Dimensional study about water based ferrofluids

Comparative study on the nanoparticles size of water based ferrofluids, prepared in our laboratories, as well as on other similar products presented in the literature reports was carried out by applying the transmission electron microscopy (TEM), atomic force microscopy (AFM) and magnetization measurements. The ferrophase magnetite core was prepared by chemical co-precipitation from ferric (FeCl 3 ) and ferrous salts (FeCl 2 ) in alkali medium (ammonia hydroxide) and functionalized with citric acid and respectively tetramethylammonium hydroxide. In both cases, the physical diameter of the ferrophase particles was measured using electron microscopy data. The diameter histograms revealed the main peak around 10 nm, which is concordant with a high degree of stability of the ferrofluid. The dimensional distribution of the ferrophase physical diameter was comparatively presented using graphical statistical method. The percentage of relatively small particles (under 5nm) was discussed comparatively with the percentage of relatively large particles (over 10nm). The presence of exceptionally large aggregates was also discussed in order to assess the quality of the magnetic colloids prepared by us in comparison with the similar products from several other countries. In order to extract complementary data on the ferrophase magnetic and physical diameter, measurements of magnetization and magnetic susceptibility were performed.