Effect of O–O bonds on p-type conductivity in Ag-doped ZnO twin grain boundaries

Based on density functional theory,first-principles calculation is applied to study the electronic properties of undoped and Ag-doped Zn O-Σ7(123^-0)twin grain boundaries(GBs).The calculated result indicates that the twin GBs can facilitate the formation and aggregation of Ag substitution at Zn sites(AgZn)due to the strain release.Meanwhile,some twin GBs can also lower the ionization energy of AgZn.The density of state shows that the O–O bonds in GBs play a key role in the formation of a shallow acceptor energy level.When AgZnbonds with one O atom in the O–O bond,the antibonding state of the O–O bond becomes partially occupied.As a result,a weak spin splitting occurs in the antibonding state,which causes a shallow empty energy level above the valence band maximum.Further,the model can be applied to explain the origin of p-type conductivity in Ag-doped Zn O.

Through-Thickness Texture Gradient in Hot-Rolled 25Mn-2.5Si-2Al TWIP Steel

Texture is one of the important factors affecting sheet metal forming performance.The through-thickness texture gradient during the hot-rolling process of twinning induced plasticity（TWIP）steel sheet was investigated using electron backscatter diffraction and X-ray diffraction.With increasing reduction of the TWIP steel,the fraction of∑1 decreased,whereas the fractions of∑3,∑9,and∑27increased.During 53%reduction,a similar trend could be found from its surface to the center.The gradients of intensities of the fibers decreased with increasing hot-rolling reduction.The intensities of face-centered cubic（fcc）shear textures E and Y were higher in the center than that at the surface for both reductions.During 20% reduction,the intensity of fcc plain strain texture S orientation increased from the center to the surface.

Correlation Between Microstructure and Corrosion Behavior of Two 90Cu10Ni Alloy Tubes

Two kinds of 90Cu10 Ni tubes with different service lives（more than 3 years and only 1 year,respectively）under identical working conditions were studied by an immersion test in a 3.5 wt% NaCl solution and the electron backscattered diffraction（EBSD） technique.The morphology after immersion showed severer corrosion attack at the grain boundaries of the tube with shorter service life compared with the tube with longer service life.The grain boundary characterization distributions（GBCDs） of the two tubes obtained by EBSD revealed more Σ3 boundaries and twins,and larger random boundary meshes in the tube with longer service life.A short immersion test in a modified Livingston＇s solution was conducted to evaluate the tendency to corrosion attack of different types of the grain boundaries.SEM and AFM were used to characterize the corrosion morphologies of the boundaries.A strong correlation between varying depths of corrosion grooves and types of the grain boundaries was obtained.The influence of deviation angle of low Σ boundaries on corrosion resistance of the grain boundaries was also discussed.It is concluded that a special ‘‘grain boundary engineering＇＇（GBE） treatment has been performed on the tube with longer service life.It is proposed that the optimized GBCD is responsible for the better service performance of the tube.