(searched for: doi:10.1016/j.jmst.2020.09.012)
Carbon, Volume 183, pp 415-427; doi:10.1016/j.carbon.2021.07.040
The introduction of heteroatom is a practical tactic that can enhance the ability of carbon materials to store Na+. In this article, N, O, P co-doped hierarchical porous carbon (NOPC) is produced via co-carbonization with phytic acid and soybean protein as precursors. Phytic acid, as a multifunctional additive, macroscopically promotes the formation of a hierarchical pore structure in which micropores and mesopores coexist. It is necessary for the transmission of Na+ and penetration of electrolytes. It microscopically regulates different types of surface functional groups, induces defects to enhance the spacing between graphite layers, and enhances the adsorption and intercalation capacity of Na+. The macroscopic and microscopic co-working changes the NOPC to have a reversible capacity of 359.5 mA h g−1 at 0.05 A g−1. Using density functional theory, it is confirmed that the co-doping of N/O/P can increase the capture capacity of Na+ and reduce the diffusion barrier of carbon materials. Ex-situ XRD, ex-situ Raman and ex-situ TEM were used to verify the structural stability and cycle stability of the NOPC. This study is based on experimental design and theoretical calculations used to prove that synthesis strategy is an effective method for preparing heteroatom-doped carbon with excellent capacity to store sodium.
Composites Science and Technology, Volume 210; doi:10.1016/j.compscitech.2021.108801
The ternary composite material [email protected] with a core-shell structure and excellent electromagnetic absorption properties has been prepared by covalently modifying reducing graphene oxide with the binary magnetic material [email protected] The ternary composite material [email protected]/rGO forms a " CO–NH ″ covalent bond between [email protected] and rGO through hydrothermal routes and mechanical stirring. By comparing the two types of the connection method covalent and non-covalent bonds, it was surprised to find that formed by covalently connecting the binary [email protected] material and rGO (C-ZPr) to obtain extremely excellent electromagnetic absorption performance. By adjusting the thickness from 1 mm to 4 mm, when the filler ratio is 20%, the minimum reflection loss (RLmin) at 2.1 mm was as low as −49.99 dB at 17.28 GHz and the effective absorption bandwidth (RL < 10 dB) was almost 4.32 GHz. The introduction of covalent bonds becomes a bridge connecting magnetic materials and dielectric materials, adjusting electromagnetic parameters, enhancing reflection loss, and achieving impedance matching and improved electromagnetic absorbing performance. This preparation method is expected to provide new ideas for the preparation of high-performance absorbing materials in the future.
Carbon, Volume 179, pp 554-565; doi:10.1016/j.carbon.2021.04.053
As a dielectric loss-type absorber, lamellar transitional metal chalcogenides (LTMCs) become more and more popular in the electromagnetic (EM) absorbing field due to their unique two-dimensional sheet structure. However, it remains challenging for metallic sulfides to obtain magnetic loss, further promoting loss mechanism. Herein, magnetic Fe3S4 LTMCs [email protected] wax gourd aerogel-derived carbon composites are fabricated through a facile pyrolysis process and subsequent hydrothermal method. Compared to a pure biomass carbon or Fe3S4, [email protected] composites exhibited an optimized and adjustable EM characteristic, which can be put down to the synergistic effects between the dielectric/magnetic loss and the impedance match. The sample shows superior EM absorption properties with a minimum reflection loss (RL) of −58.85 dB at 3.1 mm and a broad effective bandwidth (EBW) of 5.40 GHz at the matching thickness of 2.0 mm with a filling ratio of 20 wt%. In addition, the radar cross section (RCS) simulation confirms that the material can effectively suppress EMW (−8.51 dB m2 at zero degree) in practical applications. Therefore, it is believed that the as-prepared [email protected] hybrids can be one of the prospective candidates as high-efficiency EMW absorbers.
Carbon, Volume 178, pp 273-284; doi:10.1016/j.carbon.2021.03.042
Core-shell [email protected](3,4-ethylenedioxythiophene) (PEDOT) microspheres are compounded with reduced graphene oxide (rGO) to prepare [email protected]/rGO composite as an efficient electromagnetic (EM) wave absorber. The microstructure, element composition, morphology and saturation magnetization are characterized, and EM wave absorption properties are analyzed in the frequency range of 2.0–18.0 GHz. The results show that PEDOT is polymerized on the surface of Fe3O4 microspheres, and prepared core-shell microspheres are supported on rGO nanosheets. The reflection loss (RL) of [email protected]/rGO composite is −48.8 dB at 9.12 GHz, and effective absorption bandwidth (EAB) (RL < −10 dB) is 4.32 GHz, when the matching thickness is 2.9 mm. Additionally, when the matching thickness is 2.1 mm, the EAB covers 7.20 GHz. The excellent absorption performance benefits from good impedance matching, attenuation characteristic, synergistic effect of dielectric and magnetic loss, and the absorption mechanism is explained in detail in the article. Furthermore, radar cross section (RCS) analysis is adopted to simulate and calculate EM scattering performance of Al metal plate with absorption coating. The results demonstrate that [email protected]/rGO composite exhibits enhanced absorption performance and can be used as an excellent EM wave absorber.
Journal of Materials Chemistry A; doi:10.1039/d1ta01744f
A universal approach to transform Ti3C2Tx MXenes into nanoscale ionic materials (NIMs) using an electronic interaction strategy is proposed. MXene NIMs possess antioxidant ability and processability.
Ceramics International, Volume 47, pp 15958-15967; doi:10.1016/j.ceramint.2021.02.170
The inferior energy density limits the practical application and sustainable development of supercapacitors. Excellent electrode materials can effectively improve the specific capacitance and operating potential window. Thus, we deposit brush-like nickel ferrite (NiFe2O4) nanosheets and CuCo2O4/CuO nanowire arrays to construct a binder-free electrode with tree-like CuCo2O4/CuO/NiFe2O4 arrays. The resulting CuCo2O4/CuO/NiFe2O4 electrode shows an outstanding specific capacitance (2067 F/g) and wide potential window (−0.1-0.6 V). The contribution rate of surface faradaic redox reaction is calculated to be 71% at 1 mV/s and assembled CuCo2O4/CuO/NiFe2O4//AC device realizes a remarkable energy density (77.1 Wh/kg at power density of 851.4 W/kg) and cyclic performance (92.9% of initial specific capacitance retained after 10,000 cycles). Apparently, the CuCo2O4/CuO/NiFe2O4 electrode as a novel binder-free electrode has great application potential and our work offers a novel idea to construct the arrays of multicomponent composite materials.
Progress in Natural Science, Volume 31, pp 387-397; doi:10.1016/j.pnsc.2021.04.007
A general strategy has been developed here to supramolecular self-assembly of nickel (Ⅱ)-substituted α-Keggin-type polyoxometalate and polyaniline coated Fe2O3 hollow nanospindle (Fe2O3 hollow [email protected]/α-SiW11Ni composites) via electrostatic attraction and hydrothermal method. Fe3+ was first hydrolyzed and polymerized into Fe2O3, then dissolved into [Fe(H2PO4)x]3−x, resulting in hollow structure. The polyoxometalate existed in polyaniline as a proton-doped counter-ion form, rather than as a separate crystalline state. The protons and anions entered the PANI main chain and combined with N atoms of amines and imines on the PANI chain ((-NH‧+ = )/α-[SiW11Ni(H2O)O39]6-) to form poles and bipolar delocalization into π bonds of the whole polyaniline molecular chain, which leaded to conductance and polarization. The Fe2O3 hollow [email protected]/α-SiW11Ni composites were proven to be excellent microwave absorber in terms of reflection loss (RL) and bandwidth. The maximum RL value was up to −53.6 dB at 3.5 mm and 6.9 GHz. The broadest absorption bandwidth exceeding −10 dB was 6.3 GHz at a thickness of only 1.9 mm. Moreover, the ternary composites presented obvious multi-band absorption with the matching thickness range of 1.5–5 mm. The absorption peaks bandwidth reached as wide as 14.3 GHz, which included all C-Ku bands. The hollow and core-shell structures could provide non-uniform interface for the induced polarization loss and space for the reflecting and scattering of microwave. The carrier, pair-ion carrier and hydrogen bond network could lead to conduction loss. The magnetic losses were caused by eddy current effect and natural resonance. This work can lay a theoretical foundation for the design and performance regulation of new absorbing materials.
Materials Today Chemistry, Volume 20; doi:10.1016/j.mtchem.2021.100460
Znx-1NixFe2O4 samples have been synthesized by solid-state reactions. Data on the chemical composition and the surface morphology of the samples have been obtained using a scanning electron microscope. X-ray powder diffractometer has been used to establish the phase purity and to determine the unit cell parameters. It has been found that the obtained samples had the spinel structure with Fd-3m (No. 227) space group. The unit cell parameters decrease with increasing nickel concentration. The magnetic characteristics of the obtained samples are determined and discussed. The Curie point of obtained samples varies in the range of 803.5–572.7 K. The maximum spontaneous magnetization of ~74.6 emu/g at room temperature was fixed for the solid solution with x = 0.6. The maximum value of the μ/real part of ~12 and μ//imaginary part of 6 of the permeability in the frequency range of 50 MHz–10 GHz is observed for the composition with x = 0.3. The composite samples for microwave study were prepared by mixing the ferrite powders with molten paraffin wax. The largest value of the μ/ real part of ~3 and μ// imaginary part of 0.63 of permeability is found for the x = 0.4 composite. The formation of the composite significantly reduces permeability.
Journal of Colloid and Interface Science, Volume 589, pp 462-471; doi:10.1016/j.jcis.2021.01.013
Nowadays, electromagnetic (EM) radiation poses severe environmental pollution and harm to civilian and military life. To this end, it is urgent to synthesize high-efficiency microwave absorbers in terms of composition and structural design. Herein, we reported a unique hybrid nanostructure with Co particles embedded in hollow carbon polyhedron by a series of synthetic steps including carbonization and pyrolysis. Further, the nanoporous carbon (NPC) derived from wheat flour is coated onto the surface of [email protected] polyhedrons, forming a special hierarchical structure ([email protected]@NPC), which demonstrates outstanding microwave absorption properties due to the hierarchical porous structure, enhanced interfacial polarization, conduction loss, multi-reflection and matched impedance. Typically, with a 10 wt% filler content, the maximum RL of [email protected]@NPC reaches −57.2 dB at 9.6 GHz and the corresponding effective bandwidth is 5.7 GHz (from 7.5 to 13.2 GHz) with an absorber thickness of 3 mm. Besides, the filler loading of 10 wt% is much lower than other reported bio-derived absorbers. In short, the hybrid zeolitic imidazolate frameworks offer a novel idea for constructing hollow carbon skeletons and introducing biomass carbon as a green, low cost and renewable material that enhances the dielectric loss and the synergistic effect between permittivity and permeability.
Nano-Micro Letters, Volume 13, pp 1-15; doi:10.1007/s40820-021-00646-y
Phase engineering is an important strategy to modulate the electronic structure of molybdenum disulfide (MoS2). MoS2-based composites are usually used for the electromagnetic wave (EMW) absorber, but the effect of different phases on the EMW absorbing performance, such as 1T and 2H phase, is still not studied. In this work, micro-1T/2H MoS2 is achieved via a facile one-step hydrothermal route, in which the 1T phase is induced by the intercalation of guest molecules and ions. The EMW absorption mechanism of single MoS2 is revealed by presenting a comparative study between 1T/2H MoS2 and 2H MoS2. As a result, 1T/2H MoS2 with the matrix loading of 15% exhibits excellent microwave absorption property than 2H MoS2. Furthermore, taking the advantage of 1T/2H MoS2, a flexible EMW absorbers that ultrathin 1T/2H MoS2 grown on the carbon fiber also performs outstanding performance only with the matrix loading of 5%. This work offers necessary reference to improve microwave absorption performance by phase engineering and design a new type of flexible electromagnetic wave absorption material to apply for the portable microwave absorption electronic devices.
Journal of Colloid and Interface Science, Volume 588, pp 657-669; doi:10.1016/j.jcis.2020.11.058
Biomass, as a continuously available raw material, is widely used to produce hard carbon. However, many researchers have ignored the natural special morphology of biomass and the influence of oxygen on the sodium storage performance. Here, we use the cilia of the setaria viridis as the precursor to obtain a fiber-like oxygen-doped hierarchical porous hard carbon (SVC). The sodium storage mechanism of SVC is studied by controlling the pyrolysis temperature. Studies have shown that the natural fibrous structure and vertical holes of SVC can provide channels for the rapid penetration of electrolyte. The appropriate nanocrystal size affords commodious circumstances for the insertion of Na+. More importantly, the increase in carbonization temperature will change the bonding mode of carbon and oxygen, promote the rupture of single bonds and retain the existence of double bonds, which is beneficial to the improvement of coulombic efficiency and reversible capacity. The hybrid sodium storage mechanism composed of insertion behavior and capacitance behavior promotes SVC to have higher reversible capacity (285.4 mAh g−1 at 0.05 A g−1) and excellent rate performance (90.7 mAh g−1 at 5 A g−1). This research provides some new ideas for the study of hard carbon.
Advanced Functional Materials, Volume 31; doi:10.1002/adfm.202010694
Asymmetric hollow and magnetic mesoporous silica nanocomposites have great potential applications due to their unique structural–functional properties. Here, asymmetric multilayer‐sandwich magnetic mesoporous silica nanobottles (MMSNBs) are presented through an interfacial super‐assembly strategy. Asymmetric hollow silica nanobottles (SNBs) are first prepared, and Fe3O4 nanoparticles monolayers and mesoporous silica layers are uniformly super‐assembled on the surfaces of SNBs, respectively. The high Fe3O4 nanoparticles loading endows MMSNBs with a high magnetization (8.5 emu g−1), while the mesoporous silica layers exhibit high surface area (613.4 m2 g−1) and large pore size (3.6 nm). MMSNBs can be employed as a novel type of enzyme‐powered nanomotors by integrating catalase (Cat‐MMSNBs), which show an average speed of 7.59 µm s−1 (≈25 body lengths s−1) at 1.5 wt% H2O2. Accordingly, the water quality can be monitored by evaluating the movement speed of Cat‐MMSNBs. Moreover, MMSNBs act as a good adsorbent for removing more than 90% of the heavy metal ions with the advantage of the mesoporous structure. In addition, the good magnetic response enables the MMSNBs with precise directional control and is conducive to recycling for repeated operation. This bottom‐up interfacial super‐assembly construction strategy allows for a new understanding of the rational design and synthesis of multi‐functional nanomotors.
Ceramics International, Volume 47, pp 6453-6462; doi:10.1016/j.ceramint.2020.10.228
Conductor-dielectric-magnetic multicomponent coordination composites with rhombic Fe2O3 lumps doping hollow ZnFe2O4 spheres through oxidative decomposition process implanted into graphene conductive network (hollow ZnFe2O4 spheres/rhombic Fe2O3 lumps/rGO composites) were successfully constructed by a facile method. The countless hollow ZnFe2O4 spheres were compactly attached to the curled-paper rGO and larger sized-rhombic Fe2O3 lumps were relatively dispersed. Among, the hollow structure of ZnFe2O4 spheres could attenuate the electromagnetic wave by multiple reflections and scatterings. Intriguingly, hollow ZnFe2O4 spheres reacted with GO to form intermediate rhombic Fe2O3 lump products, which ameliorated the hetero-interfaces structure and helped to improve impedance matching by weakening the strong magnetic ZnFe2O4 (Ms = 91.2 emu/g) and high conductive rGO after the introduction of weakly magnetic Fe2O3 semiconductor. Moreover, all three components could induce dielectric polarization losses, such as multilayer or dipole polarization. Therefore, the maximum absorption of ternary composites was up to −64.3 dB at 7 GHz and 3.4 mm, simultaneously, and a bandwidth exceeding −10 dB was 4.2 GHz at 1.7 mm. Meanwhile, with a thin thickness range of 1.5–5 mm, the absorption bandwidth below −10 dB was from 2 to 18 GHz which occupied for 91.5% of whole study frequency range. These results provided a new approach and reference for the design and property regulation of electromagnetic materials at electronic communications, aerospace and military radar flied.
ACS Applied Nano Materials, Volume 4, pp 691-701; doi:10.1021/acsanm.0c02983
High-performance absorbers with laminated and three-dimensional structures for abundant interfaces can improve electromagnetic wave absorption property obviously. Meanwhile, the combination and dispersion of components have a positive effect on the microwave absorption (MA) property for excellent absorption bandwidth. Herein, accordion-like MXene/Co-ZIF and MXene/Ni-ZIF composites were synthesized by electrostatic self-assembly between MXene and metal–organic frameworks (Co-MOF and Ni-MOF) and then pyrolyzed in the H2/Ar mixed atmosphere (Co-MOF and Ni-MOF named as Co-ZIF and Ni-ZIF, respectively, after pyrolysis). The MXene/Co-CZIF 50% composites displayed good absorption performance with the optimal RL value of −60.09 dB at 7.36 GHz and the broadened absorption bandwidth 9.3 GHz (RL < −10 dB). MXene/Ni-CZIF 50% exhibited promising performance with the RL value measured up to −64.11 dB at 5.12 GHz, and possessed the ultrabroad effective response bandwidth of 4.56 GHz (RL < −10 dB). Furthermore, a unique accordion-like structure, magnetic–dielectric synergistic, multiple interface scatterings and reflections, and dipole polarization were said to improve MA properties. This study provided a method for the synthesis of absorbers with tunable electromagnetic properties and wide absorption bandwidth of MXene-based composites.