1、BRITISH STANDARDBS EN ISO 18757:2005Fine ceramics (advanced ceramics, advanced technical ceramics) Determination of specific surface area of ceramic powders by gas adsorption using the BET methodThe European Standard EN ISO 18757:2005 has the status of a British StandardICS 81.060.30g49g50g3g38g50g5
2、1g60g44g49g42g3g58g44g55g43g50g56g55g3g37g54g44g3g51g40g53g48g44g54g54g44g50g49g3g40g59g38g40g51g55g3g36g54g3g51g40g53g48g44g55g55g40g39g3g37g60g3g38g50g51g60g53g44g42g43g55g3g47g36g58BS EN ISO 18757:2005This British Standard was published under the authority of the Standards Policy and Strategy Com
3、mittee on 29 December 2006 BSI 2006ISBN 0 580 49891 3National forewordThis British Standard was published by BSI. It is the UK implementation of EN ISO 18757:2005. It is identical with ISO 18757:2003. It supersedes BS EN 725-6:1996 which is withdrawn.The UK participation in its preparation was entru
4、sted to Technical Committee RPI/13, Advanced technical ceramics.A list of organizations represented on RPI/13 can be obtained on request to its secretary.This publication does not purport to include all the necessary provisions of a contract. Users are responsible for its correct application.Complia
5、nce with a British Standard cannot confer immunity from legal obligations. Amendments issued since publicationAmd. No. Date CommentsEUROPEAN STANDARDNORME EUROPENNEEUROPISCHE NORMEN ISO 18757October 2005ICS 81.060.30 Supersedes EN 725-6:1996 English VersionFine ceramics (advanced ceramics, advanced
6、technicalceramics) - Determination of specific surface area of ceramicpowders by gas adsorption using the BET method (ISO18757:2003)Poudres cramiques - Dtermination de laire massique(surface spcifique) par adsorption de gaz laide de lamthode BET (ISO 18757:2003)Hochleistungskeramik - Bestimmung der
7、spezifischenOberflche keramischer Pulver durch Gasadsorption nachdem 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 EuropeanStandard
8、 the status of a national standard without any alteration. Up-to-date lists and bibliographical references concerning such nationalstandards may be obtained on application to the Central Secretariat or to any CEN member.This European Standard exists in three official versions (English, French, Germa
9、n). A version in any other language made by translationunder the responsibility of a CEN member into its own language and notified to the Central Secretariat has the same status as the officialversions.CEN members are the national standards bodies of Austria, Belgium, Cyprus, Czech Republic, Denmark
10、, 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 STANDARDIZATIONCOMIT EUROPEN DE NORMALISATIONEUROPISCHES
11、KOMITEE FR NORMUNGManagement Centre: rue de Stassart, 36 B-1050 Brussels 2005 CEN All rights of exploitation in any form and by any means reservedworldwide for CEN national Members.Ref. No. EN ISO 18757:2005: EForeword The text of ISO 18757:2003 has been prepared by Technical Committee ISO/TC 206 “F
12、ine 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, eit
13、her 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 po
14、wders 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: Determinat
15、ion 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 densificatio
16、n 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,
17、 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
18、modifications. EN ISO 18757:2005INTERNATIONALSTANDARDISO18757First edition2003-12-01Reference numberISO 18757:2003(E)Fine ceramics (advanced ceramics, advanced technical ceramics) Determination of specific surface area of ceramic powders by gas adsorption using the BET methodPoudres cramiques Dtermi
19、nation de laire massique (surface spcifique) par adsorption de gaz laide de la mthode BETEN ISO 18757:2005iiContents Page1 Scope 12 Normative references 13 Terms and definitions 14 Symbols and abbreviated terms . 25 Principle 26 Procedure . 36.1 General procedure 36.2 Sample preparation . 36.3 Exper
20、imental conditions . 56.4 Evaluation of data . 67 Test report 7Annex A (informative) Sample preparation Outgassing . 8Annex B (informative) Reference materials . 9Bibliography . 10EN ISO 18757:2005iiiForewordISO (the International Organization for Standardization) is a worldwide federation of nation
21、al standards bodies(ISO member bodies). The work of preparing International Standards is normally carried out through ISOtechnical committees. Each member body interested in a subject for which a technical committee has beenestablished has the right to be represented on that committee. International
22、 organizations, governmental andnon-governmental, in liaison with ISO, also take part in the work. ISO collaborates closely with the InternationalElectrotechnical Commission (IEC) on all matters of electrotechnical standardization.International Standards are drafted in accordance with the rules give
23、n in the ISO/IEC Directives, Part 2.The main task of technical committees is to prepare International Standards. Draft International Standardsadopted by the technical committees are circulated to the member bodies for voting. Publication as anInternational Standard requires approval by at least 75 %
24、 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 patentrights. 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 cer
25、amics.EN ISO 18757:2005iv1Fine ceramics (advanced ceramics, advanced technical ceramics) Determination of specific surface area of ceramic powders by gas adsorption using the BET method1ScopeThis International Standard provides guidelines for the determination of the total specific external and inte
26、rnalsurface area of disperse or porous (pore diameter ) fine ceramic materials by measuring the amount ofphysically adsorbed gas according to the method of Brunauer, Emmet and Teller (BET method) 1. Generalguidelines of the method are described in ISO 9277. This International Standard only focuses o
27、n specific detailsrelevant to fine ceramic materials. It should further be noted that the BET method cannot be applied to type Iisotherms (microporous materials or chemisorption behaviour) or when the solid absorbs the measuring gas.NOTE For further details on those subjects please see IUPAC referen
28、ces 2, 3 or the textbook by Gregg and Sing 4.2 Normative referencesThe following referenced documents are indispensable for the application of this document. For datedreferences, only the edition cited applies. For undated references, the latest edition of the referenced document(including any amend
29、ments) applies.ISO 9277:1995, Determination of the specific surface area of solids by gas adsorption using the BET method3 Terms and definitionsFor the purposes of this document, the following terms and definitions apply.3.1 adsorptionenrichment of the adsorbate at the external and accessible intern
30、al surfaces of a solid3.2 physisorptionweak bonding of the adsorbate, reversible by small changes in pressure or temperature3.3 adsorbatemeasuring gas to be adsorbed3.4 adsorbentsolid, which adsorbs the measuring gas3.5 surface areaarea of external surface of a fine ceramic powder plus the internal
31、surface of its accessible macro- andmesopores 2nmEN ISO 18757:200523.6 adsorption isothermrelation between the quantity of adsorbate and the equilibrium pressure of the adsorbate at constanttemperature4 Symbols and abbreviated termsTable 1 presents the symbols used in this International Standard, to
32、gether with their SI units. For comparisonpurposes, the IUPAC 3 symbols are also given. All specific dimensions are related to sample mass, in grams.5PrincipleThe method specified involves the determination of the amount of adsorbate required to cover the external andaccessible internal pore surface
33、 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:(1)Any gas may be used provided it is physically adsorbed by weak bonds at the surface of the solid (van derWaals forces), and can be desorb
34、ed by a decrease in pressure at the same temperature. Nitrogen at its boilingpoint (about ) is the most frequently used adsorbate. Krypton or argon at liquid nitrogen temperature aretwo other gases that are frequently used. The latter two gases offer an improved sensitivity for the analysis oflow su
35、rface-area samples (less than about to total surface area of the sample). Results ofmeasurements with different adsorbates may deviate from each other because of different molecular crosssectional areas, different accessibility to pores and different measuring temperatures.Table 1 SymbolsISO symbol
36、Parameter SI unitIUPAC symbolmolecular cross-sectional area occupied by an adsorbed molecule in a complete monolayerspecific surface areaBET parameter 1aAvogadro constant ( )mass of the solid samplespecific mass of gas adsorbed 1a aspecific amount of gas adsorbedaspecific monolayer capacity of adsor
37、bate; amount of adsorbate needed to cover the surface with a complete monolayer of molecules, aspecific monolayer capacity derived from multi-point measurement specific monolayer capacity derived from single-point measurement pressure of the adsorbate in equilibrium with the adsorbatesaturation vapo
38、ur pressure of the adsorbatetimetemperaturespecific volume adsorbedaaAccording to ISO 31-0, the coherent SI unit for any quantity of dimension one (at present commonly termed “dimensionless”) is the unitone, symbol 1.amnm2amasm2g1asC CL = 6,022 1023mol1Lm g mmamnamol g1nnmmol g1nmnmnm, mpmol g1nm, s
39、pmol g1p Pa pp0Pap0t s tT K TVam3g1Vp/p0na1 (p/p0)=1nm,mpC+C 1nm,mpC (p/p0)77 K1m25m2EN ISO 18757:20053The adsorbate gas is admitted to the sample container, which is held at a constant temperature. The amountsadsorbed are measured in equilibrium with the adsorbate gas pressure, , and plotted agains
40、t the relativepressure, , to give an adsorption isotherm. Adsorption isotherms may be obtained by volumetric orgravimetric measurement or by the carrier gas method using a continuous or discontinuous operational mode.Further details are described in corresponding references 2, 3.6 Procedure6.1 Gener
41、al procedureGeneral sample preparation procedures and a description of the different measurement techniques areprovided in 6.2 and 6.3 of ISO 9277:1995. Specific conditions and examples for fine ceramic materials aredescribed in 6.2 to 6.4 below.6.2 Sample preparationThe sample preparation method is
42、 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 thesolid sample, but which provide a “clean” sample surface at the beginning of the analysis. Moisture might beadsorbed in
43、 pores or the surface might be contaminated with other residues from the previoustreatment/preparation of the sample. Most ceramic materials can be outgassed at higher temperatures (to ) without irreversible changes of the surface. It is strongly recommended to evacuate the sample to apressure of (p
44、referably ) prior to and during the entire heat treatment. Outgassing for isusually sufficient to achieve a clean sample surface and to is commonly practical. However, thefollowing examples and conditions should be carefully considered for any unknown material.a) If the sample contains a large amoun
45、t of water, either physisorbed on the surface, condensed in pores orwithin its crystal structure, and if the temperature is raised too quickly and without keeping a sufficientvacuum ( to ) near the sample, hydrothermal conditions occur. These frequently result inphysical changes of the solid structu
46、re, e.g. small cracks or pores are closed whereas small particles orbumps of the surface disappear, resulting in a lower value of the measured surface area of the sample.NOTE The dotted line shows the first adsorbate layer on the surface (See ISO 9277).Figure 1 Particle with surface (solid line) det
47、ected by the adsorption methodpp/p0150C300C99,999 %1 % 0,1 %10 mm10577 K10 torr 1 333 Pa 1045m2100 m21m2100 m21m230 m20,2 m25m20,2 m25m20,02 m20,5 m277 K1mmHg= 133,32 Palog p0= A+BT+ClogT +DT +ET2p/p0= 0,3ABCD 103E 106455,57 7,510 72,832 370,075 14,362542,78 8,443EN ISO 18757:200566.4 Evaluation of
48、dataThe general procedure of the data analysis is described in Clause 7 of ISO 9277:1995.In addition, the following are special recommendations for the multi-point BET analysis of advanced ceramicmaterials:a) A minimum of 4 valid data points shall fall within the relative pressure range between 0,05
49、 and 0,30.Preferably the relative pressure of those data points shall be equally spaced within that range.b) A minimum correlation coefficient of 0,999 is required for the BET analysis over that range. The exclusion ofcertain data points is possible according to the following principles.1) If a clear deviation from the linear relationship is observed below or above a certain relative pressure thecorresponding data points can be omitted. A standard test for outliers may not be sufficient for thispro
