Alkali and Co^(2+)co-modulation has seldom been investigated as a prospective strategy to achieve high-efficient microwave absorbing(MA)materials.In this work,a new alkali and Co ion exchange co-modulation strategy wa...Alkali and Co^(2+)co-modulation has seldom been investigated as a prospective strategy to achieve high-efficient microwave absorbing(MA)materials.In this work,a new alkali and Co ion exchange co-modulation strategy was first reported,leading to broadband MA capacity through simultaneous manipulating multiple factors,such as composition,micromorphology,and heterogeneous interface.And enhancements in impedance matching and magnetic-dielectric loss were synergistically realized.Consequently,the optimized FeCo alloy@porous carbon(FPC)nanocomposite with the alkali regulation delivered an effective absorption bandwidth(EAB)of 6.72 GHz,making it the merely single FeCo-based metal-organic framework derived FPC absorber with a low filler content of 15 wt.%.Interestingly,the nanocomposites by ion exchange strategy realized the switchable“on/off”states on electromagnetic response.Furthermore,the radar cross-section(RCS)reduction value of the products reached 25.6 dB·m^(2) under the incident angle of 0°.In brief,this work not only offers the special role of alkali and Co^(2+)co-modulation in composition regulation,structure design,and MA capacity,but also provides a reliable strategy to develop smart nano-absorbers to cope with electromagnetic pollution issues.展开更多
Since microwave irradiation could promote hydrolysis and olation of chromium tanning liquor,but the influence of microwave on chromium complex component in the liquor was still unknown.Chromium sulphate solution(0%bas...Since microwave irradiation could promote hydrolysis and olation of chromium tanning liquor,but the influence of microwave on chromium complex component in the liquor was still unknown.Chromium sulphate solution(0%basicity)and 33%basicity chromium tanning liquor were subjected microwave(MW)and water bath(WB)heating,and the samples without any warming were regarded as control.Ion exchange chromatography(IEC)and gel filtration chromatography(GFC)were used to measure the charge composition and molecular size of chromium complexes in each sample.FT-IR was used to characterize the structure of chromium complexes in each composition separated by IEC.Moreover,the chromium tanning liquor after warming was used in hide powder tanning trials to illustrate whether microwave would affect its tanning ability.The results show there are more high positive charge and large molecular size complexes in chromium tanning liquor after warming but the phenomena are more significant in MW samples compared with WB due to non-thermal effect of microwave.In addition,microwave has more powerful effect on 33%basicity chromium tanning liquor hydrolysis and olation to generate larger molecular size complexes.In FT-IR results,the combination pattern between chromium and ligands are changed after warming but there is no difference between WB and MW.The chromium exhaustion and thermal stability of hide powder tanned with chromium tanning liquor after microwave irradiation are both higher.It could conclude that both thermal and non-thermal effects of microwave promote the process together,and the nonthermal effect leads to more high positive charge and large molecular size complexes and has stronger influence on high polarity system.In short,this work would provide theoretical basis for applying microwave in tanning agent modification and chrome tanning process further.展开更多
基金We are thankful for financial support from the National Nature Science Foundation of China(Nos.51971111 and 52273247)the Fund of Prospective Layout of Scientific Research for NUAA(Nanjing University of Aeronautics and Astronautics)(No.ILA220461A22)the facilities in the Center for Microscopy and Analysis at Nanjing University of Aeronautics and Astronautics.
文摘Alkali and Co^(2+)co-modulation has seldom been investigated as a prospective strategy to achieve high-efficient microwave absorbing(MA)materials.In this work,a new alkali and Co ion exchange co-modulation strategy was first reported,leading to broadband MA capacity through simultaneous manipulating multiple factors,such as composition,micromorphology,and heterogeneous interface.And enhancements in impedance matching and magnetic-dielectric loss were synergistically realized.Consequently,the optimized FeCo alloy@porous carbon(FPC)nanocomposite with the alkali regulation delivered an effective absorption bandwidth(EAB)of 6.72 GHz,making it the merely single FeCo-based metal-organic framework derived FPC absorber with a low filler content of 15 wt.%.Interestingly,the nanocomposites by ion exchange strategy realized the switchable“on/off”states on electromagnetic response.Furthermore,the radar cross-section(RCS)reduction value of the products reached 25.6 dB·m^(2) under the incident angle of 0°.In brief,this work not only offers the special role of alkali and Co^(2+)co-modulation in composition regulation,structure design,and MA capacity,but also provides a reliable strategy to develop smart nano-absorbers to cope with electromagnetic pollution issues.
基金National Natural Science Foundation of China(No.21576171).
文摘Since microwave irradiation could promote hydrolysis and olation of chromium tanning liquor,but the influence of microwave on chromium complex component in the liquor was still unknown.Chromium sulphate solution(0%basicity)and 33%basicity chromium tanning liquor were subjected microwave(MW)and water bath(WB)heating,and the samples without any warming were regarded as control.Ion exchange chromatography(IEC)and gel filtration chromatography(GFC)were used to measure the charge composition and molecular size of chromium complexes in each sample.FT-IR was used to characterize the structure of chromium complexes in each composition separated by IEC.Moreover,the chromium tanning liquor after warming was used in hide powder tanning trials to illustrate whether microwave would affect its tanning ability.The results show there are more high positive charge and large molecular size complexes in chromium tanning liquor after warming but the phenomena are more significant in MW samples compared with WB due to non-thermal effect of microwave.In addition,microwave has more powerful effect on 33%basicity chromium tanning liquor hydrolysis and olation to generate larger molecular size complexes.In FT-IR results,the combination pattern between chromium and ligands are changed after warming but there is no difference between WB and MW.The chromium exhaustion and thermal stability of hide powder tanned with chromium tanning liquor after microwave irradiation are both higher.It could conclude that both thermal and non-thermal effects of microwave promote the process together,and the nonthermal effect leads to more high positive charge and large molecular size complexes and has stronger influence on high polarity system.In short,this work would provide theoretical basis for applying microwave in tanning agent modification and chrome tanning process further.
