Most materials are made up of many different particle types of varying shapes and sizes. When characterizing these particles, your goal is to figure out how much there is of each type. A simple particle size distribution, which is typically done using laser diffraction or light obscuration, only gives you size information. This may be adequate when you have a uniform mixture, but what if you have particles of similar size that are different shapes? If that’s the case, then you should use a method that can analyze particle shape.
Many industries will analyze the shape of particles as part of their quality processes because shape can impact the performance of their raw materials or the quality of the their final product. Characteristics like texture, flowability, solubility, and reactivity can all be affected by particle shape. Here are a few examples of how particle shape analysis is utilized to ensure both product quality and process quality.
Verifying uniform particle shape for process efficiency
Column chromatography is used in a variety of industries to separate and purify complex mixtures. Uniform shape and size of column packing material creates tighter column density control, and in turn, better column performance. Using flow imaging techniques, you can easily analyze column packing material to verify particle uniformity.
The images below were captured from a column packing material batch analysis performed with the FlowCam dynamic imaging particle analysis system. Round, acceptable particles are shown on the left, and less round, unacceptable particles on the right. The analysis concluded that for a total of 9,261 particles imaged, stored and measured, 8,921 of them (97.26% by volume) were acceptable and 340 of them (2.74% by volume) were unacceptable. The batch passed because greater than 95% of the particles had acceptable shape… and the analysis took less than a minute.
One advantage of the FlowCam system and the VisualSpreadsheet software is that it provides a quick and easy way to sort images by acceptable and unacceptable attributes. You can then extrapolate the statistically significant findings to the larger population of material in short order.
Measuring particle surface roughness for quality control
Superabrasives are used extensively in applications for cutting, grinding and drilling of hard materials. The most effective particles are the ones with a uniform and smooth surface. In this example below, a batch of micronized diamonds is analyzed with a FlowCam to determine if it meets the manufacturer's specifications. At least 95% of the diamond particles need to have a uniform and smooth surface.
The images below show the result of the batch analysis of the micronized diamonds using VisualSpreadsheet. The set on the left have a relatively smooth perimeter with rounded edges, whereas the set on the right are more angular. VisualSpreadsheet lets you create specific filters to help classify your images based on different parameters, such as volume, aspect ratio, equivalent spherical diameter. This way you can quickly sort your images, analyze the contents of your sample, and determine if it meets or fails the specifications. For the example below, the percentage of angular particles was less than 5%, and therefore this batch of diamonds met the set specification.
A variety of particles measurements that can be used to determine particle surface roughness, including aspect ratio, circularity, and perimeter. The FlowCam’s VisualSpreadsheet software even has a roughness measurement that can measure the irregularity of a particle’s surface.
Identifying different particle types for process evaluation
An electronic device manufacturer uses the FlowCam to analyze wash water - devices are washed to remove traces of fibers, metals and plastics from their manufacturing process. It’s important that the wash water contain a minimum number of certain particles types - fibers, platics and metals in particular - as too many indicate a production problem and potential device failures.
A diversity of particles were found in their wash water: long, skinny fiber particles; semi-transparent metal shavings; and more opaque plastic particles. By creating libraries based on particle characteristics, each run was automatically filtered by particle type, and the corresponding volume percent, particles/ml, and PPM was calculated in real time. The images below show the sample sorted by different particle type.
With the FlowCam, the manufacturer can quickly identify and quantify particles found in the wash water, and can determine areas in the manufacturing process that may need attention.
Characterizing particles with dynamic imaging partilce analysis
Learn more about how dynamic imaging analysis can help with your particle shape analysis in our free informative e-book, The Ultimate Guide to Dynamic Imaging Particle Analysis: Discover a Better Way to Analyze Sub-Visible Particles.