Papers by Keyword: Micro-Arc Oxidation (MAO)

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Authors: Yong Qian Wang, Xu Dong Jiang, Chun Xu Pan
Abstract: In this paper, a micro-arc oxidation (MAO) approach is introduced for “in-situ” preparing TiO2 composite layer upon the surface of titanium alloy (Ti-6Al-4V) substrate. The surface morphologies, chemical compositions, crystal microstructure and photocatalytic properties of the layers were investigated by using a field emission scanning electron microscope (FE-SEM), energy dispersive spectrometer (EDS), X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), electro-chemical workstation and UV-Vis spectrophotometer. The experimental results revealed that photocatalytic performance of the TiO2 composite layers was much higher than that of the pure TiO2 layer and also exhibited absorption under the visible light irradiation.
Authors: Hui Zhao, Zhen Liu, Zhong Han
Abstract: Characteristics of ceramic coatings on AM50 magnesium alloy by micro-arc oxidation in silicate and phosphate electrolytes have been investigated in this study. This study reveals that the thickness of the ceramic coatings increases with the treated time in both electrolytes, the growth rate of ceramic layer in phosphate is faster than that in silicate electrolyte. The surface roughness of the ceramic coating formed in phosphate electrolyte is higher than that formed in silicate electrolyte. The coatings formed in silicate, containing a thicker inner barrier layer and a thinner outer porous layer, consist of MgO, Mg2SiO4 and MgSiO3 phases. For the coatings formed in phosphate, the outer porous layer is thicker than the inner layer, it consist mainly of MgO and MgAlO4 phases.
Authors: Zhen Fei Liu, Wei Qiang Wang, Min Qi
Abstract: A porous titania (TiO2) coating with vermiform slots was prepared on the Ti substrate through micro-arc oxidation (MAO) treatment using sodium tetraborate as electrolyte. Morphologies and phase structure were analyzed by scanning electron microscopy (SEM) and X-ray diffraction (XRD), respectively. Results show that the rutile phase increases and anatase decreases gradually with increasing MAO time. The electrolyte of sodium tetraborate has significant influence on the formation of vermiform coatings, which determine the corrosive patterning in the first stage during MAO processing. The evolution of vermiform morphology is proposed as followed: some corrosive pores appear on the surface before arcing; afterward, the adjacent micropores in the dense regions link each other due to the high temperature result from continuous arc action; then, the micropores grow up to big pits and combine with each other with increasing MAO treating time; finally, the vermiform morphology forms on the surface of Ti metal.
Authors: Ping Shi, Xue Dong Han
Abstract: Magnesium alloys are being used as structural components in industry because of their high strength to weight ratio. But their high electrochemical activity and poor corrosion resistance limited their applications. Therefore, surface modifications are needed for protection purpose. This paper studied the anodic micro-arc oxidation and electroless Ni-P plating surface modifications on AZ80 magnesium alloy. The SEM, XRD and EDS were used to characterize the surface coating. It shows that a micro-porous MgO layer with the pores size 5 – 20 μm was fabricated on the bare magnesium alloy. The nodule Ni-P deposition could be prepared on the out layer of MgO with Ni/P atomic ratio being 1.4. The pores in MgO layer could be sealed by the following Ni-P deposition. Therefore the corrosion resistance of the magnesium alloy could be further improved.
Authors: Ping Huang, Ke Wei Xu, Bob B. He, Yong Han
Abstract: The surface modification of titanium by micro-arc oxidation under different voltages was processed to achieve good direct oseointegration. The new technique of two-dimensional X-ray diffraction was used to measure the residual stress of the layer. The results show that a porous titania layer containing Ca and P is obtained by micro-arc oxidation. The pore size and Ca/P of the layer are affected by the voltage. The high voltage can induce forming CaTiO3. The residual stress under different voltage is compressive stress and increases with the improvement of the voltage.
Authors: Ahmet Aral, M. Gunyuz, Murat Baydogan, Nevin Gul Karaguler, Ercan Olcay, Huseyin Cimenoglu
Abstract: In this study, micro porous oxide layer was formed on a Ti6Al4V alloy by the micro arc oxidation process in an electrolyte containing (CH3COO)2CaH2O + Na3PO4 with appropriate amount of silver containing agent. A wide spectrum antibiotic was also applied to the surface. Samples were subjected to antimicrobial activity tests in accordance with JIS Z 2801 standard against E.coli and the results were compared with those of original Ti6Al4V sample. First experimental results presented here showed that the micro arc oxidation process improve the antibacterial activity of Ti6Al4V alloy surface and further improvement could be obtained upon antibiotic application in addition to the micro arc oxidation process.
Authors: Yan Tang, Jin Yong Xu, Fang Yong Ye, Cheng Gao, Jing Chun Zhang, Ya Juan Liu
Abstract: To research the tribological properties of micro-arc oxidized ceramic coating in extreme friction condition, ceramic coatings were tested with 1000# waterproof sand paper friction pair for the first time. The phase composition of ceramic coating was analyzed by X-ray diffraction (XRD).Micro structures of ceramic coating surface were observed by scanning electron microscopy (SEM). Friction coefficient of ceramic coating was measured by ball-on-disc wear tester with a 3 mm steel ball. Wear weight loss and wear rate of ceramic coating were measured and calculated by photoelectron balance. The results show that ceramic coatings in various roughnesses have different former wear rates and close wear rates at stable stage. Under water-lubricated condition, wear rate is as low as 0.2 mg/min to 0.3 mg/min. The antiwear behavior of ceramic coating is about 5.3 times compared to aluminium alloy at dry friction. While under water-lubricated condition, the antiwear behavior of ceramic coating improves about 94 times compared to aluminium alloy. The friction coefficient of loose layer is higher than compact layer at dry friction. And there are positive correlation between wear rate and surface roughness of ceramic coating. So it can be verified that compact layer has well antiwear behavior better than loose layer.
Authors: Q. Ma, Y.J. Wang, Cheng Yun Ning, Hai Mei Cheng, Zhao Yi Yin
Abstract: Porous bioactive thin film on commercially pure titanium substrate was prepared by micro-arc oxidation (MAO) in electrolytic solution, which contained calcium acetate, β-glycerol phosphate disodium salt pentahydrate (β-GP) and lanthanum nitrate. The phases and microstructure of the bioactive films were examined by X-ray diffraction, scanning electron microscopy with energy dispersive X-ray spectrometer and electron probe microanalysis. The results showed that: (1) porous bioactive films with about 10μm were formed on titanium substrate by MAO; (2) phases of the thin films were hydroxyapatite, anatase and rutile; (3) elements of Ca, P, and Ti of films were identified by EDS.
Authors: Chen Ma, Ying Hui Wang, Mu Qin Li, Li Jie Qu
Abstract: Rare earth/calcium phosphate composite coatings were fabricated on the surface of Ti-6Al-4V by micro-arc oxidation (MAO) technique. The wear properties and corrosion resistant of rare earth/ calcium phosphate composite coatings in the simulated body fluid (SBF) have been investigated and the bioactivity of the composite coatings were evaluated. The results show that the friction coefficient of the composite coatings in the SBF is only 0.15~0.18 and the anode polarization potential of the coating has been obviously enhanced about 0.18V compared with that of coatings of calcium phosphate coatings. So the composite coatings have excellent wear and corrosion resistant properties. XRD analysis indicates that the composite coatings can induce hydroxyapatite to form on its surface after soaked in SBF for 9d, which shows that the composite coatings own good bioactivity.
Authors: Dong Zhang, Bao Ping Zhang, Zhi Ge Li, Lin Wang, Bin Liu, Jin Qing Wang
Abstract: This study is to evaluate the biocompatibility of HAP/Ti gradient coating by microarc oxidation and biomimetic process. Titanium alloys were activated by microarc oxidation (MAO), and immersed in simulated body fluid to prepare HAP/Ti gradient coating. Scanning electron microscopy (SEM) had been used to investigate the microstructure of the coatings. The biocompatibility of the coatings was evaluated by animal acute and subacute toxicity test, micronucleus test, hemolysis test, and oral mucosa test. The results showed HAP/Ti gradient coating was successfully fabricated on the substrate. The animal experiment showed the coating had not short-term toxicity, oral mucosa irritation, and micronucleus occurrence rate was 3.2 ‰ and hemolysis rate was 2.5%. The HAP/Ti gradient coating made by MAO and biomimetic process showed good bio-security and compatibility, it may be new oral implant materials.
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