Overview
ISO 13318-3:2004 - Determination of particle size distribution by centrifugal liquid sedimentation methods - Part 3: Centrifugal X-ray method - specifies a laboratory method to measure particle size distributions of homogeneous particulate materials using a centrifugal liquid sedimentation (disc centrifuge) with X‑ray attenuation detection. The method converts the time‑ and radius‑dependent attenuation of a collimated X‑ray beam into Stokes diameters and cumulative mass distributions. Typical analysis range is 0.1 µm to 5 µm.
Key topics and technical requirements
- Measurement principle: a stable X‑ray beam passes through a rotating suspension; attenuation is proportional to particle mass in the beam and is converted to particle size distribution using Stokes’ law.
- Applicable samples: powders dispersible in liquids or slurries, where particles share the same effective density, chemical composition and comparable shapes.
- Material constraints: particles must be denser than the suspending liquid and must not undergo chemical or physical change in it. Materials containing elements with atomic number ≳12 generally provide adequate X‑ray opacity.
- Instrumentation: shallow X‑ray‑transparent rotating disc, X‑ray source and detector (fixed or scanning), variable motor speed (typical range documented), and data acquisition/software to produce cumulative mass vs Stokes diameter plots.
- Operating parameters to record: suspending liquid type, temperature, density, viscosity; particle and sample density; centrifuge speed; measurement radius (M) and surface radius (S); dispersion method and dispersant details.
- Quality practices: baseline (clear liquid) transmission measurement, duplicate tests, validation checks for delayed settling, temperature control, and sample concentration guidance (e.g., ~0.2% by volume initial).
- Reporting: results as cumulative mass percentage vs Stokes diameter, plus full test conditions and instrument details as listed in the standard.
Applications and users
This standard is used where accurate sub‑micrometer to low‑micrometer particle sizing is required, including:
- Research and development in materials science and nanomaterials
- Quality control in powders, pigments, ceramics, and related manufacturing
- Pharmaceutical formulation and suspension characterization
- Mineral, geological and process laboratories needing reliable sedimentation‑based particle sizing
Users include laboratory analysts, QA/QC engineers, materials scientists, and instrument manufacturers implementing or validating centrifugal X‑ray disc centrifuge methods.
Related standards
- ISO 13318-1: General principles and guidelines for centrifugal liquid sedimentation methods (normative reference).
- ISO 13318-2: Photocentrifuge method (related technique).
- ISO 13317-1 is referenced for gravitational mode blending in some instrument configurations.
Keywords: ISO 13318-3:2004, centrifugal X‑ray method, particle size distribution, centrifugal liquid sedimentation, Stokes diameter, X‑ray attenuation, disc centrifuge, powder analysis, suspension.