STUDIES ON THE DYNAMICS OF ADSORPTION AND DESORPTION FROM COMBUSTION PARTICLES, BY TEMPERATURE-DEPENDENT MEASUREMENT OF SIZE, MASS AND PHOTOELECTRIC YIELD

Carbonaceous particles in combustion exhaust exhibit significant changes of size, structure and surface chemical composition on changing the temperature T of the carrier gas. We study particles generated in a diesel engine, a spark-ignition engine and an oilburner. Total mass (TM), mass of black carbon (BC), mobility diameter and aerosol photoemission (APE) of the particles have been measured in situ as a function of temperature. Concomitantly the particles have also been deposited on a substrate and imaged by transmission electron microscopy (TEM). Photoelectric yield and diameter versus temperature curves suggest a shell structure of the particles: A core of pure BC or BC and PbBr2 is covered with a number of volatile compounds (VC), the most highly volatile species forming the outermost layer.