Coordination bonds are relatively unstable compared to covalent bonds,and common carbon-based absorbing material precursors are bonded in the form of coordination bonds.In this work,we have introduced ferrocene units ...Coordination bonds are relatively unstable compared to covalent bonds,and common carbon-based absorbing material precursors are bonded in the form of coordination bonds.In this work,we have introduced ferrocene units into conjugated microporous polymers(CMP)in one step by Suzuki reaction.By adjusting the proportion of ferrocene units,a series of magnetic Fe-C nanocomposites(Fe-P-XC)derived from conjugated ferrocene polymers without heteroatom doping(N,S,P,etc.)were formed.The Fe-P-2C composite has good absorption properties with minimum reflection loss at 4.4 GHz(-58.66 dB)and effective absorption bandwidth(EAB)of 6.28 GHz at 2.4 mm(11.72-18 GHz).Compared with the precursor materials formed by coordination bonds,the present work reveals the electromagnetic wave absorption mechanism of carbon-based materials without heteroatom doping through a simple and effective strategy.展开更多
Transition metal molybdate(RMoO4)has been extensively studied in optics,electricity and catalysis due to its low cost and multivalent Mo atoms,while its poor electrical conductivity limits its application in electroma...Transition metal molybdate(RMoO4)has been extensively studied in optics,electricity and catalysis due to its low cost and multivalent Mo atoms,while its poor electrical conductivity limits its application in electromagnetic wave absorption(EMA).Compounding molybdate with conductive materials is an effective way to improve its electrical conductivity.In this work,a homogeneous coating on the molybdate surface was achieved by utilizing a pyrrole oxidation polymerization mechanism,and then stabilized composites of Molybdate@Carbon(RMoO4@C)were obtained by high-temperature pyrolysis.The EMA properties of the nanocomposites were tuned by substituting the species of transition metal elements(RMoO_(4)@C,R=Fe,Co,Cu).Among them,Fe_(2)(MoO_(4))_(3)@C has a minimum reflection loss of−60.62 dB at an ultra-low thickness of 1.7 mm,and the effective absorption bandwidth(EAB)can reach 4.75 GHz at 3.00 mm.This work expands the range of applications for molybdate and provides a new material basis for building high-performance EMA materials.展开更多
Electrical and magnetic properties are two crucial factors for the designing of broadband electromagnetic wave absorption(EWA)materials.In this work,we synthesized various magnetic metal sulfides/carbon(M_(x)S_(y)/C)n...Electrical and magnetic properties are two crucial factors for the designing of broadband electromagnetic wave absorption(EWA)materials.In this work,we synthesized various magnetic metal sulfides/carbon(M_(x)S_(y)/C)nanocomposites from the precursor complex of metal in microporous polythiophene(MPT),and systematically investigated their EWA properties and mechanism.The characterization results indicate that M_(x)S_(y) were determined to be Fe_(7)S_(8)/C,Co_(9)S_(8)/C and Ni_(4)S_(3)/C,respectively.It is observed that M_(x)S_(y)/C nanocomposites exhibit remarkable EWA performances,where the maximal absorption gets to-51.3 dB,and efficient absorption can be realized in 10.32-18 GHz(7.68 GHz),which is superior to most reported magnetic carbonaceous EWA composites.Beside,the efficient absorption can be tuned to cover Ku band X band,demonstrating their great potential in practical applications.Improved conductance loss,obvious polarization relaxation,and apparent eddy current loss are deemed to make the predominant contributions to the high-performance EWA.This research opens up the exploration of novel nanocomposite coupling dielectric loss and magnetic loss using MPT-metal complex precursor for EWA applications.展开更多
Vanadium(V)oxides exhibit low electrical conductivity and poor polarization properties,especially in that V_(2)O_(3)has low stability and is easily oxidized to higher valence V oxides.To solve this problem,we herein p...Vanadium(V)oxides exhibit low electrical conductivity and poor polarization properties,especially in that V_(2)O_(3)has low stability and is easily oxidized to higher valence V oxides.To solve this problem,we herein provide a two-step strategy for the synthesis of carbon nanofilm stabilized twisty V_(2)O_(3)nanorods(V_(2)O_(3)@C),including a hydrothermal reaction and a controlled pyrolysis process.Conductivity tests and electron-spin resonance(ESR)spectra indicate that the coating of carbon nanofilm not only enhances the electrical conductivity but also generates abundant defects.The electromagnetic waves absorption(EMA)results suggest that V_(2)O_(3)@C exhibits excellent EMA performance at ultra-low thickness,where the effective absorption bandwidth gets to 7.21 GHz at 1.7 mm and the maximal absorption reaches–56 d B.Enhanced conductivity loss and improved multiple polarization relaxation were used to illustrate the absorbing mechanism of V_(2)O_(3)@C.This work provides new insights into the design of advanced nanocomposites for EMA applications.展开更多
基金supported by the National Natural Science Foundation of China(No.11975124)the Fundamental Research Funds for the Central universities(Nos.30920041102 and 30920041103)the Open Fund of Key Laboratory of Materials Preparation and Protection for Harsh Environment(Nanjing University of Aeronautics and Astronautics),Ministry of Industry and Information Technology(No.56XCA22042).
文摘Coordination bonds are relatively unstable compared to covalent bonds,and common carbon-based absorbing material precursors are bonded in the form of coordination bonds.In this work,we have introduced ferrocene units into conjugated microporous polymers(CMP)in one step by Suzuki reaction.By adjusting the proportion of ferrocene units,a series of magnetic Fe-C nanocomposites(Fe-P-XC)derived from conjugated ferrocene polymers without heteroatom doping(N,S,P,etc.)were formed.The Fe-P-2C composite has good absorption properties with minimum reflection loss at 4.4 GHz(-58.66 dB)and effective absorption bandwidth(EAB)of 6.28 GHz at 2.4 mm(11.72-18 GHz).Compared with the precursor materials formed by coordination bonds,the present work reveals the electromagnetic wave absorption mechanism of carbon-based materials without heteroatom doping through a simple and effective strategy.
基金the National Natural Science Foundation of China(No.52273267)the Fundamental Research Funds for the Central Universities(No.30920041102)。
文摘Transition metal molybdate(RMoO4)has been extensively studied in optics,electricity and catalysis due to its low cost and multivalent Mo atoms,while its poor electrical conductivity limits its application in electromagnetic wave absorption(EMA).Compounding molybdate with conductive materials is an effective way to improve its electrical conductivity.In this work,a homogeneous coating on the molybdate surface was achieved by utilizing a pyrrole oxidation polymerization mechanism,and then stabilized composites of Molybdate@Carbon(RMoO4@C)were obtained by high-temperature pyrolysis.The EMA properties of the nanocomposites were tuned by substituting the species of transition metal elements(RMoO_(4)@C,R=Fe,Co,Cu).Among them,Fe_(2)(MoO_(4))_(3)@C has a minimum reflection loss of−60.62 dB at an ultra-low thickness of 1.7 mm,and the effective absorption bandwidth(EAB)can reach 4.75 GHz at 3.00 mm.This work expands the range of applications for molybdate and provides a new material basis for building high-performance EMA materials.
基金financially supported by the Fundamental Research Funds for the Central Universities(No.30920021107)the National Natural Science Foundation of China(No.51702161)。
文摘Electrical and magnetic properties are two crucial factors for the designing of broadband electromagnetic wave absorption(EWA)materials.In this work,we synthesized various magnetic metal sulfides/carbon(M_(x)S_(y)/C)nanocomposites from the precursor complex of metal in microporous polythiophene(MPT),and systematically investigated their EWA properties and mechanism.The characterization results indicate that M_(x)S_(y) were determined to be Fe_(7)S_(8)/C,Co_(9)S_(8)/C and Ni_(4)S_(3)/C,respectively.It is observed that M_(x)S_(y)/C nanocomposites exhibit remarkable EWA performances,where the maximal absorption gets to-51.3 dB,and efficient absorption can be realized in 10.32-18 GHz(7.68 GHz),which is superior to most reported magnetic carbonaceous EWA composites.Beside,the efficient absorption can be tuned to cover Ku band X band,demonstrating their great potential in practical applications.Improved conductance loss,obvious polarization relaxation,and apparent eddy current loss are deemed to make the predominant contributions to the high-performance EWA.This research opens up the exploration of novel nanocomposite coupling dielectric loss and magnetic loss using MPT-metal complex precursor for EWA applications.
基金financially supported by the National Natural Science Foundation of China(No.51702161)。
文摘Vanadium(V)oxides exhibit low electrical conductivity and poor polarization properties,especially in that V_(2)O_(3)has low stability and is easily oxidized to higher valence V oxides.To solve this problem,we herein provide a two-step strategy for the synthesis of carbon nanofilm stabilized twisty V_(2)O_(3)nanorods(V_(2)O_(3)@C),including a hydrothermal reaction and a controlled pyrolysis process.Conductivity tests and electron-spin resonance(ESR)spectra indicate that the coating of carbon nanofilm not only enhances the electrical conductivity but also generates abundant defects.The electromagnetic waves absorption(EMA)results suggest that V_(2)O_(3)@C exhibits excellent EMA performance at ultra-low thickness,where the effective absorption bandwidth gets to 7.21 GHz at 1.7 mm and the maximal absorption reaches–56 d B.Enhanced conductivity loss and improved multiple polarization relaxation were used to illustrate the absorbing mechanism of V_(2)O_(3)@C.This work provides new insights into the design of advanced nanocomposites for EMA applications.
