JPH0132941B2 - - Google Patents

Description

[Detailed description of the invention] In order to measure the heat capacity of powder, liquid, or a sample with high vapor pressure by the flash method, it is necessary to use a material having an appropriate shape and size made of a material with good thermal conductivity such as aluminum. The sample must be placed in a closed container. However, if the heat conduction of the sample is poor, only the container with good heat conduction will undergo a temperature rise in a relatively short period of time due to the heat rays instantaneously irradiated on one side of the container; There is a long delay before the temperature spreads to the internal sample and reaches a uniform temperature. The heat capacity of the sample is calculated based on the value when the entire interior of the container reaches a uniform temperature through this process. However, as mentioned above, only the container with good heat conduction reaches an abnormally high temperature immediately after being irradiated with heat rays, and then the temperature drops again and becomes uniform, so only the container becomes high temperature. In this case, heat loss occurs due to heat radiation or convection, and since there is no means to compensate for this heat loss, there is a drawback that measurement values include large errors. In order to eliminate this drawback, conventional methods have been taken to effectively improve the thermal conductivity of the sample by mixing a material with good thermal conductivity, such as silver powder, into the sample. Because the sample was surrounded by the original sample, which has poor thermal conductivity, the thermal conductivity could not be made sufficiently high, and therefore a satisfactory effect could not be obtained. Therefore, the present invention provides a container that can effectively reduce the above-mentioned errors with a simple construction.

FIG. 1 is a longitudinal cross-sectional view of an embodiment of the present invention, and FIG. 2 is a cross-sectional view thereof. As described above, the flash method heat capacity measurement sample container of the present invention has a metal thin plate with good thermal conductivity such as aluminum, and has a cylindrical side surface 3 that connects the parallel upper and lower bottom surfaces 1 and 2 and the periphery thereof.
The upper and lower bottom surfaces 1 and 2 of the casing are similarly connected by a heat conductor 4 having good thermal conductivity, and powder or liquid, etc., is contained in the casing. The sample 5 is filled in the sample 5, and the thickness d of the sample 5 sandwiched between the heat conductors 4 is made sufficiently small. In addition, when manufacturing the above-mentioned sample container, first, for example, as shown in the figure, the upper bottom surface 1 is
A cylindrical body with a bottom and a side wall 3 are integrally formed by pressing an aluminum plate, and a heat conductor 4 and a similar aluminum strip plate are formed into a spiral shape as shown in the figure. After inserting or filling a sample 5 such as powder, the lower bottom surface 2 having a shallow edge 6 on the periphery is fitted, and the edge 6 and side surface 3 are bonded by crimping, welding, or brazing.
One edge of the heat conductor 4 is brought into contact with at least one bottom surface 1. Further, on the other bottom surface 2 of the container formed in this way, a thermocouple contact 7 is provided as necessary.
Attach.

When measuring the heat capacity of the sample 5 using the flash method, the container as described above is placed in a predetermined position of the apparatus, and a laser beam or the like having a known intensity is instantaneously applied to the top surface 1 as indicated by the arrow in FIG. The temperature change on the bottom surface 2 is recorded using a thermocouple contact 7 attached to the bottom surface 2. FIG. 3 shows a temperature curve recorded in this manner, with the origin at the time of laser beam irradiation and the room temperature T ₀ , with time t plotted on the horizontal axis and temperature T plotted on the vertical axis. The solid curve is the first
In the case of using the conventional container without the thermal conductor 4 shown in FIGS.
The temperature of the thermocouple contact point 7 rapidly increases due to the heat transmitted through the casing wall, which has good thermal conductivity. However, the heat from the casing wall is even worse inside Sample 5, where the heat conduction is poor.
As the temperature gradually spreads to the casing wall, the temperature of the casing wall begins to decrease, and a maximum portion 8 is formed in the curve. Once the temperature of the casing and the sample inside becomes uniform through such a process, an exponential curve 9 is observed since the temperature of the container gradually decreases due to thermal radiation or the like. Therefore, curve 9 is extended in the opposite direction to time 0.
When calculating the temperature Tm at The heat capacity C of the container is given by Q/(Tm-T ₀ ).
However, by extending curve 9, the temperature Tm at time 0 is
, the heat loss due to radiation etc. is compensated for when the container and the sample inside it maintain a uniform temperature, but the heat loss caused by the maximum area 8 as shown by the hatched area in Figure 3 is compensated for. is not compensated. Moreover, since the temperature of this part is high, heat loss is also large, causing a large error in measurement.

On the other hand, if a heat conductor 4 is provided inside the casing that contacts the upper base 1 and extends toward the lower base, and the thickness d of the sample 5 sandwiched between them is made sufficiently small, the upper base Thermal energy irradiated onto the sample 1 and absorbed by the bottom surface is transmitted through the thermal conductor 4 and quickly raises the temperature of the sample 5. Therefore, the casing and the sample 5 inside it quickly reach a uniform temperature, and the dashed line in FIG. 3 is observed. That is, since the maximum portion 10 becomes extremely small and heat loss through this portion is prevented, the curve 11 rises higher than the curve 9 when the entire sample container reaches a uniform temperature. Therefore, by extending the curve 11 in the opposite direction and finding the temperature Tp at time 0, it is possible to accurately measure the heat capacity.

[Brief explanation of drawings]

FIG. 1 is a longitudinal cross-sectional view of an embodiment of the present invention, FIG. 2 is a cross-sectional view of the container shown in FIG. 1, and FIG. 3 is a curve diagram for explaining the operation of the present invention. In the figure,
1 is the top surface, 2 is the bottom surface, 3 is the side surface, 4 is the thermal conductor, 5 is the sample, 6 is the edge of the bottom surface, and 7 is the thermocouple contact.

Claims (1)

[Claims] 1. A sealed casing is formed of parallel upper and lower bottom surfaces with plates with good heat conduction and a cylindrical side surface connecting the periphery of the cylindrical side surface, which accommodates a powdered or liquid sample inside, and the casing is A thermal conductor with good thermal conductivity is provided inside the body, and it contacts one bottom surface that is irradiated with flash light and extends toward the other bottom surface, and the thickness of the sample sandwiched between this thermal conductor is made sufficiently small. A sample container for flash method heat capacity measurement, characterized by: