JP2002055067A - Detection method for terioration of carbon material or graphite material - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method which can detect terioration due to oxidation of wear, breakdown or the like of a carbon material or a graphite material, used in a special environment, such as at a high temperature or the like, during its use and at the site. SOLUTION: In the detection method for the deterioration of the carbon material or the graphite material, the AC propagation characteristic of the carbon material or the graphite material is measured.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for detecting deterioration of a carbon material or a graphite material.

[0002]

2. Description of the Related Art Graphite materials, carbon materials and the like are often used at extremely high temperatures as materials for heating elements of electric furnaces and aerospace parts used at a temperature of 2000 ° C. or higher. Under such an environment, the carbon / graphite material has a possibility of oxidative consumption and material mechanical destruction. However, there has been no means to detect the deterioration of the carbon / graphite material during use at an ultra-high temperature, and the deterioration has been predicted by inspection and experience when the temperature is returned to room temperature after the operation is completed or interrupted.

[0003]

SUMMARY OF THE INVENTION The main object of the present invention is to:
It is an object of the present invention to provide a method capable of detecting deterioration due to oxidative consumption or destruction during use of a carbon material or a graphite material used under a special environment such as a high temperature.

[0004]

Means for Solving the Problems The present inventor has conducted intensive studies in view of the above-mentioned problems, and as a result, the AC propagation characteristics of carbon / graphite materials greatly depend on the structure of the materials. If this occurs, the AC propagation characteristics change, so we found that it is possible to detect deterioration of the material by measuring the AC propagation characteristics on the spot while using the material. The invention has been completed.

That is, the present invention provides the following method for detecting deterioration of a carbon material or a graphite material. 1. A method for detecting deterioration of a carbon material or a graphite material, comprising measuring an AC propagation characteristic of the carbon material or the graphite material. 2. A method for detecting deterioration of a carbon material or a graphite material, comprising measuring an AC propagation characteristic during use of a carbon material or a graphite material and comparing the measured AC propagation characteristic before use or immediately after the start of use. 3. Item 3. The deterioration detection method according to Item 1 or 2, wherein the AC propagation characteristic is at least one type of characteristic selected from a phase difference between voltage and current and impedance. 4. 10 kHz to 2.2 M for high density isotropic graphite
Item 3. The deterioration detection method according to Item 1 or 2, wherein a phase difference between the voltage and the current is measured in a frequency range of Hz. 5. Item 3. The method according to Item 1 or 2, wherein the phase difference between the voltage and the current is measured in a frequency range of 5 kHz to 2.2 MHz for the artificial carbon electrode.

[0006]

BEST MODE FOR CARRYING OUT THE INVENTION The carbon / graphite material has a size of crystallite which is a laminate of hexagonal carbon planes, an orientation mode and degree (fine structure) of the crystallite, and a mode of aggregation of fine structure (texture).
Can be classified into various types according to the differences. The electrical resistance of graphite crystallites has anisotropy of about 10 ⁴ , the current is much easier to flow in the direction parallel to the carbon hexagonal plane, and the current flows along the path according to the microstructure and texture of the sample. Flows. When an alternating current is used as the current flowing through the sample, it is predicted that the impedance value indicating the difficulty of the alternating current largely reflects the structure of the sample as compared with the resistance value of the direct current. For example, if the path detours, a coil component and a capacitor component will be generated there. Artificial carbon electrode, artificial graphite electrode and high density isotropic graphite (IG-11)
FIG. 1 is a graph showing the relationship between the AC frequency and the impedance for the three types, and FIG. 2 is a graph showing the relationship between the AC frequency and the phase difference between the voltage and the current. As is evident from these figures, carbon materials and graphite materials have different AC propagation characteristics such as impedance and phase difference depending on their types, and these AC propagation characteristics depend on the tissue structure. I understand.

[0007] It is considered that when oxidative consumption or material mechanical destruction occurs during use of carbon / graphite materials, crystallites, microstructures, textures, and the like change. Therefore, a carbon / graphite material that has been subjected to oxidative consumption or material mechanical destruction has a change in the AC propagation characteristics as compared with the original material.
Therefore, by knowing the change in the AC propagation characteristics, it is possible to detect the deterioration of the carbon / graphite material in use.

In the deterioration detection method of the present invention, the types of the carbon material and the graphite material to be measured are not particularly limited, and various types of carbon materials and graphite materials from amorphous carbon materials to highly crystallized materials are used. Can be measured. In particular, heating elements and heat insulators for electric furnaces; aerospace materials such as nose and nozzles for space shuttles; brakes for aircraft; materials used in energy fields such as fuel cells, fusion reactors, and nuclear reactors. Since carbon materials or graphite materials are used in special environments such as high temperatures and in nuclear reactors,
It is advantageous to detect degradation by the detection method of the invention.

According to the method of the present invention, deterioration such as oxidative consumption and destruction can be detected by measuring the AC propagation characteristics of a carbon material or a graphite material to be measured.

More specifically, for a carbon or graphite material to be measured, the AC propagation characteristics are measured before use or immediately after the start of use, and the AC propagation characteristics measured during use are measured in advance. By comparing with, it is possible to know the degree of deterioration due to oxidative consumption or destruction.

The AC propagation characteristics include a phase difference between voltage and current and impedance. Among these AC propagation characteristics, depending on the type of the material to be measured, one or two types that greatly change due to deterioration of the material.
The AC propagation characteristics of the species may be measured continuously or at appropriate intervals during use of the material. Specifically, for the material to be measured, the type of the AC propagation characteristic having a large change due to the material deterioration and the frequency range in which the change is large are determined in advance, and the frequency range is continuously or appropriately set in the frequency range during use. After that, the AC propagation characteristics may be measured.

For example, for high density isotropic graphite, 1
In the frequency range of 0 kHz to 2.2 MHz, a large change occurs in the phase difference between the voltage and the current due to deterioration. Therefore, the phase difference between the voltage and the current is measured in this frequency range during use, and the characteristics measured in advance are The deterioration can be easily detected by comparison.

For artificial carbon, the frequency of 5 kHz
In the 2.2 MHz frequency range, a large change occurs in the phase difference between the voltage and the current due to deterioration. Therefore, the phase difference between the voltage and the current is measured in this frequency range during use, and compared with the previously measured characteristics. This makes it possible to easily detect deterioration.

[0014] As an embodiment of the present invention, for example, a DC or AC current is applied as a heating element of an electric furnace to a carbon material or a graphite material which is being used. By measuring the AC propagation characteristics by applying an AC voltage, it is possible to detect the deterioration of the heating element on the spot during use.

[0015]

According to the deterioration detection method of the present invention, oxidation of a carbon material or a graphite material used in a special environment such as a high temperature or a nuclear reactor can be performed by a simple method of measuring an AC propagation characteristic. Deterioration due to wear and tear can be detected during use on the spot.

[0016]

EXAMPLES Hereinafter, the present invention will be described in more detail with reference to examples.

Example 1 High-density isotropic graphite (IG-11) was placed in a size of 10 × 10 × 120 mm ³
10mm from both ends
A hole of 3 mmφ was made in the position, and a measuring terminal was fixed with a metal screw, and impedance and a phase difference between voltage and current were measured in a frequency range of 1 Hz to 2.2 MHz.

Further, in order to simulate mechanical mechanical destruction, a notch having a width of 1 mm and a depth of 5 mm is provided between the measuring terminals.
Nine pieces of material were prepared for every mm, and the impedance and the phase difference between voltage and current were measured for this material in the same manner.

FIG. 3 shows the measurement results for impedance.
FIG. 4 shows the measurement results of the phase difference. FIG.
In FIG. 4 and FIG. 4, the curve indicated by the symbol A is the measurement result of the sample without the notch, and the curve indicated by the symbol B is the measurement result of the sample with the notch.

As is apparent from these results, by making a cut in a sample made of high-density isotropic graphite, a change occurs in both impedance and phase difference characteristics as compared with a sample without a cut. You can see that.
In particular, it is understood that deterioration can be easily detected by measuring the phase difference in the frequency range of 10 kHz to 2.2 MHz.

Example 2 Using an artificial carbon electrode as a sample, the same shape as in Example 1 was cut out, and 1 Hz to 2.2 as in Example 1.
The impedance and the phase difference between the voltage and the current were measured in the frequency range of MHz.

After the sample was oxidized in air at 600 ° C. for 1 hour, the impedance and the phase difference were measured in the same manner.

FIG. 5 shows the measurement results of the impedance.
FIG. 6 shows the measurement results of the phase difference. FIG.
In FIG. 6 and FIG. 6, the curve indicated by symbol A is the measurement result of the sample before oxidation, and the curve indicated by symbol B is the measurement result of the sample after oxidation treatment.

As is apparent from these results, it is found that the oxidation and the phase difference are changed by oxidizing the sample made of the artificial graphite electrode. In particular, 5
By measuring the phase difference in the frequency range of kHz to 2.2 MHz, it can be seen that deterioration due to oxidation is easily detected.

[Brief description of the drawings]

FIG. 1 is a graph showing a relationship between an AC frequency and impedance for a carbon / graphite material.

FIG. 2 is a graph showing a relationship between an AC frequency and a phase difference between a voltage and a current for a carbon / graphite material.

FIG. 3 is a graph showing the relationship between the AC frequency and the impedance of the sample used in Example 1.

FIG. 4 is a graph showing the relationship between the AC frequency and the phase difference between voltage and current for the sample used in Example 1.

FIG. 5 is a graph showing the relationship between the AC frequency and the impedance of the sample used in Example 2.

FIG. 6 is a graph showing the relationship between the AC frequency and the phase difference between voltage and current for the sample used in Example 2.

Claims (5)

[Claims] 1. A method for detecting deterioration of a carbon material or a graphite material, comprising measuring an AC propagation characteristic of the carbon material or the graphite material. 2. A method for measuring the AC propagation characteristic during use of a carbon material or graphite material, and comparing the measured AC propagation characteristic with the AC propagation characteristic measured before use or immediately after the start of use. Deterioration detection method. 3. The deterioration detection method according to claim 1, wherein the AC propagation characteristic is at least one characteristic selected from a phase difference between voltage and current and impedance. 4. A high-density isotropic graphite having a frequency of 10 kHz to
The deterioration detection method according to claim 1, wherein a phase difference between the voltage and the current is measured in a frequency range of 2.2 MHz. 5. An artificial carbon electrode having a frequency of 5 kHz to 2.2.
3. The method according to claim 1, wherein a phase difference between the voltage and the current is measured in a frequency range of MHz.