The development of 3D structural composites with electromagnetic(EM)wave absorption could attenuate EM waves.Herein,magnetized flower-like Cu_(9)S_(5)/ZnFe_(2)O_(4)composites were fabricated through a multistep hydrot...The development of 3D structural composites with electromagnetic(EM)wave absorption could attenuate EM waves.Herein,magnetized flower-like Cu_(9)S_(5)/ZnFe_(2)O_(4)composites were fabricated through a multistep hydrothermal method.The crystallographic and surface phase chemical information,morphological structure,and magnetic and EM parameters of the composites were analyzed.The prepared Cu_(9)S_(5)/ZnFe_(2)O_(4)composites have multiple loss paths for EM waves and present an overall 3D flower-like structure.The Cu_(9)S_(5)/ZnFe_(2)O_(4)composites exhibit a minimum reflection loss of-54.38 dB and a broad effective absorption bandwidth of 5.92 GHz.Through magnetization,ZnFe_(2)O_(4)particles are self-assembled and grown on the surfaces of Cu_(9)S_(5).Such a modification is conducive to the generation of additional cross-linking contact sites and the effective introduction of a large number of phase interfaces,crystalline defects,special three-dimensional flower-like structures,and magneto-electrical coupling loss effects.Moreover,the synergistic effect of multiple loss strategies effectively improves EM wave absorption by the material.This work can provide a strategy for the use of magnetizationmodified sulfide composite functional materials in EM wave absorption.展开更多
Defect and charge transfer efficiency of nano-photocatalysts are important factors which influence their photocatalytic performance.In this work,oxygen vacancies are successfully introduced in the synthesis process of...Defect and charge transfer efficiency of nano-photocatalysts are important factors which influence their photocatalytic performance.In this work,oxygen vacancies are successfully introduced in the synthesis process of Bi_(2)Al_(4)O_(9)/β-Bi_(2)O_(3)heterojunctions through one-step in situ selfcombustion method.High-resolution transmission electron microscopy (HRTEM),UV-Vis diffuse reflectance spectra (UV-Vis DRS),and electron spin resonance (ESR) measurements confirm the existence of oxygen vacancies.In addition,by controlling the ratio of reactants of Bi(NO_(3))_(3)to Al(NO_(3))_(3),the ratio of Bi_(2)Al_(4)O_(9)and β-Bi_(2)O_(3)in the heterojunction can be easily adjusted.Photocurrent responses and surface photovoltage spectroscopy (SPV) indicate that the construction of the Bi_(2)Al_(4)O_(9)/β-Bi_(2)O_(3)heterostructure improves the separation efficiency of the photo-generated electrons and holes.CO_(2)-TPD results imply that the amounts and stability of heterojunctions are enhanced compared with their counterparts.The Bi_(2)Al_(4)O_(9)/β-Bi_(2)O_(3)heterojunction with 14 mol%Bi_(2)Al_(4)O_(9)shows the highest photocatalytic ability for reduction of CO_(2)into CO.The enhanced photoreduction of CO_(2)performance can be ascribed to the synergistic effects of the heterojunction for electron separation and oxygen vacancies for CO_(2)activation.展开更多
The hysteresis loop changes of ferroelecric SrBi_2 Ta_2 O_9 (SBT) thin films(330nm) us the temperature of forming gas (5 percent hydrogen+95 percent nitrogen) annealing weremeasured when the annealing time was 1min an...The hysteresis loop changes of ferroelecric SrBi_2 Ta_2 O_9 (SBT) thin films(330nm) us the temperature of forming gas (5 percent hydrogen+95 percent nitrogen) annealing weremeasured when the annealing time was 1min and 10min. The selected annealing temperature was at 100deg C,200 deg C 250 deg C, 300 deg C, 350 deg C,400 deg C and 450 deg C, respectively. Our resultsshowed that the ferroelectric properties were easily destroyed and the leakage current changedabruptly when the SBT thin films were in their ferroelectric phase (<270 deg C). The space chargesat the grain boundary may take an important role' in absorption polarity molecular hydrogen when theSBT thin films were in the ferroelectric phase. The oxygen recovery experiments were also performedand investigated in this work.展开更多
基金This work was supported by the National Natural Science Foundation of China(No.51477002)the University Synergy Innovation Program of Anhui Province,China(No.GXXT-2019-028).
文摘The development of 3D structural composites with electromagnetic(EM)wave absorption could attenuate EM waves.Herein,magnetized flower-like Cu_(9)S_(5)/ZnFe_(2)O_(4)composites were fabricated through a multistep hydrothermal method.The crystallographic and surface phase chemical information,morphological structure,and magnetic and EM parameters of the composites were analyzed.The prepared Cu_(9)S_(5)/ZnFe_(2)O_(4)composites have multiple loss paths for EM waves and present an overall 3D flower-like structure.The Cu_(9)S_(5)/ZnFe_(2)O_(4)composites exhibit a minimum reflection loss of-54.38 dB and a broad effective absorption bandwidth of 5.92 GHz.Through magnetization,ZnFe_(2)O_(4)particles are self-assembled and grown on the surfaces of Cu_(9)S_(5).Such a modification is conducive to the generation of additional cross-linking contact sites and the effective introduction of a large number of phase interfaces,crystalline defects,special three-dimensional flower-like structures,and magneto-electrical coupling loss effects.Moreover,the synergistic effect of multiple loss strategies effectively improves EM wave absorption by the material.This work can provide a strategy for the use of magnetizationmodified sulfide composite functional materials in EM wave absorption.
基金financial support from the National Natural Science Foundation of China(21776059,21376061)the Natural Science Foundation for Distinguished Young Scholars of Hebei Province(B2015208010)the Research Foundation of Hebei Province Education Department(No.ZC2016007)。
文摘Defect and charge transfer efficiency of nano-photocatalysts are important factors which influence their photocatalytic performance.In this work,oxygen vacancies are successfully introduced in the synthesis process of Bi_(2)Al_(4)O_(9)/β-Bi_(2)O_(3)heterojunctions through one-step in situ selfcombustion method.High-resolution transmission electron microscopy (HRTEM),UV-Vis diffuse reflectance spectra (UV-Vis DRS),and electron spin resonance (ESR) measurements confirm the existence of oxygen vacancies.In addition,by controlling the ratio of reactants of Bi(NO_(3))_(3)to Al(NO_(3))_(3),the ratio of Bi_(2)Al_(4)O_(9)and β-Bi_(2)O_(3)in the heterojunction can be easily adjusted.Photocurrent responses and surface photovoltage spectroscopy (SPV) indicate that the construction of the Bi_(2)Al_(4)O_(9)/β-Bi_(2)O_(3)heterostructure improves the separation efficiency of the photo-generated electrons and holes.CO_(2)-TPD results imply that the amounts and stability of heterojunctions are enhanced compared with their counterparts.The Bi_(2)Al_(4)O_(9)/β-Bi_(2)O_(3)heterojunction with 14 mol%Bi_(2)Al_(4)O_(9)shows the highest photocatalytic ability for reduction of CO_(2)into CO.The enhanced photoreduction of CO_(2)performance can be ascribed to the synergistic effects of the heterojunction for electron separation and oxygen vacancies for CO_(2)activation.
基金This work sponsored by Motorola SPS Digital DNA Laboratories. It is also supported by a grant for State Key Program for Basic Research of China. We would like to thank Dr. Peir Y. Chu of Motorola SPS for his great help, useful advice and discussion.
文摘The hysteresis loop changes of ferroelecric SrBi_2 Ta_2 O_9 (SBT) thin films(330nm) us the temperature of forming gas (5 percent hydrogen+95 percent nitrogen) annealing weremeasured when the annealing time was 1min and 10min. The selected annealing temperature was at 100deg C,200 deg C 250 deg C, 300 deg C, 350 deg C,400 deg C and 450 deg C, respectively. Our resultsshowed that the ferroelectric properties were easily destroyed and the leakage current changedabruptly when the SBT thin films were in their ferroelectric phase (<270 deg C). The space chargesat the grain boundary may take an important role' in absorption polarity molecular hydrogen when theSBT thin films were in the ferroelectric phase. The oxygen recovery experiments were also performedand investigated in this work.
