采用广义弛豫时间分布法的铌电解抛光分析
Analysis of Niobium Electropolishing Using a Generalized Distribution of Relaxation Times Method
AI总结：
本研究提出结合电化学阻抗谱与弛豫时间分布法，可在铌电解抛光前或过程中检测表面状态，区分两种抛光模式，预测刻蚀情况并优化参数以获得光滑表面。
摘要：
我们利用电化学阻抗谱，设计了一种在铌经受电解抛光（EP）处理时检测其表面微观状态的方法。该方法采用电化学阻抗谱（EIS），在不中断抛光反应的前提下收集电极表面状态的信息。我们通过所谓的弛豫时间分布（DRT）方法分析EIS数据。借助DRT，无需预先掌握电极动力学的先验知识，即可将EIS数据反卷积为离散的弛豫时间峰。通过分析弛豫时间峰，我们能够区分EP反应的两种不同模式。随着抛光电压升高，电极从以单个弛豫时间峰为特征的低压EP模式，转变为以两个弛豫时间峰为特征的高压EP模式。我们推测第二个峰由电极表面氧化层的形成导致。我们还发现，这个由氧化物诱导的峰会转变为负弛豫时间，这是阻塞电极过程的标志。通过分析经EP处理的样品，我们发现以低压模式抛光的样品因晶粒刻蚀和晶面化，表面粗糙度显著更高。我们发现，只有当氧化膜峰存在且处于负弛豫时间区域时，样品的表面粗糙度才会得到改善。这表明EIS结合DRT分析可用于预测经EP处理的铌的刻蚀情况。该方法还可在EP之前或过程中实施，从而能够调整抛光参数以保证腔体内表面的光滑光洁度。
英文摘要：
Using electrochemical impedance spectroscopy, we have devised a method of sensing the microscopic surface conditions on the surface of niobium as it is undergoing an electrochemical polishing (EP) treatment. The method uses electrochemical impedance spectroscopy (EIS) to gather information on the surface state of the electrode without disrupting the polishing reaction. The EIS data is analyzed using a so-called distribution of relaxation times (DRT) method. Using DRT, the EIS data can be deconvolved into discrete relaxation time peaks without any a priori knowledge of the electrode dynamics. By analyzing the relaxation time peaks, we are able to distinguish two distinct modes of the EP reaction. As the polishing voltage is increased, the electrode transitions from the low voltage EP mode, characterized by a single relaxation time peaks, to the high voltage EP mode, characterized by two relaxation time peaks. We theorize that this second peak is caused by the formation of an oxide layer on the electrode. We also find that this oxide induced peak transitions from to a negative relaxation time, which is indicative of a blocking electrode process. By analyzing EPed samples, we show that samples polished in the low voltage mode have significantly higher surface roughness due to grain etching and faceting. We find that the surface roughness of the samples only improves when the oxide film peak is present and in the negative relaxation time region. This shows that EIS combined with DRT analysis can be used to predict etching on EPed Nb. This method can also be performed before or during the EP, which could allow for adjustment of polishing parameters to guarantee a smooth cavity surface finish.
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