Compaction-induced restructuring of aggregated nanoparticle films using the discrete element method
Compaction-induced restructuring of aggregated nanoparticle films using the discrete element method
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DOI：
10.1016/j.powtec.2018.10.038
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发表时间：
2019-01-15
影响因子：
5.2
通讯作者：
Maedler, Lutz
中科院分区：
文献类型：
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作者：
Baric, Valentin;Ciacchi, Lucio Colombi;Maedler, Lutz
聚集的纳米颗粒薄膜在气体传感、太阳能电池和电池等许多领域都有应用。这些薄膜的特点是多分散初级颗粒和烧结颗粒聚集体的尺寸分布，这决定了对外部负载的响应和功能特性，如热或电荷输运。薄膜的机械压实对这些特性有强烈的影响，这种影响可以通过施加压实压力时孔隙率和孔径分布的变化来量化。然而，聚合体系结构的确切重组机制仍然未知。本文采用离散元法（DEM）模拟火焰喷雾热解法制备的TiO2纳米颗粒膜的结构重构机制。通过非共价、湿度依赖的相互作用，烧结TiO2聚集体通过相互分离、滚动或滑动事件重排的能力对于预测对压实的正确响应至关重要。本文根据一种新的烧结桥模型，阐述了骨料弹性变形的重要性。当桥梁的拉伸和弯曲强度明显大于块体TiO2时，DEM模拟与实验结果吻合最好，且在纳米尺度结构中发生临界断裂的概率较低。(C) 2018 Elsevier B.V.版权所有
Aggregated nanoparticle films find application in many fields such as gas sensing, solar cells and batteries. These films are characterized by size distributions of polydisperse primary particles and sintered particle aggregates that dictate both the response to external load and functional properties such as heat or charge transport. Mechanical compaction of the films strongly affects these properties in a way that can be quantified by the change of porosity and pore size distributions on the applied compacting pressure. The exact restructuring mechanisms of the aggregate architecture, however, remain unknown. Here, we apply Discrete Element Method (DEM) simulations to gain access to such restructuring mechanisms in TiO2 nanoparticle films synthesized by flame-spray pyrolysis. The ability of the sintered TiO2 aggregates to rearrange via mutual detachment, rolling or sliding events dictated by non-covalent, humidity-dependent interactions are known to be crucial to predict the correct response to compaction. In this work, the importance of elastic deformation of aggregates according to a novel sinter bridge model is elucidated. The best match between DEM simulations and experiments is obtained for bridges with a tensile and bending strengths substantially larger than bulk TiO2, consistently with a low probability of critical fracture initiation in nanometer-scale structures. (C) 2018 Elsevier B.V. All rights reserved.