1、INTERNATIONAL STANDARD ISO 8008 Second edition 2005-10-15 Reference number ISO 8008:2005(E) ISO 2005 Aluminium oxide primarily used for the production of aluminium Determination of specific surface area by nitrogen adsorption Oxyde daluminium principalement utilis pour la production de laluminium Dt
2、ermination de la surface spcifique par adsorption dazoteISO 8008:2005(E) ii ISO 2005 All rights reserved PDF disclaimer This PDF file may contain embedded typefaces. In accordance with Adobes licensing policy, this file may be printed or viewed but shall not be edited unless the typefaces which are
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6、rofilm, without permission in writing from either ISO at the address below or ISOs member body in the country of the requester. ISO copyright office Case postale 56 CH-1211 Geneva 20 Tel. + 41 22 749 01 11 Fax + 41 22 749 09 47 E-mail copyrightiso.org Web www.iso.org Published in SwitzerlandISO 8008
7、:2005(E) ISO 2005 All rights reserved iii Contents Page 1 Scope 1 2 Normative references 1 3 Principle 1 4 Reagents . 1 5 Apparatus . 2 6 Sampling and sample preparation . 2 7 Procedure . 3 8 Calculation and reporting of results 4 9 Precision . 4 10 Quality control 4 11 Test report 4 Annex A (inform
8、ative) Difference between single- and multi-point-determined BET SSA 6 Annex B (informative) Results of test programme 7ISO 8008:2005(E) iv ISO 2005 All rights reserved Foreword ISO (the International Organization for Standardization) is a worldwide federation of national standards bodies (ISO membe
9、r 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, governmenta
10、l and non-governmental, in liaison with ISO, also take part in the work. ISO collaborates closely with the International Electrotechnical Commission (IEC) on all matters of electrotechnical standardization. International Standards are drafted in accordance with the rules given in the ISO/IEC Directi
11、ves, Part 2. The main task of technical committees is to prepare International Standards. Draft International Standards adopted by the technical committees are circulated to the member bodies for voting. Publication as an International Standard requires approval by at least 75 % of the member bodies
12、 casting a vote. Attention is drawn to the possibility that some of the elements of this document may be the subject of patent rights. ISO shall not be held responsible for identifying any or all such patent rights. ISO8008 was prepared by Technical Committee ISO/TC226, Materials for the production
13、of primary aluminium. This second edition cancels and replaces the first edition (ISO 8008:1986), which has been technically revised.ISO 8008:2005(E) ISO 2005 All rights reserved v Introduction This International Standard is based on Australian Standard AS 2879.4-2003, Alumina Determination of speci
14、fic surface area by nitrogen adsorption vi INTERNATIONAL STANDARD ISO 8008:2005(E) ISO 2005 All rights reserved 1 Aluminium oxide primarily used for the production of aluminium Determination of specific surface area by nitrogen adsorption WARNING Persons using this International Standard should be f
15、amiliar with normal laboratory practice. This International Standard does not purport to address all of the safety problems, if any, associated with its use. It is the responsibility of the user to establish appropriate safety and health practices and to ensure compliance with any national regulator
16、y conditions. 1S c o p e This International Standard specifies an instrumental method for the determination of specific surface area (SSA) of smelter-grade alumina (SGA) by nitrogen adsorption by a single- or multi-point method. A multi-point method is recommended due to the higher accuracy obtained
17、; if a single-point method is used, a lower result will be obtained. NOTE Annex A provides an explanation of the difference between single- and multi-point determined BET SSA. This International Standard is applicable to aluminas having a surface area between and . 2 Normative references The followi
18、ng referenced documents are indispensable for the application of this document. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies. AS 2850-1986, Chemical analysis Interlaboratory test program
19、s For determining precision of analytical method(s) Guide to the planning and conduct 3 Principle The method is based on the ability of a material to adsorb nitrogen molecules on its surface at the boiling point of liquid nitrogen. The instrument determines the quantity of nitrogen gas necessary to
20、form a monolayer of gas molecules on the sample surface. The surface area can then be calculated using the basic theory developed by Brunauer-Emmett-Teller 1) . A test sample is degassed at . The degassing process can be carried out using either vacuum or a flowing nitrogen stream. After degassing,
21、the sample is weighed. This mass, and the monolayer volume determined by the instrument, is used to calculate the specific surface area. 4R e a g e n t s Use only reagents of recognized analytical grade and only distilled water or water of equivalent purity. 1) S. Brunauer, P .H. Emmett and E. Telle
22、r, J. Am Chem. Soc. 60, p.309 (1938). 50 m 2 /g 90 m 2 /g 150 CISO 8008:2005(E) 2 ISO 2005 All rights reserved 4.1 Liquid nitrogen, with a boiling point of at 2) . CAUTION Particular care should be taken when handling cryogenic liquids. 4.2 Nitrogen gas, high purity. 4.3 Other gases, as specified by
23、 the instrument manufacturers. 4.4 Reference alumina Alcan International Limited 3)Alumina Surface Area Standard ALU-11 4) : which is a commercial product sold by Alcan International Limited as part of their in-house commitment to supply reference materials to the alumina/aluminium industry. The cer
24、tified value at confidence level of ALU-11 for single-point analysis isand for multi-point analysis is . NOTE Annex A provides an explanation of the difference between single- and multi-point determined BET SSA. 5 Apparatus 5.1 Surface-area analyser, employing low temperature ( ) nitrogen adsorption
25、. The instrument should be capable of multi-point or single-point analysis. 5.2 Degassing equipment, suitable for degassing a sample at an elevated temperature ( ) using either a flowing nitrogen stream or a vacuum system capable of maintaining a vacuum of . Sample tubes shall include sealing device
26、s to prevent contact between air and the sample after degassing. 5.3 Analytical balance, capable of weighing to an accuracy of . 6 Sampling and sample preparation A test sample is prepared from the laboratory sample using a riffle or a rotary divider, taking particular care to avoid loss of fine par
27、ticles through dusting. A representative test portion of optimum mass (depending on the requirements of the instrument and anticipated surface area) shall be taken from the test sample. The mass of sample used should be such that the total surface area is in accordance with the recommendations of th
28、e manufacturer of the surface-area analyser (5.1) and with a minimum sample mass of . Clean all sample tubes prior to each batch of samples analysed. It is recommended that the tubes be cleaned in an ultrasonic bath. To speed up the drying process, it is recommended that the tubes be rinsed with eth
29、anol before being put into the drying oven. 2) . The unit atm is deprecated. 3) Alcan International Limited, Arvida R is the mass of sample tube, sealing device and test sample after degassing, in grams; is the mass of degassed test sample, in grams. g) Using sample mass ( ), and the procedures reco
30、mmended by the instrument manufacturer, determine the specific surface area of the test sample. Record the specific surface area reported by the instrument, to the nearest . 150 C P /P o 0,162 nm 2 P o 0,000 1 g m 1 150 C2 h 0,000 1 g m 2 m 3 =m 2 m 1 m 1 m 2 m 3 m 3 0,01 m 2 /gISO 8008:2005(E) 4 IS
31、O 2005 All rights reserved 8 Calculation and reporting of results If the instrument reports only the total surface area, calculate the specific surface area of the test sample by: where is the specific surface area of the test sample, in square metres per gram; is the total surface area of the test
32、sample, in square metres, reported by the instrument; is the mass of degassed test sample, in grams. Record the calculated specific surface area to the nearest . Report the specific surface area thus calculated, or the specific surface area recorded in 7.2 g) to the nearest whole unit. 9P r e c i s
33、i o n A test programme of the method in this International Standard was carried out in accordance with AS 2850. From the results of this programme, a within-laboratory repeatability ( ) and between-laboratory reproducibility ( ), at the confidence level as given in Table 1, should be achieved. The r
34、esults of the test programme are given in Annex B. 10 Quality control The specific surface area of the reference alumina (4.4) shall be determined for every batch of samples, by repeating the procedure in 7.2 and substituting the test sample with the reference material. If this result does not lie b
35、etween for single-point determinations, or for multi- point determinations, then it shall be noted in the test report along with the certified value. 11 Test report The test report shall contain the following information: a) reference to this International Standard, i.e. ISO 8008; b) identification
36、of the sample; c) date on which the sample was taken; Table 1 Precision data for specific-surface-area determinations Determination Repeatability () Reproducibility () m 2 /g m 2 /g Single-point 0,8 2,1 Multi-point 1,0 2,5 A SSA = S m 3 A SSA S m 3 0,01 m 2 /g r R 95 % rR 67,8 2,9 m 2 /g 69,1 2,3 m
37、2 /gISO 8008:2005(E) ISO 2005 All rights reserved 5 d) date on which the test was carried out; e) specific surface area of the test sample, expressed in square metres per gram, to the nearest whole unit; f) whether the analysis was single-point or multi-point; g) information in accordance with Claus
38、e 10, if required; h) any unusual observations made during the course of the test which may have had an effect on the result.ISO 8008:2005(E) 6 ISO 2005 All rights reserved Annex A (informative) Difference between single- and multi-point-determined BET SSA Differences between single- and multi-point
39、 SSA for SGA are typically between and . The single- point solution of the BET equation is a simplification of the theory which results in a lower SSA than the multi- point solution. This difference can be calculated provided the constant is known for the material being analysed. The constant in the
40、 BET equation is a term that relates to the energy of interaction between the surface and the adsorbate. For the single-point solution, the assumption is made that is large (greater than 100) resulting in terms in the BET equation simplifying. The BET-plot intercept goes to zero and the slope is inv
41、ersely proportional to the monolayer volume. This simplification enables the BET equation to be solved by measuring the volume of adsorbate at a single partial pressure. The difference arising from the assumptions applied in the single-point formulation is: where is the partial pressure used in the
42、single-point measurement; is the adsorbate/surface-interaction energy term determined in the multi-point equation. For smelter grade aluminas, is typically between 100 and 200. Hence for and , the difference is at the level. This equates to the single-point analysis being lower than the multi-point analysis. 1m 2 /g 3 m 2 /g C C C Relative percentage difference= 1001Cx/Cx+( 1x) x C C C= 150 x= 0,3 1,5 % 70 m 2 /g 1,1 m 2 /g
