【作者】 赵性川；

【导师】 吕宇鹏；

【作者基本信息】 山东大学 ， 材料学， 2014， 博士

【摘要】 四水磷酸锌(Zn3(PO4)2·4H2O, Hopeite,简称为HP)因具有良好的耐蚀性与防护性,广泛应用于金属表面的防腐、提高涂装结合力及表面润滑等方面。近来被发现具有良好的生物相容性且在一定条件下能够转化为羟基磷灰石(HA),可以作为一种潜在的生物医用材料。另一方面,钛因具有重量轻、强度大以及良好耐蚀性等优良特性而广泛应用在国防航空航天、造船等工业领域。同时,因其与骨相近的弹性模量、良好的生物相容性等特点在临床上也得到了广泛的应用。在钛表面制备一层HP转化膜,既可以提高其表面防护性能,应用于工业军事等领域,也可以作为生物金属植入体材料表面改性应用于医学领域。但钛表面由于存在稳定的氧化膜难以进行转化膜的制备而限制了其应用。本研究首先优化出适合钛金属的化学转化液配方,并在此基础上利用不同的自制辅助外场,以场效应与化学转化法相结合的方式,成功在钛基体表面制备出HP转化涂层。根据试验需要,设计了四种不同的外场辅助手段：超声场、匀磁场、静电场以及电流场。通过调整转化时间、转化液的pH、转化温度以及各场参数,对其作用下形成转化膜的结构和性能进行研究。同时,对四种不同辅助场效应的机理进行了讨论。分别利用X射线衍射仪(XRD)、场发射扫描电子显微镜(FE-SEM)、红外光谱分析仪(FTIR)、高分辨透射电镜(HRTEM)、X射线光电子能谱仪(xPS)、扫描探针显微镜(SPM)以及三电极系统电化学工作站等手段对转化膜的相组成、形貌、原子团、微观结构、表面成分、表面粗糙度以及耐蚀性进行了系统的表征和分析。在此基础上,选取了60℃超声处理的转化膜,对人的成纤维细胞进行细胞培养,初步探讨了HP转化膜作为生物材料的生物相容性。结果表明,转化膜主要有HP组成,在不改变转化膜相组成和晶粒形状的基础上,超声作用能提高成膜形核率和结晶度,明显地减小晶粒尺寸至未经外场处理晶粒尺寸的1/5-1/10。此外,超声处理后膜厚膜重以及粗糙度都有所降低,但是致密度增加。而且超声处理使转化膜具有更加优异的耐蚀性能,250W超声功率下处理60min转化膜自腐蚀电流(Icorr)为0.06μA/cm2,相比于纯钛的17.5μA/cm2,明显降低,对应的EIS也表现出高的阻抗值。另外化学转化开始阶段超声功率能够影响转化膜的形核率,50W,100W和250W功率下,相同转化时间内形核数目随功率升高依次增多。磁场作用能够提高HP的形核率,生成的转化膜更加均匀致密,颗粒细小。随着转化时间的增加到60min,经过长时间溶解及再结品平衡过程转化膜颗粒表面呈现出层状结构,这种结构的表面积明显增大,粗糙度增加。此外,化学转化时间越长,膜的耐蚀性越好,与无磁场作用相比,相同转化时间下磁场作用下形成的转化膜表现出较好的耐蚀性能。电流场阴极电化学沉积过程中转化膜的组成随处理温度的不同发生变化,温度为60℃时,转化膜主要为HP,温度为30℃时,转化膜的主要有单质Zn组成。两者的耐蚀性表现出明显的差别,60℃下HP转化膜的自腐蚀电流比30℃的锌转化膜几乎低100倍,而阻抗值高出2-3个数量级。转化液经过铁粉熟化处理后,Fe2+的存在能够改变转化膜的形态和性能。未进行铁粉熟化的溶液中,60℃下电沉积的转化膜有蘑菇状HP和Zn组成,30℃下转化膜主要是致密板状结构的Zn组成；而铁粉熟化后的溶液中形成的转化膜在60℃时主要为板条状HP晶体,在30℃时,为空心泡状结构的单质Zn。同时,电流密度对转化膜的形成形态起到关键作用,电流密度越大,转化速度越快,在铁粉熟化后的溶液中电流密度能够改变转化膜的择优取向生长方向；随着转化膜的生长,局部电流密度的增高和不均匀性分布导致形成小片状晶体(厚度小于1μm、直径为10-30μm)的球形团簇。电场辅助化学转化过程中,生成的HP转化膜沿着(020)和(040)晶面方向发生明显的择优生长。在转化初期,电场能影响转化膜在基体上的铺展程度,无电场时形成转化膜平面铺展较阔,板条厚度较大,呈纵横交错状态。随电场强度升高,板条状的转化膜出现分散现象,铺展和交错程度降低。同时对于刚形成的转化膜,无电场时表现为不规则的小块状颗粒,而电场作用下形成的则相对圆滑、规则。更多还原

【Abstract】 Hopeite (Zn3(PO4)2·4H2O, HP for short) has been widely used for anticorrosion of metal surface, improving paint adhesion and surface lubrication due to its good corrosion resistance and protection. It has been found that HP has good biocompatibility, Recently. And under certain condition it can be transformed into hydroxyapatite (HA) which can be used as potential biomedical material. On the other hand, titanium (Ti) has been found wide application in the aerospace, shipbuilding and other industries because of its light-weight, high-strength and good corrosion resistance. Meanwhile, Ti owns the elastic modulus similar to that of bone, good biocompatibility and easy processing characteristics, which leads to widespread application in clinical of Ti. The preparation of HP coating on Ti can enhance the protection characteristics of metal surface used in industrial and military field. In addition, the preparation of HP coating on Ti can also be used as implant materials used in medical applications. Because of the presence of a passive oxide layer at its surface, Ti is difficult to get a phosphate coating by the PCC method, which has greatly limited its application.Based on the optimization of conversion solution which can be obtained by chemical conversion on titanium surface this research aimed to utilize different means of self-made auxiliary field with the combination of field effect and chemical conversion and achieved success in the preparation of zinc phosphate on the titanium substrate surface. According to the requirements of the test, four different auxiliary field methods are designed including ultrasonic field, magnetic field, electrostatic field and the cathode electrochemical deposition. At the same time, the mechanism of the four different auxiliary field effect are discussed and also the structure and properties of conversion film formed under the influence of were characterized. In addition, the properties such as phase composition, microstructure, surface composition, morphology, radicals, surface roughness, and the corrosion resistance of the conversion coating were evidenced by X-ray diffractometer (XRD), field emission scanning electron microscope (FE-SEM), infrared spectrometer (FTIR), high-resolution transmission electron microscopy (HRTEM) and X-ray photoelectron spectrometer (XPS), scanning probe microscope (SPM) and three electrode electrochemical workstation system by way of adjusting parameters like the PH of conversion liquid, the conversion time and temperature. And on this basis, we choose conversion coating by ultrasonic processing at60℃and make cell culture experiment of human fibroblasts to discuss the biocompatibility of zinc phosphate conversion coating as biomaterial preliminarily.The results show that the conversion coating is mainly composed of Zn3(PO4)2·4H2O. Furthermore, ultrasonic action can significantly reduce the grain size to1/5～1/10of the grain size formed without ultrasonic. Besides, ultrasonic increase the degree of crystallinity on the premise of not changing the phase composition and grain shape of the conversion coating. Besides, ultrasound can increase the nucleation rate of the conversion film. The thickness, weight and roughness of that are reduced but the density increased. And the coating has more excellent corrosion resistant performance after ultrasonic processing. The conversion coating with ultrasonic processing under250W for60min has the much lower corrosion current of0.06μA/cm2than that of the pure titanium of17.5μA/cm2. The corresponding EIS also showed high impedance values. Moreover, ultrasonic power can influence the nucleation rate of conversion coating at the start of the chemical conversion and the nucleation number increases as the power increases from50W to250W.Magnetic field can increase the nucleation of zinc phosphate, the coatings is more uniform and compact, also the particle is smaller. The conversion coating particles’ surface present a layered structure after dissolution for a long time and recrystallization process with increasing time to60min. As a consequence, the surface area of the structure and roughness increases. Also we can conclude that the longer time chemical conversion takes, the better the corrosion resistance of membrane will be. The conversion film formed under the effect of magnetic field shows more excellent corrosion resistance than that without magnetic field at the same conversion time.The composition of conversion coating in cathodic electrochemical deposition process changes with treatment temperature, when the temperature is60℃, the conversion coatings are mainly zinc phosphate, however when the temperature is30℃, the main composition of conversion coating is pure metal Zinc. There are clear differences between the two on the corrosion resistance, the corrosion current of60℃zinc phosphate conversion coating is almost100times lower than that of zinc conversion coating30℃, as well as2to3orders of magnitude higher than that of the impedance values. In addition, after aging process of iron powder, the presence of Fe2+in the conversion of liquid can change the shape and properties of conversion coatings. For the solution without iron powder aging process, the conversion coating of electrodeposition at60℃is composed of mushroom-shaped HP crystal and zinc, and the coatings formed at30℃mostly consists of a very thin layer of simple substance zinc. The conversion coating formed in solution with iron powder aging at60℃is mainly composed of dense lath zinc crystals, while at30℃for simple substance zinc with hollow vesicular structures.Moreover, in the process of electrochemical deposition, current density play a key role in the formation of conversion coating, the greater the current density, the faster the transformation. In the solution with iron powder aging, current density can change the preferred orientation growth direction of conversion coating. With the growth of the conversion coating, high and uneven distribution of the local current density results in the submicron level of platelet crystal clusters into spherical distribution on the previous coating.In the process of field-assisted chemical conversion, the diffraction intensity of the peaks along the (020) and (040) planes obviously increases which implies the preferred epitaxial growth of HP along the planes. In the early stages of the transformation, the electric field can affect the degree of spreading of conversion coating on the substrate, without electric field, the conversion coatings spread widely and show criss-cross, with a larger strip thickness. As the electric field intensity increases, plate strip conversion coating appears dispersion phenomenon, the degree of spreading and interleaving is reduced. Meanwhile the newly formed conversion coating is characterized by irregular small block particles without electric field, while the particles formed with electric field are relatively smooth and rules.更多还原