【作者】 王玉江；

【导师】 马欣新；

【作者基本信息】 哈尔滨工业大学 ， 材料学， 2009， 博士

【摘要】 本文采用低温熔融盐电镀/阳极氧化和磁控溅射沉积/阳极氧化两种复合工艺在医用316L不锈钢表面制备了微米级和亚微米级载药微坑,并系统研究铝镀层结构、铝镀层厚度以及阳极氧化工艺参数对微坑结构、密度及尺寸分布等的影响规律以及它们之间的内在联系。深入探讨了不同结构微坑的形成机制,并初步研究了微坑结构对不锈钢表面血液相容性的影响。利用扫描电子显微镜、X射线光电子能谱和X射线衍射技术对不锈钢表面在不同制备工艺下获得的铝镀层的表面形貌、成分和相结构进行了分析,结果表明熔融盐电镀法和磁控溅射法制备的铝镀层组织结构分别主要受电流密度和基体负偏压影响。利用磁控溅射技术制备的铝镀层较熔融盐电镀铝镀层的颗粒更为细小、组织更为致密。利用扫描电子显微镜对上述两种方法制备的微坑形貌进行分析,结果表明不锈钢表面形成两种具有典型特征的微坑:一种是其内部由大量细小微坑组成,且基体受到不同程度的腐蚀的微坑,本文称其为复合微坑;另一种是在基体上均匀分布的,内部无细小微坑结构的微坑,本文称其为常规微坑。低温熔融盐电镀/阳极氧化工艺在不锈钢表面制备微坑时所需阳极氧化电压较低,且微坑形状主要受铝镀层形貌的影响,当铝镀层形貌以片状为主时,不锈钢表面主要形成圆形或椭圆形规则微坑;当镀铝层形貌以粒状结构为主时,不锈钢表面主要形成方形规则微坑;且微坑尺寸均随着阳极氧化电压的升高和阳极氧化时间的延长而增加。磁控溅射沉积/阳极氧化法在不锈钢表面制备的微坑的形状、尺寸及数量与铝镀层的结构密切相关。当镀层中颗粒大小不均,尺寸分布在1.0~2.5μm之间,且颗粒之间有一定的孔隙和缺陷时,不锈钢表面形成大量开口尺寸在30~100μm的不均匀分布的复合微坑;当铝镀层颗粒大小趋向一致,颗粒尺寸在2μm左右,颗粒之间出现明显的衔接,镀层孔隙率显著下降时,不锈钢表面形成均匀致密的方形规则微坑,且微坑有较明显的晶体学取向,呈现出小平面特征;当铝镀层均匀致密,颗粒尺寸在1μm左右时,不锈钢表面易形成圆形规则微坑,微坑的开口尺寸随阳极氧化参数的改变,可在0.2~3μm之间进行调节;当铝镀层呈疏松多孔结构时,不锈钢基体表面形成大量开口尺寸在50~100μm之间的复合微坑。不锈钢表面形成微坑的特征除了受铝镀层形貌影响之外,还受铝镀层厚度、阳极氧化电压、阳极氧化温度及时间等诸多因素的控制,而各因素之间又相互关联相互制约。在相同的阳极氧化温度/电压下,不锈钢表面规则微坑向复合微坑转变的临界阳极氧化电压/温度值随着铝镀层厚度的增加而增加。具有相同铝镀层厚度的试样在相同阳极氧化电压和阳极氧化温度下,微坑的特征又受到阳极氧化时间的控制。通过改变电解液种类、阳极氧化参数都会对基体表面微坑形貌、尺寸及数量产生显著影响。通过对以上方法形成的微坑的形貌及其形成过程的详细分析,提出两种典型微坑的形成机制。对于复合微坑而言,阳极氧化初期微孔优先在铝镀层的某些缺陷处生成,并以这些缺陷为中心,在一定尺度范围内优先发展形成微孔群。缺陷中心处微孔向基体发展速率最快,四周依次减弱。这些微孔相继通过Al/316L界面与基体接触,在基体表面形成微小腐蚀坑,小尺寸腐蚀坑迅速汇聚在一起,在不锈钢表面形成内部具有无数微小孔洞特征的复合微坑。316L不锈钢基体上圆形规则微坑形成过程经历了铝镀层表面阳极氧化微孔的均匀形成、稳定生长、到达316L不锈钢基体并在相应位置腐蚀出微坑、基体上微坑快速合并长大及基体快速腐蚀等阶段。血液相容性研究结果表明,当不锈钢表面微坑尺寸在0.5~2.0μm之间时,能有效减少不锈钢表面血小板黏附数量,同时能提高316L不锈钢表面亲水性,改善316L不锈钢表面的血液相容性。更多还原

【Abstract】 Micro- and sub-micro drug carrier cavities were fabricated on surface of 316L stainless steel by the following two compound technologies: low temperature molten salts electrodeposition/anodization and magnetron sputtering/anodization. The effect of structure and thickness of aluminum films and anodizing process parameters on the structure, density and size distribution of the cavities were studied systematically. The formation mechanisms of different structure cavities were discussed. In addition, the preliminary investigations regarding to the structure of cavities on the blood-compatibility of 316L stainless steel were conducted in this work.The surface morphology, composition and phase structure of aluminum films deposited at different processing parameters were studied by scanning electron microscopy, X-ray photoelectron spectroscopy and X-ray diffraction methods. The results showed that the properties of aluminum films fabricated by molten salt electroplating were mainly affected by current density, while the properties of aluminum films obtained by magnetron sputtering were mainly affected by the negative bias. In comparison with molten salt electroplating process, aluminum films prepared by magnetron sputtering had finer grain size and denser structure. Morphologies of the cavities on 316L stainless steel were studied by scanning electron microscopy. The resulets showed that two typical type cavities were fabricatied on surface of 316L stainless steel. The cavities composed with numerous of small pores in the inner walls with the substrate corroded at different degree are defined as complex cavities. The cavities without small pores in the inner wall and distributed uniform on substrate are defined as general cavities.In comparison with sputtering deposition/anodizing process, the anodizing voltage used in the preparation of micro-cavities on 316L stainless steel by low-temperature molten salt electroplating/anodizing technique are lower. The shape of cavities on stainless steel surface is mainly affected by the morphology of aluminum coating. The circle or subcircle cavities corresponded to flaky aluminum layers, while the rectangle cavities corresponded to granular aluminum layers. It was also found that the cavity size increased with increasing the anodizing voltage and time.The shape, size and number of the cavities on 316L stainless steel prepared by the magnetron sputtering deposition/anodization are closely related to the aluminum coating structure. When the aluminum grain size distribution is inhomogeneous (distributed from 1.0 to 2.5μm) and there are some porosity and defects between the grains, a large number of cavities with size distributed from 30μm to 100μm will be easily formed on the surface of stainless steel; when the aluminum grain size distribution is uniform and grain size is about 2μm accompany with the decrease of porosity and defects between the grains, the uniform dense rectangle cavities with obvious crystallographic orientation can be obtained on stainless steel surface; when the aluminum film are uniform and dense with grain size of about 1μm and there are almost no defects between the grains, the regular circle cavities can be easily obtained on stainless steel surface. Cavities with the size ranging from 0.2 to 3μm can be obtained on 316L substrates by adjusting the anodizing process parameters. When aluminum films are loose and porous, a large number of cavities with size distributed from 50μm to 100μm will be easily formed on the surface of stainless steel. The characteristics of cavities on stainless steel surface not only affected by the aluminum coating morphology, but also controlled by the thickness of aluminum coating, anodizing voltage, anodizing temperature, anodizing time and some other factors. The factors are interdependence and mutual restriction. When anodizing temperature/potential nearly constant, the critical highest anodizing potential/temperature relates to the thickness of the aluminum coatings. When the aluminum coating has a certain thickness, the characteristics of the cavities on stainless steel are controlled by the anodizing time. That is to say that the change of type of electrolyte and anodizing parameters have a significant impact on the shape, size and number of the cavities forming on 316L stainless steel surface.Through carefully studying on the morphology and formation process of cavities on 316L stainless steels surface, this paper puts forward the formation mechanisms of two typical type of the cavities. For complex cavities, at the initial stage of anodizing process, the pores are preferentially formatted on the defect areas of aluminum coatings. Takes the defect areas as center, several microporous group are formed in certain scale. The micropores in defects center have the fastest migration rate from surface coating to the substrate and the migration rate of surrounding minished in order. These microporous successively arrived at the stainless steel surface and finally formed complex cavities on the surface of 316L stainless steel. And each big cavity is composed with numerous of small pores. The stages for the formation of general cavities on 316L stainless steel surface including: the uniform formation and stable growth of micropores on aluminum coating; mciropores arriving the substrate and cavities formed on substrate at the relevant position; growth and coalescence process of cavities on substrate and the quick- corrosion of the substrate.The results of the blood compatibility indicate that compared with untreated 316L stainless steel, samples with cavities in the size of 0.5~2.0μm can effectively reduce the number of platelet adhesion, increase the hydrophilic and improve the blood compatibility of 316L stainless steel.更多还原