JP2007001860A - Porous ceramic thin plate and method of manufacturing ceramic sheet using thin plate - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a porous ceramic thin plate efficiently used as a spacer or the like for obtaining a ceramic sheet having excellent surface smoothness by suppressing wave or dimple caused by the shrinkage in degreasing and firing when the ceramic sheet such as an electrolyte membrane for a flat solid electrolyte type fuel cell which suffers large lamination load or thermal stress in a state that many ceramic sheets are laminated is manufactured by firing a green sheet. <P>SOLUTION: The porous ceramic thin plate has frictional coefficient of ≤1.5 and 0.0005 m/s×kPa air permeability measured by a specific method and the method of manufacturing the ceramic sheet uses the porous thin plate. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a porous ceramic thin plate and a method for producing a ceramic sheet using the thin plate. The porous ceramic thin plate of the present invention has a smooth surface, a small coefficient of friction, and excellent air permeability. This ceramic thin plate is used as a material for a flat solid electrolyte fuel cell such as a solid electrolyte membrane, for example. When the ceramic sheet to be manufactured is manufactured by firing the ceramic green sheet, it can be effectively used as a setter on which the ceramic green sheet is placed, or a spacer when the green sheets are stacked and fired.

  For example, the structure of a flat solid electrolyte fuel cell is a cell in which anodes and cathode electrodes are attached to both sides of a solid electrolyte, or a cell in which a number of cells each having an electrolyte and a counter electrode are vertically stacked on the electrode surface. Stacks are fundamental, and at this time, each cell is placed close to each other, and a separator (interconnector) is placed between each cell so that fuel gas and air do not mix, and the electrolyte membrane and the periphery of the cell The part and separator are sealed and fixed. In addition, when there is a manifold inside the battery cell, the periphery is also sealed and fixed.

  This separator is generally made of a heat-resistant alloy or ceramic having a large specific gravity, and has a considerable mass because it is a considerably thick sheet. Moreover, the ceramic sheet used as the constituent material of the fuel cell is desired to be relatively light and thin. Furthermore, since the operating temperature of the solid oxide fuel cell is as high as about 800 to 1000 ° C., the constituent material is subjected to a large stacking load and undergoes considerable thermal stress.

  On the other hand, since a ceramic sheet such as a zirconia sheet is hard and vulnerable to external forces in the bending direction, if there are irregularities, undulations, etc. on the surface of the ceramic sheet used as a constituent material for fuel cells such as a solid electrolyte membrane, The laminating load and thermal stress are concentrated at the place, causing cracks and cracks, and the power generation performance is drastically reduced.

  Therefore, the present inventors have further studied to improve the performance and extend the life of the fuel cell by reducing the above-mentioned loading load and cracking due to thermal stress of the ceramic sheet used for the solid electrolyte membrane of the fuel cell. As part of that research, we confirmed that the occurrence of cracks and cracks could be suppressed as much as possible if the sheet warpage and maximum undulation height were kept below a certain level. (Patent Document 1, Patent Document 2).

  The ceramic sheet presented in the above publication can withstand considerable stacking load and thermal stress even if it is a thin and fairly large sheet, so that the power generation capacity as a fuel cell can be greatly increased. It is expected as an extremely effective technology for industrial application of batteries.

In any case, the ceramic sheet used for the solid electrolyte membrane has no warpage, undulation, dimples, etc., and must have a smooth surface, but a ceramic sheet excellent in such surface smoothness can be stably obtained. It is never easy. The dimple is basically a concave portion or a convex portion generated independently on the surface of the sheet, and is distinguished from the undulation continuously generated like a wave because the cause of occurrence is different.
JP-A-8-151270 JP-A-8-151271

  As a manufacturing method of the ceramic sheet, a ceramic green sheet manufactured by an extrusion method or the like is placed on a setter made of a heat-resistant material, or a plurality of ceramic green sheets are stacked and fired. In that case, firing is performed by sandwiching a heat-resistant porous ceramic sheet as a spacer between the ceramic green sheets so as not to cause bonding or the like. At this time, in order to obtain a ceramic sheet with excellent smoothness, it is important to increase the smoothness of the green sheet as a raw material. There is no guarantee that the green sheet will be excellent in surface smoothness, often unexpected undulation, dimples, etc. may occur, resulting in poor surface smoothness. The reason is considered as follows.

  That is, as the spacer used in firing the green sheet, a ceramic sheet fired in advance is used, and therefore, the spacer hardly shrinks in the green sheet firing process. On the other hand, the green sheet shrinks to a length of about 70 to 90% and an area of about 50 to 80% in the course of burning and sintering due to thermal decomposition of an organic polymer or the like contained as a binder. In the sintering process, a sliding force acts between the green sheet and the spacer.

  At this time, if the sliding between the green sheet and the spacer occurs smoothly, the shrinkage caused by the degreasing / sintering of the green sheet occurs evenly over the entire surface, so that the obtained ceramic sheet does not deform locally. . However, in reality, the slip between the green sheet and the spacer does not always occur smoothly, and a local tensile force or compressive force may act on the green sheet surface due to uneven slip on the overlapping surface of both. In addition, non-uniform internal stress is generated on the surface of the green sheet to be sintered due to the tensile force and compressive force, which causes undulation and dimples. Moreover, in the degreasing / sintering process, as described above, a large amount of cracked gas is generated along with the combustion or thermal decomposition of the organic binder, but if the release and removal of the cracked gas becomes uneven on the surface of the sheet, the resulting ceramic sheet Pinholes, dimples, undulation, etc. occur on the surface, causing product defects.

  The present invention has been made in consideration of such a situation. When a ceramic sheet used for, for example, a flat solid electrolyte membrane is manufactured by degreasing and firing a green sheet, as a spacer or the like at the time of degreasing and firing. Providing a porous ceramic thin plate that can be used to produce ceramic sheets with excellent surface smoothness without pinholes, dimples, or undulations, and a method for producing ceramic sheets using the thin plates There is to do.

The porous ceramic thin plate according to the present invention that has solved the above problems has a friction coefficient of 1.5 or less measured by the following method,
(Friction coefficient measurement method) Maximum stress when a R36W felt specified in JIS L3201 is attached to a weight with a bottom area of 15 cm ² and moved over a porous ceramic thin plate at a distance of 10 cm at 100 mm / min. Is obtained by dividing the weight by 75 g.
Preferably, the invention is further characterized in that the air permeability is 0.0005 m / s · kPa or more.

  In the porous ceramic thin plate of the present invention, the requirements for the coefficient of friction are satisfied, preferably the requirements for the air permeability are further satisfied, and further the surface undulation height is 50 μm or less and the dimple height is 50 μm or less. Some are preferred, and the thickness is preferably less than 1 mm. This porous ceramic thin plate has a small coefficient of friction on the surface, excellent slipperiness, and high air permeability. Therefore, it can be effectively used as a spacer when producing a ceramic sheet requiring surface smoothness.

  Further, the method for producing a ceramic sheet according to the present invention is to produce a ceramic sheet by stacking a plurality of ceramic green sheets and firing the porous ceramic thin plate between the ceramic green sheets. It is characterized in that a ceramic sheet having excellent surface smoothness without pinholes, dimples, undulations, etc. is obtained by sandwiching so that the peripheral edge of the metal does not protrude and usually firing in an air atmosphere.

  The porous ceramic thin plate of the present invention has a specified coefficient of friction as described above, or has been further specified for air permeability. A ceramic sheet is produced by degreasing and firing a green sheet using the thin plate as a spacer. In this case, it is possible to obtain a ceramic sheet having excellent surface smoothness by suppressing undulation and dimples due to shrinkage due to the degreasing and firing.

  Therefore, the ceramic sheet obtained using this porous ceramic thin plate has excellent stacking load resistance and heat stress resistance as a constituent material of a solid electrolyte membrane for a flat solid electrolyte fuel cell, for example, and is in operation. Generation of cracks and cracks can be suppressed as much as possible, and it is possible to manufacture a fuel cell with high performance and greatly improved durability.

  Moreover, the porous ceramic thin plate of the present invention, in addition to the spacer for firing the green sheet, makes use of its excellent friction coefficient and air permeability, and firing jigs such as a heat insulating material, a base plate, a setter, and a weighting material, Can also be effectively used for building materials such as sound-absorbing materials, damping materials, and water-permeable materials.

  Under the above-described problems, the present inventors produce a ceramic sheet that requires a high level of surface smoothness, particularly as a constituent material of a flat solid electrolyte fuel cell, by degreasing and firing a green sheet. At the same time, as a result of conducting research while paying attention to the spacer disposed between the green sheets, the friction coefficient of the porous ceramic thin plate sandwiched as the spacer as described above is specified, and preferably the air permeability is further increased. If specified, ceramics with excellent surface smoothness that can suppress pinholes, dimples, undulation, etc. caused by uneven tensile stress and compressive stress, or non-decomposition of cracked gas as described above, which occurs during degreasing and firing of green sheets. Knowing that the sheet can be manufactured reliably, the present invention has been conceived.

  Hereinafter, the reason why the characteristics of the porous ceramic thin plate are determined will be described in detail.

  First, the porous ceramic thin plate of the present invention should have a surface friction coefficient of 1.5 or less, more preferably 1.2 or less, and still more preferably 1.0 or less, obtained by the above-described method. . That is, when the green sheet is degreased and fired using the spacer as a spacer as described above, the friction coefficient of the thin sheet is made smooth by sliding with the thin sheet surface accompanying the shrinkage of the green sheet. This is an extremely important characteristic for preventing the occurrence of non-uniform tensile force and compressive force. When the friction coefficient exceeds 1.5, the green sheet is degreased and fired locally between the thin plates. In the vicinity of this, a tensile force and a compressive force are generated, and this causes not only pinholes, dimples, and undulation, but also extremes that cause tears. However, when a thin plate having a friction coefficient of 1.5 or less is used, even when the green sheet contracts during degreasing and sintering, the green sheet slides smoothly along the contraction on the surface of the thin plate. Since no local tensile force or compressive force is generated, the surface smoothness of the finally obtained ceramic sheet is very excellent.

  Next, it is necessary for the porous ceramic thin plate to smoothly dissipate the decomposition gas generated when the green sheet is degreased and fired, and to prevent pinholes and dimples due to local outgassing defects. Therefore, it is desirable that the air permeability is 0.0005 m / s · kPa or more, more preferably 0.001 m / s · kPa or more, and still more preferably 0.005 m / s · kPa or more. Therefore, if the air permeability of the thin plate is less than 0.0005 m / s · kPa, the outgassing at the time of degreasing / sintering of the green sheet becomes poor or uneven, and the effect of preventing the occurrence of pinholes and dimples is insufficient. Sometimes. The pore diameter is not particularly limited as long as such air permeability is satisfied, but the larger the pore diameter, the better the air permeability and the better the gas escape, so the average pore diameter is 0.5 μm or more, more preferably 1 μm. More preferably, the thickness is 5 μm or more.

  And in order to prevent the said obstruction at the time of green sheet degreasing and baking reliably, it is essential to satisfy | fill the said friction coefficient, However, In addition to this friction coefficient, what satisfy | fills the said air permeability requirements is preferable.

  Further, in order to more effectively exert the above-described effects according to the present invention, the surface property of the porous ceramic thin plate is that the undele height is 50 μm or less, more preferably 20 μm or less, and the maximum dimple height is 50 μm or less. It is desirable to use one having a thickness of 20 μm or less. If there are high undulations and dimples on the surface of the thin film, stress in the sliding direction concentrates on the protruding parts and obstructs smooth sliding. By suppressing them as much as possible, Smooth sliding can be ensured.

  The method for measuring the height of the sea urchins and dimples is not particularly limited. For example, a laser optical three-dimensional shape measuring apparatus is used to irradiate the sheet surface with laser light and analyze the reflected light in a three-dimensional shape. be able to. In other words, a laser optical three-dimensional shape measuring device is used when a ceramic sheet surface to be measured is irradiated with laser light to focus on the surface of the sheet, and the reflected light is uniformly imaged on a photodiode. Non-contact type micro-tertiary with a structure in which the lens is controlled so that the focal point of the objective lens is always in focus with the sheet surface by generating a signal that immediately cancels this when the image becomes uneven with respect to the displacement of the surface By detecting the amount of movement of the original shape analyzing apparatus, the unevenness of the sheet surface to be measured can be detected in a non-contact manner. The resolution is usually 1 μm or less, more preferably 0.1 μm or less. By using such an apparatus, the undulation and dimple height on the sheet surface can be accurately detected.

  Further, the surface roughness is preferably in the range of 0.1 to 5 μm in terms of the average roughness Ra, and even if the surface roughness is too rough or too smooth, the tendency of slippage tends to be deteriorated.

Further, it is desirable that the porous ceramic thin plate be as thin and light as possible. As described above, when the green sheet is degreased / sintered in a multi-layered state, if the porous ceramic thin plate disposed between the green sheets becomes thicker, the weight in the laminated state increases and the stacking load is increased. Therefore, in order to keep the lamination load as small as possible, it is desirable to use a thin and lightweight porous ceramic thin plate itself, and the thickness is 1 mm. Less than 0.8 mm, more preferably less than 0.8 mm, still more preferably 0.5 mm or less, and a weight of 0.15 g / cm ² or less, more preferably 0.1 g / cm ² or less, still more preferably 0.08 g / cm ^2. It is desirable to make it less than about. However, if the thickness is too thin, the strength is insufficient and the handling property may be adversely affected. Therefore, the thickness is preferably about 0.1 mm or more.

Still other preferable requirements for the porous ceramic thin plate according to the present invention include high temperature stability and strength. That is, the porous ceramic thin plate of the present invention is mainly used as a spacer when degreasing and firing a green sheet as described above, and is exposed to high temperature during use. Therefore, the size and breathability change under the degreasing and firing conditions. In particular, it is preferable to have a high temperature stability and, more specifically, a material having a shrinkage ratio of 1% or less and a decrease in air permeability of 1% or less even when heated to 1500 ° C. In addition, it is desirable that the bending strength is excellent in order to ensure stable handling and to prevent cracking during degreasing and firing, and it is desirable that the three-point bending strength × (thickness) ² is 5 N or more. Those are preferred.

Since the size of the porous ceramic thin plate varies depending on the size of the green sheet to be degreased and sintered, it cannot be uniformly determined, but the effect is more effectively exhibited when the surface area on one side is 100 cm. It is a large version of ² or more.

  As described above, the porous ceramic thin plate of the present invention is characterized in that the air permeability and the coefficient of friction are specified, and preferably the swell and dimple height are made as small as possible. As the porosity of the thin plate is increased to increase the undulation and dimples, the flatness of the surface decreases and the friction coefficient tends to increase.

  Therefore, in order to reduce the friction coefficient, it is desirable to adopt the following method. One method is to improve the surface smoothness by polishing the surface of a porous ceramic thin plate obtained by firing, or by sandwiching it in a flatter ceramic plate and refiring. However, in these methods, in addition to increasing the number of steps, the ceramic thin plate may be cracked in the surface polishing or re-baking step, resulting in a decrease in yield. When firing the sheet, it is desirable to employ a method in which a weight having a high surface smoothness is placed and firing is performed to prevent deformation during firing as much as possible. However, when firing with a weight, if the gas generated by the thermal decomposition of the organic binder is hindered by the weight, it will cause undulation and dimples. It is desirable to use a weight made of a porous body having a porosity of about 20% or more so that the gas can be released quickly.

  Further, in order to allow the decomposition gas to be diffused uniformly during the firing, the heating rate is adjusted according to the generation rate of the decomposition gas, or the atmospheric gas (hot air) in the vicinity of the green body to be fired is adjusted. It is effective to improve the distribution of

At this time, if the load of the weight is small, the flattening effect due to the load will be insufficient, and if it is too heavy, the green bodies will adhere to each other, or the escape of decomposition gas will be poor and undulation and dimples are likely to occur. Therefore, it is recommended to use a weight in the range of 0.05 to 1 g / cm ² . At this time, in order to prevent the bonding between the green bodies, it is very effective to interpose the powder for preventing adhesion on the overlapped surface, and interposing the powder is effective for degassing the cracked gas. It is preferable because it works effectively for promotion.

  The powder used here preferably has an average particle size in the range of 0.3 to 100 μm, and the powder having a particle size of less than 0.3 μm is too fine, so that the above-mentioned bonding prevention effect and decomposition gas emission promotion effect are effective. In particular, in the case of inorganic powder, the powder itself may be fused to the surface of the porous ceramic thin plate at the time of sintering. On the other hand, in the case of coarse particles exceeding 100 μm, the surface of the obtained porous ceramic thin plate There is a risk that the roughness increases and the friction coefficient increases. Considering such advantages and disadvantages, the more preferable average particle diameter of the powder is 2 μm or more and 80 μm or less, and further preferably 5 μm or more and 60 μm or less. Particularly preferred as the powder is one having few coarse particles, and 90% by volume of particles are 200 μm or less, more preferably 100 μm or less.

  The powder may be either organic or inorganic, but particularly preferred is an organic powder. Thus, the inorganic powder not only remains on the surface of the porous ceramic thin plate even after firing, but may be fused to the surface of the porous ceramic thin plate depending on the type, which may make it difficult to remove after firing. However, if it is an organic powder, it will be burned off under the firing conditions, so that the removal work by post-treatment is unnecessary. After the green body has been fired to become a porous ceramic thin plate, the porous ceramic thin plates are no longer likely to be bonded to each other, and the diffusion of the organic binder component is complete. There is no problem even if it does not remain. However, depending on the type of porous ceramic thin plate, it is also effective to use a small amount of inorganic powder together with the organic powder and leave a small amount of powder until the end of sintering. Even when the inorganic powder is used, it is preferable that the amount of the organic powder used is 50% by mass or more, more preferably 60% by mass or more, and still more preferably 80% by mass or more.

  The organic powder is not limited in its kind as long as it is burned off under the firing conditions as described above, natural organic powder, acrylic resin powder, sublimation resin powder such as melamine cyanurate, etc. Among these, organic powders such as wheat flour, corn starch (corn starch), sweet potato starch, potato starch, and tapioca starch are particularly preferred. This is because the starchy powder is a fine powder having a substantially spherical shape and a uniform particle size, contains almost no impurities, and has a very excellent action as a lubricant. These organic powders may be used alone or in combination of two or more as necessary.

  The kind of the inorganic powder is not particularly limited, but preferred is a natural or synthetic oxide or non-oxide such as silica, alumina, zirconia, titania, mullite, boron nitride, silicon nitride, aluminum nitride, silicon carbide. In addition to carbon, etc., these can be used alone, or two or more can be used together as necessary. Preferably, depending on the material of the porous ceramic thin plate to be used, an inorganic powder having low reactivity to these It is better to select and use.

These powders are, for example, brushed, buffed, sprayed by dispersing the powder in a dispersion medium, shaken off through a sieve, passed through the green body in the floating fluidized bed of powder or the surface of the powder reservoir. The preferable adhesion amount is 0.0001 cm ³ / cm ² or more per area of the green body to be sintered, more preferably 0.0002 cm ³ / cm ² or more. It is 1 cm ³ / cm ² or less, more preferably 0.02 cm ³ / cm ² or less.

  The type of ceramic used as the material for the porous ceramic thin plate is appropriately selected depending on the material of the ceramic green sheet to be sintered, and a material that does not react with these under the sintering conditions, but is most preferable. Is an alumina-based material that has good stability at high temperatures, hardly reacts with other ceramic materials, and is inexpensive and preferably has an alumina content of 50% by mass or more, more preferably 70% by mass or more. An alumina / silica ceramic material having a content of 30% by mass or less. At this time, it is preferable to use fibrous alumina, SiC whisker or the like because a highly breathable porous ceramic thin plate can be easily obtained. It is also effective to enhance air permeability by adding an appropriate amount of carbon black or the like as a pore generating material together with ceramic powder and whiskers.

  The production of the porous ceramic thin plate according to the present invention is not particularly limited, and examples thereof include a doctor blade method, a calender roll method, an extrusion method, a pressing method, and a papermaking method. Preferably, a slurry containing a ceramic raw material powder, an organic or inorganic binder, a dispersion medium (solvent), and if necessary, a dispersant or a plasticizer is applied to a smooth sheet, for example, a polyester sheet with an appropriate thickness and dried. A green body is obtained by volatilizing and removing the dispersant, and after punching it to an appropriate size, it is preferably stacked with a plurality of sheets, preferably via powder, and placed on a shelf made of a porous ceramic plate. A method of placing on a plate and heating and baking at a temperature of about 1,000 to 1,600 ° C. for about 2 to 5 hours in an air atmosphere is employed.

  The type of binder used here is not particularly limited, and conventionally known organic or inorganic binders can be appropriately selected and used. Examples of organic binders include ethylene copolymers, styrene copolymers, acrylate and methacrylate copolymers, vinyl acetate copolymers, maleic acid copolymers, vinyl butyral resins, and vinyl acetal resins. And vinyl formal resins, vinyl alcohol resins, waxes, celluloses such as ethyl cellulose, and the like.

  Among these, from the viewpoints of green body moldability, punching workability, strength, thermal decomposability during firing, and the like, methyl acrylate, ethyl acrylate, propyl acrylate, butyl acrylate, isobutyl acrylate, cyclohexyl acrylate, 2-ethylhexyl acrylate, etc. Alkyl acrylates having an alkyl group having 10 or less carbon atoms, and 20 carbon atoms such as methyl methacrylate, ethyl methacrylate, butyl methacrylate, isobutyl methacrylate, octyl methacrylate, 2-ethylhexyl methacrylate, decyl methacrylate, dodecyl methacrylate, lauryl methacrylate, cyclohexyl methacrylate, etc. Alkyl methacrylates having the following alkyl groups, hydroxyethyl acrylate, hydroxy Hydroxyalkyl acrylates or hydroxyalkyl methacrylates having hydroxyalkyl groups such as propyl acrylate, hydroxyethyl methacrylate, hydroxypropyl methacrylate, aminoalkyl acrylates or aminoalkyl methacrylates such as dimethylaminoethyl acrylate, dimethylaminoethyl methacrylate, (meth) A number average molecular weight of 2,000 to 200,000 obtained by polymerizing or copolymerizing at least one carboxyl group-containing monomer such as maleic acid half ester such as acrylic acid, maleic acid and monoisopropylmalate, Preferably, a 5,000 to 100,000 (meth) acrylate copolymer is recommended as a preferred one. These organic binders can be used alone or in combination of two or more as necessary. Among these, a copolymer of monomers containing 60% by mass or more of isobutyl methacrylate and / or 2-ethylhexyl methacrylate is particularly preferable.

  As the inorganic binder, zirconia sol, silica sol, alumina sol, titania sol and the like can be used alone or in admixture of two or more.

  The ratio of the raw material powder and the binder used when producing the porous ceramic thin plate is preferably in the range of 5 to 30 parts by mass, more preferably 10 to 20 parts by mass with respect to 100 parts by mass of the former. If the amount used is insufficient, the strength and flexibility of the green body will be insufficient. Conversely, if it is too much, not only will it be difficult to adjust the viscosity of the slurry, but the amount of decomposition and release of the binder component during firing will be large. In addition, it becomes difficult to obtain a porous ceramic thin plate that is homogeneous and has a stable air permeability and friction coefficient.

  Moreover, as a dispersion medium used for manufacture of a green body, alcohols, such as water, methanol, ethanol, 2-propanol, 1-butanol, 1-hexanol, ketones, such as acetone and 2-butanone, pentane, hexane, Aliphatic hydrocarbons such as heptane, aromatic hydrocarbons such as benzene, toluene, xylene and ethylbenzene, and acetates such as methyl acetate, ethyl acetate and butyl acetate are appropriately selected and used. These dispersion media can also be used alone, or two or more of them can be used in an appropriate mixture. The amount of the dispersion medium to be used should be appropriately adjusted in consideration of the viscosity of the slurry at the time of forming the green body, preferably the slurry viscosity is in the range of 1 to 100 Pa · s, more preferably in the range of 2 to 20 Pa · s. It is better to adjust as follows.

  In the preparation of the slurry, in order to promote peptization and dispersion of the ceramic raw material powder, polymer electrolytes such as polyacrylic acid and ammonium polyacrylate, organic acids such as citric acid and tartaric acid, isobutylene or styrene and maleic anhydride And a dispersant comprising a copolymer of styrene and an ammonium salt or an amine salt thereof, a copolymer of butadiene and maleic anhydride and an ammonium salt thereof; dibutyl phthalate or dioctyl phthalate for imparting flexibility to a green sheet Plasticizers made of glycols such as phthalates such as propylene glycol and glycol ethers such as propylene glycol; and the like; and surfactants and antifoaming agents can be added as necessary.

  The porous ceramic thin plate of the present invention thus obtained is effectively utilized as a spacer or the like when producing a ceramic sheet.

Examples of the ceramic used as the material for the ceramic sheet include various single, mixed or composite oxides such as zirconia, alumina, titania, aluminum nitride, borosilicate glass, cordierite, and mullite. What is a solid electrolyte membrane or electrode sheet of a flat solid electrolyte fuel cell. Zirconia-based ceramics are particularly preferable for the solid electrolyte membrane, and specifically, alkaline earth metal oxides such as MgO, CaO, SrO and BaO, Y ₂ O ₃ , La ₂ O ₃ and Ce _{2 are used.} O ₃ , Pr ₂ O ₃ , Nd ₂ O ₃ , Sm ₂ O ₃ , Eu ₂ O ₃ , Gd ₂ O ₃ , Tb ₂ O ₃ , Dy ₂ O ₃ , Ho ₂ O ₃ , Er ₂ O ₃ , Yb ₂ O ₃ rare earth metal oxides, such as, more Sc ₂ O _3, Bi ₂ O _3, an in ₂ O ₃ zirconia ceramics can be mentioned which contain one or two or more such stabilizers such, therein _May contain other additives such as SiO ₂ , Al ₂ O ₃ , Ge ₂ O ₃ , SnO ₂ , Ta ₂ O ₅ , and Nb ₂ O ₅ .

In addition, CeO ₂ or Bi ₂ O ₃ is added to CaO, SrO, BaO, Y ₂ O ₃ , La ₂ O ₃ , Ce ₂ O ₃ , Pr ₂ O ₃ , Nd ₂ O ₃ , Sm ₂ O ₃ , Eu ₂ O. ₃ , Gd ₂ O ₃ , Tb ₂ O ₃ , Dr ₂ O ₃ , Ho ₂ O ₃ , Er ₂ O ₃ , Yb ₂ O ₃ , PbO, WO ₃ , MoO ₃ , V ₂ O ₅ , Ta ₂ O ₅ , It may contain a ceria-based or bismuth-based oxide to which one or more of Nb ₂ O ₅ or the like is added, or a gallate-based oxide such as LaGaO ₃ .

In addition, as the constituent material of the anode electrode sheet, Ni, Co, Fe or oxides thereof and the like and cermet of the above zirconia and / or ceria, and further, alkaline earth such as MgO, CaO, SrO, BaO, etc. Cermets with addition of metal oxides, MgAl ₂ O _{4 and the} like, and the constituent materials of the cathode electrode sheet include lanthanum manganate, lanthanum cobaltate, or lanthanum having a perovskite crystal structure, or lanthanum Ca. , Sr, etc., or manganese partially substituted with Co, Fe, Cr, etc., and lanthanum and cobalt partially substituted with Ca, Sr, Co, Fe, etc. Is done.

  In addition, since a higher degree of thermal, mechanical, electrical, and chemical characteristics are required for the ceramic sheet used for a solid electrolyte membrane of a fuel cell, in order to satisfy these required characteristics, Zirconium oxide (tetragonal and / or cubic zirconia) stabilized with 12 mol%, more preferably 2.5 to 10 mol%, more preferably 3 to 8 mol% yttrium oxide is recommended as more preferred. The

  Further, when the zirconia sheet is put into practical use as a solid electrolyte membrane or electrode sheet for a fuel cell, in order to suppress the electric resistance as much as possible while satisfying the required strength, the sheet thickness is preferably 10 μm or more, more preferably The thickness is 50 μm or more and 500 μm or less, more preferably 300 μm or less.

Further, the shape of the sheet may be any of a circle, an ellipse, a square, a square having R (R), and the like, and a hole of a similar circle, ellipse, square, square having R, etc. in these sheets. One or two or more may be included. Further, the area of the sheet is 50 cm ² or more, preferably 100 cm ² or more. In addition, this area means the total area including the area of this hole, when there exists a hole in a sheet | seat.

  These ceramic sheets can be produced by a conventional method using a ceramic raw material powder, an organic or inorganic binder, a dispersion medium (solvent), and a slurry containing a dispersant or a plasticizer, if necessary, by a doctor blade method, a calender roll method, an extrusion method, etc. A green sheet is obtained by applying a suitable thickness on a smooth sheet, for example, a polyester sheet, and drying to volatilize and remove the dispersion medium. After punching it to an appropriate size, the porous sheet is porous as described above. A method is adopted in which a ceramic thin plate is placed or placed on a shelf plate between porous ceramic thin plates and heated and fired at a temperature of about 1,000 to 1,600 ° C. for about 2 to 5 hours in an air atmosphere. The

  At this time, in order to increase the surface homogeneity of the finished sheet and make dimples and undulations smaller, the average particle diameter is 0.1 to 0.8 μm as the raw material powder of the ceramic sheet, and the particle diameter is as uniform as possible. It is preferable to use one having a small particle size distribution, specifically, 90% by volume or more of the powder of 5 μm or less.

  There are no particular restrictions on the type of binder or dispersion medium used in producing the green sheet, and one or two organic or inorganic binders or dispersion media exemplified above as the raw material for producing the porous ceramic thin plate. The above can be selected and used as appropriate.

  Also, when preparing the slurry, in order to promote peptization and dispersion of the ceramic raw material powder, a dispersant as described above is added, or a plasticizer for imparting flexibility to the green sheet; It is also effective to add an activator or an antifoaming agent as necessary.

  The present invention is configured as described above, and by specifying the coefficient of friction, or further specifying the air permeability, and further specifying the surface undulations, dimples, etc., particularly for the flat solid oxide fuel cell. When manufacturing a ceramic plate used as a solid electrolyte membrane by degreasing and firing a green sheet, it can be used as a spacer, etc. Generation | occurrence | production etc. can be suppressed effectively and the ceramic sheet excellent in surface smoothness could be provided reliably.

  Further, the porous ceramic thin plate of the present invention makes use of its excellent friction coefficient, and in addition to the spacer, firing jigs such as setters, shelf plates, and base plates, other refractory materials and heat insulating materials, sound absorbing materials, and damping materials. As a vibration plate, a heat-resistant material, a water-permeable material, etc., it can be effectively used for applications that require moderate slip and air permeability.

  Hereinafter, the present invention will be described more specifically with reference to examples and comparative examples. However, the present invention is not limited by the following examples, and may be appropriately changed within a range that can meet the purpose described above and below. It is also possible to implement them, and they are all included in the technical scope of the present invention.

Example 1
A binder made of a methacrylate copolymer (average molecular weight: 30,000, glass transition temperature: −) with respect to 100 parts by mass of low soda alumina powder (trade name “AL-13” manufactured by Showa Denko KK) having an average particle size of 55 μm. 8 ° C., solid concentration: 50% by mass) 12 parts by mass, 2 parts by mass of dibutyl phthalate as a plasticizer, 30 parts by mass of a mixed solvent of toluene / isopropyl alcohol (mass ratio = 3/2) as a dispersion medium, A slurry was prepared by putting in a nylon pot charged with zirconia balls and kneading at about 60 rpm for 40 hours. The slurry was concentrated and defoamed to adjust the viscosity to 8 Pa · s, and coated on a polyethylene terephthalate film by a doctor blade method to obtain a green sheet for a porous ceramic thin plate.

The green sheet was cut into a predetermined size at a press stroke of 40 mm and a press speed of 80 spm by attaching a blade die to a continuous punching device (trade name “865B” manufactured by Sakamoto Machine Co., Ltd.). The cut green sheet for the porous ceramic thin plate was placed on an alumina plate whose surface was polished, and corn starch was uniformly applied thereon using a brush. In the same manner, green sheets for porous ceramic thin plates were overlapped in the same manner, and the same operation was repeated, so that a total of 10 green sheets for porous ceramic thin plates were overlapped via corn starch. Further, an alumina plate having a thickness of 1.5 mm (“Y-1” manufactured by Mitsui Kinzoku Kogyo Co., Ltd., porosity: about 26%, weight: about 0.5 g / cm ² ) was placed thereon. The height of the green sheet stack including the weight was about 5.2 mm, and the height of the column supporting the shelf board was 25 mm.

  In this state, after degreasing at 500 ° C. in an air atmosphere, the porous ceramic thin plate was obtained by firing at 1550 ° C. for 2 hours. The thickness of the ceramic thin plate was 0.3 mm, the maximum friction coefficient was 0.97, and the air permeability was 0.003 m / s · kPa.

  In addition, the surface of the 20 porous ceramic thin plates was irradiated with a laser beam using a laser optical three-dimensional shape measuring apparatus, and the three-dimensional shape analysis was performed to examine the unery height and dimple height. The maximum undulation height was 15 μm, and the maximum dimple height was 30 μm. A 10 mm × 50 mm test piece was prepared from the same thin plate, and the three-point bending strength was measured.

Example 2
A total of 100 parts by mass of 64 parts by mass of low soda alumina powder having an average particle diameter of 55 μm, 16 parts by mass of low soda alumina powder having an average particle diameter of 0.6 μm, and 20 parts by mass of carbon black as a pore agent is used as a raw material. A porous ceramic thin plate having a thickness of 0.8 mm, a maximum friction coefficient of 0.91, and a gas permeability of 0.012 m / s · kPa was obtained in the same manner as in Example 1 except that the thickness of the sheet was changed. The maximum undulation height of the porous ceramic thin plate was 20 μm, the maximum dimple height was 40 μm, and the three-point bending strength was 8 MPa.

Example 3
A green sheet using a total of 100 parts by mass of 85 parts by mass of low soda alumina powder having an average particle diameter of 55 μm, 10 parts by mass of low soda alumina powder having an average particle diameter of 0.6 μm, and 5 parts by mass of SiC whiskers. A porous ceramic thin plate having a thickness of 0.5 mm, a maximum friction coefficient of 1.0, and a breathability of 0.0006 m / s · kPa was obtained in the same manner as in Example 1 except that the thickness of the ceramic was changed. The maximum thickness of the porous ceramic thin plate was 30 μm, the maximum dimple height was 45 μm, and the three-point bending strength was 90 MPa.

Comparative Example 1
By adding a vinyl acetate binder to a silica-alumina fiber having an average length of 12 mm and an average diameter of 3 μm (alumina content: 80% by mass), mixing, forming, drying and firing, a thickness of 1. A porous ceramic thin plate having a thickness of 2 mm, a maximum friction coefficient of 1.6, and an air permeability of 0.01 m / s · kPa was obtained. The maximum undulation height of the porous ceramic thin plate was 60 μm, the maximum dimple height was 80 μm, and the three-point bending strength was 8 MPa.

Example 4
When the surface of the porous ceramic thin plate obtained in Comparative Example 1 above is uniformly polished to a thickness of 0.6 mm with a # 1200 grindstone, the undele height is 40 μm, and the maximum dimple height is 40 μm. The coefficient of friction was improved to 1.1. However, since it became thin, the strength was insufficient, and one piece was cracked when an evaluation test described later was performed.

Comparative Example 2
A green sheet for a porous ceramic thin plate was prepared in the same manner as in Example 1 except that the binder was 15 parts by mass, the kneading time was 10 hours, and the thickness at the time of green sheet formation was changed. A porous ceramic thin plate was obtained by firing. The porous ceramic thin plate has a thickness of 0.7 mm, a maximum coefficient of friction of 1.6, a breathability of 0.0004 m / s · kPa, an undulation height of 60 μm, and a maximum dimple height of 40 μm. The bending strength was 80 MPa.

Example 5
A binder made of a methacrylate copolymer (average molecular weight: 30,000, glass transition temperature) with respect to 100 parts by mass of low soda alumina powder (trade name “AL-160SG” manufactured by Showa Denko KK) having an average particle size of 0.6 μm : -8 ° C., solid content concentration: 50% by mass) 18 parts by mass, 2 parts by mass of dibutyl phthalate as a plasticizer, 50 parts by mass of a mixed solvent of ethyl acetate / toluene (mass ratio = 3/2) as a dispersion medium, The mixture was kneaded in the same manner as in Example 1, and after defoaming, it was coated on a polyethylene terephthalate film by the same method to obtain a green sheet for a porous ceramic thin plate.

  The green sheet was cut and fired in the same manner as in Example 1 except that no weight was placed thereon to obtain a porous ceramic thin plate. Since this thin plate showed slight warpage and undulation, it was refired for warping correction at 1450 ° C. sandwiched between polished dense alumina plates. The thickness of the obtained porous ceramic thin plate is 0.3 mm, the maximum friction coefficient is 1.0, the air permeability is 0.0002 m / s · kPa, the undulation height is 15 μm, the maximum dimple height is 65 μm, The three-point bending strength was 250 MPa.

Reference example 1
When stacking the green sheets, an attempt was made to produce a porous ceramic thin plate in the same manner as in Example 5 except that the application of corn starch was omitted, but a large amount of undulation was generated in the ceramic thin plate after firing. The thin plates were attached to each other and cracked when they were peeled off.

Evaluation test (production of zirconia green sheet)
For 100 parts by mass of commercially available 3 mol% yttria stabilized zirconia powder (trade name “HSY-3.0” manufactured by Daiichi Rare Element Co., Ltd., average particle diameter: 0.7 μm, 90% diameter: 1.9 μm), methacrylate 30 parts by mass of a binder made of a copolymer (molecular weight: 30,000, glass transition temperature: -8 ° C., solid content concentration: 50% by mass), 2 parts by mass of dibutyl phthalate as a plasticizer, toluene / isopropyl alcohol as a dispersion medium 50 parts by mass of the mixed solvent (mass ratio = 3/2) was put in a nylon pot charged with zirconia balls having a diameter of 10 mm, and kneaded at about 60 rpm for 40 hours to prepare a slurry.

  The slurry was concentrated and defoamed to adjust the viscosity to 3 Pa · s, and finally passed through a 200 mesh filter, and then applied onto a polyethylene terephthalate film by the doctor blade method to obtain a green sheet having a thickness of about 300 μm. .

  The green sheet was cut into a predetermined size and shape at a press stroke of 40 mm and a press speed of 80 spm by attaching a blade die to a continuous punching machine (same as above).

(Baking and evaluation of zirconia green sheet)
On the shelf board, the 42-cm square porous ceramic thin plate obtained in the above-mentioned Examples and Comparative Examples was placed, and the 40-cm square zirconia green sheet obtained above was stacked thereon, and in the same manner, Four porous ceramic thin plates and zirconia green sheets were alternately stacked, and finally the porous ceramic thin plates were placed.

  In this way, 5 sheets of each porous ceramic thin plate and zirconia green sheet were overlapped and fired at 1400 ° C. for 2 hours in an air atmosphere to obtain a zirconia sheet having a side of 300 mm and a thickness of about 220 μm. It was. By visually observing each zirconia sheet, the amount of pinholes and tears was examined. The results are collectively shown in Table 1 together with the characteristics of the porous ceramic thin plates obtained in each example and comparative example.

Claims (5)

A porous ceramic thin plate having a friction coefficient measured by the following method of 1.5 or less and an air permeability of 0.0005 m / s · kPa or more.
(Friction coefficient measurement method) Maximum stress when a R36W felt specified in JIS L3201 is attached to a weight with a bottom area of 15 cm ² and moved over a porous ceramic thin plate at a distance of 10 cm at 100 mm / min. Is divided by a weight of 75 g.   The porous ceramic thin plate according to claim 1, wherein the surface undulation height is 50 µm or less and the dimple height is 50 µm or less.   The porous ceramic thin plate according to claim 1 or 2, wherein the thickness is less than 1 mm.   The porous ceramic thin plate according to claim 1, which is used for firing a ceramic green sheet.   In producing a ceramic sheet by stacking and firing a plurality of ceramic green sheets, the porous ceramic thin plate according to any one of claims 1 to 4 is placed between the ceramic green sheets. A method for producing a ceramic sheet, characterized by sandwiching and firing so that the periphery does not protrude.