Adhesion and Attractive Forces of Flame-Formed Carbon Nanoparticles by Atomic Force Microscopy (Abstract/Poster in convegno)

Type
Label
  • Adhesion and Attractive Forces of Flame-Formed Carbon Nanoparticles by Atomic Force Microscopy (Abstract/Poster in convegno) (literal)
Anno
  • 2014-01-01T00:00:00+01:00 (literal)
Alternative label
  • G. De Falco, M. Commodo, P. Minutolo, A. D'Anna (2014)
    Adhesion and Attractive Forces of Flame-Formed Carbon Nanoparticles by Atomic Force Microscopy
    in 35th International Symposium on Combustion, San Francisco, California, USA, August 3 - August 8, 2014
    (literal)
Http://www.cnr.it/ontology/cnr/pubblicazioni.owl#autori
  • G. De Falco, M. Commodo, P. Minutolo, A. D'Anna (literal)
Note
  • Abstract (literal)
Http://www.cnr.it/ontology/cnr/pubblicazioni.owl#affiliazioni
  • Dipartimento di Ingegneria Chimica, dei Materiali e della Produzione Industriale, Università degli Studi di Napoli \"Federico II\", Napoli, Italy. Istituto di Ricerche sulla Combustione, C.N.R., Napoli, Italy (literal)
Titolo
  • Adhesion and Attractive Forces of Flame-Formed Carbon Nanoparticles by Atomic Force Microscopy (literal)
Abstract
  • Atomic force microscopy (AFM) is a well-known scanning probe technique, mainly used for its capability to achieve topographic images with subnanometer resolution. In addition to surface topographies characterization, AFM is also a powerful tool for sensitive force spectroscopy measurements. The forces acting between the AFM tip and the surface under investigation can be recorded during approach and retract of cantilever to and from the sample, and plotted as force-distance curves. From these measurements, short-range attractive and adhesive forces can be quantitatively evaluated. The purpose of this work is to study surface properties, i.e. van der Walls interactions and Hamaker constants, of different flame-formed nanoparticles as derived from AFM force-distance measurements. These properties are of fundamental relevance for a deeper understanding of the coagulation and coalescence phenomena between carbon particles occurring during soot growth process. To this aim, carbon nanoparticles were produced in fuel-rich ethylene/air laminar premixed flames with different equivalent ratios ?, and analysed at fixed height above the burner (HAB), namely 15 mm. Particles were collected on mica substrates by means of a thermophoretic sampling system and analyzed by AFM operating in contact and force spectroscopy modes. Attractive and adhesive forces between titanium nitride probe and collected particles were found to increase with flame equivalence ratio, moving from flame conditions, in which unimodal particles diameter distribution, with average size of 2-5 nm, are produced (?=1.85), up to fully-sooting conditions (?=2.58), in which 50-100 nm soot aggregates are mainly produced. Adhesive forces are 5-7 times greater than attractive forces in the same conditions. This is evidenced by the fact that particle deformation and bonding with AFM tip occurring during contact results in a curve-distance hysteresis contribution. The measurement of the attractive force by the AFM force-distance curve allowed the evaluation of the Hamaker constant for the different carbon particles, assuming that van der Walls forces are the main contribution to the attractive forces. By means of the van der Waals theory for sphere-flat surface and sphere-sphere interaction, the Hamaker constants were derived as a function of both the particle equivalent diameter as evaluated from AFM images and flame equivalence ratio. Highly-Ordered Pyrolytic Graphite (HOPG) was used as reference material. (literal)
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