Beyond particle size: What do shape parameters mean and how to use them?

If your particles aren’t perfectly spherical, what shape characteristics should you report? 

Shape parameters reveal crucial details about particle behaviour—from flowability to reactivity. Let’s break down some of the most impactful ones and how they help you predict material performance. 

Understanding Particle Form

Particle length and width are the fundamental measurements, but two key metrics—elongation and aspect ratio—help refine our understanding: 

• Elongation measures how long and thin a particle is, the longer and thinner the higher the elongation (up to a maximum of 1). 
• Aspect ratio compares length to width. Shorter, wider particles have a higher aspect ratio. 

Circularity is another key parameter; this tells you how close a particle is to a perfect circle (using the perimeter of the particle and the perimeter of a circle of the same area). The closer to 1 the more circular the particle. 

Why Particle Form Matters 

Particle form affects material behaviour in many ways, here are a couple of examples: 

• Flowability – Particles with lower elongation or higher circularity flow more smoothly, reducing the risk of interlocking. 
• Packing Density – Circular particles pack more efficiently. And in additive manufacturing, high packing density ensures better-quality finished parts 

Surface Properties: Rough vs. Smooth 

Two key parameters—convexity and solidity—help assess surface texture. Imagine wrapping an elastic band around a particle: 

• Convexity compares the elastic band’s perimeter to the particle’s perimeter. 
• Solidity compares the area within the band to the particle’s actual area. 

Higher values indicate smoother particles, while lower values suggest rougher surfaces. 

Why Surface Texture Matters 

Surface properties affect reaction rates. In pharmaceuticals, rougher particles dissolve faster, impacting bioavailability. In battery materials, greater surface area boosts power density by accelerating reactions at the particle surface. 

Measure Shape with the Morphologi 4 

The Morphologi 4 delivers high-quality particle images and reports over 20 size and shape parameters for every particle. With intuitive software, it pinpoints the most significant shape differences between samples—giving you clear, reliable insights. 

Want to explore how shape parameters impact your materials? Learn more about the Morphologi 4 and how its advanced imaging helps you make smarter decisions by joining our imaging masterclass webinars, checking out the product page, or connecting with an applications specialist today.