【作者】 胡金玲；

【导师】 张松；

【作者基本信息】 沈阳工业大学 ， 材料学， 2007， 硕士

【摘要】 钛合金具有比强度高、抗蚀性优异、生物相容性好等突出优点,在航空航天、生物医学、化工工业等领域中得到了广泛应用。本试验采用高功率连续波固体Nd:YAG激光在钛表面制备激光气体氮化层,采用脉冲Nd:YAG激光对纯钛及氮化样品进行激光微加工;采用扫描电子显微镜（SEM）、X-射线衍射仪（XRD）、恒电位仪、锁相放大器对激光表面改性层的微观组织、结构、表面形貌、电化学腐蚀性能进行了系统研究:并对激光氮化前后、激光微加工前后样品沉积类骨磷灰石的能力及生物相容性（溶血率、细胞毒性）进行评价。选择适当的激光辐照工艺参数,可在纯钛表面获得致密的TiN增强金属基复合材料改性层,改性层的表层为1～2μm厚的TiN封闭陶瓷层,改性层内部TiN增强相呈梯度分布,组织致密、无孔洞及裂纹,与基体间存在良好的冶金结合。电化学测试结果表明,经激光改性后,钛的腐蚀电位由-0.23V提高到-0.15V,腐蚀电流密度由2.5×10^-6A/cm²降低到7.6×10^-8A/cm²,从而可以有效的抑制了腐蚀反应的发生。激光微加工最佳工艺参数为:脉冲功率8W、脉冲频率10Hz、脉冲次数4次、脉冲宽度1ms。采用优化工艺参数,可以在样品表面得到呈规律排布,孔径约350～370μm,孔深约450μm,孔中心距为500μm的微孔群。氮化钛样品微孔的直径在孔深250μm左右有增加的趋势,孔底呈圆形,更加有利于骨组织的长入。生物矿化试验说明激光改性氮化层具有优异的生物相容性。钛及氮化钛激光微加工样品在SBF溶液中沉积7天,表面沉积物钙磷摩尔比分别为1.07和1.23,接近人体骨羟基磷灰石摩尔比1.67。间接接触溶血率测试结果表明,钛、氮化改性、钛微加工及氮化改性微加工样品溶血率分别为:1.2%、0.59%、3.3%、1.7%,所有样品溶血率均符合临床医用材料溶血率低于5%的要求。细胞毒性试验结果显示,4种样品在50%浸提液浓度下培养5天后的细胞毒性为1级,符合临床医学要求,4种样品均具有良好的生物相容性。更多还原

【Abstract】 Titanium alloys have been widely used in aerospace,biomedical and chemical industry because of its high specific strength,excellent corrosion resistance and biocompatibility. Laser gas nitrided（LGN） layer was fabricated on the surface of the titanium irradiated by a continuous wave Nd-YAG laser.Pulse Nd-YAG laser was used to micromachine pure titanium and laser gas nitrided titanium.SEM,EDAX,XRD,potentiostat and lock amplifier were used to study the microstructure,composition,surface morphology and electrochemical corrosion properties.The ability of deposition of bone-like apatite and biological activity including hemolysis and cytotoxicity were also investigated before and after laser micromachining.Dense TiN strengthedned metal base composite layer was obtained on the surface of titanium with proper laser irradiation parameters.The outmost of the modified layer is TiN with the thickness of 1～2μm.The modified layer distributed by graduation.Laser gas nitrided layer was dense and free of crack.There was a good metallurgical bonding between the modification layer and the NiTi alloy substrate.Electrochemical test showed that the corrosion potential of titanium was increased from - 0.23 V to - 0.15 V while the corrosion current was reduce from 2.5×10^-6 A/cm² to 7.6×10^-8 A/cm² which indicated that the corrosion reaction was inhabited effectively through laser gas nitriding.The optimized parameters of laser micromachining are the power of 8W,frequency of 10Hz,pulse number of 4 and the pulse width of 1ms.Regularly patterned holes with the diameter of 350～370μm,depth of 450μm and hole pitch of 500μm were fabricated on pure titanium and LGN samples.The diameter of the LGN sample increased at the depth of about 250μm.The bottom of the hole is circular.The shape is favorable for the bone to grow into the holes.Biomineralization tests showed that the LGN layer is excellent in biocompatibility. After immersion in SBF for 7 days,the Ca/P atomic ratio of the deposition on titanium and LGN samples were respectively 1.07 and 1.23 very close to that of bone-apatite,which has the Ca/P atomic ratio of 1.67.The hemolysis of titanium,LGN sample,micromachined Ti and LGN Ti were 1.2%,9 %,3%and 1.7%which are less than 5%,meeting the requirement of biomedical materials.Cytotoxicity test showed that the cytotoxicity grade of the four samples is one after cell cultivation in the 50%infusions for five days,which indicated that all the materials are biocompatible.更多还原