In many applications, nanoparticles appear to be in an aggregated form. Thus, a complete description of their morphology involves an analysis of their size at different scales, from the aggregate size to the primary particle size. In this study, we present an automated method for the determination of the primary particle size distribution. It is based on an image-processing algorithm operating Euclidian distance mapping leading to a function that contains information about aggregates morphology. This algorithm is first applied to virtual aggregates with point contact between spheres, generated by diffusion limited cluster aggregation code. It shows that obtained functions can be used to retrieve the parameters of the primary particle diameter size distribution. However, it also demonstrates that overlapping or necking effects between primary spheres can have an impact on the shape of the function. The analysis is also performed on real soot images generated by ethylene diffusion flame and civil aviation engine that are different from a physicochemical point of view. This leads to the definition of a calibrated morphological function that can be used for the determination of the parameters of the primary diameter distributions of real soot particles. Finally, the same method is applied to TEM images of soot generated by a commercial soot generator miniCAST. Three operating conditions were investigated showing that generators can be used to produce soot particles with morphologies similar to those produced by jet engines. Copyright 2014 American Association for Aerosol Research

The laboratory combustion technique operating on a typical combustor of a gas turbine engine is used for soot sampling. Soot particles are derived by combustion of a hydrocarbon C₃H₈–n-C₄H₁₀ mixture at typical cruise conditions. Size, morphology, microstructure, surface area, porosity, and the chemical nature of the soot surface particles are studied by transmission electron microscopy (TEM), Raman and Auger electron spectroscopies (AES), volumetry and gravimetry. Structural irregularities such as micropores determine the specific adsorbability of non-polar gases such as Kr, CH₄ and C₆H₆. With respect to water adsorption, aircraft combustor soot is far from being hydrophobic. Initial water adsorption on polar heterogeneities leads to pore filling at increasing pressures. The microstructure of soot particles is easily transformed under the influence of adsorbates, giving rise to swelling effects. Due to its specific physico-chemical properties aircraft combustor soot may act as contrail condensation nuclei at low sulfur content in the jet fuel.

The interaction of water with MgO (100) single crystal surfaces cleaved in situ has been studied by low energy electron diffraction and helium atom scattering in the temperature range 80 K–230 K. At T_crystal=100–180 K water forms a layer with a c(4×2) symmetry in good agreement with previous spot profile analysis of low energy electron diffraction experiments. Adsorption at T_crystal=185–221 K leads to the formation of a new ordered phase. The results of the low energy electron diffraction and elastic helium atom scattering experiments show that this high‐temperature phase has a (3×2) symmetry, and that the unit cell contains a glide plane. The isosteric heat of adsorption at half coverage Q_st=85.3 kJ/mol has been determined from equilibrium adsorption isotherms measured between 210 and 221 K.