Fusco Michael A, Oldham Christopher J, Parsons Gregory N
Department of Chemical and Biomolecular Engineering, North Carolina State University, Raleigh, NC 27695, USA.
Materials (Basel). 2019 Feb 24;12(4):672. doi: 10.3390/ma12040672.
Fifty nanometers of Al₂O₃ and TiO₂ nanolaminate thin films deposited by atomic layer deposition (ALD) were investigated for protection of copper in 0.1 M NaCl using electrochemical techniques. Coated samples showed increases in polarization resistance over uncoated copper, up to 12 MΩ-cm² as measured by impedance spectroscopy. Over a 72-h immersion period, impedance of the titania-heavy films was found to be the most stable, as the alumina films experienced degradation after less than 24 h, regardless of the presence of dissolved oxygen. A film comprised of alternating Al₂O₃ and TiO₂ layers of 5 nm each (referenced as ATx5), was determined to be the best corrosion barrier of the films tested based on impedance spectroscopy measurements over 72 h and equivalent circuit modeling. Dissolved oxygen had a minimal effect on ALD film stability, and increasing the deposition temperature from 150 °C to 250 °C, although useful for increasing film quality, was found to be counterproductive for long-term corrosion protection. Implications of ALD film aging and copper-based surface film formation during immersion and testing are also discussed briefly. The results presented here demonstrate the potential for ultra-thin corrosion barrier coatings, especially for high aspect ratios and component interiors, for which ALD is uniquely suited.
采用电化学技术研究了通过原子层沉积（ALD）制备的50纳米厚的Al₂O₃和TiO₂纳米层状薄膜对0.1 M NaCl溶液中铜的保护作用。与未涂层的铜相比，涂层样品的极化电阻有所增加，通过阻抗谱测量，最高可达12 MΩ·cm²。在72小时的浸泡期内，发现二氧化钛含量高的薄膜的阻抗最稳定，因为氧化铝薄膜在不到24小时后就发生了降解，无论是否存在溶解氧。根据72小时的阻抗谱测量和等效电路建模，由5纳米厚的Al₂O₃和TiO₂交替层组成的薄膜（称为ATx5）被确定为测试薄膜中最佳的腐蚀阻挡层。溶解氧对ALD薄膜稳定性的影响最小，虽然将沉积温度从150℃提高到250℃有助于提高薄膜质量，但发现这对长期腐蚀保护起反作用。还简要讨论了ALD薄膜老化以及浸泡和测试过程中铜基表面膜形成的影响。此处给出的结果表明了超薄腐蚀阻挡涂层的潜力，特别是对于高纵横比和部件内部，ALD对此具有独特的适用性。
