1、Designation: D 1993 03Standard Test Method forPrecipitated Silica-Surface Area by Multipoint BET NitrogenAdsorption1This standard is issued under the fixed designation D 1993; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the yea
2、r of last revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon (e) indicates an editorial change since the last revision or reapproval.1. Scope1.1 This test method covers a procedure which is used tomeasure the surface area of precipitated hydrated silicas by
3、 theconventional Brunauer, Emmett, and Teller (BET)2theory ofmultilayer gas adsorption behavior using multipoint determi-nations, similar to that used for carbon black in Test MethodsD 4820. This test method specifies the sample preparation andtreatment, instrument calibrations, required accuracy an
4、d pre-cision of experimental data, and calculations of the surface arearesults from the obtained data.1.2 This test method is used to determine the nitrogensurface area of precipitated silicas with specific surface areas inthe range of 1 to 50 hm2/kg (10 to 500 m2/g).1.3 The values stated in SI unit
5、s are to be regarded as thestandard. The values given in parentheses are for informationonly.1.4 This standard does not purport to address all of thesafety concerns, if any, associated with its use. It is theresponsibility of the user of this standard to establish appro-priate safety and health prac
6、tices and determine the applica-bility of regulatory limitations prior to use. The minimumsafety equipment should include protective gloves, sturdy eyeand face protection, and means to deal safely with accidentalmercury spills.2. Referenced Documents2.1 ASTM Standards:D 1799 Practice for Carbon Blac
7、kSampling PackagedShipments3D 1900 Practice for Carbon BlackSampling Bulk Ship-ments3D 4483 Practice for Determining Precision for Test MethodStandards in the Rubber and Carbon Black Industries3D 4820 Test Methods for Carbon BlackSurface Area byMultipoint B.E.T. Nitrogen Adsorption43. Significance a
8、nd Use3.1 This test method is used to measure the surface area ofprecipitated, 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. Thequantit
9、y in this hypothetical monomolecular layer is calculatedusing the BET equation. Combining this with the area occupiedby the nitrogen molecule yields the total surface area of thesolid.3.3 This test method measures the estimated quantity ofnitrogen in the monomolecular layer by adsorption at liquidni
10、trogen temperature and at several (at least five) partialpressures of nitrogen.3.4 Before a surface area determination can be made it isnecessary that the silica be stripped of any material which mayalready be adsorbed on the surface. The stripping of adsorbedforeign material eliminates two potentia
11、l errors. The first erroris associated with the weight of the foreign material. Thesecond error is associated with the surface area that the foreignmaterial occupies.4. Apparatus4.1 Commercial instruments are available5for the measure-ment of nitrogen surface area by the multipoint BET method.These
12、may be of the “flowing gas” or the “vacuum-volumetric”type.NOTE 1Automated instruments will provide results equivalent to theprocedure described herein if careful calibration of the instrument,equivalent sample preparation, adherence to manufacturers instructionfor instrument operation, and equivale
13、nt data handling and calculationsare performed.4.2 Sample Cells, and other peripheral equipment as recom-mended by the manufacturer for the instrument used.1This test method is under the jurisdiction of ASTM Committee D11 on Rubberand is the direct responsibility of Subcommittee D11.20 on Compoundin
14、g Materialsand Procedures.Current edition approved Jan. 10, 2003. Published February 2003. Originallyapproved in 1991. Last previous edition approved in 1997 as D 1993 91 (1997).2Brunauer, Emmett, and Teller, Journal of the American Chemical Society,Vol60, 1938, p. 309.3Annual Book of ASTM Standards
15、, Vol. 09.01.4Discontinuedsee 1999 Annual Book of ASTM Standards, Vol. 09.01.5Commercial automated instruments found satisfactory may be obtained fromMicromeritics Instrument Corporation, One Micromeritics Drive, Norcross, GA300931877, website: , and Quantachrome Instruments,1900 Corporate Drive, Bo
16、ynton Beach, FL 33426, website: www.quantachrome-.com.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.4.3 Balance, Analytical, with 0.1-mg sensitivity.4.4 Heating Mantles, or other sample preparation station,capable of maintaining a
17、temperature of 160 6 5C on thesample.5. Reagents5.1 Liquid Nitrogen.5.2 Nitrogen Gas, cylinder, or other source of prepurifiednitrogen gas as specified by the manufacturer of the instrument.5.3 Helium Gas, cylinder, or other source of prepurifiedhelium gas, as specified by the manufacturer of the in
18、strument.6. Standard Reference Silicas6.1 None RequiredThis test method is used to determinesurface area of candidate silicas. Reference silicas are avail-able6for checking agreement with data obtained in the inter-laboratory test used in preparation of this test method.7. Sampling7.1 No separate pr
19、actice for sampling silicas is available.However, samples may be taken in accordance with TestMethods D 1799 or D 1900, whichever is appropriate.8. Sample Preparation ProcedureAutomated Instrument8.1 Weigh (to 0.1 mg) a clean, dry, degassed sample tubewith stopper and filler rod if required. Record
20、the mass.8.2 Transfer a sample of silica to be tested so that the sampletube contains approximately 50 m2of silica surface area (seeNote 2 and 8.2.1).NOTE 2If the silica sample contains more than about 6 % moisture, itmay be dried at 110C to 2 to 6 % moisture. A very dry silica (less than1 % moistur
21、e) is difficult to transfer due to static charge buildup.8.2.1 If the surface area of the silica is unknown, assume asurface area of 7.5 hm2/kg and weigh out approximately 0.5 gof sample.8.3 Place the sample assembly (with sample) at the degasstation. Degas the sample in accordance with manufacturer
22、sinstructions.8.3.1 The silica must be completely degassed. Whilesamples at normal moisture and moderate surface area arecompletely degassed in1hat160C, the inability to holdpressure (in a vacuum-type instrument), moisture condensationin the cold part of the sample cell, or poor reproducibility arei
23、ndications that longer degassing times may be required. Donot change the degassing temperature.8.4 Set the heating for the desired temperature of 160C,and degas in accordance with manufacturers procedure.NOTE 3To obtain 160C sample temperature, a higher temperature onthe heater may be necessary. The
24、 heater temperature and set pointnecessary may be determined by way of a temperature sensor in thesample, for example, a thermometer, during a trial run.8.5 Remove from heat and allow sample and sample tube tocool to room temperature. If moisture is present at the tubeneck after 1 h, abort run and p
25、re-dry sample at 110C inaccordance with Note 2 and repeat sample preparation proce-dure. When cool, remove the sample tube from the degas portin accordance with manufacturers procedure, stopper, weigh,and record the mass to 0.1 mg. Calculate degas sample weightusing weight from 8.1 as tare. The dega
26、ssed sample weight isinserted into program of calculations.9. Measurement ProcedureAutomated Instruments9.1 For automated system insert prepared tube containingsample into isothermal jacket (if called for in manufacturersprocedure), install on analysis port, and insert run conditions/report options
27、into computer program as required.9.2 For automated system when partial pressures are re-quested, select 0.05 and 0.2 and three points between 0.05 and0.2. Begin run.9.2.1 Be sure to input degassed weight of sample obtainedin 8.5.9.3 When measurements are complete and sample tube haswarmed to room t
28、emperature, dry the sample tube, remove itfrom the instrument, and seal it with its stopper.10. Calculations10.1 For automated instruments, software automaticallycalculates results for the chosen reports.NOTE 4If the correlation coefficient calculated for the data analysis islow, see Test Methods D
29、4820 for a methodology to improve thecorrelation by discarding one or more points.11. Report11.1 Report 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 tothe nearest 0.01 hm2
30、/kg.12. Precision and Bias12.1 This precision and bias section has been prepared inaccordance with Practice D 4483, which should be referred tofor terminology and other statistical calculation details.12.2 A Type 1 interlaboratory precision was evaluated inApril 1990. Both repeatability and reproduc
31、ibility are short-term. Duplicate determinations were made on each of the testsilicas on each of two days, a few days apart. A test result, asspecified by this test method, is obtained on one measurementof the surface area.12.3 Three different precipitated silicas were used, repre-senting low (less
32、than 10.0 hm2/kg), medium (10.0 to 16.0hm2/kg) and high (greater than 16.0 hm2/kg). These weretested in five laboratories. The tests included the classicalvacuum rack (one laboratory) and the automatic instruments(four laboratories).12.4 The results of the precision calculations for repeatabil-ity a
33、nd reproducibility are given in Table 1 for each of thesilicas evaluated.6Precipitated silica samples are available from Forcoven Products, Inc., 123Martin Drive, Porter, TX 77365. Samples are available in three surface areas: A,13.8; B, 5.7; and C, 16.8 hm2/kg.D199303212.5 Repeatability, r, and rep
34、roducibility, R, vary over therange of surface areas measured.12.6 RepeatabilityThe repeatability, r, of this test methodhas been established as the appropriate value tabulated in Table1. Two single test results, obtained with this test method on thesame instrument and with the same operator, that d
35、iffer bymore than this tabulated r (for any given mean surface area)must be considered as derived from different or nonidenticalsample populations.12.7 ReproducibilityThe reproducibility, R, of this testmethod has been established as the appropriate value tabulatedin Table 1. Two single test results
36、 obtained with this testmethod, in two different laboratories, that differ by more thanthe tabulated R (for any given mean surface area) must beconsidered as derived from different or nonidentical samplepopulations.12.8 Repeatability and reproducibility expressed as a per-cent of the mean surface ar
37、ea, (r) and (R), have equivalentapplication statements as above for r and R. For the (r) and (R)statements, the difference in the two single test results isexpressed as a percent of the arithmetic mean of the two testresults.12.9 BiasIn test method terminology, bias is the differ-ence between an ave
38、rage surface area and the reference (ortrue) surface area. Reference surface areas do not exist for thistest method since the surface area is exclusively defined by thistest method. Bias, therefore, cannot be determined.13. Keywords13.1 nitrogen adsorption surface area; precipitated hydratedsilica;
39、silicas; surface areaASTM International takes no position respecting the validity of any patent rights asserted in connection with any item mentionedin this standard. Users of this standard are expressly advised that determination of the validity of any such patent rights, and the riskof infringemen
40、t of such rights, are entirely their own responsibility.This standard is subject to revision at any time by the responsible technical committee and must be reviewed every five years andif not revised, either reapproved or withdrawn. Your comments are invited either for revision of this standard or f
41、or additional standardsand should be addressed to ASTM International Headquarters. Your comments will receive careful consideration at a meeting of theresponsible technical committee, which you may attend. If you feel that your comments have not received a fair hearing you shouldmake your views know
42、n to the ASTM Committee on Standards, at the address shown below.This standard is copyrighted by ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959,United States. Individual reprints (single or multiple copies) of this standard may be obtained by contacting ASTM
43、 at the aboveaddress or at 610-832-9585 (phone), 610-832-9555 (fax), or serviceastm.org (e-mail); or through the ASTM website(www.astm.org).TABLE 1 Type 1 Precision of Surface Area of SilicaSilicaMean,hm2/kgWithin Laboratory Between LaboratoriesSr,hm2/kgr,hm2/kg(r),Sr,hm2/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 6.4D1993033
