Nonpolar Α-phase Research Articles

Highly aligned thin PVDF/Cloisite 30B nanofibers as a piezoelectric sensor

One-dimensional confined nanostructures with intense dipole orientation exhibit enhanced piezoelectric performance compared to traditional three-dimensional bulk films. Herein, we show that preparing highly aligned thin polyvinylidene fluoride (PVDF) nanofibers in the presence of a small amount of organically modified clay (Cloisite 30B) platelets induces a significant crystal polymorphism alteration from non-polar α-phase to polar β-phase rather than the randomly oriented neat PVDF nanofibers with a larger average diameter. It has been detected that the nanofiber orientation considerably contributes to the enhanced degree of crystallinity and mechanical properties. Also, the PVDF-Cloisite 30B interactions caused an improvement in the elastic modulus. The piezoelectric performance of the electrospun nanofibers was examined by sensing characteristics. It was found that the synergistic effects of nanofiber orientation and clay platelets efficiently improve sensing performance via the piezoelectric dipole orientation mechanism.

The Effect of Electric Aging on Vinylidene Fluoride Copolymers for Ferroelectric Memory.

Copolymers based on vinylidene fluoride are potential materials for ferroelectric memory elements. The trend in studies showing that a decrease in the degree of crystallinity can lead to an unexpected increase in the electric breakdown field is noted. An analysis of the literature data reveals that in fluorine-containing ferroelectric polymers, when using a bipolar triangular field, the hysteresis loop has an unclosed shape, with each subsequent loop being accompanied by a decrease in the dielectric response. In this work, the effect of the structure of self-polarized films of copolymers of vinylidene fluoride with tetrafluoroethylene and hexafluoropropylene on breakdown processes was studied. The structure of the polymer films was monitored using infrared spectroscopy (IR) and X-ray diffraction. Kelvin probe force microscopy (KPFM) was applied to characterize the local electrical properties of the polymers. For the films of the first copolymer, which crystallize in the polar β-phase, asymmetry in the dielectric response was observed at fields greater than the coercive field. For the films of the copolymers of vinylidene fluoride with hexafluoropropylene, which crystallize predominantly in the nonpolar α-phase, polarization switching processes have also been observed, but at lower electric fields. The noted phenomena will help to identify the influence of the structure of ferroelectric polymers on their electrical properties.

Controlling the polymorphs of PVDF membranes: Effects of a salt additive on PVDF polarization during phase separation processes

Polyvinylidene fluoride (PVDF) membranes, acclaimed for their outstanding chemical resistance, thermal stability, and mechanical properties, play a crucial role in diverse industrial purification applications. While various methods have been employed for fabricating PVDF membranes such as thermally induced, evaporation-induced, vapor-induced, and nonsolvent-induced phase separation processes, controlling the polarity of PVDF chains using these techniques remains challenging. Recent studies have shown that the nonpolar α-phase PVDF is susceptible to organic acid fouling owing to hydrophobic interactions, whereas the β-phase PVDF has demonstrated polarity and offers antifouling properties. Herein, porous PVDF membranes predominantly composed of the β-phase were successfully fabricated by incorporating a small amount of LiCl salt into the PVDF dope solution. The addition of LiCl influences ion–dipole moments between ions and PVDF during phase separation, simultaneously affecting the PVDF chain arrangement and membrane morphology. Since the LiCl additive alters both the pore size and structure of PVDF membranes, both freestanding and non-woven supported membranes were prepared and characterized to assess the effects of polarity and pore size on fouling tendency. Characterizations of prepared PVDF membranes revealed considerable changes in the PVDF polymorph, membrane morphology, pore size, and antifouling properties upon introducing the salt additive. Our findings imply that β-phase–dominant PVDF membranes can be effectively utilized in water purification applications.

Effects of stretching on phase transformation of PVDF and its copolymers: A review

Abstract Poly(vinylidene fluoride) (PVDF) and its copolymers are promising candidates for energy-harvesting devices because of their flexibility, environmental friendliness, lightweight, and high halogen and acid resistance. However, the relatively low piezoelectricity limits their applications. The piezoelectricity of PVDF and its copolymers highly depends on the polar β-phase, while the non-polar α-phase is the most common one. As a result, the β-phase formation and α- to β-phase transformation have attracted much attention in recent years. Stretching is a widely used method to induce the α- to β-phase transformation for the improvement of piezoelectricity. In this work, the influences of the parameters during stretching on phase evolution and piezoelectricity are discussed and summarized. Besides, nontraditional stretching methods are also introduced and discussed. This work will provide important information for preparing high-performance piezoelectric polymer films.

Supersonically sprayed PVDF and ZnO flowers with built-in nanocuboids for wearable piezoelectric nanogenerators

Healthcare implant devices that can internally generate a flow of electrical charge driven by mechanical stimuli are in demand. Such self-powered electromechanical devices are known as piezoelectric nanogenerators (PENGs). In this study, a piezo-ceramic element of hydrothermally synthesized ZnO flowers comprising built-in nanocuboids was supersonically sprayed with piezo-polymer polyvinylidene fluoride (PVDF) to fabricate ZnO-embedded PVDF films for flexible PENG devices. In the presence of ZnO, the catastrophic supersonic impact and shear flow transformed the nonpolar α-phase of PVDF into the polar β-phase. The combination of ZnO flowers with built-in nanocuboids and β-phase-rich PVDF can help enhance generated charges at interfacial sites under an applied force. The supersonically sprayed PVDF/ZnO composite exhibited a 32% increase in the β-phase compared to that exhibited by pure PVDF prior to supersonic coating. The effective piezoelectric coefficient values (d33*) of the pure PVDF and PVDF/ZnO composite films were 43 and 150 pm·V‐1, respectively; the corresponding open-circuit voltages were 1.2 and 25.5 V, respectively. These significant differences confirm the pivotal role of ZnO in increasing the β-phase within PVDF during supersonic spraying. The form of the externally applied force and frequency were varied to evaluate the electromechanical performance of PVDF/ZnO. The energy harvesting capability of the composite was demonstrated using 33 light-emitting diodes.

FTIR studies on interactions among components in PVdF-HFP:PC:MPII electrolytes

Liquid electrolytes are known to have high conductivities. However, they suffer from leakage, corrosion of electrodes and other stability issues. Solid polymer electrolytes eliminate the problems of liquid electrolytes at the cost of lower conductivity. Quasi-solid-state polymer electrolytes (QSSPE) overcome the shortcomings of both liquid electrolytes and solid polymer electrolytes. In this work, QSSPE is prepared by incorporating poly(vinylidene fluoride-co-hexafluoropropylene) (PVdF-HFP) in a propylene carbonate (PC) and 1-methyl-3-propyl imidazolium iodide (MPII) liquid electrolyte. Fourier transform infrared (FTIR) studies have been carried out to investigate the interactions among PVdF-HFP, PC and MPII. A comprehensive spectroscopic investigation on ion-solvent-polymer interactions helps to understand the mechanism of ionic conduction in the PVdF-HFP/PC/MPII electrolyte system. Interaction between MPII and PC has occurred from the changes in the ν(C=O), ν(C-O) + ω(C-H), ω(C-H) + δ(C-H) and τ of ring of PC as well as the C-N bond oscillation and of (N-C-H) of MPII. Interaction occurs via the coordination of MPIm+ cations with both oxygen atoms of PC. Complexation between PVdF-HFP and MPII has been noted. MPII suppresses the non-polar α-phase and induces the polar β and -phases of PVdF-HFP. Shift of peaks belong to the CF2 and CF3 groups of PVdF-HFP suggests the complexation occurs at the fluorine atoms in CF2 and CF3 groups. Evidence of interaction between PC and PVdF-HFP has been manifested through the change of the ν(C=O), τ(C-H) + δ(C-H) and ν of the CF2 group of PVdF-HFP. Disappearance of non-polar α-phase of PVdF-HFP is noted in the presence of PC. From this work, the authors hope to shed some light on understanding the conduction mechanism in PVdF-HFP:PC:MPII electrolytes. Understanding the conduction mechanism is important in order to find ways for conductivity improvement.

Hybrid Nanofillers Creating the Stable PVDF Nanocomposite Films and Their Effect on the Friction and Mechanical Properties.

The solvent casting method was used for five types of polyvinylidene difluoride (PVDF) nanocomposite film preparation. The effect of nanofillers in PVDF nanocomposite films on the structural, phase, and friction and mechanical properties was examined and compared with that of the natural PVDF film. The surface topography of PVDF nanocomposite films was investigated using a scanning electron microscope (SEM) and correlative imaging (CPEM, combinate AFM and SEM). A selection of 2D CPEM images was used for a detailed study of the spherulitic morphologies (grains size around 6–10 μm) and surface roughness (value of 50–68 nm). The chemical interactions were evaluated by Fourier transform infrared spectroscopy (FTIR). Dominant polar γ-phase in the original PVDF, PVDF_ZnO and PVDF_ZnO/V, the most stable non-polar α-phase in the PVDF_V_CH nanocomposite film and mixture of γ and α phases in the PVDF_V and PVDF_ZnO/V_CH nanocomposite films were confirmed. Moderately hydrophilic PVDF nanocomposite films with water contact angle values (WCA) in the range of 58°–69° showed surface stability with respect to the Zeta potential values. The effect of positive or negative Zeta-potential values of nanofillers (ζn) on the resulting negative Zeta-potential values (ζ) of PVDF nanocomposite films was demonstrated. Interaction of PVDF chains with hydroxy groups of vermiculite and amino and imino groups of CH caused transformation of γ-phase to α. The friction properties were evaluated based on the wear testing and mechanical properties were evaluated from the tensile tests based on Young’s modulus (E) and tensile strength (Rm) values. Used nanofillers caused decreasing of friction and mechanical properties of PVDF nanocomposite material films.

Fabrication of intra porous PVDF fibers and their applications for heavy metal removal, oil absorption and piezoelectric sensors

Intra porous fibrous membranes have enhanced metal ionic adsorption and oil separation abilities than those of intra nonporous fibrous membrane. In this paper, we prepared highly intra porous fibrous poly (vinylidene fluoride) (PVDF) membranes using an innovated water-mediated electrospinning approach. FTIR-ATR and XRD techniques confirmed the conversion of non-polar α-phase to polar β-phase in electrospun membranes. The porous fibrous membrane M–16 had adsorbed oil almost 120% and metal adsorption around 15%, 12%, 5%, 13% respectively for Pb2+, Cd2+, Cu2+ and Zn2+, which are larger than the counterpart of nonporous M–18. The nonporous fibrous membranes have better peak to peak output voltage (Vp-Vp) 2 to 3 times than the porous fibrous membranes (M–16). The results show apparent potential applications in wastewater/oil spill treatment as well as piezoelectric sensors.

Structure formation and depolarization relaxation processes in porous piezoactive polyvinylidene fluoride films

Piezoactive porous polyvinylidene fluoride films prepared in the process based on melt extrusion with subsequent isometric annealing, uniaxial extension and thermal fixation have been studied. It was shown that two competing orientation processes -polymorphous transition of non-polar α-phase into polar piezoactive β-phase and formation of porous structure - occur during the uniaxial extension of annealed films. It has been established that orientation degree of extruded films is the key factor determining the efficiency of both processes. Thermally stimulated depolarization method was used to investigate the dipole relaxation in oriented films, and activation energy of these processes was found. The films were polarized using corona discharge and high-voltage contact methods, both, and the dependence of piezoelectric modulus on the polarization conditions has been obtained. The maximum value of piezoelectric modulus d31=30.1 pC/N was achieved by polarization of films in corona discharge method. Keywords: polyvinylidene fluoride, porous films, supramolecular structure, piezoelectric properties, polarization, relaxation processes.

Revisiting δ-PVDF based piezoelectric nanogenerator for self-powered pressure mapping sensor

δ-phase comprising polyvinylidene fluoride (PVDF) nanoparticles are fabricated through an electrospray technique by applying a 0.1 MV/m electric field, which is 103 times lower than the typical value, required for δ-phase transformation. X-ray diffraction and selected area electron diffraction patterns clearly indicate the δ-phase formation that limits the infrared vibrational spectroscopic technique due to identical molecular chain conformations to that of non-polar α-phase. The piezo- and ferro-electric response of δ-PVDF nanoparticles have been demonstrated through a scanning probe microscopic technique based on piezoresponse force microscopy. The localized piezoelectric response, indicated by d33 coefficient, is found to be ∼−11 pm/V. To utilize the distinct electromechanical response of δ-PVDF nanoparticles, the piezoelectric nanogenerator (PNG) has been fabricated. Due to the stress confinement effect in the spherical shape of δ-PVDF nanoparticles, the PNG exhibits synergistic effect than that of the film-based counterpart. The maximum power, i.e., 930 μW/m2 determined by the PNG under ∼4.5 N of periodic force impact, indicates the potential to use it as a self-powered sensor. As a proof of concept, a self-powered pressure sensor mapping has been demonstrated for representing its realistic technological applicability.

Effect of Ions on the Flow-Induced Crystallization of Poly(vinylidene fluoride)

The flow-induced crystallization of poly(vinylidene fluoride) (PVDF)–ion composites in the presence of externally added ions was investigated by in situ wide-angle X-ray diffraction (WAXD) and ex situ Fourier transform infrared (FTIR) spectroscopy. In this work, two types of hexadecyl trimethyl ammonium bromide (CTAB) and tetrabutylammonium hydrogen sulfate (TBAHS) ions with distinct electrostatic interactions were chosen at a weight concentration of 0.5% to design different influences on crystallization. For quiescent crystallization, TBAHS ions induced the appearance of the polar γ-phase with accelerated kinetics, but CTAB ions exhibited no detectable influence in the crystallization of the nonpolar α-phase as in neat PVDF. Interestingly, flow induced the formation of β-phase with prominent piezo/ferroelectricity and the presence of ions could increase the amount of this flow-generated β-phase. With a strain of 2.7 applied at 1 s–¹, the CTAB and TBAHS ions increased the crystallinity index of the β-phase obtained just after the flow to 2.4 and 3.6%, respectively, with respect to that of 2.0% in neat PVDF. In addition, the ions could increase the enhancement amplitude of the flow-generated β-phase by increasing the strain rate over a broad range from 0.01 to 10 s–¹. Moreover, both CTAB and TBAHS ions induced the crystallization of the γ-phase during the isothermal process at a high temperature of 160 °C, where the α-phase appearing in neat PVDF was completely suppressed.

Synthesis of Silver Nanoparticles from Mimusops elengi Extract of Raw Fruits and Characterization of PVA-Silver Polymer Nanocomposite Films

The present work concerns on the synthesis of silver nanoparticles at 25 ºC using raw fruits extract of Bakul (Mimusops elengi) tree via chemical reduction route development of poly(vinyl alcohol) PVA-silver polymer nanocomposite films. The nanocomposite films were subjected to characterization by UV-visible, FTIR, X-ray diffraction, field emission scanning electron microscope (FESEM) and thermal studies. The UV-visible spectrum shows a characteristic broad absorption band observed near 465 nm suggesting presence of silver nanoparticles in polymer nanocomposites (PNCs) film. The vibrational band shift of –OH group of poly(vinyl alcohol) in the presence of nanoparticle designated the chemical interaction between –OH group of poly(vinyl alcohol) and silver nanoparticles. The FESEM study confirmed that PVA is not only acted as a capping agent, but also a cross-linking agent. X-ray diffraction study shows that the existence of AgNPs in the poly nanocomposite film and nanoaparticles are crystalline in nature. Thermal studies suggest that the enhanced thermal stability is because of the good packing of the polar crystallites in β-PVA composites as compared to the non-polar α-phase of neat poly(vinyl alcohol) (PVA).

Influence of annealing temperature on the existence of polar domain in uniaxially stretched polyvinylidene-co-hexafluoropropylene for energy harvesting applications

The structural and electroactive properties of the as-prepared random copolymer polyvinylidene-co-hexafluoropropylene thin film are explored as a function of thermal treatment at various temperature regions. The thermal treatment of the polymer thin film not only changes the structural conformations that is very natural but establishes a polar domain in the non-polar α-phase. Here, we discover an anomalous temperature-dependent crossover behavior from the non-polar α-phase to an appreciable enhancement in ferroelectric and piezoelectric responses. The maximum unipolar strain (Smax=−5.01%), an ultrahigh value of normalized piezoelectric coefficient (d33∗=−556pm/V), high electromechanical coupling factor (Kp=0.78) factor including the high dielectric constant (ϵ′=23at100Hz) at a relatively low electric field of 900 kV/cm may, therefore, be an effect of the established polar domain for the sample annealed at 105 °C. The direct piezoelectric charge coefficient (d33), a key factor for the performance of a prepared polymer thin film system as an energy harvester, lies in the range of −10±2pC/N. Also, the annealed sample exhibited a persistent polarization after several cumulative cycles of applied stress.

Ultrathin-shell PVDF/CNT nanocomposite aligned hollow fibers as a sensor/actuator single element

To facilitate a single element with the promoted dual sensing and actuation functionality, compared to the conventional individual sensors and actuators, different kinds of piezoelectric structures should be evaluated. Here, finite element method (FEM) simulations together with some aspects of the nanotechnology afforded an opportunity to simplify structure tailoring of the high performance sensor/actuator single element. First, we prepared ultrathin-shell poly (vinylidene fluoride) (PVDF) aligned hollow nanofibers. This geometrically confined nanostructure with low dielectric constant of ~3.6, efficiently increased strain, yielded to enlarge the piezoelectric voltage by ~250%, bending actuation by ~38%, and the β-phase content by ~18% when compared to the random solid nanofibers. Second, ~108% increase in sensitivity from 450 mV/N to 940 mV/N and ~21% increase in piezoelectric actuation from 14.8 μm to 18 μm obtained by addition of 0.05 wt% carbon nanotubes (CNTs) to PVDF aligned hollow nanofibers. Taking advantage of this hollow nanocomposite structure, ~45% improvement in crystallinity, ~263% enhancement in elastic modulus and complete removal of the nonpolar α-phase were occurred. The sensor/actuator single element would guarantee the adaptability, interconnectedness, and autonomy of the next generation robots, allow the size, weight, and cost of the system to be re-evaluated.

Development of In-Situ Poled Nanofiber Based Flexible Piezoelectric Nanogenerators for Self-Powered Motion Monitoring

Energy harvesting technologies have found significant importance over the past decades due to the increasing demand of energy and self-powered design of electronic and implantable devices. Herein, we demonstrate the design and application of in situ poled highly flexible piezoelectric poly vinylidene fluoride (PVDF) graphene oxide (GO) hybrid nanofibers in aligned mode for multifaceted applications from locomotion sensors to self-powered motion monitoring. Here we exploited the simplest and most versatile method, called electrospinning, to fabricate the in situ poled nanofibers by transforming non-polar α-phase of PVDF to polar β- phase structures for enhanced piezoelectricity under high bias voltage. The flexible piezoelectric device fabricated using the aligned mode generates an improved output voltage of 2.1 V at a uniform force of 12 N. The effective piezoelectric transduction exhibited by the proposed system was tested for its multiple efficacies as a locomotion detector, bio-e-skin, smart chairs and so on.

Structure tailorable triple-phase and pure double-polar-phase flexible IF-WS2@poly(vinylidene fluoride) nanocomposites with enhanced electrical and mechanical properties

A new low-cost high-permittivity flexible nanocomposite consisting of a polyvinylidene fluoride (PVDF) matrix and fullerene-like tungsten disulfide nanoparticle (IF-WS2 NP) filler was fabricated via a simple solution route. A comprehensive investigation by X-ray diffraction, attenuated total reflection-infrared spectroscopy, and differential scanning calorimetry (DSC) showed that 0.5–1 vol% of IF-WS2 induced a nonpolar α-phase to coexisting triple-phase transition in PVDF, whereas a slightly higher loading of 2 vol% induced pure double-polar β- and γ-phases. These results indicate that the structure and properties of the fabricated nanocomposite are easily tailorable. DSC during heating and cooling cycles and morphology observations further indicated that a polar phase was induced by the nucleation effect of the IF-WS2 NPs and electrostatic interactions. As a consequence of the multiphase coexistence and structure homogeneity, nanocomposites with approximately 0.5–1 vol% of IF-WS2 NPs showed enhanced dielectric and energy-storage performance as well as enhanced tensile strength and elongation. The new phase-tailorable nanocomposites with balanced properties are promising for applications as energy-storage capacitors, piezoelectric sensors, and other flexible multifunctional components. The results of this study will serve to deepen the understanding of the polymer polymorph and provide directions on new routes for fabrication of smart materials.

Wear-resistant carbon nanorod-embedded poly(vinylidene fluoride) composites with excellent tribological performance

High-tribological performance composites were prepared by incorporating wear-resistant carbon nanorod (CNR) fillers into a poly(vinylidene fluoride) (PVDF) matrix. CNRs with a diameter of 300 nm were synthesized via electrospinning a polyacrylonitrile solution followed by pyrolysis. The incorporation of the CNR filler increased the fraction of the non-polar α-phase in the PVDF matrix, which improved the friction and interfacial adhesion properties of the composites. The composites showed excellent frictional performance and wear resistance owing to self-lubricating property and scaffold effect of the CNR filler. The lowest friction coefficient was obtained at the CNR loading of 10 wt%. Compared to neat PVDF, the friction coefficient and wear rate of the PVDF/CNR composite with 10 wt% CNR loading decreased significantly from 0.43 to 0.03 and 8.43 × 10−5 to 3.70 × 10−5 mm3/N m, respectively. These values represent excellent tribological performances for polymer-based composites.

Effect of hot press temperature on β-phase, dielectric and ferroelectric properties of solvent casted Poly(vinyledene fluoride) films

Poly(vinylidene fluoride) (PVDF) films were prepared by solvent casting at different temperatures (40 °C, 50 °C, 60 °C) and each solvent casted film were hot pressed at 110 °C, 130 °C and 150 °C. The transition of electroactive β-phase from non-polar α-phase is deeply influenced by hot pressing temperature. Phase transition was studied by x-ray diffraction (XRD) and fraction of β-phase was calculated by analyzing Fourier Transform infrared (FTIR) spectra. Differential Scanning Calorimetry(DSC) was performed for all the samples to determine degree of crystallinity. Dielectric constant increased with increase in β-fraction. Remnant polarisation(Pr) and Coercive field(Ec) from ferroelectric hysteresis loop were influenced by both β-fraction and degree of crystallinity.

Effect of Poly Vinylidine Addition on Structural and Electrical Properties of Nickel Zinc Ferrite

Samples of Ni0.3Zn0.7Fe2O4 and composite films of x% Ni0.3Zn0.7Fe2O4 /PVDF, (x%=5, 10, 15, 20 and 25%) were synthesized by high energy ball milling. The sample milled at 90 hour shows that the intensity peaks of initial oxides reduced during ball milling process and completely disappeared by annealing to 1373 K. There are 2 peaks at (2θ = 18.6 and 27°) corresponding to planes (020) and (021) which are attributed to α- phase of (PVDF) where β-phase of PVDF is characterized by the peaks at (2θ = 20.8°) corresponding to the (110) planes. The phase transformation from the non-polar α-phase to the polar electroactive β-phase of PVDF by increasing NZF content has been investigated by XRD analysis and FTIR spectroscopy. The DC resistivity of the composite samples at room temperature reaches maximum at 5% NZF, above this ratio it begins to decrease. The dielectric constant and dielectric loss were studied at constant frequency.

Shielding Effectiveness Study of Barium Hexaferrite-Incorporated, β-Phase-Improved Poly(vinylidene fluoride) Composite Film: A Metamaterial Useful for the Reduction of Electromagnetic Pollution.

The present work reports the high electromagnetic interference (EMI) shielding effectiveness of ∼-93.5 dB at 8.63 GHz and -97.6 dB at 8.61 GHz in the X- and Ku-bands for 10 and 20 wt % of barium hexaferrite (BaH) nanoparticle-loaded poly(vinylidene fluoride) (PVDF)-based composite films with a thickness of ∼0.210 and 0.260 mm, respectively. BaH-PVDF composite films with a layer structure have been considered in the present report in order to establish an excellent EMI shielding material for the suppression of electromagnetic pollution, with good control on flexibility, surface area, and thickness. Structural and morphological measurements reveal that the polar β-phase crystallization of the BaH-PVDF composite films has been enhanced in comparison to the pure PVDF film, and these measurements also reveal the influence of BaH nanoparticles on structural alteration from nonpolar α-phase to the polar/electroactive β-phase of the PVDF matrix. The resultant BaH-PVDF composite films produce multiple interfaces between magnetic BaH nanoparticles and β-phase-enriched electroactive PVDF, which plays the most significant role for the enhancement of the EMI shielding effectiveness (SE) in the microwave/GHz frequency range. This high value of the EMI SE with >99.999999999% attenuation has not been found so far in the PVDF-based composite materials by anyone else. This particular feature of BaH-PVDF composite materials suggests that the BaH-PVDF composite films can be considered as the most useful ones for the fabrication of lightweight, flexible, and thickness-controlled EMI shielding materials for the reduction of pollution created by the electromagnetic waves in the microwave/GHz frequency region.