JP2005043296A - Thermogravimetry - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To heighten reliability to weight data acquired at a high temperature in thermogravimetry. <P>SOLUTION: Not only calibration by a calibration weight is performed at a room temperature before measurement but also the weight of the calibration weight is measured at a measurement finish temperature after measurement, and a weight measured value of a sample is corrected by using a calculation expression based on the measurement result. Hereby, since a sensitivity change of a balance caused by thermal expansion of a balance beam or other complicated thermal factors is corrected, the reliability of the weight data acquired at the high temperature is improved. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a thermogravimetric measurement method for measuring a change in thermal weight of a sample.

Thermogravimetry is basically performed using an apparatus that combines a balance and a heating furnace.
FIG. 2 shows a schematic configuration example of a conventional thermogravimetric measuring apparatus. In the figure, two beams (main beam 4 and sub beam 5) oscillating on a fulcrum 6 and a sub fulcrum 7 form a balance, and a sample 2 and a reference material 1 placed on the tips of both arms. Is configured to be located in the heating furnace 3, and when the temperature is changed by the heating furnace 3, if the sample is decomposed or dehydrated, a weight change due to this is observed by the balance.

In thermogravimetry, the balance of the balance is balanced by an electromagnetic mechanism (not shown) while raising the temperature of the sample from room temperature to a predetermined temperature (usually about 1000 ° C). As a measured value of weight, it is displayed or recorded two-dimensionally together with the temperature value of the sample measured by a thermocouple (not shown) at the same time.
Note that many recent thermogravimetric measuring devices are controlled by a computer and have a function of processing measurement data and storing it in a storage device.

Since accuracy is required for the weight measurement, there is also a thermogravimetric measuring device that is equipped with a calibration weight 8 and an addition / removal mechanism 9 that automatically loads or unloads the calibration weight so that calibration can be performed at any time. .
Similarly, it is also required to accurately measure the temperature of the sample 2. However, since a thermocouple cannot be brought into contact with the sample 2 on the balance, the melting is detected using a calibration sample that melts at a constant temperature. There is also an example in which the accuracy of temperature measurement is improved by performing temperature calibration (see, for example, Patent Document 1).
JP-A-9-210894

In the conventional thermogravimetry, in order to ensure the accuracy of the weight measurement, the method of calibrating using the calibration weight as described above was used. However, the calibration operation is usually performed at room temperature before the measurement, and when the temperature of the heating furnace is raised and the actual measurement is performed after that, the thermal expansion of the balance beam or other complicated thermal There is a possibility that sensitivity changes in the balance due to factors, and there is still some concern about the reliability of the weight measurement value at high temperature.
This invention is made | formed in view of such a situation, and it aims at improving the reliability with respect to the thermogravimetric measurement data acquired under high temperature.

  In order to solve the above problems, in the method according to the present invention, not only the calibration with the calibration weight is performed at room temperature before the measurement, but also the weight of the calibration weight is measured at the measurement end temperature after the measurement. The weight measurement value of the sample was corrected using a calculation formula based on the above.

  That is, in the present invention, calibration is first performed using a calibration weight at room temperature, and then the weight of the sample at the intermediate temperature T is sequentially measured while changing the temperature of the sample from room temperature to the predetermined temperature, and then the predetermined temperature is reached. The weight of the calibration weight was measured again in step 1, and the difference between the weight measurement values of the calibration weight at the predetermined temperature and room temperature was apportioned to the ratio between the temperature difference between the predetermined temperature and room temperature and the temperature difference between temperature T and room temperature. The thermogravimetry method is characterized in that the correction weight value of the sample at the temperature T is obtained by subtracting the correction value from the weight measurement value of the sample at the temperature T.

  In the thermogravimetry, the calibration weight is not only calibrated with a calibration weight at room temperature before starting the measurement, but also after the sample is measured by raising the temperature to a predetermined temperature, the weight of the calibration weight is again measured. Since the measurement is performed and correction calculation is performed on the acquired measurement data based on the measurement result, the reliability of the weight data acquired at a high temperature is improved.

The present invention is a measuring method performed using a thermogravimetric measuring apparatus having a storage and calculation function of measurement data and a calibration weight adding / subtracting mechanism as shown in FIG. 2, and FIG. 1 illustrates the method. is there.
Hereinafter, the method will be described in sequence with reference to FIG. The following (1) to (2) correspond to the conventional measuring method.

(1) Before starting measurement, a calibration weight (weight W) is loaded at room temperature Tr to obtain a weight measurement value Wr, and the calibration screw of the apparatus is adjusted so that Wr matches W (ie, Perform calibration).
(2) In accordance with predetermined analysis conditions, the temperature and weight of the sample are measured while raising the temperature to the predetermined temperature Tm, and a weight measurement value Xt at the temperature T is obtained and temporarily stored in the storage device. Since the temperature T changes from the room temperature Tr to the predetermined temperature Tm, Xt is an accumulation of a large number of data.
(3) After the temperature reaches the predetermined temperature Tm, the calibration weight is loaded again and its weight is measured to obtain the weight measurement value Wm.
(4) The weight measurement value Xt acquired and stored in (2) above is subjected to correction calculation according to the following equation to obtain a corrected weight value Yt.
Yt = Xt− (Wm−W) × (T−Tr) / (Tm−Tr)

It is a figure which shows the thermogravimetry method which becomes this invention. It is a figure which shows the example of schematic structure of a thermogravimetry apparatus.

Explanation of symbols

1 reference material 2 sample 3 heating furnace 4 main beam 5 sub beam 6 fulcrum 7 sub fulcrum 8 calibration weight 9 dosing mechanism

Claims (1)

A method for measuring a change in the thermal weight of a sample when the temperature of the sample is changed from room temperature to a predetermined temperature using a thermogravimetric measuring device equipped with means for adding and removing a calibration weight, storing measurement data, and calculating means. First, calibrate using a calibration weight at room temperature, then measure the weight of the sample at intermediate temperature T sequentially while changing the temperature of the sample from room temperature to the specified temperature, then calibrate again at the specified temperature Measures the weight of the calibration weight, and corrects the value by dividing the difference between the weight measurement value of the calibration weight between the specified temperature and room temperature into the ratio between the temperature difference between the specified temperature and room temperature and the temperature difference between temperature T and room temperature A thermogravimetric measurement method characterized in that a corrected weight value of a sample at temperature T is obtained by subtracting the correction value from a weight measurement value of the sample at temperature T.

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