【作者】 牛宗伟；

【导师】 张建华；

【作者基本信息】 山东大学 ， 机械制造及其自动化， 2005， 博士

【摘要】 羟基磷灰石(Hydroxyapatite,简称HAP)因其良好的生物相容性和骨传导性而成为重要的人工骨移植材料。但合成HAP的力学性能较差,特别是其断裂韧性很低而被严格限制在非动载环境中使用。SiCw可以有效地提高HAP生物陶瓷的强度和断裂韧性,扩大其应用范围。本文对溶胶-凝胶法合成纳米羟基磷灰石进行了热力学分析,用原位复合法制备了HAP/SiCw复合微粉,用热压烧结法得到了HAP/SiCw复合生物陶瓷,对SiCw的增韧机制进行了理论研究和有限元分析,对HAP/SiCw复合生物陶瓷进行了分形分析,最后对HAP/SiCw复合生物陶瓷的超声波加工进行了研究。对溶胶凝胶法合成羟基磷灰石时水溶液中的Ca-P2O5-H2O系和Ca(OH)2-H3PO4-H2O系进行了热力学分析,得出了合成纳米HAP的合适条件:使用二甲基甲酰胺为分散剂,在145-150℃的温度下进行反应可以得到高纯度的纳米羟基磷灰石,并可以避免使用昂贵的高压釜。对纳米羟基磷灰石进行了表征。对热压烧结过程进行了理论分析,得出了热压烧结致密化速率的表达式。首次用原位复合法制备了HAP/SiCw复合微粉。用热压烧结法制备了HAP/SiCw复合生物陶瓷,得出了合理的烧结工艺为:烧结温度1300-1310℃,保温时间30min,烧结压力30-40MPa,保护气氛为氮气。对HAP/SiCw复合生物陶瓷的微观结构和力学性能进行了研究。研究了晶须含量和晶须取向对复合材料微观结构和力学性能的影响。通过理论计算和试验分析得出了HAP/SiCw复合生物陶瓷中SiCw的最大极限含量为23. 7%。试验结果表明,材料的致密度随着晶须含量的增加而降低,当晶须含量小于理论极限值时,材料的抗弯强度和断裂韧性随着晶须含量的增加而增大,当晶须含量大于理论极限值时,材料的抗弯强度和断裂韧性开始下降。当SiCw的体积含量为23. 7%时,复合材料的力学性能最好,抗弯强度190MPa,断裂韧性2. 31MPa·m1/2。分析了晶须取向对复合材料力学性能的影响,发现SiCw择优分布在垂直于热压面内,材料在平行于热压面的方向上力学性能最好,在垂直于热压面的方向上力学性能最差。对剪滞理论进行了修正,得出了晶须端部所受应力的表达式,推导出了预报晶须桥联、晶须拔出、裂纹偏转三者协同增韧效果的表达式。对晶须增韧HAP的微观单元进行了有限元分析,发现在受外力作用时,晶须端部与基体结合处的剪切应力是传递外部载荷的主要方式,晶须端部与基体的结合强度是决定复合材料力学性能的主要因素。 用分形理论对HAP/s iCw复合生物陶瓷的断口SEM图像进行了分析,发现HAP/siCw复合生物陶瓷具有分形特征,材料的断口分维值随着晶须含量的增加而增大,而且在晶须含量达到23.7%时最大,当大于该含量时,材料的断口分维值下降。材料断口分维值随着晶须方向角的增大而增大。材料的致密度随着断口分维值的增大而降低,材料的抗弯强度和断裂韧性随着断口分维值的增大而增大。 对HAP/siCw复合生物陶瓷材料的超声波加工进行了理论分析和试验研究,发现材料去除率和加工表面粗糙度随着晶须方向角0的增大而减小。在相同的加工条件下,材料的断裂韧性越高,其材料去除率人的叼天越低。磨料工作液的浓度在1:4(磨料:水)时最为合适。关键词:复合材料,HAP/s iCw生物陶瓷,增韧,分形,超声波加工更多还原

【Abstract】 Hydroxyapatite(HAP) has become one of the most important artificial bone transplant materials because of its excellent biocompatibility and osteophony. The mechanical properties of synthesized hydroxyapatite are poor, especially its fracture toughness is very low. So that it has been strictly limited to being used in non-dynamic load circumstance. SiC whisker can be adopted to toughen HAP bio-ceramics effectively and enlarge its application range.Thermodynamics analysis on synthesizing nano HAP using sol-gel method was carried out. HAP/SiCw composite micro-powder was synthesized using in-situ composite method, and HAP/SiCw composite bio-ceramics was sintered using hot pressing method. The toughening mechanism of SiCw whisker was theoretically studied and analyzed by FEM, fractal analysis on HAP/SiCw was carried out. The ultrasonic machining of HAP/SiCw composite bio-ceramics was studied.The thermodynamics analysis of the systems of Ca-P2O5-H2O and Ca(OH)2-H3PO4-H2O in the water solution when synthesize hydroxyapatite using Sol-gel method was made the appropriate condition to synthesizing hydroxyapatite was got: using dimethylformamide as dispersant and acting under the temperature of 145-150℃ can get high purity nano HAP and avoid using expensive autoclave. Nano HAP was characterized. Theoretical analysis on hot pressing sintering process was carried out and the expression of hot press densification velocity was got. HAP/SiCw composite micro-powder was synthesized using in-situ composite method. HAP/SiCw composite bio-ceramics was sintered using hot pressing method. The proper sintering technical parameters are: the sintering temperature 1300~ 1310 ℃, the pressure 30-40MPa, the time of heat preservation 30min, and the protection gas nitrogen.The micro-structure and mechanical properties of HAP-SiCw composite bio-ceramics were investigated. The influence on micro-structure and mechanical properties of whisker content was studied. Theoretical calculation results indicate thatthe maximal critical content of SiCw in hydroxyapatite-SiCw composite bio-ceramics is 23.7%. The experimental results show that the mechanical properties are the best when the volume content of SiCw is 23.7%, the bending strength is 190MPa and the fracture toughness is 2.31MPa.m1/2. If the SiCw distributes in the plane parallel with the hot press plane, the mechanical properties are the best in the plane normal to the hot press plane, the mechanical properties are the worst in the plane which is parallel with the hot press plane.The stress expression of the whisker tip was got on the basis of modifying the shear lag theory. The expression to forecast the corporate toughening effect of whisker bridging, whisker evulsion and crackle deflexion was derived. The micro unit of HAP toughening by whisker was analyzed by FEM, and the results show that the stress transfer between the whisker tip and the matrix is the main manner to transfer stress. Therefore, the bonding strength between the whisker tip and the matrix is the key factor that determines the mechanical properties of the composite material.The fracture SEM images of HAP/SiCw composite bio-ceramics were analyzed using fractal theory. The results show that HAP/SiCw composite bio-ceramics has fractal character, the fractal dimension of the material fracture rises with the increase of the whisker content and reaches the maximum when the whisker content is 23.7%, however, the fractal dimension of the material fracture falls when the content is higher than this critical value. The fractal dimension of the material fracture rises with the increase of whisker direction angle. The density of the material decreases with the increase of the fracture fractal dimension, whereas the bending strength and fracture toughness of the material increase with the increase of the fracture fractal dimension.Theoretical analysis and experimental study were carried out upon the ultrasonic machining of HAP/SiCw composite bio-ceramics material. Research results show that the material removal rate and the surface roughnes更多还原