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1、BRITISH STANDARD BS 7591-1: 1992 Porosity and pore size distribution of materials Part 1: Method of evaluation by mercury porosimetry Licensed Copy: London South Bank University, London South Bank University, Fri Dec 08 10:54:33 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 7591-1:1992 This British
2、Standard, having been prepared under the direction of the General Mechanical Engineering Standards Policy Committee, was published under the authority of the Standards Board and comes into effect on 15 December 1992 BSI 07-1999 The following BSI references relate to the work on this standard: Commit
3、tee reference GME/29 Draft for comment 91/70115 DC ISBN 0 580 21197 5 Committees responsible for this British Standard The preparation of this British Standard was entrusted by the General Mechanical Engineering Standards Policy Committee (GME/-) to Technical Committee GME/29, upon which the followi
4、ng bodies were represented: BCIRA British Cement Association British Coal Corporation British Laboratory Ware Association Coated Abrasives Manufacturers Association Guild of Metal Perforators Institution of Chemical Engineers Institution of Mining and Metallurgy Mechanical Handling Engineers Associa
5、tion Ministry of Defence NABIM Society of Chemical Industry Society of Cosmetic Scientists Woven Wire Association The following bodies were also represented in the drafting of the standard, through subcommittees and panels: Aluminium Federation British Laboratory Ware Association China Clay Associat
6、ion Department of Trade and Industry (National Physical Laboratory) Department of Trade and Industry (Warren Spring Laboratory) GAMBICA (BEAMA Ltd.) Institution of Chemical Engineers Ministry of Defence NABIM Royal Pharmaceutical Society of Great Britain Royal Society of Chemistry Society of Chemica
7、l Industry Society of Cosmetic Scientists University of Bradford Brunel University University of Sunderland University of Technology, Loughborough Coopted members Amendments issued since publication Amd. No.DateComments Licensed Copy: London South Bank University, London South Bank University, Fri D
8、ec 08 10:54:33 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 7591-1:1992 BSI 07-1999i Contents Page Committees responsibleInside front cover Forewordii Introduction1 1Scope1 2References2 3Definitions2 4Principles2 5Apparatus and material3 6Procedures for calibration and performance4 7Procedure4 8Pre
9、sentation of results6 9Test report6 Figure 1 Types of pore space3 Figure 2 Example of cumulative pore size distribution8 Figure 3 Example of a differential pore size distribution on a linear diameter basis9 Figure 4 Example of a differential pore size distribution on a log diameter basis10 Table 1 E
10、xample of part of a computation of pore size distribution7 List of referencesInside back cover Licensed Copy: London South Bank University, London South Bank University, Fri Dec 08 10:54:33 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 7591-1:1992 ii BSI 07-1999 Foreword This Part of BS 7591 has bee
11、n prepared under the direction of the General Mechanical Engineering Standards Policy Committee and is one of a series which describe recommended methods for the evaluation of porosity and pore size distribution. This Part of BS 7591 describes the evaluation of porosity by mercury porosimetry. Other
12、 Parts of BS 7591 are as follows: Part 2: Method of evaluation by gas adsorption; Part 3: Method of evaluation by challenge test1); Part 4: Method of evaluation by liquid expulsion1). CAUTION. Care should be taken when handling mercury and providing for the removal of mercury vapour from the vicinit
13、y of the porosimeter and from the general laboratory environment (see clause 5). The symbols and units used in this Part of BS 7591 do not necessarily conform to BS 5775, but are those widely used in the industry. A British Standard does not purport to include all the necessary provisions of a contr
14、act. 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, pages 1 to 10, an inside back co
15、ver 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. 1) In preparation. Licensed Copy: London South Bank University, London South Bank University, Fri Dec 08 10:54:
16、33 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 7591-1:1992 BSI 07-19991 Introduction In general, different types of pores may be pictured as either apertures, channels or cavities within a solid body or as space (i.e. interstices or voids) between solid particles in a bed, compact or aggregate. Po
17、rosity is a term which is often used to indicate the porous nature of solid material and is more precisely defined as the ratio of the volume of accessible pores and voids to the total volume occupied by a given amount of the solid (see 3.9). In addition to the accessible pores, a solid may contain
18、closed pores which are isolated from the external surface and into which fluids are not able to penetrate. The characterization of closed pores, i.e. cavities with no access to an external surface, is not covered in this Part of this standard. Porous materials may take the form of fine or coarse pow
19、ders, compacts, extrudates, sheets or monoliths. Their characterization usually involves the determination of the pore size distribution as well as the total pore volume or porosity. For some purposes it is also necessary to study the pore shape and interconnectivity and to determine the internal an
20、d external surface area. Porous materials have great technological importance, for example in the context of the following: a) controlled drug release; b) catalysis; c) gas separation; d) filtration including sterilization; e) materials technology; f) environmental protection and pollution control;
21、g) natural reservoir rocks. It is well established that the performance of a porous solid (e.g. its strength, reactivity, permeability or adsorbent power) is dependent on its pore structure. Many different methods have been developed for the characterization of pore structure, in view of the complex
22、ity of most porous solids, it is not surprising to find that the results obtained are not always in agreement and that no single technique can be relied upon to provide a complete picture of the pore structure. The choice of the most appropriate method depends on the application of the porous solid,
23、 its chemical and physical nature and the range of pore size. The most commonly used methods are as follows. a) Mercury porosimetry where the pores are filled with mercury under pressure. This method is Suitable for many materials with pores in the approximate diameter range of 0.003 4m to 400 4m, a
24、nd especially in the range 0.1 4m to 100 4m. b) Gas adsorption where the pores are characterized by adsorbing a gas, such as nitrogen, at liquid nitrogen temperature. This method is used for pores in the approximate diameter range of 0.0004 4m to 0.04 4m (0.4 nm to 40 nm), and is an extension of the
25、 surface area estimation technique (see BS 4359-1). c) Challenge test where the effective size of the through-pores in a structure is estimated by the passage of test particles or molecules of different sizes. This method is often used for pores in the approximate diameter range of 0.005 4m to 100 4
26、m. d) Liquid expulsion where the through-pores in a structure are characterised by the pressure required to empty them of a wetting fluid. This method is normally used for pores in the approximate diameter range of 0.05 4m to 50 4m. 1 Scope This Part of BS 7591 describes a method of evaluation of po
27、re size distribution by mercury porosimetry. It is a comparative test, usually destructive, in which the volume of mercury penetrating a pore or void is determined as a function of an applied hydrostatic pressure, which can be related to a pore diameter. Practical considerations presently limit the
28、maximum applied absolute pressure to about 400 MPa (60 000 psia)2) corresponding to a minimum equivalent pore diameter of approximately 0.003 4m. The maximum diameter will be limited for samples having a significant depth due to the difference in hydrostatic head of mercury from the top to the botto
29、m of the sample. For most purposes this limit may be-regarded as 400 4m. Inter-particle and intra-particle porosity are determined but the method does not distinguish between these porosities where they co-exist. 2) psia = pounds per square inch absolute, 1 lbf/in2 = 6894 Pa and 1 Pa = 1 N/m2. Licen
30、sed Copy: London South Bank University, London South Bank University, Fri Dec 08 10:54:33 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 7591-1:1992 2 BSI 07-1999 The method is suitable for the study of most porous materials. Samples that amalgamate with mercury, such as certain metals, may be unsuit
31、able for this technique or may require a preliminary passivation. Other materials may deform or compact under the applied pressure. In some cases it may be possible to apply sample compressibility corrections and useful comparative data may still be obtained. (See 7.2.7) The mercury porosimetry tech
32、nique should be considered to be comparative, as for most porous media a theory is not available to allow an absolute calculation of results of pore size distribution. NOTEThe determination of pore size distribution of refractory materials by mercury porosimetry is described in BS 1902-3.16. 2 Refer
33、ences 2.1 Normative references This Part of BS 7591 incorporates, by reference, provisions from specific editions of other publications. These normative references are cited at the appropriate points in the text and the publications are listed on the inside back cover. Subsequent amendments to, or r
34、evisions of, any of these publications apply to this Part of BS 7591 only when incorporated in it by updating or revision. 2.2 Informative references This Part of BS 7591 refers to other publications that provide information or guidance. Editions of these publications current at the time of issue of
35、 this standard are listed on the inside back cover, but reference should be made to the latest editions. 3 Definitions (see also Figure 1) For the purposes of this Part of BS 7591, the following definitions apply. 3.1 blind pore (dead-end pore) an open pore having a single connection with an externa
36、l surface 3.2 ink bottle pore a narrow necked open pore 3.3 interconnected pore a pore which communicates with one or more other pores 3.4 open pore a cavity or channel with access to an external surface 3.5 pore diameter the diameter of a pore, assumed to be cylindrical, just penetrated by mercury
37、at a given pressure as calculated by the Washburn equation (see clause 8) 3.6 porosimeter an instrument for measuring porosity and pore size distribution 3.7 porosimetry methods for the estimation of porosity and pore size distribution 3.8 open porosity the ratio of the volume of open pores and void
38、s, which are accessible using the method employed, to the total volume occupied by a given amount of solid 3.9 total porosity the ratio of the volume of voids plus the volume of open and closed pores to the total volume occupied by a given amount of porous solid 3.10 right cylindrical pore a cylindr
39、ical pore perpendicular to the surface 3.11 through pore a pore which passes all the way through the sample 3.12 void the space between particles in a bed, i.e. inter-particle pore 3.13 pore size distribution the distribution of pore width in a porous body as calculated by application of the Washbur
40、n equation (see clause 8) which assumes a cylindrical pore model 4 Principles The pore size distribution of a porous solid can be determined by forcing mercury into an evacuated sample under increasing pressure and measuring the volume of mercury intruded as a function of pressure. The determination
41、 may proceed either with the pressure being raised in a step-wise manner and the volume of mercury intruded measured after an interval of time (equilibration time) when stability has been achieved, or by raising the pressure in a continuous (progressive) manner. Licensed Copy: London South Bank Univ
42、ersity, London South Bank University, Fri Dec 08 10:54:33 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 7591-1:1992 BSI 07-19993 The technique of mercury porosimetry is based on the relationship between pore size and applied pressure as described in clause 8. There are several assumptions inherent i
43、n the calculations and the values of contact angle and surface tension used in the calculation should be stated in the test report (see clause 9). 5 Apparatus and material WARNING NOTE.It is important that proper precautions for the protection of laboratory personnel are taken when mercury is used.
44、Samples and penetrometers are contaminated with mercury and hydraulic fluid after testing. Attention is drawn to the relevant regulations and guidance documents which include the Department of Employment Technical Data Note No. 21, published by HMSO1. 5.1 Sample holder The sample holder, referred to
45、 as a penetrometer or dilatometer, should have a uniform bore capillary tube through which the sample can be evacuated and through which mercury can enter. The capillary tube is attached to a wider bore tube in which the test sample is located. If precise measurements are required the internal volum
46、e of the capillary tube should be between 20 % and 90 % of the expected pore and void volume of the sample. Since different materials exhibit a wide range of open porosities a number of penetrometers with different diameter capillary tubes and sample volumes may be required. A special design of samp
47、le holder is often used with powdered samples to avoid the loss of powder (see 7.2.3). Figure 1 Types of pore space Licensed Copy: London South Bank University, London South Bank University, Fri Dec 08 10:54:33 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 7591-1:1992 4 BSI 07-1999 5.2 Porosimeter F
48、or convenience of operation the test may be carried out as two sequential measurements, a low pressure test up to 0.2 MPa (30 psia) and a high pressure test up to the maximum operating pressure of the porosimeter. The porosimeter may have separate ports for high and low pressure operation, or the lo
49、w pressure test may be carried out on a separate unit. Prior to any porosimetry measurement it is necessary to evacuate the sample to a maximum residual pressure of 7 Pa (0.05 torr)3), then fill the sample holder with mercury to a given low pressure. To cause intrusion of mercury there should be a means of generating pressure. It is necessary to use a hydraulic pump to generate high pressures of up to 400 MPa (60 000 psia). It is possible to use compressed gases to generate lower pressures. A means to reduce and verify the reduction of pressure to atmospher