ASTM C714-05(2015)
(Test Method)Standard Test Method for Thermal Diffusivity of Carbon and Graphite by Thermal Pulse Method
Standard Test Method for Thermal Diffusivity of Carbon and Graphite by Thermal Pulse Method
SIGNIFICANCE AND USE
3.1 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.
3.2 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.
3.3 Thermal diffusivity results in many cases can be combined with values for specific heat (Cp) and density (ρ) and used to derive thermal conductivity (λ) from the relation λ = αCpρ.
3.4 This test method can be used to characterize graphite for design purposes.
SCOPE
1.1 This test method covers the determination of the thermal diffusivity of carbons and graphite to ±5 % at temperatures up to 500 °C. It requires only a small easily fabricated specimen. Thermal diffusivity values in the range from 0.04 cm2/s to 2.0 cm2/s are readily measurable by this test method; however, for the reason outlined in Section 5, for materials outside this range this test method may require modification.
1.2 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 and health practices and determine the applicability of regulatory limitations prior to use.
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Designation: C714 − 05 (Reapproved 2015) An American National Standard
Standard Test Method for
Thermal Diffusivity of Carbon and Graphite by Thermal
Pulse Method
This standard is issued under the fixed designation C714; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
1 1
1. Scope example of which is shown in Fig. 2.If ∆ T(10 t ⁄2 )/∆ T(t ⁄2)>
1.98, the heat losses are assumed to be zero.
1.1 Thistestmethodcoversthedeterminationofthethermal
2.2.3 The oscilloscope trace must be such that ∆T , ∆
max
diffusivity of carbons and graphite to 65 % at temperatures up
1 1
T(10 t ⁄2 ), and t ⁄2 can be determined to 62%.
to 500 °C. It requires only a small easily fabricated specimen.
2.2.4 The other conditions are less critical, and the experi-
Thermal diffusivity values in the range from 0.04 cm /s to
menter is left to his discretion.
2.0 cm /s are readily measurable by this test method; however,
for the reason outlined in Section 5, for materials outside this
3. Significance and Use
range this test method may require modification.
1.2 This standard does not purport to address all of the
3.1 Thermal diffusivity is an important property required for
safety concerns, if any, associated with its use. It is the
such purposes as design applications under transient heat flow
responsibility of the user of this standard to establish appro-
conditions, determination of safe operating temperature, pro-
priate safety and health practices and determine the applica-
cess control, and quality assurance.
bility of regulatory limitations prior to use.
3.2 The flash method is used to measure values of thermal
diffusivity (α) of a wide range of solid materials. It is
2. Summary of Test Method
particularly advantageous because of the simple specimen
2.1 A high-intensity short-duration thermal pulse from a
geometry, small specimen size requirements, rapidity of
flash lamp is absorbed on the front surface of a specimen; and
measurement, and ease of handling materials having a wide
the rear surface temperature change as a function of time is
range of thermal diffusivity values over a large temperature
observed on an oscilloscope. The pulse raises the average
range with a single apparatus. The short measurement times
temperature of the specimen only a few degrees above its
involved reduce the chances of contamination and change of
initial value. The ambient temperature of the specimen is
specimen properties due to exposure to high temperature
controlled by a furnace or cryostat. Thermal diffusivity is
environments.
calculated from the specimen thickness and the time required
3.3 Thermal diffusivity results in many cases can be com-
for the temperature of the back surface to rise to one half of its
2 bined with values for specific heat (C ) and density (ρ) and
p
maximum value (1).
used to derive thermal conductivity (λ) from the relation λ =
2.2 The critical factors in this test method are:
αC ρ.
p
2.2.1 τ/t ⁄2 must be 0.02 or less.τ is the pulse time as defined
3.4 This test method can be used to characterize graphite for
in Fig. 1 and t ⁄2 is the time for the rear surface temperature to
design purposes.
rise to one half of its maximum value (see Fig. 2).
2.2.2 Heat losses from the specimen via radiation,
4. Apparatus
convection, or conduction to the specimen holder must be
small. Whether or not this condition is violated can be
4.1 The essential features of the apparatus are shown in Fig.
determined experimentally from the oscilloscope trace, an
3. The window may be any material that is transparent to the
flash source.The specimen holder should be a ceramic or other
material whose thermal conductivity is low relative to that of
This test method is under the jurisdiction of ASTM Committee D02 on the sample.
Petroleum Products, Liquid Fuels, and Lubricants and is the direct responsibility of
4.2 Thermocouple, used to monitor the transient tempera-
Subcommittee D02.F0 on Manufactured Carbon and Graphite Products.
Current edition approved Oct. 1, 2015. Published December 2015. Originally
tureresponseoftherearsurfaceofthespecimen.Thewireends
approved in 1972. Last previous edition approved in 2010 as C714 – 05 (2010).
should be prepared to minimize heat losses from the specimen
DOI: 10.1520/C0714-05R15.
to the thermocouple wires (that is, by grinding to points or
The boldface numbers in parentheses refer to the list of references at the end of
this test method. clipping) and attached in a manner that prevents penetration
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
C714 − 05 (2015)
FIG. 1 Flash Tube Response
FIG. 2 Example of Oscilloscope Trace Showing Parameters Used to Calculate Thermal Diffusivity
into the specimen. They are separated by about 1 mm so that amplifier section of the oscilloscope should have a frequency
the electrical circuit of the thermocouple is completed through response in the range from 0.06 kHz to 10 kHz to be perfectly
the specimen.
insensitive to frequency in the range of interest described in
Section 5.Aminimum vertical deflection sensitivity of 1 C⁄cm
4.3 Oscilloscope, with calibrated sweep speeds that can be
is recommended. The cathode-ray tube should have a usable
varied from 0.1 ms⁄cm to 0.5 s⁄cm or more. The vertical
C714 − 05 (2015)
FIG. 3 Schematic Diagram of Apparatus
viewing area of at least 40 mm by 100 mm. A camera is used 7. Procedure
to photograph the oscilloscope tra
...
This document is not an ASTM standard and is intended only to provide the user of an ASTM standard an indication of what changes have been made to the previous version. Because
it may not be technically possible to adequately depict all changes accurately, ASTM recommends that users consult prior editions as appropriate. In all cases only the current version
of the standard as published by ASTM is to be considered the official document.
Designation: C714 − 05 (Reapproved 2010) C714 − 05 (Reapproved 2015)An American National Standard
Standard Test Method for
Thermal Diffusivity of Carbon and Graphite by Thermal
Pulse Method
This standard is issued under the fixed designation C714; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
1. Scope
1.1 This test method covers the determination of the thermal diffusivity of carbons and graphite to 65 % at temperatures up to
500°C.500 °C. It requires only a small easily fabricated specimen. Thermal diffusivity values in the range from 0.040.04 cm /s to
2.0 cm2.0 cm /s are readily measurable by this test method; however, for the reason outlined in Section 5, for materials outside
this range this test method may require modification.
1.2 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 and health practices and determine the applicability of regulatory
limitations prior to use.
2. Summary of Test Method
2.1 A high-intensity short-duration thermal pulse from a flash lamp is absorbed on the front surface of a specimen; and the rear
surface temperature change as a function of time is observed on an oscilloscope. The pulse raises the average temperature of the
specimen only a few degrees above its initial value. The ambient temperature of the specimen is controlled by a furnace or cryostat.
Thermal diffusivity is calculated from the specimen thickness and the time required for the temperature of the back surface to rise
to one half of its maximum value (1).
2.2 The critical factors in this test method are:
1 1
2.2.1 τ/t ⁄2 must be 0.02 or less. τ is the pulse time as defined in Fig. 1 and t ⁄2 is the time for the rear surface temperature to rise
to one half of its maximum value (see Fig. 2).
2.2.2 Heat losses from the specimen via radiation, convection, or conduction to the specimen holder must be small. Whether
or not this condition is violated can be determined experimentally from the oscilloscope trace, an example of which is shown in
1 1
Fig. 2. If Δ T(10 t ⁄2)/Δ T(t ⁄2) > 1.98, the heat losses are assumed to be zero.
1 1
2.2.3 The oscilloscope trace must be such that ΔT , Δ T(10 t ⁄2), and t ⁄2can be determined to 62 %.
max
2.2.4 The other conditions are less critical, and the experimenter is left to his discretion.
3. Significance and Use
3.1 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.
3.2 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.
3.3 Thermal diffusivity results in many cases can be combined with values for specific heat (C ) and density (ρ) and used to
p
derive thermal conductivity (λ) from the relation λ = αC ρ.
p
3.4 This test method can be used to characterize graphite for design purposes.
This test method is under the jurisdiction of ASTM Committee D02 on Petroleum Products Products, Liquid Fuels, and Lubricants and is the direct responsibility of
Subcommittee D02.F0 on Manufactured Carbon and Graphite Products.
Current edition approved May 1, 2010Oct. 1, 2015. Published May 2010December 2015. Originally approved in 1972. Last previous edition approved in 20052010 as
C714C714 – 05 (2010).–05. DOI: 10.1520/C0714-05R10.10.1520/C0714-05R15.
The boldface numbers in parentheses refer to the list of references at the end of this test method.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
C714 − 05 (2015)
FIG. 1 Flash Tube Response
FIG. 2 Example of Oscilloscope Trace Showing Parameters Used to Calculate Thermal Diffusivity
4. Apparatus
4.1 The essential features of the apparatus are shown in Fig. 3. The window may be any material that is transparent to the flash
source. The specimen holder should be a ceramic or other material whose thermal conductivity is low relative to that of the sample.
4.2 Thermocouple, used to monitor the transient temperature response of the rear surface of the specimen. The wire ends should
be prepared to minimize heat losses from the specimen to the thermocouple wires (that is, by grinding to points or clipping) and
C714 − 05 (2015)
FIG. 3 Schematic Diagram of Apparatus
attached in a manner that prevents penetration into the specimen. They are separated by about 1 mm so that the electrical circuit
of the thermocouple is completed through the specimen.
4.3 Oscilloscope, with calibrated sweep speeds that can be varied from 0.10.1 ms ⁄ ms/cm cm to 0.50.5 s ⁄ s/cm cm or more. The
vertical amplifier section of the oscilloscope should have a frequency response in the range from 0.060.06 kHz to 10 kHz 10 kHz
to be perfectly insensitive to frequency in the range of interest described in Section 5. A minimum vertical deflection sensitivity
of 1 C ⁄cm is recommended. The cath
...
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