Monotetic alloy have been researched for hundred years.Recent years,researchers have prepared homogeneous monotectic alloy by electro-magnetic body force(EMBF).But the mechanism of separation and refinement of the sec...Monotetic alloy have been researched for hundred years.Recent years,researchers have prepared homogeneous monotectic alloy by electro-magnetic body force(EMBF).But the mechanism of separation and refinement of the second phase in liquid matrix by EMBF is not very clear.This paper investigated the effect of different AC EMBF on the microstructure and solidification process of Zn-10%Bi hyper-monotectic alloy by quenching the samples in water under high static magnetic field.It is shown that,the superimposing of AC EMBF can influence the moving speed of the second phase droplet and damp the gravity segregation in solidifying Zn-10%Bi alloy.When the AC EMBF reaches 5×10~5N/m^3 in different magnetic flux densities from 2 to 10 Tesla,the homogenuous distribution of bismuth particles could be achieved,A physical model is established to illustrate the mechanism of separation and refinement of the second Bi droplets at the stage of liquid-liquid separation by AC EMBF.The results show that the second droplets can be divided into two or three smaller droplets by Lorenz force caused by induced current at the former and later location of bismuth droplet.When the bismuth droplet moves at a proper speed which is adjusted by EMBF,it will be broken down by Lorenz forces.展开更多
The first part deals with the behavior of particles theoretically, and the critical electromagnetic force needed to alter the behavior of particles was deduced under different conditions. It was proposed that applying...The first part deals with the behavior of particles theoretically, and the critical electromagnetic force needed to alter the behavior of particles was deduced under different conditions. It was proposed that applying electromagnetic force would change the distribution coefficient of the particles. By using the data from literatures, the migrating rate of SiC particle by electromagnetic force was calculated, which is far more than the critical rate of solidifying interface which will result in the engulfment of the SiC particle in the Al SiC matrix metal. Therefore the possibility of controlling the behavior of the particles in front of the solidifying interface by electromagnetic field was confirmed. In the second part, by using simulative experiments, the man made alternation of the behavior of the particles in front of the solidifying interface under electromagnetic field was observed, and the idea of changing the distribution of the particles in solidified metal by electromagnetic force was verified experimentally. It is shown that, the particle, which would be engulfed by the solidifying interface, would escape from the interface under electromagnetic buoyant force (EMBF), and the particles adherent to the interface would migrate toward it and be engulfed finally under EMBF. Further more, the particles being pushed by the interface would stay at the interface, the repulsive force exerted on the particles would be counteracted by EMBF, and then the particle would turn to be engulfed. Adjusting the direction and magnitude of EMBF could alter the distribution of the particles in the solidifying metal.展开更多
Endohedral metalloazafullerenes(EMAFs)/metalloborafullerenes(EMBFs)are formed by encapsulating various metallic species inside the fullerene cages,of which some carbon atoms are replaced by nitrogen and boron,respecti...Endohedral metalloazafullerenes(EMAFs)/metalloborafullerenes(EMBFs)are formed by encapsulating various metallic species inside the fullerene cages,of which some carbon atoms are replaced by nitrogen and boron,respectively.Currently,the characterization of their exact heteroatom positions on the cage mainly depends on the calculated relative energies at T=0 K for isomers with varied heteroatom locations.In this work,density functional theory calculations were carried out to systematically investigate the structural characteristics,electronic properties,aromaticity and chemical reactivities of the recently synthesized U@C_(27)B borafullerene.Interestingly,besides the reported major U@Td-C_(27)B-[5,5,6]isomer,calculations considering the entropy effect at cage formation temperatures suggest that it may have another major U@Td-C_(27)B-[5,5,6]isomer and a minor U@Td-C_(27)B-[5,5,5]isomer with changed boron positions.The reported U@Td-C_(27)B-[5,5,6]and new U@Td-C_(27)B-[5,5,5]isomers could interconvert via a single bond rotation at elevated temperatures with energy barriers comparable to that of the classical Stone-Wales rearrangement in fullerene transformation.The internal U atom formally assumes the highest VI oxidation state regardless of the cage topology or B location.Unprecedentedly,metal-cage bonding also shows strong covalency with the U atom and the C_(27)B cage of U@Td-C_(27)B sharing the same 32 valence electrons to obey the 32-electron principle and Hirsch’s 2(N+1)^(2) rule(N=3 with a 1S^(2)1P^(6)1D^(10)1F^(14) electronic configuration)for spherical aromaticity,respectively.Such a novel mutual stabilization mechanism is similar to that of the classical organometallic compound,ferrocene.The neutral U@Td-C_(27)B isomers are radicals with one unpaired electron on the cage and thus may spontaneously form dimers with closed-shell structures.We propose that one could obtain the U@Td-C_(27)B monomer via radical addition reactions such as trifluoromethylation.Our work demonstrates the intriguing structures and properties as well as their correlations of the emerging EMBFs.The possible coexistence of multiple isomers and their interconversion are unprecedented and could also guide more in-depth studies on EMAFs as well as other types of heterofullerenes.展开更多
基金Item Sponsored by National Science Foundation of China (No.50974085No.51034010) +4 种基金Development Foundation for Talents in Shanghai (No.2009046) National High-tech R&D Program of China (No.2009AA03Z109) Key Research and Innovation Program from Shanghai Municipal Education Commission (No.09zz98) Key Project from Science and Technology Commission of Shanghai Municipality (No:09dz120640109dz1206402)
文摘Monotetic alloy have been researched for hundred years.Recent years,researchers have prepared homogeneous monotectic alloy by electro-magnetic body force(EMBF).But the mechanism of separation and refinement of the second phase in liquid matrix by EMBF is not very clear.This paper investigated the effect of different AC EMBF on the microstructure and solidification process of Zn-10%Bi hyper-monotectic alloy by quenching the samples in water under high static magnetic field.It is shown that,the superimposing of AC EMBF can influence the moving speed of the second phase droplet and damp the gravity segregation in solidifying Zn-10%Bi alloy.When the AC EMBF reaches 5×10~5N/m^3 in different magnetic flux densities from 2 to 10 Tesla,the homogenuous distribution of bismuth particles could be achieved,A physical model is established to illustrate the mechanism of separation and refinement of the second Bi droplets at the stage of liquid-liquid separation by AC EMBF.The results show that the second droplets can be divided into two or three smaller droplets by Lorenz force caused by induced current at the former and later location of bismuth droplet.When the bismuth droplet moves at a proper speed which is adjusted by EMBF,it will be broken down by Lorenz forces.
文摘The first part deals with the behavior of particles theoretically, and the critical electromagnetic force needed to alter the behavior of particles was deduced under different conditions. It was proposed that applying electromagnetic force would change the distribution coefficient of the particles. By using the data from literatures, the migrating rate of SiC particle by electromagnetic force was calculated, which is far more than the critical rate of solidifying interface which will result in the engulfment of the SiC particle in the Al SiC matrix metal. Therefore the possibility of controlling the behavior of the particles in front of the solidifying interface by electromagnetic field was confirmed. In the second part, by using simulative experiments, the man made alternation of the behavior of the particles in front of the solidifying interface under electromagnetic field was observed, and the idea of changing the distribution of the particles in solidified metal by electromagnetic force was verified experimentally. It is shown that, the particle, which would be engulfed by the solidifying interface, would escape from the interface under electromagnetic buoyant force (EMBF), and the particles adherent to the interface would migrate toward it and be engulfed finally under EMBF. Further more, the particles being pushed by the interface would stay at the interface, the repulsive force exerted on the particles would be counteracted by EMBF, and then the particle would turn to be engulfed. Adjusting the direction and magnitude of EMBF could alter the distribution of the particles in the solidifying metal.
基金financial support from the National Natural Science Foundation of China(No.22171068)the Natural Science Foundation of Hebei Province(B2022202036).
文摘Endohedral metalloazafullerenes(EMAFs)/metalloborafullerenes(EMBFs)are formed by encapsulating various metallic species inside the fullerene cages,of which some carbon atoms are replaced by nitrogen and boron,respectively.Currently,the characterization of their exact heteroatom positions on the cage mainly depends on the calculated relative energies at T=0 K for isomers with varied heteroatom locations.In this work,density functional theory calculations were carried out to systematically investigate the structural characteristics,electronic properties,aromaticity and chemical reactivities of the recently synthesized U@C_(27)B borafullerene.Interestingly,besides the reported major U@Td-C_(27)B-[5,5,6]isomer,calculations considering the entropy effect at cage formation temperatures suggest that it may have another major U@Td-C_(27)B-[5,5,6]isomer and a minor U@Td-C_(27)B-[5,5,5]isomer with changed boron positions.The reported U@Td-C_(27)B-[5,5,6]and new U@Td-C_(27)B-[5,5,5]isomers could interconvert via a single bond rotation at elevated temperatures with energy barriers comparable to that of the classical Stone-Wales rearrangement in fullerene transformation.The internal U atom formally assumes the highest VI oxidation state regardless of the cage topology or B location.Unprecedentedly,metal-cage bonding also shows strong covalency with the U atom and the C_(27)B cage of U@Td-C_(27)B sharing the same 32 valence electrons to obey the 32-electron principle and Hirsch’s 2(N+1)^(2) rule(N=3 with a 1S^(2)1P^(6)1D^(10)1F^(14) electronic configuration)for spherical aromaticity,respectively.Such a novel mutual stabilization mechanism is similar to that of the classical organometallic compound,ferrocene.The neutral U@Td-C_(27)B isomers are radicals with one unpaired electron on the cage and thus may spontaneously form dimers with closed-shell structures.We propose that one could obtain the U@Td-C_(27)B monomer via radical addition reactions such as trifluoromethylation.Our work demonstrates the intriguing structures and properties as well as their correlations of the emerging EMBFs.The possible coexistence of multiple isomers and their interconversion are unprecedented and could also guide more in-depth studies on EMAFs as well as other types of heterofullerenes.
