Nakajima Daiki, Kikuchi Tatsuya, Natsui Shungo, Suzuki Ryosuke O
Faculty of Engineering, Hokkaido University N13-W8, Kita-ku Sapporo Hokkaido 060-8628 Japan
RSC Adv. 2018 Nov 6;8(65):37315-37323. doi: 10.1039/c8ra07712f. eCollection 2018 Nov 1.
The fabrication of sticky and slippery superhydrophobic aluminum was achieved by anodizing in pyrophosphoric acid and modification with self-assembled monolayers (SAMs). In addition, the corresponding sliding behaviors of a water droplet were investigated by contact angle measurements and direct observations. For the formation of anodic alumina nanofibers, 4N aluminum plates were anodized in a concentrated pyrophosphoric acid solution at 25-75 V. The morphology of the anodic oxide successively changed to barrier oxide, porous oxide, nanofibers, bundle structures with many nanofibers, and then weak nanofibers during anodizing. The anodized specimens were immersed in a fluorinated phosphonic acid/ethanol solution to form SAMs on the surface of the anodic oxide. The contact angle hysteresis drastically changed with anodizing time: it increased with the formation of porous oxide, decreased for the nanofibers and bundle structures, and then increased once again for the weak nanofibers. Correspondingly, the adhesion interaction between the water droplet and the aluminum surface also drastically changed to show sticky, slippery, and sticky behaviors with anodizing time. More sticky and slippery aluminum surfaces can be obtained by anodizing at higher voltages. The slippery behavior was further improved through two distinct anodizing processes with the formation of ordered alumina nanofibers. A superhydrophobic aluminum surface with coexisting sticky and slippery properties was fabricated by the selective anodizing method.
通过在焦磷酸中进行阳极氧化并采用自组装单分子层（SAMs）进行改性，制备出了具有粘性和滑性的超疏水铝。此外，通过接触角测量和直接观察研究了水滴相应的滑动行为。为了形成阳极氧化铝纳米纤维，将4N铝板在25 - 75V的浓焦磷酸溶液中进行阳极氧化。在阳极氧化过程中，阳极氧化物的形态依次变为阻挡氧化物、多孔氧化物、纳米纤维、具有许多纳米纤维的束状结构，然后变为弱纳米纤维。将阳极氧化后的试样浸入氟化膦酸/乙醇溶液中，在阳极氧化物表面形成SAMs。接触角滞后随阳极氧化时间急剧变化：随着多孔氧化物的形成而增加，对于纳米纤维和束状结构则减小，然后对于弱纳米纤维又再次增加。相应地，水滴与铝表面之间的粘附相互作用也随阳极氧化时间急剧变化，呈现出粘性、滑性和粘性行为。通过在更高电压下进行阳极氧化可以获得更具粘性和滑性的铝表面。通过两个不同的阳极氧化过程形成有序的氧化铝纳米纤维，进一步改善了滑性。采用选择性阳极氧化方法制备出了具有粘性和滑性共存的超疏水铝表面。
