Composite Thick Films Research Articles

Flexible, robust, sandwich structure polyimide composite film with alternative MXene and Ag NWs layers for electromagnetic interference shielding

The design and fabrication of electromagnetic interference shielding films with a novel structure to eliminate undesirable electromagnetic pollution is an important research direction. However, it is still a challenge to combine and organize nanofillers in different dimensions into the structured network in polymer-based electromagnetic interference (EMI) shielding composites. In this work, a sandwich structure polyimide (PI) composite film with alternative 2D-MXene network and 1D-Silver nanowires (Ag NWs) network was prepared through the “electrospinning-immersion-hot pressing” method. With the increase of Ag NWs content, the EMI shielding effectiveness (SE) gradually increases while maintaining good flexibility and mechanical robustness. The EMI SE and the tensile strength of 150 μm thick sandwich composite film can reach up to 79.54 dB and 39.82 MPa, respectively. The prepared flexible and robust PI composite film with a sandwich structure has high EMI SE with less metal content, which can provide guidelines for the development of high-performance EMI polymeric films with potentials in wearable devices and equipment.

Micro size developed TiO2-CdO composite film: Exhibits diode characteristics

TiO2-CdO composite thick film deposited on Si substrate was characterised for diode applications. X-ray Diffraction (XRD) confirms the existence of anatase phase of TiO2 and a cubic phase of CdO with a maximum diffraction at (101) plane. Porous surface morphology was recognized from scanning electron microscope (SEM).The UV–visible spectra have revealed a direct band gap of 3.17 eV while photoluminescence spectra and CIE diagram show blue-green emissions at 2.33 eV. Diode parameters such as ideality factor (n) and barrier height (Φb) have been calculated with the aid of I-V characteristics. Thus extracted results indicate the suitability of TiO2-CdO composite thick films for photovoltaic applications.

Effect of Thickness Ratio on the Magnetic Properties of the Magnetostrictive Thin Film Composite

Magno-elastic coupling characteristics in giant magnetostrictive thin films depend on a myriad of factors, comprising variability in Young’s modulus, thermally induced pre-stresses, the direction of the applied magnetic field and the substrate to film thickness ratio, demagnetization field etc. Due to the aforementioned reasons, the giant magnetostrictive thin films usually display characteristics that may contrast with the bulk giant magnetostrictive materials. This work studies magnetostrictive film on a compliant substrate using a generalized 3-D magneto-thermo-elastic nonlinear constitutive model with the elasticity theory to include such stimuli sensitive coupled magneto-thermo-elastic response. The numerical simulation of the magnetostrictive film on the compliant substrate in the form of a cantilever shows good agreement with the existing experimental data. The substrate and film thickness ratio effect on the thermal strain, Young’s modulus, magnetization and magnetostriction of films was meticulously analyzed. It has been revealed that the magneto-elastic responses rely strongly on the substrate-to-film thickness ratio. Thus, it is possible to obtain the tunable properties by controlling the composite film's thickness ratio in the design state of smart devices.

Methylammonium bromocuprate (MeNH3)2CuBr3 as a new self-absorption-free solution-processable X-ray scintillator

We report the radioluminescent properties of the recently discovered hybrid bromocuprate (MeNH3)2CuBr3 in a poly(methyl methacrylate) matrix in the form of solution- produced composite thick films. The obtained films demonstrate bright turquoise photoluminescence in UV light and intense radioluminescence due to CuKα and AgKα radiation at room temperature, exceeding the radioluminescence intensity of Cs4PbBr6@CsPbBr3 films by more than an order of magnitude.

Study on the properties of solid solution of screen-printed SnTe0.5Se0.5 composite film

Tin Chalcogenide alloys and their solid solutions have been investigated largely in last few years because by changing the composition the band gap can be tailored and then their physical properties as well. In present study SnTe0.5Se0.5 alloy were prepared by direct reaction of tin, tellurium, and selenium in elemental form. SnTe0.5Se0.5 composite thick films were obtained on glass substrate by employing cost efficient screen-printing technique. Structural, morphological / compositional, optical and photoconductive properties of thick film of the solid solution of SnTe0.5Se0.5 alloy were investigated. Structure and lattice constants of film were studied from x-ray diffraction. Surface morphology and composition of the film was studied through SEM/EDAX. Energy band gap of the film were investigated by diffuse reflectance spectra. Photoconductive and photo-sensing properties of the film were studied as a function of wavelength and intensity respectively.

Flexomagnetic effects on inhomogeneously strained multiferroics composites

Herein, the origin of flexomagnetic effect in Pb[(Zr0.52Ti0.48)0.60(Fe0.67W0.33)0.40]O3]0.80-[CoFe2O4]0.20 (PZTFW–CFO) multiferroic composite is demonstrated. An external inhomogeneous strain on thick composite films significantly changes the crystal lattice constants and phonon wave numbers related to single-phase PZTFW and CFO ceramics. Surface morphology indicates that inhomogeneous strain modified the magnetic dipole moments that partly regain their original position after removing external inhomogeneous strain. The magnitude of magnetic susceptibility increased under inhomogeneous strain for a small probe of the magnetic field. The magnetic anisotropic energy (MAE) supports that under-applied inhomogeneous strain reduces surface spin disorders and is responsible for the enhancement of zero field cooled (ZFC) and field cooled (FC) magnetization. Under a high external magnetic field (>100 Oe), it would be hard to detect the weak flexomagnetic effects. This work provides a framework for the effect of macroscopic inhomogeneous strain gradient on magnetic moments in multiferroics composites suggesting its suitability for the sensors and actuators applications.

Structural, capacitive and impedance properties of graphene oxide-PVDF composites for flexible electronics

Flexible composite thick films of polyvinylidene fluoride ‘PVDF’ loaded with graphene oxide ‘GO’ as reinforcement were prepared using solution casting method. The PVDF:GO ratio was selected as 100:0 (R0), 50:50 (R5) and 40:60 (R6). The structural properties were analysed using X-ray diffraction investigations. Dielectric constant ‘ɛ’ and tangent loss ‘tanδ’ was measured as a function of frequency (1kHz to 1MHz) at different temperatures from 30 to 150°C for all the samples. Impedance ‘Z’ and capacitive modulus ‘M’ was calculated. The compositional effect on the electrical properties was investigated and a correlation was developed between the composition and property. The evaluated results suggest that the prepared composites for flexible electronic applications.

Comparison of dielectric properties of sol–gel derived pure and calcium modified lead zirconate titanate ceramics and thick films of compositions near MPB

In this work, pure and calcium modified lead zirconate titanate thick composite films of compositions near morphotropic phase boundary (Pb(1−x)CaxZr0.52Ti0.48O3; where x = 0, 0.06, 0.1) have been fabricated on platinized silicon (Pt(111)/Ti/SiO2/Si) substrate using modified sol–gel technique and employing infiltration process. The XRD patterns of the films annealed at 750 °C possess pure perovskite phase. The films are dense, free of cracks and the thickness of the films is more than 25 µm as revealed by scanning electron microscopy (SEM). The films have high dielectric constant values at room temperature and though lower but comparable in magnitude with those for corresponding sol–gel derived bulk ceramic compositions. With increasing calcium concentration, both bulk samples and thick films show decreasing trend of room temperature dielectric constant. Temperature dependence of dielectric constant show that the ferroelectric-paraelectric phase transition in the case of thick films is gradual and broader while it is comparatively much sharper for the corresponding bulk samples. In sol–gel derived bulk samples the TC decreases with increasing calcium concentration while it is same for all the studied compositions of the thick films.

Investigation of transport properties, flux pinning mechanisms and fluctuations induced conductivity of SiO2 nanoparticles doped YBa2Cu3O7-d thick films on silver substrates

In this study, we examined the pinning mechanism and fluctuations induced conductivity, and we report the superconducting critical parameters variation of fine SiO2 nanoparticles added YBa2Cu3O7−d (Y123) composite thick films of ∼100 μm in thicknesses on Ag substrate. Composite films (Y123 + x SiO2)/Ag were produced by the solid-state reaction process. Here, x = 0.00 and 0.01 wt% content of SiO2 nanoparticles (12 nm in diameter) were considered. The X-ray powder diffraction (XRD) together with Rietveld refinement and the scanning electron microscopy (SEM) were used to survey the structure and the morphology of thick films. Both composite films reveal a dense granular structure and similar compositions in phases. A small quantity of fine SiO2 particles intensifies the critical current density versus magnetic field Jc(H) and gives more weight to the strong pinning component of the Jc. Some important critical physical parameters of the composite films were obtained from the fluctuations induced conductivity analyses. The electrical conductivity was deduced from the electrical resistivity measurements and explained through Aslamazov–Larkin model. A small quantity of fine SiO2 particles upgrade the superconducting features, particularly the lower and the upper critical magnetic field (Bc1 and Bc2) at temperature 0 K.

Polymer‐Metal Oxide Composite (PPy–MoO3) for Ammonia and Ethanol Gas Sensor

AbstractPolypyrrole (PPy)–molybdenum trioxide (MoO3) is a polymer‐metal oxide composite (99.9% pure) obtained when two are mixed mechanically with different wt% in acetone medium to obtain different PPy–MoO3 composite materials. The thick films of pure PPy and PPy–MoO3 polymer‐metal oxide composite are prepared by screen printing technique. The prepared mixed composite polymer‐metal oxide materials are calcinated at 800°C for 8 h in air. The thick films are investigated for structural, electrical, and morphological properties. The surface morphology of the thick films is studied by scanning electron microscope (SEM) which shows that the films are granular and porous in nature. The gas responses of pure PPy and PPy–MoO3 polymer‐metal oxide composite thick films are studied for different gases such as ammonia gas (NH3) and ethanol gas at room temperature. The pure PPy thick film shows the poor response to ammonia and ethanol gas, while the thick film 40PPy–60MoO3 gave good responses to ethanol gas (50 ppm) at room temperature. The gas selectivity, sensitivity, stability, gas response, and recovery time of the sensor are measured and presented.

Method for the fabrication of thick multilayered nickel/iron oxide nanoparticle magnetic nanocomposites

Magnetic nanocomposites consisting of ferrite nanoparticles and magnetic metals have been of interest for use in power electronic components due to their ability to achieve relatively high magnetic permeabilities while also having low losses. Unfortunately, fabrication challenges limit the maximum achievable thickness of these films to ∼ 4 µm, though thicker films are desirable for increased power handling. To overcome these challenges this works seeks to demonstrate a fabrication method whereby thick composite films can be made by constructing sequential composite layers, performing electrophoretic deposition and electro-infiltration steps for each layer. Composite samples of iron oxide nanoparticles electro-infiltrated with nickel that are 1, 3, 5, 7, and 10 layers thick will be fabricated and characterized both structurally and magnetically. Structural measurements accomplished with SEM show that each layer appears to contribute 4 µm to the total thickness, with the one layer sample being 3.99 ± 0.12 µm thick and the ten layer sample being 39.19 ± 3.1 µm thick. Results show that the dc magnetic properties of these composites stay constant as thickness increases, having an average magnetic saturation of 464 kA/m, and coercivity of 2.5 kA/m. The ac magnetic properties similarly showed that the permeability of the composites also stayed consistent at 20. However, the dimensional resonance frequency of the composites decreased as thickness increased, lowering to ∼ 96 MHz for 1 layer (∼4 µm) to ∼ 8 MHz for 10 layers (∼40 µm), revealing a trade-off between thickness of a maximum operating frequency.

Effect of BaTiO3 on the Properties of PVC-Based Composite Thick Films.

Flexible PVC/BT (Polyvinyl chloride/Barium Titanate) composite thick films with (0–30%) volume fractions of BaTiO3 were fabricated via the solution casting method. The effects of BaTiO3 filler on the phase, microstructure and dielectric properties of composite films were investigated. The XRD results revealed that BT particles are embedded in the PVC matrix with no chemical reaction taking place between the two phases. It was observed that the glass transition temperature of PVC had increased with the addition of BT. The frequency dispersion in the dielectric constant versus temperature curves indicated the relaxor nature of the composites. The dielectric constant (εr) measured at 40 °C, increased from 7.6 for pure PVC to 16.1 for 30% of BaTiO3 content in PVC polymer matrix. It is suggested that BaTiO3 ceramic powder enhanced the dielectric properties of PVC and may be used as a flexible dielectric material.

Enhanced magnetoelectric coupling response in hot pressed BiFeO3 and polymer composite films: Effect of magnetic field on grain boundary and grain resistance

We report the effect of grain boundary resistance (GBR) and grain resistance (GR) on the magnetoelectric coupling in the multiferroic composite thick films of BiFeO3 (BFO) nanocrystalline powder and poly vinylidene-fluoride (PVDF) polymer. These composite thick films of thickness ∼ 0.2 mm were prepared via hot pressing with the weight ratio of BFO powder and PVDF polymer as 70:30 (abbreviated as BFO70), 60:40 (abbreviated as BFO60), 50:50 (abbreviated as BFO50) and 40:60 (abbreviated as BFO40), respectively. Impendence investigations (Cole-Cole plots) of these thick films demonstrate that the GBR is significantly changed on the application of magnetic field (8 kOe) in comparison to the GR. Our results indicate that the GBR plays an important role in strengthening of magnetoelectric (ME) effect in BFO-PVDF system. In addition, the ME coupling study indicates that the BFO50 sample shows better results (α33 ∼ 2.7 mV/cm-Oe) and may be suitable for device and sensor applications.

Compact and porous 3D MnO2/holey graphene films for high areal and volumetric performance in supercapacitors with high-thick electrodes

Most manganese oxide-based electrodes used for energy-storage applications suffer from poor ion and electron transport, particularly at high mass loadings and with thick electrodes. To counter this issue, 3D electrodes were developed; however, enhancing their areal and volumetric performance at high mass loadings is still a challenge. In this study, highly compact and 3D porous manganese dioxide and holey reduced graphene oxide (3D MnO2/HRGO) composite films were developed to ensure a high performance in supercapacitors at electrode thicknesses greater than 100 µm. The thick composite films were fabricated by the self-limiting deposition of MnO2 on 3D HRGO hydrogel scaffolds followed by capillary evaporation-induced drying. The 3D MnO2/HRGO electrodes optimized at a thickness of 216 μm showed outstanding specific areal and volumetric capacitances of 2.3 F cm−2 and 108.0 F cm−3 at 1 mA cm−2 and an impressive rate capability with a capacitance retention of 72.2% in the range of 1–40 mA cm−2. Furthermore, supercapacitors assembled with the 3D MnO2/HRGO electrodes with high mass loadings exhibited impressively high areal and volumetric energy densities of 149.7 μWh cm−2 and 2.8 mWh cm−3, respectively.

Hydrothermally synthesized hydroxyapatite cellulose composites thick films as ammonia gas sensor

Hydrothermally synthesized hydroxyapatite cellulose composites thick films as ammonia gas sensor

An Analysis of the Effect of ZIF-8 Addition on the Separation Properties of Polysulfone at Various Temperatures.

The transport of H2, He, CO2, O2, CH4, and N2 at three temperatures up to 65 °C was measured in dense, thick composite films formed by amorphous Polysulfone (PSf) and particles of the size-selective zeolitic imidazolate framework 8 (ZIF-8) at loadings up to 16 wt%. The morphological and structural properties of the membranes were analyzed via SEM and density measurement. The addition of ZIF-8 to PSf enhances the H2 and He permeabilities up to 480% with respect to the pure polymer, while the ideal H2/CO2 and He/CO2 selectivities of MMMs reach values up to 30–40% higher than those of pure PSf. The relative permeability and diffusivity enhancements are higher than those obtained in other polymers, such as PPO, with the same amount of filler. The Maxwell–Wagner–Sillars model is able to represent the MMM H2/CO2 separation performance for filler volume fractions below 10%.

Dielectric and Thermal Behavior of Polystyrene/Sr2TiMnO6 (STMO) Composites

Materials with high dielectric permittivity are in demand due to their potential applications in microelectronics, capacitors and related fields. Polymer/ceramic composites, due to their improved properties, can be studied to meet this demand. In this work, high permittivity double perovskite Sr2TiMnO6 (STMO) ceramics were synthesized by solid state reaction route and polystyrene (PS) composite thick films (∼200 μm) with up to 50 vol% loading of STMO were prepared by solution casting technique. The composite films were characterized using X-ray diffraction and Fourier transform infra-red spectroscopy for their structural properties. Microstructure of the composites was examined using scanning electron microscopy. Thermal behavior was studied using differential scanning calorimetry and thermo-gravimetric analysis. Dielectric properties, such as permittivity, loss and AC conductivity were measured using a dielectric impedance analyzer. Permittivity and dielectric loss of the base polymer were found to increase with the addition of STMO. Glass transition for composites shifted to higher temperature than that of pure PS. The composites exhibited enhanced thermal stability and these composite films can be explored as dielectric materials for capacitor applications.

Ferroelectric BT–PVDF Composite Thick Films for Electrical Energy Storage

Hybrid composites have been elaborated by incorporation of BaTiO3 (BT) inorganic nanoparticles into polyvinylidene fluoride (PVDF) polymer. BT–PVDF composite thick films with different volume fractions of BT (0%, 7%, 15%, and 30%) were deposited by spin-coating onto Pt/SiO2/Si substrates. The effects of the BT inorganic content in the PVDF polymeric matrix on the structural, dielectric, ferroelectric, and energy storage properties were investigated at room temperature. The crystal structure of the samples was identified by X-ray diffraction analysis, and their morphology was observed by scanning electron microscopy. Introduction of BT nanoparticles into the PVDF polymer led to a remarkable enhancement of the dielectric constant value and ferroelectric polarization. Additionally, the abnormal dielectric behavior observed for the composite with 30 vol.% BT nanoparticle volume fraction can be explained by the existence of a Debye relaxation domain at low frequency. Moreover, the stored energy density Wc was enhanced from 2.4 J/cm3 for pure PVDF polymer to 9 J/cm3 for the 30 vol.% BT nanoparticle volume fraction. Such BT–PVDF composite thick films are thus promising materials for the manufacture of electrostatic capacitors for electrical energy storage.

Dielectric studies of PVDF-BaFe12O19 film

Composite thick films of dielectrics having magnetism are promising for variety of electronics applications. Polyvinylidene fluoride (PVDF) as polymer matrix for composites is very impressive due to its high dielectric values and less loss tangent, also the ferroelectric property in β phase among other phase has also been very tempting in polymer family. Barium Hexaferrite, i.e. BaFe12O19 (BHF) is a ferromagnetic material having large saturation magnetisation and high coercively. Thus, the combination of these two materials having composite film may lead to multiferroic properties which are good for enhancing magneto-dielectric properties with the flexibility of the polymer. PVDF based BaFe12O19 (BHF) was successfully synthesized into a free standing flexible thick film by using sol gel method. The thickness of the films was in the range of 40 μm to 50 μm. Phase purity of the film was investigated by X-ray diffraction and the dielectric properties under the applied magnetic field were studied up to 10 MHz frequency. Extremely high values of dielectric permittivity values beyond 500 were observed for the composite thick films. Very small effects magnetic field was seen. A monotonous increase in the AC conductivities with increasing BHF doping in PVDF were observed. The BHF nanoparticles matrices between the chains of PVDF acts as the external source to polarise the PVDF-α, γ, δ phases into ferroelectric crystalline β-phase under the presence of electric field which helps to improve the dielectric value. Moreover, interfacial spaces between BHF and PVDF heterogeneous mixtures give raise to Maxwell-Wagner-Sillar effect which in turn enhances the dielectric permittivity of the composite thick film.

Dielectric studies and alternating current conductivity studies of polymethylmethacrylate (PMMA) doped with ferric chloride (FeCl3) in varying concentration

To understand the variations that a filler bring on its insertion in a polymeric material, the authors developed composite films of thickness 100 μm by dispersing FeCl3 in different concentration (1%, 2%, 4%, 8%) in PMMA and characterized it for their electrical properties using WAYNE KERR 6500B Impedance analyzer. The variation of electrical parameters like dielectric constant (ε′), dielectric loss (ε″), loss tangent (tanδ) and a.c. conductivity (σ) with frequency in the range (100 Hz – 100 KHz) at ambient temperature were evaluated and analyzed. The study shows that PMMA which is a non-conducting amorphous polymeric material having moderate dielectric strength, on insertion of filler show improved values of dielectric constant and a.c. conductivity so as to be used for energy storage device.