JP3227887B2 - Electrode element for chlorine gas detector and method for producing the same - Google Patents

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 detector using a solid electrolyte and a method for manufacturing the same.

[0002]

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

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 typical one is an O ₂ sensor. Gas sensors such as SO _x , NO _x , CO ₂ have also been reported. As a solid electrolyte type chlorine sensor, there has been reported a sensor using a material in which a small amount of KCl is dissolved in PbCl ₂ and SrCl ₂ to increase the conductivity as a solid electrolyte.

[0004]

However, unlike ceramics, chlorides cannot be expected to have high density by sintering, and therefore have a problem in strength. Therefore, all solid electrolytes of the conventional solid electrolyte chlorine sensor use compacts, but have not yet solved the problem of strength.

For example, a chloride electrolyte powder is compression-molded,
It is conceivable that an electrode member used for the sensor is manufactured by bonding a metal electrode such as Ag to this with an inorganic adhesive. However, in this case, the moisture contained in the inorganic adhesive is absorbed by the chloride phase, and the chloride phase becomes swelled, so that the strength is inevitably reduced. A method of pressing a compact (compact compact) of a chloride electrolyte powder together with a metal electrode material by pressing is also conceivable.
And the like, the surface of the electrode material is smooth and hardly fits into the compact, so that there is a problem that the electrode material is easily peeled off.

When the chloride electrolyte is used in the form of a compact, there is also a fundamental problem that the response of the sensor is slow.

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide an electrode element used in a chlorine gas detector having a quick response, in which the problem of strength is effectively solved, and a method of manufacturing the same.

[0008]

According to the present invention, a solid electrolyte layer made of a 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 detection device is provided.

According to the present invention, a ceramic for forming a solid electrolyte and a metal material for forming an electrode having a specific gravity higher than the chloride are filled in a ceramic Taman tube.
There is provided a method for producing an electrode element for a chlorine gas detection device, comprising heating, melting, and then cooling.

[0010]

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

For example, when the solid electrolyte and the metal material for forming an electrode are melted at the same time, the two are separated due to a 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 the two becomes extremely high.

Further, since the chloride solid electrolyte layer is once melted, it is non-porous and has few openings through which gas enters. When the surface of the electrolyte layer of the electrode element obtained by the method of the present invention and the surface of the electrolyte layer of the compact (disc-type sample treated at 1 t / cm ² for 10 minutes) were observed by SEM,
On the surface of the green compact, the size of each particle was different, cracks were generated in the large particles due to the molding pressure, and gaps were observed between the particles. On the other hand, on the electrolyte surface according to the present invention, since the particles were melted, each particle was small and uniform, and there was almost no gap where gas could enter. Therefore, in a chlorine gas detection device using a green compact, the detection gas that has entered the solid electrolyte is difficult to escape, which adversely affects the response speed. For example, the response time until the electromotive force reaches equilibrium is 10 times.
Minutes or more, but when the electrode element of the present invention is used,
There is no such problem at all, and the response is remarkably improved.

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION Solid Electrolyte In the present invention, any solid chloride can be used as long as it can be melted in an electric furnace. Typical examples thereof include lead chloride, barium chloride and strontium chloride. And the like. Further, in order to increase the conductivity, for example, an alkali chloride such as KCl can be mixed in a range of 20% by weight or less.

Metal Materials for Forming Electrodes As the metal used for forming the electrodes to be brought into close contact with the solid electrolyte, any metal can be used as long as it can be melted in an electric furnace. In order to quickly separate by simultaneous melting with the solid electrolyte, it is necessary that the solid electrolyte has a specific gravity greater than that of the solid electrolyte. In general, silver, lead, or the like is used.

[0015] In FIG 1 illustrating the structure and manufacturing process of the electrode elements of the production the present invention electrode elements, first alumina, the Tamman tube 1 made of ceramics or zirconium, chlorides and electrode-forming metal of the solid electrolyte described above Fill the material, heat and melt in an electric furnace,
Next, cooling is performed. As a result, the low specific gravity chloride and the high specific gravity metal material are separated, and the chloride forms the solid electrolyte layer 2 above and the metal material forms the electrode 3 below. 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 interposed at the interface between the two, the adhesion becomes extremely good. For example, when Ag is used as the electrode material, the thin layer 4 becomes silver chloride (AgCl).

Next, the solid electrolyte layer 2 is cut together with the tanman tube 1 with a diamond cutter or the like to expose the surface of the solid electrolyte layer 2, and a cut 5 is made in the lower tanman tube 1 containing the electrode 3. To expose the electrode 3 and connect the lead wire 6 to obtain the electrode element 10 of the present invention.
Since the electrode element 10 is almost entirely covered with the ceramic Taman tube 1, the electrode element 10 is strong and extremely strong.

Chlorine Gas Detector The above-described electrode element 10 of the present invention is provided with electrodes and the like to form a sensor probe, and is used as a chlorine gas detector. FIG. 2 shows the structure of this sensor probe.

In this sensor probe (indicated by 20 as a whole), an electrode 21 is adhered to the exposed surface of the solid electrolyte layer 2, and an insulating tube 23 is attached to the bottom of the tanman tube 1 by, for example, an inorganic adhesive 22. Are joined. As the electrode 21, any conductive material can be used as long as it has appropriate heat resistance.
Pt, carbon (C), RuO ₂ or the like is used. Further, as the insulating tube 23, a tube having electric insulation and gas-tightness is used. For example, ceramics such as alumina and zirconia, quartz, mullite, hard glass, Pyrex and the like are preferably used.

As shown in FIG. 3, the 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 therearound. Thermocouple tube 35
Is set so that the lead wire 34 is in contact with the electrode 21 and used as a chlorine gas detector. That is, in this device, the electrode 3 acts as a reference electrode and the electrode 21 acts as a measurement electrode.

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

In the above description, the left pole is the reference pole, 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 equation (1). Ag (s) + ／ · Cl ₂ = AgCl (s) (1) The change in standard free energy of equation (1) ΔG ° ₁ is represented by the following equation (2): ΔG ° ₁ = _−RT · ln (a _Agcl / A _Ag · P _Cl2 (I) ^1/2 ) (2) where R: gas constant T: temperature (K) a: activity of each component Here, a _Agcl and a _Ag can be each set to 1, and the following equation (3) is derived from the above equation (2). InP _Cl2 (I) = 2ΔG ° ₁ / RT (3) The electromotive force E of the chlorine concentration cell is represented by the following equation (4). E = RT / 2F · ln (P _Cl2 (II) / P _Cl2 (I)) (4) where 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). Can be calculated. Such a chlorine gas detection device has a fast response speed and can quickly detect the chlorine gas concentration in connection with the use of the above-described electrode element.

[0023]

EXAMPLE 1 Barium chloride dihydrate having a purity of 99.9% by weight or more and potassium chloride of a reagent grade were mixed so that BaCl ₂ : KCl = 97: 3 (weight ratio) and mixed in a vacuum. And dried and dehydrated. The obtained electrolyte powder (3.0 g) and silver powder (4.0 g) were put in an alumina tube, kept in an electric furnace at 1100 ° C. in an air atmosphere for 1 hour, and then cooled. The sample solidified in the alumina tube was separated from the top into an electrolyte layer (chloride phase) and a silver layer due to a 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 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 by using a silver paste to form an electrode element having a structure shown in FIG.

Further, an alumina tube was bonded to the bottom of the electrode element obtained above 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 manufactured.

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

A measuring gas having a known chlorine concentration was passed through the glass tube at 350 ° C. to measure the electromotive force. In FIG.
The plot of measured values and the theoretical electromotive force-chlorine concentration curve are shown.
According to this detector, the measurement result almost coincided with the theoretical electromotive force at a chlorine concentration of 50 vol ppm or more. In addition, it responds quickly to changes in the concentration of the measured gas, and the response time until it reaches a certain electromotive force is about 1 minute in a high concentration range, and 100 ppm by volume.
In the following low concentration range, it took about 2 to 5 minutes. Similar experiments were performed using electrodes other than ruthenium oxide, but almost the same results were obtained.

[0028]

According to the electrode element for a chlorine gas detector 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 the two is extremely high, and In a chlorine gas detection device configured using this electrode element, the response speed to chlorine gas is extremely high.
Further, since the entirety of the electrode element is almost entirely covered with a ceramic tube, the strength of the electrode element is high, and a sensor probe and a chlorine gas detection device using the electrode element can be extremely easily manufactured.

[Brief description of the drawings]

FIG. 1 is a view 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 using the electrode element of FIG.

FIG. 3 is a diagram showing a chlorine gas detection device using the sensor probe of FIG. 2;

FIG. 4 shows a temperature of 350 ° C. using the chlorine gas detector of Example 1.
2 shows a plot of measured values and a theoretical electromotive force-chlorine concentration curve.

[Explanation of symbols]

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

Continuation of the front page (56) References JP-A-62-43560 (JP, A) JP-A-61-155752 (JP, A) JP-A-60-256043 (JP, A) (58) Fields investigated (Int) .Cl. ⁷ , DB name) G01N 27/406 G01N 27/416 JICST file (JOIS)

Claims (5)

(57) [Claims] 1. A chlorine gas detecting device wherein a solid electrolyte layer made of chloride and an electrode layer made of metal material are formed in close contact by simultaneous melting of the chloride and 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 device according to claim 1, wherein the solid electrolyte layer and the electrode layer are held in a ceramic tube. 4. A chlorine gas comprising a step of filling a chloride for forming a solid electrolyte and a metal material for forming an electrode having a specific gravity higher than the chloride in a ceramic Taman tube, heating and melting, and then cooling. A method for manufacturing an electrode element for a detection device. 5. After cooling, the upper part of the tanman tube is cut to expose the solid electrolyte, and then a cut is formed in the lower tanman tube, and a lead wire is connected to the metal electrode through the cut. The method described in.