1、Designation: E2980 14Standard Test Methods forEstimating Average Particle Size of Powders Using AirPermeability1This standard is issued under the fixed designation E2980; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year of
2、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 These test methods use air permeability to determine anenvelope-specific surface area and its associated averageequiva
3、lent spherical diameter (from 0.2 to 75 m) of powders.Two test methods are described: One test method for inorganicmaterials (Test Method 1), and another test method for organicmaterials (Test Method 2). The values obtained are notintended to be absolute but are generally useful on a relativebasis f
4、or control purposes.1.2 UnitsWith the exception of the values for density andthe mass used to determine density, for which the use of thegram per cubic centimetre (g/cm3) and gram (g) units is thelongstanding industry practice; and the units for pressure, cmH2Oalso long-standing practice; the values
5、 in SI units are tobe regarded as standard.1.3 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 practices and determine the applica-bility of regulato
6、ry limitations prior to use.2. Referenced Documents2.1 ASTM Standards:2B330 Test Methods for Estimating Average Particle Size ofMetal Powders and Related Compounds Using Air Per-meabilityB859 Practice for De-Agglomeration of Refractory MetalPowders and Their Compounds Prior to Particle SizeAnalysisE
7、29 Practice for Using Significant Digits in Test Data toDetermine Conformance with SpecificationsE1638 Terminology Relating to Sieves, Sieving Methods,and Screening MediaE2589 Terminology Relating to Nonsieving Methods ofPowder Characterization2.2 ISO Documents:3ISO 10070 Metallic Powders: Determina
8、tions of Envelope-Specific Surface Area from Measurements of the Perme-ability to Air of a Powder Bed Under Steady-State FlowConditions3. Terminology3.1 DefinitionsMany terms used in this test method aredefined in Terminologies E1638 and E2589.3.2 Definitions of Terms Specific to This Standard:3.2.1
9、 air permeability, nmeasurement of air pressure dropacross a packed bed of powder.3.2.2 average particle size, nfor the purposes of these testmethods only, an estimate of the equivalent average sphericalparticle diameter, calculated from the measured envelope-specific surface area, assuming that all
10、 the powder particles arespherical and that all are exactly the same size.3.2.3 de-agglomeration, nprocess used to break up ag-glomerates of particles.3.2.4 envelope-specific surface area, nspecific surfacearea of a powder as determined by gas permeametry inaccordance with ISO 10070.3.2.5 HEL Sub-Si
11、eve AutoSizer (HEL SAS), na commer-cially available permeability instrument for measuringenvelope-specific surface area and estimating average particlesize from 0.2 to 75 m.3.2.6 porosity of a bed of powder, nratio of the volume ofthe void space in the powder bed to that of the overall volumeof the
12、powder bed.4. Significance and Use4.1 These test methods provide procedures for determiningthe envelope-specific surface area of powders, from which iscalculated an “average” particle diameter, assuming the par-ticles are monosize, smooth surface, nonporous, sphericalparticles. For this reason, valu
13、es obtained by these test methods1These test methods are under the jurisdiction of ASTM Committee E29 onParticle and Spray Characterization and is the direct responsibility of SubcommitteeE29.02 on Non-Sieving Methods.Current edition approved Dec. 1, 2014. Published January 2015. DOI: 10.1520/E2980-
14、14.2For 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.3Available from American National Standards Institute (ANS
15、I), 25 W. 43rd St.,4th Floor, New York, NY 10036, http:/www.ansi.org.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States1will be reported as an average particle size. The degree ofcorrelation between the results of these test methods and
16、thequality of powders in use will vary with each particularapplication and has not been fully determined.4.2 These test methods are generally applicable to allpowders, including metals (see Test Methods B330 for specificmetal powder requirements), ceramics, and organic materials,for particles having
17、 diameters between 0.2 and 75 m. Theyshould not be used for powders composed of particles whoseshape is too far from equiaxed - that is, flakes or fibers. In thesecases, it is permissible to use the test methods described onlyby agreement between the parties concerned. These test meth-ods shall not
18、be used for mixtures of different powders, nor forpowders containing binders or lubricants. When the powdercontains agglomerates, the measured surface area may beaffected by the degree of agglomeration. Methods of de-agglomeration such as that specified in Practice B859 may beused if agreed upon bet
19、ween the parties concerned.4.3 When an “average” particle size of powders is deter-mined by these methods, it should be clearly kept in mind thatthis average size is derived from the determination of thespecific surface area of the powder using a relationship that istrue only for powders of uniform
20、size and spherical shape.Thus, the results of these methods are only estimates ofaverage particle size.4.4 Reported particle size measurement is a function of boththe actual dimension and shape factor as well as the particularphysical or chemical properties of the particle being measured.Caution is
21、required when comparing data from instrumentsoperating on different physical or chemical parameters or withdifferent particle size measurement ranges. Sample acquisition,handling, and preparation can also affect reported particle sizeresults.5. Apparatus5.1 HEL Sub-Sieve AutoSizer (HEL SAS),4consist
22、ing of anair pump, a calibrated gas mass flow controller, a precision-bore sample tube, a sample tube retaining collar, a spacer tool,a gas flow metering valve, two precision pressure transducers(inlet and outlet), a stepper motor controlled ballscrew-mounted piston, and computer hardware and softwa
23、re forinstrument control and calculation and reporting of results.Included is accessory equipment consisting of a plug manipu-lator (extraction rod), two porous plugs, and a supply of paperdisks.NOTE 1When homing the piston, adjust the sample packing assembly(1) as described in the manufacturers dir
24、ections, with the plugs and paperdisks stacked together and placed on the fixed anvil spigot, or (2) using aspecially designed baseline (homing) gauge instead of the plugs and paperdisks. This baseline gauge shall have a height of 20.30 6 0.10 mm. Checkall plug heights when new plugs are purchased a
25、nd periodically thereafterto make sure all are equal in height.5.2 Powder funnel, stainless steel, with spout outside diam-eter slightly smaller than the sample tube inside diameter.5.3 The manufacturer provides instructions which should befollowed. Particular attention should be given to proper mai
26、n-tenance of the instrument with special reference to the instruc-tions on (1) “homing” the piston when turning on from anunpowered state, (2) setting the pressure and periodic checkingof the pressure, (3) condition of O-rings on the piston andsample spigot, and (4) the sample packing assembly (plug
27、s andpaper disks).5.4 Balance, having a capacity of at least 50 g and asensitivity of 0.001 g.6. Standardization of Apparatus6.1 Before proceeding with standardization of the HEL SASinstrument, the following items shall be checked:6.1.1 The sample tube and plugs shall not be worn to thepoint where r
28、esults are affected.6.1.2 Inspect the O-ring seals for tears and abrasion marks.The O-ring seals shall not be worn to the point where thesample tube moves easily by hand or the pressure readingvaries as the sample tube is moved.6.1.3 The drying agent shall be in proper condition.6.2 Whenever the ins
29、trument is turned on from an unpow-ered state, the piston shall be “homed” according to themanufacturers instructions. See Note 1 above.6.3 Before running the initial sample, the pressure shall beset to 50.0 (+0.1, 0.5) cm H2O, using the metering valve; thenchecked and reset if necessary every few h
30、ours, or if theambient temperature changes more than 62C.NOTE 2The metering valve position should not be adjusted for repeatruns of the same sample as this will likely lead to a loss of precision evenif the inlet pressure reading has drifted a little outside the 50.0 (+0.1, 0.5)cm H2O range. Further
31、 adjustment is not necessary as the pressure iscontrolled precisely during the particle size measurement.6.4 Standardization is recommended before and after anyseries of determinations or at least every 4 hours of continuedoperation. Warm-up of the instrument is required if it has beenoff for more t
32、han 30 minutes.6.5 Calibration of the pressure transducers is recommendedevery 36 months, using a traceable external pressure gaugeper the manufacturers instructions.7. Procedure7.1 Temperature of TestMake average particle size deter-minations within 62C of the temperature at which standard-ization
33、of the HEL Sub-Sieve AutoSizer was made. Reset thepressure if the temperature of the test varies more than 62C.7.2 Size of Test SampleThe mass of sample used for testsshall be equal in grams (within 65 %) to the true (pore-free)density (in g/cm3) of the powder (for example, iron, 7.8 g;tungsten, 19.
34、3 g; molybdenum, 10.2 g; tantalum, 16.6 g; nickel,8.9 g; and so forth).4The sole source of supply of the HEL Sub-Sieve AutoSizer (HEL SAS) knownto the committee is Hazard Evaluation Laboratory Limited, 9-10 Capital BusinessPark, Manor Way, Borehamwood, Hertfordshire, WD6 1GW. UK. The instrument isex
35、clusively distributed globally by Micromeritics Instrument Corporation, Particu-late Systems, 4356 Communications Drive, Norcross, GA 30093-2901, USA. If youare aware of alternative suppliers, please provide this information to ASTMInternational Headquarters. Your comments will receive careful consi
36、deration at ameeting of the responsible technical committee,1which you may attend.E2980 1427.3 Average Particle Size DeterminationThe average par-ticle size determination shall be made by the same operatorwho makes the standardizations and is started after standard-ization or the determination of an
37、other sample. Proceed ac-cording to the HEL SAS manufacturers instructions as fol-lows:7.3.1 Test Method 1 Inorganic Materials (For Example:Metals, Ceramics, Metal Oxides, Metal Carbides):7.3.1.1 Press the “Inorganics” button.7.3.1.2 Determine the mass of the sample to the nearest 0.01g.7.3.1.3 Sele
38、ct the test parameters: 3 compressions; slowdecompression; slow termination.7.3.1.4 Proceed to 7.3.3.7.3.2 Test Method2Organic Materials (For Example:Lactose):7.3.2.1 Press the “Organics” button.7.3.2.2 Determine the mass of the sample to the nearest 0.01g.7.3.2.3 Select the test parametersStarting
39、Porosity, StepSize, Final Porositypreviously determined for the particularmaterial being tested.7.3.2.4 Proceed to 7.3.3.7.3.3 Press the “Run Test” button and enter the SampleDetails, including the true density of the material and the actualmass of the sample used.7.3.4 Lay a paper disk over one end
40、 of the sample tube usingone of the porous plugs with the perforated surface of the plugagainst the surface of the paper disk. This crimps the paperaround the edges and the paper precedes the plug into thesample tube. Push the plug into the tube until it is even with theend of the sample tube. Place
41、 the sample tube in a verticalposition in a support with the paper side of the plug up.7.3.5 With the aid of the powder funnel, completely transferthe sample into the sample tube by tapping the side of the tubeand funnel. Lay a second paper disk over the top of the sampletube. Place the perforated s
42、urface of a porous brass plug on topof the paper disk and force the plug and paper disk down intothe sample tube until the plug is just inside the sample tube.7.3.6 Push the sample tube retaining collar onto the sampletube.7.3.7 Push the sample tube onto the fixed anvil spigot withthe retaining coll
43、ar below the sample tube holder, centered inthe sample tube holder and leaving enough of a gap at thebottom of the sample tube to fit the SAS spacer tool below thesample tube.NOTE 3The sample tube may eventually wear and cause faulty values.When this condition is suspected, replace the tube. Sample
44、tubes withobvious wear or scratches, or both, should be discarded.7.3.8 Insert the SAS spacer tool into the gap below thesample tube.7.3.9 Using an Allen key or cam lock device, lock thesample tube retaining collar into position just below the sampletube holder arms.7.3.10 Press the “Next” button an
45、d the test will automati-cally run.7.3.11 Monitor the test and remove the spacer after the firstcompression (Test Method 1, Inorganic Materials) or after thepiston has engaged (Test Method 2, Organic Materials).(WarningThe piston moves slowly but with considerableforce. Keep all body parts clear of
46、the mechanism while inmotion. Do not operate with any guards removed.)NOTE 4The sample tube must be held off the spigot to ensure that thefull force is applied to the sample and not dissipated through the spigot.7.3.12 When the test is finished, the results will be displayedon the instruments screen
47、. Record the Porosity, (Average)Particle Size, and Specific Surface Area (SSA). The data willautomatically be saved with the file name indicated duringentry of the sample details.NOTE 5A calculation of an equivalent spherical diameter (“averageparticle diameter,” “average particle size”), based on t
48、he relationshipbetween envelope-specific surface area and particle diameter, is automati-cally performed by the HEL Sub-Sieve AutoSizer from the values relatedto the porosity and to the permeability of the powder bed measured by theinstrument. In other words, what is determined with the instrument i
49、s thespecific surface area of the powder. When an equivalent spherical diameteris determined using the HEL Sub-Sieve AutoSizer, it should be clearlykept in mind that this equivalent spherical diameter is derived from thedetermination of the specific surface area of the powder using a relation-ship that is true only for powders of uniform size and spherical shape.Hence, the term “average particle size,” as defined in 3.2.2, is preferred todescribe the result from this instrument, rather than “particle size” or“equivalent spherical diameter.”7.3.13
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