JP2007051033A - Porous ceramic support - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a porous ceramic support which has high gas diffusing performance, high strength and high durability. <P>SOLUTION: The porous ceramic support 10 is constituted to have communication holes 16 each having a sufficiently large diameter of about 0.3-1.5 mm, an extremely high porosity of about 55%, and a high mechanical strength of about 36 MPa in three-point bending strength by using a ceramic material such as La<SB>0.6</SB>Sr<SB>0.4</SB>Ti<SB>0.3</SB>Fe<SB>0.7</SB>O<SB>3</SB>excellent in steam resistance and reduction resistance. Thereby, the porous ceramic support has high gas diffusing performance, high strength and high durability. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a porous ceramic support having a large communication hole diameter and a high porosity.

  For example, in a ceramic filter for gas separation, a solid oxide fuel cell, or a membrane reactor using these, the thinner the gas separation membrane or the electrolyte membrane, the higher the separation speed, power generation amount, and the like. For this reason, gas separation membranes and electrolyte membranes are composed of thin films, and membranes are formed on porous supports (ie, asymmetric membranes) for the purpose of supplementing their mechanical strength.

The porous support as described above is required to have mechanical strength, gas diffusion performance, membrane retention, and the like so as to reliably support the membrane and not impair its characteristics. In the asymmetric membrane in which the support exists, the gas diffusion performance in the above-mentioned application affects the gas diffusion performance because the gas diffusion in the support is slow. Among the above characteristics, for example, in order to improve the gas diffusion performance, it is necessary to ensure the gas flow path by increasing the porosity and the diameter of the communication hole penetrating the front and back, and such a porous body is conventionally used. Various proposals have been made. For example, a support having a porosity (that is, a porosity) of 30 to 97 (%) and a ratio of communication holes to 80 to 100 (%) of all the holes has been proposed (see Patent Document 1). reference). This support is composed of porous ceramics, metal, etc., for example, sintering of coarse raw material powder, vaporization foam of water-insoluble organic solvent mixed with metal powder, lamination of metal felt, metal cloth, etc., etching A porous body is obtained by forming a through hole by machining or the like.
JP 2003-317740 A

  By the way, in solid oxide fuel cells, membrane reactors, etc., the support is exposed to high temperature, high pressure, reducing atmosphere, or steam atmosphere, so it has reduction resistance, steam resistance, and high mechanical strength. However, it is desired that the porosity and the diameter of the communication hole are as large as possible. For example, when oxygen or oxygen ions are allowed to permeate through the membrane, a reducing atmosphere is formed on the supply side of the gas containing oxygen, and when the supply gas contains hydrogen, methane, etc., water is bonded to oxygen to form water vapor. This is because it occurs.

  However, although Patent Document 1 describes a wide porosity range including a relatively large porosity as described above, the reduction resistance, water vapor resistance, mechanical strength, and membrane retention of the support are described. Etc. are not considered at all. Among the supports listed in Patent Document 1, for example, a metal material cannot provide sufficient corrosion resistance over a long period of time in the above atmosphere. On the other hand, according to the ceramic material, it is easy to ensure the corrosion resistance, but it is difficult to ensure the strength while increasing the porosity and the hole diameter. For example, Patent Document 1 merely describes an example in which the support is made of ceramics and has a porosity of 40% or less. This example has low performance because of its relatively low porosity, and it is not clear how much mechanical strength it has.

  The present invention has been made against the background of the above circumstances, and an object thereof is to provide a porous ceramic support having high gas diffusion performance, high strength and high durability.

In order to achieve such an object, the gist of the porous ceramic support of the present invention is that when it is left for 24 hours in a steam atmosphere of 1000 (° C.) where the composition ratio is H ₂ O / N ₂ = 2 The thickness change amount is less than 100 (μm) and is composed of a ceramic material that does not substantially change in structure when left in an H ₂ atmosphere at 1000 (° C.) for 24 hours, and within a range of 0.2 to 10 (mm) A large number of communicating holes, a porosity within a range of 50 to 99.9 (%), and a three-point bending strength of 10 (MPa) or more.

In this way, the porous ceramic support is configured to have a sufficiently large pore diameter and porosity and high mechanical strength using a ceramic material excellent in water vapor resistance and reduction resistance. Therefore, a porous ceramic support having high gas diffusion performance, high strength and high durability can be obtained. Note that when the thickness change amount when left in a steam atmosphere at 1000 (° C.) for 24 hours is 100 (μm) or more, the steam resistance is insufficient, and also in a H ₂ atmosphere at 1000 (° C.) for 24 hours. If the structure changes when left untreated, the reduction resistance is insufficient, and in any case, it cannot be used as a support for a solid oxide fuel cell, a membrane reactor or the like. Further, if the pore diameter is less than 0.2 (mm) or the porosity is less than 50 (%), the diffusion rate of the supplied gas is insufficient, so that sufficient device performance cannot be obtained. On the other hand, the larger the hole diameter of the communication holes, the more the characteristics tend to improve. However, when the diameter exceeds 10 (mm), it becomes difficult to form a film on the support, and when the porosity exceeds 99.9 (%), the mechanical strength is increased. It becomes difficult to secure. Further, in order to use it as a support, a three-point bending strength of 10 (MPa) or more is required.

  In this application, the three-point bending strength is a value obtained by a test method in accordance with JIS R1601 that defines a bending strength test method at room temperature. Therefore, measurement with high reproducibility is difficult. Therefore, the above strength is a value measured as a size of about 6 × 8 × 20 (mm), for example, by appropriately determining the shape of the test piece according to the hole diameter, porosity, etc. so that a stable measurement result can be obtained. It is. In the present application, the porosity is a value calculated by dividing the density calculated from the mass of the support and the volume when there is no opening such as a communication hole by the true density of the constituent material.

Here, preferably, the porous ceramic support is a general formula Ln _1-x Ae _x MO ₃ (where Ln is at least one selected from lanthanoids, and Ae is selected from Sr, Ca, Ba) At least one, M is selected from Fe, Ga, Ti, Al, In, Sn, Zr, V, Cr, Zn, Ge, Sc, Y, Nb, Mn, Co, Ni, Cu, Ru, Mg It is composed of at least one of perovskite composite oxide represented by 0 ≦ x ≦ 1), stabilized zirconia, alumina, cerium oxide, and magnesium oxide. Since these materials have a small difference in thermal expansion coefficient from the ceramic membrane provided on the surface of the support for the purpose of constituting a solid oxide fuel cell, a membrane reactor, etc., the adhesion strength between the support and the membrane is increased. There are advantages to being

  In addition, when perovskite complex oxide, stabilized zirconia or the like is used as a support material, the oxygen separation membrane or electrolyte membrane formed on the support and the support can be composed of the same material. Also, by matching or substantially matching the thermal expansion coefficients of both, even when heated or cooled during the manufacturing process or use, there is also an advantage that damage due to the difference in thermal expansion amount is suitably suppressed. is there.

Examples of the perovskite composite oxide include LaSrGaFeO ₃ , LaSrTiFeO ₃ , and LaSrGaMgO ₃ . These are particularly suitable because they have a relatively high water vapor resistance and a high reduction resistance. Moreover, since these are also electrolyte materials, they have excellent oxygen ion conductivity, and there is an advantage that oxygen can permeate the support itself.

  The constituent material of the porous support is not limited to the same material as the constituent material of the oxygen separation membrane or electrolyte membrane formed thereon. For example, when the required mechanical strength is relatively high, a high strength material such as stabilized zirconia or alumina is preferable regardless of the material of the film formed on the support.

  The stabilizer for the stabilized zirconia is not particularly limited, and those added with various stabilizers such as yttria, ceria and magnesia can be used. Further, in terms of oxygen permeability, a completely stabilized one is preferable, but not limited to this, a partially stabilized or semi-stabilized one is also preferable in terms of mechanical strength.

  The alumina is preferably high in purity, but may be low purity, for example, about 90 to 60 (%). Moreover, a composite material combined with zirconia or the like is also preferably used.

  Preferably, the porous ceramic support is made of a ceramic porous body obtained by impregnating an organic porous body having a three-dimensional network structure with slurry containing ceramic fine powder, and performing a drying treatment and a firing treatment. Is. That is, the porous ceramic support is produced by burning out the organic porous body by a firing treatment and sintering the impregnated ceramic fine powder. The ceramic porous body manufactured in this way has a high porosity as a whole while having high mechanical strength because the ceramics that form the framework of the three-dimensional network structure are densely sintered. It is particularly suitable as a support for ceramic filters having a high oxygen permeation amount, solid oxide fuel cells having high power generation characteristics, and membrane reactors using these.

  Preferably, in the ceramic porous body, a diameter of each bone part (that is, a substantial part) of the skeleton constituting the three-dimensional network structure is in a range of 100 to 1000 (μm). In this way, high gas diffusion performance can be obtained while ensuring sufficient mechanical strength. When the diameter is less than 100 (μm), the mechanical strength is low, and when it exceeds 1000 (μm), the ratio of the bone portion in the porous body increases, so the gas diffusion performance decreases.

  Preferably, the ceramic fine powder for producing the ceramic porous body has an average particle size in the range of 0.2 to 20 (μm). In this way, a ceramic porous body having a skeleton having the diameter as described above can be obtained.

  Preferably, the porous ceramic support includes a plurality of unfired ceramic thin plates each having a plurality of openings each having a predetermined shape, and each of the many openings is partially formed by another unfired ceramic thin plate. It is made of a plate-like ceramic obtained by laminating so as to be covered and firing. Since the plate-like ceramics produced by laminating a plurality of thin plate-like layers can be densely constructed, each of the laminated thin plates can have a high mechanical strength. As having a high porosity. In addition, since each of the thin plate-like layers generated from the unfired ceramic thin plate is in a positional relationship that partially covers the opening of the other layer, the size of the opening is relatively large and easy to form. However, the communication hole, that is, the gas flow path formed by them can be provided in an appropriate size. Therefore, it is particularly suitable as a support for a ceramic filter having a high oxygen permeation amount, a solid oxide fuel cell having high power generation characteristics, and a membrane reactor using these. The porous ceramic support of the present invention can also be produced by casting or the like, but is preferably composed of the ceramic porous body as described above or the plate-like ceramic as described above. In addition, it is not necessary that all the openings formed in one unfired ceramic thin plate are partially covered with another unfired ceramic thin plate, and the openings are not covered at all or are completely covered. There is no problem.

  Preferably, in the plate-like ceramic, the plurality of openings provided in each of the plurality of green ceramics each have a size within a range of 0.01 × 0.01 to 10 × 10 (mm). Provided and provided with a mutual interval within a range of 0.01 to 5 (mm). In this way, a porous ceramic support having a communication hole, that is, a gas flow path having an appropriate size after firing shrinkage can be obtained.

  Preferably, the porous ceramic support is used for a ceramic filter, a solid oxide fuel cell, or a membrane reactor (GTL or the like) using these. The use of the porous ceramic support of the present invention is not particularly limited, but is suitably used for these uses. For example, in a ceramic filter application, a gas separation membrane is provided on the support, and in a solid oxide fuel cell application, a solid electrolyte membrane is provided on the support.

The above-mentioned solid electrolyte membrane material may be appropriately selected depending on the desired properties, for example, LaSrGaFeO ₃ series (for example, La 35%, Sr 15%, Ga 30%, Fe 20% in mol ratio), LaSrTiFeO ₃ system (for example, La 30%, Sr 20%, Ti 15%, Fe 35% in mol ratio) and the like can be mentioned. Further, LaSrGaO ₃ system, LaSrGaMgCoO ₃ system, LaSrTiO ₃ system, LaSrTiMgCoO ₃ system and the like are also suitable.

  Preferably, the porous ceramic support has a flat plate shape. The shape of the ceramic porous body or the plate-shaped ceramic as described above is not particularly limited, and may be a cylindrical shape such as a cylinder or a square tube. Is preferred.

  Preferably, the porous ceramic support is formed by providing an electrolyte material on one surface thereof and firing it at the same time. Simultaneous firing is preferable in order to suppress firing due to differences in firing shrinkage of the unfired material and thermal expansion and shrinkage of the fired material. For example, when the porous ceramic support and the electrolyte membrane are made of the same material, the firing conditions coincide or substantially coincide with each other, so that simultaneous firing is possible.

  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 an entire porous ceramic support 10 (hereinafter referred to as support 10) according to an embodiment of the present invention. The support 10 is used as a support for a solid oxide fuel cell, for example, by forming an electrolyte membrane on the surface 12. The support 10 has a thin disk shape as a whole. A large number of communication holes 16 penetrating through are provided. The support 10 is formed by laminating, for example, about eight layers of thin plate-like layers 18a, 18b,. These are integrated in the firing process. The overall dimensions of the support 10 are appropriately determined according to the application, but are, for example, about φ22 × t2.5 (mm), and the thickness dimension of each layer is, for example, about 0.32 (mm).

  FIG. 2 is a plan view for explaining the configuration of the thin plate layer 18a. The thin plate-like layers 18b to 18h are also configured in the same shape. The opening 16a formed in each of the thin plate-like layers 18a to 18h has a basic shape of, for example, a rectangle with a size of about L = 4.0 (mm) and about W = 0.8 (mm). It has a shape deformed along its outer periphery. The mutual interval (g1, g2) of the openings 16a is about 0.4 (mm) in both the longitudinal direction and the direction orthogonal thereto. The support 10 is configured by sequentially laminating the plurality of thin plate-like layers, for example, in such a direction that the longitudinal directions of the openings 16a are orthogonal to each other. Therefore, the communication hole 16 formed by the intersection of these openings 16a has a hole diameter (approximately circular) of about 0.3 to 1.5 (mm), and penetrates straight from the front surface 12 to the back surface 14. It is a straight tubular hole. As a result, the support 10 has an extremely high porosity of, for example, about 55 (%).

The support 10 is made of a ceramic material excellent in water vapor resistance and reduction resistance required for a solid oxide fuel cell, for example, La _0.6 Sr _0.4 Ti _0.3 Fe _0.7 O _3. The skeleton portion other than the holes 16 is sintered densely. For this reason, the support 10 is a porous body having a high porosity as described above, and has a sufficiently high strength of, for example, about 36 (MPa) at a three-point bending strength.

Therefore, according to the support 10 of the present embodiment, a ceramic material such as La _0.6 Sr _0.4 Ti _0.3 Fe _0.7 O ₃ that has excellent water vapor resistance and reduction resistance is sufficiently used, and is about _0.3 to 1.5 (mm). It has high gas diffusion performance because it has a large communication hole 16 diameter and extremely high porosity of about 55 (%) and high mechanical strength of about 36 (MPa) at 3 point bending strength. High strength and high durability.

FIG. 3 is a process diagram for explaining the manufacturing method of the support 10. In the wet mixing process PA1, a solvent, a dispersant, a plasticizer, and a binder are added to the raw material, and wet mixing is performed using cobblestone or the like to prepare a slurry. The formulation specifications are, for example, as follows. In addition, as an organic binder, a methacryl resin can be used, for example.
[Formulation specifications]
Raw material: Average particle size 0.5 to 5 (μm) 100 parts by weight Dispersant: Nonionic surfactant 1 part by weight Plasticizer: Phthalate ester 5 parts by weight Binder: Organic binder 10 parts by weight Solvent: Xylene 50 parts by weight

  Next, in the viscosity adjustment step PA2, the viscosity of the slurry is adjusted according to the desired viscosity. For example, when the viscosity is high, a solvent is added to the slurry to reduce the viscosity, and when the viscosity is low, the slurry is vacuum dried while mixing to increase the viscosity. In this way, the viscosity is adjusted to 2000 (mPa · s), for example. Next, in the defoaming step PA3, the slurry is defoamed by, for example, filtering through a filter.

  Next, in the sheet forming step PA4, an unfired ceramic sheet (that is, an unfired ceramic thin plate) is formed from the slurry using an appropriate sheet forming method such as a doctor blade method. The molding thickness is appropriately determined according to the material characteristics, the use of the support 10, and the like, and is, for example, about 0.4 (mm) to 0.1 (mm). In the drying step PA5, the formed green ceramic sheet is dried at room temperature.

  Next, in the patterning step PA6, the unfired ceramic sheet is processed into a circular shape as shown in FIG. 2 and an opening 16a is formed by an appropriate processing method such as punching or laser processing. The processing dimensions are determined in consideration of firing shrinkage so that the dimensions of each part as described above can be obtained. For example, the outer diameter is about 27.5 (mm), and the dimension of the opening 16a is about L = 5.0 (mm). W = about 1.0 (mm) and g1 = g2 = about 0.5 (mm). Next, in the lamination step PA7, a plurality of circular ceramic sheets, for example, eight unfired ceramic sheets in which the openings 16a are formed, are in contact with each other so that the longitudinal directions of the openings 16a are orthogonal to each other, that is, staggered directions. Overlap and crimp so that

Next, in the electrolyte film forming step PA8, the electrolyte film is formed by, for example, placing a separately manufactured electrolyte film on one surface of the laminated body on which the unfired ceramic sheet is laminated and pressure bonded. As the electrolyte membrane, a material made of an appropriate material according to the application can be used. For example, a material made of La _0.6 Sr _0.4 Ti _0.3 Fe _0.7 O ₃ which is the same material as the support 10 is suitable.

Said electrolyte membrane is manufactured according to the process shown, for example in FIG. First, in the slurry preparation step PS1, for example, a solvent, a dispersant, a plasticizer, and a binder are added to the electrolyte raw material powder, and wet-mixed with cobblestone or the like to prepare a slurry. The formulation specifications are, for example, as follows. As the following organic binder, for example, a methacrylic resin can be used.
[Formulation specifications]
Raw material: Average particle size 0.5-3 (μm) 100 parts by weight Dispersant: Nonionic surfactant 1 part by weight Plasticizer: Phthalate ester 2.5 parts by weight Binder: Organic binder 5 parts by weight Solvent: Xylene 100 parts by weight

  Next, in the viscosity adjustment step PS2, the viscosity of the slurry is adjusted according to the desired viscosity. For example, when the viscosity is high, a solvent is added to the slurry to reduce the viscosity, and when the viscosity is low, the slurry is vacuum dried while mixing to increase the viscosity. In this way, the viscosity is adjusted to, for example, 1000 (mPa · s). Next, in the defoaming step PS3, the slurry is defoamed, for example, by filtering with a filter.

  Next, in the sheet forming step PS4, an electrolyte material sheet is formed from the slurry using an appropriate sheet forming method such as a doctor blade method. The molding thickness is appropriately determined according to the material characteristics, application, and the like, and is, for example, about 0.12 (mm). Next, in the drying step PS5, the molded electrolyte material sheet is dried at room temperature, for example.

  Returning to FIG. 3, in the electrolyte membrane forming process PA <b> 8, the electrolyte material sheet manufactured as described above is cut into an appropriate size according to the size of the laminate for constituting the support 10. And it forms into a film on the laminated body. Next, in the firing step PA9, a firing process is performed at a firing temperature corresponding to the constituent material of the support 10 and the electrolyte membrane, for example, about 1500 (° C.) sufficiently higher than the sintering temperature, for example, for about 6 hours. . Thereby, a plate-like layer 18 is generated from each of the unfired ceramic sheets constituting the laminate, and they are bonded to each other. At the same time, an electrolyte membrane is formed on one surface 12 thereof. That is, in this embodiment, the support 10 is not manufactured alone, but is manufactured by co-firing with the electrolyte membrane.

  Therefore, in this embodiment, a plurality of unfired ceramic sheets patterned so as to have a relatively large opening 16a as described above are laminated so that the directions of the openings 16a overlap each other, and the firing process is performed. Since the support 10 is manufactured by being applied, the opening 16a forms the communication hole 16 having a large hole diameter that penetrates straight from the front surface 12 to the back surface 14 and sinters other than the opening. High strength can be obtained. Therefore, by using a material excellent in water vapor resistance and reduction resistance as described above, a support having high gas diffusion performance, high strength and high durability can be obtained.

  FIG. 5 is a process diagram for explaining another method for manufacturing the porous ceramic support 10 or a method for manufacturing a support substantially similar to the above. This manufacturing method is different from the patterning method shown in FIG. 3 in the method for producing the unfired ceramic thin plate having the openings 16a, and the lamination process PA7 and the subsequent processes are performed in the same manner.

In FIG. 5, in the preparation process PB1, an extrusion raw material is prepared according to the following preparation specifications.
[Formulation specifications]
Raw material: Average particle size 0.5-5 (μm) 100 parts by weight Plasticizer: Alkyl glycol 5 parts by weight Binder: Cellulose 5 parts by weight Lubricant: Wax 2 parts by weight Solvent: Water 5 parts by weight

  Next, in the kneader mixing step PB2, the prepared raw materials are put into the kneader and stirred and mixed for a predetermined time, for example, about 10 minutes. Next, in the extrusion molding step PB3, the mixed extrusion raw material is molded using an extrusion molding machine. At this time, by using an appropriate shape for the die of the extrusion molding machine, a molded body having a cross-sectional shape as shown in FIG. 2 or a molding in which the size of each opening 16a is smaller or larger than this. A molded body having a lattice shape or the like in which the shape of the body or the opening 16a is different from that shown in FIG. 2 is obtained.

  Next, in the cutting step PB4, the extruded molded body is cut into a desired length dimension, for example, a length dimension of about 0.5 to 10 (mm) in the extrusion direction. This cutting process PB4 can be performed, for example, every time the molded body is extruded to the cutting length from the die simultaneously with the extrusion molding process PB3. In addition, it does not interfere even if a molded object is shape | molded by an appropriate length dimension, and after drying, it cut | disconnects to a desired length dimension. Next, in the drying step PB5, the molded body is subjected to a drying process to remove moisture. The porous ceramic support 10 can also be obtained by treating the molded body thus obtained, that is, the unfired ceramic thin plate, in the lamination step PA7 or lower.

  FIG. 6 is a perspective view schematically showing the configuration of the support 20 of another embodiment of the porous ceramic support of the present invention. The overall size of the support 20 is the same as that of the support 10, for example. Further, as shown in an enlarged electron micrograph in FIG. 7, the support 20 is provided with a skeleton 22 having a three-dimensional network structure, for example, a porosity of about 84 to 91 (%). It is configured. The hole diameter of the skeleton 22 is, for example, in the range of about 0.5 to 2.0 (mm), and the opening communicates while being bent from the front surface toward the back surface or the side surface. That is, it penetrates from the front surface to the back surface.

  Further, the support 20 is made of a ceramic material excellent in water vapor resistance and reduction resistance required for a ceramic filter or the like, for example, aluminum oxide, and the substantial part of the skeleton 22 is sintered densely. It has been made. Therefore, the support 20 is a porous body having a high porosity as described above, and has a relatively high strength of, for example, about 10 (MPa) at a three-point bending strength.

  Therefore, also in the support 20 of the present embodiment, a sufficiently large pore diameter of about 0.5 to 2.0 (mm) and about 84 to 91 (%) are sufficiently obtained using a ceramic material having excellent water vapor resistance and reduction resistance. Since it is configured to have a large porosity and a sufficiently high mechanical strength of about 10 (MPa), it has high gas diffusion performance, high strength and high durability.

  FIG. 8 is a process diagram for explaining the method of manufacturing the support 20 described above. In the slurry adjustment step PC1, first, 446.5 (g) of ceramic fine powder (for example, alumina fine powder), 16.0 (g) of talc, 36.5 (g) of Kibushi clay are placed in a polyethylene pot (2 L capacity), and water 155 ( g) and dispersant 12.5 (g) are added. Next, cobblestone (for example, alumina cobblestone, about φ10 (mm)) is charged to about 1/3 of a polyethylene pot, and stirred and mixed in a pot mill for about 5 hours. Next, 127.1 (g) of Ceramo TB-01 (Daiichi Kogyo Seiyaku Co., Ltd.), which is an organic binder, is added and further stirred for about 20 hours. Thereby, a slurry or slurry containing fine alumina powder is obtained.

  Next, in the slurry impregnation step PC2, an organic porous body having an appropriate three-dimensional network structure, such as urethane foam, is introduced into the prepared slurry, and the slurry is impregnated in the voids of the urethane foam. In the surplus slurry removing step PC3, the surplus slurry is extruded from the organic porous material with a roller or the like, for example, so that the necessary minimum slurry remains in the gap. Next, in the drying step PC4, a drying process is performed for about 24 hours at an appropriate temperature in the range of room temperature to 100 (° C.), for example, a temperature of about 70 (° C.).

  Next, in the electrolyte film forming process PC5, an electrolyte film is formed by placing the electrolyte material sheet manufactured according to the process shown in FIG. 4 on the surface of the organic porous body impregnated with the slurry. In the firing step PC6, a firing process is performed at an appropriate temperature according to the type of the raw material and the electrolyte membrane, for example, a temperature of about 1600 (° C.) for about 1 hour. As a result, the organic porous body and the organic components in the slurry are burned off, and a ceramic porous body that follows the pore shape of the organic porous body is generated from the slurry. At the same time, an electrolyte membrane is generated from the electrolyte material sheet. These are fixed to each other. That is, also in the present embodiment, the electrolyte membrane is formed simultaneously with the production of the support 20.

  Therefore, in the present example, the ceramic porous body to be formed has a three-dimensional network structure according to the shape of the organic porous body. The support 20 that penetrates the back surface substantially straight is obtained. At this time, since the substantial part of the skeleton 22 has a high strength by sufficiently sintering the ceramic material, a high mechanical strength can be obtained while having excellent gas diffusion performance as described above. It will be. That is, since the size and porosity of the pores depend on the structure of the organic porous body and do not depend on the sintered state of the ceramic material, a high porosity can be ensured even if the sintering temperature is increased. Therefore, by using a material excellent in water vapor resistance and reduction resistance as described above, a support having high gas diffusion performance, high strength and high durability can be obtained.

FIG. 9 is a process diagram for explaining a method for producing a porous ceramic support by a casting method according to still another embodiment of the present invention. In the slurry preparation step PD1, for example, a solvent, a dispersant, a plasticizer, a binder, and a pore forming agent are added to the raw material, and wet-mixed with cobblestone or the like to prepare a slurry. The formulation specifications are as follows. The raw material is, for example, La _0.6 Sr _0.4 Ti _0.3 Fe _0.7 O ₃ or the like as in the case of the support 10, and the particle diameter of the pore forming agent is, for example, in the range of 50 (μm) to 3 (mm). . Also in this blending specification, for example, a methacrylic resin can be used as the organic binder.
[Formulation specifications]
Raw material: Average particle size 0.5 to 5 (μm) 100 parts by weight Dispersant: Nonionic surfactant 1 part by weight Plasticizer: Phthalate ester 5 parts by weight Binder: Organic binder 10 parts by weight Solvent: Xylene 30 parts by weight Pore formation Agent: Walnut shell or carbon 10 parts by weight

  Next, in the viscosity adjustment step PD2, the viscosity of the slurry is adjusted according to the desired viscosity. For example, when the viscosity is high, a solvent is added to the slurry to reduce the viscosity, and when the viscosity is low, the slurry is vacuum dried while mixing to increase the viscosity. In this way, the viscosity is adjusted to, for example, about 3000 (mPa · s) suitable for casting.

  Next, in the casting step PD3, for example, it is poured into a gypsum mold, cured, and taken out from the mold and cast-molded. The size and shape of the gypsum mold are appropriately determined according to the size and shape of the support to be manufactured in consideration of shrinkage during firing. Next, in the drying step PD4, for example, a drying process is performed at a temperature of about 80 (° C.).

  Next, in the electrolyte film forming process PD5, an electrolyte film is formed by placing an electrolyte material sheet manufactured according to the process shown in FIG. 4 on the surface of the molded body. In the firing step PD6, a firing process is performed at an appropriate temperature according to the type of the raw material and the electrolyte membrane, for example, a temperature of about 1600 (° C.) for about 1 hour. As a result, the organic components in the molded body, that is, the dispersant, the plasticizer, the pore-forming agent, and the like are burned off, and the raw material particles are sintered to form a porous ceramic support, and at the same time, the electrolyte material sheet is used as an electrolyte. A membrane is formed and adhered to the support surface to obtain a solid oxide fuel cell element.

  According to the production method of the present embodiment, using the ceramic material as described above excellent in water vapor resistance and reduction resistance, for example, the average pore diameter is about 0.1 to 0.5 (mm), the porosity is 50 to 60 A sufficiently large (%) support can be obtained. Since the three-point bending strength is somewhat low, about 1 to 5 (MPa), this manufacturing method is suitable when the required mechanical strength is relatively low.

  Hereinafter, the results of evaluating the characteristics of the elements of the solid oxide fuel cell manufactured using various raw materials in the above-described configuration examples and manufacturing method examples will be described.

  Table 1 below shows the composition and particle size of the support material and the electrolyte membrane material used in the evaluation. First, as a first step, the basic characteristics of the support material were evaluated. Evaluation items are oxygen mobility (that is, oxygen ion conductivity), water vapor resistance, and reduction resistance, which are desired for solid oxide fuel cell applications. Further, in order to secure the adhesion strength with the electrolyte membrane, it is desired that the difference in thermal expansion coefficient is small, so the thermal expansion coefficient was also evaluated at the same time. The results are shown in Table 2.

In Table 2 above, “O” in the “Oxygen Mobility” column indicates an oxygen transfer amount of 2 (cc / min / cm ² ) or more, “△” indicates around 1 (cc / min / cm ² ), “×” Means much lower than 1 (cc / min / cm ² ). In terms of oxygen mobility, La-based perovskite composite oxide and cerium oxide are preferable, and zirconium oxide is next preferable. However, since the support 10 and the like are configured to be porous as described above to secure a gas flow path to the electrolyte membrane, higher oxygen mobility is preferable but not essential. That is, even if the oxygen mobility is evaluated as “x”, it can be used as the support of the present invention.

  The numerical value in the “water vapor resistance” column is the amount of change in thickness measured with a scanning electron microscope (SEM) after being left in a 1000 (° C.) water vapor atmosphere (water vapor / nitrogen gas = 2) for 24 hours. . The smaller the value, the less the structural change and the better the water vapor resistance. According to the above evaluation results, silicon oxide is extremely inferior in water vapor resistance and is not suitable for applications such as solid oxide fuel cells. In addition, perovskite composite oxides other than titanium oxide, silicon nitride, and LaSrTiFe have a thickness change of about 20 to 50 (μm) and can be used, but are slightly inferior in water vapor resistance. In terms of water vapor resistance, aluminum oxide, zirconium oxide, cerium oxide, and LaSrTiFe-based perovskite composite oxides that do not change in thickness are preferable.

The column “Reduction resistance” is the result of confirming the structural change with an X-ray diffractometer (XRD) after being left in an H ₂ atmosphere at 1000 (° C.) for 24 hours. The structural change was quantified from the peak height of the measurement data, and the amount of subphase was expressed as a percentage. In Table 2, “no change” means that no subphase is observed, that is, no structural change occurs. According to the above evaluation results, silicon oxide, aluminum oxide, zirconium oxide, silicon nitride, LaSrGaFe, LaSrTiFe, LaSrGaMg have sufficiently high reduction resistance, and titanium oxide, cerium oxide, LaSrCoFe, LaSrMnFe have reduction resistance surfaces. Is insufficient.

In this evaluation test, LaSrGaFeO ₃ , LaSrTiFeO ₃ , LaSrGaO ₃ , LaSrGaMgCoO ₃ , LaSrTiO ₃ , and LaSrTiMgCoO ₃ are used as electrolyte membrane materials as shown in Table 1 above. It is preferable that the thermal expansion coefficients are approximate. For example, when the electrolyte is LaSrGaFeO ₃ or LaSrTiFeO ₃ , it is desirable that the thermal expansion coefficient of the support is about 11 × 10 ⁻⁶ (/ K). According to the measurement results described in the “Coefficient of thermal expansion” column, silicon oxide and silicon nitride are inappropriate because of their extremely small coefficients of thermal expansion. In addition, aluminum oxide, titanium oxide, and cerium oxide have a slightly low coefficient of thermal expansion, but the lack of adhesion strength between the support and the electrolyte membrane can be compensated to some extent by the structure. There is no hindrance.

From the above results, it can be seen that the support material is preferably aluminum oxide, zirconium oxide, LaSrGaFeO ₃ , LaSrTiFeO ₃ , or LaSrGaMgO ₃ . Although not described in the above evaluation results, LaSrGaO ₃ is also preferable because it has the same characteristics as the three perovskite complex oxides.

  Tables 3 and 4 below show the results of evaluating the characteristics of the porous ceramic support produced by the three kinds of production methods using the above five raw materials. However, in these evaluations, a baking treatment was performed immediately without forming an electrolyte membrane in each of the above production methods, and a support without an electrolyte membrane was produced to produce a test piece. In Tables 3 and 4, “Ceramic Home” indicates the support 20 manufactured in the manufacturing process shown in FIG. 8, and “Pattern” indicates the support 10 manufactured in the manufacturing process shown in FIG. 3 or FIG. means.

Table 3 above shows the measurement results of the porosity. The porosity (%) shown here is obtained by measuring the mass (g) and volume (cm ³ ) of the test piece, and calculating the following formula (1) from these and the true density (g / cm ³ ) known in advance. This is the value calculated in. The volume of the test piece is, for example, a value obtained by measuring the diameter (longitudinal and horizontal dimensions in the case of a rectangular bottom surface) and the thickness dimension, and multiplying the bottom area by the thickness dimension, that is, the surface It is the value calculated | required as what does not have the open pore which appears in FIG. In any case, a large porosity of 50 (%) or more is obtained. That is, the porosity is remarkably increased as compared with the conventional case where the support is only about 30%. In particular, it can be seen that a support (ceramic home) made of a ceramic porous body having a three-dimensional network structure whose process is shown in FIG. 8 can easily provide a support having a porosity exceeding 80%.
Porosity = (mass / volume / true density) × 100 (1)

  Table 4 shows the measurement results of bending strength. The three-point bending strength was measured by using a universal testing machine (Model 1123 manufactured by Instron) and measuring the number of test pieces at 5 in accordance with JIS R1601 that defines the bending strength test method at room temperature. Since the porous material of this example is difficult to measure with the test piece dimensions defined in JIS, the test piece dimensions are shown in FIG. 3 showing the manufacturing process and the casting process shown in FIG. Was set to 10 (mm) x 10 (mm) x 300 (mm), and the ceramic home was set to 10 (mm) x 20 (mm) x 300 (mm). According to the above measurement results, a very high strength cannot be obtained in the case of casting molding, but a sufficiently high strength can be obtained as a porous support in the ceramic home and patterning. In particular, the patterning has a remarkably high strength while having a porosity slightly smaller than casting.

  Therefore, according to the measurement results of the porosity and bending strength described above, it is clear that a cast-molded support can be used, but ceramic home and patterning are particularly preferable.

Next, the results of evaluating the oxygen permeation amount and the power generation characteristics of the solid oxide fuel cell using the support made of each of the above materials will be described. In the evaluation, an electrolyte membrane having a film thickness of 100 (μm) and a diameter of 30 (mm) was provided on the support, Ni was used as the fuel electrode catalyst, and La _0.8 Sr _0.2 CoO ₃ was used as the air electrode catalyst. The fuel electrode catalyst may not be provided. The test conditions were as follows: the device temperature was 800 (° C), the fuel electrode was methane or hydrogen at a speed of 200 (cc / min / cm ² ), and the air electrode was air at a speed of 500 (cc / min / cm ² ). It was supposed to be sent in each. The electrolyte membrane was provided on the fuel electrode side of the support. That is, the support was configured to be positioned on the air electrode side.

  FIG. 10 is a schematic diagram for explaining a power generation test method. An electrolyte membrane 24 is provided on the front surface 12 of the support 10 or the like, and an air electrode catalyst 26 is provided on the back surface 14. A fuel electrode catalyst 28 is provided on the electrolyte membrane 24. Further, a load 30 is provided between the air electrode and the fuel electrode so that the amount of power generation can be measured. The oxygen permeation test is performed by measuring the amount of oxygen permeating to the fuel electrode side with the same element configuration. Table 5 shows the oxygen permeation test results, and Table 6 shows the power generation measurement results.

  As shown in Table 5 above, an extremely large amount of oxygen permeation was obtained with the ceramic home and the support formed by patterning regardless of the constituent material. Also in the casting method, although not as much as the above two, a large oxygen permeation amount was obtained as compared with the conventional support. The reason why the support produced by the casting method is slightly inferior is considered to be due to the large bending of the pores in the support. That is, since the ceramic home and patterning have a remarkably large hole diameter, the communication hole penetrates substantially straight from the front surface to the back surface. Therefore, it is considered that the high characteristics as described above can be obtained.

  In Tables 5 and 6 above, the “conventional support” has characteristics of a porosity of about 30 (%) and a pore diameter of about 10 (μm). It is produced by a so-called unsintered method in which a fired raw material powder is formed and fired. Since such a conventional support has a small porosity and a small pore diameter, the support determines the oxygen diffusion in the solid oxide fuel cell. For this reason, it is considered that a high oxygen permeation amount was not obtained even when a high-performance electrolyte material was used. According to the casting method, ceramic home, and patterning of this example, the porosity and the hole diameter are both greatly increased as compared with the conventional support, so that it is considered that extremely high characteristics can be obtained.

  Further, as shown in Table 6 above, it was confirmed that in the power generation measurement results, a high power generation amount was obtained in all of the casting method, the ceramic home, and the patterning as compared with the conventional support. In particular, according to the ceramic home and patterning, a remarkably high power generation amount that is twice or more that of the conventional method can be obtained.

  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.

It is a perspective view which shows the porous ceramic support body of one Example of this invention which formed the opening part for forming a communicating hole by patterning. It is a top view which shows the non-fired ceramic sheet for comprising the porous ceramic support body of FIG. It is process drawing explaining the principal part of an example of the manufacturing method of the porous ceramic support body of FIG. It is process drawing explaining the principal part of the manufacturing method of the electrolyte membrane used for the electrolyte membrane forming process of FIG. FIG. 5 is a process diagram for explaining another method for producing the porous ceramic support of FIG. 1. It is a perspective view which shows typically the porous ceramic support body of the other Example of this invention which has a three-dimensional network structure. It is an electron micrograph for magnifying a part of porous ceramic support of Drawing 6, and explaining a structure. It is process drawing explaining the principal part of the manufacturing method of the porous ceramic support body of FIG. It is process drawing explaining the principal part of the casting method which is a manufacturing method of the further another Example of this invention. It is a figure explaining a power generation test method.

Explanation of symbols

10: porous ceramic support, 12: front surface, 14: back surface, 16: communication hole, 16a: opening, 18: thin plate layer, 20: support, 22: skeleton, 24: electrolyte membrane, 26: air electrode Catalyst, 28: Fuel electrode catalyst, 30: Load

Claims (4)

When the composition ratio is left in a steam atmosphere of 1000 (° C.) with H ₂ O / N ₂ = 2 for 24 hours, the amount of change in thickness is less than 100 (μm) and 24 hours in an H ₂ atmosphere of 1000 (° C.) It is composed of a ceramic material that does not substantially change its structure when left to stand, and has a large number of communication holes having a pore diameter in the range of 0.2 to 10 (mm), and a porosity in the range of 50 to 99.9 (%). A porous ceramic support having a three-point bending strength of 10 (MPa) or more. General formula Ln _1-x Ae _x MO ₃ (where Ln is at least one selected from lanthanoids, Ae is at least one selected from Sr, Ca, Ba, M is Fe, Ga, Ti, Al, In, Perovskite composite represented by 0 ≦ x ≦ 1), at least one selected from Sn, Zr, V, Cr, Zn, Ge, Sc, Y, Nb, Mn, Co, Ni, Cu, Ru, and Mg The porous ceramic support according to claim 1, comprising any one of oxide, stabilized zirconia, alumina, cerium oxide, and magnesium oxide.   2. The porous ceramic support according to claim 1, comprising a porous ceramic body obtained by impregnating an organic porous body having a three-dimensional network structure with slurry containing ceramic fine powder, and performing a drying treatment and a firing treatment. Laminating and firing a plurality of unfired ceramic thin plates each having a large number of openings of a predetermined shape so that each of the large numbers of openings is partially covered with other unfired ceramic thin plates The porous ceramic support according to claim 1, comprising a plate-like ceramic obtained by: