The properties of high theoretical capacity, low cost, and large potential of metallic sodium (Na) has strongly promoted the development of rechargeable sodium‐based batteries. However, the issues of ...infinite volume variation, unstable solid electrolyte interphase (SEI), and dendritic sodium causes a rapid decline in performance and notorious safety hazards. Herein, a highly reversible encapsulation‐based sodium storage by designing a functional hollow carbon nanotube with Zn single atom sites embedded in the carbon shell (ZnSA‐HCNT) is achieved. The appropriate tube space can encapsulate bulk sodium inside; the inner enriched ZnSA sites provide abundant sodiophilic sites, which can evidently reduce the nucleation barrier of Na deposition. Moreover, the carbon shell derived from ZIF‐8 provides geometric constraints and excellent ion/electron transport channels for the rapid transfer of Na+ due to its pore‐rich shell, which can be revealed by in situ transmission electron microscopy (TEM). As expected, Na@ZnSA‐HCNT anodes present steady long‐term performance in symmetrical battery (>900 h at 10 mA cm−2). Moreover, superior electrochemical performance of Na@ZnSA‐HCNT||PB full cells can be delivered. This work develops a new strategy based on carbon nanotube encapsulation of metallic sodium, which improves the safety and cycling performance of sodium metal anode.
Designing a functional encapsulation‐based sodium storage void with abundant pore structure and enriched Zn single atom sites in the inner wall is presented here. Zn single atoms provide abundant selective sodiophilic nucleation sites. Due to the rich pore structure, ZIF‐derived carbon shells can provide geometric constraints and excellent ion/electron transport channels to maintain fast electron/ion contact, benefiting for encapsulating large amounts of metallic sodium.
With the development of flexible electronic devices and large‐scale energy storage technologies, functional polymer‐matrix nanocomposites with high permittivity (high‐k) are attracting more attention ...due to their ease of processing, flexibility, and low cost. The percolation effect is often used to explain the high‐k characteristic of polymer composites when the conducting functional fillers are dispersed into polymers, which gives the polymer composite excellent flexibility due to the very low loading of fillers. Carbon nanotubes (CNTs) and graphene nanosheets (GNs), as one‐dimensional (1D) and two‐dimensional (2D) carbon nanomaterials respectively, have great potential for realizing flexible high‐k dielectric nanocomposites. They are becoming more attractive for many fields, owing to their unique and excellent advantages. The progress in dielectric fields by using 1D/2D carbon nanomaterials as functional fillers in polymer composites is introduced, and the methods and mechanisms for improving dielectric properties, breakdown strength and energy storage density of their dielectric nanocomposites are examined. Achieving a uniform dispersion state of carbon nanomaterials and preventing the development of conductive networks in their polymer composites are the two main issues that still need to be solved in dielectric fields for power energy storage. Recent findings, current problems, and future perspectives are summarized.
1D/2D carbon nanomaterial‐polymer dielectric composites are a promising way to realize excellent dielectric properties and high energy density with low filler concentration, which are essential in power energy storage application. Progress in recent years is summarized and the advantages and disadvantages of different strategies are identified to provide clearer paths for researchers in this field.
Dielectric polyimides (PIs) are ubiquitous as insulation in electrical power systems and electronic devices. Generally, dynamic polyimide is required to solve irreversible failure processes of ...electrical or mechanical damage, for example, under high temperature, pressure, and field strength. The challenge lies in the design of the molecular structure of rigid polyimide to achieve dynamic reversibility. Herein, a low‐molecular‐weight polyimide gene unit is designed to crosslink with polyimide ligase to prepare the smart film. Interestingly, due to the variability of gene unit and ligase combinations, the polyimide films combining hardness with softness are designed into three forms via a “Mimosa‐like” bionic strategy to adapt to different application scenarios. Meanwhile, the films have good degradation efficiency, excellent recyclability, and can be self‐healable, which makes them reuse. Clearly, the films can be used in the preparation of ultrafast sensors with a response time ≈0.15 s and the application of corona‐resistant films with 100% recovery. Furthermore, the construction of polyimide and carbon‐fiber‐reinforced composites (CFRCs) has been verified to apply to the worse environment. Nicely, the composites have the property of multiple cycles and the non‐destructive recycle rate of carbon fiber (CF) is as high as 100%. The design idea of preparing high‐strength dynamic polyimide by crosslinking simple polyimide gene unit with ligase could provide a good foundation and a clear case for the sustainable development of electrical and electronic polyimides, from the perspective of Mimosa bionics.
A dynamic polyimide (PI) film, which can transform among three molecular structures, is designed by imitating the behavior of the Mimosa plant. The PI film is a super‐corona‐resistant film, a matrix of high‐sensitivity humidity sensor and carbon‐fiber‐reinforced composites due to its excellent capabilities of degradation, self‐healable ability, and recyclability.
Although several laser-plasma-based methods have been proposed for generating energetic electrons, positrons and γ-photons, manipulation of their microstructures is still challenging, and their ...angular momentum control has not yet been achieved. Here, we present and numerically demonstrate an all-optical scheme to generate bright GeV γ-photon and positron beams with controllable angular momentum by use of two counter-propagating circularly-polarized lasers in a near-critical-density plasma. The plasma acts as a 'switching medium', where the trapped electrons first obtain angular momentum from the drive laser pulse and then transfer it to the γ-photons via nonlinear Compton scattering. Further through the multiphoton Breit-Wheeler process, dense energetic positron beams are efficiently generated, whose angular momentum can be well controlled by laser-plasma interactions. This opens up a promising and feasible way to produce ultra-bright GeV γ-photons and positron beams with desirable angular momentum for a wide range of scientific research and applications.
Polyimides (PIs) are widely used in circuit components, electrical insulators, and power systems in modern electronic devices and large electrical appliances. Electrical/mechanical damage of ...materials are important factors that threaten reliability and service lifetime. Dynamic (self-healable, recyclable and degradable) PIs, a promising class of materials that successfully improve electrical/mechanical properties after damage, are anticipated to solve this issue. The viewpoints and perspectives on the status and future trends of dynamic PI based on a few existing documents are shared. The main damage forms of PI dielectric materials in the application process are first introduced, and initial strategies and schemes to solve these problems are proposed. Fundamentally, the bottleneck issues faced by the development of dynamic PIs are indicated, and the relationship between various damage forms and the universality of the method is evaluated. The potential mechanism of the dynamic PI to deal with electrical damage is highlighted and several feasible prospective schemes to address electrical damage are discussed. This study is concluded by presenting a short outlook and future improvements to systems, challenges, and solutions of dynamic PI in electrical insulation. The summary of theory and practice should encourage policy development favoring energy conservation and environmental protection and promoting sustainability.
Pair production can be triggered by high-intensity lasers via the Breit-Wheeler process. However, the straightforward laser-laser colliding for copious numbers of pair creation requires light ...intensities several orders of magnitude higher than possible with the ongoing laser facilities. Despite the numerous proposed approaches, creating high-energy-density pair plasmas in laboratories is still challenging. Here we present an all-optical scheme for overdense pair production by two counter-propagating lasers irradiating near-critical-density plasmas at only ∼10
W cm
. In this scheme, bright γ-rays are generated by radiation-trapped electrons oscillating in the laser fields. The dense γ-photons then collide with the focused counter-propagating lasers to initiate the multi-photon Breit-Wheeler process. Particle-in-cell simulations indicate that one may generate a high-yield (1.05 × 10
) overdense (4 × 10
cm
) GeV positron beam using 10 PW scale lasers. Such a bright pair source has many practical applications and could be basis for future compact high-luminosity electron-positron colliders.
Polymer-based dielectrics (PDs) with improved permittivity (k) have considerable applications including capacitors, actuator devices and electrical power systems due to their flexibility, easy ...processability and low weight, etc. However, the permittivity values of commonly used polymers (usually k < 3) fails to meet the requirements of the advanced electrical components. Enormous research, including numerical and experimental works has shown that developing polymer based multi-phase materials represents the most promising avenue. This review will clarify the concepts and relationships based on the polarization mechanisms and meanwhile some key factors of improving permittivity will also be discussed including polymer chains/segments, morphology, the interface of nanofillers-matrix, processing, and multilayer structures. Combining with the recent specific advances in PDs, the latest developments in this field will be summarized which are the introduction of polar functional groups/copolymer segments, the application of core-shell nanofillers and the technology of multi-layers structures. We hope to help readers to comprehensively understand the fabrication of PDs from the selection of molecular units to the design of composites in order to provide guidance on achieving polymer based materials with high permittivity.
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•Some representative structure characteristics of high-k polymers are introduced.•To realize the high-k polymer materials by employing different routes is illustrated.•Guidance on achieving polymer based materials with high permittivity is provided.
To match the increasing miniaturization and integration of electronic devices, higher requirements are put on the dielectric and thermal properties of the dielectrics to overcome the problems of ...delayed signal transmission and heat accumulation. Here, a 3D porous thermal conductivity network is successfully constructed inside the polyimide (PI) matrix by the combination of ionic liquids (IL) and calcium fluoride (CaF2) nanofillers, motivated by the bubble‐hole forming orientation force. Benefiting from the 3D thermal network formed by IL as a porogenic template and “crystal‐like phase” structures induced by CaF2‐ polyamide acid charge transfer, IL‐10 vol% CaF2/PI porous film exhibits a low permittivity of 2.14 and a thermal conductivity of 7.22 W m−1 K−1. This design strategy breaks the bottleneck that low permittivity and high thermal conductivity in microelectronic systems are difficult to be jointly controlled, and provides a feasible solution for the development of intelligent microelectronics.
Through the dual action of calcium fluoride and ionic liquid on the polyimide (PI) matrix, the 3D porous thermal conductivity network and special “crystal‐like phase” structures are constructed in PI. These endow the PI materials with highly efficient low dielectric and thermal conductivity properties to better serve the electrical and electronic fields.
Great challenge exists in prediction of a laminate strength, due to too many tough issues involved. The constitutive relation of each lamina in the laminate is described by Bridging Model. Both ...matrix plasticity and interface debonding induced slippages have been taken into account. Significant differences do sometimes exist between predicted laminate strengths with and without matrix plasticity. Whereas stress calculation and failure detection for the fiber is relatively easy, the homogenized matrix stresses obtained micromechanically must be converted into true quantities prior to a failure assessment. The conversion for the bi-axial transverse stresses is re-established in this paper. A matrix tensile failure subjected to a 2D (two-dimensional) stress state is detected by a recently developed physics based failure criterion, while that under a 3D stress state is estimated using Tsai-Wu's criterion. Matrix compressive failures under both 2D and 3D stress states are assessed using physics based slippage failure criterion in which the normal stress influencing coefficient for the different stress state should be different. A matrix failure induced lamina failure can correspond to an ultimate failure only when an additionally critical strain condition is fulfilled. These conditions are established in the paper. All of the test cases in the first and second world wide failure exercises (WWFEs) have been analyzed using the original input data provided by the exercise organizers. All of the predictions agree well or reasonably with the available experiments. All the analyzing formulae involved are analytical and in closed-form, without any iteration for a solution.
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1.A general 3D elastic-inelastic constitutive relation for a UD lamina is shown;2.Conversion of matrix's homogenized stresses under bi-axial transverse loads into true values is obtained;3.A complete set of failure criteria for fiber and matrix induced lamina failures are developed;4.Critical strain conditions for an ultimate failure of the laminate are established;5.All of the formulae to predict laminate failures under any 3D load are analytical with independent input data.
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