JPS6029898B2 - Gas and moisture sensing elements - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a gas-sensitive and humidity-sensitive element having a simple structure.

Conventionally, as gas-sensitive elements, Sn02, Zn0, Fe3
04, Nio and other metal oxide semiconductor elements are known.

This detects the presence of gas by detecting a decrease in the resistance value of the element when gas is adsorbed, but the element must be heated to 300 to 400 qo during operation, which consumes a lot of power. Disadvantages were seen, such as significant deterioration of the element over time because the element was constantly heated.
As described above, this invention aims to provide a gas- and humidity-sensitive element that can detect the presence or absence of gas at room temperature without requiring heating of the element, and can also sense humidity. However, it is characterized in that it is made of a mixture of an inorganic polymer mainly composed of zirconium and a solid powder made of ceramic or resin that supports the inorganic polymer, and a detection electrode is formed on the surface of this mixture. be.

Inorganic polymers mainly composed of zirconium have the property of decreasing their resistance in the presence of gas or moisture, and raw materials include zirconium oxychloride, zirconium acetate, and hydrated modified products of these salts. It exists as a glass-like inorganic polymer due to evaporation of water, and at high temperatures, for example, about 150 qo or higher, it becomes amorphous.
2.

However, up to around 150q○, it exists as an inorganic polymer mainly composed of zirconium. In addition, the solid powder supporting the inorganic polymer plays the role of holding the inorganic polymer, which is mainly composed of zirconium, in a tangible solid state, and the types include titanium oxide, tin oxide, silicon oxide, zirconium oxide, clay, and talc. These include ceramic solid powders such as epoxy resins, and organic solid powders such as epoxy resins.

In short, Zr02 is an inorganic polymer mainly composed of zirconium.
Any material may be used as long as it does not destroy the external shape of the device up to 150 qo, which changes to 150 qo, and does not adversely affect the properties of the inorganic polymer. The mixing ratio of the inorganic polymer mainly composed of zirconium and the solid powder supporting this inorganic polymer is not particularly limited, and may be any mixing ratio to obtain the required resistance value. It is sufficient to mix the inorganic polymers within a range that does not impair the gas detection capacity or humidity detection ability of the inorganic polymer, does not deform its shape, and maintains its mechanical strength.

Although the gas detection mechanism of the gas- and humidity-sensitive element according to the present invention has not yet been elucidated, it is possible to detect conductivity based on the adsorption and desorption of gas and moisture on the surface of a solid powder and the adsorption and desorption of gas and moisture on the surface of an inorganic polymer. It is thought that the change in temperature can be detected through the polymeric zirconium chain, and conventional methods have been used to detect metal oxide semiconductor elements such as Sn02, Zn0, Fe304, metal oxide gases such as Fe203, A203, and moisture. It has a new function that is different from the detection mechanism that is based on changes in resistance due to adsorption and desorption. Examples of configurations of gas- and moisture-sensitive elements include bulk materials made by mixing raw materials of inorganic polymers mainly composed of zirconium and solid powder, and solidifying the paste by heat treatment, or by placing the above on a substrate. There are thin film-like products made by applying a paste-like material and heat-treating it. Of course, all of these configuration examples have electrodes for detecting gas and moisture.

This invention will be described in detail below according to examples.

Example 1 An 18% zirconium oxychloride solution was added to 1.4 mL of titanium oxide powder and mixed well to form a paste.

Platinum wires were placed opposite each other at intervals of one leg, and this paste was applied over three lengths on the facing platinum wires and dried.

After drying, a heat treatment was performed at 120° C. for 2 minutes to produce a gas-sensitive element made of a mixture of a titanium oxide carrier powder and an inorganic polymer made of zirconium oxychloride. The resistance value (R.) of the obtained element at room temperature (25qo) was measured, and then the element was placed in the gas atmosphere shown in Table 1, and the resistance value (R2) at that time was measured.
) was measured and the change in resistance value (R2/R,) before and after installation in a gas atmosphere is shown in Table 1.

In addition, we measured the resistance change ((R2/R,): R, - resistance value before installation, R2 - resistance value after installation) before and after installing the obtained gas-sensitive element in an atmosphere with a humidity of 90%. The function as a moisture sensitive element was also investigated and the results are shown in Table 1. 1st
Table Example 2 Instead of the titanium oxide powder used in Example 1, tin oxide powder 2.5 times, silicon dioxide powder 1.4 times, zirconium oxide powder 1.4 times, clay powder 1.4 times, talc powder 1.
Four powders were prepared respectively, and these powders were mixed with zirconium oxychloride in the same manner as in Example 1 to prepare a gas-sensitive element.

This gas-sensitive element was heated to a methanol concentration of 1 at room temperature (25 oo).
Measure the resistance before and after installing in a gas atmosphere, and calculate the change in resistance (R2/R, :R, - resistance value before installation in a gas atmosphere, R2 - resistance value when installed in a gas atmosphere). Table 2 shows the resistance values). In addition, this element can be used at a humidity of 90
% resistance change before and after installation (R2/R,
: R, resistance value before installation, R2 - resistance value after installation) were measured, and the moisture sensitivity characteristics were investigated, and the results are also shown in Table 2. Table 2 Example 3 2.5 parts of tin oxide powder and 10 parts of palladium chloride were added, mixed uniformly, and heat treated at 850 qo.

Next, using this powder, zirconium oxychloride was added and mixed well in the same manner as in Example 1, and a Fuji gas element was produced in the same manner as in Example 1. The gas sensitive characteristics and moisture sensitive characteristics of this gas sensitive element were measured in the same manner as in Example 2, and the results are shown in Table 3.

Table 3 In this example, palladium, which has a conventional catalytic ability, is added to the solid powdered tin oxide described in Example 2, and it can be seen that this is effective in improving the characteristics of gas detection ability.

Of course, in addition to palladium, other substances having catalytic ability may be added to improve the properties. Example 4 Titanium oxide powder 1.4% The concentration of the zirconium chloride solution added was varied to 5%, 10%, and 20%, respectively, and these were mixed to create a paste.

This was treated in the same manner as in Example 1 to produce a device. Regarding this element, the resistance value (R,
), and then measured the resistance value (R2) when installed in methyl alcohol 170 willow, and calculated the change in resistance value (R2/R,) before and after installing it in a gas atmosphere, and found that each was 0. It was 3,0.1,0.006.

Next, this element was installed in an atmosphere with humidity of 70%, 80%, and 90%, and the resistance change (R2/R, :R, resistance value before installation, R2 - resistance value after installation) was measured. The moisture sensitivity characteristics were investigated and the results are shown in Table 4.

Table 4 Example 5 Using the device obtained in Example 1, this device was placed in a gas atmosphere of 17 kg of methyl alcohol for 3 minutes, and then returned to the atmosphere.

Measure the change in resistance value (R2) at this time, compare it with the resistance value (R,) before installation, and compare it with the resistance value change (R2/R,).
As a result, the behavior shown in the dashed line in FIG. 1 was obtained. Next, this element was placed in an atmosphere with a humidity of 90% for 3 minutes, and then returned to the atmosphere.

Measure the change in resistance value (R2) at this time, compare it with the resistance value (R,) before installation, and compare it with the resistance value change (R2/R,).
As a result, the behavior shown by the solid line in FIG. 1 was obtained. As is clear from the examples described above, according to the present invention, an inorganic polymer mainly composed of zirconium is supported on solid powder of ceramics or resin,
In addition to changes in the conductivity of the solid powder itself when gas and moisture are adsorbed and desorbed on the surface of the solid powder, conduction that occurs through polymeric zirconium chains when gas and moisture are adsorbed and desorbed on the surface of an inorganic polymer mainly composed of zirconium. change in degree,
In particular, this invention mainly utilizes the change in electrical conductivity based on the gas-sensitive and moisture-sensitive characteristics of the inorganic polymer mainly composed of zirconium. Therefore, according to the present invention, the device has the characteristic of having gas detection ability even if it is installed in a gas atmosphere at room temperature without heating the device, and there is no need for a structure that requires heating with a nichrome heater as in the conventional case. It has the advantage of being inexpensive. It has particularly high sensitivity to alcohol, acetone, etc., and is useful as a gas-sensitive element for polar organic solvents. Further, according to the present invention, it can also be used as a sensitive element.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing the gas-sensitive characteristics and moisture-sensitive characteristics of the device obtained by the present invention. Figure 1

Claims (1)

[Claims] 1. A gas-sensitive and sensitive gas comprising a mixture of an inorganic polymer mainly composed of zirconium and a solid powder made of ceramic or resin supporting the inorganic polymer, and a detection electrode is formed on the surface of this mixture. Wet element.