【国外标准】 Standard Guide for Thermal Diffusivity of Carbon and Graphite by Thermal Pulse Method

5.1 Thermal diffusivity is an important property required for such purposes as design applications under transient heat flow conditions, determination of safe operating temperature, process control, and quality assurance.5.2 The flash method is used to measure values of thermal diffusivity (α) of a wide range of solid materials. It is particularly advantageous because of the simple specimen geometry, small specimen size requirements, rapidity of measurement, and ease of handling materials having a wide range of thermal diffusivity values over a large temperature range with a single apparatus. The short measurement times involved reduce the chances of contamination and change of specimen properties due to exposure to high temperature environments.5.3 Thermal diffusivity results in many cases can be combined with values for specific heat (Cp) and density (ρ) to derive thermal conductivity (λ) from the relation λ = αCpρ. For guidance on converting thermal diffusivity to thermal conductivity, refer to Practice C781.5.4 This test method described in this guide can be used to characterize graphite for design purposes.5.5 Test Method E1461 is a more detailed form of this test method described in this guide and has applicability to much wider ranges of materials, applications, and temperatures.1.1 This guide covers the determination of the thermal diffusivity of carbons and graphite at temperatures up to 500 °C. It is applicable only to small easily fabricated specimens. Thermal diffusivity values in the range from 0.04 cm2/s to 2.0 cm2/s are readily measurable by this guide; however, for the reason outlined in Section 7, for materials outside this range this guide may not be applicable.1.2 Units—The values stated in SI units are to be regarded as the standard. No other units of measurement are included in this standard.1.3 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety, health, and environmental practices and determine the applicability of regulatory limitations prior to use.1.4 This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.