One-dimensional(1D)metals are highly conductive and tend to form networks that facilitate electron hopping and migration.Hence,they have tremendous potential as microwave-absorbing(MA)materials.Traditionally,1D metals...One-dimensional(1D)metals are highly conductive and tend to form networks that facilitate electron hopping and migration.Hence,they have tremendous potential as microwave-absorbing(MA)materials.Traditionally,1D metals are mainly precious metals such as gold,silver,nickel,and their preparation methods often have low yield and are not environmentally friendly,which has limited the exploration in this area.Herein,the unique nanolaminate structure and chemical bond characteristics of Ti_(2)SnC MAX phase is successfully taken advantages for large-scale preparation of Sn whiskers,and then,core-sheath Sn/SnO_(x)heterojunctions are obtained by simply annealing at different temperatures.The heterojunction annealed at 500℃possesses favorable MA performance with an effective absorption bandwidth of 5.3 GHz(only 1.7 mm)and a minimum reflection loss value of51.97 dB;its maximum radar cross section(RCS)reduction value is 29.59 dB·m^(2),confirming its excellent electromagnetic wave attenuation ability.Off-axis electron holography is used to visually characterize the distribution of charge density at the cylindrical heterogenous interface,confirming the enhanced interfacial polarization effect.Given the diversity of MAX phases and the advantages of the fabrication method(e.g.,green,inexpensive,and easily scalable),this work provides significant guidance for the design of 1D metal-based absorbers.展开更多
In this work,SnO_(x)/activated carbon(AC)was synthesized by hydrothermal method,which was applied to acetylene hydrochlorination.Characterizations showed the SnO_(x)nanoparticles were uniformly dispersed on the carbon...In this work,SnO_(x)/activated carbon(AC)was synthesized by hydrothermal method,which was applied to acetylene hydrochlorination.Characterizations showed the SnO_(x)nanoparticles were uniformly dispersed on the carbon,with the coexistence of SnO and SnO_(2).The acetylene conversion of SnO_(x)/AC was 75%,much higher than that of SnCl_(4)/AC.It was shown that the adsorption of reactants on SnO_(x)was stronger than on SnCl_(4).Theoretical calculations showed the adsorption energies of reactants on SnO_(x)were thermodynamically favorable and suggested that Sn^(4+)and Sn^(2+)in SnO_(x)have different adsorption capacities for reactants.Through adjusting the valence ratio of SnO_(x),SnO_(x)/AC O 4 h(O for oxidation)exhibited the best catalytic performance and had the strongest adsorption capacity for the reactants.However,the SnO_(x)/AC catalyst was easily deactivated during acetylene hydrochlorination due to the loss of Sn.The doping of N effectively reduced the loss of Sn and improved the stability of the catalyst due to the anchoring effect of N on the SnO_(x)particles.展开更多
基金supported by the National Natural Science Foundation of China(52171033)the Natural Science Foundation of Jiangsu Province(BK20201283).
文摘One-dimensional(1D)metals are highly conductive and tend to form networks that facilitate electron hopping and migration.Hence,they have tremendous potential as microwave-absorbing(MA)materials.Traditionally,1D metals are mainly precious metals such as gold,silver,nickel,and their preparation methods often have low yield and are not environmentally friendly,which has limited the exploration in this area.Herein,the unique nanolaminate structure and chemical bond characteristics of Ti_(2)SnC MAX phase is successfully taken advantages for large-scale preparation of Sn whiskers,and then,core-sheath Sn/SnO_(x)heterojunctions are obtained by simply annealing at different temperatures.The heterojunction annealed at 500℃possesses favorable MA performance with an effective absorption bandwidth of 5.3 GHz(only 1.7 mm)and a minimum reflection loss value of51.97 dB;its maximum radar cross section(RCS)reduction value is 29.59 dB·m^(2),confirming its excellent electromagnetic wave attenuation ability.Off-axis electron holography is used to visually characterize the distribution of charge density at the cylindrical heterogenous interface,confirming the enhanced interfacial polarization effect.Given the diversity of MAX phases and the advantages of the fabrication method(e.g.,green,inexpensive,and easily scalable),this work provides significant guidance for the design of 1D metal-based absorbers.
基金the Taishan Scholars Program of Shandong Province(No.tsqn202103051)the Science and Technology Project of Xinjiang Bingtuan Supported by Central Government(No.2022BC001)the project of scientific research in Shihezi University(No.CXFZ202205).
文摘In this work,SnO_(x)/activated carbon(AC)was synthesized by hydrothermal method,which was applied to acetylene hydrochlorination.Characterizations showed the SnO_(x)nanoparticles were uniformly dispersed on the carbon,with the coexistence of SnO and SnO_(2).The acetylene conversion of SnO_(x)/AC was 75%,much higher than that of SnCl_(4)/AC.It was shown that the adsorption of reactants on SnO_(x)was stronger than on SnCl_(4).Theoretical calculations showed the adsorption energies of reactants on SnO_(x)were thermodynamically favorable and suggested that Sn^(4+)and Sn^(2+)in SnO_(x)have different adsorption capacities for reactants.Through adjusting the valence ratio of SnO_(x),SnO_(x)/AC O 4 h(O for oxidation)exhibited the best catalytic performance and had the strongest adsorption capacity for the reactants.However,the SnO_(x)/AC catalyst was easily deactivated during acetylene hydrochlorination due to the loss of Sn.The doping of N effectively reduced the loss of Sn and improved the stability of the catalyst due to the anchoring effect of N on the SnO_(x)particles.
