JP6388784B2 - Carbon nanotube standard blackbody furnace equipment - Google Patents

Description

  The present invention relates to a temperature standard blackbody furnace apparatus used as a comparison furnace for calibrating a non-contact type thermometer, and particularly, a high emissivity suitable for comparative calibration of a radiation thermometer having a wavelength different from that of a reference standard thermometer. The present invention relates to a carbon nanotube standard blackbody radiation source device that is independent of wavelength.

Infrared radiation thermometers near the wavelength of 10 μm, which are highly needed in the industry, including thermography, are required to be calibrated with high accuracy in a wide temperature range of about 100 ° C. to 1000 ° C. On the other hand, the radiation thermometer, which is the national standard in this temperature range, has a wavelength of 1.6 μm and 0.9 μm, so these national standard radiation thermometers calibrate infrared radiation thermometers in the 10 μm band with different wavelengths with high precision. In order to do this, a comparative calibration technique is required. Thus, as a comparative furnace for calibrating non-contact type thermometers having different wavelengths, it is essential that the effective emissivity of the cavity in the furnace is 1 as much as possible. In order to make the cavity emissivity as close to 1 as possible, the cavity must be soaked and the intrinsic emissivity of the cavity must be high. Furthermore, in order to calibrate thermometers over a wide temperature range in these fixed-point furnaces and comparative furnaces, it is desirable to cover a wide temperature range with a single thermostat. As this prior art, temperature variable blackbody furnaces such as (1) a heat pipe furnace and (2) an electric furnace have been put into practical use.
However, these conventional techniques have the following problems.
Evaluation of the temperature distribution of the cavity wall is essential both for realizing a highly uniform cavity and for accurately determining the emissivity of the cavity, but for the heat pipe furnace of (1) above, There is only an evaluation means using an equivalent contact thermometer, and this method is complicated and unreliable. Moreover, the heat pipe furnace of (1) cannot cover a wide temperature range with one furnace, and it is necessary to prepare a plurality of heat pipe furnaces. Moreover, the temperature range from 100 ° C. to 600 ° C. cannot be continuously covered.
Regarding the electric furnace of (2) above, the heater arrangement and the adjustment of the resistance value are complicated, and generally the heat uniformity of the cavity is insufficient. In addition, as in (1), since the evaluation of the temperature distribution of the cavity wall surface is difficult and the reliability is low, the accurate emissivity is unknown, and high-precision comparative calibration with a reference standard thermometer is impossible. .
The inventors have developed and manufactured an air-circulating temperature-variable blackbody furnace that can be used at 50 ° C to 500 ° C and that has a highly uniform graphite cavity that can reliably evaluate the temperature distribution of the cavity wall surface. However, a patent application has already been filed (see Patent Document 1). In this technology, a transparent glass window for measuring the cavity temperature distribution with a non-contact thermometer such as a radiation thermometer or a thermal imager is provided in the transverse direction of the furnace body, and the window is non-contact and highly reliable. The temperature distribution can be easily measured in real time. This makes it possible to accurately estimate the effective emissivity, but the emissivity is still insufficient to calibrate radiation thermometers of different wavelengths.
Therefore, in these prior arts, high-accuracy comparative calibration between radiation thermometers having different wavelengths in a single furnace in a wide temperature range up to 1000 ° C. is impossible.
On the other hand, a film-forming technique for high-quality vertically aligned carbon nanotubes (hereinafter, carbon nanotubes may be abbreviated as “CNT” in the present specification) can be implemented relatively easily. It is known that the emissivity is as high as about 0.98 in a wide wavelength range from 1 to far infrared, and there is almost no wavelength dependency (see Non-Patent Document 1).

JP 2012-145343 A

Kohei Mizuno et al., “A black body absorber from vertically aligned single-walled carbon nanotubes”, PNAS vol. 106, no. 15, p.6044-6047A (p.6044-6047A).

  In general, temperature-variable blackbody furnaces such as conventional electric furnaces have insufficient temperature uniformity in the cavities, and in order to evaluate the temperature distribution of the cavity wall surface, it is difficult to measure and has low reliability. I can't get it. As a result, since accurate emissivity cannot be determined, high-accuracy comparative calibration between radiation thermometers having different wavelengths cannot be performed. Although the heat pipe furnace has a higher temperature uniformity in the cavity than the above electric furnace or the like, only a contact-type thermometer can be used for the temperature distribution evaluation method, and as a result, an accurate emissivity cannot be determined. Furthermore, a single device cannot cover a wide temperature range, and cannot continuously cover a necessary temperature range.

FIG. 4 (side view) and FIG. 5 (front view) show an air circulation type temperature variable blackbody furnace described in Patent Document 1 previously filed by the present inventors, and includes a cavity 1 installed in the furnace. And a heat circulation fan 3 for keeping the cavity temperature uniform and constant, a heater 2 for heating the heat medium, and a thermometer 5 for temperature control of the furnace. A temperature-variable constant-temperature oven apparatus, preferably provided with a transparent window along the cavity on the furnace wall so that the temperature distribution of the cavity can be measured with a non-contact thermometer such as a radiation thermometer through the transparent window. The temperature of the cavity is controlled to be as close as possible to soaking. The cavity is made of graphite or black paint on the inner surface to increase the emissivity. With such a configuration, compared with conventional heat pipe furnaces, electric furnaces, etc., a single device can cover a wide temperature range of about 50 ° C. to 600 ° C., and the heat medium is a gas (for example, air) Therefore, it is possible to achieve a uniform temperature distribution by forming a gas flow path that circulates gas in the furnace and soaks the cavity so that there is no danger. Therefore, safe and reliable calibration can be realized.
However, since the emissivity generally decreases as the cavity length L decreases, the cavity needs to be as long as possible in order to bring the cavity emissivity closer to 1, and the apparatus has become longer. Also, since the radiation thermometer in the 10 μm band has a wide field of view, a large opening D is necessary for calibration with a comparative furnace. However, increasing the opening D naturally reduces the emissivity, so this time the emissivity is increased. As a result, the length L of the cavity needs to be increased (L / D is increased) so as not to lower it, and this contributes to an increase in the length of the apparatus. In addition, since the intrinsic emissivity of the cavity material is not sufficiently high, an emissivity sufficient for comparative calibration of radiation thermometers having different wavelengths has not yet been realized even when the apparatus is lengthened. Furthermore, in order to increase the emissivity, a cone type or a triangular type is adopted for the bottom of the cavity, and a flat bottom (generally low emissivity) that can be easily processed cannot be adopted.

In order to solve the above-mentioned problems of the prior art, the present invention provides a standard carbon nanotube standard characterized in that, in a standard blackbody furnace apparatus having a cavity, a carbon nanotube surface-treated member is disposed at the bottom of the cavity. It is a blackbody furnace device.
In the carbon nanotube standard blackbody furnace, the present invention is characterized in that the material of the cavity and the surface-treated member of the carbon nanotube is a high melting point material.
Further, the present invention is a radiation thermometer calibration method for calibrating a radiation thermometer, a thermal imaging apparatus, etc., using the carbon nanotube standard black body furnace apparatus.

In the present invention, the emissivity of the cavity can be made close to 1 by arranging the member subjected to the surface treatment of CNT at the bottom of the cavity, and radiation with different wavelengths can be performed by a single unit in a wide temperature range from room temperature to 1000 ° C. Enables high-precision comparative calibration of thermometers. Furthermore, even if the length of the cavity is shortened (L / D is small), a standard blackbody furnace device with an emissivity close to 1 can be realized, miniaturization can be achieved, and a highly accurate radiation thermometer at the industrial site Can be calibrated.
In the present invention, since the emissivity can be made close to 1 with a simple configuration in which a member subjected to the surface treatment of CNT is arranged at the bottom of the cavity, it is easy to manufacture, and the existing blackbody furnace apparatus has a cavity. A blackbody furnace apparatus having an emissivity close to 1 can be realized simply by mounting a member subjected to the surface treatment of CNT.
Further, if the carbon nanotube standard blackbody furnace apparatus of the present invention is used, the wavelength dependency is greatly reduced, and calibration of radiation thermometers having different wavelengths can be realized with high accuracy.

FIG. 1 is a diagram for explaining a performance evaluation 1, and as an example of the present invention, a graphite substrate having a surface treated with CNTs is arranged at the bottom of a cavity, and as a comparative example, only a graphite substrate without CNT is provided at the bottom of the cavity. The measured result of the brightness temperature is compared with the arranged one. FIG. 2 is a diagram for explaining the performance evaluation 2. As an example of the present invention, a graphite substrate with a CNT surface treatment arranged in a cavity and a graphite substrate without CNT as a comparative example are arranged in a cavity. The results of measuring the luminance temperature by changing the position where the substrate is arranged in each cavity are compared. FIG. 3 is a diagram for explaining the performance evaluation 3. As an example of the present invention, a graphite substrate with a CNT surface treatment arranged in a cavity and a graphite substrate without CNT as a comparative example are arranged in a cavity. The results measured using different blackbody furnace devices are compared with those obtained. The side view for demonstrating the conventional air circulation type temperature-variable blackbody furnace (sectional drawing). The front view for demonstrating the conventional air circulation type temperature variable blackbody furnace of FIG.

  As described above, vertically aligned CNTs have a very high emissivity of about 0.98 over a wide wavelength range from ultraviolet to far infrared, and have almost no wavelength dependence. However, if CNTs are used as they are as black bodies, As a comparative furnace for calibrating non-contact thermometers with different emissivities, in-plane temperature distribution is insufficient. Therefore, in the present invention, a CNT and a cavity (temperature-variable blackbody furnace) are combined to support the blackness of the CNT, the emissivity is as close to 1 as possible, and a comparative furnace that calibrates thermometers with different wavelengths is configured. did. As a result of performance evaluation, it was found that comparative calibration of radiation thermometers with different wavelength bands can be calibrated with high accuracy by simply placing a CNT substrate in the cavity, and even if the cavity length is less than half that of the conventional technology, it is wavelength dependent. There is no sex. When the CNT substrate is disposed at the bottom of the cavity, it is possible to adopt a flat bottom that is easy to process.

The temperature variable cavity blackbody furnace used for the performance evaluation employs the air circulation type temperature variable blackbody furnace apparatus (Patent Document 1) previously filed by the present inventors, and has a cavity length L = 400 mm and a cavity opening D. = 10 mm (L / D = 40), flat bottom cavity. The CNT of the present invention is obtained by subjecting a CNT surface treatment to a substrate-like graphite member having a thickness of 1 mm. The total length of the CNT, that is, the height is 100 μm, the diameter is 10 nm, and the interval between the carbon nanotubes is about 10 nm. . As a comparative example, the performance was evaluated in comparison with a comparative example using only a graphite substrate without CNT.
The performance of the cavity was evaluated using the air circulation type temperature variable blackbody furnace device previously filed by the present inventors. The present invention is characterized in that vertically aligned CNTs are arranged in the cavity. Therefore, the present invention is also effective for a conventional heat pipe furnace, electric furnace, or other temperature variable black body furnace provided with a cavity. This is not limited to the vertical alignment, and any CNT surface treated may be used. In addition, comparison furnaces with cavities made of commercially available metal with blackened paint etc. (the cavities of commercially available comparative furnaces are not made of graphite, but most of them are made of blackened paint etc.) It is also effective for fixed-point blackbody furnaces made of graphite (the cavity of fixed-point blackbody furnaces used in various countries is almost 100% made of graphite). Also, in the figure, the substrate-like member used for the surface treatment of the CNT is used, but it is not limited to the substrate shape, and may be other shapes such as a bottomed short cylinder shape, and the material is also graphite. However, any high-melting point material can be used. Furthermore, the arrangement position is not necessarily the bottom.

(Performance evaluation 1)
FIG. 1 shows the results of performance evaluation 1. The upper left diagram of FIG. 1 illustrates a state in which only the graphite substrate subjected to the surface treatment of the CNT of the present invention or the graphite substrate as a comparative example is disposed at the bottom of the cavity, and the upper right diagram illustrates the graphite subjected to the surface treatment of CNT. A substrate (left) and only a graphite substrate without CNT (right) are shown. Only the graphite substrate is placed at the bottom of the cavity (L = 400mm deep), and the brightness temperature is compared with radiation thermometers with different wavelengths (1.6μm, 5μm, and 10μm). The processed graphite substrate was placed, and the brightness temperature was compared with radiation thermometers of different wavelengths (1.6 μm, 5 μm, and 10 μm).
In the graph of FIG. 1, the horizontal axis indicates the wavelength of the radiation thermometer, and the vertical axis indicates the luminance temperature (temperature difference). The result of placing the graphite substrate on the bottom is ▲, and the result of placing the graphite substrate with the CNT surface treatment on the bottom is ●, and in radiation thermometers with wavelengths of 1.6 μm, 5 μm, and 10 μm, The brightness temperature rises by about 0.1 ° C., 0.4 ° C., and 0.8 ° C., respectively, when the graphite substrate subjected to the CNT surface treatment is placed. From this, it can be seen that the luminance temperature is greatly increased in the case where the graphite substrate subjected to the surface treatment of the CNT of the present invention is inserted. That is, it corresponds to an increase in emissivity.
In the graph, “x” indicates a value calculated by theoretical calculation by the Monte Carlo method (graphite cavity specific emissivity 0.85, CNT specific emissivity 0.98). The value of the intrinsic emissivity used for the calculation is the vertical spectral emissivity and is actually measured.

(Performance evaluation 2)
FIG. 2 shows the results of performance evaluation 2. The upper left figure of FIG. 2 is a photograph of the whole apparatus measured with a radiation thermometer with a wavelength of 10 μm and a radiation thermometer with a wavelength of 1.6 μm using an air circulation type temperature variable black body furnace apparatus. An experimental method is shown in which the cavity length is changed by moving the position of a graphite substrate (or graphite substrate) that has been subjected to CNT surface treatment. The effective cavity length is changed by moving the position of the graphite substrate (or graphite substrate) that has been surface-treated with CNT (400 mm, 350 mm, 300 mm, 250 mm, 200 mm, 150 mm), and radiation thermometers with different wavelengths ( The luminance temperature was compared at 1.6 μm and 10 μm), and the difference was obtained. In general, the shorter the cavity, the lower the emissivity and the lower the luminance temperature. (Thus, standard laboratories in each country make the cavity as long as possible, and as a result, large heat pipes and other devices are used as comparative furnaces. On the other hand, calibration companies and users who cannot introduce large-scale devices The calibration of radiation thermometers with different wavelengths is possible because a general blackbody furnace having a relatively short cavity length of about 150 mm to 200 mm but a low emissivity (about 0.99 to 0.993) is used. Can not.)
In the graph of FIG. 2, the horizontal axis indicates the position where the graphite substrate (or the graphite substrate) subjected to the CNT surface treatment is placed, that is, the cavity length, and the vertical axis indicates the luminance temperature (temperature difference). The black plots ● and ▲ are the results of putting a graphite substrate as a comparative example, the white plots ○ and △ are the results of putting the graphite substrate surface-treated with the CNT of the present invention, and the circle plots ○ and ● are As a result of measurement with a radiation thermometer with a wavelength of 1.6 μm, triangular plots Δ and ▲ are results of measurement with a radiation thermometer with a wavelength of 10 μm.
In the case of only the graphite substrate as a comparative example, the measurement result ● of the wavelength 1.6 μm radiation thermometer and the measurement result ▲ of the wavelength 10 μm radiation thermometer ▲ are in either case as the position where the graphite substrate is placed approaches the opening of the cavity In other words, the brightness temperature is greatly decreased (as the length of the cavity is shortened), and is decreased by about 5 ° C. at the position 150 mm at 1.6 μm ●, and is decreased by about 9 ° C. at the position 150 mm at 10 μm. Further, the difference ΔT (difference between ● and ▲) between the luminance temperatures of wavelengths of 1.6 μm and 10 μm ▲ increased as the graphite substrate was placed closer to the opening of the cavity, and there was no difference at the position of 400 mm. However, the difference is as large as about 4 ° C. at the position of 150 mm. This indicates that the effective emissivity decreases and the wavelength dependence increases as the cavity becomes shorter in the case of the graphite substrate alone.
On the other hand, in the case of the graphite substrate subjected to the surface treatment of CNT of the present invention, both the measurement result ○ of the wavelength 1.6 μm radiation thermometer and the measurement result Δ of the wavelength 10 μm band radiation thermometer were subjected to the surface treatment of CNT. Even if the position of the graphite substrate is moved to the vicinity of the opening (that is, the length of the cavity is shortened), the luminance temperature does not decrease much compared to the case of the graphite substrate, and the wavelengths of 1.6 μm ○ and 10 μm Δ are reduced. The difference in brightness temperature does not widen and there is almost no change. That is, even if the length of the cavity is shortened, it means that a high effective emissivity can be maintained and wavelength dependency is hardly exhibited.
The difference between the wavelength of 1.6 μm and 10 μm is that the difference between the wavelength of 1.6 μm ○ and 10 μm Δ is 0.03 ° C. at 200 mm when the CNT surface-treated graphite substrate of the present invention is added. If only the graphite substrate is placed, the difference between the wavelength of 1.6 μm ● and 10 μm ▲ is about 3 ° C. at a position of 200 mm, so that the graphite substrate treated with the CNT surface treatment of the present invention is the only graphite substrate of the comparative example. It can be seen that it is 1/100 smaller than the case of.

(Performance evaluation 3)
FIG. 3 shows performance evaluation 3. The upper diagram in FIG. 3 shows a radiation thermometer with a wavelength of 10 μm and a radiation thermometer with a wavelength of 1.6 μm using an air circulation type variable temperature black body furnace device (left) and a commercially available black body furnace device (right). 3 shows an overall view of the apparatus being measured, and the middle diagram of FIG. 3 shows a state in which a graphite substrate having a surface treated with the CNT of the present invention or a graphite substrate as a comparative example is arranged at the bottom of the cavity. ing.
In the graph of FIG. 3, the vertical axis represents the temperature (° C.) measured by the radiation thermometer, and the horizontal axis represents the wavelength (μm) of the radiation thermometer. The dotted line plots ● and ▲ are the results of putting only the graphite substrate as a comparative example, and the solid line plots ● and ▲ are the results of putting the graphite substrate subjected to the surface treatment of the CNT of the present invention. Plots ● and solid line plots ● are measured using an air-circulating temperature-variable black body furnace device, and the dotted triangle plots ▲ and solid line plots ▲ are the results measured using a commercially available black body furnace device. It is.
When only the graphite substrate of the comparative example was inserted, both the air circulation type temperature variable blackbody furnace device (dotted line plot ●) and the commercially available blackbody furnace device (dotted line plot ▲) were 1.6 μm and 10 μm. Although the difference due to the wavelength is large, when the graphite substrate with the surface treatment of the CNT of the present invention is inserted (solid line plot ●, solid line plot ▲), the difference is greatly reduced and the wavelength dependence is almost not. It turns out that it does not appear. In other words, the effect of placing the graphite substrate that has been subjected to the surface treatment of CNTs of the present invention into the cavity appears remarkably even in a commercially available blackbody furnace apparatus.

  In the above description, the CNT surface treatment was performed on the graphite substrate. However, this surface blackening treatment may be, for example, a film forming method for vertically aligning CNT or a transfer method. The substrate material may be a material other than graphite as long as it can orient CNTs. Moreover, even if the cavity is not made of graphite, it may be made of oxidized metal or blackened paint.

Claims (3)

In a standard blackbody furnace device with a cavity,
A carbon nanotube standard blackbody furnace apparatus, wherein a member subjected to a surface treatment of carbon nanotubes is disposed only at the bottom of the cavity.   2. The carbon nanotube standard blackbody furnace apparatus according to claim 1, wherein the material of the cavity and the surface-treated member of the carbon nanotube is a high melting point material. A radiation thermometer calibration method for calibrating a radiation thermometer, a thermal imaging apparatus, or the like using the carbon nanotube standard blackbody furnace apparatus according to claim 1 or 2.

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