Overview
ISO 20998-3:2017 provides internationally recognized guidelines for the measurement and characterization of particle size distributions in liquids using ultrasonic attenuation spectroscopy, specifically under conditions where non-linear effects cannot be neglected. Developed by the International Organization for Standardization (ISO), this standard addresses cases where the ultrasonic attenuation spectrum is not a linear function of particle volume fraction, due to significant particle-particle interactions at high concentrations.
This standard is essential for researchers and industry professionals working with concentrated colloids, dispersions, slurries, and emulsions. It expands the capability of ultrasonic measurements beyond the linear regime, enabling accurate, real-time particle size analysis in complex, high-concentration systems.
Key Topics
-
Non-linear Ultrasonic Attenuation
ISO 20998-3:2017 details the theoretical basis and practical implications for applying non-linear models when analyzing ultrasonic attenuation spectra. It explains when linear approximations (appropriate for dilute systems) are insufficient, and non-linear effects-such as multiple scattering and overlapping thermal and viscous wave fields-must be considered.
-
Measurement Issues in Concentrated Systems
The standard discusses practical challenges unique to concentrated suspensions and emulsions, including:
- Path length limitations due to increased attenuation
- High attenuation impacting signal-to-noise ratios
- Increased viscosity and its effects on bubble formation and flow
- Changes in sound velocity and resulting signal distortions
- Impact of agglomeration or flocculation on measurement accuracy
-
Calculation Methods
Guidelines are provided for using mathematical models to determine particle size distribution (PSD) from ultrasonic data. Empirical and semi-empirical calibrations are also discussed, with an emphasis on the importance of instrument qualification, precision, and accuracy testing using certified reference materials.
-
Limits of Applicability
ISO 20998-3:2017 is applicable for particles typically ranging from 10 nm to 3 mm in systems with dispersed phase concentrations from approximately 5% to over 50% by volume. The standard outlines how to estimate when linear theory breaks down, helping users decide when non-linear analysis is required.
Applications
-
Quality Control in Manufacturing
Real-time, in-situ measurement of particle size distributions in products like paints, pharmaceuticals, food emulsions, and mineral slurries ensures batch consistency and process optimization.
-
Emulsion and Slurry Process Monitoring
Ultrasonic attenuation spectroscopy enables dynamic monitoring of high-concentration systems without the need for sample dilution, preserving the original system's integrity.
-
Research and Development
Accurate particle characterization supports R&D in materials science, nanotechnology, and chemical engineering, especially where new formulations and dispersions demand high-precision monitoring.
-
Process Control and Optimization
Monitoring dynamic changes, such as agglomeration or flocculation, allows for better control of industrial processes, leading to improved product performance and reduced waste.
Related Standards
-
ISO 20998-1:2006
Measurement and characterization of particles by acoustic methods - Part 1: Concepts and procedures in ultrasonic attenuation spectroscopy. It provides fundamental concepts and procedures, serving as a prerequisite for understanding Part 3.
-
ISO 20998-2:2013
Measurement and characterization of particles by acoustic methods - Part 2: Guidelines for linear theory. Focuses on linear modeling applicable to dilute systems.
-
ISO 14488:2007
Particulate materials - Sampling and sample splitting for the determination of particulate properties. Relevant for ensuring representative sampling and sample handling.
By following ISO 20998-3:2017, organizations can ensure reliable, accurate measurement and monitoring of particles in complex systems using advanced ultrasonic techniques, facilitating enhanced quality, safety, and process control.