Electromagnetic interference,which necessitates the rapid advancement of substances with exceptional capabilities for bsorbing electromagnetic waves,is of urgent concern in contemporary society.In this work,CoFe_(2)O_...Electromagnetic interference,which necessitates the rapid advancement of substances with exceptional capabilities for bsorbing electromagnetic waves,is of urgent concern in contemporary society.In this work,CoFe_(2)O_(4)/residual carbon from coal gasification fine slag(CFO/RC)composites were created using a novel hydrothermal method.Various mechanisms for microwave absorption,including conductive loss,natural resonance,interfacial dipole polarization,and magnetic flux loss,are involved in these composites.Consequently,compared with pure residual carbon materials,this composite offers superior capabilities in microwave absorption.At 7.76GHz,the CFO/RC-2 composite achieves an impressive minimum reflection loss(RL_(min))of-43.99 dB with a thickness of 2.44 mm.Moreover,CFO/RC-3 demonstrates an effective absorption bandwidth(EAB)of up to 4.16 GHz,accompanied by a thickness of 1.18mm.This study revealed the remarkable capability of the composite to diminish electromagnetic waves,providing a new generation method for microwave absorbing materials of superior quality.展开更多
High piezoelectric composite films composed of poly(vinylidene fluoride-co-hexafluoropropylene)(PVDF-HFP)and ferromagnetic cobalt ferrite(CoFe_(2)O_(4))(0.00 wt%to 0.2 wt%)are prepared by a solution casting method acc...High piezoelectric composite films composed of poly(vinylidene fluoride-co-hexafluoropropylene)(PVDF-HFP)and ferromagnetic cobalt ferrite(CoFe_(2)O_(4))(0.00 wt%to 0.2 wt%)are prepared by a solution casting method accompanied by uniaxial stretching and high electric field poling.The decisive effect of the poling electric field on the power generating capability was confirmed by the experiments.For pure PVDF-HFP films,when the maximum electric field Emax is 120 MV/m,the calibrated open circuit voltage reaches 2.93 V,which is much higher than those poled at lower electric fields(70 MV/m:1.41 V;90 MV/m:2.11 V).Furthermore,the addition of CoFe_(2)O_(4)also influences the piezoelectricity dramatically.In the samples containing 0.15 wt%CoFe_(2)O_(4),the calibrated open circuit voltage increases to the maximum value of 3.57 V.Meanwhile,the relative fraction of theβ-phase and the crystallinity degree are 99%and 48%,respectively.The effects of CoFe_(2)O_(4)nanoparticles on initial crystallization,uniaxial stretching and high electric field poling are investigated by XRD,FTIR and DSC.展开更多
制备兼具稳定性和活性的电解水催化剂是大规模制氢的关键环节.通过快速燃烧法,在双金属泡沫镍铜(NCF)表面原位合成了Co Fe_(2)O_(4)纳米球.通过X射线衍射(XRD)和扫描电子显微镜(SEM)对材料的结构和组成进行了表征.采用线性扫描伏安法(L...制备兼具稳定性和活性的电解水催化剂是大规模制氢的关键环节.通过快速燃烧法,在双金属泡沫镍铜(NCF)表面原位合成了Co Fe_(2)O_(4)纳米球.通过X射线衍射(XRD)和扫描电子显微镜(SEM)对材料的结构和组成进行了表征.采用线性扫描伏安法(LSV)考察了该材料在碱性环境下对电解水析氢反应(HER)的催化性能.结果显示,析氢反应达到10 m A·cm^(-2)电流密度所需的过电位仅为148 m V,Tafel斜率为197 m V·dec^(-1),明显优于裸NCF和单金属对照材料.稳定性测试实验表明,经过2 000次循环伏安扫描后,析氢反应LSV曲线与与原始曲线基本一致;同时在100 m A·cm^(-2)的电流密度持续电解25 h,电位不发生明显变化,表明该催化剂具有良好的电催化稳定性.展开更多
基金financially supported by the Key Project of Natural Science Research in Colleges and Universities of Anhui Province,China(No.2022AH050816)the Open Research Grant of Joint National-Local Engineering Research Centre for Safe and Precise Coal Mining(Nos.EC2023013 and EC2022018)+1 种基金the National Natural Science Foundation of China(No.52200139)the Introduction of Talent in Anhui University of Science and Technology,China(Nos.2021yjrc18 and 2023yjrc79)。
文摘Electromagnetic interference,which necessitates the rapid advancement of substances with exceptional capabilities for bsorbing electromagnetic waves,is of urgent concern in contemporary society.In this work,CoFe_(2)O_(4)/residual carbon from coal gasification fine slag(CFO/RC)composites were created using a novel hydrothermal method.Various mechanisms for microwave absorption,including conductive loss,natural resonance,interfacial dipole polarization,and magnetic flux loss,are involved in these composites.Consequently,compared with pure residual carbon materials,this composite offers superior capabilities in microwave absorption.At 7.76GHz,the CFO/RC-2 composite achieves an impressive minimum reflection loss(RL_(min))of-43.99 dB with a thickness of 2.44 mm.Moreover,CFO/RC-3 demonstrates an effective absorption bandwidth(EAB)of up to 4.16 GHz,accompanied by a thickness of 1.18mm.This study revealed the remarkable capability of the composite to diminish electromagnetic waves,providing a new generation method for microwave absorbing materials of superior quality.
基金supported by National Natural Science Foundation of China(No.51703015)Fundamental Research Funds for the Central Universities(No.2020CDJQY-A008).
文摘High piezoelectric composite films composed of poly(vinylidene fluoride-co-hexafluoropropylene)(PVDF-HFP)and ferromagnetic cobalt ferrite(CoFe_(2)O_(4))(0.00 wt%to 0.2 wt%)are prepared by a solution casting method accompanied by uniaxial stretching and high electric field poling.The decisive effect of the poling electric field on the power generating capability was confirmed by the experiments.For pure PVDF-HFP films,when the maximum electric field Emax is 120 MV/m,the calibrated open circuit voltage reaches 2.93 V,which is much higher than those poled at lower electric fields(70 MV/m:1.41 V;90 MV/m:2.11 V).Furthermore,the addition of CoFe_(2)O_(4)also influences the piezoelectricity dramatically.In the samples containing 0.15 wt%CoFe_(2)O_(4),the calibrated open circuit voltage increases to the maximum value of 3.57 V.Meanwhile,the relative fraction of theβ-phase and the crystallinity degree are 99%and 48%,respectively.The effects of CoFe_(2)O_(4)nanoparticles on initial crystallization,uniaxial stretching and high electric field poling are investigated by XRD,FTIR and DSC.
文摘制备兼具稳定性和活性的电解水催化剂是大规模制氢的关键环节.通过快速燃烧法,在双金属泡沫镍铜(NCF)表面原位合成了Co Fe_(2)O_(4)纳米球.通过X射线衍射(XRD)和扫描电子显微镜(SEM)对材料的结构和组成进行了表征.采用线性扫描伏安法(LSV)考察了该材料在碱性环境下对电解水析氢反应(HER)的催化性能.结果显示,析氢反应达到10 m A·cm^(-2)电流密度所需的过电位仅为148 m V,Tafel斜率为197 m V·dec^(-1),明显优于裸NCF和单金属对照材料.稳定性测试实验表明,经过2 000次循环伏安扫描后,析氢反应LSV曲线与与原始曲线基本一致;同时在100 m A·cm^(-2)的电流密度持续电解25 h,电位不发生明显变化,表明该催化剂具有良好的电催化稳定性.
文摘为降低电解水阳极的析氧反应过电位,采用一步水热法制备了泡沫镍基钴铁混合氧化物(CoFe2O4@NF)复合材料。采用XRD、SEM、TEM和XPS等方法对复合材料进行表征,并利用三电极体系对其电解水析氧催化性能进行了测试。结果显示:Co Fe_(2)O_(4)以颗粒的形式聚集成空心球结构生长于泡沫镍基底上,其中空心球的直径大约4μm,而CoFe2O4的粒径约为40 nm左右。在1 mol·L^(-1)KOH溶液中,CoFe_(2)O_(4)@NF复合材料仅需293 mV的过电位即可达到20 m A·cm^(-2)的电流密度,Tafel斜率为51 m V·dec^(-1)。经过1000次循环伏安扫描和10 h电流时间曲线测试后,其析氧性能依旧保持高稳定性,在析氧催化材料领域有着广阔的研究前景。
