Meaning
Statistical measurements describe the width or polydispersity of a powder batch by comparing different percentile values from the cumulative distribution. The particle size distribution span is calculated by subtracting the tenth percentile diameter from the ninetieth percentile diameter and dividing by the median diameter. A lower value indicates a more uniform powder with a narrow range of sizes.
Engineers use this metric to evaluate the suitability of powders for processes like tape casting or additive manufacturing.
Sieve Analysis
Traditional classification methods utilize a series of mesh screens to separate powders into discrete size fractions. The particle size distribution span provides a more granular view of the material than simple screen sizes. Laser diffraction systems now provide the primary data for calculating the span in modern laboratories.
Packing Efficiency
Narrow distributions allow for more predictable behavior during the formation of green bodies in ceramic processing. The particle size distribution span influences how particles fill a volume and the resulting density of the compacted material. High span values often indicate a mixture of large and small particles that can lead to higher packing densities but less uniform sintering.
Optimizing the span is necessary for achieving the desired porosity and mechanical strength in the final component. Engineers manipulate the span to ensure the structural integrity of the battery electrodes.
Manufacturing Quality
Control over the atomization or milling process is demonstrated in the stability of the powder width over multiple batches. Particle size distribution span is used as a primary quality control parameter for high performance battery materials. Variations in the span can lead to inconsistent slurry viscosity and coating thickness on the current collector.
Automated classification systems help maintain the span within the tight tolerances required by the aerospace and battery industries.
