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Polyvinylidene fluoride (PVDF) film with high energy storage density has exhibited great potential for applications in modern electronics, particle accelerators, and pulsed lasers. Typically, dielectric/ferroelectric properties of PVDF film have been tailored for energy storage through stretching, annealing, and defect modification. Here, PVDF films were prepared by the solution casting method followed by an ultraviolet (UV) irradiation process, with special emphasis on how such treatment influences their dielectric and energy storage properties. Upon UV irradiation, the dielectric constant and breakdown strength of the PVDF film were enhanced simultaneously. A high energy density of 18.6 J/cm

In this study, HfO2 films were grown using a highly efficient HT-LCVD process with a large gradient (100 K mm−1) temperature field, achieving four novel microstructures which appeared simultaneously on a high-throughput sample.

Improving the interfacial impedance matching and attenuation ability of a microwave absorber is an important strategy to obtain excellent microwave absorbing performance. Here, we prepared an ultralight, hierarchical porous single-atom Co–N–C microwave absorber, in which evenly distributed single-atom Co is anchored in a porous N-doped carbon framework by N–Co bond via a facile bio-inspired method. These doped single atoms provide abundant highly active atomic absorption sites on the carbon skeleton, and considerable defects including pyridinic-N, pyrrolic-N, oxidized N, and so forth are introduced into the carbon framework owing to single Co atom doping. These doped single Co atoms and introduced defects act together as strong dipolar/interfacial polarization units, which lead to better impedance matching and a significant increase in attenuation capability of the absorber. The metal Co exists in form of a single atom, benefiting light weight of the absorber. Therefore, an extremely strong reflection loss (RL) value of − 60.9 dB is achieved at a lower filler content of 10 wt% with the absorber thickness of 2.5 mm, and the effective frequency bandwidth covered from 10.4 to 15.1 GHz with a thickness of 2.0 mm at a low filler content of 10 wt%. This research offers a novel route for designing a microwave absorber to improve microwave absorption performance and is expected to a wider range of absorbing materials with different structures.

Assembling pristine graphene into freestanding films featuring high electrical conductivity, superior flexibility, and robust mechanical strength aims at meeting the all-around high criteria of new-generation electronics. However, voids and defects produced in the macroscopic assembly process of graphene nanosheets severely degrade the performance of graphene films, and mechanical brittleness often limits their applications in wide scenarios. To address such challenges, an electrostatic-repulsion aligning strategy is demonstrated to produce highly conductive, ultraflexible, and multifunctional graphene films. Typically, the high electronegativity of titania nanosheets (TiNS) induces the aligning of negatively charged graphene nanosheets via electrostatic repulsion in the film assembly. The resultant graphene films show fine microstructure, enhanced mechanical properties, and improved electrical conductivity up to 1.285 × 10

Chemically exfoliated nanosheets have exhibited great potential for applications in various electronic devices. Solution-based processing strategies such as inkjet printing provide a low-cost, environmentally friendly, and scalable route for the fabrication of flexible devices based on functional inks of two-dimensional nanosheets. In this study, chemically exfoliated high-k perovskite nanosheets (i.e., Ca

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.

MXenes have exhibited potential for application in flexible devices owing to their remarkable electronic, optical, and mechanical properties. Printing strategies have emerged as a facile route for additive manufacturing of MXene-based devices, which relies on the rational design of functional inks with appropriate rheological properties. Herein, aqueous MXene/xanthan gum hybrid inks with tunable viscosity, excellent printability, and long-term stability are designed. Screen-printed flexible MXene films using such hybrid inks exhibit a high conductivity up to 4.8 × 10

The use of hafnia (HfO2) has facilitated recent advances in combining uprated dielectric layers (UDLs) and environmental barriers (EBs) in supercomputers. However, an extremely low deposition rate limits further development and fabrication efficiency of HfO2 films. In this study, high-throughput growth of HfO2 films was realized via laser chemical vapor deposition using a laser spot with a gradient temperature distribution. In HfO2 films fabricated by a single growth process, four regions with different morphologies could be discerned for deposition temperatures increasing from 1300 K to 1600 K: leaf-like, pyramid-like, bromeliad-like and pinecone-like. Two growth modes were observed for Regions I and II: Stranski-Krastanov and Volmer-Weber. Regions III and IV contained coexisting monoclinic and tetragonal HfO2 grains with an in-plane boundary for m-HfO2 (-110) {111}//t-HfO2 (1-11) {111}. The maximum deposition rate reached 362 μm/h, which was 102 - 104 times higher than that obtained using existing deposition methods.

Due to its great potential applications in thermal management, heat control, and quantum information, phononics has gained increasing attentions since the first publication in Rev. Mod. Phys. 84 1045 (2012). Many theoretical and experimental progresses have been achieved in the past decade. In this paper, we first give a critical review of the progress in thermal diodes and transistors, especially in classical regime. Then, we give a brief introduction to the new developing research directions such as topological phononics and quantum phononics. In the third part, we discuss the potential applications. Last but not least, we point out the outlook and challenges ahead.

Numerous voids among the incompact layer-structure of MXene films result in their low ambient stability and poor innate conductivity for electromagnetic interference (EMI) shielding. Herein, we report a bridging-sheet-size-controlled densification process of MXene films by applying graphene oxide (GO) as a bridging agent. Specifically, the sheet size of GO is tailored to quantify a negative correlation of sheet size with densification for directing the preparation of most compact MXene-GO films. Benefiting from the shortest electron-transport-distance in the most compact structure, the conductivity of the MXene-GO film achieves 1.7 times (∼1.6 × 10

We report a chemical route to synthesize centimeter-scale stoichiometric "graphenol (C

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.

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.

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 investigated high-temperature dielectric responses of high-κ perovskite nanosheet (Ca2Nb3O10), an important material platform for postgraphene technology and ultrascale electronic devices. Through in situ characterizations using conducting atomic force microscopy, we found a robust high-temperature property of Ca2Nb3O10 nanosheet even in a monolayer form (∼2 nm). Furthermore, layer-by-layer assembled nanocapacitors retained both size-free high-εr characteristic (∼200) and high insulation resistance (∼1×10(-7) A/cm2) at high temperatures up to 250 °C. The simultaneous improvement of εr and thermal stability in high-κ nanodielectrics is of critical technological importance, and perovskite nanosheet has great potential for a rational design and construction of high-temperature capacitors.

For practical application, the functional piezoelectric film in microelectromechanical systems should meet the requirement of physical properties, as well as the mechanical properties. In this article, 0.5Ba(Ti0.8Zr0.2)O3–0.5(Ba0.7Ca0.3)TiO3 (0.5BZT–0.5BCT) thin films with varied properties were prepared on (100) Si substrates via a sol–gel technique at different annealing temperatures. The effects of the annealing temperature on the morphology, piezoelectricity, hardness, and elastic modulus were studied. Particular attention was paid to the surface frictional behavior of films, and the changes in the friction force can be radically explained in terms of differences in the hardness/elastic modulus ratio and the residual stress of films. And, it reveals that the higher ratio of hardness to elastic modulus and tensile residual stress can contribute to a lower friction force for 0.5BZT–0.5BCT film during sling friction.