Powder Characterization Techniques

Abstract

Abstract Knowledge of the characteristics of powders is of paramount importance for the successful development and application of powder metallurgy and particulate materials. Early characterization techniques were related to press and sinter powder metallurgy, dealing with the relatively coarser powders and with the analysis of individual as well as mass of powders. These analyses include structure, chemistry, morphology, size, shape, their distribution, different densities, flow, porosity, compressibility, friction, shear, residual stress, and so on to obtain a defect-free product. The advent of nanopowders and nanotechnology, metal injection molding, and more recent additive manufacturing has to deal with finer powders and different processing steps, which has resulted in the advancement of traditional powder characterization techniques to the next level, evolving newer and more innovative characterization techniques. Consequently, techniques such as x-ray photoelectron spectroscopy, scanning electron microscopy, laser light diffraction, x-ray computed tomography scan, atomic force microscopy, differential thermal analysis, etc., have been used with emphasis on powder cleanliness and internal particle porosity. The widely used industrial additive manufacturing process uses powder bed fusion that bonds successive layers of powders to facilitate the fabrication of parts with complex geometries. Thus, this article also explores the emerging trends in dynamic powder testing using a powder rheometer to measure dynamic flowability from measurement of axial and rotational forces acting on the rotating blade and the study of spreadability and flowability of powders by rotating drum instruments. A judicious selection of relevant and appropriate powder characterization techniques will ensure predictable powder behavior during the manufacturing process, resulting in consistent and reliable products.