JPH06273373A - Electrode element for chloride gas detector and manufacture thereof - Google Patents

Abstract

PURPOSE:To enhance strength and response to chlorine gas by tightly laminating a solid electrolytic layer of chloride and an electrode layer of metallic material through simultaneous fusion. CONSTITUTION:A solid electrolyte of chloride and a metallic material for forming an electrode, e.g. silver or copper, are filled in a ceramic Tamman tube 1 and thermally fused at 600 deg.C in an electric furnace. When it is subsequently cooled, the chloride having a lower specific gravity is separated from the metallic material having a higher specific gravity and the chloride forms an upper solid electrolytic layer 2 whereas the metallic material forms a lower electrode 3. Furthermore, a thin film 4 of metal chloride is formed between the electrolytic layer 2 and the electrode 3 in order to enhance adhesion. The electrolytic layer 2 is then cut off to expose the surface thereof and a cut 5 is made in the bottom of the tube 1 to expose the electrode 3 which is subsequently connected with a lead wire 6 thus constituting an electrode element 10. Since the electrolytic layer 2 and the electrode 3 are formed simultaneously through fusion, the element exhibits high adhesion and quite high response to chlorine gas.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrode element used in a chlorine gas detecting device using a solid electrolyte and a manufacturing method thereof.

[0002]

2. Description of the Related Art Industrially, chlorine is the most widely used halogen element. Considering its toxicity and air pollution due to its emission, it is necessary to develop a sensor capable of monitoring the emission amount.

It is known that a gas concentration cell type sensor using a solid electrolyte is the most excellent in that the gas concentration can be measured in real time, and a representative one thereof is an O ₂ sensor. Gas sensors for SO _x , NO _x , CO _2, etc. have also been reported. As the solid electrolyte type chlorine sensor, there has been reported that a material in which a small amount of KCl is dissolved in PbCl ₂ and SrCl ₂ to increase the conductivity is used as the solid electrolyte.

[0004]

However, unlike ceramics, chloride cannot be expected to have a high density due to sintering, and therefore has a problem in strength. Therefore, the solid electrolyte of the conventional solid electrolyte type chlorine sensor is made of the green compact, but the strength problem has not been solved yet.

For example, by compressing a chloride electrolyte powder,
It is conceivable to manufacture an electrode member used in the sensor by bonding a metal electrode such as Ag to this with an inorganic adhesive. However, in this case, the water contained in the inorganic adhesive is absorbed by the chloride phase, and the chloride phase becomes in a swelled state, so that strength reduction cannot be avoided. Also, a method of pressurizing a compression molded body (compacted powder body) of chloride electrolyte powder together with a metal electrode material to perform pressure bonding can be considered.
Since the surface of the electrode material such as is not smooth with the green compact, there is a problem that it is easily peeled off.

Further, when the chloride electrolyte is used in the form of a green compact, there is a fundamental problem that the response of the sensor is slow.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide an electrode element used in a chlorine gas detecting device which effectively solves the problem of strength and has a quick response, and a manufacturing method thereof.

[0008]

According to the present invention, a solid electrolyte layer made of chloride and an electrode layer made of a metal material are formed in close contact by simultaneous melting of the chloride and the metal material. An electrode element for a chlorine gas detecting device is provided.

According to the present invention, further, a chloride for forming a solid electrolyte and a metal material for forming an electrode having a specific gravity higher than that of the chloride are filled in a ceramic Tammann tube,
Provided is a method for manufacturing an electrode element for a chlorine gas detection device, which comprises heating and melting, and then cooling.

[0010]

The electrode element of the present invention is characterized in that the solid electrolyte and the electrode are formed in close contact with each other by the simultaneous melting method, which brings various advantages.

For example, when the solid electrolyte and the metal material for electrode formation are simultaneously melted, they are separated by the difference in specific gravity, but a thin layer of metal chloride is formed at the interface, and this thin layer acts as a bridge. By exhibiting the action, the adhesion between them becomes extremely high.

Further, since the solid electrolyte layer of chloride is once melted, it is non-porous and has a small number of openings through which gas penetrates. SEM observation of the surfaces of the electrolyte layer of the electrode element obtained by the method of the present invention and the electrolyte layer of the green compact (disk type sample treated for 10 minutes at 1 t / cm ² )
The size of each particle was different on the surface of the green compact, and a crack was generated in the large particle due to the molding pressure, and a gap was also seen between the particles. On the other hand, on the surface of the electrolyte in the present invention, since the particles were melted, the particles were small and uniform, and there were hardly any gaps into which gas might penetrate. Therefore, in the chlorine gas detection device using the powder compact, the detection gas that has entered the solid electrolyte is difficult to escape, which adversely affects the response speed and, for example, the response time until the electromotive force reaches equilibrium is 10
However, when the electrode element of the present invention is used,
There is no such problem, and the responsiveness is significantly improved.

[0013]

DETAILED DESCRIPTION OF THE INVENTION Solid Electrolyte In the present invention, as the solid electrolyte, any chloride can be used as long as it can be melted in an electric furnace. Typical examples thereof are lead chloride, barium chloride and strontium chloride. Etc. can be mentioned. Further, in order to enhance the conductivity, for example, an alkali chloride such as KCl can be mixed within the range of 20% by weight.

Metal Material for Electrode Formation As the metal used for forming the electrode which is brought into close contact with the above-mentioned solid electrolyte, any metal can be used as long as it can be melted in an electric furnace, but particularly, In order to be rapidly separated by simultaneous melting with the solid electrolyte, it is necessary that the specific gravity of the solid electrolyte is larger than that of the solid electrolyte. Generally, silver, lead or the like is used.

Production of Electrode Element In FIG. 1 showing the structure and production process of the electrode element of the present invention, first, in the Tammann tube 1 made of ceramics such as alumina or zirconium, the chloride of the solid electrolyte and the metal for forming the electrode described above. Fill the material, heat and melt in an electric furnace,
Then, cooling is performed. As a result, the chloride having a low specific gravity and the metal material having a high specific gravity are separated, the chloride forms the solid electrolyte layer 2 at the upper side, and the metal material forms the electrode 3 at the lower side. Further, a thin layer 4 of metal chloride is formed between the solid electrolyte layer 2 and the electrode 3. Since the thin layer 4 is present at the interface between the two, its adhesion is extremely good. For example, when Ag is used as the electrode material, the thin layer 4 is silver chloride (AgCl).

Next, the solid electrolyte layer 2 is cut together with the Tamman tube 1 by a diamond cutter or the like to expose the surface of the solid electrolyte layer 2, and the lower part of the Tamman tube 1 accommodating the electrode 3 has a notch 5 To expose the electrode 3 and connect the lead wire 6 to obtain the electrode element 10 of the present invention.
The entire electrode element 10 is covered with the Tammann tube 1 made of ceramics, so that the electrode element 10 is sturdy and has extremely high strength.

Chlorine Gas Detection Device The above-described electrode element 10 of the present invention is provided with an electrode or the like to serve as a sensor probe, and is used as a chlorine gas detection device. The structure of this sensor probe is shown in FIG.

In this sensor probe (generally designated by 20), an electrode 21 is adhered to the exposed surface of the solid electrolyte layer 2, and a tube 23 made of an insulating material such as an inorganic adhesive 22 is attached to the bottom of the Tammann tube 1. Are joined. As the electrode 21, any conductive material can be used as long as it has appropriate heat resistance, but Au,
Pt, carbon (C), RuO ₂ or the like is used. As the insulating tube 23, one having electrical insulation and gas sealing property is used, and for example, ceramics such as alumina and zirconia, quartz, mullite, hard glass, Pyrex, etc. are preferably used.

As shown in FIG. 3, this sensor probe 20 is set in a heat resistant tube having a gas inlet 31 and a gas outlet 32, for example, a glass tube 33 made of Pyrex, and a lead wire 34 is wound around it. Thermocouple tube 35
Is set as the lead wire 34 so as to contact the electrode 21, and is used as a chlorine gas detection device. That is, in this device, the electrode 3 acts as a reference electrode and the electrode 21 acts as a measuring electrode.

For example, a small amount of KC is used as the solid electrolyte 2.
When BaCl ₂ mixed with 1 is used and Ag is used as the electrode 3 (reference electrode), the above chlorine gas detection device forms the following chlorine concentration cell. P _Cl2 (I) (Ag, AgCl) / BaCl ₂ + KCl /
P _Cl2 (II)

In the above, the left electrode is the reference electrode, and its chlorine partial pressure P _Cl2 (I) shows a constant value at a constant temperature due to the equilibrium relationship shown by the following formula (1). _{Ag (s) +1/2 · Cl 2} = AgCl (s) (1) (1) ΔG ° 1 the standard free energy change in equation, the following equation _{(2): ΔG ° 1 =} -RT · ln (a Agcl / A _Ag · P _Cl2 (I) ^1/2 ) (2) In the formula, R is a gas constant, T is a temperature (K), and a is an activity of each component. Here, since a _Agcl and a _Ag can be respectively set to 1, the following formula (3) is derived from the formula (2). lnP _Cl2 (I) = 2ΔG ° ₁ / RT (3) The electromotive force E of the above chlorine concentration battery is represented by the following formula (4). E = RT / 2F · ln (P _Cl2 (II) / P _Cl2 (I)) (4) In the formula, F: Faraday constant

Therefore, since ΔG ° ₁ is known, by measuring the electromotive force of the battery, the chlorine gas partial pressure P _Cl2 (II) in the measurement gas can be calculated from the above equations (3) and (4). It can be calculated. Such a chlorine gas detecting device has a fast response speed and can detect the chlorine gas concentration quickly in connection with the use of the above-mentioned electrode element.

[0023]

Example 1 Barium chloride dihydrate having a purity of 99.9% by weight or more and reagent grade potassium chloride were mixed in a BaCl ₂ : KCl = 97: 3 (weight ratio), and the mixture was placed in a vacuum. It was heated to 600 ° C. and dried and dehydrated. The obtained electrolyte powder (3.0 g) and silver powder (4.0 g) were placed in an alumina tube, kept in an electric furnace at 1100 ° C. for 1 hour in an air atmosphere, and then cooled. The sample solidified in the alumina tube was separated into an electrolyte layer (chloride phase) and a silver layer from above due to the difference in specific gravity, and a very thin layer of silver chloride (AgCl) was formed at the interface between the two. .

Next, the electrolyte layer portion was cut with a diamond cutter to expose the electrolyte layer, and a cut was made in the bottom alumina tube to expose the silver layer. A lead wire (silver wire) was connected to the exposed silver layer using a silver paste to form an electrode element having a structure shown in FIG.

Further, an alumina tube was adhered to the bottom of the electrode element obtained above by using an inorganic heat resistant adhesive (SUMICERAM). Further, a ruthenium oxide paste is applied to the exposed surface of the electrolyte layer and baked at 450 ° C. for 1 hour,
A sensor probe having the structure shown in FIG. 2 was produced.

Next, the above-mentioned sensor probe was set in a Pyrex glass tube having a gas inlet and a gas outlet, and the gold wire wound around the thermocouple protection tube was brought into contact with the ruthenium oxide layer, and the chlorine shown in FIG. A gas measuring device was produced. This device forms a chlorine concentration battery represented by the following formula. P _Cl2 (I) (Ag, AgCl) / BaCl ₂ + KCl /
P _Cl2 / P _Cl2 (II)

A measurement gas having a known chlorine concentration was caused to flow through the glass tube at 350 ° C. to measure the electromotive force. In Figure 4,
A plot of measured values and a theoretical electromotive force-chlorine concentration curve are shown.
According to this detection device, the measurement result that almost coincided with the theoretical electromotive force was shown at a chlorine concentration of 50 ppm by volume or more. In addition, the response time to respond to the change in the concentration of the measurement gas quickly and to reach a certain electromotive force is about 1 minute in the high concentration range, 100 ppm by volume.
It was about 2 to 5 minutes in the following low concentration range. Similar experiments were conducted using electrodes other than ruthenium oxide, but almost the same results were obtained.

[0028]

EFFECTS OF THE INVENTION In the electrode element for a chlorine gas detecting device of the present invention, since the solid electrolyte layer (chloride phase) and the electrode layer are formed by the simultaneous melting method, the adhesion between them is extremely high, and A chlorine gas detection device configured using this electrode element has an extremely fast response speed to chlorine gas.
Further, since this electrode element is almost entirely covered with a ceramic tube, the electrode element has high strength, and a sensor probe and a chlorine gas detection device can be extremely easily manufactured using this.

[Brief description of drawings]

FIG. 1 is a diagram showing a manufacturing process of an electrode element of the present invention.

FIG. 2 is a diagram showing a structure of a sensor probe formed by using the electrode element of FIG.

3 is a diagram showing a chlorine gas detection device using the sensor probe of FIG.

[Fig. 4] 350 ° C using the chlorine gas detector of Example 1
The plot of the measured value measured by and the theoretical electromotive force-chlorine concentration curve are shown.

[Explanation of symbols]

 1: Tamman tube 2: Solid electrolyte layer 3: Electrode layer 4: Metal chloride layer

Claims (5)

[Claims] 1. A chlorine gas detection device characterized in that a solid electrolyte layer made of chloride and an electrode layer made of a metal material are formed in close contact with each other by simultaneous melting of the chloride and the metal material. Electrode element. 2. Between the solid electrolyte layer and the electrode layer,
The electrode element according to claim 1, wherein a thin layer of metal chloride is interposed. 3. The electrode element according to claim 1, wherein the solid electrolyte layer and the electrode layer are held in a ceramic tube. 4. A chlorine gas comprising filling a solid electrolyte forming chloride and an electrode forming metal material having a specific gravity larger than that of the chloride into a ceramics Tamman tube, heating and melting the mixture, and then cooling. A method for manufacturing an electrode element for a detection device. 5. After cooling, the upper part of the Tammann tube is cut to expose the solid electrolyte, and then a cut is formed in the lower Tamman tube, and a lead wire is connected to the metal electrode through the cut. The method described in.