Ultraviolet‑Irradiated All‑Organic Nanocomposites with Polymer Dots for High‑Temperature Capacitive Energy Storage

Polymer dielectrics capable of operating efficiently at high electric fields and elevated temperatures are urgently demanded by next-generation electronics and electrical power systems.While inorganic fillers have been extensively utilized to improved high-temperature capacitive performance of dielectric polymers,the presence of thermodynamically incompatible organic and inorganic components may lead to concern about the long-term stability and also complicate film processing.Herein,zero-dimensional polymer dots with high electron affinity are introduced into photoactive allyl-containing poly(aryl ether sulfone)to form the all-organic polymer composites for hightemperature capacitive energy storage.Upon ultraviolet irradiation,the crosslinked polymer composites with polymer dots are efficient in suppressing electrical conduction at high electric fields and elevated temperatures,which significantly reduces the high-field energy loss of the composites at 200℃.Accordingly,the ultraviolet-irradiated composite film exhibits a discharged energy density of 4.2 J cm^(−3)at 200℃.Along with outstanding cyclic stability of capacitive performance at 200℃,this work provides a promising class of dielectric materials for robust high-performance all-organic dielectric nanocomposites.

Polymer thin-film transistor based on a high dielectric constant gate insulator

In this paper full polymer thin-film transistors （PTFTs） based on Poly （acrylonitrile） （PAN） as the gate dielectric and poly （2-methoxy-5-（2＇-ethyl-hexyloxy）-1,4-phenylene-vinylene） （MEH-PPV） as the semiconductor layer were investigated by using different channel width/length ratios. Relatively high dielectric constant of the polymer dielectric layer （6.27） can remarkably reduce the threshold voltage of the transistors to below -3V. Hole field-effect mobility of MEH-PPV of the PTFTs was about 4.8×10^-4cm^2/Vs, and on/off current ratio was larger than 10^2, which was comparable with that of transistors with widely used Poly （4-vinyl phenol） （PVP） or SiO2 as gate dielectrics.

Electrical conductivity and dielectric property of fly ash geopolymer pastes

The electrical conductivity and dielectric property of fly ash geopolymer pastes in a frequency range of 100 Hz-10 MHz were studied.The effects of the liquid alkali solution to ash ratios（L/A） were analyzed.The mineralogical compositions and microstructures of fly ash geopolymer materials were also investigated using X-ray diffraction（XRD） and scanning electron microscopy（SEM）.The 10 mol sodium hydroxide solution and sodium silicate solution at a sodium silicate-to-sodium hydroxide ratio of 1.0 were used in making geopolymer pastes.The pastes were cured at 40℃.It is found that the electrical conductivity and dielectric constant are dependent on the frequency range and L/A ratios.The conductivity increases but the dielectric constant decreases with increasing frequency.

Nanofiller Dispersion in Polymer Dielectrics

Nanodielectric composites have been developed in recent years attempting to improve the dielectric properties such as dielectric constant, dielectric strength and voltage endurance. Among various investigations, nanoparticle dispersion was particularly emphasized in this work. General Electric Global Research Center in Niskayuna NY USA has investigated various nanoparticles, nanocomposites and nanocomposite synthesis methods intending to understand particle dispersion and their impact on the nanocomposite dielectric properties. The breakdown strength and microstructures of the nanocomposites containing different particles were studied for projects related to capacitor and electrical insulation technologies. The nanocomposite synthesis methods either employed commerical nanoparticles or utilized nanoparticles that were self-assembled (in-situ precipitation) in a matrix. Our investigations have shown that nanocomposites prepared with solution chemistry were more favorable for producing uniform dispersion of nanoparticles. Structural information of nanocomposites was studied with transmission electron microscopy and the interection between particles and matrix polymers were tentatively probed using dielectric spectroscopy. In these new class of materials high energy densities on the order of 15J/cc were achievable in nanocomposites.

Study the Frequency Dependence of Dielectric Properties of Gamma Irradiated PVA_(1-x)PS_xPolymer Blends

PVA(1-x)PSx (x = 0.0, 0.25, 0.50, 0.75 and 1.0) polymer blend films were prepared by simple solution cast method using mixer of dimethyl sulphoxide (DMSO) and double distilled water (DDW) as a common solvent. Gamma irradiation studies have been carried out to investigate the potential for improvements in the electrical properties of pure and blend polymer film. The induced changes in the dielectric constant (εr), dielectric loss (tanδ) and AC conductivity (σac) properties for the unirradiated and irradiated films were studied, in the frequency range 50 Hz - 5 MHz at room temperature (27°C). Further, it was seen that the frequency dependent dielectric constant, dielectric loss and AC conductivity were found to increase with increasing γ irradiation dose for all the PVA(1-x)PSx (x = 0.0, 0.25, 0.50, 0.75 and 1.0) polymer blends. The maximum σac at 1 kHz frequency was observed to be 2.4421 × 10-6 s/m (at room temperature) for PVA film irradiated at 1.5 kGy.

Fabrication and Characterization of Semi-Crystalline and Amorphous Dielectric Polymer Films for Energy Storage

Dielectric polymer films are energy storage materials that are used in pulse power operations, power electronics and sustainable energy applications. This paper reviews energy storage devices with focus on dielectric film capacitors. Two prominent examples of polymer dielectrics Polyetherimide (PEI) and Poly (tetrafluoroethylene-hexafluoropropylene-vinylidene fluoride) (THV) have been discussed. Polyetherimide (PEI) is an amorphous polymer recognized for its high-temperature capability, low dielectric loss and high dielectric strength. THV is a semi-crystalline polymer with high dielectric constant, high-temperature capability and charge-discharge efficiency. The primary focus of this paper is to introduce the reader to the fabrication procedures and characterization techniques used in research labs for processing of dielectric polymers. The fabrication and characterization process of both polymers has been discussed in detail to shed the light on experimental process in this area of research.

A Decisive Study on Dielectric Response of Bi2O3/Polystyrene &Bi2O3/PVDF Composite as Flexible Electrodes for Energy Storage

In this manuscript a comparative study on Bi2O3/polystyrene and Bi2O3/PVDF composites has been executed via analysis of structural, bonding, surface morphology and dielectric response of composites for energy storage. The composites have been synthesized using solution cast method by varying concentrations of Bi2O3 (BO = 1 - 5 mw%) into polystyrene (PS) and polyvinylidene fluoride (PVDF) polymers respectively. X-ray diffraction confirms the generation of crystallinity, Fourier transform infrared (FT-IR) spectroscopy confirms bonding behavior and scanning electron microscopy (SEM) confirms uniform distribution of Bi2O3 (BO) in PS and PVDF polymers. Impedance spectroscopy has been employed for determination of dielectric response of the fabricated composites. The dielectric constant has been found to be increased as 1.4 times of pristine PS to BO5%PS95% composites and 1.8 times of pristine PVDF to BO5%PVDF95% composites respectively. These high dielectric composite electrodes are useful for flexible energy storage devices.

Dielectric polymer grafted electrodes enhanced aqueous supercapacitors

Supercapacitors(SCs)have become increasingly important in electrical energy storage and delivery owing to their high power densities and long lifetimes.Aqueous SCs are promising for large-scale engineering applications because of their low cost and safety.However,the low operating voltage and low energy density of aqueous SCs severely limit their practical applications.In this study,a nanoscale dielectric layer is grafted onto a graphene electrode to achieve both a high operating voltage and enhanced capacitance.Compared with an SC without dielectric grafting,a dielectric-enhanced SC(DESC)shows a higher capacitance by 2200%.The mechanism of the capacitance enhancement can be attributed to three factors:the dielectric polarization,the ions desolvation by the dielectric,and the enhanced quantum capacitance from charge transfer and ion adsorption in the polymer molecules.In addition,a 2.5 V pouch DESC with a 1 M KCl electrolyte is confirmed to cycle up to 50,000 times with a capacitance retention of 87.5%.The DESC presents the optimal electrochemical properties after it is grafted with a 5 nm dielectric layer.This study provides new insights into the design of high-voltage and high-energy-density aqueous SCs.

Synthesis,Structure,and Luminescent and Dielectric Properties of Two Novel 1D Chains Based on a T-Shaped Tripodal Ligand 4-(4,5-Dicarboxy-1H-imidazol-2-yl)pyridine Loxide

Two 1D chain metal-organic framework complexes, {Co[（C10H5N3O5）- （H2O）2？H2O]}n （1） and {Cd[（C10H5N3O5）（H2O）2]}n （2）, based on a T-shaped tripodal ligand 4-（4,5-dicarboxy- 1H-imidazol-2-yl） pyridine 1-oxide （H3DCImPyO） have been reacted under hydrothermal conditions, and were characterized by single-crystal X-ray structure analysis, fluorescent analysis and thermal gravimetric analysis. According to single-crystal X-ray determination, complex 1 crystallizes in the monoclinic system, space group P21/n with a = 9.4930（13）, b = 13.2024（18）, c = 10.5203（14） A^°, β = 98.402（2）°, Z = 4, V = 1304.4（3）A^°3; and complex 2 crystallizes in the monoclinic system, space group C2/c with a = 13.557（3）, b = 13.568（3）, c = 6.7804（13） A^°, β = 105.095（2）°, Z = 4 and V = 1204.2（4） A^°3. Fluorescent analysis of complex 2 showed an intense emission band at 466 nm when the exciting radiation was set at 360 nm. Dielectric constants of complexes 1 and 2 were measured at different frequencies with temperature variation.

Optimized growth and dielectric properties of barium titanate thin films on polycrystalline Ni foils

Barium titanate（BTO） thin films were deposited on polycrystalline Ni foils by using the polymer assisted deposition（PAD） technique.The growth conditions including ambient and annealing temperatures were carefully optimized based on thermal dynamic analysis to control the oxidation processing and interdiffusion.Crystal structures,surface morphologies,and dielectric performance were examined and compared for BTO thin films annealed under different temperatures.Correlations between the fabrication conditions,microstructures,and dielectric properties were discussed.BTO thin films fabricated under the optimized conditions show good crystalline structure and promising dielectric properties with εr～ 400 and tan δ 〈 0.025 at 100 kHz.The data demonstrate that BTO films grown on polycrystalline Ni substrates by PAD are promising in device applications.

Fabrication of BaTiO3/Epoxy Composites Exhibiting Large Dielectric Constant, Low Dielectric Loss and High Flexural Strength

BaTiO3/epoxy composites consisting of two three-dimensionally interpenetrating networks of BaTiO3 and epoxy phases were prepared using a new approach. The BaTiO3/epoxy composites exhibit a colossal dielectric constant, low dielectric loss and high flexural strength. In the BaTiO3 networks, chemically bonded grain boundaries between neighboring BaTiO3 grains were established, and they are responsible for the colossal dielectric constant and high flexural strength of the BaTiO3/epoxy composites. Furthermore, unlike the conventional ceramic/polymer composites, this approach also makes high loadings of BaTiO3 contents possible for the BaTiO3/epoxy composites without compromising their high flexural strength.

Composite Materials Damage Modeling Based on Dielectric Properties

Composite materials, by nature, are universally dielectric. The distribution of the phases, including voids and cracks, has a major influence on the dielectric properties of the composite materials. The dielectric relaxation behavior measured by Broadband Dielectric Spectroscopy (BbDS) is often caused by interfacial polarization, which is known as Maxwell-Wagner-Sillars polarization that develops because of the heterogeneity of the composite materials. A prominent mechanism in the low frequency range is driven by charge accumulation at the interphases between different constituent phases. In our previous work, we observed in-situ changes in dielectric behavior during static tensile testing, and also studied the effects of applied mechanical and ambient environments on composite material damage states based on the evaluation of dielectric spectral analysis parameters. In the present work, a two dimensional conformal computational model was developed using a COMSOL™multi-physics module to interpret the effective dielectric behavior of the resulting composite as a function of applied frequency spectra, especially the effects of volume fraction, the distribution of the defects inside of the material volume, and the influence of the permittivity and Ohmic conductivity of the host materials and defects.

Manipulating dielectric property of polymer coatings toward highretention-rate lithium metal full batteries under harsh critical conditions

Lithium(Li)metal batteries(LMBs)can potentially deliver much higher energy density but remain plagued by uncontrollable Li plating with dendrite growth,unstable interfaces,and highly abundant excess Li(>50 mAh·cm^(-2)).Herein,different from the artificial layer or three-dimensional(3D)matrix host constructions,various dielectric polymers are initially well-comprehensively investigated from experimental characterizations to theoretical simulation to evaluate their functions in modulating Li ion distribution.As a proof of concept,a 3D interwoven high dielectric functional polymer(HDFP)nanofiber network with polar C-F dipole moments electrospun on copper(Cu)foil is designed,realizing uniform and controllable Li deposition capacity up to 5.0 mAh·cm^(-2),thereby enabling stable Li plating/stripping cycling over 1400 h at 1.0 mA·cm^(-2).More importantly,under the highcathode loading(~3.1 mAh·cm^(-2))and only 0.6×excess Li(N/P ratio of 1.6),the full cells retain capacity retention of 97.4%after 200 cycles at 3.36 mA·cm^(-2)and achieve high energy density(297.7 Wh·kg^(-1)at cell-level)under lean electrolyte conditions(15μL),much better than ever-reported literatures.Our work provides a new direction for designing high dielectric polymer coating toward high-retention-rate practical Li full batteries.

Natural Rubber Based Composites Comprising Different Types of Carbon-Silica Hybrid Fillers. Comparative Study on Their Electric, Dielectric and Microwave Properties, and Possible Applications

The paper presents a comparative study on the electric, dielectric and microwave properties of natural rubber based composites comprising dual phase fillers prepared from furnace carbon black or conductive carbon black with a different amount of silica. It has been established that, the specifics of the carbon phase have a marked strong effect upon the properties mentioned above. The interpenetration of the two filler phases and the grade of isolation of the conductive carbon phase by the dielectric one depend on the ratio between them. On the other hand, that leads to a change in all properties of the studied composites, which allows tailoring those characteristics.

Preparation and properties of a POSS-containing organic-inorganic hybrid crosslinked polymer

A novel POSS-containing organic-inorganic hybrid crosslinked polymer was prepared by hydrosilylation reaction of octahydridosilsesquioxane （TsHs） with 4,4＇-bis（4-altyloxybenzoyloxy）phenyl （diene A）. Its structure and property was characterized by FFIR, 29Si NMR, TGA and ellipsometer, respectively. The results show that the hybrid polymer possesses high thermal stability and low dielectric constant of 1.97 at optical frequencies.

DIPOLE POLARIZATION RELAXATION AND MOLECULAR STRUCTURE OF MAIN-AND SIDE-CHAIN LIQUID-CRYSTALLINE POLYMERS

Molecular mobility in thermotropic polyesters and side-chain polymers with different struc-ture of mesogens and spacers has been studied by dielectrical method in dilutesolutions. The results made it possible to establish the multiplicity of dielectric relaxationtransitions which reflects the small- and large-scale types of molecular motion. It was shownthat dielectric relaxation processes occurring in accordance with local mechanism (relaxationtimes 10^(-9)--10^(-7)s. and the activation energy 10--50kJ/mol) are due to the mobility of kineticchain elements of different length within a monomer units. It was found that the dielectricrelaxation process connected with a large-scale form of molecular motion (relaxation times10^(-5)--10^(-6)s. and the activation energy 100kJ/mol) did not depend on the molecular massbut was infiuenced by factors changing the conformational state of the macromolecule. It isestablished tha the cooperative reorientation mobility of associated mesogenic fragments isthe source of the large-scale process.

STUDY ON CASTOR OIL POLYURETHANE/POLY (METHYL METHACRYLATE) AB CROSSLINKED POLYMERS

Castor oil polyurethane/poly(methyl methacrylate) AB crosslinked polymers (ABCP) were synthesized by free radical copolymerization of MMA and vinyl-terminated castor oil polyurethane which was obtained from isocyanate-terminated castor oil polyurethane and hydroxyethyl methacrylate The mechanical properties, transition and relaxation, as well as compatibility and morphology of the ABCP were investigated by changing the component. The results show that the ABCP is a semicompatible system and the compatibility of the two components decreases with increasing content of the hard segment. The mechanical and damping properties of the ABCP are obviously superior to that of their homopolymers. The damping value is mainly controlled by cross[ink density of the ABCP but the T-g value by component.

All-organic nanocomposite dielectrics contained with polymer dots for high-temperature capacitive energy storage

High-temperature polymer dielectrics with high energy density are urgently needed for capacitive energy storage fields.However,the huge conduction loss at elevated temperatures makes the capacitive performance of polymers degrade sharply,limiting the application of them.Herein,the polymer dots(PDs)with high-electron-affinity were introduced into high-temperature polymers to prepare all-organic nanocomposite dielectrics by solution casting.It is found that polymer dots capture injected electrons via strong electrostatic attraction and impede charges transport and accumulation inside composites,thus reducing leakage current density and improving high-temperature energy storage performance.Consequently,the high-temperature capacitance performance of nanocomposites was improved significantly and reached over 2.5 times that of the pristine polymers,e.g.,the energy density of polyetherimide(PEI)/PD reached 3.24 J·cm^(-3)with excellent electrical fatigue reliability over 20,000 times.This work addresses the current problem of poor discharged energy density of polymer dielectrics at high temperatures with a simple and universal method.

High energy density and superior charge/discharge efficiency polymer dielectrics enabled by rationally designed dipolar polarization

Although many dielectric polymers exhibit high energy storage density(Ue)with enhanced dipolar polarization at room temperature,the substantially increased electric conduction loss at high applied electric fields and high temperatures remains a great challenge.Here,we report a strategy that high contents of medium-polar ester group and end-group(St)modification are introduced into a biode-gradable polymer polylactic acid(PLA)to synergistically reduce the loss and enhance Ue and charge-discharge efficiency(h).The resultant St-modified PLA polymer(PLA-St)exhibits an Ue of 6.5 J/cm^(3)with an ultra-high h(95.4%),far outperforming the best reported dielectric polymers.It is worth noting that the modified molecular structures can generate deep trap centers and restrict the local dipole motions in the polymer,which are responsible for the reduction of conduction loss and improvements in high-temperature capacitive performance.In addition,the PLA-St polymer shows intrinsically excellent self-healing ability and cyclic stability surviving over 500000 charge-discharge cycles.This work offers an efficient route to next-generation eco-friendly dielectric polymers with high energy density,low loss,and long-term stability.

Improving the Dielectric Properties of High Density Polyethylene by Incorporating Clay-Nanofiller

Polymer nanocomposites have been used for various important industrial applications. The preparation of high density polyethylene composed with Na-montmorillonite nanofiller using melt compounding method for different concentrations of clay-nanofiller of 0%, 2%, 6%, 10%, and 15% has been successfully done. The morphology of the obtained samples was optimized and characterized by scanning electron microscope showing the formation of the polymer nanocomposites. The thermal stability and dielectric properties were measured for the prepared samples. Thermal gravimetric analysis results show that thermal stability in polymer nanocomposites is more than that in the base polymer. It has been shown that the polymer nanocomposites exhibit some very different dielectric characteristics when compared to the base polymer. The dielectric breakdown strength is enhanced by the addition of clay-nanofiller. The dielectric constant (εr) and dissipation factor (Tan δ) have been studied in the frequency range 200 Hz to 2 MHz at room temperature indicating that enhancements have been occurred in εr and Tan δ by the addition of clay-nanofiller in the polymer material when compared with the pure material.