Tunable Atomic Layer Deposition into Ultra-High-Aspect-Ratio (>60000:1) Aerogel Monoliths Enabled by Transport Modeling
Tunable Atomic Layer Deposition into Ultra-High-Aspect-Ratio (>60000:1) Aerogel Monoliths Enabled by Transport Modeling
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DOI：
10.1021/acs.chemmater.1c00770
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发表时间：
2021-07
影响因子：
8.6
通讯作者：
Andrew J. Gayle;Zachary J. Berquist;Yuxin Chen;Alexander J. Hill;Jacob Y. Hoffman;Ashley R. Bielinski;A. Lenert;N. Dasgupta
中科院分区：
文献类型：
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作者：
Andrew J. Gayle;Zachary J. Berquist;Yuxin Chen;Alexander J. Hill;Jacob Y. Hoffman;Ashley R. Bielinski;A. Lenert;N. Dasgupta
原子层沉积（ALD）修饰超高宽高比结构（bbb10, 000:1）是一个强大的平台，在催化、过滤和能量转换方面有着广泛的应用。然而，在这些宽高比下沉积适形和可调ALD涂层仍然具有挑战性，导致前驱体利用率和反应时间之间的经验权衡。在这里，我们展示了ALD渗透到气凝胶单体（AM）的深度可调控制，并建立了一个反应扩散模型来准确描述涂层过程。具体来说，我们研究了ALD暴露时间和前驱体剂量，以保形涂覆孔径为~ 20 nm，整体厚度为~ 2.5 mm，宽高比超过60,000:1的二氧化硅AM。我们展示了完全渗透到AM中，这是通过元素映射量化的。建立了一个反应扩散模型，该模型考虑了在暴露步骤中多次剂量和ALD室中的前体耗竭。实验验证的模型能够预测和调整渗透深度到弯曲的高纵横比结构中，例如AM，从而允许合理设计的材料结构的合成。此外，该模型允许共同优化总沉积时间和未反应前驱体的百分比，这对ALD处理的可制造性和可持续性很重要。最后，我们证明了超薄ALD al2o3涂层可以通过限制表面积和整体体积的变化来稳定二氧化硅AMs，防止在高温退火条件下（700-800°C）的结构降解。这种改进的高温稳定性对许多气凝胶的应用具有重要意义，包括催化和隔热。
Atomic layer deposition (ALD) modification of ultra-high-aspect-ratio structures (>10000:1) is a powerful platform with applications in catalysis, filtration, and energy conversion. However, the deposition of conformal and tunable ALD coatings at these aspect ratios remains challenging, resulting in empirical trade-offs between the precursor utilization and reaction time. Here, we demonstrate tunable control of the ALD infiltration depth into an aerogel monolith (AM) and develop a reaction-diffusion model to accurately describe the coating process. Specifically, we investigate the ALD exposure time and precursor dose needed to conformally coat a silica AM with pore sizes of ∼20 nm, a monolith thickness of ∼2.5 mm, and aspect ratios exceeding 60000:1. We demonstrate complete infiltration into the AM, which is quantified by elemental mapping. A reaction-diffusion model is developed, which accounts for multiple doses and the precursor depletion in the ALD chamber during an exposure step. The experimentally validated model enables the prediction and tuning of infiltration depth into a tortuous, high-aspect-ratio structure such as an AM, allowing for the synthesis of rationally designed material architectures. Additionally, the model allows for co-optimization of the total deposition time and percentage of unreacted precursor, which are important for the manufacturability and sustainability of ALD processing. Lastly, we demonstrate that ultrathin ALD Al2O3coatings can be used to stabilize silica AMs against structural degradation under high-temperature annealing conditions (700–800 °C) by limiting changes in the surface area and monolith volume. This improved high-temperature stability has implications for numerous aerogel applications, including catalysis and thermal insulation.