JP2005177693A - Filter and its production method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve the problem that strength deterioration, micropore change or else is easily caused, on the other hand, a component eluted from a filter easily reacts with corrosive liquid or gas to form hydroxides, the hydroxides are easily deposited and, therefore, the micropores are blocked, in the filter used in the corrosive gas and liquid. <P>SOLUTION: The filter 1 is made by forming an anti-corrosive film 3 composed essentially of Y<SB>2</SB>O<SB>3</SB>on at least one surface of porous ceramic body 2. Therein, the value obtained by dividing the intensity value at the maximum crystal peak of a reaction product between a porous ceramic body 2 component and Y element of an anti-corrosive film 3 component in X-ray diffraction of the anti-corrosive film 3 by the intensity value at the maximum crystal peak of Y<SB>2</SB>O<SB>3</SB>is made to be 0.1 or less. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a filter in which a corrosion-resistant film is formed on a ceramic porous body and a method for producing the same, and is particularly effective in a place where it comes into contact with a corrosive liquid or gas.

  In recent years, ceramic porous bodies have been used in various filters for separating solids, liquids and gases, respectively, compared to organic polymer membranes used for similar applications, heat resistance, corrosion resistance, durability, It is known that it is excellent in pressure resistance and physical strength.

  However, for example, in the ceramic porous body made of alumina ceramics, when exposed to alkaline liquid or vapor for a long time, Si component, Ca component, etc. contained in the alumina ceramics are eluted. There has been a problem that a hydroxide is formed by reacting with a vapor component and deposited in the liquid or vapor to block the pores of the ceramic porous body. Further, there have been problems such as deterioration of strength and enlargement of pore diameter at locations where Si component, Ca component and the like are eluted after being exposed to alkaline liquid or steam for a long time.

  For example, Patent Document 1 discloses a ceramic composite member comprising a ceramic porous support and a ceramic layer in which a pore diameter of 1 nm or less accounts for 80% or more of the total pore volume when used as a ventilation filter. However, the corrosive liquid or vapor that has penetrated into the ceramic composite member erodes the ceramic composite member and deteriorates the reliability, or the Si component and Ca component elute like the alumina ceramic. There is a real concern that hydroxides formed by reaction with water and steam block the pores, deteriorate the strength of the portion where the Si component and Ca component are eluted, and enlarge the pore diameter.

For this reason, in the case of a liquid such as an ink adjusted to be alkaline, the field is different, but as shown in Patent Document 2, it contains SiO ₂ , CaO, and MgO other than alumina in alumina ceramics, By setting the content within a desired range, a method is shown in which crystals having poor corrosion resistance are prevented from precipitating and the glass component in the alumina ceramic is prevented from eluting into the ink.

Patent Document 3 describes a method of preventing ink aggregation by setting the amount of Na in a ceramic sintered body containing alumina or an alumina compound to 0.5% by weight or less in terms of Na ₂ O. ing.

  Recently, as a member with excellent corrosion resistance in place of silica and alumina ceramics, the surface exposed to plasma in a halogen-based corrosive gas atmosphere such as fluorine-based or chlorine-based oxides of Group 3a elements of the periodic table In addition, while it is proposed to form with a fluoride, on the other hand, by using a member that has been used conventionally as a base material, a corrosion-resistant film or a corrosion-resistant layer is formed thereon, thereby taking advantage of the characteristics of the conventional member and its corrosion resistance. There are proposals to improve this.

As such a proposal, as shown in Patent Document 4, a ceramic member in which the base material is alumina and an yttrium aluminum garnet (Y ₃ Al ₅ O ₁₂ , hereinafter referred to as YAG) layer is formed on the surface is proposed. Has been.

  Moreover, in patent document 5, the corrosion-resistant film which consists of a sintered compact which has at least 1 sort of a periodic table group 2 or a group 3 element as a main component on the ceramic base material surface, and the reaction layer of a base material and a corrosion-resistant film are provided. Corrosion-resistant members joined via are proposed.

As a method for producing such a corrosion-resistant member, first, a raw material to be a base material component is pressed at a constant pressure by, for example, die press molding to form a base material compact, and then on the base material compact Are filled with a corrosion-resistant material and pressed with a constant pressure to form a corrosion-resistant molded body on the substrate molded body to obtain a composite molded body. Thereafter, firing is performed at about 1500 ° C. to 1750 ° C. in an air atmosphere. When a YAG or Y ₂ O ₃ layer is formed on the surface of a substrate made of alumina, YAlO ₃ and Y ₄ AlO ₉ produced by the reaction of the substrate component and the corrosion-resistant film component between the corrosion-resistant film and the substrate. And the like, and the anti-corrosion film is firmly fixed to the substrate by the mutual diffusion layer.
JP-A-11-216303 JP 2001-179968 A JP 2003-1822 A Japanese Patent Laid-Open No. 2002-87894 JP 2002-192655 A

  However, in recent years, due to the diversification of locations where the porous ceramic body is used, the liquids or vapors that come into contact therewith are also diversified. In particular, in the locations where the porous ceramics are in contact with corrosive liquids or vapors, Due to the deterioration of the strength of the porous body, the change in the pore diameter, or the eluted component reacts with the liquid or gas to form a hydroxide, precipitate, or foreign matter present in the liquid or vapor, There was a problem of blocking.

  For this purpose, a chemical cleaning method is generally used in which a strong alkaline liquid, for example, a sodium hydroxide solution is used to dissolve hydroxide and foreign matter deposited on the surface of the ceramic porous body, thereby eliminating clogging. However, when this chemical cleaning method is used, Na and Ca dissolved in the ceramics start to change and the pore diameter changes, allowing foreign substances that had been blocked to pass therethrough, and conversely hydroxylation. There is a problem in that the ceramic porous body is destroyed because the mechanical strength is further lowered, such as the generation of a product to block the pores and the water passage performance is lowered.

When the liquid to be used is ink, the field is different, but as shown in Patent Document 3, the amount of Na in the ceramic sintered body containing alumina or an alumina compound is set to 0. _{2 in} terms of Na ₂ O. Although a method for preventing the aggregation of ink by setting it to 5% by weight or less is described, even if the technique shown in Patent Document 3 is used, the ceramic porous body as shown in Patent Document 1 is used. When a product having a small pore diameter is required, the same problem that agglomeration of a liquid formed with a small amount of Na blocks the pores has occurred.

  Moreover, in the method shown in patent document 4 and patent document 5, in the corrosion-resistant member which has the mutual diffusion layer which consists of a compound of the base material component and the corrosion-resistant film component as described above, the thickness of the mutual diffusion layer becomes 20 μm or more. When the cross section of the interdiffusion layer is observed, since it is an unstable gradient layer as a compound, a sufficiently corrosion-resistant member can be obtained when the thickness of the corrosion-resistant film is 20 μm or more, but the thickness is 20 μm or less. In the case of forming a thin corrosion-resistant film such as this, most of the corrosion-resistant film is composed of an interdiffusion layer formed by the reaction between the base material component and the corrosion-resistant film component, and the corrosion resistance is lowered. doing.

When a thin corrosion-resistant film having a thickness of 20 μm or less is formed and heat-treated at a high temperature, the interdiffusion layer becomes thick, and the base material component in the X-ray diffraction of the surface of the corrosion-resistant member and the Y element that is the corrosion-resistant film component The ratio of the intensity value at the highest crystal peak of the reaction product to the intensity value at the highest crystal peak of Y ₂ O ₃ exceeds 0.1, and the corrosion resistance of the corrosion resistant film is lowered as described above.

In addition, a thin corrosion-resistant film made of YAG or Y ₂ O ₃ whose main component is at least one element of Group 2 or Group 3 of the Periodic Table and having a thickness of 20 μm or less is formed on a base material made of ceramic containing Si element. In this case, a reaction product such as Y ₂ Si ₂ O ₇ (disilicate) which is an oxide of Si as a base material component and Y element as a corrosion-resistant film component is generated. Due to the large size, the compound has an unstable gradient layer, and there is a problem that the corrosion resistance is lowered.

Therefore, the filter of the present invention is a filter formed by forming a corrosion-resistant film containing Y ₂ O ₃ as a main component on at least one surface of a ceramic porous body, and the ceramic porous body in the X-ray diffraction of the corrosion-resistant film A value obtained by dividing the intensity value at the highest crystal peak of the reaction product of the component Y with the corrosion-resistant film component by the intensity value at the highest crystal peak value of Y ₂ O ₃ is 0.1 or less. .

The filter of the present invention is characterized in that the half-value width of the highest crystal peak of Y ₂ O ₃ by the X-ray diffraction is 1.3 ° or less.

  Furthermore, the filter of the present invention is characterized in that the ceramic porous body has an average pore diameter of 0.05 to 80 μm and a porosity of 10 to 70%.

  And the manufacturing method of the filter of this invention forms a corrosion-resistant film | membrane by heat-processing at 500-1200 degreeC, after forming the film | membrane of the sol liquid which has Y as a main component on one surface of the said ceramic porous body. It is characterized by that.

  In addition, the filter manufacturing method of the present invention forms a sol solution film having a thickness of 0.1 to 2.5 μm by immersing the ceramic porous body in the sol solution or coating the ceramic porous body on the ceramic porous body. Thereafter, a corrosion-resistant film having a predetermined thickness is formed by repeating the heat treatment at 500 ° C. to 1200 ° C.

The filter of the present invention is a ceramic porous body component and a corrosion-resistant film component in X-ray diffraction of the corrosion-resistant film by forming a corrosion-resistant film mainly composed of Y ₂ O ₃ on at least one surface of the ceramic porous body. Since the value obtained by dividing the intensity value at the highest crystal peak of the reaction product with the Y element by the intensity value at the highest crystal peak value of Y ₂ O ₃ is 0.1 or less, the components of the ceramic porous body and the corrosion resistant film There are very few reaction products with the Y element which is a component, and most of the surface of the corrosion-resistant film is covered with Y ₂ O ₃ and has high corrosion resistance.

Moreover, the filter of the present invention obtains a Y ₂ O ₃ corrosion-resistant film exhibiting higher corrosion resistance by setting the half width of the highest crystal peak of Y ₂ O ₃ by X-ray diffraction to 1.3 ° or less. Can do.

  Furthermore, the filter of the present invention can be suitably used as various filters because the pores communicate with each other when the average pore diameter of the ceramic porous body is 0.05 to 80 μm and the porosity is 10 to 70%. it can.

  According to the method for producing a filter of the present invention, after forming a sol film containing Y as a main component on one surface of the ceramic porous body, heat treatment is performed at 500 to 1200 ° C. It is possible to obtain a corrosion-resistant film with improved corrosion resistance by reducing the number of interdiffusion layers composed of a compound of a material component and a corrosion-resistant film component.

  In addition, after forming a sol solution film having a thickness of 0.1 to 2.5 μm by immersing or applying the ceramic porous material, which is a method for producing the filter of the present invention, to the ceramic porous material By repeating the process of heat treatment at 500 ° C. to 1200 ° C., a thin corrosion resistant film having a thickness of 20 μm or less can be formed, and the corrosion resistant film can be prevented from shrinking and generating cracks on the surface during the heat treatment. it can.

  Next, the best mode for carrying out the present invention will be described using a filter for filtration as an example.

  1A is a perspective view of a filter for filtration using the filter of the present invention, FIG. 1B is a cross-sectional view taken along line XX of FIG. 1A, and FIG. 1C is an enlarged view of FIG. The partial expanded sectional view is shown.

  The filtration filter 1 has a cylindrical shape with both ends open, and includes a ceramic porous body 2 having a plurality of pores and a corrosion-resistant film 3 on the surface thereof. Here, the corrosion-resistant film 3 is provided on the outer peripheral surface side. It is formed.

  And such a filter 1 for filtration can be effectively used as the filter 1 for filtration in the module for filtration as shown in FIG. FIG. 2 shows a perspective view in which a part of the filtration module 8 using the filtration filter 1 of the present invention is broken.

  The filtration module 8 is provided with a liquid inlet 5 in the outer peripheral portion of a sealed cylindrical interior of the module body 7, parallel to the central axis of the module body 7, and at one end with a silicon plug 4. The side of the filter 1 shown in FIG. 1 that is sealed and opened with the other end as the liquid outlet 6 is inserted and fixed inside, and the liquid outlet 6 side becomes the outside of the module body 7. It is set and configured as follows.

  In order to filter the liquid using the filtration module 8, when the liquid is introduced from the liquid inlet 5, the inside of the module body 7 is filled with the liquid and passes through the pores of the filtration filter 1. The filtered liquid is discharged from the liquid outlet 6 through the hollow portion inside the filter 1 for filtration. At this time, if the pore diameter of the filter for filtration 1 is appropriately selected, various filtration substances can be separated from the liquid that has entered.

  The filtering filter 1 of the present invention shown in FIG. 1 and FIG. 2 is provided with a corrosion-resistant film 3 on the surface of the ceramic porous body 2, so that the ceramic porous body 2 is strong by corrosive liquid or vapor. Without causing deterioration or change in the pore diameter, it is possible to prevent a problem that the eluted component reacts with the liquid or gas to form and precipitate a hydroxide and block the pore diameter. Moreover, it can be used effectively for filtration of liquids containing highly corrosive substances. For example, when water is treated using the above-described filtration filter 1, foreign matter that has been fixed by continuing filtration for a long time is used. Even when it cannot be removed, a chemical cleaning method can be employed in which the foreign matter on the surface of the filter 1 for filtration is dissolved with a sodium hydroxide solution or the like to eliminate clogging.

Here, the anticorrosion film 3 in the filter 1 for filtration of the present invention is mainly composed of Y ₂ O ₃ , and is composed of the ceramic porous body 2 component in the X-ray diffraction of the anticorrosion film 3 and the Y element which is the anticorrosion film 3 component. A value obtained by dividing the intensity value at the highest crystal peak of the reaction product by the intensity value at the highest crystal peak value of Y ₂ O ₃ (hereinafter simply referred to as intensity ratio) is specified to be 0.1 or less.

When the strength ratio is 0.1 or less, there are very few reaction products between the ceramic porous body 2 component and the corrosion-resistant film 3 component Y element, and most of the surface of the corrosion-resistant film 3 is covered with Y ₂ O ₃ crystals. This is because it has high corrosion resistance.

  In addition, since the reaction product of the ceramic porous body 2 component and the Y element which is the corrosion resistant film 3 component is generated as a part of the corrosion resistant film 3 on the surface of the corrosion resistant film 3, it is not generated in order to improve the corrosion resistance. Is more preferable.

In this case, since the surface of the corrosion-resistant film is composed only of Y ₂ O ₃ crystals, the peak of the reaction product in X-ray diffraction is not detected, and the intensity ratio of Y ₂ O _{3 to} the maximum crystal peak intensity value is 0. It is more preferable that

  On the other hand, when the intensity ratio is 0.1 or more, the reaction product has an unstable gradient layer region, a dense film cannot be obtained, and a large number of pores are present on the surface of the corrosion-resistant film 3, This is because the surface area in contact with the corrosive liquid or vapor increases and the corrosion resistance decreases.

As an example of the present invention, FIG. 3 shows a crystal peak when the porous ceramic body 2 is formed of silicon nitride ceramics and the surface of a corrosion-resistant film of Y ₂ O ₃ having a thickness of about 10 μm formed on the surface is subjected to X-ray diffraction. The spectrum figure of is shown.

FIG. 3 is a spectrum diagram in which the X-ray intensity diffracted by a crystal such as Y ₂ O ₃ is recorded in the form of a diffraction pattern, where the vertical axis is the peak intensity and the horizontal axis is the X-ray incident on the surface of the corrosion-resistant film 3. The angle 2θ is shown when the angle is θ.

  The X-ray diffraction is measured with an incident angle of 2θ = 10 ° to 80 °, and a RINT1400V type manufactured by Rigaku Corporation is used as a measuring apparatus.

In Figure 3, □ is _Y 2 _{O 3,} ○ is _Si 3 _{N 4,} △ is a reaction product of a Y element of Si element and corrosion resistant film 3 of the silicon nitride ceramic porous body 2 _Y 2 Si ₂ O ₇ represents the crystal peak.

In FIG. 3, the highest crystal peak of Y ₂ O _{3 is in} the vicinity of 2θ = 29 °, and the highest crystal peak of Y ₂ Si ₂ O ₇ exists between 2θ = 32 ° and 33 °. The intensity ratio of these _Y 2 _Si 2 _{O 7} becomes 0.1 or less.

  The intensity ratio is usually controlled by the firing temperature and time.

Furthermore, in the present invention, it is more preferable that the intensity ratio of Y ₂ Si ₂ O ₇ existing between 2θ = 32 to 33 ° is 0.

Thus, the strength ratio of the reaction product in the X-ray diffraction of the surface of the corrosion-resistant film 3 made of Y ₂ O ₃ can be 0.1 or less, which is characterized by its production method, and will be described in detail later. When the corrosion-resistant film 3 is formed on the surface of the ceramic porous body 2, it can be obtained by using a sol solution composed of Y.

The above reaction product is mainly Y ₂ Si ₂ O ₇ when the ceramic porous body 2 component is silicon nitride or silicon carbide, and YAG (Y ₃ Al ₅ when the ceramic porous body is alumina. O ₁₂ ), YAP (YAlO ₃ ), and YAM (Y ₄ Al ₂ O ₉ ), which are expressed by chemical formulas having both the Y element and the ceramic porous body two components.

  And about the said alumina, although the reaction product was listed, in fact, the said reaction product is rarely produced, and it is few even if it generate | occur | produces.

  Furthermore, when the ceramic porous body 2 is zirconia, no reaction product is generated, so the strength ratio is zero.

Further, the corrosion resistant film 3 preferably has a half width of 1.3 or less at the highest crystal peak of Y ₂ O ₃ in the X-ray diffraction described above.

  If this half width is greater than 1.3, the corrosion-resistant film 3 is not sufficiently crystallized and unstable, and it becomes difficult to obtain a dense film, so that the corrosion resistance is lowered.

The half width is the midpoint position obtained from the maximum crystal peak intensity of Y ₂ O _{3 in} the vicinity of 2θ = 29 ° by using the half-value width midpoint method in the diffraction angle reading method in X-ray diffraction. The half width in FIG. 3 is 0.6 °.

  Further, the thickness of the corrosion-resistant film 3 is preferably 0.1 to 20 μm, and it is possible to coat even a complex shape of the ceramic porous body 2, and if the thickness is 10 μm or less, it becomes a finer shape. Further, when the pore diameter of the ceramic porous body 2 exceeds 0.5 μm and the coating thickness is less than 0.2 μm, the surface of the pores can be coated, which is more preferable.

Furthermore, the corrosion resistant film 3 preferably has an average crystal grain size of 0.01 μm or less, and the pores of the ceramic porous body 2 forming the corrosion resistant film 3 can be prevented from being filled with the corrosion resistant film 3. .
The ceramic porous body 1 that forms such a corrosion-resistant film 3 can use various ceramics such as alumina, cordierite, mullite, silicon nitride, silicon carbide, zirconia. In particular, since alumina is easy to manufacture and relatively inexpensive, it can be widely applied as the ceramic porous body 2. Further, the mechanical characteristics necessary for the filter 1 for filtration can be obtained by taking advantage of the mechanical characteristics of the ceramic porous bodies 2.

  Moreover, it is important that the pores of the ceramic porous body 2 communicate with each other, and the average pore diameter is preferably 0.05 μm to 80 μm and the porosity is preferably 10 to 70%. The voids between the crystals can be used for communication, the pores are not blocked by the corrosion-resistant film 3, and mechanical strength can be imparted.

  If the average pore diameter is smaller than 0.05 μm, the pores may be blocked when forming the corrosion-resistant film 3. If the average pore diameter is larger than 80 μm, the corrosion-resistant film 3 formed on the surface is ceramic. It is not preferable because the surface state of the corrosion-resistant film 3 is not uniform because it penetrates deep into the pores of the porous body 1 and the corrosion-resistant film is easily damaged by contact or vibration.

  Further, the range of the average pore diameter is more preferably 0.1 to 10 μm in order to simultaneously exhibit the functions of strength, pore communication, and formation of the corrosion-resistant film 3.

  Furthermore, it can be used as a water treatment filter if the average pore diameter is less than 1 μm, as a particulate filter if the average pore diameter is 50 μm or less, and as a ventilation filter if the average pore diameter is 1 μm to 70 μm. .

  In addition, the average pore diameter of the ceramic porous body 1 is a value measured using a mercury intrusion method.

  Further, when the porosity of the ceramic porous body 2 is less than 10%, the pores are difficult to communicate, and when the porosity is greater than 70%, mechanical strength can be imparted, and handling is facilitated. A range of 10% to 70% is preferable.

  In addition, in order to obtain such a ceramic porous body 2, a general ceramic porous body in which an organic substance is added and fired in advance or the ceramic porous body 2 is fired at a temperature lower than the temperature at which the ceramic porous body 2 is sintered is used. It can be easily produced by a method for producing a material.

  Further, as will be described in detail later, as a method of forming the corrosion-resistant film 3, a method of applying a sol solution is used to immerse in a sol solution and then deaerate in a vacuum atmosphere. Thereafter, the pores can be prevented from being blocked by, for example, a method of firing after aeration or by adding an organic substance to the sol liquid and firing.

  Here, the manufacturing method of the filter 1 for filtration mentioned above is demonstrated.

  First, the ceramic porous body 2 is formed into a required shape using a general molding method such as die press molding, extrusion molding, injection molding, etc., using a ceramic raw material having an average crystal particle diameter of 1.0 μm to 30 μm. And firing.

  The ceramic porous body 2 can be easily produced by a method of adding an organic material in advance as described above, or a general method of producing a ceramic porous body by firing at a temperature lower than the temperature at which the porous body is sintered. . Further, it is possible to adjust the pore diameter by utilizing the generally known fact that the larger the particle diameter of the raw material powder is, the larger the pore diameter is, and the pore diameter is adjusted by the particle diameter of the organic substance added in advance. You can also. Moreover, it can be set as a desired value by adjusting the temperature which the ceramic porous body 2 sinters.

  And in order to form the corrosion-resistant film | membrane 3 on the surface of this ceramic porous body 2, the sol liquid which consists of Y is apply | coated. As a coating method, a dip coating method in which the ceramic porous body 2 is dipped in a sol solution composed of Y and is pulled up is preferable, and can be applied to any shape of the ceramic porous body 2. In addition, a coating method using a spray method, a brush, or the like, which is a general coating method, or a transfer method can also be applied.

  Then, after applying the sol solution, the coating can be performed without blocking the pores by degassing in a vacuum atmosphere or removing the excess sol solution by centrifugation or the like.

In addition, it is more preferable to use an aqueous solution of 3 to 10% by weight in terms of Y ₂ O ₃ for the sol liquid to be used, and the purity of Y ₂ O ₃ in the sol liquid is preferably 95% by weight or more. The pH (hydrogen ion concentration index) is greater than 7 and has alkalinity.

Next, the ceramic porous body 2 having the surface coated with the sol liquid is subjected to heat treatment. The heat treatment is preferably performed at a temperature from 500 ° C. at which Y ₂ O ₃ begins to crystallize to 1200 ° C. at which the reaction between the ceramic porous body 2 component and the Y ₂ O ₃ component is small. In order to raise, it is more suitable to heat-process at 500-1000 degreeC.

Unlike the prior art in that the heat treatment is performed in a low temperature range of 500 to 1200 ° C. as described above, the ceramic porous body 2 component and the Y ₂ O ₃ component that is the corrosion-resistant film 3, particularly Y The reaction with the element can be suppressed, and even when the film thickness is 0.1 to 20 μm or less, it is dense, and the reaction product can be prevented from appearing on the surface of the corrosion-resistant film 3. Corrosion-resistant film 3 can be formed only with ₂ O ₃ , and high corrosion resistance can be imparted.

  Moreover, it is preferable to heat-treat in advance in a temperature range of 700 ° C. to 1000 ° C. before applying the sol solution to the surface of the ceramic porous body 2.

  By this heat treatment, organic substances adhering to the surface of the ceramic porous body 2 are removed and an oxide film is formed, so that the wettability with the sol solution is improved and uniform application can be achieved.

  Furthermore, as a more preferable method for forming the corrosion-resistant film 3, a thin film having a thickness of 0.1 to 2.5 μm or less is formed on the surface of the ceramic porous body 2 using the sol solution, and then 500 to 1200 ° C. is more preferable. For example, by repeating the heat treatment step at a temperature of 500 to 1000 ° C. to form the corrosion resistant film 3 having a thickness of 0.1 to 20 μm, the corrosion resistant film 3 contracts during the heat treatment and is generated on the surface of the corrosion resistant film 3. It is also possible to apply a method for preventing cracking.

The filtration filter 1 obtained in this way has very few reaction products, and most of the surface of the corrosion-resistant film 3 is covered with Y ₂ O ₃ crystals and has high corrosion resistance.

  Further, the filter of the present invention is not limited to the above-described embodiment, and it goes without saying that various modifications may be made without departing from the gist thereof. In the above-described embodiment, the filter for filtration is used. Although it demonstrated using the example of 1, it is not limited to this filter 1 for filtration, It can apply also to other filters, such as a ventilation filter, and is contained in the scope of the present invention. In addition, the present invention has been described with an example in which the filter is used as it is. However, an inorganic or organic corrosion-resistant film or water-repellent film having further corrosion resistance may be formed and used based on the filter of the present invention. All are well within the scope of the present invention.

  Examples of the present invention will be specifically described below.

  First, the filter 1 for filtration as shown in FIG. 1 is produced.

  A cylindrical body made of silicon nitride ceramics and alumina ceramics having a length of 40 mm, a diameter of 20 mm, and a thickness of 2 mm was produced as a ceramic porous body. At this time, the average pore diameter is 0.5 μm, and the porosity is 40%. In order to obtain this ceramic porous body, extrusion molding is performed using a raw material powder having an average crystal particle diameter of 3 μm, silicon nitride ceramics are in a vacuum atmosphere at a temperature range of 1000 to 1500 ° C., and alumina ceramics are in an oxidizing atmosphere. Calcination was performed in a temperature range of 800 to 1300 ° C.

Further, a Y (OH) ₃ sol solution was prepared as a sol solution composed of Y as a corrosion-resistant film. Using a dip coating method in which these test pieces are dipped in a Y (OH) ₃ sol solution and pulled up, the Y (OH) ₃ sol solution (Y ₂ O ₃ equivalent concentration 5.5 wt% aqueous solution) has a thickness of 1 μm. It apply | coated to the ceramic porous body surface.

Thereafter, the process of evaporating and drying the solvent of the Y (OH) ₃ sol solution applied to the ceramic porous body at a temperature of about 100 ° C. and heat-treating it at a temperature of 500 to 1700 ° C. is repeated to provide corrosion resistance on the ceramic porous body. A film was formed with a thickness of 10 μm, and sample No. 1-13 were produced.

As comparative examples, the sample No. _{2 was} a Y ₂ O ₃ sintered body having the same shape as described above, and a Si ₃ N ₄ sintered body, which had no corrosion-resistant film. 14 and 15 were prepared.

Then, XRD analysis of each sample was performed, and Y ₂ Si ₂ O ₇ equal intensity ratio (peak intensity in Table 1) which is a reaction product of each ceramic porous body component and Y element of Y ₂ O ₃ corrosion-resistant film. The half width at the highest crystal peak of Y ₂ O ₃ was measured.

  Furthermore, the surface of the corrosion-resistant film of the prepared sample was observed with a binocular microscope, the state of the surface was confirmed, and the presence or absence of cracks and the surface roughness were investigated.

  Moreover, in order to measure the corrosion resistance of each sample, after each filter sample was produced, the module for filtration as shown in FIG. 2 was produced. Then, a water passage test of the filtration module is performed. After that, 10% by weight of caustic soda solution is filled in the filtration module 8 and left for 24 hours, and then a water passage test using pure water is performed again. If the water flow rate does not change, the corrosion resistance is excellent, ◎, the increase rate of water flow rate is 2% or less, the corrosion resistance is good, ○ 5% or less, the corrosion resistance is slightly inferior, but can be used △, the thing exceeding it was evaluated as x because corrosion resistance was inferior and it was unusable.

  In the water flow test, pure water is filled from the water inlet, pressurized and set so that the water flow differential pressure becomes constant at 1 MPa, and the change in the amount of filtered water flowing out from the water outlet is measured. The rate of increase in water flow was evaluated.

Table 1 shows the results.

As is apparent from the results in Table 1, after applying the sol solution to the ceramic porous body, the samples (No. 1 to 5) subjected to heat treatment at 500 to 1200 ° C. The reaction product of Si ₃ N ₄ and Y ₂ O ₃ was less than 0.1, and it was found that the corrosion resistance was excellent.

In particular, it was found that samples (Nos. _{2 to} 4) having a heat treatment temperature of 500 to 1000 ° C. were satisfactory because Y ₂ O ₃ was sufficiently crystallized and densified, and were more excellent in corrosion resistance.

Since the sample (No. 1) having a low heat treatment temperature was insufficient in crystallization of Y ₂ O ₃ , the sample (No. 15) having no corrosion-resistant film of only the Si ₃ N ₄ sintered body of the comparative example was used. Although it has higher corrosion resistance, the half-width is not good, so the volume reduction rate is slightly larger than that of the sample (No. 2 to 4).

Furthermore, although the sample (No. 5) having a high heat treatment temperature has a higher corrosion resistance than the sample (No. 15) having only the Si ₃ N ₄ sintered body without the corrosion resistant film, the surface roughness of the corrosion resistant film is somewhat rough, and the corrosion resistance. Therefore, the volume reduction rate is slightly larger than that of the sample (Nos. 2 to 4).

On the other hand, the sample with high heat treatment temperature (No. 6) had a peak intensity ratio exceeding 0.1, resulting in a large amount of reaction products of Si ₃ N ₄ and Y element, resulting in poor corrosion resistance. .

Further, in the samples (Nos. 7 and 8) having a higher heat treatment temperature, most of the Y ₂ O ₃ corrosion-resistant film is a reaction product of Si ₃ N ₄ and Y element as a base material, and Y ₂ O ₃ alone The peak intensity ratio could not be calculated. Therefore, it was confirmed that the corrosion resistance has a large volume reduction rate compared to the samples (Nos. 1 to 5) and is inferior to the corrosion resistance.

In addition, as a result of etching by reverse sputtering with argon, the Si ₃ N ₄ sintered body has an etching rate of 10 times or more compared with the corrosion resistance of the Y ₂ O ₃ sintered body, and the film thickness is increased by the conventional method. Even when the thickness was 1 μm, the etching rate was 7 times, and the corrosion resistance was low.

Furthermore, sample no. In 9 to 13, the test was carried out above the ceramic porous body as alumina _(Al 2 _{O 3).}

As a result, the reaction product of the Y element of Y ₂ O ₃ and alumina (Al ₂ O ₃ ) as the base material was a little detected, but the above-mentioned was carried out using Si ₃ N ₄ as the base material. It was confirmed that the same tendency as the test result was exhibited.

In particular, the samples (Nos. 10 to 12) having a heat treatment temperature of 500 to 1000 ° C. are slightly inferior in corrosion resistance to the samples (No. 14) made of a Y ₂ O ₃ sintered body as a comparative example. There was no result.

Further, in preparing a sample similar to that in Example 1, the material of the ceramic porous body is alumina ceramics, and a sol liquid mainly composed of Y ₂ O ₃ is applied to the ceramic porous body once. As shown in Table 2, various changes were made and applied, and the thickness, peak intensity ratio, and half-value width of the corrosion-resistant film were measured, and the same evaluation as in Example 1 was performed. In addition, special notes are described in the remarks column.

The results are shown in Table 2.

  As is clear from Table 2, a sample (No. 19 to 24, 26) in which the sol solution was applied to the ceramic porous body at a thickness of 0.1 to 2.5 μm and the heat treatment temperature was 700 ° C. -29) all had a peak intensity ratio of 0.1 or less, a half-value width of 1.3 ° or less, and excellent corrosion resistance with ◎.

  In the sample (No. 25) having a high heat treatment temperature of 1500 ° C., the half-value width exceeded 1.3, and although the weight change occurred, the corrosion resistance was acceptable Δ.

  In addition, the sample (No. 16 to 18) having a film thickness of 0.05 μm applied once for the sol solution has a usable Δ, but the film thickness applied only once for the sol solution is actually thin. Since it is a film | membrane, there exists a problem that productivity is inferior.

  On the other hand, in the sample (No. 30) in which the film thickness of one sol solution was 3 μm, the corrosion resistance was acceptable Δ, but some cracks were observed.

  From the above results, as the filter of the present invention, the peak intensity ratio needs to be 0.1 or less, and the half width is preferably 1.3 ° or less. It turned out that it is suitable to heat-treat at 500-1200 degreeC by making sol liquid film thickness into 0.1-2.5 micrometers.

(A) is a perspective view of the filter for filtration using the filter of this invention, (b) is the fragmentary sectional view of the figure (a), (c) is an expanded sectional view of the figure (b). It is the perspective view which fractured | ruptured a part of module for filtration incorporating the filter using the filter of this invention. It is a spectrum figure which shows the crystal peak in the X-ray diffraction of the filter of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Filter for filtration 2 Ceramic porous body 3 Corrosion-resistant film 4 Silicon plug 5 Water inlet 6 Water outlet 7 Module body 8 Module for filtration

Claims (5)

A filter formed by forming a corrosion-resistant film mainly composed of Y ₂ O ₃ on at least one surface of a ceramic porous body, wherein Y is a ceramic porous body component and a corrosion-resistant film component in X-ray diffraction of the corrosion-resistant film A filter obtained by dividing the intensity value at the highest crystal peak of a reaction product with an element by the intensity value at the highest crystal peak value of Y ₂ O ₃ is 0.1 or less. _2. The filter according to claim 1, wherein the half width of the highest crystal peak of Y ₂ O ₃ by the X-ray diffraction is 1.3 ° or less. The filter according to claim 1 or 2, wherein the ceramic porous body has an average pore diameter of 0.05 to 80 µm and a porosity of 10 to 70%. The method for producing a filter according to any one of claims 1 to 3, wherein a film of a sol solution containing Y as a main component is formed on one surface of the ceramic porous body, and then heat treated at 500 to 1200 ° C. A method for producing a filter, characterized by forming a corrosion-resistant film by doing A step of heat-treating at 500 ° C. to 1200 ° C. after forming a sol liquid film having a thickness of 0.1 to 2.5 μm by immersing the ceramic porous body in a sol liquid or coating the ceramic porous body on the ceramic porous body. 5. The method for producing a filter according to claim 4, wherein the corrosion-resistant film having a predetermined thickness is formed by repeating.

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