JP2013036757A - Differential thermal analyzer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce variations in temperature of a sample mounting position of a sample stand 4 on which a sample S to be measured and a reference sample R are mounted when differential thermal analysis is performed in which the temperature difference between the sample S to be measured and the reference sample R is used as a direct object to be measured.SOLUTION: In order to measure average temperature among a plurality of positions in a sample mounting position of a sample stand 4 on which a sample S to be measured and a reference sample R are mounted, circular openings 5a, 6a are provided in the center parts of a chromel plate 5 and a chromel plate 6 which are made of a circular metal plate for rear face-side thermocouple joined to the rear face of the sample mounting position.

Description

  The present invention relates to a differential thermal analyzer that analyzes the thermal properties of a sample to be measured from the temperature difference generated between the two samples when the sample to be measured and a reference sample are heated in a heating furnace under the same conditions.

  In differential thermal analysis (DTA), in general, a sample to be measured and a reference sample are heated according to a preset temperature raising program, and the temperature difference between the two samples is detected in the heating process to detect the sample. Analyzes various physical properties, phase transitions, chemical reactions, etc. of the measurement sample.

A schematic configuration of a conventional differential thermal analyzer for performing the thermal analysis is as shown in FIG.
2A is a front view (sectional view), FIG. 2B is a top view, and FIG. 2C is a bottom view of the sensor unit 41. The differential thermal analyzer shown in FIG. 2 includes a sensor unit 41 that measures the temperature difference between the sample S to be measured and the reference sample R, a heating furnace 42 and a furnace lid 43 that house the sensor unit 41, and heats the heating furnace 42. It comprises a heater (not shown).

  The sensor unit 41 has respective bowl-shaped portions on which the sample S to be measured and the reference sample R are placed, and is formed on a back surface of the sample stage 44 made of a constantan material and the bowl-shaped sample stage parts 44a and 44b. A plurality of spot-welded chromel plates 45 and 46, a constantan wire 47 spot-welded to the sample stage 44, and chromel wires 48 and 49 spot-welded to the chromel plates 45 and 46. The constant temperature sample base portion 44a and the plurality of spot welding points on the chromel plate 45 constitute a thermocouple thermometer, whereby the average temperature at the plurality of locations on the sample base portion 44a is measured. The same applies to the sample stage 44b. Patent Document 1 discloses a “means for filtering thermal vibration harmful to the stability of heat flux by fixing a differential heat flow detector on a bottom plate of a heating furnace via a heat buffer plate”. Yes.

  The bowl-shaped sample base portion 44a and the chromel plate 45, and the sample base portion 44b and the chromel plate 46 also serve as thermocouples, and detect the temperature of the sample base portions 44a and 44b. The sample S to be measured and the reference sample R are placed on the sample bases 44a and 44b while being accommodated in the sample container 50. The sample stage 44 of the sensor unit 41 is brazed to the bottom plate part 42a of the heating furnace 42. A signal from the sensor unit 41 is taken out via the heating furnace 42.

JP 2001-33411 A

  In differential thermal analysis, the sample S to be measured and the reference sample R are placed in the same thermal environment as much as possible, and the temperature difference between the two when the temperature is changed is directly measured, but the sample itself Since it is difficult to measure the temperature of the sample, the temperature of the sample mounting position on the sample stage is regarded as the sample temperature.

  Therefore, conventionally, in order to reduce the difference between the measured temperature and the actual sample temperature, the upper surface of the sample table 44 and the lower surface of the sample container 50 are brought into close contact with each other to reduce the contact thermal resistance as much as possible. Furthermore, there is always a temperature variation at the sample placement location of the sample stage 44 on which the sample container 50 is placed, but it is required to reduce the temperature variation.

  In order to solve the above-described problems, the present invention provides a sample stage on which a sample to be measured and a reference sample are placed, and detection means for detecting a temperature difference between the sample to be measured and the reference sample on the sample stage. And a differential thermal analyzer having a heating furnace that houses and heats the sensor unit, wherein the sensor unit includes a sample stage side thermocouple metal plate, the sample stage side thermocouple metal plate, and a thermocouple. A back side thermocouple metal plate to be formed, the back side thermocouple metal plate having a circular opening in the center, and the back side of the sample mounting portion of the sample base side thermocouple metal plate Are joined at a plurality of locations.

  In the conventional example, in order to obtain the average temperature of the sample container installation location, a plurality of thermocouples are installed on the back surface of the sample container installation location so as to surround the sample container installation location.

  However, when heating is performed according to a preset temperature rising program, the thermal capacity of the circular metal plate for the back side thermocouple joined to the back side of the sample container installation location is large. A delay in the rise occurs, and the temperature variation increases.

  By means of solving the above-mentioned problems, the heat capacity is reduced by providing an opening in the circular backside metal plate for the thermocouple bonded to the backside of the location where the sample container is installed, and as a result, the temperature gradient of the heat transfer path is reduced. , Increase the responsiveness of temperature rise and reduce temperature variation. By the way, in the simulation calculation, when a hole of about ½D was provided in the back-side thermocouple metal plate having the outer diameter D, the temperature variation on the back-side thermocouple metal plate was reduced by about 20%.

It is a schematic block diagram of the differential thermal analyzer which is embodiment of this invention. 1A is a front view (sectional view), FIG. 1B is a top view, and FIG. 1C is a bottom view of the sensor unit 1. It is a schematic block diagram of the conventional differential thermal analyzer. 2A is a front view (sectional view), FIG. 2B is a top view, and FIG. 2C is a bottom view of the sensor unit 41.

  FIG. 1 shows a schematic configuration of a differential thermal analyzer which is an embodiment of the present invention. 1A is a front view (cross-sectional view), FIG. 1B is a top view, and FIG. 1C is a bottom view of the sensor unit 1. The differential thermal analyzer shown in FIG. 1 is a sensor unit 1 that measures a temperature difference between a sample S to be measured and a reference sample R, a heating furnace 2 and a furnace lid 3 that house the sensor unit 1, and heats the heating furnace 2. It comprises a heater (not shown).

  The sensor unit 1 includes a sample table 4 made of a constantan material, chromel plates 5 and 6 bonded to the back surface of the sample table 4, and constantan wires 7 and chromel wires 8 and 9 forming a thermocouple thermometer. Has been.

  The sample stage 4 has bowl-shaped sample stage parts 4a and 4b for mounting the sample S to be measured and the reference sample R, respectively, and a donut shape having openings 5a and 6a in the center on the back side. The chromel plates 5 and 6 are spot-welded in a plurality of places, and each point of the welding forms a thermocouple thermometer. In order to extract the output signal from the thermocouple to the outside, constantan wire 7 is spot-welded to sample stage 4 and chromel wires 8 and 9 are spot-welded to chromel plates 5 and 6. For example, when there are n welding points that form a thermocouple, an average value of output signals of n welding points is output. This is exactly the same as when n dry batteries are connected in parallel.

  The bowl-shaped sample stage 4a and the chromel plate 5, and the sample stage 4b and the chromel plate 6 also serve as thermocouples, and detect the temperature of the sample stage 4a and 4b. The sample to be measured S and the reference sample R are placed on the sample tables 4a and 4b while being accommodated in the sample container 10. Since the sample stage 4 of the sensor unit 1 is brazed all around the bottom plate part 2 a of the heating furnace 2, heat is transferred from the outer peripheral part to the sample container 10 via the sample stage 4 by conduction. A signal from the sensor unit 1 is taken out via the heating furnace 2.

  The purpose of providing openings in the chromel plates 5 and 6 is to reduce the heat capacity of the chromel plates 5 and 6, and consequently, the temperature gradient of the heat transfer path is reduced, the temperature rise responsiveness is increased, It is to reduce the variation. By the way, in the simulation calculation, when the chromel plate having the outer diameter D is provided with about 1 / 2D punch holes, the temperature variation on the chromel plate is reduced by about 20%. However, reducing the heat capacity and reducing the heat capacity to such an extent that the spot welding work for joining the chromel plates 5 and 6 to the back surfaces of the sample base parts 4a and 4b becomes complicated or requires a lot of work time. Not desirable.

  As the thermocouple, the thermocouple material is not limited to the combination of constantan and chromel.

1, 41 Sensor part 2, 42 Heating furnace 2a, 42a Bottom plate part 3, 43 Furnace lid
4, 44 Sample stage 4a, 4b, 44a, 44b Sample stage 5, 6 Chromel plate 5a, 6a Opening 7, 47, Constantan wire 8, 9, 48, 49, Chromel wire 10, 50 Sample container 45, 46 Chromel Plate S Sample to be measured R Reference sample

Claims (1)

  A sample stage on which the sample to be measured and the reference sample are placed; a sensor unit having a detecting means for detecting a temperature difference between the sample to be measured and the reference sample on the sample stage; In the differential thermal analyzer equipped with a heating furnace for heating, the sensor unit includes a sample base side thermocouple metal plate, the sample base side thermocouple metal plate, and a circular back side thermocouple metal plate forming a thermocouple. The back surface side thermocouple metal plate has a circular opening in the center, and is joined to the back surface of the sample mounting portion of the sample base side thermocouple metal plate at a plurality of locations. Differential thermal analyzer.

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