ASTM C714-05e1
(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.
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 500C. It requires only a small easily fabricated specimen. Thermal diffusivity values in the range from 0.04 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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An American National Standard
´1
Designation:C714–05
Standard Test Method for
Thermal Diffusivity of Carbon and Graphite by Thermal
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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.
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´ NOTE—Editorial corrections were made to the end of 4.3 and 7.1 in January 2006.
1. Scope experimentally from the oscilloscope trace, an example of
1 1
which is shown in Fig. 2.If D T (10 t ⁄2 )/D T (t ⁄2 ) > 1.98, the
1.1 Thistestmethodcoversthedeterminationofthethermal
heat losses are assumed to be zero.
diffusivity of carbons and graphite to 65 % at temperatures up
2.2.3 The oscilloscope trace must be such that DT , D T
to 500°C. It requires only a small easily fabricated specimen. max
1 1
2
(10 t ⁄2 ), and t ⁄2 can be determined to 62%.
Thermal diffusivity values in the range from 0.04 to 2.0 cm /s
2.2.4 The other conditions are less critical, and the experi-
are readily measurable by this test method; however, for the
menter is left to his discretion.
reason outlined in Section 5, for materials outside this range
this test method may require modification.
3. Significance and Use
1.2 This standard does not purport to address all of the
3.1 Thermaldiffusivityisanimportantpropertyrequiredfor
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
2. Summary of Test Method diffusivity (a) of a wide range of solid materials. It is
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 mea-
flash lamp is absorbed on the front surface of a specimen; and
surement, and ease of handling materials having a wide range
the rear surface temperature change as a function of time is
of thermal diffusivity values over a large temperature range
observed on an oscilloscope. The pulse raises the average
with a single apparatus.The short measurement times involved
temperature of the specimen only a few degrees above its
reduce the chances of contamination and change of specimen
initial value. The ambient temperature of the specimen is
properties due to exposure to high temperature environments.
controlled by a furnace or cryostat. Thermal diffusivity is
3.3 Thermal diffusivity results in many cases can be com-
calculated from the specimen thickness and the time required
bined with values for specific heat (C ) and density (r) and
for the temperature of the back surface to rise to one half of its p
2
used to derive thermal conductivity (l) from the relation l =
maximum value (1).
aC r.
2.2 The critical factors in this test method are: p
3.4 This test method can be used to characterize graphite for
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2.2.1 t/t ⁄2 must be 0.02 or less. t is the pulse time as defined
design purposes.
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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).
4. Apparatus
2.2.2 Heat losses from the specimen via radiation, convec-
4.1 The essential features of the apparatus are shown in Fig.
tion, or conduction to the specimen holder must be small.
3. The window may be any material that is transparent to the
Whether or not this condition is violated can be determined
flash source.The specimen holder should be a ceramic or other
material whose thermal conductivity is low relative to that of
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This test method is under the jurisdiction of ASTM Committee D02 on
the sample.
Petroleum Products and Lubricants and is the direct responsibility of Subcommittee
4.2 Thermocouple, used to monitor the transient tempera-
D02.F0 on Manufactured Carbon and Graphite Products.
tureresponseoftherearsurfaceofthespecimen.Thewireends
Current edition approved Nov. 1, 2005. Published November 2005. Originally
approved in 1972. Last previous edition approved in 2000 as C714–85(2000). DOI:
should be prepared to minimize heat losses from the specimen
10.1520/C0714-05E01.
to the thermocouple wires (that is, by grinding to points or
2
The boldface numbers in parentheses refer to the list of references at the end of
this test method.
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