髋关节整体替代陶瓷材料

许多材料在医学领域应用广泛,例如,整体替换硬组织或软组织的元件(如骨盆、骨头、关节、植牙等)、修补、诊断或矫正仪器(如起搏器、心脏阀等)。这些材料不仅要有好的力学性能,还要保持长期稳定,不能与人体相排斥。由于陶瓷材料在生理环境中具有强度高、生物相容性强和稳定性好的优点,人们研究用陶瓷材料替换骨骼。从20 世纪70 年代起,欧洲人用陶瓷组件置换整个髋关节。这些组件主要由氧化铝和氧化锆单体制成。然而,在有水环境中,氧化锆会发生低温降解。目前人们的研究重点在于提高陶瓷组件的强度和耐磨性,同时缩小其尺寸并延长其使用寿命。研究中使用的材料是氧化锆增韧的氧化铝复合陶瓷和其它氧化铝复合陶瓷,不再是单体陶瓷。另外,还可以使用氧化铝和氧化锆功能梯度复合材料。该梯度材料可以利用电泳沉积法(EPD)制得,其表面为纯氧化铝,中心部分为均匀的氧化铝、氧化锆复合材料,中间过渡部分是呈连续梯度渐变的氧化铝、氧化锆复合材料,烧成后会产生剩余热应力。设计这样的梯度结构是为了使复合材料具有最大表面压应力和最小内部张应力,与纯氧化铝组件相比,提高了强度和耐磨性。

CERAMICS FOR TOTAL HIP REPLACEMENT

Many materials are used in medicine for a variety of applications ranging from total replacement of hard or soft tissues(such as bone plates, pins, joint, dental implants, etc.), repair, diagnostic or corrective devices (such as pacemakers, heartvalves, etc.). Not only are the mechanical properties important, but also the material should be biocompatible with the humanbody and stable for a long period. Due to their excellent properties such as high strength, biocompatibility and stability inphysiological environments, ceramics are investigated as bone substitute materials. In this way, ceramic components havebeen used for total hip replacement components in Europe since the early 1970s. Alumina and zirconia monoliths are mainlyused for these components. However, zirconia can undergo low temperature degradation in aqueous environment.Current research is focusing on increasing the strength and wear resistance, meanwhile reducing the size and extendingthe lifetime of ceramic components. Instead of ceramic monoliths, ceramic composites like zirconia toughened alumina andother alumina matrix composites are currently investigated. Another possibility is to use components based on alumina andzirconia with a functionally graded composition. The composition gradient can be established during shaping by means ofelectrophoretic deposition (EPD) to obtain a pure alumina surface region and a homogeneous alumina/zirconia core with in-termediate continuously graded regions to generate thermal residual stresses after sintering. The gradient profiles are de-signed to obtain maximum compressive surface stresses and minimum tensile stresses in the core of the component to in-crease the strength and wear resistance compared to pure alumina components.