The corrosion behavior of plasma sprayed 8YSZ(ZrO2 stabilized by 8 wt.%Y2O3)coating on the surface of carbon steel in seawater was investigated.The electrochemical impedance spectroscopy was used as a non-destructive evaluation technique to monitor the protection properties of the coating when it was immersed in seawater,and corrosion products were characterized by scanning electron microscopy,energy dispersive spectrometry and X-ray photoelectron spectroscopy.The results indicated that three time constants were obtained during the initial immersion period,and then a new time constant appeared due to the formation of rust layer,which was corresponding to the corrosion process.Corrosion products were formed on the coating surface as well as inside the coating,and the crystalline composition of the rust layer mainly consisted of γ-FeOOH.
CeF3 and CeF3:Tb3+ nanocrystals were successfully synthesized by the ultrasound assisted ionic liquid(IL) method at room temperature. X-ray diffraction(XRD), scanning electron microscopy(SEM), transmission electron microscopy(TEM), selected area electron diffraction(SAED), high-resolution transmission electron micrographs(HRTEM) and photoluminescence(PL) spectra were employed to characterize the nanocrystals. The results of XRD indicated that the obtained samples crystallized well with a hexagonal phase crystal structure. SEM and TEM images demonstrated that the obtained CeF3:Tb3+ nanocrystals had a discoid shape in the presence of ultrasound and IL, whereas only granular nanoparticles were obtained by magnetic stirring. The possible formation mechanisms of the crystal growth were proposed. The PL spectra of the CeF3:Tb3+ nanodisks exhibited a strong green emission when excited at 254 nm. Furthermore, the photoluminescence intensity of CeF3:Tb3+ of the discoid particles was largely improved compared with that of the granular nanoparticles.
The Eu3+–Y3+ double-doped Zr O2(8YSZ:Eu3+) phosphors with different doping concentrations of Eu3+ were synthesized by hydrothermal method. The dependences of the intensities of visible emission, decay lifetimes and crystal structures on Eu3+ doping concentration were investigated. The optimal doping concentration of Eu3+ in 8YSZ:Eu3+ nanophosphors was determined. The morphology and crystal structure of the resulting phosphors were characterized by scanning electron microscopy, transmission electron microscopy, X-ray diffraction and Raman spectra. The fluorescence properties of the resulting phosphors were investigated by photoluminescence spectra and decay curve. In this paper, 3 mol.% Eu3+ ions in 8YSZ:Eu3+ phosphors was the optimal doping concentration. When doping concentration was 3 mol.%, the nanophosphor had a pure tetragonal phase structure, the emission intensity was intense and decay lifetime was long, furthermore this system could be used to indicate the extent of phase transformation of thermal barrier coatings.
