Experimental and computational analysis of the forces acting on highly porous nanoparticle scaffolds/layers during liquid imbibition

最近，我们开发了一种新的两步层转移工艺，用于在各种基底上制造高度多孔的纳米颗粒层。首先，在火焰喷雾热解中合成纳米颗粒并在滤纸上积累。随后，通过低压层压将该滤饼转移到第二基底上。所得到的层的孔结构可以通过所施加的压力来调节。在几种不同的吸液速度的液体中进行了浸没实验。它们揭示了在液体环境中从层中的颗粒损失对吸液速度、液体性质（例如表面张力）和层的性质（例如孔隙率和孔结构）的依赖性。通过层压压力调整孔隙结构，我们能够制造出能够承受液体环境的稳定层。 以往的研究主要集中在高孔隙度地层的渗吸速度和渗透率方面。在吸胀过程中结构上发生的力尚未详细研究。在这个项目中，我们寻求对高度多孔颗粒层中液体吸胀机制的基本理解，以量化这些发生的力。这使得能够预测避免在吸入期间重构或颗粒去除所需的条件。为此，将在实验研究中分析纳米颗粒层中不同液体的吸液特性。此外，将对层结构进行建模，并模拟作用在层内每个纳米颗粒上的力。实验和理论研究的结合将导致对吸胀过程中发生机制的基本理解。这一理解将应用于项目的最后一部分。在这里，将研究在聚合物基质中用纳米颗粒支架合成的复合材料。将调节纳米颗粒层的性质以实现单体的吸胀的足够稳定性。此外，将研究纳米颗粒层中的固化收缩及其对颗粒-颗粒接触的影响。这些研究使得能够合成聚合物-纳米颗粒复合材料，与具有各种应用的常规复合材料相比，该聚合物-纳米颗粒复合材料具有显著更低的颗粒含量，例如具有聚合物性质的导电或磁性材料。

Recently, we developed a new two-step layer transfer process for the fabrication of highly porous nanoparticle layers on various substrates. First, the nanoparticles are synthesized in a Flame-Spray-Pyrolysis and accumulated on a filter paper. Subsequently, this filter cake is transferred to a second substrate via low pressure lamination. The resulting pore structure of the layer can be adjusted by the applied pressure. Submersion experiments in several liquids with different imbibition velocities were performed. They revealed a dependence of the particle loss from the layer in the liquid environment on the imbibition velocity, liquid properties (e.g. surface tension) and the properties of the layer (e.g. porosity and pore structure). By adjusting the pore structure through the lamination pressure, we were able to fabricate stable layers withstanding liquid environments. Previous studies mostly concentrate on the imbibition velocity in highly porous layers and their permeability. The occurring forces on the structure during imbibition are not studied in detail, yet. Within this project, we seek fundamental understanding of the mechanisms of liquid imbibition in highly porous particulate layers to quantify these occurring forces. This enables a prediction of the conditions needed to avoid restructuring or particle removal during imbibition. For this purpose, the imbibition properties of different liquids in nanoparticle layers will be analyzed in an experimental study. Additionally, the layer structure will be modelled and the forces acting on each nanoparticle within the layer will be simulated. The combination of experimental and theoretical investigations shall lead to a fundamental understanding of the occurring mechanisms during imbibition. This understanding will be applied in the last part of the project. Here, composite materials synthesized with percolating nanoparticle scaffolds in polymer matrices will be investigated. The properties of the nanoparticle layer will be adjusted to achieve a sufficient stability for the imbibition of the monomer. Furthermore, the cure shrinkage in nanoparticle layers and its influence on the particle-particle contacts will be studied. These studies enable the synthesis of polymer-nanoparticle composite materials with significantly lower particle contents compared to conventional composites having various applications as e.g. conductive or magnetic materials with polymer properties.