Dielectric materials with good thermal transport performance and desirable dielectric properties have significant potential to address the critical challenges of heat dissipation for microelectronic devices and power equipment under high electric field. This work reported the role of synergistic effect and interface on through-plane thermal conductivity and dielectric properties by intercalating the hybrid fillers of the alumina and boron nitride nanosheets (BNNs) into epoxy resin. For instance, epoxy composite with hybrid fillers at a relatively low loading shows an increase of around 3 times in through-plane thermal conductivity and maintains a close dielectric breakdown strength compared to pure epoxy. Meanwhile, the epoxy composite shows extremely low dielectric loss of 0.0024 at room temperature and 0.022 at 100 ℃ and 10−1 Hz. And covalent bonding and hydrogen-bond interaction models were presented for analyzing the thermal conductivity and dielectric properties.
Dielectric films are the foundation of power electronic equipment for energy storage in capacitors. However, typical dielectric films exhibit undesirable energy storage density and thermal stability, limiting its further application in the advanced field. For both pure polymers and composites‐based dielectrics, the macromolecular matrix greatly determines the performances. This paper summarizes the research progress of all‐organic polymer materials for the dielectric application from the perspective of molecular structure design. Systematic comparisons on properties, including dielectric constant and dielectric loss, glass transition temperature, and energy density are given, expecting to inspire researchers to devote further efforts in this area. An outlook for the future of all‐polymer dielectrics is also presented.
Zeolite imidazolate framework-67 (ZIF-67)-derived layered double hydroxides (LDH) via hydrolysis reaction have aroused widespread interest for oxygen evolution reaction (OER), while the role of the electron-deficient 2-methylimidazole (MIM) of ZIF-67...
Hydrogen is one of the prime candidates for clean energy source with high energy density. However, current industrial methods of hydrogen production are difficult to provide hydrogen with high purity, thus there are hard to meet the requirements in many application scenarios. Consequently, the development of large-scale and low-cost hydrogen separation technology is urgently needed. In this work, the gas separation properties of a newly synthesized two-dimensional nanoporous graphene (NPG) membrane material with patterned dumbbell-shaped nanopores are investigated. The permeation energy barriers of different gases through this membrane are calculated using the density functional theory (DFT) calculations. Molecular dynamics (MD) simulations are also employed to study the permeation behavior of H 2 in binary mixtures with O 2 , CO 2 , CO, and CH 4 . Both the DFT and MD calculation results show that this newly synthesized NPG membrane material can provide high permeability as well as ultrahigh selectivity simultaneously, making it a prospective H 2 separation membrane with superior performance.
The
practical application of lithium-/sodium-metal batteries is
currently hindered by severe safety issues caused by uncontrolled
continuous dendrite growth. Semiconductive nanoporous g-C3N4 film has been demonstrated to be an effective protection
layer for lithium-/sodium-metal anode, which can suppress the growth
of dendrite. However, the underlying mechanism of how this semiconductive
flexible thin film works to suppress dendrite growth remains unclear.
In this work, we investigate the detailed working mechanism of g-C3N4 protection layer employing both density functional
theory calculations and ab initio molecular dynamics simulations.
The calculation results indicate that g-C3N4 layers show strong adhesion toward the lithium-/sodium-metal surface.
When contacting with lithium/sodium metal, the intrinsic triangular
nanopores of g-C3N4 will be quickly filled with
lithium/sodium atoms, turning the semiconductive g-C3N4 into a metallic material. Lithium/sodium atoms can migrate
through the triangular nanopores of stacked g-C3N4 layers via a vacancy-mediated approach with moderate energy barriers
of 0.42 and 0.61 eV, respectively. With a low current density, the
newly deposited lithium/sodium atoms can permeate through the g-C3N4 protection layers, therefore resulting in a
flat electrode surface with no dendrite; with a high current density,
however, the newly deposited lithium/sodium atoms cannot transport
across the protection layer timely, which will result in the aggregation
of lithium/sodium atoms on the surface of the g-C3N4 protection layer.
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