Ｘ線マイクロＣＴスキャン装置の粉体工学への応用

Abstract

X-ray computed tomography is widely used for the observation of internal organs in medical diagnosis. Recently, X-ray micro computer tomography with a micrometer scale resolution has been developed and is now being applied in the field of engineering including powder and particle technology. X-ray micro CT can be used not only for the observation of internal structure of a particle or a powder bed but also for the quantitative measurement of a particle or powder packed bed characteristics. For example, the volume and the surface area of a particle can be calculated by integrating the cross sectional area and the perimeter of particle images captured by X-ray micro CT. Based on the measured volume and the surface area of a particle, we obtained the 3-dimensional particle shape factor such as Wadell's sphericity and the sphericity was compared with traditional 2-dimensional shape indices such as circularity. We also applied X-ray micro CT to the measurement of the void fraction distribution near the bottom of a spherical particle packing bed and the change in void fraction profils of a fine powder packed bed during the compression by a piston and a centrifugal force. Our experimental results showed that the local void fraction in fine powder packed bed increases with the depth of powder layer when compressed by a piston while it decreases with the depth of powder layer in the case of centrifugal packing. X-ray micro computed tomography is a new tool for powder characterization and will be widely used for various powder processes and powder product inspections in the near future.