【作者】 张天林；

【导师】 黄文浩；

【作者基本信息】 中国科学技术大学 ， 精密仪器及机械， 2008， 博士

【摘要】 纳米压痕技术由于具有试样制备简单、操作方便以及高重复性的测量结果等优点被广泛应用,目前已成为微纳计量、材料科学和表面科学中检测和表征微观力学性能的主要手段之一。本文在国家自然科学基金(No.50335050)和863基金(No.2006AA042311)的资助下完成。论文主要从薄膜基底和针尖尺寸效应两个方面研究了纳米压入技术中对测量结果的可靠性影响的重要问题。本论文的主要研究内容和成果包括以下几个方面:首先,利用有限元方法探讨了薄膜/基底体系中材料的力学性能对纳米压入测量结果的影响。针对软膜在硬基底(软膜/硬基)和硬膜在软基上(硬膜/软基)两种结构体系,研究了薄膜和基底在压头压入过程中的弹塑性变形行为及其演化过程。分析了不同力学性能的膜/基体系材料及薄膜厚度对硬度测量结果的影响。在此基础上,阐述了引起这种基底效应行为的作用机理。该工作对纳米压入技术检测方法和评估膜类结构材料的微观力学性能以及对测量结果的可靠性分析都有着重要意义。其次,通过理论和数值分析的方法探讨了纳米压入过程中非理想压头尖端曲率半径的变化对测量结果的影响,结果表明对于不同曲率半径的针尖,硬度的测量结果呈现出明显的尺寸效应。在此基础上,对引起这种针尖尺寸效应的作用机理做出了分析和解释;理论推导出了一个硬度与曲率半径和压入深度关系的半经验公式。另外,利用数值分析还得到了不同曲率半径的压头压入过程中材料的弹塑性变形场的分布及其演化过程。分析结果表明,引起针尖尺寸效应的主要原因是由于压头尖端曲率半径的存在导致对压入过程中接触深度的估计过低。另外,不同曲率半径的压头引起压头下方弹塑性变形场的分布有所不同,这种由于压头几何形状的非相似性导致材料变形场的非相似性对这种针尖尺寸效应也有一定的影响。再次,利用纳米压入技术、原子力显微镜(AFM)和X射线衍射分析技术(XRD)实验研究了射频式(RF)磁控溅射多晶氧化锌(ZnO)薄膜在软、硬不同基底上的力学特性;分析了不同退火温度对膜的力学性能和微观结构的影响。实验结果表明,对于磁控溅射ZnO薄膜,在450℃下退火得到的膜的硬度和弹性模量分别具有最大值,且薄膜具有最佳结晶品质。最后,总结了本论文的研究内容和主要创新点,并展望了纳米压入技术未来研究和发展方向。更多还原

【Abstract】 Nanoindentation is applied in many research fields for its advantages such as convenient sample preparation,easy operation,and highly repeatable results.Up to now,nanoindentation has become one of the main and the most important methods to measure the material mechanical properties in micro/nano-metrology,material science and surface science.This dissertation is supported by National Natural Science Fund of China (No.50335050)and State 863 Projects(No.2006AA04Z311).To enhance the reliable analysis of the measured results by nanoindentation,two important issues on substrate and tip radius effects in nanoindentaion applications are discussed here.The main research contents of this dissertation are summarized in following aspects:Firstly,the influence of materials mechanical properties in film/substrate systems in the nanoindentation results is investigated by finite element method(FEM).For soft film on hard substrate and hard film on soft substrate systems,the elastic and plastic deformation and the deformation evolvement process in films and substrates are analyzed respectively.Also the effects of mechanical properties of the film and the substrate in different systems on the hardness measurements are analyzed,as well as the film thickness.Further more,the mechanism of this kind of substrate effect is discussed.All these results have important meaning in measurement,evaluation and reliability analysis of the mechanical properties of film structure materials by nanoindentaion.Secondly,the effects of tip radius of the blunt indenter on the nanoindentation results are investigated by theoretical analysis and FEM method.The results show that the measurement values of hardness by nanoindentation have different and obvious depth size effects for the blunt indenters with different tip radii.Based on the results,we also analyzed and explained the mechanism of the tip radius size effects.A semi-empirical relation,which depicts hardness with tip radius and indentation depth is derived by theoretical analysis.And also,the elastic and plastic deformation and the deformation evolvement process in materials under different tip radius indenters are simulated by FEM.The simulation results indicate that the tip size effect in nanoindentaion is caused mainly by the underestimate of the contact area due to the indenter bluntness.And this kind of tip radius size effect becomes more and more obvious as the tip radius increases.For the elastic and plastic deformation distributions in materials under the indenters with different tip radii are different,the physical dissimilarity due to geometrical dissimilarity will also influence the tip size effect,although it is a factor with minor influence.Thirdly,the mechanical properties of radio frequency(RF)magnetron sputtering zinc oxide(ZnO)thin film on different substrates are investigated by nanoindentation, atomic force microscopy(AFM),and X-ray diffraction(XRD)technology.The mechanical properties and the nanostructures of RF magnetron sputtering ZnO film under different annealing temperatures are also discussed.Results show that proper anneal treatment can improve the crystal quality and enhance the mechanical properties of ZnO film.The film has a maximum hardness and elastic modulus value at 450℃annealing temperature in air.Finally,the research contents and the main innovations in this dissertation are summarized,and the future research directions of the nanoindentation application are discussed.更多还原