1、Designation: D 5604 96 (Reapproved 2006)Standard Test Methods forPrecipitated SilicaSurface Area by Single Point B.E.T.Nitrogen Adsorption1This standard is issued under the fixed designation D 5604; the number immediately following the designation indicates the year oforiginal adoption or, in the ca
2、se of revision, the year 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 These test methods cover a procedure to measure thesurface area of precipitated hydrated
3、silicas by, a single pointapproximation of the Brunauer, Emmett, and Teller (B.E.T.)2theory of multilayer gas adsorption. These test methods specifythe sample preparation and treatment, instrument calibrations,required accuracy and precision of experimental data, andcalculations of the surface area
4、results from the obtained data.1.2 These test methods are used to determine the singlepoint nitrogen surface areas in the range of 10 to 50 hm2kg (10to 500 m2/g).1.3 The values stated in SI units are to be regarded as thestandard. The values in parentheses are for information only.1.4 This standard
5、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 practices and determine the applica-bility of regulatory limitations prior to use. The minimumsafety equipment shou
6、ld include protective gloves, sturdy eyeand face protection.2. Referenced Documents2.1 ASTM Standards:3D 1799 Practice for Carbon BlackSampling PackagedShipmentsD 1900 Practice for Carbon BlackSampling Bulk Ship-mentsD 1993 Test Method for Precipitated Silica-SurfaceArea byMultipoint BET Nitrogen Ad
7、sorption3. Summary of Test Methods3.1 Solids adsorb nitrogen and, under specific conditions,the adsorbed molecules approach a monomolecular layer. Thequantity of gas in this hypothetical monomolecular layer iscalculated using an approximation of the B.E.T. equation.Combining this with the area occup
8、ied by the nitrogen mol-ecule yields an approximation of the total surface area of thesolid.3.2 These test methods measure the estimated quantity ofnitrogen in the monomolecular layer formed by adsorption atliquid nitrogen temperature and at a fractional saturationpressure of 0.30 6 0.01.3.3 Before
9、a surface area determination can be made it isnecessary that any material which may already be adsorbed onthe surface of the silica be removed. Removal of adsorbedforeign material (by heating under vacuum or in a steam ofnon-adsorbing gas) eliminates two potential errors. The firsterror is due to th
10、e mass of the foreign material. The seconderror is due to interference by the foreign material to access bynitrogen the silica surface.4. Significance and Use4.1 These test methods measure the approximate surfacearea of precipitated hydrated silicas that is available to thenitrogen molecule using an
11、 approximation of the B.E.T.method. While the multi-point version of the B.E.T. method isgenerally accepted as being less prone to errors arising fromthe varying surface properties of individual samples, thesingle-point approximation is often adequate due to the shortertime per test and relative sim
12、plicity of the instrumentationneeded. Quality control applications and comparative tests onnear-identical samples of close chemical and micro-structuralcomposition are likely to be the applications of greatest value.5. ASTM D11 Standard Reference Silicas5.1 None RequiredThis test method is used to d
13、eterminesurface area of candidate silicas. Reference silicas are avail-able4for determining agreement with data obtained in theinterlaboratory test used for multi-point procedure Test MethodD 1993.1These test methods are under the jurisdiction of ASTM Committee D11 onRubber and are the direct respon
14、sibility of Subcommittee D11.20 on CompoundingMaterials and Procedures.Current edition approved Oct. 1, 2006. Published November 2006. Originallyapproved in 1994. Last previous edition approved in 2001 as D 5604 96 (2001).2Brunauer, Emmett, and Teller, Journal of the American Chemical Society,Vol60,
15、 1938, p. 309.3For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandards volume information, refer to the standards Document Summary page onthe ASTM website.4The sole source of supply of precipitated samp
16、les known to the committee atthis time is Forcoven Products, P.O. Box 1556, Humble, TX 77338. (Samples areavailable in three surface areas: A138; B.57; and C.168 X103m2/kg.) If you areaware of alternative suppliers, please provide this information to ASTM Interna-tional Headquarters. Your comments w
17、ill receive careful consideration at a meetingof the responsible technical committee,1which you may attend.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.TEST METHOD A SURFACE AREA BYSTATIC VOLUMETRIC APPARATUS6. Apparatus6.1 Static
18、-Volumetric Gas Adsorption Apparatus, withdewar flasks and all other accessories required for operation.6.2 Oven, vacuum-type, capable of temperature-regulationto 65C at 110C. Pressure should be less than 13.5 Pa (0.1mmHg).6.3 Sample Cells, which, when attached to the adsorptionapparatus, will maint
19、ain isolation of the sample from theatmospheric pressure equivalent to a helium leak rate of#105standard cubic centimeters per minute, per atmosphere ofpressure difference.6.4 McCleod Gage, or equivalent means to measure thepressure. (May be part of the adsorption apparatus.)6.5 Pressure Gage or Tra
20、nsducer, known to be accurate to60.25 % of reading or 60.067 kPa (60.5 mmHg), whicheveris greater and covering the 0 to 101.3 kPa (760 mmHg)pressure range. (May be part of the adsorption apparatus.)6.6 Analytical Balance, with 0.1 mg sensitivity.6.7 Glass Vials, small (30 cm3) glass vials with caps
21、foroven drying samples.6.8 Heating Mantle, or equivalent, capable of maintaining atemperature of 160 6 5C.6.9 Volumetric Calibration Apparatus, with valve or stop-cock and 6.4 mm tubing adapter to gas adsorption sampleconnector. See Fig. 1.7. Reagents7.1 Purity of ReagentsReagent grade chemicals sha
22、ll beused in all tests. Unless otherwise indicated, it is intended thatall reagents shall conform to the specifications of the Commit-tee on Analytical Reagents of the American Chemical Society,where such specifications are available.5Other grades may beused, provided it is established that they are
23、 of sufficiently highpurity to use without lessening the accuracy of the determina-tion.7.2 Purity of WaterUnless otherwise indicated, referencesto water (and ice prepared from it) shall be understood to meandistilled water or water of equal purity.7.3 Liquid Nitrogen, 98 % or higher purity.7.4 Ultr
24、a-High Purity Nitrogen Gas, cylinder, or othersource of prepurified nitrogen gas.7.5 Ultra-High Purity Helium Gas, cylinder, or other sourceof prepurified helium gas.8. Sampling8.1 No separate practice for sampling silicas is available.However, samples may be taken in accordance with PracticesD 1799
25、 or D 1900, whichever is appropriate.9. Preparation and Verification of Calibration of Static-Volumetric ApparatusNOTE 1Perform this procedure for initial calibration, periodically forquality control, and following repairs or adjustments. If a commercialapparatus is used, consult the users manual fo
26、r specific instructions incarrying out the following steps.9.1 Attach the very low and atmospheric pressure gages ortransducers (see 6.4 and 6.5) to the apparatus and evacuate it,the manifold, and all internal pressure/vacuum sensors to 2.7Pa (20 mHg) or below.9.2 Verify that the internal vacuum sen
27、sor(s) are readingcorrectly and that the internal pressure sensor(s) are readingcorrectly in the vicinity of zero pressure subject to the expectedresolution and stability limits. Make adjustments as needed.9.3 Close the vacuum path and admit nitrogen gas to build101.3 kPa 6 1 % (760 mmHg 6 7.6 mmHg)
28、 of pressure.Verify that the pressure sensors read the correct pressure towithin 60.25 %. Make adjustments as needed.9.4 Thoroughly clean and dry an empty sample holder.Attach it to the apparatus and evacuate it to 2.7 Pa (20 mHg).Apply a 160C heating mantle and continue evacuation for atleast 1 h a
29、nd until the rate of pressure rise upon temporarilyclosing off the vacuum path is under .4 Pa (3 mHg) perminute.9.5 Perform a sample analysis on this clean empty sampletube at 0.30 6 0.01 P/Po.UseaPoof 101.3 kPa (760 mmHg)and a sample mass of 1 g.9.6 Examine the volume adsorbed quantity obtained. Id
30、eallyit should be zero. An error amount exceeding 0.25 standardcubic centimeters is unacceptable and requires correction. Anerror amount of 0.125 standard cubic centimeter or less isacceptable.9.7 Obtain a cylindrical or spherical calibration volumemade of glass or corrosion resistant metal and havi
31、ng aninternal volume between 75 cm3and 500 cm3. It must have atubing connection and an in-line valve or stopcock as shown inFig. 1.9.8 Determine the internal volume below the valve orstopcock by the mass difference when first empty and thenwhen filled completely with distilled water. Measure the wat
32、ertemperature and correct for the water density to obtain the5Reagent Chemicals, American Chemical Society Specifications , AmericanChemical Society, Washington, DC. For suggestions on the testing of reagents notlisted by the American Chemical Society, see Analar Standards for LaboratoryChemicals, B
33、DH Ltd., Poole, Dorset, U.K., and the United States Pharmacopeiaand National Formulary, U.S. Pharmacopeial Convention, Inc. (USPC), Rockville,MD.FIG. 1 Volumetric ApparatusD 5604 96 (2006)2exact volume of water contained. It may be necessary toimmerse the device in boiling water to ensure complete f
34、illingand degassing. Repeat the procedure until the calibrationvolume is known to better than 60.1 %. Empty the calibrationvolume and thoroughly dry it overnight in the vacuum oven at70 6 5C.9.9 Connect the calibrated volume to a sample port of thegas adsorption apparatus, open the valve or stopcock
35、, andevacuate the volume to below 0.0027 kPa (20 mHg). Con-tinue evacuation for 1 h more. Close off the path to the vacuumsource and note whether any rise in pressure occurs. Thepressure must remain below 2.7 Pa (20 mHg) with an increaserate of less than 0.4 Pa (3 mHg) per minute. When this hasbeen
36、achieved, close the valve or stopcock to retain the vacuumwithin the calibration volume.9.10 Leave the closed-off, evacuated calibration volume inplace. Raise a dewar flask around the volume and pack wet,crushed ice firmly around the volume as in Fig. 2. Remove anydewars or other equipment that migh
37、t interfere with a samplerun. Start a sample run with a target relative pressure of 0.30 60.01 P/Po.Usea1gsample weight and a Poof 101.3 kPa (760mmHg). Upon the beginning of dosing open the valve orstopcock on the evacuated volume and complete the samplerun.9.11 Examine the volume adsorbed. The volu
38、me adsorbedshould be within 61 % of the gas volume, V, computed by thefollowing formula:V 5SP760DVv5 P/Po!SPo760DVv(1)where P/Pois the relative pressure at which the point wasactually equilibrated and Vvis the internal volume determinedby weighing in 9.8.9.12 Successful completion of this series of
39、tests indicatesthat the gas adsorption apparatus meets the basic requirementsof adequate vacuum level, compensation for free space errors,linearity, and accuracy of nitrogen gas metering.10. Sample Preparation Procedure10.1 If the silica sample contains more than about 6 %moisture, it may be dried a
40、t 110C to 2 to 6 % moisture.Averydry silica (less than 1 % moisture) is difficult to transfer due tostatic charge buildup.10.2 Weigh a sample cell to the nearest 0.0001 g and recordthe mass. Include the stopper.10.3 Into the cell, weigh a sample of the silica to be testedthat has been dried as requi
41、red in 10.1, so that the cell containsapproximately 50 m2of surface area for the silica includingstopper.NOTE 2When not measuring a standard reference silica, and the typeof silica is unknown, assume a surface area of 75 m2/g and weigh outapproximately 0.5 g. Record the combined mass of the cell and
42、 silicaincluding stopper.10.4 With the apparatus at atmospheric pressure, place thesample cell containing the silica onto the degassing apparatus.10.5 Begin the degassing procedure as appropriate for theapparatus.10.6 Place a heating mantle or other source of heat aroundthe sample cell and degas the
43、 sample at 160 6 5C for12 horlonger as required to obtain and hold a pressure less than 1.3 Pa(10 mHg) if low pressure degassing is in use. If flowing gaspurging is used, all traces of moisture condensing in the top ofthe tube must be absent. Once the typical degas times havebeen determined, if desi
44、red, future samples can be degassed onthe basis of time alone, allowing a reasonable margin of excesstime. Some samples will be found to require less than 30 minespecially if moisture exposure has been minimal. In thesecases, the minimum time which gives a stable surface area maybe used for degassin
45、g.10.7 Remove the sample from the heat source and allow thesample cell to cool to room temperature. Continue the flow ofpurging gas if that technique is in use.10.8 Go directly to Section 15 and continue the remainingprocedures.TEST METHOD B SINGLE-POINT SURFACEAREA BY FLOWING GAS APPARATUS11. Appar
46、atus11.1 Flowing gas adsorption apparatus, with dewar flasksand all other accessories required for operation.11.2 Oven, vacuum-type, capable of temperature-regulationto 65C at 110C. Pressure should be less than 13 Pa (0.1mmHg).11.3 Sample Cells, which, when attached to the adsorptionapparatus, will
47、maintain isolation of the sample from theatmospheric pressure equivalent to a helium leak rate of#105standard cubic centimeters per minute, per atmosphere ofpressure difference.11.4 Analytical Balance, with 0.1 mg sensitivity.11.5 Glass Vials, small (30 cm3) glass vials with caps foroven drying samp
48、les.11.6 Heating Mantle, or equivalent, capable of maintaininga temperature of 160 6 5C.11.7 Syringes, precision, 1 cm3and5cm3.FIG. 2 Volumetric Apparatus Installed and Readied for GasAdsorption Instrument Calibration VerificationD 5604 96 (2006)312. Reagents12.1 Purity of ReagentsReagent grade chem
49、icals shall beused in all tests. Unless otherwise indicated, it is intended thatall reagents shall conform to the specifications of the Commit-tee on Analytical Reagents of the American Chemical Society,where such specifications are available.5Other grades may beused, provided it is established that they are of sufficiently highpurity to use without lessening the accuracy of the determina-tion.12.2 Purity of WaterUnless otherwise indicated, refer-ences to water (and ice prepared from it) shall be understood tomean distilled water or water of equ
