PROCESS FOR PRODUCING A COMPONENT CONSTITUTING AN INTERCONNECTOR OF AN HTE ELECTROLYSER OR OF AN SOFC FUEL CELL

Abstract

Improved process for producing a component constituting an interconnector of an HTE electrolyser or of an SOFC fuel cell. The invention relates to a process for preparing a component (1), intended to constitute an interconnector for a fuel cell (SOFC) or a high-temperature electrolyser (HTE), comprising the following steps: a/preparing a substrate made of metal alloy (12), the base element of which is iron (Fe) or nickel (Ni), the substrate having two main flat faces, b/tape casting a thick ceramic layer (13); c/localized removal at one or more locations (14), of material of the tape-cast thick ceramic layer; d/hot pressing the green thick ceramic layer tape; e/grooving the thick ceramic layer so as to delimit channels that are suitable for distributing and/or collecting gases. It also relates to the component obtained according to the process.

Claims

1. A process for preparing a component (1), the process comprising: preparing a substrate made of metal alloy, of chromia-forming type, a base element of which being iron or nickel, the substrate having two main flat faces; tape casting a thick ceramic layer, thereby producing a tape-case thick ceramic layer; locally removing at one or more locations of material of the tape-cast thick ceramic layer; hot pressing a green thick ceramic layer tape; and grooving the thick ceramic layer so as to delimit channels that are suitable for distributing and/or collecting gases.

2. The process according to claim 1, wherein the locally removing is carried out by laser ablation.

3. The process according to claim 2, wherein the locally removing is carried out by means of a CO.sub.2 laser.

4. The process according to claim 1, wherein removed material zones forms holes, each hole having a surface area of between 10.sup.−9 and 10 mm.sup.2.

5. The process according to claim 1, wherein removed material zones are uniformly distributed on a surface of the thick ceramic layer.

6. The process according to claim 1, wherein removed material zones each has a cylinder shape opening onto a metal substrate.

7. The process according to claim 1, wherein the grooving is carried out by laser ablation before carrying out the hot-pressing.

8. The process according to claim 1, wherein the hot pressing is carried out at a temperature between 60 and 130° C.

9. The process according to claim 1, wherein the hot pressing being carried out for a time of less than 2 h.

10. A component obtained by the process according to claim 1, wherein the material of the tape-cast thick ceramic layer is chosen from a lanthanum manganite of formula La.sub.1-x—Sr.sub.xMO.sub.3 with M (transition metals)=Ni, Fe, Co, Mn, Cr, alone or as a mixture, or materials of lamellar structure such as lanthanide nickelates of formula Ln.sub.2NiO.sub.4 (Ln=La, Nd, Pr), or another electrically conductive perovskite oxide.

11. The component according to claim 10, wherein a thickness of the ceramic layer is between 30 and 800 μm.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0059] FIG. 1 is a schematic front view of an interconnecting plate of an HTE electrolyser according to the prior art.

[0060] FIG. 1A is a detailed cross-sectional view of an interconnecting plate according to FIG. 1.

[0061] FIG. 1B is a view similar to that of FIG. 1A showing the current lines passing through the plate.

[0062] FIG. 2 is a schematic front view of another interconnecting plate of an electrolyser according to the prior art.

[0063] FIG. 3 is a photographic reproduction of a plate according to FIG. 1, obtained by mechanical machining.

[0064] FIG. 4 is a photographic reproduction of a plate according to FIG. 1, obtained by drawing.

[0065] FIG. 5 is a front photographic reproduction on the side of a thick LSM layer once the hot-pressing step has been carried out in accordance with the process according to patent FR2996065B1.

[0066] FIG. 6 is a front photographic reproduction on the side of a thick LSM layer once the channel grooving step has been carried out in accordance with the process according to patent FR2996065B1.

[0067] FIG. 7 is a schematic view showing the step of localized removal of material from the thick ceramic layer according to the invention;

[0068] FIG. 8 is a front photographic reproduction on the side of a thick LSM layer before the hot-pressing step in accordance with the process according to the invention.

DETAILED DESCRIPTION

[0069] FIGS. 1 to 6, which relate to the prior art have already been commented on in the preamble. They are there fore not described in detail hereinbelow.

[0070] FIG. 7 illustrates an example of localized removal of material from a thick ceramic layer 13 which takes place after the tape casting of the latter in accordance with the invention.

[0071] The purpose of this removal of material is to suppress, or at the very least reduce, the bubble phenomenon observed, as shown in FIG. 5 with the consequences shown in FIG. 6.

[0072] The zones 14 devoid of thick layer are preferably uniformly distributed over the layer 13 and have preferably the shape of cylinders opening onto the underlying metal alloy substrate.

[0073] The various steps for preparing an example of a thick ceramic layer with its channels, obtained according to the process of the invention in the targeted applications, i.e. SOFC fuel cells and HTE electrolysers, are described below.

[0074] Step a/: a substrate 12 is provided consisting of a commercial ferritic alloy of CROFER 22 APU type, having a thickness of 1.5 mm.

[0075] Step b/: manufacture of a green LSM strip.

[0076] A mixture is prepared between a compound with a weight of 60 g of lanthanum manganite of formula La.sub.0.8Sr.sub.0.2MnO.sub.3 with 0.8% by weight of oleic acid as dispersant, 15.7% of 2-butanone and 15.7% of ethanol as solvents.

[0077] The mixture is milled in a planetary mill. The operating cycle of the planetary mill is as follows: [0078] speed of rotation: 400 rpm; [0079] duration: 1 hour.

[0080] A weight of 3.2 g of polyvinyl butyral (PVB 90) and 5.5 g of polyethylene glycol (PEG 400) as solvent are then added to the milled mixture, and everything is then mixed using a planetary mill. The operating cycle of the planetary mill is as follows: [0081] speed of rotation: 200 rpm; [0082] duration: 10 hours.

[0083] The mixture is then deaerated using a mixer of roll type. The operating cycle of the roll mixer is as follows: [0084] speed of rotation: 20 rpm; [0085] duration: 24 hours.

[0086] The suspension obtained after deaeration is then cast as a tape using a scraper blade. The active height of the blade is equal to 1000 μm. The casting speed is equal to 1.5 m/min. The casting is performed onto a sheet of silicone-treated polymer (polyester) so as to promote the detachment of the tape once dried.

[0087] Next, drying of the green tape obtained by casting is performed, in ambient air for a duration of 3 hours.

[0088] The dried green tape of LSM is finally chopped to the sizes corresponding to an air electrode in an SOFC cell, against which the tape is intended to bear. The cutting may be performed, for example, using a laser cutting table.

[0089] Step c/: material is removed from the tape-cast thick ceramic layer by laser ablation using a CO.sub.2 laser.

[0090] As shown in FIG. 8, the zones 14 devoid of material have a cylindrical shape and are distributed uniformly over the surface of the layer 13.

[0091] By way of example, each of these zones 14 has a diameter of 0.1 mm and the density of the zones 14 is around 1 per cm.sup.2.

[0092] Step d/: hot pressing

[0093] The green tape of LSM is then placed on the substrate 12 and is then welded thereto by hot-pressing using a press. The thickness of the green tape of LSM is 325 μm.

[0094] The operating cycle of the press is as follows: [0095] pressing force: 1 kg/mm.sup.2; [0096] pressing duration: 2 hours; [0097] regulated temperature of the two press plates: 80° C.

[0098] After cooling to room temperature, the assembly prepared between the green tape of LSM and the thin sheet of ferritic steel is removed from the press.

[0099] Step e/: Production of the grooves

[0100] Grooving is performed by laser ablation of the green tape of LSM. The ablation is performed using a flatbed plotter equipped with a CO.sub.2 laser of variable power up to a maximum power of 50 watts. The speed of movement of the laser is also variable, up to a maximum speed of 2 cm/s. The use of such a machine is particularly advantageous since it makes it possible by means of its variable operating characteristics to burn, i.e. to perform abrasion, more or less deeply the polymers constituting the green tape, which thus releases the associated charge, the LSM. More or less deep grooves (furrows) may thus be dug. Where appropriate, several passes of the CO.sub.2 laser over the green tape may be performed to increase the depth and/or width of the grooves to a greater or lesser extent.

[0101] After this step e/, it is observed that the scrap rate of the components 1 thus manufactured is less than 1%.

[0102] The invention is not limited to the examples that have just been described; in particular, characteristics of the examples illustrated may be combined within variants not shown.

[0103] Other variants and improvements may be envisaged without however departing from the scope of the invention.

LIST OF REFERENCES CITED

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