Search2023 Vol. 30, No. 3
Display Method:
2023, vol. 30, no. 3, pp.
405-427.
https://doi.org/10.1007/s12613-022-2555-8
Abstract:
At present, metal–organic framework (MOF)-derived nano–micro architectures are actively explored for electromagnetic (EM) wave absorption owing to their flexible composition and structural manipulation that enhance dielectric and magnetic attenuations. However, the basic design principles in MOF-derived microwave absorption materials have not been summarized. This review is devoted to analyzing design principles in MOF-derived microwave absorption materials from the following perspectives: diverse monomers (ligands and ions of MOFs), topologies, chemical states, and physical properties. The derived essential information regarding the EM wave absorption mechanism and the structural–functional dependency is also comprehensively summarized. Finally, a clear insight into the challenges and perspectives of the industrial revolution upgrading in this promising field is proposed.
At present, metal–organic framework (MOF)-derived nano–micro architectures are actively explored for electromagnetic (EM) wave absorption owing to their flexible composition and structural manipulation that enhance dielectric and magnetic attenuations. However, the basic design principles in MOF-derived microwave absorption materials have not been summarized. This review is devoted to analyzing design principles in MOF-derived microwave absorption materials from the following perspectives: diverse monomers (ligands and ions of MOFs), topologies, chemical states, and physical properties. The derived essential information regarding the EM wave absorption mechanism and the structural–functional dependency is also comprehensively summarized. Finally, a clear insight into the challenges and perspectives of the industrial revolution upgrading in this promising field is proposed.
2023, vol. 30, no. 3, pp.
428-445.
https://doi.org/10.1007/s12613-022-2546-9
Abstract:
Transition metal dichalcogenides (TMDs) show great advantages in electromagnetic wave (EMW) absorption due to their unique structure and electrical properties. Tremendous research works on TMD-based EMW absorbers have been conducted in the last three years, and the comprehensive and systematical summary is still a rarity. Therefore, it is of great significance to elaborate on the interaction among the morphologies, structures, phases, components, and EMW absorption performances of TMD-based absorbers. This review is devoted to analyzing TMD-based absorbers from the following perspectives: the EMW absorption regulation strategies of TMDs and the latest progress of TMD-based hybrids as EMW absorbers. The absorption mechanisms and component-performance dependency of these achievements are also summarized. Finally, a straightforward insight into industrial revolution upgrading in this promising field is proposed.
Transition metal dichalcogenides (TMDs) show great advantages in electromagnetic wave (EMW) absorption due to their unique structure and electrical properties. Tremendous research works on TMD-based EMW absorbers have been conducted in the last three years, and the comprehensive and systematical summary is still a rarity. Therefore, it is of great significance to elaborate on the interaction among the morphologies, structures, phases, components, and EMW absorption performances of TMD-based absorbers. This review is devoted to analyzing TMD-based absorbers from the following perspectives: the EMW absorption regulation strategies of TMDs and the latest progress of TMD-based hybrids as EMW absorbers. The absorption mechanisms and component-performance dependency of these achievements are also summarized. Finally, a straightforward insight into industrial revolution upgrading in this promising field is proposed.
2023, vol. 30, no. 3, pp.
446-473.
https://doi.org/10.1007/s12613-022-2562-9
Abstract:
Growing electromagnetic pollution has plagued researchers in the field of electromagnetic (EM) energy dissipation for many years; it is increasingly important to solve this problem efficiently. Metal–organic frameworks (MOFs), a shining star of functional materials, have attracted great attention for their advantages, which include highly tunable porosity, structure, and versatility. MOF-derived electromagnetic wave (EMW) absorbers, with advantages such as light weight, thin matching thickness, strong capacity, and wide effective bandwidth, are widely reported. However, current studies lack a systematic summary of the ternary synergistic effects of the precursor component–structure–EMW absorption behavior of MOF derivatives. Here we describe in detail the electromagnetic (EM) energy dissipation mechanism and strategy for preparing MOF-derived EMW absorbers. On the basis of this description, the following means are suggested for adjusting the EM parameters of MOF derivatives, achieving excellent EM energy dissipation: (1) changing the metal and ligands to regulate the chemical composition and morphology of the precursor, (2) controlling pyrolysis parameters (including temperature, heating rate, and gas atmosphere) to manipulate the structure and components of derivatives, and (3) compounding with enhancement phases, including carbon nanomaterials, metals, or other MOFs.
Growing electromagnetic pollution has plagued researchers in the field of electromagnetic (EM) energy dissipation for many years; it is increasingly important to solve this problem efficiently. Metal–organic frameworks (MOFs), a shining star of functional materials, have attracted great attention for their advantages, which include highly tunable porosity, structure, and versatility. MOF-derived electromagnetic wave (EMW) absorbers, with advantages such as light weight, thin matching thickness, strong capacity, and wide effective bandwidth, are widely reported. However, current studies lack a systematic summary of the ternary synergistic effects of the precursor component–structure–EMW absorption behavior of MOF derivatives. Here we describe in detail the electromagnetic (EM) energy dissipation mechanism and strategy for preparing MOF-derived EMW absorbers. On the basis of this description, the following means are suggested for adjusting the EM parameters of MOF derivatives, achieving excellent EM energy dissipation: (1) changing the metal and ligands to regulate the chemical composition and morphology of the precursor, (2) controlling pyrolysis parameters (including temperature, heating rate, and gas atmosphere) to manipulate the structure and components of derivatives, and (3) compounding with enhancement phases, including carbon nanomaterials, metals, or other MOFs.
2023, vol. 30, no. 3, pp.
474-484.
https://doi.org/10.1007/s12613-022-2499-z
Abstract:
Porous carbon-based materials are promised to be lightweight dielectric microwave absorbents. Deeply understanding the influence of graphitization grade and porous structure on the dielectric parameters is urgently required. Herein, utilizing the low boiling point of Zn, porous N-doped carbon was fabricated by carbonization of ZIF-8 (Zn) at different temperature, and the microwave absorption performance was investigated. The porous N-doped carbon inherits the high porosity of ZIF-8 precursor. By increasing the carbonization temperature, the contents of Zn and N elements are decreased; the graphitization degree is improved; however, the specific surface area and porosity are increased first and then decreased. When the carbonization temperature is 1000°C, the porous N-doped carbon behaves enhanced microwave absorption. With an ultrathin thickness of 1.29 mm, the ideal RL reaches −50.57 dB at 16.95 GHz and the effective absorption bandwidth is 4.17 GHz. The mechanism of boosted microwave absorption is ascribed to the competition of graphitization and porosity as well as N dopants, resulting in high dielectric loss capacity and good impedance matching. The porous structure can prolong the pathways and raise the contact opportunity between microwaves and porous carbon, causing multiple scattering, interface polarization, and improved impedance matching. Besides, the N dopants can induce electron polarization and defect polarization. These results give a new insight to construct lightweight carbon-based microwave absorbents by regulating the graphitization and porosity.
Porous carbon-based materials are promised to be lightweight dielectric microwave absorbents. Deeply understanding the influence of graphitization grade and porous structure on the dielectric parameters is urgently required. Herein, utilizing the low boiling point of Zn, porous N-doped carbon was fabricated by carbonization of ZIF-8 (Zn) at different temperature, and the microwave absorption performance was investigated. The porous N-doped carbon inherits the high porosity of ZIF-8 precursor. By increasing the carbonization temperature, the contents of Zn and N elements are decreased; the graphitization degree is improved; however, the specific surface area and porosity are increased first and then decreased. When the carbonization temperature is 1000°C, the porous N-doped carbon behaves enhanced microwave absorption. With an ultrathin thickness of 1.29 mm, the ideal RL reaches −50.57 dB at 16.95 GHz and the effective absorption bandwidth is 4.17 GHz. The mechanism of boosted microwave absorption is ascribed to the competition of graphitization and porosity as well as N dopants, resulting in high dielectric loss capacity and good impedance matching. The porous structure can prolong the pathways and raise the contact opportunity between microwaves and porous carbon, causing multiple scattering, interface polarization, and improved impedance matching. Besides, the N dopants can induce electron polarization and defect polarization. These results give a new insight to construct lightweight carbon-based microwave absorbents by regulating the graphitization and porosity.
2023, vol. 30, no. 3, pp.
485-493.
https://doi.org/10.1007/s12613-022-2520-6
Abstract:
In recent years, electromagnetic wave (EMW) absorption has been extensively investigated for solving EMW radiation and pollution. The metal–organic frameworks (MOFs) have attracted attention due to their low density and unique structure, which can meet the requirements of strong reflection loss (RL) and wide absorption bandwidth of EMW absorption materials. In this manuscript, indium nanoparticles/porous carbon (In/C) nanorods composites were prepared via the pyrolysis of nanorods-like In-MOFs at a low temperature of 450°C. Indium nanoparticles are evenly attached and embedded on porous carbon. Low electrical conductivity of In/C nanorods is unfavorable to EMW absorption performance, which is due to the low temperature carbonization. Thus, graphene (Gr) nanosheets with high electrical conductivity are introduced to adjust electromagnetic parameters of In/C nanorods for enhancing EMW absorption. The minimum RL of the In/C-Gr-4 composite is up to −43.7 dB with a thin thickness of 1.30 mm. In addition, when the thickness is further reduced to 1.14 mm, the minimum RL of −39.3 dB at 16.1 GHz and effective absorption bandwidth of 3.7 GHz (from 14.3 to 18.0 GHz) can be achieved. This work indicates that In/C-Gr composites show excellent EMW absorption performance.
In recent years, electromagnetic wave (EMW) absorption has been extensively investigated for solving EMW radiation and pollution. The metal–organic frameworks (MOFs) have attracted attention due to their low density and unique structure, which can meet the requirements of strong reflection loss (RL) and wide absorption bandwidth of EMW absorption materials. In this manuscript, indium nanoparticles/porous carbon (In/C) nanorods composites were prepared via the pyrolysis of nanorods-like In-MOFs at a low temperature of 450°C. Indium nanoparticles are evenly attached and embedded on porous carbon. Low electrical conductivity of In/C nanorods is unfavorable to EMW absorption performance, which is due to the low temperature carbonization. Thus, graphene (Gr) nanosheets with high electrical conductivity are introduced to adjust electromagnetic parameters of In/C nanorods for enhancing EMW absorption. The minimum RL of the In/C-Gr-4 composite is up to −43.7 dB with a thin thickness of 1.30 mm. In addition, when the thickness is further reduced to 1.14 mm, the minimum RL of −39.3 dB at 16.1 GHz and effective absorption bandwidth of 3.7 GHz (from 14.3 to 18.0 GHz) can be achieved. This work indicates that In/C-Gr composites show excellent EMW absorption performance.
2023, vol. 30, no. 3, pp.
494-503.
https://doi.org/10.1007/s12613-022-2524-2
Abstract:
Lightweight and efficient carbon-based microwave absorbents are significant in addressing the increasing severity of electromagnetic pollution. In this study, hierarchical NiO/Ni nanosheets with a tuneable phase and morphology supported on a carbon fiber substrate (CF@NiO/Ni) were fabricated using a hydrothermal approach and post-annealing treatment. As the annealing temperature increases, more metallic Ni is formed, and an apparent porosity appears on the sheet surface. Benefiting from the advantages of a three-dimensional (3D) conducting network, hierarchical porous structure, reinforced dipole/interface polarization, multiple scattering, and good impedance matching, the CF@NiO/Ni-500 composite exhibits an excellent microwave absorption performance even at a filling rate of only 3wt%. Specifically, its minimal reflection loss is −43.92 dB, and the qualified bandwidth is up to 5.64 GHz. In addition, the low radar cross-section area of the CF@NiO/Ni composite coating confirms its strong ability to suppress electromagnetic wave scattering. We expect that this work could contribute to a deeper understanding of the phase and morphology evolution in enhancing microwave absorption.
Lightweight and efficient carbon-based microwave absorbents are significant in addressing the increasing severity of electromagnetic pollution. In this study, hierarchical NiO/Ni nanosheets with a tuneable phase and morphology supported on a carbon fiber substrate (CF@NiO/Ni) were fabricated using a hydrothermal approach and post-annealing treatment. As the annealing temperature increases, more metallic Ni is formed, and an apparent porosity appears on the sheet surface. Benefiting from the advantages of a three-dimensional (3D) conducting network, hierarchical porous structure, reinforced dipole/interface polarization, multiple scattering, and good impedance matching, the CF@NiO/Ni-500 composite exhibits an excellent microwave absorption performance even at a filling rate of only 3wt%. Specifically, its minimal reflection loss is −43.92 dB, and the qualified bandwidth is up to 5.64 GHz. In addition, the low radar cross-section area of the CF@NiO/Ni composite coating confirms its strong ability to suppress electromagnetic wave scattering. We expect that this work could contribute to a deeper understanding of the phase and morphology evolution in enhancing microwave absorption.
2023, vol. 30, no. 3, pp.
504-514.
https://doi.org/10.1007/s12613-022-2509-1
Abstract:
Cobalt ferrite (CoFe2O4), with good chemical stability and magnetic loss, can be used to prepare composites with a unique structure and high absorption. In this study, CoFe2O4@mesoporous carbon hollow spheres (MCHS) with a core–shell structure were prepared by introducing CoFe2O4 magnetic particles into hollow mesoporous carbon through a simple in situ method. Then, the microwave absorption performance of the CoFe2O4@MCHS composites was investigated. Magnetic and dielectric losses can be effectively coordinated by constructing the porous structure and adjusting the ratio of MCHS and CoFe2O4. Results show that the impedance matching and absorption properties of the CoFe2O4@MCHS composites can be altered by tweaking the mass ratio of MCHS and CoFe2O4. The minimum reflection loss of the CoFe2O4@MCHS composites reaches −29.7 dB at 5.8 GHz. In addition, the effective absorption bandwidth is 3.7 GHz, with the thickness being 2.5 mm. The boosted microwave absorption can be ascribed to the porous core–shell structure and introduction of magnetic particles. The coordination between the microporous morphology and the core–shell structure is conducive to improving the attenuation coefficient and achieving good impedance matching. The porous core–shell structure provides large solid–void and CoFe2O4–C interfaces to induce interfacial polarization and extend the electromagnetic waves’ multiple scattering and reflection. Furthermore, natural resonance, exchange resonance, and eddy current loss work together for the magnetic loss. This method provides a practical solution to prepare core–shell structure microwave absorbents.
Cobalt ferrite (CoFe2O4), with good chemical stability and magnetic loss, can be used to prepare composites with a unique structure and high absorption. In this study, CoFe2O4@mesoporous carbon hollow spheres (MCHS) with a core–shell structure were prepared by introducing CoFe2O4 magnetic particles into hollow mesoporous carbon through a simple in situ method. Then, the microwave absorption performance of the CoFe2O4@MCHS composites was investigated. Magnetic and dielectric losses can be effectively coordinated by constructing the porous structure and adjusting the ratio of MCHS and CoFe2O4. Results show that the impedance matching and absorption properties of the CoFe2O4@MCHS composites can be altered by tweaking the mass ratio of MCHS and CoFe2O4. The minimum reflection loss of the CoFe2O4@MCHS composites reaches −29.7 dB at 5.8 GHz. In addition, the effective absorption bandwidth is 3.7 GHz, with the thickness being 2.5 mm. The boosted microwave absorption can be ascribed to the porous core–shell structure and introduction of magnetic particles. The coordination between the microporous morphology and the core–shell structure is conducive to improving the attenuation coefficient and achieving good impedance matching. The porous core–shell structure provides large solid–void and CoFe2O4–C interfaces to induce interfacial polarization and extend the electromagnetic waves’ multiple scattering and reflection. Furthermore, natural resonance, exchange resonance, and eddy current loss work together for the magnetic loss. This method provides a practical solution to prepare core–shell structure microwave absorbents.
2023, vol. 30, no. 3, pp.
515-524.
https://doi.org/10.1007/s12613-022-2496-2
Abstract:
With the gradually increasing protection awareness about electromagnetic pollution, the demand for absorbing materials with renewability and environmental friendliness has attracted widespread attention. In this work, composites consisting of straw-derived biochar combined with NiCo alloy were successfully fabricated through high-temperature carbonization and subsequent hydrothermal reaction. The electromagnetic parameters of the porous biocarbon/NiCo composites can be effectively modified by altering their NiCo content, and their improved absorbing performance can be attributed to the synergy effect of magnetic–dielectric characteristics. An exceptional reflection loss of −27.0 dB at 2.2 mm thickness and an effective absorption bandwidth of 4.4 GHz (11.7–16.1 GHz) were achieved. These results revealed that the porous biocarbon/NiCo composites could be used as a new generation absorbing material because of their low density, light weight, excellent conductivity, and strong absorption.
With the gradually increasing protection awareness about electromagnetic pollution, the demand for absorbing materials with renewability and environmental friendliness has attracted widespread attention. In this work, composites consisting of straw-derived biochar combined with NiCo alloy were successfully fabricated through high-temperature carbonization and subsequent hydrothermal reaction. The electromagnetic parameters of the porous biocarbon/NiCo composites can be effectively modified by altering their NiCo content, and their improved absorbing performance can be attributed to the synergy effect of magnetic–dielectric characteristics. An exceptional reflection loss of −27.0 dB at 2.2 mm thickness and an effective absorption bandwidth of 4.4 GHz (11.7–16.1 GHz) were achieved. These results revealed that the porous biocarbon/NiCo composites could be used as a new generation absorbing material because of their low density, light weight, excellent conductivity, and strong absorption.
2023, vol. 30, no. 3, pp.
525-535.
https://doi.org/10.1007/s12613-022-2491-7
Abstract:
Porous carbon (PC) is a promising electromagnetic (EM) wave absorbing material thanks to its light weight, large specific surface area as well as good dissipating capacity. To further improve its microwave absorbing performance, silver coated porous carbon (Ag@PC) is synthesized by one-step hydro-thermal synthesis process making use of fir as a biomass formwork. Phase compositions, morphological structure, and microwave absorption capability of the Ag@PC has been explored. Research results show that the metallic Ag was successfully reduced and the particles are evenly distributed inward the pores of the carbon formwork, which accelerates graphitization process of the amorphous carbon. The Ag@PC composite without adding polyvinyl pyrrolidone (PVP) exhibits higher dielectric constant and better EM wave dissipating capability. This is because the larger particles of Ag give rise to higher electric conductivity. After combing with frequency selective surface (FSS), the EM wave absorbing performance is further improved and the frequency region below −10 dB is located in 8.20–11.75 GHz, and the minimal reflection loss value is −22.5 dB. This work indicates that incorporating metallic Ag particles and FSS provides a valid way to strengthen EM wave absorbing capacity of PC material.
Porous carbon (PC) is a promising electromagnetic (EM) wave absorbing material thanks to its light weight, large specific surface area as well as good dissipating capacity. To further improve its microwave absorbing performance, silver coated porous carbon (Ag@PC) is synthesized by one-step hydro-thermal synthesis process making use of fir as a biomass formwork. Phase compositions, morphological structure, and microwave absorption capability of the Ag@PC has been explored. Research results show that the metallic Ag was successfully reduced and the particles are evenly distributed inward the pores of the carbon formwork, which accelerates graphitization process of the amorphous carbon. The Ag@PC composite without adding polyvinyl pyrrolidone (PVP) exhibits higher dielectric constant and better EM wave dissipating capability. This is because the larger particles of Ag give rise to higher electric conductivity. After combing with frequency selective surface (FSS), the EM wave absorbing performance is further improved and the frequency region below −10 dB is located in 8.20–11.75 GHz, and the minimal reflection loss value is −22.5 dB. This work indicates that incorporating metallic Ag particles and FSS provides a valid way to strengthen EM wave absorbing capacity of PC material.
2023, vol. 30, no. 3, pp.
536-547.
https://doi.org/10.1007/s12613-022-2570-9
Abstract:
Reduced graphene oxide (rGO) aerogels are emerging as very attractive scaffolds for high-performance electromagnetic wave absorption materials (EWAMs) due to their intrinsic conductive networks and intricate interior microstructure, as well as good compatibility with other electromagnetic (EM) components. Herein, we realized the decoration of rGO aerogel with Mo2C nanoparticles by sequential hydrothermal assembly, freeze-drying, and high-temperature pyrolysis. Results show that Mo2C nanoparticle loading can be easily controlled by the ammonium molybdate to glucose molar ratio. The hydrophobicity and thermal insulation of the rGO aerogel are effectively improved upon the introduction of Mo2C nanoparticles, and more importantly, these nanoparticles regulate the EM properties of the rGO aerogel to a large extent. Although more Mo2C nanoparticles may decrease the overall attenuation ability of the rGO aerogel, they bring much better impedance matching. At a molar ratio of 1:1, a desirable balance between attenuation ability and impedance matching is observed. In this context, the Mo2C/rGO aerogel displays strong reflection loss and broad response bandwidth, even with a small applied thickness (1.7 mm) and low filler loading (9.0wt%). The positive effects of Mo2C nanoparticles on multifunctional properties may render Mo2C/rGO aerogels promising candidates for high-performance EWAMs under harsh conditions.
Reduced graphene oxide (rGO) aerogels are emerging as very attractive scaffolds for high-performance electromagnetic wave absorption materials (EWAMs) due to their intrinsic conductive networks and intricate interior microstructure, as well as good compatibility with other electromagnetic (EM) components. Herein, we realized the decoration of rGO aerogel with Mo2C nanoparticles by sequential hydrothermal assembly, freeze-drying, and high-temperature pyrolysis. Results show that Mo2C nanoparticle loading can be easily controlled by the ammonium molybdate to glucose molar ratio. The hydrophobicity and thermal insulation of the rGO aerogel are effectively improved upon the introduction of Mo2C nanoparticles, and more importantly, these nanoparticles regulate the EM properties of the rGO aerogel to a large extent. Although more Mo2C nanoparticles may decrease the overall attenuation ability of the rGO aerogel, they bring much better impedance matching. At a molar ratio of 1:1, a desirable balance between attenuation ability and impedance matching is observed. In this context, the Mo2C/rGO aerogel displays strong reflection loss and broad response bandwidth, even with a small applied thickness (1.7 mm) and low filler loading (9.0wt%). The positive effects of Mo2C nanoparticles on multifunctional properties may render Mo2C/rGO aerogels promising candidates for high-performance EWAMs under harsh conditions.
2023, vol. 30, no. 3, pp.
548-558.
https://doi.org/10.1007/s12613-022-2517-1
Abstract:
A new type of composite filler was designed by a modified sol–gel method using fly ash (FA), Fe(NO3)3∙9H2O, and Ni(NO3)2∙6H2O as raw materials. The composite filler was a spherical core–shell structure composed of FA as the core and NiFe2O4 as the shell. Further, the composite filler was added into the silicone rubber to fabricate the high temperature vulcanized microwave absorption materials; X-ray diffraction, fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, and scanning electron microscope confirmed that NiFe2O4 was successfully coated on the surface of FA and formed a uniform and continuous coating layer. As expected, silicone rubber filled with the composite filler had a minimum reflection loss of −23.8 dB at 17.5 GHz with the thickness of 1.8 mm, while the effective absorption bandwidth was as high as 12 GHz. The addition of the composite filler greatly enhanced the microwave absorption properties of the system, which was resulted from multiple losses mechanism: interface polarization losses, magnetic losses, and multiple reflection losses. Also, silicone rubber filled with the composite filler exhibited excellent thermal stability, flexibility, environmental resistance, and hydrophobicity compared with traditional silicone rubber. Therefore, this work not only responds to the green chemistry to achieve efficient FA recovery, but also devises a new strategy to prepare microwave absorption materials with strong potential for civilian applications.
A new type of composite filler was designed by a modified sol–gel method using fly ash (FA), Fe(NO3)3∙9H2O, and Ni(NO3)2∙6H2O as raw materials. The composite filler was a spherical core–shell structure composed of FA as the core and NiFe2O4 as the shell. Further, the composite filler was added into the silicone rubber to fabricate the high temperature vulcanized microwave absorption materials; X-ray diffraction, fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, and scanning electron microscope confirmed that NiFe2O4 was successfully coated on the surface of FA and formed a uniform and continuous coating layer. As expected, silicone rubber filled with the composite filler had a minimum reflection loss of −23.8 dB at 17.5 GHz with the thickness of 1.8 mm, while the effective absorption bandwidth was as high as 12 GHz. The addition of the composite filler greatly enhanced the microwave absorption properties of the system, which was resulted from multiple losses mechanism: interface polarization losses, magnetic losses, and multiple reflection losses. Also, silicone rubber filled with the composite filler exhibited excellent thermal stability, flexibility, environmental resistance, and hydrophobicity compared with traditional silicone rubber. Therefore, this work not only responds to the green chemistry to achieve efficient FA recovery, but also devises a new strategy to prepare microwave absorption materials with strong potential for civilian applications.
2023, vol. 30, no. 3, pp.
559-569.
https://doi.org/10.1007/s12613-022-2488-2
Abstract:
To deal with the growing electromagnetic hazards, herein a Co@CuFe2O4 absorbing agent with excellent impedance matching at thin thickness was obtained via an innovative route of ball-milling assisted chemical precipitation and annealing. The as-prepared composite possesses excellent interface polarization ability due to sufficient contact between CuFe2O4 NPs and flat Co, and this compressed Co lamella can also provide sufficient eddy current loss. Moreover, the dipole polarization, electron hopping/conduction, and structural scattering also contribute to the broadband microwave absorption of the composite. Thus, the minimum microwave reflection loss achieves −35.56 dB at 12.93 GHz for 1.8 mm thickness, and the broadest efficient absorption bandwidth can reach 6.74 GHz for a thinner thickness of 1.72 mm. The preparation method reported here can be referenced as a new-type route to manufacture electromagnetic absorbers with outstanding performance.
To deal with the growing electromagnetic hazards, herein a Co@CuFe2O4 absorbing agent with excellent impedance matching at thin thickness was obtained via an innovative route of ball-milling assisted chemical precipitation and annealing. The as-prepared composite possesses excellent interface polarization ability due to sufficient contact between CuFe2O4 NPs and flat Co, and this compressed Co lamella can also provide sufficient eddy current loss. Moreover, the dipole polarization, electron hopping/conduction, and structural scattering also contribute to the broadband microwave absorption of the composite. Thus, the minimum microwave reflection loss achieves −35.56 dB at 12.93 GHz for 1.8 mm thickness, and the broadest efficient absorption bandwidth can reach 6.74 GHz for a thinner thickness of 1.72 mm. The preparation method reported here can be referenced as a new-type route to manufacture electromagnetic absorbers with outstanding performance.
2023, vol. 30, no. 3, pp.
570-580.
https://doi.org/10.1007/s12613-022-2476-6
Abstract:
For electromagnetic wave-absorbing materials, maximizing absorption at a specific frequency has been constantly achieved, but enhancing the absorption properties in the entire band remains a challenge. In this work, a 3D porous pyrolytic carbon (PyC) foam matrix was synthesized by a template method. Amorphous carbon nanotubes (CNTs) were then in-situ grown on the matrix surface to obtain ultralight CNTs/PyC foam. These in-situ grown amorphous CNTs were distributed uniformly and controlled by the catalytic growth time and can enhance the interface polarization and conduction loss of composites. When the electromagnetic wave enters the internal holes, the electromagnetic energy can be completely attenuated under the combined action of polarization, conductivity loss, and multiple reflections. The ultralight CNTs/PyC foam had a density of 22.0 mg·cm−3 and a reflection coefficient lower than −13.3 dB in the whole X-band (8.2–12.4 GHz), which is better than the conventional standard of effective absorption bandwidth (≤−10 dB). The results provide ideas for researching ultralight and strong electromagnetic wave absorbing materials in the X-band.
For electromagnetic wave-absorbing materials, maximizing absorption at a specific frequency has been constantly achieved, but enhancing the absorption properties in the entire band remains a challenge. In this work, a 3D porous pyrolytic carbon (PyC) foam matrix was synthesized by a template method. Amorphous carbon nanotubes (CNTs) were then in-situ grown on the matrix surface to obtain ultralight CNTs/PyC foam. These in-situ grown amorphous CNTs were distributed uniformly and controlled by the catalytic growth time and can enhance the interface polarization and conduction loss of composites. When the electromagnetic wave enters the internal holes, the electromagnetic energy can be completely attenuated under the combined action of polarization, conductivity loss, and multiple reflections. The ultralight CNTs/PyC foam had a density of 22.0 mg·cm−3 and a reflection coefficient lower than −13.3 dB in the whole X-band (8.2–12.4 GHz), which is better than the conventional standard of effective absorption bandwidth (≤−10 dB). The results provide ideas for researching ultralight and strong electromagnetic wave absorbing materials in the X-band.
2023, vol. 30, no. 3, pp.
581-590.
https://doi.org/10.1007/s12613-022-2556-7
Abstract:
BaTiO3/TiO2@polypyrrole (PPy) composites with hollow multishelled structure (HoMS) were constructed to enhance the electromagnetic wave absorbing properties of BaTiO3-based absorbing material. BaTiO3/TiO2 HoMSs were prepared by hydrothermal crystallization using TiO2 HoMSs as template. Then, FeCl3 was introduced to initiate the oxidative polymerization of pyrrole monomer, forming BaTiO3/TiO2@PPy HoMSs successfully. The electromagnetic wave absorbing properties of BaTiO3/TiO2 HoMSs and BaTiO3/TiO2@PPy HoMSs with different shell number were investigated using a vector network analyzer. The results indicate that BaTiO3/TiO2@PPy HoMSs exhibit improved microwave absorption compared with BaTiO3/TiO2 HoMSs. In particular, tripled-shelled BaTiO3/TiO2@PPy HoMS has the most excellent absorbing performance. The best reflection loss can reach up to −21.80 dB at 13.34 GHz with a corresponding absorber thickness of only 1.3 mm, and the qualified absorption bandwidth of tripled-shelled BaTiO3/TiO2@PPy HoMS is up to 4.2 GHz. This work paves a new way for the development of high-performance composite microwave absorbing materials.
BaTiO3/TiO2@polypyrrole (PPy) composites with hollow multishelled structure (HoMS) were constructed to enhance the electromagnetic wave absorbing properties of BaTiO3-based absorbing material. BaTiO3/TiO2 HoMSs were prepared by hydrothermal crystallization using TiO2 HoMSs as template. Then, FeCl3 was introduced to initiate the oxidative polymerization of pyrrole monomer, forming BaTiO3/TiO2@PPy HoMSs successfully. The electromagnetic wave absorbing properties of BaTiO3/TiO2 HoMSs and BaTiO3/TiO2@PPy HoMSs with different shell number were investigated using a vector network analyzer. The results indicate that BaTiO3/TiO2@PPy HoMSs exhibit improved microwave absorption compared with BaTiO3/TiO2 HoMSs. In particular, tripled-shelled BaTiO3/TiO2@PPy HoMS has the most excellent absorbing performance. The best reflection loss can reach up to −21.80 dB at 13.34 GHz with a corresponding absorber thickness of only 1.3 mm, and the qualified absorption bandwidth of tripled-shelled BaTiO3/TiO2@PPy HoMS is up to 4.2 GHz. This work paves a new way for the development of high-performance composite microwave absorbing materials.
2023, vol. 30, no. 3, pp.
591-599.
https://doi.org/10.1007/s12613-022-2534-0
Abstract:
Under the background of a transformation of the global energy structure, coal gasification technology has a wide application prospect, but its by-product, the coal gasification residue (CGR), is still not being efficiently utilized for recycling. The CGR contains abundant carbon components, which could be applied to the microwave absorption field as the carbon matrix. In this study, Fe/CGR composites are fabricated via a two-step method, including the impregnation of Fe3+ and the reduction process. The influence of the different loading capacities of the Fe component on the morphology and electromagnetic properties is studied. Moreover, the loading content of Fe and the surface morphology of the Fe/CGR can be reasonably controlled by adjusting the concentration of the ferric nitrate solution. Meanwhile, Fe particles are evenly inserted on the CGR framework, which expands the Fe/CGR interfaces to enhance interfacial polarization, thus further improving the microwave-absorbing (MA) properties of composites. Particularly, as the Fe3+ concentration is 1.0 mol/L, the Fe/CGR composite exhibits outstanding performance. The reflection loss reaches −39.3 dB at 2.5 mm, and the absorption bandwidth covers 4.1 GHz at 1.5 mm. In this study, facile processability, resource recycling, appropriately matched impedance, and excellent MA performance are achieved. Finally, the Fe/CGR composites not only enhance the recycling of the CGR but also pioneer a new path for the synthesis of excellent absorbents.
Under the background of a transformation of the global energy structure, coal gasification technology has a wide application prospect, but its by-product, the coal gasification residue (CGR), is still not being efficiently utilized for recycling. The CGR contains abundant carbon components, which could be applied to the microwave absorption field as the carbon matrix. In this study, Fe/CGR composites are fabricated via a two-step method, including the impregnation of Fe3+ and the reduction process. The influence of the different loading capacities of the Fe component on the morphology and electromagnetic properties is studied. Moreover, the loading content of Fe and the surface morphology of the Fe/CGR can be reasonably controlled by adjusting the concentration of the ferric nitrate solution. Meanwhile, Fe particles are evenly inserted on the CGR framework, which expands the Fe/CGR interfaces to enhance interfacial polarization, thus further improving the microwave-absorbing (MA) properties of composites. Particularly, as the Fe3+ concentration is 1.0 mol/L, the Fe/CGR composite exhibits outstanding performance. The reflection loss reaches −39.3 dB at 2.5 mm, and the absorption bandwidth covers 4.1 GHz at 1.5 mm. In this study, facile processability, resource recycling, appropriately matched impedance, and excellent MA performance are achieved. Finally, the Fe/CGR composites not only enhance the recycling of the CGR but also pioneer a new path for the synthesis of excellent absorbents.
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