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Showing papers on "Dielectric published in 2022"


Journal ArticleDOI
TL;DR: In this article , comprehensive views toward dielectric loss mechanisms including interfacial polarization, dipolar polarization, conductive loss, and defect-induced polarization are provided, and in-depth losses and mechanisms regulation strategies instead of regular components compositing are summarized to provide inspiring thoughts toward simple and effective EM wave attenuation behavior modulation.
Abstract: Electromagnetic (EM) wave absorbing materials play an increasingly important role in modern society for their multi‐functional in military stealth and incoming 5G smart era. Dielectric loss EM wave absorbers and underlying loss mechanism investigation are of great significance to unveil EM wave attenuation behaviors of materials and guide novel dielectric loss materials design. However, current researches focus more on materials synthesis rather than in‐depth mechanism study. Herein, comprehensive views toward dielectric loss mechanisms including interfacial polarization, dipolar polarization, conductive loss, and defect‐induced polarization are provided. Particularly, some misunderstandings and ambiguous concepts for each mechanism are highlighted. Besides, in‐depth dielectric loss study and novel dielectric loss mechanisms are emphasized. Moreover, new dielectric loss mechanism regulation strategies instead of regular components compositing are summarized to provide inspiring thoughts toward simple and effective EM wave attenuation behavior modulation.

246 citations


Journal ArticleDOI
TL;DR: In this paper , a laminate-stacked sphere-shaped trimetallic CoNiMnO@C composites were designed to investigate the polarization loss mechanism, which facilitates the improvement of electromagnetic loss capacity.
Abstract: Polymeric metal‐organic framework (MOF)‐derived composites are promising functional materials because of their exceptional chemical homogeneity, designable components, and adjustable pore size. The modulation of oxygen and Mn vacancies via the introduction of heteroatoms and changes in the annealing temperature in MOFs‐derived composites can be a possible solution to investigate the polarization loss mechanism, which facilitates the improvement of electromagnetic loss capacity. Herein, the design of laminate‐stacked sphere‐shaped trimetallic CoNiMn‐MOFs is presented. The derived CoNi/MnO@C composites retain the original topography of the MOFs. The concentration of oxygen vacancies increases with the incorporation of heteroatoms, but decreases with annealing temperature, which prevails in the polarization loss mechanism rather than the contribution of Mn2+ vacancies and heterogeneous interfaces. Therefore, the minimum reflection loss of the CoNi/MnO@C sample demonstrates −55.2 dB at 2.6 mm and the broad effective absorption bandwidth reaches 8.0 GHz at 2.1 mm. This work is expected to provide meaningful insights into the significant effect of ion vacancy modulation on the EM wave‐absorbing performance of Mn‐based MOFs‐derived composites.

149 citations


Journal ArticleDOI
TL;DR: In this paper , a hierarchical double-shelled nanotubes (DSNTs) were designed and constructed to investigate the interfacial relaxation mechanism, and magnetic loss, closely related to the micrometer-scale magnetic units, is mainly clarified by the magnetic interaction composed of magnetic coupling and magnetic diffraction; both of them are clearly confirmed by Lorentz off-axis electron holography.
Abstract: Hierarchical engineering of suitable dielectric‐magnetic multicomponents shows good performance for microwave absorbers, but still face bottlenecks. Herein, hierarchical double‐shelled nanotubes (DSNTs), in which the inner magnetic tubular subunits are assembled by magnetic‐heteroatomic components through cation‐exchange reactions, and the outer dielectric MnO2 nanosheets strengthen the synergistic interactions between confined heterogeneous interfaces are ingeniously designed and constructed. Hetero‐interfaces induced polarization is proposed to investigate the interfacial relaxation mechanism, and magnetic loss, closely related to the micrometer‐scale magnetic units, is mainly clarified by the magnetic interaction composed of magnetic coupling and magnetic diffraction; both of them are clearly confirmed by Lorentz off‐axis electron holography. The obtained hierarchical DSNTs demonstrate efficient microwave absorption with an optimal reflection loss of −54.7 dB and qualified absorption bandwidth of 9.5 GHz owing to desirable heterogeneous interfaces, multiple magnetic heteroatomic components and hollow hierarchical microstructures. This strategy inspires a generalized methodology for the engineering of hollow hierarchical configurations with multishells, the combination of proposed hetero‐interfaces induced polarization and microscale magnetic interaction broadens the dielectric‐magnetic synergistic mechanism of the topography–performance relationship for microwave absorption materials.

148 citations


Journal ArticleDOI
TL;DR: In this article , a spatial confined growth strategy is proposed to encapsulate small-size metal-organic frameworks (MOFs) derivatives into hollow carbon nanocages, and the effect of phase hybridization on dielectric polarization is deeply visualized.
Abstract: Precisely reducing the size of metal-organic frameworks (MOFs) derivatives is an effective strategy to manipulate their phase engineering owing to size-dependent oxidation; however, the underlying relationship between the size of derivatives and phase engineering has not been clarified so far. Herein, a spatial confined growth strategy is proposed to encapsulate small-size MOFs derivatives into hollow carbon nanocages. It realizes that the hollow cavity shows a significant spatial confinement effect on the size of confined MOFs crystals and subsequently affects the dielectric polarization due to the phase hybridization with tunable coherent interfaces and heterojunctions owing to size-dependent oxidation motion, yielding to satisfied microwave attenuation with an optimal reflection loss of -50.6 dB and effective bandwidth of 6.6 GHz. Meanwhile, the effect of phase hybridization on dielectric polarization is deeply visualized, and the simulated calculation and electron holograms demonstrate that dielectric polarization is shown to be dominant dissipation mechanism in determining microwave absorption. This spatial confined growth strategy provides a versatile methodology for manipulating the size of MOFs derivatives and the understanding of size-dependent oxidation-induced phase hybridization offers a precise inspiration in optimizing dielectric polarization and microwave attenuation in theory.

139 citations




Journal ArticleDOI
TL;DR: In this paper, a magnetic ferrite CuFe2O4/MoS2 composite was constructed to achieve a wide effective absorption bandwidth (EAB) of 8.16 GHz (9.84 GHz −18 GHz) at 2.3 mm.

127 citations



Journal ArticleDOI
Xiaoxiao Chen1
TL;DR: In this paper , a magnetic ferrite CuFe2O4/MoS2 composite was constructed to achieve a wide effective absorption bandwidth (EAB) of 8.16 GHz (9.84 GHz −18 GHz) at 2.3 mm, when the optimum reflection loss is −40.33 dB.

113 citations


Journal ArticleDOI
TL;DR: In this paper , a pyrolysis-based method was proposed to prepare Co/ZnO/[email protected] ([email protected]) composites with high-performance electromagnetic wave absorbers to eliminate electromagnetic pollution.

112 citations


Journal ArticleDOI
TL;DR: In this paper, the effect of Fe doping on the dielectric and magnetic properties of LCFOs and the strong hybridization of Co/Fe-3d with O-2p was successfully demonstrated.

Journal ArticleDOI
01 Apr 2022
TL;DR: In this paper , the effect of Fe doping on the dielectric and magnetic properties of LCFOs and the strong hybridization of Co/Fe-3d with O-2p was successfully demonstrated.
Abstract: Perovskite LaCoO3 is of great potential in electromagnetic wave absorption considering its outstanding dielectric loss as well as the existing magnetic response with the magnetic doping. However, the dissipation mechanism of the magnetic doping on the microwave absorption is lack of sufficient investigated. In this paper, LaCo1-xFexO3 (x=0, 0.05, 0.1, 0.15, 0.2, 0.25, 0.3, LCFOs) perovskites with different Fe doping amounts were prepared successfully by the sol-gel method and subsequent heat treatment in the air atmosphere. The structure characterization carried out by the first-principles calculations shows the effect of Fe doping on the dielectric and magnetic properties of LCFOs and the strong hybridization of Co/Fe-3d with O-2p in the LCFOs system was successfully demonstrated. Particularly, when x=0.1 and the thickness is only 1.95 mm, the LaCo0.9Fe0.1O3 exhibits the best microwave absorption performance with the minimum reflection loss (RL) value of about -41 dB. The typical samples achieve a broad effective absorption bandwidth (EAB) of 5.16 GHz (7.92-13.08 GHz), which covers the total X band (8-12 GHz). Considering that, the especial Fe doping perovskite is promising to be a candidate as efficient microwave absorbers.

Journal ArticleDOI
01 Jan 2022
TL;DR: In this article , a multifunctional hyperbranched additive (BDHDP) was synthesized for epoxy resins, which catalyzed the curing of epoxy resin because of its tertiary amine and hydroxyl groups.
Abstract: Flame-retardant epoxy resins (EPs) with superior optical, mechanical and dielectric properties are highly desired in high-tech industries. In this work, a multifunctional hyperbranched additive (BDHDP) was synthesized for EPs. Our results showed that BDHDP catalyzed the curing of epoxy resin because of its tertiary amine and hydroxyl groups. At a low addition level (<3.0 wt%), BDHDP increased the glass-transition temperature and maintained the optical transmittance of epoxy thermoset. Meanwhile, BDHDP improved the mechanical strength and toughness, and reduced the dielectric constant and loss of EP because of the rigid phosphaphenanthrene groups and intra-molecular cavities. Moreover, BDHDP reduced the heat release and smoke generation during the EP combustion. Adding 1.5 wt% of BDHDP led to a UL-94 V-0 rating, and reduced the total smoke production by 16.4%. Hence, this study offers an effective method to create transparent EP thermosets with outstanding mechanical, dielectric and fire-retardant properties via incorporating a P/N/B-containing hyperbranched oligomer.

Journal ArticleDOI
TL;DR: In this paper , the authors review the impressive achievements of low and multi-frequency EMW absorbers and analyzes the design strategies that may enable low and multiple-frequency absorption.
Abstract: Vigorous development of 5G communication technologies can boost mobile networks yet bring in electromagnetic interferences and safety concerns in utilizing electronic devices. Particularly, 5G network can not only involve a low‐frequency band of n78 (3.3–3.8 GHz) but also cover multi‐frequency bands of n77 (3.3–4.2 GHz) and n79 (4.4–5.0 GHz), displaying multiple electromagnetic radiations. Countless efforts have been devoted to investigating electromagnetic wave (EMW) absorbers with low‐ and multi‐band absorption properties. However, in terms of emerging materials and designs, few reports propose the mechanisms related to those properties. This perspective briefly reviews the impressive achievements of low‐ and multi‐frequency EMW absorbers and analyzes the design strategies that may enable low‐ and multi‐frequency absorption. Furthermore, the cutting‐edge mechanisms of corresponding electromagnetic responses, such as Snoek limit, quarter wavelength, and dielectric‐magnetic synergy effects are elaborated. Thus, this perspective can shed light on the new trends and ongoing challenges for EMW absorbers and further promote their practical application.

Journal ArticleDOI
Liang Chen, Shiqing Deng, Hui Liu, Jie Wu, He Qi, Jun Chen 
TL;DR: In this article , the authors proposed a high-entropy strategy to design local polymorphic distortion including rhombohedral-orthorhombic-tetragonal-cubic multiphase nanoclusters and random oxygen octahedral tilt, resulting in ultrasmall polar nanoregions, an enhanced breakdown electric field, and delayed polarization saturation.
Abstract: Abstract Next-generation advanced high/pulsed power capacitors rely heavily on dielectric ceramics with high energy storage performance. However, thus far, the huge challenge of realizing ultrahigh recoverable energy storage density ( W rec ) accompanied by ultrahigh efficiency ( η ) still existed and has become a key bottleneck restricting the development of dielectric materials in cutting-edge energy storage applications. Here, we propose a high-entropy strategy to design “local polymorphic distortion” including rhombohedral-orthorhombic-tetragonal-cubic multiphase nanoclusters and random oxygen octahedral tilt, resulting in ultrasmall polar nanoregions, an enhanced breakdown electric field, and delayed polarization saturation. A giant W rec ~10.06 J cm −3 is realized in lead-free relaxor ferroelectrics, especially with an ultrahigh η ~90.8%, showing breakthrough progress in the comprehensive energy storage performance for lead-free bulk ceramics. This work opens up an effective avenue to design dielectric materials with ultrahigh comprehensive energy storage performance to meet the demanding requirements of advanced energy storage applications.

Journal ArticleDOI
TL;DR: In this paper , the authors proposed a dielectric capacitors with high operating temperature applied in electric vehicles, aerospace and underground exploration require dielectrics materials with high temperature resistance and high energy density.
Abstract: Dielectric capacitors with a high operating temperature applied in electric vehicles, aerospace and underground exploration require dielectric materials with high temperature resistance and high energy density.

Journal ArticleDOI
TL;DR: In this article , a synergistic optimization strategy was proposed to enhance DBS by tailoring grain size to submicron scale and inducing the temperature range between the maximum dielectric permittivity temperature ( T max ) and the Burns temperature (T B ) to room temperature, for solving the bottleneck.

Journal ArticleDOI
TL;DR: In this paper , the influence of polymer film thickness on the dielectric properties, film quality issues in thinner polymer films with different filler contents, and major processing methods in decreasing polymeric film thickness are discussed.

Journal ArticleDOI
TL;DR: In this paper, the influence of polymer film thickness on the dielectric properties, film quality issues in thinner polymer films with different filler contents, and major processing methods in decreasing polymeric film thickness are discussed.

Journal ArticleDOI
TL;DR: In this paper , the magnetized Ni flower/MXene hybrids are successfully assembled on the surface of melamine foam (MF) through electrostatic self-assembly and dip-coating adsorption process, realizing the integration of microwave absorption, infrared stealth and flame retardant.
Abstract: The development of multifunctional and efficient electromagnetic wave absorbing materials is a challenging research hotspot. Here, the magnetized Ni flower/MXene hybrids are successfully assembled on the surface of melamine foam (MF) through electrostatic self-assembly and dip-coating adsorption process, realizing the integration of microwave absorption, infrared stealth, and flame retardant. Remarkably, the Ni/MXene-MF achieves a minimum reflection loss (RLmin) of - 62.7 dB with a corresponding effective absorption bandwidth (EAB) of 6.24 GHz at 2 mm and an EAB of 6.88 GHz at 1.8 mm. Strong electromagnetic wave absorption is attributed to the three-dimensional magnetic/conductive networks, which provided excellent impedance matching, dielectric loss, magnetic loss, interface polarization, and multiple attenuations. In addition, the Ni/MXene-MF endows low density, excellent heat insulation, infrared stealth, and flame-retardant functions. This work provided a new development strategy for the design of multifunctional and efficient electromagnetic wave absorbing materials.


Journal ArticleDOI
TL;DR: In this article , the dependence of crystal structure and bond characteristics on microwave dielectric properties was investigated systemically, and the X-ray diffraction patterns indicated that the single-phase Pr2Zr3(MoO4)9 structure was formed in all the specimens.

Journal ArticleDOI
TL;DR: In this article, the effect of N-doped carbon skeletons on the absorption ability of carbon-based absorbers has been investigated, and the authors provided a valuable approach for fabricating high-efficiency microwave absorption materials by combining the control of morphology and Ndoped effect on the absorbers.

Journal ArticleDOI
TL;DR: In this paper, NiFe2O4/polypyrrole nanocomposites are prepared by a simple surface-initiated polymerization method and demonstrate negative permittivity in the low frequency regions.


Journal ArticleDOI
01 May 2022
TL;DR: In this article , NiFe2O4/polypyrrole nanocomposites are prepared by a simple surface-initiated polymerization method and demonstrate negative permittivity in the low frequency regions.
Abstract: NiFe2O4/polypyrrole (NiFe2O4/PPy) nanocomposites are prepared by a simple surface-initiated polymerization method and demonstrate negative permittivity in the low frequency regions. These nanocomposites also exhibit significantly enhanced electromagnetic wave (EMW) absorption property in the high frequency regions. Compared with pure PPy, the enhanced negative permittivity is observed in the NiFe2O4/PPy nanocomposites with a NiFe2O4 loading of 5.0, 10.0, 20.0 and 40.0 wt%, indicating the formation of metal-like electrical conducting network in NiFe2O4/PPy nanocomposites. Moreover, the negative permittivity could be tuned by changing the NiFe2O4 loading. The minimum reflection loss (RL) of -40.8 dB is observed in the 40.0 wt% NiFe2O4/PPy composites with a thickness of only 1.9 mm. The effective absorption bandwidth below -10.0 and -20.0 dB reaches 6.08 and 2.08 GHz, respectively. The enhanced EMW absorption performance benefits from the improved independence matching, EMW attenuation capacity, and synergistic effects of conduction loss, dielectric loss (interfacial and dipole polarizations) and magnetic loss (exchange and natural resonances). This research work provides a guidance for the fabrication of nanocomposites with an excellent EMW absorption.

Journal ArticleDOI
TL;DR: In this article , the effects of microwave dielectric ceramics on their microstructures, sintering behaviors, and microwave die-lectric properties were systematically investigated using the Phillips-Van Vechten-Levine (PV-L) theory.
Abstract: Abstract Dense microwave dielectric ceramics of Ce 2 [Zr 1 − x (Al 1/2 Ta 1/2 ) x ] 3 (MoO 4 ) 9 (CZMAT) ( x = 0.02–0.10) were prepared by the conventional solid-state route. The effects of (Al 1/2 Ta 1/2 ) 4+ on their microstructures, sintering behaviors, and microwave dielectric properties were systematically investigated. On the basis of the X-ray diffraction (XRD) results, all the samples were matched well with Pr 2 Zr 3 (MoO 4 ) 9 structures, which belonged to the space group $$R\bar 3c$$ R 3 ¯ c . The lattice parameters were obtained using the Rietveld refinement method. The correlations between the chemical bond parameters and microwave dielectric properties were calculated and analyzed by using the Phillips—Van Vechten—Levine (P—V—L) theory. Excellent dielectric properties of Ce 2 [Zr 0.94 (Al 1/2 Ta 1/2 ) 0.06 ] 3 (MoO 4 ) 9 with a relative permittivity ( ε r ) of 10.46, quality factor ( Q × f ) of 83,796 GHz, and temperature coefficient of resonant frequency ( τ f ) of −11.50 ppm/°C were achieved at 850 °C.

Journal ArticleDOI
TL;DR: In this article, bismuth-based high entropy compound (HEC), Bi(Zn0.2Al 0.2Sn0.1)O3 (BZMASZ), was introduced into BaTiO3-Na0.5Bi0.3 (BT-NBT) matrix, in order to improve the comprehensive energy storage performance.

Journal ArticleDOI
Xiaoxiao Chen1
01 Jun 2022
TL;DR: In this article , a series of loosely packed accordion-like 3D NiCo/CeO2/Ti3C2Tx with tunable and high-efficient EMW absorption were fabricated by introducing self-assembled NiCo alloys on the surface of Ti3C 2Tx and subsequent anchoring of CeO2.
Abstract: The single dielectric/magnetic loss mechanism and invalid polarization loss are the crucial issues which limit the exploitation of multi-component electromagnetic wave (EMW) absorption materials, especially Ti3C2Tx MXene based absorption materials. In this work, a series of loosely packed accordion-like 3D NiCo/CeO2/Ti3C2Tx with tunable and high-efficient EMW absorption were fabricated by introducing self-assembled NiCo alloys on the surface of Ti3C2Tx and subsequent anchoring of CeO2. On the one hand, the magnetic NiCo particles and highly conductive Ti3C2Tx achieved the dielectric-magnetic dual-loss. On the other hand, the triple interfacial polarization among NiCo/CeO2/Ti3C2Tx further enhanced the relaxation loss. In addition, the effects of cerium ions on tuning the compositional structure, electromagnetic parameters and impedance behavior of the composites are explored. The NiCo/CeO2/Ti3C2Tx-0.1 performed a wide absorption bandwidth of 6.32 GHz at 1.9 mm, as well as, the minimum reflection loss value of -42.48 dB at 2.0 mm. This work putted forward a new synergistic regulation strategy of dielectric-magnetic dual-loss and triple heterointerface polarization via magnetic MXene for high-performance EMW absorption, which may shed new light on the fabrication of multiple-component synergistic loss absorption materials.

Journal ArticleDOI
TL;DR: In this article, a series of manganese oxides/porous carbon (MnxOy@C) hybrid composites are obtained by a two-step process, and the authors demonstrated that the addition of porous carbon is vital for enhancing EMA performance of composites, which not only coordinates impedance matching allowing more EM waves enter the absorber, but also provides the path for electron movement.