JPH05297961A - Thermal analyzing device - Google Patents

Abstract

PURPOSE:To enhance thermal resolution ability and to execute the simulation analysis of a sintering process of ceramics at the time of observing a decomposition phenomenon of a sample by executing simply a variation speed of a physical signal to be measured through a control of temperature in the thermal analyzing device. CONSTITUTION:This device is provided with a differentiator 14 for differentiating a measured physical signal by time, a differential value condition setting device 15 in which the upper limit value and the lower limit value are stored, a comparator 16 for comparing the differential value with the upper limit value and the lower limit value, and a function generator 17 for generating a program signal for heating a sample. The function generator 17 is constituted so that when a signal for informing a fact that the differential value exceeds the upper limit value is inputted from the comparator 16, a heating program for decreasing a heating speed is outputted, and a signal for informing a face that the differential value becomes below the lower limit value is inputted from the comparator 16, a heating program for decreasing a heating speed is outputted. When a reaction such as a decomposition reaction, etc., becomes intense due to heating, the heating speed becomes low, and the reaction process can be observed with high accuracy.

Description

Detailed Description of the Invention

[0001]

The present invention relates to the physical properties of materials such as
The present invention relates to so-called thermal analysis devices such as thermogravimetric and thermomechanical measuring devices for measuring the weight and length of a sample as a function of temperature and time.

[0002]

2. Description of the Related Art In conventional thermal analyzers, the sample temperature is generally changed at a constant rate and the physical change of the sample at that time is measured. Therefore, in this case, the temperature raising program for raising the temperature of the sample was to raise the temperature linearly with respect to time. On the other hand, in recent years, thermal analyzers that employ a linear heating program having a plurality of linear heating programs having different inclinations in multiple stages have been widely used.

Recently, a thermogravimetric analyzer (hereinafter referred to as TG) is used for a sample in which a plurality of decomposition reactions occur at close temperatures.
In order to analyze each decomposition reaction of the sample with high resolution, the thermogravimetric measuring device which holds the sample temperature isothermally based on the signal indicating the weight of the sample has been proposed. Further, when ceramics or a sintered substance such as powder metallurgy is sintered, the material shrinks, but when the shrinkage of the material is measured by a thermomechanical measuring device (hereinafter referred to as TMA), the conventional isothermal When the temperature rises rapidly, the shrinkage rate of the material is not constant,
Since the material easily becomes unstable, TMA in which temperature control is performed so as to keep the shrinkage rate constant is considered.

[0004]

In the thermal analysis device,
The idea of controlling the temperature of the sample so that the rate of change of the weight or length of the sample is constant has existed for a long time,
Its purpose was also clear. However, no specific satisfactory means have been proposed so far. The biggest reason is that the change in weight or length is detected and the detected signal is fed back.
When the temperature of the sample is controlled, the response delay changes in the feedback control depending on the thermal inertia due to the heat capacity of the heating furnace used and the change in the physical properties of the sample itself. Therefore, there is a problem that control oscillation and overshoot of the sample temperature occur.

[0005]

SUMMARY OF THE INVENTION The present invention is to solve the above-mentioned problems and its main constitution is programmed with respect to the heating furnace for heating the sample and the time for controlling the sample temperature. A function generator for generating a temperature signal, a physical property measuring device for continuously measuring the physical property of a heated sample as a function of time, and a differentiating circuit for differentiating the measured physical property value of the physical property measuring device with respect to time And a differential value condition setter that presets the upper limit value and the lower limit value of the differential value, the differential circuit connected to the differential circuit and the differential value condition setting circuit, and compares the differential value with the upper limit value and the lower limit value, And a comparator that outputs a signal for changing the program to the function generator.

[0006]

First, the upper and lower limits of the differential value measured by the differential condition setting device are preset. Then, the thermal analysis of the sample is started from room temperature by the present thermal analysis device. If the change in the physical property value of the sample measured by the physical property measuring device, that is, the output of the differentiation circuit (in absolute value) is between the upper limit value and the lower limit value, the sample is heated by the programmed temperature signal. To be done. Here, when the decomposition reaction occurs in the sample at a certain temperature, the change in the physical property value of the sample usually becomes large. That is, the output value of the differentiating circuit exceeds the upper limit value. Here, the comparator outputs to the function generating circuit that the output value of the differentiating circuit exceeds the upper limit value, and the function generating circuit changes the program for controlling the sample temperature.

Normally, this program generates a signal for slowing the heating rate of the sample by a constant factor, and the heating rate of the sample becomes slow. That is, each decomposition reaction of the sample can be analyzed with high resolution. At this time, if the decomposition reaction progresses more and more, the above-mentioned situation will occur and the heating rate of the sample will further decrease. Here, if the sample temperature rises to some extent and the decomposition reaction of the sample disappears, the change in the physical property value of the sample measured by the physical property measuring device becomes small. At this time, since the heating rate of the sample is slow, the output of the differentiating circuit becomes smaller than the normal (initial) value, and the output of the differentiating circuit becomes smaller than the lower limit value. Here, the comparator outputs to the function generating circuit that the output value of the differentiating circuit is below the lower limit value, and the function generating circuit changes the program for controlling the sample temperature. Normally, this program generates a signal for increasing the heating rate of the sample by a constant factor, the heating rate of the sample is increased, and this is repeated to return to the original heating rate.

As described above, the time differential value of the physical property value is measured, the value is compared with the upper limit value and the lower limit value, and the heating program of the sample is changed, so that each decomposition reaction of the sample can be resolved with good resolution. Can be analyzed.

[0009]

Embodiments of the present invention will be described below with reference to the drawings. (Embodiment 1) FIG. 1 is a schematic block diagram of a TG. A sample-side beam 2 and a reference-side beam 3 that form a pair of beams are horizontally inserted into a heating furnace 1 that heats a sample and a reference substance. A sample holder 4 is fixed to the tip of the sample side beam 2, and a reference holder 5 is fixed to the tip of the reference side beam 3. A sample (not shown) to be thermally analyzed by TG is placed on the sample holder 4, and a chemically stable reference substance (not shown) is placed on the reference holder 5. Each beam 2,
Coils 6, 6 are fixed to the central portion of 3. The coils 6, 6 are arranged in the magnetic field created by the magnets 7, 7, respectively. Further, the holders 4 and 5 are rotatably supported in the vertical direction by a structure (not shown) at the central portions of the beams 2 and 3.

Further, slits 8 and 8 are attached to the other ends of the beams 2 and 3, respectively. Lamps 9 and 9 are provided so that light passes through the respective slits 8 and 8. Photodiodes 10 and 10 are fixed at positions where the light passing through the slits 8 and 8 is received. Signals from Photodio Auto 10, 10 are PI
The D control circuits 11 and 11 output the outputs to the respective current detectors 12 and 12, and detect the amount of current to be fed back to the coils 6 and 6 in order to keep the beams 2 and 3 horizontal. And supply is done. Coils 6, 6
The electric current sent to the beams 7 and 8 applies a rotating torque to the beams 2 and 3 in a direction that suppresses (eliminates) the displacement of the beams 2 and 3 by the action of the magnets 7 and 7 and the coils 6 and 6.

The above-mentioned coils 6, 6, magnets 7, 7,
Slits 8, 8, lamps 9, 9, photodiode 1
The feedback circuit system including 0, 10, PID control circuits 11 and 11 and current detectors 12 and 12 always continues to operate during the operation of the TG, so that the sample placed on the sample boulder 4 is decomposed and its weight is reduced. Each beam 2,3, even when varied, visually appears to be stationary.

Each of the current detectors 12 and 12 is also output to one differential amplifier 13. In the differential amplifier 13,
The difference between the current value required to stop the sample-side beam 2 and the current value required to stop the reference-side beam 3 is taken and amplified. That is, the output of the differential amplifier 13 represents the difference in rotational torque required to restore the sample-side beam 2 and the reference-side beam 3.

Here, if a thermally stable reference substance is placed on the reference boulder 5, a sample to be measured is placed on the sample holder 4, and thermal analysis is performed, the output of the differential amplifier 13 is properly normalized. If done (multiplied by the appropriate factor), it would represent the weight change of the sample, and the thermogravimetric (TG) signal, or
It is the physical property itself. The output signal of the differential amplifier 13 (T
The G signal) is sent to the differentiating circuit 14 and differentiated in time.
The differentiated TG signal (differentiated physical property value) indicates the rate of weight change of the sample.

Here, the differential value condition setter 15 is capable of externally setting two reference values, an upper limit value and a lower limit value. The upper limit value indicates the maximum value of the rate of weight change of the sample (differentiated physical property value), and the lower limit value indicates the minimum value of the rate of weight change of the sample. The differentiating circuit 14 and the differential value condition setter 15 are connected to the comparator 16. The comparator 16 compares the upper limit value and the lower limit value output from the differential value condition setter 15 with a signal output from the differentiating circuit 14 and indicating the rate of change in weight of the sample.

The comparator 16 is connected to the function generator 17. The function generator 17 is connected to the furnace 1 for heating the sample and the reference substance via a temperature control circuit 18 and generates a temperature signal programmed with respect to time for controlling the sample temperature. Here, when the output of the differentiating circuit 14 exceeds the upper limit value, the time scale of the subsequent time point of the programmed temperature signal is doubled from the comparator 16 to the function generator 17 with the time point as the time origin. Is sent. That is, when the rate of change in the weight of the sample (differentiated physical property value) becomes faster than a certain reference value, the comparator 16 instructs the temperature control circuit 18 to slow down the rate of increase in the temperature of the sample. After this, the function generator 17
The rate of change of the output of is halved.

Conversely, when the output of the differentiating circuit 14 falls below the lower limit value, the comparator 16 sends the function generator 17 the time origin as the time origin, and the time scale of the programmed temperature signal thereafter is halved. A command is sent to reduce the size. That is, when the speed of change in the weight of the sample (differentiated physical property value) becomes slower than a certain reference value, the comparator 16 instructs the temperature control circuit 18 to increase the rising speed of the temperature of the sample. After that, the changing speed of the output of the function generator 17 is doubled.

The function generating circuit 17 stores a function which is a temperature program for heating the sample, and the function is a function of time and temperature. As a result of such a series of temperature control, for example, when the sample is heated and the weight change (weight / deg) of the sample becomes fast, the output from the differentiating circuit 14 becomes higher than the upper limit value, and the comparator 16 It is possible to analyze the decomposition reactions of the sample with high resolution by slowing the heating rate of the sample through the function generator 17 and the temperature control circuit 18 to suppress the reaction. Further, when the heating temperature of the sample is further increased and the original weight change (weight / deg) is returned, the heating rate is slow, so the output from the differentiating circuit 14 becomes smaller than the lower limit value, The heating rate of the sample will be restored. Therefore, during the measurement, the reaction rate [change in weight (weight / hour)] is kept such that it falls within the upper and lower limit values set in advance by the differential value condition setting unit 15.

Next, an example of actual measurement will be described. In the case of TG, the physical quantity measured is weight, and the upper limit of the rate of change in weight (weight / hour) is 100 μgr. / Mi
n. , And a lower limit value of 80 μgr. / Min. Is set in the differential value condition setter 15. And the function generator 17
Also, a function of time and temperature is input in advance at 40 ° C./min. When the comparator 16 outputs a signal indicating that the differentiating circuit 14 exceeds the upper limit value, the function generator 17 causes the time scale of the programmed function (the relational expression between temperature and time) to be an integral multiple (for example, Double the original heating rate to 40
In the case of ° C / min, it becomes 20 ° C / min) and output. Conversely, when the comparator 16 outputs a signal indicating that the differentiating circuit 14 has exceeded the lower limit value, the function generator 17 changes the time scale of the programmed function (the relational expression between temperature and time) to that value. Reciprocal multiple of an integer
If the original heating rate is 20 ℃ / min, 40 ℃ / min
Output).

Here, a sample, which is a ceramic powder compact, is placed on the sample holder 4, and a thermally stable standard sample is placed on the reference holder 5. Then, in order to start the TG measurement, the furnace and the standard sample are heated in accordance with the temperature program stored in the function generator 17 of the furnace 1. The heating rate is 40 ° C./min which is set in advance. At the beginning of heating, the sample did not undergo a decomposition reaction, but the volatile components contained therein gradually volatilized, but the weight change was 80 to 100 μgr. / Min range.
Since the output of the differentiating circuit 14 does not exceed the upper limit value and does not fall below the lower limit value, the sample is continuously heated at a heating rate of 40 ° C./min.

When the temperature of the sample reaches the decomposition temperature of the substance contained in the sample, the weight of the sample decreases rapidly, and the output of the differentiating circuit 14 becomes 100 μgr. / Min will be exceeded. Therefore, the comparator 16 compares the upper and lower limit values set in the differential value condition setting unit 15 and outputs to the function generator 17 that the output of the differentiating circuit 14 exceeds the upper limit value. The function generator 17 doubles the time scale of the function to be the temperature program, and outputs it to the temperature control circuit 18.
Doubling the time scale of the function that is the temperature program means halving the heating rate (temperature / time). In the case of this embodiment, the heating rate is 20 ° C. /
It will be min. That is, the sample is gradually heated.

Here, even if the heating rate is 20 ° C./min, the weight change of the sample is large, and the output of the differentiating circuit 14 is 100 μgr. When / min is exceeded, the function generator 17 again doubles the time scale of the function to be the temperature program and outputs it to the temperature control circuit 18. That is, the heating rate becomes 10 ° C./min, and the heating rate becomes slower. Thus, the weight change of the sample is 10
0 μgr. The time scale of the function serving as the temperature program is expanded until the temperature becomes equal to or lower than / min, and the heating rate gradually approaches 0 ° C./min. Change in sample weight is 100 μg
r. When it is lower than / min, the temperature rising rate (temperature / time) of the sample becomes constant from that point.

When the temperature of the sample rises to a certain extent and the decomposition reaction of the sample ends, the weight change due to heating of the sample becomes small. Therefore, the output from the differentiating circuit 14 is
The lower limit value of the differential condition setting device 15 is 80 μgr. / M
in. It becomes the following. The function generator 17 multiplies the time scale of the programmed function (the relational expression of temperature and time) by the reciprocal of its integer (for example, 1/2. If the original heating rate is 10 ° C./min. In this case, it becomes 20 ° C./min) and output. Further still, the output from the differentiating circuit 14 is 80 μ which is the lower limit value of the differential value condition setter 15.
gr. / Min. Function generator 17 if:
Outputs the time scale of the programmed function by 1/2 (40 ° C./min).

That is, the rate of weight change of the sample is 80 to 10
In the range of 0 μgr / min, the temperature rising rate of the sample does not change, but when it exceeds 100 μgr / min, the temperature rising rate is reduced by half. Also, the weight change speed is 80
When it falls below μgr / min, the temperature rising rate is doubled. That is, the weight change of the sample is always 80-100.
It is controlled in the range of μgr / min.

However, when the weight of the sample hardly changes even if the sample is heated, the heating rate becomes infinite, so that the heating rate is limited. For example, the heating rate is 40 ℃
/ Min, the output from the differentiation circuit 14 is 80 μg
Even in the case of r / min or less, the function generator 17 does not output the signal for increasing the temperature rising rate of the sample, but outputs the function of the original temperature rising program. (Embodiment 2) Next, an embodiment of the present invention using TMA will be described. In FIG. 2, the heating furnace 1 is fixed to a substrate 23 by a moving mechanism 22 so as to be vertically movable. A cylindrical sample holder 2 with a bottom for mounting a sample 26 in the heating furnace 1
5 is inserted. The sample holder 25 is vertically movably attached to the base body 23 via the micrometer 24. A rod-shaped probe 27 is placed on the sample 26. The probe 27 has a core 28 made of a magnetic material.
Is attached. A differential transformer 29 is installed at a position surrounding the core 28. Sample 26
The expansion of is detected by the displacement detection circuit 35 as the relative position of the differential transformer 29 and the core 28 changes.

On the other hand, an arm 30 is rotatably attached to the upper end of the base 23 at its substantially central portion. The mounting position is called a fulcrum 30b. A probe 27 is rotatably attached to one end of the arm 30.
The mounting position is called the sub-fulcrum 30a. Furthermore, a coil holder 31 is fixed to the other end of the arm 30, and a ring-shaped coil 32 is wound around the coil holder 31.
The magnet 33 is attached to the base 23 via the base 34 so as to surround the coil 32. And
The Macnet 33 forms a radial magnetic field perpendicular to the coil 32. The coil 32 is electrically connected to a current generator (not shown), and a controlled current from the current generator is passed through the coil 32, so that the Macnet 33
An attractive force or repulsive force acts between the coil 32 and the coil 32. That is, by controlling the current flowing through the coil 32,
The probe 27 can be pressed against the sample 26 by an arbitrary force via the arm 30.

The output signal of the displacement detector 35 is the sample 26
Shows a change in the length of the, which is a kind of physical property value and is generally called a thermomechanical analysis (TMA) signal. The signal from the displacement detector 35 is input to the differentiating circuit 14, and thereafter, the configuration is the same as that of the first embodiment and the operation is the same as that of the first embodiment. The operation will be briefly described below. The differentiating circuit 14 differentiates the input signal with respect to time and sends it to the comparator 16. The comparator 16 compares the signal from the differentiating circuit 14 with the upper limit value and the lower limit value stored in the differential value condition setting unit 15. The upper limit value stored in the differential value condition setter 15 is the maximum value of the change amount of the sample length per time in the TMA measurement of the sample 26, and the minimum value is the sample length per time. Is the minimum change amount of Here, the differentiation circuit 1
When the output of 4 exceeds the upper limit value, the comparator to the function generator 1
A command is sent to 7 to double the time scale of the subsequent ond program with that time point as the origin. Therefore, for the output of the function generator 17 thereafter, the heating rate of the sample so far is halved. Conversely, the differentiating circuit 14
When the output of is below the lower limit, the comparator to the function generator 1
7, a command is sent to make the time scale of the subsequent temperature program 1/2 times, with the time point as the origin.
Therefore, the output of the function generator 17 thereafter is twice the heating rate of the sample up to now.

The signal output from the function generator 17 is sent to the temperature control circuit 18 to control the heating temperature of the heating furnace 1 by a conventional method, and is placed on the sample boulder 25 in the heating furnace 1. The temperature of the prepared sample 26 is controlled. By such a series of temperature control, when the change in the length of the sample 26 is faster than the preset upper limit value, the length change is suppressed, and when the change is slower than the preset lower limit value, The heating rate of the sample is adjusted to accelerate the change in length. Therefore, the changing speed (length / time) of the length of the sample 26 during the measurement falls within the preset upper and lower limit values.

[0028]

As described above, according to the present invention, the rate of change of the physical properties is obtained by differentiating the physical property measurement signal of the sample with respect to time, and the rate of change of the predetermined rate of change is calculated. By comparing the upper limit value and the lower limit value, the rate of change of physical properties during measurement can be controlled. Therefore, the temperature resolution can be improved in the thermal analysis for observing the decomposition phenomenon. It is especially effective in TG measurement. Moreover, in TMA measurement, simulation of an appropriate sintering process of ceramics can be easily performed. Furthermore, the rate of change of sample temperature is
It is varied in steps, and the change in sample size over time becomes almost exponential. Therefore, the oscillation of the sample temperature and the phenomenon of overshoot can be suppressed. Then, the reliability of the measurement data is improved.

[Brief description of drawings]

FIG. 1 is a block diagram of a TG measuring apparatus that is Embodiment 1 of the present invention.

FIG. 2 is a block diagram of a TMA measuring apparatus that is Embodiment 2 of the present invention.

[Explanation of symbols]

 1 Heating Furnace 13 Differential Amplifier 14 Differentiation Circuit 15 Differential Value Condition Setter 16 Comparator 17 Function Generator 18 Temperature Control Circuit 35 Displacement Detection Circuit

Claims (5)

[Claims] 1. A heating furnace for heating a sample, a function generator for generating a temperature signal programmed against time for controlling the temperature of the sample, and a physical property of the heated sample as a function of time. , A differentiating circuit that differentiates the measured physical property value of the physical property measuring device with respect to time, a differential value condition setting device that presets the upper limit value and the lower limit value of the differential value, and the differential A circuit and a comparator that is connected to the differential value condition setting circuit, compares the differential value with the upper limit value and the lower limit value, and outputs the result to the function generator with a signal for changing the program. Characteristic thermal analysis device. 2. The thermal analyzer according to claim 1, wherein the physical property measuring device measures the weight of the sample. 3. The thermal analyzer according to claim 1, wherein the physical property measuring device measures the length of the sample. 4. The comparator outputs a signal for delaying the programmed temperature signal with respect to time when the differential value is larger than an upper limit value of the differential value, and the differential value is equal to the differential value. The thermal analysis device according to claim 1, wherein a signal that accelerates the programmed temperature signal with respect to time is output when it is smaller than a lower limit value. 5. The signal output from the comparator when the differential value is larger than the upper limit value of the differential value is a signal that multiplies the time coefficient of the programmed temperature signal by a constant, and the differential value is The thermal analyzer according to claim 4, wherein the signal output from the comparator when the differential value is smaller than the lower limit value is a signal that multiplies the time coefficient of the programmed temperature signal by a reciprocal of a constant.