Ku Chin-An, Hung Chia-Wei, Chung Chen-Kuei
Department of Mechanical Engineering, National Cheng Kung University, Tainan 701, Taiwan.
Nanomaterials (Basel). 2024 Jul 17;14(14):1216. doi: 10.3390/nano14141216.
For commercial processes, through-hole AAO membranes are fabricated from high-purity aluminum by chemical etching. However, this method has the disadvantages of using heavy-metal solutions, creating large amounts of material waste, and leading to an irregular pore structure. Through-hole porous alumina membrane fabrication has been widely investigated due to applications in filters, nanomaterial synthesis, and surface-enhanced Raman scattering. There are several means to obtain freestanding through-hole AAO membranes, but a fast, low-cost, and repetitive process to create complete, high-quality membranes has not yet been established. Here, we propose a rapid and efficient method for the multi-detachment of an AAO membrane at room temperature by integrating the one-time potentiostatic (OTP) method and two-step electrochemical polishing. Economical commercial AA1050 was used instead of traditional high-cost high-purity aluminum for AAO membrane fabrication at 25 °C. The OTP method, which is a single-step process, was applied to achieve a high-quality membrane with unimodal pore distribution and diameters between 35 and 40 nm, maintaining a high consistency over five repetitions. To repeatedly detach the AAO membrane, two-step electrochemical polishing was developed to minimize damage on the AA1050 substrate caused by membrane separation. The mechanism for creating AAO membranes using the OTP method can be divided into three major components, including the Joule heating effect, the dissolution of the barrier layer, and stress effects. The stress is attributed to two factors: bubble formation and the difference in the coefficient of thermal expansion between the AAO membrane and the Al substrate. This highly efficient AAO membrane detachment method will facilitate the rapid production and applications of AAO films.
对于商业工艺，通孔阳极氧化铝（AAO）膜是通过化学蚀刻由高纯度铝制成的。然而，这种方法存在使用重金属溶液、产生大量材料浪费以及导致孔结构不规则等缺点。由于在过滤器、纳米材料合成和表面增强拉曼散射中的应用，通孔多孔氧化铝膜的制备已得到广泛研究。有几种方法可以获得独立的通孔AAO膜，但尚未建立一种快速、低成本且可重复的工艺来制造完整、高质量的膜。在此，我们提出一种在室温下通过整合一次性恒电位（OTP）方法和两步电化学抛光来多次分离AAO膜的快速有效方法。在25°C下制备AAO膜时，使用经济的商用AA1050代替传统的高成本高纯度铝。OTP方法是一种单步工艺，用于制备具有单峰孔径分布且直径在35至40nm之间的高质量膜，在五次重复过程中保持高度一致性。为了反复分离AAO膜，开发了两步电化学抛光以最小化膜分离对AA1050基板造成的损伤。使用OTP方法制备AAO膜的机制可分为三个主要部分，包括焦耳热效应、阻挡层的溶解和应力效应。应力归因于两个因素：气泡形成以及AAO膜与铝基板之间热膨胀系数的差异。这种高效的AAO膜分离方法将有助于AAO薄膜的快速生产和应用。
