Poly Vinylidene Fluoride Composites Research Articles

Human motion interactive mechanical energy harvester based on all inorganic perovskite-PVDF

Benefited with the advantage of easy assembly and conformal structure, flexible and self-powered piezoelectric nanogenerators (PNGs) have become a sustainable and accessible energy alternative. Here, novel piezoelectric sensor is fabricated by a composite of room temperature processed all-inorganic cesium lead bromide (CsPbBr 3 ) perovskite rod and polyvinylidene fluoride (PVDF) nanofiber. CsPbBr 3 enables nucleation of electroactive β phase in PVDF >90% and makes it suitable for piezoelectric energy harvesting. Piezoelectric energy generation from the devices has been investigated under several simple human movements like hammering by hand, finger touch, toe pressing, bending by arm, etc. Optimized CsPbBr 3 -PVDF composite (with 5 wt% of CsPbBr 3 loading) based PNG delivered an output power 4.24 mW with high open-circuit voltage of 120 V and short-circuit current of 35 μA. Such high output value for the composite sample suggests much improved energy conversion efficiency as compared to the building blocks separately. Fatigue test of the PNG under continuous mechanical impact (over 4 months) showed its possibilities as a robust wearable mechanical energy harvester. This device is also able to light up several commercial LEDs. Increase in output values is attributed to the improved polarization in PVDF by CsPbBr 3 incorporation. Additionally, photosensitivity of the composite is demonstrated under light, which indicates its potential as photodetector. Considering the photoresponse and electroactive features, a new class of self-powered photoactive piezoelectric energy harvester has also been fabricated. Such results highlight the rational design of all inorganic perovskite based nanoforms in maximizing device performance and thereby providing a useful pathway to develop new materials for piezo-phototronics. • CsPbBr 3 perovskite has been utilized as a filler material in piezoelectric nanogenerator in PVDF matrix. • Strong cyan emission capability of the device is useful in optoelectronic fields. • PNG delivered an output power 4 mW with high open-circuit voltage of 120 V and a short-circuit current 35 μA. • DFT shows the change of electronic property in composite due to intercalation between Pb and F atom.

Hydrothermal carbon nanospheres assisted-fabrication of PVDF ultrafiltration membranes with improved hydrophilicity and antifouling performance

The hydrophobicity of polyvinylidene fluoride (PVDF) membrane in nature can result in permeability decline and critical membrane fouling, limiting its further development and application in the field of purification and separation. Novel composite PVDF ultrafiltration membranes containing 0.1–0.6 wt% of synthesized hydrothermal carbon nanospheres (CNS) were prepared with phase inversion method. The CNS had the mean diameter between 170 and 177 nm and the reactive oxygen functionalities such as hydroxyl, carbonyl, and carboxylic groups on outer carbon surface. The various characterizations revealed that the amount of CNS had a significant effect on composite membrane properties. The membrane of PVDF-2 exhibited the superior properties because of its lowest surface roughness and highest hydrophilicity, thermal stability, surface energy, porosity and mean pore size. Evaluations by pure water flux, bovine serum albumin (BSA) rejection and antifouling performance test further demonstrated the enhancement of membrane performance properties by the introduction of CNS into PVDF. The highest pure water flux, BSA rejection and flux recovery ratio (FRR) were achieved with the composite membrane blended with an amount of 0.2 wt% CNS (PVDF-2), reaching 956.72 L m−2 h−1, 95.8% and 83.21% respectively. The overall improved permeability and antifouling performance suggested a great potential application of carbonaceous spheres being used in composite PVDF membrane fabrication.

Effect of morphology and role of conductivity of embedded metallic nanoparticles on electromagnetic interference shielding of PVDF-carbonaceous-nanofiller composites

In this work, EMI shielding behaviors in the X-band frequency have been investigated for flexible polyvinylidene fluoride (PVDF) composites containing globular- and tubular-shaped carbonaceous nanostructures embedded with mono-metallic (Ni) and bi-metallic (FeNi, CoNi, MnNi) alloy nanoparticles. Pyrolysis was carried out at two different temperatures (800 °C and 1000 °C) to synthesize carbonaceous materials with two different morphologies. Carbon nanotubes (CNTs) are predominantly seen in the samples synthesized at lower temperature (800 °C), whereas carbon globules (CGs) are observed for the samples synthesized at higher temperature (1000 °C). The PVDF-CNT composites show superior microwave shielding behavior than the PVDF-CG composites, which is attributed to the enhanced absorption of the microwave through Ohmic conduction and interfacial polarization loss. The 1-D structure of CNTs provides the required conduction path for the electrons and forms a network to trap the microwave within them via multiple scattering. The microwave absorption behavior of the composites predominantly results from the metallic nature of the embedded nanoparticles, the graphitic layer encapsulating them and the graphitic walls of the CNTs. We further demonstrate the direct correlation of the EMI shielding behavior of the nanocomposites with the morphology of carbonaceous nanomaterials and the conductivity of the embedded metallic nanoparticles.

PVDF/ZnO composite films for photocatalysis: A comparative study of solution mixing and melt blending methods

AbstractHeterogeneous photocatalysis represents a solution for several environmental problems. However, achieving photocatalyst separation from reaction media on a large scale remains a challenge, one that might be overcome by the immobilization of photocatalysts into supports. To this end, composites of polyvinylidene fluoride and zinc oxide (ZnO) were prepared by three different techniques: solution mixing (SM) followed by Nonsolvent Induced Phase Separation; and melt blending at both low‐ and high‐shear rates (LS and HS) in a rheometer and mixing chamber, respectively, to compare the resultant morphology in photocatalysis. Photocatalytic efficiency was assessed by methylene blue (MB) discoloration in a batch reactor liquid phase and by resazurin (RZ) reduction. The changes promoted by nanoparticle inclusion, processing conditions and UV effect were demonstrated by FTIR‐ATR, XRD, DSC, and SEM. Results showed that ZnO incorporation was successful under all processing conditions, providing effective photocatalytic composites. However, samples prepared by SM had a twofold increase in discoloration efficiency and fourfold increase in surface photoactivity, when compared with LS or HS‐produced samples, explained by its higher porosity of 88% ± 1.3%. The covering of the photocatalyst surface was also evident on SEM analysis for melt blended samples, further contributing to reduction in their photocatalytic activity.

Comprehensive Analysis of Mechanical Properties of CB/SiO2/PVDF Composites.

Damage is a key problem that limits the application of polymer membranes. In this paper, conductive carbon black (CB) and silicon dioxide (SiO2)-reinforced polyvinylidene fluoride (PVDF) composites were prepared using a solution mixing method. Through a uniaxial tensile test, the fracture and damage characteristics of the material were analyzed. When the structure had inevitable notch damage, changing the notch angle was very helpful for the material to bear more load. In addition, when there were two kinds of fillers in the PVDF matrix at the same time, there was an interaction between particles. The microstructure of the composite was characterized by scanning electron microscopy (SEM), energy-dispersive spectrometry (EDS), and thermogravimetric (TG) analysis. The experimental results indicate that, when the ratio of CB:SiO2:PVDF was 1:4:95, the general mechanical properties of the composite were the best.

Interface modification and energy storage properties of barium titanate-based/ polyvinylidene fluoride composite

With the development of power electronic device equipment towards miniaturization and high performance, the dielectric materials with high energy storage density, high charge and discharge efficiency, easy processing and molding, and stable performance are urgently needed. At present, Barium titanate-based dielectric ceramics have a high dielectric constant, but low breakdown field strength and poor flexibility. Polymer-based dielectric materials have ultra-high functional density, ultra-fast charge and discharge response time, good flexibility, high breakdown field strength, light weight and other advantages, but low dielectric constant and low polarization strength. Their energy storage density is low, which limits the power capacitor component size and application scope. In order to obtain material with high energy storage performance, it was proposed to add high dielectric constant inorganic ceramic fillers to the polymer through a composite method to improve the energy storage performance of the material. The interface plays a vital role in the performance of the composite material. In this article, we review the latest research advance in the interface design and control of barium titanate/polyvinylidene fluoride composite dielectric materials. The effects of interface modification methods such as organic surface modification, inorganic functionalization and organic-inorganic synergistic modification on the polarization and energy storage performance of composite materials are summarized. The existing interface models and theoretical research methods are discussed, and the existing challenges and practical limitations, and the future research directions are prospected.

Flexible electrospun PVDF-BaTiO3 hybrid structure pressure sensor with enhanced efficiency.

Ceramic doped-polymer structures as organic and inorganic hybrid structures constitute a new area of advanced materials for flexible and stretchable sensors and actuators. Here, uniform ceramic-polymer composites of tetragonal BaTiO3 and polyvinylidene fluoride (PVDF) were prepared using solution casting to improve the pressure sensitivity. By introducing Ba–TiO3 nanoparticles to PVDF nanofibers, piezoelectricity and pressure sensitivity of hybrid nanofiber mats were significantly improved. In addition, we proposed a novel flexible and stretchable multilayered pressure sensor composed of electrospun nanocomposite fibers with high electrical sensitivity up to 6 mV N−1 compared to 1.88 mV N−1 for the pure PVDF sensors upon the application of cyclic loads at 2.5 Hz frequency and a constant load of 0.5 N. Indeed, this work provides a composition-dependent approach for the fabrication of nanostructures for pressure sensors in a wide variety of wearable devices and technologies.

Effects of suface hydroxylated strontium titanate nanofibers on dielectric and energy storage properties of polyvinylidene fluoride composites

With the rapid development of the electronics industry, the dielectric materials with high energy storage density, fast charge and discharge speed, easy-to-process and easy-to-mold, and stable performance are urgently needed to meet the requirements for lightweight and miniaturization of electronic component equipment. Dielectric ceramics has a high dielectric constant, but low breakdown field strength. Polyvinylidene fluoride (PVDF) has the advantages of good flexibility, high breakdown field strength, and light weight, but its dielectric constant is low. Achieving the ability to tailor the interface between dielectric ceramics filler and PVDF polymer matrix is a key issue for realizing the desirable dielectric properties and high energy density in the nanocomposites. As a result, much effort has been made to prepare the polymer composites through the surface modification of the nanoparticles with high dielectric constant fillers dispersed in a matrix, with the hope of preparing composites containing the high dielectric constant of the ceramic fillers and the high breakdown strength of polymers. In this work, in order to obtain the high dielectric-constant and high-energy-storage-density dielectric ceramics, the electrospinning method is used to prepare the SrTiO<sub>3</sub> one-dimensional nanofibers as the inorganic fillers and the casting method is adopted to prepare PVDF as the polymer matrix. To improve the interface between inorganic nanofiber fillers and PVDF matrix, the SrTiO<sub>3</sub> nanofibers are modified by surface hydroxylation. The effects of suface hydroxylated SrTiO<sub>3</sub> nanofibers on the dielectric properties and energy storage properties of PVDF composites are studied. The correlation between interface modification and energy storage performance of composites is investigated to reveal the mechanism of enhanced energy storage performance of SrTiO<sub>3</sub> nanofibers/PVDF composites. The results show that the dispersion of surface-hydroxylating SrTiO<sub>3</sub> nanofibers in PVDF polymer can be improved. The composites exhibit improved dielectric properties and enhanced breakdown strength. When the filling quantity of the surface-hydroxylating SrTiO<sub>3</sub> nanofiber fillers is 2.5 vol%, the energy storage density of the composite reaches 7.96 J/cm<sup>3</sup>. Suface-hydroxylating SrTiO<sub>3</sub> nanofibers exhibit excellent dispersion in the PVDF polymer matrix and strong interfacial adhesion with the matrix, leading the composites to possess excellent dielectric constant and energy storage performance. The surface hydroxylation of ceramic fillers can improve the energy storage performance of the composites.

In situ-grown organo-lead bromide perovskite-induced electroactive γ-phase in aerogel PVDF films: an efficient photoactive material for piezoelectric energy harvesting and photodetector applications.

The unique combination of piezoelectric energy harvesters and light detectors progressively strengthens their application in the development of modern electronics. Here, for the first time, we fabricated a polyvinylidene fluoride (PVDF) and formamidinium lead bromide nanoparticle (FAPbBr3 NP)-based composite aerogel film (FAPbBr3/PVDF) for harvesting electrical energy and photodetector applications. The uniform distribution of FAPbBr3 NPs in FAPbBr3/PVDF was achieved via the in situ synthesis of FAPbBr3 NPs in the PVDF matrix, which led to the stabilization of the γ-phase. The freeze-drying process induced an interconnected porous architecture in the composite film, making it more sensitive to small mechanical stimuli. Owing to this unique fabrication technique, the constructed aerogel film-based nanogenerator (FPNG) exhibited an output voltage and current of ∼26.2 V and ∼2.1 μA, respectively, which were 5-fold higher than that of the nanogenerator with the pure PVDF film. Also, the sensitivity of FPNG upon the irradiation of light was demonstrated by the output voltage reduction of ∼38%, indicating its capability as a light sensing device. Furthermore, the prepared FAPbBr3/PVDF composite was found to be an efficient candidate for light detection applications. A simple planar photodetector was fabricated with the 8.0 wt% FAPbBr3 NP-loaded PVDF composite, which displayed very high responsivity (8 A/W) and response speed of 2.6 s. Thus, this exclusive combination of synthesis and fabrication for the preparation of electro-active films opens a new horizon in the piezoelectric community for effective energy harvesting and light detector applications.

Effect of BaTiO3 on the sensing properties of PVDF composite-based capacitive humidity sensors

Capacitive humidity sensors consisting of materials such as polymers, ceramics, and piezoelectrics are widely used to monitor relative humidity levels. The effect of barium titanate (BaTiO3) nanoparticles on the humidity sensing properties, dielectric response, thermal stability, and hydrophilicity of the polyvinylidene fluoride (PVDF)-BaTiO3 composite films is investigated. Hydrophilicity and surface morphology of the PVDF-BaTiO3 composite films are modified for the development of a good humidity sensor. The nanocomposite solutions are prepared by mixing an optimized concentration (2.5 wt%) of PVDF with different concentrations (0.5, 1, and 2 wt%) of BaTiO3 nanoparticles. X-ray diffraction, thermogravimetric analysis, field emission scanning electron microscopy, and contact angle measurements are used to characterize the structure, morphology, thermal stability, and hydrophilicity of the spin-coated sensing films. The dielectric study of PVDF-BaTiO3 composite film shows that as the concentration of BaTiO3 particles increase, the dielectric constant of the composite films increases as well. PVDF-BaTiO3 (2.5 wt%-1 wt%) based capacitive sensors show stable capacitive response and low hysteresis as compared to the other concentrations of the PVDF-BaTiO3 composites. The maximum hysteresis of the capacitive PVDF-BaTiO3 (2.5 wt%- 1 wt%) humidity sensor is found to be ~2.5%. The response and recovery times of the PVDF-BaTiO3 (2.5 wt%-1 wt%) based capacitive sensors are determined as 40 s and 25 s, respectively, which are significantly lower than those reported for the other PVDF composite based sensors.

Effect of Adding BaTiO3 to PVDF as Nano Generator

Piezoelectric nanogenerator based on a composite structure formed of Polyvinylidene Fluoride (PVDF) as the matrix and Barium Titanate BaTiO3 nanospherical after dissolving them in a solvent of Dimethyl Sulfoxide DMSO/Acetone in (1/3 v/v) then spanning it’s homogeneous solution on Aluminum foil. structural and morphology analyses that of fabricated nanofibers characterized by X-ray diffraction, Scanning Electron Microscope and the electrical output of piezoelectric membrane devices was measured by using oscilloscope. The electrical output of different samples were measured for the pure powder PVDF and for composite PVDF& BaTiO3. The highest PVDF composite piezoelectrically generated voltage for samples with BaTiO3 (20%PVDF & 25% BT) wt. %. where improved to 6 V in general the addition of BT Nc increases the piezoelectric response of electrospun PVDFnanofibers.

Surface-concentrated chitosan-doped MIL-100(Fe) nanofiller-containing PVDF composites for enhanced antibacterial activity

Antibacterial properties are a major issue for the membrane-based wastewater treatment since the biofilm on membranes generated by bacterial growth can significantly reduce water flux. Here, the surface-concentrated MIL-100(Fe)/chitosan (MIL100-CS)-embedded polyvinylidene fluoride (PVDF) composite membranes (i.e., PVDF-S/MIL100-CS) were successfully fabricated by the newly developed fabrication method, so-called solvent-assisted nanoparticle embedding (SANE). The SANE method was modified from the conventional nonsolvent-induced phase separation method by the addition of an intermediate step for the selective arrangement of hydrophilic nanofillers on top of the nascent PVDF film. The additional step in the SANE method enabled the surface-selective filler distribution with the open surface of fillers, resulting in the hydrophilic surface. Also, it facilitated to form the sponge-like pore structures mostly due to the dilution effect of additional solvent. The PVDF/MIL100-CS microfiltration (MF) composite membranes acquired by SANE exhibited the higher antibacterial activity and the substantially enhanced biofouling resistance for E. coli cells than those of the pristine PVDF due to the surface-selective arrangement of MIL100-CS fillers which include both hydrophilic and biocidal properties. The live/dead test for antibacterial activities with E. coli cells further confirmed the enhanced suppression of the biofouling resistance in the asymmetric PVDF/MIL100-CS composite membranes relative to that of PVDF. Our current study offers a new platform for fabricating asymmetric MF composite membranes with enhanced antibacterial activity and biofouling resistance.

Carbonized Charcoal‐Loaded PVDF Polymer Composite: A Promising EMI Shielding Material

Microcomposites of charcoal‐loaded polyvinylidene fluoride (PVDF) polymer have been prepared by solution mixing and hot compression method for electromagnetic interference (EMI) shielding applications. Electrical conductivity, dielectric properties and EMI shielding efficiency of these composites have been studied in the X-band (8.2–12.4 GHz) frequency region. An increase in the conductivity from ~ 1.47 × 10−14 S/cm for pure PVDF to 23.2 S/cm for 80 wt.% charcoal‐loaded PVDF composite is obtained with improved mechanical strength. High effective dielectric constant $$ ( \in^{'} ) $$ value of 116.06 and dielectric loss $$ ( \in^{{\prime \prime }} ) $$ of 233.59 are obtained at a frequency of 8.2 GHz. A high value of total shielding (SET), shielding due to absorption (SEA) and shielding due to reflection (SER) are measured to be 70.1 dB, 59.3 dB and 9.2 dB, respectively, for 80 wt.% charcoal‐incorporated PVDF polymer composite, respectively. Dispersion studies suggest that SET of the charcoal‐loaded PVDF polymer composite is independent of frequency and is mainly absorption dominant which makes it a suitable material for EMI shielding applications.

Study on barium titanate and graphene reinforced PVDF matrix for 4D applications

This article reports the experimental investigations of polyvinylidene fluoride (PVDF) matrix-based composite feedstock filament (reinforced with barium titanate (BTO) and graphene (Gr) for possible 4-D printing applications) using fused deposition modeling (FDM). The mechanical, rheological, thermal, and morphological properties of in-house prepared FDM filament are also reported. The FDM feedstock filament was prepared with a twin-screw extruder (TSE). The process parameters of TSE for preparation of smart material-based filament with uniform dispersion of reinforcement (BTO and Gr) in the PVDF matrix have also been explored. Finally, the prepared filament has been used on FDM setup (without any change in hardware/software) for printing piezoelectric sensor with 4-D capabilities. The results of the study suggest that BTO and Gr have significant effect on the melt flow index of PVDF. The composite prepared with reinforcement of BTO and Gr shows a continuous flow, along with better thermal stability (based upon differential scanning calorimetry analysis), when 10–20 wt% BTO was added to the PVDF matrix. The observed maximum peak and break strength of the PVDF composite was 29.57 MPa and 26.50 MPa, respectively. The scanning electron microscopy and energy-dispersive X-ray analysis results reveal that the filament prepared with 20% BTO and extruded at 200°C with a screw speed of 40 r/min has better dispersion of reinforcement among the selected parametric settings. Finally, a piezoelectric response of 20 pC/N has been measured on the FDM-printed thermally stable sample suitable for 4-D applications.

Enhanced Wave Absorption and Mechanical Properties of Cobalt Sulfide/PVDF Composite Materials

A cobalt sulfide/PVDF(Polyvinylidene Fluoride) composite was prepared by a simple blending method, and the microstructure of the composite was investigated through X-ray diffraction, scanning electron microscopy, and field emission scanning electron microscopy. Increased absorption properties at frequencies ranging from 2 GHz to 18 GHz were studied, and the mechanical properties were investigated via tensile tests and finite element method simulations. The results indicated that the cobalt sulfide/PVDF composites exhibited strong microwave absorption intensities (−43 dB at 6.6 GHz) with a low filler loading (5.0 wt%). The elastic modulus increased with the cobalt sulfide mass fraction. Cobalt sulfide could improve the mechanical properties of the composite, especially in the lengthwise direction.

Ultra-High Electromagnetic Absorption Property of One-Dimensional Carbon-Supported Ni/Mo2C and Polyvinylidene Fluoride.

A novel one-dimensional carbon-supported Ni/Mo2C (Ni/Mo2C-C) nanocomposite with excellent electromagnetic wave absorption properties was successfully synthesized by annealing NiMoO4@PDA directly, and then the (Ni/Mo2C-C)/polyvinylidene fluoride (PVDF) composites were fabricated using a simple blending and hot-molding technique. An excellent reflection loss (RL) of −55.91 dB at 9.28 GHz with a low filler loading (15 wt%) and effective bandwidth (RL < −10 dB) of 14.12 GHz in the thickness range of 1.5–5.0 mm was obtained. Dielectric loss is considered to be the dominant mechanism of (Ni/Mo2C-C)/PVDF, which was confirmed by the Debye relaxation process and attenuation theory.

Piezoelectric and Dielectric Properties of (0.970(0.95(K0.485Na0.515) NbO3-0.05LiSbO3)-0.015CuO-0.015Al2O3)/PVDF Composites at Different Immersing Conditions

(KNNLS-CA)/PVDF composites were fabricated by a hot-pressing process using 0.970(0.95(K0.485Na0.515) NbO3-0.05LiSbO3)-0.015CuO-0.015Al2O3 (KNNLS-CA) ceramic powder and polyvinylidene fluoride (PVDF). The crystalline structures, morphology, densities, conductivity, dielectric and piezoelectric properties of (KNNLS-CA)/PVDF 0–3 composites were investigated. It is found that the phase structure is perovskite with orthorhombic symmetry for KNNLS-CA ceramic. When the ceramic content is 60 wt.%, the lattice strain reaches the maximum value. In addition, the ceramic particles can increase the relative fraction of the β-phase and restrain α-phase in PVDF matrix. By immersing the samples under different conditions (de-ionized water and NaOH/KOH solutions), it is found that K+ ions are easier to form electrolytes and enhance the dielectric properties. Water solution can delay the neutralization between alkali metal ions especially Na+ ions and space charges, and improve the piezoelectric properties. In this study, a dielectric constant as ultrahigh as 185723 is obtained at 0.2 M KOH (aq) (100 Hz), which is about 928 times higher than that of the untreated composites. The dielectric properties are well explained in terms of an interfacial percolation model. The piezoelectric coefficient as high as 75 pC/N is obtained at 0.05 M NaOH (aq) and increases more than 97% of that of untreated samples. All samples have good piezoelectric stability.

Influence of adding carbon black on electrical conductivity in dynamically vulcanized of poly (vinylidene fluoride)/fluoroelastomer composites

The present work was focused on studying the effects of different CB loadings on the rheological, thermal, tensile, dynamic mechanical, and electrical properties of polyvinylidene fluoride and FKM composites. To these ends, dynamic mechanical thermal analysis (DMTA) was conducted, and the CB grade and method chosen for compound preparation were CB (N330) by melt mixing with different shear effects were examined, respectively. The composites were melt-blended with CB at 190 °C in an internal mixer, after which the properties of filled and unfilled composites were compared. The DMTA analysis revealed that the area under the loss tangent (tanδ) peak decreased and that the tanδ temperature of the rubber phase increased with CB loading. The presence of CB improved the mechanical properties, such as the Young’s modulus and tensile strength, of the composites and increased thermal stability given the high thermal stability of CB and the interaction between the CB particles and the polymer matrices. The increase in the electrical conductivities of the composites under different CB loadings was also examined with different shear effects because of the different dispersion states of CB. The percolation threshold of conductive thermoplastic vulcanizate composite based on conductive CB was observed and the experimental data could be well fitted to the general equation model.

Dielectric and energy storage properties of PVDF/Nd-BaTiO3@Al2O3 composite films

Flexible Nd-doped BaTiO3@Al2O3/polyvinylidene fluoride (PVDF) composites have been successfully developed. With the reaction temperature of 70∘C, Nd-doped BaTiO3@Al2O3 particles display uniform core–shell structures and disperse well in the PVDF matrix. Due to the benign dielectric properties of Nd-doped BaTiO3 and great suppression of the Al2O3 coating on the leakage current and dielectric loss, the Nd-doped BaTiO3@Al2O3/PVDF composites with different Nd-doped BaTiO3@Al2O3 filling ratios (0–4[Formula: see text]vol.%) exhibit relatively good dielectric and energy storage performance. Among them, the maximum discharged energy density of 8.6[Formula: see text]J/cm3 was achieved in the composite with 1[Formula: see text]vol.% Nd-doped BaTiO3@Al2O3 loading.

A molecular level performance manipulation of thermal conductivity and moisture diffusivity through a composite membrane considering interfacial resistance

A molecular dynamics simulation (MDS) technique is used to study the heat and mass transfer inside the composite PVDF (polyvinylidene fluoride)/SiO2 (Si aerogel) bilayer membrane at molecular level. The reverse non-equilibrium molecular dynamics (RNEMD) simulation method is employed to determine the thermal conductivity at each layer and at the interface. Moisture diffusivity is also modeled by the mean square displacements (MSD) of water vapor in the materials. In combination with macro scale resistance models for porous media, the heat conductivity and moisture diffusivity through the whole membrane are calculated. It is found that the interface has a great influence on the membrane overall resistance, especially for thinner membranes. Molecular groups can be manipulated to adjust this resistance. When the hydroxyl groups are increased from 58% to 100%, the membrane overall heat conductivity can be increased by 57%, and the diffusivity can be increased by 48%. The fractional free volume, vibrational density of states (VDOS), adhesion energy, thermal and moisture resistance in each layer and at the interface are investigated to disclose the transport mechanisms. Membranes of low conductivity and high moisture diffusivity that are desired for air humidification applications can be obtained by such molecular level manipulations. By this work, a multi-scale model for interfacial heat and mass transfer resistance between two contacting materials, that considers both macro-scale roughness and porosity and micro-scale molecular interacting, is provided.