14 research outputs found

    Bio-Inspired Fluoro-polydopamine Meets Barium Titanate Nanowires: A Perfect Combination to Enhance Energy Storage Capability of Polymer Nanocomposites

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    Rapid evolution of energy storage devices expedites the development of high-energy-density materials with excellent flexibility and easy processing. The search for such materials has triggered the development of high-dielectric-constant (high-<i>k</i>) polymer nanocomposites. However, the enhancement of <i>k</i> usually suffers from sharp reduction of breakdown strength, which is detrimental to substantial increase of energy storage capability. Herein, the combination of bio-inspired fluoro-polydopamine functionalized BaTiO<sub>3</sub> nanowires (NWs) and a fluoropolymer matrix offers a new thought to prepare polymer nanocomposites. The elaborate functionalization of BaTiO<sub>3</sub> NWs with fluoro-polydopamine has guaranteed both the increase of <i>k</i> and the maintenance of breakdown strength, resulting in significantly enhanced energy storage capability. The nanocomposite with 5 vol % functionalized BaTiO<sub>3</sub> NWs discharges an ultrahigh energy density of 12.87 J cm<sup>–3</sup> at a relatively low electric field of 480 MV m<sup>–1</sup>, more than three and a half times that of biaxial-oriented polypropylene (BOPP, 3.56 J cm<sup>–3</sup> at 600 MV m<sup>–1</sup>). This superior energy storage capability seems to rival or exceed some reported advanced nanoceramics-based materials at 500 MV m<sup>–1</sup>. This new strategy permits insights into the construction of polymer nanocomposites with high energy storage capability

    Tailoring Dielectric Properties and Energy Density of Ferroelectric Polymer Nanocomposites by High‑<i>k</i> Nanowires

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    High dielectric constant (<i>k</i>) polymer nanocomposites have shown great potential in dielectric and energy storage applications in the past few decades. The introduction of high-<i>k</i> nanomaterials into ferroelectric polymers has proven to be a promising strategy for the fabrication of high-<i>k</i> nanocomposites. One-dimensional large-aspect-ratio nanowires exhibit superiority in enhancing <i>k</i> values and energy density of polymer nanocomposites in comparison to their spherical counterparts. However, the impact of their intrinsic properties on the dielectric properties of polymer nanocomposites has been seldom investigated. Herein, four kinds of nanowires (Na<sub>2</sub>Ti<sub>3</sub>O<sub>7</sub>, TiO<sub>2</sub>, BaTiO<sub>3</sub>, and SrTiO<sub>3</sub>) with different inherent characteristics are elaborately selected to fabricate high-<i>k</i> ferroelectric polymer nanocomposites. Dopamine functionalization facilitates the excellent dispersion of these nanowires in the ferroelectric polymer matrix because of the strong polymer/nanowire interfacial adhesion. A thorough comparative study on the dielectric properties and energy storage capability of the nanowires-based nanocomposites has been presented. The results reveal that, among the four types of nanowires, BaTiO<sub>3</sub> NWs show the best potential in improving the energy storage capability of the proposed nanocomposites, resulting from the most signficant increase of <i>k</i> while retaining the rather low dielectric loss and leakage current

    Core–Shell Structured Biopolymer@BaTiO<sub>3</sub> Nanoparticles for Biopolymer Nanocomposites with Significantly Enhanced Dielectric Properties and Energy Storage Capability

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    Flexible high-dielectric-constant (high-κ) nanocomposite dielectrics comprising polymer matrix and ceramic nanoparticles have important applications in the fields of electrical insulation and energy storage. However, most of the flexible high-κ nanocomposites are fabricated by using nonbiodegradable polymers as matrixes, which may not meet the increasing demands of society for environmental sustainability. In this study, using biodegradable polylactic acid (PLA) as a matrix and core–shell structured BaTiO<sub>3</sub> (BT) nanoparticles as high-κ filler, we report the preparation and structure–property relationship of environmentally friendly flexible high-κ polymer nanocomposites. Two types of core–shell structured high-κ nanoparticles [polydopamine-encapsulated BT (BT@PDA) and PLA-encapsulated BT@PDA (BT@PDA@PLA)] as well as as-prepared BT nanoparticles were used as filler of the PLA-based high-κ nanocomposites. It was found that, compared with the as-prepared BT nanocomposites, the core–shell nanoparticle-based composites show enhanced dielectric constant, suppressed dielectric loss tangent, and enhanced breakdown strength. In addition, the BT@PDA@PLA nanocomposites have much higher dielectric constant and energy density. The nanoparticle–PLA compatibility and its influence on the dielectric and energy storage properties of the nanocomposites were also investigated. Because the polymer matrix is environmentally friendly and the preparation process of the core–shell nanoparticles is facile and nontoxic, the nanocomposites reported here may be used in the next generation of environmentally friendly high-performance energy storage devices

    Three-Dimensional Highly Conductive Graphene–Silver Nanowire Hybrid Foams for Flexible and Stretchable Conductors

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    Graphene foams have showed huge application potentials owing to their unique 3D structure and superior properties. Thus, it is highly desired to develop a simple and effective pathway to fabricate high performance graphene-based foams. Here, we present a polymer template-assisted assembly strategy for fabricating a novel class of graphene/AgNW hybrid foams. The hybrid foams show 3D ordered microstructures, high thermal stability, and excellent electrical and mechanical properties, and demonstrate huge application potential in the fields of flexible and stretchable conductors. Importantly, the polymer-template assisted assembly technique is simple, scalable, and low-cost, providing a new synthesis protocol for various multifunctional graphene hybrid foam-based composites

    Core@Double-Shell Structured BaTiO<sub>3</sub>–Polymer Nanocomposites with High Dielectric Constant and Low Dielectric Loss for Energy Storage Application

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    Polymer nanocomposites with high dielectric constant have extensive applications in the electronic and electrical industry because of ease of processing and low cost. Blending and <i>in situ</i> polymerization are two conventional methods for the preparation of polymer nanocomposites. However, the resulting nanocomposites, particularly highly filled nanocomposites, generally have some disadvantages such as high dielectric loss and low dielectric constant and thus show low energy density and low energy efficiency. Here we developed a core@double-shell strategy to prepare barium titanate (BT)-based high performance polymer nanocomposites, in which the first shell is hyperbranched aromatic polyamide (HBP) and the second shell is poly­(methyl methacrylate) (PMMA). This method utilized the advantages of both polymer shells, resulting in superior dielectric property which cannot be achieved in nanocomposites prepared by the conventional blending methods. It is found that, compared with the conventional solution blended BT/PMMA nanocomposites, the core@double-shell structured BT@HBP@PMMA nanocomposites had higher dielectric constant and lower dielectric loss. The energy densities of BT@HBP@PMMA nanocomposites were higher than that of BT/PMMA nanocomposites accordingly. The dielectric response of the nanocomposites was analyzed, and the mechanisms resulting in the higher dielectric constant and lower dielectric loss in BT@HBP@PMMA nanocomposites were proposed. This study suggests that the core@double-shell strategy shows strong potential for preparing polymer nanocomposites with desirable dielectric properties

    Fluoro-Polymer@BaTiO<sub>3</sub> Hybrid Nanoparticles Prepared via RAFT Polymerization: Toward Ferroelectric Polymer Nanocomposites with High Dielectric Constant and Low Dielectric Loss for Energy Storage Application

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    Polymer nanocomposites with high energy density and low dielectric loss are highly desirable in electronic and electric industry. Achieving the ability to tailor the interface between polymer and nanoparticle is the key issue to realize desirable dielectric properties and high energy density in the nanocomposites. However, the understanding of the role of interface on the dielectric properties and energy density of polymer nanocomposites is still very poor. In this work, we report a novel strategy to improve the interface between the high dielectric constant nanoparticles (i.e., BaTiO<sub>3</sub>) and ferroelectric polymer [i.e., poly­(vinylidene fluoride-co-hexafluoro propylene)]. Core–shell structured BaTiO<sub>3</sub> nanoparticles either with different shell thickness or with different molecular structure of the shell were prepared by grafting two types of fluoroalkyl acrylate monomers via surface-initiated reversible addition–fragmentation chain transfer (RAFT) polymerization. The dielectric properties and energy storage capability of the corresponding nanocomposites were investigated by broadband dielectric spectroscopy and electric displacement-electric field loop measurement, respectively. The results show that high energy density and low dielectric loss are successfully realized in the nanocomposites. Moreover, the energy storage densities of the P­(VDF-HFP)-based nanocomposites could be tailored by adjusting the structure and thickness of the fluoro-polymer shell. The approach described is applicable to a wide range of nanoparticles and polymer matrix, thereby providing a new route for preparing polymer-based nanocomposites used in electronic and electric industry

    Core@Double-Shell Structured Nanocomposites: A Route to High Dielectric Constant and Low Loss Material

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    This work reports the advances of utilizing a core@double-shell nanostructure to enhance the electrical energy storage capability and suppress the dielectric loss of polymer nanocomposites. Two types of core@double-shell barium titanate (BaTiO<sub>3</sub>) matrix-free nanocomposites were prepared using a surface initiated atom transfer radical polymerization (ATRP) method to graft a poly­(2-hydroxylethyle methacrylate)-<i>block</i>-poly­(methyl methacrylate) and sodium polyacrylate-<i>block</i>-poly­(2-hydroxylethyle methacrylate) block copolymer from BaTiO<sub>3</sub> nanoparticles. The inner shell polymer is chosen to have either high dielectric constant or high electrical conductivity to provide large polarization, while the encapsulating outer shell polymer is chosen to be more insulating as to maintain a large resistivity and low loss. Finite element modeling was conducted to investigate the dielectric properties of the fabricated nanocomposites and the relaxation behavior of the grafted polymer. It demonstrates that confinement of the more conductive (lossy) phase in this multishell nanostructure is the key to achieving a high dielectric constant and maintaining a low loss. This promising multishell strategy could be generalized to a variety of polymers to develop novel nanocomposites

    Role of Interface on the Thermal Conductivity of Highly Filled Dielectric Epoxy/AlN Composites

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    The interface between filler and matrix has long been a critical problem that affects the thermal conductivity of polymer composites. The effects of the interface on the thermal conductivity of the composite with low filler loading are well documented, whereas the role of the interface in highly filled polymer composites is not clear. Here we report on a systematic study of the effects of interface on the thermal conductivity of highly filled epoxy composites. Six kinds of surface treated and as received AlN particles are used as fillers. Three kinds of treated AlN are functionalized by silanes, i.e., amino, epoxy, and mercapto group terminated silanes. Others are functionalized by three kinds of materials, i.e., polyhedral oligomeric silsesquioxane (POSS), hyperbranched polymer, and graphene oxide (GO). An intensive study was made to clarify how the variation of the modifier would affect the microstructure, density, interfacial adhesion, and thus the final thermal conductivity of the composites. It was found that the thermal conductivity enhancement of the composites is not only dependent on the type and physicochemical nature of the modifiers but also dependent on the filler loading. In addition, some unexpected results were found in the composites with particle loading higher than the percolation threshold. For instance, the composites with AlN treated by the silane uncapable of reacting with the epoxy resin show the most effective enhancement of the thermal conductivity. Finally, dielectric spectroscopy was used to evaluate the insulating properties of the composites. This work sets the way toward the choice of a proper modifier for enhancing the thermal conductivity of highly filled dielectric polymer composites

    Decorating TiO<sub>2</sub> Nanowires with BaTiO<sub>3</sub> Nanoparticles: A New Approach Leading to Substantially Enhanced Energy Storage Capability of High‑<i>k</i> Polymer Nanocomposites

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    The urgent demand of high energy density and high power density devices has triggered significant interest in high dielectric constant (high-<i>k</i>) flexible nanocomposites comprising dielectric polymer and high-<i>k</i> inorganic nanofiller. However, the large electrical mismatch between polymer and nanofiller usually leads to earlier electric failure of the nanocomposites, resulting in an undesirable decrease of electrical energy storage capability. A few studies show that the introduction of moderate-<i>k</i> shell onto a high-<i>k</i> nanofiller surface can decrease the dielectric constant mismatch, and thus, the corresponding nanocomposites can withstand high electric field. Unfortunately, the low apparent dielectric enhancement of the nanocomposites and high electrical conductivity mismatch between matrix and nanofiller still result in low energy density and low efficiency. In this study, it is demonstrated that encapsulating moderate-<i>k</i> nanofiller with high-<i>k</i> but low electrical conductivity shell is effective to significantly enhance the energy storage capability of dielectric polymer nanocomposites. Specifically, using BaTiO<sub>3</sub> nanoparticles encapsulated TiO<sub>2</sub> (BaTiO<sub>3</sub>@TiO<sub>2</sub>) core–shell nanowires as filler, the corresponding poly­(vinylidene fluoride-<i>co</i>-hexafluoropylene) nanocomposites exhibit superior energy storage capability in comparison with the nanocomposites filled by either BaTiO<sub>3</sub> or TiO<sub>2</sub> nanowires. The nanocomposite film with 5 wt % BaTiO<sub>3</sub>@TiO<sub>2</sub> nanowires possesses an ultrahigh discharged energy density of 9.95 J cm<sup>–3</sup> at 500 MV m<sup>–1</sup>, much higher than that of commercial biaxial-oriented polypropylene (BOPP) (3.56 J cm<sup>–3</sup> at 600 MV m<sup>–1</sup>). This new strategy and corresponding results presented here provide new insights into the design of dielectric polymer nanocomposites with high electrical energy storage capability

    Novel Three-Dimensional Zinc Oxide Superstructures for High Dielectric Constant Polymer Composites Capable of Withstanding High Electric Field

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    High dielectric constant polymer composites capable of withstanding a high electrical field have much application in electronic devices and electrical equipment because of their ease of processing, flexibility, and low cost. Conventional polymer composites with a high dielectric constant, namely ceramic particulate composites and conductive filler based percolative composites, either show low dielectric enhancement or cannot withstand high electric field. Here we report a new strategy for preparing high dielectric constant polymer composites by using novel three-dimensional zinc oxide (3D ZnO) superstructures as fillers. Two kinds of 3D ZnO (flower-like and walnut-like) superstructures were prepared via a template-free solvothermal method. Their poly­(vinylidene fluoride) (PVDF) composites as well as commercial ZnO filled PVDF composite were investigated by a broadband dielectric spectroscopy at a wide temperature range (−50 to +150 °C). Our results showed that, compared with the commercial ZnO, the newly synthesized ZnO superstructures not only significantly increase the dielectric constant of their PVDF composites but also show similar effect on the breakdown strength of their composites. For instance, the dielectric constants (100 Hz) of the composite samples with commercial ZnO, flower-like, and walnut-like ZnO superstructures are 19.4, 221.1, and 104.9, respectively, whereas their breakdown strengths are 45, 42, and 40 kV/mm, respectively. The dielectric investigation evidenced that the higher dielectric constant in the composites with ZnO superstructures should be attributed to the formation of a ZnO percolation network
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