【作者】 刘艳；

【导师】 何国；

【作者基本信息】 上海交通大学 ， 材料科学与工程， 2016， 硕士

【摘要】 钛及钛合金由于生物相容性良好,同时弹性模量较低,是目前广泛使用的人体植入材料。根据结构的不同,可以将其分为实体钛和多孔钛。实体钛的弹性模量高于人体骨骼,植入后容易产生“应力屏蔽”效应。而多孔钛的弹性模量较低,可以减少“应力屏蔽效应”,同时相互贯通的多孔结构有利于人体骨细胞在其中的生长。传统的粉末烧结法得到的多孔钛脆性较高,不利于在体内使用。近年来开发出的一种缠绕型多孔钛克服了上述不足,然而在其缠绕结构中,钛丝与钛丝之间为简单的相互搭接,在很小的外力作用下就可以产生相对滑移,这导致其弹性模量和屈服强度均低于传统烧结法制备的多孔钛。通过固定钛丝间自由结点来强化其多孔结构是一个可行的方法。本文通过采用双酚A甲基丙烯酸缩水甘油酯(BisGMA)固定钛丝间结点,制备得到了BisGMA增强缠绕型多孔钛材料,与缠绕型多孔钛相比,其弹性模量不仅得到极大提高,同时其相互贯通的多孔结构保持不变。并系统研究了不同工艺参数(BisGMA含量、钛丝丝径、初始孔隙率)对BisGMA增强缠绕型多孔钛的结构及性能的影响。通过对BisGMA增强缠绕型多孔钛的结构分析发现,由于BisGMA仅涂覆在钛丝间的结点附近,因此自由结点被固定,同时材料仍然保持多孔的缠绕结构。材料在横纵截面上形貌不同,表现出明显的各向异性。在其他条件相同时,纵截面上的平均孔隙大小小于横截面,同时大孔所占的比例也相对较小。BisGMA含量的增加、钛丝丝径的减小以及初始孔隙率的减小都会导致样品孔隙数量、孔径尺寸及孔隙连通率的减少。BisGMA增强缠绕型多孔钛的压缩应力-应变曲线与大多数多孔金属材料类似,具有三阶段应力-应变响应行为,即线弹性阶段、平台阶段和致密化阶段。不同之处在于其线弹性阶段是一条曲线;BisGMA含量较低时其应力-应变曲线上没有明显的屈服点;平台阶段其应力仍然增加,因此是一个伪平台。BisGMA含量为0-20%时,材料的压缩弹性模量和屈服强度分别为0.2-1.3GPa、7.29-53MPa,与人体疏质骨相匹配,并随BisGMA含量的增加而增大;随着钛丝丝径及初始孔隙率的增加,材料的压缩力学性能降低。而在准静态拉伸载荷作用下,BisGMA增强缠绕型多孔钛的应力-应变曲线与其他多孔金属的单阶段或两阶段变形不同,为特殊的三阶段应力-应变响应行为:伪线弹性阶段、伪平台阶段以及松散化阶段。同时其拉伸应变量超过80%,远高于其它多孔金属材料。随着BisGMA含量的增加或钛丝丝径的减小,其拉伸弹性模量和屈服强度均随之增加,如BisGMA含量为0%时,弹性模量和屈服强度分别为0.05GPa和1.8MPa,当BisGMA含量增加到5%时,弹性模量和屈服强度分别提高到0.67GPa和2.7MPa。压缩应变量相同时,样品的能量吸收能力随BisGMA含量的增加而增加,而随钛丝丝径或初始孔隙率的增加而减小;而BisGMA含量相同时,样品的能量吸收能力随着应变量的增大而增大,钛丝丝径相同或初始孔隙率相同时吸能行为的变化与之相同。在拉伸载荷下,样品表现出明显的负泊松比效应,通过观察及查阅相关文献提出了拉胀模型,其具有内凹结构及固定交联结点这两方面特点。而模拟体液实验表明,BisGMA增强缠绕型多孔钛具有良好的耐腐蚀性能,同时是一种生物惰性材料,因此有望成为一种潜在的医用承力植入材料。更多还原

【Abstract】 Titanium and its alloys have long been widely used as biomedical materials on account of their excellent mechanical properties and reasonable biocompatibility.According to the structural distinction,titanium biomaterials can be clarified into solid titanium and porous titanium.The solid titanium possesses a critical issue related to the mismatch of the elastic modulus between Titanium implant and cortical/cancellous bone,which can lead to stress shielding over the surrounding bone.Porous titanium with interconnected structure can reduce the stress-shielding effect due to its low elastic modulus,and can also provide inner spaces for the ingrowth of new bone tissue and vascularization.The conventional metallurgical methods to fabricate porous titanium are mainly powder sintering technique,having the disadvantages of low ductility that may lead to breaking of the porous titanium implants in the body’s environment under uncertain overloading or accidental impact.A new entangled titanium material with flexible framework developed recent years has overcome this problem.However,due to the flexibility,its yielding strength and elastic modulus(when the porosity exceeds about 50%)are lower than that of the porous titanium manufactured by conventional methods.Therefore,inhibiting the structural flexibility by fixing the cross wire nodes may improve the stiffness of the entangled titanium material,and any biocompatible material with adequate strength and elasticity can be selected as a bonding agent so as to fix the free nodes in the entangled structure.In this case,in order to improve the mechanical properties of the entangled titanium material,an attempt to fix the free nodes in the entangled structure has been made.A biomaterial,Bisphenol A glycidyl methacrylate(BisGMA),commonly used in dental restorations and some bone cements was selected as a bonding material,because it can provide a strong bonding strength.The entangled titanium material enhanced by BisGMA has been fabricated successfully in this paper,and the structural characterization and mechanical properties of the BisGMA enhanced porous titanium with the entangled wire structure have been discussed systematically.Through the structural analysis of the BisGMA enhanced porous titanium,we found that the free cross wire nodes were fixed and the entangled and through-connected porous structure was still well maintained because BisGMA was mainly coated on the joints of the near cross titanium wires.The titanium wires of the transverse and longitudinal section showed different characteristics.With the same porosity,the average pore size of the longitudinal section was smaller than that of cross section.With the increase of BisGMA and decrease of titanium wire diameter and initial porosity,the porosity amount,porosity diameter and porosity interconnectivity of the sample decreased.Similar to the majority of porous metal materials,The compressive stress-strain curve of BisGMA enhanced porous titanium exhibited a three-stage stress-strain behavior,which is elastic stage,platform stage and densification stage.The difference is that the elastic stage was a curve;and the yielding point was not obvious when the volume fraction of BisGMA was comparatively low,and the stress still increased during the platform stage.The enhanced materials with the BisGMA content of 0-20% exhibited the elastic modulus in the range of 0.2-1.3GPa and the yielding strength in the range of 7.29-53 MPa,which were comparable to that of cancellous bones.The elastic modulus and yielding strength of the enhanced materials increased with the increase of BisGMA content and the decrease of titanium wire diameter and initial pososity.The BisGMA enhanced porous titanium exhibited a special three-stage tensile stress-strain curve: pseudo elastic stage,pseudo platform stage and loosing stage,which is different to that of other porous metals.The tension strain of BisGMA enhanced porous titanium exceeded 80%,much higher than that of other porous metals.With the increase of BisGMA content or decrease of titanium wire diameter,the elastic modulus and yielding strength increased.When the BisGMA content was 0%,the elastic modulus and yielding strength were 0.05 GPa and 1.8MPa,when the BisGMA content increased to 5%,the elastic modulus and yielding strength reached 0.67 GPa and 2.7MPa,respectively,With the same compression strain,the energy absorption capacity of the sample increased with the increase of BisGMA content,and decreased with the increase of titanium wire diameter or initial porosity;while with the same BisGMA content or titanium wire diameter or initial porosity,the energy absorption capacity increased with the increase of compression strain.The samples exhibited noticeable negative poisson ratio effect under tensile test,which could be explained by a new auxetic model with the features of indented structure and fixed cross wire nodes.The simulated body fluid experiment indicated that BisGMA enhanced porous titanium has good corrosion resistance and bioinertia,suggesting potentials for load-bearing bio applications.更多还原