1、Designation: B821 10 (Reapproved 2016)Standard Guide forLiquid Dispersion of Metal Powders and RelatedCompounds for Particle Size Analysis1This standard is issued under the fixed designation B821; the number immediately following the designation indicates the year oforiginal adoption or, in the case
2、 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. Scope1.1 This guide covers the dispersion in liquids of metalpowders and related compounds for subseq
3、uent use in particlesize analysis instruments. This guide describes a generalprocedure for achieving and determining dispersion; it alsolists procedures that are currently in general use for certainmaterials.1.2 This guide is limited to metal powders and related metalcompounds. However, the general
4、procedure described hereinmay be used, with caution as to its significance, for otherparticulate materials, such as ceramics, pigments, minerals, etc.1.3 The values stated in inch-pound units are to be regardedas the standard. The values given in parentheses are forinformation 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.2. Referenced Documents2.1 ASTM
6、Standards:2B243 Terminology of Powder MetallurgyB430 Test Method for Particle Size Distribution of Refrac-tory Metal Powders and Related Compounds by Turbidi-metryB761 Test Method for Particle Size Distribution of MetalPowders and Related Compounds by X-Ray Monitoringof Gravity SedimentationB822 Tes
7、t Method for Particle Size Distribution of MetalPowders and Related Compounds by Light Scattering3. Terminology3.1 DefinitionsDefinitions of powder metallurgy termscan be found in Terminology B243.4. Significance and Use4.1 The method of powder dispersion in a liquid has asignificant effect on the r
8、esults of a particle size distributionanalysis. The analysis will show a too-coarse, unstable, ornonrepeatable distribution if the powder has not been dispersedadequately. It is therefore important that parties wishing tocompare their analyses use the same dispersion technique.4.2 This guide provide
9、s established powder dispersion tech-niques for certain materials and the means of deriving tech-niques for materials not listed. It should be used by all partiesperforming liquid-dispersed particle size analysis of all of thematerials covered by this guide (see 1.1, 1.2, and 4.1).4.3 This guide sho
10、uld be used in the preparation of powdersfor use in Test Methods B430, B761, and B822 and otherprocedures that analyze metal powder particle size distribu-tions in liquid-dispersed systems.5. Apparatus5.1 Microscope, suitable for observation of particles in thesize range of 5 to 1000 m.5.2 Ultrasoni
11、c Probe,12 -in. (25.4-mm) tip, with the powerlevel to be determined by this guide.5.3 Ultrasonic BathPower level to be determined by thisguide.6. Reagents6.1 Purity of ReagentsReagent grade chemicals should beused in all tests. Unless otherwise indicated, it is intended thatall reagents should confo
12、rm to the specifications of theCommittee on Analytical Reagents of the American Chemical1This guide is under the jurisdiction of ASTM Committee B09 on MetalPowders and Metal Powder Products and is the direct responsibility of Subcom-mittee B09.02 on Base Metal Powders.Current edition approved Oct. 1
13、, 2016. Published October 2016. Originallyapproved in 1992. Last previous edition approved 2010 as B821 10. DOI:10.1520/B0821-10R16.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandards volume inform
14、ation, refer to the standards Document Summary page onthe ASTM website.*A Summary of Changes section appears at the end of this standardCopyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States1Society.3Other grades may be used, provided it is
15、firstascertained that the reagent is of sufficiently high purity topermit its use without lessening the accuracy of the determi-nation.6.2 SurfactantsSuggested surfactants are listed in Table 1and footnotes 4 through 6.4,5,67. General Dispersion Procedure7.1 The general procedure for determining and
16、 achievingproper dispersion is outlined in Fig. 17and described in detailbelow:7.1.1 Place a test portion of the powder to be analyzed in abeaker containing the carrier liquid, selected according to7.1.2.3Reagent Chemicals, American Chemical Society Specifications , AmericanChemical Society, Washing
17、ton, DC. For suggestions on the testing of reagents notlisted by the American Chemical Society, see Analar Standards for LaboratoryChemicals, BDH Ltd., Poole, Dorset, U.K., and the United States Pharmacopeiaand National Formulary, U.S. Pharmacopeial Convention, Inc. (USPC), Rockville,MD.4Allen, T.,
18、Particle Size Measurement, 4th Edition, Chapman and Hall, London,UK, 1991.5Nelson, R. D., Dispersing Powders in Liquids, Elsevier, New York, NY, 1988.6SediGraph III 5120 Operators Manual, Micromeritics Corporation, Norcross,GA, 1998, pp. C-3, C-4, and H-3.7Microtrac Course Manual, Leeds and Northrup
19、 Company, St. Petersburg, FL,1989.TABLE 1 Recommended Dispersion ProceduresMaterialCarrierLiquidSurfactantSurfactantConcentrationUltrasonicTreatmentTypePowerLevel, WTime, minChromium carbide water none . noneorAbath.25.5Copper water Tween 21B35 dropsCbath 80 1Ferroalloys isopropyl alcohol Tween 21B1
20、0 % bath 80 1Iron/steel water Tween 21B35 dropsCbath 80 1Manganese sulfide water Tween 21B35 dropsCbath 80 1Molybdenum water sodium hexametaphosphate 0.01 % probeorbathorAbath16080253105Nickel water Tween 21B35 dropsCbath 80 1Tantalum water sodium hexametaphosphate 0.01 % probeorbath16080310Tantalum
21、 carbide water sodium hexametaphosphate 0.01 % probeorbathorAbath16080253105Tungsten water sodium hexametaphosphate 0.01 % probeorbathorAbath16080253105Tungsten carbide water sodium hexametaphosphate 0.01 % probeorbathorAbath16080253105AAs described in Test Method B430.BTween 21, chemically known as
22、 polyoxyethylene6sorbitan monolaurate, is manufactured by Croda International PLC, and is available from various chemical suppliers.CThree to five drops Tween 21 in 30 to 50 mL water.FIG. 1 General Dispersion ProcedureB821 10 (2016)27.1.2 Selection of Carrier Liquid:NOTE 1The selected carrier liquid
23、 must be compatible with thecomponents of the instrument used for the particle size analysis.7.1.2.1 If the powder reacts with, or is soluble in, water andorganic liquids, it must be analyzed in the dry state, and theremainder of this guide is then not applicable.7.1.2.2 If the powder reacts with, o
24、r is soluble in, water, butnot organic liquids, select an appropriate organic liquid.7.1.2.3 If the powder is neither reactive nor soluble in water,select distilled or deionized water as the carrier liquid.7.1.3 Selection of SurfactantIf the powder is not wettableby the chosen carrier liquid, select
25、 a suitable surfactant(dispersing agent).NOTE 2Ultrasonic energy treatment may be necessary to separateparticles so that the individual particles may be wetted by the carrier liquidor liquid/surfactant solution.NOTE 3Suggested surfactants are listed in Table 1 and footnotes 4through 6.4,5 ,67.1.3.1
26、The appropriate surfactant and its concentration aredetermined by trial and error; a series of concentrations ofdifferent candidate surfactants must be tried on separatesamples and the resultant particle size distribution analysescompared. The optimum surfactant and concentration areusually those th
27、at produce the finest particle size distributionresults.NOTE 4Excess surfactant may cause a coarser particle size distribu-tion in the subsequent particle size analysis.7.1.4 Dispersion Check:7.1.4.1 Determine whether the powder is dispersed in theliquid by examining it carefully in a beaker during
28、and afterstirring. If the powder appears to be distributed uniformlythroughout the liquid, and does not flocculate within a fewseconds after the discontinuation of stirring, particle sizeanalysis can then be performed (9.1) and the results evaluated.7.1.4.2 Ultrasonic Energy TreatmentEven if the pow
29、derappears to be uniformly dispersed, ultrasonic energy treatmentmay be necessary.NOTE 5Ultrasonic treatment may also be necessary to break upagglomerates in powders that appear to be dispersed, unless the agglom-erate distribution is desired from the subsequent analysis.7.1.4.3 Disperse the sample
30、by placing the carrier liquid/sample beaker in an ultrasonic bath or by inserting an ultra-sonic probe into the liquid/sample mixture. Continuous stirringof the liquid/sample mixture may be necessary through part orall of the ultrasonic treatment. As with surfactant selection(7.1.3.1), the appropria
31、te time and power level for ultrasonictreatment must be determined by trial and error. Select the timeand power level by using the minimums necessary to ensureprecision and adequate dispersion, as determined in 7.1.4.1.The optimum ultrasonic treatment is usually that which pro-duces the finest parti
32、cle size distribution results without frac-turing the individual particles.NOTE 6Particle fracture can be evaluated by examining the treatedpowder in a suitable microscope and noting whether the particle shape ordistribution has changed significantly as the power level or treatment timehas been incr
33、eased. Fracture of particles is also often indicated by a shiftfrom a unimodal to bimodal particle size distribution as the ultrasonicpower level or treatment time is increased.NOTE 7Some indication of the type of equipment, starting times, andpower levels for ultrasonic energy treatment may be obta
34、ined from Table1.7.1.4.4 Check for dispersion, as in 7.1.4.1. If the powder isnow well-dispersed, continue with the particle size analysis(9.1).7.1.4.5 If the powder is still not well-dispersed after ultra-sonic energy treatment, select a different surfactant and repeatthe steps given in 7.1.3 and 7
35、.1.4 (and their relevant subpara-graphs). Continue with this repetitive process until dispersionis attained.8. Recommended Dispersion Procedures8.1 Table 1 lists the dispersion procedures currently ingeneral use for several metals and metal compounds. Theseprocedures have been shown by experience to
36、 produceconsistent, reproducible particle size analysis results for thematerials listed.9. Particle Size Distribution Analysis9.1 After dispersion has been achieved by one of the abovetechniques, immediately perform the required particle sizeanalysis by whatever method is applicable (for example, Te
37、stMethods B430, B761,orB822).10. Keywords10.1 liquid dispersion; metal powders; particle size analysis;powder metallurgyASTM 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 express
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40、end. 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 Drive, PO Box C700, West Conshohocken, PA 19428-2959,United States.
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