Electromagnetic-wave absorbing(EMA)materials that have efficient absorption performances,great me-chanical properties and chemical stability are rare and yet essential for communication security and pro-tection.Herein...Electromagnetic-wave absorbing(EMA)materials that have efficient absorption performances,great me-chanical properties and chemical stability are rare and yet essential for communication security and pro-tection.Herein,flaky interstitial-carbon-doped FeCoNiCu high entropy alloys(HEAs)as novel EMA ma-terials were successfully prepared by high-energy ball-milling method.Interstitial-carbon doping as a modulating approach impacted the phase forming,morphology and electromagnetic properties of Fe-CoNiCu HEAs.Impedance matching was significantly optimized via tuning interstitial carbon contents.The carbon-doped FeCoNiCu HEAs with appropriate carbon contents delivered superior EMA performance compared with other HEAs EMA materials.Strong reflection loss as low as-61.1 dB in the Ku band,broad effective absorption bandwidth of 5.1 GHz was achieved for FeCoNiCuC_(0.04).Moreover,the carbon-doped FeCoNiCu HEAs exhibited excellent mechanical hardness and chemical stability.This work not only suggests that interstitial-carbon doping is an available approach to tuning electromagnetic properties of HEAs,but also presents carbon-doped FeCoNiCu HEAs as promising EMA materials for civilian and mili-tary due to the efficient absorption,broad bandwidth,great durability and stability.展开更多
Five sets of high entropy alloys(HEAs)FeCoNiCu_(x)(x=0.5,1.0,1.5,2.0,2.5)were produced by vacuum induction smelting.The effects of Cu content on the microstructure and mechanical properties of the alloys were interrog...Five sets of high entropy alloys(HEAs)FeCoNiCu_(x)(x=0.5,1.0,1.5,2.0,2.5)were produced by vacuum induction smelting.The effects of Cu content on the microstructure and mechanical properties of the alloys were interrogated by X-ray diffractometer(XRD),field scanning electron microscope(FESEM)and tensile mechanical test.The result shows that the HEAs form single FCC solid solution phase.With the increase of Cu content,the diffraction peak first deviated to the right and then shifted to the left.The alloys changed from equiaxed crystal structure to refined dendritic crystal structure,as Cu content increased.A large number of Cu atoms are isolated in the inter-crystalline region.The tensile mechanical tests show that with the increase of Cu content,the ultimate tensile strength first increased and then decreased.When x is 2.0,the ultimate tensile strength reaches a maximum of 473 MPa,the percent elongation is 43.0%,and the fracture presents ductile behaviour.展开更多
In order to improve the photocatalytic response of TiO_(2)to UV and visible light for hydrogen photoproduction,low cost M/TiO_(2)semiconductor catalysts were prepared by the impregnation method of five different first...In order to improve the photocatalytic response of TiO_(2)to UV and visible light for hydrogen photoproduction,low cost M/TiO_(2)semiconductor catalysts were prepared by the impregnation method of five different first row transition metals(M=Fe,Co,Ni,Cu or Zn)on a commercial titania support.The maximum hydrogen production efficiency was achieved for the Cu/TiO_(2)photocatalyst,with∼5000 and∼220µmol h^(−1)g^(−1)H_(2)production rates for UV and visible irradiation,respectively.Ni/TiO_(2)and Co/TiO_(2)also showed a significant photocatalytic activity when UV light was used.The best performing catalyst,Cu/TiO_(2),was characterized by TEM and XPS measurements.The data showed that Cu was highly dispersed over the TiO_(2)support and the copper species existed as both reduced Cu^(0)/Cu^(+)and oxidized Cu2+on TiO_(2).Besides,during the hydrogen production reaction,the reduced Cu was partially oxidized to Cu^(2+)by the transfer of photogenerated holes under UV or visible light irradiation.With UV and visible lamps,the H_(2)production rates were higher than those obtained with non-impregnated TiO_(2)by factors of 16 and 3,respectively.These results demonstrated that a Cu/TiO_(2)photocatalyst could be considered a promising low-cost alternative to the well-known Pt/TiO_(2)system for hydrogen production,making the Cu-based catalyst an ideal cost-effective candidate for this reaction.展开更多
基金financially supported by the Natural Science Foundation of China (No. 51701098)the Natural Science Foundation of Ningbo Municipality (No. 2019A610064)sponsored by K. C. Wong Magna Foundation in Ningbo University
文摘Electromagnetic-wave absorbing(EMA)materials that have efficient absorption performances,great me-chanical properties and chemical stability are rare and yet essential for communication security and pro-tection.Herein,flaky interstitial-carbon-doped FeCoNiCu high entropy alloys(HEAs)as novel EMA ma-terials were successfully prepared by high-energy ball-milling method.Interstitial-carbon doping as a modulating approach impacted the phase forming,morphology and electromagnetic properties of Fe-CoNiCu HEAs.Impedance matching was significantly optimized via tuning interstitial carbon contents.The carbon-doped FeCoNiCu HEAs with appropriate carbon contents delivered superior EMA performance compared with other HEAs EMA materials.Strong reflection loss as low as-61.1 dB in the Ku band,broad effective absorption bandwidth of 5.1 GHz was achieved for FeCoNiCuC_(0.04).Moreover,the carbon-doped FeCoNiCu HEAs exhibited excellent mechanical hardness and chemical stability.This work not only suggests that interstitial-carbon doping is an available approach to tuning electromagnetic properties of HEAs,but also presents carbon-doped FeCoNiCu HEAs as promising EMA materials for civilian and mili-tary due to the efficient absorption,broad bandwidth,great durability and stability.
基金Funded by the National Natural Science Foundation of China(Nos.51371098,51571118)National Undergraduate Training Program for Innovation and Entrepreneurship(No.201910288094Z)。
文摘Five sets of high entropy alloys(HEAs)FeCoNiCu_(x)(x=0.5,1.0,1.5,2.0,2.5)were produced by vacuum induction smelting.The effects of Cu content on the microstructure and mechanical properties of the alloys were interrogated by X-ray diffractometer(XRD),field scanning electron microscope(FESEM)and tensile mechanical test.The result shows that the HEAs form single FCC solid solution phase.With the increase of Cu content,the diffraction peak first deviated to the right and then shifted to the left.The alloys changed from equiaxed crystal structure to refined dendritic crystal structure,as Cu content increased.A large number of Cu atoms are isolated in the inter-crystalline region.The tensile mechanical tests show that with the increase of Cu content,the ultimate tensile strength first increased and then decreased.When x is 2.0,the ultimate tensile strength reaches a maximum of 473 MPa,the percent elongation is 43.0%,and the fracture presents ductile behaviour.
基金Ministerio de Economía y Competitividad of Spain(CTQ2015-68951-C3-3-R and MAT2016-80933-R)Ministerio de Ciencia,Innovación y Universidades of Spain(Project RTI2018-099668-B-C22)and FEDER funds.
文摘In order to improve the photocatalytic response of TiO_(2)to UV and visible light for hydrogen photoproduction,low cost M/TiO_(2)semiconductor catalysts were prepared by the impregnation method of five different first row transition metals(M=Fe,Co,Ni,Cu or Zn)on a commercial titania support.The maximum hydrogen production efficiency was achieved for the Cu/TiO_(2)photocatalyst,with∼5000 and∼220µmol h^(−1)g^(−1)H_(2)production rates for UV and visible irradiation,respectively.Ni/TiO_(2)and Co/TiO_(2)also showed a significant photocatalytic activity when UV light was used.The best performing catalyst,Cu/TiO_(2),was characterized by TEM and XPS measurements.The data showed that Cu was highly dispersed over the TiO_(2)support and the copper species existed as both reduced Cu^(0)/Cu^(+)and oxidized Cu2+on TiO_(2).Besides,during the hydrogen production reaction,the reduced Cu was partially oxidized to Cu^(2+)by the transfer of photogenerated holes under UV or visible light irradiation.With UV and visible lamps,the H_(2)production rates were higher than those obtained with non-impregnated TiO_(2)by factors of 16 and 3,respectively.These results demonstrated that a Cu/TiO_(2)photocatalyst could be considered a promising low-cost alternative to the well-known Pt/TiO_(2)system for hydrogen production,making the Cu-based catalyst an ideal cost-effective candidate for this reaction.
