ASTM_C_721_-_15.pdf

Designation:C72115Standard Test Methods forEstimating Average Particle Size of Alumina and SilicaPowders by Air Permeability1This standard is issued under the fixed designation C721;the number immediately following the designation indicates the year oforiginal adoption or,in the case 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.Scope*1.1 These test methods cover the estimation of the averageparticle size in micrometres of alumina and silica powdersusing an air permeability method.The test methods areintended to apply to the testing of alumina and silica powdersin the particle size range from 0.2 to 75 m.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 thelong-standing industry practice;and the units for pressure,cmH2Oalso long-standing practice;the values 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 regulatory 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-meabilityE29 Practice for Using Significant Digits in Test Data toDetermine Conformance with SpecificationsE456 Terminology Relating to Quality and StatisticsE691 Practice for Conducting an Interlaboratory Study toDetermine the Precision of a Test Method3.Terminology3.1 Definitions of Terms Specific to This Standard:3.1.1 air permeability,nmeasurement of air pressure dropacross a packed bed of powder.3.1.2 agglomerate,nseveral particles adhering together.3.1.3 average particle size,n(for the purposes of thesetest methods only)an estimate of the equivalent averagespherical particle diameter,calculated from the measuredenvelope-specific surface area,assuming that all the powderparticles are spherical and that all are exactly the same size.The average particle size obtained by this procedure is acalculated average based on air permeability.It will have avalue that is numerically equal to six times the total volume ofthe sample under test divided by the total envelope-specificsurface area of all the particles contained in the sample,or:davg5 6s(1)davg=the estimated average particle size obtained by thisprocedure,m,=absolute density of the particles,g/cm3,ands=total envelope-specific surface area of the sample,m2/g.NOTE1The value of davgwill probably not be numerically equal tothe average particle size as obtained by particle size distribution analysismethods since it is independent of particle shape or size distribution.Thetest methods actually measure sample surface area by air permeability andconverts that to an average particle diameter.3.1.4 de-agglomeration,nprocess used to break up ag-glomerates of particles.3.1.5 envelope-specific surface area,nspecific surfacearea of a powder as determined by gas permeametry.3.1.6 Fisher calibrator tube,njewel with a precisionorifice mounted in a tube similar to a sample tube;thecalibrator tube value is directly traceable to the master tubemaintained by ASTM International Subcommittee B09.03 onRefractory Metal Powders.3.1.7 Fisher Number,ncalculated value equated to anaverage particle diameter,assuming all the particles are spheri-cal and of uniform size.1These test methods are under the jurisdiction of ASTM Committee C21 onCeramic Whitewares and Related Products and is the direct responsibility ofSubcommittee C21.04 on Raw Materials.Current edition approved Dec.1,2015.Published January 2015.Originallyapproved in 1951.Last previous edition approved in 2014 as C721 14.DOI:10.1520/C0721-15.2For 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.*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 States1 3.1.8 Fisher Sub-Sieve Sizer(FSSS),na permeabilityinstrument for measuring envelope-specific surface area andestimating average particle size(Fisher Number)from 0.5 to50 m.3.1.9 MICSub-sieveAutoSizer(MICSAS),nacommercially-available permeability instrument for measuringenvelope-specific surface area and estimating average particlesize from 0.2 to 75 m.3.1.10 porosity of a bed of powder,nratio of the volume ofthe void space in the powder bed to that of the overall volumeof the powder bed.4.Significance and Use4.1 The estimation of average particle size has two chieffunctions:first,as a guide to the degree of fi