Stabilization of Mesoporous Iron Oxide Films against Sintering and Phase Transformations via Atomic Layer Deposition of Alumina and Silica
Stabilization of Mesoporous Iron Oxide Films against Sintering and Phase Transformations via Atomic Layer Deposition of Alumina and Silica
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DOI：
10.1002/admi.201800360
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发表时间：
2018-07
影响因子：
5.4
通讯作者：
Katrin Kraffert;M. Karg;Roman Schmack;G. Clavel;C. Boissière;T. Wirth;N. Pinna;R. Kraehnert
中科院分区：
文献类型：
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作者：
Katrin Kraffert;M. Karg;Roman Schmack;G. Clavel;C. Boissière;T. Wirth;N. Pinna;R. Kraehnert
晶相和纳米结构形态的稳定是介孔材料应用驱动设计的一个重要课题。许多应用，例如催化作用，要求高温高湿。典型的金属氧化物在这种条件下从亚稳定的低结晶材料转变为热力学上更有利的形式，即在氧化铁的情况下从水铁矿转变为赤铁矿。恶劣的条件还会引起构成孔壁的微晶的生长，导致多孔网络的烧结并最终崩溃。本文报道了一种稳定介孔模板金属氧化物以防止烧结和孔塌陷的新方法。该方法采用原子层沉积（ALD）在中孔内部表面涂覆氧化铝或二氧化硅薄层。作者证明，二氧化硅具有非常强大的影响力：它将赤铁矿的形成温度从 400 °C 转移到 600 °C，并将赤铁矿的烧结温度从 600 °C 转移到 900 °C。通过氧化铝和二氧化硅进行稳定化之间的差异可以通过 ALD 材料和水铁矿薄膜之间不同的相互作用强度来合理化。所提出的方法可以使用亚单层量的 ALD 材料来稳定需要高结晶温度的介孔薄膜，并将介孔材料应用于高温应用。
The stabilization of crystal phases and nanostructured morphologies is an essential topic in application‐driven design of mesoporous materials. Many applications, e.g. catalysis, require high temperature and humidity. Typical metal oxides transform under such conditions from a metastable, low crystalline material into a thermodynamically more favorable form, i.e. from ferrihydrite into hematite in the case of iron oxide. The harsh conditions induce also a growth of the crystallites constituting pore walls, which results in sintering and finally collapse of the porous network. Herein, a new method to stabilize mesoporous templated metal oxides against sintering and pore collapse is reported. The method employs atomic layer deposition (ALD) to coat the internal mesopore surface with thin layers of either alumina or silica. The authors demonstrate that silica exerts a very strong influence: It shifts hematite formation from 400 to 600 °C and sintering of hematite from 600 to 900 °C. Differences between the stabilization via alumina and silica are rationalized by a different interaction strength between the ALD material and the ferrihydrite film. The presented approach allows to stabilize mesoporous thin films that require a high crystallization temperature, with submonolayer quantity of an ALD material, and to apply mesoporous materials for high temperature applications.