JP2002201084A - Method of manufacturing ceramic porous membrane having high surface area - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method of manufacturing ceramic porous membrane having high surface area. SOLUTION: The method of manufacturing the ceramic porous membrane is characterized in the following: the membrane is including a lot of fine pores, the incremental thickness of the membrane per one dipping process is 0.15-0.77 μm, and high surface area of roughness factor per 1 μm membrane thickness is 69-170; a process dropping metal alkoxide into water containing polyethylene glycol or dropping metal alkoxide into water and adding polyethylene glycol after deposition is obtained, and by heating the hydrolyzed deposition with added acid or alkali, the uniform sol solution is prepared; the process by dip coating a substrate with the sol solution, the membrane is formed after drying, and heating it.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to the production of a transparent and high-surface-area porous ceramic film material, and more particularly, to a method of forming a porous and film-shaped ceramic such as titanium oxide or aluminum oxide on a substrate. The present invention relates to a novel method for producing a ceramic porous film material that can significantly increase the roughness factor (the ratio of the actual surface area inside the film to the area of the substrate) by forming the film thick.

[0002]

2. Description of the Related Art When a ceramic thin film is formed by a sol-gel method, a dip coating method is generally used. The dip coating method based on the sol-gel method can relatively easily perform uniform coating over a large-area substrate using a coating solution containing a metal alkoxide or the like. Also, by changing the type of coated ceramics, it is a useful method that can provide the substrate with new functional properties such as mechanical, chemical protection, optical properties, electromagnetic properties, and catalytic properties.

[0003] The ceramic porous membrane developed by the conventional method is characterized by having pores with uniform pore diameters on the surface (Japanese Patent Application Laid-Open Nos. 8-196903 and 8-2).
45278, JP-A-10-259074). However, these methods were suitable for producing a thin film having a small thickness, but in order to produce a film on the order of μm, the coating operation had to be repeated more than ten times or more. It was virtually difficult. Accordingly, although the film itself is porous, the roughness factor representing the actual surface area of the film is low due to the small film thickness. Also, the general dip coating method is suitable for producing a thin film, but is not suitable for producing a thick film.

[0004]

Under such circumstances, the present inventors have developed a method for forming a porous and thick ceramic film on a substrate in view of the above prior art. As a result of intensive research with the goal of, after coating the substrate with a specific ceramic sol solution that devised a method of adding a solvent and polyethylene glycol,
By heating and baking, a ceramic porous film having a large number of pores inside and a high surface area can be manufactured, and the surface area and the film thickness can be controlled by changing the amount of polyethylene glycol to be added. Have led to the present invention. In view of the above, the present invention has a large number of pores inside the membrane, has a high surface area due to the synergistic effect of the thicker film, and has a catalyst, a catalyst carrier, an adsorbent material, a deodorant / deodorant material, It is an object of the present invention to provide a ceramic porous membrane having excellent properties as a release material, a sensor, and the like, and a simple and economical method for producing the same.

[0005]

The present invention for solving the above problems is constituted by the following technical means. (1) It has a large number of pores inside, and the film thickness is 0.15 to 0.77 μm by one dip coating operation, and the roughness factor per 1 μm of the film thickness is 69 to 170.
A method for producing a ceramic porous membrane having a high surface area, wherein a metal alkoxide is dropped into water containing polyethylene glycol, or a metal alkoxide is dropped into water, and polyethylene glycol is added after a precipitate is obtained, A step of preparing a uniform sol solution by heating the precipitate obtained by hydrolysis by adding an acid or an alkali, dip coating the uniform sol solution on a substrate, drying, and heat-treating the film. A method for producing a porous ceramic film. (2) The method for producing a ceramic porous film according to (1), wherein the film has a roughness factor of 69 to 400. (3) A film having a maximum thickness of 0.77 μm is produced by one coating operation.
The method for producing a ceramic porous membrane according to the above. (4) The method for producing a ceramic porous film according to (1), wherein the thickness of the ceramic porous film is increased by repeating the operations of dip coating and heat treatment. (5) A ceramic porous film produced by any one of the above (1) to (4), having a large number of pores inside, and having a film thickness of 0.1 mm by one dip coating operation. A porous ceramic film having a high surface area of 15 to 0.77 μm and a roughness factor of 69 to 170 per 1 μm of film thickness.

[0006]

Next, the present invention will be described in more detail. The ceramic sol solution used in the present invention is obtained by dropping a metal alkoxide into distilled water, heating the precipitate obtained by adding an acid or an alkali, and heating the precipitate, thereby peptizing the precipitate. At this time, polyethylene glycol is previously dissolved in distilled water in which the metal alkoxide is dropped, or the metal alkoxide is dropped in distilled water, and after the precipitate is obtained, the polyethylene glycol is dissolved. Thus, a uniform ceramic sol solution can be obtained. In a conventional method, for example, a method of adding polyethylene glycol or the like to a ceramic sol solution and coating the same is known.
The sol aggregates to form a precipitate, and a uniform solution cannot be obtained. In the present invention, it is important to add polyethylene glycol before the sol is formed and to use a uniform sol solution. By using the uniform sol solution obtained by the above method, it has a large number of pores inside, a film thickness of 0.15 to 0.77 μm (by one dip coating operation), and a roughness factor of 69. ~
A ceramic porous film having a high surface area of 170 (per 1 μm of film thickness) and excellent durability can be manufactured.

In the present invention, all metal alkoxides are used as a metal alkoxide for preparing a sol solution of ceramics. In particular, alkoxides such as Ti and Al are exemplified as preferable ones. It can be appropriately used as long as it does, and is not limited thereto. Suitable examples of the acid or alkali to be added include nitric acid, hydrochloric acid, and aqueous ammonia. As the coating method, for example, a dip coating method, a spin coating method, a screen printing method, a spray method and the like are exemplified as preferable examples. They can be used as appropriate and are not limited to these. There is no problem if the heating conditions are 400 ° C. or higher at which polyethylene glycol is burned off, but since the sintering progresses with an increase in the heat treatment temperature, the roughness factor decreases. Lower temperatures are desirable as long as the adhesion is not reduced. Examples of the substrate include glass, nesa glass, ceramics, concrete, and metal, but any material may be used as long as it can withstand the heat treatment temperature. The shape may be any shape such as a plate, a cylinder, a prism, a cone, a sphere, and a fiber.

In the present invention, the uniform sol solution obtained by the above method is coated on a substrate by a dip coating method, a spin coating method, a screen printing method, a spray method or the like, and the substrate coated with a liquid film is dried. Thereafter, heat treatment is performed at a temperature of 400 ° C. or higher to form a film. By repeating the above-mentioned coating / heating treatment operation, the film thickness can be increased. In the present invention, the amount of polyethylene glycol to be added is, for example, 10
By adjusting the thickness to 1 to 10 per 0 ml, the film thickness is 0.15 to 0.1 in one dip coating operation.
The thickness can be controlled to 77 μm, and the roughness factor per 1 μm of the film thickness can be controlled to 69 to 170. For example, the film can have a roughness factor of 69 to 400.

The characteristics of the ceramic porous film produced according to the present invention are, in particular, 1) the film thickness is 0.15 to 0.77 μm in one dip coating operation;
2) The roughness factor is 69 to 1 per 1 μm of film thickness.
70), 3) high adhesion to the substrate, 4) high transparency of the film, 5) high uniformity of the film, and the like.

[0010]

Next, the present invention will be described in detail with reference to examples, but the present invention is not limited to the examples. Example 1 (1) Preparation of Ceramic Sol Solution In this example, a titanium oxide porous film was prepared. Preparation of a titanium oxide sol solution containing polyethylene glycol as a dip coating solution for preparing a titanium oxide porous membrane was performed as follows. A predetermined amount of polyethylene glycol (molecular weight: 2) is added to 300 ml of distilled water.
000) was dissolved. A tetraisopropyl titanate (56.6 ml) / isopropanol (50 ml) solution was gradually added dropwise to the aqueous polyethylene glycol solution to hydrolyze the alkoxide of titanium. Concentrated nitric acid (2.5 ml) was added to the resulting white suspension, and the mixture was heated to about 80 ° C. to remove isopropanol and peptize. Subsequently, heating was continued at the same temperature, and 100 ml of the sol solution was
To a volume of. Similarly, several kinds of solutions having different contents of polyethylene glycol were prepared.

(2) Preparation of porous film The prepared coating solution was coated on a glass substrate at a rate of 5 mm / min using a dip coating apparatus, dried, and then heated in an electric furnace at 500 ° C. for 30 minutes. A titanium oxide film was formed. To facilitate the measurement of the thickness and roughness factor of the titanium oxide porous film, dip coating and heat treatment were repeated three times to increase the thickness of the titanium oxide porous film.

(3) Measurement Method In order to measure the film thickness of the produced porous titanium oxide film, a cross section of the film was observed using a scanning electron microscope (SEM). In order to evaluate the porosity of the produced titanium oxide film, a Ru dye adsorbing a monolayer on the titanium oxide surface was adsorbed on the titanium oxide film, and the roughness factor was calculated from the amount of the dye adsorbed. The roughness factor is obtained as a ratio of the surface area inside the porous film to the projected area of the substrate, and represents the actual surface area of the porous film. The adsorption of the dye was oxidized to an ethanol solution (3.0 × 10 ⁻³ M) of the dye (cis-di (titocyanato) bis (2,2′-bipyridyl-4,4′-dicarboxylate) Ru (II)). This was performed by impregnating a titanium film, heating and refluxing for 1 hour, washing with ethanol, and drying. The transmittance of the porous titanium oxide film before and after dye adsorption was measured with a spectroscope, and the change in the transmittance at the absorption wavelength (540 nm) of the dye molecules was measured.
Based on the change in transmittance and the molar extinction coefficient of the dye molecule, the amount of dye adsorbed on the titanium oxide porous membrane was roughly estimated from Lambert-Beer's law. The roughness factor of the titanium oxide film was calculated from the dye adsorption amount and the size of the dye molecule (molecular diameter: 1.4 nm).

(4) Results Four types of titanium oxide sol (15 wt%) solutions were prepared by adding polyethylene glycol at a concentration of 1, 3, 5, 10 g / 100 ml-solution. Each of these solutions was coated three times by the dip coating method and 50 times.
A heat treatment was performed at 0 ° C. to form a titanium oxide film. Each of the produced porous titanium oxide films was a transparent and homogeneous film.

For each titanium oxide porous membrane, S
The cross section of the EM was observed to measure the film thickness, and the relationship with the amount of polyethylene glycol added to the dip coating solution was examined (FIG. 1). As is clear from this figure, it was confirmed that the thickness of the titanium oxide film increased with an increase in the amount of added polyethylene glycol. A maximum thickness of about 0.8 μm was obtained in one coating operation. This is considered to be because the viscosity of the coating solution was increased by the addition of polyethylene glycol, and the film thickness of the coating solution applied to the substrate during dip coating was increased. In general dip coating, when the coating speed is increased to increase the coating solution thickness, cracks and peeling often occur in the film after the heat treatment. However, this time, in the sol solution to which polyethylene glycol was added,
Although the liquid film and the film thickness were large, a uniform film could be produced.

A Ru complex dye was adsorbed on the prepared titanium oxide film, the transmittance of the titanium oxide film before and after dye adsorption was measured by a spectroscope, and a roughness factor was calculated from the amount of dye adsorbed and the size of the dye molecule. FIG. 2 shows the relationship between the amount of polyethylene glycol added and the roughness factor. As can be seen from this figure, the roughness factor increased with the amount of polyethylene glycol added. In order to examine the effect of adding polyethylene glycol in more detail, FIG. 3 also shows the roughness factor converted into unit film thickness. Since the roughness factor per film thickness increases with the amount of polyethylene glycol added, it is concluded that the addition of polyethylene glycol not only increases the film thickness but also has the effect of making the titanium oxide film structure porous. Is done.

In general, in the preparation of an oxide thin film by the sol-gel method, at a relatively low heat treatment temperature at which sintering does not easily occur, a porous film is obtained due to the influence of traces of evaporation of the solvent in the drying process. Easy to be. By adding polyethylene glycol, polyethylene glycol stays in the gel film even after the solvent (water) evaporates in the drying process, and the remaining polyethylene glycol in the heat treatment process is burned off to form more pores. It is thought to be done. In addition, the residual polyethylene glycol in the gel film
It is considered that the heat treatment process prevents the shrinkage of the titanium oxide film, that is, the approach between the sol particles, and makes it possible to form a uniform film without cracks or peeling.

[0017]

As described in detail above, the present invention provides a sol
By adding polyethylene glycol to the dip coating solution prepared by the gel method in advance, it is possible to produce a transparent and porous ceramic film such as a titanium oxide film. According to the present invention, by adjusting the content of polyethylene glycol, the thickness of a ceramic film such as a titanium oxide film can be adjusted to 0.15 to 0.77 μm in one dip coating operation, and per 1 μm of the film thickness. The roughness factor can be controlled in the range of 69 to 170. The method for producing a ceramic film such as a titanium oxide film developed in the present invention is useful as a promising technique applicable to various materials such as photocatalysts, dye-sensitized solar cells, and sensor materials.

[Brief description of the drawings]

FIG. 1 shows the relationship between the amount of polyethylene glycol added and the thickness of a titanium oxide film.

FIG. 2 shows the relationship between the amount of polyethylene glycol added and the roughness factor of a titanium oxide film.

FIG. 3 shows the relationship between the amount of polyethylene glycol added and the roughness factor of a titanium oxide film per unit film thickness.

Claims (5)

[Claims] 1. A film having a large number of pores therein and having a thickness of 0.15 to 0.77 μm by one dip coating operation.
m and roughness factor per 1 μm of film thickness is 69
A method for producing a ceramic porous membrane having a high surface area of from about 170 to about 170, wherein a metal alkoxide is dropped into water containing polyethylene glycol, or a metal alkoxide is dropped into water, and polyethylene glycol is added after a precipitate is obtained. A step of preparing a uniform sol solution by adding an acid or an alkali to the precipitate obtained by hydrolysis and heating, dip coating the uniform sol solution on a substrate, drying and heating. A method for producing a ceramic porous film, comprising: 2. The method for producing a ceramic porous film according to claim 1, wherein the film has a roughness factor of 69 to 400. 3. A maximum of 0.7 in one coating operation.
The method for producing a ceramic porous film according to claim 1, wherein a film having a thickness of 7 µm is produced. 4. The method for producing a ceramic porous film according to claim 1, wherein the operation of dip coating and heat treatment is repeated to increase the film thickness. 5. A ceramic porous film produced by the method according to claim 1, which has a large number of pores therein and has a thickness of 0.15 by one dip coating operation. A ceramic porous film having a high surface area of about 0.77 μm and a roughness factor of 69 to 170 per 1 μm of film thickness.