JP5070570B2 - Thermal expansion coefficient measuring method and measuring apparatus - Google Patents

Description

  The present invention relates to a thermal expansion coefficient measuring method and a measuring apparatus for measuring a thermal expansion coefficient in a temperature range exceeding 400 ° C.

  Materials such as carbon materials such as graphite and ceramics may be used in a temperature range exceeding 400 ° C., and a coefficient of thermal expansion in a temperature range exceeding 400 ° C. is required as basic data.

  Generally, the coefficient of thermal expansion is measured by placing a sample in a high temperature furnace and heating the sample. In this case, there is a problem that the measurement error due to the non-uniformity of the sample temperature tends to increase. Moreover, there is a problem that a high-temperature furnace for heating the sample is necessary and the apparatus becomes large.

  As a method for measuring the coefficient of thermal expansion that can solve the above-described problem, in Patent Document 1, a sample is energized and heated by passing a pulsed current in the length direction of the sample, and during this heating, Thermal expansion of the sample due to the difference in potential difference that occurs between the pair of movable voltage probes that are fixed on the side of the sample and move with the sample, and the pair of fixed voltage probes that slide on the side of the sample at a constant interval A method for measuring the rate has been proposed.

  According to such a method, since a pulse current is supplied to the sample and the sample is directly energized and heated to raise the temperature, equipment such as a high-temperature furnace is not necessary, and the apparatus can be simplified. .

  However, as described in Patent Document 1, such a method is a method suitable for measuring a material such as a metal having higher electrical conductivity than graphite. Further, this method has a problem that the expansion in the length direction of the sample is measured and the temperature of the entire sample or at least the measurement portion must be uniform. If the temperature in the measurement part is non-uniform, it cannot be measured accurately.

Also, since the coefficient of thermal expansion is obtained by measuring the potential difference between the probes or the amount of movement of the probe or movable voltage, it is necessary to provide a fixed voltage probe and a movable voltage probe or movable electrode, which complicates the device. There was a problem to do.
Japanese Patent Application Laid-Open No. 08-128977

  An object of the present invention is to provide a thermal expansion coefficient measuring method and a measuring apparatus capable of easily and accurately measuring the thermal expansion coefficient of carbon materials such as graphite and ceramics in a temperature range exceeding 400 ° C. There is.

The present invention is a method for measuring a coefficient of thermal expansion in a temperature range exceeding 400 ° C., wherein a direct current is passed through a sample and heated so that the temperature of the measuring portion exceeds 400 ° C. And a step of measuring the amount of movement of the edge in the radial direction of the measurement part at the time of temperature rise to obtain a coefficient of thermal expansion, wherein the sample is isotropic graphite , The radial direction is a direction perpendicular to the direction in which the direct current flows.

  In the present invention, the sample is heated by applying a direct current to the sample so that the temperature of the measurement unit exceeds 400 ° C. and the temperature of the measurement unit is increased. For this reason, the conventional high temperature furnace is not required, and the coefficient of thermal expansion can be measured easily.

  Moreover, since a direct current is used, a function waveform generator is not required. In order to produce the pulse wave in Patent Document 1, these waveform generators are required in addition to the DC power supply.

  Further, in the present invention, the coefficient of thermal expansion is obtained by measuring the amount of movement of the edge in the radial direction of the measurement part when the temperature rises using a sample having the measurement part. Since the expansion in the radial direction, that is, the width direction of the measurement unit is measured, the temperature distribution is uniform as compared with the conventional case of measuring the expansion in the length direction. Moreover, the variation accompanying the temperature nonuniformity of a measurement part can be reduced, and a thermal expansion coefficient can be measured accurately.

  In the present invention, the coefficient of thermal expansion is preferably measured as described above, and the electrical resistivity of the sample in a temperature range exceeding 400 ° C. is preferably measured. Such measurement of electric resistivity can be performed by an electric resistivity measuring means described later.

  In this invention, it is preferable to measure the moving amount | distance of the edge of the radial direction of a measurement part by irradiation of a laser beam. For example, it is possible to measure the amount of movement of the edge in the radial direction of the measurement unit using a laser displacement meter. The coefficient of thermal expansion can be obtained from the amount of movement and the temperature difference that caused the amount of movement.

  The sample for measuring the coefficient of thermal expansion in the present invention is not particularly limited, and examples thereof include carbon materials including graphite. Further, since the sample is heated by passing a direct current, it is preferable that the sample used in the present invention has electrical conductivity.

The thermal expansion coefficient measuring apparatus of the present invention is an apparatus for measuring the thermal expansion coefficient by the measurement method of the present invention, and an atmosphere adjustment for adjusting the measurement chamber in which the sample is installed and the atmosphere in the measurement chamber. Means, a holding member for holding the sample in the measurement chamber, a direct current power source for supplying a direct current to the sample held by the holding member, and a temperature measuring means for measuring the temperature of the measurement part of the sample, And a moving amount measuring means for measuring the moving amount of the edge in the radial direction of the measuring part, the sample is isotropic graphite , and the radial direction is orthogonal to the direction in which the direct current flows. It is characterized by direction.

  In the thermal expansion coefficient measuring apparatus of the present invention, the sample is heated by passing a DC current from a DC power source and heating the sample. Therefore, a high-temperature furnace or the like is not required as in the prior art, and the apparatus can be easily and miniaturized.

  In addition, since the coefficient of thermal expansion is obtained by measuring the amount of movement of the edge in the radial direction of the measuring part, the part that can be heated uniformly can be the part to be measured, and the coefficient of thermal expansion can be accurately Can be measured.

  Examples of the moving amount measuring means in the present invention include optical measuring means, and specific examples include a laser displacement meter. By using a laser displacement meter to measure the amount of movement by irradiation with laser light, it is possible to measure without using a standard sample, and it is possible to measure the amount of movement easily and accurately.

  The thermal expansion coefficient measuring apparatus of the present invention may further include an electrical resistivity measuring means for measuring the electrical resistivity of the sample in a temperature range exceeding 400 ° C. Examples of the electrical resistivity measuring means include a pair of measuring terminals capable of measuring a voltage drop and a voltmeter capable of measuring a voltage between the pair of measuring terminals. The electrical resistivity measures the electrical resistivity of the measurement part of the sample that is uniformly heated.

  The atmosphere adjusting means in the present invention is for adjusting the atmosphere in the measurement chamber. As the atmosphere in the measurement chamber, generally, for example, an inert gas such as Ar, Ne, Kr, an atmosphere such as nitrogen gas, Alternatively, a reduced pressure atmosphere is selected. Accordingly, examples of the atmosphere adjusting means include a device for supplying an inert gas such as Ar, Ne, Kr, and nitrogen gas, and / or a vacuum pump or a decompression pump.

  The holding member in the present invention is a member for holding the sample in the measurement chamber. You may use this holding member as a pair of electrode terminal for supplying with a direct current from direct current power supply.

  The temperature measuring means in the present invention is for measuring the temperature of the measurement part of the sample. Examples of such temperature measuring means include an infrared thermometer and a thermocouple.

  According to the thermal expansion coefficient measuring method of the present invention, the thermal expansion coefficient in a temperature range exceeding 400 ° C. can be measured easily and accurately.

  According to the thermal expansion coefficient measuring apparatus of the present invention, the thermal expansion coefficient in a temperature range exceeding 400 ° C. can be measured easily and accurately according to the thermal expansion coefficient measuring method of the present invention.

  Hereinafter, although this invention is demonstrated by embodiment, this invention is not limited to the following embodiment.

  FIG. 1 is a schematic diagram showing an embodiment of a thermal expansion coefficient measuring apparatus according to the present invention.

  In the thermal expansion coefficient measuring apparatus 20 shown in FIG. 1, a sample 1 that is a measurement target for measuring a thermal expansion coefficient is installed in a measurement chamber 4.

  FIG. 2 is a side view showing the sample 1. As shown in FIG. 2, the sample 1 has a rod-like shape, and has a measurement part 1a having a reduced diameter at the center. The measurement part 1a has a cylindrical shape whose diameter is substantially the same.

  As shown in FIG. 1, the sample 1 is installed in the measurement chamber 4 by holding both ends of the sample 1 with the holding member 2 and the holding member 3.

  FIG. 3 is a perspective view showing a state in which the sample 1 is held by the holding member 2 and the holding member 3. As shown in FIG. 3, both ends of the sample 1 are held by holding members 2 and 3, respectively, and are installed in a measurement chamber 4. The holding members 2 and 3 are connected to a DC power source (not shown in FIG. 1), and a DC current from the DC power source is supplied to the sample 1 with the holding members 2 and 3 as a pair of electrodes.

  As shown in FIG. 1, optical windows 8a and 8b are respectively provided on the walls of the measurement chamber 4 on both sides of the measurement unit 1a so that the measurement unit 1a of the sample 1 can be irradiated with laser light. In addition, a laser displacement meter 7a on the light projecting side for irradiating laser light is provided outside the optical window 8a.

  On the outside of the optical window 8b, a laser displacement meter 7b on the light receiving side for receiving the laser light emitted from the laser displacement meter 7a on the light projecting side is provided. The laser beam from the laser displacement meter 7a on the light projecting side is irradiated onto the measuring unit 1a of the sample 1, and the laser beam is received by the laser displacement meter 7b on the light receiving side, whereby the diameter of the measuring unit 1a shown in FIG. The position of the edge 1b in the direction can be detected. Therefore, when the sample 1 is heated by applying a direct current and the measurement part 1a is thermally expanded, the movement amount when the edge 1b is moved by the thermal expansion can be measured by the laser displacement meters 7a and 7b. .

  As shown in FIG. 1, a decompression pump 5 for adjusting the atmosphere in the measurement chamber 4 is attached to the measurement chamber 4 via a pipe 6. The inside of the measurement chamber 4 can be decompressed by the decompression pump 5. In the present embodiment, the decompression pump 5 is provided as an atmosphere adjusting means, but the atmosphere in the measurement chamber 4 can be changed to, for example, an inert gas such as Ar, Ne, or Kr or a nitrogen gas. As the adjusting means, a decompression pump and an inert gas or nitrogen gas supply device such as Ar, Ne, or Kr may be used.

  A thermocouple 11 for measuring the temperature of the measurement unit 1a is provided in the vicinity of the measurement unit 1a. Further, in order to measure the temperature when the measuring unit 1a becomes high temperature, the optical window 10 is attached to the wall portion of the measuring chamber 4, and the infrared thermometer 9 is provided outside the optical window 10. Yes. The infrared thermometer 9 can detect the infrared rays emitted from the measuring unit 1a and measure the temperature.

  In addition, voltage drop measurement terminals 12a and 12b for measuring the electrical resistivity of the measurement unit 1a of the sample 1 are attached to the measurement unit 1a of the sample 1. By measuring the voltage drop between the terminals 12a and 12b, the electrical resistivity of the measuring unit 1a can be obtained.

  4 and 5 are cross-sectional views showing a thermal expansion coefficient measuring apparatus 30 of a more specific embodiment according to the present invention.

  4 is a cross-sectional view in the horizontal direction, and FIG. 5 is a cross-sectional view in the vertical direction. As shown in FIG. 4, the sample 1 is held in the measurement chamber 4 by holding both ends thereof with holding members 2 and 3. The holding member 2 is connected to a DC power supply introduction unit 31, and the holding member 3 is connected to a DC power supply introduction unit 32. The DC power supply introduction units 31 and 32 are connected to a DC power supply (not shown), and a DC current is supplied to both ends of the sample 1 through the holding members 2 and 3.

  A cylindrical heat insulating material 33 is provided around the sample 1. Examples of the heat insulating material 33 include a reflector (reflector) made of a material such as C, Fe, or W, or a felt-like heat insulating material made of C / C. In addition, the tip of the thermocouple 11 is disposed in the vicinity of the measurement unit 1 a of the sample 1.

  In the measurement chamber 4, for example, a gas inlet 6 a for introducing an inert gas such as Ar, Ne, Kr and a gas outlet 6 b for discharging the gas in the measurement chamber 4 are provided. The air in the measurement chamber 4 may be exhausted from the gas exhaust port 6b and measured in a reduced pressure state, or after decompression, an inert gas such as Ar, Ne, Kr, for example, may be introduced from the gas inlet port 6a. The atmosphere in the measurement chamber 4 can be measured using, for example, an inert gas such as Ar, Ne, or Kr.

  Further, a cooling water inlet 34 and a cooling water outlet 35 are provided to cool the periphery of the measurement chamber 4 with cooling water. The cooling water introduced from the cooling water inlet 34 is circulated around the measurement chamber 4, and after cooling the measurement chamber 4, the cooling water can be discharged from the cooling water outlet 35.

  As shown in FIG. 5, optical windows 8 a and 8 b are provided on the walls facing each other in the horizontal direction of the measurement chamber 4, and the light projecting side laser displacement meter provided outside the optical window 8 a. The laser beam irradiated from (not shown) is irradiated to the measuring part 1a of the sample 1, and the irradiated laser beam is received by a light receiving side laser displacement meter (not shown) provided outside the optical window 8b. The position of the edge 1b in the radial direction of the measurement unit 1a can be detected by receiving light.

  Above the measurement chamber 4, a thermocouple installation section 36 for installing the thermocouple 11, a voltage drop measurement terminal installation section 37 for installing the voltage drop measurement terminals 12a and 12b shown in FIG. 1, and FIG. An infrared thermometer installation part 38 for attaching the infrared thermometer 9 shown is provided.

  Referring to FIG. 4, in order to measure the coefficient of thermal expansion of sample 1, a direct current from a direct current power source (not shown) is passed through direct current power supply introduction portions 31 and 32, and holding members 2 and 3 are used as electrodes. To both ends. By supplying a direct current to both ends of the sample 1, the sample 1 is energized and heated, and the temperature of the measurement unit 1a rises. While measuring the temperature of the measurement part 1a using the thermocouple 11 or the infrared thermometer 9 (illustrated in FIG. 1), and using the laser displacement meters 7a and 7b shown in FIG. The position of the edge 1b is detected, and the amount of movement of the radial edge 1b due to the temperature rise is obtained. The coefficient of thermal expansion of sample 1 is calculated using the amount of movement and the value of temperature rise.

  During the measurement of the coefficient of thermal expansion, the inside of the measurement chamber 4 may be a reduced pressure atmosphere, for example, an inert gas such as Ar, Ne, Kr, or an atmosphere of nitrogen gas.

  Moreover, the electrical resistivity of the measurement part 1a in measurement temperature can be calculated | required by making the voltage drop measurement terminals 12a and 12b shown in FIG. 1 contact the measurement part 1a, and measuring the voltage drop between terminals.

  FIG. 6 is a flowchart showing the output signal and current flow in the embodiment.

  As shown in FIG. 6, the temperature of the measurement unit 1 a of the sample 1 is measured by the infrared thermometer 9, and an output signal of the measurement unit is given to the data logger 41 by the converter 43. In the low temperature range, the temperature of the measuring unit 1 a is measured by the thermocouple 11, and a temperature signal is given to the data logger 41 through the converter 44.

  Further, the moving amount of the edge in the radial direction of the measuring unit 1 a is measured by the laser displacement meters 7 a and 7 b, and the measurement data is given to the data logger 41.

  Further, the voltage drop between the measurement terminals 12 a and 12 b of the measurement unit 1 a is measured by the voltmeter 12, and an output signal of the electrical resistivity of the measurement unit 1 a is given to the data logger 41.

  The current from the DC power supply 40 passes through the voltmeter 47 and the ammeter 46 and is supplied to both ends of the sample 1 to heat the measuring unit 1a to a predetermined temperature.

  The current value measured by the ammeter 46 passes through the converter 45 and is given to the data logger 41.

  The output signal and current flow as described above are controlled by the digital program controller 42.

  The voltage and current of the DC power supply 40 are not particularly limited. For example, a DC power supply with a current of 500 A can be used.

  As described above, in the above-described embodiment according to the present invention, the sample is heated by supplying a direct current to the sample and conducting heating. For this reason, there is no need to provide a conventional high-temperature furnace, and the measuring apparatus can be easily and miniaturized.

  Moreover, in the said embodiment, the thermal expansion coefficient is calculated | required by measuring the moving amount | distance of the edge of the radial direction of the measurement part 1a of the sample 1. FIG. The measurement region of the measurement unit 1a is a limited radial region, and the temperature distribution is substantially uniform, so that there is little variation in temperature. For this reason, the coefficient of thermal expansion can be accurately measured.

  In this embodiment, since the moving amount of the edge of the measuring unit in the radial direction is measured using a laser displacement meter, it is possible to easily measure the thermal expansion coefficient without using a standard substance or the like. .

  A sample for measuring the coefficient of thermal expansion is not particularly limited, but suitable examples include carbon materials such as graphite, among which isotropic graphite having an isotropic coefficient of thermal expansion. Is mentioned.

The schematic diagram which shows the thermal expansion coefficient measuring apparatus of one Embodiment according to this invention. The side view which shows the sample used by one Embodiment according to this invention. The perspective view which shows the holding member holding the sample and sample in one Embodiment according to this invention. The transverse direction sectional view showing the coefficient of thermal expansion measuring device of the more concrete embodiment according to the present invention. The longitudinal direction sectional view showing the coefficient of thermal expansion measuring device of the more concrete embodiment according to the present invention. FIG. 6 is a flowchart showing an output signal and current flow in the embodiment shown in FIGS. 4 and 5.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Sample 1a ... Sample measuring part 1b ... Radial edge of sample measuring part 2, 3 ... Holding member 4 ... Measuring chamber 5 ... Decompression pump 6 ... Pipe 6a ... Gas inlet 6b ... Gas outlet 7a ... Throw Optical side laser displacement meter 7b ... Light-receiving side laser displacement meter 8a, 8b, 10 ... Optical window 9 ... Infrared thermometer 11 ... Thermocouple 12 ... Voltmeter 12a, 12b ... Voltage drop measurement terminal 20 ... Thermal expansion coefficient measuring device DESCRIPTION OF SYMBOLS 30 ... Thermal expansion coefficient measuring device 31, 32 ... DC power supply introduction part 33 ... Insulation material 34 ... Cooling water introduction port 35 ... Cooling water discharge port 36 ... Thermocouple installation part 37 ... Voltage drop measurement terminal installation part 38 ... Infrared temperature Meter installation unit 40 ... DC power supply 41 ... data logger 42 ... digital program controller 43, 44, 45 ... converter 46 ... ammeter 47 ... voltmeter

Claims (6)

A method for measuring a coefficient of thermal expansion in a temperature range exceeding 400 ° C.,
Applying a direct current to the sample and heating the temperature of the measurement unit to a temperature range exceeding 400 ° C., and increasing the temperature of the measurement unit;
Measuring the amount of movement of the edge in the radial direction of the measurement part at the time of the temperature rise and obtaining a coefficient of thermal expansion,
The sample is isotropic graphite ;
The method of measuring a coefficient of thermal expansion, wherein the radial direction is a direction orthogonal to a direction in which the direct current flows.   The thermal expansion coefficient measuring method according to claim 1, further comprising a step of measuring an electrical resistivity of the sample in a temperature range exceeding 400 ° C.   The thermal expansion coefficient measuring method according to claim 1, wherein an amount of movement of the edge in the radial direction of the measuring unit is measured by an optical measuring unit. An apparatus for measuring a coefficient of thermal expansion by the method according to any one of claims 1 to 3 ,
A measurement chamber in which the sample is installed;
Atmosphere adjustment means for adjusting the atmosphere in the measurement chamber;
A holding member for holding the sample in the measurement chamber;
A direct current power source for passing a direct current through the sample held by the holding member;
Temperature measuring means for measuring the temperature of the measurement part of the sample;
A moving amount measuring means for measuring the moving amount of the radial edge of the measuring unit;
The sample is isotropic graphite ,
The thermal expansion coefficient measuring apparatus according to claim 1, wherein the radial direction is a direction orthogonal to a direction in which the direct current flows. 5. The thermal expansion coefficient measuring apparatus according to claim 4 , further comprising electrical resistivity measuring means for measuring electrical resistivity of the sample in a temperature range exceeding 400 ° C. The thermal expansion coefficient measuring apparatus according to claim 4 or 5 , wherein the moving amount measuring means is an optical measuring means.

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