Name: ISO 20379:2018 — Fine ceramics (advanced ceramics, advanced technical ceramics) — Measurement of thixotropic behaviour of ceramic slurry by use of a rotational viscometer
SKU: ISO 20379:2018
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Overview

ISO 20379:2018 specifies a standardized method to measure the thixotropic behaviour of high-solid loaded ceramic slurry using a rotational viscometer. Targeted at fine ceramics (advanced/technical ceramics) manufacturing, the standard covers measurement principles, apparatus requirements, sample pretreatment, measurement procedures and analysis methods for evaluating time-dependent viscosity changes in non-Newtonian ceramic slurries.

Key search keywords: ISO 20379:2018, thixotropic behaviour, ceramic slurry, rotational viscometer, fine ceramics, viscosity measurement.

Key topics and technical requirements

Scope and limitations
- Applies to high-solid loading ceramic slurries used in ceramic processes (e.g., slip casting, tape casting, screen printing).
- Measurement geometries limited to: coaxial double cylinder, cone-and-plate, and parallel plate rotational viscometers.
Measurement principles
- Two evaluation approaches:
  - Hysteresis measurement of the flow curve (shear-rate sweep up/down to quantify hysteresis area).
  - Time-dependence of shear stress at constant low shear rate (monitor recovery after high-shear disruption).
Apparatus and performance
- Viscometer must permit defined shear-rate generation and torque measurement.
- Recommended instrument accuracy: torque within ±2% of full-scale, rotational frequency within ±2%, repeatability ±2%.
- Periodic calibration using standard viscosity solutions; calibration temperature must match measurement temperature.
Sample preparation and measurement conditions
- Avoid bubble generation when loading slurry; degassing by decompression must be reported if used.
- Avoid heating by high-speed dispersion (stirring/ultrasonication) which can alter dispersants/binders.
- Preferred measurement temperature 23 ± 0.2 °C; thermostat control accuracy recommended within ±0.2 °C.
- Example procedural recommendations: maximum shear rate ~300 s⁻¹ (where practical), ~90 s for shear-rate increase and decrease, rest 3–5 min, repeat measurements at least three times.
Analysis
- Hysteresis quantified dimensionlessly as (A − B)/(A + B), where A and B are areas under increasing and decreasing flow curves.
- Time-dependent recovery analyzed from shear-stress vs time at low shear rate.

Applications and users

Practical uses:
- Characterizing slurry behavior for casting, coating, tape casting, screen printing, granulation and other ceramic forming processes.
- Quality control, formulation optimization and process troubleshooting where time-dependent viscosity (thixotropy) affects coating uniformity, sedimentation, or forming performance.
Primary users:
- Materials scientists, ceramic process engineers, R&D labs, QC laboratories in ceramics and electronic-ceramic manufacturing, and instrument manufacturers.

Related information

ISO 20379:2018 contains no normative references. For broader rheology and calibration practices, consult general standards and guidelines on viscometer calibration and rheological testing from national or international bodies.

ISO 20379:2018 PDF

Abstract

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Overview

Key topics and technical requirements

Applications and users

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