JP2836177B2 - Differential heat / thermogravimeter - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a thermal analyzer for measuring physical properties of a material, and more particularly to a differential thermal analysis (hereinafter, referred to as DTA) or a differential scanning calorimetry (hereinafter, referred to as DSC). The present invention relates to a differential thermal / thermogravimetric simultaneous measurement device in which a differential heat measurement device and a thermogravimetry (hereinafter, referred to as TG) device are combined so as to be capable of simultaneously measuring the differential heat measurement and the TG.

(Prior Art) In DTA, a sample and a reference substance are heated or cooled under the same thermal condition, and a temperature difference generated between the two is measured with respect to the sample temperature. In DSC, the sample and the reference material are thermally separated, and energy is separately applied to measure the difference in energy input required to keep the temperature of the two equal. In any of the measurement methods, the specific heat capacity, the calorific value, and the transition temperature are measured by measuring the area of the difference between the measurement curve and the baseline or measuring the peak. Therefore, the measurement conditions are set so that the baseline is stabilized.

Conventionally, a differential thermal / thermogravimetric simultaneous measuring device capable of simultaneously measuring DTA and TG for the same sample has been known. However, even in such a simultaneous measurement device, the DTA signal and the TG signal are separately extracted and recorded.

(Problems to be Solved by the Invention) When the temperature of the sample is raised or lowered, the amount of the sample may change due to vaporization, liquefaction, or solidification of the sample. In such a case, a heat capacity difference with the reference material occurs,
Even if the heat capacity is matched between the reference material and the sample at room temperature when setting the sample, the baseline of DTA or DSC drifts and the measurement result becomes inaccurate.

SUMMARY OF THE INVENTION An object of the present invention is to provide a differential thermal / thermogravimetric simultaneous measurement device that can obtain an accurate measurement result by correcting a differential heat measurement signal even when a sample amount changes during measurement. .

(Means for Solving the Problems) In the present invention, a sample weight signal measured by TG is reflected on a DTA signal or a DSC signal to correct a drift of a baseline due to a difference in heat capacity. Specifically, it was proportional to the weight signal
Dividing means for dividing the DTA signal and the DSC signal by the TG signal is provided.

(Action) Baseline position (ΔT) ₀ in DTA is expressed by the following equation (1).

(ΔT) ₀ −αR (Cs−Cr) (1) where α is a heating rate, R is a device constant, Cs is a heat capacity of the sample, and Cr is a heat capacity of the reference material. Assuming that the specific heat of the sample is cs, since the heat capacity is Cs = m · cs (m is the mass of the sample), the equation (1) is transformed into the equation (2).

(ΔT) ₀ −αRm · cs + αRCr (2) By dividing equation (2) by the sample mass m, the following equation (3) is obtained.
It is transformed like the expression.

｛(ΔT) ₀ −αRCr｝ / m = αRcs (3) Although the sample mass m may change during the measurement, (3)
By subtracting a constant number αRCr from the baseline differential heat measurement signal (ΔT) _{0 as in the} equation and dividing by the sample mass m, a constant value is obtained regardless of the sample mass change. Therefore, if this is set as a new baseline, the DTA baseline will be stable.

 The same can be considered for DSC.

(Example) The figure shows the example which applied this invention to the DTA-TG simultaneous measurement apparatus.

Reference numeral 1 denotes a heating furnace, in which a DTA detector 2 is disposed. The DTA detector 2 is provided with a sample cell 31 for storing a sample and a reference substance 32 for storing a reference substance. The DTA detector 2 is attached to a balance mechanism of the weight measuring unit 4, and is provided with an automatic measuring mechanism conventionally used for measuring the weight of the balance mechanism. As such an automatic weight measuring mechanism, for example, the inclination of the beam of the balance is detected by a differential transformer or an optical method or an electric contact,
It is possible to use a so-called zero-point weighing system in which a current is applied to a solenoid coil mounted on the balance system and positioned in the magnetic field of the permanent magnet to return the inclination of the beam of the balance.

Reference numeral 5 denotes a weight signal amplifying circuit for amplifying the weight signal W detected by the weight measuring unit 4, and the amplified weight signal is output to a recorder.

In the DTA detector 2, a thermocouple is provided directly below the sample cell 31 and the reference substance cell 32, respectively. 6 is DTA detector 2
Is a temperature difference signal amplifying circuit for detecting and amplifying a temperature difference ΔT between a sample temperature and a reference material temperature by a thermocouple in the above. Numeral 7 denotes an integrating circuit as a dividing means, which receives the amplified weight signal W and the amplified temperature difference signal ΔT, and performs a division of ΔT and W with respect to weight, as represented by equation (3). It has. The output of the integrating circuit 7 is sent to the recorder as the vertical axis of the DTA signal. So this DTA
The vertical axis of the signal is the temperature difference normalized by weight.

A sample temperature signal Ts is extracted from the thermocouple on the sample cell 31 side of the DTA detector 2. The heating furnace 1 is also provided with a thermocouple, and a heating furnace temperature signal Tf is extracted from the thermocouple. Reference numeral 8 denotes a temperature signal amplifier circuit for detecting and amplifying the sample temperature signal Ts and the heating furnace temperature signal Tf, respectively. The sample temperature Ts amplified by the temperature signal amplifier circuit 8 is sent to the recorder as the horizontal axis of the DTA curve.

9 is a heating furnace temperature control circuit, and a temperature signal amplification circuit 8
Is supplied to the heater of the heating furnace 1 so that the heating furnace temperature rises or falls according to a program.

 Next, the operation of the present embodiment will be described.

A sample is placed in the sample cell 31 of the DTA detector 2, a certain amount of the reference substance is placed in the reference substance cell 32, and the heating furnace temperature control circuit 9
Raises the temperature of the heating furnace 1 according to a program, for example.

In the TG device, the change in weight of the sample is output via the weight signal amplifier circuit 5 according to the temperature rise, and the sample temperature Ts
Is output from the temperature signal amplifier circuit 8 to the recorder, and the recorder records the weight change W of the sample with respect to the sample temperature Ts.

On the other hand, in the DTA device, the temperature difference ΔT between the sample and the reference substance is normalized by weight by the integrating circuit 7 and output to the recorder. As a result, the recorder has a temperature signal amplifier circuit 8.
A DTA curve is obtained in which the abscissa represents the sample temperature Ts output from, and the ordinate represents the temperature difference normalized by weight.

(Effect of the Invention) In a DTA device or a DSC device, strictly speaking, a change in the amount of a sample always accompanies unless the sample cell is a closed cell.
Since the signal and DSC signal are corrected by weight, the DTA curve and DSC
The baseline of the curve is stabilized, and the temperature reading of the transition temperature and the quantitativeness of calorimetry are improved.

In the case of a sample with a drastic change in sample amount, for example, a sample with thermal decomposition, etc., it was difficult to measure DTA with a conventional DTA single-function device or a DTA-TG simultaneous measuring device. The DTA measurement can be performed on a simple sample.

Since the DTA signal and the DSC signal output according to the present invention are standardized by weight, comparison between data having different sample amounts becomes easy.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic configuration diagram showing one embodiment. 1 ... heating furnace, 2 ... DTA detector, 4 ... weight measuring section,
5 weight signal amplifier circuit 6 temperature difference signal amplifier circuit
7: integrating circuit as dividing means, 8: temperature signal amplifying circuit, 9: heating furnace temperature control circuit, 31: sample cell,
32 Reference cell.

Claims (1)

(57) [Claims] 1. A differential calorimeter or a differential scanning calorimeter or the like and a thermogravimetric measuring device are combined so as to be capable of simultaneously measuring the differential calorimetry and the thermogravimetric measurement to form a single measuring device. A differential thermogravimetric / thermogravimetric simultaneous measurement device provided with a dividing means for continuously dividing a signal by a thermogravimetric signal and outputting a new differential calorimetric signal with a corrected baseline.