【作者】 李慕勤；

【导师】 杨士勤；

【作者基本信息】 哈尔滨工业大学 ， 材料加工工程， 2007， 博士

【摘要】 生物涂层设计模仿人骨结构、功能和成分,采用高速火焰喷涂方法,将底层和表层材料复合,获得Ti6Al4V表面仿生生物涂层,即人工骨涂层材料。涂层的线膨胀系数、孔隙度、生物活性、涂层晶粒尺寸、骨性结合均实现梯度变化,底层和工作层皆具有人工骨功能。喷涂材料底层以钛为主,添加底釉生物玻璃(G),工作层粉体为HA,添加生物活性玻璃(BG),研究粉体粒度和添加剂加入量对涂层特性的影响。采用机械拉伸法测定涂层结合强度;基于掠入射X射线衍射方法测量涂层的宏观残余应力;在模拟体液环境下,对涂层进行极化曲线测定,研究涂层腐蚀行为;采用TG-DSC研究粉体和涂层析晶、分解和晶化处理温度,计算粉体的析晶活化能;通过XRD、SEM、TEM、AFM等手段研究涂层组织结构和界面特性;采用体外模拟研究底层和工作层表面类骨磷灰石的生长及涂层材料与成骨细胞的生物学行为;以犬为种植对象研究种植体的骨性连接行为。生物涂层的结合强度受喷涂粉体粒度、G和BG添加量、晶化处理工艺影响。其中,80wt.%Ti-20wt.%G底层,80wt.%HA-20wt.%BG为工作层,晶化处理后涂层结合强度分别为52MPa和33MPa,达到口腔种植体要求的标准。喷涂生物涂层产生残余压应力,压应力的大小与喷涂材料及材料的粒子尺寸有关。压应力的原因主要是喷射冲击残余应力。通过G和BG调整涂层线膨胀系数,使涂层的热应力下降。涂层断裂形式为层片剥离、粒子内部开裂和粒子间断裂。生物涂层组织结构和界面特征受喷涂送粉方式、G和BG粒度、添加量、晶化处理影响。在Ti粉中添加20wt.%的G,Ti/G复合析晶活化能高于单体G;在HA中加入20 wt.%的BG, HA/BG复合,使析晶活化能进一步降低。涂层经晶化处理后,在Ti6Al4V基体与底层界面结合处存在3μm左右过渡带,伴随有微米和纳米粒子析出,使基体与喷涂界面接触部位通过氧化、扩散和玻璃浸润实现冶金结合。Ti/G底层有R-TiO2、A-TiO2、Na2Ti6O13相沿涂层裂纹处析出,起到愈合作用。HA/BG工作层也同时析出纳米级和微米级的HA和Na2Ca(PO4)F,增加了表层的生物活性。在体外模拟环境下对涂层表面类骨磷灰石的生长规律研究得出,Ti/G涂层中TiO2能够为类骨磷灰石提供成核位置形成针状纳米级类骨磷灰石(CHA)。工作层中BG的加入使涂层表面溶解倾向加大,有利于磷灰石的生长。以8Ti2G为底层,8H2B为工作层形成的生物复合涂层具有抗电化学腐蚀能力,而且对成骨细胞的生物学行为无干扰、无抑制,能促进成骨细胞的黏附、生长。以犬为种植对象,种植体的骨性结合能力为8H2B>HA>8Ti2G。8H2B中由于BG活性高、溶解快,使涂层和体液中Ca-P向界面迁移,形成微孔为成骨细胞向涂层中生长提供通道和生长空间,利于在种植材料表面形成CHA,达到生物化学键合,从而增加种植体初期稳定性。更多还原

【Abstract】 High velocity flame spraying was adopted in this study to prepare biocoating on Ti6Al4V substrate. Bio-coating was designed on the basis of simulating the structure, the function and the chemical composition of the natural bone. Ti6Al4V with a surface biomemtic coating, i.e., coating materials of artificial bone, in which a bottom layer and a surface layer were integrated, was prepared by high velocity flame spraying. The coating has characteristics of gradient change of linear expansion coefficient, controlled porosity, bioactivity and crystal size. Both the bottom layer and the working layer have the function of artificial bone, insuring the service life and the stability of implant at initial stage.The coating material for the bottom layer was mainly pure titanium powder with addition of glaze glass (G). The coating material for the working layer was mainly HA powder with doped bioactive glass (BG). Effects of the powder size and the additive content on the characteristics of the coatings were investigated. The bonding strength of the coatings was tested by tensile testing. The residual macro-stress in the coatings was characterized by grazing incidence X-ray diffraction. Polarization curves were measured to study the corrosion behavior of the coatings in simulated body fluid (SBF) environment. By the use of TG-DSC, crystallization, docomposition and heat treatment temperature of the powder and coatings were determined. The crystallization activation energies of powders were also calculated. The microstructure and the interface characteristics of the coatings were examined by means of XRD, SEM, TEM and AFM. The growth of bone-like apatite on the surface of coatings and the biological behavior of coating materials and osteoblast were investigated in vitro. The osseointegration behavior on the implants inserted into dogs was studied in vivo.The bonding strength of biocoating was affected by the granularity of the spraying powder, the addition content of G and BG, and the crystallization process. The bonding strength of the bottom layer (80wt.%Ti-20wt.%G) and the working layer(80 wt.% HA-20wt.%BG), were 52MPa and 33MPa, respectively, meeting the standard requirements for dental implants. The residual compressive stress in the coatings has relationship to the sprayed materials and the particle size. The spraying impact stress plays an important role in the generation of the residual stress. The addition of G and BG powder adjusts the linear coefficient of thermal expansion and reduces the heat stress in the coating. The fracture modes are manly spalling, and breaking in and between particles.Powder feeding mode, granularity and additive content of the powder and crystallization treatment affect the structural and interfacial characteristics of the coatings. The crystallization dynamic calculation shows that G and BG materials have a low active energy of crystallization. The addition of 20 wt.% G into Ti increases the activation energy of pure G. The addition of 20 wt.% BG into HA reduces the crystallization activation energy further. After crystallization treatment, there exists a transitional zone with 3μm in width, in which microsize and nanosize particles were precipitated, at the interface between substrate and the bottom layer, achievingthe metallurgical bonding between the substrate and the coating through oxidation, diffusion reaction and glass soakage. Anatase TiO2, rutile TiO2, and Na2Ti6O13 were precipitated in cracks in Ti/G bottom layer, healing up the cracks. The bioactivity of the coating surface was increased by the precipitation of HA and Na2Ca(PO4) with size from nanometer to micron.The study on the growth of bone-like apatite in vitro shows that TiO2 in bottom glaze glass can provide nucleation site for apatite, and bone-like apatite with needle-like shape can be formed. BG in the working layer increases the dissolution trend of the coating, contributing to the growth of apatite. The coating, with 8Ti2G as bottom layer and 8H2B as working layer, has electrochemical corrosion resistance. Both 8Ti2G and 8H2B have no disturbance and inhibition for the biological behavior of osteoblasts, and can facilitate osteoblasts attachment and proliferation. The osseointegration ability of dog’s implant was followed by 8H2B>HA>8Ti2G. BG in 8H2B shows the high activity and the fast dissolution, making Ca.and P ions migrating towards interface. Then, the micropores were formed, providing the channels and spaces for osteoblasts, which contributs to the formation of CHA on the implant materials surface. Therefore, a chemical bonding can be formed, increasing the stability of the implants at initial stage.更多还原