In situ composite coating of titania-hydroxyapatite on titanium substrate by micro-arc oxidation coupled with electrophoretic deposition processing

In situ composite coating of hydroxyapatite (HA)/TiO₂ were produced on titanium (Ti) substrate by micro-arc oxidation coupled with electrophoretic deposition (MAO&EPD) technique with different concentrations of HA particles in the 0.2 M NaOH electrolyte solution. The surface morphology and chemical composition of the hybrid coating were effected by HA concentration. The amount of HA particles incorporated into coating layer increased with increasing HA concentration used in the electrolyte solution. The corrosion behavior of the coating layer in simulated body fluids (SBF) was evaluated using a potentiodynamic polarization test. The corrosion resistance of the coated sample was increased compared to the untreated Ti sample. The in vitro bioactivity assessment showed that the MAO&EPD treated Ti substrate possessed higher apatite-forming ability than the untreated Ti. Moreover, the apatite-forming ability had a positive correlation with HA concentration. In addition, the cell behavior was also examined using cell proliferation assay and alkaline phosphatase ability. The coating formed at HA concentration of 5 g/L exhibited the highest cell ability.     

Preparation of hydroxyapatite-containing titania coating on titanium substrate by micro-arc oxidation

Hydroxyapatite-containing titania coatings on titanium substrates were formed by micro-arc oxidation (MAO) in electrolyte containing calcium acetate monohydrate (CH₃COO)₂Ca·H₂O) and sodium phosphate monobasic dihydrate (NaH₂PO₄·2H₂O) using a pulse power supply. Scanning electron microscopy (SEM) with Energy dispersive X-ray spectrometer (EDX) and X-ray diffraction (XRD) were employed to characterize the microstructure, elemental composition and phase components of the coatings. The coatings were rough and porous, without apparent interface to the titanium substrates. All the oxidized coatings contained Ca and P as well as Ti and O, and the porous coatings were made up of anatase, rutile and hydroxyapatite. Such MAO films are expected to have significant applications as artificial bone joints and dental implants.     

Alumina coating formed on medical NiTi alloy by micro-arc oxidation

Al₂O₃ coatings were prepared on NiTi alloy by micro-arc oxidation in an aluminate solution. Thin-film X-ray diffraction (TF-XRD) indicated that the coating consisted of only Al₂O₃ crystal phase. Energy dispersive X-ray spectrometer (EDS) showed that there was about 2.53 at.% Ni in the surface layer, which was greatly lower than that of NiTi substrate. Scanning electron microscopy (SEM) showed that the coating exhibited a typical porous surface and excellent adhesive interface between the coating and the substrate. Direct pull-off test showed that the coating had a mean coating-substrate bonding strength of 28 ± 2 MPa. The results of electrochemical impedance spectroscopy (EIS) study and potentiodynamic polarization test indicated that the corrosion resistance of the coated sample was increased by two orders of magnitude compared with uncoated sample.     

Ultraviolet-enhanced bioactivity of ZrO2 films prepared by micro-arc oxidation

Macroporous and nano-crystallized monoclinic zirconia (m-ZrO₂) film was prepared by micro-arc oxidation (MAO). The effect of ultraviolet (UV) irradiation on the microstructure, water contact angle and bioactivity of the film were investigated. The MAO-formed ZrO₂ film exhibits high hardness and elastic modulus. UV irradiation of the ZrO₂ film does not alter surface morphology, grain size and phase component, however, can significantly improve hydrophilicity and bioactivity of the film. The enhanced hydrophilicity and bioactivity are thought to result from the abundant basic Zr-OH groups on the UV-irradiated film, which have relative long-term stability.     

Chemical etching of micro-plasma oxidized titania film on titanium alloy and apatite deposited on the surface of modified titania film in vitro

TiO₂ film was deposited on titanium alloy by micro-plasma oxidization (MPO) in an electrolyte containing (NaPO₃)₆ and NaOH. A chemical etching (NaOH aqueous solution) was used to modify the surface of the MPO film to form specific surface structure favorable for apatite deposition. The surface of the MPO film was mainly composed of anatase, while that of the chemically etched MPO (CE-MPO) film shows anatase phase containing Na, Ti and O. Moreover, ribbon-like products with an interlaced morphology were found on the surface of the CE-MPO film. During the chemical etching process, phosphorus of the surface of the MPO film dissolved into the NaOH aqueous solution. Negatively charged HTiO₃⁻ ions are formed on the MPO film surface due to the attack of OH⁻ ions on TiO₂ phase of the MPO film. The negatively charged HTiO₃⁻ ions could incorporate sodium ions from the NaOH aqueous solution to form sodium titanate. When incubated in a simulated body fluid (SBF) for 7 and 14 days, the MPO film does not exhibit apatite-forming ability; however, apatite was deposited on the CE-MPO film probably due to the formation of hydroxyl functionalized surface via an ionic exchange between Na⁺ ions of the CE-MPO film and H₃O⁺ ions of the SBF.     

高能喷丸预处理对钛表面组织及生物活性微弧氧化层的影响

为了提高钛表面的生物活性,利用微弧氧化工艺分别在普通粗晶钛和表面高能喷丸细晶钛上制备了多孔TiO2氧化层。经光镜和透射电镜观察,喷丸钛表面形成厚度40μm,直径100～200nm的等轴晶结构层。利用扫描电镜(带能谱分析)和X射线衍射仪对氧化层表面形貌、成分和相组成进行分析。结果表明,高能喷丸钛的表面生成的氧化层中含有α-Ca3(PO4)2相且钙磷百分含量提高。在粗糙的高能喷丸钛表面,微弧氧化速度在不同位置有所不同,氧化层与基体形成微机械咬合,基层结合力提高。     

TA4微弧氧化陶瓷膜层的结构与性能研究

利用微弧氧化法在纯钛TA4表面制备以Ti O2为主体富含钙磷的多孔陶瓷膜层。采用扫描电镜、X射线能谱仪、X射线衍射仪、拉曼光谱仪、接触角测量仪及电化学工作站观测与分析陶瓷膜层的微观形貌、元素成分及相组成,探讨微弧氧化对其润湿性及耐蚀性能的影响。结果表明,TA4微弧氧化陶瓷膜层表面粗糙多孔,为锐钛矿相与金红石相Ti O2的混晶结构,金红石相的质量分数约为74.39%。TA4经微弧氧化改性后,表面粗糙度增加了1个数量级,接触角明显下降,表面能提高了87.05%,极性力分量增加了166.07%,体现出更好的润湿性能;自腐蚀电位正移0.53 V,腐蚀电流密度与腐蚀速率均减少了3个数量级,表现出更优的耐腐蚀性能。     

Effect of surfactants on surface morphology of ceramic coatings fabricated on magnesium alloys by micro-arc oxidation

Ceramic coatings fabricated by micro-arc oxidation generally possess a foam-like structure with high bulk porosity which restricts them from even wider technical application. Based on interfacial tension modifying theory, different surfactants are added into the electrolyte to inhibit the generation of pores within ceramic coatings. The results indicate that surfactants influence strongly the morphology of ceramic coatings and play an essential role to fabricate a ceramic coating with low porosity. Once surfactants are added into the solution, all the coatings exhibit almost identical morphology and reveal a considerable decrease of pores' number.     

Influence of cathodic current on composition, structure and properties of Al2O3 coatings on aluminum alloy prepared by micro-arc oxidation process

Alumina coatings on aluminum alloy were prepared by micro-arc oxidation (MAO) process using DC and AC power supplies, respectively. In comparison with the coating deposited by DCMAO, the influence of the cathodic current on the composition, structure and properties of the ACMAO coating was investigated. It is found that the coating deposited by DCMAO is composed of α-Al₂O₃, whereas the coating deposited by ACMAO has a mixture composition of α-Al₂O₃ and γ-Al₂O₃. The results of properties show that compared with the coatings deposited by DCMAO, the ACMAO coatings possess higher density, hardness and corrosion resistance. It can be attributed to that the DCMAO coating is rougher and existing much more micro-cracks in its inner layer. As a result, the adhesion of the DCMAO coating to the substrate decreases.     

Study on bioactivity and bonding strength between Ti alloy substrate and TiO2 film by micro-arc oxidation

In this study, the Ti alloy substrate was simultaneously coated with TiO₂ film and hydroxyapatite using micro-arc oxidation, a relatively new surface modification technique where thick, hard, and anticorrosive oxide coatings can be easily and cost-effectively fabricated. Pulsed DC power and various voltages were applied to the Ti alloy substrate. Citric acid, ethylene diamine, and ammonium phosphate were also dissolved as electrolytes followed by the dispersion of hydroxyapatite nanoparticles into those prepared electrolytes. The effects of the composition and applied voltage on the bonding strength, bioactivity, cell attachment and cytotoxicity were investigated. It was observed that the simultaneously coated TiO₂ and hydroxyapatite samples showed improved bioactivity, cell attachment and viability, while maintaining the bonding strength between the coated film and substrate.     

TC11微弧氧化膜制备及其结构性能研究

在Na2SiO3-Na2WO4-NaOH混合电解液中,利用微孤氧化(MAO)技术在TC11合金表面制备了氧化膜.用扫描电镜(SEM),X射线能谱仪(EDS),X射线衍射仪(XRD)对氧化膜微观结构、化学成分、厚度以及相组成进行了分析,采用HVS-1000维氏显微硬度计、MFT-4000划痕试验机、电化学测量系统完成氧化...     

MAO-DCPD composite coating on Mg alloy for degradable implant applications

Magnesium (Mg) is a promising metallic material for use as degradable orthopedic implants. The density and Young's modulus of Mg are close to those of human bone, and it is non-toxic and degradable in body fluids. However, the realization of Mg as an implant material is hampered by its high corrosion rate. The present article aims at improving the corrosion resistance and bioactivity of a Mg alloy AZ80 via surface treatment. AZ80 was coated with a composite coating consisting of an oxide layer formed by micro-arc oxidation (MAO) and a top layer of dicalcium phosphate dihydrate (DCPD, CaHPO₄·2H₂O) fabricated by electrodeposition. The corrosion behavior and apatite-forming ability in simulated body fluids (SBFs) were studied using hydrogen evolution measurements and SEM. The results show that the MAO-DCPD composite coating significantly reduces the corrosion rate of AZ80 and at the same time enhances the deposition of apatite on the coating.     

Direct synthesis and characterization of bifunctional Me-Zr-MCM-41

Methyl group functionalized Zr-MCM-41 was synthesized by the hydrothermal method. The obtained Me-Zr-MCM-41 materials were characterized by X-ray diffraction, N₂ physisorption, transmission electron microscopy, Fourier transform infrared spectroscopy and Ultraviolet-visible diffuse reflectance spectroscopy. The results indicated that Zr was highly dispersed in the framework of MCM-41, and methyl group was stable enough to endure the acid treatment for removing the template. The measurement results of the surface hydrophobic/hydrophilic properties showed that the surface hydrophobicity of Me-Zr-MCM-41 materials increased with increasing the content of methyl groups.     

通过仿生法在硅橡胶表面制备磷灰石薄膜的研究

用CaCl2的乙醇溶液和K2HPO4溶液对硅橡胶进行预处理,将处理过的硅橡胶分别浸渍于模拟体液和钙磷饱和溶液中来制备磷灰石薄膜.利用薄膜X射线衍射、红外吸收光谱和扫描电子显微镜对形成的薄膜进行了表征.结果表明,分别在模拟体液中7d和在钙磷饱和溶液中5d后,硅橡胶表面形成了一层磷灰石薄膜;在模拟体液中的薄膜表面呈网状并分布有许多球状晶粒,在钙磷饱和溶液中的薄膜为结晶良好的片状晶体.     

镁合金微弧电泳复合膜层的微观结构和抗腐蚀性能

采用恒压模式在硅酸盐系电解液中制备镁合金微弧氧化陶瓷层,对比研究了微弧电泳和直接电泳镁合金的截面形貌、结合力大小以及抗腐性能差异.结果表明:在镁合金微弧氧化陶瓷层的表面可制备电泳有机层,简化了电泳工艺;在微弧电泳复合膜层间形成机械咬合力和化学键力,附着力等级可达1级;经800 h中性盐雾腐蚀试验后,复合膜层腐蚀增重量和样品表面的形貌均没有明显的变化;与微弧氧化陶瓷层和直接电泳有机层相比,微弧电泳复合膜层的电化学稳定性显著增强,腐蚀电流相分别减少了约5个和2个数量级.     

钛合金微弧氧化一步制备含石墨的减摩涂层

为了进一步提高钛合金表面微弧氧化陶瓷涂层的摩擦磨损性能,在石墨分散的Na2CO3-Na2SiO3-KOH电解液溶液中一步制备了含自润滑微粒的微弧氧化复合涂层.利用X射线衍射仪(XRD)、X射线光电子能谱仪(XPS)和扫描电子显微镜(SEM)研究了未添加和添加石墨微弧氧化涂层的相组成和微结构,采用往复式球-盘试验机评价了两种涂层的摩擦学性能.结果表明:加入到电解液中的石墨在微弧氧化过程中进入到涂层中,从而得到含有固体润滑微粒的复合涂层;在干摩擦条件下,含石墨的微弧氧化涂层相比于不含石墨的涂层具有更小的摩擦系数.     

镁锂合金表面陶瓷膜的制备工艺及耐蚀性能

在硅酸盐体系中,利用单相脉冲微弧氧化技术在Mg-5wt%Li合金表面原位生长陶瓷膜.利用扫描电镜、X射线衍射、电化学分析、盐水浸泡等方法研究了陶瓷膜的形貌特征、相结构及耐腐蚀性能.结果表明:硅酸盐电解液体系中生长的陶瓷膜主要含有MgO相和少量的MgSiO3相,微弧氧化陶瓷膜试样与基体相比,耐点腐蚀性能显著提高,盐水浸泡过程中陶瓷膜主要发生严重腐蚀.通过正交试验优化耐蚀膜层的制备工艺条件,得到最佳工艺为电流密度2A/dm2、频率300Hz、占空比80%、处理时间20min.     

医用多孔NiTi合金表面微弧氧化改性研究

为解决多孔Ni Ti合金耐蚀性降低和Ni离子释放量增大而引起的使用安全性问题.本文采用微弧氧化技术对医用多孔Ni Ti合金进行表面改性处理,研究结果表明,微弧氧化处理并未改变多孔Ni Ti合金原有的孔隙结构和孔隙率,只在其外表面和孔隙内表面均形成了典型的微弧氧化多孔涂层.该涂层主要由氧化铝相组成,并含有少量的Ti和Ni元素,且外表面涂层的Ti和Ni含量要略低于孔隙内表面涂层.微弧氧化涂层提高了多孔Ni Ti合金的表面接触角,将原有的亲水表面转变成了疏水表面.经微弧处理后,多孔Ni Ti合金的耐蚀性较基体提高了1个数量级以上,Ni离子释放量也较基体降低了1个数量级以上.     

Nanoporous composite of carbon nanosheets and functional titania nanoparticles formed by reassembling of exfoliated graphite oxides with colloidal titania

Reassembling of exfoliated graphite oxide (GO) layers by contacting with titania clear sol gives a novel nanoporous composite of carbon nanosheets and functional titania nanoparticles, in which titania particles with an evident brookite structure or a mixed phases of anatase and brookite are encapsulated on the basal plane of and in between the inner surfaces of carbon nanosheets without aggregating together or depositing only on the edges of carbon nanosheets. These composites successfully combine properties of carbon nanosheets and titania nanoparticles, exhibiting an enhanced adsorptivity and a good photocatalytic activity toward organic dyes due to its unique structure, better porosity, and compatible surface affinity.     

AZ80镁合金表面冷喷涂铝/微弧氧化复合涂层耐蚀性能

采用冷喷涂技术在 AZ80 镁合金表面制备一层纯铝涂层,然后通过微弧氧化技术在纯铝涂层表面成功制备纯铝/氧化铝复合涂层.使用扫描电镜(SEM)、能谱仪(EDS)、X 射线衍射仪(XRD)分析涂层的表面和截面形貌、成分、相结构,并利用动电位扫描技术和电化学阻抗谱研究涂层在 3.5%NaCl(质量分数)溶液中浸泡不同时间(30 min和 7 天)的腐蚀行为.结果表明:浸泡 30 min后,纯铝涂层和纯铝/氧化铝复合涂层的腐蚀电流密度分别为 3.7×10－6 ,8.0×10－7 A·cm－2 ;浸泡 7 天后,腐蚀电流密度分别为 9.0×10－6 ,1.8×10－6 A·cm－2 ,纯铝/氧化铝复合涂层和冷喷涂铝涂层均能有效延缓镁合金基体腐蚀.其中,微弧氧化复合涂层的耐蚀性约为冷喷涂纯铝涂层的 5 倍,耐蚀性的进一步提高归因于微弧氧化陶瓷层优异的物理屏障作用.