KR950010394B1 - Gas sensor manufacturing method - Google Patents

Abstract

The method for manufacturing a gas sensor sensing device for city gas comprises the steps of; mixing aluminum sol, alumina and distilled water to make paste; attaching the paste to a platinum line to obtain a sinter; depositing and then drying the sinter into catalyst water solution made by mixing palladium chloride, platinum acid chloride, hydrochloric acid and distilled water; making plastic under dry air and then making plastic under vapor; depositing at the catalyst water solution identical with that of the third step and then drying; and making plastic under dry air.

Description

Manufacturing method of gas sensor sensing element for city gas

1 is a graph showing a conventional heat treatment process.

2 is a graph showing a sensitivity characteristic with respect to the conventional humidity.

3 is a graph showing a heat treatment process of the present invention.

4 is a graph illustrating sensitivity characteristics different from high temperature and high humidity according to the present invention.

Figure 5 is a graph of sensitivity characteristics according to the habit.

6 is a configuration diagram of a sensing element.

* Explanation of symbols for main parts of the drawings

1 carrier 2 terminal

3: base 4: stainless steel support

5: stainless steel net

The present invention relates to a sensing element of a gas sensor, and more particularly, to a method of manufacturing a moisture-proof sensing element of a contact combustion gas sensor for a city gas capable of sufficiently detecting a leakage of city gas even in a humid place.

In connection with the present invention, the present applicant has previously filed Korean Patent Application No. 90-19636.

Here, a paste obtained by mixing aluminum sol, alumina and distilled water is made, which is attached to a platinum wire and calcined to obtain a sintered body.

Palladium chloride, chloroplatinic acid, hydrochloric acid, and distilled water were then deposited in a mixed catalyst solution at a ratio of 3g: 1g: 2cc: 7 / cc to attach the catalyst, followed by natural drying, as shown in FIG. 1 under dry air supply. Likewise fired for 2 hours at 400 ℃ and again immersed in an aqueous catalyst solution, dried and then fired for 3 hours at 600 ℃ to obtain a sintered body as a gas sensor sensing element.

The sintered body thus produced is called a carrier.

6 is a configuration diagram showing a sensing element. After the carrier 1 is fixed by spot welding (spot welding) on the terminal 2, two stainless steel meshes 5 (STS 100mesh) are mounted on the upper surface of the base 3 After assembling with the support 4, the terminal 2 to which the carrier 1 is attached is inserted and fixed therein. This assembly is called a sensing element or gas sensor.

Such a prior application for obtaining the carrier 1 in such a configuration has improved the performance of temperature and humidity changes than the conventional sensor (Japanese Patent Publication No. 60-26458), but as shown in FIG. As it increases, the combustion temperature is lowered by absorbing combustion heat due to the combustion of the combustible gas, and accordingly, the resistance change of the sensing element is reduced, thereby reducing the output voltage (output sensitivity).

Therefore, in the kitchen and bathhouse, etc., where the humidity is high, the sensitivity is lowered due to the influence of water vapor, and there is a problem in that it is not suitable for use at a high temperature and high humidity.

Therefore, the present invention has an object to improve the conventional problems by preventing the sensitivity is lowered when used in high temperature and high humidity.

Hereinafter, the present invention will be described.

In the present invention, alumina oxide, aluminum sol, and distilled water are mixed to form a paste, which is then attached to a platinum wire, dried, and then calcined at 800 ° C. for 8 hours to form a sintered body. The above sintered body is dipped and dried in an aqueous catalyst solution in which palladium chloride: chloroplatinic acid: hydrochloric acid: distilled water is mixed with 6 g: 2 g: 2 cc: 52 cc.

And it bakes, heating gradually to 500 degreeC in presence of dry air.

Subsequently, at a temperature of 500 ° C., water vapor was supplied and calcined for about 3-4 hours, and then immersed in an aqueous catalyst solution, dried, and then calcined at 500 ° C. for 1 hour in a dry air atmosphere. Obtained.

As described above, the present invention differs from the prior application in that the mixing ratio of platinum and palladium in the aqueous catalyst solution is increased, and is fired while blowing water vapor at around 500 ° C. during the heat treatment process.

The present invention prevents a decrease in sensitivity even when the heat of combustion of gas is lost by moisture even in a humid place due to the action of platinum chloride and palladium, which are heavier than the prior application. That is, the heat of reaction of the gas

C ₄ H ₁₀ + O ₂ → CO ₂ + H ₂ O + 685.65 kcal / Mol (isobutane gas). … … … … Ⓛ

CH ₄ + O ₂ → CO ₂ + H ₂ O + 212.8 kcal / Mol (methane). … … … … … … … ②

H ₂ + O ₂ → H ₂ O + 68.32 kcal / Mol (hydrogen gas)... … … … … … … … … … … … ③

By maintaining the surface temperature of the sensing element at 350-450 ° C. at all times, so that the combustion gas is burned at 350-450 ° C. by the weighted catalyst.

In the case where there is a lot of water vapor, the above equation (3) proceeds in the reverse direction. In the first application, heat loss occurs and the combustion temperature is lowered, thereby lowering the sensitivity. However, in the present invention, the combustion reaction is promoted by the weighted catalyst, as shown in FIG. Sensitivity can be maintained.

In addition, the heat treatment process of the present invention is calcined by heating slowly to 500 ° C. under a dry air atmosphere as shown in FIG. 3, but calcining for about 3-4 hours while supplying water vapor at 500 ° C., and then immersing in an aqueous catalyst solution and drying again. It is calcined at 500 ° C. for 1 hour under dry air atmosphere. Thus, water vapor is supplied for reduction and then oxidation is performed under dry air supply. Therefore, the activity of the catalyst is increased and the catalyst dispersibility is improved. Sensitivity change can be reduced by increasing the sensitivity characteristic even in the presence of moisture.

That is, the pyrolysis operation in the steam atmosphere has a resistance to water vapor and the like.

EXAMPLE

After pulverizing alumina oxide, aluminum sol and distilled water were mixed with 68g: 50g: 5cc and stirred for 10 minutes or more in a magnetic stirrer, followed by stirring for 20 minutes in a general stirrer and then for 1 hour or more in a ball mill.

The air is then defoamed for 2-5 hours at 720-730 mHg.

And after apply | coating the said mixed composition to a thin platinum wire, it bakes at 800 degreeC for 8 hours, and makes a sintered compact.

Then, it was immersed in a catalyst solution mixed with palladium chloride: chloroplatinic acid: hydrochloric acid: distilled water at a ratio of 6g: 2g: 2cc: 52cc, dried, and then slowly heated and calcined to 500 ° C under a dry air atmosphere of a heat treatment furnace, followed by 500 ° C. From 3 to 4 hours firing while supplying water vapor of about 100 ℃ conduction, it was again immersed in the aqueous catalyst solution and dried again, and then calcined for about 1 hour at 500 ℃ under dry air supply to disperse the catalyst well and stabilize the device. Get

As described above, the present invention is characterized by obtaining a carrier sintered body having good sensitivity even under high temperature and high humidity as shown in FIG. .

Claims (3)

A first step of mixing aluminum sol, alumina, and distilled water into a paste, a second step of attaching and baking the paste to a platinum wire and firing the sintered body, and the sintered body with palladium chloride, platinum chloride acid, hydrochloric acid, and distilled water. The second step of immersing in the catalyst aqueous solution by mixing and drying, and the fourth step of firing under dry air supply and then firing under steam supply, and again immersed in the same catalyst solution as the third step and dried And a fifth step and a step of firing again under a supply of dry air. The method of claim 1, wherein the aqueous catalyst solution is prepared by mixing a palladium chloride: chloroplatinic acid, hydrochloric acid: distilled water in the ratio of 6g: 2g: 2cc: 52cc. Way. The catalyst according to claim 1 or 2, wherein the sintered compact is immersed in an aqueous catalyst solution, dried, and then calcined by heating gradually to 500 ° C under dry air supply, and then calcining for 3-4 hours while supplying water vapor at the same temperature. The method of manufacturing a gas sensor detecting element for a combustion-fired city gas, characterized in that the immersion, drying and supplying dry air at a temperature of 500 ℃ again.