ASTM_B_922_-_17.pdf

Designation:B92217Standard Test Method forMetal Powder Specific Surface Area by Physical Adsorption1This standard is issued under the fixed designation B922;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 This test method covers determination of surface area ofmetal powders.The test method specifies general proceduresthat are applicable to many commercial physical adsorptioninstruments.The method provides specific sample outgassingprocedures for listed materials.It includes additional generaloutgassing instructions for other metals.The multipoint equa-tion of Brunauer,Emmett and Teller(BET),2along with thesingle point approximation of the BET equation,forms thebasis for all calculations.1.2 This test method does not include all existing proce-dures appropriate for outgassing metallic materials.The pro-cedures included provided acceptable results for samplesanalyzed during interlaboratory testing.The investigator shalldetermine the appropriateness of listed procedures.1.3 The values stated in SI units are to be regarded asstandard.No other units of measurement are included in thisstandard.1.3.1 State all numerical values in terms of SI units unlessspecific instrumentation software reports surface area usingalternate units.In this case,present both reported and equiva-lent SI units in the final written report.Many instruments reportsurface area as m2/g,instead of using correct SI units(m2/kg).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 and health practices and determine the applica-bility of regulatory limitations prior to use.2.Referenced Documents2.1 ASTM Standards:3B215 Practices for Sampling Metal PowdersB243 Terminology of Powder Metallurgy3.Terminology3.1 Definitions:3.1.1 Refer to Terminology B243 for additional terms spe-cific to metal powders.3.2 Definitions of Terms Specific to This Standard:3.2.1 adsorbate,nmaterial that has been retained by theprocess of adsorption.3.2.2 adsorbent,nany solid having the ability to concen-trate or collect significant quantities of other substances on itssurface.3.2.3 adsorption,na process in which fluid molecules areconcentrated or collected on a surface by chemical or physicalforces,or both.3.2.4 adsorptive,nany substance available for adsorption.3.2.5 outgassing,nthe evolution of gas from a material ina vacuum or inert gas flow,at or above ambient temperature.3.2.6 physical adsorption(van der Waals adsorption),nthe binding of an adsorbate to the surface of a solid byforces whose energy levels approximate those of condensation.3.2.7 surface area,nthe total area of the surface of apowder or solid including both external and accessible internalsurfaces(from voids,cracks,open porosity,and fissures).Thearea may be calculated by the BET(Brunauer,Emmett,andTeller)equation from gas adsorption data obtained underspecific conditions.It is useful to express this value as thespecific surface area,for example,surface area per unit mass ofsample(m2/kg).3.2.8 surface area(BET),nthe total surface area of a solidcalculated by the BET(Brunauer,Emmett,Teller)equation,from nitrogen adsorption or desorption data obtained underspecific conditions.3.2.9 surface area,specific,nthe area,per unit mass of agranular or powdered or formed porous solid,of all externalplus internal surfaces that are accessible to a penetrating gas orliquid.4.Summary of Test Method4.1 An appropriately sized sample(to provide at least theminimum surface area required for reliable results for theinstrument used)is outgassed under appropriate conditionsprior to analysis.1This test method is under the jurisdiction of ASTM Committee B09 on MetalPowders and Metal Powder Products and is the direct responsibility of Subcom-mittee B09.03 on Refractory Metal Powders.Current edition approved Jan.1,2017.Published February 2017.Originallyapproved in 2002.Last previous edition approved in 2010 as B92210.DOI:10.1520/B0922-17.2Brunauer,S.,Emmett,P.H.,and Teller,E.“Adsorption of Gases in Multimo-lecular Layers.”Journal of the American Chemical Society,Vol.60,1938,pp.309-319.3For 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.*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 StatesThis international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for