INVESTIGATIONS OF A NEW AEROSOL GENERATOR FOR THE PRODUCTION OF CARBON AGGREGATE PARTICLES

The operating characteristics of a new aerosol generator for the produ ction of ''soot-like'' particles have been investigated. The aerosol i s produced by a spark discharge between two graphite electrodes in arg on as carrier gas. The particle mass flow rate can be varied between 2 0 mug h-1 and 7 mg h-1 by simply changing the spark frequency. The dis charge voltage is kept constant by a control mechanism that adjusts th e distance between the electrodes. This results in a very constant ope ration of the generator over time periods of several hours. The mass p roduction rate of the instrument has been determined gravimetrically a nd a well reproducible linear relation with the spark frequency was fo und. The shape of the particles was determined by scanning electron mi croscopy as well as by transmission electron microscopy. The size of t he primary particles is in the range of 5 nm forming agglomerates betw een 50 and 200 nm. The size distibution of the aerosol was measured fo r different operating parameters using a differential mobility analyse r and an aerosol electrometer. The size distibution turned out to be m ainly influenced by the coagulation process that forms the agglomerate s. The final mean size of the particles can be controlled by the amoun t of dilution air that the aerosol is mixed with directly at the gener ator outlet.