The introduction of dynamic image analysis (DIA) has put particle characterization on a whole new level. Users of DIA analyzers such as Microtrac’s CAMSIZER P4 and CAMSIZER X2 benefit from a multitude of advantages:
• short analysis time (2-3 minutes)
• high level of automation
• high accuracy and reproducibility
Furthermore, DIA can replace the timeconsuming and error-prone sieve analysis. High resolution cameras provide an unambigious and direct size and shape measurement for a great variety of sample materials. With a data acquisition rate of 60 images per second (CAMSIZER P4) or more than 300 images per second (CAMIZER X2), the instruments generate data files containing information from tens of thousands to even millions of particles. These raw data files can easily build up to several gigabytes within one typical measurement and are therefore processed and presented as a meaningful chart or data table. However, it is often helpful to have access to the image data that the measurement result is based upon. This is now possible with the new Particle X-Plorer software module which is available for both CAMSIZER P4 and CAMSIZER X2.
Image Evaluation
After the measurement is completed, the operator can browse through all saved images and display the relevant size and shape data with a single mouse click.
Fig. 1: Single particle evaluation of a glass sphere
Fig. 2: All particles in the respective image can be displayed in a comprehensive overview (left side). In this image, taken by the CAMSIZER P4, single glass beads and fused bead are visible.
Particle List
Measurement and image data are easily imported into the database of the Particle X-Plorer. This database offers various options for further evaluation. Filters may be applied to find and display particles with specific size or shape characteristics.
Fig. 3: Applying filters for particle display
Each particle can be displayed in an overview as the original raw data image and the corresponding perimeter. All relevant size and shape data are listed directly next to the particle image. Figure 4 shows particles from two different sand samples with clearly visible variations in particle shape. The sand grains on the left are angular whereas the grains on the right are well rounded. This reflects the different geological history of the material: sand grains are rounded as they are transported over great distances and over a long period of time. Characterizing the shape of sand grains is also important for industrial applications since shape has a great influence on the usability e. g. of building material, filter material, or proppant.
Fig. 4a: Particle list for angular sand
Fig. 4b: Particle list for round sand
3D scatterplots
It is possible to create 3D scatter plots of all selected particles. Each data point corresponds to one particle. Axis definitions and scaling may be changed by the user and the plot can be rotated around each axis. This function helps to understand correlation of size and shape for a specific material.
Fig. 5: 3-D scatterplot generated with the particle X-Plorer
Example: Metal powder measured with CAMSIZER X2
Various metal powders are used as raw material for powder metallurgy like e. g. additive manufacturing (3D printing). Uniform size distribution and round particles are required for an efficient process. The Particle X-Plorer can find and identify particles with certain characteristics and therefore helps to set up a reliable routine for quality control. Fig. 6 shows examples of perfectly round spheres compared with beads fused together with smaller particles (satellites). Note that the CAMSIZER X2 can reliably find particles with satellites, even for very fine powders: in this case, the size range is 30 µm – 70 µm. The measurement values of the various shape parameters like aspect ratio (b/l), sphericity (SPHT), symmetry (Symm) or convexity (Conv) are significanty lower for the fused beads. Once a reasonable threshold to discriminate between “good” and “defective” particles is established, the software calculates the percentage of “satellites” in a sample.
Fig. 6a: Round, whole particles
Fig. 6b: Particles with satellites
The graphs below (Fig. 7) show a comparison between two metal powders used in additive manufacturing. The size distribution is almost identical (left diagram), the shape however is quite different (right diagram). Sample A has lower values in aspect ratio than Sample B. Only image analysis is capable of characterizing the differences between the two samples.
Fig. 7a: Analysis of two metal powder samples with the CAMSIZER X2. Sample A (red) and Sample B (blue) have almost identical size distributions.
Fig. 7b: Shape analysis with the CAMSIZER X2 shows that the aspect ratios of Sample A (red) and Sample B (blue) are significantly different. Sample A has a higher content of particles with low aspect ratio, indicating a larger amount of satellites.
Example: Sugar crystals measured with CAMSIZER P4
Particle X-Plorer can be used to understand differences between different particle morphology. In this example differences between single sugar crystals are shown. This is also a way of identifying agglomerates.
Fig. 8a: Sugar crystals: twins
Fig.8b: Sugar crystals
Example: Advanced data processing
The particle X-Plorer gives access to all available measurement data for every saved particle (fig. 9, table on the left). The list can be browsed, sorted and filtered. Data may be extracted to calculate a result based on selected particles.
Fig. 9: Data list for selected plastic pellets (extrudates)