SiOC-based ceramics are considered promising electromagnetic wave-absorbing materials because of their lightweight,high-temperature resistance,and heat insulation properties.Herein,SiOC@C ceramic nanospheres were prep...SiOC-based ceramics are considered promising electromagnetic wave-absorbing materials because of their lightweight,high-temperature resistance,and heat insulation properties.Herein,SiOC@C ceramic nanospheres were prepared using a liquid-phase method combined with a polymer-derived ceramic(PDC)method,followed by heat treatment in N_(2) and Ar atmospheres at different temperatures.The morphology,microstructure,phase composition,and electromagnetic wave absorption performance of the SiOC@C ceramic nanospheres were investigated in detail.The SiOC@C ceramic nanospheres obtained in the Ar atmosphere showed a minimum reflection loss(RL_(min))of−67.03 dB,whereas the SiOC@C ceramic nanospheres obtained in the N_(2) atmosphere exhibited an RLmin value of−63.76 dB.The outstanding electromagnetic wave absorption performance of the SiOC@C ceramic nanospheres was attributed to the synergistic effect between conductive loss,interfacial/defect polarization loss,multiple reflections,and scattering.Therefore,this research provides valuable insights into the design and fabrication of SiOC ceramic-based electromagnetic wave absorbers.展开更多
Currently,the microwave absorbers usually suffer dreadful electromagnetic wave absorption(EMWA)performance damping at elevated temperature due to impedance mismatching induced by increased conduction loss.Consequently...Currently,the microwave absorbers usually suffer dreadful electromagnetic wave absorption(EMWA)performance damping at elevated temperature due to impedance mismatching induced by increased conduction loss.Consequently,the development of high-performance EMWA materials with good impedance matching and strong loss ability in wide temperature spectrum has emerged as a top priority.Herein,due to the high melting point,good electrical conductivity,excellent environmental stability,EM coupling effect,and abundant interfaces of titanium nitride(TiN)nanotubes,they were designed based on the controlling kinetic diffusion procedure and Ostwald ripening process.Benefiting from boosted heterogeneous interfaces between TiN nanotubes and polydimethylsiloxane(PDMS),enhanced polarization loss relaxations were created,which could not only improve the depletion efficiency of EMWA,but also contribute to the optimized impedance matching at elevated temperature.Therefore,the TiN nanotubes/PDMS composite showed excellent EMWA performances at varied temperature(298-573 K),while achieved an effective absorption bandwidth(EAB)value of 3.23 GHz and a minimum reflection loss(RLmin)value of−44.15 dB at 423 K.This study not only clarifies the relationship between dielectric loss capacity(conduction loss and polarization loss)and temperature,but also breaks new ground for EM absorbers in wide temperature spectrum based on interface engineering.展开更多
The development of multifunctional composites with desirable electromagnetic wave absorption and antibacterial performance for the medical field has aroused wide interest.In this work,SioC/Ag composites were successfu...The development of multifunctional composites with desirable electromagnetic wave absorption and antibacterial performance for the medical field has aroused wide interest.In this work,SioC/Ag composites were successfully fabricated via the liquid-phase method.When the filler content of SiOC/Ag-3 is 40wt%,SiOC/Ag-3exhibits excellent electromagnetic wave absorption performance,achieving a minimum reflection loss(RL_(min))value of-58.03 dB with a matching thickness of only 2.82 mm.The superior electromagnetic wave absorption performance is attributed to(i)multiple reflections,(ii)conductive loss,and(iii)interfacial polarization loss.In addition,the radar cross-section(RCS)simulation indicates that all RCS values of the perfect electric conductor(PEC)with the SioC/Ag-3 coating are below-20 dB-m^(2)across the incident angle range from-60°to 60,indicating strong radar stealth performance.Moreover,SiOC/Ag composites also achieve excellent antibacterial ability against E.coli and S.aureus through the generation of reactive oxygen species(ROS)under visible light irradiation.This work provides new insights into the design and development of bifunctional composites with electromagnetic wave absorption and antibacterial performancefor application in medical devices.展开更多
To solve the severe electromagnetic(EM)radiation from the widespread application of electronic equipment,we developed a simple template-guided oxypolymerization strategy to synthesize polypyrrole(PPy)planar helixes as...To solve the severe electromagnetic(EM)radiation from the widespread application of electronic equipment,we developed a simple template-guided oxypolymerization strategy to synthesize polypyrrole(PPy)planar helixes as an efficient EM wave(EMW)absorber,and systematically investigated the morphology-dependent chirality,conductivity,and microwave absorption properties.As HCl concentration[HCl]varied from 0 to 2.0 M,the morphology evolved from planar helix to 3D cross-linking network structures,the conductivity increased from 0.0019 to 0.0302 S/cm,and the EM parameters peaked at[HCl]=0.5 M.Compared to other absorbers,the PPy planar helix formed at[HCl]=0 M possessed wider absorption band(5.84 GHz),smaller matching thickness(1.6 mm),lower loading(25 wt.%),and intenser absorption(-48.17 dB).The reason lies in the strong attenuation capability,multiple resonances,multiple scattering,and good impedance matching generated by chiral PPy planar helixes with a distinctive helical configuration,doped heteroatoms(O,S),and a local conductive network.Our results suggest that PPy planar helixes offer great promise for fields such as chiral sensors,electronics,optics,chiral catalysis,and EMW absorption and shielding due to their distinctive morphology,tunable conductivity,and outstanding EMW absorption properties(EMWAPs).展开更多
基金supported by the National Natural Science Foundation of China(No.52360018)the Shiyanjia Lab(www.shiyanjia.com)for the support of thermogravimetric(TG)tests.
文摘SiOC-based ceramics are considered promising electromagnetic wave-absorbing materials because of their lightweight,high-temperature resistance,and heat insulation properties.Herein,SiOC@C ceramic nanospheres were prepared using a liquid-phase method combined with a polymer-derived ceramic(PDC)method,followed by heat treatment in N_(2) and Ar atmospheres at different temperatures.The morphology,microstructure,phase composition,and electromagnetic wave absorption performance of the SiOC@C ceramic nanospheres were investigated in detail.The SiOC@C ceramic nanospheres obtained in the Ar atmosphere showed a minimum reflection loss(RL_(min))of−67.03 dB,whereas the SiOC@C ceramic nanospheres obtained in the N_(2) atmosphere exhibited an RLmin value of−63.76 dB.The outstanding electromagnetic wave absorption performance of the SiOC@C ceramic nanospheres was attributed to the synergistic effect between conductive loss,interfacial/defect polarization loss,multiple reflections,and scattering.Therefore,this research provides valuable insights into the design and fabrication of SiOC ceramic-based electromagnetic wave absorbers.
基金the National Nature Science Foundation of China(No.22305066).
文摘Currently,the microwave absorbers usually suffer dreadful electromagnetic wave absorption(EMWA)performance damping at elevated temperature due to impedance mismatching induced by increased conduction loss.Consequently,the development of high-performance EMWA materials with good impedance matching and strong loss ability in wide temperature spectrum has emerged as a top priority.Herein,due to the high melting point,good electrical conductivity,excellent environmental stability,EM coupling effect,and abundant interfaces of titanium nitride(TiN)nanotubes,they were designed based on the controlling kinetic diffusion procedure and Ostwald ripening process.Benefiting from boosted heterogeneous interfaces between TiN nanotubes and polydimethylsiloxane(PDMS),enhanced polarization loss relaxations were created,which could not only improve the depletion efficiency of EMWA,but also contribute to the optimized impedance matching at elevated temperature.Therefore,the TiN nanotubes/PDMS composite showed excellent EMWA performances at varied temperature(298-573 K),while achieved an effective absorption bandwidth(EAB)value of 3.23 GHz and a minimum reflection loss(RLmin)value of−44.15 dB at 423 K.This study not only clarifies the relationship between dielectric loss capacity(conduction loss and polarization loss)and temperature,but also breaks new ground for EM absorbers in wide temperature spectrum based on interface engineering.
基金supported by the Science Foundation of Jiangxi Provincial Department of Education(No.GJ2400915)the Early Career Youth Science and Technology Talent Training Project of Jiangxi Province(No.20244BCE52206)the National Natural Science Foundation of China(No.52360018).
文摘The development of multifunctional composites with desirable electromagnetic wave absorption and antibacterial performance for the medical field has aroused wide interest.In this work,SioC/Ag composites were successfully fabricated via the liquid-phase method.When the filler content of SiOC/Ag-3 is 40wt%,SiOC/Ag-3exhibits excellent electromagnetic wave absorption performance,achieving a minimum reflection loss(RL_(min))value of-58.03 dB with a matching thickness of only 2.82 mm.The superior electromagnetic wave absorption performance is attributed to(i)multiple reflections,(ii)conductive loss,and(iii)interfacial polarization loss.In addition,the radar cross-section(RCS)simulation indicates that all RCS values of the perfect electric conductor(PEC)with the SioC/Ag-3 coating are below-20 dB-m^(2)across the incident angle range from-60°to 60,indicating strong radar stealth performance.Moreover,SiOC/Ag composites also achieve excellent antibacterial ability against E.coli and S.aureus through the generation of reactive oxygen species(ROS)under visible light irradiation.This work provides new insights into the design and development of bifunctional composites with electromagnetic wave absorption and antibacterial performancefor application in medical devices.
基金supported by the National Natural Science Foundation of China(Grant No. 52073260)the Public Utility Items of Zhejiang Province (Grant No. LGG21E020002)+1 种基金the Industrial Key Projects of Jinhua City (Grant No.2019A12238)the Self-Topic Fund of Zhejiang Normal University(Grant No. 2020ZS04)
文摘To solve the severe electromagnetic(EM)radiation from the widespread application of electronic equipment,we developed a simple template-guided oxypolymerization strategy to synthesize polypyrrole(PPy)planar helixes as an efficient EM wave(EMW)absorber,and systematically investigated the morphology-dependent chirality,conductivity,and microwave absorption properties.As HCl concentration[HCl]varied from 0 to 2.0 M,the morphology evolved from planar helix to 3D cross-linking network structures,the conductivity increased from 0.0019 to 0.0302 S/cm,and the EM parameters peaked at[HCl]=0.5 M.Compared to other absorbers,the PPy planar helix formed at[HCl]=0 M possessed wider absorption band(5.84 GHz),smaller matching thickness(1.6 mm),lower loading(25 wt.%),and intenser absorption(-48.17 dB).The reason lies in the strong attenuation capability,multiple resonances,multiple scattering,and good impedance matching generated by chiral PPy planar helixes with a distinctive helical configuration,doped heteroatoms(O,S),and a local conductive network.Our results suggest that PPy planar helixes offer great promise for fields such as chiral sensors,electronics,optics,chiral catalysis,and EMW absorption and shielding due to their distinctive morphology,tunable conductivity,and outstanding EMW absorption properties(EMWAPs).
