1、BRITISH STANDARD BS ISO 8008:2005 Aluminium oxide primarily used for the production of aluminium Determination of specific surface area by nitrogen adsorptionICS 71.100.10 BS ISO 8008:2005 This British Standard was published under the authority of the Standards Policy and Strategy Committee on 23 Ja
2、nuary 2006 BSI 23 January 2006 ISBN 0 580 47298 1 National foreword This British Standard reproduces verbatim ISO 8008:2005 and implements it as the UK national standard. It supersedes BS 4140-23:1987 which is withdrawn. The UK participation in its preparation was entrusted to Technical Committee CI
3、I/24, Raw materials for the aluminium industry, which has the responsibility to: A list of organizations represented on this committee can be obtained on request to its secretary. Cross-references The British Standards which implement international publications referred to in this document may be fo
4、und in the BSI Catalogue under the section entitled “International Standards Correspondence Index”, or by using the “Search” facility of the BSI Electronic Catalogue or of British Standards Online. This publication does not purport to include all the necessary provisions of a contract. Users are res
5、ponsible for its correct application. Compliance with a British Standard does not of itself confer immunity from legal obligations. aid enquirers to understand the text; present to the responsible international/European committee any enquiries on the interpretation, or proposals for change, and keep
6、 UK interests informed; monitor related international and European developments and promulgate them in the UK. Summary of pages This document comprises a front cover, an inside front cover, the ISO title page, pages ii to v, a blank page, pages 1 to 7 and a back cover. The BSI copyright notice displ
7、ayed in this document indicates when the document was last issued. Amendments issued since publication Amd. No. Date CommentsINTERNATIONAL STANDARD ISO 8008 Second edition 2005-10-15 Reference number ISO 8008:2005(E) Aluminium oxide primarily used for the production of aluminium Determination of spe
8、cific surface area by nitrogen adsorption Oxyde daluminium principalement utilis pour la production de laluminium Dtermination de la surface spcifique par adsorption dazoteBS ISO 8008:2005ii iii Contents Page 1 Scope 1 2 Normative references 1 3 Principle 1 4 Reagents . 1 5 Apparatus . 2 6 Sampling
9、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 (informative) Difference between single- and multi-point-determined BET SSA 6 Annex B (informative) Results of test programme 7 BS ISO 8008:2005iv Forewor
10、d 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 technica
11、l 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 ele
12、ctrotechnical standardization. International Standards are drafted in accordance with the rules given in the ISO/IEC Directives, Part 2. The main task of technical committees is to prepare International Standards. Draft International Standards adopted by the technical committees are circulated to th
13、e member bodies for voting. Publication as an International Standard requires approval by at least 75 % of the member bodies casting a vote. Attention is drawn to the possibility that some of the elements of this document may be the subject of patent rights. ISO shall not be held responsible for ide
14、ntifying any or all such patent rights. ISO8008 was prepared by Technical Committee ISO/TC226, Materials for the production of primary aluminium. This second edition cancels and replaces the first edition (ISO 8008:1986), which has been technically revised. BS ISO 8008:2005v Introduction This Intern
15、ational Standard is based on Australian Standard AS 2879.4-2003, Alumina Determination of specific surface area by nitrogen adsorption. BS ISO 8008:2005vi blank1 Aluminium oxide primarily used for the production of aluminium Determination of specific surface area by nitrogen adsorption WARNING Perso
16、ns using this International Standard should be familiar 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
17、to ensure compliance with any national regulatory 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
18、 recommended due to the higher accuracy obtained; 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
19、between and . 2 Normative references The following referenced documents are indispensable for the application of this document. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies. AS 2850-1986
20、, Chemical analysis Interlaboratory test programs 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 deter
21、mines the quantity of nitrogen gas necessary to 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
22、 or a flowing nitrogen stream. After degassing, 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 p
23、urity. 1) S. Brunauer, P .H. Emmett and E. Teller, J. Am Chem. Soc. 60, p.309 (1938). 50 m 2 /g 90 m 2 /g 150 C BS ISO 8008:20052 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 gas
24、es, as specified by 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/aluminiu
25、m industry. The certified 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 ( )
26、nitrogen adsorption. 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 inc
27、lude sealing devices 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 avo
28、id loss of fine particles 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 re
29、commendations of the 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
30、 be rinsed with ethanol 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
31、the procedures recommended 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 /g B
32、S ISO 8008:20054 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 sample, in
33、 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 i o n A te
34、st 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 results of
35、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 between for
36、 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 of the sam
37、ple; 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 2 /g BS IS
38、O 8008:20055 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 Clause 10, if required; h) any unusual obser
39、vations made during the course of the test which may have had an effect on the result. BS ISO 8008:20056 Annex A (informative) Difference between single- and multi-point-determined BET SSA Differences between single- and multi-point SSA for SGA are typically between and . The single- point solution
40、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 BET equation is a term that relates to the energy of interaction be
41、tween 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 inversely proportional to the monolayer volume. This simplification ena
42、bles 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 single-point measurement; is the adsorbate/surface-interaction energ
43、y 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 BS ISO 8008:2005
