Flexible /PET/batio3/ layer–layer composite film with enhanced dielectric properties fabricated by highly loaded /batio3/ coating with acrylic resin as binder

Flexible layer–layer poly(ethylene phthalate) (PET)/BaTiO₃ composite films with enhanced dielectric permittivity were fabricated by spin coating method, consisting of PET substrate film layer and modified BaTiO₃/acrylic resin hybrid coating layer. The thickness of coating layer was less than 3 μm (about 2% of PET film thickness), and therefore, the PET/barium titanate (BT) composite films remained flexible even at high volume fraction of BaTiO₃ fillers. The volume contents of BaTiO₃ were varied from 0 to 80%, and the solid contents of BaTiO₃/acrylic resin were in the range of 51.8–72.9%. Scanning electron microscopy showed strong interaction of finely dispersed BaTiO₃ particles with acrylic resin. Morphological profile also displayed uniform coating layer of modified BaTiO₃/acrylic resin and its strong adhesion with PET film. The dielectric constant of the PET/BaTiO₃ composite films increased by about 26% at 60 vol % BaTiO₃ loading when compared with the pristine PET film, whereas the dielectric loss decreased slightly. In addition, PET‐grafted poly(hydroxylethyl methacrylate) brushes were used as substrate to introduce covalent bonding with the coating layer. Further enhancement of dielectric constant and reduction of dielectric loss were realized when compared with the composite films with bare PET substrate. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42508.     

Embedded Capacitor Technology Using Aerosol Deposition

Embedded passives, which achieve miniaturization, cost reduction, and higher performance, are regarded as one of the most promising technologies for a future RF module substrate. Currently, a BaTiO₃/Polymer composite is being used for the embedded capacitors in printed wiring boards. One of the drawbacks of this composite is its relatively low dielectric constant, because the polymer component with a low dielectric constant suppresses the dielectric constant of the whole composite. We propose a resin build-up circuit board with passive functions embedded in a ceramic film without any polymer component for the next-generation low-cost RF modules. We have already manufactured a prototype board with ceramic capacitors embedded in an FR-4 substrate using a unique ceramic deposition technology: aerosol deposition (ASD) in which many kinds of ceramics can be deposited on a substrate at room temperature by making use of accelerated ceramic nanoparticle aerosol bombardment with a nozzle. In this study, first we examine the effects of the characteristics of raw ceramic powder on the crystal structure and the dielectric properties of ASD films. As a result, we confirmed that dense BaTiO₃ dielectric films can be deposited when raw powder without strain is used. From the resulting polarization versus electrical field (P–E curve), we confirmed that paraelectric was observed in the dense films, while the porous BaTiO₃ films deposited using milled powder exhibit a small hysteresis loop. We also clarified that dense BaTiO₃ dielectric films exhibit a nanostructure with a texture consisting of particles under 10 nm in diameter. We also examine the interfacial behavior between BaTiO₃ dielectric films and the Cu electrode, in order to investigate the deposition temperature and the reliability of a BaTiO₃ ASD film under high temperature (250°C), high humidity (100 Rh%), thermal cycle condition (−55°C to 150°C), and bias DC voltage (5 V). We clarified that the BaTiO₃ ASD film satisfies the criteria of reliability in the microelectronic packaging area.     

Synthesis,structure and properties of polyimide–silica hybrid composites based on biphenyltetracarboxylic dianhydride

A simple and efficient way of synthesizing nanocomposite films using a dispersion technique is reported, with the resulting films having improved mechanical and thermal properties. Nano‐SiO₂ was used in a biphenyltetracarboxylic dianhydride‐based poly(amic acid) precursor and found to be dispersed up to 7 wt% without any additives. The composites were cast to make 10 µm solid films to establish structure and property relationships between liquid and solid film. The structures of the liquid composite materials were studied using NMR and Fourier transform infrared spectroscopy. Solid film properties such as tensile strength, contact angles and thermal behaviour were evaluated for comparison. The properties of the composite films were found to be enhanced compared to polyimide film itself. Atomic force microscopy and macroscale mechanical measurements showed that composite films with more dipolar bonding interactions have higher elastic moduli and are more deformable. They yield higher adhesion energies, and therefore composite coatings offer greater adhesion. There was a limitation in the film formation beyond 5 wt% of silica. Copyright © 2011 Society of Chemical Industry     

Dielectric property of polyimide/barium titanate composites and its influence factors (Ⅱ)

Using poly(amic acid) (PAA) as a precursor followed by thermal imidization, the polyimide/barium titanate composite films were successfully prepared by a direct mixing method and in situ process. The influence of processing factors, such as particle size, distribution mode and polymerization method on dielectric properties was studied. Results revealed that the dielectric constant (ɛ) of the composite film increased by using bigger fillers or employing in situ polymerization and bimodal distribution. When the composite film containing 50 Vol-% of BaTiO₃ with size in 100 nm was prepared via in situ process, its dielectric constant reached 45 at 10 kHz. __________ Translated from Journal of Functional Materials, 2008, 39(2): 264–267 [译自: 功能材料]     

Preparation,characterization and dielectric properties of polyetherimide nanocomposites containing surface‐functionalized BaTiO3 nanoparticles

Polyetherimide (PEI)/hydroxyl‐functionalized barium titanate (BaTiO₃) nanocomposite films were successfully prepared through solution‐casting followed by subsequent thermal imidization. The results of Fourier transform infrared spectroscopy confirmed that the chemical treatment with hydrogen peroxide (H₂O₂) could efficiently derive hydroxyl groups on the surface of BaTiO₃ nanoparticles. The strong interaction between the hydroxyl‐functionalized BaTiO₃ and the PEI matrix greatly enhanced the particle dispersion as well as the interfacial adhesion, as evidenced by scanning electron microscopy. The PEI nanocomposite with hydroxyl‐functionalized BaTiO₃ nanoparticles (50 vol% BaTiO₃ loading) showed an increased dielectric permittivity of 52.78 at 1 kHz compared with the dielectric permittivity (33.87) of PEI/raw BaTiO₃ composite. The loss tangent was still low (less than 0.03) when the content of hydroxyl‐functionalized BaTiO₃ was 50 vol%. For PEI/BaTiO₃ nanocomposites, the frequency and temperature dependences of the dielectric properties were significantly reduced through functionalizing the surface of BaTiO₃ nanoparticles with H₂O₂. Different theoretical approaches were employed to predict the effective permittivity of the nanocomposite systems and the results are compared with the experimental results. Copyright © 2012 Society of Chemical Industry     

Thermal and electrical behavior of polyimide/silica hybrid thin films

Silica‐containing polyimide films were prepared by sol‐gel technique using a poly(amic acid) and tetraethoxysilane. The poly(amic acid) was synthesized by solution polycondensation reaction of 4,4′‐oxydiphthalic anhydride with 2,6‐bis(3‐aminophenoxy)benzene and an aminosilane coupling agent, 3‐aminopropyltriethoxysilane. The properties of these films, such as water vapors sorption capacity, dynamic contact angles and contact angle hysteresis, thermal, and electrical behavior have been evaluated with respect to their structure. The polymer films exhibited good thermal stability having the initial decomposition temperature above 450°C, glass transition temperature in the range of 223?228°C, and low‐dielectric constant in the range of 2.64?3.16. Two subglass transitions, γ and β, were evidenced by dynamic mechanical analysis and dielectric spectroscopy. The surface morphology and the roughness were investigated by atomic force microscopy and scanning electron microscopy. POLYM. ENG. SCI., 2010. © 2009 Society of Plastics Engineers     

Electrical properties of polyimide composite films containing TiO2 nanotubes

A study on the dielectric behavior of polyimide composite films containing different amounts of TiO₂ nanotubes (TNs) was performed. The films were prepared by casting solutions resulting from direct mixing of a poly(amic acid) and TNs onto glass plates, followed by thermal imidization. The influence of TNs content on the properties of polyimide composites was investigated. AFM and SEM analyses showed good compatibility between the filler and polymer matrix. Dynamic mechanical analysis and broadband dielectric spectroscopy were used to evidence relaxation processes into the films. The electrical properties were evaluated on the basis of dielectric constant and dielectric loss, and their variation with frequency and temperature. At moderate temperature a secondary β relaxation was observed while incorporation of TNs decreased the activation energy and facilitated the appearance of an additional β ₁ process. An α relaxation and a conductivity process were evidenced at higher temperatures. The values of dielectric constant and dissipation factor increased with TNs amount, and the maximum of σ relaxation peak shifted to higher temperatures. POLYM. COMPOS., 38:2584–2593, 2017. © 2015 Society of Plastics Engineers     

High permittivity nanocomposites fabricated from electrospun polyimide/BaTiO3 hybrid nanofibers

High dielectric permittivity, good mechanical properties, and excellent thermal stability are highly desired for the dielectric materials used in the embedded capacitors and energy‐storage devices. This study reports polyimide (PI)/barium titanate (BaTiO₃) nanocomposites fabricated from electrospun PI/BaTiO₃ hybrid nanofibers. The PI/BaTiO₃ nanocomposites were investigated using Fourier transform infrared spectroscopy, scanning electron microscope, transmission electron microscope, thermal gravimetric analysis, an electromechanical testing machine, a LCR meter and an electric breakdown strength tester. The results showed that BaTiO₃ fillers were uniformly dispersed up to 50 vol% in PI matrix. The dielectric permittivity of the composite (50 vol% BaTiO₃) was 29.66 with a dielectric loss of 0.009 at 1 kHz and room temperature. The dielectric permittivity showed a very small dependence on temperature (up to 150°C) and frequency (100 Hz–100 kHz). The nanocomposites also showed high thermal stability and good mechanical properties. The PI/BaTiO₃ nanocomposites will be a promising candidate for uses in embedded capacitors, especially in high temperature circumstance. POLYM. COMPOS., 37:794–801, 2016. © 2014 Society of Plastics Engineers     

Preparation and properties of polyimide films codoped with barium and titanium oxides

Polyimide hybrid films containing bimetalic compounds were obtained by codoping poly(amic acid) with a barium and titanium precursor prepared from BaCO₃, Ti(OBu)₄, and lactic acid followed by casting and thermal curing. FTIR, WAXD, and XPS measurements showed that barium and titanium precursor could be transformed to BaTiO₃ at a temperature above 650°C, while the mixed oxides were only found in hybrid films. The measurements of TEM and AFM indicated a homogeneous distribution of inorganic phase with particle sizes less than 50 nm. The hybrid films exhibited fairly high thermal stability, good optical transparency, and promising mechanical properties. The incorporation of 10 wt % barium and titanium oxide lowered surface and volume electrical resistivity by 2 and 5 orders, respectively, increasing dielectric constant from 3.5 to 4.2 and piezoelectric constant from 3.8 to 5.2 × 10^?12 c/N, relative to the nondoped polyimide film. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 83: 1810–1816, 2002     

Rapid Formation of Nanocrystalline BaTiO3 and Its Highly Stable Sol

Ultrafine BaTiO₃ nanoparticles and their highly stable sols are prepared by a novel and rapid route. In this method, the formation mechanism that lies between the chemical precipitation and the sol–gel process is proposed. The BaTiO₃ nanocrystal sols are synthesized in as fast as 15 min in an air atmosphere. Dynamic light scattering analysis and the observation of the Tyndall effect confirm the existence of crystalline nanoparticles in these sols. After careful separation, nanocrystalline BaTiO₃ powders with an average particle size as small as 2.8 nm are obtained. These particles have perovskite phase structures as determined by X‐ray diffraction and selected‐area electron‐diffraction analysis. Fourier transform infrared spectroscopy (FT‐IR) and thermal analysis are used to detect the characteristic functional groups of the solvents on the particles to reveal the formation mechanism. Uniform BaTiO₃ nanocrystal films with high dielectric constants, low dielectric losses, and paraelectric behavior are prepared through solvent evaporation of the nanocrystal sols, providing a new low‐temperature route for the fabrication of perovskite thin films.     

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.     

Characteristics of polyimide/barium titanate composite films

In this study, the characteristics of the polyimide/BaTiO₃ composite films with various amounts of BaTiO₃ were evaluated. Modifier 1-methoxy-2-propyl acetate was added during composite preparation to disperse the BaTiO₃ particles in polyimide matrix. Conversion of polyamic acid (PAA) to polyimide was not completed for the composite film with a high BaTiO₃ loading (90 wt%). Dielectric constant of the film increases from 3.53 to 46.50, at the sweep frequency of 10 kHz, as the BaTiO₃ content increases from 0 to 90 wt% (0–67.5 vol.%), which is mainly due to the relatively high dielectric constant of BaTiO₃ particles in the polyimide matrix. The dielectric losses at 10 kHz is ranging from 0.005 to 0.015, which is due to the switching of the domain wall. Water absorption decreases considerably with increasing BaTiO₃ content. With 10 wt% (2.5 vol.%) BaTiO₃ addition, the water absorption of the composite film reduces 45% from that of pure polyimide. Also, high loading of BaTiO₃ is not beneficial to reduce the water absorption of the composite film.     

Fabrication of BaTiO3-PTFE composite film for embedded capacitor employing aerosol deposition

The potential for using aerosol deposition (AD) as an alternative fabrication method to the conventional polymer composite process for embedded capacitors was examined. In order to achieve a high relative dielectric permittivity, BaTiO₃-polytetrafluoroethylene (PTFE) composite thick films were attempted by AD at room temperature. For the high dielectric constant, the BaTiO₃-PTFE composite films grown by AD should satisfied the following two critical conditions: a reduced decrement in ceramic particle size and a relieved distortion of the crystal structure. However, the relative permitivity of the composite films was too low compared with that of the BaTiO₃ films grown by AD. By predicting the dielectric constant in several composite models using the Hashin-Shtrikman bounds theory and 3-dimenstional (3-D) electrostatic simulation, we confirmed that the connectivity between ceramic particles is a highly critical factor for achieving a high dielectric constant in composite films.     

Multi-phase coexistence and temperature-stable dielectric properties in BaTiO3/ZnO composite ceramics

BaTiO₃:100xZnO composite ceramics with different ZnO particle sizes were prepared by using a conventional solid-state method. Phase constitution, microstructure and dielectric properties of BaTiO₃:100xZnO composite ceramics are investigated. Compared to micrometer scaled ZnO particles, nanometer scaled ZnO particles tend to agglomerate at lower ZnO contents in the BaTiO₃:100xZnO composite ceramics. The introduction of ZnO in BaTiO₃ leads to the reduction of grain size, decrease of the tetragonality and shift of phase transition temperature. The optimum composition is BaTiO₃ with 20 wt. % nanometer scaled ZnO particles, which has stable permittivity and low dielectric loss from -100 to 160 °C. The stable dielectric properties are proposed to be beneficiated from the stress induced multi-phase coexistence.     

Synergistic enhancement of mechanical,crystalline and dielectric properties of polyarylene ether nitrile‐based nanocomposites by unidirectional hot stretching–quenching

Copper tetra‐amine phthalocyanine (NH₂‐CuPc) was grafted onto barium titanate (BaTiO₃) whose surface was modified by carboxylic polyarylene ether nitrile (CPEN) to afford a nano‐filler (CPEN‐f‐BaTiO₃@NH₂‐CuPc). Through a solution‐casting method combined with ultrasonic dispersion technology, the obtained CPEN‐f‐BaTiO₃@NH₂‐CuPc was successfully incorporated into biphenyl polyarylene ether nitrile (BP‐PEN) matrix to prepare nanocomposite films with various mass fractions of CPEN‐f‐BaTiO₃@NH₂‐CuPc (0, 2.0, 5.0, 10.0 and 20.0 wt%). After that, the nanocomposite films were unidirectionally stretched with various stretching ratios at 280 °C. All the nanocomposite films show excellent mechanical and thermal stability, which is provided by the BP‐PEN matrix. The crystallinity and mechanical, thermal and dielectric properties of the nanocomposite films are efficiently enhanced after the unidirectional hot‐stretching process. The results show that hot‐stretching is a useful method for improving the mechanical and crystallization behaviors as well as the thermal and dielectric properties of the nanocomposite films. © 2017 Society of Chemical Industry     

Preparation and characterization of silica/polyimide nanocomposite films based on water‐soluble poly(amic acid) ammonium salt

In this article, a series of new silica/polyimide (SiO₂/PI) nanocomposite films with high dielectric constant (>4.0), low dielectric loss (<0.0325), high breakdown strength (288.8 kV mm⁻¹), and high volume resistivity (2.498 × 10¹⁴ Ω m) were prepared by the hydrolysis of tetraethyl orthosilicate in water‐soluble poly(amic acid) ammonium salt (PAAS). The chemical structure of nanocomposite films compared with the traditional pure PI was confirmed by Fourier transform infrared spectroscopy and X‐ray diffraction patterns. The results indicated that both the PAAS and the polyamide acid (PAA) material were effectively converted into the corresponding PI material through the thermal imidization and the amorphous SiO₂ was embedded in the nanocomposite films without structural changes. Thermal stability of the nanocomposite films was increased though mechanical property was generally decreased with increasing the mass fraction of SiO₂. All the nanocomposite films exhibited an almost single‐step thermal decomposition behavior and the average decomposition temperature was about 615°C. It was concluded that the effective dispersion of SiO₂ particles in PI matrix vigorously improved the comprehensive performance of the SiO₂/PI nanocomposite films and expanded their applications in the electronic and environment‐friendly industries. POLYM. COMPOS., 38:774–781, 2017. © 2015 Society of Plastics Engineers     

Thermal and morphological studies on γ‐Fe2O3 polystyrene composites and the affect of additives

γ‐Fe₂O₃polystyrene (PS) composite films were prepared by a gel‐casting technique to obtain monodisperse composite films. To understand the effect of additives on the prepared composite films, additives such as rice husk ash and thiourea were made to disperse into the PS matrix. The as‐prepared γ‐Fe₂O₃ PS composite films, along with their additives, were subjected to characterization and study by X‐ray diffraction, scanning electron microscopy, thermal, IR, and dielectric measurement techniques. These studies showed monodisperse and chemically homogenous composite films with an increase in thermal behavior. An interesting self‐assembly of rod‐like nanoparticles of γ‐Fe₂O₃ particles into the polymer matrix, which formed spherical packets, was observed for the γ‐Fe₂O₃PS composite film. The electrical behavior of these films was interesting, as some showed conduction whereas others showed an increase in dielectric behavior. This nature was explained by the dielectric measurements. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 93: 778–788, 2004     

Reduced sedimentation of barium titanate nanoparticles in poly(vinylidene fluoride) films during solution casting by surface modification

Reduced sedimentation of barium titanate (BaTiO₃, BT) nanoparticles during solution casting to prepare the BT/poly(vinylidene fluoride) (PVDF) films is systematically investigated by surface modification of the BT nanoparticles. The surface of BT nanoparticles is hydroxylated by hydrogen peroxide (H₂O₂) or aminated by γ‐aminopropyl triethoxysilane (γ‐APS). It is found that the compatibility between the fillers and polymer matrix is remarkably improved by such surface treatments. As a result, the agglomeration and sedimentation of BT nanoparticles in the BT/PVDF composite films are significantly reduced, which is supported by morphology observation. Better dielectric properties such as higher dielectric constant, higher breakdown strength, and lower dielectric loss are also obtained for the composite films with surface‐modified fillers than those with raw fillers. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42662.     

Surface modification of BaTiO3 inclusions in polydicyclopentadiene nanocomposites for energy storage

A new nanocomposite system displaying high breakdown strength, improved permittivity, low dielectric loss, and high thermal stability is presented. Free‐standing nanocomposite films were prepared via a solvent‐free in‐situ polymerization technique whereby 5 vol % BaTiO₃ (BT) nanocrystals with tailored surface chemistry were dispersed in dicyclopentadiene (DCPD) prior to initiation of ring opening metathesis polymerization by a second generation Grubbs catalyst. The relative permittivity was enhanced from 1.7 in the neat poly(DCPD) film to a maximum of 2.4 in the composite, while the dielectric loss tangent was minimized below 0.7%. Surface modification of the BT nanocrystals mitigated reduction in breakdown strength of the resulting nanocomposites such that only a 13% reduction in breakdown strength was observed relative to the neat polymer films. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40290.     

Thin films of organic polymer composites with inorganic aerogels as dielectric materials: polymer chain orientation and properties

Summary High temperature poly(p-phenylene biphenyltetracarboximide) nanocomposite films with inorganic particulates, which are applicable to the fabrication of microelectronic devices, were prepared from the poly(amic acid) and silica aerogels with a size of ca. 150 nm in diameter by solution blending and subsequent conventional polyimide film formation process. The structure and properties were measured. By the composite formation, the optical and dielectric properties were improved due to the low dielectric constant characteristic of silica aerogels, whereas the interfacial stress and thermal expansion coefficient were significantly degraded by a large disturbance in the polymer chain in-plane orientation caused by silica aerogels despite of their low thermal expansivity. This indicates that in the rigid type of polymer composites with inorganic particulates, the orientation of polymer chains still plays a critical role on the physical properties.