The application of scanning electron microscopy for the characterization of powders

Abstract

The examination of powder surfaces is limited in optical microscopy due to its short depth of focus, and in transmission electron microscopy due to sample preparation requirements. A relatively new and fast developing technique-scanning electron microscopy—offers many features most attractive in the study of powders in metallic and nonmetallic systems. The unique advantages of the scanning electron microscope include direct examination, a very large depth of focus, a wide range of magnifications, minimal or no sample preparation, a low specimen current, and sufficient resolution for most work involving direct examination of powder surface. The principle of operation of SEM is briefly discussed. The results of examination of 12 metal and alloy powders by the SEM and optical microscope are presented and compared. The SEM should be very useful in the field of powder studies in providing information pertaining to size, shape, surface topography and texture, porosity and pore shape, surface contamination, oxides and absorbed layer on surfaces, microstructure and agglomeration tendencies.