Evolution of the surface energy of BaTiO3 nanoparticles in the course of dispersant coating: An inverse gas chromatography study

Understanding the surface energy characteristics of nanoparticles is crucial for controlling their stability, dispersion, and subsequent material properties. In this study, we employed inverse gas chromatography (IGC) to investigate the changes in surface energy and its homogeneity of BaTiO3 nanoparticles during coating with a model dispersant, stearic acid (SA), at various coverage levels. The IGC results revealed that the SA coating led to a more stable and homogeneous dispersive surface energy, enhancing the overall stability of the nanoparticles. However, it also introduced heterogeneity in the specific surface energy, with a notable shift towards higher levels. The observed evolution of surface energy characteristics was consistent with trends of the adlayer formation as determined through conventional surface characterization techniques, including thermogravimetric analysis-gas chromatography mass spectrometry and diffuse reflectance infrared Fourier transform spectroscopy. The combined approach of IGC and conventional techniques suggested that the changes in surface energy characteristics were associated with the formation of a disordered organic adlayer through SA chemisorption at various surface sites on crystalline facets with diverse coordination configurations. This highlights the potential of IGC as a powerful monitoring tool for investigating molecular coatings on ceramic nanopowders. It enables not only the quantification of average surface states but also provides insights into their distribution, which is not practically achievable through other surface characterization techniques.