Particle Size Analysis

Definition

Particle size analysis is the systematic process of determining the size distribution and shape characteristics of a population of particles within a powder, suspension, or emulsion. It provides quantitative data regarding the range and frequency of particle dimensions, which is critical for ensuring quality and performance in various industrial and scientific applications.

Main Content

1. Equivalent Spherical Diameter

• Particles are rarely perfect spheres; therefore, instruments assign an "equivalent diameter" to describe them.
• This represents the diameter of a theoretical sphere that would behave in the same way as the irregular particle under the measurement conditions.

2. Particle Size Distribution (PSD)

• PSD refers to the range of particle sizes present in a sample. It is often expressed as a cumulative distribution curve or a frequency distribution histogram.
• Key metrics include D10, D50 (median), and D90, which indicate the size at which 10%, 50%, and 90% of the sample volume is smaller.

3. Measurement Techniques

• Sieving: Uses physical meshes to sort particles by size (mechanical separation).
• Light Scattering: Measures the diffraction pattern of laser light as it hits particles to calculate size distribution.
• Microscopy: Directly observes and measures particle dimensions using visual magnification.

Working / Process

1. Sample Preparation

• The representative sample must be obtained to ensure it reflects the bulk material.
• If necessary, particles are dispersed in a liquid medium using surfactants or ultrasonic energy to prevent aggregation (clumping).

2. Data Acquisition

• The dispersed sample is introduced into the analyzer (e.g., a laser diffraction system).
• The system interacts with the particles (using light, gravity, or airflow) to measure physical responses.

3. Computational Analysis

• Algorithms convert the raw physical data into a size distribution profile.
• Results are plotted on a graph, typically showing the volume percentage against the log of particle diameter.

Particle Dispersion Process:
[Clumped Particles] + [Dispersant/Energy] = [Individual Particles]
      |                        |                 |
    (Bulk)                  (Mixing)         (Measured)

Advantages / Applications

• Pharmaceuticals: Controls the dissolution rate and bioavailability of drugs; smaller particles usually dissolve faster.
• Manufacturing: Improves the flowability and compaction properties of powders used in 3D printing and tablet manufacturing.
• Quality Control: Ensures consistency between batches of raw materials, preventing defects in final products like paints, ceramics, or food powders.

Summary

Particle size analysis is a fundamental characterization technique used to determine the distribution and physical dimensions of particles in a sample. By converting irregular shapes into equivalent spherical diameters, scientists can use methods like laser diffraction or sieving to optimize product performance. Important terms include PSD (Particle Size Distribution), D-values (size percentiles), and Dispersant.