The effect of addition of different concentrations of Ce on high-cycle fatigue behavior of die-cast magnesium alloy AZ91D was investigated. Mechanical fatigue tests were conducted at the stress ratio of R = 0.1, and f...The effect of addition of different concentrations of Ce on high-cycle fatigue behavior of die-cast magnesium alloy AZ91D was investigated. Mechanical fatigue tests were conducted at the stress ratio of R = 0.1, and fatigue strength was evaluated using up-and-down loading method. The results show that the grain size of AZ91D alloy is remarkably refined, and the amount of porosity decreases and evenly distributes with the addition of Ce. The fatigue strength of AZ91D alloy at room temperature increases from 96.7 up to 116.3 MPa （ 1% Ce） and 105.5 MPa （2 % Ce）, respectively, at the number of cycles to failure, Nf = 1 × 10^7. The fatigue crack of AZ91D alloy initiates at porosities and inclusions, and propagates along grain boundaries. The fatigue striations on fractured surface appear with Ce addition. The fatigue fracture surface of test specimens shows mixed-fracture characteristics of quasi-cleavage and dimple.展开更多
High density polyethylene filled with condutuctive carbon black was prepared by conventional meltmixing method. The effect of unidirectional pressure on the conductivity was studied. Wide angle X-ray diffraction （ WA...High density polyethylene filled with condutuctive carbon black was prepared by conventional meltmixing method. The effect of unidirectional pressure on the conductivity was studied. Wide angle X-ray diffraction （ WAXD ） was used to slum： the influence of pressure on the aggregate structure of the polymer filled with carbon black （CB） fillers. A model on the basis of the formation and destruction of conductive networks was proposed to explain the change in the conductivity with the application of pressure.展开更多
Electrocatalysts with high activity and long-term durability are vital toward large-scale hydrogen pro-duction from electrocatalytic water splitting.Here,the self-supported electrode(FeO_(χ)H_(y)@Ni_(3)B/NF)with hier...Electrocatalysts with high activity and long-term durability are vital toward large-scale hydrogen pro-duction from electrocatalytic water splitting.Here,the self-supported electrode(FeO_(χ)H_(y)@Ni_(3)B/NF)with hierarchical heterostructure was simply prepared by using Ni_(3)B chunks grown on nickel foam as sub-strate to in situ form vertical FeO_(χ)H_(y)nanosheets.Such hybrid shows efficient oxygen evolution reaction activity with overpotentials as low as 267 and 249 mV at 100 mA cm^(-2)in 1 M KOH solution and 30 wt%KOH solution,respectively.Meanwhile,it also exhibits excellent catalytic stability,sustaining catalysis at 500 mA cm^(-2)in 1 M KOH solution for 200 h,and even for 200 h at 1000 mA cm^(-2)in 30 wt%KOH solution.Further experimental results reveal that the FeO_(χ)H_(y)@Ni_(3)B/NF is endowed with superhydrophilic and superaerophobic surface properties,which not only provide more mass transport channels,as well as facilitated the diffusion of reaction intermediates and gas bubbles.Also,it holds faster reaction kinetics,more accessible active sites and accelerated electron transfer rates due to strong synergistic interactions attheheterogeneous interface.展开更多
基金Project supported bythe Key Technologies Fifteen R &D Programme (2001BA311A07-2) 985-Automotive Engineering ofJilin University
文摘The effect of addition of different concentrations of Ce on high-cycle fatigue behavior of die-cast magnesium alloy AZ91D was investigated. Mechanical fatigue tests were conducted at the stress ratio of R = 0.1, and fatigue strength was evaluated using up-and-down loading method. The results show that the grain size of AZ91D alloy is remarkably refined, and the amount of porosity decreases and evenly distributes with the addition of Ce. The fatigue strength of AZ91D alloy at room temperature increases from 96.7 up to 116.3 MPa （ 1% Ce） and 105.5 MPa （2 % Ce）, respectively, at the number of cycles to failure, Nf = 1 × 10^7. The fatigue crack of AZ91D alloy initiates at porosities and inclusions, and propagates along grain boundaries. The fatigue striations on fractured surface appear with Ce addition. The fatigue fracture surface of test specimens shows mixed-fracture characteristics of quasi-cleavage and dimple.
文摘High density polyethylene filled with condutuctive carbon black was prepared by conventional meltmixing method. The effect of unidirectional pressure on the conductivity was studied. Wide angle X-ray diffraction （ WAXD ） was used to slum： the influence of pressure on the aggregate structure of the polymer filled with carbon black （CB） fillers. A model on the basis of the formation and destruction of conductive networks was proposed to explain the change in the conductivity with the application of pressure.
基金supported by the National Natural Science Foundation of China (12234018,52101256,51872115)
文摘Electrocatalysts with high activity and long-term durability are vital toward large-scale hydrogen pro-duction from electrocatalytic water splitting.Here,the self-supported electrode(FeO_(χ)H_(y)@Ni_(3)B/NF)with hierarchical heterostructure was simply prepared by using Ni_(3)B chunks grown on nickel foam as sub-strate to in situ form vertical FeO_(χ)H_(y)nanosheets.Such hybrid shows efficient oxygen evolution reaction activity with overpotentials as low as 267 and 249 mV at 100 mA cm^(-2)in 1 M KOH solution and 30 wt%KOH solution,respectively.Meanwhile,it also exhibits excellent catalytic stability,sustaining catalysis at 500 mA cm^(-2)in 1 M KOH solution for 200 h,and even for 200 h at 1000 mA cm^(-2)in 30 wt%KOH solution.Further experimental results reveal that the FeO_(χ)H_(y)@Ni_(3)B/NF is endowed with superhydrophilic and superaerophobic surface properties,which not only provide more mass transport channels,as well as facilitated the diffusion of reaction intermediates and gas bubbles.Also,it holds faster reaction kinetics,more accessible active sites and accelerated electron transfer rates due to strong synergistic interactions attheheterogeneous interface.
