Zhao Hua Jiang

Influences of Calcination Ambiences on Phase Composition and High Temperature Oxidation Resistance Property of Ceramic Coatings on Ti–6Al–4V Alloy by Micro-Plasma Oxidation

Compound ceramic coatings with the main crystalline of Al2TiO5 (as-coated samples) were prepared on Ti-6Al-4V alloy by pulsed bi-polar micro-plasma oxidation (MPO) in NaAlO2 solution. The coated samples were calcined in Ar and air at 1000oC, respectively. The phase composition, morphology and element content of the coatings were investigated by XRD, SEM and XRF. The samples treated in Ar and the as-coated ones were calcined in air at 1000oC to study the oxidation resistance of the samples. The results showed that Al2TiO5 decomposed and transformed into corundum and rutile TiO2 during the high temperature calcination. Al2TiO5 decomposed very quickly in air and the proportion of Al2O3 to TiO2 was 44:55 after a complete decomposition. On the contrary, Al2TiO5 decomposed very slowly in argon with the final proportion of Al2O3 to TiO2 of 81:18 on the coating surface. The morphology of the ceramic coatings after the calcination was also different. The coatings calcined in argon were fined: the grains and pores were smaller than those of the coatings calcined in air. The weight gains of both coatings changed in the form of parabola law, and the weight gains of the coated samples treated in argon were comparatively lower than that of the as-coated samples. During the high temperature calcination, the samples treated in argon cannot distort easily, compared with the as-coated ones.

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.

Synthesis, Characterization and Luminescent Properties of a Rare Earth Complex Eu(TTA)3(TPPO)2

A complex of Eu(Ⅲ), HTTA and TPPO was synthesized in alcohol (HTTA= 2-Thenoyltrifluoroacetone and TPPO=Triphenyl phosphine oxide )and its corresponding single crystal was obtained. The complex was characterized by IR,UV, X-ray single crystal diffraction.The photoluminescent and electroluminescent properties of the complex were studied. The results showed that the spectra structure characterization is consistent with that of single-crystal diffraction. The complex exhibited ligand-sensitized red emission, and it has higher sensitized luminescent efficiency and good thermal stability.In device ITO/PVK/ Eu(TTA)3(TPPO)2/Al, Eu3+ may be excited by intramolecular energy transfer from ligand as observed by electroluminescence. The main emitting peak at 614 nm can be attributed to the europium of 5D0→7F2 of Eu 3+ ion and this process results in the enhancement of red emission from electroluminescence device. The present study may be important and helpful for the development of red color rare earth display applications.

Preparation and Photocatalytic Property of WO3-TiO2 /Ti Ceramic Film via Anodic Oxidation Treatment

The high efficient WO3-TiO2/Ti ceramic film was prepared on the surface of titanium by the approach of anodic oxidation in order to make the absorbable spectrum of catalyst spread to the visible region and restrain the high recombination rate of electron-hole pairs during photoreaction. The surface morphology and the distribution of elements were studied with scanning electron microscopy and energy dispersive spectroscopy. The phase composition of the films was investigated with XRD. The results showed that the main components in the coating were WO3, rutile TiO2 and anatase TiO2. The compound WO3-TiO2/Ti ceramic film enlarged the range of the reacting visible light and increased the absorbing intensity. The rhodamine B was successfully photodegraded under visible light irradiation by WO3-TiO2/Ti catalyst films. It was found that the highest degradation rate of rhodamine B was achieved through an optimal W dosage of 4.2 %(wt %) in WO3-TiO2/Ti ceramic film. It was also confirmed that the recombination rate of electron-hole pairs in WO3-TiO2/Ti ceramic film declined due to the existence of WO3 in TiO2/Ti ceramic film.

Preparation of Ceramic Composite Coatings on Ti-6Al-4V Alloy by Surface Nanocrystallization/Micro-Arc Oxidation

Nanostructured surface layer was produced on the Ti-6Al-4V alloy by surface mechanical attrition treatment (SMAT) technique, and then the ceramic composite coatings of surface nanocrystallization/ micro-arc oxidation (SNC/MAO) were prepared on the nanocrystallized surface of Ti-6Al-4V alloy by pulsed single-polar micro-arc oxidation in NaAlO2 solution. The phase composition, morphology of surface and section and element content of the nanostructured surface layer and the ceramic coatings were investigated by XRD, TEM, SEM and EDS, respectively. The results showed that after the SMAT technique treatment for a short period of time, the surface layer was refined into ultrafine grains. The thickness of the coatings on the substrate treated by SMAT technique is about 10μm by micro-arc oxidation, which is thicker than the ones on the substrate untreated by SMAT technique, and the ceramic coatings are mainly composed of Al2TiO5. Besides, a bright interface layer comes out between the substrate and the coating when the substrate treated by SMAT technique. The influences of the SMAT technique on the surface morphology of the ceramic coatings also changed. The coatings using the SMAT technique were more compact and less porous than the ones on the substrate untreated by SMAT technique. The content of elements in the nanostructured surface layer on Ti-6Al-4V alloy had changed after the SMAT technique: the content of Ti increased, the content of V decreased, and the content of Al changed a little. The contents of Al and P in the coating increased while the content of Ti decreased.

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.

Self-Assembly of Large Scale CdS/TiO2 Film Photocatalyst

CdS/TiO2 composite films with different Cd:Ti atomic ratio were prepared by a new straightforward particulate layer-by-layer method. Titanium dihydroxide and thiourea were used as precursors. Raman and X-ray photoelectron spectroscopy analysis for the composite films revealed that the TiO2 formed from titanium precursor retarded the crystal growth of CdS. Luminescence and UV–vis absorption spectra investigation showed that emission and absorption band of CdS/TiO2 blue shifted as crystal size of CdS decreased. Furthermore, hydrogen formation curves revealed that hydroxyl of CdS/TiO2 films plays an important role in water splitting reaction under both UV and visible light irradiations.

Influence of Cu2+ Doping on the Photocatalytic Activity of TiO2 Film

With the approach of anodic oxidation, TiO2/Ti film doped with Cu2+ was produced in H2SO4 electrolyte mixed with CuSO4. The surface morphology and the roughness of the films were studied with atomic force microscopy. The phase composition of the films was studied by X-ray diffraction. The photocatalytic activity of the films was compared through the photocatalytic degradation rate of phenol. The relations of the photocatalytic activity to the concentration of Cu2+, the microstructure and the surface roughness of the film were investigated. The results showed that Cu2+ increased the surface roughness and restrained the growth of crystal. In addition, the phenol in aqueous solution was successfully photodegraded under visible light irradiation by Cu2+-TiO2/Ti film. The composition and structure of the film affected the catalytic activity greatly. Compared with TiO2/Ti film, the recombination rate of e- and h+ of Cu2+-TiO2/Ti film was decreased.

Preparation of Micro-Arc Oxidation Ceramic Coating and Application in Degradation Rhodamine B

A ceramic coating grows on the surface of Q235 carton steel in situ by the micro-arc oxidation method and the silicate electrolyte system; and the phase composition, surface topography and elementary composition of the ceramic coating are analyzed by X-ray diffractometer (XRD), scanning electron microscope (SEM) and X-ray photoelectron spectroscopy (EDS). The results show that the ceramic coating growing on the surface of Q235 carton steel in situ presents an irregular porous structure; and the electrolyte and the element in the basal body exist in the ceramic coating in the form of amorphous state. And then, the author degrades the rhodamine B solution by the home-made ceramic coating and H2O2 Fenton system, so that the degradation rate of the rhodamine B solution can reach 97%; and meanwhile, the degradation rate is not reduced along the increased using times.

Microstructure and Protertise of Self-Lubricative Ceramic Coatings on Carbon Steel by PEO in Aluminate Electrolyte Containing Graphite

Self-lubricative ceramic coatings were prepared on Q235 carbon steel by plasma electrolytic oxidation (PEO) in aluminate electrolyte containing graphite. The microstructure of the PEO coatings were examined. Influence of graphite in electrolyte on the coating growth properties was analyzed according to the voltage vs. time plots. Effect of graphite concentration on the properties of the coatings such as bonding strength, surface roughness and thickness were studied. The tribological behavior of the coating was primarily evaluated.The results showed that the self-lubricative coatings consisted of FeAl2O4, Fe3O4 and a certain amount of graphite. With increasing the concentration of graphite in the electrolyte, the coating growth gradually became stable with lower breakdown voltage and end voltage. The bonding strength and the thickness of the coating were not strongly affected by the graphite concentration whose value remained approximately 19Mpa and 110μm, respectively. With increasing the graphite concentration, the surface roughness first decreased and then increased a little. The friction coefficient of the coatings also varied with the concentration of graphite. When the concentration of graphite was 8 g/l, the tribological property of the coatings was the most excellent with the friction coefficient bellow 0.1.