ASTM C714-2005(2015) Standard Test Method for Thermal Diffusivity of Carbon and Graphite by Thermal Pulse Method《使用热脉冲法测定碳和石墨热扩散率的标准试验方法》.pdf
《ASTM C714-2005(2015) Standard Test Method for Thermal Diffusivity of Carbon and Graphite by Thermal Pulse Method《使用热脉冲法测定碳和石墨热扩散率的标准试验方法》.pdf》由会员分享,可在线阅读,更多相关《ASTM C714-2005(2015) Standard Test Method for Thermal Diffusivity of Carbon and Graphite by Thermal Pulse Method《使用热脉冲法测定碳和石墨热扩散率的标准试验方法》.pdf(4页珍藏版)》请在麦多课文档分享上搜索。
1、Designation: C714 05 (Reapproved 2015) An 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 adopt
2、ion 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. Scope1.1 This test method covers the determination of the thermaldiffusivity of ca
3、rbons and graphite to 65 % at temperatures upto 500 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 5, for materials outside thisrange thi
4、s test method may require modification.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 l
5、imitations prior to use.2. Summary of Test Method2.1 A high-intensity short-duration thermal pulse from aflash lamp is absorbed on the front surface of a specimen; andthe rear surface temperature change as a function of time isobserved on an oscilloscope. The pulse raises the averagetemperature of t
6、he specimen only a few degrees above itsinitial value. The ambient temperature of the specimen iscontrolled by a furnace or cryostat. Thermal diffusivity iscalculated from the specimen thickness and the time requiredfor the temperature of the back surface to rise to one half of itsmaximum value (1).
7、22.2 The critical factors in this test method are:2.2.1 /t12 must be 0.02 or less. is the pulse time as definedin Fig. 1 and t12 is the time for the rear surface temperature torise to one half of its maximum value (see Fig. 2).2.2.2 Heat losses from the specimen via radiation,convection, or conducti
8、on to the specimen holder must besmall. Whether or not this condition is violated can bedetermined experimentally from the oscilloscope trace, anexample of which is shown in Fig. 2.If T(10 t12 )/ T(t12 )1.98, the heat losses are assumed to be zero.2.2.3 The oscilloscope trace must be such that Tmax,
9、 T(10 t12 ), and t12 can be determined to 62%.2.2.4 The other conditions are less critical, and the experi-menter is left to his discretion.3. Significance and Use3.1 Thermal diffusivity is an important property required forsuch purposes as design applications under transient heat flowconditions, de
10、termination of safe operating temperature, pro-cess control, and quality assurance.3.2 The flash method is used to measure values of thermaldiffusivity () of a wide range of solid materials. It isparticularly advantageous because of the simple specimengeometry, small specimen size requirements, rapi
11、dity ofmeasurement, and ease of handling materials having a widerange of thermal diffusivity values over a large temperaturerange with a single apparatus. The short measurement timesinvolved reduce the chances of contamination and change ofspecimen properties due to exposure to high temperatureenvir
12、onments.3.3 Thermal diffusivity results in many cases can be com-bined with values for specific heat (Cp) and density () andused to derive thermal conductivity () from the relation =Cp.3.4 This test method can be used to characterize graphite fordesign purposes.4. Apparatus4.1 The essential features
13、 of the apparatus are shown in Fig.3. The window may be any material that is transparent to theflash source. The specimen holder should be a ceramic or othermaterial whose thermal conductivity is low relative to that ofthe sample.4.2 Thermocouple, used to monitor the transient tempera-ture response
14、of the rear surface of the specimen. The wire endsshould be prepared to minimize heat losses from the specimento the thermocouple wires (that is, by grinding to points orclipping) and attached in a manner that prevents penetration1This test method is under the jurisdiction of ASTM Committee D02 onPe
15、troleum 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 December 2015. Originallyapproved in 1972. Last previous edition approved in 2010 as C714 05 (2010).DOI:
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