1、Designation: D 1993 03 (Reapproved 2008)Standard 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
2、 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. Scope1.1 This test method covers a procedure which is used tomeasure the surface area of precipitated hy
3、drated silicas by 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, req
4、uired accuracy and 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
5、stated in SI units are to be regarded asstandard. No other units of measurement are included in thisstandard.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
6、 and health practices 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:3D 1799 Practic
7、e for Carbon BlackSampling PackagedShipmentsD 1900 Practice for Carbon BlackSampling Bulk Ship-mentsD 4483 Practice for Evaluating Precision for Test MethodStandards in the Rubber and Carbon Black ManufacturingIndustriesD 4820 Test Methods for Carbon Black-Surface Area byMultipoint B.E.T. Nitrogen A
8、dsorption43. Significance and 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 mono
9、molecular layer. Thequantity 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 laye
10、r by adsorption at liquidnitrogen 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 mater
11、ial eliminates two potential 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 m
12、ultipoint BET method.These 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 instrum
13、ent operation, and equivalent data handling and calculationsare performed.1This test method is under the jurisdiction of ASTM Committee D11 on Rubberand is the direct responsibility of Subcommittee D11.20 on Compounding Materialsand Procedures.Current edition approved July 1, 2008. Published Septemb
14、er 2008. Originallyapproved in 1991. Last previous edition approved in 2003 as D 1993 03.2Brunauer, Emmett, and Teller, Journal of the American Chemical Society,Vol60, 1938, p. 309.3For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.or
15、g. For Annual Book of ASTMStandards volume information, refer to the standards Document Summary page onthe ASTM website.4Withdrawn.5Commercial automated instruments found satisfactory may be obtained fromMicromeritics Instrument Corporation, One Micromeritics Drive, Norcross, GA300931877, website: ,
16、 and Quantachrome Instruments,1900 Corporate Drive, Boynton Beach, FL 33426, website: www.quantachrome-.com.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.4.2 Sample Cells, and other peripheral equipment as recom-mended by the manuf
17、acturer for the instrument used.4.3 Balance, Analytical, with 0.1-mg sensitivity.4.4 Heating Mantles, or other sample preparation station,capable of maintaining a temperature of 160 6 5C on thesample.5. Reagents5.1 Liquid Nitrogen.5.2 Nitrogen Gas, cylinder, or other source of prepurifiednitrogen ga
18、s 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 instrument.6. Standard Reference Silicas6.1 None RequiredThis test method is used to determinesurface area of candidate silicas. Reference
19、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 practice for sampling silicas is available.However, samples may be taken in accordance with PracticeD 1799 or D 1900, whichever is appropri
20、ate.8. Sample Preparation ProcedureAutomated Instrument8.1 Weigh (to 0.1 mg) a clean, dry, degassed sample tubewith stopper and filler rod if required. Record 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 an
21、d 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 % moisture) 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/
22、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 manufacturersinstructions.8.3.1 The silica must be completely degassed. Whilesamples at normal moisture and moderate surface area arecompletely degassed
23、in1hat160C, the inability to holdpressure (in a vacuum-type instrument), moisture condensationin the cold part of the sample cell, or poor reproducibility areindications that longer degassing times may be required. Donot change the degassing temperature.8.4 Set the heating for the desired temperatur
24、e of 160C,and degas in accordance with manufacturers procedure.NOTE 3To obtain 160C sample temperature, a higher temperature onthe heater may be necessary. The heater temperature and set pointnecessary may be determined by way of a temperature sensor in thesample, for example, a thermometer, during
25、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 pre-dry sample at 110C inaccordance with Note 2 and repeat sample preparation proce-dure. When cool, remove the sample tube from the degas por
26、tin 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 degassed sample weight isinserted into program of calculations.9. Measurement ProcedureAutomated Instruments9.1 For automated system insert prepa
27、red tube containingsample 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 re-quested, select 0.05 and 0.2 and three points betwee
28、n 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 temperature, dry the sample tube, remove itfrom the instrument, and seal it with its stopper.10. Calculations10.1 For automated instruments, s
29、oftware automaticallycalculates results for the chosen reports.NOTE 4If the correlation coefficient calculated for the data analysis islow, see Test Methods D 4820 for a methodology to improve thecorrelation by discarding one or more points.11. Report11.1 Report the following information:11.1.1 Prop
30、er 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/kg.12. Precision and Bias12.1 This precision and bias section has been prepared inaccordance with Practice D 4483, which should be referred
31、tofor terminology and other statistical calculation details.12.2 A Type 1 interlaboratory precision was evaluated inApril 1990. Both repeatability and reproducibility are short-term. Duplicate determinations were made on each of the testsilicas on each of two days, a few days apart. A test result, a
32、sspecified by this test method, is obtained on one measurementof the surface area.12.3 Three different precipitated silicas were used, repre-senting low (less 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
33、 the classicalvacuum rack (one laboratory) and the automatic instruments(four laboratories).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.D 1993 03 (2008)212
34、.4 The results of the precision calculations for repeatabil-ity and reproducibility are given in Table 1 for each of thesilicas evaluated.12.5 Repeatability, r, and reproducibility, R, vary over therange of surface areas measured.12.6 RepeatabilityThe repeatability, r, of this test methodhas been es
35、tablished 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 differ bymore than this tabulated r (for any given mean surface area)must be considered as derived from different or nonidenticalsamp
36、le populations.12.7 ReproducibilityThe reproducibility, R, of this testmethod has been established as the appropriate value tabulatedin Table 1. Two single test results obtained with this testmethod, in two different laboratories, that differ by more thanthe tabulated R (for any given mean surface a
37、rea) must beconsidered as derived from different or nonidentical samplepopulations.12.8 Repeatability and reproducibility expressed as a per-cent of the mean surface area, (r) and (R), have equivalentapplication statements as above for r and R. For the (r) and (R)statements, the difference in the tw
38、o 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 average surface area and the reference (ortrue) surface area. Reference surface areas do not exist for thistest method since the surfac
39、e area is exclusively defined by thistest method. Bias, therefore, cannot be determined.13. Keywords13.1 nitrogen adsorption surface area; precipitated hydratedsilica; silicas; surface areaASTM International takes no position respecting the validity of any patent rights asserted in connection with a
40、ny item mentionedin this standard. Users of this standard are expressly advised that determination of the validity of any such patent rights, and the riskof infringement of such rights, are entirely their own responsibility.This standard is subject to revision at any time by the responsible technica
41、l 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 for additional standardsand should be addressed to ASTM International Headquarters. Your comments will receive careful consideration
42、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 known to the ASTM Committee on Standards, at the address shown below.This standard is copyrighted by ASTM International, 100 Barr Harbor
43、 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 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 6.4D 1993 03 (2008)3
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