One simple and environmental friendly synthesis strategy for preparing low-cost magnetic Fe3C@C materials has been facilely developed using a modified sol-gel approach,wherein natural magnetite acted as the iron sourc...One simple and environmental friendly synthesis strategy for preparing low-cost magnetic Fe3C@C materials has been facilely developed using a modified sol-gel approach,wherein natural magnetite acted as the iron source.A chelating polycarboxylic acid such as citric acid(CA)was employed as the carbon source,and it dissolved Fe very effectively,Fe3O4 and natural magnetite to composite an iron-citrate complex with the assistance of ammonium hydroxide.The core-shell structure of the as-prepared nanocomposites was formed directly by high-temperature pyrolysis.The Fe3C@C materials exhibited superparamagnetic properties(38.09 emu/mg),suggesting potential applications in biomedicine,environment,absorption,catalysis,etc.展开更多
The impedance matching of absorbers is a vital factor affecting their microwave absorption(MA)properties.In this work,we controllably synthesized Material of Institute Lavoisier 88C(MIL-88C)with varying aspect ratios(...The impedance matching of absorbers is a vital factor affecting their microwave absorption(MA)properties.In this work,we controllably synthesized Material of Institute Lavoisier 88C(MIL-88C)with varying aspect ratios(AR)as a precursor by regulating oil bath conditions,followed by one-step thermal decomposition to obtain carbon-coated iron-based composites.Modifying the precursor MIL-88C(Fe)preparation conditions,such as the molar ratio between metal ions and organic ligands(M/O),oil bath temperature,and oil bath time,influenced the phases,graphitization degree,and AR of the derivatives,enabling low filler loading,achieving well-matched impedance,and ensuring outstanding MA properties.The MOF-derivatives 2(MD_(2))/polyvinylidene Difluoride(PVDF),MD_(3)/PVDF,and MD4/PVDF absorbers all exhibited excellent MA properties with optimal filler loadings below 20 wt%and as low as 5 wt%.The MD_(2)/PVDF(5 wt%)achieved a maximum effective absorption bandwidth(EAB)of 5.52 GHz(1.90 mm).The MD_(3)/PVDF(10 wt%)possessed a minimum reflection loss(RL_(min))value of−67.4 at 12.56 GHz(2.13 mm).A symmetric gradient honeycomb structure(SGHS)was constructed utilizing the high-frequency structure simulator(HFSS)to further extend the EAB,achieving an EAB of 14.6 GHz and a RL_(min) of−59.0 dB.This research offers a viable inspiration to creating structures or materials with high-efficiency MA properties.展开更多
The mesostructure at the cross section of the Fe-based nanocrystalline (Fe73.5Cu1Nb3Si13.5B9) ribbon was observed with atomic force microscopy (AFM). An apparent mesostructural difference was found between the stickin...The mesostructure at the cross section of the Fe-based nanocrystalline (Fe73.5Cu1Nb3Si13.5B9) ribbon was observed with atomic force microscopy (AFM). An apparent mesostructural difference was found between the sticking roller face area (SRFA) and the free face area (FFA) of the ribbon crystallized after annealing. In SRFA there is a pre-ponderance of rough grain gathering in longitudinal ar-rangement, while in FFA a fine grain gathering arranged transversely dominates. This phenomenon could be due to the different residual stress remained in the different areas of the amorphous ribbon resulting from the single-roller quenching technique.展开更多
基金supported by the National Natural Science Foundation of China(No.51876046 and No.51711540032)。
文摘One simple and environmental friendly synthesis strategy for preparing low-cost magnetic Fe3C@C materials has been facilely developed using a modified sol-gel approach,wherein natural magnetite acted as the iron source.A chelating polycarboxylic acid such as citric acid(CA)was employed as the carbon source,and it dissolved Fe very effectively,Fe3O4 and natural magnetite to composite an iron-citrate complex with the assistance of ammonium hydroxide.The core-shell structure of the as-prepared nanocomposites was formed directly by high-temperature pyrolysis.The Fe3C@C materials exhibited superparamagnetic properties(38.09 emu/mg),suggesting potential applications in biomedicine,environment,absorption,catalysis,etc.
基金financially supported by the National Natural Science Foundation of China(51972049,52073010,and 52373259)the Projects of the Science and Technology Department of Jilin Province(20230201132GX)the Projects of the Education Department of Jilin Province(JJKH20220123KJ)。
文摘The impedance matching of absorbers is a vital factor affecting their microwave absorption(MA)properties.In this work,we controllably synthesized Material of Institute Lavoisier 88C(MIL-88C)with varying aspect ratios(AR)as a precursor by regulating oil bath conditions,followed by one-step thermal decomposition to obtain carbon-coated iron-based composites.Modifying the precursor MIL-88C(Fe)preparation conditions,such as the molar ratio between metal ions and organic ligands(M/O),oil bath temperature,and oil bath time,influenced the phases,graphitization degree,and AR of the derivatives,enabling low filler loading,achieving well-matched impedance,and ensuring outstanding MA properties.The MOF-derivatives 2(MD_(2))/polyvinylidene Difluoride(PVDF),MD_(3)/PVDF,and MD4/PVDF absorbers all exhibited excellent MA properties with optimal filler loadings below 20 wt%and as low as 5 wt%.The MD_(2)/PVDF(5 wt%)achieved a maximum effective absorption bandwidth(EAB)of 5.52 GHz(1.90 mm).The MD_(3)/PVDF(10 wt%)possessed a minimum reflection loss(RL_(min))value of−67.4 at 12.56 GHz(2.13 mm).A symmetric gradient honeycomb structure(SGHS)was constructed utilizing the high-frequency structure simulator(HFSS)to further extend the EAB,achieving an EAB of 14.6 GHz and a RL_(min) of−59.0 dB.This research offers a viable inspiration to creating structures or materials with high-efficiency MA properties.
文摘The mesostructure at the cross section of the Fe-based nanocrystalline (Fe73.5Cu1Nb3Si13.5B9) ribbon was observed with atomic force microscopy (AFM). An apparent mesostructural difference was found between the sticking roller face area (SRFA) and the free face area (FFA) of the ribbon crystallized after annealing. In SRFA there is a pre-ponderance of rough grain gathering in longitudinal ar-rangement, while in FFA a fine grain gathering arranged transversely dominates. This phenomenon could be due to the different residual stress remained in the different areas of the amorphous ribbon resulting from the single-roller quenching technique.
