SIST EN ISO 10070:2020
(Main)Metallic powders - Determination of envelope-specific surface area from measurements of the permeability to air of a powder bed under steady-state flow conditions (ISO 10070:2019)
Metallic powders - Determination of envelope-specific surface area from measurements of the permeability to air of a powder bed under steady-state flow conditions (ISO 10070:2019)
This document specifies a method of measuring the air permeability and the porosity of a packed bed of metal powder, and of deriving therefrom the value of the envelope-specific surface area. The permeability is determined under steady-state flow conditions, using a laminar flow of air at a pressure near atmospheric. This document does not include the measurement of permeability by a constant volume method. Several different methods have been proposed for this determination, and several test devices are available commercially. They give similar, reproducible results, provided that the general instructions given in this document are respected, and the test parameters are identical. This document does not specify a particular commercial test device and corresponding test procedure. However, for the convenience of the user, an informative annex has been included (see Annex A) which is intended to give some practical information on three specific methods: - the Lea and Nurse method, involving a test device which can be built in a laboratory (see A.1); - the Zhang Ruifu method, using a similar test device (see A.2); - the Gooden and Smith method, involving a test device which can be built in a laboratory but for which a commercial test device also exists. (Two types of commercial test device exist; one of these is no longer available for purchase, but is still being used, see A.3.) These methods are given as examples only. Other test devices available in various countries are acceptable within the scope of this document. This testing method is applicable to all metallic powders, including powders for hardmetals, up to 1 000 μm in diameter, but it is generally used for particles having diameters between 0,2 μm and 75,0 μm. It is not intended to be used for powders composed of particles whose shape is far from equiaxial, i.e. flakes or fibres, unless specifically agreed upon between the parties concerned. This testing method is not applicable to mixtures of different metallic powders or powders containing binders or lubricant. If the powder contains agglomerates, the measured surface area can be affected by the degree of agglomeration. If the powder is subjected to a de-agglomeration treatment (see Annex B), the method used is to be agreed upon between the parties concerned.
Metallpulver - Ermittlung der spezifischen Außenoberfläche durch Messung der Luftdurchlässigkeit einer Pulverprobe unter gleichförmigen Strömungsbedingungen (ISO 10070:2019)
Dieses Dokument legt ein Verfahren zur Messung der Luftpermeabilität und der Porosität eines verdichteten Pulverbetts und daraus die Ableitung des Wertes für die spezifische Außenoberfläche fest. Die Permeabilität wird unter gleichförmigen Strömungsbedingungen mithilfe eines laminaren Luftstromes bei nahezu atmosphärischem Druck bestimmt. Dieses Dokument umfasst nicht die Messung der Permeabilität mithilfe des Verfahrens bei konstantem Volumen.
Für diese Bestimmung wurden mehrere unterschiedliche Verfahren vorgeschlagen und viele kommerzielle Prüfgeräte stehen zur Verfügung. Sie ergeben ähnliche, wiederholbare Ergebnisse, vorausgesetzt, die allgemeinen Anweisungen dieses Dokuments werden eingehalten und die Prüfparameter sind identisch.
Dieses Dokument behandelt kein bestimmtes kommerzielles Prüfgerät mit dem dazugehörigen Prüfverfahren. Trotzdem ist zur besseren Benutzerfreundlichkeit ein informativer Anhang mit praktischen Hinweisen zu drei spezifischen Verfahren angefügt (siehe Anhang A):
- das Verfahren nach Lea und Nurse, einschließlich eines Prüfgeräts, das in einem Labor aufgebaut werden kann (siehe A.1);
- das Verfahren nach Zhang Ruifu mit ähnlichem Prüfgerät (siehe A.2);
- das Verfahren nach Gooden und Smith, einschließlich eines Prüfgeräts, das in einem Labor aufgebaut werden kann, für das aber auch ein kommerzielles Prüfgerät existiert. (Es stehen zwei kommerzielle Prüfgeräte zur Verfügung; eines davon ist nicht mehr käuflich erwerbbar, wird jedoch nach wie vor eingesetzt – siehe A.3).
Diese Verfahren sind lediglich Beispiele. Innerhalb des Anwendungsbereiches dieses Dokuments sind auch andere Prüfgeräte, die in den verschiedenen Ländern zur Verfügung stehen, zulässig.
Dieses Prüfverfahren ist für alle Metallpulver, einschließlich Hartmetallpulver, mit einem Teilchendurchmesser bis 1 000 µm anwendbar, wird aber im Allgemeinen für Pulverteilchen mit einem Durchmesser von 0,2 µm bis 75,0 µm angewendet. Es dient nicht dazu, bei Pulvern angewendet zu werden, deren Pulverteilchen stark von der äquiaxialen Form abweichen, d. h. flocken- und nadelförmig, außer das wurde zwischen den beteiligten Parteien speziell vereinbart.
Dieses Prüfverfahren ist nicht anwendbar bei Gemischen aus verschiedenen Metallpulvern oder bei Pulvern, die Bindemittel oder Gleitmittel enthalten.
Wenn das Pulver Agglomerate enthält, kann die gemessene Oberfläche durch den Agglomerationsgrad beeinflusst sein. Wenn das Pulver einer Desagglomerationsbehandlung unterzogen wird (siehe Anhang B), muss das angewendete Verfahren zwischen den beteiligten Parteien vereinbart werden.
Poudres métalliques - Détermination de la surface spécifique d'enveloppe à partir de mesures de la perméabilité à l'air d'un lit de poudre dans des conditions d'écoulement permanent (ISO 10070:2019)
Le présent document spécifié une méthode de mesure de la perméabilité à l'air et de la porosité d'un lit de poudre métallique tassé, et permettant de déduire une valeur de la surface spécifique d'enveloppe. La perméabilité est déterminée dans des conditions d'écoulement permanent, à l'aide d'un débit d'air laminaire à une pression voisine de la pression atmosphérique. Le présent document ne traite pas de la mesure de la perméabilité à volume constant.
Plusieurs méthodes sont proposées pour remplir l'objectif fixé. De nombreux appareils d'essai, disponibles dans le commerce, permettent de mener à bien la détermination. Ces appareils d'essai donnent des résultats similaires et reproductibles dans la mesure où les instructions générales données dans le présent document sont respectées et où les paramètres d'essai identiques.
II n'est pas possible, dans le présent document, de se limiter à un appareil d'essai du commerce particulier et au mode opératoire d'essai correspondant. En vue d'aider néanmoins l'utilisateur, une annexe est prévue (voir Annexe A) pour donner des renseignements pratiques sur trois méthodes spécifiques:
— la méthode Lea et Nurse, impliquant un appareil d'essai conçu en laboratoire (voir A.1);
— la méthode Zhang Ruifu, utilisant un appareil d'essai similaire (voir A.2);
— la méthode Gooden et Smith impliquant un appareil d'essai qui peut être conçu en laboratoire, mais correspond aussi à un modèle du commerce. (Deux types d'appareil d'essai du commerce existent; l'un d'eux n'est plus disponible à l'achat, mais est toujours utilisé, voir A.3.
Ces méthodes sont données uniquement à titre d'exemple, mais n'excluent pas l'emploi d'autres matériels commercialisés dans certains pays et conformes au présent document.
La méthode d'essai est applicable à toutes les poudres métalliques, y compris les poudres de métaux durs, jusqu'à 1 000 μm de diamètre, mais est généralement réservée aux particules de diamètre comprises entre 0,2 et 75 μm. Elle n'est pas destinée à être utilisée pour les poudres composées de particules dont la forme s'écarte trop de I'équiaxialité, par exemple du type flocons ou fibres. Dans ce cas, il est admis de ne l'utiliser qu'avec le consentement de toutes les parties concernées.
La méthode d'essai n'est pas utilisable pour les mélanges de poudres métalliques différentes ou de poudres renfermant des liants ou lubrifiants.
Lorsque la poudre contient des agglomérats, la surface mesurée peut être affectée par le degré d'agglomération. Si la poudre est soumise à un traitement de désagglomération (voir Annexe B), la méthode utilisée doit être subordonnée à l'accord des parties concernées.
Kovinski prah - Ugotavljanje specifične ovojne površine z merjenjem zračne prepustnosti nasute plasti prašnih delcev pri ustaljenem toku zraka skoznjo (ISO 10070:2019)
Ta dokument določa metodo za merjenje zračne prepustnosti in poroznosti plasti kovinskega prahu in za izpeljevanje vrednosti specifične ovojne površine iz tega. Prepustnost se določa pod ustaljenimi pogoji pretoka, z uporabo laminarnega zračnega toka pri tlaku, ki je blizu atmosferskemu. Ta dokument ne vključuje merjenja prepustnosti po metodi konstantne prostornine. Za to ugotavljanje je bilo predlaganih več različnih metod in komercialno je na voljo več preskusnih naprav. Te naprave dajejo podobne rezultate z možnostjo reprodukcije pod pogojem, da se upoštevajo splošna navodila, podana v tem dokumentu, in da so preskusni parametri enaki. Ta dokument ne določa posebne komercialne preskusne naprave in ustreznega preskusnega postopka. Vendar je bil v pomoč uporabniku vključen informativni dodatek (glej dodatek A), katerega namen je podati nekaj praktičnih informacij glede treh specifičnih metod: – metoda Lea in Nurse, ki vključuje preskusno napravo, ki jo je mogoče izdelati v laboratoriju (glej A.1); – metoda Zhang Ruifu, pri kateri se uporablja podobna preskusna naprava (glej A.2); – metoda Gooden in Smith, ki vključuje preskusno napravo, ki jo je mogoče izdelati v laboratoriju, vendar zanjo obstaja tudi komercialna preskusna naprava. (Obstajata dva tipa komercialne preskusne naprave; eden od njiju ni več na voljo za nakup, a se še vedno uporablja, glej A.3.) Te metode so podane le kot primer. Druge preskusne naprave, ki so na voljo v različnih državah, so sprejemljive znotraj področja uporabe tega dokumenta. Ta metoda za preskušanje se uporablja za vse vrste kovinskega prahu, vključno s prahom za trde kovine, s premerom do 1000 μm, vendar se običajno uporablja za delce s premerom med 0,2 μm in 75,0 μm. Metoda ni namenjena za uporabo pri prahu, sestavljenem iz delcev, katerih oblika je daleč od enakoosne, tj. kosmi ali vlakna, razen če se glede tega zadevni stranki izrecno ne dogovorita drugače. Ta metoda za preskušanje se ne uporablja za mešanice različnega kovinskega prahu ali prahu, ki vsebuje veziva ali mazivo. Če prah vsebuje aglomerate, lahko stopnja aglomeracije vpliva na izmerjeno površino. Če prah ni izpostavljen deaglomeracijski obdelavi (glej dodatek B), se morata o uporabljeni metodi dogovoriti obe zadevni stranki.
General Information
Standards Content (Sample)
SLOVENSKI STANDARD
SIST EN ISO 10070:2020
01-marec-2020
Kovinski prah - Ugotavljanje specifične ovojne površine z merjenjem zračne
prepustnosti nasute plasti prašnih delcev pri ustaljenem toku zraka skoznjo (ISO
10070:2019)
Metallic powders - Determination of envelope-specific surface area from measurements
of the permeability to air of a powder bed under steady-state flow conditions (ISO
10070:2019)
Metallpulver - Ermittlung der spezifischen Außenoberfläche durch Messung der
Luftdurchlässigkeit einer Pulverprobe unter gleichförmigen Strömungsbedingungen (ISO
10070:2019)
Poudres métalliques - Détermination de la surface spécifique d'enveloppe à partir de
mesures de la perméabilité à l'air d'un lit de poudre dans des conditions d'écoulement
permanent (ISO 10070:2019)
Ta slovenski standard je istoveten z: EN ISO 10070:2019
ICS:
77.160 Metalurgija prahov Powder metallurgy
SIST EN ISO 10070:2020 en,fr,de
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.
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SIST EN ISO 10070:2020
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SIST EN ISO 10070:2020
EN ISO 10070
EUROPEAN STANDARD
NORME EUROPÉENNE
December 2019
EUROPÄISCHE NORM
ICS 77.160
English Version
Metallic powders - Determination of envelope-specific
surface area from measurements of the permeability to air
of a powder bed under steady-state flow conditions (ISO
10070:2019)
Poudres métalliques - Détermination de la surface Metallpulver - Bestimmung der spezifischen
spécifique d'enveloppe à partir de mesures de la Außenoberfläche durch Messung der Permeabilität von
perméabilité à l'air d'un lit de poudre dans des Luft in einem Pulverbett unter gleichförmigen
conditions d'écoulement permanent (ISO 10070:2019) Strömungsbedingungen (ISO 10070:2019)
This European Standard was approved by CEN on 14 December 2019.
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 CEN-CENELEC Management Centre 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 CEN-CENELEC Management
Centre has the same status as the official versions.
CEN members are the national standards bodies of Austria, Belgium, Bulgaria, Croatia, Cyprus, Czech Republic, Denmark, Estonia,
Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway,
Poland, Portugal, Republic of North Macedonia, Romania, Serbia, Slovakia, Slovenia, Spain, Sweden, Switzerland, Turkey and
United Kingdom.
EUROPEAN COMMITTEE FOR STANDARDIZATION
COMITÉ EUROPÉEN DE NORMALISATION
EUROPÄISCHES KOMITEE FÜR NORMUNG
CEN-CENELEC Management Centre: Rue de la Science 23, B-1040 Brussels
© 2019 CEN All rights of exploitation in any form and by any means reserved Ref. No. EN ISO 10070:2019 E
worldwide for CEN national Members.
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SIST EN ISO 10070:2020
EN ISO 10070:2019 (E)
Contents Page
European foreword . 3
2
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SIST EN ISO 10070:2020
EN ISO 10070:2019 (E)
European foreword
This document (EN ISO 10070:2019) has been prepared by Technical Committee ISO/TC 119 "Powder
metallurgy" in collaboration with Technical Committee CEN/SS M11 “Powder metallurgy” the
secretariat of which is held by CCMC.
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 June 2020, and conflicting national standards shall be
withdrawn at the latest by June 2020.
Attention is drawn to the possibility that some of the elements of this document may be the subject of
patent rights. CEN shall not be held responsible for identifying any or all such patent rights.
According to the CEN-CENELEC Internal Regulations, the national standards organizations of the
following countries are bound to implement this European Standard: Austria, Belgium, Bulgaria,
Croatia, Cyprus, Czech Republic, Denmark, Estonia, Finland, France, Germany, Greece, Hungary, Iceland,
Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Republic of
North Macedonia, Romania, Serbia, Slovakia, Slovenia, Spain, Sweden, Switzerland, Turkey and the
United Kingdom.
Endorsement notice
The text of ISO 10070:2019 has been approved by CEN as EN ISO 10070:2019 without any modification.
3
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SIST EN ISO 10070:2020
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SIST EN ISO 10070:2020
INTERNATIONAL ISO
STANDARD 10070
Second edition
2019-12
Metallic powders — Determination of
envelope-specific surface area from
measurements of the permeability to
air of a powder bed under steady-state
flow conditions
Poudres métalliques — Détermination de la surface spécifique
d'enveloppe à partir de mesures de la perméabilité à l'air d'un lit de
poudre dans des conditions d'écoulement permanent
Reference number
ISO 10070:2019(E)
©
ISO 2019
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SIST EN ISO 10070:2020
ISO 10070:2019(E)
COPYRIGHT PROTECTED DOCUMENT
© 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
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Phone: +41 22 749 01 11
Fax: +41 22 749 09 47
Email: copyright@iso.org
Website: www.iso.org
Published in Switzerland
ii © ISO 2019 – All rights reserved
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SIST EN ISO 10070:2020
ISO 10070:2019(E)
Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Symbols . 3
5 General principles . 4
5.1 Permeability . 4
5.2 Carman-Arnell and Kozeny-Carman formulae . 4
5.3 General . 5
5.4 Envelope density . 5
6 Procedure. 6
6.1 Preparation of test portion . 6
6.2 Preparation of packed powder bed . 6
6.3 Determination . 6
7 Expression of results . 6
8 Test report . 7
Annex A (informative) Examples of methods of determining the permeability to air of a
powder bed . 8
Annex B (informative) Preliminary treatment of powder for de-agglomeration .17
Bibliography .18
© ISO 2019 – All rights reserved iii
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SIST EN ISO 10070:2020
ISO 10070:2019(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.
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 119, Powder metallurgy, Subcommittee
SC 2, Sampling and testing methods for powders (including powders for hardmetals).
This second edition cancels and replaces the first edition (ISO 10070:1991), which has been technically
revised.
The main changes compared to the previous edition are as follows:
— introduction of an automated test device based on the Gooden and Smith method, including
procedure and calibration.
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
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SIST EN ISO 10070:2020
ISO 10070:2019(E)
Introduction
The measurement of the permeability of a packed powder bed to a laminar gas flow is the basis of this
document. The determination can be made either at constant pressure drop (steady-state flow) or at
variable pressure drop (constant volume). This document deals only with determinations made under
steady-state flow conditions.
The permeability measured is influenced by the porosity of the powder bed. For a given particle shape,
the values of permeability and porosity can be used to calculate a specific surface area of the powder by
means of different formulae.
The surface area so calculated includes only those walls of the pores in the powder bed which are swept
by the gas flow. It does not take into account closed or blind pores. It is known as the envelope-specific
surface area. It can be very different from the total surface area of particles as measured, for instance,
by gas adsorption methods.
A single equation is used in the standard methods described in this document. It entails certain
limitations with respect to the type of powder (particle shape) and the porosity of the powder bed for
which the method is applicable. Consequently, this is not an absolute method, and the value obtained
depends upon the procedure used and the assumptions made.
The specific surface area determined can be converted into a mean equivalent spherical diameter (see
Clause 3).
© ISO 2019 – All rights reserved v
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SIST EN ISO 10070:2020
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SIST EN ISO 10070:2020
INTERNATIONAL STANDARD ISO 10070:2019(E)
Metallic powders — Determination of envelope-specific
surface area from measurements of the permeability to air
of a powder bed under steady-state flow conditions
1 Scope
This document specifies a method of measuring the air permeability and the porosity of a packed
bed of metal powder, and of deriving therefrom the value of the envelope-specific surface area. The
permeability is determined under steady-state flow conditions, using a laminar flow of air at a pressure
near atmospheric. This document does not include the measurement of permeability by a constant
volume method.
Several different methods have been proposed for this determination, and several test devices are
available commercially. They give similar, reproducible results, provided that the general instructions
given in this document are respected, and the test parameters are identical.
This document does not specify a particular commercial test device and corresponding test procedure.
However, for the convenience of the user, an informative annex has been included (see Annex A) which
is intended to give some practical information on three specific methods:
— the Lea and Nurse method, involving a test device which can be built in a laboratory (see A.1);
— the Zhang Ruifu method, using a similar test device (see A.2);
— the Gooden and Smith method, involving a test device which can be built in a laboratory but for
which a commercial test device also exists. (Two types of commercial test device exist; one of these
is no longer available for purchase, but is still being used, see A.3.)
These methods are given as examples only. Other test devices available in various countries are
acceptable within the scope of this document.
This testing method is applicable to all metallic powders, including powders for hardmetals, up to
1 000 µm in diameter, but it is generally used for particles having diameters between 0,2 µm and
75,0 µm. It is not intended to be used for powders composed of particles whose shape is far from
equiaxial, i.e. flakes or fibres, unless specifically agreed upon between the parties concerned.
This testing method is not applicable to mixtures of different metallic powders or powders containing
binders or lubricant.
If the powder contains agglomerates, the measured surface area can be affected by the degree of
agglomeration. If the powder is subjected to a de-agglomeration treatment (see Annex B), the method
used is to be agreed upon between the parties concerned.
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 3954, Powders for powder metallurgical purposes — Sampling
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
© ISO 2019 – All rights reserved 1
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SIST EN ISO 10070:2020
ISO 10070:2019(E)
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
envelope density
mass of a powder bed divided by its envelope volume (3.3)
Note 1 to entry: The envelope density may be less than the solid density when particles contain pores that do not
contribute to the gas flow through the powder bed.
3.2
envelope-specific surface area
specific surface area of a powder as determined by gas permeametry
3.3
envelope volume
volume occupied by the particles in a powder bed, excluding the volume of the interstices (3.5)
Note 1 to entry: In permeametry, the envelope volume comprises the volume of the solid matter plus the volume
of all the pores which do not contribute to gas flow (closed pores, blind pores, micropores, surface micropores,
surface roughness, etc.). Since this volume cannot be measured by any known method, it is taken, for the purposes
of this document, as being equal to the effective volume, as determined by pyknometry.
3.4
equivalent sphere diameter
diameter of theoretical non-porous spherical particles of identical size, with which the same method
of permeametry as that used for the powder under examination would give the same volume-specific
surface area (3.9)
3.5
interstices
spaces between particles in a powder bed, through which the air flows
3.6
mass-specific surface area
surface area of a powder divided by its mass
Note 1 to entry: This area depends on the type of method used for its determination.
3.7
permeability
ability of a porous material to allow a fluid to flow through it
Note 1 to entry: to entry In this document, the fluid used is dry air.
3.8
permeable porosity
volume of interstices (3.5) divided by the volume of the powder bed
3.9
volume-specific surface area
surface area of a powder divided by its effective volume (i.e. by its envelope volume)
2 © ISO 2019 – All rights reserved
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SIST EN ISO 10070:2020
ISO 10070:2019(E)
4 Symbols
Table 1 — Symbols used in the text
Symbol Meaning Unit Observations
Powder bed
2
A Cross-sectional area m Area of whole cross-section of
powder bed perpendicular to
flow direction:
2
πd
A=
4
d Diameter of measuring cell m
L Thickness (or height) m
m Mass of powder kg
3
ϱ Envelope density kg/m
e
3
ϱ Solid density kg/m
ɛ Permeable porosity
m
p
ε =−1
p
AL
e
ɛ Total porosity
m
ε= 1−
AL
Gas flow
3
q Volume flow rate m /s Converted to standard conditions
(STP - 0 °C, 1 atm)
2
p Mean gas pressure N/m
2
Δp Pressure drop N/m
2
η Viscosity of gas Ns/m
T Temperature of gas K
M Molar mass of gas kg/mol M = 0,029 kg/mol for air
R Molar gas constant
J J
R=83, 1
molK molK
Calculation
K Kozeny-Carman factor For the purposes of this document,
K = 5,0
δK Compound constant For the purposes of this document,
0
the generally accepted value of
2,25 is used
2
S Mass-specific surface area m /kg
w
−1
S Kozeny term m Formula (3)
K
−1
S Slip flow term m Formula (4)
m
−1
S Volume-specific surface area m
SS=
V
Ve w
2
Φ Permeability m
D Equivalent sphere diameter m
66
D==
SS
Vwe
© ISO 2019 – All rights reserved 3
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SIST EN ISO 10070:2020
ISO 10070:2019(E)
5 General principles
5.1 Permeability
Basically, permeametry is the experimental determination of the permeability, Φ, of a powder bed, the
porosity of which is known.
The permeability is determined by measuring the volume flow rate, q, and the drop-in pressure, Δp, of a
dry gas (generally air) continuously traversing the powder bed under laminar flow conditions.
The permeability is then calculated from Darcy's law, as shown in Formula (1):
qLη
Φ= (1)
ApΔ
5.2 Carman-Arnell and Kozeny-Carman formulae
The Carman-Arnell formula, as shown in Formula (2), relates specific surface area to the porosity and
permeability of a packed bed of powder and takes into account both the viscous flow and the slip flow.
This formula can be written as:
2
ε ε δηK ε
pp 8 2RT 0 p
Φ = +× (2)
2
Kη 3 πM
2 pS 1−ε
()
S 1−ε
Vp
()
Vp
The solution of Formula (2), which is quadratic in S , can be simplified by calculating the value of two
V
terms, the Kozeny term S and the slip flow term S , and then combining them to give S .
K m V
The Kozeny term S is given by Formula (3):
K
3
ApΔ ε
p
S = (3)
K
2
KL1−εηq
()
p
The Kozeny term is identical to the Kozeny-Carman formula for S and gives the contribution to the
V
surface area of the powder due to streamline flow.
The slip flow term S is given by Formula (4)
m
2
δεK
ApΔ 8 2RT
0 p
S =× × (4)
m
KLq 3 πM
p 1−ε
()
p
or, in the case of air, Formula (5):
1−εη
()
p
2
SS=×81 T (5)
mK
pε
p
S is then given by Formula (6):
v
2
SS
mm
2
S =+ +S (6)
V K
24
4 © ISO 2019 – All rights reserved
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SIST EN ISO 10070:2020
ISO 10070:2019(E)
and the mass-specific surface area S by Formula (7):
w
S
V
S = (7)
w
e
The equivalent sphere diameter D is given by Formula (8):
66
D== (8)
SS
Ve w
The Carman-Arnell formula, Formula (2), shall be used when the volume-specific surface area is greater
6 −1
than 10 m (mean particle size less than 6 µm), because the slip flow component of the permeability
becomes significant in addition to the viscous flow term.
For coarser powders, the Kozeny-Carman formula, Formula (3), may be used by agreement between the
parties concerned; the error introduced by neglecting slip flow is about 10 % at a mean particle size of
6 µm and increases as the powder becomes finer.
The mass-specific surface area, S is given by Formula (9):
w,
3
ε ApΔ
p
S = (9)
w
2
2
Kq1−εηL
()
pe
5.3 General
The methods and test devices used in practice differ depending on the way in which the volume flow
rate of the gas and the pressure drop are measured. Annex A describes three methods by way of
example. The Kozeny-Carman relation applies only over a limited range of powder bed porosities, the
range depending on the type of powder. It applies best to equiaxial powders. The Kozeny factor K varies
with the particle shape and particle size distribution. In this document, the value of K is taken to be 5,0
but other values may be used by agreement between the parties concerned.
Due to the limitations of the Kozeny-Carman relation, the variation of the specific surface area as a
function of porosity shall first be determined experimentally for any particular type of powder.
For example, make several successive determinations of the permeability, using test portions of the
same mass from the same laboratory sample, and packing the powder bed to give a decreasing series of
porosities. Over a certain range of porosities, the specific surface area will be practically constant. Only
determinations made within this range shall be taken as valid.
5.4 Envelope density
In Formulae (1) to (9), the permeable porosity ɛ of the powder bed and the envelope density ϱ of the
p e
particles are used. They are related by Formula (10):
m
ε =−1 (10)
p
AL
e
The envelope density ϱ is equal to the solid density only for smooth, non-porous particles. In such
e
cases, ε = ε.
p
In all other cases, the envelope density ϱ shall be measured by an appropriate pyknometric method.
e
The solid density value ϱ, or another density, may be adopted instead of the envelope density by
agreement between the parties concerned.
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SIST EN ISO 10070:2020
ISO 10070:2019(E)
6 Procedure
6.1 Preparation of test portion
Sampling shall be carried out in accordance with ISO 3954. The test portion shall be taken from the
test sample in the as-delivered state. Drying, in an appropriate atmosphere, or de-agglomeration (see
Annex B), is only permitted by agreement between the parties concerned.
Weigh the test portion to within 0,1 %.
6.2 Preparation of packed powder bed
The thickness, L, of the powder bed shall be not less than 50 times the mean particle diameter and the
powder bed diameter shall be not be less than 100 times the mean particle diameter.
NOTE At the surface of a test powder bed, discontinuities occur due to wall and end effects. These effects are
negligible (producing an error of less than 2 % in the permeability), provided that the diameter and thickness of
the test powder bed are as specified above.
The test portion is held in the cell by means of a porous paper disc at each end and supported by a rigid
perforated plate.
Introduce the test portion into the measuring cell in one pour, gently tapping the side of the cell to settle
the powder. Pack the test portion by covering it with a porous paper disc, using a piston with grooves
or holes to facilitate the expulsion of gas from the powder during the packing operation. Packing is
achieved by applying a force slowly on the piston, up to a value which will give a porosity in the desired
range and/or uniform packing of the powder bed.
If there is evidence that the porosity of the packed powder bed is not homogeneous, then incremental
pouring and packing is recommended.
Extract the piston using a rotary motion to minimize disturbance of the powder bed.
6.3 Determination
Measure the thickness of the powder bed to within 0,25 %. The temperature during the test shall not
vary by more than ± 3 °C from the temperature at which the test device was calibrated.
Pass a constant flow of gas through the powder bed. When the gas flow has stabilized, measure the
volume flow rate and pressure drop. The pressure drop shall be small compared with atmospheric
2
pressure (less than about 4 000 N/m ), so that the effect of the compressibility of the gas is negligible
(see A.2, for a case in which the compressibility effect is taken into account and corrected for).
If necessary, a blank test shall be carried out to correct for the effect of the paper disc.
7 Expression of results
The specific surface area of the powder is calculated either by using Formulae (3), (5) and (6), or from
Formula (9).
The result shall be expressed in terms of one or more of the following quantities, using the units
indicated:
— mass-specific surface area, S , in square metres per kilogram or square metres per gram;
w
— volume-specific surface area, S , in square metres per cubic metre or square centimetres per cubic
V
centimetre;
— equivalent sphere diameter D from Formula (8), in metres or micrometres.
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SIST EN ISO 10070:2020
ISO 10070:2019(E)
8 Test report
The test report shall include the following information:
a) a reference to this document, i.e. ISO 10070:2019;
b) all details necessary for complete identification of the sample;
c) the method and test device used;
d) any drying or de-agglomeration procedure used;
e) the density adopted (see 5.4);
f) the permeable porosity ɛ of the powder bed;
p
g) the formula used for the calculation of the specific surface area;
h) the value of the Kozeny-Carman factor if not taken as equal to 5,0 (see 5.3);
i) the result obtained;
j) details of any incident which may have affected the test result;
k) any operation not specified in this document is regarded as optional.
© ISO 2019 – All rights reserved 7
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...
SLOVENSKI STANDARD
oSIST prEN ISO 10070:2019
01-junij-2019
Kovinski prah - Ugotavljanje specifične ovojne površine z merjenjem zračne
prepustnosti nasute plasti prašnih delcev pri ustaljenem toku zraka skoznjo
(ISO/DIS 10070:2019)
Metallic powders - Determination of envelope-specific surface area from measurements
of the permeability to air of a powder bed under steady-state flow conditions (ISO/DIS
10070:2019)
Metallpulver - Ermittlung der spezifischen Außenoberfläche durch Messung der
Luftdurchlässigkeit einer Pulverprobe unter gleichförmigen Strömungsbedingungen
(ISO/DIS 10070:2019)
Poudres métalliques - Détermination de la surface spécifique d'enveloppe à partir de
mesures de la perméabilité à l'air d'un lit de poudre dans des conditions d'écoulement
permanent (ISO/DIS 10070:2019)
Ta slovenski standard je istoveten z: prEN ISO 10070
ICS:
77.160 Metalurgija prahov Powder metallurgy
oSIST prEN ISO 10070:2019 en,fr,de
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.
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oSIST prEN ISO 10070:2019
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oSIST prEN ISO 10070:2019
DRAFT INTERNATIONAL STANDARD
ISO/DIS 10070
ISO/TC 119/SC 2 Secretariat: SIS
Voting begins on: Voting terminates on:
2019-03-29 2019-06-21
Metallic powders — Determination of envelope-specific
surface area from measurements of the permeability to air
of a powder bed under steady-state flow conditions
Poudres métalliques — Détermination de la surface spécifique d'enveloppe à partir de mesures de la
perméabilité à l'air d'un lit de poudre dans des conditions d'écoulement permanent
ICS: 77.160
THIS DOCUMENT IS A DRAFT CIRCULATED
This document is circulated as received from the committee secretariat.
FOR COMMENT AND APPROVAL. IT IS
THEREFORE SUBJECT TO CHANGE AND MAY
NOT BE REFERRED TO AS AN INTERNATIONAL
STANDARD UNTIL PUBLISHED AS SUCH.
IN ADDITION TO THEIR EVALUATION AS
ISO/CEN PARALLEL PROCESSING
BEING ACCEPTABLE FOR INDUSTRIAL,
TECHNOLOGICAL, COMMERCIAL AND
USER PURPOSES, DRAFT INTERNATIONAL
STANDARDS MAY ON OCCASION HAVE TO
BE CONSIDERED IN THE LIGHT OF THEIR
POTENTIAL TO BECOME STANDARDS TO
WHICH REFERENCE MAY BE MADE IN
Reference number
NATIONAL REGULATIONS.
ISO/DIS 10070:2019(E)
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
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oSIST prEN ISO 10070:2019
ISO 10070:####(E)
ISO/DIS 10070:2019(E)
Contents
Foreword .iv
Introduction. v
1 Scope .1
2 Normative references .1
3 Terms and definitions.1
4 Symbols and their meaning .3
5 General principles .3
5.1 Permeability.3
5.2 Carman-Arnell and Kozeny-Carman equations .4
5.3 General .5
5.4 Envelope density.5
6 Procedure .6
6.1 Preparation of test portion .6
6.2 Preparation of packed powder bed .6
6.3 Determination.6
7 Expression of results .7
8 Test report .7
Annex A (informative) Annex title e.g. Example of a figure and a table.8
Annex B (informative) Preliminary treatment of powder for de-agglomeration. 18
Bibliography. 19
COPYRIGHT PROTECTED DOCUMENT
© 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
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Phone: +41 22 749 01 11
Fax: +41 22 749 09 47
Email: copyright@iso.org
Website: www.iso.org
Published in Switzerland
© ISO #### – All rights reserved iii
ii © ISO 2019 – All rights reserved
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oSIST prEN ISO 10070:2019
ISO/DIS 10070:2019(E)
Contents
Foreword . iv
Introduction. v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Symbols and their meaning . 3
5 General principles . 3
5.1 Permeability . 3
5.2 Carman-Arnell and Kozeny-Carman equations . 4
5.3 General . 5
5.4 Envelope density . 5
6 Procedure . 6
6.1 Preparation of test portion . 6
6.2 Preparation of packed powder bed . 6
6.3 Determination. 6
7 Expression of results . 7
8 Test report . 7
Annex A (informative) Annex title e.g. Example of a figure and a table . 8
Annex B (informative) Preliminary treatment of powder for de-agglomeration . 18
Bibliography . 19
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oSIST prEN ISO 10070:2019
ISO/DIS 10070:2019(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.
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 [or Project Committee] ISO/TC 119, Powder
metallurgy, Subcommittee SC 2, Sampling and testing methods for powders (including powders for
hardmetals).
This second edition cancels and replaces the first edition (ISO 10070:1991) which has been technically
revised.
The main changes compared to the previous edition are as follows:
— Introduction of an automated apparatus based on the Gooden and Smith method, including
procedure and calibration.
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.
© ISO 2019 – All rights reserved
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oSIST prEN ISO 10070:2019
ISO/DIS 10070:2019(E)
Introduction
The measurement of the permeability of a packed powder bed to a laminar gas flow is the basis of this
International Standard. The determination can be made either at constant pressure drop (steady-state
flow) or at variable pressure drop (constant volume). This International Standard deals only with
determinations made under steady-state flow conditions.
The permeability measured is influenced by the porosity of the bed. For a given particle shape, the values
of permeability and porosity can be used to calculate a specific surface area of the powder by means of
equations of different types.
The surface area so calculated includes only those walls of the pores in the bed which are swept by the
gas flow. It does not take into account closed or blind pores. It is defined as the envelope-specific surface
area. It may be very different from the total surface area of particles as measured, for instance, by gas
adsorption methods.
A single equation is used in the standard methods described and this entails certain limitations with
respect to the type of powder (particle shape) and the porosity of the powder bed for which the method
is applicable. Consequently this is not an absolute method, and the value obtained depends upon the
procedure used and the assumptions made.
The specific surface area determined can be converted into a mean equivalent spherical diameter (see
definitions, clause 3).
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ISO/DIS 10070:2019(E)
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oSIST prEN ISO 10070:2019
ISO/DIS 10070:2019(E)
Metallic powders — Determination of envelope-specific surface
area from measurements of the permeability to air of a powder
bed under steady-state flow conditions
1 Scope
This International Standard specifies a method of measuring the air permeability and the porosity of a
packed bed of metal powder, and of deriving therefrom the value of the envelope-specific surface area.
The permeability is determined under steady-state flow conditions, using a laminar flow of air at a
pressure near atmospheric. This International Standard does not include the measurement of
permeability by a constant volume method.
Several different methods have been proposed for this determination, and several instruments are
available commercially. They give similar, reproducible results, provided the general instructions given
in this International Standard are respected and the test parameters are identical.
This International Standard does not specify a particular commercial apparatus and corresponding test
procedure. However, for the convenience of the user, an informative annex has been included (annex A)
which is intended to give some practical information on three specific methods:
— the Lea and Nurse method, involving an apparatus which can be built in a laboratory (see A.1);
— the Zhang Ruifu method, using similar equipment (see A.2);
— the Gooden and Smith method, involving an apparatus which can be built in a laboratory but for
which a commercial apparatus also exists. (Two types of commercial apparatus exist; one of these is no
longer available for purchase, but is still being used - see A.3.).
These methods are given as examples only. Other equipment available in various countries is acceptable
within the scope of this International Standard.
This testing method is applicable to all metallic powders, including powders for hardmetals, up to 1 000
µm in diameter, but it is generally used for particles having diameters between 0,2 µm and 50 75 µm. It
should not be used for powders composed of particles whose shape is far from equiaxial, i.e. flakes or
fibres, unless specifically agreed upon between the parties concerned.
This testing method is not applicable to mixtures of different metallic powders or powders containing
binders or lubricant.
If the powder contains agglomerates, the measured surface area may be affected by the degree of ag-
glomeration. If the powder is subjected to a de-agglomeration treatment (see annex B), the method used
shall be agreed upon between the parties concerned.
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 3954:1977, Powders for powder metallurgical purposes — Sampling
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
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oSIST prEN ISO 10070:2019
ISO/DIS 10070:2019(E)
3.1
permeability
ability of a porous material to allow a fluid to flow through it.
NOTE 1 to entry In this standard, the fluid used is dry air.
3.2
interstices
spaces between particles in a powder bed, through which the air flows
3.3
permeable porosity
volume of interstices divided by the volume of the bed.
3.4
envelope volume
volume occupied by the particles in a powder bed, excluding the volume of the interstices. In
permeametry, the envelope volume comprises the volume of the solid matter plus the volume of all the
pores which do not contribute to gas flow (closed pores, blind pores, micropores, surface micropores,
surface roughness, etc.). Since this volume cannot be measured by any known method, it is taken, for the
purposes of this International Standard, as being equal to the effective volume, as determined by liquid
pyknometry.
3.5
envelope density
mass of a powder bed divided by its envelope volume. The envelope density may be less than the solid
density when particles contain pores that do not contribute to the gas flow through the bed.
3.6
mass-specific surface area
the surface area of a powder divided by its mass. This area depends on the type of method used for its
determination.
3.7
envelope-specific surface area
the specific surface area of a powder as determined by gas permeametry in accordance with this
International Standard
3.8
volume-specific surface area
the surface area of a powder divided by its effective volume (i.e. by its envelope volume)
3.9
equivalent sphere diameter
diameter of theoretical non-porous spherical particles of identical size, with which the same method of
permeametry as that used for the powder under examination would give the same volume-specific
surface area.
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
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oSIST prEN ISO 10070:2019
ISO/DIS 10070:2019(E)
— IEC Electropedia: available at http://www.electropedia.org/
4 Symbols and their meaning
Table 1 — Symbols used in text
Symbol Meaning Unit Observations
Powder bed
Area of whole cross-section of bed
2
A Cross-sectional area m
perpendicular to flow direction:
2
π𝑑
𝐴 =
4
d Diameter of measuring cell m
L Thickness (or height) m
m Mass of powder kg
3
ϱe Envelope density kg/m
3
ϱ Solid density kg/m
𝑚
ɛ Permeable porosity
p ɛ = 1 −
𝑝
𝐴𝐿ϱ
𝑒
𝑚
ɛ Total porosity ɛ = 1 −
𝐴𝐿ϱ
Gas flow
Converted to standard conditions (STP)
3
q Volume flow rate m /s
2
p Mean gas pressure N/m
2
Δp Pressure drop N/m
2
η Viscosity of gas Ns/m
T Temperature of gas K
M Molar mass of gas kg/mol M = 0,029 kg/mol for air
𝐽
𝐽
R Molar gas constant Calculation
R = 8,31
𝑚𝑜𝑙 𝐾
𝑚𝑜𝑙 𝐾
Calculation
For the purposes of this International
K Kozeny-Carman factor
Standard, K = 5,0
For the purposes of this International
δK Compound constant
0
Standard, the generally accepted value
of 2,25 is used
2
S Mass-specific surface area m /kg
w
-1
SV Volume-specific surface area m 𝑆 = ϱ 𝑆
𝑉 𝑒 𝑤
2
Φ Permeability m
6 6
D Equivalent sphere diameter m
𝐷 = =
𝑆 ϱ 𝑆
V 𝑒 w
5 General principles
5.1 Permeability
Basically, permeametry is the experimental determination of the permeability Φ of a powder bed, the
porosity of which is known.
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oSIST prEN ISO 10070:2019
ISO/DIS 10070:2019(E)
The permeability is determined by measuring the volume flow rate q and the drop in pressure Δp of a dry
gas (generally air) continuously traversing the bed under laminar flow conditions.
The permeability coefficient is then calculated from Darcy's law:
qηL
Φ = (1)
A Δp
5.2 Carman-Arnell and Kozeny-Carman equations
The Carman-Amell equation relates specific surface area to the porosity and permeability of a packed bed
of powder and takes into account both the viscous flow and the slip flow. This equation can be written:
2
𝜀 𝜀 𝛿𝐾 𝜂𝜀
8 2𝑅𝑇
𝑝 𝑝 0 𝑝
√
𝛷 = [ + × ] (2)
2 2
𝐾𝜂 3 𝜋𝑀 𝑝𝑆 (1 − 𝜀 )
𝑆 (1 − 𝜀 )
𝑉 𝑝
𝑉 𝑝
The solution of equation (2), which is quadratic in S , can be simplified by calculating the value of two
V
terms, the Kozeny term S and the slip flow term S , and then combining them to give S .
K m V
The Kozeny term S is given by the equation
K
3
𝐴 𝛥𝑝𝜀
𝑝
√ (3)
𝑆 =
𝐾
2
𝐾(1 − 𝜀 ) 𝐿𝜂𝑞
𝑝
This term is identical to the Kozeny-Carman equation for S and gives the contribution to the surface area
V
of the powder due to streamline flow.
The slip flow term S is given by the equation
m
2
𝐴 𝛥𝑝 8 2𝑅𝑇 𝛿𝐾 𝜀
0 𝑝
(4)
√
𝑆 = × ×
𝑚
𝐾𝐿𝑞 3 𝜋𝑀 𝑝(1 − 𝜀 )
𝑝
or, in the case of air,
(1 − 𝜀 )𝜂
𝑝
2
𝑆 = 81 × 𝑆 √𝑇
(5)
𝑚 𝐾
𝑝 𝜀
𝑝
S is then given by
v
2
𝑆 𝑆
𝑚 𝑚
2
√ (6)
𝑆 = + + 𝑆
𝑉 𝐾
2 4
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oSIST prEN ISO 10070:2019
ISO/DIS 10070:2019(E)
and the mass-specific surface area S by
w
𝑆
𝑉
𝑆 =
(7)
𝑤
𝜚
𝑒
The equivalent sphere diameter D is given by
6 6
𝐷 = =
(8)
𝑆 𝜚 𝑆
𝑉 𝑒 𝑤
The Carman-Arnell equation (2) shall be used when the volume-specific surface area is greater than
6 -1
10 m (mean particle size less than 6 µm), because the slip flow component of the permeability becomes
significant in addition to the viscous flow term.
For coarser powders, the Kozeny-Carman equation (3) may be used by agreement between the parties
concerned; the error introduced by neglecting slip flow is about 10 % at a mean particle size of 6 µm and
increases as the powder becomes finer.
The mass-specific surface area S is given by the equation
W
3
𝜀 𝐴 𝛥𝑝
𝑝
√ (9)
𝑆 =
𝑤
2 2
5,0(1 − 𝜀 ) 𝑞𝜂𝐿𝜚
𝑝 𝑒
5.3 General
The methods and instruments used in practice differ depending on the way in which the volume flow rate
of the gas and the pressure drop are measured. Annex A describes three methods by way of example: the
Lea and Nurse method, the Zhang Ruifu method and the Gooden and Smith method.
The Kozeny-Carman relation applies only over a limited range of bed porosities, the range depending on
the type of powder. It applies best to equiaxial powders. The Kozeny factor K varies with the particle
shape and particle size distribution. In this International Standard, the value of K is taken to be 5,0 but
other values may be used by agreement between the parties concerned.
Due to the limitations of the Kozeny-Carman relation, the variation of the specific surface area as a
function of porosity shall first be determined experimentally for any particular type of powder.
For example, make several successive determinations of the permeability, using test portions of the same
mass from the same laboratory sample, and packing the powder bed to give a decreasing series of
porosities. Over a certain range of porosities, the specific surface area will be practically constant. Only
determinations made within this range shall be taken as valid.
5.4 Envelope density
In the above equations, the permeable porosity ɛ of the powder bed and the envelope density 𝜚 of the
p
𝑒
particles are used. They are related by the equation
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𝑚
𝜀 = 1 −
𝑝 (10)
𝐴 𝐿 𝜚
𝑒
The envelope density 𝜚 is equal to the solid density only for smooth, non-porous particles. In such
𝑒
cases, 𝜀 = 𝜀 .
𝑝
In all other cases, the envelope density ϱ shall be measured by an appropriate pyknometric method. The
e
solid density value ϱ, or another density, may be adopted instead of the envelope density by agreement
between the parties concerned.
6 Procedure
6.1 Preparation of test portion
Sampling shall have been carried out in accordance with ISO 3954. The test portion shall be taken from
the test sample in the as-delivered state. Drying, in an appropriate atmosphere, or de-agglomeration (see
annex B), is only permitted by agreement between the parties concerned.
Weigh the test portion to within 0,1 %.
6.2 Preparation of packed powder bed
The thickness L of the bed shall be not less than 50 times the mean particle diameter and the bed diameter
shall be not be less than 100 times the mean particle diameter.
NOTE 2 At the surface of a test bed, discontinuities occur due to wall and end effects. These effects are negligible
(producing an error of less than 2 % in the permeability), provided that the diameter and thickness of the test bed are as
specified above.
The test portion is held in the cell by means of a porous paper disc at each end, and supported by a rigid
perforated plate.
Introduce the test portion into the measuring cell in one pour, gently tapping the side of the cell to settle
the powder. Pack the bed, covered with a porous paper disc, using a piston with grooves or holes to
facilitate the expulsion of gas from the powder during the packing operation. Packing is achieved by
applying a force slowly on the piston, up to a value which will give a porosity in the desired range and/or
uniform packing of the bed.
NOTE 3 If there is evidence that the porosity of the packed bed is not homogeneous, then incremental pouring and packing
is recommended.
Extract the piston using a rotary motion to minimize disturbance of the powder bed.
6.3 Determination
Measure the thickness of the bed to within 0,25 %. The temperature during the test shall not vary by
more than ± 3 °C from the temperature at which the apparatus was calibrated.
Pass a constant flow of gas through the powder bed. When the gas flow has stabilized, measure the flow
rate and pressure drop. The pressure drop shall be small compared with atmospheric pressure (less than
2
about 4 000 N/m ), so that the effect of the compressibility of the gas is negligible (see annex A, clause
A.2, for a case in which the compressibility effect is taken into account and corrected for).
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If necessary, a blank test shall be carried out to correct for the effect of the paper disc.
7 Expression of results
The specific surface area of the powder is calculated either by using equations (3), (5) and (6), or from
equation (9).
The result shall be expressed in terms of one or more of the following quantities, using the units indicated:
— mass-specific surface area S , in square metres per kilogram or square metres per gram;
w
— volume-specific surface area S , in square metres per cubic metre or square centimetres per cubic
V
centimetre;
— equivalent sphere diameter D from equation (8), in metres or micrometres.
8 Test report
The test report shall include the following information:
a) a reference to this International Standard;
b) all details necessary for complete identification of the sample;
c) the method and apparatus used;
d) any drying or de-agglomeration procedure used;
e) the density adopted (see 5.6);
f) the permeable porosity ɛ of the bed;
p
g) the equation used for the calculation of the specific surface area;
h) the value of the Kozeny-Carman factor if not taken as equal to 5,0 (see 5.4);
i) the result obtained;
j) details of any incident which may have affected the test result;
k) any operation not specified in this international standard is regarded as optional
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Annex A
(informative)
Annex title e.g. Example of a figure and a table
A.1 Lea and Nurse method
(see figure A.1)
In this method, a steady-state flow of dry air is fed first through the powder bed and then through the
fixed capillary resistance of a flowmeter open to the atmosphere. The pressure drop Δp across the bed is
measured by means of a manometer (reading h ) and the flow rate q by means of the capillary flowmeter
1
(reading h ). The relationship between the flow rate q and the flowmeter reading h can be established
2 2
by a suitable calibration method.
...
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