Aerosol particles, surface roughness

Wu, M.K. The roughness of aerosol particles surface fractal dimension measured using nitrogen adsorption. Aerosol Sci. Technol. 1996, 25, 392-398. 

Kamer, S., Littringer, E. M., Urbanetz, N. A. (2014). Triboelectrics The influence of particle surface roughness and shape ot charge acquisition during aerosolization and the DPI ptrfOTmance. Powder Technology, 262, 22-29. 

Condensed phase interactions can be divided roughly into two further categories chemical and physical. The latter involves all purely physical processes such as condensation of species of low volatility onto the surfaces of aerosol particles, adsorption, and absorption into liquid cloud and rainwater. Here, the interactions may be quite complex. For example, cloud droplets require a CCN, which in many instances is a particle of sulfate produced from SO2 and gas-particle conversion. If this particle is strongly acidic (as is often the case) HNO3 will not deposit on the aerosol particle rather, it will be dissolved in liquid water in clouds and rain. Thus, even though HNO3 is not very soluble in... 

Podczeck F. The influence of particle size distribution and surface roughness of carrier particles on the in vitro properties of dry powder inhalations. Aerosol Sci Technol 1999 31 (4) 301 321. 

Thus the energy of attraction becomes infinite as the particle approaches a flat surface. For this reason, it is usually assumed that a surface acts as a p>erfect sink in the theory of aerosol diffusion that is, when a particle penetrates to a distance one radiu.s from the surface, the particles adhere. This holds best for submicron particles moving at thermal velocities. Rebound occurs for larger particles moving at high velocities (Chapter 4). This analysis does not lake into account the effects of surface roughness of the scale of the particle size or of layers or patches of adsorbed gases or liquids. Such factors may be important in practical applications. 

The phenomena that influence particle sizes are shown in an idealized schematic in Figure 2.7, which depicts the typical distribution of surface area of an atmospheric aerosol. Particles can often be divided roughly into modes. The nucleation (or nuclei) mode comprises particles with diameters up to about 10 nm. The Aitken mode spans the size range from about lOnm to lOOnm (0.1 pm) diameter. These two modes account for the... 

The electrocharged aerosol particles interact with the surface, and as a result of their impact, the analyte is desorbed from the surface and ionized. Then, ions are transferred to the mass spectrometer by an ambient pressure sample transfer line, and mass spectra are recorded using an unmodified commercial mass spectrometer equipped with an atmospheric pressure interface (see Fig. 2). DESI ionize both small and large molecules (up to small proteins), and the efficiency of the desorption/ionization depends mainly on three factors (i) physicochemical properties of the analytes (ii) the spray mixture, i.e., the solvent composition, pH, viscosity, volatility, etc. and finally (iii) DESI surface on which the analyte is deposited. Indeed, the chemical composition, roughness, surface energy, and conductivity of the surface are all factors that determine the behavior of a DESI surface. 

It has to be kept in mind that particulate materials are dispersions. In fact, the classical powder is a concentrated dispersion of solid particles in air. At a very low concentration, very Lne particles (micron, submicron size) can form an aerosol. In such a case-ewing to the large interparticulate distance-fhe particle-particle interactions can be neglected. In general, a particle can exhibit a substructure, that is, a particle may have external and internal pores. An external pore can be related to the roughness of the surface of a particle. 

The concentration of rough-disperse particles with r > 0.14 pm constituted about 0.5 cm" These particles contribute most to the aerosol mass. Undoubtedly, they are driven from remote regions. Covering the surface, these particles form aerosol insertions into polar ice. Their long-term concentration variations can serve as indicators of paleoclimate changes. 

Williamson, R.D., 1989, The deposition of iron oxide particles on surfaces from turbulent aqueous suspension. PhD Thesis, University of Birmingham. Wood, N.B., 1981, A simple method for the calculation of turbulent deposition to smooth and rough surfaces. J. Aerosol Sci. 12, 3, 275 - 290. 

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