Construction of a Scanning Electrochemical Microscope for Evaluation of the Heterogeneity of Passive Films

成功地搭建了一台扫描电化学显微镜(SECM)来评价钝化膜的非均质性。将直径为10微米的铂丝的横截面密封在玻璃管中作为扫描探针电极。将商品型恒电位仪改进为可独立控制探头电极和样品电极电位的双恒电位仪。所构建的SECM的横向分辨率为20um，是探针电极直径的两倍。在pH8.4的硼酸盐溶液中，将两块镶嵌在环氧树脂中的铁片在不同的电位下进行阳极极化，形成不同厚度的钝化膜。然后，在含Fe(CN)_6^&lt；4-&gt；的pH8.4的硼酸盐溶液中，在Fe(CN)_6^&lt；4-&gt；的电位下极化，而在Fe(CN)_6^&lt；3-&gt；的电位下极化两块铁板。…厚度的差异两个铁板上的钝化膜之间的更多可以从探头电流图像中区分出来。用同样的方法研究了多晶铁电极上形成的不均匀钝化膜。探针电流像依赖于晶粒取向，且探针电流按晶粒取向、{100}、{111}、{110}的顺序增大。这种探头电流的差异是由于钝化膜厚度的不同造成的。在pH 8.4的硼酸盐溶液中，电解抛光的钛样品被阳极氧化形成钝化膜。用扫描电子显微镜(SECM)对钝化膜的非均质性进行了分析，发现在4V&lt；Se&gt；以上，随阳极成膜电位的增加，钝化膜的非均质性增加。这种不均一性与每个基片颗粒的形状相对应，表明每个基片颗粒上的钝化膜在厚度和缺陷结构上是不同的。扫描光电化学显微镜(SPECM)是通过在SECM的探针电极上连接光纤来开发的，SPECM将有助于评估钝化膜缺陷结构的差异。较少

A scanning electrochemical microscope (SECM) was successfully constructed to evaluate the heterogeneity of passive films. A cross section of Pt wire with a diameter of 10mum sealed into glass tube was used as a scanning probe electrode. A commercial type of potentiostat was improved to a bipotentiostat which is capable of controlling independently the potentials of probe and specimen electrodes. The constructed SECM has a lateral resolution of 20mum, wich is two times as much as a diameter of probe electrode.Two iron plates embedded in epoxy resin were anodically polarized at different potentials in pH8.4 borate solution to form passive films with different thickness. Afterward, in pH8.4 borate solution containing Fe (CN) _6^<4->, the probe electrode was polarized at the potentioal at which Fe (CN) _6^<4-> can be oxidized to Fe (CN) _6^<3->, whereas the two iron plates were polarized at the potetial at which Fe (CN) _6^<3-> can be reduced to Fe (CN) _6^<4->. The difference in thickness … More between passive films on two iron plates could be distinguished from the probe current image. The heterogeneity of passive film formed on polycrystalline iron electrode with distinct grains was also examined in the same manner. The probe current image depended on the grain orientation and the probe current increased in the order of grain orientation, {100}, {111}, and {110}. This difference in probe current results from the difference in thickness of passive films.An electropolished titanium specimen was anodically oxidized in pH 8.4 borate solution to form the passive film. The heterogeneity of the passive film was evaluated using the SECM.It is found from the probe current image that the heterogeneity of the passive film increases with increasing anodic potential for film formation above 4 V_<SHE>. This heterogeneity corresponds to the shape of each substrate grain, suggesting that the passive film on each substrate grain differs in thickness and defective structure.A scanning photoelectrochemical microscope (SPECM) is being developed by attaching an optical fiber to the probe electrode of SECM.SPECM would be useful to evaluate the difference in defective structures of the passive films. Less