While porous anodic oxides have been extensively studied, there is limited research on the specific role of fluoride ions in the anodization. This study compares the morphology of titanium anodization products before and after the addition of ammonium pentaborate to the NH₄F electrolyte. The current–time curve in anodization is analyzed to elucidate the real role of fluoride ions. The findings indicate that the real role of fluoride ions in the anodization is to form an anionic contaminated layer and cause the generation of electronic current, triggering the oxygen bubble mold effect and promoting nanotube growth. However, when pentaborate anions are introduced in the anionic contaminated layer, they hinder the production of electronic current, leading to a significant reduction in electronic current. Consequently, the growth rate of nanotubes decreases, resulting in the formation of bulb-shaped nanotube embryos. This study provides interesting evidence supporting the role of fluoride ions by combining the ionic and electronic current theory with the oxygen bubble mold effect. These pieces of evidence cast doubt on the simple chemical dissolution of fluoride ions in the traditional field-assisted dissolution theory. The experimental results significantly contribute to our understanding of the growth mechanism of porous anodic oxides.

中文翻译：

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氟离子在阳极 TiO2 纳米管生长中的真实作用

虽然多孔阳极氧化物已被广泛研究，但对氟离子在阳极氧化中的具体作用的研究有限。本研究比较了向NH ₄ F电解液中添加五硼酸铵前后钛阳极氧化产物的形貌。分析阳极氧化中的电流-时间曲线，以阐明氟离子的真正作用。研究结果表明，氟离子在阳极氧化中的真正作用是形成阴离子污染层并引起电子电流的产生，引发氧泡模效应并促进纳米管生长。然而，当阴离子污染层中引入五硼酸根阴离子时，它们会阻碍电子电流的产生，导致电子电流显着减少。因此，纳米管的生长速率降低，导致形成灯泡形纳米管胚。这项研究通过将离子流和电子流理论与氧泡模效应相结合，提供了支持氟离子作用的有趣证据。这些证据对传统场辅助溶解理论中氟离子的简单化学溶解提出了质疑。实验结果极大地有助于我们理解多孔阳极氧化物的生长机制。