针对开发高性能水系铜电池电极材料的迫切需求,通过简易的共沉淀法制备钒基普鲁士蓝类似物铁氰化钒(VHCF)用作水系铜电池正极,考察反应温度及转速对VHCF样品表面形貌及微观结构的影响,探究不同VHCF样品在电化学性能上的差异,并分析VHCF...针对开发高性能水系铜电池电极材料的迫切需求,通过简易的共沉淀法制备钒基普鲁士蓝类似物铁氰化钒(VHCF)用作水系铜电池正极,考察反应温度及转速对VHCF样品表面形貌及微观结构的影响,探究不同VHCF样品在电化学性能上的差异,并分析VHCF样品的铜离子储存机理。研究结果表明:通过适当提升反应温度及搅拌器的转速,可以制备出[Fe(CN)_(6)]^(4-)含量多,粒径小且结构稳定的立方相VHCF;丰富的[Fe(CN)_(6)]^(4-)可以为Cu^(2+)离子提供更多的化学活位点,较小的粒径有利于提高Cu^(2+)离子的扩散速率,与普鲁士蓝骨架结合更稳定的结晶水则能改善电池循环稳定性;电化学反应过程中,Cu^(2+)离子会取代VHCF骨架中的V5+离子形成不可逆新相。VHCF正极在0.1 A/g电流密度下的首次放电比容量高达146.5 m A·h/g,循环500次后,保留了56.1 m A·h/g的可逆容量;在1.0 A/g的大电流密度下的放电比容量仍有60.1 m A·h/g。因此,钒基普鲁士蓝类似物VHCF在水系铜电池中的应用,为设计及发展水系铜电池高性能电极材料提供了新的可能性。展开更多
An improved understanding of fatigue behavior of a cast aluminum alloy（2-AS5U3G-Y35）in very high cycle regime is developed through the ultrasonic fatigue test in axial and torsion loading.The new developed torsion f...An improved understanding of fatigue behavior of a cast aluminum alloy（2-AS5U3G-Y35）in very high cycle regime is developed through the ultrasonic fatigue test in axial and torsion loading.The new developed torsion fatigue system is presented.The effects of loading condition and frequency on the very high cycle fatigue（VHCF）are investigated.The cyclic loading in axial and torsion at 35 Hz and 20 kHz with stress ratio R=-1 is used respectively to demonstrate the effect of loading condition.S-N curves show that the fatigue failure occurs in the range of 105—1010 cycles in axial or torsion loading and the asymptote of S-N curve is inclined,but no fatigue limit exists under the torsion and axial loading condition.The fatigue fracture surface shows that the fatigue crack initiates from the specimen surface subjected to the cyclic torsion loading.It is different from the fatigue fracture characteristic in axial loading in which fatigue crack initiates from subsurface defect in very high cycle regime.The fatigue initiation is on the maximum shear plane,the overall crack orientation is on a typical spiral 45° to the fracture plane and it is the maximum principle stress plane.The clear shear strip in the torsion fatigue fracture surface shows that the torsion fracture is the shear fracture.展开更多
The influence of hydrogen embrittlement on the fatigue behaviors of AISI 304 stainless steel is investigated. The fatigue endurance limits of the untreated and hydrogen-embrittled materials were almost the same at 400...The influence of hydrogen embrittlement on the fatigue behaviors of AISI 304 stainless steel is investigated. The fatigue endurance limits of the untreated and hydrogen-embrittled materials were almost the same at 400 MPa, and hydrogen embrittlement had little influence even though the sample contained about 8.1 times more hydrogen. Thus, the sensitivity of hydrogen gas in this material is very low. A surface crack initiation, growth, coalescence, and micro ridge model is proposed in this study. Slip line formation?⇒microcrack formation?⇒increases in the crack width, and blunting of the crack tip as it grows?⇒formation of many slip lines because of deformation in the shear direction?⇒growth of the crack in the shear direction, forming micro ridges, coalescence with adjacent cracks ⇒?continuous initiation, growth, coalescence, and ridge formation of surface cracks and specimen breakage.展开更多
Fatigue failure can still occur beyond 107 cycles,i.e.very-high-cycle fatigue(VHCF),in many metallic materials,such as aluminium alloys and high-strength steels.For VHCF of high-strength steels,a fine granular area(FG...Fatigue failure can still occur beyond 107 cycles,i.e.very-high-cycle fatigue(VHCF),in many metallic materials,such as aluminium alloys and high-strength steels.For VHCF of high-strength steels,a fine granular area(FGA)surrounding an inclusion is commonly identified as the characteristic region of crack initiation on the fracture surface.However,no such FGA feature and related crack initiation behaviour were observed in VHCF of conventionally cast or wrought aluminium alloys.Here,we first reported the distinct mechanisms of crack initiation and early growth,namely the microstructure feature and the role of FGA in VHCF performance for an additively manufactured(AM)AlSi10Mg alloy.The AM pores play a key role in fatigue crack initiation similar to that of the inclusions in high-strength steels,resulting in almost identical FGA behaviour for different materials under a range of mean stress with a stress ratio at R<0 or R>0.The profile microstructure of FGA is identified as a nanograin layer with Si rearrangement and grain boundary transition.This process consumes a large amount of cyclic plastic energy making FGA undertake a vast majority of VHCF life.These results will deepen the understanding of VHCF nature and shed light on crack initiation mechanism of other aluminium and AM alloys.展开更多
文摘针对开发高性能水系铜电池电极材料的迫切需求,通过简易的共沉淀法制备钒基普鲁士蓝类似物铁氰化钒(VHCF)用作水系铜电池正极,考察反应温度及转速对VHCF样品表面形貌及微观结构的影响,探究不同VHCF样品在电化学性能上的差异,并分析VHCF样品的铜离子储存机理。研究结果表明:通过适当提升反应温度及搅拌器的转速,可以制备出[Fe(CN)_(6)]^(4-)含量多,粒径小且结构稳定的立方相VHCF;丰富的[Fe(CN)_(6)]^(4-)可以为Cu^(2+)离子提供更多的化学活位点,较小的粒径有利于提高Cu^(2+)离子的扩散速率,与普鲁士蓝骨架结合更稳定的结晶水则能改善电池循环稳定性;电化学反应过程中,Cu^(2+)离子会取代VHCF骨架中的V5+离子形成不可逆新相。VHCF正极在0.1 A/g电流密度下的首次放电比容量高达146.5 m A·h/g,循环500次后,保留了56.1 m A·h/g的可逆容量;在1.0 A/g的大电流密度下的放电比容量仍有60.1 m A·h/g。因此,钒基普鲁士蓝类似物VHCF在水系铜电池中的应用,为设计及发展水系铜电池高性能电极材料提供了新的可能性。
基金Supported by the National Natural Science Foundation of China(50775182)the Scientific Research Foundation for the Returned Scholars of the Ministry of Education of China~~
文摘An improved understanding of fatigue behavior of a cast aluminum alloy（2-AS5U3G-Y35）in very high cycle regime is developed through the ultrasonic fatigue test in axial and torsion loading.The new developed torsion fatigue system is presented.The effects of loading condition and frequency on the very high cycle fatigue（VHCF）are investigated.The cyclic loading in axial and torsion at 35 Hz and 20 kHz with stress ratio R=-1 is used respectively to demonstrate the effect of loading condition.S-N curves show that the fatigue failure occurs in the range of 105—1010 cycles in axial or torsion loading and the asymptote of S-N curve is inclined,but no fatigue limit exists under the torsion and axial loading condition.The fatigue fracture surface shows that the fatigue crack initiates from the specimen surface subjected to the cyclic torsion loading.It is different from the fatigue fracture characteristic in axial loading in which fatigue crack initiates from subsurface defect in very high cycle regime.The fatigue initiation is on the maximum shear plane,the overall crack orientation is on a typical spiral 45° to the fracture plane and it is the maximum principle stress plane.The clear shear strip in the torsion fatigue fracture surface shows that the torsion fracture is the shear fracture.
文摘The influence of hydrogen embrittlement on the fatigue behaviors of AISI 304 stainless steel is investigated. The fatigue endurance limits of the untreated and hydrogen-embrittled materials were almost the same at 400 MPa, and hydrogen embrittlement had little influence even though the sample contained about 8.1 times more hydrogen. Thus, the sensitivity of hydrogen gas in this material is very low. A surface crack initiation, growth, coalescence, and micro ridge model is proposed in this study. Slip line formation?⇒microcrack formation?⇒increases in the crack width, and blunting of the crack tip as it grows?⇒formation of many slip lines because of deformation in the shear direction?⇒growth of the crack in the shear direction, forming micro ridges, coalescence with adjacent cracks ⇒?continuous initiation, growth, coalescence, and ridge formation of surface cracks and specimen breakage.
基金financially supported by the National Natural Science Foundation of China(No.11932020).
文摘Fatigue failure can still occur beyond 107 cycles,i.e.very-high-cycle fatigue(VHCF),in many metallic materials,such as aluminium alloys and high-strength steels.For VHCF of high-strength steels,a fine granular area(FGA)surrounding an inclusion is commonly identified as the characteristic region of crack initiation on the fracture surface.However,no such FGA feature and related crack initiation behaviour were observed in VHCF of conventionally cast or wrought aluminium alloys.Here,we first reported the distinct mechanisms of crack initiation and early growth,namely the microstructure feature and the role of FGA in VHCF performance for an additively manufactured(AM)AlSi10Mg alloy.The AM pores play a key role in fatigue crack initiation similar to that of the inclusions in high-strength steels,resulting in almost identical FGA behaviour for different materials under a range of mean stress with a stress ratio at R<0 or R>0.The profile microstructure of FGA is identified as a nanograin layer with Si rearrangement and grain boundary transition.This process consumes a large amount of cyclic plastic energy making FGA undertake a vast majority of VHCF life.These results will deepen the understanding of VHCF nature and shed light on crack initiation mechanism of other aluminium and AM alloys.
