JPS5823891B2 - Flash method thermal constant measurement device - Google Patents

Description

[Detailed description of the invention] When radiation such as a laser beam is instantaneously incident on the surface of a sample formed into a flat plate, the temperature of the surface increases over time and reaches a certain temperature after a certain time. .

In this case, by determining the energy absorbed by the sample, the temperature rise on the back side of the sample, and the time it takes for this temperature to rise by half, we can calculate the three thermal constants of the sample: heat capacity, thermal diffusivity, and thermal conductivity. can be measured.

Conventionally, thermocouple contacts were attached to such flash method thermal constant measuring devices to detect temperature changes on the back side of the sample, but this resulted in large errors due to heat conduction loss, complicated bonding work, and It has drawbacks such as easy separation when heated.

Therefore, recently, non-contact detection devices using infrared detectors have been attracting attention, but since some of the radiation that irradiates the sample is scattered by the sample surface, some of the scattered radiation may not be connected to the sample. Since the light enters the detector through the gap with the holder, it has the drawback that measurement errors are likely to occur.

The present invention seeks to eliminate these drawbacks.

FIG. 1 is a longitudinal cross-sectional view of an embodiment of the present invention, in which a cylindrical sample storage cylinder 1 is formed with a heat insulating material such as Alumina, and this storage cylinder is inserted into an electric furnace 2. The upper end of the radiation shielding cylinder 3 is opposed to the lower end of the housing cylinder.

The storage cylinder 1 has a sample insertion opening 4 on the side surface of its lower part and an annular collar 5 that protrudes inward at the lower end, and a disk-shaped sample holding table 6 with a hole in the center. The sample 7 attached to the holder was inserted through the insertion opening 4 and placed on the collar 5.

The holding table 6 is made of alumina or the like, and as shown in FIG. 2 and FIG. For example, three pins 8 and 9 made of an insulating material are implanted.

Place the disk-shaped sample 7 horizontally on the tip of this pin 8,
The tip of the pin 9 is used to hold down the circumferential surface 1 of the sample.

Further, an annular radiation shielding plate 10 formed in a truncated conical shape with a sub-ray shielding plate such as a platinum plate having a thickness of about 0.5 mm is placed on the holding plate 6, and the tip or inner portion of the annular radiation shielding plate 10 is placed on the holding plate 6. The circumferential portion was opposed to the lower surface of the sample 7 with a small gap therebetween.

Furthermore, a cylindrical radiation shielding tube 11 made of a similar platinum plate is placed vertically on the holding table 6, and the sample 7 is placed inside this shielding tube.

In the above-mentioned apparatus, the sample γ is held at a desired temperature in the furnace 2, and a laser beam, for example, is instantaneously irradiated from above on the upper surface of the sample as shown by the arrow a, and the shielding tube 3 is emitted from the lower surface of the sample.
Changes in the heat rays emitted as shown by the arrows are detected by an indium antimony, lead sulfide, or other suitable infrared detector via a toroidal mirror or the like.

FIG. 4 shows the relationship between the temperature T of the lower surface of the sample detected in this way and the time t.

That is, when the laser beam is irradiated at time to, sample 7
The temperature on the lower surface of the casing shows the highest temperature rise ΔT at a time t1 after a few hundredths of a minute, for example.

The heat capacity of the sample is calculated from this temperature rise ΔT and the energy of the laser light absorbed by the sample.

In addition, the thermal diffusivity is calculated from the time tx that causes a temperature rise of ΔT/2 and the thickness of the sample 7, and the thermal conductivity is calculated from the heat capacity and diffusivity of the sample obtained as described above and the density of the sample. be done.

In the above measurement, the apparatus of the present invention places the sample 7 inside the heat shield tube 11 as in the previous embodiment, and also provides an annular heat shield plate 10 whose inner periphery forms a minute gap around the periphery of the sample. They are facing each other through the middle.

Therefore, when the sample 7 is irradiated with a laser beam or the like, a portion of the laser beam is scattered on the surface of the sample, the surface of the holding table 6, etc., but most of this scattered radiation is absorbed by the shield cylinder 11.

Furthermore, the laser light further reflected on the surface of the shielding cylinder 11 is almost completely blocked by the shielding plate 10, and hardly enters the infrared detector.

That is, the peak p in FIG. 4 is due to this leaked laser light, but since the amount of laser light that is scattered on the surface of the sample and enters the detector as described above is extremely small, the peak p must be made sufficiently small. The above mentioned time tx
This does not cause any problem in the measurement of .

That is, if the shield tube 11 and the shield plate 10 are not provided, the scattered laser light passes through the gap between the sample 7 and the holding table 60, or is further scattered by the sample storage tube 1, etc., and enters the detector. As shown by the broken line q, an extremely large peak was generated, which caused trouble in measuring the time tx.

Moreover, since the shielding cylinder 11 also functions as a heat sink, it has the effect of stably maintaining the sample temperature.

Furthermore, since the shielding plate 10 is not in contact with the sample 7, there is no risk of measurement errors due to conduction of heat.

[Brief explanation of drawings]

Fig. 1 is a longitudinal sectional view of an embodiment of the present invention, Fig. 2 is an enlarged view of a part of Fig. 1, Fig. 3 is a plan view of the device shown in Fig. 2, and Fig. 4 is a detailed explanation of the present invention. This is an example of a measurement curve for sudame. In the figure, 1 is a sample storage cylinder, 2 is an electric furnace, 3 is a shielding cylinder, 4 is a sample insertion port, 5 is a collar, 6 is a sample holding stand, and 7
is a sample, 8.9 is a pin, 10 is a radiation shielding plate, and 11 is a radiation shielding tube.

Claims (1)

[Claims] 1 By attaching it to a holding table with a heat insulating pin and maintaining it at a desired temperature, one side is momentarily irradiated with radiation and the changes in the heat rays emitted from the other side are emitted by an infrared detector. A plate-shaped sample whose thermal constant is to be measured is placed inside a radiation shielding cylinder, and one peripheral edge is connected to the holding table between the holding table and the sample, and the other peripheral edge is connected to the upper peripheral edge of the sample. A flash method thermal constant measuring device characterized by having annular radiation shielding plates facing each other with a minute gap interposed therebetween.