The electronic structures and optical properties of Y-doped ZnO are calculated using first-principles calculations.It is found that the replacement of Zn by the rare-earth element Y presents a shallow donor,and the Fermi level moves into the conduction band(CB).The high dispersion and s-type character of CB is expected to result in an increase in conductivity.Moreover,the absorption spectrum of the Y-doped ZnO system exhibits a slight blue shift with an increase of Y concentration,and a higher transparency in visible light is expected.Therefore,the Y-doping in ZnO would enhance the mobility and hence increase the electrical conductivity without sacrificing the optical transparency,which is essential for the improvement of ZnO's behavior and its performance in extension applications.
An organic-magnesium complex conversion(OMCC)coating on AZ91D magnesium alloy was obtained by treating in a solution containing organic compounds.SEM,FESEM and XPS were used to examine the surface morphology,thickness and structure of the conversion coatings.The results show that the continuous and uniform conversion coating is deposited on AZ91D alloy and the main component of the coatings is organic compound containing benzene ring,which forms a chemical bond with magnesium.The polarization measurement and salt spray test show that the corrosion resistance of the conversion coating is much higher than that of traditional chromate conversion coating.
Nanocrystalline Cu with average grain sizes ranging from ～ 24.4 to 131.3 nm were prepared by the electric brushplating technique.Nanoindentation tests were performed within a wide strain rate range,and the creep process of nanocrystalline Cu during the holding period and its relationship to dislocation and twin structures were examined.It was demonstrated that creep strain and creep strain rate are considerably significant for smaller grain sizes and higher loading strain rates,and are far higher than those predicted by the models of Cobble creep and grain boundary sliding.The analysis based on the calculations and experiments reveals that the significant creep deformation arises from the rapid absorption of high density dislocations stored in the loading regime.Our experiments imply that stored dislocations during loading are highly unstable and dislocation activity can proceed and lead to significant post-loading plasticity.
Nanocrystalline (NC) and coarse-grained Ni with different grain sizes (from 16 nm to 2 μm) were fabricated by direct current electrodeposition. Effect of grain size on the electrochemical corrosion behavior of these Ni deposits in different corrosion media was characterized by using potentiodynamic polarization test, electrochemical impedance spectroscopy (EIS), X-ray photoelectron spectroscopy (XPS) and immersion corrosion test. Results show that in the NaOH or NaCl solution, the NC Ni exhibits improved corrosion resistance with the decrease of grain size. But in H2SO4 solution, the higher grain boundary density accelerates corrosion due to no passive process and the corrosion resistance of NC Ni decreases with refining grain size. The distinct experimental results of NC Ni in corrosion behavior can be reasonably explained by the positive or negative effect of high-density grain boundaries in different corrosion media.
ZnO film with claviform structure was synthesized on quartz substrates through a hydrothermal method at 90℃.The microstructure of the film is composed of clusters of submicrometer rods,which therefore endues the film with good superhydrophobicity.Meanwhile,the film with such tanglesome structure also shows highly crystalline quality testified by a strong ultra-violet (UV) emission and very low deep-level emission observed on the photoluminescence (PL) spectrum as well as high transparence of about 89% transmittance in visible light range.
