JP5993735B2 - Thermal constant measurement method - Google Patents

Description

  The present invention relates to a method for measuring a thermal constant of a sample using a thermal resonance phenomenon.

  In the design of industrial equipment such as heat exchangers, electronic devices, and heat sinks, physical properties such as thermal diffusivity and thermal conductivity of materials are indispensable, and a method of measuring these using the thermal conduction phenomenon Is widely known. For example, Patent Document 1 proposes a method for calculating the thermal diffusivity and the thermal conductivity from the phase difference between the AC temperature on the surface of the sample and the AC temperature on the back surface. More specifically, in the method in Patent Document 1, first, a sample in which metal film resistors of the same material are provided on the front surface and the back surface is prepared, and AC power is supplied to the metal film resistor on the front surface side to heat the sample. Then, the gradient in the characteristic line of the phase difference between the AC temperature signal due to the resistance change of the metal film resistance on the back side and the AC power applied to the metal film resistance on the front side is obtained, and the thermal diffusivity of the sample is calculated based on this gradient. calculate. Further, the thermal conductivity is calculated based on the thermal diffusivity, the AC temperature signal and the AC power described above.

JP-A-7-103921

  However, in the method as described above, it is difficult to measure the phase difference between the AC temperature on the front surface and the AC temperature on the back surface, particularly in the case of a small sample, a sample having a complicated shape, or a sample having a high thermal conductivity. There has been a problem that heat constants such as thermal diffusivity and thermal conductivity cannot be measured accurately.

  Then, this invention makes it a subject to provide the method which can measure the thermal constant of a sample correctly.

  The present invention is for solving the above-described problem, and is a method for measuring the thermal constant of a sample using a thermal resonance phenomenon, the method of determining a mode of thermal resonance generated in the sample, A step of generating a thermal resonance of the determined mode by instantaneously heating a first portion located in the abdomen of the thermal resonance of the determined mode; Measuring the temperature of the second portion located in the abdomen of the thermal resonance of the selected mode for a predetermined time, calculating the attenuation coefficient based on the time change of the temperature of the second portion, and based on the attenuation coefficient Calculating the thermal diffusivity of the sample.

  The “thermal resonance phenomenon” used in the above method means that a specific temperature distribution depending on the shape of the sample spatially occurs in the sample when heat is applied to the sample from the outside. The temperature distribution reaches equilibrium with time. According to the above method, the thermal diffusivity of the sample is obtained by generating thermal resonance of a predetermined mode in the sample to be measured and examining only the temporal change in the temperature of the second part located at the abdomen of this thermal resonance. Can be calculated. That is, in the above method, it is not necessary to obtain the phase difference between the temperature of the heated portion of the sample and the temperature of the other portion, unlike the conventional method using the heat conduction phenomenon. Regardless of the size, shape, and thermal conductivity, the thermal constant can be accurately measured.

  In the above method, the first portion may be a dot-like portion located at the antinode of the thermal resonance of the determined mode.

  Alternatively, in the above method, the first portion may be a portion extending in a band shape along the abdomen of the thermal resonance of the determined mode.

  In the above method, the second portion may be a dot-like portion located at the abdomen of the determined mode of thermal resonance.

  Or in the said method, a 2nd part can also be made into the part extended in strip | belt shape along the abdominal part of the thermal resonance of the determined mode.

  In the above method, it is preferable that the first portion is instantaneously heated by irradiation with a pulse laser.

  In the above method, a black body can be provided on the upper surface of the sample.

  In this case, the black body may be provided only at a position in the sample that coincides with the determined abdomen of the thermal resonance mode.

  The method may further include a step of calculating the thermal conductivity of the sample based on the thermal diffusivity.

  According to the present invention, the thermal constant of a sample can be accurately measured.

It is a schematic diagram of a measuring device concerning each embodiment of the present invention. It is a partial schematic diagram of a measuring device concerning each embodiment of the present invention. It is a conceptual diagram (figure in a certain sample size ratio) in the case of seeing the sample concerning each embodiment of the present invention from the upper part. It is a schematic perspective view which shows the excitation position and detection point of the sample which concern on each embodiment of this invention, and a graph which shows the example of calculation of the time change of the temperature change rate of a sample using dimensionless time. In the measuring method which concerns on 1st Embodiment of this invention, it is a schematic perspective view which shows the excitation part and detection part of a sample, and the graph which shows the change of the reflectance of a sample. It is a schematic perspective view which shows the excitation part and detection part of the sample which concern on 2nd Embodiment of this invention. It is a schematic perspective view which shows the excitation part and detection part of the sample which concern on 3rd Embodiment of this invention. It is a schematic perspective view which shows the excitation part and detection part of the sample which concern on 4th Embodiment of this invention. It is a schematic perspective view which shows the excitation part and detection part of the sample which concern on 5th Embodiment of this invention. In the measuring method which concerns on the modification of each said embodiment, it is a schematic perspective view which shows the excitation part and detection part of a sample, and the graph which shows the change of the reflectance of a sample. It is a schematic plan view of the sample which concerns on the modification of each said embodiment. It is a flowchart which shows the measuring method which concerns on each embodiment to this invention. It is a graph which shows the simulation result which concerns on 1st Example of this invention. It is a graph which shows the simulation result which concerns on 2nd Example of this invention. It is a graph which shows the simulation result which concerns on 3rd Example of this invention.

{First embodiment}
Hereinafter, a first embodiment of the present invention will be described with reference to the drawings. In FIG. 3, the direction perpendicular to the paper surface is the Z-axis direction, the direction along the long side of the sample is the X-axis direction, the direction perpendicular to these is the Y-axis direction, and the same coordinate system is used hereinafter.

  First, the measuring apparatus used in order to implement the thermal constant measuring method according to the first embodiment will be described. As shown in FIG. 1, the measurement apparatus 10 includes an excitation light source 1 that emits excitation light toward the sample S, a detection light source 2 that emits detection light toward the sample S, and the reflectance of the detection light at the sample S. And a measuring instrument 3 for measuring. The measuring apparatus 10 includes reflecting mirrors 4a and 4b that reflect the excitation light and an objective lens 5a that collects the excitation light. Furthermore, the measuring apparatus 10 includes a reflecting mirror 4c that reflects the detection light, a beam splitter 6 that separates the detection light, an objective lens 5b that collects the detection light, and reflecting mirrors 4d and 4e that reflect the reflected light, It has.

  The excitation light source 1 is an Nd: YAG laser oscillator, and emits excitation light L1 that is a pulse laser as shown in FIG. The excitation light L1 is applied to the sample S via the reflecting mirrors 4a and 4b and the objective lens 5a, and thereby thermal resonance described later occurs in the sample S. The pulse width of the excitation light L1 is preferably shorter, and can be, for example, 2 nanoseconds or less. The repetition frequency of the excitation light L1 is preferably adjusted so that the excitation light L1 is not irradiated again on the sample S while the thermal resonance in the sample S does not reach an equilibrium state.

  The detection light source 2 is a titanium sapphire laser oscillator, and emits detection light L2 that is a pulse laser as shown in FIG. The detection light L2 enters the beam splitter 6 via the reflecting mirror 4c and is divided by the beam splitter 6. Then, a part of the detection light L21 enters the measuring device 3, and a part of the detection light L22 is irradiated onto the sample S through the objective lens 5b. The sample S reflects the detection light L22, and this reflected light L3 enters the measuring device 3 through the objective lens 5b, the beam splitter 6, and the reflecting mirrors 4d and 4e. The reflectance of the detection light L21 is the same as the reflectance of the detection light L22.

  The measuring device 3 measures the reflectance of the detection light L22 on the sample S based on the difference between the intensity of the incident reflected light L3 and the intensity of the detection light L21. Since the reflectance of the light in the sample S has a correlation with the temperature, the temporal change in the temperature of the portion of the sample S irradiated with the detection light L22 can be derived from the temporal change in the reflectance of the detection light L22.

  The sample S is formed in a rectangular parallelepiped shape using a material whose thermal conductivity is isotropic. As shown in FIG. 2, the sample S may be supported by a temperature regulator 7 when measuring the thermal constant. By exchanging heat between the temperature regulator 7 and the sample S, the temperature control of the sample S is performed. The temperature regulator 7 is preferably in contact with a position corresponding to a node portion of the thermal resonance so that a heat flow caused by thermal resonance described later does not leak to the outside of the sample S through the temperature regulator 7. In FIG. 2, the temperature regulator 7 is in contact with the sample S at positions corresponding to nodes N5a and N5b of a thermal resonance MODE 5 (FIG. 3E) described later.

The sample S is not particularly limited, but may have a small size and a high thermal conductivity, such as synthetic diamond, which has conventionally been difficult to measure the thermal constant. For example, the sample S has at least a length in the X-axis direction (width direction) of 1 mm or more, a length in the Y-axis direction (depth direction) of 1 mm or more, and a length in the Z-axis direction (height direction). It may be 0.2 mm or more. Moreover, the high thermal conductivity here means a thermal conductivity of 1000 W / (m ² · K) or more. However, since the dimensions and thermal conductivity that have a significant effect are not individually specified, they are determined by the relative relationship between the attenuation coefficient of the mode to be measured and the sample size. Even dimensions can be measured in principle. Specifically, if dimensionless time τ and dimensionless attenuation coefficient λ ′ are introduced, the attenuation behavior depends only on the sample dimensions, regardless of the material properties of the sample, and can be measured from the sensitivity limit of the temperature measurement method. The relationship between the sample size and the thermal conductivity is determined. Here, there is a relationship of Equation (1) between τ and the dimensional time t, and a relationship of Equation (2) between λ ′ and the dimensional attenuation coefficient λ. L is a representative length, for example, the length of the side along the X-axis direction. It does not depend on the material of the sample.

For example, FIG. 4 shows a calculation example by a numerical simulation using a finite difference method of the time change of the temperature change rate using dimensionless time (when the vertical axis is 0, it is the equilibrium temperature). In the example shown in FIG. 4, the center of the side (back side) along the X-axis direction of the aluminum sample is the excitation position, the detection point 1 is the same position as the excitation position, the detection point 2 is the center of the upper surface, and the apex is on the lower side of the lower surface. Detection point 3 is set. Assuming that the measurement method can sense a temperature change of about 10 ⁻⁴ as a ratio, it is possible to measure the decay process occurring in the range of about τ = 0.6 in the non-dimensional temperature range. Based on the relationship of equation (1), for example, if the thermal conductivity κ of the sample is small and, as a result, the time to reach thermal equilibrium is long (λ value is small), the sample dimension L can be reduced. It is possible to find conditions under which the thermal resonance attenuation can be observed. By using such a numerical simulation, it is possible to determine an appropriate sample size.

  Hereinafter, a method for measuring the thermal constant of the sample S using the measuring instrument 10 configured as described above will be described.

  First, the mode of thermal resonance generated in the sample S to be measured is determined. FIG. 3 is a conceptual diagram of thermal resonance when the sample S having a certain size ratio of the three sides is viewed from above. The order in which the MODE patterns appear depends on the sample size ratio. The hatching of the node and abdomen in FIG. 3 is shown in a simplified manner, but in reality, the amplitude of the temperature change is continuously distributed from the node to the abdomen. Cannot be defined. When the thermal resonance is excited at a location where the amplitude of the temperature change is large, the excitation position and the measurement position are technically regarded as the abdomen as long as the temperature change over time can be measured accurately. As shown in FIG. 3, there are a plurality of modes of thermal resonance that can occur in the sample S, but from the viewpoint of the length of time until thermal resonance reaches an equilibrium state (selectivity of modes of thermal resonance), attenuation is performed. It is preferable to select a mode in which the coefficient is expected to be small. For this reason, in the first embodiment, thermal resonance (MODE 5 (FIG. 3 (e)), MODE 10 (FIG. 3 (j)), and MODE 11 (MODE 11) that can occur in the sample S when an excitation unit E 5 a described later is excited. In FIG. 3 (k))), the thermal resonance of MODE5, which is expected to have the smallest attenuation coefficient, was selected. In FIG. 3, l, m, and n are the number of periods of the temperature distribution wave in the X-axis, Y-axis, and Z-axis directions, respectively. For example, in the case of MODE5, l = 2, m = 0, n = Since it is 0, it means that a wave of temperature distribution is generated only in the X-axis direction and the number of cycles of the wave is 2.

  Next, as shown in FIGS. 1 and 5, the sample S is set in the measurement apparatus 10, and the dot-like portion (detection unit) D <b> 5 a located in the thermal resonance abdomen A <b> 5 a of MODE <b> 5 (FIG. 3E) Preparation for measuring the reflectance of the detection light L22 is performed. Specifically, in the measurement apparatus 10, the detection light L 2 that is a pulse laser is emitted from the detection light source 2, the detection light L 21 is incident on the measuring device 3, and the detection light L 22 is irradiated on the detection unit D 5 a of the sample S. Keep this state. At this time, the measuring instrument 3 measures the reflectance of the detection light L22 in the detection unit D5a when thermal resonance does not occur in the sample S. The detection unit D5a corresponds to the “second part” in the present invention.

  Subsequently, as shown in FIG. 5, the excitation light L1, which is a pulse laser, is applied to the dot-like part (excitation part) E5a located in the abdominal part A5b of the thermal resonance of MODE 5 (FIG. 3E) in the sample S. Irradiated by the excitation light source 1. Thereby, the excitation part E5a of the sample S is instantaneously heated, and thermal resonance of the MODE 5 occurs in the sample S. At this time, since the excitation unit E5a is a node of thermal resonance of MODEs 1-3, 6-9, and 12, no thermal resonance of MODEs 1-3, 6-9, and 12 occurs in the sample S. On the other hand, in the sample S, thermal resonance of MODE 10 (FIG. 3 (j)) and MODE 11 (FIG. 3 (k)) can occur, but the thermal resonance of MODE 10 and MODE 11 has a large damping coefficient and is higher than that of MODE 5. Equilibrium is reached as soon as possible. As shown in the equation (6), when the values of l, m, and n are increased, the mode attenuation coefficient is also increased. For this reason, the thermal resonance of MODE 10 and MODE 11 generated in the sample S has little influence on the measurement of the reflectance corresponding to the thermal resonance of MODE 5. The excitation part E5a corresponds to the “first part” in the present invention.

  When thermal resonance of MODE 5 occurs in the sample S, as shown in FIG. 5, the reflectance of the detection light L22 applied to the detection unit D5a changes. The measuring device 3 measures the change in the reflectance of the detection light L22 applied to the sample S based on the difference between the intensity of the reflected light L3 and the intensity of the detection light L21 before being applied to the sample S. The change in the reflectance of the detection light L22 in the detection unit D5a increases instantaneously when thermal resonance of MODE 5 occurs in the sample S, and then reaches an equilibrium state over time.

  After the change in the reflectance of the detection light L22 in the detection unit D5a reaches the equilibrium state, the detection unit during this period is based on the time change of the reflectance change from the occurrence of thermal resonance to the equilibrium state in the sample S. The time change of the temperature at D5a is derived. The change rate of the temperature is set as an attenuation coefficient corresponding to the thermal resonance of MODE5.

  Here, a general formula for calculating the thermal constant of the sample will be described. When a heat conduction equation such as Equation (3) is considered, a general solution in the case of a rectangular parallelepiped sample is represented by Equation (4). That is, in the case of a rectangular parallelepiped sample, when heat is applied from the outside, the temperature distribution in the sample reaches an equilibrium state according to Equation (4). In equation (3), ρ is density, C is specific heat, κ is thermal conductivity, T is temperature, and t is time.

In the formula (4), l, m, n are, X-axis, respectively, Y-axis, Z-axis direction of the periodicity of the _{wave, A lmn} is the _{area, k l, k m, k} n is, X-axis, respectively, Y-axis , _Wave number in the Z-axis direction, λ _lmn is an attenuation coefficient. _{k l,} k m, k _n is Equation (5) ~ (7), λ lmn is expressed by Equation (8). In Expression (8), L _x , L _y , and L _x are the lengths of the sample in the X-axis, Y-axis, and Z-axis directions, κ is the thermal conductivity, and κ / ρC is the thermal diffusivity.

  Returning to the method for measuring the thermal constant of the sample S in the first embodiment, the description will be continued. In the first embodiment, MODE 5 is selected as the mode of thermal resonance generated in the sample S. As shown in FIG. 3E, the wave number of thermal resonance of MODE 5 is l = 2, m = 0, and n = 0. Therefore, when this is substituted into the above equation (8), the following equation (9 ) Is derived. In the first embodiment, since MODE5 with m = 0 and n = 0 is selected, the second and third terms in the equation (8) are zero, but other modes are selected. In this case, at least one of the second term and the third term in the equation (8) becomes larger than zero.

As described above, since the attenuation coefficient corresponding to heat the resonance of MODE5 is already measured, by substituting the length in the X-axis direction of the attenuation coefficient and the sample S in lambda ₂₀₀ and L _x of formula (9) The thermal diffusivity κ / ρC is calculated.

  Furthermore, if the density ρ and specific heat C of the sample S are known, the thermal conductivity κ can be calculated from the thermal diffusivity κ / ρC.

  As described above, in the first embodiment, thermal diffusivity and thermal conductivity of the sample S are calculated by generating thermal resonance of the MODE 5 in the sample S and examining only the time change of the temperature of the detection unit D5a. be able to. For this reason, there is no need to obtain the phase difference between the temperature of the heated portion of the sample and the temperature of the other portions, unlike the conventional method using the heat conduction phenomenon, and the size, shape, and heat of the sample. Regardless of the magnitude of conductivity, the thermal diffusivity and thermal conductivity can be accurately measured.

{Second Embodiment}
Hereinafter, a second embodiment of the present invention will be described.

  The second embodiment is the same as the first embodiment except that there are a plurality of excitation portions in the sample S. In the following embodiments, the same components as those in the first embodiment are denoted by the same reference numerals and description thereof is omitted.

  As shown in FIG. 6, in the second embodiment, as in the first embodiment, the excitation light source 1 (FIG. 1) is applied to the excitation unit E5a located in the thermal resonance antinode A5b of MODE 5 (FIG. 3 (e)). The excitation light L1 is irradiated. At the same time, the excitation light L1 from the excitation light source 1 is also applied to the excitation part E5b located in the thermal resonance antinode A5a of the MODE5. Thereby, thermal resonance of MODE 5 occurs in the sample S. The method for irradiating the excitation light L1 simultaneously to the excitation parts E5a and E5b is not particularly limited, and the excitation light L1 from one excitation light source 1 may be branched halfway to irradiate the excitation parts E5a and E5b. Alternatively, the excitation light L1 from the two excitation light sources 1 may be applied to the excitation units E5a and E5b, respectively. However, when a plurality of excitation lights are used, it is desirable that they are synchronized (phases are aligned on the sample surface).

  Thus, in the second embodiment, in the sample S, the excitation light L1 is irradiated not only on the excitation part E5a located in the abdominal part A5b of the thermal resonance of MODE5 but also on the excitation part E5b located in another abdominal part A5a. For this reason, in the sample S, the thermal resonance of MODE 5 can be reliably generated.

  In addition, in 2nd Embodiment, although the excitation part demonstrated the example of two places, the excitation part may be three or more places. However, each excitation part needs to be located in the abdominal part of the thermal resonance of the selected mode.

{Third embodiment}
Hereinafter, a third embodiment of the present invention will be described.

  The third embodiment is the same as the first embodiment except for the shape of the excitation part in the sample S. As shown in FIG. 7, in the third embodiment, in the sample S, a band-like portion along the abdominal portion A5b of thermal resonance in MODE 5 (FIG. 3 (e)) is defined as an excitation portion E5c. The entire excitation section E5c is irradiated with the strip-shaped excitation light L1 from the excitation light source 1 (FIG. 1), and thermal resonance of MODE 5 is generated in the sample S.

  In the third embodiment, an example in which the excitation part is one has been described. However, in the sample S, the other abdominal part A5a and / or A5c is also provided with a belt-like excitation part, and the excitation light L1 is simultaneously supplied to a plurality of excitation parts. Irradiation is also possible. Further, in the sample S, a slit may be formed along each band-like excitation part.

{Fourth embodiment}
The fourth embodiment of the present invention will be described below.

  The fourth embodiment is the same as the first embodiment except that there are a plurality of detection units in the sample S. As shown in FIG. 8, in the fourth embodiment, as in the first embodiment, the detection light source 2 (FIG. 1) is applied to the detection unit D5a located in the thermal resonance antinode A5a of MODE 5 (FIG. 3 (e)). The detection light L22 is irradiated. At the same time, in the sample S, the detection light L22 from the detection light source 2 is also radiated to the detection part D5b located in the abdominal part A5b of the thermal resonance of MODE5. In addition, the method of irradiating the detection light L22 to the detection units D5a and D5b at the same time is not particularly limited, and the detection light L22 may be branched on the way to irradiate the detection units D5a and D5b, or two detection light sources The detection light L22 from 2 may be applied to the detection units D5a and D5b, respectively.

  In the sample S, thermal resonance of the MODE 5 is generated by irradiation of the excitation light L1, so that the measuring device 3 changes the reflectance of the detection light L22 in the detection unit D5a and the reflectance of the detection light L22 in the detection unit D5b. Get change and. Thereafter, an attenuation coefficient is calculated based on a change in reflectance in the detection unit D5a, and an attenuation coefficient is calculated based on a change in reflectance in the detection unit D5b.

  As described above, in the fourth embodiment, two attenuation coefficients are calculated based on the reflectance changes in the two detection units D5a and D5b. In the sample S, thermal resonance of modes other than the selected MODE 5 may also occur, but it can be confirmed that the calculated attenuation coefficient corresponds to the MODE 5 by comparing the two attenuation coefficients. Thereby, the reliability of the calculated attenuation coefficient is improved, and as a result, the reliability of the thermal diffusivity and thermal conductivity calculated from the attenuation coefficient is also improved.

  In addition, in 4th Embodiment, although the detection part demonstrated the example of two places, the detection part may be three or more places. However, each detection part needs to be located in the abdominal part of the thermal resonance of the selected mode.

{Fifth embodiment}
The fifth embodiment of the present invention will be described below.

  The fifth embodiment is the same as the first embodiment except for the shape of the detection unit in the sample S. As shown in FIG. 9, in the fifth embodiment, in the sample S, a band-shaped portion along the abdominal portion A5a of the thermal resonance of MODE 5 (FIG. 3E) is set as a detection unit D5c. The entire detection unit D5c is irradiated with the band-shaped detection light L22 from the detection light source 2 (FIG. 1), and a change in the reflectance of the detection light L22 in the detection unit D5c when the sample 5 undergoes thermal resonance of MODE5 is measured. Get by 3.

  In the fifth embodiment, an example in which one detection unit is provided has been described. However, in the sample S, other abdominal portions A5b and / or A5c are also provided with band-like detection units, and the detection light L22 is simultaneously supplied to a plurality of detection units. Irradiation is also possible.

  In 2nd-5th embodiment, although the case where the shape and number of an excitation part and a detection part differ was demonstrated separately, the excitation part and detection part of 2nd-5th embodiment can be combined suitably. For example, the sample S may be provided with a plurality of point-like excitation parts and one band-like detection part, or may be provided with one band-like excitation part and a plurality of point-like detection parts. Also good. In addition, a plurality of excitation units and detection units may exist, and the shape may be a dot shape or a belt shape. Further, in the sample S, a point-like excitation part and a band-like excitation part may be mixed, or a point-like detection part and a band-like detection part may be mixed.

  The first to fifth embodiments of the present invention have been described above, but the present invention is not limited to the above-described embodiments, and various modifications can be made without departing from the spirit of the present invention.

  For example, in each of the above embodiments, MODE 5 (FIG. 3E) is selected as the mode of thermal resonance generated in the sample S, but the time change of the temperature of the portion corresponding to the abdomen of thermal resonance is accurately measured. Other modes may be selected if possible. For example, as shown in FIG. 10, when MODE 1 (FIG. 3A) is selected as the mode of thermal resonance to be generated in the sample S, the excitation light L1 is applied to the excitation unit E1a located at the abdominal part A1a of thermal resonance of MODE 1. Irradiation excites thermal resonance of MODE1, and the reflectance of the detection light L22 may be measured by the detection unit D1a located in the abdomen A1a. When thermal resonance of a plurality of modes occurs in the sample S, the thermal resonance of the mode with a large attenuation coefficient reaches an equilibrium state relatively quickly, and it is difficult to measure the time change of temperature. It is preferable to select a mode that is as small as possible. From the graphs shown in FIGS. 5 and 10, the reflectance corresponding to the thermal resonance of MODE 1 is slower to reach the equilibrium state than the thermal resonance of MODE 5, and the attenuation coefficient in the thermal resonance of MODE 1 is the thermal resonance of MODE 5. It can be seen that it is smaller than the attenuation coefficient at.

  In each of the above embodiments, only the thermal resonance of MODE 5 (FIG. 3E) is selectively excited and detected in the sample S. However, the thermal resonance of a plurality of modes is selectively excited and detected. You can also. For example, as shown in FIG. 5, when the excitation light E1 is irradiated to the excitation part E5a of the sample S, the thermal resonance of MODE5, MODE10 (FIG. 3 (j)), and MODE11 (FIG. 3 (k)) is applied to the sample S. Will occur. For each of MODE5, MODE10, and MODE11, when the change over time of the reflectance of the detection light L22 in the portion corresponding to the abdomen of thermal resonance in the sample S is measured, the attenuation coefficients of MODE5, MODE10, and MODE11 can be obtained.

  In each of the above embodiments, the detection light source 22 is irradiated with the detection light L22, which is a pulse laser, and the reflectance is measured to derive the temperature of the sample S. However, the present invention is not limited to this. For example, you may measure the temperature of the detection part of the sample S using sensors, such as a thermocouple.

  In each of the above embodiments, the excitation light source 1 irradiates the excitation part with the excitation light L1 that is a pulse laser. However, the present invention is not limited to this as long as thermal resonance in a predetermined mode can be excited in the sample.

  Further, as shown in FIG. 11, a black body 8 for absorbing and radiating heat given from the outside can be provided on the upper surface of the sample S. As shown in FIG. 11, the black body 8 may be provided only on the abdomen of the thermal resonance mode generated in the sample S, but may be provided on the entire upper surface of the sample S. Moreover, since it is only necessary to instantaneously heat the portion corresponding to the abdominal part of the thermal resonance in the sample S via the black body 8, the points described in the first embodiment are applied to the black body 8. Excitation light may be irradiated, or strip excitation light as described in the third embodiment may be applied.

  In each of the above embodiments, the sample S is formed of a material whose thermal conductivity is isotropic, but the material of the sample is not particularly limited. Even for a sample formed of a material whose thermal conductivity is anisotropic, the thermal constant can be measured by utilizing thermal resonance of a plurality of modes. For example, in a sample having two independent thermal conductivities, if two modes of thermal resonance are generated to obtain attenuation coefficients corresponding to the respective modes, these two thermal conductivities can be determined. it can.

Moreover, in each said embodiment, although the thermal constant of the rectangular parallelepiped sample S was measured, the thermal constant of the sample of a complicated shape can also be measured. In this case, although the above equation (4) is not applicable, for example, by solving the eigenvalue problem based on the heat conduction equation of the above equation (3) by a known method such as a finite element method or a spectrum method, the temperature distribution of the sample, That is, a mode of thermal resonance that can occur in the sample may be obtained. If the mode of thermal resonance generated in the sample is determined, the thermal diffusivity and the thermal conductivity of the sample can be obtained from the attenuation coefficient based on the time variation of the measured temperature, as in the above embodiments. Specifically, if a dimensionless eigenvalue of a measurement target mode having a certain shape obtained by solving the eigenvalue equation is set to −λ, a measurable dimensional attenuation coefficient λ _m corresponding to the left side of the above equation (9) is obtained. There is a relationship of the following formula (10) between them. In addition, L of Formula (10) is a representative length. From this equation, the thermal conductivity and the like can be calculated.

  Here, the common concept of the thermal constant measurement method according to each of the above embodiments will be described with reference to the flowchart of FIG.

  As shown in FIG. 12, first, the mode of thermal resonance generated in the sample is determined (step S1). At this time, as described above, it is preferable to select a thermal resonance mode in which the attenuation coefficient is expected to be as small as possible from the viewpoint of the selectivity of the mode of thermal resonance generated in the sample.

  Next, in the sample, a portion corresponding to the abdomen of the thermal resonance mode determined in step S1 (excitation portion) is instantaneously heated to generate thermal resonance in that mode (step S2). Then, from the occurrence of thermal resonance until the equilibrium state is reached, the temperature of the portion corresponding to the abdomen of the thermal resonance mode (detection unit) is measured in the sample (step S3).

  Thereafter, an attenuation coefficient is calculated based on the time variation of the temperature measured in step S3 (step S4), and the thermal diffusivity of the sample is calculated based on the attenuation coefficient (step S5). In addition, when the density and specific heat of the sample are known, the thermal conductivity may be obtained from the thermal diffusivity.

  Hereinafter, the present invention will be described in more detail with reference to examples. However, the present invention is not limited to the following examples.

Example 1
The length L _{x in the} X-axis direction (width direction) is 1.978 mm, the length L _{y in} the Y-axis direction (depth direction) is 1.492 mm, and the length L _z in the Z-axis direction (height direction) is 1. For a 011 mm aluminum rectangular parallelepiped (sample S), a simulation that reproduces the thermal resonance phenomenon of MODE5 (FIG. 3E) was constructed, and the theoretical value of the damping coefficient was obtained.

As shown in FIG. 13, in Example 1, the upper surface center point P11 of the sample S is used as an excitation point, and the upper surface center point P11, the center point P12 on the right side of the upper surface, and the center point P13 on the near side of the upper surface. Simulation was performed as a detection point. Note that all of the detection points P11 to P13 are located in the abdomen of thermal resonance of MODE5. The theoretical damping coefficient λ ₁ derived by the simulation of Example 1 was 980.4 s ⁻¹ . On the other hand, the attenuation coefficient λ ₂₀₀ calculated by the measurement method described in the above embodiments was 985.74 s ⁻¹ .

(Example 2)
A simulation that reproduces the thermal resonance phenomenon of MODE 1 (FIG. 3A) was constructed for the same sample as in Example 1, and the theoretical value of the damping coefficient was obtained.

As shown in FIG. 14, in Example 2, the center point P21 on the left side of the upper surface of the sample S is used as the excitation point, the center point P21 on the left side of the upper surface, the upper surface center point P22, and the vertex P23 on the lower surface side. A simulation was carried out using as a detection point. The detection points P21 and P23 are located at the antinodes of the thermal resonance of MODE1, while the detection points P22 are located at the nodes of the thermal resonance of MODE1. The theoretical damping coefficient λ ₂ derived by the simulation of Example 2 was 246.6 s ⁻¹ . On the other hand, the attenuation coefficient λ ₁₀₀ calculated by the measurement method described in each of the above embodiments was 246.6 s ⁻¹ .

(Example 3)
For the same sample as in Example 1, a simulation that reproduces the thermal resonance phenomenon in mode 2 (FIG. 3B) was constructed, and the theoretical value of the damping coefficient was obtained.

As shown in FIG. 15, in Example 3, the center point P31 of the side on the back side of the upper surface of the sample S is used as an excitation point, the center point P31 of the side on the back side of the top surface, the top surface center point P32, and the back side of the bottom surface. A simulation was performed using the vertex P33 as a detection point. Although the detection points P31 and P33 are located at the antinodes of the mode 2 thermal resonance, the detection points P32 are located at the nodes of the mode 2 thermal resonance. The theoretical damping coefficient λ ₃ derived by the simulation of Example 3 was 432.3 s ⁻¹ . On the other hand, the attenuation coefficient λ ₀₁₀ calculated by the measurement method described in the above embodiments was 433.13 s ⁻¹ .

(Evaluation)
As described above, by the simulation of the thermal resonance phenomenon in the sample S, the attenuation coefficient calculated by the measurement method described in the above embodiments can be reproduced almost accurately. By using this simulation, for example, when the sample S is supported as shown in FIG. 2, it is possible to select a mode that is not easily affected by the support.

S Sample A1a, A5a-A5c Abdominal part E1a, E5a-E5c Excitation part (1st part)
D1a, D5a to D5a detector (second part)
8 Black body

Claims (9)

A method for measuring the thermal constant of a sample using a thermal resonance phenomenon,
Determining a mode of thermal resonance generated in the sample;
Generating a thermal resonance of the determined mode by instantaneously heating a first portion located in the abdomen of the thermal resonance of the determined mode in the sample;
Measuring a temperature of a second portion located in an abdomen of the determined mode thermal resonance for a predetermined time in the sample in which the thermal resonance occurs;
Calculating an attenuation coefficient based on a temporal change in temperature of the second portion;
Calculating a thermal diffusivity of the sample based on the attenuation coefficient;
A method for measuring a thermal constant.   The method of measuring a thermal constant according to claim 1, wherein the first portion is a point-like portion located at an antinode of thermal resonance of the determined mode.   The method of measuring a thermal constant according to claim 1, wherein the first portion is a portion extending in a band shape along an abdomen of thermal resonance of the determined mode.   The method of measuring a thermal constant according to any one of claims 1 to 3, wherein the second part is a point-like part located at an abdomen of the thermal resonance of the determined mode.   The method of measuring a thermal constant according to any one of claims 1 to 3, wherein the second portion is a portion extending in a band shape along an abdomen of the thermal resonance of the determined mode.   The method of measuring a thermal constant according to claim 1, wherein the first portion is instantaneously heated by irradiation with a pulse laser.   The method of measuring a thermal constant according to claim 1, wherein the sample has a black body on an upper surface.   The method of measuring a thermal constant according to claim 7, wherein the black body is provided only at a position in the sample that coincides with an abdomen of the determined thermal resonance mode.   The method for measuring a thermal constant according to claim 1, further comprising a step of calculating a thermal conductivity of the sample based on the thermal diffusivity.

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