EP0325600A1

EP0325600A1 - Process for manufacturing cermets, and composites manufactured according to this process, and the use thereof

Info

Publication number: EP0325600A1
Application number: EP87906185A
Authority: EP
Inventors: Bernhard Farkasch
Original assignee: Individual
Current assignee: Individual
Priority date: 1986-10-01
Filing date: 1987-09-29
Publication date: 1989-08-02
Also published as: DE3633406A1; AU8027987A; WO1988002355A1

Abstract

Pour fabriquer des composites céramiques ou céramo-métalliques, on place entre deux feuilles métalliques minces (11, 12), de préférence d'une épaisseur comprise entre 0,5 mum et 200 mum, un matériau céramique (13) bien moins compact, puis on presse les uns contre les autres les éléments du composite que l'on vitrifie ensuite. Le pressage entraîne souvent une modification fondamentale de la forme tridimensionnelle. Les composites obtenus trouvent de nombreuses applications, que ce soit comme armature dans des briques coulées par fusion, comme filtre ou comme fils supraconducteurs.To manufacture ceramic or ceramo-metallic composites, a much less compact ceramic material (13) is placed between two thin metal sheets (11, 12), preferably with a thickness of between 0.5 μm and 200 μm, then the elements of the composite are pressed against each other and then vitrified. Pressing often results in a fundamental change in the three-dimensional shape. The composites obtained find many applications, whether as reinforcement in fusion-cast bricks, as filters or as superconducting wires.

Description

Process for producing ceramic-metallic composite bodies, as well as composite bodies produced by the process and their use.

Technical field

The invention relates to a method for producing ceramic-metallic composite bodies, and to composite bodies produced by the method and their use.

State of the art

Ceramic materials as well as ceramic-metallic composite materials are made from granular components. The shaping is carried out by pressing, casting, slip casting, etc. These processes have in common that the ceramic and metallic components are present unconnected after the shaping, that is to say that they are not connected to one another by solid bridges. They obtain their "green strength" from binders, adhesion and tension forces. The final strength is achieved by sintering at high temperatures. In order to increase the porosity, organic materials are added to the starting mixtures before they are shaped, which burn out when heated. Salts, which are removed after shaping, serve the same purpose. With these methods, however, no complex pores and material structures with precise pore diameters can be introduced into the parts.

The use of binders in the form of organic adhesives is disadvantageous because they envelop the grains and then only in slight, direct contact

ER C. A ' standing and sintering badly. Inorganic adhesives form phases that impair the material obtained. Such adhesives generally have an insulating effect in ceramic superconductors. If water glass is used as the adhesive, the application limit temperature is reduced.

Presentation of the invention

The present invention is based on the object of simply creating thin ceramic or ceramic-metallic composite bodies as comparatively thin-walled bodies with possible different spatial shapes and with predictable properties, in particular porosity, which at the same time have multiple uses, in particular as a filter and these binders can be used as superconducting ceramic structures or as reinforcement in refractory bodies.

To achieve this object, it is proposed according to the invention in a method for producing ceramic or ceramic-metallic composite bodies that a ceramic material is introduced between two thin metal foils and then this composite is pressed together and then sintered.

The ceramic material is inorganic, non-metallic substances. These inorganic materials can be powdery, granular, but also in the form of fibers. If they are in the form of fibers, they can be inserted between the metal foils in the form of mats. The metal foils can consist of iron alloys, but also metal alloys, provided that they are not pure metals. As a rule, they consist of aluminum, copper or zirconium. They have a small thickness as foils, so they are usually 0.5 to 200 μm, in particular 20 to 40 μm thick.

In a further embodiment according to the invention it is proposed that the pressing creates a fundamentally different spatial shape. For example, depressions can be introduced into the structure, for example as channels. With the pressing, however, another fundamental change in the spatial shape can take place in such a way that a flat composite body is given an arched or round cross-sectional shape with the pressing.

The method is particularly advantageous in that the ceramic material is applied to a first metal foil, then another metal foil with another identical or different ceramic material is applied to it, and this composite is pressed together at room temperature and then sintered.

It is also possible to add the loose composite body

To subject room temperature to a first pressing, then to heat this pre-pressed composite body and then to press it in a highly heated state, for example in order to obtain a denser structure. Then the body pressed several times in this way is brought to the high sintering temperature so that a further intimate connection of the materials forming the composite body is achieved by the sintering. The sintering can be carried out in an oxidizing atmosphere. It then generally results that the metal foil also partially or completely oxidizes, so that the metal foil is transformed into a ceramic material which, due to the sintering, forms an intimate connection with the other ceramic material.

However, sintering can also take place in a neutral atmosphere. This is done, for example, if the metal foil is to be retained. It can also be provided that the ceramic substances are added with oxygen-releasing substances which result in an oxide layer on the inside of the metal foils in order to improve the bond with the ceramic substances.

The composite wires can be compressed ^• the pressing or after the first pressing to ceramic as electrically superconducting

To be able to use structures. For this purpose, long strips, optionally made from a flat-rolled wire, are advantageously pressed in connection with the ceramic materials and then sintered. However, pressing, in particular into a wire, can also be carried out by rolling or in a nozzle.

In a further embodiment according to the invention, it is proposed that the ceramic or metal-ceramic composite body be treated with liquid plastic, liquid metal or molten oxide or be surrounded by these liquid substances. In the latter case, they are then reinforcements in plastic, metal or a stone obtained from molten oxide, which is used as a refractory stone, for example in melting furnaces or in furnaces. A finished composite body is characterized according to the invention by one or more metal foils, between which ceramic materials are arranged, with which they are intimately connected by pressing and sintering.

In a further embodiment according to the invention it is proposed that one or more metal foils, in particular the inner metal foil, are provided with openings. The outer metal foils can have openings, in particular for use as a filter. In many cases it is also expedient to provide the inner metal foil layers with openings or to create the openings by pressing through coarse ceramic grains.

The ceramic materials as grains or fibers can have approximately the same grain size. But they can also have different grain sizes. According to the present invention, it is possible to create an adjustable or predictable porosity by selecting the grain sizes in the individual layers. At the same time, a predictable strength can be created. Therefore, the ceramic composite material, usually of low overall thickness, can be used in many ways, for example as reinforcement in a refractory brick.

As a wire, the ceramic composite material meets the requirements for a superconductor. Description of the drawing

The invention is illustrated by way of example in the drawings.

Show it:

FIGURE 1 essentially schematic of the ceramic material present between two metal foils before pressing, ^*

FIGURE 2 the body of FIGURE 1 after pressing,

FIGURE 3 the body of FIGURE 2 after sintering,

FIG. 3A shows a partial section from FIG. 3 in a larger representation,

FIGURE 4 essentially schematically the fundamental change of the spatial shape with the pressing,

FIG. 5 shows a ceramic body with three layers of metal foil and ceramic grains of different grain sizes arranged between them before pressing,

FIGURE 6 the body of FIGURE 5 after pressing,

7 shows a modification with four metal foils, FIGURE 8 shows another structure before pressing,

FIGURE 9 the body of FIGURE 8 after pressing,

FIGURE 10 in a basic representation the structure for a superconductor before pressing,

FIGURE 11 shows the arrangement of FIGURE 10 after pressing,

FIGURE 12 shows a further structure for a superconductor before pressing,

FIGURE 13 shows the arrangement of FIGURE 12 after pressing,

FIGURE 14 is a vertical section through a housing with filters made of ceramic elements,

15 shows a plate made of metal foils with a ceramic material arranged between them before pressing,

FIGURE 16 shows the arrangement of FIGURE 15 after pressing,

FIGURE 17 the installation of the pressed and sintered bodies in a melt-cast oxidic stone. Best ways to carry out the invention.

Figure 1 shows the initial situation for producing a ceramic or metal-ceramic body. Between the two metal foils 11 and 12 with a thickness of 0.5 to 200 μm, preferably made of aluminum or zirconium, a ceramic material 13 is introduced, which according to the embodiment consists of grains of approximately the same grain size. However, depending on the desired porosity, a grain structure with different grains can also be present. The solution according to the invention of creating small composite bodies in thickness permits a very fine gradation here.

Figure 2 shows the composite after pressing. According to the exemplary embodiment, it has a total thickness of 100 μm, i.e. H. 0.1 mm.

Figure 3 shows the composite after sintering with the proviso that the unit of the metal foils with the ceramic material after sintering is to be represented by the hatching. Depending on the metal foils and the conditions during the sintering, for example whether in a neutral or oxidizing atmosphere, the metal foils are retained or they also oxidize to form a ceramic material, so that the bond to the ceramic material present between the original foils is thereby achieved is improved. The chemical nature of the

Metal foils and the ceramic material, the foil thickness and grain size allow many modifications, so that exactly predictable properties can be achieved. Figure 4 shows the deformation after pressing.

FIG. 5 shows that a central metal foil 14 is arranged between the outer metal foils 11 and 12. The grains have different grain sizes, such as the coarse grains 13a and the fine grains 13b. With the pressing, the coarse grains 13 partially penetrate the middle metal foil or partially dig into the inner sides of the outer metal foils, so that an intimate connection by anchoring already takes place with the pressing. This intimate connection is increased by sintering at the appropriately adjusted sintering temperature.

Figure 7 shows that the upper metal foil is provided with numerous openings 15, 15a. In the same way, the lower metal foil 11 can also be provided with these openings. Such breakthroughs are present, for example, when the finished ceramic or metal-ceramic bodies are used as filters in a housing. After pressing and sintering, a total thickness of 400 μm, ie. H. 0.4 mm available.

FIG. 8 shows the starting product in such a way that the central metal foil 14 is provided with initial perforations in order to increase the bond. Figure 9 shows the intimate connection after pressing.

Industrial applicability

FIG. 10 shows stiff metal foils 11, 12, between which ceramic materials 13, for example in the form of fibers, are arranged. The edge regions of the foils 11, 12 and 13 are connected to one another by pressing. This can be done through application an adhesive that is not present in the ceramic in superconductors. Welding or soldering can take place. Finally, the metal foils can be connected during sintering.

FIG. 12 shows a metallic strip with a meandering cross section so that the ceramic material 13 can be introduced between the film layers. In this form of training, too, the metallic layers are connected with the pressing. With the pressing, as shown in FIG. 13a in a cross section, a bend can be made into a wire-like configuration.

FIG. 14 shows a filter housing 16 with the inlet 17 and the outlet 18. The metal-ceramic or ceramic plate-shaped structures 10a, 10b are present on the inside. If the metal foils have been preserved, then they have the openings 15, 15a described in FIG. 7, in order to give the filter medium a corresponding passage. However, it can also be provided that the metal foils have become a ceramic material by oxidation and then the filter structure is also present in the area of the earlier metal foils.

FIG. 15 shows a plate 13 which, after pressing, as shown in FIG. 16, has channel-like depressions 19, 19a and 19b which are alternately present on one and the other side. The metal-ceramic or ceramic body 10 is then installed in a refractory stone 20. It is preferably a melt-cast stone. FIG. 17 shows the front side 23, which is highly stressed by the temperature, so that the ceramic structure extends in the longitudinal direction of the temperature gradient.

However, other spatial arrangements can also be present.

Since the metal-ceramic and ceramic plate-shaped elements have a predetermined porosity, the result is that cracks occurring in the stone at high temperatures cannot propagate because they end at the porous inlays.

The solution according to the invention allows the metal-ceramic or ceramic plates, in particular as thin plates or strips themselves, to have a fire resistance which is greater than the stone material in which they are installed. With the invention, a selection can be made here that corresponds to optimal requirements and special features.

The ceramic or metal-ceramic plates or wires or similar structures have a total thickness after sintering, which preferably the

Amount of 1000 μm, i.e. H. Should not exceed 1 mm.

Claims

1. A process for the production of ceramic or ceramic-metallic composite bodies, so that a loose ceramic material (13) is introduced between two thin metal foils (12, 13) and then this composite is pressed together and then sintered.

2. The method of claim 1, d a d u r c h g e k e n n z e i c h n e t that the metal foils (12, 13) with a thickness of 0.5 to 200 microns are used.

3. The method according to claims 1 and 2, d a d u r c h g e k e n n z e i c h n e t that metal foils made of aluminum and / or zirconium are used.

4. The method of claim 1, d a d u r c h g e k e n n z e i c h n e t that a fundamental change in the spatial shape is created with the pressing.

5. The method according to claim 1, characterized in that a ceramic granular or fibrous material (13) applied to a first metal foil (13), then placed on this another metal foil (12) and applied to this metal foil another ceramic granular or fibrous material is and this composite is pressed together at preferably room temperature and then sintered.

6. The method according to claims 1 to 5, d a d u r c h g e k e n n z e i c h n e t that the sintering is carried out in an oxidizing atmosphere.

7. The method according to claims 1 to 5, where the sintering is carried out in a neutral atmosphere,

8. The method according to claims 1 to 5, d a d u r c h g e k e n n z e i c h n e t that the elongated composite body is pressed into a wire.

9. The method of claim 6, d a d u r c h g e k e n n z e i c h n e t that the wire is twisted after its manufacture and then the sintering is carried out.

0- Method according to claim 6, so that the layers (11, 12) made of metal foils and the ceramic material (13) are twisted and then the pressing is carried out.

11. The method of claim 1, d a d u r c h g e k e n n z e i c h n e t that the pressing is carried out by rolling or in a nozzle.

12. The method according to claim 1 and one or more of claims 2 to 11, d a d u r c h g e k e n n z e i c h n e t that the composite body with liquid plastic, liquid metal or molten oxide are treated or surrounded.

1 13. Composite body, produced by one or more of the methods 1 to 12, characterized ¬ characterized by one or more metal foils (11, 12), between which a ceramic material (13) is arranged, with which they are intimately connected by pressing and sintering are.

14. Composite body according to claim 13, so that one or more metal foils (11, 12), in particular the inner metal foil (14) with openings (15, 15a) are provided.

15. Composite body according to claim 13, d a d u r c h 5 g e k e n n z e i c h n e t that the ceramic

Material (13) consists of grains of substantially the same grain size.

16. Composite body according to claim 13, d a d u r c h g e k e n n z e i c h n e t that between coarse

Grains (13a) of approximately the same grain size are fine grains (13b) made of a ceramic material.

°

17. Composite body according to claim 13, d a d u r c h g e k e n n z e i c h n e t that the ceramic material consists of fibers.

18. Composite body according to claim 14, so that the grains (13a, 13b) of different grain sizes are of the same or approximately the same chemical nature.

19. Composite body according to claim 13, characterized 5 in that it is a superconducting wire.

20. Composite body according to claim 19, so that the wire consists of at least two metal foil strips (11, 12) which are connected to one another at their longitudinal edges and enclose the ceramic material (13).

21. Composite body according to claim 13, so that it as a sintered body has a thickness of less than 1.5 mm, preferably 0.1 mm to 0.5 mm.

22. Use of the composite body according to claim 13 and one or more of claims 14 to 19, so that one or more composite bodies (10, 10a etc.) are arranged in a melt-cast oxidic stone (20).

23. Use of the composite body according to claim 13 and one or more of claims 14 to 18, d a d u r c h g e k e n n z e i c h n e t that they are arranged as filter elements (10a, 10b) in a filter housing (16).

24. Use of the composite body according to claim 3, so that they are used as superconducting ceramic or metal-ceramic bodies.