【作者】 佟宇；

【导师】 郭天文； 弥谦；

【作者基本信息】 第四军医大学 ， 口腔临床医学， 2009， 博士

【摘要】 钛具有良好的机械力学性能,化学稳定性和生物相容性,已在航空航天、航海、军事和生物医学领域广泛应用。纯钛在口腔医学中主要用于制作义齿支架、冠与固定桥、正畸托槽、种植体及钛烤瓷修复体等。钛是自钝化性金属,常温下表面形成一层稳定而致密的氧化膜,因而具有良好的耐腐蚀性。但纯钛的硬度偏低,耐磨性差,纯钛修复体在口腔中行使功能时,钛表面氧化膜在磨擦力、剪切力等应力作用下,容易受到擦伤和磨损,龋齿预防剂如含氟牙膏、凝胶对这层氧化膜亦有一定的破坏作用。本课题研究对铸造纯钛进行表面改性处理,以增强其耐磨性和耐腐蚀性,改善表面颜色,从而提高口腔纯钛修复体的性能和美学效果。一、铸造纯钛等离子氮化处理的实验研究纯钛TA2常规铸造、机械抛光后置于等离子氮化炉中,在氨气气氛中进行辉光等离子渗氮处理,辉光电压700V,电流13～15A,炉内真空度150Pa,渗氮温度700℃,渗氮时间1～4h,研究等离子渗氮对纯钛显微硬度、耐磨性和耐腐蚀性的影响。纯钛铸件等离子氮化处理后,表面呈现淡黄色,边界部分颜色较淡,这是辉光放电的“边界效应”造成的。显微硬度、耐磨性及在人工唾液中的耐腐蚀性显著提高,主要是由于渗氮过程中,表面形成渗氮复合层,渗氮复合层含有TiN和Ti₂N相,TiN和Ti₂N的硬度较高,渗氮复合层下方为氮扩散层,含有大量氮原子向钛基体扩散形成的间隙固溶体,渗氮复合层与钛基体的结合强度较高,渗氮复合层和扩散层的形成大大提高了纯钛的显微硬度与耐磨性。随着等离子渗氮时间的增加,纯钛铸件的显微硬度、耐磨性与耐腐蚀性逐渐增强,主要原因是钛表面渗氮复合层的厚度逐渐增大。等离子渗氮用于纯钛主要存在的问题是颜色不均匀,渗氮时间较长,要在纯钛表面形成有效的渗层,渗氮时间一般大于1h。二、铸造纯钛表面氮化钛镀膜的实验研究应用脉冲真空电弧离子镀技术,在铸造纯钛表面制备TiN膜。钛铸件经机械抛光、超声清洗后置于镀膜机真空室中,抽真空至4×10-3Pa时充入氩气,将试件溅射清洗5min,然后充入氮气,制备氮化钛薄膜。改变镀膜工艺参数,对不同条件下制备的TiN薄膜的特征进行表征。其中弧源电流分别设置为55A、75A、90A和110A,基体偏压分别为50V、100V和150V,氮分压分别为1.1×10-1, 1.5×10-1,1.7×10-1和1.9×10-1Pa,钛基体的温度分别为300、400、500和600℃。钛铸件表面沉积氮化钛膜后,呈金黄色外观,显微硬度、耐磨性和耐腐蚀性明显提高;牙刷磨耗实验机摸拟口腔环境,用含氟牙膏分别刷洗镀氮化钛膜的钛铸件和未镀膜钛铸件,结果显示:刷洗后未镀膜的钛铸件出现了失泽和变色,而表面镀氮化钛膜的钛铸件则无明显的颜色改变,表明镀膜的钛铸件颜色稳定性较好;表面镀氮化钛膜的钛铸件表面形貌无明显改变,而未镀膜的钛铸件表面粗糙度增大,表面形貌有较大的改变,表明氮化钛膜对钛铸件有较好的磨损保护作用。改变氮分压,氮化钛膜可呈现不同的颜色。当氮分压为1.7×10-1Pa,弧源电流55A,基体偏压100V时,制备的TiN薄膜呈金黄色。增大氮分压,TiN薄膜颜色偏向红黄,减小氮分压,TiN薄膜颜色偏向淡黄。氮分压增大,TiN薄膜的显微硬度开始增大,氮分压为1.7×10-1Pa时,薄膜硬度达到最大值,继续增大氮分压,薄膜硬度开始下降。薄膜硬度的改变与薄膜相结构的改变有关,氮分压低时,氮化钛膜的主要结构为Ti₂N、TiN多相共存,随着氮分压的增高,氮化钛膜逐渐转变为TiN结构。氮分压为1.7×10-1Pa时,薄膜硬度达到最大,此时薄膜中有大量的Ti₂N,这种多相共存的结构提高了薄膜的硬度。电弧离子镀兼具真空蒸镀的沉积速率高和溅射镀膜沉积粒子能量高的特点,还具有膜层与基体结合力强,金属离化率高,绕射性好等优点;缺点是镀膜过程中易产生液滴。基体施加脉冲偏压代替直流偏压,应用磁过滤器,可使薄膜中大颗粒的尺寸和数量明显减少,提高薄膜质量。脉冲电弧离子镀同等离子渗氮相比,具有明显的优势:可在纯钛表面形成均匀的氮化钛薄膜,镀膜过程中基体温度较低,镀膜时间较短,一般为30min。缺点是薄膜的耐磨性低于等离子渗氮。将等离子渗氮和脉冲真空电弧离子镀结合起来,钛铸件镀膜前先进行等离子渗氮,可以获得较厚的与基体结合牢固的表面硬化层,对离子镀硬质氮化钛膜起到强有力的支撑,不仅可使膜层的抗变形能力提高,而且使膜层到基体的应力分布连续性较好,从而提高膜基结合力。对纯钛进行复合表面处理,可以克服等离子渗氮颜色不均匀和电弧离子镀制备的TiN膜耐磨性差的缺点,达到理想的表面改性效果。对义齿钛支架进行等离子渗氮、电弧离子镀氮化钛复合表面处理后,表面光滑,呈金黄色外观,色彩稳定性较好,耐磨性和耐腐蚀性显著提高,具有较大的临床意义。更多还原

【Abstract】 Titanium and its alloys are widely used in many areas such as aerospace, marine and biomedical areas due to their outstanding properties such as good mechanical property, chemical stability and biocompatibility. Pure titanium has been used to make crowns and fixed partial denture, denture framework, implants and orthodontic brackets. Titanium is easily passivated and a condense and stable oxide film formed on its surface at room temperature, so it has excellent corrosion resistance. The main problem in using titanium as medical materials is its low hardness and wear resistance. When titanium prosthesis functions in the oral environment, the surface passivation layer is easily destroyed by frictional force, shearing force and other forms of stress. Carries preventive agent such as fluoride-containing toothpaste, gel can also destroy the passivation film to some extent. TiN is known to possess high hardness, good tribological properties, excellent chemical stability and biocompatibility. TiN can be produced either by nitriding on the Ti alloys or by some coating techniques such as physical vapor deposition （PVD）, chemical vapor deposition（CVD）. In this study plasma nitriding and PVD （arc ion-plating） were used to improve wear and corrosion resistance, surface color of pure cast titanium, the results is expected to improve properties of denture made from titanium.1 Plasma nitriding of pure cast titaniumCP Ti （TA2） was cast in dental titanium casting machine （LZ-2）, the specimens were placed into nitriding chamber after being mechanically polished and ultrasonically cleaned and then plasma nitrided in the NH3 atmosphere. The nitriding temperature was 700℃, glow voltage 700V, current intensity 13-15A, chamber pressure 150Pa and nitriding time 1-4h.After plasma nitrided, the titanium specimens appeared dark golden in color, it was not uniform and reduced to the edges due to the“edges effect”of glow discharge. Microhardness, wear resistance and corrosion resistance in artificial saliva improved significantly. During the process of nitriding, a compound nitriding layer containing TiN and Ti₂N formed on the specimen surface, underneath the compound layer was diffusion layer that consisted of an interstitial solution of nitrogen in theα-Ti, the compound layer adhered to the substrate well, the formation of diffusion layer and compound layer increased the wear and corrosion resistance of pure cast titanium greatly.With the increase of nitriding time, microhardness, wear resistance and corrosion resistance in artificial saliva increased gradually. The main reason is that the thickness of compound layer increased with the increase of nitriding time. The main problem of plasma nitriding is that the color is not uniform and treatment time is long. In order to acquire useful nitrided layer, the nitriding time is 1h at least.2 Deposition of TiN film on pure cast titanium by pulsed bias arc ion platingPulsed vacuum arc ion plating was used to deposit TiN film on surface of pure cast titanium. The cast titanium specimens were mechanically polished, ultrasonically cleaned before being placed into vacuum chambers. The base pressure of the vacuum chamber before operation was 8×10-3Pa, the Ar gas was introduced and the specimens were cleaned by Ar ion bombardment for 15min, then deposition of Ti began at a substrate bias of 400V with an arc current of 70A for 3min. After that deposition of TiN began by introducing N2 into the vacuum chamber and the substrate bias was 100V. The deposition lasted for 30min and the arc current was controlled at 70A. The processing parameters were adjusted and the TiN film was characterized deposited at different conditions, the arc current was controlled at 55A, 70A and 90A , the substrate bias at 50V, 100V and 150V, nitrogen pressure at 1.1×10-1, 1.5×10-1, 1.7×10-1 and 1.9×10-1Pa,the substrate temperature was controlled at 400, 500 and 600℃respectively. The film was characterized using a range of analytical and measurement techniques, including scanning electron microscopy （SEM）, X-ray diffraction（XRD）, XPS, and nanoindentation, etc.After TiN film was deposited on the surface of cast titanium specimens, the specimens appeared bright and golden, microhardness, wear resistance and corrosion resistance improved significantly. Oral environment was simulated by a toothbrushing wear testing machine in which untreated titanium samples and TiN coated samples were toothbrushed with fluoride-containing toothpaste slurry, after being brushed, to the untreated titanium samples, surface roughness increased, surface morphologies changed obviously, discoloration and tarnish could be observed, while surface morphologies and color of TiN coated samples didn’t change significantly indicating TiN has good color stability and can protect cast titanium from excessive abrasion.Color of TiN film was different when the N2 pressure was changed, it appeared bright and golden in color when N2 pressure was 1.7×10-1Pa, arc current 55A and substrate bias 100V, the color leaned to red yellow when N2 pressure increased and to light yellow when N2 pressure decreased. Microhardness of TiN increased when N2 pressure increased, the hardness was largest when N2 gas pressure was 1.7×10-1Pa, then the hardness began to decrease when N2 gas pressure continued to increase. The change of hardness is related with the change of phase structure. If the N2 gas pressure was low, the film was mixed with Ti₂N and TiN, the phases changed to TiN structure gradually with the increase of N2 gas pressure. The maximum hardness was attained when N2 pressure was 1.7×10-1Pa, there were plenty of Ti₂N phases at this time and the multiphase structure increased the film hardness.Arc ion plating possess the advantage of evaporation coating（high deposition rate） and sputtering coating（high energy deposition particles）, besides it has the advantage of high ioning rate, good film substrate adhesion and . The drawback of ion plating is the formation of macrodroplet during coating process. The use of magnetron filter and pulsed substrate bias instead of direct bias can decrease size and quantity of macroparticle and improve film property. Compared with plasma nitriding, pulsed bias arc ion plating has many advantages including an even TiN film formed on surface of titanium specimens, the temperature of substrate was low and treatment time was short, usually the deposition time was 30min. But the wear resistance of ion-plated TiN film needs improving.Combined with plasma nitriding and pulsed bias arc ion plating is a good way to improve film property, it can overcome the color ununiformity problem of plasma nitriding and improve the wear resistance of ion plated TiN film. Cast titanium is plasma nitrided before TiN film deposition to acquire surface hardening layer which adheres to the substrate well, the layer acts as an interlayer and can support the hard TiN film without plastic deformation when subjected to a high-intensity loading, it can also optimize the stress distribution from the film to the substrate and enhance the film adhesion.After titanium framework of denture was plasma nitrided and TiN coated, its surface was smooth and appeared bright and golden, it had good color stability, its wear and corrosion resistance improved significantly, so the compound surface treatment of pure titanium has major significance in stomatology.更多还原