KR101694846B1 - Sensing aggregation for gas sensor, method for manufacturing thereof, and gas sensor comprising the sensing aggregation - Google Patents

Abstract

The present invention relates to a sensing assembly for a gas sensor, a method of manufacturing the sensing sensor, and a gas sensor including the sensing sensor. More particularly, The present invention relates to a sensing assembly for a gas sensor, which prevents detachment of a protective layer that can protect against chemical external factors and thereby prevents degradation of the output of the gas sensor from external factors, will be.

Description

TECHNICAL FIELD [0001] The present invention relates to a sensing assembly for a gas sensor, a manufacturing method thereof, and a gas sensor including the sensing sensor,

The present invention relates to a sensing assembly for a gas sensor, a method of manufacturing the sensing sensor, and a gas sensor including the sensing sensor. More particularly, The present invention relates to a sensing assembly for a gas sensor, which prevents detachment of a protective layer that can protect against chemical external factors and thereby prevents degradation of the output of the gas sensor from external factors, will be.

H ₂ S, H ₂ , CO, NO _x , SO _x , NH ₃ , VOC _s, etc.) due to air pollution, environmental pollution, There is an increasing need for a gas sensor. Among them, H ₂ S is a gas contained in bad smell such as bad smell and bad breath, and it must be measured in order to purify the environment and establish a pleasant living environment. And CO is the gas contained in exhaust gas of gasoline automobile and soot discharged from industrial site. It controls the emission amount of running vehicle on the road, prevents environmental pollution by controlling CO gas inflow in the following automobile interior, Measurement is necessary to maintain the environment.

In particular, gas sensors capable of measuring oxygen, hydrogen, carbon monoxide, carbon dioxide, nitrogen oxides (NOx) and the like for detecting a specific gas component in an exhaust gas or measuring the concentration thereof in an internal combustion engine or the like are widely used.

Generally, the gas sensor includes a sensing electrode portion for measuring a difference in electromotive force due to a difference in concentration of a specific gas component, a reference electrode portion for collecting specific gas component ions, a heater portion for heating the electrode of the sensing electrode portion to a temperature at which ion conductivity is imparted Are stacked in this order.

The gas sensor may be installed in an exhaust gas discharging engine of an internal combustion engine to detect a gas component to be measured or to measure the concentration of the gas component. Japanese Patent No. 4691095 discloses a sensor device for measuring a physical property of a measuring gas .

However, since the exhaust gas includes liquid substances such as water and / or oil, such liquid materials can be brought into contact with a sensing electrode or a heater unit of a gas sensor, particularly, a gas sensor in which a temperature higher than room temperature can occur. The liquid material in contact with the gas sensor provides stress and thermal shock to the gas sensor, which can cause cracking in the gas sensor. In addition, the exhaust gas includes poisoning substances such as silicon and phosphorus, and the gas sensor is exposed to the poisoning substance, which may hinder accurate sensing of the gas to be measured.

In order to solve such a problem, an external sensing part, which is generally in contact with a gas to be inspected in the atmosphere, includes a protective layer, and the protective layer has a porous structure so that the gas to be inspected can pass through.

More specifically, FIG. 1 is a cross-sectional view of a conventional stacked type gas sensor having a porous protective layer. Referring to FIG. 1, a sensing unit 20 including a porous electrode protection layer 22 formed on an external sensing electrode 21 And a gas sensor 100 including a reference electrode portion 40, a heater portion 60, and a terminal electrode 70, which are sequentially positioned below. The porous electrode protection layer 22 protects the electrode from thermal shock, poisoning and the like. When the electrode protection layer 22 is composed of one layer, the porous electrode protection layer 22 is vulnerable to protecting the electrode from thermal shock, There is a weak problem in protecting the heat sink from thermal shock.

As a result, cracking or cracking of the protective layer interface, which is responsible for cracking due to thermal shock of the external sensing electrode of the gas sensor and protection of the electrode from the external poisonous substance, is prevented, Is urgently needed.

Japanese Patent Publication No. 4691095

SUMMARY OF THE INVENTION The present invention has been made in order to solve the above problems, and it is a first object of the present invention to provide a gas sensor in which adhesion force between a protective layer capable of protecting a gas sensor from an external impact and a liquid material is remarkably improved, , Peeling and cracking are prevented, durability that can protect the gas sensor from external physical impact and physical / chemical external factors such as liquid substances and poisonous substances in the gas to be inspected is improved, and at the same time, A sensor assembly for a gas sensor and a method of manufacturing the same.

A second problem to be solved by the present invention is to provide a gas sensor which exhibits excellent durability even in an extreme environment such as heat, vibration and poisonous substances, has a long service life and can exhibit its performance to the maximum.

According to a first aspect of the present invention, there is provided a sensing assembly for a gas sensor including a sensing substrate for sensing a gas to be inspected and a porous electrode protection layer provided on the sensing substrate, And a thermal shock protection layer formed on the porous electrode protection layer, wherein a center line average roughness (Ra) of 0.1 to 5 占 퐉 is formed on one surface of the porous electrode protection layer facing the thermal shock protection layer Aggregate.

According to a preferred embodiment of the present invention, the porous electrode protection layer may include a ceramic powder having a dielectric constant of 1.4 or more, represented by the following relational formula 1, and at least a part of the ceramic powder particles may be fused to each other.

[Relation 1]

The ceramic powder may be at least one selected from the group consisting of Al ₂ O ₃ , SiO ₂ , TiO ₂ , ZrO ₂ , AlN, Si ₃ N ₄ , Ti ₃ N ₄ , Zr ₃ N ₄ , Al ₄ C ₃ , SiC, TiC, ZrC, AlB, _{Si 3 B 4, Ti 3 B} 4, Zr 3 B 4, 3Al 2 O 3 · 2SiO 2 And MgAl ₂ O ₄ .

The ceramic powder may contain at least 50% by weight of a ceramic powder having a degree of deformation of 1.4 or more.

The degree of deformation of the ceramic powder may be 2.0 to 4.2.

The cross-sectional shape of the ceramic powder satisfying the above-described dissimilarity condition may be at least one of elliptical shape, dumbbell shape, polygonal shape, star shape, horn shape, cross shape, cross shape, star shape, alphabet shape, groove shape and dumbbell shape.

In addition, the diameter of the inscribed circle of the cross section of the ceramic powder satisfying the above-described dissimilarity condition may be 0.1 to 2 탆.

The thickness of the porous electrode protection layer may be 20 to 200 mu m.

In addition, the porosity of the porous electrode protection layer may be 20 to 60% and the average pore diameter may be 5.5 to 42 탆.

According to another preferred embodiment of the present invention, the center line average roughness (Ra) formed on one surface of the porous electrode protection layer may be 0.4 to 3.3 탆.

In order to solve the above-described first problem, the present invention provides a method of manufacturing a sensing device, comprising the steps of: (1) forming a porous electrode protective layer on at least one surface of a sensing substrate; And (2) forming a thermal shock protection layer on the outer surface of the porous electrode protection layer, wherein the outer surface of the porous electrode protection layer in step (2) And a center line average roughness (Ra) of the center line average roughness (Ra) is formed.

According to a preferred embodiment of the present invention, the composition for forming a porous electrode protection layer includes a ceramic powder, a binder and a solvent, and the ceramic powder may include a ceramic powder having a degree of variance of 1.4 or more expressed by the following relational formula .

The degree of deformation according to the following relational expression (1) of the ceramic powder may be 1.8 to 4.2.

[Relation 1]

The step (1) may include: 1-1) applying a composition for forming a porous electrode protective layer on at least one surface of a sensing substrate; 1-2) oxidizing the applied porous electrode protective layer forming composition; And 1-3) sintering the porous electrode protection layer.

The ceramic powder satisfying the above-described mold releasing condition may be at least 50% by weight of the total ceramic powder.

The degree of deformation of the ceramic powder may be 2.0 to 4.2.

In addition, the step 1-3) may be performed at a sintering temperature of 1300 to 1700 캜 for 30 minutes to 4 hours.

In addition, the thermal shockproof protective layer in the step (2) may be formed by spraying a thermal shockproof protective layer forming powder.

In order to solve the above second problem, the present invention provides a gas sensor including a sensing assembly for a gas sensor according to the present invention.

Hereinafter, terms used in the present invention will be described.

In the description of a preferred embodiment of the present invention, the layered and laminated shape includes both " direct " and " indirect ". For example, the shape in which the first layer and the second layer are laminated is a " direct " in which a third layer is not interposed between the first and second layers or a "Quot; indirect "

The present invention relates to a gas sensor which is capable of protecting a gas sensor from external physical impact and physical / chemical external factors such as liquid substances and poisonous substances in a gas to be tested, It is possible to prevent the output of the gas sensor from being deteriorated from the external factors described above and to have a long use period, and the durability can be remarkably improved.

 In addition, peeling and separation do not occur between the protective layers of multiple layers even under the extreme conditions of heat, moisture, and continuous vibration, so that the maximum performance of the gas sensor can be maximized. It can be applied to many other fields.

1 is a schematic cross-sectional view of a stacked type gas sensor in which a conventional porous protective layer is formed.
2 is a schematic cross-sectional view of a gas sensor provided with a thermal shock protection layer.
3 is a cross-sectional schematic diagram of a sensing assembly for a gas sensor according to a preferred embodiment of the present invention.
4 is a cross-sectional view of a ceramic powder included in a preferred embodiment of the present invention.
5 is a cross-sectional view of a ceramic powder having a cross-section of a circular cross section according to a preferred embodiment of the present invention.
6 is a cross-sectional view of a ceramic powder having a dumbbell-shaped cross section according to a preferred embodiment of the present invention.
7 is a cross-sectional view of a ceramic powder having a haze-shaped cross section according to a preferred embodiment of the present invention.
8 is a cross-sectional view of a ceramic powder having a star-shaped cross section according to a preferred embodiment of the present invention.
9 is a cross-sectional view of a ceramic powder having a triangular cross section according to a preferred embodiment of the present invention.
10 is a cross-sectional view of a ceramic powder having a rectangular cross section according to a preferred embodiment of the present invention.
11 is a cross-sectional view of a ceramic powder having a pentagonal cross section according to a preferred embodiment of the present invention.
12 is a cross-sectional view of a ceramic powder having a hexagonal cross section according to a preferred embodiment of the present invention.
13 is a cross-sectional view of a ceramic powder having a cross-sectional shape according to a preferred embodiment of the present invention.
14 is a cross-sectional view of a ceramic powder having a cross-section according to a preferred embodiment of the present invention.
15 is a cross-sectional view of a ceramic powder having a hollow elliptical cross section according to a preferred embodiment of the present invention.
16 is a cross-sectional view of a ceramic powder having a groove-shaped cross section according to a preferred embodiment of the present invention.
17 is a flow chart showing a manufacturing process of a sensing assembly for a gas sensor according to a preferred embodiment of the present invention.
18 is an exploded perspective view of a stacked type gas sensor according to a preferred embodiment of the present invention.

Hereinafter, the present invention will be described in more detail.

As described above, the porous protective layer included in the sensing part of the conventional gas sensor can not completely block the liquid material, and cracks may be generated in the external sensing electrode due to the thermal shock due to the temperature difference between the liquid material and the gas sensor, There is a problem in that the poisoning material of the gas sensor reaches the gas sensor directly. To solve this problem, a gas sensor as shown in FIG. 2 having a separate thermal shock protection layer may be considered. 2 is a cross-sectional view of a gas sensor provided with a thermal shock protection layer. FIG. 2 is a cross-sectional view of a gas sensor having a thermal shock protection layer, which includes a porous electrode protection layer 22 formed on an external sensing electrode 21, The gas sensor 100 including the reference electrode unit 40, the heater unit 60 and the terminal electrode 70 positioned sequentially below the sensing unit 20 including the thermal shock protection layer 23, .

As shown in FIG. 2, the gas sensor having the thermal shock protection layer 23 can improve the effect of protecting the sensing electrode from thermal shock. However, the interface between the porous electrode protection layer 22 and the thermal shock protection layer 23 The cracking problem of the external sensing electrode can be reemerged in case of peeling and cracking in A), and this problem has a problem of shortening the use period of the gas sensor. Particularly, when the environment in which the gas sensor is used is an automobile exposed by frequent vibration or the like, the problem of separating the different types of protection layers due to vibration can be further exacerbated.

Accordingly, the present invention provides a sensing assembly for a gas sensor including a sensing substrate sensing a gas to be inspected and a porous electrode protection layer provided on the sensing substrate, wherein the sensing assembly for a gas sensor includes a thermal shock protection And a center electrode average roughness (Ra) of 0.1 to 5 占 퐉 is formed on one surface of the porous electrode protection layer facing the thermal shock protection layer. .

If the protective layer is formed in multiple layers to protect the gas sensor from external physical impacts and physical / chemical external factors such as liquid substances and poisonous substances in the gas under test, cracks, peeling, separation, etc. It is possible to prevent the output of the gas sensor from deteriorating from the external factors, and it is possible to have a long use period, and the durability can be remarkably improved.

First, a sensing assembly for a gas sensor including a sensing substrate for sensing gas to be inspected and a porous electrode protection layer and a thermal shock protection layer sequentially formed on the sensing substrate will be described.

3 is a cross-sectional view of a sensing assembly 1000 for a gas sensor according to an exemplary embodiment of the present invention. FIG. 3 is a cross-sectional view of a sensing assembly 1000, (700). The sensing assembly 200 includes a porous electrode protection layer 220 formed on the outer surface of the sensing substrate 210 and a thermal shock protection layer 230 formed on the outer surface of the porous electrode protection layer 220, The aggregate 200 may further include a sensor sheet (not shown) below the sensing substrate 210 through which ions of the gas to be measured can pass.

The sensing aggregate 200 means a portion capable of measuring the difference in electromotive force due to the difference in the concentration of gas with respect to the gas to be inspected passing in the order of the porous electrode protection layer from the thermal shock protection layer 230 in the air or the gas under test environment And a portion of the gas sensor responsible for such a function may be included in the sensing aggregate and may have other configurations for maximizing or assisting such a function in addition to the configuration of the sensing aggregation described above.

First, a sensing substrate 210 included in a preferred embodiment of the present invention will be described.

The sensing substrate 210 is typically formed on the reference electrode portion of the gas sensor (40 in FIG. 1 or 40 in FIG. 2) and serves to oxidize and / or reduce a specific gas to be inspected. The sensing substrate 210 may include a sensing electrode. The sensing electrode may be a sensing electrode that is in direct contact with a gas to be detected by a gas sensor. The material, shape, thickness, and the like are not particularly limited in the present invention Do not.

Zirconia and / or a mixture of platinum and zirconia may be used as a material of the sensing electrode. In the case of the platinum / zirconia mixture, zirconia may be added to the platinum, It is possible to use a molded form.

The sensing electrode may be formed by a method such as screen printing, wash coating, wet powder spraying, flame spraying, plasma spraying, PVD (physical vapor deposition), CVD (chemical vapor deposition), but is not limited thereto. The formation of the sensing electrode can be performed by a method commonly known in the art for the method.

The thickness of the sensing electrode may be designed differently considering the response speed of the target gas to be inspected, and is not particularly limited in the present invention, but may be preferably 0.1 to 10 탆.

Next, the porous electrode protection layer 220 formed on the outer surface of the sensing substrate 210 will be described.

The porous electrode protection layer 220 protects the sensing substrate 210 and serves as a channel for moving the gas to be measured to the electrode of the sensing substrate. The porous electrode protection layer 220 may be a porous protective layer for protecting a sensing electrode of a conventional gas sensor, or a porous protective layer made of a conventional ceramic powder.

However, in the prior art, a porous electrode protection layer is provided to prevent cracking of the sensing substrate including the sensing electrode through thermal shock due to moisture. However, when moisture or the like is introduced into only the porous electrode protection layer, It is impossible to prevent the cracking of the sensing substrate due to the thermal shock due to the temperature difference between the two. When the thermal shock protection layer is further included to improve the adhesion, the adhesive force between the thermal shock protection layer and the porous electrode protection layer formed on the electrode is weak, so that cracks, peeling, And the like, and this problem can cause frequent replacement due to deterioration of output, performance and durability of the gas sensor by preventing the role of each layer from being performed properly.

The inventors of the present invention have found that when the thermal shock protection layer 230 to be described later is provided while continuing the study to solve such a problem, the porous electrode protection layer 220 is formed to improve adhesion with the thermal shock protection layer 230. [ (Ra) of 0.1 to 5 占 퐉 is formed on the outer surface of the protective layer, the bonding force between the two protective layers is remarkably improved, and the interface separation between the protective layers does not occur even in an extreme environment where vibration is severe or thermal shock due to moisture Which led to the present invention.

First, the surface roughness, which is a condition for achieving a remarkable adhesive performance between the interfaces of the two protective layers, will be described.

The porous electrode protection layer has a center line average roughness Ra of 0.1 to 5 탆 on one side facing the thermal shock protection layer, and preferably a center line average roughness Ra of 0.4 to 3.3 탆. This can achieve a significantly improved adhesion between the porous electrode protective layer and the thermal shock protective layer. The one surface facing the thermal shock protection layer may include all surfaces of the porous electrode protection layer facing the thermal shock protection layer. If the center line average roughness is less than 0.4 탆, the adhesion between the thermal shock protection layer and the porous electrode protection layer is significantly reduced, and the thermal shock protection layer can be peeled off or separated. If the center line average roughness is formed to exceed 5 탆, Cracks are generated in the porous protective layer in the process of forming the thermal shock protective layer on the outer surface of the layer or the thickness of the thermal shock protective layer is not uniformly effective to protect the sensing electrode from thermal shock or transmit the gas to be detected Or the like may not be able to be implemented.

The porous electrode protection layer is not particularly limited as to the kind of the base material and the particle diameter of the base material when the center line average roughness condition according to the present invention is satisfied. However, it may be a particle made of a material which becomes a porous electrode protective layer base material for a gas sensor and may protect the gas sensor from external physical / chemical factors, _{Al 2 O 3, SiO 2,} TiO 2, ZrO 2, AlN, Si 3 N 4, Ti 3 N 4, Zr 3 N 4, Al 4 C 3, SiC, TiC, ZrC, AlB, Si 3 B 4, Ti _{3 B 4, Zr 3 B 4} , 3Al 2 O 3 · 2SiO 2 And MgAl ₂ O ₄ , and more preferably at least one of alumina, zirconia, and yttrium oxide, and more preferably at least one of yttrium Stabilized zirconia.

There is no particular limitation on the method for forming the centerline average roughness condition on the outer surface of the porous electrode protection layer. Preferably, the ceramic powder includes a ceramic powder having a degree of variance of 1.4 or more expressed by the following relational formula 1, And more preferably a ceramic powder having a degree of separation of 1.6 or more, and more preferably a degree of separation of 2.0 to 4.2, and through which a thermal shock protection The surface roughness formed on one surface of the porous electrode protection layer facing the layer may be more advantageous to satisfy the desired range and it may be more advantageous to realize the porosity required for the porous electrode protection layer and the pore diameter.

[Relation 1]

4 is a cross-sectional view of a ceramic powder used in the production of the porous electrode protection layer according to a preferred embodiment of the present invention. The diagram of the relational expression 1 is the diameter D of the circumscribed circle of the cross section of the ceramic powder of FIG. 4, Diameter (d).

In the case of the porous electrode protection layer formed with ceramic powder having a deviation of less than 1.4, it may be difficult to realize a desired centerline average roughness on the outer surface, and thus it may be difficult to realize the desired physical properties such as peeling of the thermal shock protection layer easily .

The cross-sectional shape of the ceramic powder satisfying the heterogeneity condition of the relational expression 1 according to the present invention is not particularly limited in the present invention as far as the degree of deformation is 1.4 or more, but preferably the ceramic powder satisfying the above- The cross-sectional shape may have a shape of any one or more of polygonal, star, horn, alphabet, ellipse, dumbbell, crosshair, cross and groove. The alphabetic type may be C-shaped, E-shaped, F-shaped, H-shaped, L-shaped, S-shaped, T-shaped, U-shaped or W-shaped.

4 to 16 are sectional views of the ceramic powder included in a preferred embodiment of the present invention. 4 is a cross-sectional view of a ceramic powder having a three-lobed cross-section. 5 is a cross-sectional view of a ceramic powder having an alternating circular cross section, in which two circles have a cross-sectional shape cross-linked. In this case, the major axis length a of the intersecting circle is the diameter of the circumscribed circle, and the minor axis length b is the diameter length of the inscribed circle. Fig. 6 is a dumbbell shape, in which the long axis length (a) of the dumbbell is the diameter of the circumscribed circle, and the short axis length (b) is the diameter length of the inscribed circle. Fig. 7 is a double-dashed line in which d is the diameter of the inscribed circle and D is the diameter of the circumscribed circle. 8 is a star shape, where r is the diameter of the inscribed circle and R is the diameter of the circumscribed circle. 9 is a cross-sectional shape of the metal powder in a triangle, Fig. 10 is a rectangle, Fig. 11 is a pentagon, and Fig. Fig. 13 shows a cross-sectional shape, and Fig. 14 shows a ceramic powder having a cross-section. Fig. 15 shows a ceramic powder having a recessed elliptical shape and Fig. 16 shows a groove-shaped cross section.

The modified cross-sections of the ceramic powders shown in Figs. 4 to 16 are all examples that can be applied to the present invention, and ceramic powders having a shape appropriately modified within the range of the above-described dissimilarity degree can be used. The ceramic powder having various cross-sectional shapes according to the present invention may be manufactured by a mechanical method such as a ball mill using a bead-shaped ceramic powder having a particle size of 1 to 200 mu m. The ball mill may be made of zirconia ZrO ₂ , steel, or tungsten may be used. The specific method of the ball mill, the time conditions, and the like may be designed differently depending on the desired mold releasability. Thus, the present invention is not particularly limited thereto, For 1 minute to 36 hours.

In addition, among the ceramic powders to be the base material of the porous electrode protection layer having the surface roughness according to the present invention, the ceramic powder having a degree of variability of 1.4 or more, which is the above-described dissimilarity condition, may be contained in an amount of 50 wt% or more, % Or more, and even more preferably 85 wt% or more. If it is contained in an amount of less than 50% by weight, it may be difficult to form a desired surface roughness on the outer surface of the porous electrode protection layer, and a dense porous electrode protection layer may be formed, There is a problem that the physical properties of the gas sensor can not be realized.

On the other hand, when the particles of the ceramic powder forming the porous electrode protective layer including the ceramic powder satisfying the above-described dissimilarity condition are melted and bonded to each other, at least a part of each of the particles to be melted is in the shape of particles, Size, and positional relationship between neighboring particles. For example, when the shape of the particle cross-section is a hexagon as shown in FIG. 12, it may be a boundary region where the surface of the particle outer surface meets the surface or a surface portion of the particle, Depending on the sintering conditions, the volume of the area may vary.

According to a preferred embodiment of the present invention, the size of the ceramic powder satisfying the above-described dissimilarity condition may vary according to the degree of deformation, but the diameter of the inscribed circle of the ceramic powder cross-section may be 0.1 to 2 탆. If the diameter of the inscribed circle of the cross section of the powder is less than 0.01 탆, dense pores are formed, and the gas flow to the sensing electrode may not be smooth in the porous electrode protection layer. If the diameter of the inscribed circle exceeds 2 탆, the partial volume of the particles to be partially melted in the sintering process of the ceramic powder of the porous electrode protective layer may be considerably small, so that the bonding due to melting between the particles may be weak, The mechanical strength of the protective layer itself may be considerably deteriorated and the porous electrode protective layer of the thin film may be difficult to produce the porous electrode protective layer. If the temperature and / or the time for sintering is increased to solve such a problem, there is a possibility that the sensing substrate formed on the lower part of the porous electrode protection layer may be damaged or the desired surface roughness may not be formed, It may be difficult to realize an expressed gas sensor.

The thickness of the porous electrode protection layer 220 may be 20 탆 to 200 탆, preferably 50 탆 to 100 탆, according to a preferred embodiment of the present invention. That is, liquid materials such as water and / or oil that can cause cracks in the sensing substrate 210 are generally blocked by the thermal shock protection layer, but some penetrate into the pores of the porous electrode protection layer 210 The porous electrode protection layer 210 is formed on the surface of the gas sensor of the present invention to a thickness of 20 m or more so that the liquid materials can be dispersed before contacting the gas sensor. In other words, if the porous electrode protection layer 210 is formed on the surface of the gas sensor at a thickness of less than 20 占 퐉, the gas sensor can not be sufficiently protected from external impact and liquid material. In addition, if it is formed with a thickness exceeding 200 mu m, it is not only inefficient in terms of manufacturing cost of the gas sensor, but also slows down the response speed, and it may become difficult to measure the measurement gas concentration more accurately. However, the thickness of the porous electrode protection layer 210 is not limited thereto, and may be designed differently according to the purpose.

The porous electrode protection layer 210 may have an average porosity of 20 to 60%, preferably 30 to 50%, per unit volume. If the average porosity per unit volume of the porous electrode protection layer 210 is less than 20%, the gas permeability is lowered and the supply and / or discharge of the measurement gas to the gas sensor is difficult to smoothly proceed, If it exceeds 60%, the mechanical strength may be significantly lowered, and the pores may be collapsed, cracks, thin films, and the like may be caused.

In addition, the porous electrode protection layer 210 may have an average pore diameter of 5.95 to 42 탆, preferably 16 to 32 탆. If the average diameter of the pores is less than 5.95 占 퐉, the gas permeability to the porous electrode protection layer 210 is lowered, and the supply and / or discharge of the measurement gas to the sensing substrate is difficult to proceed smoothly. The output can be reduced, and if it is more than 42 탆, the liquid substance, poisoning substance in the exhaust gas which can permeate into the pores can penetrate into the porous electrode protection layer and reach the gas sensor, And it is difficult to supply an appropriate amount of the measurement gas to the gas sensor, so that it becomes difficult to more accurately measure the measured gas concentration.

The porous electrode protection layer 210 may be formed of a single layer or a multilayer, and may be changed according to the purpose.

Next, the thermal shock protection layer 230 formed on the outer surface of the porous electrode protection layer 220 will be described.

The thermal shock protection layer 230 serves to prevent damage to the sensing substrate 210 and / or the porous electrode protection layer 220, which may occur due to thermal shock due to moisture. In addition, the thermal shock protection layer 230 has a porous structure so that the gas to be measured in the air can flow into and move into the sensing aggregate.

It is preferable that the porous structure of the thermal shock protection layer 230 has a porous structure having an appropriate porosity and an average diameter as the degree of denseness tends to be opposite to that of the gas sensor. The average diameter of the pores formed in the thermal shock protection layer is preferably smaller than the average diameter of the pores formed in the porous electrode protection layer. This can improve the movement speed of the gas to be inspected through the porous electrode protection layer in the thermal shock protection layer, And at the same time, there is an advantage that the sensing substrate can be better protected from the thermal shock due to moisture by the effect of the insulation due to air contained in the pores.

The thermal shockproofing protective layer 230 may be made of any one of Al ₂ O ₃ , SiO ₂ , TiO ₂ , ZrO ₂ , AlN, Si ₃ N ₄ , Ti ₃ N ₄ , Zr ₃ N ₄ , Al ₄ C ₃ , SiC, TiC, ZrC, _{AlB, Si 3 B 4, Ti} 3 B 4, Zr 3 B 4, 3Al 2 O 3 · 2SiO 2 And MgAl ₂ O _{4. The} powder may be formed of spinel (MgAl ₂ O ₄ ), but is not limited thereto.

The thickness of the thermal shockproofing protective layer 230 may preferably be 200 to 500 占 퐉. If the thickness is less than 200 占 퐉, the sensing aggregate may not be protected at a thermal shock due to moisture, If the thickness is more than 500 μm, the flow of the test gas into the sensing aggregate is not smooth and the response speed of the gas sensor may be lowered.

The porosity is preferably 10 to 60%. If the porosity is less than 10%, the gas to be inspected in the atmosphere may be difficult to flow into the thermal shock protection layer, which may cause a decrease in the response speed of the gas sensor. If the porosity exceeds 60% There may be a problem.

As described above, the sensing assembly for a gas sensor according to a preferred embodiment of the present invention can be manufactured through the following manufacturing method. However, the present invention is not limited to the following manufacturing method.

Specifically, FIG. 17 is a flowchart illustrating a method of manufacturing a sensing assembly for a gas sensor according to a preferred embodiment of the present invention. In step (1), a porous electrode protection layer is formed on at least one surface of a sensing substrate (S1) (2), a thermal shock protection layer is formed on the outer surface of the porous electrode protection layer (S2) to produce a sensing aggregate for a gas sensor. At this time, the outer surface of the porous electrode protective layer in step (2) may be formed to have a center line average roughness of 0.1 to 5 탆.

First, in step (1) according to a preferred embodiment of the present invention, a step of forming a porous electrode protection layer on at least one surface of a sensing substrate is performed.

The sensing substrate may be a sensing substrate included in a sensing assembly for a gas sensor, and a detailed description thereof will be omitted.

 At least one surface of the sensing substrate may include at least one surface of the sensing substrate that is exposed to the atmosphere when the porous electrode protection layer is not formed. However, when the gas sensor is implemented through the sensing aggregate The exposed region of the sensing substrate may be varied depending on the shape of the specific gas sensor, and therefore the present invention is not limited thereto.

As a specific method of forming the porous electrode protection layer on at least one surface of the sensing substrate, a method of forming a porous electrode protection layer from a sensing aggregate for a general gas sensor can be used. Specifically, the composition for forming a porous electrode protection layer is subjected to screen printing, But the present invention is not limited thereto, for example, by a method such as wash coating, wet powder spraying, flame spraying, plasma spraying, PVD (physical vapor deposition), CVD (chemical vapor deposition)

According to a preferred embodiment of the present invention, the step (1) comprises: 1-1) applying a composition for forming a porous electrode protective layer on at least one surface of a sensing substrate; 1-2) oxidizing the applied porous electrode protective layer forming composition; And 1-3) sintering the porous electrode protection layer.

First, in step 1-1), a step of applying a composition for forming a porous electrode protective layer may be performed on at least one surface of the sensing substrate.

The composition for forming a porous electrode protection layer may include a ceramic powder as a main body of the porous electrode protection layer, a pore forming agent for forming pores of the porous electrode protection layer, and a binder and a solvent for improving the adhesion between the ceramic powder and the ceramic powder.

The ceramic powder may be a particle made of a material serving as a base material of the conventional porous electrode protection layer, and the description thereof is the same as that of the ceramic powder of the above-described porous electrode protection layer.

However, in order to form a desired surface roughness on the outer surface of the porous electrode protection layer, the ceramic powder preferably includes a ceramic powder having a degree of variability of 1.4 or more expressed by the following relational formula 1, May be 2.0 to 4.2. In addition, the ceramic powder satisfying the above-described dissimilarity condition may contain at least 50 wt%, more preferably at least 70 wt%, even more preferably at least 85 wt%, and still more preferably at least 95 wt% of the total ceramic powder . Critical significance of the distribution condition and content is the same as described above, so that the description is omitted.

 [Relation 1]

The above-described composition for forming a porous electrode protection layer may contain 20 to 60 parts of a pore-forming agent per 100 parts of ceramic powder. If the pore forming agent is contained in less than 20 parts skin, it may be difficult to realize the desired porosity. If the pore forming agent exceeds 60 parts skin, pores of the porous electrode protective layer may be collapsed or the mechanical properties may be significantly deteriorated have.

The pore-forming agent can be a pore-forming agent used in the production of a conventional porous electrode protection layer, can easily be formed by pore formation, can be easily removed by physical and / or chemical dissolution, Non-pore forming agents may be used without limitation. However, it is preferably selected from the group consisting of a polymer of a monomer selected from the group consisting of a radically polymerizable monomer, a polyfunctional crosslinking monomer, and a combination thereof, a radically polymerizable monomer, a polyfunctional crosslinking monomer, and combinations thereof microemulsion polymer beads of the monomer; silicon dioxide (SiO _2), titanium dioxide (TiO- ₂₎ and an oxide selected from the group consisting of;, carbon water is selected from carbon, carbohydrates and combinations thereof ; And a mixture thereof.

Specific examples of the radically polymerizable monomers include styrene, p-methylstyrene, m-methylstyrene, p-ethylstyrene, m-ethylstyrene, p-chlorostyrene, m-chlorostyrene, Aromatic vinyl monomers such as chloromethylstyrene, styrenesulfonic acid, pt-butoxystyrene, mt-butoxystyrene, fluorostyrene, alphamethylstyrene, vinyltoluene and chlorostyrene; Acrylates such as methyl (meth) acrylate, ethyl (meth) acrylate, butyl (meth) acrylate, octyl (meth) acrylate, stearyl Fluoroethyl acrylate, trifluoroethyl methacrylate, pentafluoropropyl methacrylate, fluoroethyl methacrylate, hexafluoroethane,

(Meth) acrylate monomers such as butyl (meth) acrylate, hexafluoroisopropyl methacrylate, perfluoroalkyl acrylate and octafluorophenyl methacrylate; And unsaturated carboxylic acids such as vinyl acetate, vinyl propionate, vinyl butyrate, vinyl ether, allyl butyl ether, allyl glycidyl ether, (meth) acrylic acid, maleic acid; Alkyl (meth) acrylamides; A vinyl cyanide monomer of (meth) acrylonitrile; Or a mixture thereof. Representative examples of the polymer of the radical polymerizable monomers include polystyrene and polymethyl (meth) acrylate.

Examples of the multifunctional crosslinking monomer include allyl compounds such as divinylbenzene, 1,4-divinyloxybutane, divinyl sulfone, diallyl phthalate, diallyl acrylamide, triallyl (iso) cyanurate and triallyl trimellitate , Hexanediol diacrylate, ethylene glycol dimethacrylate, diethylene glycol methacrylate, triethylene glycol dimethacrylate, trimethylene propane trimethacrylate, 1,3-butanediol methacrylate, 1,6- Tri (meth) acrylate, pentaerythritol tri (meth) acrylate, pentaerythritol tri (meth) acrylate, trimethylol propane, tri (meth) Acrylate, dipentaerythritol hexa (meth) acrylate, dipentaerythritol penta (meth) acrylate, glycerol tri (meth) acrylate, allyl (meth) It may include water

Specific examples of the carbonaceous material may include disaccharides such as graphite, carbon, carbon black, glucose, sucrose and the like, disaccharides such as sucrose or starch, and polysaccharides such as starch.

Preferably, the pore-forming agent is in the form of particles, and the particles have an average particle diameter of 100 nm to 50 m when the particles are formed. In order to form a diameter gradient of the pores of each height in the cross-section of the porous electrode protective layer, Is preferably at least two kinds, more preferably from two to four kinds. When a pore-forming agent having two kinds of average particle sizes is used, a pore-forming agent having a large average particle size forms pores having a large diameter, and a pore-forming agent having a small average particle size forms pores having a small diameter, A star diameter gradient can be derived.

The binder component enhances the bonding force between the ceramic powder particles and functions to further improve the adhesion between the sensing substrate and the porous electrode protective layer. A binder component ordinarily used in the art may be used, and preferably a polyvinyl compound such as polyvinyl butyral, a fluorine compound such as ethyl cellulose, polyester, epoxy, polyvinylidene fluoride, At least one selected from the group consisting of terpineol, and the like.

The solvent may be used without limitation as long as it can facilitate the dispersion of the porous electrode protective layer forming composition and / or the dissolution of the binder component. Examples of the solvent include water, ethanol, isopropyl alcohol, n-propyl alcohol And butyl alcohol, but is not limited thereto.

The above-described composition for forming a porous electrode protection layer may contain 20 to 60 parts of a pore-forming agent per 100 parts of ceramic powder. If the pore forming agent is contained in less than 20 parts skin, it may be difficult to realize the desired porosity. If the pore forming agent exceeds 60 parts skin, pores of the porous electrode protective layer may be collapsed or the mechanical properties may be significantly deteriorated have.

In addition, the binder component may include 8 to 26 parts by weight based on 100 parts by weight of the ceramic powder, and the solvent may include 20 to 50 parts by weight. If the binder component is contained in an amount of less than 8 parts by weight, the adhesion between the sensing substrate and the porous electrode protective layer to be produced is weakened, so that the porous electrode protective layer is separated from the gas sensor or the bonding force between the ceramic powders is weakened, Cracks and the like may occur more easily. If it exceeds 26 parts by weight, the binder component may block the pores of the porous electrode protection layer, and thus it may be difficult to realize the desired porosity and pore diameter. In the case of the solvent, if the viscosity of the composition for forming the porous electrode protective layer can be maintained to a desired thickness, the content of the solvent may be changed and used.

Next, steps 1-2) are performed to oxidize the composition for forming a porous electrode protection layer. By performing the step 1-2), it is easier to perform the sintering according to the following steps 1-3), has a desired porous structure, can realize a more improved mechanical strength and can suppress cracking.

The oxidation may be carried out in an air atmosphere or a nitrogen atmosphere, or by forcibly blowing compressed and / or uncompressed air, and may be carried out by drawing out the gas while venting the air to form an air flow.

The temperature at which the oxidation is carried out may be designed differently depending on the kind of the pore-forming agent used, and is not particularly limited in the present invention. When a polymer such as a polymer is used as the pore-forming agent, the temperature is preferably 0.1 to 5 ° C / min And the temperature can be maintained within 10 hours at the temperature. Thereafter, the temperature may be raised to 400 to 800 ° C at a rate of 0.1 to 10 ° C / min and maintained at that temperature within 10 hours.

When carbon water such as graphite is used as the pore-forming agent, these are completely removed to give strength of the porous electrode protection layer so as to suppress the strength reduction and cracks, and to prevent deterioration of performance and sinterability due to impurities, May be heated to 400 to 800 ° C at a rate of 0.1 to 10 ° C / min and maintained at that temperature for 10 hours or less.

Next, steps 1-3) may be performed to sinter the porous electrode protection layer. The sintering may be performed under the conditions used in a conventional sintering process of the porous electrode protection layer, but preferably at a sintering temperature of 1300 to 1700 캜 for 30 minutes to 4 hours, thereby improving the mechanical properties There is an advantage that an electrode protective layer can be produced.

The outer surface of the porous electrode protection layer, which is exposed to the outside in the assembled body manufactured through the above-described step (1) and is brought into contact with the thermal shock protection layer described later, has a center line average roughness Ra of 0.1 to 5 탆, The centerline average roughness (Ra) may be 0.4 to 3.3 탆. This makes it possible to achieve a remarkably improved adhesion between the porous electrode protection layer and the thermal shockproof protective layer prepared through the following step (2). The critical meaning of the center line average roughness is the same as that described above, and a description thereof is omitted. There is no limitation on the method of forming the surface roughness of the outer surface of the porous electrode protection layer. However, It is possible to realize a surface protective layer having a desired degree of porosity and pore diameter, and may be more advantageous in the development of desired physical properties.

Next, as step (2) performed after step (1), (2) step of forming a thermal shockproof protective layer on the outer surface of the porous electrode protection layer will be described.

According to a preferred embodiment of the present invention, the thermal shock protection layer in step (2) may be formed by spraying a thermal shock protection layer-forming powder on the outer surface of the porous electrode protection layer implemented in step (1).

The kind of the thermal shockproofing layer-forming powder is the same as described above, and the diameter of the powder may be changed according to the desired porosity, pore diameter, etc., and is not particularly limited in the present invention, but is preferably 5 to 200 탆 . Meanwhile, it is also possible to spray the thermal shockproofing layer-forming powder in a state of slurry including an extra solvent in addition to the powder mentioned above.

The method of spraying the above-described thermal shockproofing layer-forming powder onto the outer surface of the porous electrode protective layer can be carried out by employing a known thermal spraying method in the art, and is not particularly limited in the present invention. Preferably, the spray is sprayed onto the outer surface of the porous electrode protective layer through an atmospheric plasma spray (APS) process, a high velocity oxygen-fuel spray (HVOF), a vacuum plasma spray (VPS) process, or a kinetic spray Can be sprayed.

In the case of plasma spraying, it is possible to carry out through a spray gun including a spray gun, wherein the spray gun melts the thermal shockproof protective layer forming powder using a plasma flame, and melts and / or partially melts the heat shockproof protective layer Forming powder can be sprayed on the outer surface of the porous electrode protection layer. More specifically, the plasma flame may be formed by dissociating part of the plasma gas including argon gas (Ar), nitrogen gas (N ₂ ), hydrogen gas (H ₂ ), helium gas (He)

The distance between the spray gun and the surface of the porous electrode protection layer may be 1 mm to 300 mm. The angle (θ) of spraying the thermal shockproofing layer-forming powder onto the surface of the porous electrode protection layer may be 50 ° to 90 °. However, the step (2) according to a preferred embodiment of the present invention is not limited by the above specific spraying conditions.

After the step (2), preferably, the step of supporting the catalyst on the produced thermal shock protection layer may be further performed. The catalyst may preferably be platinum, and the liquid platinum may be supported by being transferred to the thermal shock protection layer. If the thermal shock protection layer carries a catalyst, the particulate matter such as carbon which can accumulate in the pores contained in the thermal shock protection layer during the sensor operation is burned by a method of giving a voltage higher than usual to the sensor element heater There is an advantage that platinum acts as a catalyst to effectively remove particulate matter.

On the other hand, the present invention includes a gas sensor having a sensing assembly for a gas sensor according to the present invention, which can be manufactured by the above-described manufacturing method.

The gas sensor can be used without limitation in a gas sensor, and there is no particular limitation on the gas detection system and structure.

18 is an exploded perspective view of a stacked type gas sensor according to a preferred embodiment of the present invention. The gas sensor 1000 includes a sensing aggregate 200, a reference electrode unit 400 and a heater unit 600 May be stacked in order from the top to the bottom.

The sensing assembly 200 may include an external sensing electrode 210 and a sensor sheet 250. The sensing electrode assembly 210 may include a sensing electrode 210, The electrode protection layer 220 and the thermal shock protection layer 230 may be sequentially stacked on the external sensing electrode 200. [

18, the electrode protection layer 220 and the thermal shock protection layer 230 are formed on a part of the external sensing electrode 210. However, the electrode protection layer 220 and the thermal shock protection layer 230 may be different depending on the type and structure of the gas sensor, And may be formed to cover the entire one surface or the outer surface of the gas sensor 1000 including the external sensing electrode 210 exposed on any one surface.

The sensor sheet 250 may be stacked under the external sensing electrode 210 to move a specific measurement gas oxidized and / or reduced at the external sensing electrode 210. The sensor sheet 250 may be made of various materials having high temperature ionic conductivity and high temperature durability, and preferably zirconia can be used as the material.

Next, the reference electrode unit 400 may include insulating layers 420 and 460, an internal reference electrode 440, and a reference sheet 480, which are capable of collecting specific measurement gas ions, The insulating layer 420, the internal reference electrode 440, the insulating layer 460, and the reference sheet 480 may be stacked in order from the top to the bottom.

The insulating layers 420 and 460 serve to insulate the heater assembly 64 and the sensing assembly 200, which will be described later. The insulating layers 420 and 460 may be made of various materials having insulating properties, and preferably alumina may be used.

The internal reference electrode 440 serves to collect specific measurement gas ions. The inner reference electrode 440 may be made of various electrode materials having electrical conductivity, and preferably a platinum, zirconia, and / or platinum / zirconia mixture may be used as the material.

The reference sheet 480 can move heat generated in the heater unit 60. The reference sheet 48 may be made of various materials having thermal conductivity and high temperature durability, and preferably zirconia can be used as a material.

Next, the heater unit 600 heats the external sensing electrode 210 of the sensing assembly 200 to a temperature at which ion conductivity is imparted. The heater unit 600 includes insulating layers 620 and 660, a heater electrode 640, a tunnel sheet 680 and a tunnel electrode 700 and preferably an insulating layer 620, a heater electrode 640, an insulating layer 660, a tunnel sheet 680, and a tunnel electrode 700, As shown in FIG.

The insulating layers 620 and 660 of the heater unit 600 may be the same as or different from the insulating layers 420 and 460 of the reference electrode unit 400.

The heater electrode 640 generates heat to heat the external sensing electrode 210 to a temperature at which ion conductivity is imparted. The heater electrode 640 may be formed of a variety of materials having exothermic properties by the supply of electric resistive power. Preferably, platinum, alumina, lead, a platinum / lead mixture and / or a platinum / have.

The tunnel sheet 680 serves to insulate the stacked type gas sensor 1000 excluding the tunnel electrode 700 and the tunnel electrode 700. The tunnel sheet 680 may be made of various materials having insulating properties, and preferably alumina may be used.

The tunnel electrode 700 connects the gas sensor 1000 and an external terminal for supplying power to the gas sensor 1000. The tunnel electrode 700 may be made of a variety of conductive materials, and preferably platinum, alumina, and / or a platinum / alumina mixture may be used.

The present invention will now be described more specifically with reference to the following examples. However, the following examples should not be construed as limiting the scope of the present invention, and should be construed to facilitate understanding of the present invention.

≪ Example 1 >

A powder of yttrium-stabilized zirconia (95.5 mol% of zirconia and 4.5 mol% of yttrium) powder having a particle size of 30 μm was subjected to a ball milling process for 30 minutes so as to have a deformation degree of 1.8 and a hexagonal cross-sectional shape as shown in FIG. 10, The composition for forming a porous electrode protection layer including 70 g of zirconia powder as a binder component, 12 g of polyvinyl butyral as a binder component, 25 g of butyl alcohol as a solvent, and 30 g of graphite having a diameter of 5 m as a pore- The upper part of the substrate (210 in Fig. 18), which is platinum, was applied to an average thickness of 70 mu m after sintering.

After that, the temperature was raised from room temperature to 150 ° C at a rate of 2.5 ° C / min in an atmospheric environment for heat treatment, and then the temperature was raised to 400 ° C at a rate of 1 ° C / min to perform a first oxidation process. Thereafter, the temperature was raised to a second oxidation temperature of 800 ° C at a rate of 2.5 ° C / minute, and then maintained at 800 ° C for 1 hour to perform a second oxidation process. Thereafter, the temperature was raised to 1470 ° C at a rate of 1 ° C / minute, and then the sintering process was terminated at 1470 ° C for 2 hours to prepare a porous electrode protective layer.

Then, to form a thermal shockproof protective layer on the outer surface of the porous electrode protective layer, the thermal sprayed protective layer having a thickness of 330 탆 was formed by plasma spraying a spinel powder having an average particle diameter of 35 탆 at a power of 23 kW. After forming the thermal shockproof protective layer, the thermal shock protective layer was immersed in liquid phase platinum to prepare a thermal shock protective layer containing 2 wt% of the platinum catalyst in the thermal shock protective layer. .

≪ Examples 2 to 9 &

The same procedure as in Example 1 was carried out to prepare a sensing aggregate for a gas sensor as shown in Tables 1 and 2 below, by changing the degree of deformation of the ceramic powder as shown in Table 1 below.

≪ Comparative Example 1 &

The same procedure as in Example 1 was carried out to prepare a sensing aggregate for a gas sensor as shown in Table 2 below, in which the degree of deformation of the ceramic powder was changed as shown in Table 1 below.

≪ Comparative Example 3 &

Except that a porous electrode protection layer alone was formed without forming a thermal shock protection layer to prepare a sensing assembly for a gas sensor as shown in Table 2 below.

<Experimental Example 1>

The center line average roughness of the porous electrode protection layer was measured by using LSM (Laser Scanning Microscope, Carl Zeiss) after sintering the porous electrode protection layer in the manufacturing process of the sensing aggregate for the gas sensor of Examples and Comparative Examples, The results are shown in Tables 1 and 2 below.

<Experimental Example 2>

A stacked type gas sensor as shown in Fig. 18 including the sensing aggregates for gas sensors of the above-mentioned Examples and Comparative Examples was manufactured. While keeping the temperature of the gas sensor at 800 占 폚, 10 占 퐇 of water drops were dropped 20 times onto the top of the thermal shock protection layer The following physical properties were measured and the results are shown in Tables 1 and 2 below.

1. Crack occurrence of gas sensor

After removing the porous electrode protection layer and the thermal shock protection layer on the platinum electrode as a sensing substrate in the sensing assembly of the gas sensor, a dyeing penetration test was carried out to observe the occurrence of a crack in the electrode under an optical microscope, As 0, and 1 to 5 as the degree of occurrence is greater.

2. Evaluation of gas sensor output

The gas sensor output was measured under the condition that the temperature of the gas sensor was set to 700 DEG C, and the rate of change of the gas sensor output was calculated by the following equation (1). The closer the rate of change of the gas sensor output is to zero, the smaller the gas diffusion resistance of the porous electrode protection layer and the more smooth gas can be supplied to the gas sensor. As the base gas sensor, a stacked type oxygen gas sensor not including a porous electrode protective layer was used.

<Experimental Example 3>

In order to evaluate the adhesion strength between the heat shockproof protective layer and the porous electrode protective layer, a blue tape (Duct tapes 3015 and 3M) was attached to the top of the thermal shockproof protective layer, and then a heat shock protective layer and / The evaluation was made as to whether or not the electrode protection layer was on the blue tape. When the protective layer did not appear at all, 0 was marked.

Example 1 Example 2 Example 3 Example 4 Example 5 Porous
Among the composition for forming the electrode protective layer, the ceramic powder The first ceramic powder
(Weight ratio) 1.5 / 100 1.8 / 100 2.1 / 100 4.0 / 100 4.5 / 100 The second ceramic powder
(Weight ratio) - - - - - Gas sensor Presence of thermal shock protection layer ○ ○ ○ ○ ○ Centerline average roughness of the porous electrode protective layer
(Ra, 占 퐉) 2.2 2.5 2.6 3.2 3.5 Cracking of the sensing substrate 0 0 0 0 2 Evaluation of output of gas sensor -2.1 -2.1 -1.9 -2.3 -4.4 Adhesive strength evaluation 0 0 0 0 One

Example 6 Example 7 Example 8 Comparative Example 1 Comparative Example 2 Porous
Among the composition for forming the electrode protective layer, the ceramic powder The first ceramic powder
(Weight ratio) 1.5 / 45 1.5 / 55 1.3 / 100 1/100 1.5 / 100 The second ceramic powder
(Weight ratio) 1.0 / 55 1.0 / 45 - - - Gas sensor Presence of thermal shock protection layer ○ ○ ○ ○ × Centerline average roughness of the porous electrode protective layer
(Ra, 占 퐉) 0.2 0.5 2.1 0.06 2.2 Cracking of the sensing substrate One One 2 2 4 Evaluation of output of gas sensor -2.8 -2.7 -2.7 -4.9 -1.7 Adhesive strength evaluation 3 One 0 4 2

Specifically, as can be seen from Tables 1 and 2,

It can be confirmed that surface roughness is formed on the outer surface of the porous electrode protection layer formed of the ceramic powder having the dissociation diagram. However, as in Comparative Example 1, the surface roughness was hardly generated on the outer surface of the porous electrode protective layer prepared through the ceramic powder having a dielectric constant of 1, and thus the adhesion strength to the thermal shock protective layer was remarkably low.

In addition, it can be confirmed that cracking of the sensing substrate occurred due to a decrease in the mechanical strength of the protective layer in Comparative Example 1, and the output of the gas sensor was also inferior to that of Example 1. [

Further, in the case of Comparative Example 2, which does not have a heat-shockproof protective layer, the output of the gas sensor is improved, but it can be confirmed that the cracks of the sensing substrate have increased significantly.

On the other hand, it can be confirmed that the surface roughness of the porous electrode protective layer is increased while the degree of deformation of the ceramic powder is increased from 1.5 (Example 1) to 4.5 (Example 5), but in Example 5, the surface roughness is too large, It can be seen that cracking of the sensing substrate occurred due to the implementation of the protective layer, the output of the gas sensor was not good, and the bonding strength with the porous electrode protective layer was also lowered.

In addition, in Example 6, in which the ceramic powder having a degree of differentiation of 1.5 from the ceramic powder was not contained in 50% by weight of the total ceramic powder, the surface roughness was not formed properly as compared with Example 7, And the adhesive strength is also lower.

Claims (18)

delete A sensing assembly for a gas sensor comprising a sensing substrate sensing a gas to be inspected and a porous electrode protection layer provided on the sensing substrate,
And a thermal shock protection layer formed on the porous electrode protection layer,
A center line average roughness (Ra) of 0.1 to 5 탆 is formed on one surface of the porous electrode protection layer facing the thermal shock protection layer, and the porous electrode protection layer is a ceramic powder having a degree of variance of 1.4 to 4.2 represented by the following relational expression And at least a part of the ceramic powder particles are fused to each other.
[Relation 1]

3. The method of claim 2,
The ceramic powder is _{Al 2 O 3, SiO 2,} TiO 2, ZrO 2, AlN, Si 3 N 4, Ti 3 N 4, Zr 3 N 4, Al 4 C 3, SiC, TiC, ZrC, AlB, Si 3 _{B 4, Ti 3 B 4,} Zr 3 B 4, 3Al 2 O 3 · 2SiO 2 And MgAl ₂ O _{4. 2.} A sensing assembly for a gas sensor, comprising: a substrate;
3. The method of claim 2,
Wherein the ceramic powder comprises at least 50% by weight of a ceramic powder having a degree of deformation of from 1.4 to 4.2.
3. The method of claim 2,
Wherein the separation degree is 2.0 to 4.2.
3. The method of claim 2,
The cross-sectional shape of the ceramic powder satisfying the dissimilarity condition is at least one of an elliptical shape, a dumbbell shape, a polygonal shape, a star shape, a horn shape, a grasshopper shape, a cross shape, a star shape, an alphabet shape, a groove shape and a dumbbell shape. aggregate.
3. The method of claim 2,
Wherein the diameter of the inscribed circle of the cross-section of the ceramic powder satisfying the above-described dissimilarity condition is 0.1 to 2 占 퐉.
3. The method of claim 2,
Wherein the thickness of the porous electrode protection layer is 20 to 200 占 퐉.
3. The method of claim 2,
Wherein the porous electrode protection layer has a porosity of 20 to 60% and an average pore diameter of 5.5 to 42 μm.
3. The method of claim 2,
Wherein a central line average roughness (Ra) formed on one surface of the porous electrode protection layer is 0.4 to 3.3 占 퐉.
(1) applying a composition for forming a porous electrode protective layer on at least one surface of a sensing substrate to form a porous electrode protective layer; And
(2) forming a thermal shock protection layer on the outer surface of the porous electrode protection layer,
In the step (2), a center line average roughness (Ra) of 0.1 to 5 탆 is formed on the outer surface of the porous electrode protection layer,
Wherein the composition for forming a porous electrode protection layer comprises a ceramic powder, a binder and a solvent, and the ceramic powder has a degree of variability of 1.4 to 4.2 represented by the following relational expression (1).
[Relation 1]

delete 12. The method of claim 11, wherein step (1)
1-1) applying a composition for forming a porous electrode protective layer on at least one surface of a sensing substrate;
1-2) oxidizing the applied porous electrode protective layer forming composition; And
1-3) sintering the porous electrode protection layer.
12. The method of claim 11,
Wherein the ceramic powder is at least 50 wt% of all the ceramic powder that satisfies the above-described dissimilarity condition.
12. The method of claim 11,
Wherein the ceramic powder has a degree of deformation of 2.0 to 4.2.
14. The method of claim 13,
Wherein the step 1-3) is performed at a sintering temperature of 1300 to 1700 캜 for 30 minutes to 4 hours.
12. The method of claim 11,
Wherein the thermal shock protection layer in step (2) is formed by spraying thermal shockproof protective layer forming powder.
A gas sensor comprising a sensing assembly for a gas sensor according to any one of claims 2 to 10.

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