Influence of particle shape on size distribution measurements by 3D and 2D image analyses and laser diffraction Arnaud Califice ⁎, Frédéric Michel, Godefroid Dislaire, Eric Pirard University of Liege, ArGEnCo, GeMMe, B52 Chemin des Chevreuils 1, 4000 Liege, Belgium abstract article info Article history: Received 29 August 2012 Received in revised form 31 December 2012 Accepted 5 January 2013 Available online 12 January 2013 Keywords: Image analysis Laser diffraction Particle shape Particle size distribution This paper highlights the fact that particle size distribution (PSD) is not unique for the same product, and is dependent on the chosen measurement technique, especially for asymmetric shapes. Laser diffraction and 2D image analysis are commonly used PSD measurement techniques. However, the results may not be representative of the true physical dimensions of the particles. The influence of particle shape on PSD results obtained from 2D/3D image analysis and laser diffraction was investigated. Two metallic powders presenting extreme shape properties (round and elongated particles) were analyzed, as well as a blend of the two pure products. 2D image analysis and laser diffraction results were compared to 3D image analysis (measuring the true particle size). This paper compares the PSD results obtained from the three methods. Some commonly used size parameters in image analysis software did not give meaningful results in regard of the true physical dimensions of the particles. The existence of the two populations (products with extremely different shape and size characteristics) could not be identified with such size parameters, and laser diffraction also performed poorly. The PSD obtained from more precise size parameters (image analysis) better corres- ponded to the true dimensions of the particles. This study highlights the strengths and weaknesses of particle size analysis techniques when studying products presenting diverse particle shapes, and points out that caution is required in the choice of the size parameters, and in the interpretation of PSD results. © 2013 Elsevier B.V. All rights reserved. 1. Introduction Sieving has been widely used for decades to calculate the particle size distribution of particulate matter. More recent techniques allow the investigation of new size ranges, and the measure of new size and shape parameters. Laser diffraction is a method routinely used in many industries, and image analysis instruments are also spreading rather quickly in the particle technology world. The influence of particle shape on PSD results obtained from sieving has already been studied and the authors highlighted that the size dis- tribution of a product was dependent on the shape of its particles [1–3]. Several authors also studied the relations existing between particle shape and particle size distribution obtained by laser diffraction [4–6]. However, for any particle size measurement technique, the obtained results are always a combination of the size and shape of the particles. No instrument can really measure the particle size dis- tribution independently of particle shape. Although it is possible to obtain information about particle shape with laser diffraction [7], only image analysis allows the true characterization of particle size and shape. 2D image analysis gives only partial information on the particle size and shape, whereas 3D image analysis allows the measurement of the true characteristics of the particle. In this paper, we discuss the ability of the selected measurement techniques (laser diffraction and 2D and 3D image analyses) to identify the existence of two populations in blends of differently shaped products. The influence of particle shape on particle size distribution results was also investigated. The true measured 3D dimensions of the particles allow the discussion of the accuracy of the other methods. Blends of two products presenting extreme particle shape were prepared to address the matter. Two powders made of round particles and elongated particles were selected. However, the particle volume and density were comparable. Samples of the raw products were prepared, as well as intermediary blends of the two powders. X-ray microtomography was used for the acquisition of 3D images. 2D image analysis was performed with two different particle size and shape analyzers, and the particle size distributions of all samples were also measured by laser diffraction. 2. Materials and methods The choice of the two powders was based on several criteria: nature of the material, volume of the particles, size of the particles and particle shape. Steel powders were selected, because the images Powder Technology 237 (2013) 67–75 ⁎ Corresponding author. Tel.: +32 4 3669525; fax: +32 4 3669520. E-mail address: arnaud.califice@gmail.com (A. Califice). 0032-5910/$ – see front matter © 2013 Elsevier B.V. All rights reserved. http://dx.doi.org/10.1016/j.powtec.2013.01.003 Contents lists available at SciVerse ScienceDirect Powder Technology journal homepage: www.elsevier.com/locate/powtec