1、Designation:C71417An American National StandardStandard Test Method forThermal Diffusivity of Carbon and Graphite by ThermalPulse Method1This standard is issued under the fixed designation C714;the number immediately following the designation indicates the year oforiginal adoption or,in the case of
2、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 the determination of the thermaldiffusivity of carbons and graphite at temper
3、atures up to500 C.It requires only a small easily fabricated specimen.Thermal diffusivity values in the range from 0.04 cm2/s to2.0 cm2/s are readily measurable by this test method;however,for the reason outlined in Section 7,for materials outside thisrange this test method may require modification.
4、1.2 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.1.3 This internati
5、onal standard was developed in accor-dance with internationally recognized principles on standard-ization established in the Decision on Principles for theDevelopment of International Standards,Guides and Recom-mendations issued by the World Trade Organization TechnicalBarriers to Trade(TBT)Committe
6、e.2.Referenced Documents2.1 ASTM Standards:2C781 Practice for Testing Graphite and Boronated GraphiteMaterials for High-Temperature Gas-Cooled Nuclear Re-actor ComponentsD7775 Guide for Measurements on Small Graphite Speci-mensE1461 Test Method for Thermal Diffusivity by the FlashMethod3.Terminology
7、3.1 Definitions:3.1.1 thermal conductivity,nthe rate at which heat passesthrough a material,expressed as the amount of heat that flowsper unit time through a unit area with a temperature gradient ofone degree per unit distance.3.1.2 thermal diffusivity,na measure of the ability of amaterial to condu
8、ct thermal energy relative to its ability to storethermal energy;it is equal to the thermal conductivity dividedby density and specific heat capacity at constant pressure.4.Summary of Test Method4.1 A high-intensity short-duration thermal pulse from aflash lamp is absorbed on the front surface of a
9、specimen;andthe rear surface temperature change as a function of time isobserved on an oscilloscope.The pulse raises the averagetemperature of the specimen only a few degrees above itsinitial value.The ambient temperature of the specimen iscontrolled by a furnace or cryostat.Thermal diffusivity isca
10、lculated from the specimen thickness and the time requiredfor the temperature of the back surface to rise to one half of itsmaximum value(1).34.2 The critical factors in this test method are:4.2.1/t12must be 0.02 or less.is the pulse time as definedin Fig.1 and t12is the time for the rear surface te
11、mperature torise to one half of its maximum value(see Fig.2).4.2.2 Heat losses from the specimen via radiation,convection,or conduction to the specimen holder must besmall.Whether or not this condition is violated can bedetermined experimentally from the oscilloscope trace,anexample of which is show
12、n in Fig.2.If T(10 t12)/T(t12)1.98,the heat losses are assumed to be zero.4.2.3 The oscilloscope trace must be such that Tmax,T(10 t12),and t12can be determined to 62%.4.2.4 The other conditions are less critical,and the experi-menter is left to his discretion.5.Significance and Use5.1 Thermal diffu
13、sivity is an important property required forsuch purposes as design applications under transient heat flow1This 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 a
14、nd Graphite Products.Current edition approved May 1,2017.Published May 2017.Originallyapproved in 1972.Last previous edition approved in 2015 as C714 05(2015).DOI:10.1520/C0714-17.2For referenced ASTM standards,visit the ASTM website,www.astm.org,orcontact ASTM Customer Service at serviceastm.org.Fo
15、r Annual Book of ASTMStandards volume information,refer to the standards Document Summary page onthe ASTM website.3The boldface numbers in parentheses refer to the list of references at the end ofthis test method.*A Summary of Changes section appears at the end of this standardCopyright ASTM Interna
16、tional,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 theDevelopment of International Standards,Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade(TBT)Committee.1 conditions,determination of safe operating temperature,pro-cess control,and quality assurance.5.2
