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
Transition metal impurities such as chromium(Cr)and vanadium(V)in solution deteriorate electrical conductivity of smelter grade aluminium(Al).These impurities can be removed from solution via boron treatment in which ...Transition metal impurities such as chromium(Cr)and vanadium(V)in solution deteriorate electrical conductivity of smelter grade aluminium(Al).These impurities can be removed from solution via boron treatment in which borides form upon their in-situ reaction with boron(B)-bearing substances.However,Cr removal from smelter grade Al solution is not well understood.A disagreement related to chromium boride(CrB_(2))formation in molten Al in the presence of other transition metals(V,Ti,Zr,Fe)by adding Al−B master alloy has been reported in literatures.This study presents an effort to understand the mechanism of Cr removal from Al−0.50%Cr−0.50%V(mass fraction)alloy by adding Al−B(AlB_(12))master alloy at 1023 K in the Al alloy solution.Results indicate that Cr removal from molten Al−0.50%Cr−0.50%V alloy by forming stable borides cannot be achieved at 1023 K;whereas excess of B in the solution preferentially forms aluminium boride(AlB2)over CrB_(2) during boron treatment of molten Al.The underlying kinetics of V removal from molten Al−0.50%Cr−0.50%V alloy revealed that early reaction stage is controlled by[B]/[V]mass transfer through liquid phase and mass transfer coefficient(km)was measured to be 9.6×10^(−4) m/s.The later reaction stage was controlled by[B]/[V]diffusion through boride(VB_(2))ring.This study,therefore,advocates to investigate alternative ways to remove Cr from molten Al.展开更多
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.
基金Taif University Researchers Supporting Project(No.TURSP-2020/293)Taif University,Taif,Saudi Arabia.
文摘Transition metal impurities such as chromium(Cr)and vanadium(V)in solution deteriorate electrical conductivity of smelter grade aluminium(Al).These impurities can be removed from solution via boron treatment in which borides form upon their in-situ reaction with boron(B)-bearing substances.However,Cr removal from smelter grade Al solution is not well understood.A disagreement related to chromium boride(CrB_(2))formation in molten Al in the presence of other transition metals(V,Ti,Zr,Fe)by adding Al−B master alloy has been reported in literatures.This study presents an effort to understand the mechanism of Cr removal from Al−0.50%Cr−0.50%V(mass fraction)alloy by adding Al−B(AlB_(12))master alloy at 1023 K in the Al alloy solution.Results indicate that Cr removal from molten Al−0.50%Cr−0.50%V alloy by forming stable borides cannot be achieved at 1023 K;whereas excess of B in the solution preferentially forms aluminium boride(AlB2)over CrB_(2) during boron treatment of molten Al.The underlying kinetics of V removal from molten Al−0.50%Cr−0.50%V alloy revealed that early reaction stage is controlled by[B]/[V]mass transfer through liquid phase and mass transfer coefficient(km)was measured to be 9.6×10^(−4) m/s.The later reaction stage was controlled by[B]/[V]diffusion through boride(VB_(2))ring.This study,therefore,advocates to investigate alternative ways to remove Cr from molten Al.
