Particle Shape, Size, and Surface Area

PARTICLE SHAPE, SIZE, AND SURFACE AREA 2.1. Particle Shape 

Particle shape is an important parameter which can have a significant effect on the bulk properties of a powder. It is well known that spherical particles flow better, pack better, and have a lower surface to volume ratio. Despite the well-recognized importance of particle shape, the method of shape determination has not been clearly defined owing to the complexity and variability of the three-dimensional particles. In general, shape measurement methods are only able to define accurately the shape if the shape of constituent particles can be correctly predicted based on a two-dimensional model. 

Shape of particles may be assessed descriptively by terms such as spherical, elongated, acicular, angular, or a host of other terms. Although these are descriptive terms, if accurately used, they can convey a general idea of the particle shape. However, they reveal little about the degree to which the particles take upon a particular shape. Without a comparable quantitative measure, it may be difficult to assess the effects of particle shape on a process or product. 

From the linear dimensional description of breadth, length, and height, some shape data can be derived. Breadth is usually defined as the minimum distance between two parallel lines bracketing the particle while length is the maximum distance between two parallel lines enclosing the particle and is perpendicular to 

There are a large number of transformation models which can be used to analyze the image dimensional parameters in the determination of particle shape. Some methods require additional information of particle surface area, volume or thickness to give better estimates of shape but for most purposes, a simple approach is often preferred. The common treatment of data, namely, breadth, length, perimeter, and area to reflect the particle shape (1,2) is given as follows  

---