Coupette Fabian, Zhang Long, Kuttich Björn, Chumakov Andrei, Roth Stephan V, González-García Lola, Kraus Tobias, Schilling Tanja
Institute of Physics, University of Freiburg, Hermann-Herder-Straße 3, 79104 Freiburg, Germany.
INM-Leibniz Institute for New Materials, Campus D2 2, 66123 Saarbrücken, Germany.
J Chem Phys. 2021 Sep 28;155(12):124902. doi: 10.1063/5.0058503.
We examine network formation and percolation of carbon black by means of Monte Carlo simulations and experiments. In the simulation, we model carbon black by rigid aggregates of impenetrable spheres, which we obtain by diffusion-limited aggregation. To determine the input parameters for the simulation, we experimentally characterize the micro-structure and size distribution of carbon black aggregates. We then simulate suspensions of aggregates and determine the percolation threshold as a function of the aggregate size distribution. We observe a quasi-universal relation between the percolation threshold and a weighted average radius of gyration of the aggregate ensemble. Higher order moments of the size distribution do not have an effect on the percolation threshold. We conclude further that the concentration of large carbon black aggregates has a stronger influence on the percolation threshold than the concentration of small aggregates. In the experiment, we disperse the carbon black in a polymer matrix and measure the conductivity of the composite. We successfully test the hypotheses drawn from simulation by comparing composites prepared with the same type of carbon black before and after ball milling, i.e., on changing only the distribution of aggregate sizes in the composites.
我们通过蒙特卡罗模拟和实验研究了炭黑的网络形成和渗流。在模拟中，我们用不可穿透球体的刚性聚集体对炭黑进行建模，这些聚集体通过扩散限制聚集获得。为了确定模拟的输入参数，我们对炭黑聚集体的微观结构和尺寸分布进行了实验表征。然后我们模拟聚集体的悬浮液，并确定渗流阈值作为聚集体尺寸分布的函数。我们观察到渗流阈值与聚集体集合的加权平均回转半径之间存在准通用关系。尺寸分布的高阶矩对渗流阈值没有影响。我们进一步得出结论，大炭黑聚集体的浓度对渗流阈值的影响比小聚集体的浓度更强。在实验中，我们将炭黑分散在聚合物基体中并测量复合材料的电导率。通过比较球磨前后用相同类型炭黑制备的复合材料，即仅改变复合材料中聚集体尺寸的分布，我们成功地验证了从模拟得出的假设。
