In the present study,2024 aluminum alloy specimen was anodized in acetic acid and oxalic acid electrolytes.Effects of the current density on the microstructure and corrosion resistance of anodic oxide film have been investigated.The steady voltage increases from 11 V to 71 V with the current density increase from 0.5 A /dm^2 to 2.5 A /dm^2.The SEM reveals that there are pits,cavities and irregular pores in the anodic film,and their size and morphologies change with the current density.The corrosion resistance of the film was evaluated by potentiodynamic polarization and electrochemical impedance in 0.1 mol /L FeCl_3 solution at room temperature.The results show that corrosion resistance of the anodic oxide film changes with the current density,and the anodic film formed at the current density of 1.0 A /dm^2 has the best corrosion resistance.These observations indicate that anodic film formed at J = 1.0 A /dm^2 can serve as a support material for the Cu micrometallic patterns.
In the present study,anodic films on aluminium alloy was used as the dielectric layer for Cu thinfilm temperature sensor,and then Cu film was deposited by unbalanced magnetron sputtering ion plating as the sensitive layer.Microstructure and surface morphologies of Cu film were investigated by optical microscope(OM),atomic force microscope(AFM) and scanning electron microscope(SEM).Electrical properties of Cu thin-film temperature sensor were tested by four-point probe technique and Digit Multimeter.The results showed that the surface roughness of anodic films can be reduced from Ra 58.096 nm to Ra 16.335 nm by proper polishing.Continual Cu stripes can be obtained both on polished anodic alumina film and smooth alumina wafer by etching after Cu film annealing.The resistivity of Cu films before and after 300 ℃ as well as 400 ℃ annealing are 12.48 mΩ·cm,5.48 mΩ·cm and 4.83 mΩ·cm,respectively.The resistances of Cu thin-film temperature sensor in 70 ℃ and 0 ℃ are 946.5 Ω and 761.15 Ω respectively.The temperature coefficient of resistivity(TCR) of the sensor is 3479 × 10^(- 6) /℃.
A series of doped barium hexaferrites BaFe12-2xMnxSnxO19 (x = 0.0-1.0) particles were prepared by the co-precipitation/molten salt method. The particle size and crystalline of the samples BaFe12-2xMnxSnxO19 decrease with an increase in the doping amount x. When x is less than 0.8, the pure BaFe12-2xMnxSnxO19 particles with hexagonal plate morphology are obtained. The effects of substitution on magnetic properties were evaluated and compared to nomal BaFe12O19. The specific magnetizations (Ms) of doped materials have been significantly improved. Among all these compositions, the BaFe10.4Mn0.8Sn0.8O19 sample has the highest Ms value of 81.8 A?m2?kg-1 at room temperature and its intrinsic coercivity (Hc) is 44.5 kA?m-1. The as-prepared doped barium ferrites exhibit a low temperature coefficient of coercivity close to zero. The coercivity is independent of temperature when x is in the a range 0.5-0.7.
