Yun Long Wang

Microstructure characterisation of alumina coating on steel by PEO

Abstract Alumina ceramic coating was prepared on Q235 carbon steel by plasma electrolytic oxidation. The discharge process was analysed according to the voltage–time curve. The microstructure of the ceramic coating was investigated by scanning electron microscopy, X-ray diffractometry and energy dispersive X-ray spectroscopy. The bonding strength, thickness, hardness, surface roughness and corrosion properties of the coatings were studied. The results indicated that coating on Q235 carbon steel mainly consisted of α-Al2O3 and γ-A12O3. The coating showed coarse and porous surface. The surface roughness of the coating was 1·8 μm, and the average diameter of the pores was 3–4 μm. The hardness of the coating was 1854 HV. The thickness of the coating was ∼28 μm, and the bonding strength was 23 MPa. The corrosion tests indicated that the corrosion current density of alumina coated Q235 in 3·5%NaCl was 8·289×10−7 A cm−2, which was decreased by two orders of magnitude compared with the uncoated one. The corrosion potential was increased to −0·379 V, which shifted positively by 0·303 V compared to the uncoated one.

Microstructure and visible light photocatalytic activity of Fe–TiO2 films on steel by PEO

Abstract Fe doped TiO2 ceramic films were fabricated on carbon steel by plasma electrolytic oxidation. The microstructure of the film was characterised, and the photocatalytic activities of the films were evaluated. The results showed that the phases of the films were anatase TiO2 and Al2TiO5. The film surface was rough and porous. With increasing the treatment time, the pores on film surfaces gradually became deep and large, which made the film surfaces rougher. Fe–TiO2 films showed red shift in photoresponse towards the visible region. The photocatalytic activities of the films were evaluated by photocatalytic oxidation of Rhodamine B aqueous under visible light irradiation. The results revealed that the film showed visible light photocatalytic activity. With increasing treatment time, the degradation rate of rhodamine B gradually increased and the highest degradation rate was ∼80% in visible light irradiation for 6 h.

Characterization of Graphite Containing Ceramic Coating Prepared on Carbon Steel by Plasma Electrolytic Oxidation

Ceramic coatings containing graphite were prepared on Q235 carbon steel by plasma electrolytic oxidation (PEO) in aluminate electrolyte with graphite dispersed in electrolyte. The microstructure and properties of the coatings including phase composition, surface and cross section morphology, thickness and bonding strength were characterized. The results showed that the coating consisted of FeAl2O4, Fe3O4 and a certain amount of graphite. The coating was typically characterized by micro pores and ball-shaped round grains distributed on the surface. With increasing the treating current density, the pores became bigger and the ball-shaped round grains became more. Coatings obtained with various current densities showed a good interface between the coating and substrate. The bonding strength of the coatings decreased a little when increasing the current densities, the values of which were all above 20MPa. The coating grew both inwards and outwards to the substrate surface. With increasing the treating current density, the consumption of substrate gradually increased but the whole thickness was not strongly affected by the current density and the value was about 115 μm.

Structure and Photocatalytic Properties of Fixed Porous TiO2 Composite Film on Steel Prepared by Plasma Electrolytic Oxidation

TiO2 composite photocatalytic film was fixed on steel by by plasma electrolytic oxidation. The microstructure of the composite film were investigated by XRD, EDS and SEM. The photocatalytic properties of the film were studied by testing the photocatalytic degradation of Rhodamine B. The results showed that the ceramic film was composed of A-TiO2 and R-TiO2. The EDS revealed that the film consisted Ti, O, Si and Fe elements. The SEM pictures showed that the film surface was rough and porous. The photocatalytic experiment results showed that the the TiO2 composite film fixed on steel by plasma electrolytic oxidation exhibited relatively high photocatalytic photodegradation of Rhodamine B, whose removal ratio reached 90% in 2 hours, irradiation of ultraviolet light.

Synthesis and Characterization of Aluminum Nitride Ceramic Coating on Aluminum Alloy by Plasma Electrolytic Oxidation in CO(NH2)2 Electrolyte

aluminum nitride ceramic coating were obtained on LY12 aluminum alloy by plasma electrolytic oxidation in CO(NH2)2 electrolyte. The microstructure of the ceramic coating including phase and elements composition, surface and cross section morphology were investigated. The properties of the ceramic coatings such as surface roughness, thickness and bonding strength were primarily studied. The results show that the ceramic coating on LY12 aluminum alloy surface was AlN coating with the thickness of 12 um. The AlN ceramic coating showed rough and porous. The average diameter of the pores was 6 um and the surface roughness was 1.5 um. The bonding strength of the coating was 18 ± 2 MPa.

Enhancement of Corrosion Resistance of PEO Coating on AZ91 Biomedical Magnesium Alloy by Surface Laser Treating

Ceramic coating was fabricated on AZ91 biomedical magnesium alloy by plasma electrolytic oxidation. The coating was then subjected to surface laser treating, and the influence of laser treating on the morphologies and corrosion resistance of the coating were investigated. The results showed that PEO coating without laser treating showed coarse and porous surface and the pores on coating surface were big. When subjected to laser treating, the pores on coating surface became little and few. The corrosion tests in SBF indicated that corrosion resistance of PEO coating on magnesium alloy sample could improve the corrosion resistance of the substrate, and surface laser treating could further increase the corrosion resistance.

Raman Spectral of Ce/Mn Co-Doped LiNbO3 Crystal

Ce:Mn:LiNbO3 single crystals with different [L/[N were used for the measurement of Raman spectrum. Each peak appeared in the Raman spectrum was ascribed to the basic vibration modes of the LiNbO3 crystal according to the basic analysis and the achievements obtained by the earlier researches. The results showed that the peak width at half height (FWHM) of the A1(TO1) vibration mode become wide gradually with the increase of the [L/[N. However, the FWHM of A1(TO2) and A1(TO4) vibration mode decrease with the increase of the [L/[N in the crystal. The FWHM of the E(TO1) vibration mode was decrease with the increase of [L/[N in the crystal, and also the linear relationship between the FWHM of the E(TO1) vibration mode and the [L/[N in the crystal. According to the relationship between the [L/[N in the crystal and the FWHM of the E(TO1) vibration mode for the pure LiNbO3 crystal, the quantitative relation for the Ce/Mn co-doped LiNbO3 crystal was revealed by amending the empirical formula for pure LiNbO3 crystal on the basis of the results measured by ICP-AES. The quantitative relation of the FWHM of the E(TO1) vibration mode and the [L/[N was given by the Polynomial Fit of the experimental data.

Chemical Composition of Cerium and Manganese Co-Doped Lithium Niobate Single Crystal

Ce:Mn:LiNbO3 single crystals were grown from the melts with different [Li]/[Nb] by top seed crystal method, while the concentration of Ce was 0.1mol% and the concentration of Mn was 0.015wt%. The concentration of each element in the crystal was determined by inductively coupled plasma atomic emission spectrometry (ICP-AES). The location of the doping ion in the crystal was studied. The results revealed that Ce (or Mn) replace the location of Li in the Ce:Mn:LiNbO3. The dependence of crystal constitute on the material proportioning is given in the paper. The exact chemical formula was given by the relationship between the composition of crystal and the raw material on the basis of the Li vacancy model.

Fabrication of Al2O3 Ceramic Coating on AZ91 Biomedical Magnesium Alloy and the Corrosion Resistance in SBF

Al2O3 ceramic coating was fabricated on AZ91 biomedical magnesium alloy by plasma electrolytic oxidation. The microstructure of the coatings was characterized. The corrosion behavior of the coated magnesium alloy in simulated body fluids (SBF) was evaluated. The results showed that the as prepared coating was composed of crystal Al2O3, including much α-Al2O3 and some γ-Al2O3. The Al2O3. coating showed porous surface and the biggest diameters of the holes were about 6-7 um, and the smallest were about 1 um. The corrosion tests in SBF indicated that corrosion resistance of Al2O3 coated sample was significantly improved compared to the uncoated sample.

Characterization of TiO2 Composite Film on Steel Obtained in Aluminate Electrolyte by PEO and the Photocatalytic Activities

TiO2 composite photocatalytic film was prepared on steel by plasma electrolytic oxidation in aluminate electrolyte. The microstructure of the composite film was investigated by XRD and SEM. The photocatalytic properties of the films treated with different time were studied by photocatalytic degradation of Rhodamine B with various irradiation time. The results revealed that the as prepared film was composed of crystal phase of much A-TiO2 and a little γ-Al2O3. The film surface was rough and porous. The pores are in the dimensions of 2-8 μm. The photocatalytic experimental results showed that for the same irradiation time, the removal ratio of Rhodamine B of the films gradually increased with increasing the treating time. For each film, the removal ratio of Rhodamine B of the film also gradually increased when increase the irradiation time. The 30 min treated sample exhibited a removal ratio of 80% in 2h irradiation of ultraviolet light.