【作者】 魏大庆；

【导师】 周玉；

【作者基本信息】 哈尔滨工业大学 ， 材料学， 2008， 博士

【摘要】 本文采用微弧氧化法在Ti6Al4V合金表面制备了TiO₂基含磷和含钙磷微弧氧化涂层。通过后续碱热处理对微弧氧化涂层进行表面改性,并采用模拟体液（SBF）浸泡在碱热处理涂层表面形成仿生磷灰石。采用X射线衍射（XRD）、扫描电子显微镜（SEM）、原子力显微镜（AFM）、X-射线光电子谱（XPS）、扫描饿歇纳米探针（AES）、傅立叶变化红外光谱（FT-IR）、透射电子显微镜（TEM）等分析手段研究了微弧氧化涂层碱热处理前后、SBF浸泡前后表面的显微组织结构。深入探讨了碱热处理涂层的形成过程以及诱导仿生磷灰石的机理,并初步评价了碱热处理涂层表面的MG63细胞繁殖行为。以（NaPO₃）₆+NaOH为电解液,制备了TiO₂基含磷微弧氧化涂层（PW） （注:P表示含磷,W表示未修饰涂层）。以Ca（H₂PO₄）₂+Ca（CH₃COO）₂+ EDTA-2Na+NaOH为电解液,制备了TiO₂基含钙磷微弧氧化涂层（CPW） （注:CP表示含钙磷,W表示未修饰涂层）。在一定电压下,钛合金表面的多孔钝化膜被击穿,表面被氧化,溶液中的PO₄^3-、CaY^2-和OH^-等负离子将会被注入涂层中。达到预设电压后,涂层生长分为快速和慢速生长两个阶段。300V下制备PW和CPW涂层表面具有均匀的多孔结构。随着电压升高,涂层中形成金红石相,表面变得粗糙,微孔孔径增大,微孔密度降低,涂层厚度增加,且CPW涂层中钙磷含量及钙磷比增加。在涂层内部Ti、O、Ca和P等元素具有梯度分布特征,膜基界面结合良好。碱处理过程中,PW和CPW涂层表面的Ca、P和Al发生溶解,涂层中的TiO₂相受到碱溶液中OH-离子的攻击形成HTiO₃-离子。对于碱处理PW涂层（PA）（注:A表示碱处理）,HTiO₃-离子进一步与碱溶液中的Na+离子反应形成钛酸钠水合物,且该水合物交错分布形成多孔网络状形貌。后续热处理（400⁷00℃）改变了PA涂层的表面形貌,同时钛酸钠水合物出现脱水并晶化形成Na₂Ti₉O₁₉相。对于碱处理CPW涂层（CPA）（注:A表示碱处理）,HTiO₃-离子进一步吸引碱溶液中溶解的Ca²⁺离子,在涂层表面形成片状钛酸钙水合物,最终CPA涂层表面形成蜂窝状结构。提高碱浓度,有利于钛酸钙水合物形成。CPA涂层经过后续热处理（400⁸00℃）,涂层表面的钛酸钙水合物也出现脱水并晶化形成CaTi₂1O₃8以及CaTiO₃,同时表面形貌发生变化。由于钙的引入,CPW涂层的磷灰石诱导能力高于PW涂层。低电压（200及250V）形成的CPW涂层由于表面释放的钙磷较少,相对降低了SBF的过饱和度,从而降低了磷灰石的诱导能力。高电压（350V⁴50V）会促使涂层中形成大量的金红石,而金红石的磷灰石诱导能力比锐钛矿差,高电压也降低了涂层的磷灰石诱导能力。因此,适中的电压（300V）制备的CPW涂层有利于磷灰石的形成。CPW涂层经过直接热处理（400⁸00℃）以后,涂层中非晶态磷酸钙晶化形成Ca₃（PO₄）₂。热处理导致了涂层的钙磷离子释放能力下降,进一步导致了涂层的磷灰石诱导能力降低。PW和CPW涂层经过碱处理以后,磷灰石诱导能力明显提高。原因是SBF浸泡过程中,涂层表面钛酸盐中Ca2+和Na+离子与SBF中的H3O+离子发生离子交换,形成了丰富的Ti-OH功能团,促进了磷灰石的形核生长。后续的热处理降低了钛酸盐中Ca²⁺和Na⁺离子的释放能力,从而降低了Ti-OH功能团的形成能力,进一步降低了磷灰石的诱导能力。但对于800℃处理CPA涂层具有良好的磷灰石诱导能力。原因是涂层中形成了钙钛矿CaTiO₃,而钙钛矿CaTiO₃（ 0 22）晶面与HA（0001）晶面具有良好的晶体学匹配,可能为磷灰石的形核提供良好的形核位点,两者之间可能形成较小的接触角。所有涂层诱导的仿生磷灰石具有以下特征:含有CO₃^2-、HPO₄^2-功能团以及Mg²⁺离子等,多孔纳米网络状结构和可控的结晶度,且磷灰石在（0001）晶面上具有定向生长特征。Ca₁₀（PO₄）₆（CO₃）_0.5（OH）和Ca₉（HPO₄）_0.5（P O₄）₅（CO₃）_0.5（OH）在热力学和动力学上讲具有形核长大优势。碱处理、碱热处理以及热处理提高了微弧氧化涂层表面的润湿性,增大了涂层表面的粗糙度。MG63细胞在PW、CPW、PA和CPA涂层表面展现了良好的繁殖能力。综上,微弧氧化电压及电解液组成对涂层的组织结构有较大影响。微弧氧化涂层经过碱热处理形成了特殊的表面结构,有利于仿生磷灰石的形成。磷灰石的形成主要受到异质形核能及涂层表面形貌的影响。SBF过饱和度以及晶核与基体的接触角是决定异质形核能大小的两个重要因素。本文中影响涂层表面附近SBF的过饱和度的主要因素有:Ti-O结构对钙磷离子的吸附、Ti-OH功能团的形成和涂层中钙磷的释放含量。磷灰石晶体结构与基体涂层晶体结构的匹配关系对接触角可能有影响。涂层表面具有合适的粗糙度、润湿性则有利于细胞繁殖。更多还原

【Abstract】 TiO₂-based coatings containing P （PW）, as well as containing Ca and P （CPW）, were prepared on the surface of Ti6Al4V by microarc oxidation （MAO）. Alkali- and heat-treatment was proposed to modify the surfaces of the MAO coatings for improving their apatite-forming ability. Biomimetic apatite was obtained by immersing the modified MAO coatings in a simulated body fluid （SBF）. The surface structures of the non- and modified MAO coatings before and after SBF immersion were analysed by X-ray diffraction （XRD）, scanning electron microscopy （SEM）, atomic force microscopy （AFM）, X-ray photoelectron spectroscopy （XPS）, auger electron spectroscopy （AES）, Fourier transform infrared spectroscopy （FT-IR） and transmission electron microscopy （TEM） etc.. The formation mechanism of alkali- and heat-treated MAO coatings and their inducation mechanism for biomimetic apatite formation were disscused thoroughly. In addition, the preliminary investigations regarding to the MG63 cell proliferations on the surfaces of the non- and modified MAO coatings were conducted in this work.An electrolyte containing （NaPO₃）6 and NaOH was used to prepare the PW coatings. And the CPW coatings were prepared in an electrolyte containing Ca（CH₃COO）₂·H₂O, Ca（H₂PO₄）₂·H₂O, EDTA-2Na and NaOH. Under certain applied voltage, the initial passivating film on the surface of Ti6Al4V was broken, and the surface of Ti₆Al₄V was oxidized. Under the applied electric field, the negatively charged PO₄^3-, CaY^2- and OH^- ions etc. could be injected into the MAO coatings. Under the setting voltage, the formation of the MAO coatings shows two stages of quick and slow growth. The MAO coatings formed at 300V show uniform surfaces with porous structure. With increasing the applied voltage, the rutile was formed in the MAO coatings, and the surfaces of the MAO coatings became rougher. At the same time, the thickness of the MAO coatings and the size and number of the MAO pores increased. Moreover, the contents of the Ca and P and the Ca/P ratio in the CPW coatings also increased. In the MAO coatings Ti, O, Ca and P atoms show a graded distribution. In addition, the PW and CPW coatings both show good adhesion with the Ti6Al4V substrate.During the alkali treatment process, the Ca, P and Al of the PW and CPW coatings were dissolved into the alkali solution. TiO₂ phase of the PW and CPW coating was attacked by OH^- ions to form HTiO₃^- ions. In the case of alkali-treated PW coating （PA）, the HTiO₃^- ions could absorb Na⁺ ions from the alkali solution to form sodium titanate hydrates. And a network structure was formed on the surface of the PA coating by the interlacement of the sodium titanate hydrates. After heat-treatment of the PA coating at 400⁷00℃, the surface morphology of the PA was changed and the sodium titanate hydrates were dehydrated and then crystallized forming Na2Ti9O19 phase. In the case of alkali-treated CPW coating （CPA）, the negatively charged HTiO₃- ions could be combined with released Ca2+ ions in alkali solution, forming calcium titanate hydrates with flake-like morphology. And the surface of the CPA coating shows a honeycombed structure. Increasing the alkali concentration facilitates the formation of calcium titanate hydrates. After heat-treatment of the CPA coating at 400⁸00℃, the surface morphology of the CPA was altered and the calcium titanate hydrates was dehydrated and then crystallized forming CaTi21O₃8 and CaTiO₃ phases.The CPW coating shows higher apatite-forming ability compared with the PW coating due to the introducation of Ca element. In the case of the CPW coatings formed at low applied voltage （200 and 250V）, the contents of the Ca and P released from these coatings were little and then the SBF supersaturation decreased relatively, which could futher lower the apatite-forming ability of these coatings. High applied voltages （350⁴50V） would lead to the formation of rutile in the MAO coatings, which does not facilitate the apatite formation. Thus the CPW coating formed at moderate applied voltage of 300V shows good apatite-forming ability. After only heat-treatment of the CPW coatings at 400⁸00℃, the amorphous calcium phosphate was crystallized to form Ca₃（PO₄）₂ phase. Moreover, the ability to release Ca and P of the CPW coating decreased, resulting in a low apatite-forming ability.After alkali-treatment, the apatite-forming ability of the PW and CPW coatings were improved. The reseaon for this is that abundant Ti-OH groups were formed on the surfaces of the PA and CPA coatings during the SBF immersion process via an ionic exchange between Ca²⁺ and Na⁺ ions of the titanates and H3O+ ions of the SBF. The subsequent heat-treatment of the PA and CPA coatings decreased their ability to release Ca2+ and Na+ ions, thus decreasing the formation ability of Ti-OH group, which will further result in a lower apatite-forming ability. However the CPA coating after heat-treatment at 800oC shows good apatite-forming ability due to the formation of perovskite CaTiO₃ phase. The perovskite CaTiO₃ （ 0 22） plane has good crystallographic matching with HA （0001） plane probably providing good sites for apatite nucleation by the epitaxial deposition process, probably forming a small contacting angle between CaTiO₃ and apatite. Biomimetic apatite induced by all the coatings show important characters including: 1) containing CO₃^2-, HPO₄^2- and Mg²⁺ ions etc., 2) pore networks on the nanometer scale and 3) controllable crystallinity. And the apatite is oriented to the （0001） crystal plane. The Ca₁₀（PO₄）₆（CO₃）_0.5（OH） and Ca₉（HPO₄）_0.5（PO₄）₅（CO₃）_0.5（OH） were formed easily relatively according to the analysis of thermodynamics and kinetics.The roughness and wetting ability of the MAO coatings were improved by alkali-treatment, alkali- and heat-treatment and heat-treatment. The PW, CPW, PA and CPA coatings can provide surfaces suitable for the proliferation of the MG63 cells.In short, the applied voltage and electrolyte composition have a significant effect on the structures of the MAO coatings. The alkali- and heat-treatment of the MAO coatings result in special surface structures, facilitating the apatite formation. In this work, apatite formation and growth were mainly affected by the heterogeneous nucleation energy and the surface morphology of the coatings. The SBF supersaturation and the contacting angle between apatite nucleus and substrate have effects on the heterogeneous nucleation energy. In this work, the main factors to affect the SBF supersaturation could involove: 1) the absorption of Ti-O band to Ca2+ ions and phosphate radicals etc., 2) the formation of Ti-OH groups and 3) the contents of Ca and P released from the coating surfaces. In addition, the crystallographic matching relation of apatite and substrate could affect the contacting angle. Furthermore, the coatings with moderate roughness and wetting ability facilitate the cell proliferation.更多还原