsorption materials.

Analysis and optimization design of internal pressure resistance of flexible composite pipe

Flexible composite pipes have the advantages of light weight, corrosion resistance, scale resistance, and low cost compared to carbon steel pipes, and have attracted much attention in the application of onshore oil and gas gathering and transportation systems. Understanding the relationship between the pressure-bearing mechanical properties of composite pipes and their structural characteristics is crucial for guiding their process application. To investigate the mechanical behavior of flexible composite pipes under internal pressure loads, discrete and combined finite element models were established to analyze the stress-strain characteristics of flexible composite pipes. The bursting strength was predicted, and the influence of winding angle and number of reinforcement layers on the pressure-bearing capacity of flexible composite pipes was revealed. The applicability of the two models in the analysis of internal pressure resistance of flexible composite pipes was evaluated using whole pipe strain testing and instantaneous hydrostatic burst experiments. The results showed that the reinforcement layer is the main pressure-bearing layer of flexible composite pipes, and the innermost reinforcement layer bears the highest pressure. The pressure-bearing capacity of flexible composite pipes significantly increases when the winding angle is greater than 53°, and the increase in pressure-bearing capacity slows down when the number of reinforcement layers exceeds 3. Under the combination model, the strain and bursting strength of flexible composite pipes were closer to the experimental results. The study clearly defines the stress-strain characteristics of flexible composite pipes under internal pressure load and the impact of process parameters, providing a basis for the optimization design of single well oil transmission pipelines in Xinjiang oilfield.

Development of lightweight structural concrete with artificial aggregate manufactured from local clay and solid waste materials

The partial replacement of conventional natural coarse aggregate (NCA) with artificial light weight aggregate (LWA) manufactured from local clay and solid waste to develop a lightweight aggregate concrete (LWAC) for the structural use was studied in this paper. Red clay and Savar clay were used individually with solid wastes like rice husk ash (RHA) and waste glass to produce LWA. The suitability of raw materials and LWA was evaluated by investigating various properties. The mechanical, thermal and durability properties of manufactured LWAC were explored. The results of physical, chemical, thermal and geotechnical properties revealed that Red clay is better than Savar clay for the preparation of LWA. All the physical and mechanical properties of LWA prepared from Red clay are suitable for the preparation of LWAC compared to Savar clay. The test results demonstrated that the concrete manufactured by replacing 30 % of NCA with LWA produced a concrete of lightweight properties. The compressive strength of LWAC for 7 and 28 days was observed as 28 and 48 MPa, respectively. The results of modulus of elasticity, splitting tensile strength, flexural deformation, and creep test of LWAC revealed that these mechanical properties meet the requirements for the structural concrete. The RCP test proves that chlorine permeability of LWAC is comparable with NCA. It was observed that the superior performance of LWAC can be achieved only when the optimized mix designed is followed strictly. The suitability of the replacement of natural aggregate by LWA may be helpful for Bangladesh due to the scarcity of natural coarse aggregate and reusability of solid waste materials.

Thermite frass biomass and surface modified biowaste coir fiber reinforced biocomposites-Conversion of waste to useful products.

Polymer composites are known for its light weight and specific mechanical characteristics. This study examines sodium hydroxide (NaOH)-treated coir fiber, an agro-leftover, stuffed in a polyester matrix with termite frass powder, a bio-leftover for possible use in light-weight structural applications. Composite samples were made using compression molding and NaOH-treated coir fiber reinforced hybrid polymer composite (TCRHPC) with 40 wt% treated coir fiber and 1, 2, 3, and 4 wt% termite frass powder. TCRHPC samples mechanical, water captivation, tribological, and thermal properties were affected by termite frass powder wt%. The TCRHPC sample with 3 wt% termite frass powder has excellent mechanical properties, which improved by tensile (41.6%), flexural (28.57%), impact (43.7%), and hardness (18.84%) properties. With perfect water captivation and low weight increases in normal water (0.017 g), seawater (0.015 g), and NaOH solution (0.010 g), the identical composite sample with thermal stability up to 238°C also reduced wear mass by 5.27%. Conversely, filler agglomeration and heterogeneous dispersion in composite sample impair thermo-mechanical characteristics of TCRHPC containing 4 wt% termite frass powder. The bonding among polyester, treated coir fiber, and termite frass powder in composites were appraised with the aid of fractographic images of TCRHPC samples. The results show that TCRHPC material suits well for support structures requiring lesser weight.

PDMS micro check valve with 3D valve disk for reducing fluid resistance

Check valves are essential components in various biomedical, chemical, medical diagnostic, and process applications, as they allow fluid flow in the forward direction while blocking the reverse flow. This paper presents a method to enhance the performance of unibody micro check valves composed of polydimethylsiloxane using 3D design and printing technologies. Passive micro check valves, which are known for their structural simplicity, miniaturization, and light weight, have shown improved performance with the application of 3D valve disks formed via 3D printing technology. The performance of various valve disk designs was evaluated using simulations and experiments, which revealed that cone-shaped 3D valve disks offer a 58.33% improvement in blocking pressure performance compared to traditional two-dimensional designs. This underscores the potential for efficient fluid control in micro check valves using 3D structures while highlighting the importance of 3D printing technology in the design and manufacturing processes of microfluidic devices.

Multifiller-based polymer composites for shielding high energy ionising radiation.

Polydimethyl silicone rubber-based polymer composites filled with molybdenum and bismuth were fabricated using simple open mold cast technique. The physical and chemical structure and gamma shielding parameters like attenuation coefficient, half-value layer (HVL) thickness and relaxation length have been investigated for the said novel materials using X-ray diffraction (XRD), Fourier transform Infrared spectroscopy (FTIR) and gamma ray spectrometer. XRD study reveals the crystalline nature of the composites. It is evident from FTIR studies that there is no chemical interaction between the polymer matrix and filler particles. The results of attenuation studies reveal that the linear attenuation coefficient increases with addition of Bi and Mo and is found to be 0.653, 1.341 and 1.017, 1.793 and 0.102, 0.152cm-1 for 1MMB and 2MMB polymer composites at 80, 356 and 662keV gamma rays, respectively. The HVL thickness of the materials is found to be 1.06, 0.51 and 0.68, 0.38 and 6.73, 4.532cm for 1MMB (20Mo+10Bi phr) and 2MMB (40Mo+20Bi phr) at these energies, respectively. The mass attenuation coefficient of the novel composites 1MMB and 2MMB is found to be higher than the conventional materials like lead and barite for 356keV gamma rays. In addition, the material is found to be light weight and flexible enabling to be molded in required forms, thus being a substitute for the material lead that is known to be heavy and toxic by nature.

Fabrication and Testing of Hybrid Polymer Composite Material by Using Carbon, Glass, Kevlar Fibers

Composites which made up of fiber reinforcements are universally endorsed option for the automobiles with a lightweight. Due to the unique properties of fiber-reinforced composites, it became a perfect alternative for traditionally used materials. Most of the automobile industries prefer polymer matrix fiber-reinforced composites for the reason that its light weight helps in carbon emission reduction and Additive manufacturing (AM) produces a complex shaped product from its data, layer by layer, with high precision and much less material wastage. As compared to the conventional manufacturing process, there are many positive environmental advantages of additive manufacturing technologies. Most importantly, there is less waste of raw material and the use of new and smart materials. In this work, we first focused on creating the composite material utilizing the Hand Lay-Up method with materials such as Carbon Fiber/Epoxy Composite with Copper Oxide (CuO) Nanoparticles and Banana Glass Fiber. Following that, we readied ASTMD638 specimens for both compressive and tensile testing. We created an ASTMD638 model for the investigation's tensile and compressive tests using Solid Works design program, and we then saved the design model in STL format. This STL format was uploaded into the CURA software for slicing. The slicing model was then saved into G-code format, and it was printed in a fused deposition modeling machine. Lastly, we tested both specimens using a compressive test setup in a Universal Testing Machine model (INSTRON-3369) UTM, and the results showed 3D printed files. Keywords: Glass Fiber, Banana Fiber, Carbon Fiber, Copper Oxide Nano filler, 3D printing Machine,Corbon Fiber Filament.

Facile synthesis of samarium (Sm3+) doped cobalt-iron oxide nano ferrite as an advanced electrode material for possible supercapacitor applications

Herein, we present design and fabrication of Samarium (Sm3+) doped cobalt-iron oxide ferrites nanocomposite electrode as an efficient energy storage material for supercapacitors. We employed a simple, low cost and quick one step solution combustion method to synthesize CoFe2-xSmxO4 (x = 0.0, 0.050, 0.075 and 0.1) ferrites. The morphological and structural features of synthesized CoFe2-xSmxO4 ferrites were analysed through various analytical and spectroscopic characterization methods such as scanning electron microscope (SEM), energy dispersive X-ray spectroscopy (EDS), transmission electron microscope (TEM), X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR). These analytical techniques confirm the successful doping of Samarium (Sm3+) into cobalt-iron ferrite, and the doping does not affect the crystalline structure of pure ferrite. The electrochemical properties of the synthesized ferrites were significantly improved after Samarium (Sm3+) doping into the host cobalt-iron-oxide. The highest specific capacity about 314 F/g was achieved for CoFe2-xSmxO4 (x = 0.1) composite electrode material, in comparison to pure CoFe2-xSmxO4 (x = 0) which is about 125 F/g. However, CoFe2-xSmxO4 (x = 0.1) ferrite shows a superior capacitance retention of the order of 98 % even after 5000 cycles of operation at a scan rate of 250 mV/s. The electrode material fabricated by using CoFe2-xSmxO4 ferrite renders an energy density of 30.16 W h/kg at a power density of 400 W h/kg. The results obtained in presented studies opens new avenues for the fabrication high-performance electrode material for supercapacitor that could be well suited for light weight electronic devices, electric vehicles, and forthcoming generation supercapacitor applications.

CFE-YOLOv8s: Improved YOLOv8s for Steel Surface Defect Detection

Due to the low detection accuracy in steel surface defect detection and the constraints of limited hardware resources, we propose an improved model for steel surface defect detection, named CBiF-FC-EFC-YOLOv8s (CFE-YOLOv8s), including CBS-BiFormer (CBiF) modules, Faster-C2f (FC) modules, and EMA-Faster-C2f (EFC) modules. Firstly, because of the potential information loss that convolutional neural networks (CNN) may encounter when dealing with miniature targets, the CBiF combines CNN with Transformer to optimize local and global features. Secondly, to address the increased computational complexity caused by the extensive use of convolutional layers, the FC uses the FasterNet block to reduce redundant computations and memory access. Lastly, the EMA is incorporated into the FC to design the EFC module and enhance feature fusion capability while ensuring the light weight of the model. CFE-YOLOv8s achieves mAP@0.5 values of 77.8% and 69.5% on the NEU-DET and GC10-DET datasets, respectively, representing enhancements of 3.1% and 2.8% over YOLOv8s, with reductions of 22% and 18% in model parameters and FLOPS. The CFE-YOLOv8s demonstrates superior overall performance and balance compared to other advanced models.

Simulation study on the dynamic characteristics of natural circulation coupled phase change material for equal height difference passive containment cooling system

The passive containment cooling system (PCCS) plays a significant role in ensuring the safety of nuclear power plants. To further reduce peak pressure in the containment during a loss of coolant accident (LOCA), phase change materials (PCMs) are utilized to improve the system’s cooling effectiveness. The dynamic simulation model of PCCS has been developed using Apros software. This article focuses on examining the system’s dynamic characteristics related to various tube startup methods and comparatively analyzing the impact of different PCM thicknesses on heat transfer capacity. The results indicate that post-accident, PCM significantly suppresses peak pressure in the containment. Under the full tube startup method with 4 mm PCM, the peak pressure decreases to 1.75 MPa, whereas under the empty tube startup method, it is reduced to 1.69 MPa. With natural circulation empty tube startup method, PCM can reduce pressure change intensity in the containment but negatively affects natural circulation heat transfer. Although the full tube startup method underperforms the empty tube startup method on suppressing peak pressure, PCM can positively affect natural circulation heat transfer in the early stages of the accident. Empty tube startup offers the advantages of higher heat transfer capacity and lighter weight, making it the optimal choice for ocean nuclear platforms. Additionally, the higher peak power of PCM heat transfer under the empty tube startup method indicates that system can withstand larger thermal shocks.

Hierarchical microstructure changes of oriented poly(vinylidene fluoride) foam via supercritical carbon dioxide with increased piezoelectric performance

Light weight poly (vinylidene fluoride) (PVDF) has attracted wide attention for energy supply. In this work, oriented PVDF foams were prepared using supercritical carbon dioxide (CO2) physical foaming associated with a constraint mold. The corresponding micro-nanostructures and electrical performances were researched comprehensively. It reveals that the cell structure and molecular chains of PVDF foams are oriented due to the limitation of gas diffusion paths. Because of the realization of uniaxial stretching during cell growth, the β phase content is increased. Besides, after foaming, the regularity of the chain segments in amorphous region is improved, which is caused by the decrease in the quantity of free-volume cavities. The 1D-149 °C oriented PVDF foam exhibits a high voltage output (8 V), due to the ultralow dielectric constant (1.8) and high compressive strength. This study provides a theoretical foundation for the design of oriented PVDF foams, showing the potential of energy collector.