In-situ atomic-scale electrically induced ion migration and structural evolution of functional oxides

With the support of the National Natural Science Foundation of China,two original studies by the research group led by Prof.Gu Lin(谷林)and Prof.Zhang Qinghua(张庆华)from the Institute of Physics,Chinese Academy of Sciences demonstrate the in-situ atomic-scale electrically induced

Influence of electric field on the quenched-in vacancy and solute clustering during early stage ageing of Al-Cu alloy

The effects of electric field on the evolution of excess quenched-in vacancy as well as solute clustering in Al-4wt%Cu alloy, and on the vacancy migration and formation enthalpy of pure aluminum were investigated, using positron annihilation lifetime spectroscopy, high-angle annular dark-field scanning transmission electron microscopy, transmission electron microscopy, hardness measurement and four-probe electrical resistivity measurement. The results showed that the electric field improved age hardening response obviously and postponed the decay of excess vacancies for 30rain during the early stage ageing of Al-4wt%Cu alloy. A large number of 2-4nm GP zones with dense distribution were observed after 1 min ageing with an electric field applied. The electric field-assisted-aged sample owned a lower coarsening rate of GP zone, which was about three fifths of that in the aged sample without an electric field, from 1 min to 120 rain ageing. The electric field contributed 8% increase of the vacancy migration enthalpy （0.663 ±0.021 eV） of pure Al, comparing with that （0.611 ±0.023 eV） of pure Al without an electric field. The increase of vacancy migration enthalpy, induced by the electric field, was responsible for the difference on evolution of quenched-in vacancy, rapid solute clustering and age hardening improvement during the early stage ageing of Al-4wt%Cu alloy.

Structures of sodium vanadate solution under different conditions

Combined with Fourier transform infrared spectroscopy（FTIR） analysis of sodium vanadate solution,the relationship between conductivity and structure was investigated by measuring the electric conductivity of the solution under different alkali concentrations and molar ratios of NaOH to V2O5. Results suggest that the polymerization vanadium acid radical ions gradually transform into monomer with the solution diluting. When the solution is diluted to a certain extent,only the vanadium acid radical ion with V-OH chemical bond exists in the solution. At NaOH concentration of below 105.21 g·L^（-1）,the vanadate anions mainly exist in the form of vanadium acid radical ion with V-OH chemical bond and the ion transference number is approximately from 0.58 to 0.82. In the medium NaOH concentration range of 105.21-117.03 g·L^（-1）, the vanadate anions mostly exist in the form of vanadium acid radical ion with V-OH and V-O-V chemical bonds and the ion transference number is approximately 3.29. At NaOH concentration of above 117.03 g·L^（-1）, vanadate anions exist in the form of vanadium acid radical ion with V-OH and V-O-V chemical bonds.