Small angle x-ray scattering study for determining the particle size of colloidal materials

The average particle size of two monodispersed colloidal silica HS-40 and SM-30 and one polydispersed colloidal ferrite has been estimated from the small angle X-ray scattering (SAXS) data using four methods proposed by Guinier, Fankuchen, Hosemann and Porod. The same information was also obtained by the transmission electron microscope (TEM) and calculated from the specific surface area (SSA) data measured by the nitrogen gas adsorption technique. The values of the average particle size of colloidal silica and colloidal ferrite estimated from the SAXS data using four methods were found to be of the same order of magnitude. These SAXS values of colloidal silica HS-40 and SM-30 also agree well with those determined by both the TEM and SSA measurements. However, it should be noted that in the case of colloidal ferrite the SAXS and TEM are almost the same, whereas a significant difference is found when comparing the value estimated from the SSA data. This can be attributed to the strong agglomeration of ferrite particles after drying.