Nanotechnology. 2013 Nov 29;24(47):475707. doi: 10.1088/0957-4484/24/47/475707.
The deformation mechanism and mechanical properties of carbon nanotube (CNT) forests conformally coated with alumina using atomic layer deposition (ALD) are investigated using in situ and ex situ micro-indentation. While micro-indentation of a CNT forest coated with a thin discontinuous layer using 20 ALD cycles results in a deformation response similar to the response of uncoated CNT forests, a similar test on a CNT forest coated with a sufficiently thick and continuous layer using 100 ALD cycles causes fracture of both the alumina coatings and the core CNTs. With a 10 nm coating, 4-fold and 14-fold stiffness increases are measured using a flat punch and a Berkovich tip, respectively. Indentation testing with the Berkovich tip also reveals increased recoverability at relatively low strains. The results show that ALD coated CNT forests could be useful for applications that require higher stiffness or recoverability. Also, fracturing of the nanotubes shows that upper limits exist in the loading of conformally coated CNT forests.
采用原子层沉积（ALD）在碳纳米管（CNT）林中进行氧化铝的共形涂层，通过原位和异位微压痕法研究其变形机制和力学性能。在对使用 20 个 ALD 循环涂覆有薄不连续层的 CNT 林进行微压痕测试时，其变形响应类似于未涂覆 CNT 林的响应，而对使用 100 个 ALD 循环涂覆有足够厚且连续层的 CNT 林进行类似测试时，会导致氧化铝涂层和核心 CNT 的断裂。使用 10nm 涂层，分别使用平头压头和 Berkovich 压头测量到的 4 倍和 14 倍的刚度增加。使用 Berkovich 压头进行压痕测试还显示出在相对较低的应变下恢复能力的提高。结果表明，ALD 涂层的 CNT 林可用于需要更高刚度或可恢复性的应用。此外，纳米管的断裂表明，在对共形涂层的 CNT 林进行加载时存在上限。
