SIST EN ISO 18757:2006
(Main)Fine ceramics (advanced ceramics, advanced technical ceramics) - Determination of specific surface area of ceramic powders by gas adsorption using the BET method (ISO 18757:2003)
Fine ceramics (advanced ceramics, advanced technical ceramics) - Determination of specific surface area of ceramic powders by gas adsorption using the BET method (ISO 18757:2003)
ISO 18757:2003 provides guidelines for the determination of the total specific external and internal surface area of disperse or porous (pore diameter greater than 2 nm) fine ceramic materials by measuring the amount of physically adsorbed gas according to the method of Brunauer, Emmett and Teller (BET method). This International Standard only focuses on specific details relevant to fine ceramic materials. It should further be noted that the BET method cannot be applied to type I isotherms (microporous materials or chemisorption behaviour) or when the solid adsorbs the measuring gas.
Hochleistungskeramik - Bestimmung der spezifischen Oberfläche keramischer Pulver durch Gasadsorption nach dem BET-Verfahren (ISO 18757:2003)
Diese Internationale Norm gibt Leitlinien zur Bestimmung der gesamten spezifischen äußeren und inneren
Oberfläche von dispergierten oder porösen (Porendurchmesser > 2 nm) feinkeramischen Werkstoffen, wobei
nach dem Verfahren von Brunauer, Emmet und Teller (BET-Verfahren) [1] die Menge des physikalisch
adsorbierten Gases gemessen wird. Allgemeine Verfahrensleitlinien werden in ISO 9277 beschrieben. Die
vorliegende Internationale Norm konzentriert sich auf bestimmte Einzelheiten, die für feinkeramische
Werkstoffe von Bedeutung sind. Es sollte berücksichtigt werden, dass das BET-Verfahren nicht auf
Isothermen des Typs I (Werkstoffe mit Mikroporen oder chemisorptivem Verhalten) oder in den Fällen
angewendet werden kann, in denen der Feststoff das Messgas absorbiert.
ANMERKUNG Weitere Einzelheiten zum Anwendungsbereich sind aus den Literaturhinweisen [2], [3] mit Empfeh-lungen
von IUPAC oder aus dem Lehrbuch von Gregg und Sing [4] zu entnehmen.
Céramiques techniques - Détermination de la surface spécifique (aire massique) des poudres céramiques par adsorption de gaz a l'aide de la méthode BET (ISO 18757:2003)
L'ISO 18757:2003 donne des lignes directrices pour la détermination de la surface spécifique (aire massique) totale externe et interne des matériaux céramiques fins dispersés ou poreux (diamètre de pore supérieur à 2 nm) par mesurage de la quantité de gaz physiquement adsorbée, conformément à la méthode de Brunauer, Emmet et Teller (méthode BET). Les grandes lignes de la méthode sont décrites dans l'ISO 9277. L'ISO 18757:2003 n'est axée que sur les détails particuliers applicables aux céramiques fines. Il convient de noter par ailleurs que la méthode BET n'est pas utilisable pour les isothermes de type 1 (matériaux microporeux ou pour lesquels le contact se fait par chimisorption) ou pour les solides qui absorbent le gaz de mesure.
Fina keramika (sodobna keramika, sodobna tehnična keramika) – Določanje specifične površine keramičnih praškov z adsorpcijo plina po metodi BET (ISO 18757:2003)
General Information
Relations
Standards Content (Sample)
SLOVENSKI STANDARD
SIST EN ISO 18757:2006
01-julij-2006
)LQDNHUDPLND VRGREQDNHUDPLNDVRGREQDWHKQLþQDNHUDPLND ±'RORþDQMH
VSHFLILþQHSRYUãLQHNHUDPLþQLKSUDãNRY]DGVRUSFLMRSOLQDSRPHWRGL%(7 ,62
Fine ceramics (advanced ceramics, advanced technical ceramics) - Determination of
specific surface area of ceramic powders by gas adsorption using the BET method (ISO
18757:2003)
Hochleistungskeramik - Bestimmung der spezifischen Oberfläche keramischer Pulver
durch Gasadsorption nach dem BET-Verfahren (ISO 18757:2003)
Céramiques techniques - Détermination de la surface spécifique (aire massique) des
poudres céramiques par adsorption de gaz a l'aide de la méthode BET (ISO
18757:2003)
Ta slovenski standard je istoveten z: EN ISO 18757:2005
ICS:
81.060.30
SIST EN ISO 18757:2006 en
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.
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EUROPEAN STANDARD
EN ISO 18757
NORME EUROPÉENNE
EUROPÄISCHE NORM
October 2005
ICS 81.060.30 Supersedes EN 725-6:1996
English Version
Fine ceramics (advanced ceramics, advanced technical
ceramics) - Determination of specific surface area of ceramic
powders by gas adsorption using the BET method (ISO
18757:2003)
Poudres céramiques - Détermination de l'aire massique Hochleistungskeramik - Bestimmung der spezifischen
(surface spécifique) par adsorption de gaz à l'aide de la Oberfläche keramischer Pulver durch Gasadsorption nach
méthode BET (ISO 18757:2003) dem BET-Verfahren (ISO 18757:2003)
This European Standard was approved by CEN on 19 September 2005.
CEN members are bound to comply with the CEN/CENELEC Internal Regulations which stipulate the conditions for giving this European
Standard the status of a national standard without any alteration. Up-to-date lists and bibliographical references concerning such national
standards may be obtained on application to the Central Secretariat or to any CEN member.
This European Standard exists in three official versions (English, French, German). A version in any other language made by translation
under the responsibility of a CEN member into its own language and notified to the Central Secretariat has the same status as the official
versions.
CEN members are the national standards bodies of Austria, Belgium, Cyprus, Czech Republic, Denmark, Estonia, Finland, France,
Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Slovakia,
Slovenia, Spain, Sweden, Switzerland and United Kingdom.
EUROPEAN COMMITTEE FOR STANDARDIZATION
COMITÉ EUROPÉEN DE NORMALISATION
EUROPÄISCHES KOMITEE FÜR NORMUNG
Management Centre: rue de Stassart, 36 B-1050 Brussels
© 2005 CEN All rights of exploitation in any form and by any means reserved Ref. No. EN ISO 18757:2005: E
worldwide for CEN national Members.
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EN ISO 18757:2005 (E)
Foreword
The text of ISO 18757:2003 has been prepared by Technical Committee ISO/TC 206 “Fine ceramics” of the
International Organization for Standardization (ISO) and has been taken over as EN ISO 18757:2005 by
Technical Committee CEN/TC 184 “Advanced technical ceramics” the secretariat of which is held by BSI.
This European Standard shall be given the status of a national standard, either by publication of an identical
text or by endorsement, at the latest by April 2006, and conflicting national standards shall be withdrawn at the
latest by April 2006.
This document supersedes EN 725-6:1996.
CEN/TC 184 has prepared EN 725 Advanced technical ceramics — Methods of test for ceramic powders in
twelve parts as follows:
Part 1: Determination of impurities in alumina
Part 2: Determination of impurities in barium titanate
Part 3: Determination of oxygen content of non-oxides by thermal extraction
Part 4: Determination of oxygen content of non-oxides by XRF analysis
Part 5: Determination of particle size distribution
Part 6: Determination of specific surface area
Part 7: Determination of absolute density
Part 8: Determination of tapped density
Part 9: Determination of untamped bulk density
Part 10: Determination of compaction properties
Part 11: Determination of the densification on natural sintering
Part 12: Chemical analysis of zirconia
According to the CEN/CENELEC Internal Regulations, the national standards organizations of the following
countries are bound to implement this European Standard: Austria, Belgium, Cyprus, Czech Republic,
Denmark, Estonia, Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania,
Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Slovakia, Slovenia, Spain, Sweden, Switzerland
and United Kingdom.
Endorsement notice
The text of ISO 18757:2003 has been approved by CEN as EN ISO 18757:2005 without any modifications.
2
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INTERNATIONAL ISO
STANDARD 18757
First edition
2003-12-01
Fine ceramics (advanced ceramics,
advanced technical ceramics) —
Determination of specific surface area of
ceramic powders by gas adsorption using
the BET method
Poudres céramiques — Détermination de l'aire massique (surface
spécifique) par adsorption de gaz à l'aide de la méthode BET
Reference number
ISO 18757:2003(E)
©
ISO 2003
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ISO 18757:2003(E)
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©
ii ISO 2003 – All rights reserved
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ISO 18757:2003(E)
Contents Page
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Symbols and abbreviated terms . 2
5 Principle . 2
6 Procedure . 3
6.1 General procedure . 3
6.2 Sample preparation . 3
6.3 Experimental conditions . 5
6.4 Evaluation of data . 6
7 Test report . 7
Annex A (informative) Sample preparation — Outgassing . 8
Annex B (informative) Reference materials . 9
Bibliography . 10
©
ISO 2003 – All rights reserved iii
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ISO 18757:2003(E)
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.
International Standards are drafted in accordance with the rules given in the ISO/IEC Directives, Part 2.
The main task of technical committees is to prepare International Standards. Draft International Standards
adopted by the technical committees are circulated to the member bodies for voting. Publication as an
International Standard requires approval by at least 75 % of the member bodies casting a vote.
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.
ISO 18757 was prepared by Technical Committee ISO/TC 206, Fine ceramics.
©
iv ISO 2003 – All rights reserved
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INTERNATIONAL STANDARD ISO 18757:2003(E)
Fine ceramics (advanced ceramics, advanced technical
ceramics) — Determination of specific surface area of ceramic
powders by gas adsorption using the BET method
1Scope
This International Standard provides guidelines for the determination of the total specific external and internal
surface area of disperse or porous (pore diameter > 2nm) fine ceramic materials by measuring the amount of
physically adsorbed gas according to the method of Brunauer, Emmet and Teller (BET method) [1]. General
guidelines of the method are described in ISO 9277. This International Standard only focuses on specific details
relevant to fine ceramic materials. It should further be noted that the BET method cannot be applied to type I
isotherms (microporous materials or chemisorption behaviour) or when the solid absorbs the measuring gas.
NOTE For further details on those subjects please see IUPAC references [2], [3] or the textbook by Gregg and Sing [4].
2 Normative references
The following referenced documents are indispensable for the application 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 9277:1995, Determination of the specific surface area of solids by gas adsorption using the BET method
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
3.1
adsorption
enrichment of the adsorbate at the external and accessible internal surfaces of a solid
3.2
physisorption
weak bonding of the adsorbate, reversible by small changes in pressure or temperature
3.3
adsorbate
measuring gas to be adsorbed
3.4
adsorbent
solid, which adsorbs the measuring gas
3.5
surface area
area of external surface of a fine ceramic powder plus the internal surface of its accessible macro- and
mesopores
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ISO 18757:2003(E)
3.6
adsorption isotherm
relation between the quantity of adsorbate and the equilibrium pressure of the adsorbate at constant
temperature
4 Symbols and abbreviated terms
Table 1 presents the symbols used in this International Standard, together with their SI units. For comparison
purposes, the IUPAC [3] symbols are also given. All specific dimensions are related to sample mass, in grams.
Table 1 — Symbols
IUPAC
ISO symbol Parameter SI unit
symbol
molecular cross-sectional area occupied by an adsorbed molecule in a complete
2
a nm a
m m
monolayer
2 −1
a specific surface area m g a
s s
a
C BET parameter 1 C
23 −1
L Avogadro constant (= 6,022× 10 ) mol L
m mass of the solid sample g m
a a
m specific mass of gas adsorbed 1 m
a
−1
a
n specific amount of gas adsorbed mol g n
a
specific monolayer capacity of adsorbate; amount of adsorbate needed to cover
−1 a
n mol g n , n
m m m
the surface with a complete monolayer of molecules
−1
n specific monolayer capacity derived from multi-point measurement mol g —
m, mp
−1
n specific monolayer capacity derived from single-point measurement mol g —
m, sp
p pressure of the adsorbate in equilibrium with the adsorbate Pa p
0
p saturation vapour pressure of the adsorbate Pa
0 p
t time s t
T temperature K T
3 −1 a
V specific volume adsorbed m g V
a
a
According to ISO 31-0, the coherent SI unit for any quantity of dimension one (at present commonly termed “dimensionless”) is the unit
one, symbol 1.
5Principle
The method specified involves the determination of the amount of adsorbate required to cover the external and
accessible internal pore surface of a solid with a complete monolayer of adsorbate (see Figure 1).
This monolayer capacity can be calculated from the adsorption isotherm using the BET equation:
p/p 1 C− 1
0
= + × (p/p ) (1)
0
n [1− (p/p )] n C n C
a 0 m,mp m,mp
Any gas may be used provided it is physically adsorbed by weak bonds at the surface of the solid (van der
Waals forces), and can be desorbed by a decrease in pressure at the same temperature. Nitrogen at its boiling
point (about 77 K) is the most frequently used adsorbate. Krypton or argon at liquid nitrogen temperature are
two other gases that are frequently used. The latter two gases offer an improved sensitivity for the analysis of
2 2
low surface-area samples (less than about 1m to 5m total surface area of the sample). Results of
measurements with different adsorbates may deviate from each other because of different molecular cross
sectional areas, different accessibility to pores and different measuring temperatures.
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ISO 18757:2003(E)
NOTE The dotted line shows the first adsorbate layer on the surface (See ISO 9277).
Figure 1 — Particle with surface (solid line) detected by the adsorption method
The adsorbate gas is admitted to the sample container, which is held at a constant temperature. The amounts
p
adsorbed are measured in equilibrium with the adsorbate gas pressure, , and plotted against the relative
pressure, p/p , to give an adsorption isotherm. Adsorption isotherms may be obtained by volumetric or
0
gravimetric measurement or by the carrier gas method using a continuous or discontinuous operational mode.
Further details are described in corresponding references [2], [3].
6 Procedure
6.1 General procedure
General sample preparation procedures and a description of the different measurement techniques are
provided in 6.2 and 6.3 of ISO 9277:1995. Specific conditions and examples for fine ceramic materials are
described in 6.2 to 6.4 below.
6.2 Sample preparation
The sample preparation method is one of the most crucial steps during the surface area analysis procedure.
The sample has to be outgassed (also commonly termed “degassed”) under conditions, which will not alter the
solid sample, but which provide a “clean” sample surface at the beginning of the analysis. Moisture might be
adsorbed in pores or the surface might be contaminated with other residues from the previous
◦
treatment/preparation of the sample. Most ceramic materials can be outgassed at higher temperatures (150 C
◦
to 300 C) without irreversible changes of the surface. It is strongly recommended to evacuate the sample to a
< 1Pa < 0,1 Pa 8 h
pressure of (preferably ) prior to and during the entire heat treatment. Outgassing for is
usually sufficient to achieve a clean sample surface and 0,5 h to 3 h is commonly practical. However, the
following examples and conditions should be carefully considered for any unknown material.
a) If the sample contains a large amount of water, eithe
...
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