Polyurea(PUA)is widely valued in protective coatings and structural reinforcement because of its impressive mechanical strength and resistance to corrosion.Its high flammability,together with the poor dispersion that ...Polyurea(PUA)is widely valued in protective coatings and structural reinforcement because of its impressive mechanical strength and resistance to corrosion.Its high flammability,together with the poor dispersion that often comes with simply blending in flame retardants,continues to limit its use in demanding environments.To overcome these issues,this study introduces a different approach.We grafted 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide(DOPO)onto the surface of a metal-organic framework(MOF)and then partially amino-functionalized the DOPO layer,ultimately creating an amino-modified DOPO-MOF hybrid.The introduced amino groups can directly react with the isocyanate(-NCO)groups in the PUA matrix,allowing the flame-retardant component to be integrated via reactive integration rather than physical blending.This approach helps avoid the interfacial defects and the mechanical weakening typically observed in conventional blending.With 5 wt% ZIF-67@DOPO-NH2 added to the PUA system,the composite successfully reached a UL-94 V-0 classification and showed a notable increase in limiting oxygen index(LOI),from19.2% to 23.8%.The peak heat release rate and total heat release dropped by 36.3% and 38.7%,respectively.Meanwhile,the tensile strength decreased from 25.74 to 22.52 MPa,while the elongation at break remained above 300%,indicating that the material maintained excellent toughness.展开更多
The advantages of Fe,Ni metals and one-dimensional(1D)carbon materials are combined in this study using a simple method to prepare FeNi/C nanofibers for electromagnetic microwave(EM)absorption.The prepared FeNi/C nano...The advantages of Fe,Ni metals and one-dimensional(1D)carbon materials are combined in this study using a simple method to prepare FeNi/C nanofibers for electromagnetic microwave(EM)absorption.The prepared FeNi/C nanofibers exhibit excellent EM absorption performance under dielectric/magnetic synergistic effect.At a frequency of 13.3 GHz,the minimum reflection loss(RLmin)reaches-57.15 dB,and effective absorption bandwidth(EAB)is as high as 4.0 GHz(12.5-16.5 GHz),with a thickness and filling rate of only 1.6 mm and 30 wt.%,respectively.Analysis shows that the EM absorption performance of FeNi/C nanofibers far exceeds that of single-component nanofibers and pure carbon fibers,and the excellent EM absorption performance is due to its unique microstructure and excellent electromagnetic properties.The FeNi alloy loaded on carbon nanofibers forms rich heterogeneous interfaces,and the three-dimensional(3D)conductive network composed of 1D carbon fibers increases the migration path of electrons.In addition,FeNi alloy,as an impedance regulation factor,strengthens the dielectricity of the carbon matrix while providing multidimensional magnetism,achieving impedance matching.This work is thought to contribute to the promotion of emerging absorbers by providing a novel strategy for the development of new 1D magnetic carbon-based high-performance EM absorbing materials.展开更多
Tetraamido-oxacalix[4]arene derivatives have been synthesized via the reactions of tetraamino-oxacalix[4]arene with excess butyryl chloride, octanoyl chloride, benzoyl chloride and p-toluenesulfonyl chloride, respecti...Tetraamido-oxacalix[4]arene derivatives have been synthesized via the reactions of tetraamino-oxacalix[4]arene with excess butyryl chloride, octanoyl chloride, benzoyl chloride and p-toluenesulfonyl chloride, respectively. JH NMR results suggest that these oxacalix[4]arene derivatives preferentially adopt the 1,3-alternate （saddle-like） con- formation in solution, which were also the case in the solid state as demonstrated by single crystal X-ray analysis. A dimerized slipped capsule could be formed by tetra-butyramido-oxacalix[4]arene in the solid state via intermolecu- lar hydrogen bond interactions under the assistance of two encapsulated methanol molecules. On the other hand, a molecular cavity was formed by tetra-p-toluenesulfonamido-oxacalix[4]arene which can encapsulate a solvent molecule of ethyl acetate.展开更多
基金financially supported by Natural Science Foundation of Shandong Province(Grant No.ZR2021ME019).
文摘Polyurea(PUA)is widely valued in protective coatings and structural reinforcement because of its impressive mechanical strength and resistance to corrosion.Its high flammability,together with the poor dispersion that often comes with simply blending in flame retardants,continues to limit its use in demanding environments.To overcome these issues,this study introduces a different approach.We grafted 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide(DOPO)onto the surface of a metal-organic framework(MOF)and then partially amino-functionalized the DOPO layer,ultimately creating an amino-modified DOPO-MOF hybrid.The introduced amino groups can directly react with the isocyanate(-NCO)groups in the PUA matrix,allowing the flame-retardant component to be integrated via reactive integration rather than physical blending.This approach helps avoid the interfacial defects and the mechanical weakening typically observed in conventional blending.With 5 wt% ZIF-67@DOPO-NH2 added to the PUA system,the composite successfully reached a UL-94 V-0 classification and showed a notable increase in limiting oxygen index(LOI),from19.2% to 23.8%.The peak heat release rate and total heat release dropped by 36.3% and 38.7%,respectively.Meanwhile,the tensile strength decreased from 25.74 to 22.52 MPa,while the elongation at break remained above 300%,indicating that the material maintained excellent toughness.
基金supported by the Natural Science Foundation of Shandong Province(Nos.ZR2021ME019 and ZR2019BB063).
文摘The advantages of Fe,Ni metals and one-dimensional(1D)carbon materials are combined in this study using a simple method to prepare FeNi/C nanofibers for electromagnetic microwave(EM)absorption.The prepared FeNi/C nanofibers exhibit excellent EM absorption performance under dielectric/magnetic synergistic effect.At a frequency of 13.3 GHz,the minimum reflection loss(RLmin)reaches-57.15 dB,and effective absorption bandwidth(EAB)is as high as 4.0 GHz(12.5-16.5 GHz),with a thickness and filling rate of only 1.6 mm and 30 wt.%,respectively.Analysis shows that the EM absorption performance of FeNi/C nanofibers far exceeds that of single-component nanofibers and pure carbon fibers,and the excellent EM absorption performance is due to its unique microstructure and excellent electromagnetic properties.The FeNi alloy loaded on carbon nanofibers forms rich heterogeneous interfaces,and the three-dimensional(3D)conductive network composed of 1D carbon fibers increases the migration path of electrons.In addition,FeNi alloy,as an impedance regulation factor,strengthens the dielectricity of the carbon matrix while providing multidimensional magnetism,achieving impedance matching.This work is thought to contribute to the promotion of emerging absorbers by providing a novel strategy for the development of new 1D magnetic carbon-based high-performance EM absorbing materials.
基金Financial support from National Natural Science Foundation of China，Shanghai Commission for Science and Technology，"Strategic Priority Research Program" of the Chinese Academy of Sciences (No.XDA01020304) is acknowledged
文摘Tetraamido-oxacalix[4]arene derivatives have been synthesized via the reactions of tetraamino-oxacalix[4]arene with excess butyryl chloride, octanoyl chloride, benzoyl chloride and p-toluenesulfonyl chloride, respectively. JH NMR results suggest that these oxacalix[4]arene derivatives preferentially adopt the 1,3-alternate （saddle-like） con- formation in solution, which were also the case in the solid state as demonstrated by single crystal X-ray analysis. A dimerized slipped capsule could be formed by tetra-butyramido-oxacalix[4]arene in the solid state via intermolecu- lar hydrogen bond interactions under the assistance of two encapsulated methanol molecules. On the other hand, a molecular cavity was formed by tetra-p-toluenesulfonamido-oxacalix[4]arene which can encapsulate a solvent molecule of ethyl acetate.
