Understanding and Improving FIB-SEM Techniques for Polyolefins
by: Maciej Paśniewski, ExxonMobil Chemical Europe Inc., European Technology Center, Machelen, Belgium
Location: Campus Groenenborger, U.408
Polyolefins such as polyethylene, polypropylene and associated rubber compounds are produced at a scale of 1010 kg per year globally. They play a crucial role in improving the daily life of billions of people by providing low-cost, light-weight, strong and effective packaging (improving hygiene, preserving food and reducing waste), household objects, car parts, etc. New technologies provide stronger materials allowing down-gauging and light-weighting, thus reducing carbon footprint and waste. New developments also focus on improving the recyclability of polymers, thus contributing to a sustainable cyclic economy.
In all cases, the development of new properties is guided by an in-depth understanding of the microstructure of the materials, at a molecular and supra-molecular scale. Microscopy techniques such as SEM, TEM and AFM provide such microstructural characterization. These techniques require sample preparation, such as cross-sectioning, without changing the material. However, organic materials in general, and polymers in particular, are very sensitive to damage by particle beams and mechanical stresses.
Focused Ion Beam Scanning Electron Microscopy (FIB-SEM) is a promising technique to provide microstructural information at a nanometer scale. The ion beam is used to create cross-sections, which can then be imaged by the electron beam or other techniques. Unlike other sectioning methods, FIB does not involve any mechanical forces, however, the ion beam may cause artefacts.
FIB-SEM is well established in materials science, especially in semiconductor industry and is increasingly applied to organic materials. Several studies have been performed on potential artefacts with FIB-SEM in organic materials and some polymers, but to our knowledge only a few studies exist on the industrially and societally important class of polyolefins.
Therefore, we propose a systematic study is in order to understand and optimize FIB-SEM for polyolefins. The mechanisms causing artefacts and ways to minimize them will be studied. The optimized methods will then be applied to real-world samples to evaluate their effectiveness. This will include the use of the FIB-SEM as a microstructural characterization tool in two and three dimensions, and as a preparation tool for other techniques, such as TEM and AFM. In addition, we hope to explore the possibilities of FIB-SEM as a nano-machining and nano-manipulation tool for novel in situ characterization experiments.
The improved FIB-SEM methods will allow better and more efficient micro-structural characterization of polyolefins, accelerating the development of new and improved materials for society. The fundamental understanding of the beam-sample interactions will be relevant to all researchers involved in electron and ion beam methods for beam sensitive materials.