Quantification of the three-dimensional nanoparticle distribution in polymer nanocomposites

For many technical applications nanofillers are added to polymeric materials in order to modify the electrical, thermal or mechanical properties. However, nanoparticles tend to agglomerate, which can have a great impact on their ability to influence the macroscopic material characteristics. To overcome the limited insight provided by two-dimensional images, the focus of this study is on theoretical and experimental techniques to quantify the three-dimensional dispersion of particles in nanocomposites. For this purpose three different nanocomposites based on epoxy are produced in the lab by means of a nanomizer. Thin slices with a thickness of 200 nm each are cut and the three-dimensional nanoparticle distribution is reconstructed from serial transmission electron microscopy images. By means of the three-dimensional free-space length and the three-dimensional pair-correlation function two methods are provided to analyze the dispersion of the nanoparticles with respect to its agglomeration, uniformity or randomness. This way the nanofiller distributions of the investigated nanocomposites can be characterized quantitatively.