JP2004020509A - Calorimeter - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a calorimeter capable of measuring up to the very small heating value level of 10 nanowatt order by enhancing the stability of a baseline in measuring heat flux. <P>SOLUTION: A first countermeasure to this calorimeter is to improve a heating/cooling control method by performing temperature control in multiple stages, that is, the temperature of inside space of double heat insulating shields 24 and 26 is roughly controlled by a heater 20 on the outside of the heat insulating shields 24 and 26. In addition, heating/cooling of metal blocks 30, 32 and 34 is precisely controlled using a thermo-module 28 formed of a Peltier element, inside the heat insulating shields 24 and 26. A second countermeasure is to optimize a thermal distance between heat flux sensors 40 and 42, and the thermo-module 28, that is, the metal blocks 30, 32 and 34 with a thickness of 6-60mm are arranged between the thermo-module 28 and the heat flux sensors 40 and 42. A third countermeasure is to use semiconductor thermoelements 40 and 42 as the heat flux sensors to acquire high sensitivity. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a calorimeter capable of measuring a minute amount of heat on the order of 10 nanowatts.
[0002]
[Prior art]
A calorimeter such as a differential scanning calorimeter (DSC) is described in “Basics and Application of Thermal Analysis, Third Edition” (edited by the Japan Society of Thermometry, Realize, 1994), p. As described in No. 10, the components and shapes are generalized. However, such generalized specifications are only capable of measuring heat fluxes up to microwatts at best, and are not suitable for measuring small amounts of heat on the order of 10 nanowatts. On the other hand, in various industrial fields and research fields, such as research on stable structures of proteins, demands for measurement of a minute calorific value on the order of 10 nanowatts have recently become increasingly stronger.
[0003]
The above generalized specifications have the following problems when measuring a minute amount of heat. (1) The thickness of the metal soaking plate on which the sample is placed is as thin as 1 to 3 mm, and the temperature stability is insufficient. (2) Since the metal block for maintaining the uniformity of the heating temperature is located at a distance that is thermally close to the sample (small thermal diffusivity), it is easily affected by the temperature fluctuation of the metal block. (3) The sensitivity for detecting the temperature difference between the sample and the reference sample is insufficient because a thermocouple or a platinum resistance thermometer is used. (4) Since only one temperature control heater is used, disturbance factors such as room temperature fluctuation cannot be sufficiently removed. (5) Since a heater is used for temperature control, only heating control can be performed.
[0004]
Due to these problems, the baseline stability when measuring heat flux was insufficient, and calorimeters with generalized specifications only measured at most the microwatt level. Smaller amounts of heat were buried in the noise level and could not be measured.
[0005]
On the other hand, in order to overcome the problem of general specifications, a minute calorimeter having a noise level of about 200 nanowatts has been devised and used. For example, "Modern Chemistry", February 1998, p. The microcalorimeter described in 38-40 has the following features. (1) The error caused by taking in and out of the sample is reduced by using the fixed sample type. (2) The heat flux detection sensitivity is increased by using multiple thermocouples. (3) The temperature stability around the sample is devised by doubly controlling the heat around the sample. However, even with such measures, the noise level remained at about 200 nanowatts.
[0006]
By the way, in the differential scanning calorimeter, the following known techniques are known as those which are made to have high sensitivity by using a semiconductor thermoelectric element instead of a thermocouple as a heat flux sensor. Japanese Patent Application Laid-Open No. Sho 50-66282 discloses that two ends of an N-type semiconductor thermoelectric element are fixed to a measurement sample container and a standard sample container, respectively, and the other ends of these semiconductor thermoelectric elements are fixed to a metal plate. The difference between the thermoelectromotive forces of the two semiconductor thermoelectric elements is measured to detect the temperature difference between the two sample containers. By using a semiconductor thermoelectric element in this way, a high-sensitivity thermoelectromotive force of 160 μV / K is obtained, and the rate of temperature rise or fall can be reduced, thereby greatly improving the temperature resolution of transition and the like. Can be. JP-A-57-206839 also discloses that an unknown sample container and a reference sample container are brought into contact with one end of a semiconductor thermoelectric element, respectively, and the other end of the semiconductor thermoelectric element is brought into contact with a metal block. The difference between the thermoelectromotive forces of the two semiconductor thermoelectric elements is measured to detect the temperature difference between the two sample containers. Thereby, heat capacity measurement can be performed with high resolution.
[0007]
In addition, the following known technology is known as a calorimeter using a Peltier element to enable both heating and cooling. Japanese Patent Application Laid-Open No. 2000-329718 discloses a thermal conductivity measuring device in which hot plates are arranged on both sides of a plate-shaped sample via a heat flow meter. These hot plates are composed of semiconductor heating / cooling modules utilizing the Peltier effect.
[0008]
[Problems to be solved by the invention]
In the measurement of thermal phenomena such as phase transition, it has recently been required to measure very fine signals with a very high resolution with a very small amount of sample. Measuring with high resolution alone is difficult, but measuring very fine signals with a small amount of sample at high resolution is even more difficult. That is, when a small amount of sample is measured, the signal becomes smaller in proportion to the amount of sample. Further, in order to perform measurement with high resolution, it is necessary to reduce the heating rate or the cooling rate, and in that case, the signal decreases in proportion to the heating rate or the cooling rate.
[0009]
Conventional commercial calorimeter specifications are described in “Hyundai Kagaku”, February 1998, p. 38-40, the limit was about 0.01 K / min for the one with the lowest heating rate, and 200 nanowatts for the one with the smallest noise.
[0010]
To overcome these limitations and enable the measurement of very small amounts of heat on the order of 10 nanowatts, it is necessary to significantly increase the stability of the baseline when measuring the heat flux. The specific issues for that are as follows. (1) In the conventional apparatus, the minimum control width of the temperature control for controlling the heating rate is at least about 2 mK. This minimum temperature control width becomes a factor that disturbs the stability of the baseline. Therefore, it is necessary to significantly reduce the temperature control width. (2) Even if the above-mentioned minimum temperature control width is present to some extent, temperature fluctuation at the position for detecting the temperature for temperature control is not likely to be disturbed at the position of the heat flux sensor. (3) Even if the temperature around the device (for example, room temperature) changes, the device is designed so that the temperature change does not affect the signal of the heat flux sensor. (4) Minimize the noise entering when amplifying the output difference (signal related to heat flux) between the sample sensor and the reference sample sensor.
[0011]
An object of the present invention is to provide a calorimeter capable of measuring a minute calorific value on the order of 10 nanowatts by solving the above problems at once.
[0012]
[Means for Solving the Problems]
In order to solve the above-mentioned problems, a calorimeter of the present invention has the following configuration. (A) A metal block having a thickness of 6 to 60 mm. (B) a first semiconductor thermoelectric element having one end in contact with the measurement sample container and the other end in contact with the metal block; (C) a second semiconductor thermoelectric element having one end in contact with the reference sample container and the other end in contact with the metal block; (D) a thermo module in contact with the metal block, wherein the thermo module can heat and cool the metal block by a Peltier effect. (E) A temperature control element for precision control for detecting the temperature of the metal block. (F) at least a double adiabatic shield surrounding the metal block, the first semiconductor thermoelectric element, the second semiconductor thermoelectric element, and the thermomodule; (G) A heater and a temperature detecting element for coarse control provided outside the heat insulating shield. (H) a thermo-module power supply that controls power supplied to the thermo-module based on the output of the temperature control element for precision control. (I) A heater power supply for controlling the power supplied to the heater based on the output of the coarse control temperature detecting element. (J) A thermo-electromotive force difference detection device for detecting a thermo-electromotive force difference between the first semiconductor thermoelectric element and the second semiconductor thermoelectric element.
[0013]
Hereinafter, the role of each component of the present invention will be described. In order to achieve the above object, the present invention takes the following measures. (1) Improve the heating / cooling control method. (2) Optimize the thermal distance between the heat flux sensor and the heating / cooling element. (3) Make the heat flux sensor highly sensitive.
[0014]
As an improvement in the heating / cooling control method, first, the temperature control is multistage. That is, a heater is provided outside the heat-insulating shield, and power supplied to the heater is controlled to roughly control the temperature of the space inside the heat-insulating shield. In addition, inside the heat shield, the temperature of the metal block is precisely controlled using a thermo module that can be heated and cooled by the Peltier effect. By performing rough control for controlling the heating rate using a heater provided outside the heat insulating shield, most of the electric power required for heating the central portion of the apparatus is supplied from the heater. On the other hand, precise control of the heating (or cooling) speed is performed by a Peltier device. In this case, since the electric power required for raising (or lowering) the temperature is very small, the heating or cooling can be rapidly and reversibly performed as needed by the Peltier device. As a result, precise control of the heating (or cooling) speed was made possible, and the minimum control width of the temperature control became within 0.2 mK. As a result, much more precise temperature control became possible compared to a general calorimeter.
[0015]
The optimization of the thermal distance between the heat flux sensor and the heating / cooling element is discussed in detail between the heating / cooling element (thermo module) and the heat flux sensor (first and second semiconductor thermoelectric elements). , A metal block having a thickness in the range of 6 to 60 mm is arranged. When the thickness of the metal block is set to 6 mm or less, the temperature uniformity of the metal block becomes insufficient, and the thermal distance between the thermo module and the heat flux sensor becomes too short, so that the temperature fluctuation of the metal block (disturbance). Is easily transmitted to the heat flux sensor. On the other hand, when the thickness is 60 mm or more, it takes too much time to raise or lower the temperature of the metal block, and the responsiveness of temperature control deteriorates. The metal block may be a single metal block, or a plurality of metal blocks may be stacked. When laminating, the total thickness is set in the range of 6 to 60 mm. In addition, the thermal distance (thermal resistance) between the thermo module and the heat flux sensor is increased by sandwiching a material with low thermal conductivity, such as a heat-resistant plastic sheet or ceramic plate, between the laminated metal blocks. You can also.
[0016]
To increase the sensitivity of the heat flux sensor, a semiconductor thermoelectric element is used instead of a commonly used thermocouple. By detecting the difference in thermoelectromotive force between the first semiconductor thermoelectric element and the second semiconductor thermoelectric element, the temperature difference between the measurement sample and the reference sample can be accurately detected, and based on this, the heat flux flowing through the measurement sample is determined. You can ask. If the heat flux is known, the calorific value or heat absorption due to the phase transition of the measurement sample or the like can be obtained.
[0017]
Further, in order to prevent the influence of thermal disturbance, the metal block, the first semiconductor thermoelectric element, the second semiconductor thermoelectric element, and the thermo module are surrounded by at least a double adiabatic shield.
[0018]
According to the present invention, by taking the above measures, the stability of the baseline is remarkably enhanced, and a detection signal can be obtained with sufficient sensitivity even when the heating rate at the time of measuring the heat flux is reduced.
[0019]
BEST MODE FOR CARRYING OUT THE INVENTION
FIG. 1 is a front sectional view showing the inside of a differential scanning calorimeter according to one embodiment of the present invention. Inside the cylindrical container 10 whose upper and lower sides are closed, a cylindrical outer insulating shield 12 made of copper and whose upper and lower sides are closed is arranged. Since it is in a space outside of the heater 20 (described below), it will be referred to as an "outer" adiabatic shield. A base 14 is disposed below the inside of the outer heat-insulating shield 12. On the base 14, a disk-shaped heat transfer block 16 (made of metal) having a thickness of 10 mm, and a cylinder having a closed upper part are provided. A metal plate 18 (which also functions as a heat insulating shield) is fixed. The outer peripheral surface of the side wall of the heat transfer block 16 is surrounded by the inner surface of the lower end of the metal plate 18. A resistance heater 20 and a first platinum resistance thermometer 22 are embedded inside the side wall of the metal plate 18. The first platinum resistance thermometer 22 is for temperature detection for coarse control, and controls the electric power of the resistance heater 20 so that the temperature detected by the first platinum resistance thermometer 22 becomes a desired temperature.
[0020]
In the space inside the metal plate 18, a first inner heat insulating shield 24 made of ceramics and having a closed cylindrical shape is disposed. In the space inside the first inner heat insulating shield 24, a second inner heat insulating shield 26 made of copper and having a closed cylindrical shape is arranged. The first inner heat insulating shield 24 made of ceramic has a strong function of enhancing the heat insulating property, and has an effect of preventing a temperature change outside of the shield from affecting the sample. As the ceramic material, for example, mullite or alumina is used. Since the second inner heat insulating shield 26 made of copper has a good thermal conductivity, the temperature of the space around the sample is made uniform to fulfill the function of a constant temperature wall. If the materials of the two heat shields 24 and 26 are reversed (the heat shield 24 is made of metal and the material of the heat shield 26 is made of ceramic), the temperature stability is poor. The lower end of the second inner heat shield 26 rests on the upper surface of the heat transfer block 16. The two inner insulation shields 24, 26 are called “inside” insulation shields because they are in the space inside the heater 20. These two inner heat shields 24 and 26 constitute "at least a double heat shield" in the present invention. This inner heat shield can be tripled or more.
[0021]
One end (lower surface) of the thermo module 28 is fixed to the upper surface of the heat transfer block 16 with an adhesive. The thermo-module 28 is made of a Peltier element and is capable of heating and cooling the metal block thereon. A disc-shaped first metal block 30 is fixed to the other end (upper surface) of the thermo module 28 with an adhesive. A second platinum resistance thermometer 36 is fixed to the lower surface of the first metal block 30. The second platinum resistance thermometer 36 is for temperature detection for precise control, and controls the power of the thermo module 28 so that the detected temperature becomes a desired temperature. A disk-shaped second metal block 32 is fixed on the first metal block 30, and a disk-shaped third metal block 34 is further fixed thereon. Each of these three metal blocks 30, 32, 34 is made of copper and has a thickness of 10 mm. The diameter of the second metal block 32 is smaller than that of the first metal block 30, and the diameter of the third metal block 34 is smaller than that of the second metal block 32. The reason why the diameters of the three metal blocks are made smaller as going upward, and the entire outer shape is made step-shaped, is so that the heat insulating shield can be mounted on the step-shaped step portion. The three metal blocks 30, 32, and 34 constitute a "metal block" in the present invention. The total thickness is 30 mm in this embodiment.
[0022]
Inside the second inner heat insulating shield 26, a third inner heat insulating shield 38 made of copper and having a closed cylindrical shape is disposed. The lower end of the third inner heat shield 38 rests on the upper surface (step portion) of the first metal block 30. Since this third inner heat shield does not surround the thermo module 28, it is not included in the "at least double heat shield" in the present invention.
[0023]
One end (lower surface) of the two semiconductor thermoelectric elements 40 and 42 is fixed to the upper surface of the third metal block 34 with an adhesive. These semiconductor thermoelectric elements 40 and 42 are arranged symmetrically with respect to the center of the third metal block 34. On the other end (upper surface) of the first semiconductor thermoelectric element 40, a measurement sample container 44 is placed. On the other end (upper surface) of the second semiconductor thermoelectric element 42, a reference sample container 46 is placed. These containers 44 and 46 are made of aluminum (or silver), and are placed on the semiconductor thermoelectric elements 40 and 42 with a small amount of grease to maintain good thermal contact with the semiconductor thermoelectric elements 40 and 42. ing. A measurement sample is put in the measurement sample container 44, and a reference sample is put in the reference sample container 46. The measurement sample container 44 and the reference sample container 46 are separated from each other by about 10 to 30 mm. Since the measurement sample container 44 is simply placed on the semiconductor thermoelectric element 40, the measurement sample container 44 can be easily taken out of the differential scanning calorimeter. That is, the sample can be easily exchanged.
[0024]
The semiconductor thermoelectric elements 40 and 42 are obtained by connecting 18 pairs of thermoelectric elements in series. In this embodiment, Ferro. Tech. Inc. The product of Model No. 9500/018/012 manufactured by the company is used.
[0025]
At the center of the upper surface of the third metal block 34, a third platinum resistance thermometer 48 is fixed with an adhesive. This third platinum resistance thermometer 48 is for monitoring the sample temperature. The detected temperature is not used for temperature control.
[0026]
Next, the flow of heat near the sample of the differential scanning calorimeter will be described. FIG. 2 is an equivalent circuit diagram of heat in the vicinity of the sample of the differential scanning calorimeter. Considering the heat flow between the heat source 50 (corresponding to the thermo module 28) for controlling the sample temperature and the measurement sample position 52, four thermal resistances 54, 56, 58, It can be considered that 60 are connected in series and four heat sinks 62, 64, 66, 68 are connected in parallel. The first heat resistor 54 and the first heat sink 62 are provided by the first metal block 30. The second heat resistance 56 and the second heat sink 64 are provided by the second metal block 32. The third heat resistance 58 and the third heat sink 66 are provided by the third metal block 34. The fourth heat resistance 60 and the fourth heat sink 68 are provided by the first semiconductor thermoelectric element 40. Also, by sandwiching a material with low thermal conductivity, such as a heat-resistant plastic sheet or ceramic plate, between the laminated metal blocks, the thermal distance (thermal resistance) between the thermo module and the heat flux sensor can be increased. It can be increased. If the heat sink or thermal resistance is increased too much, the responsiveness of the temperature control will deteriorate, and it will take too long for the sample heating or cooling rate to become constant. Can't be too fast. Therefore, if the total thickness of the metal block is set within 60 mm, such a problem is not so noticeable.
[0027]
Next, an electric circuit of the differential scanning calorimeter will be described with reference to FIG. The heater power supply 70 supplies electric power to the resistance heater 20. The temperature of the metal plate in which the resistance heater 20 is embedded is detected by the first platinum resistance thermometer 22 (coarse control temperature detection element), and the output is fed back to the heater power supply 70. Then, electric power is supplied from the heater power supply 70 to the resistance heater 20 by PID control so that the temperature of the thermometer 22 becomes a desired program temperature. Thereby, the temperature of the space inside the metal plate 18 (FIG. 1) is roughly controlled.
[0028]
The thermo module power supply 72 supplies power to the thermo module 28. The temperature of the first metal block 30 with which the upper surface of the thermo module 28 is in contact is detected by a second platinum resistance thermometer 36 (temperature detection element for precision control), and the output is fed back to the thermo module power supply 72. You. Then, power is supplied from the thermo module power supply 72 to the thermo module 28 by PID control so that the temperature of the thermometer 36 becomes a desired program temperature. At that time, the heating and cooling of the first metal block 30 can be switched by changing the direction of the current flowing through the thermo module 28. Thereby, the temperature of the first metal block 30 is precisely controlled.
[0029]
In the above description, the first platinum resistance thermometer 22 is used for coarse control, and the second platinum resistance thermometer 36 is used for precision control, but the thermometer itself has the same specifications. It is used for coarse control, so it is referred to as coarse control, and used for precision control, it is used for precision control.
[0030]
The thermoelectromotive force difference detection device 74 detects a difference between the thermoelectromotive forces of the first semiconductor thermoelectric element 40 and the second semiconductor thermoelectric element 42. The first semiconductor thermoelectric element 40 generates a thermoelectromotive force proportional to the temperature difference between the measurement sample container and the third metal block 34, and the second semiconductor thermoelectric element 42 generates the thermoelectric force between the reference sample container and the third metal block 34. Generates a thermoelectromotive force proportional to the temperature difference. Further, since the first semiconductor thermoelectric element 40 and the second semiconductor thermoelectric element 42 are differentially connected, regardless of the temperature of the third metal block 34, the temperature difference between the measurement sample container and the reference sample container is obtained. Can be detected. Since the reference sample does not generate heat or absorb heat even when the temperature changes, the above-described difference in thermoelectromotive force is caused by a heat generation phenomenon or an endothermic phenomenon of the measurement sample. In the thermoelectromotive force difference detection device 74, the thermoelectromotive force difference between the two semiconductor thermoelectric elements is amplified by a low-noise preamplifier, and noise during amplification (attributable to fluctuations in room temperature and power supply) is reduced as much as possible.
[0031]
In order to convert the thermoelectromotive force of a semiconductor thermoelectric element into a heat flux, the following is performed. First, a standard alumina having a known heat capacity is placed in a sample container, and the thermoelectromotive force is measured. Thereby, a device constant for converting the thermoelectromotive force at each temperature into a heat flux is obtained from the heat capacity document value and the value of the heating rate. Once the device constants are obtained at each temperature, the heat flux at any temperature can be converted to heat capacity by placing a standard mass of different mass in the sample container and measuring the thermoelectromotive force. Such data conversion work is known, and is described in detail in, for example, “Basics and Application of Thermal Analysis, Third Edition”, p. 56-57, 1994, edited by the Japan Society of Thermometry.
[0032]
The third platinum resistance thermometer 48 bonded to the upper surface of the third metal block 34 is used to monitor the temperature of the third metal block 34, and the output is input to the sample temperature monitor 76. ing.
[0033]
Next, the operation of multi-stage temperature control that combines coarse control and precision control will be described. By controlling the power of the resistance heater 20, the temperature of the space inside the metal plate 18 (FIG. 1) is roughly controlled. The minimum control width of the temperature control of the metal plate 18 is about 1 mK. Such a coarse control prevents a change in the temperature (for example, room temperature) around the differential scanning calorimeter from affecting the heat flux sensor. Although temperature fluctuation of about 1 mK is inevitable in controlling the temperature of the metal plate 18, the provision of the two inner heat shields 24 and 26 (FIG. 1) prevents such temperature fluctuation from affecting the heat flux sensor. I have to. The temperature of the first metal block 30 is precisely controlled by controlling the power of the thermo module 28. The minimum control width of the temperature control of the first metal block 30 is about 0.2 mK. In the present embodiment, since the semiconductor thermoelectric element is used as the heat flux sensor, 7.6 mV / K is obtained as the detection sensitivity of the temperature difference between the measurement sample and the reference sample. This is much better than the sensitivity of ordinary thermocouples. In this embodiment, a temperature rising program curve that is a target temperature when the temperature is controlled by the power control of the resistance heater 20 and a temperature rising program curve that is the target temperature when the temperature is controlled by the power control of the thermomodule 28 are as follows. I use the same.
[0034]
Measurement example 1
FIG. 4 is a graph showing the baseline stability of the differential scanning calorimeter shown in FIG. The horizontal axis is time (showing measurement results for about 2 hours). The vertical axis is a value measured by the thermoelectromotive force difference detection device 74 (FIG. 3), and is a value obtained by converting the difference between the detected thermoelectromotive forces into a heat flux. The measurement was performed with nothing put in the measurement sample container and the reference sample container. The measurement results vary within a range of about ± 5 nanowatts centered on zero nanowatts, indicating that the noise level of this differential scanning calorimeter is within ± 5 nanowatts. Therefore, a heat flux of the order of 10 nanowatts can be sufficiently detected. This noise level is 10 mK when converted to the temperature difference between the measurement sample container and the reference sample container.
[0035]
Measurement example 2
FIG. 5 is a graph showing the measurement of the heat flux in the temperature rising direction using EBBA (Ethoxy-p-benzilidene-n-butylylaniline) as a measurement sample, and FIG. 6 is a graph showing the measurement of the heat flux in the temperature decreasing direction. is there. In each graph, the horizontal axis is temperature (unit: K), and the vertical axis is heat flux. The above-described EBBA was put in the measurement sample container, and the reference sample was put in the reference sample container for measurement. FIG. 5 shows a temperature rise rate of 1 mK / sec and FIG. 6 shows a temperature decrease rate of -1 mK / sec. A phase change was clearly observed in both the temperature increasing direction (FIG. 5) and the temperature decreasing direction (FIG. 6). In the graph of the temperature rising direction in FIG. 5, a phase transition from the crystal to the liquid crystal was observed at about 308K, and a phase transition from the liquid crystal to the liquid was observed at about 352K. On the other hand, in the graph in the temperature decreasing direction of FIG. 6, a phase transition from liquid to liquid crystal was observed at around 349K, and a phase transition from liquid crystal to crystal was observed at around 282K. In the temperature decreasing direction, the phase transition temperature and the heat flux peak height are different from the values in the temperature increasing direction due to the supercooling phenomenon.
[0036]
Measurement example 3
FIG. 7 shows nC as a measurement sample. ₃₂ H ₆₆ 5 is a graph of heat flux measurement in a temperature decreasing direction using the method shown in FIG. The horizontal axis is temperature (unit: K), and the vertical axis is heat flux. The sample amount is as small as 1.0 mg, and the temperature decreasing rate is very slow at −0.04 mK / sec (ie, −2.4 mK / min). Although this sample solidifies around 343K, the graph in Fig. 7 shows the measurement results in a very narrow temperature range (within 1K) in a temperature range slightly lower than its freezing point (that is, the state near the end of the solidification phenomenon). ). In the solidification process, particles of about several μm are generated, but a small amount of heat is generated by crystallization of molecules in an irregular state near the interface of the particles. In the graph of FIG. 7, many such exothermic peaks were observed. In FIG. 7, the peak height of the trace heat generation is large, on the order of 10 microwatts (0.01 mW), and small, on the order of 1 microwatt. With the conventional apparatus, the above-mentioned trace heat generation phenomenon could not be observed because of the large heat generation peak at the freezing point. However, by using the differential scanning calorimeter of FIG. Was observed. As described above, the differential scanning calorimeter of the present invention makes it possible to observe a heat flux with high sensitivity, high resolution, and a low cooling rate (low heating rate).
[0037]
Measurement example 4
FIG. 8 is a graph showing the temperature dependence of the specific heat capacity of alumina using alumina as a measurement sample. Alumina is placed in the measurement sample container and nothing is put in the reference sample container. Smooth curves are literature values and jagged curves are measured values. The measured value is within 1% of the literature value, indicating that not only relative measurement but also absolute measurement can be performed with sufficient accuracy.
[0038]
The present invention is not limited to the above embodiment, and the following changes are possible. Instead of laminating the three metal blocks 30, 32, and 34, one metal block may be cut to form a disk having the same shape (a disk having a thickness of 30 mm and a step). The third inner heat-insulating shield 38 is mounted on the step.
[0039]
The above embodiment relates to a differential scanning calorimeter, but can also be applied to other calorimeters, that is, a thermostatic wall calorimeter that does not use a reference sample.
[0040]
【The invention's effect】
By using the calorimeter of the present invention, it becomes possible to measure a minute heat flux and a minute calorific value which are at least about one digit more sensitive than a conventional apparatus. The specific effects are as follows. (1) The stability of the baseline is about ± 5 nanowatts, and a heat flux on the order of 10 nanowatts can be measured. (2) Precise control of the heating rate and the cooling rate is possible, and a clear signal can be obtained even at an extremely slow heating rate and a cooling rate of about 2.4 mK / min. (3) Since the sensitivity of calorimetric measurement is high, sufficient measurement is possible with a small amount of sample of about 0.1 mg. (4) Since high sensitivity can be obtained without using a fixed sample, the sample can be easily replaced with high sensitivity. (5) Absolute measurement of calorific value is possible with an error of 1% or less.
[Brief description of the drawings]
FIG. 1 is a front sectional view showing the inside of a differential scanning calorimeter according to one embodiment of the present invention.
FIG. 2 is an equivalent circuit diagram of heat in the vicinity of a sample of the differential scanning calorimeter of FIG.
FIG. 3 is an electric circuit diagram of the differential scanning calorimeter of FIG. 1;
FIG. 4 is a graph showing the baseline stability of the differential scanning calorimeter of FIG. 1;
FIG. 5 is a graph showing the measured heat flux of the EBBA sample in the temperature rising direction.
FIG. 6 is a graph showing the measured heat flux of the EBBA sample in the temperature decreasing direction.
FIG. 7: nC ₃₂ H ₆₆ It is a graph of the heat flux measurement in the temperature-fall direction using a sample.
FIG. 8 is a graph showing the temperature dependence of the specific heat capacity of an alumina sample.
[Explanation of symbols]
10 containers
12. Outer insulation shield
14 base
16 Heat transfer block
18 Metal plate
20 Resistance heater
22. First platinum resistance thermometer
24 1st inner heat insulation shield (made of ceramics)
26 Second inner insulation shield (copper)
28 Thermo module (Peltier element)
30 1st metal block
32 Second metal block
34 Third metal block
36 Second platinum resistance thermometer
38 Third inner heat shield (copper)
40 First semiconductor thermoelectric element
42 Second semiconductor thermoelectric element
44 Measurement sample container
46 Reference sample container
48 Third Platinum Resistance Thermometer
50 heat sources
52 Sample position
54 First Thermal Resistance
56 Second thermal resistance
58 Third thermal resistance
60 Fourth thermal resistance
62 First heat sink
64 Second heat sink
66 Third heat
68 Fourth Heat Drain
70 heater power supply
72 Thermo module power supply
74 Thermoelectromotive force difference detector
76 Sample temperature monitor

Claims (3)

A calorimeter having the following configuration.
(A) A metal block having a thickness of 6 to 60 mm.
(B) a first semiconductor thermoelectric element having one end in contact with the measurement sample container and the other end in contact with the metal block;
(C) a second semiconductor thermoelectric element having one end in contact with the reference sample container and the other end in contact with the metal block;
(D) a thermo module in contact with the metal block, wherein the thermo module can heat and cool the metal block by a Peltier effect.
(E) A temperature control element for precision control for detecting the temperature of the metal block.
(F) at least a double adiabatic shield surrounding the metal block, the first semiconductor thermoelectric element, the second semiconductor thermoelectric element, and the thermomodule;
(G) A heater and a temperature detecting element for coarse control provided outside the heat insulating shield.
(H) a thermo-module power supply that controls power supplied to the thermo-module based on the output of the temperature control element for precision control.
(I) A heater power supply for controlling the power supplied to the heater based on the output of the coarse control temperature detecting element.
(J) A thermo-electromotive force difference detection device for detecting a thermo-electromotive force difference between the first semiconductor thermoelectric element and the second semiconductor thermoelectric element. The calorimeter according to claim 1, wherein the at least two-fold heat insulation shield includes at least one heat insulation shield made of ceramic and at least one heat insulation shield made of metal. The metal block has a shape in which a plurality of disks having different diameters are stacked concentrically in the vertical direction. The diameter of the upper disk is smaller, and at least one heat shield is placed on the step. The calorimeter according to claim 1, wherein:

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