Atomic scale investigation of FCC→HCP reverse phase transformation in face-centered cubic zirconium

Mechanism of FCC→HCP reverse phase transformation in face-centered cubic zirconium(FCC-Zr)along with a concomitant 70.5°rotation ofα-Zr matrix were investigated in zircaloy-4(Zr-4)cladding tube by using transmission electron microscopy(TEM).Results showed that the interaction among a secondary phase particle(SPP)and three FCC-Zr grains resulted in the formation of cross stacking faults in SPP and exerted a drag force on minor axis of the adjacent FCC-Zr phase.Moreover,when the shear stress along[112]_(FCC-Zr)direction was large enough to initiate the emission of 1/6[112]Shockley partial dislocation on every other(111)_(FCC-Zr)close-packed plane,the stacking sequence would change from ABC ABCA to AB ABABA viz.(0001)planes of the daughter HCP phase.Thus,FCC→HCP reverse phase transformation in FCC-Zr was presented.

Reversible aqueous zinc-ion battery based on ferric vanadate cathode

Rechargeable aqueous zinc-ion batteries have attracted extensive interest because of low cost and high safety.However,the relationship between structure change of cathode and the zinc ion storage mechanism is still complex and challenging.Herein,open-structured ferric vanadate(Fe_(2)V_(4)O_(13))has been developed as cathode material for aqueous zinc-ion batteries.Intriguingly,two zinc ion storage mechanism can be observed simultaneously for the Fe2V4O13 electrode,i.e.,classical intercalation/deintercalation storage mechanism in the tunnel structure of Fe_(2)V_(4)O_(13),and reversible phase transformation from ferric vanadate to zinc vanadate,which is verified by combined studies using various in-situ and ex-situ techniques.As a result,the Fe_(2)V_(4)O_(13) cathode delivers a high discharge capacity of 380 mAh/g at 0.2 A/g,and stable cyclic performance up to 1000 cycles at 10 A/g in the operating window of 0.2-1.6 V with 2 mol/L Zn(CF_(3)SO_(3))_(2) aqueous solution.Moreover,the assembled Fe_(2)V_(4)O_(13)//Zn flexible quasi-solid-state battery also exhibits a relatively high mechanical strength and good cycling stability.The findings reveal a new perspective of zinc ion storage mechanism for Fe_(2)V_(4)O_(13),which may also be applicable to other vanadate cathodes,providing a new direction for the investigation and design of zinc-ion batteries.