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Visualization and Quantitative Profiling of Mixing and Segregation of
Granules Using Synchrotron Radiation X-ray Microtomography
and Three Dimensional Reconstruction

Keywords: Mixing; Segregation; Synchrotron radiation X-ray computed microtomography; Three dimensional reconstruction; Frequency distribution; Mixing index

Tomographic imaging techniques have great potential for improving understanding of the dynamics of granular materials during manufacturing, handling, and storage. In this study, the synchrotron radiation X-ray computed microtomography (SR-μCT) was used non-invasively to monitor blend homogeneity of binary mixtures. Granular samples of microcrystalline cellulose and starch were characterized using the SR-μCT individually. Simultaneously, particle distribution was investigated by calculating the frequency distribution of a statistic for testing sphericity. Then, the microcrystalline cellulose and starch granules were blended in a cylindrical container. Influences of the time of rotations TR and the time of vibration TV on the mixture homogeneity were studied with the SR-μCT and statistical evaluation. The mixing index is also adopted to evaluate the mixture homogeneity of the particle system. The results showed that mixture homogeneity is improved with increasing TR. Furthermore, segregation increased with longer TV when particles are different in size and shape. The larger starch granules of non-spherical shape have a tendency to rise to the top, while the smaller microcrystalline cellulose granules which are spherical tend to migrate to the bottom of the mixture. Therefore, we demonstrate that SR-μCT can investigate the mixing and segregation of granular materials in three-dimensions combined with statistic method. The research was conducted at the SSRF beamline 13W1.

Ruihao Liu, Xianzhen Yin, Haiyan Li, Qun Shao, Peter York, You He, Tiqiao Xiao, Jiwen Zhang

International Journal of Pharmaceutics, Available online 9 February 2013.