en Research Paper Research Paper Abstract: Nanoparticles exhibit a high reactivity and strong tendency towards agglomeration. In this study, aluminum oxide (alumina) nanoparticles were characterized by gas adsorption (BET), transmition electron microscopy (TEM) and photon correlation spectroscopy (PCS) techniques to assess the agglomeration of the particles. There is a good correlation between the BET and TEM measurements but PCS was larger in the mean and median size and with a degree of agglomerates being detected. Some agglomeration was evident, but most of the particles existed as discrete objects as observed in the (HR) TEM images which were in good agreement with the agglomeration factor. Agglomeration, Alumina, Aggregation, Nanoparticles, Thermal plasma 15 19 http://ijmse.iust.ac.ir/browse.php?a_code=A-10-3-45&slc_lang=en&sid=1 M. Pirhadi Tavandashti 18003194753284600405 18003194753284600405 No M. Zandrahimi m.zandrahimi@mail.uk.ac.ir 18003194753284600406 18003194753284600406 Yes B. Akbari 18003194753284600407 18003194753284600407 No