Quantitative Study of Interface/Interphase in Epoxy/Graphene-Based Nanocomposites by Combining STEM and EELS

Area of Science:

• Materials Science
• Nanotechnology
• Polymer Science

Background:

• Understanding the interphase region is crucial for optimizing the properties of polymer nanocomposites.
• Graphene-based nanofillers, such as graphene nanoplatelets (GNPs) and graphene oxide (GO), are widely investigated for enhancing epoxy matrices.
• Characterizing the interface between nanofillers and polymer matrices is essential for predicting material performance.

Purpose of the Study:

• To quantitatively investigate the interphase and interface characteristics of graphene nanoplatelets (GNPs)/epoxy and graphene oxide (GO)/epoxy composites.
• To determine the thickness and density variations within the interphase regions.
• To correlate experimental findings with existing theories on interphase behavior.

Main Methods:

• Utilizing scanning transmission electron microscopy (STEM) for high-resolution imaging.
• Employing electron energy-loss spectroscopy (EELS) to analyze the electronic structure and chemical composition of the interphase.
• Performing spectral acquisitions along lines traversing the interface to map variations.

Main Results:

• Clearly identified interphase regions in both GNPs/epoxy and GO/epoxy systems through plasmon peak discrepancies in EELS spectra.
• Measured interphase thicknesses of approximately 13 nm for GNPs/epoxy and 12.5 nm for GO/epoxy.
• Observed a density increase of 2.89% in the GNPs/epoxy interphase and a decrease of 1.37% in the GO/epoxy interphase compared to the neat epoxy matrix.

Conclusions:

• The study provides quantitative insights into the interphase structure of graphene-epoxy composites.
• The measured interphase thicknesses align with the transition layer theory, suggesting a gradual variation in material properties.
• These findings can guide the functionalization of nanofillers to enhance the overall properties of carbon-based polymer composites.