【作者】 徐丽娟；

【导师】 陈玉勇； 陈子勇；

【作者基本信息】 哈尔滨工业大学 ， 材料加工工程， 2007， 博士

【摘要】 钛及其合金具有优越的机械性能、生物相容性和耐腐蚀性等优点,广泛应用于牙科修复材料。以往使用的合金有Ti-6Al-4V和Ti-6Al-7Nb等合金,但这些合金中含有有毒元素Al和V。近年来,国内外许多学者都集中于无毒牙科修复用钛合金的研究。Mo、Nb属于β相稳定元素,可以提高合金强度和塑性,有利于降低合金的弹性模量,且生物相容性良好。本文采用LZ5型离心铸钛机制备了Ti-Mo、Ti-Nb及Ti-Mo-Nb合金材料,系统研究了Ti-Mo、Ti-Nb及Ti-Mo-Nb合金的显微组织、力学性能、摩擦磨损特性和腐蚀特性,并对优化的β型Ti-Mo-Nb合金的生物相容性和铸造性能进行了研究,采用熔模精密铸造工艺制备了口腔修复用牙冠。研究结果表明,随着Mo含量的增加,Ti-Mo合金的显微组织细化,压缩强度降低,塑性增强;随着Nb含量的增加,Ti-Nb合金的显微组织发生明显变化,压缩弹性模量降低;Ti-20Nb合金的压缩强度最大,Ti-5Nb合金的塑性最好。Mo、Nb加入量相同时,Ti-Mo合金的维氏硬度、压缩强度及压缩弹性模量高于Ti-Nb合金。三种Ti-Mo-Nb合金由等轴晶组成,随着Nb含量的增加,合金的密度、维氏硬度、压缩强度和压缩弹性模量降低,抗弯强度增高、塑性增强。与Ti-10Mo合金相比,Ti-10Mo-10Nb合金的维氏硬度和压缩弹性模量降低,压缩强度、抗弯强度和塑性增强。摩擦磨损试验表明,Ti-Mo合金中Ti-10Mo合金的稳态摩擦系数最小,随着Mo含量的增加,Ti-Mo合金的磨损深度减小,抗磨能力增强;Ti-Nb合金中Ti-10Nb合金的稳态摩擦系数最小,Ti-5Nb合金的磨损深度最小,耐磨性较好,Ti-15Nb合金的磨损深度最大,耐磨性较差。随着Nb含量的增加,Ti-Mo-Nb合金的磨损深度减小,抗磨性增强。加载载荷对Ti-10Mo-10Nb合金耐磨性的影响不大;Hank’s溶液对Ti-10Mo-10Nb合金有润滑减磨的作用;Ti-10Mo-10Nb合金的氧化膜中含有TiO₂和Nb2O5,其抗磨性增强,氧化时间增长,氧化膜中TiO₂的含量增加,表面变疏松。Ti-Mo、Ti-Nb及Ti-Mo-Nb合金的磨损机制为粘着磨损和磨粒磨损共同作用。腐蚀试验表明,Hank’s溶液和pH2.5乳酸溶液中,Ti-Mo及Ti-Nb合金中Ti-10Mo合金的自腐蚀电位较高;0.9%NaCl溶液中,Ti-5Mo合金的自腐蚀电位较高。在Hank’s溶液中,Ti-Mo及Ti-Nb合金中Ti-5Nb合金易钝化且钝化区间较宽;在0.9%NaCl溶液中,Ti-20Mo合金易钝化且钝化区间较宽;在pH2.5乳酸溶液中,Ti-10Nb合金易钝化且钝化区间较宽。Hank’s溶液、0.9%NaCl溶液和pH2.5乳酸溶液中,Ti-15Mo合金的钝化膜较稳定。在Hank’s溶液和pH2.5乳酸溶液中,Ti-10Mo-10Nb合金的自腐蚀电位与纯钛相近。在Hank’s溶液、0.9%NaCl溶液和pH2.5乳酸溶液中,Ti-10Mo-10Nb合金与其它两种Ti-Mo-Nb合金和纯钛相比更容易从活化态进入到钝化态,而且钝化区间较长。几种Ti-Mo-Nb合金钝化膜的稳定性相差不大。从钝化膜的形成难易程度和钝化膜的稳定性两方面考虑,Ti-10Mo-10Nb合金的耐蚀性好于纯钛。Ti-10Mo-10Nb合金在pH值为2的乳酸溶液中的自腐蚀电位较高,在pH值为2.5的乳酸溶液中易钝化,且钝化区间较宽,在pH值为4的乳酸溶液中钝化膜较稳定。Ti-10Mo-10Nb合金的钝化膜中含有TiO₂及少量的Nb2O5和MoO3。在含有Cl-的腐蚀介质中,Ti-10Mo-10Nb合金发生了点蚀。Ti-10Mo-10Nb合金的生物相容性试验表明,该合金的溶血率为0.883%,远远小于5%,不会引起急性溶血;口腔粘膜刺激试验中肉眼及组织学观察均未见明显的炎症及上皮增长等组织学改变,表明该合金对口腔粘膜无刺激性或损伤。该合金植入白鼠4周后的组织中,纤维包膜较疏松,与组织的界限不清,可见少量炎细胞,主要为中性细胞、淋巴细胞、单核细胞和浆细胞,未见多核巨细胞和异物巨细胞;植入8周后,纤维囊壁趋向变薄,炎细胞数量减少,主要为单核细胞和淋巴细胞,该合金引起的组织反应为轻度。生物相容性试验表明Ti-10Mo-10Nb合金具有良好的生物相容性。铸造性能试验表明,Ti-10Mo-10Nb合金在牙科专用铸钛机上具有良好的铸造性能,室温下铸流率（CV）可达98%,并用该合金成功的制备了牙冠。Ti-10Mo-10Nb合金与铸钛专用包埋料的反应层中,Al元素扩散层的厚度大约为20μm,Si、Zr元素在反应层中分布不均匀,扩散层的厚度大约为15μm,Ti、Mo元素出现了偏析现象。以上所有试验结果表明,Ti-10Mo-10Nb合金具有优异的综合性能,适宜作为牙科材料。更多还原

【Abstract】 Titanium and its alloys are promising candidate materials for dental applications due to their excellent mechanical properties, biocompatibility and corrosion resistance. Ti-6Al-4V and Ti-6Al-7Nb alloys have been used ago. But elements Al and V exhibit high cytotoxicity. Recently, many researchers have concentrated on developing new type of titanium alloys without toxic elements. Asβphase stabilizer in titanium alloys, Mo and Nb have shown good biocompatibility. Adding Mo and Nb to titanium alloy can increase its strength and ductility, while can decrease its elastic modulus. In present paper, Ti-Mo, Ti-Nb and Ti-Mo-Nb alloys were prepared using LZ5 type centrifugal casting technique. The microstructures, mechanical properties, wear resistance and corrosion resistance of Ti-Mo, Ti-Nb and Ti-Mo-Nb alloys were investigated. The compatibility and casting characteristic of selectedβtype Ti-Mo-Nb alloy that has the excellent properties have been studied. The dental crawn has been made by investment casting technique.The investigations have shown that with the increase of Mo content, Ti-Mo alloys revealed refined microstructure, reduced compression strength, but increased plasticity. For Ti-Nb alloys, the increase of Nb content modified the microstructure of Ti-Nb alloys significantly and decreased their compression elastic modulus, in which Ti-20Nb alloy showed the largest compression strength and Ti-5Nb alloy showed the best plasticity. With same content in Ti, Mo addition results in higher Vickers hardness, compression strength and elastic modulus than Nb does. All the three kinds of Ti-Mo-Nb alloys show equiaxed crystalline microstructure. The increasing Nb contents of Ti-Mo-Nb alloys result in the decrease of density, Vickers hardness, compression strength and compression elastic modulus, and the increase of bending strength and plasticity. Comparing to Ti-10Mo alloy, a lower Vickers hardness and compression elastic modulus and higher compression strength, bending strength and plasticity were obtained for Ti-10Mo-10Nb alloy.Wear tests showed that the increasing Mo content leads to a reduction of wear depth of Ti-Mo alloy and increase of wear resistance, with a smallest steady friction coefficient for Ti-10Mo alloy. For Ti-Nb alloys, Ti-10Nb alloy shows a smallest steady friction coefficient, Ti-5Nb alloy shows the smallest wear depth and best wear resistance and Ti-15Nb alloy shows the largest wear depth and worst wear resistance. For Ti-Mo-Nb alloys, the increasing Nb content reduced the wear depth and increased wear resistance. The applied load did not influence evidently the wear resistance of Ti-10Mo-10Nb alloys. Hank’s solution was found to act as lubricant during wear tests for Ti-10Mo-10Nb alloys. After surface oxidation treatment, TiO₂ and Nb2O5 formed on the surface of Ti-10Mo-10Nb alloys, leading to an increase of wear resistance. The prolonged oxidation resulted in the formation of larger volume fraction of TiO₂ and surface became loosen. The wear mechanism for all the tested alloys is a combination of adherence wearing and debris wearing.Corrosion tests revealed Ti-10Mo alloy showed higher self-corrosion potential for all Ti-Mo and Ti-Nb alloys in Hank’s solution and pH2.5 lactic acid solution. Ti-5Mo alloy showed higher self-corrosion potential for all Ti-Mo and Ti-Nb alloys in 0.9%NaCl solution. For all Ti-Mo and Ti-Nb alloys, Ti-5Nb alloy was easy to passivate with a wider passivation range in Hank’s solution, Ti-20Mo alloy was easy to passivate with a wide passivation range in 0.9%NaCl solution and Ti-10Nb alloy was easy to passivate with a wide passivation range in pH2.5 lactic acid solution. For all Ti-Mo and Ti-Nb alloys, the passivation film of Ti-15Mo alloy was stabler in Hank’s solution, 0.9%NaCl solution and pH2.5 lactic acid solution.In Hank’s solution and pH2.5 lactic acid solution, the self-corrosion of Ti-10Mo-10Nb alloy and pure titanium was nearly. In Hank’s solution, 0.9%NaCl solution and pH2.5 lactic acid solution, Ti-10Mo-10Nb alloy was easier to progress from activation state to passivation state with a wider passivation range, comparing to other two Ti-Mo-Nb alloys and pure titanium. However, no evident difference was found for the dissolution rate of the passivation film for all Ti-Mo-Nb alloys. Considering the stability and easiness of formation of the passivation film, Ti-10Mo-10Nb alloy showed a better corrosion resistance than pure titanium does. Ti-10Mo-10Nb alloy showed a highest self-corrosion potential in pH2 lactic acid solution, an easy passivation and wide passivation range in pH2.5 lactic acid solution, and a stable passivation film in pH4 lactic acid solution. The passivation film consists of mainly TiO2 and small amount of Nb2O5 and MoO3. Pit corrosion had taken place when Cl- ion contained solution was applied to Ti-10Mo-10Nb alloy.Biocompatibility tests revealed a hemolysis coefficient of 0.883% for Ti-10Mo-10Nb alloy, which was much smaller than 5% and wouldn’t cause acute hemolysis. No evident inflammation and histological change such as epidermic growth were observed in stimulation tests of mucous membranes of mouth, indicating that Ti-10Mo-10Nb alloy isn’t irritant and trauma to the mucous membranes of mouth. 4 weeks after implantation of Ti-10Mo-10Nb alloy into white rat, the fabulous capsule was found to be loose without a clear boundary with tissues, while small amount of inflammation cells were observed such as neutrophil cells, lymphocytes, monocytes and plasma cells, no multinuclear girnt cells and foreign body giant cells were found. 8 weeks after the implantation, fabulous capsule wall turned thinner, the amount of inflammation cells reduced with remaining monocytes and lymphocytes. The histological reaction is regarded as light for this alloy. Biocompatibility tests revealed that Ti-10Mo-10Nb alloy has the excellent biocompatibility.Casting characteristic tests revealed that an excellent casting performance of Ti-10Mo-10Nb alloy in the specified dental titanium casting machine. A 98% of casting value can be reached at room temperature. Crowns have been cast successfully using this alloy. In the reaction layer of Ti-10Mo-10Nb alloy with investment materials, Al showed a diffusion thickness of about 20μm, the distribution of Si and Zr was not uniform with a diffusion thickness of about 15μm, and segregation was observed for Ti and Mo. The all test results indicated that Ti-10Mo-10Nb alloy has the excellent properties and is suitable to be as dentisty mateial.更多还原