Method and device for three-dimensionally coating a porous material

Abstract

The invention provides a device and a method for the device (100) for at least partially three-dimensionally coating a porous material (1). The device (100) comprises: a coating chamber (110); a guide apparatus (120) which is designed to continuously guide a porous material (1) to be coated through the coating chamber; and a coating apparatus (130) which is designed to coat a respective part of the material (1) to be coated currently located in the coating chamber (110) with a coating material (2) by means of physical vapour deposition in a vacuum (3), wherein the physical vapour deposition takes place at a deposition rate of 0.1 micrometres per second or higher.

Description

[0001] title

[0002] Method and apparatus for three-dimensional coating of a porous material

[0003] Technical field

[0004] The present invention relates to a method and a device for the - at least partial - three-dimensional coating of a porous material, in particular a woven fabric, a non-woven fabric, a knitted fabric, a braid, a fleece, a felt, a grid, a net, a nanostructure and / or a durable foam structure such as a metal foam.

[0005] Technical background

[0006] Several techniques for coating three-dimensional (3D) structures already exist in the prior art, for example, physical vapor deposition (PVD). In this process, a coating material is introduced into a gaseous phase and guided to the material to be coated, where it is deposited by resublimation. Classical PVD processes operate on a line-of-sight basis; that is, only areas that are directly accessible from the source of the coating material can be coated.

[0007] Physical vapor deposition on perforated metal strips is described, for example, in WO 2023 / 152305 Al. For relatively thin sheets with relatively large perforations, such as sheet thicknesses of 0.9 mm and hole radii of 2.5 mm, the process described therein can be used very efficiently. However, challenges still exist for deposition on materials with complex internal structures (such as woven or non-woven fabrics) with a large number of undercuts.

[0008] Summary of the invention

[0009] Based on the above, there is therefore a need for an improved method and an improved device for coating porous material.

[0010] A solution is provided by the features of the independent patent claims.

[0011] According to a first aspect, the invention provides a method for at least partially three-dimensional coating of a porous material, comprising at least the steps of: continuously guiding a porous material to be coated through a coating chamber; and continuously coating each part of the porous material to be coated currently located in the coating chamber with a coating material by means of physical vapor deposition in a vacuum.

[0012] The term "porous material" is used here as a general term for materials into which fluids (i.e., liquids or gases) can penetrate in some way, especially in a macroscopic manner, such that internal areas of the porous material can be touched or wetted by such fluids, and the porous material is permeable to fluids in this way. Numerous examples of such materials will be given below, which, in addition to typical porous materials such as various porous ceramics (e.g., foam ceramics, directly foamed ceramics, or granular ceramics), can also include (especially textile) sheet structures (such as a woven fabric, a nonwoven fabric, a knitted fabric, a braid, a fleece, a felt—for example, a carbon felt—or the like), as well as grids, nets, or nanomaterials. The porous material can have interconnected pores, i.e., interconnected porosity.exhibit "interconnected porosity".

[0013] The porous material is, in particular, a material with a large number of undercuts. The advantages of the present teaching are especially evident in such materials.

[0014] The porous material to be coated preferably comprises a woven fabric, a non-woven fabric, a knitted fabric, a braid, a fleece, a felt, and / or a durable foam structure.

[0015] The inventors have discovered that a large number of promising combinations for all possible applications arise from, on the one hand, a multitude of different porous materials, and on the other hand, a multitude of coating materials, each with interesting properties, for example, in catalyst technology or for gas diffusion electrodes. The present invention provides a method for producing a multitude of such combinations, which were previously impossible or inefficient to manufacture, not only in the laboratory but also on an industrial scale.

[0016] Physical vapor deposition is preferably carried out at a deposition rate of 0.1 micrometers per second or higher, particularly at a deposition rate of 0.2 micrometers per second or higher, for example at 0.5 micrometers per second or higher, for example in the range of 0.5 micrometers per second to 5 micrometers per second. Physical vapor deposition is advantageously carried out by a plasma evaporator, as described in WO 2023 / 152305 Al.

[0017] A fundamental idea of ​​the present disclosure is based on the realization that, above a sufficiently high deposition rate (of the coating material on the material to be coated), which correlates with a high particle velocity of the coating material in the area of ​​the porous material to be coated, a particularly good penetration of the pore structures with the coating material is enabled.

[0018] The settings required for the process, including in particular the plasma power of the plasma evaporator, can be determined for each device used in the process by simple and routine test procedures. For example, once steady-state operation has been established, the deposition rate can be determined from the evaporation rate, since in steady-state operation the mass of the coating material evaporated per unit time must be deposited on the material to be coated, which is cooler in relation to the coating chamber (or "confinement"). Given the surface area F of the material to be coated (a sample can be used for measurement), the plasma power P of the plasma evaporator, the enthalpy of vaporization AH, and the mass density p of the coating material, the deposition rate r can be calculated according to...

[0019] The deposition rate r can also be determined by simply measuring the layer thickness of the coating material on the porous material being coated using the process, as well as measuring the time that each section of the porous material spent in the coating chamber. Particularly on the outer surface of a sample, which can also be a non-porous material, the deposition rate (or coating rate) can be easily determined and thus correlated with the fluid-mechanical properties of the coating material immediately upstream of the material to be coated.For this purpose, or additionally, typical approximations applicable here, such as the ideal gas law, the mean velocity of particles in a gas from the kinetic theory of gases, Maxwell-Boltzmann statistics, and / or similar methods, can be used, for example, to indirectly calculate the pressure in the coating device as an intermediate quantity. The plasma power P can thus remain, for example, as an important, or even the only, control variable for the process.

[0020] Partial three-dimensional coating means that the three-dimensional coating is applied at least partially, i.e., not every externally accessible section of the porous material to be coated needs to be coated. However, in some variations, the coating can be applied completely.

[0021] Continuous feeding and coating can be understood as follows: one piece of the porous material to be coated is inserted into the coating chamber one after the other, coated there, and then removed from the coating chamber, so that only one piece is present in the coating chamber at any given time and is being coated (so-called "piecewise continuous coating"), whereby the piece may, for example, be completely within the coating chamber during coating.

[0022] The porous material to be coated can therefore be in the form of lumpy goods, so that repeatedly an end edge of a first piece of the porous material to be coated leaves the coating chamber and (simultaneously, before, or after) a front edge of a second piece of the porous material to be coated enters the coating chamber.

[0023] Preferably, continuous feeding and continuous coating should be understood as follows: different sections of the (continuous) porous material to be coated are successively introduced into the coating chamber, coated, and removed again, whereby it may happen that a first part (or: section) of the porous material to be coated leaves the coating chamber, while at the same time a second part (or: section) of the porous material to be coated is being coated, while at the same time a third part (or: section) of the porous material to be coated is being introduced into the coating chamber (so-called "section-by-section continuous coating").

[0024] Sectional continuous coating is advantageous, for example, in the case of a textile fabric and / or reeled material as the porous material to be coated, since these often have an elongated shape and the aforementioned continuous sectional coating can be carried out with a device whose dimensions are smaller than the total length of the porous material to be coated.

[0025] The porous material to be coated can, for example, also be in the form of an "endless strip," meaning that further porous material to be coated is continuously added (welded, tacked, etc.) to the front and continuously coated porous material is removed from the rear, while in between, a continuous coating of a different section of the endless strip is carried out. According to some preferred embodiments, variants, or refinements of embodiments, the coating material exhibits fluid-mechanical properties in the Knudsen region in a region on and / or immediately in front of the porous material to be coated (i.e., for example, at least in a region up to 1 cm in front of the porous material to be coated) (or: is located in the Knudsen region).

[0026] Another idea of ​​the present disclosure is based on the finding that a coating material which is located in the Knudsen region, i.e., has fluid-mechanical properties in the Knudsen region, is very well suited to penetrating the spaces of the porous material to be coated and effectively coating undercuts there as well.

[0027] Without further ado, it is assumed that the good results of coating with coating material in the Knudsen range are based on the fact that, on the one hand, the particles of the coating material must not collide with each other too much, as they would otherwise lose kinetic energy too early to penetrate sufficiently into the pores of the porous material to be coated, and on the other hand, must collide with each other enough so that the initially one-sided direction of movement of the particles (from the evaporator to the porous material to be coated) is transformed into complex movement patterns on the porous material to be coated, so that even complex pore geometries with undercuts etc. can be sufficiently wetted by the particles.

[0028] A material in the Knudsen range is understood to mean, in particular, that the Knudsen number Kn for the material is less than or equal to 10, especially greater than or equal to 0, 01 and less than or equal to 10, i.e.

[0029] 0.01 < Kn < 10. The Knudsen number Kn for the material is particularly preferred to be in the range of 0.05 to 0.5.

[0030] The Knudsen number Kn is defined by

[0031] Kn = X / L, where X is the mean free path of the coating material and L is the characteristic length of the flow field of the coating material in the coating chamber, particularly in the region of the coating chamber where the coating takes place. In other words, the coating of the porous material to be coated is advantageously carried out in a vacuum with a coating material in Knudsen flow. The characteristic length L can, in particular, be understood as a hydraulic diameter DH of the coating chamber in the region of the coating (i.e., around the porous material to be coated and / or immediately in front of it) (i.e., L = DH), where the hydraulic diameter DH is given by the standard definition: where A is the cross-sectional area through which the flow passes and U is the circumference wetted by the flow. In the case of a cylindrical coating chamber with a cylinder radius of R, which is an advantageous embodiment, the hydraulic diameter DH is therefore which in this case therefore also corresponds to the cylinder diameter. For other structures, for example cuboid coating chambers with a square or rectangular cross-section, correspondingly different hydraulic diameters DH result, such as the edge length a for a square cross-section.

[0032] It has been found that if the coating material is located in the Knudsen region immediately before coating, the fluid-mechanical properties of the coating material are particularly favorable for fully penetrating coating, even within the porous material to be coated.

[0033] The mean free path of the coating material, which is also necessary for calculating the Knudsen number, can be determined via the pressure p in the coating device, for (approximately, as here) ideal gases by means of with the temperature T, the Boltzmann constant ks, and the effective molecular diameter d of the coating material. In principle, the pressure in the coating device could be measured directly; however, this places very high demands on the pressure measuring device, so indirect solutions are often easier to implement. The pressure can be calculated, in particular, from the deposition rate r (known from measurements after coating in steady-state operation) via the particle density and the particle flux density, which in turn can be traced back to the power of the evaporator, especially the plasma power of a plasma evaporator.

[0034] Thus, indirectly, possibly after a few test runs, the evaporator's power can be adjusted (and then set) so that the coating material, with fluid-mechanical properties in the Knudsen range, comes into contact with the porous material to be coated. According to some preferred embodiments, variants, or refinements of the design, the coating material comprises or consists of a metallic material (e.g., an elemental metal). The coating material can comprise or consist of an alloy of several metals, or be a material whose main component is a metal.

[0035] Suitable metallic materials include copper, nickel, manganese, or silver, as well as corresponding alloys or mixtures whose main component consists of one or more of these metals.

[0036] Platinum, ruthenium, iridium and / or rhenium are also suitable as coating materials, especially for catalysts, but also other catalytically active substances or material mixtures.

[0037] Another possible coating material, for example for battery electrodes (such as in a zinc-air battery), is carbon.

[0038] According to some preferred embodiments, variants, or refinements of the design, the coating material is silicon. Silicon is the subject of ongoing research and exhibits a multitude of promising properties.

[0039] According to some preferred embodiments, variants or refinements of embodiments, the coating material has a vapor pressure of 10 at its respective melting point. A -6 millibar to 10 millibar, especially from 10 A-3 millibar to 1 millibar. The inventors have found that such coating materials achieve the best results.

[0040] According to some preferred embodiments, variants or

[0041] In refined versions of the design, the coating material has a melting point between 300°C and 1500°C, in particular between 400°C and 1200°C.

[0042] According to some preferred embodiments, variants or refinements of the design, the porous material to be coated has a pore size of 1 mm or less, and / or a specific surface a s after the BET procedure of 0.1 m 2 G -1 or larger.

[0043] The pores can be, in particular, macropores with a pore size between 50 nm and 1 mm, or mesopores with a pore size between 2 nm and 50 nm, in each case according to or based on ISO 15901:3:2007 [3] , 3.10 and 3.11. A mixture of macropores and mesopores may also be present.

[0044] The specific surface area a s The specific surface area is determined using the BET method according to ISO 9277:2010, "Determination of the specific surface area of ​​solids by gas adsorption". The porous material to be coated advantageously has a specific surface area a s of 0.1 m 2 G -1 (“square meters per gram”) or larger, especially between 0.1 m 2 G -1 and 100 m 2 G -1 , especially preferably between 0.5 m 2 G -1 and 50 m 2 G -1 .

[0045] As an example of a porous material to be coated, graphite felts can have specific surface areas of between 2 and 3 m². 2 G -1 exhibit, or carbon-graphite felts specific surface areas of between 0.2 m 2 G -1 and 0.8 m 2 G -1 , especially between 0.4 m 2 G -1 and 0.6 m 2 G -1 As another example, activated carbon has a specific surface area of ​​550 m². 2 G -1 on.

[0046] According to some preferred embodiments, variants, or refinements of the process, the porous material to be coated is supplied on reels. Preferably, during the process, it is unwound from a reel before continuous coating and / or wound onto a reel after continuous coating. In this way, a large quantity of the material to be coated can be coated gradually and efficiently stored before and after. Alternatively, the porous material to be coated can also be supplied on coils and, accordingly, unwound from a coil before continuous coating and / or wound back onto a coil after continuous coating.

[0047] According to some preferred embodiments, variants or refinements of embodiments, the process includes a heat treatment of the coated material, e.g. outside the coating chamber after coating, for example tempering a steel component (e.g. to achieve a desired hardness or toughness) and / or diffusion annealing (e.g. to reduce inhomogeneities).

[0048] Preferably, the heat treatment is carried out in a vacuum. The coating chamber, in which a vacuum is maintained, can, for example, also comprise a coating area where the coating takes place and a separate heat treatment area where the heat treatment is carried out, still in a vacuum. In the case of coiled material, the heat treatment preferably takes place before coiling.

[0049] According to some preferred embodiments, variants or refinements of embodiments, the porous material to be coated can be negatively polarized for the coating, wherein the resulting voltage or potential difference to the coating material can preferably be between 5 V and 100 V, particularly preferably between 30 V and 60 V, for example 50 V.

[0050] The potential difference (or voltage) relative to the (especially plasma-like) coating material can increase the velocity of partially ionized vapor towards the material to be coated compared to the case without polarization, proportionally to the voltage (or potential difference). This increases the kinetic energy of individual resublimating (or condensing) particles, which in turn can lead to better adsorption onto the surface of the porous material to be coated.

[0051] A deposition rate of 0.1 pm / s or higher, as preferred, can help to reduce or compensate for any sputtering effects.

[0052] Furthermore, bombarding the surface of the porous material to be coated with increased kinetic energy can, via thermal effects, reduce the adhesion coefficient on the outer surface of the material compared to its inner core. This effect can counteract (or compensate for) the typically lower particle density of the coating material in the core, resulting in a more uniform coating thickness between the outer surface and the core of the material.

[0053] The polarization of the porous material to be coated can be achieved, for example, by an electrical polarization roller configured to be in electrical contact with the porous material. If the porous material to be coated is electrically conductive, the electrical polarization roller can be arranged with great design freedom, preferably within the vacuum created in the coating chamber.

[0054] In the case of an electrically non-conductive porous material to be coated, the electrical polarization roller (in the transport direction of the porous material to be coated) can be arranged after the coating area in the coating chamber, such that it electrically contacts the coating material on the porous material to be coated. If heat treatment is planned, the electrical polarization roller can be arranged, in particular, between the coating area and the heat treatment area in the coating chamber.

[0055] According to some preferred embodiments, variants, or refinements of embodiments, the guiding and coating are carried out such that the coating material (from an outer surface of the porous material to be coated) penetrates substantially only to 5% to 45%, preferably 10% to 40%, for example 30% or 35%, of the thickness of the porous material to be coated. For many applications, complete internal coating of the porous material to be coated is not desirable or simply not necessary.

[0056] Alternatively, or to put it another way, the coating material can be applied to cover, for example, only up to 20%, up to 50%, or up to 90% of the pore surfaces (but not just the outer surface of the porous material to be coated). A portion of the pores may be filled in the process.

[0057] According to some preferred embodiments, variants or refinements of embodiments, the coating is carried out on one side or on both sides, i.e. only from a single outer surface of the porous material to be coated, or from two (or more) different outer surfaces of the porous material to be coated, in particular from two opposing outer surfaces.

[0058] Double-sided coating allows for the particularly efficient coating of a large, externally accessible internal volume of the porous material to be coated. If, for example, 5%, 20%, or 40% of the thickness of the porous material is coated from each of two opposing outer surfaces, then 10%, 40%, or 80% of the internal volume of the porous material to be coated, respectively, will be covered.

[0059] According to some preferred embodiments, variants, or refinements of the design, the coated porous material (i.e., the porous material to be coated after it has been coated) is at least partially compressed after leaving the coating chamber, in particular to permanently reduce its thickness and / or permanently increase its density. In this way, for example, an inelastically compressible porous material can first be coated more efficiently, easily, and / or quickly (since the pore size is larger in the uncompressed state, or the internal volumes and undercuts of the porous material are more accessible), and then compressed to a desired lower thickness and / or higher density.

[0060] According to some preferred embodiments, variants, or refinements of the invention, the coated porous material is used as a gas diffusion electrode or as part of a gas diffusion electrode. In other words, the coated porous material can be used to manufacture a gas diffusion electrode, so the invention also comprises a method for manufacturing a gas diffusion electrode, wherein, according to an embodiment of the first aspect, a porous material is first coated, and this is then used for (or in) the manufacture of the gas diffusion electrode.

[0061] Such a gas diffusion electrode can be used, for example, in a fuel cell (e.g., a hydrogen cell), in electrolysis, in hydrogen peroxide production, in wastewater treatment, etc. Suitable materials for a gas diffusion electrode include felt as a porous material to be coated (such as carbon felt) and a metallic catalyst as the coating material.

[0062] According to a second aspect, the present invention provides a device for at least partial 3-dimensional coating of a porous material, comprising: a coating chamber; a guide device which is configured to continuously guide a porous material to be coated through the coating chamber;and a coating device which is configured to coat a portion of the material to be coated currently located in the coating chamber with a coating material by means of physical vapor deposition in a vacuum, wherein the coating device is further configured such that the physical vapor deposition takes place at a deposition rate of 0.1 micrometers per second or higher, in particular at a deposition rate of 0.2 micrometers per second or higher, for example at 0.5 micrometers per second or higher, for example in the range of 0.5 micrometers per second to 5 micrometers per second.

[0063] Preferably, the coating device is also configured such that the coating material in an area on and / or immediately in front of the porous material to be coated has fluid-mechanical properties in the Knudsen range, in particular a Knudsen number between 0, 1 and 10.

[0064] The coating device can include a vacuum source (in particular a vacuum pump), a plasma evaporator, and other elements. Further advantageous embodiments, variants, and refinements of embodiments will become apparent from the following detailed description with reference to the figures.

[0065] Brief description of the characters

[0066] The invention is explained in more detail below with reference to exemplary embodiments shown in the figures of the drawings. These show:

[0067] Fig. 1 shows a schematic representation of a device according to one embodiment of the present invention;

[0068] Fig. 2 shows a schematic representation of a variant of the device from Fig. 1;

[0069] Fig. 3 shows a schematic representation of a variant of the device from Fig. 2 and

[0070] Fig. 4 is a schematic flowchart to explain a method according to a further embodiment of the present invention.

[0071] The naming and numbering of the process steps does not necessarily imply a sequence, but serves for better differentiation, although in some variants the sequence may also correspond to the sequence of the numbering.

[0072] Detailed description of the figures

[0073] Fig. 1 shows a schematic representation of a

[0074] Device 100 according to one embodiment of the present invention, i.e., a device 100 for at least partially coating a porous material 1 in three dimensions. The device 100 comprises a coating chamber 110 and a guide device 120, which is configured to continuously guide the porous material 1 to be coated through the coating chamber 110 (confinement).

[0075] The guide device 120 can be configured in a variety of ways, each adapted to the properties of the porous material 1 to be coated. In Fig. 1, the guide device 120 is shown, for example, as having rollers, where one or more rollers can be feed rollers, while the other rollers can simply be guide rollers. The rollers can be arranged on one side under the porous material 1 to be coated, for example, if it is a heavy and / or stiff material, or arranged on both sides, as shown by way of example in Fig. 1. If coating on one side is desired, the guide device 120 can, for example, also include a conveyor belt on which the porous material 1 to be coated is conveyed.

[0076] As already explained, the porous material 1 to be coated can optionally be reel material, which is unwound from a first reel 151 or from a first coil before coating and / or wound onto a second reel 152 or into a second coil after coating, in each case directly or with one or more intermediate steps. Alternatively, a device for cutting or dividing the coated porous material 1 can also be provided after coating. The first reel 151 and / or the second reel 152, or corresponding holders, can thus be part of the device 100, for example, the guide device 120.

[0077] The device 100 also has a coating device 130, which is configured to coat a portion of the porous material 1 currently located in the coating chamber 110 with a coating material 2 by means of physical vapor deposition in a vacuum 3.

[0078] The coating device 130 is preferably arranged within the coating chamber 110, which in turn is advantageously arranged within a vacuum chamber 140, which can be evacuated by means of a vacuum source 141, for example a vacuum pump, and is evacuated during the coating process.

[0079] In the illustrated example, the coating chamber 110 is roughly cylindrical, with the coating device 130 arranged in a first axial half of the cylinder, and the porous material 1 to be coated passing through a second axial half of the cylinder. Where the porous material 1 to be coated enters and exits the coating chamber 110, the coating chamber 110 advantageously has outwardly directed, elongated projections 111, which contribute to a slower exchange of the atmosphere inside the coating chamber 110 with the surrounding vacuum in the vacuum chamber 140. The projections 111 can extend, for example, at least 5 cm, preferably at least 10 cm, and particularly preferably at least 15 cm, beyond the rest of the coating chamber 110.

[0080] The coating device 130 comprises an evaporator 131, for example a plasma evaporator such as is known from the prior art for PVD devices, for example from WO 2023 / 152305 Al. The teaching of WO 2023 / 152305 Al is hereby incorporated in its entirety into the present disclosure by reference. The evaporation rate can be adjusted, in particular by means of the power of the evaporator 131, for example the plasma power of the plasma evaporator, and thus the fluid-mechanical properties at and / or immediately in front of the porous material 1 to be coated can also be adjusted.

[0081] Preferably, the coating device 130 is configured such that the coating material 2 exhibits fluid-mechanical properties in the Knudsen range at and / or immediately in front of the porous material 1 to be coated. As explained above, this is usually achieved by indirect measurements due to the typically very high pressures in the coating chamber 110.

[0082] The characteristic length L for calculating the Knudsen number is preferably, as schematically (and not to scale) shown in Fig. 1, a hydraulic diameter DH of the coating chamber 110 in the area at and / or immediately in front of the material 1 to be coated. For the present, exemplary cylindrical shape of the coating chamber 110, the characteristic length L would therefore be equal to the diameter of the cylinder. For other shapes (cuboid shapes, etc.), the hydraulic diameter DH can be calculated accordingly.

[0083] In the coating chamber 110, guiding devices 112 can be arranged to direct or guide the coating material 2 discharged by the evaporator 131 within the coating chamber 110, for example to ensure homogeneous (one-sided or two-sided) application of the coating material 2 to the porous material 1 to be coated. The guiding devices 112 can, for example, comprise mechanical guide plates and / or electromagnetic guiding devices.

[0084] The coating chamber 110 itself is preferably heated and maintained at a temperature (or target temperature) above the melting point or evaporation point of the coating material 2 by means of a heating device (not shown), while the porous material 1 to be coated has a lower temperature, for example, an ambient temperature outside the vacuum chamber 140, i.e., it remains unheated or is even cooled. In this way, the deposition of the coating material 2 is promoted primarily or exclusively on the porous material 2 to be coated.

[0085] For example, the coating chamber 110 can be heated and maintained at a target temperature of 1000 °C or more, 1200 °C or more, 1400 °C or more, e.g., 1500 °C or 1600 °C. The coating chamber 110 is accordingly constructed from a material or material mixture that does not melt at the respective target temperature and can therefore, for example, comprise or consist of molybdenum and / or wolfram.

[0086] The guide device 120 can be configured to guide the porous material 1 to be coated substantially horizontally (as exemplified in Fig. 1) or substantially vertically through the coating chamber 110. Particularly with vertical belt travel, the process can be carried out in two stages, so that the porous material 1 to be coated is first guided in one direction, for example upwards, then deflected outside the coating chamber 110, and subsequently guided downwards back into the coating chamber 110 to achieve a symmetrical coating of the porous material 1 to be coated from both sides.

[0087] The guide device 120 advantageously comprises guide rollers 121 at the perimeter of the vacuum chamber 140, over which the porous material 1 to be coated can be introduced into the vacuum chamber 140. The guide device 120 can also include further elements (not shown), in particular feed rollers, guide elements, forming elements, and the like. In versions where the protrusions 111 are present, the porous material 1 to be coated is introduced into the coating chamber 110 via a first protrusion 111 and guided out of the coating chamber 110 via a second protrusion 11. In this way, despite the necessary inlet and outlet to and from the coating chamber 110, there is only minimal atmospheric exchange with the surrounding vacuum chamber 140.

[0088] As already explained, the guide device 120 and the coating device 130 can be configured or adjusted such that the coating material 2 (from an outer surface of the porous material 1 to be coated) penetrates essentially only to a thickness of 5% to 45%, preferably 10% to 40%, for example 30% or 35%, of the porous material 1 to be coated. With coating on both sides (either simultaneously or sequentially by deflection as described above), the value can thus be doubled in each case, based on the volume of the porous material 1 to be coated.

[0089] There are various options for pre- and / or post-treatment of the porous material 1 to be coated or of the coated porous material 1 before or after coating.

[0090] Fig. 2 shows a schematic representation of a variant of the device 100 from Fig. 1. It illustrates how the porous material 1 to be coated is first introduced by the guide device 120 into a (particularly chemical) cleaning device 101, then into a pretreatment device 102 (e.g., a plasma pretreatment device), and only then into the coating chamber 110. It is also schematically shown that, after coating, the porous material 1 to be coated can be guided, for example, into a heat treatment device 103 and / or a press 104.

[0091] In the pretreatment unit 102, in particular the plasma pretreatment unit, a plasma treatment can be carried out, for example, to modify the surface of the porous material 1 to be coated, such as plasma etching. This can, for example, achieve microstructuring of the surface (e.g., to improve adhesion) of the porous material 1 to be coated and / or the removal of unwanted layers (oxide layers, varnishes) on / of the porous material 1 to be coated.

[0092] The heat treatment unit 103 can, for example, be set up for tempering a steel component (e.g. to achieve a desired hardness or toughness) and / or for diffusion annealing (e.g. to reduce inhomogeneities).

[0093] The device 100 can include one, several, or all of the cleaning device 101, pretreatment device 102, heat treatment device 103, and / or press 104, with various arrangement sequences possible. As already shown with reference to Fig. 1, the guide device 120 can remove the porous material 1 to be coated from a first reel 151 or a first coil and wind the coated porous material 1 into a second reel 152 or onto a second coil.

[0094] Each of the aforementioned post-processing operations can be carried out either section by section or after the entire porous material 1 has been coated. Fig. 3 shows a variant of the device 100 from Fig. 2, which additionally includes an electrical polarization roller 105 by means of which the porous material 1 to be coated can be negatively polarized relative to the coating material during the coating process. The resulting voltage or potential difference to the coating material is preferably between 5 V and 100 V, particularly preferably between 30 V and 60 V, for example 50 V.

[0095] In the case of an electrically non-conductive porous material to be coated 1, the electrical-

[0096] The polarization roller 105 (in the transport direction of the porous material 1 to be coated) is advantageously arranged after a coating area 51 in the coating chamber 101, such that it electrically contacts the coating material 1 on the already coated porous material. If heat treatment is provided, the electrical polarization roller 105 can be arranged, in particular, between a coating area 51 (where the coating takes place) and a heat treatment area 53 (where the heat treatment device 103 acts on the coated porous material 1) in the coating chamber 110 under vacuum 3.

[0097] In the case of an electrically conductive porous material to be coated, the electric polarization roller 105 can be arranged at any location where it is in electrical contact with the porous material to be coated, which is located in the coating area 51, preferably also in the vacuum 3 within the coating chamber 110.

[0098] Fig. 4 shows a schematic flowchart to explain a method according to one embodiment of the present invention, i.e., a method for at least partially three-dimensionally coating a porous material 1. The method according to Fig. 4 can be carried out using the device 100 from Fig. 1, but also independently of it. The method can be adapted according to all embodiments, options, variants, and refinements described with respect to the device 100 according to the invention, and vice versa. Therefore, reference numerals from Figs. 1 to 3 are also used in the following for illustrative purposes, without this implying a mandatory use of the device 100.

[0099] In step S 10, the porous material 1 to be coated is continuously guided through a coating chamber 110, for example as described above with reference to the guide device 120 and the coating chamber 110.

[0100] In step S20, a continuous coating of a portion of the porous material 1 currently located in the coating chamber 110 is carried out by means of physical vapor deposition in a vacuum 3 with a coating material 2. The physical vapor deposition preferably takes place with a deposition rate of 0.1 micrometers per second or higher, in particular with a deposition rate of 0.2 micrometers per second or higher, for example with 0.5 micrometers per second or higher, for example in the range of 0.5 micrometers per second to 5 micrometers per second.

[0101] Furthermore, the coating material 2 preferably exhibits Knudsen-type fluid dynamic properties in a region on and / or immediately in front of the porous material 1 to be coated (i.e., for example, at least in a region up to 1 cm in front of the porous material 1 to be coated). For this purpose, given the dimensions of a coating chamber 110 in which the process is carried out, the parameters of the process, in particular the power of an evaporator 132 (e.g., a plasma power of a plasma evaporator) and / or the conveying speed of the conveying device 120, can be adjusted accordingly after simple test runs and by means of the described measurements and calculations.

[0102] The coating of S20 can be carried out in the manner already described above with reference to the coating device 130. In particular, the coating of S20 can be carried out on one or both sides (the latter simultaneously or sequentially), partially or completely.

[0103] Physical vapor deposition is advantageously carried out by a plasma evaporator 132, as described in WO 2023 / 152305 Al.

[0104] As already explained in detail above, the porous material 1 to be coated can be at least one of the following:

[0105] - a porous ceramic (e.g. a foam ceramic, directly foamed ceramic, or granular ceramic) ,

[0106] - a permanent foam structure (e.g. a metal foam or the aforementioned foam ceramic) ,

[0107] - a porous (especially textile) surface structure,

[0108] (e.g. a woven fabric, a nonwoven fabric, a knitted fabric, a braid, a fleece, a felt - especially a carbon felt)

[0109] - a grid,

[0110] - a network,

[0111] - a nanomaterial, and / or the like. A variety of the aforementioned materials and material combinations are suitable as coating material 2, for example copper, nickel, manganese, silver, platinum, ruthenium, iridium, rhenium, silicon, or carbon.

[0112] In general, materials are preferred as coating material 2 which have a vapor pressure of 1 microbar to 10 millibar, in particular of 0.1 millibar to 5 millibar at their respective melting point and / or have a melting point between 300°C and 1500°C, in particular between 400°C and 1200°C.

[0113] Prior to the actual coating S20 of the porous material 1 to be coated in the coating chamber 110, optional preliminary steps can be carried out, which can be provided depending on the porous material 1 to be coated and the coating material 2.

[0114] For example, if the porous material 1 to be coated is reel or coilware, it can be unwound from a (first) reel 151 or coil in one step SOI.

[0115] In step S02, a chemical pre-cleaning of the porous material 1 to be coated can be carried out, for example with the cleaning device 101.

[0116] In step S03, a vacuum-based pretreatment using plasma can be performed, for example with the pretreatment unit 102. The vacuum-based pretreatment can include, for example, plasma etching.

[0117] Likewise, various advantageous processing steps of the then coated porous material 1 can also be carried out after coating S20.

[0118] For example, in step S100, a heat treatment can be carried out, such as tempering a steel component (e.g., to achieve a desired hardness or toughness) and / or diffusion annealing (e.g., to reduce inhomogeneities). This can be done, for example, in the heat treatment unit 103 of the device 100.

[0119] As explained in particular with reference to Fig. 3, an electrical potential difference can also be generated between the porous material 1 to be coated (or at least its coating material after coating) and the coating material during the coating process. The resulting voltage or potential difference to the coating material is preferably between -5 V and -100 V, more preferably between -30 V and -60 V, for example -50 V.

[0120] Alternatively or additionally, in step S200 the porous material 1 to be coated can be pressed, in particular to permanently reduce its thickness and / or permanently increase its density, for example with the press 104 of the device 100.

[0121] Furthermore, if the coated porous material 1 is reel material or coil material, it can be wound onto a (second) reel 152 or coil in a step S300.

[0122] The process may include the fabrication of a gas diffusion electrode using the coated porous material 2, wherein the coated porous material 1 is used as the gas diffusion electrode or as part of the gas diffusion electrode. In this case, the process may also be described as a process for fabricating a gas diffusion electrode.

[0123] For example, the porous material to be coated may be

[0124] Material 2 is a carbon felt, initially wound onto a first reel 151. After unwinding from the first reel 151 and chemical cleaning (S 02), the carbon felt is continuously fed into the coating chamber 110 (S 10) and continuously coated there (S20). The continuous coating (S20) can be carried out, in particular, with a catalyst material, such as platinum, ruthenium, iridium, and rhenium, or more generally with a metal or alloy, including, in particular, copper, nickel, manganese, and / or silver.

[0125] After coating S20, the coated carbon felt can be pressed S200 and then wound onto the second reel 152 S300.

[0126] The coated carbon felt can ultimately be used, for example, as a gas diffusion electrode or as part of a gas diffusion electrode.

[0127] In the preceding detailed description, various features have been summarized in one or more examples to improve the clarity of the presentation. However, it should be clear that the above description is merely illustrative and in no way limiting. It serves to cover all alternatives, modifications, and equivalents of the various features and embodiments. Many other examples will be immediately and directly clear to the person skilled in the art based on their technical knowledge, given the above description.

[0128] The exemplary embodiments were selected and described to best illustrate the principles underlying the invention and its practical applications. This allows those skilled in the art to optimally modify and utilize the invention and its various exemplary embodiments with regard to their intended purpose. Reference list

[0129] 1. Material to be coated

[0130] 2 Coating material

[0131] 3 Vacuum

[0132] 51 Coating area

[0133] 53 Heat treatment area

[0134] 100 Device

[0135] 101 Cleaning equipment

[0136] 102 Pre-treatment facility

[0137] 103 Heat treatment facility

[0138] 104 Press

[0139] 105 Electric polarization roller

[0140] 110 Coating chamber

[0141] 111 protrusions

[0142] 112 guidance systems

[0143] 120 Guide system

[0144] 121 Lock roller

[0145] 130 coating equipment

[0146] 131 evaporators

[0147] 140 vacuum chamber

[0148] 141 Vacuum source

[0149] 151 first reel

[0150] 152 second reel

[0151] L characteristic length

[0152] 501 Discontinue

[0153] 502 Chemical Cleaning

[0154] 503 Pretreatment

[0155] S 10 Continuous Leading

[0156] S20 Continuous Coating

[0157] S 100 heat treatment

[0158] S200 Presses

[0159] S300 Winding

Claims

Patent claims 1. Method for at least partially coating a porous material in three dimensions, comprising: continuously guiding (S10) a porous material (1) to be coated through a coating chamber (110); and continuously coating (S20) a portion of the porous material (1) currently located in the coating chamber (110) with a coating material (2) by means of physical vapor deposition in a vacuum (3), wherein the physical vapor deposition is carried out at a deposition rate of 0.1 micrometers per second or higher.

2. Method according to claim 1, wherein the porous material to be coated (1) comprises a woven fabric, a nonwoven fabric, a knitted fabric, a braid, a fleece, a felt, and / or a permanent foam structure.

3. Method according to claim 1 or 2, wherein the coating material (2) has a Knudsen number between 0.1 and 10 in an area on and / or immediately in front of the porous material (1) to be coated.

4. Method according to any one of claims 1 to 3, wherein the porous material to be coated (1) comprises or consists of a carbon felt or a metal foam.

5. Method according to any one of claims 1 to 4, wherein the coating material (2) is or comprises a metallic material, in particular copper, nickel, manganese or silver, or an alloy with at least one of these metals or a material whose main component is one of these metals.

6. Method according to any one of claims 1 to 5, wherein the coating material (2) is or comprises silicon.

7. Method according to any one of claims 1 to 6, wherein the coating material (2) has a vapor pressure at the respective melting point of IO-6 exhibits values ​​from mbar to 10 mbar.

8. Method according to any one of claims 1 to 7, wherein the coating material (2) has a melting point between 300°C and 1500°C, in particular between 400°C and 1200°C.

9. Method according to any one of claims 1 to 8, wherein the porous material to be coated (1) has a pore size of 1 mm or less, and / or a specific surface area according to the BET method of 0.1 m² 2 G -1 or larger.

10. Method according to any one of claims 1 to 9, wherein the porous material to be coated (1) is a reel material and in particular is unwound from a reel (151) before the continuous coating (S20) and / or wound onto a reel (152) after the continuous coating (S20) during the process.

11. Method according to any one of claims 1 to 10, comprising a heat treatment (S100) of the coated material (1) outside the coating chamber (110) after coating (S20) .

12. Method according to any one of claims 1 to 11, wherein the guiding (S10) and the coating (S20) are carried out such that the coating material (2) penetrates substantially only to 5 to 45% of the thickness of the porous material (1) to be coated.

13. Method according to any one of claims 1 to 12, wherein the coating (S20) is carried out on one side or on both sides.

14. Method according to any one of claims 1 to 13, wherein the coated porous material (1) is at least partially pressed (S200) after leaving the coating chamber (110) in order to permanently reduce its thickness and / or permanently increase its density.

15. Method according to any one of claims 1 to 14, wherein the coated porous material (1) is used as a gas diffusion electrode or as part of a gas diffusion electrode.

16. Device (100) for at least partial 3-dimensional coating of a porous material (1), comprising: a coating chamber (110); a guide device (120) configured to continuously guide a porous material (1) to be coated through the coating chamber; and a coating device (130) configured to apply a coating to a porous material (1) currently in the The coating chamber (110) contains the part of the material (1) to be coated by means of physical vapor deposition in a vacuum (3) with a coating material (2), wherein the coating device (130) is also configured such that the physical vapor deposition takes place at a deposition rate of 0.1 micrometers per second or higher.

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