JP2720751B2 - Differential thermal analyzer - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a differential thermal analyzer using a vertical cylindrical heating furnace.

[0002]

2. Description of the Related Art A sample and a reference material are placed side by side in a heating furnace, and a temperature difference ΔT between the two is heated while heating both at a constant rate.
Is a technique for measuring the temperature as a function of temperature T using differential thermal analysis (Diff
erential Thermal Analysis (DTA). Since a physical change or a chemical change of a sample generally involves a change in heat capacity or generation of reaction heat, use a substance (generally α-alumina) that does not cause a heat change as a reference substance. By measuring the temperature difference ΔT, the thermal characteristics of the sample can be measured. This temperature difference ΔT with respect to the temperature T is called a temperature difference curve (DTA curve), and a baseline shift and an endothermic / exothermic peak appear in response to a change in the heat of the sample.

A conventional differential thermal analyzer (Differential The
An outline of the Rmal Analyzer (DTA) will be described with reference to FIG. The apparatus includes a vertical cylindrical heating furnace 50 and a control device such as a main control unit 61. The heating furnace 50 includes a main body 51, a hood 54 provided above the main body 51, and a main body 51.
The connecting portion 53 is provided at the lower part of the base portion 55. The connecting portion 53 is airtightly inserted into the base portion 55 for use. The heater wire 52 for heating is provided only in the main body 51.

The first and second sample dishes 20, 21 arranged side by side are arranged substantially at the center of the inside of the main body 51 of the heating furnace 50.
Is provided. Both sample dishes 20, 21 are the hot ends of two sets of thermocouples 22, 23, 24 sharing one line, one on which the sample to be measured is placed and the other on which the reference substance is placed. You. Thermocouples 22, 23, 24 are connected to main controller 61 through conduit 25. The main control unit 61 sends a control signal to the temperature control unit 62 so as to heat the sample according to a predetermined temperature raising program, measures the voltage between the terminals of the thermocouples 22, 23, and 24, and connects the sample to be measured with the thermocouple. Temperature difference Δ with reference material
T is detected. The data of the temperature T and the temperature difference ΔT of the sample are sent from the main control unit 61 to the recording unit 63 and recorded on recording paper. Further, by analyzing the DTA curve in the main control section 61, the decomposition temperature and the like of the sample are detected.

[0005]

In the differential thermal analyzer having the above-mentioned structure, the heater wire 52 serves as a heating source, thereby heating the sample and the reference material. Due to the convection of the air inside, when the temperature becomes high, it is heated by radiation from the furnace wall. However, in the above-described conventional configuration, since the upper and lower portions of the sample and the reference material are hollow, there is no radiation from above and below, and on the contrary, heat escapes by the radiation from the sample. For this reason, there is a problem that radiation unevenness occurs between the sample and the reference material due to the non-uniformity of the shape and the temperature of the space above the sample and the reference material, and accurate thermal analysis cannot be performed.

[0006] Such a problem is not limited to the differential thermal analyzer, but can be applied to general thermal analyzers using a vertical cylindrical heating furnace, such as a thermogravimetric measuring device and an expansion measuring device (thermomechanical measuring device). The present invention has been made to solve such a problem, and an object of the present invention is to make a sample (when a reference material is used, a sample and a reference material).
An object of the present invention is to provide a thermal analyzer capable of performing accurate thermal analysis by reducing heating unevenness.

[0007]

Means for Solving the Problems A differential thermal analyzer according to the present invention made to solve the above-mentioned problem is a differential thermal analyzer in which a sample is arranged at substantially the center of a vertically long cylindrical heating furnace. A transverse wall connected to the furnace wall is provided at a position 1/4 to 1/2 of the furnace length from the upper end of the heating furnace.

[0008]

The sample (in the case of using a reference material, the sample and the reference material) is placed at the substantially center of a vertically long cylindrical (both cylindrical and polygonal) heating furnace, and the transverse wall is heated. It is arranged at a position 1/4 to 1/2 of the furnace length from the upper end of the furnace. For this reason, the transverse wall exists immediately above or near the sample (and the reference substance), and covers the upper portion of the sample. Since this transverse wall is connected to the furnace wall of the heating furnace, heat is supplied from the furnace wall by heat transfer, and there is still a furnace wall heated by the heater above the transverse wall (at least). (1/4 is present), so the temperature of the transverse wall is approximately equal to the temperature of the furnace wall. Thus, the sample receives substantially uniform radiation from the surrounding sidewalls and the upper transverse wall, and the sample (and reference material) receives uniform heating. Since the lower part of the sample has a wide cavity, the sample and the reference substance are heated almost uniformly by convection of air in the furnace at a relatively low temperature, similarly to the conventional heating furnace.

[0009]

FIG. 1 shows a heating furnace of a differential thermal analyzer according to a first embodiment of the present invention. In the differential thermal analyzer of the present embodiment, the hood is not provided on the main body 11 of the heating furnace 10, but instead, at about 1/3 from the upper part of the main body 11, from the inner wall of the main body 11 to the inside. A canopy portion 14 (transverse wall) extending substantially horizontally is provided. First and second sample dishes 2
Since the reference numerals 0 and 21 are located at substantially the same positions as those of the conventional differential thermal analyzer (FIG. 3), the canopy 14 covers almost directly above the sample and the reference substance. In the differential thermal analyzer of the present embodiment, in order to adjust the atmosphere at the time of measurement,
A hole 15 for releasing the atmospheric gas is provided at the center of the canopy portion 14. Further, since the base portion is the same as the conventional one shown in FIG. 3, illustration is omitted.

Since the heating furnace 10 of the differential thermal analyzer of the present embodiment has the above-described structure, when the heater wire 12 is energized and heated, the heat is transferred to the inner wall of the cylindrical main body 11. And transmitted to the canopy part 14 through the inner wall. Here, the heater wire 12 of the main body 11 is
The canopy 14 has almost no temperature difference with the inner wall. Therefore, the sample and the reference material on the first and second sample dishes 20 and 21 receive radiation uniformly from the surroundings and the upper portion, and both are uniformly heated.

FIG. 2A shows the configuration of a heating furnace of a differential thermal analyzer according to a second embodiment of the present invention. Heating furnace 30 of the present embodiment
Is used when the atmosphere of the sample is not adjusted, and since there is no need to provide a vent hole for releasing the atmosphere gas, the canopy part 34 is flattened, and the top of the sample and the reference material is completely covered. Emit even radiation.

FIG. 2 (b) shows a configuration of a heating furnace of a differential thermal analyzer according to a third embodiment of the present invention. Heating furnace 40 of the present embodiment
Is used to adjust the atmosphere, as in the first embodiment. In addition to the canopy 44 with the vent hole 45 used in the first embodiment, a ceramic reflector plate 47 is provided from the lower part of the furnace. The first and second sample dishes 20 and 21 are inserted to the positions directly below. Thus, the sample and the reference material receive uniform radiation from the surroundings and the upper portion, and furthermore, radiation loss from the lower surface is minimized, so that more uniform heating is performed. Note that a metal layer such as platinum may be provided on the upper surface of the reflection plate 47 in order to increase the reflection efficiency.

[0013]

[0014]

In the differential thermal analyzer according to the present invention, the sample (and the reference substance) has a cross-section wall having a temperature almost equal to that of the surrounding furnace wall immediately above the sample (and the reference substance). The sample receives substantially uniform radiation from the surrounding side wall and the upper transverse wall, and receives uniform heating (when the sample and the reference material are juxtaposed, both are heated equally).
Therefore, an accurate analysis without a baseline shift can be performed.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view of a heating furnace of a differential thermal analyzer according to a first embodiment of the present invention.

FIG. 2 is a longitudinal sectional view of a heating furnace of the differential thermal analyzer according to the second and third embodiments of the present invention.

FIG. 3 is a longitudinal sectional view of a heating furnace of a conventional differential thermal analyzer and a block diagram of a control device.

[Explanation of symbols]

10, 30, 40, 50, 70 ... heating furnace 11, 51 ... heating furnace main body 12, 52 ... heater wire 14, 34, 44 ... canopy 20, 21 ... first and second sample dishes 22, 23, 2
4: Thermocouple 47: Reflector

Claims (1)

(57) [Claims] 1. A differential thermal analyzer in which a sample is arranged at substantially the center of a vertically long cylindrical heating furnace, connected to a furnace wall at a position 1/4 to 1/2 of the furnace length from an upper end of the heating furnace. A differential thermal analyzer characterized by having a crossed wall provided.