JP5258700B2 - Porous body with coating - Google Patents

Description

The present invention relates to a porous body decomposing hardly porous body and is joined with other ceramics when bonding with other ceramics.

  For example, it has been proposed to obtain a large or complex structure having high heat resistance and wear resistance by bonding ceramics to each other (see, for example, Patent Documents 1 and 2). Hard and brittle ceramics are limited in the shape that can be processed, and the processing cost increases significantly when trying to obtain a complicated shape. Is done.

  Further, for example, silicon-based ceramics such as silicon nitride have high strength and high heat resistance and wear resistance, and are therefore used in structural component materials such as internal combustion engines for the purpose of improving thermal efficiency and reducing weight. . In addition, in power generation system applications such as pressurized fluidized bed combustion combined power generation and coal gasification combined power generation, for the purpose of improving thermal efficiency, for example, a dust removal filter or gas separation filter that can be used at a high temperature of about 1000 (° C) or higher, Development of membrane reactors such as molten carbonate fuel cell power generation systems with operating temperatures of 800 ° C or higher is underway. In such applications, even when the size is increased for the purpose of improving the processing capacity, an inexpensive manufacturing technique by bonding is useful.

  Conventionally, various ceramic bonding methods have been proposed. For example, there is one in which silicon nitride ceramics are bonded to each other using an alloy containing silicon (Si) and calcium (Ca) or magnesium (Mg) (see, for example, Patent Document 1). In this joining method, Ca and Mg are considered to play a role of improving the wettability by lowering the melting point of the alloy as the joining material. In addition, there is one in which ceramic sintered bodies having the same composition are joined to each other using a metal or an alloy thereof which is a constituent component of the ceramic sintered body (see, for example, Patent Document 2). According to these joining methods, even if the shape is complicated, joining is easy as compared with a method of performing diffusion joining by pressurizing the abutted interface and performing a diffusion joining or a fitting method using a difference in thermal expansion. In addition, since the melted metal or alloy enters the gaps between the sintered ceramics, smoothness of the joint surface is not required, so there is an advantage that precision machining of the joint surface is unnecessary. Moreover, according to the joining method of Patent Document 2, since the metal at the joint is homogenized with the object to be joined by performing nitriding treatment or oxidation treatment after joining, the high-temperature strength and heat resistance of the joint are increased. It is done.

  However, the conventional ceramic joined body has not yet had sufficient heat resistance at the joint. Accordingly, the applicants of the present application proposed joining silicon-based ceramics in a high-temperature and high-vacuum state using a joining material obtained by adding aluminum (Al) or germanium (Ge) to metal silicon (Patent Document 3, See 4). According to these technologies, the silicon ceramics and the bonding material are integrated because the silicon ceramic components and Si, Al, and Ge are interdiffused, so the heat resistance is high and the strength is high. The body is obtained.

Japanese Patent Application Laid-Open No. 61-13269 Japanese Patent No. 3057932 JP 2006-182597 A JP 2007-112687 A JP 2006-282419 A JP 2007-153700 A JP 2009-007230 A JP 2009-007232 A

  By the way, the joined body described in Patent Documents 3 and 4 is used for a gas separation membrane module by forming a gas separation membrane on the surface of a porous body, for example. Since it becomes difficult to bond strength, the film forming process is performed after the bonding process. However, in the joining methods described in Patent Documents 3 and 4, since the members are heated to a high temperature at the time of joining, the objects to be joined are decomposed and the surfaces thereof are easily covered with decomposition products. If the surface is covered with the decomposition product, it becomes difficult to form a uniform and reproducible gas separation membrane on the surface. This problem is conspicuous in a porous body having a large surface area, and is particularly problematic in a non-oxide material that is easily decomposed. Moreover, when bonding is performed under high temperature and high vacuum as shown in Patent Documents 3 and 4, decomposition is more likely to occur. Conventionally, many proposals have been made regarding the joining of porous bodies, but none of the above-described attention has been paid to the decomposition during joining, and suppression of this has not been considered.

  For example, porous ceramics having an average pore diameter of 10 to 150 (μm), a maximum pore diameter of 230 (μm) or less, and 95% or more of the entire pores of 200 (μm) or less are joined to other ceramics with a brazing material. A technique has been proposed (see, for example, Patent Document 5). By satisfying these conditions, penetration of the brazing material into the pores is suppressed, and the air permeability is not impaired. In addition, by heat treatment at 750 to 1700 (° C.), an oxide film is formed on the inner and outer surfaces of the silicon carbide porous ceramic, and another silicon carbide ceramic is bonded to the film forming portion using a silicon brazing material. It has been proposed (see, for example, Patent Document 6). According to this joining technique, joining can be performed without impairing the air permeability of the porous ceramics.

  Further, when bonding porous bodies made of silicon carbide or between porous bodies and dense bodies using silicon or the like as a bonding material, the porous bodies are heat-treated in the atmosphere to remove residual carbon, or nitriding aluminum or boron There has been proposed a method in which an object is infiltrated into a porous body, carbon is applied to a joining surface, and joining is performed through a joining material (see, for example, Patent Documents 7 and 8). According to these techniques, since the bonding material is prevented from excessively penetrating into the porous body, a sufficient amount of the bonding material exists at the bonding interface, so that high bonding strength can be obtained.

  However, none of the above contributed to the suppression of the decomposition of the objects to be joined at the time of joining. In addition, as described in Patent Document 6, it may be possible to suppress decomposition by forming an oxide film on the surface of the porous ceramic, but the strength of the porous ceramic is reduced during the oxidation treatment. There is also a problem. In addition, as disclosed in Patent Document 8, it is considered that the decomposition of the surface layer portion of the porous body can also be suppressed by infiltrating the nitride, but this technique is a post-process because the pores are blocked by the nitride. Therefore, it is necessary to remove this, so that it is difficult to apply to applications where a film is formed after bonding.

The present invention has been made against the background of the above circumstances, and an object of the present invention is to provide a porous body that does not easily decompose under high temperature and high vacuum.

In order to achieve such an object, the gist of the coated porous body of the present invention includes (a) a large number of pores having a pore diameter of 0.01 to 10 (μm) opening on the outer surface. A base material made of porous non-oxide ceramics, and (b) provided so that the outer surface of the base material does not block the numerous pores and is not exposed in the vicinity of the outer surface. And a dense film made of ceramic derived from the polysilazane material.

Thus to lever, on the outer surface of the substrate made of a non-oxide ceramic porous, as coating dense consisting polysilazane-based material from the ceramic is not exposed the substrate at the outer surface near Since it is provided, the heat resistance of the base material is enhanced. For example, the decomposition of the base material is suppressed even under a high temperature of 1200 (° C.) or higher and a high vacuum of 100 (Pa) or lower. When the coating has sufficient heat resistance and is difficult to decompose, the substrate is protected by the coating, but the substrate is decomposed even if the heat resistance is insufficient. The gas partial pressure in the vicinity of the outer surface of the substrate changes to form an atmosphere in which the substrate is difficult to decompose. For this reason, for example, when joining to other members made of ceramics using a metal brazing material, even if the base material is exposed to the atmosphere as described above, its decomposition is suppressed, and as a result, Since the outer surface is suppressed from being covered, film formation does not become difficult after bonding. That is, the decomposition of the base material can be suppressed while maintaining the heat treatment conditions at the time of joining, which are difficult to change because they are determined according to the metal brazing material used. In addition, since the coating made of the ceramic derived from the polysilazane material is provided without blocking many pores on the outer surface of the substrate, the air permeability of the substrate is kept equal to the case where the coating is not provided. It is. Note that “without blocking” ideally means a state in which all of the pores opening on the surface are not blocked, but some pores can be used as long as the air permeability before film formation is maintained. Including the case where is blocked. The polysilazane-based material is a substance composed of Si, N, H, and C. For example, [—Si (H) (CH ₃ ) —NH—], [—Si (CH ₃ ) ₂ —NH—], and [ It consists of a repeating structure having —SiH ₂ —NH—] as a basic unit. The polysilazane-based material is allowed to stand at room temperature or subjected to a baking treatment to undergo a crosslinking / polymerization reaction to turn into a ceramic, and to form a thin film on the outer surface of the substrate. At this time, since the volume shrinks and densifies, what is on the opening is fixed to the peripheral edge or the inner peripheral surface of the opening, so that a coating covering the outer surface is formed without closing the opening.

Here, preferably, the film with the porous body, the polysilazane-based material is applied to the outer surface of the base material, the number by performing a baking process at a temperature in the range of 1300 to 1500 (° C.) A film made of a ceramic covering the outer surface of the base material without closing the pores is generated from the polysilazane material. In order to sufficiently accelerate the crosslinking / polymerization reaction, the firing temperature needs to be 1300 (° C.) or higher, and in order to maintain the porosity of the substrate, the firing temperature needs to be 1500 (° C.) or lower.

Also, preferably, the film with the porous body is a conjugate other parts material made of ceramics is bonded via a metal brazing material. Thus, since the degradation of the substrate during the bonding it is suppressed by coating, because the decomposition products are not generated on the outer surface, easily forming a film in a later step on the outer surface of the joint body it can.

Preferably, the polysilazane material is organopolysilazane or perhydropolysilazane. Although port Rishirazan based material can be used having the composition as appropriate, for example, organopolysilazane and perhydropolysilazane is preferably used.

The coated porous body of the present invention can be applied to any oxide ceramics such as alumina (Al ₂ O ₃ ) and non-oxide ceramics such as silicon nitride (Si ₃ N ₄ ). When applied to non-oxide ceramics that are easily decomposed when exposed to high temperatures compared to oxide ceramics, a particularly remarkable effect is obtained. Examples of non-oxide ceramics to which the present invention is applied include sialon (SiAlON), silicon carbide (SiC), aluminum nitride (AlN) and the like in addition to the above silicon nitride.

  Preferably, the substrate and the coating are each made of silicon nitride. The composition of the coating produced from the polysilazane-based material differs depending on the atmosphere during the crosslinking / polymerization reaction. For example, silica is produced in an oxidizing atmosphere, and silicon nitride is produced in a nitrogen atmosphere or an ammonia atmosphere. A substrate made of silicon nitride is suitable as a support for the gas separation membrane, but the coating is made of the same material or the same system material as the substrate from the viewpoint of preventing breakage due to differences in the amount of thermal expansion. It is preferable. Therefore, when the substrate is made of silicon nitride, the coating is preferably made of silicon nitride.

  Preferably, the pore diameter of the large number of pores is within a range of 0.01 to 10 (μm). If it does in this way, the said porous body with a film can be used suitably as a support body of a gas separation membrane. Considering the thickness required to ensure the mechanical strength required for the support, if the pore diameter is less than 0.01 (μm), the air permeability is remarkably lowered, so that the separation performance cannot be obtained. On the other hand, when the pore diameter exceeds 10 (μm), defects tend to occur in the separation membrane formed on the outer surface.

The material of the prior SL other member is not particularly limited, also applies to non-oxide ceramics to oxide ceramics. However, the material of the base material, the coating film, the other members, and the brazing material is preferably determined in consideration of the coefficient of thermal expansion and the bonding property so that high bonding strength can be obtained. For example, when silicon-based ceramics are used as the substrate, it is preferable that the coating film and other members are also composed of silicon-based ceramics, and it is preferable to use a silicon-based brazing material as the brazing material. In this way, since the base material and the other member are integrated through the brazing material by diffusion of other constituent elements of silicon and ceramics to each other during joining, the constituent members are integrated with high joint strength. A joined body having a complicated structure can be obtained.

  Further, in the case where each constituent member is a silicon-based ceramic as described above, it is preferable that the brazing material is a Si—Al alloy brazing material having a weight ratio of 9: 1. The joining with the member is preferably performed by heating to 1400 (° C.) in an atmosphere of 100 (Pa) or less. Since silicon has a high melting point, it is difficult to use it alone as a brazing material, but when aluminum that forms a eutectic (also called eutectic mixture) with silicon at a lower melting point is mixed, the mixing ratio is increased. Accordingly, the melting point of the brazing material is lowered. Since the melting point becomes lower as the mixing amount increases, it is preferable that the aluminum mixing amount is small in order to ensure the heat resistance of the joined body. However, in order to suppress the decomposition and deformation of the silicon-based ceramics, the mixing of aluminum is preferable. It is preferable to keep the treatment temperature during bonding to 1400 (° C.) or less by increasing the amount sufficiently. The weight ratio is determined so that the heat treatment temperature is 1400 (° C.) in consideration of these balances. In order to suppress decomposition of the silicon-based ceramics and oxidation of the brazing material during the bonding process, it is desirable that the degree of vacuum is as high as possible, and at least 100 (Pa) or less is preferable. Incidentally, since silicon and aluminum are easily oxidized, the brazing material becomes difficult to melt if the degree of vacuum in the heating atmosphere is low.

  In addition, when joining the silicon-based ceramics with the Si-Al alloy brazing as described above, in order to airtightly join the base material and other members, the brazing material is used under a high vacuum of 100 (Pa) or less. It is preferable to heat at a temperature 10-50 (° C.) higher than the melting point. For example, when the 9: 1 Si—Al alloy brazing as described above is used, the processing temperature is 1400 to 1450 (° C.). However, when the substrate is made of silicon nitride, it is easily decomposed at this temperature. There's a problem. Theoretically, due to the relationship between the standard free energy of formation of silicon nitride and the temperature, 1400 (° C.) easily decomposes at 100 (Pa) or less. In particular, in the case of a porous material, since the surface area is large, it becomes easier to decompose.

Preferably, the porous body with a coating comprises: (a) an application step of applying the polysilazane material to the outer surface of the substrate; and (b) a temperature within a range of 1300 to 1500 (° C.). It is manufactured by each process including a baking process in which a coating film made of ceramics covering the outer surface is formed from the polysilazane-based material without blocking the numerous pores by performing a baking process.
Preferably, the manufacturing method includes a drying step of drying the substrate coated with the polysilazane-based material in a non-oxidizing atmosphere after the coating step, and the baking in the non-oxidizing atmosphere after the drying. Including a preliminary heat treatment step in which heat treatment is performed at a lower temperature than the step, and the firing step is performed after the preliminary heat treatment step. If the baking process is carried out immediately after the coating process or just by performing the drying process, defects such as cracks may occur in the coating produced from the polysilazane-based material, but by applying the preliminary heat treatment process as described above The occurrence of defects can be suppressed. The drying step is performed, for example, at room temperature under a nitrogen atmosphere, and the preliminary heat treatment step is performed, for example, at a temperature within the range of 600 to 800 (° C.), for example, 650 (° C.), under an ammonia atmosphere.

  Preferably, after the preliminary heat treatment step, a second coating step of coating the polysilazane material on the film generated from the polysilazane material by the preliminary heat treatment, and a drying treatment in a non-oxidizing atmosphere are applied thereto. A second drying step to be applied, and a second preliminary heat treatment step in which heat treatment is performed at a temperature intermediate between the baking step and the preliminary heat treatment step in a non-oxidizing atmosphere after the drying. This is performed after the preliminary heat treatment step. By repeating the coating and preliminary heat treatment in this manner, the possibility of defects in the coating can be reduced, and the film thickness can be easily controlled. That is, the coating can be provided with an appropriate film thickness according to the required protection performance. The second drying step is performed, for example, at room temperature under a nitrogen atmosphere, and the second preliminary heat treatment step is performed, for example, at a temperature within a range of 800 to 950 (° C.), for example, 950 (° C.), under an ammonia atmosphere.

  Preferably, the firing step is performed in a nitrogen atmosphere. In this way, a film made of silicon nitride is formed on the surface of the substrate. For example, when the base material is made of silicon nitride, it is preferable to use a nitrogen atmosphere in order to form the coating film with a similar material. For example, as described above, when the firing step is performed in a nitrogen atmosphere, the preliminary heat treatment step and the second preliminary heat treatment step are preferably performed in a non-oxidizing atmosphere such as the ammonia atmosphere described above.

Preferably, in the coating step, the polysilazane material is diluted with an appropriate solvent and the substrate is immersed in the solution. In this way, the polysilazane material can be easily applied to the surface of the substrate.

It is a perspective view which shows the whole support body of one Example of the porous body with a film of this invention. It is a figure explaining the cross-sectional structure of the support body of FIG. 1, Comprising: (a) showed the part in a longitudinal direction, (b) expanded and showed the b part of (a) typically. is there. It is a figure which expands and shows the surface vicinity of the cross section of FIG.2 (b). It is process drawing for demonstrating the manufacturing method of the support body of FIG. It is a perspective view which shows the whole joining body which joined the support body of FIG. 1 of multiple pieces with the end cap. It is a figure explaining the cross-sectional structure of the conjugate | zygote of FIG. It is an electron micrograph of the base-material surface which has not provided the film. It is an XRD chart of the base-material surface of FIG. It is an electron micrograph of the support surface which provided the film. 10 is an electron micrograph of the surface after the support of FIG. 9 has been subjected to high temperature and high vacuum treatment. It is a XRD chart of the support surface of FIG. It is an electron micrograph of the surface after giving the high temperature and high vacuum process to the base material of FIG. FIG. 13 is an XRD chart of the substrate surface in FIG. 12.

  Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings. In the following embodiments, the drawings are appropriately simplified or modified, and the dimensional ratios, shapes, and the like of the respective parts are not necessarily drawn accurately.

  FIG. 1 is a perspective view showing the entire support 10 which is an embodiment of the coated porous body of the present invention. The support 10 is a porous body having a bottomed cylindrical shape, and has, for example, an outer diameter of about 12 (mm), an inner diameter of about 9 (mm), and a length dimension of about 500 (mm). Yes.

  As schematically shown in the cross-sectional structure in FIGS. 2A and 2B, the support 10 has a coating 14 made of a dense ceramic covering the outer peripheral surface of a substrate 12 made of a porous ceramic. It is provided. The base material 12 includes an inner layer 16 having a thickness dimension of about 1.5 (mm) located on the inner peripheral side, and an outer layer 20 having a thickness dimension of about 20 to 50 (μm) covering the surface 18 of the inner layer 16. ing. The coating 14 is provided with a film thickness of about 200 (nm) which is much thinner than the outer layer 20.

  The inner layer 16 is a porous body having a pore diameter of 1.0 (μm) or more and a porosity of about 30 to 38 (%), for example. The outer layer 20 is a porous body having a pore diameter of 0.3 (μm) or less and a porosity of about 42 to 50 (%), for example. That is, the outer layer 20 has a smaller pore diameter and a higher porosity than the inner layer 16. Both the inner layer 16 and the outer layer 20 are made of silicon nitride containing alumina and yttria as sintering aids. The coating 14 is also made of similar silicon nitride, and the support 10 is entirely made of silicon nitride.

  FIG. 3 is a cross-sectional view schematically showing an enlarged vicinity of the surface 22 of the outer layer 20. The outer layer 20 is provided with a large number of pores 24 that open to the surface 22. The inner layer 16 shown in FIG. 2B is also provided with a large number of pores (not shown) that open to the inner peripheral surface 26, and the pores 24 communicate with the pores of the inner layer 16. Therefore, the base material 12 is provided with a large number of pores penetrating between the inner and outer peripheral surfaces 22 and 26.

  In FIG. 2 (b), the entire surface of the substrate 12 is drawn so as to be completely covered with the coating 14, but this is a typical state in which the coating 14 is provided on the entire surface. It is shown in The actual film formation state is as shown in FIG. 3, and the coating 14 is formed on the surface 22 of the outer layer 20 and the inner wall 28 of the pore 24 that opens to the surface 22 in the vicinity of the surface 22. They are formed along the surface 22 and the inner wall surface 28. The coating 14 is dense with a porosity of approximately 0 (%). However, since the coating 14 is formed with a thin film thickness along the inner wall surface 28 and the like, the pores 24 are blocked. Not. Further, since the coating film 14 is formed along the irregularities of the surface 22 of the outer layer 20 as described above, the outer layer 20 is not exposed at least in the vicinity of the surface 22.

Incidentally, when the hydrogen gas permeation rate of the base material 12 was compared before and after the formation of the coating film 14, before the formation of the coating film 14, it was about 5 × 10 ^{−6 to} 9 × 10 ⁻⁶ (mol / m ² / Pa / s). On the other hand, after the formation, it was about 5 × 10 ^{−7 to} 7 × 10 ⁻⁷ (mol / m ² / Pa / s). Although the pore diameter was slightly reduced by forming the coating film 14 on the inner wall surface 28 of the pore 24, it was confirmed that a sufficiently high hydrogen gas permeation rate was maintained after the formation.

  FIG. 4 is a process diagram for explaining a method of manufacturing the support 10, that is, a method of forming the coating film 14 on the substrate 12. In FIG. 4, in the dipping step P1, a base material 12 made of a porous silicon nitride bottomed cylinder having the above-mentioned characteristics is prepared and immersed in a polysilazane solution. The polysilazane solution was prepared, for example, by diluting perhydropolysilazane (product number: NCP100H) manufactured by Chisso Corporation to about 30% with a solvent such as toluene. The impregnation time is about 10 seconds, for example, and the polysilazane solution penetrates into the surface layer portion of the substrate 12.

  Next, in the drying step P2, the base material 12 taken out from the polysilazane solution is placed in a glove box, and left for about 3 hours at room temperature in a nitrogen atmosphere, for example, to perform a drying process. Since polysilazane easily undergoes crosslinking and polymerization reaction even at room temperature, if it is left in the air in this drying step P2, it will be difficult to perform nitriding in a later step.

  Next, in the ammonia firing step P3, the base material 12 taken out from the glove box is subjected to a firing treatment at, for example, 650 (° C.) in a high purity ammonia atmosphere of, for example, 3N or more. As a result, the organic solvent in the solution is burned out, and polysilazane is crosslinked and polymerized to form a film made of silicon nitride. The holding time at the peak temperature is, for example, about 1 hour.

  Next, in the dipping step P4, as in the dipping step P1, the substrate 12 is immersed in a polysilazane solution, and polysilazane is applied on the film generated in each of the above steps. In this step, the concentration of the polysilazane solution is 10 (%), but other conditions are the same as those in the dipping step P1. As a result, a polysilazane film thinner than the process P1 is formed on the film generated from polysilazane.

  Next, in the drying step P5 and the ammonia firing step P6, the drying treatment is performed in the same manner as the drying step P2, and then the firing treatment is performed in an ammonia atmosphere. The firing conditions are the same as in the ammonia firing step P3 except that the peak temperature is 950 (° C.). Thereby, a silicon nitride film is laminated on the surface of the silicon nitride film.

  The dipping step P4 to the ammonia baking step P6 are performed as a precaution so that the silicon nitride film is formed on the surface of the substrate 12 without any defects. If no defects occur, the second film is formed. The forming process is unnecessary. Moreover, when a defect can occur even in two steps, the steps P4 to P6 can be repeated as necessary.

  Next, in the nitriding treatment step P7, the base material 12 on which the silicon nitride film is formed is subjected to a firing treatment at 1400 (° C.), for example, in a high purity nitrogen atmosphere of 3N or more. The holding time at the peak temperature is, for example, about 1 hour. By thus heating in a nitrogen atmosphere, the silicon nitride film formed in the steps P1 to P6 is completely nitrided and densified to obtain the coating film 14. That is, the support 10 is obtained.

  FIG. 5 shows a joined body 30 which is an example of a utilization mode of the support 10 on which the coating 14 is formed as described above. The joined body 30 is prepared by, for example, preparing seven support bodies 10 and joining them to a disc-shaped end cap 32 which is separately manufactured, and integrating them. Is provided with a porous membrane functioning as a gas separation membrane after bonding. Thereby, since the specific gas according to the pore diameter of the porous film can selectively permeate between the outer peripheral surface of the porous film and the inner peripheral surface of the support 10, the specific gas is changed from the mixed gas. A gas separation membrane module for separating the gas is obtained. For example, when used for hydrogen separation, a porous membrane having a pore diameter of about 0.5 (nm) may be provided.

  FIG. 6 is a cross-sectional view showing a cross section of the bonded body 30 along the longitudinal direction of the support 10. The end cap 32 is made of, for example, dense silicon nitride, and includes seven stepped holes 34 penetrating in the thickness direction. An open end of the support 10 is inserted into the stepped hole 34 from the large diameter side, and is airtightly fixed by a brazing material 38 in a state of being abutted against the annular protrusion 36 on the small diameter side. The brazing material 38 is made of, for example, about 90 (wt%) Si and about 10 (wt%) Al.

  According to the gas separation membrane module in which the porous membrane is provided on the support 10 of the bonded body 30 configured as described above, for example, when a mixed gas is supplied from the outer periphery of the support 10, the pore diameter of the porous membrane is larger than that of the porous membrane. A gas having a sufficiently small moving diameter passes through the peripheral wall 40 and flows into the support 10, and flows out from the small diameter portion of the stepped hole 34 of the end cap 32 through the open end. Therefore, if the gas separation membrane module is disposed in the airtight container and the stepped hole 34 of the end cap 32 is connected to the outside of the airtight container, the desired gas is separated and recovered from the mixed gas supplied into the airtight container. can do. Note that the mixed gas supply side and the separation gas recovery side may be configured oppositely to the above.

  By the way, joining of said support body 10 and end cap 32 is performed as follows, for example. First, a binder and a solvent are added to a mixed powder of Si powder and Al powder for constituting the brazing material 38 to prepare a brazing material paste. As the Si powder, for example, an average particle diameter of about 15 (μm) is used, and as the Al powder, for example, an average particle diameter of about 18 (μm) is used. The binder is, for example, an acrylic resin, and the solvent is, for example, terpineol. In preparing the paste, a mixed powder of Si powder and Al powder was mixed with a binder, and a solvent was added to adjust the viscosity.

  Next, the paste is applied to the end cap 32 and the support 10, and the support 10 and the end cap 32 are assembled as shown in FIGS. 5 and 6. Next, for example, by performing a heat treatment at 1400 (° C.) and 0.1 (Pa) for about 1 hour, the binder and the solvent in the paste are burned off, and the mixed powder is melted, and the produced brazing material 38 ends. The cap 32 and the support body 10 are joined. The heat treatment temperature is set to a temperature sufficiently higher than this because the melting point of the mixed powder is about 1375 (° C.).

  Moreover, formation of a porous membrane is performed as follows, for example. First, polysilazane is diluted with an appropriate organic solvent such as toluene to prepare a film forming solution. The concentration of the solution is appropriately determined according to the film thickness to be formed, and is, for example, about 50 to 60 (wt%). Next, the support 10 is immersed in the film-forming solution, and the solution is adhered to the surface of the support 10 and dried at, for example, room temperature to 100 (° C.). The immersion time is appropriately determined according to the viscosity, composition, etc. of the solution, and may be, for example, about 5 to 10 seconds. Note that various known methods such as a spin coating method, a spray method, and a transfer method may be used instead of the coating method as described above. The number of coatings is determined so as to obtain a desired film thickness, and is once or twice or more. Next, for example, by performing a baking process at 650 (° C.) in an ammonia atmosphere, the organic solvent is burned out, and a silicon nitride film is formed from polysilazane by a crosslinking / polymerization reaction.

  As described above, the support 10 of this embodiment is used by being joined to the end cap 32 and further provided with a porous membrane. As described above, the bonding is performed at a high temperature and high vacuum of 1400 (° C.) and 0.1 (Pa), as described above. However, the substrate 12 is kept in a substantially initial state without being decomposed. As a result, in forming the porous membrane after joining, the porous membrane is firmly fixed to the support 10 without unevenness, so that a separation membrane module with high separation performance can be obtained.

Here, the test result which evaluated the difference in the heat resistance of the support body 10 and the base material 12 by the presence or absence of the said film | membrane 14 is demonstrated. FIG. 7 is an electron micrograph of the surface of the substrate 12 on which the coating film 14 is not provided, and FIG. 8 is an XRD chart of the surface. Below this XRD chart, the peak position of silicon nitride (Si ₃ N ₄ ) is shown. On the surface of the base material 12, fine and uniform crystals derived from the finely divided silicon nitride raw material are arranged and have a relatively smooth surface property. Further, according to the XRD chart, only the silicon nitride peak is recognized from the surface of the base material 12. In addition, since the alumina and yttria contained as a sintering aid are trace amounts, a remarkable peak is not generated to the extent that it can be observed.

  FIG. 9 is an electron micrograph of the surface of the support 10 in which the coating film 14 is provided on the substrate 12. Since the coating 14 is extremely thin, as is apparent from comparison with FIG.

FIG. 10 is an electron micrograph of the surface after the support 10 is subjected to heat treatment under the same high temperature and high vacuum of 1400 (° C.) and 0.1 (Pa) as the above-mentioned bonding treatment conditions. In contrast to FIG. 9, changes in the surface properties are recognized but remain slight. FIG. 11 shows an XRD chart of the surface of FIG. Below the XRD chart, the peak position of silicon nitride is shown in the upper part, and the peak position of alumina (Al ₂ O ₃ ) is shown in the lower part. As is clear from comparison with the XRD chart before the heat treatment shown in FIG. 8, although a small peak of alumina is observed slightly, the peak of silicon nitride is substantially maintained. As shown in FIGS. 10 and 11, even when the support 10 is subjected to heat treatment under high temperature and high vacuum, the decomposition hardly occurs.

FIG. 12 is an electron micrograph of the surface after the base material 12 not provided with the coating 14 is subjected to heat treatment under the same high temperature and high vacuum of 1400 (° C.) and 0.1 (Pa) as the bonding processing conditions. . Compared with FIG. 7 before the heat treatment, it can be seen that the surface properties are remarkably changed by the heat treatment and large irregularities are generated. The degree of change is significantly different from that in FIG. FIG. 13 shows an XRD chart of the surface of FIG. Below the XRD chart, the peak positions of silicon nitride, yttrium aluminum garnet (Al ₅ Y ₃ O ₁₂ : YAG), aluminum yttrium (Al ₂ Y), and yttria (Y ₂ O ₃ ) are shown in order from the top. The peak of other compounds of silicon nitride appears prominently, and it is clear that decomposition occurred by heat treatment.

  According to the above test results, the base material 12 is decomposed by heat treatment under high temperature and high vacuum at the time of joining using the brazing material 38 unless any treatment is performed, but this is a coating made of silicon nitride derived from polysilazane. The support 10 provided with 14 is sufficiently suppressed from being decomposed under the same heat treatment conditions. In addition, when the decomposition product by heat processing arises on the surface of the base material 12, it will become difficult to provide the porous membrane which functions as the said separation membrane on the surface uniformly and with sufficient reproducibility. Since the decomposition is suppressed by providing the coating 14, there is an advantage that the porous film can be firmly fixed without defects.

  In short, according to the present embodiment, since the coating film 14 made of polysilazane-derived silicon nitride is provided on the surface 22 of the base material 12 made of porous silicon nitride, the heat resistance of the base material 12 is enhanced, Decomposition is also suppressed during heat treatment at high temperatures and high vacuum of 1400 (° C) and 0.1 (Pa). For this reason, when the Si—Al alloy brazing material 38 is used to join the end cap 32, decomposition of the base material 12 is suppressed, so that a porous membrane that functions as a separation membrane can be easily formed thereafter. Moreover, since the coating film 14 does not block the pores of the substrate 12, there is an advantage that the air permeability that is inferior when the coating film 14 is not provided is maintained.

  In addition, according to the present embodiment, the base material 12 is made of silicon nitride, which is one of non-oxide ceramics that are likely to be decomposed at the time of joining, so that the effect of providing the coating film 14 can be obtained more remarkably.

  Moreover, according to the present Example, since the coating film 14 is formed in two layers by repeating the application, drying, and baking processes of polysilazane twice, the coating film 14 is formed as compared with the case where it is composed of only one layer. Defects are unlikely to occur. Therefore, there exists an advantage which can suppress further decomposition | disassembly of the base material 12 at the time of joining.

  As mentioned above, although this invention was demonstrated in detail with reference to drawings, this invention can be implemented also in another aspect, A various change can be added in the range which does not deviate from the main point.

10: support, 12: base material, 14: coating, 16: inner layer, 18: surface, 20: outer layer, 22: surface, 24: pore, 26: inner peripheral surface, 28: inner wall surface, 30: joined body , 32: End cap

Claims (4)

A substrate made of porous non-oxide ceramics having a large number of pores having a pore diameter of 0.01 to 10 (μm) opening on the outer surface;
A dense coating made of a ceramic derived from a polysilazane material provided so as not to block the large number of pores on the outer surface of the base material and so that the base material is not exposed in the vicinity of the outer surface. A porous body with a film characterized by the above. The coated porous body according to claim 1 , wherein the polysilazane material is organopolysilazane or perhydropolysilazane . The polysilazane-based material is applied to the outer surface of the base material, the outer surface of the substrate without occluding the number of pores by applying a baking treatment at a temperature in the range of 1300 to 1500 (° C.) The porous body with a coating according to claim 1 or 2, wherein a coating made of ceramic to cover is produced from the polysilazane-based material . A coated porous body according to any one of claims 1 to 3 other parts material made of ceramics are those that are joined via a brazing filler metal.