JP4534565B2 - Method for producing ceramic porous - Google Patents

Description

The present invention relates to a method of producing a ceramic porous plate, more particularly a manufacturing method of Rousset La mix porous plate used in automobile parts such as gas sensors and filters.

  In general, a ceramic porous plate is different from a ceramic with a dense structure (see FIG. 1). For example, a ceramic slurry and a dispersion medium are mixed with a binder, a dispersing agent, a foam stabilizer, a foam stabilizer, etc. to produce a raw material slurry. Then, after stirring and foaming, it is formed into a plate shape containing bubbles, then dried and fired (see FIG. 2).

  Here, the binder is added for the purpose of increasing the strength of the molded body after drying and facilitating the molding operation, and increasing the viscosity of the slurry to increase the efficiency of foaming and to stabilize the foam. . The dispersant is added for the purpose of dispersing the ceramic powder in the dispersion medium to enable high concentration of the raw material slurry and increasing the density of the ceramic portion in the formed body. The foam stabilizer is added for the purpose of helping foaming of the raw slurry and increasing the porosity of the molded body. The foam stabilizer is added in order to stabilize the foam of the raw material slurry generated by foaming and prevent the foam from disappearing while the molded body is dried. The dispersion medium is used for uniformly mixing the raw material slurry with each additive and imparting moldable fluidity.

  The firing method, conditions, and the like when drying and firing the molded body from the slurry are substantially the same as those for the dense ceramic. Moreover, the porosity of the ceramic porous plate was adjusted by the amount of the foam stabilizer added to the raw slurry and the degree of stirring.

  With respect to the conventional ceramic porous plate, high-precision control such as porosity, pore diameter, volume distribution and the like required by a normal measurement method has been difficult depending on the manufacturing process described above. In other words, in order to obtain a ceramic porous plate having a uniform porosity in the conventional methods for producing a ceramic porous plate, it is necessary to rely on control of the material characteristics and manufacturing conditions, and the porosity. There is a problem that it is very difficult to control the system with high accuracy.

  As described above, in the conventional ceramic porous plate, the porosity and the like are controlled by the particle size of the ceramic powder to be contained in the raw slurry, the blending ratio of additives such as a foam stabilizer, the degree of stirring, the firing conditions, etc. Therefore, it was difficult to control the porosity with high accuracy.

  On the other hand, an ALD (Atomic Layer Deposition (hereinafter the same)) method, also called an atomic layer growth method, is known as one of thin film formation methods. As its general characteristics, it is possible to control the film thickness of the thin film in the order of atomic layer or molecular layer, and two or more different source gases are alternately supplied onto the deposition substrate, and adsorption, desorption, Since surface reaction utilizing reaction action is used, the surface coverage is excellent. In many cases, such a method is usually formed on a substrate having a flat surface, and few examples have been applied to porous substrates.

As one application example of the ALD method, a porous alumina film modified with Al ₂ O ₃ by the ALD method is known (see Non-Patent Document 1). However, the porous alumina film has a total thickness of about 60 μm consisting of a porous layer of about 57 μm and a dense layer of 2 μm or less.

  Furthermore, it is known to form a tin oxide film on a porous silicon layer by an atomic layer epitaxy method (see Non-Patent Document 2). However, the porous silicon layer has a thickness of about 2 μm.

  Thus, there are some examples in which the ALD method is applied to a porous film or a porous layer. However, in any case, there is no example in which the ALD method is applied to a plate-like ceramic porous material having a thickness of at most about 60 μm and a thick thickness.

A. Ott and J. Claus: Chem. Mater., 9, 707 (1997) (4th paragraph, left column on page 709) C. Ducso and N.C. Khanh: J. Cryst. Growth, 143, 683 (1996) (2nd paragraph, right column on page 683)

In gas sensors that control the diffusion of gas by the porosity of a plate-like ceramic porous material such as a solid electrolyte sensor, it is essential to control the porosity with high accuracy, and it is controlled with high accuracy and uniformity. It is desirable to supply a ceramic porous material having a high porosity. The present invention facilitates high-precision control of the porosity, which was difficult with the conventional method, and is a plate-like ceramic having a thickness of 0.5 mm or more with high-precision control and uniform porosity. It aims at providing the manufacturing method of a porous material.

The present invention relates to a plate-like ceramic porous material having a highly accurate porosity controlled by forming a thin film on the pore inner wall surface of a ceramic porous substrate using the ALD method, and the plate-like ceramic porous material. those concerning the manufacturing method for providing a porous ceramic material.

That is, the present invention is a ceramic porous plate having openings on both sides of the porous plate and having pores with an average pore diameter of 5 nm to 200 μm penetrating the porous plate and having a thickness of 0.5 mm or more. A method for producing a ceramic porous plate, characterized in that a thin film whose film thickness is controlled at the molecular layer or atomic layer level by an ALD method is formed on at least a part of the inner wall of the pore. Is.

As a preferred embodiment of the ceramic porous plate produced in the present invention, the thin film is a layer formed by the ALD method of a material selected from the group consisting of metals, metal oxides, metal nitrides and metal oxynitrides. Examples thereof include any one layer, or the same or different layers stacked.

In a preferred embodiment of the thin film, the metal oxide for forming the thin film is SiO ₂ , Al ₂ O ₃ , TiO ₂ , Ta ₂ O ₅ , ZnO, Y ₂ O ₃ , SnO ₂ or ZrO ₂ . Some are listed. In addition, the metal nitride for forming the thin film may be Si ₃ N ₄ , AlN or TiN. Furthermore, as another preferred embodiment of the thin film, a metal oxynitride for forming the thin film is SiON, AlON, TiON, TaON or SnON. Moreover, the metal for forming the thin film is copper, tungsten, or platinum.

Further, as a preferred embodiment of the ceramic porous plate produced in the present invention , the ceramic material is a group consisting of SiO ₂ , Si ₃ N ₄ , Al ₂ O ₃ , AlN, ZrO ₂ , Y ₂ O ₃ and MgO. And those containing any one of the compounds selected from or a combination thereof. As a more preferable ceramic porous plate, the main component of the ceramic material is a compound selected from the group consisting of SiO ₂ , Si ₃ N ₄ , Al ₂ O ₃ , AlN, ZrO ₂ , Y ₂ O ₃ and MgO. Any one or a combination thereof may be mentioned.

According to the present invention, there is provided a method for producing a ceramic porous plate having a thin film whose film thickness is controlled at a molecular layer or atomic layer level on at least a part of an inner wall of a pore by an ALD method, on both surfaces of a porous substrate. ALD source gas is supplied to one surface side of a ceramic porous substrate having an opening and a pore passing through the porous substrate, and the gas flows out from the other surface side of the ceramic porous substrate Forming the ALD thin film by passing the source gas through the pores , repeating the cycle of forming the ALD thin film , the pressure (P ₁ ) on the one surface side and the other surface side the pressure differential (P ₁ -P ₂₎ and to grasp the relationship between the porosity of the ceramic porous plate, the pressure differential reaching the desired porosity by the thin film forming pressure _{(P 2) (P 1 -P} 2 ) as they become, ALD thin film formed Characterized by stopping the cycle, method for producing a ceramic porous plate is provided.

  As a more preferable embodiment of the method for producing a ceramic porous plate, there is a production method including a step of further heat-treating the ceramic porous plate on which a thin film is formed by the ALD method.

In the present invention, a molecular layer or at least a part of the inner wall of the pore portion, comprising a chamber including an ALD source gas introduction chamber and an exhaust chamber, the source gas introduction means, and a gas exhaust means, is provided. An apparatus for manufacturing a ceramic porous plate having a thin film whose thickness is controlled at an atomic layer level by an ALD method, wherein the ceramic has openings on both sides of the porous substrate and has pores penetrating the porous substrate. The introduction chamber and the exhaust chamber, the pressure in the introduction chamber (P ₁ ) and the pressure in the exhaust chamber (P ₂ ) are monitored via the porous substrate, and the pressure difference (P ₁ -P ₂ ) is detected. means for, characterized by comprising a control means for controlling the thin film forming cycle by the ALD method by pressure difference (P ₁ -P _2), can be preferably used an apparatus for manufacturing a ceramic porous plate .

Further , according to the present invention , the ceramic porous material having openings on both sides of the porous plate and pores having an average pore diameter of 5 nm to 200 μm penetrating the porous plate and having a thickness of 0.5 mm or more. A porous ceramic plate characterized in that a thin film whose film thickness is controlled at the molecular layer or atomic layer level by an ALD method is formed on at least a part of the inner wall of the pore. Can provide a filter.

Moreover , according to this invention , the catalyst support | carrier which uses the same ceramic porous board can be provided.

Furthermore , according to this invention , the gas sensor which uses the same ceramic porous board can be provided.

  Usually, the ALD method is also called an atomic layer epitaxy method. Although the present invention is described as an ALD method, an atomic layer epitaxy method is also included in the present invention.

  One feature of the ceramic porous plate on which a thin film is formed by the ALD method of the present invention is plate-like and has a thickness of 0.5 mm or more. The thickness is preferably 0.5 to 10 mm, more preferably 0.5 to 5 mm, and particularly preferably 0.5 to 2 mm. If the thickness is less than 0.5 mm, it is not practically important in applying the method of the present invention, and if the thickness exceeds 10 mm, there is difficulty in effectively permeating the raw material gas, This is not preferable because it is not easy to produce by this method.

  Further, the ceramic porous plate in which a thin film is formed by the ALD method of the present invention has pores that have openings on both sides of the porous plate and penetrate the porous plate, and the average pore diameter (diameter) is Another feature is that it has a pore portion of 5 nm to 200 μm. The lower limit is preferably 20 nm, more preferably 50 nm, and particularly preferably 0.1 μm. The upper limit is preferably 100 μm, more preferably 50 μm, and particularly preferably 10 μm. The preferable range of the average pore diameter is 20 nm to 100 μm, more preferably the average pore diameter is 50 nm to 50 μm, and particularly preferably the average pore diameter is 0.1 to 10 μm. If the average pore diameter is less than 5 nm, it is difficult to effectively permeate the raw material gas, and the production by the method in the present invention is not easy, and if the average pore diameter exceeds 200 μm, the molecular layer or Although pores such as porosity are controlled by forming a thin film at the atomic layer level, it is practically difficult, and the effect obtained thereby cannot be seen.

  As a preferable ceramic porous plate on which such a thin film is formed, the porosity is usually 5% or more, preferably 5% to 85%, more preferably 20% to 85%, and particularly preferably 40%. ~ 80%. Preferably, those having continuous pores with a normal porosity of 5% to 85% and an average pore diameter of 5 nm to 200 μm can be mentioned. More preferably, those having continuous pores having a porosity of 20% to 85% and an average pore diameter of 100 nm to 200 μm can be mentioned. Particularly preferred are those having continuous pores having a porosity of 40% to 80% and an average pore diameter of 1 to 50 μm. Further, those in which the pores are distributed substantially uniformly are preferable. When the porosity is lower than 5%, it is difficult to effectively permeate the raw material gas, and it is not preferable because the production by the method of the present invention is not easy. When the porosity is higher than 85%, it is practically difficult to control the pores such as the porosity by forming a thin film at the molecular layer or atomic layer level. Absent.

There are various methods for measuring the porosity. Here, the open porosity obtained by a general Archimedes method and the total porosity obtained by a geometric method are used. That is, the open porosity is obtained by the following equation (1).
Porosity = (saturated mass-dry mass) / (saturated mass-mass in water) x 100 (%) (1)
Further, the total porosity is obtained by the following equation (2).
Total porosity = (1−bulk density / true density) × 100 (%) (2)
Furthermore, the bulk density is obtained by the following equation (3).
Bulk density = total mass / L x W x T (3)
Here, the saturated mass means the mass when water is completely supplied, the dry mass means the mass at the time of drying, the mass in water means the mass in water, the true density means the weight density, L Means the vertical size of the porous plate, W means the horizontal size, and T means the thickness.

Furthermore, measuring the pore diameter and volume in the porous plate is also important for considering the porosity. As a method for measuring these characteristics, a mercury intrusion method is usually used. The principle is that pressure is applied to mercury that does not react with most substances and does not leak, so that it is pressed into solid pores, and the pressure applied at that time and mercury that is pushed into (invaded) the pores. The size and volume of the pores are measured by measuring the relationship with the volume. In the measurement, the gas in the porous plate needs to be completely deaerated. The relationship between the applied pressure and the pore diameter at which mercury can enter at that pressure is derived from the equation (4) of Washburn.
D = -4γcosθ / P (4)
Where P is the applied pressure (N / m ² )), D is the pore diameter (diameter) (m), γ is the surface tension of mercury (0.48 N / m), and θ is the contact angle between mercury and the pore wall surface. Usually it is 140 degrees. γ and θ are constants, and the relationship between the applied pressure and P and the pore diameter D is obtained from Washburn's equation (4). By measuring the intrusion volume at that time, the pore diameter and the volume distribution can be derived. Furthermore, the average pore diameter is derived.

The ceramic porous plate manufactured according to the present invention is that the porosity is controlled with high accuracy by forming a thin film on the inner wall surface of the porous plate of the ceramic porous plate using the ALD method. Features. That is, uniform film thickness control of the thin film at the molecular layer or atomic layer level is performed by the ALD method.

The ceramic porous plate produced according to the present invention has a smaller internal volume and porosity than the ceramic porous substrate before the thin film is formed by forming a thin film in the pores by the ALD method. is doing. It should be noted that the degree of porosity reduction can vary greatly depending on the average pore diameter of the porous substrate.

The ceramic porous plate produced according to the present invention is characterized by thin film formation by ALD method on a ceramic porous substrate produced by a conventional method, and the material of the ceramic porous substrate itself as a raw material, and its production method Is not particularly limited. Furthermore, it may be a porous glass, and can be applied to a microfabricated porous plate manufactured by chemical or physical etching such as porous silicon or mesoporous. The ceramic porous substrate as a raw material of the present invention is made of any one or a combination of compounds selected from the group consisting of SiO ₂ , Si ₃ N ₄ , Al ₂ O ₃ , AlN, ZrO ₂ , Y ₂ O ₃ and MgO. The inclusion is preferred. Any one of the compounds selected from the group consisting of SiO ₂ , Si ₃ N ₄ , Al ₂ O ₃ , AlN, ZrO ₂ , Y ₂ O ₃ and MgO or a combination thereof constitutes the main component of the ceramic, Particularly preferred. More specifically, those having physical constants such as Young's modulus, thermal expansion coefficient, Poisson's ratio and the like are preferable, and are substantially equal to the composition of the base material in terms of adhesion and thermal expansion coefficient difference (thermal stress). Is preferred.

  The thickness of the raw material ceramic porous substrate is substantially equal to the thickness of the ceramic porous plate after the thin film is formed. Moreover, about the average pore diameter of the pore part, 10 nm-200 micrometers are preferable. More preferably, the average pore diameter is 50 nm to 100 μm, and particularly preferably the average pore diameter is 0.1 to 10 μm.

  Moreover, the porosity of the raw material ceramic porous substrate is sufficient if it can permeate the raw material gas at the time of film formation, and is preferably 5% or more, particularly preferably 20% or more. Further, it is preferably 85% or less, particularly preferably 60% or less.

Examples of the thin film formed by controlling the film thickness by ALD method on at least a part of the pore inner wall of the ceramic porous plate manufactured according to the present invention include, for example, metals as stable thin film materials, metals such as semiconductors, etc. oxides, the more any layer by the ALD method ones selected from the group consisting of nitrides and metal oxynitride of a metal or virtuous preferable ones are formed identical or in a different layer laminate, . If the method for forming the thin film is an ALD method, the material of the thin film is not particularly limited. What is necessary is just to determine the thin film formed according to the objective and a characteristic.

As the metal oxide used in the thin _{film, SiO 2, Al 2 O 3} , TiO 2, Ta 2 O 5, ZnO, it is Y ₂ O _3, SnO ₂ and ZrO ₂ preferably, especially SiO _2, Al ₂ O ₃ and TiO ₂ are preferred. As the metal nitride, Si ₃ N ₄ , AlN and TiN are preferable, and Si ₃ N ₄ is particularly preferable. Further, as the metal oxynitride, SiON, AlON, TiON, TaON and SnON are preferable, and AlON and TiON are particularly preferable. More specific examples of the metal include copper, tungsten, and platinum, and platinum is particularly preferable.

Particularly suitable as the thin film in the present invention are very chemically and thermally stable SiO ₂ , Si ₃ N ₄ , and Al ₂ O ₃ . Further, nitrides or oxynitrides of AlON, AlN, and TiN may be used.

  The thin film is usually formed of any one of these compounds or metal components, or the same or different layers are laminated. If necessary, different layers are combined and laminated to obtain a target film thickness, a target porosity, a pore diameter, and the like. When two or more different source gases composed of these compounds or metal components are alternately supplied onto the ceramic porous plate to be deposited, and surface reaction utilizing adsorption, desorption, or reaction action is used, the surface Excellent coverage.

  In addition, thin film materials have chemical functions, photocatalysts, magnetic thin films, semiconductors, solid electrolytes, gas sensitive films, electrode materials, barrier metals for electrodes, thin films for interface control such as adhesion to other substances, and functions that have a deodorizing effect. The film may be used in combination with a thin film formed by the ALD method.

The method for producing a ceramic porous plate according to the present invention comprises a porous ceramic substrate having openings on both sides of the porous substrate and having pores penetrating through the porous substrate. A step of forming a thin film at least in part, wherein a raw material gas of ALD is circulated from a raw material gas introduction side to an exhaust side, and the raw material gas is passed through the pores of the ceramic porous substrate, The process of forming is included. Furthermore , in the step of forming the thin film, the pressure difference (P ₁ -P ₂ ) between the pressure on the one surface side (P ₁ ) and the pressure on the other surface side (P ₂ ) and the ceramic porous plate It is characterized in that the relationship with the porosity is grasped, and the thin film formation cycle is stopped when the pressure difference (P ₁ −P ₂ ) reaching the desired porosity is reached by the thin film formation. Good Mashiku, as the exhaust chamber communicating with the inlet chamber and an exhaust pump of the raw material gas through the ceramic porous substrate is formed by placing the ceramic porous plate inside a chamber of the ALD, ALD The manufacturing method which performs the thin film formation by a method is mentioned.

The main production method of the ceramic porous plate used in the production method of the present invention, having pores on both sides of the porous plate and having pores penetrating the porous plate, is usually about 3000 ° C. A method of forming a three-dimensional network structure in which a part of high-melting-point ceramics is melted by using a high-temperature reaction and the ceramics are fused together is exemplified. As described above, the ceramic includes one or a combination of compounds selected from the group consisting of SiO ₂ , Si ₃ N ₄ , Al ₂ O ₃ , AlN, ZrO ₂ , Y ₂ O ₃ and MgO. Is preferred.

  In the production method of the present invention, a raw material gas for forming a thin film simultaneously with an inert gas such as argon or nitrogen is supplied into the pores of the ceramic porous plate and the gas is allowed to pass through the pores. It has been found that it is particularly effective to form a thin film on the inner wall of the hole. By forming a thin film inside the pores, the volume of the pores can be reduced, and as a result, the cross-sectional area of the path of the continuous pores through which gas or liquid can pass can be reduced. Thereby, the target porosity, pore diameter, etc. can be controlled with high accuracy. That is, if a thin film is formed by the ALD method, a molecular layer or an atomic layer of one monolayer or less is formed for each ALD deposition cycle, so that the pore volume and the continuous pore path are interrupted. It is possible to reduce the area at the molecular layer level (see FIG. 3).

  In FIG. 3, a thin film in which a small sphere group is composed of ceramic particles, a portion where the small sphere group does not exist is a pore, and a layer extending in a layered manner along the outer contour of the small sphere group is formed by the ALD method. Are schematically shown. FIG. 2 schematically shows the part of the particle group constituting the ceramic and the pore part before the thin film is formed by the ALD method.

In the production method of the present invention, the thin film formation cycle by the ALD method is determined by the pressure difference (P ₁ −P ₂ ) obtained by monitoring the pressure on the introduction side (P ₁ ) and the pressure on the exhaust side (P ₂ ). Control. The pressure difference (P ₁ −P ₂ ) is generated due to the gas permeability of the ceramic porous plate. Gas permeability of the ceramic porous plate as (may be replaced with porosity) is higher, the pressure difference (P ₁ -P ₂₎ is small, the pressure difference the smaller the porosity by a thin film forming (P ₁ -P ₂₎ Is getting bigger. By grasping the relationship between this pressure difference (P ₁ −P ₂ ) and the porosity of the ceramic porous plate, it becomes possible to stop the film formation when the desired porosity is reached by the thin film formation. . In this way, by accurately stopping this film forming process at a desired porosity while forming a thin film on the ceramic porous plate, a ceramic having a highly reproducible and highly controlled porosity, pore diameter, etc. The porous plate can be manufactured stably with high efficiency (productivity).

The specific modes of the pressures P ₁ and P ₂ and the pressure difference (P ₁ −P ₂ ) to be controlled can be appropriately set according to the target ceramic porous plate. More specifically, for example, the introduction of a certain raw material gas is started, and the raw material gas is supplied at each pressure P ₁ 400 to 700 Pa and P ₂ 100 to 400 Pa, and the pressure difference (P ₁ −P ₂ ) is, for example, 300 Pa. The introduction of the raw material gas is stopped at the time of lowering, for example, after the purge on the introduction side and the exhaust side for 1 to 10 seconds, the introduction of the next raw material gas is started if necessary, and the predetermined thin film A formation cycle is performed.

In a more preferred embodiment of the production method of the present invention, the ceramic porous plate is formed in an ALD chamber so that an ALD source gas introduction chamber and an exhaust chamber communicating with an exhaust pump are formed through the ceramic porous plate. Specifically, as the step of installing inside, the source gas is allowed to flow only from the introduction chamber to the exhaust chamber through the ceramic porous plate. That is, mounting the ceramic porous plate so that the introduction chamber and the exhaust chamber are completely separated by the ceramic porous plate is effective in controlling the thin film formation cycle with high accuracy. That is, if the ceramic porous plate is arranged so as to be completely separated into the introduction chamber and the exhaust chamber, the pressure difference (P ₁ −P ₂ ) between the gas introduction chamber and the exhaust chamber can be accurately monitored, and the ceramic While forming a thin film on the porous plate, it is possible to accurately stop the film forming process at a desired porosity, and to manufacture a porous plate with highly reproducible and highly controlled porosity.

  The temperature of the ceramic porous plate in the ALD method in the production method of the present invention can be appropriately set according to the target thin film formed on the ceramic porous plate. More specifically, before starting the introduction of a certain raw material gas, for example, the temperature of the ceramic porous plate that is the raw material is set to 100 to 500 ° C. In order to stably control the thin film formation cycle with high accuracy, such temperature control is important, and a more limited temperature range according to the target thin film, for example, within set temperature ± 10 ° C., more preferably set temperature ± 1 ° C. Within is more desirable.

  In a further preferred embodiment of the production method of the present invention, the step of heat-treating the ceramic porous plate on which the thin film is formed increases the adhesion between the thin film and the raw material ceramic porous plate, and improves the consistency with the thin film material. It is effective for the purpose of removing unreacted residual substances in the thin film, stabilizing the support, recrystallizing the thin film, and improving the chemical and physical stability of the thin film. The temperature and atmosphere are not particularly limited, and it is desirable to perform a heat treatment corresponding to predetermined characteristics of the target ceramic porous plate.

The present invention is a manufacturing apparatus for accurately manufacturing a ceramic porous plate having a thin film controlled at high accuracy at the atomic layer level as described above by an ALD method, and comprises an ALD chamber, A source gas introduction chamber provided by installing the ceramic porous substrate in the chamber, including ALD source gas introduction means connected to the upstream side and exhaust pump means connected to the downstream side of the chamber And a means for monitoring the pressure (P ₁ ) in the introduction chamber and the pressure (P ₂ ) in the introduction chamber and detecting the pressure difference (P ₁ -P ₂ ). An apparatus for producing a ceramic porous plate having a control means for controlling a thin film formation cycle by the ALD method by the pressure difference (P ₁ -P ₂ ) is preferably used .

FIG. 4 schematically shows a prototype of a ceramic porous plate production apparatus used in the production method of the present invention. As shown in the figure, the substrate is fixed so that the ceramic porous substrate, which is the raw material, completely isolates the interior of the ALD chamber into the source gas introduction chamber and the exhaust chamber connected to the exhaust pipe connected to the exhaust pump. It is installed with a jig. A substrate heating heater is provided in the exhaust chamber in order to heat the ceramic porous plate, which is a raw material, installed in the chamber to a predetermined temperature. The substrate heating heater is connected to a temperature control means (not shown), and may be provided on the source gas introduction chamber side as necessary. Separate connection to both the gas introduction chamber and the exhaust chamber downstream piping for efficient removal of used gas when film formation is completed, or when film formation is repeated with the same or different source gas as required Purged piping and purge switching valve means for connecting them are provided.

FIG. 6 is a schematic view of an embodiment of a ceramic porous plate manufacturing apparatus preferably used in the present invention. In the manufacturing apparatus shown in FIG. 4, the pressures P ₁ and P ₂ in both the gas introduction chamber and the exhaust chamber are further set. Pressure difference monitoring means (not shown) for monitoring by each pressure gauge P _in , P _out and detecting a pressure difference (P ₁ −P ₂ ) based on each pressure P ₁ , P ₂ in conjunction with them. Is installed. More preferably, a control means (not shown) for controlling the thin film formation cycle by the ALD method is provided by the pressure difference (P ₁ -P ₂ ).

  For the purpose of comparison with the present invention, for example, in the apparatus shown in FIG. 4, a small porous substrate that does not reach the lower substrate fixing jig is attached only to the upper substrate fixing jig, and the raw material gas has pores. Even if film formation by the ALD method is performed without passing through the inside, the film is formed only near the surface of the porous substrate, and it is difficult to form the film to the inside of the pores of the porous substrate. A porous ceramic plate having a uniform film formed on the entire porous substrate cannot be obtained.

  In addition, examples of the use of the ceramic porous plate in which the pore diameter, the porosity, etc. are controlled with high accuracy in this way include porous plates for gas sensors such as oxygen sensors and air-fuel ratio sensors. Among them, it is useful to use as a solid electrolyte sensor using zirconia. That is, the permeability and diffusion coefficient of a gas such as oxygen to the porous plate can be controlled with high accuracy.

Moreover, as an example of the filter using the ceramic porous plate manufactured by this invention, the use, such as a biochemical separation membrane, ion exchange, gas separation, and molecular sieve, does not ask | require. Especially, it is suitable for the transmittance | permeability control as various separation membranes.

Examples of the catalyst carrier using the ceramic porous plate produced according to the present invention include a catalyst carrier having a film formed of platinum or the like, and in particular, as a substrate for a catalyst carrier used for an automobile exhaust gas catalyst or the like. Is also useful. Furthermore, you may use as base materials, such as a deodorizer, an optical catalyst, and an antibacterial catalyst. In addition, the ceramic porous plate of the present invention is useful as a base material for a soundproof wall.

According to the present invention, the production method, and therefore the thin films thickness control with high precision of the atomic layer or molecular layer level it can be produced with good productivity stably uniformly formed plate-like ceramic porous material throughout A manufacturing apparatus for use in the present invention is provided. Furthermore, a filter, a catalyst carrier, and a gas sensor using such an excellent ceramic porous plate are provided.

[ Reference example ]
A conventional method for producing an alumina porous body, that is, alumina powder and a dispersion medium are mixed together with a binder, a dispersing agent, a foam stabilizer, and a foam stabilizer to prepare a raw material slurry. As shown in FIG. 4, an alumina porous substrate (thickness 1 mm, porosity 30%, size 50 mm × 50 mm) obtained by forming into a plate shape in a contained state, then drying and then firing, The ALD reaction chamber was disposed so as to be completely separated into a gas introduction chamber serving as an ALD raw material and an exhaust chamber exhausted using an exhaust pump. At this time, a substrate fixing jig was installed in the chamber so that the gap between the chamber and the porous ceramic plate was completely closed. An example in which the alumina porous substrate is placed in such a manner, an Al ₂ O ₃ thin film is formed inside the pores, and the pore diameter, porosity, etc. are adjusted is shown below. In the reference example, alumina is used as the ceramic porous plate, but other materials may be used.

FIG. 5 shows the formation of an ALD thin film in which a thin film of Al ₂ O ₃ was formed from trimethylaluminum (TMA) and H ₂ O using the above-described alumina porous substrate using the apparatus shown in FIG. The film formation process including a cycle is shown. That is, the ALD chamber was evacuated to about 40 Pa, the alumina porous substrate was heated with a substrate heating heater while flowing nitrogen gas at about 400 cm ³ / min, and the substrate temperature was stabilized at 350 ° C. Thereafter, TMA and H ₂ O (distilled water) were vaporized at room temperature in a raw material bottle (not shown), and alternately introduced into the ALD chamber at 400 cm ³ / min together with nitrogen gas as a carrier gas. That is, in order to remove excess TMA present in the gas phase other than the molecules adsorbed on the surface of the porous alumina substrate after first introducing vaporized TMA for 0.6 seconds as the gas to the ALD chamber. As a purge, nitrogen gas was introduced for 5 seconds, and then the purge switch valve was opened to purge the TMA gas remaining in the gas introduction chamber completely. After the purge switching valve was closed again, similarly vaporized H ₂ O was introduced for 1.0 second, and then nitrogen purge was introduced for 5 seconds to form a film.

This TMA introduction → purge → H ₂ O introduction → purge ALD film formation cycle was repeated 1000 times to form a film, and the surface of the alumina porous substrate and the thin film of 80 nm inside the pores were uniform over the entire porous substrate. Formed. The thickness of the obtained alumina porous plate was substantially 1 mm without change, and the porosity was 29%.

[ Example ]
Further , as an example, it is possible to form a film by the ALD method using the same alumina porous substrate and using the apparatus shown in FIG. As shown in FIG. 6, the pressures in the source gas introduction chamber and the exhaust chamber are monitored by the respective pressure gauges P _in and P _out to detect the differential pressure (P ₁ −P ₂ ). As the pressure, for example, a stable pressure of nitrogen purge (a step not through the purge line) is monitored. The differential pressure between the measured pressures is detected every film formation cycle. Since the differential pressure (P ₁ −P ₂ ) is affected by the porosity of the ceramic porous plate or the film thickness of the deposited film, the differential pressure (P ₁ −P ₂ ) ascertained in advance. From the relationship between and the porosity, the film formation cycle can be stopped when a desired porosity is obtained. Thereby, it is possible to control the porosity with high accuracy in-line without being influenced by the porosity of the initial ceramic porous substrate.

FIG. 7 shows a specific ALD film forming process in the embodiment carried out using the apparatus shown in FIG. Specifically, in the same manner as in the reference example , the film formation cycle of TMA introduction → purging → H ₂ O introduction → purging is repeated about 1000 times, and the differential pressure (P ₁ −P ₂ ) is a predetermined value. When reaching the value, the film forming cycle is stopped. Similar to the reference example , a thin film of about 80 nm is formed on the surface of the ceramic porous substrate and inside the pores. As described above, in the apparatus shown in FIG. 6, the cycle is stopped more accurately than the film formation by the apparatus of FIG. 4, so that highly accurate film formation can be performed with high productivity.

  As shown in FIG. 7, after the film formation, the alumina porous plate taken out from the ALD chamber was further heated in a heating furnace (not shown) at a temperature of 800 ° C. for 60 minutes. Then, it is cooled to 150 ° C. and taken out from it, and heat treatment is performed. The adhesion between the thin film and the raw material alumina porous substrate is enhanced, the consistency with the thin film material is enhanced, removal of unreacted residual material in the thin film, stabilization of the alumina porous substrate, recrystallization of the thin film, and The chemical and physical stability of the thin film can be improved.

1 is a schematic diagram of a fine structure of a dense ceramic. 1 is a schematic diagram of a fine structure of a ceramic porous body. 1 is a schematic diagram of a microstructure of a ceramic porous plate produced according to the present invention. 1 is a schematic diagram of a prototype of an ALD film forming chamber structure of a ceramic porous plate according to the present invention. 1 shows a prototype of an ALD film forming process for a ceramic porous plate according to the present invention. FIG. 2 is a schematic diagram of an ALD film forming chamber structure (addition of a pressure monitor function) of a ceramic porous plate used in the practice of the present invention. 1 illustrates an ALD film forming process (including a heat treatment process) of a ceramic porous plate according to the present invention.

Claims (3)

A method for producing a ceramic porous plate having a thin film whose film thickness is controlled at a molecular layer or atomic layer level on at least a part of an inner wall of a pore by an ALD (Atomic Layer Deposition; hereinafter the same) method A source gas of the ALD method is supplied to one surface side of the ceramic porous substrate having openings on both sides of the porous substrate and having pores penetrating the porous substrate, and the ceramic porous substrate Gas is flowed out from the surface side of the substrate and the source gas is passed through the pores to form an ALD thin film, the cycle of the ALD thin film formation is repeated , and the pressure on the one surface side (P ₁ ) and grasp the pressure difference between the pressure (P ₂₎ of the other surface side (P ₁ -P ₂₎ the relationship between the porosity of the ceramic porous plate, we until the desired porosity by a thin film formation That when it becomes the pressure difference (P ₁ -P _2), characterized by stopping the ALD film formation cycle, method for producing a ceramic porous plate.   The method for producing a ceramic porous plate according to claim 1, wherein an average pore diameter of pores in the ceramic porous substrate is 10 nm to 200 µm, and a thickness of the ceramic porous substrate is 0.5 mm or more.   The manufacturing method of the ceramic porous board of Claim 1 or 2 which further includes the process of heat-processing the ceramic porous board in which this thin film was formed.

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