JP6380987B2 - Method for producing integrated reference electrode and integrated reference electrode - Google Patents

Description

  The present invention relates to a method for producing an integrated reference electrode and an integrated reference electrode, and is particularly useful when applied to the measurement of corrosion potential (ECP) of a light water reactor structural material or the like.

  Measurement of corrosion potential (ECP) of light water reactor structural materials is the most suitable technique for monitoring the environment in the reactor. In-furnace ECP measurement requires a reference electrode that operates stably for a long period of time, but there is no electrode that can be easily used under irradiation. Therefore, a metal / oxide electrode using a ceramic tube as an oxygen conductor has been proposed for this type of application. Such metal / oxide electrodes are chemically stable and unaffected by the redox system. Therefore, application as a reference electrode for a furnace can be expected (for example, see Non-Patent Document 1 and Non-Patent Document 2).

  In this type of metal / oxide electrode, an M / O electrode formed of a metal / metal oxide mixture is enclosed as a solid electrolyte in a ceramic tube. Here, the ceramic tube is made of, for example, yttria stabilized zirconia (YSZ), and the M / O electrode is made of, for example, Ni / NiO. In addition, the ceramic tube is installed at a predetermined measurement site such as in a nuclear reactor in a state where the ceramic tube is fixed to a metal case as a structural material by brazing at its upper end. The tip of the conducting wire is brought into contact with the M / O electrode so that the potential of the M / O electrode can be measured externally.

  However, when this type of metal / oxide electrode is placed under irradiation, corrosion may occur at the joint between the ceramic tube enclosing the M / O electrode and the metal case, and this portion may be damaged. In the case of breakage, the environmental solution may flow into the ceramic tube, or the powdered metal / metal oxide forming the M / O electrode may flow out of the ceramic tube into the environmental solution and contaminate it. There is.

  As a metal / oxide electrode for solving such a problem, the present invention proposed an integrated reference electrode described in Patent Document 1. Such an integrated reference electrode is shown in FIG. As shown in the figure, in the integrated reference electrode II, the metal oxide film 02B is formed on the metal substrate 02A, and the ceramic thin film 01 is formed on the metal oxide film 02B so as to cover the surface of the metal oxide film 02B. Is formed. Here, the metal substrate 02A and the metal oxide film 02B constitute the M / O electrode 02. The ceramic thin film 01, the metal oxide film 02B, and the metal substrate 02A are integrated by covering both ends with a covering member 03 such as a metal. Further, the potential information of the M / O electrode 02 is taken out via the conductive wire 04.

  Such an integrated reference electrode II does not have a ceramic tube and its joint which are the main cause of breakage of the conventional metal / oxide electrode, so that not only can the leakage of the solid electrolyte into the solution be avoided, By using a ceramic film, the thickness can be easily reduced, and the impedance of the electrode can be reduced. As a result, the electrode potential at room temperature can be measured. In addition, the ceramic membrane can separate the solution, which is a component of the environment, from the solid electrolyte, the electrode potential is not affected by the redox atmosphere in the solution, and the integrated reference electrode potential is determined only by the pH in the solution. The Accordingly, the integrated reference electrode according to the present invention has a number of features such as being able to be used as a reference electrode when the pH in the solution is known.

JP 2014-016335 A

EPRI report, NP-7142 (1991) L. W. Niedrach J. et al. Electrochem. Soc. 127,2122

  However, although the integrated reference electrode II described in Patent Document 1 is an integrated type, it is integrated by covering both ends of the ceramic thin film 01, the metal oxide film 02B, and the metal substrate 02A with a covering member 03 such as a metal. As a result, the solution is damaged by the penetration of the solution from the gaps between both ends of the ceramic thin film 01, the metal oxide film 02B and the metal substrate 02A and the covering member 03 when used under radiation irradiation. There is a case.

  An object of the present invention is to provide an integrated reference electrode manufacturing method and an integrated reference electrode that can maintain a function as a reference electrode that is stable for a long period of time even in a radiation environment.

The present invention for achieving the above object
A first step of introducing ceramic powder into the internal space of the die, which is a cylindrical member;
A first punch having a convex portion at the center and formed to be insertable into the internal space is inserted into the internal space through the opening of the die, and the first punch is lowered. A second step of compressing the ceramic powder and forming a recess corresponding to the protrusion;
A second punch, which is a cylindrical member having an internal space communicating with the opening of the concave portion, is inserted into the internal space of the die through the opening of the die and lowered to move the second punch. A third step of installing the internal space of the punch so as to communicate with the concave portion and be positioned above the concave portion;
A fourth step of introducing a metal which is a component of the metal oxide electrode and a metal powder which is a powder of the oxide from the opening of the second punch;
From the opening of the die, a fifth step of adding ceramic powder and covering the metal powder,
A sixth step of standing the conductive wire on the metal powder by inserting a lower portion of the conductive wire serving as an electrode into the metal powder through the ceramic powder charged in the fifth step;
In the fifth step, the third punch is inserted into the internal space of the die through the opening of the die and lowered by inserting the third punch into which the conductive wire is inserted into the through hole. A seventh step of compressing the ceramic powder charged;
And an eighth step of sintering and integrating the ceramic powder and metal powder compressed and integrated in the first to seventh steps in a state of being pressed in the axial direction of the conductive wire. There is a method for manufacturing an integrated reference electrode.

  According to the present invention, since the ceramic powder and the metal powder compressed and integrated in the first to seventh steps are fired and integrated in a state of being pressed in the axial direction of the conductive wire, the metal and its A metal oxide electrode made of metal powder, which is an oxide powder, and a ceramic powder covering the metal oxide electrode can be manufactured as a complete integrated body. As a result, even when used in a radiation environment for a long time, the mechanical strength is not impaired, and the function as a stable reference electrode can be maintained for a long time.

The second aspect of the present invention is:
In the method for producing an integrated reference electrode described in the first aspect,
In the fifth step, the mixed powder of the ceramic powder and the metal powder is put on the ceramic powder in such a mixing ratio that the ratio of the metal powder to the ceramic powder gradually increases from the boundary with the ceramic powder. At the end, we put a simple metal powder,
In the sixth step, the conductor is erected on the ceramic powder, the mixed powder and the metal powder by inserting the lower part of the conductor through the ceramic powder, the mixed powder and the metal powder. The method of manufacturing an integrated reference electrode characterized by the above.

  According to this aspect, when the integrated reference electrode is installed at a predetermined location such as a light water reactor, it is easily and stably fixed to the metal at the installation location by brazing or the like through a metal portion formed by pressing metal powder. can do.

The third aspect of the present invention is:
An integrated reference electrode manufactured by the manufacturing method described in the first or second aspect.

  The integrated reference electrode according to the present aspect includes a boundary between parts in a state where the ceramic powder and the metal powder compressed and integrated in the predetermined step shown in the first or second aspect are pressed in the axial direction of the conductor. Since the gap between the parts is completely removed and integrated, a metal oxide electrode and ceramic powder made of a metal and an oxide metal powder, which is a powder of the oxide thereof, are manufactured as a complete integrated body. It is a body-shaped reference electrode. As a result, even when used in a radiation environment for a long time, the mechanical strength is not impaired, and the function as a stable reference electrode can be maintained for a long time.

  According to the present invention, a predetermined integrated reference electrode is manufactured by heating and compressing various materials to be matched, so that mechanical strength is not impaired even when used in a radiation environment for a long time. Thus, an integrated reference electrode that can maintain the function as a stable reference electrode over a long period of time can be easily obtained.

It is explanatory drawing which shows notionally the integrated reference electrode which concerns on embodiment of this invention. It is explanatory drawing which shows the jig | tool used for preparation of the integrated reference electrode which concerns on embodiment of this invention. It is explanatory drawing which shows the manufacturing process of the integrated reference electrode which concerns on embodiment of this invention. It is explanatory drawing which shows the manufacturing process of the integrated reference electrode which concerns on embodiment of this invention. It is explanatory drawing which shows the manufacturing process of the integrated reference electrode which concerns on a prior art.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
FIG. 1 is an explanatory diagram conceptually showing an integrated reference electrode according to an embodiment of the present invention. As shown in the figure, an integrated reference electrode I according to this embodiment is formed by covering a metal oxide electrode (hereinafter referred to as an M / O electrode) 2 with a ceramic 1 and integrating it by a manufacturing method described in detail later. Is. The M / O electrode 2 is integrated by, for example, mixing Ni powder, which is a metal powder, and NiO powder, which is a metal oxide powder of the oxide, by heating and pressing. The ceramic 1 is made of, for example, yttria stabilized zirconia (YSZ). Here, a conductive wire 4 is connected to the M / O electrode 2. Therefore, the potential information detected by the M / O electrode 2 is extracted to the outside through the lead wire 4.

  A connecting portion 3 extending along the axial direction of the conductive wire 4 is formed on the surface of the ceramic 1 to which the conductive wire 4 is connected. The connecting portion 3 is also produced by a method for producing the integrated reference electrode I, which will be described in detail later, and is integrated with the M / O electrode 2, and is composed of three layers of a ceramic layer 3A, a mixed layer 3B, and a metal layer 3C. The ceramic layer 3A is formed by pressing and heating ceramic powder of the same material as the ceramic 1. Similarly, the mixed layer 3B is formed by pressing and heating a mixed powder of a ceramic powder of the same material as the ceramic 1 and a metal powder of the same material as the M / O electrode 2. Further, the metal layer 3C is formed by pressurizing and heating metal powder of the same material as the M / O electrode 2.

  In FIG. 1, the ceramic layer 3A, the mixed layer 3B, and the metal layer 3C are clearly separated into three layers, but actually, the metal layer 3C is separated from the end surface of the ceramic layer 3A on the M / O electrode 2 side. Both are mixed so that the ratio of the metal powder to the ceramic powder gradually increases toward the end surface opposite to the mixed layer 3B. That is, the ceramic powder is 100% at the end face on the M / O electrode 2 side of the ceramic layer 3A, but the ratio of the metal powder gradually increases toward the metal layer 3C, and the end face of the metal layer 3C opposite to the mixed layer 3B. Then, it has adjusted so that the ratio of metal powder may be 100%.

  In such an integrated reference electrode I, the gap between the boundary portions of each part in a state in which the powder of the ceramic 1 compressed and integrated in a predetermined process described later and the powder of the metal and its oxide are pressed and heated. Since the ceramics 1 and the M / O electrode 2 are integrated with the covering member 03 as shown in FIG. 5 according to the prior art, the ceramic 1 and the M / O electrode 2 are manufactured as a complete integrated body. be able to. As a result, even when used in a radiation environment for a long time, the mechanical strength is not impaired, and the function as a stable reference electrode can be maintained for a long time.

  FIG. 2 is an explanatory view showing a jig used for manufacturing an integrated reference electrode according to an embodiment of the present invention. FIG. 2A shows the die 11. The die 11 has an internal space in which the opening 11A opens upward, and the opening on the opposite side of the opening 11A is closed with a bottom member 12 that is a cylindrical member shown in FIG. 2B. . Of course, the die 11 may itself be a bottomed member having an integral bottom member that closes the opening opposite to the opening 11A. Here, the inner diameter φ1 of the inner space of the opening 11A is slightly larger than the outer diameter φ2 of the bottom member 12. As will be described in detail later, prior to inserting the bottom member 12 into the die 11, it is necessary to insert a shielding member 18 (see FIG. 3; the same applies hereinafter) into the inner peripheral surface of the die 11. Therefore, the inner diameter φ1 is made larger than the outer diameter φ2 by the thickness of the shielding member 18. However, φ1≈φ2.

  FIG. 2C shows the first punch 13. The first punch 13 is a cylindrical member having an outer diameter φ2, and a convex portion 13A is formed at the center of one end face thereof. FIG. 2D shows the second punch 14. The second punch 14 is a cylindrical member having an outer diameter φ2, and the inner space 14A has an inner diameter φ3. FIG. 2E shows the third punch 15. The third punch 15 is a cylindrical member having an outer diameter φ2, and a through hole 15A having an inner diameter φ4 is formed at the center thereof.

  FIG. 2 (f) shows the carbon felt 16. The carbon felt 16 is used to improve heat efficiency by shutting off heat when the integrated reference electrode I is pressed and heated in the final step by a plasma sintering (SPS) method described later. FIG. 2F shows the pressing jig 17. The pressing jig 17 is used to press the integrated reference electrode I from above and below when the integrated reference electrode I is finally pressed by the SPS method.

  FIG. 3 and FIG. 4 are explanatory views showing a manufacturing process of the integrated reference electrode according to the embodiment of the present invention. A method for manufacturing an integrated reference electrode according to this embodiment will be described with reference to FIG.

<First step>
A die 11 is prepared (see FIG. 3A), a cylindrically shaped shielding member 18 is set in contact with the inner peripheral surface of the die 11 (see FIG. 3B), and a flat plate-shaped shield is provided. The bottom member 12 with the member 19 attached to the upper surface is inserted into the internal space of the die 11 from below (see FIG. 3C). In this state, ceramic powder (for example, yttria-stabilized zirconia powder) 20 that becomes the ceramic 1 of the integrated reference electrode I (see FIG. 1, the same applies hereinafter) 20 is passed through the opening 11A from the opening 11A to the internal space of the die 11. Fill (FIG. 3 (d)). Here, the shielding members 18 and 19 are for isolating the die 11 and the ceramic powder 20 from each other to prevent direct contact and reaction. Therefore, when the die 11 is made of graphite, the shielding members 18 and 19 are preferably made of boron nitride. In this embodiment, the flat shielding members 18 and 19 are used. However, this can be replaced by applying a liquid containing boron nitride to the inner peripheral surface of the die 11 or the surface of the bottom member 12, for example. .

<Second step>
The first punch 13 is inserted into the internal space of the die 11 from the opening 11A of the die 11 with the convex portion 13A facing downward (see FIG. 3E). Thereafter, the ceramic powder 20 is compressed by lowering the first punch 13 and a recess 20A corresponding to the protrusion 13A is formed (see FIG. 3F).

<Third step>
The second punch 14, which is a cylindrical member having an internal space communicating with the opening of the recess 20 </ b> A, is inserted into the internal space of the die 11 through the opening 11 </ b> A of the die 11, and is lowered to move the second punch 14. The punch 14 is installed so that the internal space thereof communicates with the recess 20A and is positioned above the recess 20A (see FIG. 3G). Here, the inner diameter φ3 is substantially equal to the width of the opening of the recess 20A.

<4th process>
A metal powder 21 which is a mixed powder of a metal (for example, Ni) and a metal oxide (for example, NiO) serving as a component of the metal oxide electrode is introduced from the opening of the second punch 14 (FIG. 3 (h)). reference). As a result, the recess 20A is filled with the metal powder 21 (see FIG. 4A).

<Fifth step>
Ceramic powder 22 is further introduced from the opening 11A of the die 11 to cover the metal powder 21 (see FIG. 4B).

<Sixth step>
The lower part of the conducting wire 4 serving as an electrode is inserted into the metal powder 21 through the ceramic powder 22 introduced in the fifth step (see FIG. 4C). As a result, the conductor 4 is erected on the metal powder 21. Thereafter, the surface of the ceramic powder 22 is covered with a shielding member 23 (see FIG. 4D).

<Seventh step>
The third punch 15 in which the lead wire 4 is inserted into the through hole 15A having the inner diameter φ4 is inserted into the internal space of the die 11 through the opening 11A of the die 11 and is lowered, thereby lowering the third punch 15 by The ceramic powder 22 charged in the fifth step is compressed (see FIG. 4E). Here, the inner diameter φ4 of the through hole 15A is formed to be substantially equal to the outer diameter of the conducting wire 4.

<Eighth process>
The ceramic powders 20 and 22 compressed and integrated in the first to seventh steps and the metal powder are fired and integrated in a state of being pressed in the axial direction of the conductive wire 4. Such pressurization and heat firing are performed by the SPS method. Specifically, the jig part is surrounded by the carbon felt 16 for heat insulation, the pressing jig 17 presses the upper surface of the third punch 15 and the lower surface of the bottom member 12, and is heated and integrated by discharge plasma. (See FIGS. 4F and 4G).

<Production process of connection part>
In the case of forming the connection portion 3 shown in FIG. 1, the ratio of the metal powder to the ceramic powder 22 gradually increases on the ceramic powder 22 from the boundary with the ceramic powder 22 in the fifth step. A mixed powder of the ceramic powder 22 and the metal powder is added at a mixing ratio, and finally a simple metal powder is added, and in the sixth step, the ceramic powder 22, the mixed powder, and the metal powder are penetrated to conduct the wire. 4 is inserted into the ceramic powder 22, the mixed powder and the metal powder, and the pressure and heat treatment by the SPS method in the embodiment shown in the seventh and eighth steps. Should be done.

The present invention can be effectively used in industrial fields such as the nuclear power industry where it is necessary to detect the soundness of sealed reactor structures.

I Integrated reference electrode 1 Ceramics 2 Metal oxide electrode (M / O electrode)
DESCRIPTION OF SYMBOLS 3 Connection part 4 Conductor 11 Dice 11A Opening part 13 1st punch 13A Convex part 14 2nd punch 15 3rd punch 15A Through-hole 20, 22 Ceramic powder 21 Metal powder

Claims (3)

A first step of introducing ceramic powder into the internal space of the die, which is a cylindrical member;
A first punch having a convex portion at the center and formed to be insertable into the internal space is inserted into the internal space through the opening of the die, and the first punch is lowered. A second step of compressing the ceramic powder and forming a recess corresponding to the protrusion;
A second punch, which is a cylindrical member having an internal space communicating with the opening of the concave portion, is inserted into the internal space of the die through the opening of the die and lowered to move the second punch. A third step of installing the internal space of the punch so as to communicate with the concave portion and be positioned above the concave portion;
A fourth step of introducing a metal which is a component of the metal oxide electrode and a metal powder which is a powder of the oxide from the opening of the second punch;
From the opening of the die, a fifth step of adding ceramic powder and covering the metal powder,
A sixth step of standing the conductive wire on the metal powder by inserting a lower portion of the conductive wire serving as an electrode into the metal powder through the ceramic powder charged in the fifth step;
In the fifth step, the third punch is inserted into the internal space of the die through the opening of the die and lowered by inserting the third punch into which the conductive wire is inserted into the through hole. A seventh step of compressing the ceramic powder charged;
And an eighth step of sintering and integrating the ceramic powder and metal powder compressed and integrated in the first to seventh steps in a state of being pressed in the axial direction of the conductive wire. A method for producing an integrated reference electrode. In the manufacturing method of the integrated reference electrode of Claim 1,
In the fifth step, the mixed powder of the ceramic powder and the metal powder is put on the ceramic powder in such a mixing ratio that the ratio of the metal powder to the ceramic powder gradually increases from the boundary with the ceramic powder. At the end, we put a simple metal powder,
In the sixth step, the conductor is erected on the ceramic powder, the mixed powder and the metal powder by inserting the lower part of the conductor through the ceramic powder, the mixed powder and the metal powder. A method for producing an integrated reference electrode. An integrated reference electrode manufactured by the manufacturing method according to claim 1.