EP3790656A1

EP3790656A1 - Method for producing porous composite bodies with thermally conductive support structure

Info

Publication number: EP3790656A1
Application number: EP19724376.9A
Authority: EP
Inventors: Joachim Baumeister; Jörg Weise; Olga YEZERSKA; Sebastian-Johannes Ernst
Original assignee: Fraunhofer Gesellschaft zur Forderung der Angewandten Forschung eV
Current assignee: Fraunhofer Gesellschaft zur Forderung der Angewandten Forschung eV
Priority date: 2018-05-08
Filing date: 2019-05-07
Publication date: 2021-03-17
Also published as: DE102018207143A1; US20210363024A1; WO2019215163A1

Abstract

In a method for producing porous composite bodies which have a support structure made of a material having good thermal conductivity and which have at least one functional material, a multiplicity of shaped bodies (1) made of the functional material are coated with the material having good thermal conductivity and a solid connection between the coated shaped bodies (1) is established in order to form the support structure made of the material having good thermal conductivity. The coating (2) is generated with a porous structure or is provided with a porous structure which, after the solid connection has been established, permits access for a liquid or gaseous medium through the coating to the functional material. The method permits cost-effective production of porous composite bodies with very good heat transfer properties.

Description

Process for the preparation of porous composite bodies having a heat-conductive carrier structure

Technical application

The present invention relates to a process for the preparation of porous composite bodies, which have a support structure of a thermally conductive material and at least one functional material, in particular for the production of sorbent bodies or

Catalysts. The invention also relates to porous composite bodies which can be produced by the method.

Especially in the field of adsorption technology, for example adsorption refrigeration machines or adsorption heat pumps, porous composite bodies are required which have a good heat-conducting carrier structure and suitable adsorbent materials as functional material. The support structure must have, among other things, good thermal coupling conditions, good internal heat transport and a

have mechanical stability. Furthermore, the support structure should have a large surface area for the heat transfer processes and the fixation of the functional material, the lowest possible weight, a small installation space and a low thermal mass.

State of the art

DE 101 59 652 A1 describes a method for producing a porous composite body in which a Foam-like matrix of a metal foam

is provided, in which the sorbent material is infiltrated as a bed. However, in such an embodiment, the thermal contact between the functional material and the thermally conductive support structure is not optimal.

DE 197 30 697 A1 describes a

Adsorption heat pump, in which the adsorbent as

Granules applied to the surface of a heat exchanger surface and connected via an adhesive to this heat exchanger surface. However, the use of an adhesive between the functional material and the heat-conductive support structure is disadvantageous since such adhesives often have a poor heat conductivity ability. The thermal connection of the

Functional material on the thermally conductive surface is therefore low. DE 10 2008 023 481 B4 describes a process for the production of thermally conductive composite adsorbents, in which the functional material is not subsequently incorporated, but is already integrated into it in the production of a highly porous metal structure. In one embodiment, an adsorbent-containing melt of the thermally conductive material is foamed in order to form the composite body. In another embodiment, a mixture of the adsorbent and the thermally conductive material is introduced into a pre-formed porous preform, so that after removal of the preform a sponge-like adsorbent structure is obtained. From DE 10 2005 001 056 B4 a method for producing a porous composite structure with functional materials is known in which a bed of sorbent material is provided in granular form and then infiltrated with an aluminum melt as a heat-conductive material capable.

DE 10 2006 048 445 A1 describes a method for producing a composite body for storing and releasing thermal energy. The composite body consists of a thermally conductive carrier, on the surface of microstructures

are applied or formed with a

Functional material are covered.

From EP 2 532 421 A1, a composite material of a porous polymer matrix, in which zeolite particles are embedded as functional material, as well as a metallic material is known. The metallic material can be embedded, for example, in the form of a perforated metal plate or a metal grid or in particle form.

The object of the present invention is to provide a process for the production of porous

Composite bodies with a support structure made of a good thermal conductivity material and at least one

Provide functional material, which achieves particularly good heat transfer properties with low material usage and are inexpensive to manufacture. Presentation of the invention

The object is achieved with the method and the porous composite body according to claims 1 and 13. Advantageous embodiments of the method and of the proposed composite body are

Subject of the dependent claims or can be the following description and the

Refer to exemplary embodiments. In the proposed method for producing porous composite bodies, which is a support structure made of a preferably good thermal conductivity material, in particular a metallic material, and

have at least one functional material, a plurality of moldings is provided from the functional material. These moldings are preferably granules or tubes or rods of the functional material. These moldings are then coated with the highly thermally conductive material and it is made a firm connection between the coated moldings to the

Carrier structure of the good thermal conductivity material to form. In the process, the coating becomes

either already produced with a porous structure or provided after the coating process with a porous structure, which allows for the preparation of the solid compound access for a liquid or gaseous medium through the coating to the functional material.

In contrast to known methods of the prior art, the proposed method thus does not involve a carrier structure which is highly thermally conductive Functional materials coated. Rather, shaped bodies made of the functional material are coated with the good heat-conductive material. The (porous) layer of the thermally conductive material is thus between the functional material and the surrounding

The atmosphere. The mass transfer with the atmosphere, e.g. Water vapor transport, through the thermally conductive support layer therethrough. The proposed method allows the setting of very large contact surfaces between the thermally conductive material and the functional material. The proposed approach also allows extended design freedoms for the forest. By coating the moldings of the functional material with the good thermal conductivity material is carried out the thermal

Contact on the entire outer surface of the mold body, where most of the heat in the ent speaking processes, in particular adsorption or catalytic processes, arises. The heat dissipation can thus be very efficient. As thermally conductive materials, for example, metals, carbon, carbides or thermally conductive polymers

be used. The thermally conductive materials preferably have a thermal conductivity (at 0 °) of at least 100 W / (m-K).

Compared to a process in which the

Interstices of a bed of a granulate of the functional material to be filled with the highly conductive material, requires the proposed

Method with comparable heat dissipation a smaller amount of thermally conductive material. So wear most of the thermally conductive material in the interstices of a bed not contribute to the thermal bonding of the granules and also its contribution to the total heat transport is - based on the mass - less than in layers that are close to the interface with the granules. This can be with the pre-proposed method with low material use particularly good heat transfer properties of

Achieve composite body and the composite can therefore be manufactured inexpensively.

In an advantageous embodiment of the pre-proposed method, the solid compound of the coated molded body takes place by a sintering process. Does not the coating of the good thermal conductivity material before the sintering process yet

required porous structure, so this porous structure can be achieved by the sintering process. If the porous structure already exists, then the remains

Porosity of the coating obtained by the sintering process at least partially.

The coating can be carried out in such a way that the required open-porous structures already form on the surface of the functional material shaped bodies by the coating process. Alternatively, if a coherent closed and non-porous layer is applied or deposited, then this layer must be subsequently structured or opened in order to make the functional material accessible.

The opening can be by heat treatment, for example, by the preferably performed sintering process, by removing incorporated in the layer Platzhalter, mechanically or chemically, for example, by etching done.

The coating of the molded body with the good heat conductive material can be done for example by a deposition process. So can one

Deposition of a metallic material on the

Molded bodies made of functional material by means of PVD (PVD: Physical Vapor Deposition) or by electrochemical or galvanic deposition, which, if necessary, then a sintering process can be Runaway leads. The galvanic deposition can also be carried out in such a way that the deposition process already creates a porous but stable network of the metallic material.

Another possibility is in the

Coating the moldings using a

suitable binder. For this purpose, the moldings with the binder and particles or fibers of the well

thermally conductive material mixed to coat the shaped body via the binder with the particles or fibers of good thermal conductivity material. Either

Particles as well as fibers of good thermal conductivity

Materials should have dimensions that are significantly smaller than the dimensions of the moldings in order to achieve a coating of the moldings. Preferably, therefore, the particles or fibers of the highly thermally conductive material have dimensions that are smaller than the smallest dimensions of the shaped bodies in one, two or all three dimensions by a factor of 10. In such a coating process by mixing the components involved is

preferably a mixing ratio between the

Functional material and the thermally conductive material selected in which - at a porosity of

Coating between 5 and 25vol% - the volume fraction of the functional or active material between 40 and 70vol% and the volume fraction of the thermally conductive

Material is between 10 and 30vol%. The sum of the volume fractions and the porosity is always 100%. The layer thickness of the thermally conductive material on the moldings of the functional or active material can assume very different values for typical sizes of the active material granules (50 microns-3mm), which may for example be between 1 and 200 mih.

The coating and the training of a

Sustainable forest structure can take place simultaneously or in succession in one step. Furthermore, in one of the steps of the proposed

Process, in particular in the preparation of the solid compound between the coated moldings, already a connection to bodies or fabrics made of a heat transfer material such as a metallic tube or a metal-coated textile fabric.

In principle, in the proposed

Process different steps with each other

be connected or take place at the same time. In the following, some examples are given in which as a functional material zeolite in the form of granules and be used as a thermally conductive material copper (Cu). The examples can also be carried out in this form with other functional materials and / or other thermally conductive materials.

Thus, for example, by electrochemical deposition of Cu directly a sufficiently porous Cu layer can be produced on the zeolite granules. This porous structure becomes one during subsequent sintering of the coated granules

Maintain forest that makes up the composite. Pipes or other heat transfer body can be sintered by the sintering process with equal or afterwards, for example by means of soldering, connected to the composite body. This also applies to the other examples.

In another example, largely closed Cu layers are deposited on the zeolite granules by means of PVD. During the subsequent sintering together of the coated granules, the layers form around and form a kind of porous network.

It is also possible, a porous layer of Cu powder with the help of a binder on the

Apply zeolite granules. When the coated granules sinter together, the porosity remains

Powder layer at least partially, so that also in this way the porous composite body can be obtained.

The proposed porous shaped body, which can be produced by the method, has a corresponding Variety of coated with the good thermal conductivity material moldings of the functional material, which are firmly connected to each other via the good heat conductive material. The coating has a porous structure passing through the coating

through an access for a liquid or

gaseous medium to the functional material allows.

The proposed method and the porous composite bodies produced therewith can be used in many fields in which a good

Heat dissipation of functional materials is required. Examples are sorption heat pumps or else

Applications in gas storage systems, gas separation or catalysis.

Brief description of the drawings

The proposed method will be explained in more detail using exemplary embodiments in conjunction with the drawings. Hereby show:

Fig. 1 is a schematic representation of according to the proposed method

coated and firmly bonded moldings;

Fig. 2 is a representation of the zeolite content of the overall structure as a function of the diameter of a spherical

Zeolite granules and the coating thickness at a porosity of 20vol%; Fig. 3 is a further representation of the zeolite proportion of the total structure in FIG

Dependence of the diameter of the spherical zeolite granules and the coating thickness at a porosity of 20%;

Fig. 4 is a photograph of the structure of a with

Method of produced composite body;

Fig. 5 a representation of one with copper

coated spherical shaped body of zeolite; and

Fig. 6 is a representation of a copper-coated tubular shaped body made of zeolite.

Ways to carry out the invention

In the proposed method, a highly thermally conductive thin layer, for example made of copper, on the surface of moldings of a

Functional material such as zeolite

deposited or applied. Either already during the coating or in a subsequent one

Process step, a porous structure of this layer is generated. The coated moldings are then bonded together to form an overall structure that forms the porous composite body. This can be done for example by sintering. Also a connection via a possibly during the coating used binder can be used. Preference, the whole structure is subsequently or simultaneously with the connection process with peripheral elements, such as pipes, housings, etc.

connected.

FIG. 1 shows a highly schematic four

coated spherical shaped bodies 1 of zeolite coated with a thin Cu layer 2 and over this thin layer by a sintering process

connected to each other. The thin Cu layer has a sufficiently porous structure (not visible in the figure) to allow access of liquid or gaseous media to the zeolite. Figure 1 shows with the four moldings only a very small section of the forest in

schematic representation.

Exemplary volume ratios for the

Functional material in the forest, i. the

Composite bodies can be seen in Figures 2 and 3, each using the example of the zeolite as

Functional material, the zeolite content of the total structure depending on the diameter of the zeolite granules used in this example and the

Show coating thickness. Figure 2 shows this

Granule diameter between 50 and 250 mih at

Coating thicknesses of 1, 3 and 5 mih with Cu, Figure 3 Granule diameter between 1000 and 3000 mih at coating thicknesses of 50, 100 and 150 mih. The

Volume fractions of the zeolite are each preferably in the range between 0.5 and 0.75. Volume fractions of the zeolite of about 70 vol.% Are particularly advantageous. In the following, various examples of the preparation of porous composite bodies with the pre

described methods. In a first example, Y zeolite granules are stirred with a 63-125 mg fraction with water and an organic binder (e.g., ExOne®). Then Cu-UFIO powder (<10mih) is added. The mass is stirred, placed in a mold, for example a cylindrical mold, and

dried. Subsequently, a temperature treatment of 420 ° C. for 1 hour in air is performed to burn out the binder and sintering under a hydrogen atmosphere at 600 ° C. for 3 hours. The result is a cylinder that is sturdy enough for easy handling. The zeolite still has a good after sintering

Water intake on. The sintering conditions have not led to a degradation of the zeolite. FIG. 4 shows by way of example a photograph of a structure of FIG

Cylinder. From this figure it can be seen that the zeolite granules are only superficially covered with a porous layer of Cu particles. The stability of the entire body is produced by the sintered contacts of the Cu layers with each other. It is also possible in this example, the

To save temperature treatment of 420 ° C / lh in air and to cause the burning out of the binder by observing a temperature ramp in the sintering treatment. If the first example with round Y zeolite

Granules carried out (granule diameter about 2 to 3 mm), so there are coarser structures, the porous copper layer on the zeolite particles also after the sintering is still porous and in addition

Shrinkage cracks, which makes the zeolite good

make available. In a second example, Y zeolite granules

(Fraction 63-125 mih) mixed with water and a suitable binder. Cu-UFIO powder is added and the mass is stirred. A copper-plated polyamide fabric is laid flat and the mass on the textile

painted on. This is followed by drying in air,

Burn out of binder and polyamide and oxidize at 420 ° C for lh. Finally, the structure is sintered for 3h at 600 ° C in H2. The thin layers out

Copper powder ensure a good sintering

Cohesion of the Y zeolite with each other and to a

Connection to the tissue. The fabric serves both to mechanically stabilize the overall structure and as a directional, heat-conducting structure (strong

directed thermal conductivity). Such coated textiles can be very well connected with cooling tubes. For example, the coated fabric may be bonded to a copper flat tube during sintering. The fabric is aligned with the flat tube and accordingly dissipates the heat there well.

In a third example, Y zeolite granules (fraction 63-125 mih) are mixed with water and silicone-based binder (eg P80X). Subsequently, Cu-UFIO powder is added. The mass is stirred again and then dried. Then, an oxidation treatment is carried out at 420 ° C for 1 hour in air and sintering at 600 ° C for 2 hours in a hydrogen atmosphere. As the temperature-resistant binder even after sintering still has a good strength, which is based

mechanical strength of the forest is not

solely on the strength of the sintered contacts in or between the copper layers. The proportion of copper can therefore be reduced to a level which is just sufficient for the thermal requirements (thermal conductivity). As a result, additional costs can be saved. In a fourth example, Y zeolite granules

(Fraction> 400mih) with water and a suitable binder stirred. Here, only so much water and binder are added that no coherent slip forms, but the granules spheres are coated individually and thus remain free-flowing. The coated balls are then

dried and can be stored longer. The coated granules can later be filled in

Hollow structures are filled. A sintering treatment, as in the first example

described, then leads to a connection of the

Granules with each other and with the surrounding

Envelope structure. Another way of producing the porous composite utilizes material rearrangements in sintering processes. It is known that by means of fluidized bed PVD method homogeneous copper layers on

ceramic granules, such as cenospheres (aluminum silicates) can be deposited. With the help of such layers, the granules can be sintered together to form solid structures. A well-known but so far unused effect is that at certain sintering conditions the compact copper layers rearrange to porous flat networks.

This is used in the present example to create the porous structure.

Finally, FIG. 5 shows an example of a spherical shaped body of zeolite coated with copper particles, FIG. 6 shows an example of

Zeolite tubes coated with copper fibers. In the proposed method, each of many such coated moldings are produced and bonded together to form the porous composite body. When using metallic material as a good thermally conductive material in the process by a sintering process each a cohesive, metallic and electrically conductive connection to a metal structure as a thermally conductive carrier structure is achieved.

Claims

claims

1. Process for producing porous composite

bodies that make up a support structure

thermally conductive material and at least one

Have functional material, in particular for the production of sorbent bodies or

Catalysts in which

- A variety of moldings (1) from the

Functional material is provided,

- The moldings (1) are coated with the thermally conductive material, and

- A firm connection between the coated moldings is made to the

the support structure of the thermally conductive

To form material

- Wherein the coating (2) of the shaped body (1) is produced with a porous structure or provided with a porous structure according to

Preparation of the solid compound allows access for a liquid or gaseous medium through the coating (2) to the functional material.

2. The method according to claim 1,

characterized,

that the solid compound of the coated

Molded body is produced by a sintering process.

3. The method according to claim 2,

characterized,

the porous structure of the coating (2) is produced by the sintering process.

4. The method according to any one of claims 1 to 3,

characterized,

the coating (2) of the shaped bodies (1) is applied by a deposition process.

5. The method according to claim 4,

characterized,

the coating (2) of the shaped bodies (1) is applied by PVD.

6. The method according to claim 4,

characterized,

the coating (2) of the shaped bodies (1) is applied by electrochemical deposition of a porous layer of the thermally conductive material.

7. The method according to any one of claims 1 to 3,

characterized,

in that, to coat the shaped bodies (1) with the thermally conductive material, the shaped bodies (1) are mixed with a binder and particles or fibers of the thermally conductive material.

8. The method according to claim 7,

characterized,

the particles or fibers of the thermally conductive material have dimensions which are smaller by at least one factor than 10 in at least one dimension Dimensions of the molded body (1) are.

9. The method according to claim 7 or 8,

characterized,

in that the shaped bodies (1) and the particles or fibers of the thermally conductive material are mixed in a mixing ratio in which - with a porosity of the coating (2) between 5 and 25% by volume - the volume fraction of the functional material is between 40 and 70% by volume and the volume fraction of the thermally conductive material is between 10 and 30vol%.

10. The method according to any one of claims 1 to 9,

characterized,

that the functional material as granules, in the form of sticks or in the form of tubes is bereitge provides.

11. The method according to any one of claims 1 to 10,

characterized,

in that the shaped bodies (1) consist of an adsorbent material or a catalyst material as

Functional material are provided.

12. The method according to any one of claims 1 to 11,

characterized,

that the coated moldings in the preparation of the solid compound with a

thermally conductive body, in particular a pipe, a housing or a plate, are connected.

13. Porous composite body comprising a support structure of a thermally conductive material and a plurality of moldings (1) of at least one

Functional material having a coating (2) of the thermally conductive material and on the coating (2) firmly together

are connected, wherein the coating (2) has a porous structure, which by the

Coating (2) through an access for a liquid or gaseous medium to the functional material allows.