JP6211868B2 - Method for inspecting ceramic sheet for solid electrolyte membrane of solid oxide fuel cell and method for producing the ceramic sheet - Google Patents

Description

  The present invention relates to a method for inspecting a ceramic sheet for a solid electrolyte membrane of a solid oxide fuel cell, and a method for producing the ceramic sheet.

  Ceramic sheets have excellent mechanical strength, electrical insulation, toughness, wear resistance, chemical resistance, corrosion resistance, etc., so they are used in various electronic materials, various structural materials, blades, firing setters, etc. Yes. Among them, a ceramic sheet mainly composed of zirconia is used as a solid electrolyte membrane of a solid oxide fuel cell (hereinafter also referred to as SOFC) because it has high oxygen ion conductivity.

  When the ceramic sheet is used as a solid electrolyte membrane of SOFC, the ceramic sheet is intermittently exposed to high temperatures during power generation. Moreover, although an electrode is formed on a ceramic sheet, the volume of an electrode containing a base metal changes during oxidation and reduction. Further, in the SOFC, since the ceramic sheet and the cell including the electrode are stacked in series, a large load is applied to the ceramic sheet. As a result, if the ceramic sheet has deformations in the thickness direction such as warpage or undulation, surface defects such as scratches or chips, and internal defects such as bubbles, it will easily break from that point. . As described above, since cells are stacked in series in SOFC, the amount of power generation is greatly reduced even if one ceramic sheet is damaged. Therefore, in order to use for SOFC, it is very important to obtain a ceramic sheet having no defects or few even if present, and it is required to inspect finer defects with high accuracy and good reproducibility in a short time. ing.

  Various techniques for detecting defects in various sheets, not limited to ceramic sheets, have been developed so far.

For example, in Patent Document 1, based on an image obtained using a CCD camera, the surface of a ceramic sheet that rises due to transmitted light or the area of foreign matter or scratches existing on the inside of a ceramic sheet is 0.1 mm ² or more. A method for detecting the number is disclosed. However, a mere CCD camera does not provide sufficient information in the minute height (depth) direction of the sheet surface, which makes it difficult to satisfy the strict inspection standards required for electrolyte membranes for fuel cells. Yes.

  In Patent Document 2, a soft green sheet surface with a thickness of about 0.2 mm has a gentle slope with a height or depth of 5 to 20 μm and a width or diameter of about 0.1 to 2 mm. There is disclosed a method for detecting minute irregularities such as isuzu, blisters, dents and cracks by optical inspection. However, the detector used is a CCD linear sensor that detects in a one-dimensional manner, which can only photoelectrically convert a linear image, so that the above-mentioned defect having a steep inclination and a very small height (depth) direction. The defects (for example, microcracks) have not been detected with sufficient accuracy.

  Furthermore, in Patent Document 3, as a method of inspecting a ceramic sheet for a solid electrolyte membrane of SOFC, a step of detecting warpage of the sheet with a triangulation displacement sensor, then chipping, deposits, dents, scratches, cracks, etc. A process of detecting defects existing on the surface of the sheet and inside the sheet such as foreign matters and bubbles using a transmission type photoelectric sensor, in particular, using both a transmission type CCD line sensor and a transmission type laser sensor in combination. A detection method is disclosed. However, with respect to scratches and dents, detection accuracy is not necessarily sufficient for fine scratches and dents of less than 30 μm in the sheet depth direction.

Republished patent WO99 / 55639 JP-A-4-216904 JP 2011-53190 A

  As described above, various techniques for detecting defects on the sheet surface have been developed. However, for example, in an SOFC that is being put into practical use, in order to improve reliability, a method capable of more efficiently and accurately inspecting various types of surface defects appearing on a large amount of ceramic sheets is required. .

  In the case of a ceramic sheet used as a solid electrolyte membrane of SOFC, particularly in the case of a thin film sheet having a sheet thickness of 150 μm or less, there are defects such as fine scratches and dents having a depth of less than 30 μm that are present on the sheet surface. These defects, when the cell is exposed to a high temperature or repeatedly exposed to a high temperature and a low temperature (room temperature), cause cell damage starting from the defect and cause a decrease in the reliability of the fuel cell. Therefore, it is very important to detect the extremely small defect and use a sheet having no or few such defects.

  Therefore, the present invention is applicable to automatic inspection of ceramic sheets for SOFC solid electrolyte membranes, and provides a method for efficiently and accurately detecting defects such as scratches and dents from a large amount of ceramic sheets. The purpose is to do.

  The inventors of the present invention have made extensive studies to solve the above problems. As a result, it has been found that by using a three-dimensional camera, defects such as scratches and dents in the three-dimensional depth of the finer depth existing on the sheet surface can be detected accurately and efficiently, and the present invention has been completed.

  A method for inspecting a ceramic sheet for a solid electrolyte membrane of a solid oxide fuel cell according to the present invention includes a defect detection step of detecting defects in the ceramic sheet using a three-dimensional camera and a transmission photoelectric sensor. To do. In the method of the present invention, the defect detection step further includes a step of detecting a defect existing at least on the surface using a three-dimensional camera, and a step of detecting a defect present at least inside using a transmission photoelectric sensor. It is preferable that it is included in order to keep the defect detection accuracy high. Furthermore, it is preferable to include a step of detecting the warpage of the ceramic sheet using a triangulation displacement sensor.

  The method for producing a ceramic sheet for an electrolyte membrane of a solid oxide fuel cell according to the present invention comprises mixing a slurry raw material containing powder, a solvent and a binder made of a ceramic material for an electrolyte membrane of a solid oxide fuel cell. The step of preparing; the step of coating the obtained slurry on a film; the step of drying the slurry coated on the film to form a green sheet; the step of firing the green sheet; and the ceramic sheet obtained above It includes a step of inspecting by the method of the present invention.

  According to the present invention, defects such as flaws and dents in the depth direction existing on the surface of the ceramic sheet can be efficiently obtained even if the amount of the defects is small or the defects are minute and fine. Since the inspection can be performed accurately, a large amount of ceramic sheets can be automatically inspected. Moreover, if the said inspection method is applied, a more efficient manufacture of a ceramic sheet | seat will be attained. Therefore, the method of the present invention is very useful industrially as it can be applied to inspection of ceramic sheets that can be used for SOFC electrolyte membranes.

It is the schematic of the apparatus for enforcing the inspection method of the ceramic sheet which concerns on this invention. It is the schematic of the apparatus for enforcing the inspection method of the conventional ceramic sheet.

The ceramic sheet to be inspected by the method of the present invention is a ceramic sheet for an electrolyte membrane of SOFC. The size of the ceramic sheet to be inspected is not particularly limited. The ceramic sheet to be inspected can be preferably manufactured as follows.
(1) Slurry preparation process First, the slurry raw material containing a ceramic powder, a solvent, and a binder is mixed and a slurry is prepared.

  Examples of the ceramic powder that is the main material of the SOFC electrolyte membrane ceramic sheet include zirconia powder, ceria powder, lanthanum gallate powder, and composite powders of two or more of these.

Examples of the zirconia powder include oxides of alkaline earth metals such as MgO, CaO, SrO, and BaO, Sc ₂ O ₃ , Y ₂ O ₃ , La ₂ O ₃ , CeO ₂ , Pr ₂ O ₃ , and Nd _2. Oxides of rare earth elements such as 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 , Bi Powders made of zirconia in which one or more oxides of other metals such as ₂ O ₃ and In ₂ O ₃ are dissolved as a stabilizer, and further Al ₂ O ₃ , TiO ₂ , Ta ₂ O ₅ and a powder made of composite zirconia to which Nb ₂ O ₅ or the like is added as a dispersion strengthening agent. Among the above, zirconia-based powders having higher thermal characteristics, mechanical characteristics, chemical characteristics, and oxygen ion conductivity characteristics, stabilized with at least one oxide selected from scandia, yttria, and ceria More preferably, the powder is composed of partially stabilized zirconia having a tetragonal crystal structure or completely stabilized zirconia having a cubic crystal structure, 4 to 12 mol% scandia powder, 8 to 11 mol% scandia and 0.5 to 2 Particular preference is given to powders consisting of zirconia stabilized with mol% ceria or 3 to 10 mol% yttria.

Examples of the ceria-based powder include ceria doped with one or more metal elements selected from the group consisting of Y, Sm, Gd, Nd, Pr, Sc, and Ga, and more specifically, Ce. _1-x M _x O _2-y (wherein M represents one or more metal elements selected from the group consisting of Y, Sm, Gd, Nd, Pr, Sc, Ga; 0.05 ≦ x ≦ 0.4 and 0 ≦ y <0.5)). As the ceria-based powder, a ceria-based material in which at least one selected from the group consisting of Y, Sm and Gd is doped, and the total amount of doped Y, Sm and Gd is in the range of 10 to 30 mol% That is, a powder made of a ceria material in which M is at least one selected from the group consisting of Y, Sm and Gd and 0.10 ≦ x ≦ 0.30 in the above formula is preferable. Further, from a ceria-based material doped with 15 to 25 mol% of Sm and / or Gd, that is, a ceria-based material where M is Sm and / or Gd and 0.15 ≦ x ≦ 0.25 in the above formula. More preferred is a powder.

As the lanthanum gallate-based powder, La GaO ₃ perovskite has a basic structure, and La ₁₋ is partially substituted with Sr, Ca, Ba, Mg, In, Co, Fe, Ni, Cu, and the like. _{x Sr x Ga 1-y Mg} y O 3-δ, La 1-x Sr x Ga 1-y Mg y Co z O 3-δ, La 1-x Sr x Ga 1-y Fe y O 3-δ, La _1-x Sr _x Ga _1-y Ni _y O _3−δ (where 0 <x ≦ 0.2, 0 <y ≦ 0.2, 0 <z ≦ 0.1; δ is oxygen deficiency) Is preferred because it exhibits high oxygen ion conductivity.

  Examples of the solvent for the slurry include water; alcohols such as methanol, ethanol, 2-propanol, 1-butanol, and 1-hexanol; modified alcohols; ketones such as acetone, 2-butanone, and methyl ethyl ketone; pentane, hexane, heptane, and the like. Aliphatic hydrocarbons such as benzene, toluene, xylene, and ethylbenzene; and acetates such as methyl acetate, ethyl acetate, and butyl acetate. These solvents may be used alone or in combination of two or more. The amount of the solvent used is preferably adjusted so that the viscosity is suitable for molding when the slurry is molded into a sheet.

  There is no restriction | limiting in the kind of binder added to a slurry, A well-known organic binder can be selected suitably and can be used. Examples of the binder include ethylene copolymers, styrene copolymers, acrylate copolymers, methacrylate copolymers, vinyl butyral resins, vinyl acetal resins, vinyl formal resins, vinyl alcohol resins, Examples include celluloses such as ethyl cellulose.

  In addition to the ceramic powder, the solvent and the binder, a plasticizer or a dispersant may be added to the slurry as necessary. Examples of the plasticizer include phthalic acid esters such as dibutyl phthalate and dioctyl phthalate; glycols such as propylene glycol; glycol ethers; polyethylene glycol derivatives and the like. Examples of the dispersant include polyelectrolytes such as polyacrylic acid and ammonium polyacrylate; organic acids such as citric acid and tartaric acid; copolymers of isobutylene or styrene and maleic anhydride; ammonium salts of the polymer; Examples include amine salts; esters of polyalcohols such as glycerin and sorbitan; polyethers and polyalcohols; amines.

In the slurry preparation step of the present invention, a slurry is prepared by mixing appropriate amounts of the above components. At that time, milling may be performed using a ball mill, a bead mill or the like in order to disintegrate the ceramic powder and to uniformly mix the components. In mixing, the order of addition of each component is not particularly limited.
(2) Slurry coating process and drying process Next, the slurry is continuously coated on a film and then dried to obtain a long green tape.

  The coating method is not particularly limited, and a doctor blade method, an extrusion method, or the like can be used, but the doctor blade method is preferable.

  Drying conditions are not particularly limited, and may be appropriately adjusted according to the solvent used. The thickness of the green tape to be produced may be adjusted according to the target thickness of the ceramic sheet, but can usually be 50 μm or more and 500 μm or less.

The obtained green tape is cut into a desired shape such as a round shape, an oval shape, a square shape such as a square, or a square shape having R by an arbitrary method using a cutting die, a Thomson blade, or the like to obtain a green sheet. . Further, one or more holes such as a circle, an ellipse, a square such as a square, and a square having an R may be formed. Moreover, you may roughen the surface of a green sheet to 0.1 micrometer or more and 3 micrometers or less by Ra as needed.
(3) Firing step Next, the obtained green sheet is fired to degrease and sinter it into a ceramic sheet. Specific firing conditions are not particularly limited, and may be based on a conventional method.

  For example, in order to remove organic components such as a binder and a plasticizer from the green sheet, the temperature ranges from 150 ° C. to 600 ° C., more preferably from 250 ° C. to 500 ° C. for 5 hours or more, 80 Degrease by heating for less than an hour. Next, a ceramic sheet is obtained by holding and sintering in a temperature range of 1300 ° C. or more and 1800 ° C. or less, more preferably 1300 ° C. or more and 1600 ° C. or less for 2 hours or more and 10 hours or less. In particular, the zirconia green sheet is preferably fired in an air atmosphere at a temperature range of 1350 ° C. or higher and 1500 ° C. or lower.

  The zirconia sheet, ceria sheet, and lanthanum gallate sheet according to the present invention are made of the zirconia powder, ceria powder, and lanthanum gallate powder used in the slurry preparation step, respectively.

  The shape of the ceramic sheet produced through the above process is not particularly limited, and may be, for example, a circle, an ellipse, a square such as a square, a square having R, or the like. It may have one or more holes such as a square such as a square or a square having R.

Plane area of the ceramic sheet is not particularly limited, for example, 1 cm ² or more, it can be 1000 cm ² or less, 30 cm ² or more, more preferably 800 cm ² or less, 50 cm ² or more, 600 cm ² or less is more preferred. In addition, the said planar area shall mean the total area including the area of a hole, when the hole is formed in the sheet | seat.

The thickness of the ceramic sheet is not particularly limited, but may be, for example, 50 μm or more and 300 μm or less, more preferably 250 μm or less, and further preferably 200 μm or less. In particular, as described above, fine defects such as scratches and dents on the surface, which can be detected by the inspection method of the present invention, have a large effect on the sheet strength. The inspection method of the present invention is particularly useful for ceramic sheets of 150 μm or less, particularly 120 μm or less.
The method for producing a ceramic sheet for an electrolyte membrane of a solid oxide fuel cell according to the present invention comprises a step of producing a ceramic sheet by the above-mentioned production method, a defect of the ceramic sheet obtained in the step, a three-dimensional camera and a transmission type photoelectric cell. It is a manufacturing method including the defect detection process detected using a sensor.
That is, the manufacturing method comprises a step of preparing a slurry by mixing a slurry material containing a powder made of a ceramic material for an electrolyte membrane of a solid oxide fuel cell, a solvent, and a binder; and coating the obtained slurry on a film A step of drying the slurry coated on the film to form a green sheet; a step of firing the green sheet; and detecting defects in the obtained ceramic sheet using a three-dimensional camera and a transmission photoelectric sensor A method for producing a ceramic sheet comprising a defect detection step.

  The inspection method according to the present invention will be described below.

In the inspection method of the present invention, the defect to be detected includes a defect present on the surface of the ceramic sheet and a defect present inside the ceramic sheet. Examples of defects present on the surface of the ceramic sheet include scratches, dents, chips, cracks, protrusions, foreign matter, and bubbles.
In the following description, a simple sheet means a ceramic sheet to be inspected according to the present invention. Defects present inside the sheet include foreign matter and bubbles. These defects reduce the strength of the ceramic sheet, and in the case of a ceramic sheet for an electrolyte membrane of a fuel cell, cause defects in characteristics such as oxygen ion conductivity.

  Scratches are comparatively elongated streak-like depressions on the surface of the sheet. Usually, the process of producing a sheet from a green sheet as a precursor, specifically, when the green sheet is dried, fired, or sintered, is a precursor. This occurs when the body green sheet and its degreased body contract while contacting the setter and spacer. A dent is a dent made on the sheet surface and has a width such as a circle or an ellipse. The chipping is a chipping of the sheet end surface, which is considered to be caused by a collision with another object or peeling due to heat shrinkage during firing. Cracks are cracks that occur during drying, firing, and sintering of the sheet, and are shaped like streaks or dots.

  The protrusion is a relatively small bulge protruding from the surface of the sheet. The foreign matter is dust, rust, hair or the like mixed from the outside and cannot be removed even by cleaning the sheet surface described later. The bubbles are generated due to insufficient deaeration of the slurry used for preparing the green sheet, and are spaces in which air contained inside the sheet exists.

  Among these defects, scratches and dents, when using a conventional inspection method, for example, an inspection method using a transmission photoelectric sensor described in Patent Document 3, has a depth resolution of 30 μm even if a transmission laser sensor is used. Due to the limit, it was not possible to detect minute scratches or dents having a depth of less than 30 μm. For this reason, when electrodes are formed by screen printing on a ceramic sheet that has passed the conventional inspection method, cracking of the sheet may occur, for example, when the printing speed is increased. Such a problem is more likely to occur as the ceramic sheet with a smaller thickness is used, and is particularly noticeable when a ceramic sheet with a thickness of 150 μm or less is used. When the inspection using the three-dimensional camera of the present invention is performed, the height detection capability can be reduced to several μm or less, so that the occurrence of the cracking problem as described above is suppressed, and a ceramic sheet having a thickness of 150 μm or less is used. High productivity and yield can be achieved.

  Here, the three-dimensional camera is a camera used for photographing a subject to be examined three-dimensionally for display on a three-dimensional display. In the present specification, a three-dimensional camera may be referred to as a 3D camera and a three-dimensional camera as a 3D camera. The configuration is such that, for example, laser light or LED light is used as a light source, this light is incident on the ceramic sheet obliquely, and the 3D shape of the surface of the sheet is measured from the straightness of the reflected light. CMOS is used, 3D image processing is performed by an analysis method such as an ultrasonic method, a light cutting method, a pattern projection method, or a holographic method to recognize a 3D shape, and determination based on the depth of a flaw or a dent can be performed.

  Defects other than the scratches and dents described above are detected on the surface and / or inside of the ceramic sheet using a transmission type photoelectric sensor that detects the defect from the difference between the amount of light applied to the ceramic sheet and the amount of transmitted light. To do. Specifically, for example, chipping / foreign matter is detected by a CCD line sensor, and protrusions / cracks / bubbles are detected by a laser sensor.

  The photoelectric sensor used above has at least a projector and a light receiver, and detects a defect from the difference between the amount of light irradiated to the ceramic sheet and the amount of transmitted light. The ceramic sheet is irradiated with light from the light projector of the photoelectric sensor, and the amount of transmitted light is measured by the light receiver. If there is a defect on the path of the irradiated light, the light is scattered at that position. As a result, when measuring the amount of transmitted light, the amount of light to be measured is lower than when there is no defect. However, when the amount of transmitted light is measured, the transmitted light is blocked when there is a foreign substance, so that the photoelectric sensor can detect the presence or absence of defects on the surface and / or inside of the ceramic sheet based on the measured light amount.

  As a light source of a photoelectric sensor, there are one using an LED as a light source and one using a laser as a light source. In general, a photoelectric sensor using an LED as a light source has high resolution, and for example, it is possible to detect brown deposits and foreign matters that are difficult to detect by using blue light. A photoelectric sensor using a laser as a light source can efficiently inspect a wide range by, for example, irradiating laser light in the width direction.

An example of a photoelectric sensor using an LED as a light source is a transmissive CCD line sensor. As a transmissive CCD line sensor, for example, a blue LED having a wavelength in the range of 420 nm or more and 470 nm or less, more preferably, a wavelength of about 450 nm is used as a light source, and the transmitted light is received by a CCD camera, and the amount of light can be measured. Things can be used. The CCD camera is a camera composed of a photodiode which is a semiconductor element that converts the intensity of received light into an electric signal, and can detect a defect having a size of 14 μm or more. The foreign matter, diameter 200μm or less, more preferably be suitably detect the following 170 [mu] m, as the chipping, the plane area of 0.025 mm ² or more, 2.25 mm ² or less, more preferably 0.0625 mm ² or more, Those of 1.0 mm ² or less can be suitably detected. In order to suppress the detection leakage of the foreign matter existing inside the sheet, it is preferable to measure one surface of the ceramic sheet, then reverse the sheet and measure again from the other surface.

  As a photoelectric sensor using a laser as a light source, for example, a laser beam having a wavelength in the range of about 650 nm or more and about 780 nm or less, such as red visible light having a wavelength of about 660 nm, can be received by a photomultiplier tube. Things can be used. More specifically, it includes a laser projector, a light receiver, a control unit that performs image processing on a received light signal, an image processing computer that processes an image signal from the control unit as a defect view, and the like. As the crack, those having a length of 11 μm or more, more preferably 30 μm or more, further preferably 40 μm or more, and particularly preferably 50 μm or more can be suitably measured. As the bubbles, those having a diameter of 15 μm or more, more preferably 30 μm or more, further preferably 50 μm or more, and particularly preferably 100 μm or more can be suitably measured. Similar to the case of using a transmission type CCD line sensor, even in the case of a transmission type laser sensor, in order to suppress detection leakage of foreign substances existing inside the sheet, after measuring one surface of the ceramic sheet, the sheet is inverted. It is preferable to measure again from the other side. For example, after one surface of a ceramic sheet is continuously inspected with a transmission CCD line sensor and a transmission laser sensor, the ceramic sheet is inverted, and the other surface is again connected with a transmission CCD line sensor and a transmission laser sensor. The mode of inspecting automatically is particularly preferable. In addition, a method in which a translucent device and a light receiving device are installed up and down and measurement is performed without inverting the ceramic sheet is also possible.

  In addition to the defects described above, the ceramic sheet may be warped. If there is a warp, it will cause a decrease in the accuracy of defect detection under high-speed conditions as will be performed later, so in addition to the above defect inspection, it is preferable to inspect for the presence of warp, prior to the above defect inspection More preferably.

  The warpage of the ceramic sheet is a warpage in a relatively wide range of thickness direction that occurs at least on one side of the sheet, which occurs due to firing of the green sheet. Examples of such warpage include a deformation in which one surface of the sheet is concave over the entire surface and the other surface is convex over the entire surface (so-called warpage), or a deformation in which the sheet end surface is generated with a width of about 3 mm from the periphery of the sheet. (A so-called burr), a deformation in which a mountain-shaped convex portion is generated on one side of the sheet (so-called uplift), and a deformation in which a mountain range and a valley are continuously generated on both sides of the sheet (so-called undulation).

  Ceramic sheet warpage is highly accurate, suitable for measuring small areas, suitable for inspection of ceramic sheets, has a wide measuring range, especially for detecting defects in the thickness direction such as warpage. Since it is excellent, it is preferable to use a triangulation type displacement sensor.

  Since warpage existing on the surface of the ceramic sheet has a relatively wide range of deformation (burrs) at the peripheral edge of the sheet, it is preferable to use a plurality of triangulation displacement sensors. The light used in the triangulation displacement sensor is spot light and cannot be inspected over a wide range at once, but it is a relatively wide range of defects by using multiple triangulation displacement sensors. It becomes possible to detect warpage efficiently and accurately. In particular, since the warpage at the edge of the sheet is very small, the resolution is 0.1 μm or less, the beam can be narrowed down, and it is necessary to accurately measure a minute displacement of about 5 μm. It is difficult for a sensor to detect warpage with the same accuracy as a triangulation displacement sensor, and it is not suitable for measuring warpage of an electrolyte sheet for a fuel cell.

  The triangulation distance displacement sensor includes, for example, a projector, a light receiver, a control unit that performs image processing on a light reception signal, an image processing computer that processes an image signal from the control unit as a defect view, and the like. The triangulation type displacement sensor irradiates the ceramic sheet with light from the projector and detects the reflected light with a light receiver, detects the displacement of the ceramic sheet in the height direction by triangulation, and deforms in the thickness direction. It is to detect.

  In the triangulation-type displacement sensor, the angle of light emitted from the projector is fixed. In the light receiver, the reflected light from the ceramic sheet is collected on the one-dimensional position detection element by the light receiving lens. If the reflection position of the irradiation light on the ceramic sheet changes, the imaging position on the position detection element changes, and the output balance of the position detection element changes, so if the outputs before and after the change are A and B, respectively, A / (A + B) is calculated, and a displacement amount = [A × k / (A + B) + C] can be obtained from an appropriate span coefficient k and offset C. From this result, the angle of the reflected light received can be measured, and the distance and angle between the light receiving position in the light receiver and the projector can be calculated. Therefore, since one side and the angle | corner of the both ends are decided, the irradiation position of the irradiation light to a ceramic sheet, ie, the height of a ceramic sheet, can be measured.

  For example, when a ceramic sheet to be inspected is placed on a servo slider to automatically detect deformation, the ceramic sheet moves by a belt conveyor, and when the irradiated light is irradiated to the warped part of the end, The angle of the reflected light to be measured changes. From this angle, the irradiation position of the irradiation light on the ceramic sheet, that is, the height of the ceramic sheet can be measured by the triangulation method as described above.

  As the triangulation distance displacement sensor used in the present invention, an optical sensor having a light source with a wavelength in the range of 650 nm or more and 720 nm or less is suitably used as a sensor suitable for the purpose of detecting warpage of the ceramic sheet. .

  As an optical triangulation type displacement sensor, for example, an LED triangulation type displacement sensor using an LED emitting red visible light having a wavelength of about 700 nm or a red visible laser beam having a wavelength of about 670 nm is used. And laser triangulation displacement sensor.

  If the LED triangulation displacement sensor has a resolution of 1 μm or less, the warp of 11 μm or more, more preferably 30 μm or more, and even more preferably 40 μm or more with respect to a sheet length (in-plane length) of 100 mm. Can be detected effectively. Further, warping such as bulging or waviness can be sufficiently detected if the diameter is 15 μm or more, more preferably 30 μm or more, still more preferably 40 μm or more, and particularly preferably 50 μm or more.

  On the other hand, since the warp (burr) at the end is smaller than other deformations, the resolution is 0.1 μm or less, the beam diameter can be reduced, and a minute displacement of about 5 μm can be accurately measured. It is preferable to detect with a laser triangulation displacement sensor. If it is a laser triangulation type displacement sensor, it can be detected effectively if it has a height of 5 μm or more, more preferably 20 μm or more, and even more preferably 30 μm or more with respect to the sheet length (in-plane length) of 100 mm. it can.

  As described above, warpage, bulging and undulation of the entire sheet can be detected effectively using the LED triangulation displacement sensor, and warpage (burr) at the end can be detected effectively using the laser triangulation displacement sensor. If both distance measuring displacement sensors are used, deformation in the thickness direction can be detected particularly well. In this case, either the inspection using the LED triangulation displacement sensor or the inspection using the laser triangulation displacement sensor may be performed first.

  In principle, the triangulation displacement sensor uses spot light, so in order to detect warping that is a relatively wide range of defects, use multiple sensors to reduce warping. It is preferable to enable efficient detection.

  Moreover, in the case of a ceramic sheet with warpage, it has been found that the inspection speed must be reduced in order to accurately inspect defects on the surface and inside of the sheet. The reason for this may be that if the ceramic sheet is warped, the light emitted from the optical sensor is affected by the deformation in order to detect defects on the sheet surface and inside.

  Therefore, as an inspection method that can detect defects with high accuracy without reducing the inspection speed, inspect the presence or absence of warpage in advance when detecting defects on the surface and inside with a 3D camera and a photoelectric sensor. It is preferable to keep it. In other words, it is preferable to first detect warpage with a triangulation displacement sensor and then detect defects on the surface and inside with a 3D camera and a photoelectric sensor. Even if the inspection speed is increased, the ceramic sheet can be accurately inspected and inspected. Can also be automated.

  Furthermore, after the step of detecting the warpage of the ceramic sheet, it is preferable to detect defects present on the surface and / or inside of the sheet after removing the defective ceramic sheet in which the warpage has been detected. By removing the defective ceramic sheet having warpage, it is possible to accurately detect the defects existing on the surface and / or inside of the ceramic sheet without overlooking the defect, and the number of inspections of the ceramic sheet is reduced, so that the inspection can be performed more efficiently. Can do.

  The removal of the ceramic sheet in which the warpage has been detected may be performed manually. However, for more efficient inspection, it is more preferable to provide a removal device that works in conjunction with a triangulation displacement sensor to automatically remove defective sheets.

  In the inspection method of the present invention, it is preferable to perform inspection (measurement) while moving the ceramic sheet, and it is more preferable to perform it while continuously moving the ceramic sheet. The sheet moving speed is not particularly limited, but is preferably 30 mm / second or more with respect to the sheet length (in-plane length) direction. Even at such a high moving speed, the inspection method of the present invention enables accurate inspection. On the other hand, if the speed is too high even in the method of the present invention, a storage yard with a large exclusive area is required to prepare a ceramic sheet for inspection and store the ceramic sheet that has passed the inspection, so the speed is set to 300 mm / second or less. It is preferable.

  Inspecting a ceramic sheet for defects requires starting from one end of the sheet and performing it to multiple ends. For this purpose, the detection device may be moved with the sheet fixed, or the sheet may be moved continuously with the detection device fixed.

  Usually, inspection of ceramic sheets is sufficient in one axis (X-axis) direction, but it is not possible to inspect in two axes (X-axis, Y-axis) depending on the shape of the sheet or for accurate inspection at the sheet end surface. preferable. In particular, when a laser triangulation displacement sensor is used in the warp detection process, it is preferable to inspect the Y-axis direction by rotating the sheet 90 ° in the plane direction after inspecting in one plane direction. For example, an elongated defect such as a scratch may be difficult to detect depending on its direction, but by performing a similar inspection by rotating 90 °, it is possible to detect such a defect without omission.

  In addition, when inspecting a ceramic sheet by the inspection method of the present invention, as a matter of course, in order to inspect only the defect of the ceramic sheet itself, the influence of the inspection environment such as dust that affects the inspection result is minimized. Need to be eliminated. Specifically, in the detection process with a transmissive photoelectric sensor, dust adhering to the inspection ceramic sheet surface appears black in the inspection image, and this black portion is regarded as the same defect as an actual crack or foreign object. May be determined as NG in the pass / fail inspection. Therefore, it is preferable to set the cleanliness level in the inspection work room to an environment of class 10,000 or less and remove dust before putting the inspection ceramic sheet into the inspection machine. The dust here refers to minute lint, hair, minute paper pieces of cardboard, minute fragments of cushion material, and the like. The dust removal method includes a system that cleans the surface of the sheet with a clean brush, a system that removes dust adhering to one or both sides of the sheet by passing the inspection ceramic sheet between the clean rolls, and the clean roll. There is a system that cleans one or both sides of the sheet while removing dust with an adhesive roll to keep the clean roll clean.

  The dust removal system is preferably performed before passing the inspection ceramic sheet in each defect detection step. In particular, it is particularly preferable that the sheet is first disposed on a roller conveyor or a servo slider for moving the sheet to a step of detecting warpage by a triangulation displacement sensor.

  Hereinafter, the preferable specific example for implementing the inspection method of the ceramic sheet which concerns on this invention demonstrated above is demonstrated.

  FIG. 1 shows an LED triangulation displacement sensor and laser triangulation displacement sensor as a triangulation distance displacement sensor, a 3D camera, and a transmission CCD line sensor and transmission laser sensor as a transmission photoelectric sensor. It is a schematic diagram of the example which test | inspected the ceramic sheet.

  The ceramic sheet a to be inspected is conveyed by the servo slider J, and after being inspected for the presence of warpage, bulging, and undulation of the entire sheet by the LED triangulation displacement sensor A1, the laser triangulation displacement is detected. The sensor A2 is mainly inspected for warping (burr) of the sheet end face. Next, the sheet is rotated by 90 ° by the rotating part G, returned to the laser triangulation type displacement sensor A2, and re-inspected. Then, it is conveyed with the roller conveyor K.

  When the sheet reaches the pass / fail ceramic sheet separation part F (F1), warpage of a predetermined height or more is detected by either the LED triangulation displacement sensor A1 or the laser triangulation displacement sensor A2. The ceramic sheet c (c1) is conveyed to the rejected ceramic sheet storage unit I.

  The ceramic sheet in which no warpage of a predetermined height or more is detected is further inspected for scratches and dents by the 3D camera B. The ceramic sheet c (c2) that is rejected by the 3D camera is conveyed to the rejected ceramic sheet storage portion I, and the ceramic sheet in which scratches and dents of a predetermined depth or more are not detected is further transmitted by the transmission laser sensor C. Get inspected for cracks and bubbles. After the inspection with the transmission type laser sensor C, the sheet is rotated by 90 ° by the rotating part G, returned to the transmission type laser sensor C, and subjected to a re-inspection. After passing through the 90 ° rotating portion G, the transmissive CCD line sensor D is chipped and inspected for the presence of foreign matter, and then conveyed by the roller conveyor K.

  When the sheet reaches the acceptance / rejection ceramic sheet separation part F (F2), the surface or the inside is detected either by two inspections by the transmission laser sensor C and inspection by the transmission CCD line sensor D in total three times. The ceramic sheet c (c3) in which the defect was recognized was conveyed to the unacceptable ceramic sheet storage part I, and only the ceramic sheet in which no defect was recognized in any of the three inspections was inspected as the inspection-accepting ceramic sheet b. It is conveyed to the acceptable ceramic sheet storage part H.

  ADVANTAGE OF THE INVENTION According to this invention, the defect of a ceramic sheet can be test | inspected very efficiently and correctly, and the high quality ceramic sheet for electrolyte membranes of SOFC can be provided. Therefore, the method of the present invention can also be applied to industrial production of high-quality ceramic sheets for electrolyte membranes.

EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples. However, the present invention is not limited by the following examples, but may be appropriately modified within a range that can meet the purpose described above and below. Of course, it is possible to implement them, and they are all included in the technical scope of the present invention.
Example 1 Inspection of zirconia-based sheet (1) Production of zirconia-based sheet 100 parts by mass of commercially available 6 mol% scandia-stabilized zirconia powder, methacrylate-based copolymer (number average molecular weight: 100,000, glass transition temperature: -8 15 parts by mass in terms of solid content, 50 parts by mass of a mixed solvent of toluene / isopropanol (mass ratio: 3/2), and 3 parts by mass of dibutyl phthalate as a plasticizer Then, 2 parts by mass of a sorbitan fatty acid ester surfactant as a dispersant was mixed while being pulverized by a ball mill to obtain a slurry.

  The obtained slurry was transferred to a jacketed round bottom cylindrical vacuum degassing vessel with an internal volume of 50 L equipped with an irrigation type agitator, and the jacket temperature was reduced under reduced pressure (about 4 to 21 kPa) while rotating the agitator at a speed of 30 rpm. Concentration and defoaming were performed at 40 ° C., the viscosity was adjusted to 3 Pa · s, and a slurry for coating was obtained. The slurry for coating is transferred to a slurry dam of a coating apparatus, coated on a PET film by a doctor blade method, and a dryer (3 zones of 50 ° C., 80 ° C., 110 ° C.) following the coating unit is set to 0.00. By passing it at a speed of 2 m / min and drying, a long green sheet having a width of 95 cm and a thickness of about 150 μm was obtained.

  The obtained green sheet was punched into a size of about 130 mm × 130 mm and fired at 1400 ° C. in an air atmosphere to obtain 3000 scandia-stabilized zirconia sheets having a 100 mm square and a thickness of 120 μm.

The scandia-stabilized zirconia sheet was inspected using the same inspection apparatus as shown in FIG. Details will be described in (2) to (5).
(2) Detection of deformation in the thickness direction by a triangulation displacement sensor All the scandia-stabilized zirconia sheets are 50 mm / mm by a servo slider (product name “SGSP (MS) 26-200”) manufactured by Sigma Koki Co., Ltd. While moving horizontally at a speed of seconds, sheet warpage over the entire surface was detected by triangulation using an LED displacement sensor (product name “Z4D-F04A”) manufactured by OMRON.

When a sheet warp was found to cause a height difference of 110 μm or more, 58 sheets out of 3000 sheets were warped.
(3) Detection of surface defects using a 3D camera From the results obtained in Example 1 (2) above, 2942 scandia-stabilized zirconia sheets in which no sheet warp defects were observed were moved horizontally at a speed of 50 mm / sec. While doing so, scratches and dent defects on the sheet were detected with a 3D camera.

For example, surface scratches and dents were detected by a 3D camera surface shape inspection device manufactured by Taiyo Electric Co., Ltd. According to the obtained results, scratches and dent defects were observed in 42 out of 2942 scandia-stabilized zirconia sheets.
(4) Detection of defects by transmission type CCD line sensor From the results obtained in Examples 1 (2) and (3), 2900 sheets of scandia-stabilized zirconia in which no sheet warp, scratch or dent defect was observed. While moving the sheet horizontally at a speed of 50 mm / sec, surface defects and internal defects of the sheet were detected by a CCD line sensor.

Specifically, using the following apparatus, slit light was irradiated vertically from the back surface of the sheet, and transmitted light was photographed from the opposite surface by a CCD line sensor.
CCD line sensor: NED, line camera e2048D
Lens for the above line sensor: Nikon Corporation, Ai Micro Nikkor 55mm F2.8
According to the obtained results, 38 out of 2900 scandia-stabilized zirconia sheets were found to have chipping and foreign matter defects.
(5) Detection of defects with a transmission type laser sensor Further, 2841 scandia-stabilized zirconia sheets, in which no sheet warp, scratches, or dent defects were observed, were moved horizontally at a speed of 50 mm / sec while moving the surface of the sheet. Defects and internal defects were detected by a laser sensor.

  Specifically, while moving a scandia-stabilized zirconia sheet with a servo slider, a laser projector / receiver (manufactured by Taiyo Electric Co., Ltd., LD-01) is used to perform laser from an angle of 60 ° with respect to the horizontal direction from the back of the sheet. Light was irradiated, the light was incident on the light receiving portion at a position 25 mm away from the opposite surface of the sheet on the same axis of the irradiated laser light, and was imaged linearly at intervals of 50 μm and converted into a two-dimensional image. According to the obtained results, cracks and bubble defects were observed in 7 out of 2893 ceramic sheets. The results are shown in Table 1.

Comparative Example 1
Example of the same lot of scania-stabilized zirconia sheet produced in the same manner as in Example 1 except that a defect including a scratch and a dent is detected by the transmission laser sensor without using a 3D camera. The same inspection as 1 was performed.

  According to the obtained results, in the detection of defects by the CCD line sensor, 39 scandia-stabilized zirconia sheets were found to have defects and foreign matter defects. In the detection of defects using a laser sensor, flaws, dents, cracks and bubbles were found in 21 scandia-stabilized zirconia sheets. The results are shown in Table 1.

  According to the inspection method of the ceramic sheet of the present invention from Table 1, the number of sheets classified as unacceptable by scratches and dents by a 3D camera is 42, and the number of sheets classified as unacceptable by cracks and bubbles by a transmission type laser sensor is 7 sheets. On the other hand, the number of rejected sheets due to scratches, dents, cracks and bubbles by the transmission type laser sensor of the conventional inspection method is 21 sheets. In other words, the number of rejected sheets derived from the presence of scratches and dents detected by the transmission type laser sensor is calculated to be about 14 (21-7 sheets) in comparison with the inspection result in the present invention (Example). Is done. Therefore, by using a 3D camera in the present invention, minute scratches and dents that could not be detected by the conventional method are detected, and the number thereof is about 28 (42-14), and many rejects. The goods are separated.

  In terms of the ratio of rejected sheets including warpage, this is 4.0% to 4.8% of the conventional inspection method, and scratches that have not been detected by the inspection method of the present invention. It was found that dents were detected in the present invention, and the ratio was 0.8%.

  Accordingly, the accuracy of detection of defects such as scratches and dents is greatly improved by the inspection method of the present invention, and the ceramic sheet for electrolyte membrane of SOFC provided by using the inspection method of the present invention and the inspection process by the inspection method of the present invention are performed. It can be said that the ceramic sheet for electrolyte membrane of SOFC obtained by the manufacturing method including it is a high-quality electrolyte sheet in which scratches and dents are greatly reduced.

a: Ceramic sheet for inspection, b: Ceramic sheet that passed inspection, c: Ceramic sheet that failed inspection, A1: LED triangulation displacement sensor, A2: Laser triangulation displacement sensor, B: 3D camera C: Transmission type Laser sensor, D: Transmission type CCD line sensor, E: Inspection sheet surface cleaning system, F: Pass / fail ceramic sheet sorting part, G: Inspection ceramic sheet 90 ° rotating part, H: Inspection pass ceramic sheet storage part , I: Inspection corner angle ceramic sheet storage, J: Servo slider, K: Roller conveyor

Claims (5)

A method for inspecting a ceramic sheet for a solid electrolyte membrane of a solid oxide fuel cell,
The test method is seen containing a defect detection step of detecting using defective three-dimensional camera and transmission-type photoelectric sensor of the ceramic sheet,
The ceramic sheet has a thickness of 50 μm or more and 150 μm or less,
In the defect detection step, a defect having a depth of at least less than 30 μm is detected using the three-dimensional camera.
Inspection method for ceramic sheets. It said defect detecting step comprises the steps of detecting defects present at least on the surface using the three-dimensional camera, is intended to include a step of detecting a defect existing in the interior at least using the transmission type photoelectric sensor, claim The inspection method of the ceramic sheet of 1. 3. The defect detection step according to claim 1, wherein a defect of the ceramic sheet, in which no defect is detected using the three-dimensional camera, is detected using the plurality of transmission photoelectric sensors having different light sources. Inspection method for ceramic sheets. Furthermore, the inspection method of the ceramic sheet | seat of any one of Claims 1-3 including the process of detecting the curvature of the said ceramic sheet | seat using a triangulation type displacement sensor. A method for producing a ceramic sheet for an electrolyte membrane of a solid oxide fuel cell, comprising:
A step of preparing a slurry by mixing a slurry raw material including a powder made of a ceramic material for an electrolyte membrane of a solid oxide fuel cell, a solvent, and a binder;
Coating the obtained slurry on a film;
Drying the slurry coated on the film into a green sheet;
A method for producing a ceramic sheet, comprising: a step of firing a green sheet; and a step of inspecting the obtained ceramic sheet by the method according to any one of claims 1 to 4 .

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