【作者】 徐勇；

【导师】 蒋建中；

【作者基本信息】 浙江大学 ， 材料学， 2010， 博士

【摘要】 由于非晶合金薄膜具有独特的性能,如高硬度、高耐磨性、较好的耐腐蚀性、优异的催化性能,因此既有着重要的科学价值又有着广泛的应用前景。然而低成本的制备特定成分的非晶合金薄膜还是一大挑战。同时,人们对非晶合金薄膜生长机理和变形机制的认识依然较少。本论文中,我们首先通过电沉积方法制备了Pd40Ni40P20非晶合金薄膜。伏安极化曲线和计时电位曲线分析表明,Pd元素在生长的初期阶段起主导作用。通过成分、形貌以及电化学分析,可将电沉积Pd40Ni40P20的过程叙述为Pd诱导的PdNiP共沉积过程,并伴随着析氢反应。接着,为了定量地描述表面演变过程,通过原子力显微镜和电化学分析方法研究了PdNiP非晶薄膜的表面动力学粗化。结果发现界面宽度w(l,t)服从奇异标度行为,主要标度指数为：H=0.60±0.06,βloc=0.47±0.03 andβ=0.19±0.03.结果分析表明,PdNiP薄膜的动力学粗化可能由两个因素控制：大的沉积过电位和扩散的不稳定。然后,结合原子力显微镜和基于同步辐射的相衬成像技术,分别对二元PdP和NiP非晶薄膜表面的生长粗化进行了研究。结果在PdP体系中发现了奇异标度行为：H=0.75±O.06,βloc=0.49±0.07 andβ=0.38±0.08.相反的是,NiP体系却表现为近似正常标度的行为：H=0.70±0.02,βloc≈0 andβ=O.16±0.03.结果表明,薄膜生长时剧烈的析氢反应(HER)所产生的局域作用会造成扩散的不稳定,从而影响着薄膜生长的标度行为,令表面的生长粗化由正常标度(例如NiP体系)转变为奇异标度(例如PdP和PdNiP体系)。最后,采用弯曲方法研究了PdP非晶合金薄膜的变形行为。结果表明当PdP非晶合金薄膜的厚度尺寸降低到某一临界值时,室温下的非晶合金在压应力作用下会发生均匀变形。这一临界尺寸和温度相关：随着变形温度的升高,临界尺寸增大。在薄膜进行均匀变形过程中未观察到温度的升高及硬度的变化。但是,本文研究的所有的薄膜样品在拉伸应力下都产生裂纹,这表明非晶合金的变形模式强烈依赖于应力状态。更多还原

【Abstract】 Metallic glass thin films are both scientifically important and of broad practical applications for their unique properties, such as high hardness, high wear resistance, high corrosion resistance and excellent catalytic properties. However the growth of metallic glass thin film with desired composition by low-cost method is still a challenge and the growth mechanisms and deformation physics of these thin films remain less firmly established as compared with their bulk counterparts.In this thesis, we firstly prepared Pd40Ni40P20 (a classical bulk metallic glass former) metallic glass thin films by electrodeposition. Voltammetric curves and potential-time transient indicate the leading role of Pd in the initial growth stage. Based on compositional, morphological, and electrochemical analyses, the successful electrodeposition of Pd40Ni40P20 is regarded as Pd-induced PdNiP co-deposition accompanying with hydrogen evolution reaction.Then, to quantitatively describe the surface evolution, kinetic surface roughening of electrodeposited metallic glass PdNiP films was investigated by atomic force microscopy combined with electrochemical techniques. Interface width w(l,t) of the films obeys anomalous scaling behavior, with H=0.60±0.06,βloc=0.47±0.03 andβ=0.19±0.03. The results suggest that kinetic roughening of PdNiP films could be controlled by two factors:large overpotential and diffusion instability.Thirdly, kinetic roughening of electrodeposited PdP and NiP metallic glass films during growth was also investigated by atomic force microscopy and synchrotron X-rays phase-contrast radiography. Anomalous scaling of the interface width was observed for PdP system, with H=0.75±0.06,βloc=0.49±0.07 andβ= 0.38±0.08. In contrast, NiP system shows an almost-normal scaling behavior, with H =0.70±0.02,βloc≈0 andβ= 0.16±0.03. The results suggest that surface roughening during film growth is strongly influenced by diffusion instability due to local behaviors like hydrogen evolution reaction (HER), which shifts surface roughening from normal scaling (e.g., in NiP system) to anomalous scaling (e.g., in PdP and PdNiP systems). Finally, we studied the deformation behavior of the PdP metallic glass thin films by bending. The results show that PdP metallic glass thin films deform homogeneously at room temperature under compressive stress when the thickness of the thin film is less than a critical value. This critical value is dependent on the temperature:the higher the temperature, the larger the critical size. During homogeneous deformation, the temperature rise and hardness change can not be found. However, under tensile stress, all the specimens we observed deform by shearing. This indicates that the change of deformation mode in metallic glass is strongly dependent on the stress state.更多还原