APPLICATION OF ATOMIC FORCE MICROSCOPY NANOINDENTATION FOR THE MECHANICAL CHARACTERIZATION OF SOOT NANOPARTICLES

In this work, we report an experimental characterization of the nanomechanical properties of flame-formed carbon nanoparticles performed for the first time using the atomic force microscopy (AFM) nanoindentation technique. Layers of soot particles with different size and nanostructure were produced in atmospheric laminar flames of ethylene and air and collected by thermophoresis on mica substrates. Atomic force microscopy was used to image the topology of the samples in semicontact mode. Then, force-distance curves were acquired by measuring the tip-sample interaction forces in contact spectroscopy mode. The instrument was operated so that the tip of the AFM probe acted as a nanoindenter and the maximum applied force was derived from the force curves. The hardness of the sample was determined from the maximum applied force in combination with semicontact atomic force microscopy images of the indents performed on the sample surface. Also, the Young's modulus of the sample was measured by fitting the linear part of the retraction force curves. AFM nanoidentation showed the potential to furnish information on the layer properties, as well as on the nanostructure and composition of particles composing the layers when in combination with a numerical simulation analysis.