JP2016217751A - Hydrogen gas sensor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a hydrogen gas sensor having a high hydrogen gas detection accuracy and a high durability.SOLUTION: A hydrogen gas sensor 100 includes: a hydrogen detection film 10 for detecting hydrogen gas; a heater 30 for heating the hydrogen detection film 10; and a latent heat storage unit 40 disposed between the heater 30 and the hydrogen detection film 10. The latent heat storage unit 40 includes a first latent heat storage material 41 for causing phase transition.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a hydrogen gas sensor.

  In recent years, in order to solve environmental and energy problems, the movement of hydrogen society in Japan is accelerating. For example, a fuel cell vehicle that generates electricity using a chemical reaction between hydrogen and oxygen and runs by rotating a motor has been developed. On the other hand, hydrogen gas is colorless and transparent, does not smell, and it is difficult to detect leakage even though the concentration in the atmosphere is an explosion region in a wide range of 4 to 75%. For this reason, interest in a hydrogen gas sensor for leak detection is increasing.

As such a hydrogen gas sensor, for example, a hydrogen gas sensor described in Patent Document 1 below is known. The following Patent Document 1, adsorbed hydrogen gas and protons (H ⁺⁾ electrons ^- and protons generated in the catalyst and the activity has an action to dissociate the a (H ⁺⁾ Electronic (e) ^- (e) and There is disclosed a hydrogen gas sensor that has a detection film made of a metal oxide whose conductivity is increased by this reaction and a heater for heating the detection film, and detects hydrogen from a change in the conductivity of the metal oxide.

JP 2006-162365 A

  However, the hydrogen gas sensor described in Patent Document 1 has the following problems.

  That is, in the hydrogen gas sensor described in Patent Document 1, when the detection film is heated by the heater, the temperature change of the heater is likely to occur due to the ambient temperature change. Therefore, the temperature of the hydrogen detection film also changes with the temperature change of the heater, the amount of adsorption of hydrogen gas to the hydrogen detection film becomes unstable, and there is a possibility that the hydrogen gas detection accuracy is lowered. In addition, since the heater temperature is likely to change due to a change in ambient temperature, if the heater temperature temporarily rises excessively, the temperature of the hydrogen detection film also temporarily rises. When the temperature of the hydrogen detection film is repeatedly excessively increased, the hydrogen detection film is repeatedly distorted, the hydrogen detection film is cracked, or the hydrogen detection film is peeled off. As a result, the durability of the hydrogen gas sensor may be reduced.

  Therefore, the hydrogen sensor described in Patent Document 1 described above has room for improvement in terms of hydrogen gas detection accuracy and hydrogen detection film durability. Here, it is conceivable to control the temperature of the hydrogen detection film by performing PID control of the heater, but this method is still improved in terms of appropriately controlling the temperature of the hydrogen detection film and thus improving the durability. There was room.

  The present invention has been made in view of the above circumstances, and an object thereof is to provide a hydrogen gas sensor having excellent hydrogen gas detection accuracy and durability.

  In order to solve the above problems, the present inventor has found that the above problems can be solved by providing a latent heat storage part between the heater and the hydrogen detection film in the hydrogen gas sensor.

  That is, the present invention includes a hydrogen detection film that detects hydrogen gas, a heater that heats the hydrogen detection film, and a latent heat storage unit provided between the heater and the hydrogen detection film, and the latent heat storage unit Is a hydrogen gas sensor having a first latent heat storage material that causes a phase transition.

  In the hydrogen gas sensor of the present invention, when the hydrogen detection film is heated by the heater, the latent heat storage unit is first heated by the heater, and heat is transmitted from the latent heat storage unit to the hydrogen detection film. At this time, when the temperature of the heater is set to a temperature slightly lower than the phase transition temperature of the first latent heat storage material included in the latent heat storage unit, the temperature of the heater is temporarily changed by the ambient temperature change. Even if the temperature rises beyond the temperature, the temperature of the hydrogen detection film is sufficiently suppressed from rising excessively while the first latent heat storage material undergoes a phase transition. For this reason, it is sufficient that the hydrogen detection film is repeatedly excessively heated to repeatedly strain the hydrogen detection film, resulting in cracks in the hydrogen detection film itself or peeling of the hydrogen detection film. To be suppressed. Therefore, the hydrogen gas sensor of the present invention can have excellent durability. Further, as described above, since the temperature of the hydrogen detection film is sufficiently suppressed from being excessively increased, it is possible to stabilize the amount of hydrogen gas adsorbed to the hydrogen detection film. Therefore, the hydrogen gas sensor of the present invention can also have excellent hydrogen gas detection accuracy.

  In the hydrogen gas sensor, it is preferable that the latent heat storage unit further includes a second latent heat storage material that causes a phase transition at a lower phase transition temperature than the first latent heat storage material.

  In this case, if the heater temperature is set to a temperature between the phase transition temperature of the first latent heat storage material and the phase transition temperature of the second latent heat storage material included in the latent heat storage unit, the heater temperature is Is temporarily reduced below the phase transition temperature of the second latent heat storage material, it is sufficiently suppressed that the temperature of the hydrogen detection film is excessively lowered while the second latent heat storage material undergoes the phase transition. The For this reason, it becomes possible to stabilize the adsorption amount of the hydrogen gas to the hydrogen detection film. Therefore, the hydrogen gas sensor of the present invention can have better hydrogen gas detection accuracy.

  In the hydrogen gas sensor, the phase transition is preferably a phase transition between solid phases.

  In this case, since the latent heat storage unit remains in the solid phase even when the phase transition occurs, the shape of the latent heat storage unit can be maintained.

  In the hydrogen gas sensor, the phase transition between solid phases is preferably an electronic phase transition.

  In this case, during the electronic phase transition, the structure does not change before and after the phase transition. Therefore, distortion due to a change in structure does not occur in the latent heat storage unit. For this reason, when the hydrogen detection film | membrane and the latent heat storage part are contacting directly, it can fully suppress that an excessive stress is added by the distortion of a latent heat storage part in the interface of a hydrogen detection film | membrane and a latent heat storage part. Therefore, it can suppress that a hydrogen detection film | membrane peels from a latent-heat storage part, and it becomes possible for a hydrogen gas sensor to have the outstanding durability.

  Furthermore, in the hydrogen gas sensor, it is preferable that a phase transition temperature when the phase transition occurs is 100 to 500 ° C.

  In this case, compared with the case where the phase change temperature of the 1st latent heat storage material or the 1st latent heat storage material and the 2nd latent heat storage material is less than 100 ° C, hydrogen becomes easy to adsorb to the hydrogen detection film. Therefore, the hydrogen gas sensor of the present invention can have a better detection speed. Moreover, compared with the case where the phase transition temperature of the first latent heat storage material, or the first latent heat storage material and the second latent heat storage material is greater than 500 ° C., the hydrogen detection film is less likely to be exposed to excessively high temperatures, Deterioration of the detection film is more sufficiently suppressed. Therefore, the hydrogen gas sensor of the present invention can have more excellent durability.

  Furthermore, the hydrogen gas sensor further includes a pair of electrodes provided on the hydrogen detection film, and an insulating layer provided between the latent heat storage part and the hydrogen detection film, wherein the latent heat storage part is electrically conductive. It is preferable to have.

  In this case, the latent heat storage unit has conductivity, but since the latent heat storage unit and the hydrogen detection film are electrically insulated by the insulating layer, the pair of electrodes provided on the hydrogen detection film causes the latent heat storage unit to The electric resistance of only the hydrogen detection film can be measured without measuring the electric resistance. Therefore, the hydrogen gas sensor of the present invention can have better hydrogen gas detection accuracy.

  According to the present invention, a hydrogen gas sensor having excellent hydrogen gas detection accuracy and durability is provided.

It is an end view which shows 1st Embodiment of the hydrogen gas sensor of this invention. It is an end view which shows 2nd Embodiment of the hydrogen gas sensor of this invention. It is an end view which shows 3rd Embodiment of the hydrogen gas sensor of this invention.

  Hereinafter, embodiments of the hydrogen gas sensor of the present invention will be described in detail.

<First Embodiment>
First, a first embodiment of the hydrogen gas sensor of the present invention will be described with reference to FIG. FIG. 1 is an end view showing a first embodiment of the hydrogen gas sensor of the present invention.

  As shown in FIG. 1, the hydrogen gas sensor 100 includes a hydrogen detection film 10 that detects hydrogen gas, a pair of electrodes 20 provided on the hydrogen detection film 10, a heater 30 that heats the hydrogen detection film 10, and a heater 30. And a latent heat storage unit 40 provided between the hydrogen detection film 10 and the hydrogen detection film 10. The latent heat storage unit 40 includes a second latent heat storage material 42 provided so as to be in contact with the heater 30 and a first latent heat storage material 41 provided so as to be sandwiched between the second latent heat storage material 42 and the hydrogen detection film 10. doing.

Here, the second latent heat storage material 42 is made of a material having a phase transition temperature (T ₂ ) that causes a phase transition between solid phases, and the first latent heat storage material 41 is a phase transition temperature that causes a phase transition between solid phases. _{(T 1)} made of a material having a. In the present embodiment, the phase transition temperature (T ₂ ) of the second latent heat storage material 42 is lower than the phase transition temperature (T ₁ ) of the first latent heat storage material 41.

  Note that the hydrogen gas sensor 100 of the present embodiment measures the electrical resistance value of the hydrogen detection film 10 that changes when the hydrogen detection film 10 is adsorbed by applying a voltage between the pair of electrodes 20, Hydrogen gas is detected by the change in the electrical resistance value.

  According to the hydrogen gas sensor 100, since the hydrogen gas sensor 100 has the latent heat storage unit 40, when the hydrogen detection film 10 is heated by the heater 30, the latent heat storage unit 40 is first heated by the heater 30, and the latent heat storage unit 40 is heated. The heat is transferred from the gas to the hydrogen detection film 10.

At this time, the temperature (T) of the heater 30 is, for example, a temperature between the phase transition temperature (T ₂ ) of the second latent heat storage material 42 and the phase transition temperature (T ₂ ) of the first latent heat storage material 41 by PID control. Even if the temperature is set to (set temperature T ₀ ), the temperature (T) itself of the heater 30 actually fluctuates around the set temperature (T ₀ ) due to fluctuations in ambient temperature.

At this time, even if the temperature (T) of the heater 30 temporarily rises above the phase transition temperature (T ₁ ) of the first latent heat storage material 41 due to a change in ambient temperature, the first latent heat storage material 41 is in phase. While the transition occurs, the temperature of the hydrogen detection film 10 is sufficiently suppressed from rising excessively. For this reason, when the hydrogen detection film 10 is repeatedly excessively heated, the hydrogen detection film 10 is repeatedly distorted. As a result, the hydrogen detection film 10 itself is cracked, or the hydrogen detection film 10 is peeled off. Is sufficiently suppressed. Therefore, the hydrogen gas sensor 100 can have excellent durability. Further, as described above, excessively increasing the temperature of the hydrogen detection film 10 is sufficiently suppressed, so that the amount of hydrogen gas adsorbed on the hydrogen detection film 10 can be stabilized. Therefore, the hydrogen gas sensor 100 can also have excellent hydrogen gas detection accuracy.

On the other hand, even if the temperature (T) of the heater 30 temporarily drops below the phase transition temperature (T ₂ ) of the second latent heat storage material 42 due to the ambient temperature change, the second latent heat storage material 42 undergoes a phase transition. While this occurs, the temperature of the hydrogen detection film 10 is sufficiently suppressed from decreasing excessively. For this reason, it is possible to further stabilize the amount of adsorption of hydrogen gas to the hydrogen detection film 10. Therefore, the hydrogen gas sensor 100 can have better hydrogen gas detection accuracy.

  Further, since the phase transition in the first latent heat storage material 41 and the second latent heat storage material 42 is a phase transition between solid phases, the first latent heat storage material 41 and the second latent heat storage material 42 are solid even if a phase transition occurs. Remains in phase. For this reason, the shape of the first latent heat storage material 41 and the second latent heat storage material 42 can be maintained.

  Hereinafter, each of the hydrogen detection film 10, the heater 30, and the latent heat storage unit 40 described above will be described in detail.

<Hydrogen detection membrane>
In the present embodiment, the hydrogen detection film 10 is generated by a catalyst having an action of finally dissociating the adsorbed hydrogen gas into protons (H ⁺ ) and electrons (e ⁻ ), and a hydrogen gas dissociation action by the catalyst. And a metal oxide whose electrical resistance is increased by electrons.

(catalyst)
The catalyst only needs to have an action of dissociating the adsorbed hydrogen gas into protons (H ⁺ ) and electrons (e ⁻ ). Examples of such a catalyst include platinum (Pt), palladium (Pd), iridium (Ir), nickel (Ni), rhodium (Rh), and ruthenium (Ru). You may use these individually by 1 type or in combination of 2 or more types. Among the above catalysts, platinum (Pt) is particularly preferable.

(Metal oxide)
The metal oxide may be any metal oxide whose electric resistance is reduced by electrons (e ⁻ ) generated by the dissociation action of hydrogen gas by the catalyst. Examples of the metal oxide include molybdenum trioxide (MoO ₃ ), tungsten trioxide (WO ₃ ), titanium dioxide (TiO ₂ ), vanadium pentoxide (V ₂ O ₅ ), nickel oxide (NiO ₂ ), and the like. . You may use these individually by 1 type or in combination of 2 or more types. Among the metal oxides, tungsten trioxide (WO ₃ ) is preferable.

<Heater>
Any heater 30 may be used as long as it can heat the hydrogen detection film 10. Examples of the heater 30 include a ceramic heater and a bare heating element. Among these, a ceramic heater is preferable. In this case, since the heating element (resistor) is not in contact with the outside air, oxidation of the heating element can be suppressed, and disconnection and deterioration with time of the heating element can be more sufficiently suppressed.

<Latent heat storage unit>
In the present embodiment, the first latent heat storage material 41 and the second latent heat storage material 42 included in the latent heat storage unit 40 are made of a material having a phase transition temperature that causes a phase transition between solid phases. Here, the phase transition temperature refers to a phase transition temperature when measured at a rate of temperature increase of 5 ° C./min by differential scanning calorimetry (DSC).

  The phase transition between solid phases refers to a solid phase-solid phase transition, and examples of the phase transition between solid phases include an electronic phase transition and a structural phase transition.

  Especially, it is preferable that the phase transition between solid phases is an electronic phase transition. In this case, during the electronic phase transition, the structure does not change before and after the phase transition. For this reason, the latent heat storage unit 40 is not distorted by a structural change. For this reason, it is possible to sufficiently suppress application of excessive stress due to distortion of the latent heat storage unit 40 at the interface between the hydrogen detection film 10 and the latent heat storage unit 40. Therefore, it can suppress that the hydrogen detection film | membrane 10 peels from the latent heat storage part 40, and it becomes possible for the hydrogen gas sensor 100 to have the outstanding durability.

The phase transition temperature (T ₁ ) of the first latent heat storage material 41 is preferably 100 to 500 ° C. In this case, the hydrogen detection film 10 is heated to a temperature of 100 to 500 ° C. Therefore, compared with the case where T ₁ is less than 100 ° C., the hydrogen gas is easily adsorbed to the hydrogen detection film 10. Therefore, when the phase transition temperature (T ₁ ) of the first latent heat storage material 41 is 100 to 500 ° C., the hydrogen gas sensor 100 can have a more excellent detection speed. Further, when the phase transition temperature of the first phase change material 41 _{(T 1)} is at 100 to 500 ° C., so that the hydrogen detecting film 10 is heated to a temperature of 100 to 500 ° C.. Therefore, when the phase transition temperature (T ₁ ) of the first latent heat storage material 41 is 100 to 500 ° C., the hydrogen detection film 10 is less likely to be exposed to an excessively high temperature than when T ₁ is greater than 500 ° C. Thus, the deterioration of the hydrogen detection film 10 is more sufficiently suppressed. Therefore, the hydrogen gas sensor 100 can have more excellent durability.

The phase transition temperature (T ₁ ) of the first latent heat storage material 41 is more preferably 100 to 300 ° C.

The phase transition temperature (T ₂ ) of the second latent heat storage material 42 is preferably 100 to 500 ° C. However, the phase transition temperature (T ₂ ) of the second latent heat storage material 42 needs to be lower than the phase transition temperature (T ₁ ) of the first latent heat storage material 41. In this case, the hydrogen detection film 10 is heated to a temperature of 100 to 500 ° C. In this case, compared with the case where the hydrogen detection film | membrane 10 is heated at less than 100 degreeC, hydrogen gas becomes easy to adsorb | suck to the hydrogen detection film | membrane 10. FIG. Therefore, the hydrogen gas sensor 100 can have a better detection speed. Further, when the phase transition temperature of the first phase change material 41 _{(T 1)} is at 100 to 500 ° C., so that the hydrogen detecting film 10 is heated to a temperature of 100 to 500 ° C.. In this case, as compared with the case T ₂ is greater than 500 ° C., the hydrogen detecting film 10 is hardly exposed to excessively high temperatures, degradation of the hydrogen detecting film 10 can be more sufficiently suppressed. Therefore, the hydrogen gas sensor 100 can have more excellent durability.

The phase transition temperature (T ₂ ) of the second latent heat storage material 42 is more preferably 100 to 300 ° C.

The difference between the phase transition temperature of the first phase change material 41 _{(T 1)} and the phase transition temperature of the second phase change material _{42 (T 2) (= T} 1 -T 2) may be larger than 0 ° C., in particular Although not limited, it is preferably 50 ° C or lower, more preferably 10 ° C or lower.

The first phase change material 41 may be made of a material having a phase transition temperature at which the solid phase phase transition but, as such materials, for example _{VO 2, LiMn 2 O 4,} LiVS 2, LiVO 2 , NaNiO ₂ , LiRh ₂ O ₄ , V ₂ O ₃ , V ₄ O ₇ , V ₆ O ₁₁ , Ti ₄ O ₇ , SmBaFe ₂ O ₅ , EuBaFe ₂ O ₅ , GdBaFe ₂ O ₅ , TbBaFe ₂ O ₅ , DyBaFe _{2 O 5, HoBaFe 2 O 5} , YBaFe 2 O 5, PrBaCo 3 O 5.5, DyBaCo 2 O 5.54, HoBaCo 2 O 5.48, and composite metal oxides such as YBaCo ₂ O _5.49 . You may use these individually by 1 type or in combination of 2 or more types. Among the above, the first latent heat storage material 41 is preferably LiVO ₂ .

As the 2nd latent heat storage material 42, the composite metal oxide similar to the 1st latent heat storage material 41 can be used, for example. Here, the second latent heat storage material 42 preferably includes a composite oxide in common with the first latent heat storage material 41. In this case, the second phase transition temperature of the latent heat storage material 42 (T ₂₎ and the phase transition temperature of the first phase change material 41 (T ₁₎ and can be brought close to the temperature of the hydrogen detecting film 10 to a desired temperature It can be controlled accurately.

When the second latent heat storage material 42 includes a composite oxide common to the first latent heat storage material 41, the phase transition temperature (T ₂ ) of the second latent heat storage material 42 is changed to the phase transition temperature (T _In order to make it smaller than ₁ ), for example, the metal in the composite oxide contained in the second latent heat storage material 42 may be replaced with an element such as tungsten (W), tantalum (Ta), or molybdenum (Mo). Specifically, when LiVO ₂ is used as the first latent heat storage material 41, it is possible to use Li (V _x W _1-x ) O ₂ as the second latent heat storage material 42 so that the phase transition temperature per substitution amount. This is preferable because of the large change amount.

  In addition, the 2nd latent heat storage material 42 should just be comprised with the latent heat storage material, and may be comprised with materials other than the composite metal oxide similar to the 1st latent heat storage material 41. FIG.

Second Embodiment
Next, a second embodiment of the hydrogen gas sensor of the present invention will be described with reference to FIG. FIG. 2 is an end view showing a second embodiment of the hydrogen gas sensor of the present invention. In FIG. 2, the same or equivalent components as those in the first embodiment are denoted by the same reference numerals, and redundant description is omitted.

  As shown in FIG. 2, the hydrogen gas sensor 200 of the present embodiment further includes an insulating layer 50 provided between the latent heat storage unit 40 and the hydrogen detection film 10, and the second feature is that the latent heat storage unit 40 has conductivity. It differs from the hydrogen gas sensor 100 of one embodiment.

  According to the hydrogen gas sensor 200, the latent heat storage unit 40 has conductivity, but the conductive latent heat storage unit 40 and the hydrogen detection film 10 are electrically insulated by the insulating layer 50. For this reason, the electrical resistance of only the hydrogen detection film 10 can be measured by the pair of electrodes 20 without measuring the electrical resistance of the latent heat storage unit 40. Therefore, the hydrogen gas sensor 200 can have better hydrogen gas detection accuracy.

The material constituting the insulating layer 50 may be an insulating material. Examples of such a material include inorganic insulating materials such as SiO ₂ and Al ₂ O ₃ and insulating resins such as epoxy resins.

  The present invention is not limited to the above embodiment. For example, in the said embodiment, although the latent heat storage part 40 is comprised by two layers, the 1st latent heat storage material 41 and the 2nd latent heat storage material 42, like the hydrogen gas sensor 300 shown in FIG. The first latent heat storage material 41 may be a single layer. Alternatively, the latent heat storage unit 40 is a single layer having a phase transition temperature different from that of the first latent heat storage material 41 and the second latent heat storage material 42 in addition to the two layers of the first latent heat storage material 41 and the second latent heat storage material 42. You may further provide the above latent heat storage material.

  Moreover, in the said embodiment, although the 1st latent heat storage material 41 and the 2nd latent heat storage material 42 are comprised with the material which raise | generates a solid phase phase transition, in the vicinity of the temperature which operates the hydrogen detection film | membrane 10, it is a liquid phase. -It may be composed of a material that causes a phase transition between solid phases. However, in this case, from the viewpoint of maintaining the shapes of the first latent heat storage material 41 and the second latent heat storage material 42, the first latent heat storage material 41 and the second latent heat storage material 42 are accommodated in a container such as a capsule. It is necessary to

  In the above embodiment, the hydrogen gas sensors 100, 200, and 300 have a pair of electrodes 20 for measuring the electrical resistance of the hydrogen detection film 10. However, in the above embodiment, the hydrogen detection film 10 is made of hydrogen gas. The electrode 20 is not necessarily required because it is made of a gas chromic material that changes its color by adsorption or desorption, and it is possible to detect hydrogen gas by changing the color of the hydrogen detection film 10. Is possible. However, when hydrogen gas is detected by a change in the color of the hydrogen detection film 10, the hydrogen gas sensor preferably includes an optical device for detecting a change in the color of the hydrogen detection film 10. As such an optical device, for example, any optical device that irradiates the hydrogen detection film 10 with light and a light detection device that detects reflected light from the hydrogen detection film 10 may be used.

  Hereinafter, the content of the present invention will be described more specifically with reference to examples. However, the present invention is not limited to the following examples.

Example 1
First, a ceramic heater having a thickness of 2 mm and a diameter of 10 mm was prepared. Here, the ceramic heater is one in which resistance wiring is embedded in a sintered body of alumina.

Next, a LiVO ₂ polycrystal having a thickness of 500 μm was produced as follows. First, V ₂ O ₅ powder is reduced by hydrogen to form V ₂ O ₃ , which is reacted with Li ₂ CO ₃ in a hydrogen stream at 1000 ° C. for 10 hours, sintered, and then wire-sawed. LiVO ₂ polycrystal was obtained by cutting into a plate. When the phase transition temperature of the obtained LiVO ₂ polycrystal was measured by DSC under the condition of a heating rate of 5 ° C./min, the phase transition temperature was 206 ° C.

On the other hand, a Li (V _x W _1-x ) O ₂ polycrystal having a thickness of 300 μm was produced as follows. First, V ₂ O ₅ powder is hydrogen-reduced to form V ₂ O ₃ , which is mixed with WO _3, and the mixture is reacted with Li ₂ CO ₃ in a hydrogen stream at 1000 ° C. for 10 hours. After being sintered, Li (V _x W _1-x ) O ₂ polycrystal was obtained by cutting into a plate shape with a wire saw. At this time, WO ₃ was mixed with V ₂ O ₃ such that W in the Li (V _x W _1-x ) O ₂ polycrystal was substituted by 1000 ppm for W. When the phase transition temperature of the obtained Li (V _x W _1-x ) O ₂ polycrystal was measured by DSC at a temperature elevation rate of 5 ° C./min, the phase transition temperature was 203 ° C.

Next, the 300 μm-thick Li (V _x W _1-x ) O ₂ polycrystal obtained as described above was bonded onto the ceramic heater using a high thermal conductive adhesive, A LiVO ₂ polycrystal having a thickness of 500 μm was bonded using a high thermal conductive adhesive.

Next, an insulating layer made of SiO ₂ was formed on the LiVO ₂ polycrystal by a sputtering method so as to have a thickness of 500 nm.

Subsequently, a step of applying a sol-gel solution containing a solid compound semiconductor (WO ₃ ) and uniformly dispersing chloroplatinic acid as a catalytic metal compound at a molecular level on the insulating layer and baking to form a film Was repeated until the thickness reached 300 nm. Thereafter, a Pt-supported WO ₃ film having a diameter of 10 mm as a hydrogen detection film was formed by heat treatment in dry air at 400 ° C. for 30 minutes.

Finally, a pair of comb-shaped electrodes made of gold was produced on the Pt-supported WO ₃ film by vapor deposition. At this time, in each pair of comb-tooth electrodes, the length of the comb-tooth was 5 mm. The interval between the comb teeth of the pair of comb-teeth electrodes was 25 μm, and the number of comb-teeth pairs was 15.

  Thus, a hydrogen gas sensor was produced.

(Comparative Example 1)
On the ceramic heater, neither a Li (V _x W _1-x ) O ₂ polycrystal nor a LiVO ₂ polycrystal was formed, and a 300 nm thick Pt-supported WO ₃ film was directly formed as a hydrogen detection film. A hydrogen gas sensor was fabricated in the same manner as in Example 1 except that.

  And the hydrogen gas sensor of Example 1 and Comparative Example 1 was arrange | positioned so that it might adjoin in a stainless steel chamber for explosion prevention, and the hydrogen gas was detected in the same environment. At this time, the temperature of the heater was PID controlled so that the temperature of the hydrogen detection film was 204 ° C. Hydrogen gas was detected by measuring the electrical resistance value between a pair of comb electrodes.

  As a result, it was found that the hydrogen gas sensor of Example 1 had relatively little variation in electric resistance value in the hydrogen detection film and higher hydrogen gas detection accuracy than the hydrogen gas sensor of Comparative Example 1.

  Further, after hydrogen gas was detected for 1000 hours for the hydrogen gas sensors of Example 1 and Comparative Example 1, the hydrogen detection films in the hydrogen gas sensors of Example 1 and Comparative Example 1 were visually observed. As a result, in the hydrogen gas sensor of Example 1, no crack or peeling of the hydrogen detection film was observed. On the other hand, in the hydrogen gas sensor of Comparative Example 1, cracks were observed. From this, it was found that the hydrogen gas sensor of Example 1 was superior in terms of durability compared to the hydrogen gas sensor of Comparative Example 1.

  From the above, it was confirmed that the hydrogen gas sensor of the present invention has excellent hydrogen gas detection accuracy and durability.

DESCRIPTION OF SYMBOLS 10 ... Hydrogen detection film | membrane 20 ... Electrode 30 ... Heater 40 ... Latent heat storage material 41 ... 1st latent heat storage material 42 ... 2nd latent heat storage material 50 ... Insulating layer 100,200,300 ... Hydrogen gas sensor

Claims (6)

A hydrogen detection film for detecting hydrogen gas;
A heater for heating the hydrogen detection film;
A latent heat storage unit provided between the heater and the hydrogen detection film,
The hydrogen gas sensor, wherein the latent heat storage unit includes a first latent heat storage material that causes phase transition.   The hydrogen gas sensor according to claim 1, wherein the latent heat storage unit further includes a second latent heat storage material that causes a phase transition at a phase transition temperature lower than that of the first latent heat storage material.   The hydrogen gas sensor according to claim 1 or 2, wherein the phase transition is a phase transition between solid phases.   The hydrogen gas sensor according to claim 3, wherein the phase transition between solid phases is an electronic phase transition.   The hydrogen gas sensor according to any one of claims 1 to 4, wherein a phase transition temperature when causing the phase transition is 100 to 500C. A pair of electrodes provided on the hydrogen detection film;
An insulating layer provided between the latent heat storage unit and the hydrogen detection film;
The hydrogen gas sensor according to any one of claims 1 to 5, wherein the latent heat storage unit has conductivity.

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