JP2018080922A - Method of analyzing thermal diffusivity - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method of analyzing thermal diffusivity, which is suitable for analysis of thermal diffusivity in the vanishing process of an opaque film formed on a diathermic material and made of an opaque material, a high melting point metal or the like.SOLUTION: The method of analyzing thermal diffusivity analyzes thermal diffusivity of a diathermic material by forming opaque films 16 and 17 respectively on a front surface and a rear surface of a measurement sample 11 made of the diathermic material and includes: an A step of obtaining an approximate thermal diffusivity α under the condition of no radiation loss of the measurement sample 11 by using temperature data on the rear surface of the measurement sample 11, which is obtained with the time of laser beam irradiation, and taking the approximate thermal diffusivity α lowered with the time of irradiation to enter a stable state, as a thermal diffusivity minimum α; a D step of obtaining a radiation loss correction factor kby using a half time tobtained from the thermal diffusivity minimum ain a B step and a damping time constant τ obtained in a C step; and an E step of multiplying the thermal diffusivity minimum αby the radiation loss correction factor kto obtain the thermal diffusivity of the diathermic material.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a thermal diffusivity analysis method using a laser flash method, and more specifically, a disappearance process of an opaque film formed on a material (that is, a situation in which some leakage light of a laser beam is generated). The thermal diffusivity analysis method is suitable for analysis in (1) (which can also be applied to normal analysis without laser light leakage).

For measuring the thermal conductivity of a material, a method is often used in which the density, specific heat, and thermal diffusivity are individually measured, and the thermal conductivity is obtained from the product of these. Of these, the thermal diffusivity is often measured by a laser flash method (see, for example, Patent Document 1).
The laser flash method is a method in which a sample surface is irradiated with laser pulse light (hereinafter also referred to as laser light) and heated to measure the back surface temperature of the sample, and the thermal diffusivity is obtained from the data. Thus, as a method for obtaining the thermal diffusivity from the back surface temperature of the sample, there are many conventional analysis methods (see, for example, Non-Patent Document 1).

These methods are applicable when the laser beam is completely absorbed by the sample surface and there is no laser beam leakage.
For example, the metal material is a material that can measure the back surface temperature without worrying about the leakage light of the laser beam, but the laser beam penetrates into the sample and passes through the ceramic material as it is. For this reason, when measuring the thermal diffusivity of a sample made of a ceramic material by the laser flash method, the front and back surfaces of the sample are made opaque with an opaque film such as a blackened film so that the laser beam does not enter the sample. Processing (coating).

  A normally used blackening film has heat resistance up to about 1000 ° C., but peels off from the sample and falls off in a temperature range exceeding 1000 ° C. For this reason, when measuring in a temperature range exceeding 1000 ° C., a high melting point metal is sputtered on the front and back surfaces of the sample, and a blackening film is applied thereon. In this case, the laser beam is absorbed by the blackened film up to about 1000 ° C., and after the blackened film is lost in the temperature range exceeding 1000 ° C., the refractory metal film absorbs the laser light.

Japanese Patent No. 3568271

JIS R1611 (2010)

However, the above-described refractory metal film is also easily lost due to peeling or the like in a temperature range exceeding 1500 ° C. In such a state, the laser light penetrates into the sample and is transmitted, and the thermal diffusivity cannot be measured. Specifically, Mo, Nb, or the like is used as the refractory metal film material, but when the refractory metal film starts to disappear, leakage light of the laser light is generated.
At present, there is no further countermeasure, and it has been difficult to measure the thermal diffusivity of ceramic materials in a high temperature range exceeding 1500 ° C.

  The present invention has been made in view of such circumstances, and a thermal diffusivity analysis method suitable for analyzing thermal diffusivity in the disappearance process of an opaque material such as an opaque material or a refractory metal formed on a heat-permeable material. The purpose is to provide.

In the thermal diffusivity analysis method according to the first invention that meets the above-mentioned object, an opaque film is formed on each of the front and back surfaces of a measurement sample made of a heat-permeable material, and laser light is irradiated from the front side of the measurement sample. In the method of analyzing the thermal diffusivity of the heat-permeable material, using the temperature data on the back side of the measurement sample obtained by
Using the temperature data obtained with the lapse of the laser light irradiation time, an approximate thermal diffusivity α is obtained on the condition that there is no radiation loss of the measurement sample, and the stable state decreases with the lapse of the laser light irradiation time. A step of setting the approximate thermal diffusivity α to be a thermal diffusivity minimum value α _min ;
B step for obtaining a half time t _1/2 required for the back side of the measurement sample to rise to half the maximum temperature from the thermal diffusivity minimum value α _min ;
C step for obtaining the decay time constant τ in the decay region of the temperature data;
D step for _obtaining a radiation loss correction coefficient k _rhl using the half time t _1/2 obtained in the step B and the decay time constant τ obtained in the step C;
And E step of _obtaining the thermal diffusivity of the heat-permeable material by multiplying the minimum value α _min of the thermal diffusivity obtained in the step A by the radiation loss correction coefficient _krhl obtained in the step D.

  In the thermal diffusivity analysis method according to the first invention, the approximate thermal diffusivity α of the step A is preferably obtained using the following equation.

  Here, T is temperature data on the back side of the measurement sample, Q is the absorbed energy of the measurement sample, ρ is the density of the measurement sample, c is the specific heat of the measurement sample, L is the thickness of the measurement sample, and t is time.

  In the thermal diffusivity analysis method according to the first aspect of the invention, the analysis of the thermal diffusivity of the heat-permeable material is suitable for being performed at a temperature at which the opaque film disappears from the measurement sample.

  In the thermal diffusivity analysis method according to the first invention, the opacifying film can be formed of one or both of a refractory metal and an opaque material.

The thermal diffusivity analysis method according to the second invention in accordance with the above object uses the temperature data on the back surface side of the measurement sample obtained by irradiating laser light from the front surface side of the measurement sample, and calculates the thermal diffusivity. In the analysis method,
Using the temperature data obtained with the lapse of the laser light irradiation time, an approximate thermal diffusivity α is obtained on the condition that there is no radiation loss of the measurement sample, and the stable state decreases with the lapse of the laser light irradiation time. A step of setting the approximate thermal diffusivity α to be a thermal diffusivity minimum value α _min ;
B step for obtaining a half time t _1/2 required for the back side of the measurement sample to rise to half the maximum temperature from the thermal diffusivity minimum value α _min ;
C step for obtaining the decay time constant τ in the decay region of the temperature data;
D step for _obtaining a radiation loss correction coefficient k _rhl using the half time t _1/2 obtained in the step B and the decay time constant τ obtained in the step C;
And E step of _obtaining a thermal diffusivity by multiplying the minimum value α _min of the thermal diffusivity obtained in the step A by the radiation loss correction coefficient _krhl obtained in the step D.

Since the analysis method of the thermal diffusivity according to the first invention has A process to E process, the disappearance process of the opaque material such as an opaque material or a refractory metal formed on the heat-permeable material, The thermal diffusivity of the heat-permeable material can be obtained even in a situation where a slight amount of laser light leaks.
In addition, since the thermal diffusivity analysis method according to the second invention also includes the steps A to E, the thermal diffusivity of the measurement sample can be obtained.

(A) is explanatory drawing of the measuring apparatus which applies the analysis method of the thermal diffusivity which concerns on one embodiment of this invention, (b) is explanatory drawing of a measurement sample. It is a graph which shows transition of the back surface temperature of a measurement sample when radiation loss is disregarded. It is a graph which shows the relationship between the temperature data of the back surface side of a measurement sample for confirming the method of calculating | requiring an approximate thermal diffusivity, and a bio number. It is the graph which normalized the temperature data of FIG. 3 with the maximum value of each temperature. It is a graph which shows transition of the approximate thermal diffusivity calculated | required using the data of FIG. It is a graph which shows transition of the temperature data of the back surface side of the measurement sample which concerns on an Example. It is a graph which shows transition of the approximate thermal diffusivity calculated | required using the data of FIG.

Next, embodiments of the present invention will be described with reference to the accompanying drawings for understanding of the present invention.
First, a measurement apparatus 10 to which a thermal diffusivity analysis method according to an embodiment of the present invention is applied will be described with reference to FIGS. 1 (a) and 1 (b).

  The measuring apparatus 10 is an apparatus for irradiating a laser beam (heating light) on the surface side of a measurement sample (hereinafter also simply referred to as a sample) 11 made of a heat-permeable material to obtain the thermal diffusivity of the heat-permeable material. A laser beam generator 12 for generating the laser beam, a half mirror 14 for distributing the generated laser beam to the laser beam detector 13 and the measurement sample 11, and a temperature measurement unit for measuring the temperature change of the back surface of the measurement sample 11. 15.

Here, the heat-permeable material is a translucent material such as a ceramic material, a heat insulating material, or a porous material.
The measurement sample 11 produced using this heat-permeable material is, for example, a disk shape having a diameter of about 10 mm and a thickness of several millimeters, but various shapes and dimensions can be changed depending on the measurement conditions.
Opaque films 16 and 17 are formed on the front and back surfaces (both end surfaces in the thickness direction) of the measurement sample 11, respectively. The opaque films 16 and 17 are composed of refractory metals 18 and 19 and opaque materials 20 and 21, and the refractory metals 18 and 19 and opaque materials 20 and 21 are in close contact with the front and back surfaces of the measurement sample 11, respectively. However, the opaque film may be composed of only the refractory metal or the opaque material, and the refractory metal or the opaque material may be disposed in close contact with the front and back surfaces of the measurement sample 11.

For the refractory metals 18 and 19, for example, Mo (molybdenum) or Nb (niobium) having a melting point of 2000 ° C. or more can be used, and the refractory metals 18 and 19 are closely attached to the front and back surfaces of the measurement sample 11 by sputtering or vapor deposition.
Further, the opaque materials 20 and 21 can be blackened films (for example, thin plates made of ceramics such as carbon) in which heat transfer is caused only by diffusion heat transfer, and are in close contact with the surfaces of the refractory metals 18 and 19. The The opaque materials 20 and 21 can be disposed in close contact with the surfaces of the refractory metals 18 and 19 by applying fine powder and baking or vapor deposition, or by carbon spraying.

Thus, the opacifying film 16 is brought into close contact with the surface of the measurement sample 11 (here, the refractory metal 18 and the opaque material 20 are brought into close contact sequentially, but only the refractory metal or only the opaque material is brought into close contact. Therefore, the energy of the laser beam irradiated from the surface side of the measurement sample 11 (on the surface of the opacifying film 16) can be absorbed by 100% on the surface of the opacifying film 16. Furthermore, the absorbed heat can be supplied to the measurement sample 11 according to diffusion heat transfer.
On the other hand, the opacifying film 17 is brought into close contact with the back surface of the measurement sample 11 (here, the refractory metal 19 and the opaque material 21 are brought into close contact sequentially, but only the refractory metal or the opaque material may be brought into close contact. Thus, the heat that has passed through the measurement sample 11 can be received and moved according to diffusion heat transfer.

The laser beam generator 12 is sandwiched between the opacifying film 16 and the opacifying film 17 (specifically, between the refractory metal 18, the opaque material 20, the refractory metal 19, and the opaque material 21). Even when the measurement sample 11, that is, the heating object 22 is held in a high temperature atmosphere, for example, a ruby laser oscillator capable of injecting thermal energy exceeding the thermal fluctuation of the atmosphere to the surface can be used. .
The laser beam detector 13 detects the heating waveform (laser beam waveform) of the laser beam generated from the laser beam generator 12.
The half mirror 14 is formed of a base material having a material with extremely low laser light absorption and extremely high transparency. For example, a coating layer that reflects a predetermined amount of laser light from incident laser light and allows the remaining part to pass therethrough may be provided on the surface of the substrate.

Therefore, the optical axis of the light receiving part is adjusted so that the laser light generated from the laser light generating part 12 is reflected by the half mirror 14 and reaches the light receiving part (not shown) of the laser light detecting part 13. Thus, a part of the laser light emitted from the laser light generator 12 can be incident on the laser light detector 13 and the heating waveform of the laser light can be measured.
In addition, by matching the optical axis of the half mirror 14 with the central axis (along the thickness direction) of the heating object 22, the surface of the heating object 22 is irradiated with the laser light that has passed through the half mirror 14. Can be heated.

  The temperature measurement unit 15 needs to have a function capable of measuring the temperature change of the back surface of the heating object 22 irradiated with the laser light at high speed and with high accuracy. For example, a temperature detection sensor such as a thermocouple or a radiation thermometer. A temperature measuring device with can be used.

Further, the measuring device 10 obtains the temperature data on the back side from the signal output from the temperature measuring unit 15, and obtains the thermal diffusivity of the heat-permeable material from the temperature data, and the arithmetic processing unit 23 And an output device 24 for displaying the obtained thermal diffusivity.
The arithmetic processing unit 23 is a computer capable of calculating the thermal diffusivity of the heat-permeable material by performing each process of the A process to the E process, which will be described later, using a preset program. The computer is a conventionally known computer that includes a RAM, a CPU, a ROM, an I / O, and a bus for connecting these elements, but is not limited thereto.
For the output device 24, for example, a display device for a computer and a printing device can be used.

Next, a thermal diffusivity analysis method according to an embodiment of the present invention will be described with reference to FIGS.
The method for analyzing the thermal diffusivity of a translucent material is a method for analyzing the thermal diffusivity of a heat-permeable material using a laser flash method, and includes a preparation process and A processes to E processes. This will be described in detail below.

(Preparation process)
First, the measurement sample 11 is produced from the translucent material to be measured. Then, the high melting point metals 18 and 19 and the opaque materials 20 and 21 are arranged in close contact with each other on the front and back surfaces of the measurement sample 11 to form the heating object 22. Note that only the refractory metal or only the opaque material can be disposed in close contact with the front and back surfaces of the measurement sample 11 according to, for example, the measurement conditions of the thermal diffusivity.
Next, the heating object 22 is set in a sample holder provided in a sample chamber (not shown) of the measuring apparatus 10, and the atmosphere in the sample chamber is adjusted (for example, in a vacuum state).

Subsequently, the temperature in the sample chamber is controlled to be a preset measurement temperature, and when the temperature of the heating object 22 reaches the measurement temperature and is stabilized, the laser light is emitted from the laser light generator 12 to the half mirror 14. Fire towards.
Here, the emitted laser light reaches the half mirror 14, a part of the light amount of the laser light is reflected by the half mirror 14 and enters the laser light detection unit 13, and the waveform of the laser light is obtained. Data is input to the arithmetic processing unit 23. Further, the remaining laser light transmitted through the half mirror 14 reaches the surface of the heating object 22 and heats the surface.

When the surface of the heating object 22 is heated by the laser light, the thermal energy injected into the surface of the one opaque material 20 is conducted toward the back surface of the heating object 22. The temperature rises gradually.
The temperature change at this time is measured by, for example, the temperature measuring unit 15 including a radiation type thermometer, and the obtained temperature data is input to the arithmetic processing unit 23.

(1) Back surface temperature formula The back surface temperature T of a single layer sample is represented by Formula (1)-Formula (4).

Here, α: thermal diffusivity, h: bio number (dimensionless number representing radiation loss), Q: absorbed energy, ρ: density, c: specific heat, L: thickness, t: time, β _n : eigenvalue, t ₀ : characteristic time (t ₀ = L ² / (π ² α)).

In the above-described sample back surface temperature formula (1), the ratio of the size of n = 1 to 3 (second to fourth terms) to n = 0 (first term) is estimated.
Here, when the constant is m and the ratio of the magnitude of the n-th term to the first term (n = 0) at time t = mt ₀ is the case where the radiation loss is negligible (the temperature at which the radiation loss near room temperature etc. can be ignored). Corresponding to the region), given by the general formula (5).

  Table 1 shows the results of calculating the ratio of the value after the second term (n = 1) to the first term (n = 0) using the above equation (5).

From this, in the time (m ≧ 2) that is twice or more the characteristic time t ₀ , the second term (n = 1) is the main one, and the influence after the third term (n = 2) is small.

In the sample back surface temperature formula (1), α = 1.0 × 10 ⁻⁵ (m ² / s), L = 1 × 10 ⁻³ (m), h = 0.1, and n = 15 FIG. 2 shows the results obtained for the cases up to and n = 2. The horizontal axis in FIG. 2 is the time with reference to the characteristic time (t ₀ ), and the vertical axis is an equation in which the maximum back surface temperature is 1 when there is no radiation loss and the bio number h = 0. (1) is used.
From this, it can be confirmed that after irradiation with the laser light, the sum of up to n = 2 can be approximated with good accuracy in the sample back surface temperature equation (1) with t / t ₀ ≧ 1.5.

(2) Thermal diffusivity analysis method in the presence of leaked light As a sample back surface temperature formula when there is no radiation loss (bio number h = 0), a region where time is about 1.5 times or more of characteristic time (t ≧ 1) .5t ₀ ), the sample back surface temperature is approximated by equation (6).

  In a region where this approximation is established, the thermal diffusivity is given by equation (7).

T is temperature data on the back side of the measurement sample, Q is the absorption energy of the measurement sample, ρ is the density of the measurement sample, c is the specific heat of the measurement sample, L is the thickness of the measurement sample, and t is time.
Here, in order to confirm the method for obtaining the approximate thermal diffusivity, the data shown in Table 2 was used for examination. The back surface temperature is created using the above-described equation (1) and shown in FIG.

FIG. 4 shows the temperature data of the back surface of the sample in FIG. 3 normalized by the maximum value of each temperature.
Using this data, the thermal diffusivity analysis procedure will be described while examining the analysis method of the thermal diffusivity without using the data of the initial rising portion of the back surface temperature.

(Process A)
First, the approximate thermal diffusivity α on the condition that there is no radiation loss of the measurement sample 11 is calculated by the above-described equation (7) using the temperature data obtained with the lapse of the irradiation time of the laser light (see FIG. 5).
Next, the thermal diffusivity minimum value α _min that becomes minimum (becomes stable as the laser beam irradiation time elapses) at the rising portion of the back surface temperature (the region surrounded by the dotted circle shown in FIG. 5). Ask. Table 3 shows the time (t) for giving the thermal diffusivity minimum value α _min and the value obtained by dividing the time by the characteristic time (t ₀ ).

The time (t) for giving the thermal diffusivity minimum value α _min is characterized by being behind the half time (t _1/2 ) when the bio number is relatively small. In this case, there is a minimum value of thermal diffusivity in the time domain that is not easily affected by the leaked light of the laser beam, and even if there is some leaked light, the thermal diffusion is smaller than the conventional method using half time. It is considered possible to obtain the rate.
The half time (t _1/2 ) is defined as the time required for the back side of the measurement sample 11 to rise to half the maximum temperature after the laser light irradiation.

Here, there is a relationship shown in Formula (8) between the half time (t _1/2 ) and the characteristic time (t ₀ ).

Note that t and t _1/2 are substantially equal when the bio number h is 0.05, and t is greater than t _1/2 when the bio number is smaller than this.

(Process B)
Using the thermal diffusivity minimum value α _min , the half time t _1/2 is obtained by equation (9) (see Table 3).
Since the half time t _1/2 is not an actual measurement value and is obtained using the equation (9) as described above, it is also referred to as a half time equivalent t _1/2 here.

(Process C)
A decay time constant τ in the decay region of the temperature data is obtained (see Table 3).
The decay time constant τ is defined by equation (10).

(D process)
The radiation loss correction coefficient _krhl of the thermal diffusivity is obtained using the half time equivalent t _1/2 obtained in the above-mentioned B process and the decay time constant τ obtained in the C process.
For example, the radiation loss correction coefficient k _rhl can be calculated using the equation (11) described in JIS R1611 (2010) (see Table 3).

Note that the calculation of the radiation loss correction coefficient k _rhl is not limited to the calculation using the above equation (11), and for example, using another equation described in the above JIS R1611 (2010). You can ask for it.

(E process)
The thermal diffusivity α _corrected of the heat-permeable material is _obtained by multiplying the minimum value α _min of the thermal diffusivity obtained in the aforementioned step A by the radiation loss correction coefficient k _rhl obtained in the step D. That is, α _corrected = k _rhl × α _min (see Table 3).
The obtained thermal diffusivity α _corrected has an error of about 1% with respect to the true value.
Although the amount of temperature data used for the analysis of the thermal diffusivity is 100 points, it is considered that the accuracy of the thermal diffusivity can be further improved by using the usual temperature data of several thousand points.

From the above results, it has been clarified that the thermal diffusivity α _corrected of the heat-permeable material is obtained by the analysis method described above.
From this, it is considered that the thermal diffusivity minimum value α _min obtained in the above-described Step A is the thermal diffusivity obtained by the half-time method of Expression (12).

The analysis of the thermal diffusivity of the heat-transmitting material described above is suitable when it is performed at a temperature in the process where the opaque material 20 and the refractory metal 18 disappear from the measurement sample 11 due to the influence of the heating temperature and laser light. . Specifically, it is suitable when the analysis temperature of the thermal diffusivity of the heat-permeable material is higher than 1500 ° C., more preferably 1600 ° C. or higher, more preferably 1700 ° C. or higher. In addition, although it does not specifically limit about an upper limit, Actually, it is about 2000 degreeC, for example.
In addition, when only the refractory metal or only the opaque material is placed in close contact with the front and back surfaces of the measurement sample 11, the analysis of the thermal diffusivity of the heat-permeable material is based on the temperature at which the refractory metal or opaque material disappears. Suitable when done.

Next, examples carried out for confirming the effects of the present invention will be described.
Here, a description will be given of a result obtained by measuring an alumina-based material (heat-permeable material) at 1800 ° C. and analyzing a thermal diffusivity.
First, a measurement sample was prepared using an alumina-based material. Next, Nb, which is a refractory metal, was sputtered on the front and back surfaces of the measurement sample, and then a fine powder was applied onto the Nb film to form a blackened film (opaque material) (an opaque film was formed). did).
Subsequently, the surface of the measurement sample was irradiated with laser light, and the thermal diffusivity was analyzed while sequentially measuring the temperature. An example of the temperature data on the back side of the measurement sample obtained at this time is shown in FIG.

In the analysis of the thermal diffusivity, the Nb film began to disappear at 1800 ° C., and the leaked light was confirmed immediately after the laser beam irradiation. Therefore, the thermal diffusivity could not be obtained by the usual analysis method. Although it cannot be asserted that the temperature data excluding the leakage light region immediately after irradiation represents the back surface temperature, Nb remains on the front and back surfaces of the sample after measurement, and temperature data close to the back surface temperature is measured. It is speculated that there is.
Using this temperature data, the thermal diffusivity is obtained by applying the analysis method described above.

1) Approximate thermal diffusivity α is calculated using the above equation (7) for the temperature data on the back side of the measurement sample. The result is shown in FIG.
2) Although the value of the approximate thermal diffusivity α is large for a short time after irradiation due to the influence of leakage light, the approximate thermal diffusivity α is stabilized after a certain period of time. In this time domain, the minimum thermal diffusivity α _min when there is no radiation loss is obtained. In addition, in the case of FIG. 7, it becomes about 1.40 * 10 < ^-6 > (m < ² > / s) (above, A process).
3) Using the above-described minimum thermal diffusivity α _min , half time equivalent t _1/2 is calculated by equation (9) to obtain t _1/2 = 6.67 × 10 ⁻² (s) (B Process).

4) The attenuation time constant τ is obtained from the temperature data in the attenuation region of FIG. 6 using Equation (10) to obtain τ = 1.96 (s) (step C).
5) Using the above half-time equivalent t _1/2 and the decay time constant (τ), the radiation loss correction coefficient k _rhl is calculated by the equation (11) to obtain k _rhl = 0.916 (step D).
6) By multiplying the above-mentioned minimum thermal diffusivity α _min by the radiation loss correction coefficient k _rhl , 1.28 × 10 ⁻⁶ (m ² / s) can be obtained as the thermal diffusivity α _corrected of the alumina-based material. Yes (E step).
Here, the case where the opaque film is made of a refractory metal (Nb) and an opaque material (blackened film) has been described, but the opaque film is made of only a refractory metal or only an opaque material. In some cases, the thermal diffusivity α _corrected was obtained.

As described above, the present invention has been described with reference to the embodiment. However, the present invention is not limited to the configuration described in the above embodiment, and the matters described in the scope of claims. Other embodiments and modifications conceivable within the scope are also included. For example, a case where the thermal diffusivity analysis method of the present invention is configured by combining a part or all of the above-described embodiments and modifications is also included in the scope of the right of the present invention.
In the above embodiment, the thermal diffusivity analysis method is based on the disappearance process of an opaque material such as an opaque material or a refractory metal film formed on a heat-transmitting material, that is, some laser light leaks. Although the case where it applied to the condition was demonstrated, it is applicable also to the normal analysis without the leakage light of a laser beam.
In the embodiment, the case where the measurement sample is made of a heat-permeable material has been described. For example, the measurement sample is made of a metal material, graphite, a composite material, or a ceramic material other than the above-described ceramic material. It can also be configured. In this case, it is preferable to form a material (for example, a blackened film) that increases the absorption rate of the laser beam energy on the front and back surfaces of the measurement sample as necessary.

10: measurement device, 11: measurement sample, 12: laser light generation unit, 13: laser light detection unit, 14: half mirror, 15: temperature measurement unit, 16, 17: opaque film, 18, 19: refractory metal , 20, 21: opaque material, 22: heating object, 23: arithmetic processing unit, 24: output device

Claims (5)

Using the temperature data on the back surface side of the measurement sample obtained by irradiating laser light from the front surface side of the measurement sample by forming an opaque film on the front and back surfaces of the measurement sample made of a heat-permeable material, In the method of analyzing the thermal diffusivity of a heat-permeable material,
Using the temperature data obtained with the lapse of the laser light irradiation time, an approximate thermal diffusivity α is obtained on the condition that there is no radiation loss of the measurement sample, and the stable state decreases with the lapse of the laser light irradiation time. A step of setting the approximate thermal diffusivity α to be a thermal diffusivity minimum value α _min ;
B step for obtaining a half time t _1/2 required for the back side of the measurement sample to rise to half the maximum temperature from the thermal diffusivity minimum value α _min ;
C step for obtaining the decay time constant τ in the decay region of the temperature data;
D step for _obtaining a radiation loss correction coefficient k _rhl using the half time t _1/2 obtained in the step B and the decay time constant τ obtained in the step C;
And E step of _obtaining the thermal diffusivity of the heat-permeable material by multiplying the minimum value α _min of the thermal diffusivity obtained in the step A by the radiation loss correction coefficient _krhl obtained in the step D. Characteristic thermal diffusivity analysis method. The thermal diffusivity analysis method according to claim 1, wherein the approximate thermal diffusivity α of the step A is obtained using the following equation.

Here, T is temperature data on the back side of the measurement sample, Q is the absorbed energy of the measurement sample, ρ is the density of the measurement sample, c is the specific heat of the measurement sample, L is the thickness of the measurement sample, and t is time.   3. The thermal diffusivity analysis method according to claim 1, wherein the thermal diffusivity of the heat-permeable material is analyzed at a temperature at which the opaque film disappears from the measurement sample. Analysis method of diffusivity.   The thermal diffusivity analyzing method according to any one of claims 1 to 3, wherein the opaque film is formed of one or both of a refractory metal and an opaque material. Rate analysis method. In the method of analyzing the thermal diffusivity, using the temperature data on the back side of the measurement sample obtained by irradiating laser light from the front side of the measurement sample,
Using the temperature data obtained with the lapse of the laser light irradiation time, an approximate thermal diffusivity α is obtained on the condition that there is no radiation loss of the measurement sample, and the stable state decreases with the lapse of the laser light irradiation time. A step of setting the approximate thermal diffusivity α to be a thermal diffusivity minimum value α _min ;
B step for obtaining a half time t _1/2 required for the back side of the measurement sample to rise to half the maximum temperature from the thermal diffusivity minimum value α _min ;
C step for obtaining the decay time constant τ in the decay region of the temperature data;
D step for _obtaining a radiation loss correction coefficient k _rhl using the half time t _1/2 obtained in the step B and the decay time constant τ obtained in the step C;
A thermal diffusion characterized by comprising a step E of multiplying the minimum value α _min of the thermal diffusivity obtained in the step A by the radiation loss correction coefficient _krhl obtained in the step D to obtain a thermal diffusivity. Rate analysis method.

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