ISO 21821:2019

Fine ceramics (advanced ceramics, advanced technical ceramics) — Determination of densification properties of ceramic powders on natural sintering

This document specifies the test method to determine the extent to which ceramic powder compacts made of granulated or ungranulated ceramic powders are densified, when they are sintered at a high temperature without the application of any external pressure or external densification force. The test method is applicable to pure oxides, mixtures of oxides and solid solutions, and is also applicable to non-oxides (e.g. carbides, nitrides) that can be sintered under vacuum or constant gas pressure (1 bar or less) to prevent oxidation or decomposition. The test method is not applicable to ceramics that can only be sintered using pressure-assisted sintering techniques such as hot pressing (HP), hot isostatic pressing (HIP), gas pressure sintering (GPS) or spark plasma sintering (SPS). Inorganic sintering additives can be used where their presence is reported.

Céramiques techniques (céramiques avancées, céramiques techniques avancées) — Détermination des propriétés de densification des poudres céramiques lors d’un frittage naturel

Le présent document spécifie la méthode d’essai permettant de déterminer dans quelle mesure les comprimés de poudre céramique constitués de poudres céramiques granulées ou non sont densifiés, lorsqu’ils sont frittés à haute température sans appliquer de pression externe ni de force de densification externe. La méthode d’essai s’applique aux oxydes purs, aux mélanges d’oxydes et de solutions solides, et également aux matériaux ne contenant pas d’oxyde (par exemple carbures, nitrures) qui peuvent être frittés sous vide ou sous pression de gaz constante (à 1 bar ou moins) pour empêcher l’oxydation ou la décomposition. La méthode d’essai ne s’applique pas aux céramiques qui ne peuvent être frittées qu’à l’aide de techniques de frittage assistées par pression telles que la compression à chaud («hot pressing», HP), la compression isostatique à chaud («hot isostatic pressing», HIP), le frittage sous pression de gaz («gas pressure sintering», GPS) ou le frittage flash («spark plasma sintering», SPS). Des additifs de frittage inorganiques peuvent être utilisés lorsque leur présence est signalée.

General Information

• Status: Published
• Publication Date: 22-Oct-2019
• ICS: 81.060.30 - Advanced ceramics
• Technical Committee: ISO/TC 206 - Fine ceramics
• Drafting Committee: ISO/TC 206/WG 2 - Powders
• Current Stage: 9020 - International Standard under periodical review
• Start Date: 15-Oct-2024
• Completion Date: 15-Oct-2024

Relations

• Consolidated By: ISO 11403-1:2021 - Plastics — Acquisition and presentation of comparable multipoint data — Part 1: Mechanical properties
• Effective Date: 06-Jun-2022

Standards Content (Sample)

INTERNATIONAL ISO
STANDARD 21821
First edition
2019-10
Fine ceramics (advanced ceramics,
advanced technical ceramics) —
Determination of densification
properties of ceramic powders on
natural sintering
Céramiques techniques (céramiques avancées, céramiques techniques
avancées) — Détermination des propriétés de densification des
poudres céramiques lors d’un frittage naturel
Reference number
©
ISO 2019
© ISO 2019
All rights reserved. Unless otherwise specified, or required in the context of its implementation, no part of this publication may
be reproduced or utilized otherwise in any form or by any means, electronic or mechanical, including photocopying, or posting
on the internet or an intranet, without prior written permission. Permission can be requested from either ISO at the address
below or ISO’s member body in the country of the requester.
ISO copyright office
CP 401 • Ch. de Blandonnet 8
CH-1214 Vernier, Geneva
Phone: [phone]
Fax: [phone]
Email: [e-mail]
Website: www.iso.org
Published in Switzerland
ii © ISO 2019 – All rights reserved

Contents Page
Foreword .iv
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Principle . 1
5 Symbols and designation . 2
6 Apparatus . 3
7 Sampling . 6
8 Procedure. 6
8.1 Compaction . 6
8.2 Heat treatment . 6
8.2.1 Selection of test temperatures . 6
8.2.2 Thermal cycle. 6
8.3 Measurement . 7
9 Expression of results . 7
9.1 Calculation . 7
9.2 Densification curve . 7
10 Test report . 9
Bibliography .11
Foreword
ISO (the International Organization for Standardization) is a worldwide federation of national standards
bodies (ISO member bodies). The work of preparing International Standards is normally carried out
through ISO technical committees. Each member body interested in a subject for which a technical
committee has been established has the right to be represented on that committee. International
organizations, governmental and non-governmental, in liaison with ISO, also take part in the work.
ISO collaborates closely with the International Electrotechnical Commission (IEC) on all matters of
electrotechnical standardization.
The procedures used to develop this document and those intended for its further maintenance are
described in the ISO/IEC Directives, Part 1. In particular, the different approval criteria needed for the
different types of ISO documents should be noted. This document was drafted in accordance with the
editorial rules of the ISO/IEC Directives, Part 2 (see www .iso .org/directives).
Attention is drawn to the possibility that some of the elements of this document may be the subject of
patent rights. ISO shall not be held responsible for identifying any or all such patent rights. Details of
any patent rights identified during the development of the document will be in the Introduction and/or
on the ISO list of patent declarations received (see www .iso .org/patents).
Any trade name used in this document is information given for the convenience of users and does not
constitute an endorsement.
For an explanation of the voluntary nature of standards, the meaning of ISO specific terms and
expressions related to conformity assessment, as well as information about ISO's adherence to the
World Trade Organization (WTO) principles in the Technical Barriers to Trade (TBT) see www .iso
.org/iso/foreword .html.
This document was prepared by Technical Committee ISO/TC 206, Fine ceramics.
Any feedback or questions on this document should be directed to the user’s national standards body. A
complete listing of these bodies can be found at www .iso .org/members .html.
iv © ISO 2019 – All rights reserved

INTERNATIONAL STANDARD ISO 21821:2019(E)
Fine ceramics (advanced ceramics, advanced technical
ceramics) — Determination of densification properties of
ceramic powders on natural sintering
1 Scope
This document specifies the test method to determine the extent to which ceramic powder compacts
made of granulated or ungranulated ceramic powders are densified, when they are sintered at a high
temperature without the application of any external pressure or external densification force. The test
method is applicable to pure oxides, mixtures of oxides and solid solutions, and is also applicable to
non-oxides (e.g. carbides, nitrides) that can be sintered under vacuum or constant gas pressure (1 bar
or less) to prevent oxidation or decomposition. The test method is not applicable to ceramics that can
only be sintered using pressure-assisted sintering techniques such as hot pressing (HP), hot isostatic
pressing (HIP), gas pressure sintering (GPS) or spark plasma sintering (SPS). Inorganic sintering
additives can be used where their presence is reported.
2 Normative references
The following documents are referred to in the text in such a way that some or all of their content
constitutes requirements of this document. For dated references, only the edition cited applies. For
undated references, the latest edition of the referenced document (including any amendments) applies.
ISO 3611, Geometrical product specifications (GPS) — Dimensional measuring equipment: Micrometers for
external measurements — Design and metrological characteristics
ISO/IEC 17025, General requirements for the competence of testing and calibration laboratories
ISO 17172, Fine ceramics (advanced ceramics, advanced technical ceramics) — Determination of
compaction properties of ceramic powders
3 Terms and definitions
No terms and definitions are listed in this document.
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/
4 Principle
When ceramic powder compacts are heat-treated at high temperatures, they shrink and are densified
due to sintering. The mass, dimensions (diameter and height), volume and apparent density of a ceramic
powder compact are measured before and after sintering through thermal treatment. The variations in
mass, dimensions, volume and apparent density depend on maximum temperature, dwell time, heating
rate and apparent density after compaction, and can be expressed as a function of these parameters.
For example, the variation in relative density can be plotted as a function of sintering temperature for
each compacting pressure.
5 Symbols and designation
Symbols used throughout this document and their designations are given in Table 1.
Table 1 — Symbols, designations and units of mass, volume, density, dimension and sintering
temperature
Symbol Designation Unit Formula
D Diameter of sample before sintering mm —
a
D Diameter of sample after sintering mm —
H Height of sample before sintering mm —
a
H Height of sample after sintering mm —
m Mass before sintering g —
a
m Mass after sintering g —
V Volume before sintering cm —
a
V Volume after sintering cm —
T Sintering temperature °C —
DD
Relative diameter variation (shrinkage) at the end of sintering — (3)
D
a
DH
Relative height variation (shrinkage) at the end of sintering — (4)
H
a
Dm
Relative mass variation at the end of sintering — (5)
m
a
DV
Relative volume variation at the end of sintering — (6)
V
a
Dρ
Relative density variation at the end of sintering — (7)
ρ
a
ρ Apparent density before sintering g/cm (1)
a
ρ Apparent density after sintering g/cm (2)
ρ Theoretical density g/cm —
th
These characteristics are linked by relations in Formulae (1) to (7):
m
a
ρ = (1)
a
V
a
m
ρ= (2)
V
()DD−
DD
a
= (3)
D D
a a
()HH−
DH
a
= (4)
H H
a a
2 © ISO 2019 – All rights reserved

()mm−
Dm
a
= (5)
m m
a a
()VV−
DV
a
= (6)
V V
a a
()ρρ−
Dρ
a
= (7)
ρ ρ
a a
6 Apparatus
6.1 Cylindrical die, either double acting (floating type – see Figure 1) or single acting (see Figure 2),
shall be made from hard material, preferably hardened steel or tungsten carbide. Upper and lower
punches of adequate dimensions as indicated in Figure 1 and Figure 2 shall be used for producing
cylindrical powder compacts. The upper part of the die shall be preferably designed to avoid damage to
the powder compact during ejection due to spring-back. An ejection cone of height 5 mm, allowing an
increase of the diameter at the top and the bottom of the die of approximately 1 %, as shown in Figure 1
and Figure 2, should be used.
The die shall be of the floating type or of the type suspended from a spring (mode 1, see Figure 1), or of
stationary type with only one moveable upper punch (mode 2, see Figure 2). The die shall be capable
of making cylindrical powder compacts with a diameter of 10 mm to 26 mm and a height-to-diameter
ratio of between 0,3 and 0,5 (mode 1), or with a diameter of 10 mm to 32 mm and a height-to-diameter
ratio of between 0,15 and 0,25 (mode 2).
6.2 Furnace, should have a hot zone large enough to accommodate the required size and number of
test pieces, and be capable of maintaining the test temperature (T) so that the maximum temperature
variation in the hot zone is 10 °C. The furnace shall allow a constant heating rate, which can be controlled
to within 2 °C/h. The furnace heating elements, thermal insulation and kiln furniture shall be selected to
be chemically compatible with the test pieces, avoiding both surface reaction and generation of vapour
pressure. The kiln furniture used to support the test pieces shall be a sintered piece of the test material
with at least 80 % of theoretical density. If required, as is for non-oxides, the furnace shall be additionally
capable of supplying constant vacuum or constant gas pressure (1 bar or less) of, for example, argon or
nitrogen.
6.3 Press, capable of applying sufficient force with a precision of ±2 %.
6.4 Balance, capable of weighing at least 10 g with a resolution of ±0,001 g.
6.5 Micrometer, according to ISO 3611, or other suitable measuring device for measuring the
dimensions of ceramic powder compacts with a resolution of ±0,01 mm.
a)  Die
b)  Upper and lower punch
Key
1 ejection cone (height: 5 mm; increase of diameter: c. 1 %)
2 shrink ring
3 hard material
4 upper punch, l = H – 10
5 lower punch, l = H + 35
Figure 1 — Example of cylindrical die and punches for mode 1 compaction
4 © ISO 2019 – All rights reserved

a)  Die
b)  Lower punch
c)  Upper punch
Key
1 ejection cone
Figure 2 — Example of cylindrical die and punches for mode 2 compaction
7 Sampli
...

Deleted: /FDIS
ISO TC 206/WG 2
Secretariat: JISC
Fine ceramics (advanced ceramics, advanced technical ceramics) — Determination of
densification properties of ceramic powders on natural sintering

Warning for WDs and CDs
This document is not an ISO International Standard. It is distributed for review and comment. It is
subject to change without notice and may not be referred to as an International Standard.
Recipients of this draft are invited to submit, with their comments, notification of any relevant patent
rights of which they are aware and to provide supporting documentation.

© ISO 2019, Published in Switzerland
All rights reserved. Unless otherwise specified, no part of this publication may be reproduced or
utilized otherwise in any form or by any means, electronic or mechanical, including photocopying,
or posting on the internet or an intranet, without prior written permission. Permission can be
requested from either ISO at the address below or ISO’s member body in the country of the
requester.
ISO copyright office
Ch. de Blandonnet 8 • CP 401
CH‐1214 Vernier, Geneva, Switzerland
Tel. + 41 22 749 01 11
Fax + 41 22 749 09 47
[e-mail]
www.iso.org
ii © ISO 2019 – All rights reserved

Contents
Foreword . iv
1  Scope . 1
2  Normative references . 1
3  Terms and definitions . 1
4  Principle . 1
5  Symbols and designation . 2
6  Apparatus . 3
7  Sampling . 6
8  Procedure . 6
8.1  Compaction . 6
8.2  Heat treatment . 6
8.2.1  Selection of test temperatures . 6
8.2.2  Thermal cycle. 6
8.3  Measurement . 7
9  Expression of results . 7
9.1  Calculation . 7
9.2  Densification curve . 8
10  Test report . 9
Bibliography . 11

© ISO 2019 – All rights reserved iii

Foreword
ISO (the International Organization for Standardization) is a worldwide federation of national
standards bodies (ISO member bodies). The work of preparing International Standards is normally
carried out through ISO technical committees. Each member body interested in a subject for which a
technical committee has been established has the right to be represented on that committee.
International organizations, governmental and non‐governmental, in liaison with ISO, also take part in
the work. ISO collaborates closely with the International Electrotechnical Commission (IEC) on all
matters of electrotechnical standardization.
The procedures used to develop this document and those intended for its further maintenance are
described in the ISO/IEC Directives, Part 1. In particular, the different approval criteria needed for the
different types of ISO documents should be noted. This document was drafted in accordance with the
editorial rules of the ISO/IEC Directives, Part 2 (see www.iso.org/directives).
Attention is drawn to the possibility that some of the elements of this document may be the subject of
patent rights. ISO shall not be held responsible for identifying any or all such patent rights. Details of
any patent rights identified during the development of the document will be in the Introduction and/or
on the ISO list of patent declarations received (see www.iso.org/patents).
Any trade name used in this document is information given for the convenience of users and does not
constitute an endorsement.
For an explanation of the voluntary nature of standards, the meaning of ISO specific terms and
expressions related to conformity assessment, as well as information about ISO's adherence to the
World Trade Organization (WTO) principles in the Technical Barriers to Trade (TBT)
see www.iso.org/iso/foreword.html.
This document was prepared by Technical Committee ISO/TC 206, Fine ceramics.
Any feedback or questions on this document should be directed to the user’s national standards body. A
complete listing of these bodies can be found at www.iso.org/members.html.
iv © ISO 2019 – All rights reserved

Fine ceramics (advanced ceramics, advanced technical
ceramics) — Determination of densification properties of ceramic
powders on natural sintering
1 Scope
This document specifies the test method to determine the extent to which ceramic powder compacts
made of granulated or ungranulated ceramic powders are densified, when they are sintered at a high
temperature without the application of any external pressure or external densification force. The test
method is applicable to pure oxides, mixtures of oxides and solid solutions, and is also applicable to
non‐oxides (e.g. carbides, nitrides) that can be sintered under vacuum or constant gas pressure (1 bar
or less) to prevent oxidation or decomposition. The test method is not applicable to ceramics that can
only be sintered using pressure‐assisted sintering techniques such as hot pressing (HP), hot isostatic
pressing (HIP), gas pressure sintering (GPS) or spark plasma sintering (SPS). Inorganic sintering
additives can be used where their presence is reported.
2 Normative references
The following documents are referred to in the text in such a way that some or all of their content
constitutes requirements of this document. For dated references, only the edition cited applies. For
undated references, the latest edition of the referenced document (including any amendments) applies.
ISO 3611, Geometrical product specifications (GPS) — Dimensional measuring equipment: Micrometers
for external measurements — Design and metrological characteristics
ISO/IEC 17025, General requirements for the competence of testing and calibration laboratories
ISO 17172, Fine ceramics (advanced ceramics, advanced technical ceramics) — Determination of
compaction properties of ceramic powders
3 Terms and definitions
No terms and definitions are listed in this document.
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/
4 Principle
When ceramic powder compacts are heat‐treated at high temperatures, they shrink and are densified
due to sintering. The mass, dimensions (diameter and height), volume and apparent density of a
ceramic powder compact are measured before and after sintering through thermal treatment. The
variations in mass, dimensions, volume and apparent density depend on maximum temperature, dwell
time, heating rate and apparent density after compaction, and can be expressed as a function of these
parameters. For example, the variation in relative density can be plotted as a function of sintering
temperature for each compacting pressure.
© ISO 2019 – All rights reserved 1

5 Symbols and designation
Symbols used throughout this document and their designations are given in Table 1.
Table 1 — Symbols, designations and units of mass, volume, density, dimension and sintering
temperature
Symbol Designation Unit Formula
D Diameter of sample before sintering mm — Moved down [1]: Diameter of
a
sample after sintering
Deleted: ¶
D Diameter of sample after sintering mm —
D
Deleted: mm¶
Ha Height of sample before sintering mm —
Moved (insertion) [1]
H Height of sample after sintering mm —
Deleted: ¶
m Mass before sintering g —
a
H
m Mass after sintering g —
Moved down [2]: Height of
sample after sintering
V Volume before sintering cm —
a
Deleted: mm¶
V Volume after sintering cm —
Moved (insertion) [2]
T Sintering temperature °C —
Deleted: ¶
DD
m
Relative diameter variation (shrinkage) at the end of sintering — (3)
D
a
Moved down [3]: Mass after
sintering
DH
Deleted: g¶
Relative height variation (shrinkage) at the end of sintering — (4)
H
a
Moved (insertion) [3]
Dm
Deleted: ¶
Relative mass variation at the end of sintering — (5)
V
m
a
Moved down [4]: Volume after
DV
sintering
Relative volume variation at the end of sintering — (6)
V
Deleted: cm¶
a
Moved (insertion) [4]
D
Relative density variation at the end of sintering — (7)

a
3 Deleted: ¶
ρ Apparent density before sintering g/cm (1)
a
ρ¶
ρ Apparent density after sintering g/cm (2) ρth
Moved down [5]: Apparent
ρ Theoretical density g/cm —
th
density after sinteringTheoretical
These characteristics are linked by relations in Formulae (1) to (7):
Moved down [6]: Theoretical
density
m
a
  (1)
a
Moved down [7]: g/cm
V
a
Moved down [8]: g/cm
m
Deleted: ¶
 (2)
V
(2)¶
Moved (insertion) [5]
()DD
DD
a
 (3)
Moved (insertion) [7]
DD
aa
Moved (insertion) [6]
Moved (insertion) [8]
2 © ISO 2019 – All rights reserved

()HH
DH
a
 (4)
HH
aa
()mm
Dm
a
 (5)
mm
aa
()VV
DV
a
 (6)
VV
aa
()
D
a
 (7)

aa
6 Apparatus
6.1 Cylindrical die, either double acting (floating type – see Figure 1) or single acting (see Figure 2),
shall be made from hard material, preferably hardened steel or tungsten carbide. Upper and lower
punches of adequate dimensions as indicated in Figure 1 and Figure 2 shall be used for producing
cylindrical powder compacts. The upper part of the die shall be preferably designed to avoid damage to
the powder compact during ejection due to spring‐back. An ejection cone of height 5 mm, allowing an
increase of the diameter at the top and the bottom of the die of approximately 1 %, as shown in Figure 1
and Figure 2, should be used.
The die shall be of the floating type or of the type suspended from a spring (mode 1, see Figure 1), or of
stationary type with only one moveable upper punch (mode 2, see Figure 2). The die shall be capable of
making cylindrical powder compacts with a diameter of 10 mm to 26 mm and a height‐to‐diameter
ratio of between 0,3 and 0,5 (mode 1), or with a diameter of 10 mm to 32 mm and a height‐to‐diameter
ratio of between 0,15 and 0,25 (mode 2).
6.2 Furnace, should have a hot zone large enough to accommodate the required size and number of
test pieces, and be capable of maintaining the test temperature (T) so that the maximum temperature
variation in the hot zone is 10 °C. The furnace shall allow a constant heating rate, which can be
controlled to within 2 °C/h. The furnace heating elements, thermal insulation and kiln furniture shall be
selected to be chemically compatible with the test pieces, avoiding both surface reaction and generation
of vapour pressure. The kiln furniture used to support the test pieces shall be a sintered piece of the test
material with at least 80 % of theoretical density. If required, as is for non‐oxides, the furnace shall be
additionally capable of supplying constant vacuum or constant gas pressure (1 bar or less) of, for
example, argon or nitrogen.
6.3 Press, capable of applying sufficient force with a precision of ±2 %.
6.4 Balance, capable of weighing at least 10 g with a resolution of ±0,001 g.
6.5 Micrometer, according to ISO 3611, or other suitable measuring device for measuring the
dimensions of ceramic powder compacts with a resolution of ±0,01 mm.
© ISO 2019 – All rights reserved 3

a)  Die Deleted: (
Deleted: (
b)  Upper and lower punch
Key
1 ejection cone (height: 5 mm; increase of diameter: c. 1 %)
2 shrink ring
3 hard material
4 upper punch, l = H – 10
5 lower punch, l = H + 35
Figure 1 — Example of cylindrical die and punches for mode 1 compaction
4 © ISO 2019 – All rights reserved

a)  Die
Deleted: (
b)  Lower punch
Deleted: (
c)  Upper punch
Deleted: (
Key
1 ejection cone
© ISO 2019 – All rights reserved 5

Figure 2 — Example of cylind
...

NORME ISO
INTERNATIONALE 21821
Première édition
2019-10
Céramiques techniques (céramiques
avancées, céramiques techniques
avancées) — Détermination des
propriétés de densification des
poudres céramiques lors d’un frittage
naturel
Fine ceramics (advanced ceramics, advanced technical ceramics) —
Determination of densification properties of ceramic powders on
natural sintering
Numéro de référence
DOCUMENT PROTÉGÉ PAR COPYRIGHT
© ISO 2019
Tous droits réservés. Sauf prescription différente ou nécessité dans le contexte de sa mise en œuvre, aucune partie de cette
publication ne peut être reproduite ni utilisée sous quelque forme que ce soit et par aucun procédé, électronique ou mécanique,
y compris la photocopie, ou la diffusion sur l’internet ou sur un intranet, sans autorisation écrite préalable. Une autorisation peut
être demandée à l’ISO à l’adresse ci-après ou au comité membre de l’ISO dans le pays du demandeur.
ISO copyright office
Case postale 401 • Ch. de Blandonnet 8
CH-1214 Vernier, Genève
Tél.: [phone]
E-mail: [e-mail]
Web: www.iso.org
Publié en Suisse
ii
Sommaire Page
Avant-propos .iv
1 Domaine d’application . 1
2 Références normatives .1
3 Termes et définitions . 1
4 Principe. 1
5 Symboles et désignation . 2
6 Appareillage . 3
7 Prélèvement . 6
8 Mode opératoire . 6
8.1 Énergie . 6
8.2 Traitement thermique . 6
8.2.1 Sélection des températures d’essai . 6
8.2.2 Cycle thermique. 6
8.3 Mesurage . 7
9 Expression des résultats . 7
9.1 Calcul . 7
9.2 Courbe de densification . 8
10 Rapport d’essai . 9
Bibliographie .11
iii
Avant-propos
L'ISO (Organisation internationale de normalisation) est une fédération mondiale d'organismes
nationaux de normalisation (comités membres de l'ISO). L'élaboration des Normes internationales est
en général confiée aux comités techniques de l'ISO. Chaque comité membre intéressé par une étude
a le droit de faire partie du comité technique créé à cet effet. Les organisations internationales,
gouvernementales et non gouvernementales, en liaison avec l'ISO participent également aux travaux.
L'ISO collabore étroitement avec la Commission électrotechnique internationale (IEC) en ce qui
concerne la normalisation électrotechnique.
Les procédures utilisées pour élaborer le présent document et celles destinées à sa mise à jour sont
décrites dans les Directives ISO/IEC, Partie 1. Il convient, en particulier, de prendre note des différents
critères d'approbation requis pour les différents types de documents ISO. Le présent document a
été rédigé conformément aux règles de rédaction données dans les Directives ISO/IEC, Partie 2 (voir
www.iso.org/directives).
L'attention est attirée sur le fait que certains des éléments du présent document peuvent faire l'objet de
droits de propriété intellectuelle ou de droits analogues. L'ISO ne saurait être tenue pour responsable
de ne pas avoir identifié de tels droits de propriété et averti de leur existence. Les détails concernant
les références aux droits de propriété intellectuelle ou autres droits analogues identifiés lors de
l'élaboration du document sont indiqués dans l'Introduction et/ou dans la liste des déclarations de
brevets reçues par l'ISO (voir www.iso.org/brevets).
Les appellations commerciales éventuellement mentionnées dans le présent document sont données
pour information, par souci de commodité, à l’intention des utilisateurs et ne sauraient constituer un
engagement.
Pour une explication de la nature volontaire des normes, la signification des termes et expressions
spécifiques de l'ISO liés à l'évaluation de la conformité, ou pour toute information au sujet de l'adhésion
de l'ISO aux principes de l’Organisation mondiale du commerce (OMC) concernant les obstacles
techniques au commerce (OTC), voir www.iso.org/avant-propos.
Le présent document a été élaboré par le comité technique ISO/TC 206, Céramiques techniques.
Il convient que l’utilisateur adresse tout retour d’information ou toute question concernant le présent
document à l’organisme national de normalisation de son pays. Une liste exhaustive desdits organismes
se trouve à l’adresse www.iso.org/fr/members.html.
iv
NORME INTERNATIONALE ISO 21821:2019(F)
Céramiques techniques (céramiques avancées, céramiques
techniques avancées) — Détermination des propriétés de
densification des poudres céramiques lors d’un frittage
naturel
1 Domaine d’application
Le présent document spécifie la méthode d’essai permettant de déterminer dans quelle mesure les
comprimés de poudre céramique constitués de poudres céramiques granulées ou non sont densifiés,
lorsqu’ils sont frittés à haute température sans appliquer de pression externe ni de force de densification
externe. La méthode d’essai s’applique aux oxydes purs, aux mélanges d’oxydes et de solutions solides,
et également aux matériaux ne contenant pas d’oxyde (par exemple carbures, nitrures) qui peuvent être
frittés sous vide ou sous pression de gaz constante (à 1 bar ou moins) pour empêcher l’oxydation ou la
décomposition. La méthode d’essai ne s’applique pas aux céramiques qui ne peuvent être frittées qu’à
l’aide de techniques de frittage assistées par pression telles que la compression à chaud («hot pressing»,
HP), la compression isostatique à chaud («hot isostatic pressing», HIP), le frittage sous pression de gaz
(«gas pressure sintering», GPS) ou le frittage flash («spark plasma sintering», SPS). Des additifs de
frittage inorganiques peuvent être utilisés lorsque leur présence est signalée.
2 Références normatives
Les documents suivants sont cités dans le texte de sorte qu’ils constituent, pour tout ou partie de leur
contenu, des exigences du présent document. Pour les références datées, seule l’édition citée s’applique.
Pour les références non datées, la dernière édition du document de référence s’applique (y compris les
éventuels amendements).
ISO 3611, Spécification géométrique des produits (GPS) — Équipement de mesurage dimensionnel:
Micromètres d’extérieur — Caractéristiques de conception et caractéristiques métrologiques
ISO/IEC 17025, Exigences générales concernant la compétence des laboratoires d'étalonnages et d'essais
ISO 17172, Céramiques techniques — Détermination des propriétés de compaction des poudres céramiques
3 Termes et définitions
Aucun terme n’est défini dans le présent document.
L’ISO et l’IEC tiennent à jour des bases de données terminologiques destinées à être utilisées en
normalisation, consultables aux adresses suivantes:
— ISO Online browsing platform: disponible à l’adresse https:// www .iso .org/ obp
— IEC Electropedia: disponible à l’adresse https:// www .electropedia .org/
4 Principe
Lorsque les comprimés de poudre céramique font l’objet d’un traitement thermique à haute température,
ils se rétractent et se densifient par frittage. La masse, les dimensions (diamètre et hauteur), le volume
et la masse volumique apparente d’un comprimé de poudre céramique sont mesurés avant et après
frittage par traitement thermique. Les variations de masse, de dimensions, de volume et de masse
volumique apparente dépendent de la température maximale, du temps de maintien, de la vitesse
de montée en température et de la masse volumique apparente après compactage, et peuvent être
exprimées en fonction de ces paramètres. Par exemple, la variation de la masse volumique relative peut
être tracée en fonction de la température de frittage pour chaque pression de compactage.
5 Symboles et désignation
Les symboles utilisés dans le présent document et leurs désignations sont donnés dans le Tableau 1.
Tableau 1 — Symboles, désignations et unités de masse, de volume, de masse volumique,
de dimension et de température de frittage
Symbole Désignation Unité Formule
D Diamètre de l’échantillon avant frittage mm —
a
D Diamètre de l’échantillon après frittage mm —
H Hauteur de l’échantillon avant frittage mm —
a
H Hauteur de l’échantillon après frittage mm —
m Masse avant frittage g —
a
m Masse après frittage g —
V Volume avant frittage cm —
a
V Volume après frittage cm —
T Température de frittage °C —
DD
Variation relative du diamètre (retrait) à la fin du frittage — (3)
D
a
DH
Variation relative de la hauteur (retrait) à la fin du frittage — (4)
H
a
Dm
Variation relative de la masse à la fin du frittage — (5)
m
a
DV
Variation relative du volume à la fin du frittage — (6)
V
a
Dρ
Variation relative de la masse volumique à la fin du frittage — (7)
ρ
a
ρ Masse volumique apparente avant frittage g/cm (1)
a
ρ Masse volumique apparente après frittage g/cm (2)
ρ Masse volumique théorique g/cm —
th
Ces caractéristiques sont liées par les relations des Formules (1) à (7):
m
a
ρ = (1)
a
V
a
m
ρ= (2)
V
()DD−
DD
a
= (3)
D D
a a
()HH−
DH
a
= (4)
H H
a a
()mm−
Dm
a
= (5)
m m
a a
()VV−
DV
a
= (6)
V V
a a
()ρρ−
Dρ
a
= (7)
ρ ρ
a a
6 Appareillage
6.1 Matrice cylindrique, à double effet (type flottant – voir Figure 1) ou simple effet (voir Figure 2),
devant être constituée d’un matériau dur, de préférence de l’acier trempé ou du carbure de tungstène.
Des poinçons supérieur et inférieur de dimensions adéquates telles qu’indiquées à la Figure 1 et
à la Figure 2 doivent être utilisés pour produire les comprimés de poudre cylindriques. La partie
supérieure de la matrice doit, de préférence, être conçue de façon à éviter toute détérioration du
comprimé de poudre pendant l’éjection due au phénomène dit d’effet ressort. Il convient d’utiliser un
cône d’éjection d’une hauteur de 5 mm, permettant une augmentation de diamètre au niveau supérieur
et inférieur de la matrice de 1 % environ, comme indiqué à la Figure 1 et à la Figure 2.
La matrice doit être de type flottant ou suspendu à un ressort (mode 1, voir Figure 1), ou de type fixe
avec un seul poinçon supérieur mobile (mode 2, voir Figure 2). La matrice doit pouvoir réaliser des
comprimés de poudre cylindriques d’un diamètre compris entre 10 mm et 26 mm, avec un rapport
hauteur/diamètre compris entre 0,3 et 0,5 (mode 1), ou d’un diamètre compris entre 10 mm et 32 mm,
avec un rapport hauteur/diamètre compris entre 0,15 et 0,25 (mode 2).
6.2 Four; il convient qu’il possède une zone chaude suffisamment grande pour loger les dimensions
et le nombre d’éprouvettes requis, et qu’il soit capable de maintenir la température d’essai (T) de sorte
que la variation maximale de température dans la zone chaude soit de 10 °C. Le four doit permettre
une vitesse de montée en température constante pouvant être régulée à 2 °C/h près. Les éléments
chauffants, l’isolation thermique et les accessoires intérieurs du four doivent être choisis de manière à
être chimiquement compatibles avec les éprouvettes, en évitant les réactions de surface et la génération
de pression de vapeur. Les accessoires intérieurs du four servant à por
...