ASTM E2585-09
(Practice)Standard Practice for Thermal Diffusivity by the Flash Method
Standard Practice for Thermal Diffusivity by the Flash Method
SIGNIFICANCE AND USE
Thermal diffusivity is an important property, required for such purposes under transient heat flow conditions, such as design applications, determination of safe operating temperature, process control, and quality assurance.
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 simple specimen geometry, small specimen size requirements, rapidity of measurement and ease of handling.
Under certain strict conditions, specific heat capacity of a homogeneous isotropic opaque solid sample can be determined when the method is used in a quantitative fashion (see E 1461, Appendix 1).
Thermal diffusivity results, together with related values of specific heat capacity (Cp) and density (ρ) values, can be used in many cases to derive thermal conductivity (λ), according to the relationship:
SCOPE
1.1 This practice covers practical details associated with the determination of the thermal diffusivity of primarily homogeneous isotropic solid materials. Thermal diffusivity values ranging from 10-7 to 10-3 m2/s are readily measurable by this from about 75 to 2800 K.
1.2 This practice is adjunct to E 1461.
1.3 This practice is applicable to the measurements performed on materials opaque to the spectrum of the energy pulse, but with special precautions can be used on fully or partially transparent materials.
1.4 This practice is intended to allow a wide variety of apparatus designs. It is not practical in a document of this type to establish details of construction and procedures to cover all contingencies that might offer difficulties to a person without pertinent technical knowledge, or to stop or restrict research and development for improvements in the basic technique. This practice provides guidelines for the construction principles, preferred embodiments and operating parameters for this type of instruments.
1.5 This practice is applicable to the measurements performed on essentially fully dense materials; however, in some cases it has shown to produce acceptable results when used with porous specimens. Since the magnitude of porosity, pore shapes, and parameters of pore distribution influence the behavior of the thermal diffusivity, extreme caution must be exercised when analyzing data. Special caution is advised when other properties, such as thermal conductivity, are derived from thermal diffusivity obtained by this method.
1.6 The flash can be considered an absolute (or primary) method of measurement, since no reference materials are required. It is advisable to use only reference materials to verify the performance of the instrument used.
1.7 This method is applicable only for homogeneous solid materials, in the strictest sense; however, in some cases it has been shown to produce data found to be useful in certain applications:
1.7.1 Testing of Composite Materials—When substantial non-homogeneity and anisotropy is present in a material, the thermal diffusivity data obtained with this method may be substantially in error. Nevertheless, such data, while usually lacking absolute accuracy, may be useful in comparing materials of similar structure. Extreme caution must be exercised when related properties, such as thermal conductivity, are derived, as composite materials, for example, may have heat flow patterns substantially different than uniaxial. In cases where the particle size of the composite phases is small compared to the specimen thickness (on the order of 1 to 25 % of thickness) and where the transient thermal response of the specimen appears homogenous when compared to the model, this method can produce accurate results for composite materials. Anisotropic materials can be measured by various techniques, as long as the directional thermal diffusivities (two dimensional or three dimensional) are mutually orthogonal and the measurement and specimen preparation produce heat flow only...
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Designation: E2585 − 09
StandardPractice for
1
Thermal Diffusivity by the Flash Method
This standard is issued under the fixed designation E2585; 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 1.7 This method is applicable only for homogeneous solid
materials, in the strictest sense; however, in some cases it has
1.1 This practice covers practical details associated with the
been shown to produce data found to be useful in certain
determination of the thermal diffusivity of primarily homoge-
applications:
neous isotropic solid materials. Thermal diffusivity values
-7 -3 2 1.7.1 Testing of Composite Materials—When substantial
ranging from 10 to 10 m /s are readily measurable by this
non-homogeneity and anisotropy is present in a material, the
from about 75 to 2800 K.
thermal diffusivity data obtained with this method may be
1.2 This practice is adjunct to Test Method E1461.
substantially in error. Nevertheless, such data, while usually
1.3 This practice is applicable to the measurements per- lacking absolute accuracy, may be useful in comparing mate-
rials of similar structure. Extreme caution must be exercised
formed on materials opaque to the spectrum of the energy
pulse, but with special precautions can be used on fully or when related properties, such as thermal conductivity, are
derived, as composite materials, for example, may have heat
partially transparent materials.
flow patterns substantially different than uniaxial. In cases
1.4 This practice is intended to allow a wide variety of
where the particle size of the composite phases is small
apparatus designs. It is not practical in a document of this type
compared to the specimen thickness (on the order of 1 to 25 %
to establish details of construction and procedures to cover all
of thickness) and where the transient thermal response of the
contingencies that might offer difficulties to a person without
specimen appears homogenous when compared to the model,
pertinent technical knowledge, or to stop or restrict research
this method can produce accurate results for composite mate-
and development for improvements in the basic technique.
rials. Anisotropic materials can be measured by various
This practice provides guidelines for the construction
techniques, as long as the directional thermal diffusivities (two
principles, preferred embodiments and operating parameters
dimensional or three dimensional) are mutually orthogonal and
for this type of instruments.
the measurement and specimen preparation produce heat flow
1.5 This practice is applicable to the measurements per-
only along one principle direction. Also, 2D and 3D models
formed on essentially fully dense materials; however, in some
and either independent measurements in one or two directions,
cases it has shown to produce acceptable results when used
or simultaneous measurements of temperature response at
with porous specimens. Since the magnitude of porosity, pore
different locations on the surface of the specimen, can be
shapes, and parameters of pore distribution influence the
utilized.
behavior of the thermal diffusivity, extreme caution must be
1.7.2 Testing Liquids—This method has found an especially
exercised when analyzing data. Special caution is advised
useful application in determining thermal diffusivity of molten
when other properties, such as thermal conductivity, are
materials. For this technique, specially constructed specime
derived from thermal diffusivity obtained by this method.
enclosures must be used.
1.7.3 Testing Layered Materials—This method has also
1.6 The flash can be considered an absolute (or primary)
been extended to test certain layered structures made of
method of measurement, since no reference materials are
dissimilar materials, where the thermal properties of one of the
required. It is advisable to use only reference materials to
layers are considered unknown. In some cases, contact con-
verify the performance of the instrument used.
ductance of the interface may also be determined.
1.8 The values stated in SI units are to be regarded as
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standard. No other units of measurement are included in this
This practice is under the jurisdiction of ASTM Committee E37 on Thermal
Measurements and is the direct responsibility of Subcommittee E37.05 on Thermo-
standard.
physical Properties.
1.9 This standard does not purport to address all of the
Current edition approved March 15, 2009. Published July 2009. DOI: 10.1520/
E2585-09. safety concerns, if any, associated with its use. It is the
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