www bzfxw com BRITISH STANDARD BS EN 725 6 1996 Advanced technical ceramics — Methods of test for ceramic powders — Part 6 Determination of the specific surface area The European Standard EN 725 6 199[.]
BRITISH STANDARD Advanced technical ceramics — Methods of test for ceramic powders — Part 6: Determination of the specific surface area The European Standard EN 725-6:1996 has the status of a British Standard ICS 81.060.10 BS EN 725-6:1996 BS EN 725-6:1996 Committees responsible for this British Standard The preparation of this British Standard was entrusted to Technical Committee RPI/13, Advanced technical ceramics, upon which the following bodies were represented: AEA Technology Aluminium Federation British Ceramic Research Ltd British Industrial Ceramic Manufacturers’ Association Department of Trade and Industry (National Physical Laboratory) Flat Glass Manufacturers’ Association GAMBICA (BEAMA Ltd.) Institute of Refractories Engineers Ministry of Defence Refractories Association of Great Britain Society of British Aerospace Companies Ltd University of Manchester This British Standard, having been prepared under the direction of the Sector Board for Materials and Chemicals, was published under the authority of the Standards Board and comes into effect on 15 September 1996 © BSI 07-1999 The following BSI references relate to the work on this standard: Committee reference RPI/13 Draft for comment 92/49116 DC ISBN 580 25842 Amendments issued since publication Amd No Date Comments BS EN 725-6:1996 Contents Committees responsible National foreword Foreword Text of EN 725-6 © BSI 07-1999 Page Inside front cover ii i BS EN 725-6:1996 National foreword This British Standard has been prepared by Technical Committee RPI/13 and is the English language version of EN 725-6:1996 Advanced technical ceramics — Methods of test for ceramic powders — Part 6: Determination of the specific surface area published by the European Committee for Standardization (CEN) EN 725-6:1996 was produced as a result of international discussions in which the UK took an active part NOTE International and European Standards as well as overseas standards, are available from Customer Services, BSI, 389 Chiswick High Road, London, W4 4AL A British Standard does not purport to include all the necessary provisions of a contract Users of British Standards are responsible for their correct application Compliance with a British Standard does not of itself confer immunity from legal obligations Summary of pages This document comprises a front cover, an inside front cover, pages i and ii, the EN title page, pages to 13 and a back cover This standard has been updated (see copyright date) and may have had amendments incorporated This will be indicated in the amendment table on the inside front cover ii © BSI 07-1999 EUROPEAN STANDARD EN 725-6 NORME EUROPÉENNE January 1996 EUROPÄISCHE NORM ICS 81.060.10 Descriptors: Ceramics, powdery materials, tests, determination, specific area, absorption, nitrogen English version Advanced technical ceramics — Methods of test for ceramic powders — Part 6: Determination of the specific surface area Céramiques techniques avancées — Méthodes d’essai pour les poudres céramiques — Partie 6: Détermination de la surface spécifique Hochleistungskeramik — Prüfverfahren für keramische Pulver — Teil 6: Bestimmung der spezifischen Oberfläche ｗｗｗ．ｂｚｆｘｗ．ｃｏｍ This European Standard was approved by CEN on 1995-11-02 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, Denmark, Finland, France, Germany, Greece, Iceland, Ireland, Italy, Luxembourg, Netherlands, Norway, Portugal, Spain, Sweden, Switzerland and United Kingdom CEN European Committee for Standardization Comité Européen de Normalisation Europäisches Komitee für Normung Central Secretariat: rue de Stassart 36, B-1050 Brussels © 1996 All rights of reproduction and communication in any form and by any means reserved in all countries to CEN and its members Ref No EN 725-6:1996 E EN 725-6:1996 Foreword This European Standard was prepared by CEN/TC184, Advanced technical ceramics, the Secretariat of which is held by BSI This European Standard shall be given the status of a national standard or by endorsement, at the latest by July 1996, and conflicting national standards shall be withdrawn at the latest by July 1996 The method given is closely based on ISO 8008:1987 Aluminium oxide primarily used for the production of aluminium — Determination of specific surface area by nitrogen absorption (single point method), published by the International Organization for Standardization (ISO) EN 725 Advanced technical ceramics — Methods of test for ceramic powders, consists of eleven Parts: — Part 1: Determination of impurities in alumina; — Part 2: Determination of impurities in barium titanate (ENV); — Part 3: Determination of oxygen content of non-oxides by thermal extraction; — Part 4: Determination of oxygen content of non-oxides by XRF analysis (ENV); — 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 (ENV) In accordance with the Common CEN/CENELEC Rules, the following countries are bound to implement this European Standard: Austria, Belgium, Denmark, Finland, France, Germany, Greece, Iceland, Ireland, Italy, Luxembourg, Netherlands, Norway, Portugal, Spain, Sweden, Switzerland, United Kingdom Contents Foreword Scope Principle Apparatus Procedure Expression of results Test report Figure — Adsorption apparatus Figure — Thermostat for the heating of the adsorption bottles in the desorption procedure Figure — Additional device for degassing under vacuum Figure — Nomogram Table — Recommended masses of sample Table — B1, B2 = f(Tz) Table — Quantities and symbols Page 3 13 4 12 10 11 ｗｗｗ．ｂｚｆｘｗ．ｃｏｍ © BSI 07-1999 EN 725-6:1996 Scope This Part of EN 725 specifies a method for the determination of the specific surface area of powders used for technical ceramics, by a nitrogen adsorption, single-point method The method is limited to the measurement of surface areas of over m2/g Principle The method is based on the property of the solids to adsorb gas molecules at their surface In the range between 0,05 to 0,3 times the saturation vapour pressure of the measuring gas, the multilayer adsorption begins The formation of the first monolayer of adsorbed molecules can be detected from the behaviour of the adsorption isotherm in this range; this is the only process relevant to the present method Nitrogen is introduced at ambient temperature and at atmospheric pressure into two bottles of equal volume, one of which contains the test portion while the other is empty The connected bottles are immersed in a refrigerant bath of liquid nitrogen Since some nitrogen is adsorbed by the sample, a differential pressure occurs between the two bottles and is measured by means of a differential manometer From this difference, the number of molecules adsorbed on the surface is calculated This number is multiplied by the known area occupied by a single adsorbed molecule so that the total surface area is obtained The area occupied by an adsorbed nitrogen molecule is taken as 16,2 × 10–20 m2 Apparatus 3.1 Adsorption apparatus (see Figure 1) The apparatus consists of a reference bottle (7) and a sample adsorption bottle (8) which are moved on to the two connecting pieces, with sealing rings in between to make the joint gas-tight At each connecting piece, there is a valve (1 and 2), by which the bottles can be connected to the atmosphere The measuring gas is admitted to the bottle through the capillaries inside the connecting pieces The bottles, made of shock-resisting glass, have a volume of about 100 cm3 The difference between the volume of the two bottles shall not exceed 0,1 % The necks of the bottles consist of calibrated glass tubes with an internal diameter of mm ± 0,02 mm Each tube has an upper and lower mark In this way, several bottles can be used as either sample or reference bottles without compensating the volumes for each combination of bottles A differential manometer containing dibutyl phthalate is arranged between the two bottles The legs of the differential manometer are connected to the two inlet capillaries of the adsorption bottles By means of the valve 4, the two bottles, i.e the two inlet capillaries, can be separated from or connected to each other By means of the valve 5, the liquid in the two legs of the differential manometer can be separated or connected The legs of the differential manometer consist of calibrated glass tubes with an internal diameter of mm ± 0,02 This ensures that the change in volume during the adsorption measurement can be calculated with sufficient accuracy The inlet capillary of the sample bottle, being the shorter of the two, is connected to a compensating volume (10), which is adjusted during preparation of the apparatus The measuring gas is admitted to the apparatus via the valve If the valves 1, and are open, the measuring gas is passed through both bottles If the valves and are closed, the reference bottle is shut off and only the sample bottle is purged with the measuring gas During measurement, only a part of the gas volume, which is downstream of the valve and upstream of the valves and 2, is cooled by liquid nitrogen to the measuring temperature The gas volume remaining at room temperature shall be limited to 10 % of the total volume at maximum For this reason, the connections to the adsorption bottles are capillaries, which occupy most of the necks of the bottles in order to keep the portion remaining at room temperature as small as possible The adsorption bottle has calibrated volume of 100 cm3 To facilitate weighing of the sample as well as the cleaning of the adsorption bottle, two-piece bottles are applied The two pieces are connected by ground joints and fixed by hooks and springs 3.2 Thermostat, for heating the adsorption bottles in the desorption procedure (see 4.3 and Figure 2) 3.3 Device, for degassing under vacuum (see Figure 3) 3.4 Cooling bath, containing boiling nitrogen 3.5 Water bath, capable of being controlled at 22 °C ± °C or at approximately 40 °C, as required ｗｗｗ．ｂｚｆｘｗ．ｃｏｍ © BSI 07-1999 EN 725-6:1996 ｗｗｗ．ｂｚｆｘｗ．ｃｏｍ Figure — Adsorption apparatus © BSI 07-1999 EN 725-6:1996 ｗｗｗ．ｂｚｆｘｗ．ｃｏｍ Figure — Thermostat for the heating of the adsorption bottles in the desorption procedure © BSI 07-1999 EN 725-6:1996 ｗｗｗ．ｂｚｆｘｗ．ｃｏｍ Figure — Additional device for degassing under vacuum Procedure 4.1 Test portion Choose the mass of sample to be used depending on the supposed specific surface area Recommended values are given in Table © BSI 07-1999 EN 725-6:1996 Table — Recommended masses of sample Supposed specific surface area Mass of sample –1 g m g 5 10 50 from 0,7 to 1,0 100 from 0,2 to 0,3 NOTE If the surface area is completely unknown, preliminary tests are necessary to find the best test portion 4.2 Preparation of apparatus 4.2.1 Checking of new apparatus 4.2.1.1 General New apparatus shall be checked to ensure that the compensating volume (10) is adjusted correctly and that the apparatus is gas-tight 4.2.1.2 Checking the equalization of volumes The valve shall be gas-tight when the equalization of the volumes is checked Fit the empty adsorption bottles to the connecting pieces; the upper mark of the bottle neck shall coincide with the lower sealing ring Purge the apparatus with nitrogen by opening all the valves and allowing the gas to flow at approximately 10 1/h During purging, the bottles are immersed in the water bath (see 3.5), up to the lower mark on the neck, in order to bring them to the set temperature of 22 °C ± °C When the equalization of the temperature can be assumed (after at least min), shut off the apparatus from the atmosphere and shut off the two bottles from each other, by closing the valves in the sequence 1, 2, and On shutting the valve 4, a small pressure difference can appear If this pressure difference changes within the next min, a complete temperature equalization has not been reached in the adsorption bottles In this case, open the valves again in the sequence 4, 3, and 1, and purge the apparatus further with nitrogen After a few minutes, repeat this check If temperature equalization is achieved, close valve Remove the bottles from the water bath, dry any drops of water adhering to them, and immerse the bottles up to the lower mark in the cooling bath (see 3.4) When the bottles have attained the temperature of the boiling nitrogen (with empty bottles after about min), open the valve slowly If the volumes of the sample and reference sides have been fully equalized, no pressure difference occurs In this case, close the valve again and open the valve Then remove the cooling bath and replace it by the water bath (see 3.5), maintained at approximately 40 °C, to thaw out the bottles Remove the warm water bath as soon as the bottles have reached ambient temperature again After min, reopen the valves 3, and in that sequence, and purge the apparatus with nitrogen During the cooling and heating of the bottles, great pressure differences may occur momentarily so that the measuring liquid in the manometer may be transferred into other parts of the apparatus For this reason, not open the valve before temperature equalization If the pressure difference should occur during the preparation of the apparatus, change the compensating volume (10) in such a way that the volumes on both sides of the differential manometer are equal To check the equalization of the volumes, repeat the test described above 4.2.1.3 Checking of tightness If, after the slow opening of valve 5, steadily increasing or very great pressure differences occur (more than 400 mm of liquid column), during the equalization of volume at the temperature of boiling nitrogen, then the apparatus will have a leakage to the atmosphere (for instance, caused by the valves 1, 2, 3) Leakage of valve cannot be recognized by a pressure difference and the following special check shall be carried out Immerse the bottles in the cooling bath (see 3.4), close the valves 2, and 4, and open the valves and By means of valve 1, create a pressure difference of approximately 300 mm of liquid column Close the valve Within the next 10 min, the liquid column of the differential manometer shall not sink more than mm © BSI 07-1999 EN 725-6:1996 4.2.2 Checking of functioning When the apparatus is put into operation, and later from time to time, check its functioning by measuring a solid with a known specific surface area Measure the specific surface area of the test substance by the same method 4.2.3 Maintenance Replace the measuring liquid of the differential manometer when it is dirty or at least every year Change the used drying agent in the drying tower 4.3 Degassing of samples Weigh the adsorption bottle and record its mass Dry the test sample and place it in the adsorption bottle in such a way that no powder adheres to the neck of the bottle Weigh the bottle again Evacuate the bottle and sample using a pressure of about 0,01 bar Purge intermittently with pure nitrogen The time necessary will vary for each type of powder and is reported (see clause 6) It is essential that the sample is completely degassed before the adsorption measurement Weigh the bottle again after degassing Then heat the bottle in the thermostat (see 3.2) The temperature used will also vary for each type of powder and shall be reported (see clause 6) NOTE For example, alumina powders require approximately 30 at 200 °C 4.4 Adsorption measurement Open the valves and 3, pass nitrogen through the apparatus and connect the adsorption bottle filled with the pretreated sample and nitrogen to the connecting piece Then open the valves 1, and 5, and warm the bottles in the water bath (3.5), maintained at approximately 22 °C When the equilibrium pressure is attained, close the valves 1, 2, and and check the sample bottle and the reference bottle for temperature equalization If a pressure difference appears, reopen the valves in the sequence 4, 3, and and continue purging with nitrogen When temperature equalization is achieved, close the valve and shut off the nitrogen flow Immerse the bottles in the cooling bath (see 3.4) down to the lower mark, and open the valve very slowly If the existing pressure difference has become constant, read off this difference to an accuracy of 0,5 mm NOTE The time to reach a constant pressure difference can be quite long for some materials, for example those having micropores or a low thermal conductivity Report the time interval from immersion of the bottles until reading of the pressure difference After having finished the measurement, close the valve and open the valve Replace the cooling bath (see 3.4) by the water bath (see 3.5), maintained at approximately 40 °C After a few minutes, start the nitrogen flow and open the valves 3, 2, and in that sequence When the connecting pieces are at ambient temperature, close the valves 1, and and change the sample bottle to carry out a new measurement Expression of results 5.1 Equations The specific surface area Sm is given by the following equation: (1) where the symbols are as defined in Table In this equation, the single-point calculation of the BET equation has been assumed and the correcting factor of 1,05 which represents the density of the liquid in the differential manometer introduced For practical purposes, (BN2, V, Vz, Tk, po have been taken as constants In addition, the expression Vz¹p/Tz is small compared with the other terms of the sum in the first square brackets and has been neglected Incorporating the numerical values and the units given in Table 3, the following numerical equation is obtained with Tz = 295 K for calculating the mass-related surface area: (2) © BSI 07-1999 EN 725-6:1996 The second, Vp containing term of the sum of this equation can be neglected, if the specific surface areas Sm are $ 10 m2g–1 The equilibrium pressure p in equation (2) is calculated according to the following unit equation: (3) where %p = Ôg%h (4) For practical purposes, are taken as constants Incorporating the numerical values and units given in Table 3, the following numerical equation is obtained at Tz = 295 K: p = 0,278pB – 1,025 × 10–4%h (5) If Tz deviates from Tz = 295 K by more than ± K, the two constants in equations (2) and (5) have to be corrected and the actual room temperature Tz shall be taken into account: (6) p = B2pB – 1,025 × 10–4 %h (7) Incorporating the numerical values and the units given in Table 3, one obtains for B1 and B2: (8) (9) where the symbols and constants used have the meanings shown in Table © BSI 07-1999 EN 725-6:1996 Table — B1, B2 = f(Tz) B1 × 105 Tz in K B2 × 10 291 6,747 2,817 292 6,724 2,807 293 6,701 2,798 294 6,678 2,789 295 6,656 2,780 296 6,633 2,770 297 6,611 2,761 298 6,588 2,752 299 6,566 2,743 300 6,544 2,734 301 6,523 2,725 302 6,501 2,717 303 6,480 2,708 304 6,458 2,699 305 6,437 2,691 306 6,416 2,682 307 6,395 2,673 308 6,374 2,666 5.2 Calculation by means of a nomogram The calculation may be simplified using the nomogram indicated in Figure Knowing the atmospheric pressure and the pressure difference read off on the differential manometer, the factor A is taken from the nomogram (see Figure 4) The specific surface area of the sample, expressed in square metres per gram, is given by the formula: S m = A¹h -m (10) where: ¹h is the pressure difference, in millimetres; m is the mass, in grams, of the test portion The nomogram allows the calculation of specific surface area in the range from 10 m2·g–1 to 300 m2·g–1 approximately For values less than 10 m2·g–1 or greater than 300 m2·g–1, which are generally not of interest in the ceramics industry, use equations (6) and (7) for the calculation 5.3 Precision Repeatability: ± 0,5 % Reproducibility: ±1% NOTE 10 These figures are repeated from the International standard mentioned in the foreword © BSI 07-1999 EN 725-6:1996 Table — Quantities and symbols Symbol Quantity Unit Sm Mass-related surface area m2·g–1 p Equilibrium pressure bar %h Difference in height on the differential manometer mm Vp Volume of the solid sample cm3 m Mass of the test portion g pB Filling pressure (atmospheric pressure) bar po Saturation pressure of boiling nitrogen (po = 1,05 bar) bar NL Loschmidt number Avogadro constant (NL = 6,023 × 1023 mol–1) mol–1 R Molar gas constant (R = 8,314 j·mol–1·K–1) j·mol ·K–1 Ô Density of dibutyl phthalate (Ô = 1,05 g·cm–3) g·cm g Acceleration of free fall (g = 981 cm·s–2) cm·s–2 BN Area occupied by a nitrogen molecule ( B N2 = 16,2 × 1020 m2) m2 V Volume of the adsorption bottle, into which the capillary is introduced, up to cm3 the level of the cooling bath (V = 101,2 cm3) Vz Volumes of the sample part and the reference part from the level of the cooling bath to the zero level of the differential manometer (These volumes remain at room temperature during measurement.) (Vz = 8,35 cm3) cm3 Vx Change of volume in one leg of the differential manometer during measurement cm3 r Internal radius of the tube of the differential manometer (r = 0,25 cm) cm TK Temperature of the cooling bath (4.4) (TK = 77,6 K) K Tz Ambient temperature and temperature of the water bath (4.5) K %p Pressure difference bar B1 B2 © BSI 07-1999 Abbreviations, see equations (8) and (9) 11 EN 725-6:1996 To determine the factor A, connect by means of a ruler the pressure difference at equilibrium %h on the left-hand scale with the barometric pressure pB on the right-hand scale Read off the factor A at the interrupt of the straight connecting line with the centre scale Figure — Nomogram 12 © BSI 07-1999 EN 725-6:1996 Test report The test report shall contain the following information: a) the name of the testing establishment; b) date of the test, report identification and number, operator, signatory; c) a reference to this European standard, i.e determined in accordance with EN 725-6; d) a description of the powder (material type, manufacturer, batch or code number); e) pre-treatment of the sample: temperature and time of preliminary drying, temperature and time of desorption heating, application of nitrogen or of vacuum during desorption heating; f) the atmospheric pressure during the measurement, temperature of the water bath during the measurement, time from immersion of the adsorption bottles in the cooling bath until reading of the pressure difference; g) the difference in height which is read from the differential manometer; h) the specific surface area of the sample and, where required, the mean value and its standard deviation; i) comments about the test or test results © BSI 07-1999 13 BS EN 725-6:1996 BSI — British Standards Institution BSI is the independent national body responsible for preparing British Standards It presents the UK view on standards in Europe and at the international level It is incorporated by Royal Charter Revisions British Standards are updated by amendment or revision Users of British Standards should make sure that they possess the latest amendments or editions It is the constant aim of BSI to improve the quality of our products and services We would be grateful if anyone finding an inaccuracy or ambiguity while using this British Standard would inform the Secretary of the technical committee responsible, the identity of which can be found on the inside front cover Tel: 020 8996 9000 Fax: 020 8996 7400 BSI offers members an individual updating service called PLUS which ensures that subscribers automatically receive the latest editions of standards Buying standards Orders for all BSI, international and foreign standards publications should be addressed to Customer Services Tel: 020 8996 9001 Fax: 020 8996 7001 In response to orders for international standards, it is BSI policy to supply the BSI implementation of those that have been published as British Standards, unless otherwise requested Information on standards BSI provides a wide range of information on national, European and international standards through its Library and its Technical Help to Exporters Service Various BSI electronic information services are also available which give details on all its products and services Contact the Information Centre Tel: 020 8996 7111 Fax: 020 8996 7048 Subscribing members of BSI are kept up to date with standards developments and receive substantial discounts on the purchase price of standards For details of these and other benefits contact Membership Administration Tel: 020 8996 7002 Fax: 020 8996 7001 Copyright Copyright subsists in all BSI publications BSI also holds the copyright, in the UK, of the publications of the internationalstandardization bodies Except as permitted under the Copyright, Designs and Patents Act 1988 no extract may be reproduced, stored in a retrieval system or transmitted in any form or by any means – electronic, photocopying, recording or otherwise – without prior written permission from BSI This does not preclude the free use, in the course of implementing the standard, of necessary details such as symbols, and size, type or grade designations If these details are to be used for any other purpose than implementation then the prior written permission of BSI must be obtained BSI 389 Chiswick High Road London W4 4AL If permission is granted, the terms may include royalty payments or a licensing agreement Details and advice can be obtained from the Copyright Manager Tel: 020 8996 7070