1、Designation: D1993 03 (Reapproved 2013)1D1993 18Standard Test Method forPrecipitated Silica-Surface Area by Multipoint BET NitrogenAdsorption1This standard is issued under the fixed designation D1993; the number immediately following the designation indicates the year oforiginal adoption or, in the
2、case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon () indicates an editorial change since the last revision or reapproval.1 NOTEEditorially corrected 2.1 and related references in February 2016.1. Scope1.1 This test method
3、 covers a procedure which is used to measure the surface area of precipitated hydrated silicas by theconventional Brunauer, Emmett, and Teller (BET)2 theory of multilayer gas adsorption behavior using multipoint determinations,similar to that used for carbon black in Test Method D6556. This test met
4、hod specifies the sample preparation and treatment,instrument calibrations, required accuracy and precision of experimental data, and calculations of the surface area results from theobtained data.1.2 This test method is used to determine the nitrogen surface area of precipitated silicas with specif
5、ic surface areas in the rangeof 1 to 50 hm2/kg (10 to 500 m2/g).1.3 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.1.4 This standard does not purport to address all of the safety concerns, if any, associated with its use. It
6、is the responsibilityof the user of this standard to establish appropriate safety safety, health, and healthenvironmental practices and determine theapplicability of regulatory limitations prior to use. The minimum safety equipment should include protective gloves, sturdy eyeand face protection, and
7、 means to deal safely with accidental mercury spills.1.5 This international standard was developed in accordance with internationally recognized principles on standardizationestablished in the Decision on Principles for the Development of International Standards, Guides and Recommendations issuedby
8、the World Trade Organization Technical Barriers to Trade (TBT) Committee.2. Referenced Documents2.1 ASTM Standards:3D1799 Practice for Carbon BlackSampling Packaged ShipmentsD1900 Practice for Carbon BlackSampling Bulk ShipmentsD4483 Practice for Evaluating Precision for Test Method Standards in the
9、 Rubber and Carbon Black Manufacturing IndustriesD5900 Specification for Physical and Chemical Properties of Industry Reference Materials (IRM)D6556 Test Method for Carbon BlackTotal and External Surface Area by Nitrogen Adsorption3. Significance and Use3.1 This test method is used to measure the su
10、rface area of precipitated, hydrated silicas that is available to the nitrogenmolecule using the multipoint (B. E. T.) method.3.2 Solids adsorb nitrogen and, under specific conditions, the adsorbed molecules approach a monomolecular layer. Thequantity in this hypothetical monomolecular layer is calc
11、ulated using the BET equation. Combining this with the area occupiedby the nitrogen molecule yields the total surface area of the solid.3.3 This test method measures the estimated quantity of nitrogen in the monomolecular layer by adsorption at liquid nitrogentemperature and at several (at least fiv
12、e) partial pressures of nitrogen.1 This test method is under the jurisdiction of ASTM Committee D11 on Rubber and Rubber-like Materials and is the direct responsibility of Subcommittee D11.20 onCompounding Materials and Procedures.Current edition approved Nov. 1, 2013June 1, 2018. Published January
13、2014July 2018. Originally approved in 1991. Last previous edition approved in 20082013 asD1993 03 (2008).(2013)1. DOI: 10.1520/D1993-03R13E01.10.1520/D1993-18.2 Brunauer, Emmett, and Teller, Journal of the American Chemical Society, Vol 60, 1938, p. 309.3 For referencedASTM standards, visit theASTM
14、website, www.astm.org, or contactASTM Customer Service at serviceastm.org. For Annual Book of ASTM Standardsvolume information, refer to the standards Document Summary page on the ASTM website.This document is not an ASTM standard and is intended only to provide the user of an ASTM standard an indic
15、ation of what changes have been made to the previous version. Becauseit may not be technically possible to adequately depict all changes accurately, ASTM recommends that users consult prior editions as appropriate. In all cases only the current versionof the standard as published by ASTM is to be co
16、nsidered the official document.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States13.4 Before a surface area determination can be made it is necessary that the silica be stripped of any material which may alreadybe adsorbed on the surface
17、. The stripping of adsorbed foreign material eliminates two potential errors. The first error is associatedwith the weight of the foreign material. The second error is associated with the surface area that the foreign material occupies.4. Apparatus4.1 Commercial instruments are available4 for the me
18、asurement of nitrogen surface area by the multipoint BET method. Thesemay be of the “flowing gas” or the “vacuum-volumetric” type.NOTE 1Automated instruments will provide results equivalent to the procedure described herein if careful calibration of the instrument, equivalentsample preparation, adhe
19、rence to manufacturersmanufacturers instruction for instrument operation, and equivalent data handling and calculations areperformed.4.2 Sample Cells, and other peripheral equipment as recommended by the manufacturer for the instrument used.4.3 Balance, Analytical, with 0.1-mg sensitivity.4.4 Heatin
20、g Mantles, or other sample preparation station, capable of maintaining a temperature of 160 6 5C on the sample.5. Reagents5.1 Liquid Nitrogen.5.2 Nitrogen Gas, cylinder, or other source of prepurified nitrogen gas as specified by the manufacturer of the instrument.5.3 Helium Gas, cylinder, or other
21、source of prepurified helium gas, as specified by the manufacturer of the instrument.6. Standard Reference Silicas6.1 None RequiredThis test method is used to determine surface area of candidate silicas. Reference silicas are available5 forchecking agreement with data obtained in the interlaboratory
22、 test used in preparation of this test method.7. Sampling7.1 No separate practice for sampling silicas is available. However, samples may be taken in accordance with Practice D1799or D1900, whichever is appropriate.8. Sample Preparation ProcedureAutomated Instrument8.1 Weigh (to 0.1 mg) a clean, dry
23、, degassed sample tube with stopper and filler rod if required. Record the mass.8.2 Transfer a sample of silica to be tested so that the sample tube contains approximately 10 to 50 m2 of silica surface areain accordance with the recommendations of the manufacturers procedure (see Note 2 and 8.2.1).N
24、OTE 2If the silica sample contains more than about 6 % moisture, it may be dried at 110C to 2 to 6 % moisture. A very dry silica (less than 1 %moisture) is difficult to transfer due to static charge buildup.8.2.1 If the surface area of the silica is unknown, assume a surface area of 7.5 hm2/kg and w
25、eigh out approximately 0.5 g ofsample.8.3 Place the sample assembly (with sample) at the degas station. Degas the sample in accordance with manufacturersinstructions.8.3.1 The silica must be completely degassed. While samples at normal moisture and moderate surface area are completelydegassed in 1 h
26、 at 160C, the inability to hold pressure (in a vacuum-type instrument), moisture condensation in the cold part ofthe sample cell, or poor reproducibility are indications that longer degassing times may be required. Do not change the degassingtemperature.8.4 Set the heating for the desired temperatur
27、e of 160C, and degas in accordance with manufacturers procedure.NOTE 3To obtain 160C sample temperature, a higher temperature on the heater may be necessary. The heater temperature and set point necessarymay be determined by way of a temperature sensor in the sample, for example, a thermometer, duri
28、ng a trial run.8.5 Remove from heat and allow sample and sample tube to cool to room temperature. If moisture is present at the tube neckafter 1 h, abort run and pre-dry sample at 110C in accordance with Note 2 and repeat sample preparation procedure. When cool,4 Commercial automated instruments fou
29、nd satisfactory may be obtained from Micromeritics Instrument Corporation, One Micromeritics Drive, Norcross, GA300931877, website: , and Quantachrome Instruments, 1900 Corporate Drive, Boynton Beach, FL 33426, website: .5 Precipitated IRM 100 Silica according to Specification D5900, surface area: 1
30、6.79 hm2/kg, is available from Balentine Enterprises, Inc., 227 Somerset St., Borger TX79007. Other precipitated silica samples are available from Forcoven Products, Inc., 123 Martin Drive, Porter, TX 77365. Samples are available in three surface areas: A,13.8; B, 5.7; and C, 16.8 hm2/kg.D1993 182re
31、move the sample tube from the degas port in accordance with manufacturers procedure, stopper, weigh, and record the massto 0.1 mg. Calculate degas sample weight using weight from 8.1 as tare. The degassed sample weight is inserted into program ofcalculations.9. Measurement ProcedureAutomated Instrum
32、ents9.1 For automated system insert prepared tube containing sample into isothermal jacket (if called for in manufacturersprocedure), install on analysis port, and insert run conditions/report options into computer program as required.9.2 For automated system when partial pressures are requested, se
33、lect 0.05 and 0.2 and three points between 0.05 and 0.2. Beginrun.9.2.1 Be sure to input degassed weight of sample obtained in 8.5.9.3 When measurements are complete and sample tube has warmed to room temperature, dry the sample tube, remove it fromthe instrument, and seal it with its stopper.10. Ca
34、lculations10.1 For automated instruments, software automatically calculates results for the chosen reports.NOTE 4If the correlation coefficient calculated for the data analysis is low, see Test Method D6556 for a methodology to improve the correlation bydiscarding one or more points.11. Report11.1 R
35、eport the following information:11.1.1 Proper sample identification.11.1.2 Number of data points used to obtain the results.11.1.3 The nitrogen surface area of the sample reported to the nearest 0.01 hm2/kg.12. Precision and Bias12.1 This precision and bias section has been prepared in accordance wi
36、th Practice D4483, which should be referred to forterminology and other statistical calculation details.12.2 A Type 1 interlaboratory precision was evaluated in April 1990. Both repeatability and reproducibility are short-term.Duplicate determinations were made on each of the test silicas on each of
37、 two days, a few days apart. A test result, as specifiedby this test method, is obtained on one measurement of the surface area.12.3 Three different precipitated silicas were used, representing low (less than 10.0 hm2/kg), medium (10.0 to 16.0 hm2/kg) andhigh (greater than 16.0 hm2/kg). These were t
38、ested in five laboratories. The tests included the classical vacuum rack (onelaboratory) and the automatic instruments (four laboratories).12.4 The results of the precision calculations for repeatability and reproducibility are given in Table 1 for each of the silicasevaluated.12.5 Repeatability, r,
39、 and reproducibility, R, vary over the range of surface areas measured.12.6 RepeatabilityThe repeatability, r, of this test method has been established as the appropriate value tabulated in Table 1.Two single test results, obtained with this test method on the same instrument and with the same opera
40、tor, that differ by more thanthis tabulated r (for any given mean surface area) must be considered as derived from different or nonidentical sample populations.12.7 ReproducibilityThe reproducibility, R, of this test method has been established as the appropriate value tabulated in Table1. Two singl
41、e test results obtained with this test method, in two different laboratories, that differ by more than the tabulated R (forany given mean surface area) must be considered as derived from different or nonidentical sample populations.12.8 Repeatability and reproducibility expressed as a percent of the
42、 mean surface area, (r) and (R), have equivalent applicationstatements as above for r and R. For the (r) and (R) statements, the difference in the two single test results is expressed as a percentof the arithmetic mean of the two test results.TABLE 1 Type 1 Precision of Surface Area of SilicaSilica
43、Mean,hm2/kgWithin Laboratory Between LaboratoriesSr,hm 2/kgr,hm2/kg (r),Sr,hm 2/kgR,hm2/kg (R),A 13.78 0.141 0.399 2.9 0.148 0.419 3.0B 5.67 0.079 0.223 3.9 0.094 0.267 4.71C 16.78 0.201 0.569 3.4 0.377 1.067 6.4D1993 18312.9 BiasIn test method terminology, bias is the difference between an average
44、surface area and the reference (or true) surfacearea. Reference surface areas do not exist for this test method since the surface area is exclusively defined by this test method. Bias,therefore, cannot be determined.13. Keywords13.1 nitrogen adsorption surface area; precipitated hydrated silica; sil
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