JP3130833U - Differential scanning calorimeter - Google Patents

Abstract

A differential scanning calorimeter capable of correcting a baseline drift indicated by a DSC curve is provided.
A heating furnace 1 having a DSC detector 2 provided with a temperature sensor 24, 25 for detecting the temperature of the sample pan 21, 22 in contact with a sample pan 21, 22 containing a sample S and a reference substance R, and Two types of thermal resistors 31 and 32 having different thermal conductivities with different thicknesses are superposed and fixed by a holding ring 33, and an adjustment lever 34 is provided on the holding ring 33 so that it can be rotated on a plane. The combined thermal resistor 3 is disposed, and the combined thermal resistor 3 is heated by the heater 8. The drift of the baseline is corrected by rotating the synthetic thermal resistor 3 on a plane and adjusting its position to change the heat transfer rate to the sample pans 21 and 22.
[Selection] Figure 1

Description

  The present invention relates to a differential scanning calorimetry apparatus that heats a sample, performs differential scanning calorimetry, and evaluates material properties.

  A differential scanning calorimetry (DSC) apparatus measures a temperature difference between a sample to be measured contained in the furnace body and a thermally inactive reference material such as alumina powder while changing the furnace body temperature. Therefore, the amount of heat that enters and exits the sample per unit time is obtained, and it is widely used for evaluating material properties.

  In the conventional differential scanning calorimeter, as shown in FIG. 5, the heating furnace 1 is fixed to the base housing 7 by inserting the thermal resistor 3A with a screw 13, and the heat generated by the heater 8 through the thermal resistor 3A. The sample S and the reference material R are accommodated and heated. The sample S is accommodated in the sample pan 21 and the reference substance R is accommodated in the sample pan 22 and placed on the DSC detector 2 in the heating furnace 1.

  The DSC detector 2 is a mounting table provided with temperature sensors 24 and 25 for detecting the temperatures of the sample S in the sample pan 21 and the reference substance R in the sample pan 22, respectively. The detected temperature signals of the sample S and the reference material R are sent to the DSC signal detection circuit 101 that constitutes the measurement / control unit 100. The DSC signal detection circuit 101 obtains a DSC signal indicating the amount of heat entering and exiting the sample S per unit time based on the temperature difference between the sample S and the reference material R, and this DSC signal is combined with the sample temperature signal. The amount of heat that is sent to the computer 103 and flows into or out of the sample S, that is, the amount of change in the enthalpy of the sample is measured. The temperature control circuit 102 controls the detection signal of the temperature sensor 26 installed in the vicinity of the heater 8 so as to coincide with the temperature increase program signal output from the computer 103.

  In the differential scanning calorimeter, a temperature raising program is set in the computer 103, and the temperature of the furnace body Tf of the heating furnace 1 is raised with time as illustrated in FIG. When the sample S has no thermal change, the temperature of the sample S and the reference material R rises in the same manner as the furnace temperature Tf rises. For example, the sample temperature Ts melts. When the temperature is reached, the temperature rise of the sample S stops until the end of melting. When the melting ends, the temperature of the system immediately returns to the system temperature, and the temperature increase is resumed at the original temperature increase rate. Such behavior of the sample temperature Ts is detected as a DSC signal W based on the temperature difference between the sample temperature Ts and the reference temperature Tr.

The DSC signal W is expressed by the equation (1) where Tf is the furnace temperature, Ts is the sample temperature, Tr is the reference material temperature, dTr / dt is the temperature rising rate of the reference material R, Rt is the thermal resistance, and A is the proportionality constant. (See Patent Document 1).
W = −ARt (Ts−Tr) dTr / dt (1)
JP 2000-193618 A

The conventional differential scanning calorimeter is configured as described above. However, the displacement of the arrangement position of the sample pan 21 containing the sample S and the sample pan 22 containing the reference material R, the dimensional error of the components, or the assembly accuracy As a result, the temperature difference between the sample S and the reference material R changes even if there is no thermal change in the former, and as shown by the curve D1 or D2 in FIG. Prone to drift in which the baseline of the signal increases or decreases. Usually, the drift of the baseline is apparently canceled by data processing. However, physically, the sample S and the reference material R have an extra temperature difference, which is not desirable.
The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a differential scanning calorimeter capable of removing baseline drift by adjusting the amount of heat supplied to a sample pan. is there.

In order to achieve the above object, the differential scanning calorimeter of the present invention includes a heating furnace that heats a sample and a reference material, and a thermal resistance that is interposed between the heating furnace and a heater that is a heating means to perform heat exchange. In the differential scanning calorimetry apparatus comprising a body, temperature control means for controlling the temperature of the heating furnace, and a detector in the heating furnace for detecting a temperature difference between a sample and a reference material, the thermal resistor is It is composed of two types of thermal resistors having different thermal conductivities and different thicknesses in the circumferential direction, and provided with a rotating mechanism for rotating the thermal resistors.
The differential scanning calorimeter of the present invention further includes a drift correction amount storage means for storing the rotation amount of the thermal resistor for correcting the baseline drift during blank measurement, and is automatically stored during actual sample measurement. And a drift correction means for correcting the drift of the baseline by rotating the thermal resistor by the amount of rotation of the thermal resistor.
The differential scanning calorimeter of the present invention is configured as described above, can correct the baseline drift, and can accurately measure the differential scanning calorific value.

  Regardless of dimensional tolerance of parts or assembly accuracy, DSC signal baseline drift can be physically corrected, and by realizing ideal thermal symmetry, more accurate enthalpy variation and Specific heat capacity can be measured.

  An embodiment of a differential scanning calorimeter according to the present invention will be described in detail with reference to the drawings. FIG. 1 is a cross-sectional view showing the structure of a differential scanning calorimeter according to the present invention, FIG. 2 is a plan view (A) of the synthetic thermal resistor according to the embodiment, its A-A cross section (B), and FIG. It is an external view of a differential scanning calorimeter. In addition, the same number is attached | subjected to the structural member which has a function similar to the differential scanning calorimetry apparatus of the prior art example shown in FIG.

  The differential scanning calorimeter according to the embodiment of the present invention includes a heating furnace 1 for heating the sample S and the reference material R as shown in FIG. The heating furnace 1 is composed of a furnace body 11 having an opening at the top and a lid 12, and is formed with a thick wall surface using a metal having good thermal conductivity such as silver or copper in order to make the temperature distribution in the furnace uniform. Has been. A concave sample container 1a is formed in the upper part, and the DSC detector 2 is disposed therein.

  The DSC detector 2 includes a sample pan 21 for storing the sample S and the reference material R and a plate 23 for mounting the sample pan 22, and a temperature sensor such as a thermocouple provided on the back surface of each sample pan 21, 22. The temperature of the sample S and the reference material R is detected by the temperature sensors 24 and 25. The upper opening of the furnace body 11 is closed by the lid 12 after the sample pans 21 and 22 are placed.

  The heating furnace 1 is fixed to the base housing 7 with four screws 13 with a synthetic thermal resistor 3 interposed between the heating furnace 1 and the inner surface of the heating furnace 1 so as to form a uniform temperature atmosphere. An inert gas is sealed and a heat insulating cover 4 is covered. As shown in the plan view (A) and the AA sectional view (B) in FIG. 2, the synthetic thermal resistor 3 has two thicknesses of thermal resistors 31 and 32 having different thermal conductivities. Is provided with an adjustment lever 34 that is provided with a gradient so as to continuously change, overlaps in different thickness directions, is fixed by a holding ring 33 and is rotated on the holding ring 33 in a plane direction.

  In the differential scanning calorimeter, as shown in FIG. 3, the periphery of the heat shield cover 4 is covered with an outer cover 5 and covered with an outer lid 6 to block the influence of the external environment temperature on the heating furnace 1. ing. The outer cover 5 is provided with a scaled opening 5a for measuring a rotation angle when the adjustment lever 34 is rotated in the plane direction.

  As shown in FIG. 1, a heater 8 for heating the synthetic thermal resistor 3 is fixed to the upper portion of the base casing 7. The heater 8 is heated by the current supplied from the temperature control circuit 102 to heat the synthetic thermal resistor 3. The heater current is generated by a temperature detection signal from a temperature sensor 25 of the DSC detector 2 or a temperature sensor (not shown) provided separately from a setting signal generated from a temperature raising program of the computer 103 that raises the temperature Tr of the reference material R. Controlled to be equal. As a result, the temperature of the reference material R rises corresponding to the temperature raising program, and the temperature of the sample S also rises.

  Baseline drift correction is performed in a state where the sample S and the reference material R are not placed on the sample pans 21 and 22, that is, blank measurement. If the base line drifts in the heat generation direction indicated by the curve D1 in FIG. 7 assuming that the thermal conductivity of the thermal resistor 31 is smaller than the thermal conductivity of the thermal resistor 32, the adjustment lever 34 is used to correct this drift. Rotate in the direction of the arrow A1. As a result, the thickness of the thermal resistor 32 on the sample pan 22 side increases and the amount of heat transfer to the sample pan 22 side relatively increases, so that the baseline approaches the baseline indicated by the curve D0. Then, the adjustment lever 34 is set to a position where the base line is almost the curve D0, and the scale position is stored. When the base line drifts in the endothermic direction indicated by the curve D2, the adjustment lever 34 is rotated in the direction of the arrow A2. As a result, the thickness of the thermal resistor 32 on the sample pan 21 side is increased and the amount of heat transfer to the sample pan 21 side is relatively increased, so that the baseline approaches the baseline indicated by the curve D0. Then, the position of the adjustment lever 34 is set so that the base line is substantially the curve D0, and the scale position is stored. Thereafter, measurement is performed at this scale position.

  FIG. 4 shows another embodiment of the synthetic thermal resistor 3, and this synthetic thermal resistor 3B adds a drift correction function that can automatically perform baseline drift correction to the synthetic thermal resistor 3. It is a thing. That is, the synthetic thermal resistor 3B is obtained by adding a drive mechanism 9 including a shaft 91, a coupling 92, and a stepping motor 93 to the synthetic thermal resistor 3. The synthetic thermal resistor 3B is used in place of the synthetic thermal resistor 3 in FIG. 1, and the DSC signal is measured by stopping the stepping motor 93 in a state where the sample S and the reference material R are not placed (blank measurement), and the amount of drift Is stored in the computer 103. At the time of actual sample measurement, the combined thermal resistor 3B is driven by the stepping motor 93 by the drift signal from the computer 103 to correct the drift and measure the DSC signal.

  Also, learning is performed by inputting the baseline drift amount during blank measurement, outputting the rotation angle of the stepping motor 93, and performing feedback control with the control target as the drift amount 0, and storing the change in the rotation angle at this time in the computer 103. The function AI can be provided to the synthetic thermal resistor 3B. As a result, during actual sample measurement, this feedback control is stopped so as not to malfunction due to a true baseline change caused by the sample change, and the dynamic operation of canceling the drift by rotating the stepping motor 93 based on the stored rotation angle information It can be performed.

  Used in a differential scanning calorimeter.

1 is an overall cross-sectional view of a differential scanning calorimeter according to an embodiment of the present invention. It is the top view (A) of the synthetic | combination thermal resistor which concerns on an Example, and its AA sectional drawing (B). 1 is an overall external view of a differential scanning calorimeter. It is a block diagram of the synthetic | combination thermal resistor by another Example. It is a side sectional view of a heating furnace of a conventional differential scanning calorimeter, a block diagram (A) of a measurement / control unit, and an AA sectional view (B) thereof. It is a figure which shows the sample temperature characteristic Ts and the reference | standard substance temperature characteristic Tr with respect to the heating furnace internal temperature Tf. It is a figure which shows the temperature drift of the baseline of a DSC signal

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Heating furnace 1a Sample accommodating part 11 Furnace body 12 Cover 13 Screw 2 DSC detector 21 Sample pan 22 Sample pan 23 Plate 24 Temperature sensor 25 Temperature sensor 26 Temperature sensor 3 Synthetic thermal resistor 3A Thermal resistor 3B Synthetic thermal resistor 31 Thermal resistor 32 Thermal resistor 33 Holding ring 34 Adjustment lever 4 Heat shield cover 5 Outer cover 5a Scaled opening 6 Outer lid 7 Base housing 8 Heater 9 Drive mechanism 91 Shaft 92 Coupling 93 Stepping motor 100 Measurement / control unit 101 DSC signal detection circuit 102 Temperature control circuit 103 Computer

Claims (2)

A heating furnace that heats the sample and the reference material, a thermal resistor that is interposed between the heating furnace and a heater that is a heating means, a temperature control means that controls the temperature of the heating furnace, and the heating furnace In the differential scanning calorimetry apparatus provided with a detector for detecting a temperature difference between the sample and the reference material, the thermal resistor has two kinds of thermal conductivity different from each other and thickness different in the circumferential direction. A differential scanning calorimeter having a rotation mechanism configured to rotate the thermal resistor. Drift correction amount storage means for storing the amount of rotation of the thermal resistor for correcting the baseline drift during blank measurement, and the thermal resistor for the amount of rotation of the thermal resistor automatically stored during actual sample measurement The differential scanning calorimetry apparatus according to claim 1, further comprising a drift correction unit that rotates and corrects a drift of the baseline.

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