The exploration of remarkable electromagnetic wave(EMW)absorbing materials with temperature-stable absorbing properties at a wide temperature range holds significant implications for both military operations and civil...The exploration of remarkable electromagnetic wave(EMW)absorbing materials with temperature-stable absorbing properties at a wide temperature range holds significant implications for both military operations and civilian life.Herein,the titanium nitride/zirconium oxide/carbon(TiN/ZrO_(2)/C)ternary nanofiber membranes have been synthesized by electrospinning followed by preoxidation-nitridation process.Thanks to the flexibility of the prepared ceramic membranes,the corresponding metacomposites,characterized by a unique hierarchical structure,were fabricated through the systematic incorporation of subwavelength scale functional units(square fiber membranes)within a polydimethylsiloxane(PDMS)matrix.This approach effectively expanded the transmission path of EMW,contributing to additional multiple reflections and scattering within the system.As a result,when the content of the functional units was as low as 10.0 wt%,the engineered metacomposites exhibited exceptional EMW absorption properties across a broad temperature range(298–573 K).This performance can be attributed to the synergistic effects of optimized impedance matching and enhanced attenuation capacity.Furthermore,the metacomposites achieved a minimum reflection loss(RL)value of−51.7 dB at 453 K,with an effective absorption bandwidth(EAB)spanning 2.3 GHz.This study may serve as a valuable reference for the design of high attenuation capacity EMW absorbing materials under complex variable high-temperature conditions.展开更多
A facile and selective route for O-alkylation of highly hydrophilic, multifunctional hyperbranched polyglycerol (PG) under non-aqueous phase transfer catalyzed conditions in dimethyl sulfoxide was developed, through w...A facile and selective route for O-alkylation of highly hydrophilic, multifunctional hyperbranched polyglycerol (PG) under non-aqueous phase transfer catalyzed conditions in dimethyl sulfoxide was developed, through which several kinds of groups were introduced onto PG.展开更多
Homopolymerization of N-pyrimidinyl acrylamide (NPA) was reported for the first time. The polymer (polyNPA) was soluble only in acidic media and fluoroalcohols, and only in fluoroalcohol was homogeneous polymerization...Homopolymerization of N-pyrimidinyl acrylamide (NPA) was reported for the first time. The polymer (polyNPA) was soluble only in acidic media and fluoroalcohols, and only in fluoroalcohol was homogeneous polymerization of NPA feasible. 1H NMR analysis proved that a 1:1 H-bonding complex could be formed between NPA and α,α-bis(trifluoromethyl)phenyl propan-2-ol (BTMP). Cumyl dithiobenzoate mediated reversible addition-fragmentation chain transfer (RAFT) polymerization of NPA in BTMP was carried out. 1H NMR analyses proved that the molecular weight increased linearly with the monomer conversion. The polymer prepared in conventional solvents was atactic while in protic media the syndiotacticity was slightly enhanced.展开更多
Silica-supported branched polyethylenimine（Sil@PEI） is a conventional adsorbent and shows a limited affinity to anionic surfactants and small dyes（K = 106？107 L/mol）. If the PEI is alkylated with cetyl groups（C1...Silica-supported branched polyethylenimine（Sil@PEI） is a conventional adsorbent and shows a limited affinity to anionic surfactants and small dyes（K = 106？107 L/mol）. If the PEI is alkylated with cetyl groups（C16）, the K of the resulting adsorbents（Sil@PEI@C16-x, where x is the fraction of PEI units being alkylated） is significantly improved. Optimization shows that Sil@PEI@C16-0.15 can best reduce aqueous surfactants to a residue around 10？10 mol/L; while Sil@PEI@C16-0.6 can reduce even small aqueous dyes to a residue below 10？10 mol/L, nearly 105-fold lower than that by Sil@PEI. The adsorbents are well recyclable. It is believed that in the case of dyes, the dense cetyl shell can isolate the PEI from the bulky water and thus suppress the competitive binding by water; while in the case of surfactants, the semiclosed cetyl shell can simultaneously meet electrostatic complement and hydrophobic complement to the surfactants.展开更多
Nanocrystalline Mn0.6Zn0.4Fe2O4 particles are synthesized under magnetic fields of O and 6 T, and their structural and magnetic properties are investigated. The magnetic field enhances the grain size and the lattice s...Nanocrystalline Mn0.6Zn0.4Fe2O4 particles are synthesized under magnetic fields of O and 6 T, and their structural and magnetic properties are investigated. The magnetic field enhances the grain size and the lattice strain. Magnetic measurements show that the majority of the 6 T nanoparticles are superparamagnetic nearly from 40 to 300 K. It is interesting that the saturation magnetization of the 6 T sample is about 18% and 16% higher than that of the 0 T sample at 120 and 300K, respectively.展开更多
High-performance microwave-absorbing materials(MAMs)should meet both impedance matching and attenuation performance.Commonly,it is hard to maintain excellent microwave absorption(MA)per-formance at an elevated tempera...High-performance microwave-absorbing materials(MAMs)should meet both impedance matching and attenuation performance.Commonly,it is hard to maintain excellent microwave absorption(MA)per-formance at an elevated temperature because the reliance on impedance matching and dielectric loss about temperature mutually restricts.In this work,the pomegranate-like antimony-doped tin dioxide(ATO)/silica dioxide(SiO_(2))spheres were fabricated via a simple spray drying process.When the spheres were used as functional units and dispersed in the matrix,the corresponding composites exhibit an out-standing anti-reflection effect on microwaves.Moreover,the unique pomegranate-like structure of the ATO/SiO_(2)spheres provides both the effective local eddy current and abundant heterogeneous interface,which therefore contribute harvest enhanced dielectric relaxation and improved absorption performance when compared with that of the corresponding ATO/SiO_(2)composition.As a result,the maximum re-flection loss of the ATO/SiO_(2)spheres composites can reach-47.8 dB at 9.7 GHz with a thickness of 1.8 mm,while the reflection loss could reach-47.3 dB at 573 K and the effective absorption bandwidth is 2.4 GHz.This work reveals the importance of local eddy current loss in optimizing the electromagnetic wave(EMW)absorption performance and impedance matching,providing novel guidance on designing advanced high-temperature MAMs.展开更多
High-efficiency and temperature-insensitive microwave absorbing materials(MAMs) are ideal for hightemperature electromagnetic attenuation.Herein,the titanium nitride/boron nitride(TiN/BN) composite with TiN as the los...High-efficiency and temperature-insensitive microwave absorbing materials(MAMs) are ideal for hightemperature electromagnetic attenuation.Herein,the titanium nitride/boron nitride(TiN/BN) composite with TiN as the loss unit and BN as the impedance matching unit has been constructed by the in-situ synthesis method.The insulating BN not only effectively regulates and optimizes the conductivity and impedance matching of the material but also imparts steady cyclic microwave absorption properties.The steady dielectric loss ensures that TiN/BN composite has robust high-temperature absorption properties at X-band,with a minimum reflection loss(RL_(min)) of-16.74 dB at 873 K and an effective absorption bandwidth(EAB) of 3.26 GHz in the temperature range of 293-873 K.Compared with the TiN/SiO2absorbers with a single system,the TiN/BN/SiO2composite keeps reliable high temperature absorbing properties at873 K.This work confirms that wave-transparent materials for dielectric property modulation can resolve poor temperature stability of effective absorption and non-reusability for high-temperature absorbing materials,providing inspirations for designing efficiency high-temperature microwave absorbers.展开更多
Simultaneous development of well impedance matching and strong loss capability has become a mainstream method for achieving outstanding electromagnetic microwave absorption(EMWA)performances over wide temperature rang...Simultaneous development of well impedance matching and strong loss capability has become a mainstream method for achieving outstanding electromagnetic microwave absorption(EMWA)performances over wide temperature range.However,it is difficult to pursue both due to the mutual restraint of relationship between impedance matching and loss capability about temperature.Here,we propose a flexible regulation engineering of titanium nitride(TiN)nanofibrous membranes(NMs,TNMs),which could be distributed uniformly in the polydimethylsiloxane(PDMS)matrix and contributed to the formation of abundant local conductive networks,generating the local conductive loss and enhancing the loss ability of EMWs.Moreover,when the TNMs are used as functional units and dispersed in the matrix,the corresponding composites exhibit an outstanding anti-reflection effect on microwaves.As hoped,under the precondition of good impedance matching,local conductive loss and polarization loss together improve the loss capacity at room temperature,and polarization loss can compensate the local conductive loss to acquire effective dielectric response at elevated temperature.Benefiting from the reasonably synergistic loss ability caused by flexible regulation engineering,the corresponding composites exhibit the perfect EMWA performances in a wide temperature range from 298 to 573 K.This work not only elaborates the ponderable insights of independent membrane in the composition-structure-function connection,but also provides a feasible tactic for resolving coexistence of well impedance matching and strong loss capability issues in wide temperature spectrum.展开更多
Due to the temperature and frequency response of electromagnetic(EM)loss,how to realize the effective design of microwave absorption materials(MWAMs)at elevated temperature is highly desirable for practical applicatio...Due to the temperature and frequency response of electromagnetic(EM)loss,how to realize the effective design of microwave absorption materials(MWAMs)at elevated temperature is highly desirable for practical applications.Herein,transition metaldoped titanium nitride(M-TiN,M=Fe or Co)fibers were fabricated,the distortion of TiN lattice could cause the adjustable charge enrichment,which played a profound influence on the dielectric response and EM microwave absorption(EMWA)performances.Benefiting from the negative correlation between dielectric loss and temperature,more loss mechanism could be introduced,which would effectively enhance dielectric loss and EMWA performances at elevated temperature.The optimal EMWA performances of Fe-TiN fibers/polydimethylsiloxane(PDMS)composites were realized with a wide temperature range(298–423 K):the reflection loss(RL)could reach 99%(RL<−20 dB)at 12.2 GHz with 1.8 mm,when the filler content was only 15.0 wt.%.Compared with the undoped-TiN fibers/PDMS and Co-TiN fibers/PDMS composites,the excellent EMWA of Fe-TiN fibers/PDMS composite could be attributed to the reasonably synergistic polarization loss and conduction loss.Based on systematic analysis of the variable-temperature EM parameters and EMWA performances,the optimization of EMWA performances in wide temperature domain could be realized by introducing appropriate polarization loss and its compensating.Hopefully,this work provides a new strategy for regulating the dielectric response and designing effective MWAMs at elevated temperature.展开更多
With the increasing advance of fifth generation(5G)network and the gradual expansion of digital devices,harsh working environment for electronic devices has spawned higher requirements for microwave absorbing material...With the increasing advance of fifth generation(5G)network and the gradual expansion of digital devices,harsh working environment for electronic devices has spawned higher requirements for microwave absorbing materials(MAMs).Since both the electromagnetic response and energy conversion character vary with temperature,to achieve temperature insensitive microwave absorption behaviour in wide temperature range has become extremely challenging.In this work,structured metacomposites containing sub-wavelength reduced graphene oxide(RGO)@carbon spheres were fabricated,and the microwave absorption was further improved through structural and composition design of the RGO@carbon units.Due to the unique anti-reflection effect on microwave of the metacomposites,the temperature-insensitive electromagnetic performance at elevated temperature could be exhibited.Moreover,both the dielectric relaxation behaviour and microwave absorption proformance of the system could be further increased.As a result,the effective absorption bandwidth(reflection loss(RL)<−10 dB)of the metacomposites with only 3.0 wt.%filler content could cover the entire X-band(8.2–12.4 GHz)frequency ranging from 298 to 473K.The metacomposite proposed in this work provides a“de-correlating”strategy to break the linkage between microwave absorption behaviour and temperature,which offers an interesting plateau for fabricating efficient high-temperature microwave absorption structures with tunable and designable advantages.展开更多
基金supported by the National Nature Science Foundation of China(Nos.22475065 and 22305066)the Natural Science Foundation of Henan Province Youth Fund(No.242300421466).
文摘The exploration of remarkable electromagnetic wave(EMW)absorbing materials with temperature-stable absorbing properties at a wide temperature range holds significant implications for both military operations and civilian life.Herein,the titanium nitride/zirconium oxide/carbon(TiN/ZrO_(2)/C)ternary nanofiber membranes have been synthesized by electrospinning followed by preoxidation-nitridation process.Thanks to the flexibility of the prepared ceramic membranes,the corresponding metacomposites,characterized by a unique hierarchical structure,were fabricated through the systematic incorporation of subwavelength scale functional units(square fiber membranes)within a polydimethylsiloxane(PDMS)matrix.This approach effectively expanded the transmission path of EMW,contributing to additional multiple reflections and scattering within the system.As a result,when the content of the functional units was as low as 10.0 wt%,the engineered metacomposites exhibited exceptional EMW absorption properties across a broad temperature range(298–573 K).This performance can be attributed to the synergistic effects of optimized impedance matching and enhanced attenuation capacity.Furthermore,the metacomposites achieved a minimum reflection loss(RL)value of−51.7 dB at 453 K,with an effective absorption bandwidth(EAB)spanning 2.3 GHz.This study may serve as a valuable reference for the design of high attenuation capacity EMW absorbing materials under complex variable high-temperature conditions.
文摘A facile and selective route for O-alkylation of highly hydrophilic, multifunctional hyperbranched polyglycerol (PG) under non-aqueous phase transfer catalyzed conditions in dimethyl sulfoxide was developed, through which several kinds of groups were introduced onto PG.
文摘Homopolymerization of N-pyrimidinyl acrylamide (NPA) was reported for the first time. The polymer (polyNPA) was soluble only in acidic media and fluoroalcohols, and only in fluoroalcohol was homogeneous polymerization of NPA feasible. 1H NMR analysis proved that a 1:1 H-bonding complex could be formed between NPA and α,α-bis(trifluoromethyl)phenyl propan-2-ol (BTMP). Cumyl dithiobenzoate mediated reversible addition-fragmentation chain transfer (RAFT) polymerization of NPA in BTMP was carried out. 1H NMR analyses proved that the molecular weight increased linearly with the monomer conversion. The polymer prepared in conventional solvents was atactic while in protic media the syndiotacticity was slightly enhanced.
文摘Silica-supported branched polyethylenimine（Sil@PEI） is a conventional adsorbent and shows a limited affinity to anionic surfactants and small dyes（K = 106？107 L/mol）. If the PEI is alkylated with cetyl groups（C16）, the K of the resulting adsorbents（Sil@PEI@C16-x, where x is the fraction of PEI units being alkylated） is significantly improved. Optimization shows that Sil@PEI@C16-0.15 can best reduce aqueous surfactants to a residue around 10？10 mol/L; while Sil@PEI@C16-0.6 can reduce even small aqueous dyes to a residue below 10？10 mol/L, nearly 105-fold lower than that by Sil@PEI. The adsorbents are well recyclable. It is believed that in the case of dyes, the dense cetyl shell can isolate the PEI from the bulky water and thus suppress the competitive binding by water; while in the case of surfactants, the semiclosed cetyl shell can simultaneously meet electrostatic complement and hydrophobic complement to the surfactants.
基金Supported by the Shanghai Rising-Star Program Grant No 07QA14026, the National Natural Science Foundation of China Grant Nos 10804072, 50703029 and 10774097, STCSM Grant Nos 08JC1410400, 0752nm012, and 0952nm02700, and FNEDAEDT under Grant No 200235.
文摘Nanocrystalline Mn0.6Zn0.4Fe2O4 particles are synthesized under magnetic fields of O and 6 T, and their structural and magnetic properties are investigated. The magnetic field enhances the grain size and the lattice strain. Magnetic measurements show that the majority of the 6 T nanoparticles are superparamagnetic nearly from 40 to 300 K. It is interesting that the saturation magnetization of the 6 T sample is about 18% and 16% higher than that of the 0 T sample at 120 and 300K, respectively.
基金the financial support of the National Nature Science Foundation of China(No.U1704253).
文摘High-performance microwave-absorbing materials(MAMs)should meet both impedance matching and attenuation performance.Commonly,it is hard to maintain excellent microwave absorption(MA)per-formance at an elevated temperature because the reliance on impedance matching and dielectric loss about temperature mutually restricts.In this work,the pomegranate-like antimony-doped tin dioxide(ATO)/silica dioxide(SiO_(2))spheres were fabricated via a simple spray drying process.When the spheres were used as functional units and dispersed in the matrix,the corresponding composites exhibit an out-standing anti-reflection effect on microwaves.Moreover,the unique pomegranate-like structure of the ATO/SiO_(2)spheres provides both the effective local eddy current and abundant heterogeneous interface,which therefore contribute harvest enhanced dielectric relaxation and improved absorption performance when compared with that of the corresponding ATO/SiO_(2)composition.As a result,the maximum re-flection loss of the ATO/SiO_(2)spheres composites can reach-47.8 dB at 9.7 GHz with a thickness of 1.8 mm,while the reflection loss could reach-47.3 dB at 573 K and the effective absorption bandwidth is 2.4 GHz.This work reveals the importance of local eddy current loss in optimizing the electromagnetic wave(EMW)absorption performance and impedance matching,providing novel guidance on designing advanced high-temperature MAMs.
基金financially supported by the National Nature Science Foundation of China (Nos.U1704253 and 21671057)the Key Project of Innovation Training Plan for College Students in Henan Province (No.202010475005)。
文摘High-efficiency and temperature-insensitive microwave absorbing materials(MAMs) are ideal for hightemperature electromagnetic attenuation.Herein,the titanium nitride/boron nitride(TiN/BN) composite with TiN as the loss unit and BN as the impedance matching unit has been constructed by the in-situ synthesis method.The insulating BN not only effectively regulates and optimizes the conductivity and impedance matching of the material but also imparts steady cyclic microwave absorption properties.The steady dielectric loss ensures that TiN/BN composite has robust high-temperature absorption properties at X-band,with a minimum reflection loss(RL_(min)) of-16.74 dB at 873 K and an effective absorption bandwidth(EAB) of 3.26 GHz in the temperature range of 293-873 K.Compared with the TiN/SiO2absorbers with a single system,the TiN/BN/SiO2composite keeps reliable high temperature absorbing properties at873 K.This work confirms that wave-transparent materials for dielectric property modulation can resolve poor temperature stability of effective absorption and non-reusability for high-temperature absorbing materials,providing inspirations for designing efficiency high-temperature microwave absorbers.
基金support of the National Natural Science Foundation of China(Nos.22305066 and U1704253).
文摘Simultaneous development of well impedance matching and strong loss capability has become a mainstream method for achieving outstanding electromagnetic microwave absorption(EMWA)performances over wide temperature range.However,it is difficult to pursue both due to the mutual restraint of relationship between impedance matching and loss capability about temperature.Here,we propose a flexible regulation engineering of titanium nitride(TiN)nanofibrous membranes(NMs,TNMs),which could be distributed uniformly in the polydimethylsiloxane(PDMS)matrix and contributed to the formation of abundant local conductive networks,generating the local conductive loss and enhancing the loss ability of EMWs.Moreover,when the TNMs are used as functional units and dispersed in the matrix,the corresponding composites exhibit an outstanding anti-reflection effect on microwaves.As hoped,under the precondition of good impedance matching,local conductive loss and polarization loss together improve the loss capacity at room temperature,and polarization loss can compensate the local conductive loss to acquire effective dielectric response at elevated temperature.Benefiting from the reasonably synergistic loss ability caused by flexible regulation engineering,the corresponding composites exhibit the perfect EMWA performances in a wide temperature range from 298 to 573 K.This work not only elaborates the ponderable insights of independent membrane in the composition-structure-function connection,but also provides a feasible tactic for resolving coexistence of well impedance matching and strong loss capability issues in wide temperature spectrum.
基金support of the National Nature Science Foundation of China(No.U1704253)the Key Scientific Research Project Plan in Universities of Henan Province(No.23A430037)the Science and Technology Planning Project of Henan Province(No.212102210474).
文摘Due to the temperature and frequency response of electromagnetic(EM)loss,how to realize the effective design of microwave absorption materials(MWAMs)at elevated temperature is highly desirable for practical applications.Herein,transition metaldoped titanium nitride(M-TiN,M=Fe or Co)fibers were fabricated,the distortion of TiN lattice could cause the adjustable charge enrichment,which played a profound influence on the dielectric response and EM microwave absorption(EMWA)performances.Benefiting from the negative correlation between dielectric loss and temperature,more loss mechanism could be introduced,which would effectively enhance dielectric loss and EMWA performances at elevated temperature.The optimal EMWA performances of Fe-TiN fibers/polydimethylsiloxane(PDMS)composites were realized with a wide temperature range(298–423 K):the reflection loss(RL)could reach 99%(RL<−20 dB)at 12.2 GHz with 1.8 mm,when the filler content was only 15.0 wt.%.Compared with the undoped-TiN fibers/PDMS and Co-TiN fibers/PDMS composites,the excellent EMWA of Fe-TiN fibers/PDMS composite could be attributed to the reasonably synergistic polarization loss and conduction loss.Based on systematic analysis of the variable-temperature EM parameters and EMWA performances,the optimization of EMWA performances in wide temperature domain could be realized by introducing appropriate polarization loss and its compensating.Hopefully,this work provides a new strategy for regulating the dielectric response and designing effective MWAMs at elevated temperature.
基金the National Natural Science Foundation of China(Nos.U1704253 and 21671057).
文摘With the increasing advance of fifth generation(5G)network and the gradual expansion of digital devices,harsh working environment for electronic devices has spawned higher requirements for microwave absorbing materials(MAMs).Since both the electromagnetic response and energy conversion character vary with temperature,to achieve temperature insensitive microwave absorption behaviour in wide temperature range has become extremely challenging.In this work,structured metacomposites containing sub-wavelength reduced graphene oxide(RGO)@carbon spheres were fabricated,and the microwave absorption was further improved through structural and composition design of the RGO@carbon units.Due to the unique anti-reflection effect on microwave of the metacomposites,the temperature-insensitive electromagnetic performance at elevated temperature could be exhibited.Moreover,both the dielectric relaxation behaviour and microwave absorption proformance of the system could be further increased.As a result,the effective absorption bandwidth(reflection loss(RL)<−10 dB)of the metacomposites with only 3.0 wt.%filler content could cover the entire X-band(8.2–12.4 GHz)frequency ranging from 298 to 473K.The metacomposite proposed in this work provides a“de-correlating”strategy to break the linkage between microwave absorption behaviour and temperature,which offers an interesting plateau for fabricating efficient high-temperature microwave absorption structures with tunable and designable advantages.
