ISO 20379:2018

Fine ceramics (advanced ceramics, advanced technical ceramics) - Measurement of thixotropic behaviour of ceramic slurry by use of a rotational viscometer

ISO 20379:2018 specifies a method for measurement of thixotropic behaviour of ceramic slurry with rotational viscometer. The slurry with high-solid loading, which is used in ceramic manufacturing, has a generally non-Newtonian property. This method is limited to measurement of thixotropic behaviour of high-solid loaded ceramic slurry with "coaxial double cylinder viscometer", "cone and plate viscometer" and "a parallel plate viscometer" as rotational viscometers.

Céramiques techniques (céramiques avancées, céramiques techniques avancées) — Mesurage du comportement thixotropique d’une barbotine de céramique à l’aide d’un viscosimètre rotatif

General Information

• Status: Published
• Publication Date: 12-Feb-2018
• ICS: 81.060.30 - Advanced ceramics
• Technical Committee: ISO/TC 206 - Fine ceramics
• Drafting Committee: ISO/TC 206/WG 2 - Powders
• Current Stage: 9093 - International Standard confirmed
• Start Date: 15-Jun-2023
• Completion Date: 13-Dec-2025

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.

Standards Content (Sample)

INTERNATIONAL ISO
STANDARD 20379
First edition
2018-02
Fine ceramics (advanced ceramics,
advanced technical ceramics) —
Measurement of thixotropic behaviour
of ceramic slurry by use of a rotational
viscometer
Céramiques techniques (céramiques avancées, céramiques techniques
avancées) — Mesurage du comportement thixotropique d’une
barbotine de céramique à l’aide d’un viscosimètre rotatif
Reference number
©
ISO 2018
© ISO 2018
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ii © ISO 2018 – All rights reserved

Contents Page
Foreword .iv
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Principle . 2
4.1 Evaluation of thixotropic behaviour by hysteresis measurement of flow curve . 2
4.2 Evaluation of thixotropic behaviour by time-dependence of shear stress at
constant low shear rate . 2
5 Apparatus . 2
5.1 Measuring system . 2
5.2 Basic capacity of the instrument . 2
5.3 Calibration of rotational viscometer . 3
5.4 Temperature control device . 3
6 Pretreatment of the slurry samples . 3
6.1 General . 3
6.2 Degassing . 3
6.3 Dispersion by stirring, mixing and ultrasonication. 3
7 Measurement condition . 3
7.1 Setting of ceramic slurry to rotational viscometer . 3
7.2 Temperature . 3
8 Measurement procedure . 4
8.1 Measurement of thixotropic behaviour by hysteresis measurement of flow curve . 4
8.1.1 Condition of shear rate and setting of measurement range . 4
8.1.2 Measurement procedure . 4
8.1.3 Analysis method of measurement results . 4
8.2 Measurement of thixotropic behaviour by time-dependence of shear stress at
constant low shear rate . 5
8.2.1 Setting of measurement programme . 5
8.2.2 Measurement procedure . 5
8.2.3 Analysis method of measurement results . 5
9 Test report . 6
Bibliography . 8
Foreword
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This document was prepared by Technical Committee ISO/TC 206, Fine ceramics.
iv © ISO 2018 – All rights reserved

INTERNATIONAL STANDARD ISO 20379:2018(E)
Fine ceramics (advanced ceramics, advanced technical
ceramics) — Measurement of thixotropic behaviour of
ceramic slurry by use of a rotational viscometer
1 Scope
This document specifies a method for measurement of thixotropic behaviour of ceramic slurry with
rotational viscometer. The slurry with high-solid loading, which is used in ceramic manufacturing, has a
generally non-Newtonian property. This method is limited to measurement of thixotropic behaviour of
high-solid loaded ceramic slurry with “coaxial double cylinder viscometer”, “cone and plate viscometer”
and “a parallel plate viscometer” as rotational viscometers.
2 Normative references
There are no normative references in this document.
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
ISO and IEC maintain terminological databases for use in standardization at the following addresses:
— ISO Online browsing platform: available at https:// www .iso .org/ obp
— IEC Electropedia: available at http:// www .electropedia .org/
3.1
shear stress
force developed on the plane which is perpendicular to the shear force when there is shear applied to
the fluid
3.2
shear rate
proportion of laminar flow rate change perpendicular to the fluid flow
3.3
Newtonian property
slurry property of which the shear stress is proportional to the shear rate
3.4
non-Newtonian property
slurry property of which the shear stress is not proportional to the shear rate
3.5
viscosity
proportion of shear stress and shear rate
Note 1 to entry: The proportion is a representation of resistance to flow.
3.6
flow curve
curve showing the relationship between shear rate and shear stress
3.7
thixotropic behaviour
behaviour of fluid which has time-dependence of flow behaviour so that the apparent viscosity
decreases with time at controlled shear and recovers gradually with removal of the shear force
3.8
ceramic slurry
suspension of grinding ceramic powders mixed or dispersed in water or other liquid
Note 1 to entry: The suspension is used in the ceramic process, for example screen printing, slip casting, tape
casting, granule production.
4 Principle
4.1 Evaluation of thixotropic behaviour by hysteresis measurement of flow curve
Measurement of flow curve of ceramic slurry is performed using a rotational viscometer, which can
monitor shear rate and shear stress at the same time. The thixotropic behaviour is evaluated from the
magnitude of hysteresis that is indicated by the process of the flow curve.
4.2 Evaluation of thixotropic behaviour by time-dependence of shear stress at constant
low shear rate
Measurement of the flow curve of ceramic slurry is performed using a rotational viscometer, which
can monitor shear rate and shear stress at the same time. After the viscosity of ceramic slurry is
decreased by destruction of aggregated or flocculated structure in ceramic slurry at high shear rate,
the thixotropic behaviour is evaluated by measuring the recovery process of viscosity at low shear rate.
The relationship between fabrication of re-flocculated structure and time can be detected at low shear
rate. Therefore, the thixotropic behaviour is evaluated by using data from low shear rate.
5 Apparatus
A rotational viscometer has various measuring geometrics. In this document, the rotational viscometers
with defined shear rate are a coaxial double cylinder system, a cone and plate system and a parallel
plate system.
5.1 Measuring system
The measuring
...