JPS60107556A - Method for measuring relative specific heat and absolute specific heat of sample such as powder by ac calorimeter - Google Patents

Abstract

PURPOSE:To determine absolute values of relative sp. heat, sp. heat of a sample by mounting the sample such as powder on a surface of a foil or a thin plate having high thermal conductivity, and measuring an AC temp. component of the foil or thin plate by an intermittent heat current. CONSTITUTION:An adhesive for cryogenic temp. is painted thinly on a surface of a satisfactorily thin metallic foil 2 having low sp. heat and high thermal conductivity, sample powder 1 is spattered uniformly thereon, and thermocouples 3, 4 for measuring AC temp. component and sample temp. are adhered to another surface. Said body is attached to an AC calorimeter, and intermittent light is irradiated to the foil 2 to measure the relative sp. heat of the sample. When measuring the absolute value of sp. heat, an AC temp. component of a copper plate is measured without mounting the sample, next, the AC temp. component is measured by mounting the sample on the copper plate, and the absolute value of sp. heat is obtained by an equation. Here, Cp<n> is sp. heat of the sample, Tac<k> is the AC temp. component of the copper plate, Cp<k> is the heat capacity of the copper plate, and Tac<k+n> is the AC temp. component of the copper plate mounting the sample.

Description

[Detailed Description of the Invention] A well-known method for measuring the specific heat of a sample using an AC calorimeter is as follows:
Changes in specific heat of a sample due to changes in external temperature can be measured with high sensitivity, specific heat can be measured by continuously changing temperature, magnetic field, etc., or specific heat measurement can be easily automated using a computer, etc. Although it has the characteristics of cL11Ml
It has been believed that this measurement method can be formed into the following foil shape and can be applied only to samples with relatively good thermal conductivity, and that it is difficult to determine the absolute value of specific heat.

The object of the present invention is to provide a method for measuring the relative specific heat and absolute value of specific heat of a powder sample, liquid or semi-fluid sample, etc. using an AC calorimeter. The method is characterized in that the total relative specific heat of the sample such as powder is measured by placing a sample such as powder on the plate and measuring the AC temperature component of the foil or thin plate due to intermittent heat flow. AC temperature component of the foil or thin plate due to intermittent heat flow when a sample such as powder is placed on one side of the conductive foil or thin plate and when it is not placed on the surface of the foil or thin plate
IL0 is measured, and the absolute value of the specific heat of the sample such as the powder is determined from the following formula where Cn: heat capacity of the sample.

Examples of the measuring method of the present invention will be described below.

150 rometsushi to measure thermal uniformity as a material.
For example, copper Chevrel (On, . . .
A sufficiently thin metal foil (such as kitchen foil made of aluminum or the like) having a low specific heat and high thermal conductivity was prepared as a substrate for the sample.

A diluted ultra-low temperature adhesive is applied to one side of the metal foil, and the sample powder (1) is evenly sprinkled thereon as shown in the drawing, so that the base metal foil (2) is covered with the sample powder +1). On the other side of the metal foil (2), an ultrafine wire thermocouple +3+ for measuring the AC temperature component and sample temperature is attached.
Attach or spot weld +41 to each.

The above sample, metal foil, etc. were attached to a known AC calorimeter, and the thermocouples +31 to +41 were connected to a lock-in amplifier and a DC amplifier, respectively.

In this way, intermittent light is irradiated onto the metal foil (2) in the direction of the arrow to heat the metal foil (2), and the output of the thermocouple (3) is amplified with a lock-in amplifier and recorded with a reflector. The output of the thermocouple (4) was amplified with a DC amplifier and recorded with a refuder, and the relative specific heat of the powder sample with respect to the sample temperature was determined from the recorded data.

As a sample, we also used a liquid crystal material, which was 15111
The sample was deposited to a thickness of 100 μm on a copper plate having a thickness of 11 and measured in the same manner as described above.

When measuring the absolute value of specific heat, proceed as follows. First, measure the AC temperature component of the copper plate without placing any sample on it.

Assuming that the heat capacity of the copper plate is Ck (known n), there is a relationship between Q: heat flow ω imparted to the copper plate: interruption angular frequency Tk of the heat flow, and AC temperature component of the copper plate [LQ].

Next, a liquid crystal sample, for example, is placed on the copper plate, and the alternating current temperature component ILdn of the copper plate is measured.

The sum of the heat capacity of the copper plate ([and the heat capacity Cn of the liquid crystal is Ck10n
-...(2) p p 2mTa.

Therefore, the equation (2) and equation (1) can be obtained.

Thus, the specific heat of the liquid crystal can be determined from this equation (3).

In the case of powder samples, solid samples, etc., first place the sample on the metal foil.
If you measure and calibrate by attaching another piece of copper with adhesive instead of the measurement sample, you can use the procedure described above to measure the unknown sample without being affected by the heat capacity of the metal foil or adhesive. The absolute value of the specific heat can be determined.

As described above, according to the present invention, if a sample such as powder is placed on one surface of a thermally conductive foil or thin plate and the alternating current temperature component of the foil or thin plate is measured due to intermittent heat flow, the relative It has the effect of being able to measure the specific heat as well as determining the absolute value of the specific heat.

[Brief explanation of drawings]

The drawing shows an enlarged side view of a sample mounting section used for carrying out the measurement method of the present invention. (1)...Sample powder (2)...Metal foil (3)...
・Thermocouple for measuring AC temperature component (4)...Thermocouple for measuring sample temperature

Claims (1)

[Claims] 1. A sample such as a powder is placed on one side of a thermally conductive foil or thin plate, and the relative specific heat of the sample such as the powder is determined by measuring the AC temperature component of the foil or thin plate due to intermittent heat flow. A method for measuring the relative specific heat of a sample such as a powder using an AC calorimeter, which is characterized by measuring the relative specific heat of a sample such as a powder. 2 AC temperature component of the foil or thin plate due to intermittent heat flow when a sample such as powder is placed on one side of a thermally conductive foil or thin plate with known heat capacity flC and when not placed on the surface of the foil or thin plate ``+''
A method for measuring the absolute value of the specific heat of a sample such as powder using an AC calorimeter, characterized in that the absolute value of the specific heat of the sample such as powder is determined from the heat capacity of the sample using the following formula. .