Magnetic levitation of the fusion target by coating a thin MgB_(2)superconducting shell on its outer surface has recently been proposed in inertial confinement fusion(ICF)to realize a noncontact support of the target ...Magnetic levitation of the fusion target by coating a thin MgB_(2)superconducting shell on its outer surface has recently been proposed in inertial confinement fusion(ICF)to realize a noncontact support of the target at~20 K to boost the implosion performance and fusion yield.To avoid possible effects on target ablation,the coated MgB_(2)shell is anticipated to be as thin as possible while fulfilling the target levitation requirements.Under this circumstance,the fabrication of an MgB_(2)shell with reduced thickness has been explored using a hybrid physical-chemical vapour deposition method.By gradually decreasing the deposition time,a set of MgB_(2)shells were grown on 1 mm diameter Si_(3)N_(4)spheres with the thickness reducing from 720 nm to 200 nm.The spherical shells all have a polycrystalline structure characterized by closely packed hexagonal grains,with both the grain size and thickness diminishing as the shell thickness decreases.The superconducting transition temperature Tcof the shells,as determined by both resistance and magnetization measurements,is in the range of 38-40 K and all shells exhibit ideal diamagnetism at low temperatures.For the thinnest shell of 200 nm,the superconducting critical current density Jcat 20 K reaches 8.0×10^(6)A/cm^(2)and 2.1×10^(5)A/cm^(2)under zero and 2 T applied field,respectively.The results indicate that it is experimentally feasible to fabricate MgB_(2)spherical shells with a thickness as low as 200 nm while maintaining the high Tcand Jc,thereby taking a further step towards the application of the shell in superconducting magnetic levitation for ICF.展开更多
As a typical reactive composite hydrogen storage system,2LiBH_(4)-MgH_(2)holds an ultrahigh hydrogen storage capacity of 11.5 wt%.However,it suffers from sluggish hydrogen storage kinetics due to the difficult nucleat...As a typical reactive composite hydrogen storage system,2LiBH_(4)-MgH_(2)holds an ultrahigh hydrogen storage capacity of 11.5 wt%.However,it suffers from sluggish hydrogen storage kinetics due to the difficult nucleation of MgB_(2).Herein,amorphous VB_(2)nanoparticles with an average size of approximately 32 nm are synthesized to enhance the hydrogen storage performance of 2LiBH_(4)-MgH_(2)composite.VB_(2),sharing the same hexagonal structure with MgB_(2)with a d-value mismatch ratio of only 2.28%,could serve as effective nucleation sites for promoting the formation of MgB_(2).Theoretical calculations reveal that the introduction of VB_(2)significantly reduces the binding energies of B and Mg,facilitating in situ nucleation of MgB_(2).As a result,after the introduction of VB_(2)nanoparticles,complete hydrogen desorption of 9.23 wt%is achieved for 2LiBH_(4)-MgH_(2)within 2 h at 400℃,which is 4 times shorter than the time required for pure 2LiBH_(4)-MgH_(2),and no nucleation incubation period for hydrogen desorption is observed even at a low temperature of380℃.More importantly,a reversible capacity of9.3 wt%,corresponding to a capacity retention of 100%,could be preserved after 10 cycles of hydrogen storage,demonstrating stable reversible hydrogen storage performance.This study provides a novel technological pathway for improving the reversible hydrogen storage performance of composite metal hydrides and offers significant insights into the development of high-performance hydrogen storage materials.展开更多
文摘Magnetic levitation of the fusion target by coating a thin MgB_(2)superconducting shell on its outer surface has recently been proposed in inertial confinement fusion(ICF)to realize a noncontact support of the target at~20 K to boost the implosion performance and fusion yield.To avoid possible effects on target ablation,the coated MgB_(2)shell is anticipated to be as thin as possible while fulfilling the target levitation requirements.Under this circumstance,the fabrication of an MgB_(2)shell with reduced thickness has been explored using a hybrid physical-chemical vapour deposition method.By gradually decreasing the deposition time,a set of MgB_(2)shells were grown on 1 mm diameter Si_(3)N_(4)spheres with the thickness reducing from 720 nm to 200 nm.The spherical shells all have a polycrystalline structure characterized by closely packed hexagonal grains,with both the grain size and thickness diminishing as the shell thickness decreases.The superconducting transition temperature Tcof the shells,as determined by both resistance and magnetization measurements,is in the range of 38-40 K and all shells exhibit ideal diamagnetism at low temperatures.For the thinnest shell of 200 nm,the superconducting critical current density Jcat 20 K reaches 8.0×10^(6)A/cm^(2)and 2.1×10^(5)A/cm^(2)under zero and 2 T applied field,respectively.The results indicate that it is experimentally feasible to fabricate MgB_(2)spherical shells with a thickness as low as 200 nm while maintaining the high Tcand Jc,thereby taking a further step towards the application of the shell in superconducting magnetic levitation for ICF.
基金financially supported by the National Key R&D Program of China(No.2021YFB 3802400)the National Natural Science Foundation of China(Nos.U2130208,22279020 and 52301264)the Science and Technology Commission of Shanghai Municipality(Nos.23ZR1406500 and 22ZR1406500)
文摘As a typical reactive composite hydrogen storage system,2LiBH_(4)-MgH_(2)holds an ultrahigh hydrogen storage capacity of 11.5 wt%.However,it suffers from sluggish hydrogen storage kinetics due to the difficult nucleation of MgB_(2).Herein,amorphous VB_(2)nanoparticles with an average size of approximately 32 nm are synthesized to enhance the hydrogen storage performance of 2LiBH_(4)-MgH_(2)composite.VB_(2),sharing the same hexagonal structure with MgB_(2)with a d-value mismatch ratio of only 2.28%,could serve as effective nucleation sites for promoting the formation of MgB_(2).Theoretical calculations reveal that the introduction of VB_(2)significantly reduces the binding energies of B and Mg,facilitating in situ nucleation of MgB_(2).As a result,after the introduction of VB_(2)nanoparticles,complete hydrogen desorption of 9.23 wt%is achieved for 2LiBH_(4)-MgH_(2)within 2 h at 400℃,which is 4 times shorter than the time required for pure 2LiBH_(4)-MgH_(2),and no nucleation incubation period for hydrogen desorption is observed even at a low temperature of380℃.More importantly,a reversible capacity of9.3 wt%,corresponding to a capacity retention of 100%,could be preserved after 10 cycles of hydrogen storage,demonstrating stable reversible hydrogen storage performance.This study provides a novel technological pathway for improving the reversible hydrogen storage performance of composite metal hydrides and offers significant insights into the development of high-performance hydrogen storage materials.
