Applied Chemicals and Materials Division, MS647, National Institute of Standards and Technology;
Applied Chemicals and Materials Division, MS647, National Institute of Standards and Technology.
J Vis Exp. 2020 Dec 4(166). doi: 10.3791/61636.
Measuring the size distribution of the particles in a powder is a common activity in science and industry. Measuring the shape distribution of the particles is much less common. However, the shape and size of powder particles are not independent quantities. All known size/shape measurement techniques either assume a spherical shape or measure the shape in two dimensions only. The X-ray computed tomography (XCT) based method presented here measures both size and shape in 3D without making any assumptions. Starting from a 3D image of particles, the method can mathematically classify particles according to shape, for example particles composed of several smaller particles welded together as opposed to single particles that are not necessarily spherical. Of course, defining a single number as the "size" or "shape" of a random non-spherical particle is not possible in principle, leading to many ways to estimate particle size and shape via various interlinked parameters, which can all be generated from this complete 3D characterization in the form of averages and distributions. The necessary experimental procedures, mathematical analysis, and computer analysis are described and an example is given for a metal powder. The technique is limited to particles that can be imaged by XCT with a minimum of about 1000 voxels per particle volume.
测量粉末中颗粒的大小分布是科学和工业中常见的活动。测量颗粒的形状分布则要少见得多。然而，粉末颗粒的形状和大小并不是相互独立的量。所有已知的尺寸/形状测量技术要么假设为球形，要么仅测量二维形状。这里提出的基于 X 射线计算机断层扫描 (XCT) 的方法无需做出任何假设即可在 3D 中同时测量大小和形状。从颗粒的 3D 图像开始，该方法可以根据形状对颗粒进行数学分类，例如由几个较小颗粒焊接在一起组成的颗粒，而不是不一定是球形的单个颗粒。当然，从理论上讲，对于随机非球形颗粒，不可能用单个数字来表示“大小”或“形状”，这导致了通过各种相互关联的参数来估计颗粒大小和形状的许多方法，这些方法都可以通过这种完整的 3D 特征化以平均值和分布的形式生成。本文描述了必要的实验程序、数学分析和计算机分析，并给出了一个金属粉末的示例。该技术仅限于可以用 XCT 成像的颗粒，每个颗粒体积的最小体素数量约为 1000 个。
