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Addressing microstructure-property relations of polymer nanocomposites is vital for designing advanced dielectrics for electrostatic energy storage. Here, we develop an integrated phase-field model to simulate the dielectric response, charge transport, and breakdown process of polymer nanocomposites. Subsequently, based on 6615 high-throughput calculation results, a machine learning strategy is schemed to evaluate the capability of energy storage. We find that parallel perovskite nanosheets prefer to block and then drive charges to migrate along with the interfaces in x-y plane, which could significantly improve the breakdown strength of polymer nanocomposites. To verify our predictions, we fabricate a polymer nanocomposite P(VDF-HFP)/Ca2Nb3O10, whose highest discharged energy density almost doubles to 35.9 J cm−3 compared with the pristine polymer, mainly benefit from the improved breakdown strength of 853 MV m−1. This work opens a horizon to exploit the great potential of 2D perovskite nanosheets for a wide range of applications of flexible dielectrics with the requirement of high voltage endurance.

Ferroelectric polymers are the mainstay of advanced flexible electronic devices. How to tailor the ferroelectric polymer films for various applications via simple processing approaches is challenging. Here we demonstrate the tuning of ferroelectric responses can be achieved in polymer blends of poly(vinylidene fluoride-trifluoroethylene) (P(VDF-TrFE)) and polymethyl methacrylate (PMMA) prepared via a simple two-step process. The proposed two-step process endows the polymer blends with a random distribution of P(VDF-TrFE) crystalline phase, hence decoupling the coherent ferroelectric domain interactions between continuous ordered crystalline phases that ubiquitously existed in common P(VDF-TrFE) film. The incorporation of the miscible non-crystalline PMMA chains with low-polarity results in reversal dipoles and a transition from ferroelectric to antiferroelectric-like behavior, overcoming the trade-off between the polarization and depolarization fields. In particular, resultant excellent mechanical and electrical properties of the polymer blend films give rise to remarkably improved breakdown strength and energy storage performance, surpassing P(VDF-TrFE) and commercial biaxial-oriented polypropylene films. This work provides a simple and effective strategy to tailor the ferroelectric response of polymeric materials with great potential for flexible electrical energy storage applications.

We report a chemical route to synthesize centimeter-scale stoichiometric "graphenol (C6OH1)", a 2D crystalline alcohol, via vapor phase hydroxylation of epitaxial graphene on Cu(111). Atomic resolution scanning tunneling microscopy revealed this highly-ordered configuration of graphenol and low energy electron diffraction studies on a large-area single crystal graphene film demonstrated the feasibility of the same superstructure being achieved at the centimeter length scale. Periodic density functional theory (DFT) calculations about the formation of C6(OH)1 and its electronic structure are also reported.

Triboelectric nanogenerator (TENG) is an effective way to convert mechanical energy into electricity, which has been approved as new types of energy harvesting and strain sensor technology. In this study, we design and fabricate a flexible and transparent TENG based on a nanocomposite film made of PVDF and titania monolayer (TOML). The PVDF/TOML composite TENG with 1.5 wt% TOML generates output signals of 52.8 V and 5.69 μA/cm2 and a 50-fold enhancement in output power, compared to the pure PVDF-based TENG. It is found that the synergy between efficient electron capture and high dielectric constant of TOML leads to enhancing the performance of the TENG. Besides, the nanocomposite maintains high performance of the stability and durability due to the excellent compatibility between the inorganic TOML and organic PVDF.

Two-dimensional (2D) mesoporous VO2 microarrays have been prepared using an organic–inorganic liquid interface. The units of microarrays consist of needle-like VO2 particles with a mesoporous structure, in which crack-like pores with a pore size of about 2 nm and depth of 20–100 nm are distributed on the particle surface. The liquid interface acts as a template for the formation of the 2D microarrays, as identified from the kinetic observation. Due to the mesoporous structure of the units and high conductivity of the microarray, such 2D VO2 microarrays exhibit a high specific capacitance of 265 F/g at 1 A/g and excellent rate capability (182 F/g at 10 A/g) and cycling stability, suggesting the effect of unique microstructure for improving the electrochemical performance. Electronic supplementary material The online version of this article (10.1186/s11671-018-2557-7) contains supplementary material, which is available to authorized users.

A flexible polymer nanocomposite has been developed via introducing Nd-doped BaTiO3 nanoparticles into the poly(vinylidene fluoride). This nanocomposite delivers a discharged energy density up to 12.5 J/cm3 under an electric field of 420 kV/mm with only a small loading of 1 vol.% Nd-BaTiO3. High discharged energy density, mechanical flexibility, light weight, ease fabrication and low cost makes it attractive for advanced microelectronics and electrical power systems. Our results demonstrate that ceramics with giant dielectric permittivity as viable fillers for polymer nanocomposite dielectrics with higher energy density.

The present work demonstrated the tunable negative permittivity and permeability properties of a two-phase composite material consisting of conductive matrix [polyaniline (PANI)] and magnetic filler [yttrium iron garnet (YIG)]. The negative permittivity observed in the YIG/PANI composites is accompanied by the formation of conductive PANI network, which induced the plasma oscillation of carriers in PANI obeying the Drude model. Through theoretical calculation, negative permeability can be realized and further adjusted by external magnetic field via the domain wall and spin resonances of YIG.

The process of oxidation of a copper surface coated by a layer of graphene in water-saturated air at 50 °C was studied where it was observed that oxidation started at the graphene edge and was complete after 24 h. Isotope labeling of the oxygen gas and water showed that the oxygen in the formed copper oxides originated from water and not from the oxygen in air for both Cu and graphene-coated Cu, and this has interesting potential implications for graphene as a protective coating for Cu in dry air conditions. We propose a reaction pathway where surface hydroxyl groups formed at graphene edges and defects induce the oxidation of Cu. DFT simulation shows that the binding energy between graphene and the oxidized Cu substrate is smaller than that for the bare Cu substrate, which facilitates delamination of the graphene. Using this process, dry transfer is demonstrated using poly(bisphenol A carbonate) (PC) as the support layer. The high quality of the transferred graphene is demonstrated from Raman maps, XPS, ...

We explored a support-free method for transferring large area graphene films grown by chemical vapor deposition to various fluoric self-assembled monolayer (F-SAM) modified substrates including SiO2/Si wafers, polyethylene terephthalate films, and glass. This method yields clean, ultrasmooth, and high-quality graphene films for promising applications such as transparent, conductive, and flexible films due to the absence of residues and limited structural defects such as cracks. The F-SAM introduced in the transfer process can also lead to graphene transistors with enhanced field-effect mobility (up to 10,663 cm(2)/Vs) and resistance modulation (up to 12×) on a standard silicon dioxide dielectric. Clean graphene patterns can be realized by transfer of graphene onto only the F-SAM modified surfaces.

An excellent ternary composite photocatalyst consisting of silver orthophosphate (Ag3PO4), attapulgite (ATP), and TiO2 was synthesized, in which heterojunction was formed between dissimilar semiconductors to promote the separation of photo-generated charges. The ATP/TiO2/Ag3PO4 composite was characterized by SEM, XRD, and UV-vis diffuse reflectance spectroscopy. The co-deposition of Ag3PO4 and TiO2 nanoparticles onto the surface of ATP forms a lath-particle structure. Compared with composite photocatalysts consisting of two phases, ATP/TiO2/Ag3PO4 ternary composite exhibits greatly improved photocatalytic activity for degradation of rhodamine B under simulated solar irradiation. Such ternary composite not only improves the stability of Ag3PO4, but also lowers the cost by reducing application amount of Ag3PO4, which provides guidance for the design of Ag3PO4- and Ag-based composites for photocatalytic applications.

Complex perovskite oxides offer tremendous potential for controlling their rich variety of electronic properties, including high-TC superconductivity, high-κ ferroelectricity, and quantum magnetism. Atomic-scale control of these intriguing properties in ultrathin perovskites is an important challenge for exploring new physics and device functionality at atomic dimensions. Here, we demonstrate atomic-scale engineering of dielectric responses using two-dimensional (2D) homologous perovskite nanosheets (Ca2Nam–3NbmO3m+1; m = 3–6). In this homologous 2D material, the thickness of the perovskite layers can be incrementally controlled by changing m, and such atomic layer engineering enhances the high-κ dielectric response and local ferroelectric instability. The end member (m = 6) attains a high dielectric constant of ∼470, which is the highest among all known dielectrics in the ultrathin region (

We demonstrate a flexible radiofrequency filter based on graphene assembly films with a high conductivity up to 106 S/m and a thickness of 10 μm. The flexible high-conductivity graphene film (HCGF) used in the filter has a fifth-order low-pass Chebyshev frequency response, and it operates at 3.6 GHz with a 0.82 dB in-band maximum insertion loss and 26.21 dB insertion loss at 5 GHz. Such performance observed in the HCGF-based flexible filters is comparable to that of commercial copper-based filters in passband and roll-off. The HCGF exhibits good mechanical flexibility even after 200 cycles of bending. Nearly no mechanical failure or performance degradation occurs during 20 cycles of 0°–50° bending for the flexible HCGF filter. Our results suggest that the flexible HCGF filter has good repetitive bending stability. This makes this type of filter suitable for future applications in flexible wireless communication.

Multiferroic materials, in which the electronic polarization can be switched by a magnetic field and vice versa, are of fundamental importance for new electronic technologies. However, there exist very few single-phase materials that exhibit such cross-coupling properties at room temperature, and heterostructures with a strong magnetoelectric coupling have only been made with complex techniques. Here, we present a rational design for multiferroic materials by use of a layer-by-layer engineering of 2D nanosheets. Our approach to new multiferroic materials is the artificial construction of high-quality superlattices by interleaving ferromagnetic Ti0.8Co0.2O2 nanosheets with dielectric perovskite-structured Ca2Nb3O10 nanosheets. Such an artificial structuring allows us to engineer the interlayer coupling, and the (Ti0.8Co0.2O2/Ca2Nb3O10/Ti0.8Co0.2O2) superlattices induce room-temperature ferroelectricity in the presence of the ferromagnetic order. Our technique provides a new route for tailoring artificial multiferroic materials in a highly controllable manner.

cited By 4; International audience; Few-layer graphenes, supported on Si with a superficial oxide layer, were subjected to a Birch-type reduction using Li and H2O as the electron and proton donors, respectively. The extent of hydrogenation for bilayer graphene was estimated at 1.6-24.1% according to Raman and X-ray photoelectron spectroscopic data. While single-layer graphene reacts uniformly, few-layer graphenes were hydrogenated inward from the edges and/or defects. The role of these reactive sites was reflected in the inertness of pristine few-layer graphenes whose edges were sealed. Hydrogenation of labeled bilayer (12C/13C) and trilayer (12C/13C/12C) graphenes afforded products whose sheets were hydrogenated to the same extent, implicating passage of reagents between the graphene layers and equal decoration of each graphene face. The reduction of few-layer graphenes introduces strain, allows tuning of optical transmission and fluorescence, and opens synthetic routes to long sought-after films containing sp3-hybridized carbon.

Epitaxial graphene grown on single crystal Cu(111) foils by chemical vapor deposition is found to be free of wrinkles and under biaxial compressive strain. The compressive strain in the epitaxial regions (0.25-0.40%) is higher than regions where the graphene is not epitaxial with the underlying surface (0.20-0.25%). This orientation-dependent strain relaxation is through the loss of local adhesion and the generation of graphene wrinkles. Density functional theory calculations suggest a large frictional force between the epitaxial graphene and the Cu(111) substrate, and this is therefore an energy barrier to the formation of wrinkles in the graphene. Enhanced chemical reactivity is found in epitaxial graphene on Cu(111) foils as compared to graphene on polycrystalline Cu foils for certain chemical reactions. A higher compressive strain possibly favors lowering the formation energy and/or the energy gap between the initial and transition states, either of which can lead to an increase in chemical reactivity.