Carbon最新文献

This study explores the structural changes of hard carbon (HC) negative electrodes in sodium-ion batteries induced by insertion of Na ions during sodiation. X-ray Raman spectroscopy (XRS) was used to record both C and Na K-edge absorption spectra from bulk HC anodes carbonized at different temperatures and at several points during sodiation and desodiation. Comparing the ${\pi }^{\ast }$/${\sigma }^{\ast }$ regions in the C K-edge spectra ${\mathrm{sp}}^2$/${\mathrm{sp}}^3$ hybridization ratio of material was determined. Higher carbonization temperatures led to increased order in graphitic structure and shorter

Achieving excellent electromagnetic-wave absorption (EMA) performances and outstanding multifunctional physicochemical properties in complicated application environments is a great challenge for high-entropy alloys (HEAs) absorber. To accomplish this goal, a novel mechanochemical carbonitriding technique is designed. Carbonitriding FeCoNiCu HEAs with flake-like morphology is successfully prepared by a mechanochemical method using the cyano-compound (melamine, C₃H₆N₆) and metal powders as raw materials. Through the investigation of phase structure, magnetic properties, corrosion resistance, oxidation resistance and EMA performances of the samples, it can be found that the carbonitriding process optimizes the high-frequency electromagnetic matching of HEAs, and realizes excellent EMA performances. With the introduction of melamine, S003 (FeCoNiCuM_0.03) sample has a reflection loss of −55.8 dB with an effective absorption bandwidth (EAB) of 3.82 GHz, and S006 (FeCoNiCuM_0.06) sample achieves a strong absorption of −61.8 dB. In addition, the carbonitriding FeCoNiCu HEAs exhibit excellent corrosion resistance and mechanical hardness. This work not only demonstrates the potential of carbonitriding HEAs for EMA applications, but also provides a new concept for optimizing the electromagnetic impedance matching of HEAs.

Aqueous zinc-ion batteries (AZIBs) have become a hot topic in study owing to their abundance of zinc resources, environmental friendliness, high capacity, and low cost. Nevertheless, the majority of cathode materials utilized in AZIBs frequently exhibit suboptimal electrical conductivity and structural instability, which restrict their application in energy storage. Here, a carbon-coated manganese oxide anchored on carbon skeleton (MnO–C@C) hybrid was synthesized using a simple and scalable method. The electrical conductivity of MnO can be enhanced by the double carbon layer. The presence of carbon skeleton effectively inhibits the agglomeration phenomenon of MnO and exposes more active sites. Meanwhile, the interaction force between the coated carbon and MnO effectively increases the structural stability of MnO. Taking advantage of the synergistic effect, the MnO–C@C hybrid shows an exceptional specific capacity of 409 mAh g⁻¹ at 50 mA g⁻¹ and outstanding cycling stability of 1000 cycles at 2000 mA g⁻¹ (low decay rate of 0.0058 % per cycle). Besides, the reaction mechanisms are investigated via various characterizations. This work presents an inspired solution for developing manganese-based cathode materials in AZIBs.

The friction of water within a carbon nanotube (CNT) is influenced by the interplay between energy barriers and water structure. In this work, we employ a series of regular polygonal CNTs, whose energy barriers remain constant with size, to examine the influence of water structure on solid-water friction using the molecular dynamics (MD) method. Polygonal CNTs with radii under 0.45 nm show friction coefficients an order of magnitude higher than their circular counterparts. While water exhibits an ordered phase within 0.5–0.6 nm-radius polygonal CNTs, resulting in a significant 80 % reduction in the friction coefficients compared to bulk like water. The force distribution analysis confirms the constancy of energy barriers. Further analysis of water density, hydrogen bond number distribution, average structure factor, and density correlation time demonstrates that the density correlation time predominantly impacts solid-liquid friction. The observed reduction in friction is primarily due to the collective movement of water molecules in an ordered arrangement. These findings illuminate nanoscale drag reduction mechanisms, offering insights for micro-nano flow system design.

Extensive research has been conducted on carbonaceous materials due to their unique combination of physical, chemical, and mechanical properties, which significantly rely on the hybridization of carbon atoms. Scanning transmission electron microscopy-electron energy loss spectroscopy is a powerful technique that enables the identification of carbon allotropes with high spatial resolution, utilizing specific spectral features. However, anisotropic materials like graphite and carbon nanotubes can exhibit variations in these spectral features based on their orientation relative to the electron beam. Optimized experimental conditions, referred to as magic angle conditions, permits overcoming this challenge. By implementing such conditions, we have successfully mapped the hybridization in a heterogeneous system containing three carbon allotropes, i.e. nanodiamonds, multi-walled carbon nanotubes, and lacey carbon. Moreover, a convolutional neural network has been created and trained to accurately identify and map these carbonaceous phases. Thus, the reported innovative approach allows nanoscale mapping of both hybridization and phase distributions for complex heterogeneous carbon systems.

By correlating structural information with catalytic activity, it is possible to determine the active structure of a catalyst. However, this is far from straightforward and the active structure remains debated even in the well-studied reaction of graphitic carbon formation using noble metal catalysts such as platinum (Pt). One major hindrance is that static observations do not provide access to transitional catalyst states. Here we prove the formation of transitional surface Pt carbide several layers deep as well as a Pt-carbon composite phase during the growth process of carbon nanotubes using atomic-resolution gas in situ transmission electron microscopy combined with density functional theory. Knowledge of the active structure of noble metal Pt is of great interest due to its usage in heterogeneous catalysis. Most importantly, it opens up new avenues to suppress catalyst coking. The unwanted build-up of carbon is the major source of catalyst deactivation in important industrial reactions including propane dehydrogenation, with major financial and environmental consequences.

Multifunctional cotton fabric holds great promise across domestic and healthcare sectors. However, the challenge lies in developing a simple, sustainable method to create versatile, multifunctional cotton fabric. Herein, we designed novel 3D bimetallic organic frameworks (Ag/MIL125-NH₂) for the first time and fabricated BM125@COT, a superhydrophobic cotton fabric adorned with porous hierarchical grooves. This was achieved by spraying Ag/MIL125-NH₂ onto the cotton fabric's surface, followed by post-synthetic treatment with non-fluorinated myristic acid, resulting in superhydrophobic BM125@COT. The coated fabric showed a water contact angle (WCA) of 162.2° and a water sliding angle (WSA) of 4° ± 1. Surface morphology, size, structural and chemical composition, and anti-wetting properties of synthesized MOFs and BM125@COT were evaluated by SEM, EDS, TEM, XRD, XPS, UV/Vis, ATR, DSC, and Optical Tensiometer. Durability tests, including splash tests, abrasion resistance, tape peeling, washing, pH effects, and ultrasonication cycles, underscored the fabric's robust mechanical stability and chemical resistance. Moreover, superhydrophobic BM125@COT demonstrated UV-blocking efficiency, impressive self-cleaning capabilities, and enhanced antibacterial activity. This low-cost, scalable, and sustainable fabric, fabricated through a straightforward one-step spray coating technique, holds immense potential for versatile applications.

Thermal interface materials (TIMs) that block electromagnetic interference (EMI) and current leakage are essential for high-density, high-power devices and compact form factors of electronic and mobility platforms. However, their coupled thermal-electrical-electromagnetic characteristics involve mismatches in thermal conductivity, electrical insulation, and EMI shielding, limiting the multifunctionality. Herein, a sandwich-like structural design that rationally combines graphene nanoplatelets (GNPs), hexagonal boron nitride nanosheets (BNNSs) and cellulose nanofibers (CNFs) is presented toward multifunctional trilayer TIMs enabling high thermal conductivity, EMI shielding, electrical insulation, mechanical compatibility and flame retardancy. The top and bottom BNNSs serve as electrically insulating yet thermally conductive layers while the GNPs in the central layer mitigate EMI and the CNFs as a binder complete the mechanical properties for the lamella-like trilayers. The resulting TIM exhibits a high in-plane thermal conductivity (25.5 W/m·K), and the LED cooling system using the TIM demonstrates the capability of reducing the operating temperature. Furthermore, it shows a high-volume resistivity (4.12 × 10¹³ Ω cm) and EMI shielding effectiveness (29.0 dB) at X-band frequencies. Its mechanical robustness is confirmed with tensile strength and elongation of 65.0 MPa and 2.36 %, and the high flame retardancy is validated. The outcomes will inspire tailoring multifunctional TIMs using lamellar structures that optimally combine micro/nanomaterials.

Graphene possesses unique combination of characteristics (i.e., inertness, impermeability and toughness) to qualify as ideal coating material for corrosion resistance, and graphene coatings on nickel and copper have been shown to provide excellent and durable corrosion resistances. However, growing graphene directly on mild steel by chemical vapour deposition (CVD), is prohibitively challenging due to high solubility of carbon in mild steel at high temperatures. The non-trivial challenge was circumvented through surface modification of steel by electroplating with Cu and Ni, accounting for the critical consideration, i.e., the inter-diffusivity of iron in nickel or copper. However, the key finding was that the undesirably high thicknesses of the electroplated Cu and Ni layers were detrimental, and optimization of their thicknesses was essential for successful deposition of the required quality graphene. The optimised thicknesses were derived on the basis of the fundamental diffusion calculations. The uniform multi-layered graphene coating on the suitably modified mild steel surface provided remarkable corrosion resistance in an aqueous chloride solution, and electrochemically validation of the corrosion durability for extended exposure (>1000 h) was characterised.