Electrochemical anodizations of metals and alloys have attracted increasing attention as a method to fabricate highly ordered porous films. The popular formation mechanism of porous anodic oxides is dissolution equilibrium theory, which indicates that the equilibrium between oxide growth and dissolution via digging manner at the bottom of pores is the major cause of tubular structure. Here, terminated nanotubes with sealed bottoms were discovered while titanium foils were anodized under different conditions. In one terminated nanotube, oxide at the bottom does not grow whereas dissolution from electrolyte still exists. According to the estimated dissolution rate, it only takes approximately 20 s for the bottom of the terminated nanotube to be penetrated absolutely based on dissolution equilibrium theory. Apparently, most anodizations in this work all last for more than 20 s after the appearance of terminated nanotubes. Therefore, the bottom of the terminated nanotube is bound to be penetrated absolutely. Nevertheless, its bottom is sealed completely, namely the experimental results are not consistent with theoretical results based on dissolution equilibrium theory. Hence, terminated nanotubes are evidence against the dissolution equilibrium theory.

作为制造高度有序的多孔膜的一种方法，金属和合金的电化学阳极氧化引起了越来越多的关注。多孔阳极氧化物的流行形成机理是溶解平衡理论，这表明在孔底部通过挖孔方式氧化物生长与溶解之间的平衡是管状结构的主要原因。在这里，发现了具有密封底部的封端纳米管，同时在不同条件下对钛箔进行了阳极氧化处理。在一个封端的纳米管中，底部的氧化物不生长，而仍然存在电解质的溶解。根据估计的溶出速率，基于溶出平衡理论，仅需约20 s即可完全穿透封端纳米管的底部。显然，在终止的纳米管​​出现后，这项工作中的大多数阳极氧化过程都持续了超过20 s。因此，封端的纳米管的底部必然被绝对地穿透。然而，它的底部是完全密封的，即实验结果与基于溶出平衡理论的理论结果不一致。因此，封端的纳米管是反对溶解平衡理论的证据。