ASTM_D_7542_-_15.pdf

Designation:D754215An American National StandardStandard Test Method forAir Oxidation of Carbon and Graphite in the Kinetic Regime1This standard is issued under the fixed designation D7542;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 recommends a standard procedure formeasuring oxidation rates in air of various grades of nucleargraphite and/or manufactured carbon.Following the standardprocedure recommended here,one can obtain kinetic param-eters that characterize the oxidation resistance of tested mate-rials and that can be used to for materials selection andqualification,and for quality control purposes in the fabricationprocess.1.2 This test method covers the rate of oxidative weight lossper exposed nominal geometric surface area,or per initialweight of machined test specimens of standard size and shape,or both.The test is valid in the temperature range where therate of air oxidation of graphite and manufactured carbon islimited by reaction kinetics.1.3 This test method also provides a standard oxidationtemperature(as defined in 3.1.7),and the kinetic parameters ofthe oxidation reaction,namely the activation energy and thelogarithm of pre-exponential factor in Arrhenius equation.Thekinetic parameters of Arrhenius equation are calculated fromthe temperature dependence of oxidation rates measured overthe temperature range where Arrhenius plots(as defined in3.1.8)are linear,which is defined as the“kinetic”or“chemicalcontrol”oxidation regime.For typical nuclear grade graphitematerials it was found that the practical range of testingtemperatures is from about 500 C to 550 C up to about700 C to 750 C.1.4 The values stated in SI units are to be regarded asstandard.No other units of measurement are included in thisstandard.1.5 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:2C559 Test Method for Bulk Density by Physical Measure-ments of Manufactured Carbon and Graphite ArticlesE691 Practice for Conducting an Interlaboratory Study toDetermine the Precision of a Test MethodE898 Test Method of Testing Top-Loading,Direct-ReadingLaboratory Scales and BalancesE1582 Practice for Calibration of Temperature Scale forThermogravimetryE1970 Practice for Statistical Treatment of ThermoanalyticalData3.Terminology3.1 Definitions:3.1.1 Definitions are ordered by oxidation rates first,fol-lowed by activation energy as calculated from oxidation rates.3.1.2 area-normalized oxidation rate(ORa)rate of weightloss due to oxidation of a machined test specimen at a giventemperature,divided by the nominal geometric surface area ofthe specimen.3.1.2.1 DiscussionThe rate of weight loss is determinedby a linear fit of the weight loss plotted against time in therange from 5%to 10%loss of original specimen weight.Theunits of area-normalized oxidation rate,ORa,are g h-1m-2.3.1.3 weight-normalized oxidation rate(ORw)rate ofweight loss due to oxidation of a machined specimen at a giventemperature,divided by the initial weight of the specimen.3.1.3.1 DiscussionThe rate of weight loss is determinedby a linear fit of the weight loss plotted against time in therange from 5%to 10%loss of original specimen weight.Theunits of weight-normalized oxidation rate,ORware:goxidized!#gspecimen!#21h21or,equivalent,h21!(1)3.1.4 nominal geometric surface areaexposed area(A)ofthe test specimen determined by measuring its diameter(D)and height(H)before testing and using the formula:A 5 2D2/41DH(2)The units of nominal geometric surface area are m2.1This test method is under the jurisdiction of ASTM Committee D02 onPetroleum Products,Liquid Fuels,and Lubricants and is the direct responsibility ofSubcommittee D02.F0 on Manufactured Carbon and Graphite Products.Current edition approved Oct.1,2015.Published November 2015.Originallyapproved in 2009.Last previous edition approved in 2009 as D7542 09.DOI:10.1520/D7542-15.2For 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 3.1.5 weight-normalized standard oxidation rate(SORw)value of weight-normalized oxidation rate corresponding to1%weight loss in 24 h(equivalent to SORw=4.17 10-4gg-1h-1).3.1.6 area-normalized standard oxidation rate(SO